回复16楼 余军
回复16楼 余军:回复12楼 薛传恽
全文搬出来了。原文的格式很复杂，在这里表现不出来。被这个网站约束以后的样子就如下所示。一些图表都不见了。不过没关系，大家只要看个大概就够。我要翻译不照他。不过翻译会很艰苦。我现在效率很低。大家要多等些时间。
Ursocholanic acid rescues mitochondrial function
in common forms of familial Parkinson’s disease
Heather Mortiboys,1 Jan Aasly2 and Oliver Bandmann1
1 Sheffield Institute for Translational Neuroscience (SITraN), University of Sheffield, Sheffield, UK
2 Department of Neurology, St Olav’s Hospital, Trondheim, Norway
Correspondence to: Oliver Bandmann, MD PhD
Sheffield Institute for Translational Neuroscience (SITraN),
Department of Neuroscience,
University of Sheffield,
385a Glossop Road,
Sheffield S10 2HQ, UK
E-mail: o.bandmann@sheffield.ac.uk
Previous drug screens aiming to identify disease-modifying compounds for Parkinson’s disease have typically been based on
toxin-induced in vitro and in vivo models of this neurodegenerative condition. All these compounds have failed to have a reliable
disease-modifying effect in subsequent clinical trials. We have now established a novel approach, namely to screen an entire
compound library directly in patient tissue to identify compounds with a rescue effect on mitochondrial dysfunction as a crucial
pathogenic mechanism in Parkinson’s disease. The chosen Microsource Compound library contains 2000 compounds, including
1040 licensed drugs and 580 naturally occurring compounds. All 2000 compounds were tested in a step-wise approach for their
rescue effect on mitochondrial dysfunction in parkin (PARK2) mutant fibroblasts. Of 2000 compounds, 60 improved the mitochondrial
membrane potential by at least two standard deviations. Subsequently, these 60 compounds were assessed for their toxicity
and drug-like dose-response. The remaining 49 compounds were tested in a secondary screen for their rescue effect on intracellular
ATP levels. Of 49 compounds, 29 normalized ATP levels and displayed drug-like dose response curves. The mitochondrial rescue
effect was confirmed for 15 of these 29 compounds in parkin-mutant fibroblasts from additional patients not included in the initial
screen. Of 15 compounds, two were chosen for subsequent functional studies, namely ursocholanic acid and the related compound
dehydro(11,12)ursolic acid lactone. Both compounds markedly increased the activity of all four complexes of the mitochondrial
respiratory chain. The naturally occurring compound ursolic acid and the licensed drug ursodeoxycholic acid are chemically closely
related to ursocholanic acid and dehydro(11,12)ursolic acid lactone. All four substances rescue mitochondrial function to a similar
extent in parkin-mutant fibroblasts, suggesting a class effect. The mitochondrial rescue effect depends on activation of the
glucocorticoid receptor with increased phosphorylation of Akt and was confirmed for both ursocholanic acid and ursodeoxycholic
acid in a Parkin-deficient neuronal model system. Of note, both ursocholanic acid and ursodeoxycholic acid also rescued mitochondrial
function in LRRK2G2019S mutant fibroblasts. Our study demonstrates the feasibility of undertaking drug screens in
Parkinson’s disease patients’ tissue and has identified a group of chemically-related compounds with marked mitochondrial
rescue effect. Drug repositioning is considered to be a time- and cost-saving strategy to assess drugs already licensed for a different
condition for their neuroprotective effect. We therefore propose both ursolic acid as a naturally occurring compound, and ursodeoxycholic
acid as an already licensed drug as promising compounds for future neuroprotective trials in Parkinson’s disease.
Keywords: Parkinson’s disease; parkin; LRRK2; mitochondria; disease-modifying therapy
Abbreviations: DUA = dehydro(11,12)ursolic acid lactone; MPTP = 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine
doi:10.1093/brain/awt224 Brain 2013: Page 1 of 13 | 1
Received January 21, 2013. Revised May 29, 2013. Accepted June 9, 2013.
The Author (2013). Published by Oxford University Press on behalf of the Guarantors of Brain. All rights reserved.
For Permissions, please email: journals.permissions@oup.com
Brain Advance Access published September 2, 2013
Downloaded from http://brain.oxfordjournals.org/ at Serials Department on September 9, 2013
Introduction
Parkinson’s disease is a common and relentlessly progressive,
incurable neurodegenerative condition. Its world-wide prevalence
is expected to double by 2030 (Dorsey et al., 2007). Currently
available drugs only result in symptomatic improvement with
limited efficacy. In the past, compounds were typically tested for
their putative neuroprotective effect in toxin-induced, in vitro and
in vivo models of Parkinson’s disease. However, exposure to
toxins such as 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine
(MPTP) only partially resembles the mechanisms leading to
Parkinson’s disease, if at all. Subsequently undertaken clinical
trials failed to confirm a beneficial, disease-modifying effect for
any compound with a promising initial effect in these traditional
MPTP models (Lang, 2006). Mitochondrial dysfunction is a key
mechanism in the pathogenesis of both sporadic and familial
Parkinson’s disease (Exner et al., 2012). Mutations in the autosomal
recessively inherited parkin (also known as PARK2) gene are
the most common identifiable cause of early-onset Parkinson’s
disease. The LRRK2G2019S mutation is the most common identifiable
cause of monogenically inherited late-onset Parkinson’s disease
(Hardy, 2010). We have previously demonstrated abnormal
mitochondrial function with specific lowering of complex I activity
of the mitochondrial respiratory chain in skin fibroblasts of parkinmutant
patients with Parkinson’s disease (Mortiboys et al., 2008).
We and others subsequently also reported mitochondrial dysfunction
in fibroblasts from patients with the LRRK2G2019S mutation
(Mortiboys et al., 2010; Papkovskaia et al., 2012).
The aim of this study was to undertake an in vitro compound
screen in Parkinson’s disease mutant patient tissue to identify
mitochondrial rescue compounds. Our project is based on the hypothesis
that any compound with a robust mitochondrial rescue
effect in Parkinson’s disease patient tissue is more likely to exert a
subsequent beneficial effect in clinical trials than those compounds
that have only been tested in toxin-induced model systems. Two
thousand compounds from the Microsource Spectrum Collection
(www.msdiscovery.com) were assessed for their rescue effect on
mitochondrial function in several stages. This compound library
consists of 1040 licensed drugs, 580 natural compounds and
420 other bioactive compounds. The large proportion of licensed
drugs and natural compounds made it plausible to assume that
any positive hits in our compound screen could rapidly be taken
into clinical trials.
Materials and methods
Patients
The project was reviewed by the local ethics committee. Informed
consent was taken from all research participants (see Supplementary
Table 1 for further information on all patients included in this study).
There was no significant difference in age between the four parkinmutant
patients and their four matched controls (age in years SD
parkin-mutant patients, 40.5 6.5; controls, 38.5 5.5). Similarly,
there was no significant difference in age between the three
LRRK2G2019S mutant patients and their three matched controls
(LRRK2G2019S mutant patients, age 59 5.5; controls, age 61 4.5).
Groups were also sex matched.
Methods
Fibroblast cell culture conditions as well as measurement of mitochondrial
membrane potential, respiratory chain function and cellular ATP
production were carried out as previously described (Mortiboys et al.,
2008).
Z-scores
In order to assess the robustness and reproducibility of the assays used
as primary and secondary screens we undertook rigorous testing using
Z’ and SW score calculations as described (http://www.ncats.nih.
gov/). See Supplementary material for further information.
Primary drug screen
Stage 1
Parkin-mutant fibroblasts from two parkin-mutant patients were incubated
with all 2000 Microsource Spectrum Collection compounds for
24 h at a concentration of 10 mM. Each drug treatment was carried out
in duplicate, thus, a total of four drug exposure experiments were
carried out at the first stage for each compound. A positive hit was
defined a priori as a compound that would improve the mitochondrial
membrane potential by more than 3 standard deviations (SD) in at
least three of the experiments and by at least 2 SD in the fourth
experiment. Positive hits were then tested further in cell-free assays
to exclude a possible false-positive effect due to autofluorescence of
the drug or a drug interaction with tetramethylrhodamine methyl ester
(TMRM). In addition, compounds were tested for any cellular toxicity
effects using the lactate dehyodrogenase (LDH) assay as described
previously (Mortiboys et al., 2008). Furthermore, dose-response
assessments (0.01, 0.03, 0.1, 0.3, 1, 3, 10, 30 and 100 mM) were
undertaken to determine the shape of the dose response curves.
Stage 2
Positive hits from the Stage 1 experiments were assessed for their
rescue effect on intracellular ATP levels. As before, parkin-mutant
fibroblasts from the same two patients and matched controls were
treated twice at a concentration of 10 mM for 24 h. A positive hit at
Stage 2 was again defined as a compound that improved intracellular
ATP levels by at least 3 SD in at least three experiments and by at least
2 SD in the fourth. Positive hits were tested for dose response curves
(0.01–100 mM) again. Positive hits with a sigmoidal dose-response
curve were tested for their recovery effects on ATP levels in an additional
two parkin-mutant patient and matched control fibroblast lines.
Stage 3
Selected top hits from Stage 2 were then assessed further for their
effect on the four individual mitochondrial respiratory chain complexes
in fibroblasts from four parkin-mutant patients and matched control
subjects. Fibroblasts (1.4 107 cells) were treated for 24 h with
100nM of each compound before being harvested by trypsinization
and used for all further analyses. Mitochondrially enriched fractions
and individual mitochondrial respiratory chain assays were all done
as described previously (Mortiboys et al., 2008). All data are expressed
to mg protein. Protein was measured using the Bradford assay (Peirce)
as per the manufacturers’ instructions.
2 | Brain 2013: Page 2 of 13 H. Mortiboys et al.
Downloaded from http://brain.oxfordjournals.org/ at Serials Department on September 9, 2013
Functional studies
Pharmacological inhibition of glucocorticoid receptor
Fibroblasts were plated (5000 cells per well) into 96 well plates. After
24 h, cells were treated with 1 mM RU486 for 4 h before adding either
100nM of selected compounds (see ‘Results’ section). Cellular ATP
levels were measured 24 h later as described above.
Small interfering RNA glucocorticoid receptor
knockdown
Small interfering RNA oligonucleotides were targeted to the
glucocorticoid receptor gene (NR3C1), target sequence AAGTG
CAAACCTGCTGTGTTT or scramble control small interfering RNA
(both Qiagen). Small interfering RNAs (10 nM) (NC3C1-targeted or
scramble negative) were transfected into fibroblasts using 0.5mM
Lipofectamine 2000 according to the manufacturers’ instructions.
Knockdown efficiency of the glucocorticoid receptor protein was
assessed using the glucocorticoid receptor ELISA (Abnova) at 48 h
post-transfection as per the manufacturer’s instructions. Twenty-four
hours post-transfection cells were treated with 100nM of selected
compounds; cellular ATP levels were measured 24 h later as described
above.
Quantification of total Akt and phosphorylated
Akt at Ser473
Akt and phosphorylated (p)Akt Ser473 ELISAs (Invitrogen) were performed
on fibroblast cell lysates as per the manufacturer’s instructions
using the provided standards to calculate the amount of protein present.
All data are presented as a ratio of pAkt (Ser473): total Akt.
Pharmacological inhibition of the Akt pathway
Fibroblasts were plated (5000 cells per well) into 96 well plates. After
24 h, cells were treated with 1 mM LY294002 or 50nM triciribine for
15 min before adding 100nM of selected compounds. Cellular ATP
levels were measured 24 h later as described above.
Confirmatory experiments
Mouse cortical neurons were prepared from embryonic Day 15 mouse
embryos as previously described (Kasher et al., 2009). Approximately
6 104 neurons were plated into each well of a 96-well plate (previously
coated with poly-L-lysine) or 2 105 neurons were plated into
each well of a 24-well plate for either ATP assays or harvesting for
western blot analysis or fixed for imaging. After 5 days in culture
neurons we transfected using the Accell siRNA and Accell siRNA
media (as per the manufacturer’s instructions, Dharmacon) with
either scramble-negative control small interfering RNA (Accell mouse
control siRNA kit, Dharmacon) or parkin small interfering RNA
(sequence GUUUCCACUUGUAUUGUGU). Forty-eight hours posttransfection
neurons were dosed with various concentrations of compounds
and 24 h later the cellular ATP assay was performed as
described above, or neurons were harvested for western blotting.
Western blotting was performed as described previously (Mortiboys
et al., 2008). Coverslips were fixed with 4% paraformaldehyde for
30 min with subsequent PBS washes. Cells were permeabilized with
0.1% TritonTM X-100 for 10 min at room temperature and blocked
with 1% goat serum for 1 h. Cells were incubated with primary antibodies
(rabbit anti-Parkin; Abcam and mouse anti-TOM-20; BD
Biosciences) at 1:500 overnight at 4C with subsequent PBS washes
and incubation with rabbit anti-mouse and goat anti-rabbit secondary
antibodies for 1 h at room temperature. Cells were stained with
Hoescht and then mounted into glass slides using ProLong Gold
(Invitrogen).
Cellular ATP levels were measured as described previously
(Mortiboys et al., 2008) in fibroblasts from three LRRK2G2019S
mutant patients with Parkinson’s disease and three age and sexmatched
controls. The cells were treated with 100nM of the selected
compounds for 24 h before measurement.
Statistical analysis
Values from multiple experiments were expressed as means SE (standard
error). Statistical significance (Bonferroni corrected) was assessed
using Student’s t-test for data with a normal distribution, a non-parametric
t-test was used for data with a skewed distribution. The effect of
multiple factors was assessed using a two-way ANOVA test.
Results
A summary of our screening strategy is given in Fig. 1. Of 2000
compounds, 60 improved the mitochondrial membrane potential
in parkin-mutant fibroblasts by 43 SD in three of the four
experiments and by 42 SD in the fourth. Two compounds elicited
an increase in the TMRM fluorescence signal in subsequent cellfree
assays and were thus excluded as false-positive. A further
nine compounds had to be excluded due to their toxicity
(Table 1). Full dose-response curves were established for all 49
remaining compounds, which were then also further assessed for
their effect on total intracellular ATP levels. Of 49 compounds, 35
increased the ATP levels in the parkin-mutant fibroblasts by 43
SD in at least three experiments and by 42 SD in the fourth
(Table 1). Full dose-response curves were carried out using these
top 35 compounds. Six compounds did not display a drug-like,
sigmoidal dose response curve and were therefore excluded, leaving
29 compounds.
Each of these 29 compounds was then tested for their rescue
effect on cellular ATP levels in a further two patient fibroblast lines
and two control fibroblast lines. Of 29 compounds, 15 rescued
cellular ATP levels by 43 SD in all four parkin-mutant fibroblast
lines tested (Table 2).
Of 15 compounds, two, namely ursocholanic acid and dehydro
(11,12) ursolic acid lactone (DUA), were selected for further
assessment. Reasons for not investigating the remaining 13 compounds
forward at this stage are listed in Table 2 and, in greater
detail, in the Supplementary material. Ursocholanic acid and DUA
were then further assessed for their effect on the activity of complexes
I–IV of the respiratory chain. Ursocholanic acid significantly
rescued and increased the activity of complexes I–IV by 200–
500% (Fig. 2). Treatment with DUA achieved very similar results
(Supplementary Fig. 1).
Interestingly, 7 of the 15 Stage 2 positive hits were steroids or
related compounds with four carbon rings forming the (steroid)
backbone of each particular compound, including ursocholanic
acid and DUA (Table 2). We therefore hypothesized that their
observed rescue effect was mediated through activation of the
glucocorticoid receptor. To further test this hypothesis, parkinmutant
cells were pretreated with the glucocorticoid receptor antagonist
RU486 to determine whether glucocorticoid receptor
Ursocholanic acid in familial PD Brain 2013: Page 3 of 13 | 3
Downloaded from http://brain.oxfordjournals.org/ at Serials Department on September 9, 2013
inhibition may abolish the observed rescue effect of DUA and
ursocholanic acid on ATP levels. As predicted, RU486 completely
eliminated the rescue effect of all tested compounds on cellular
ATP levels (Fig. 3A). To further validate these results, we used a
different method, namely small interfering RNA-mediated glucocorticoid
receptor knockdown before treatment with ursocholanic
acid or DUA. Glucocorticoid receptor protein knockdown was confirmed
to be 75% 3.8% (mean SD) using ELISA at 48 h post
transfection (data not shown). As predicted, small interfering
RNA-mediated glucocorticoid receptor knockdown abolished the
rescue effect of 100nM ursocholanic acid or DUA on intracellular
ATP levels (Fig. 3B).
Ursolic acid and ursodeoxycholic acid were not part of the initially
screened Microsource Compound Library, but are chemically related
to ursocholanic acid and DUA (Fig. 4). Ursolic acid exerts its beneficial
effect on muscle atrophy through Akt activation, namely by
increased phosphorylation of Akt at Ser473 (Kunkel et al., 2011).
Similarly, ursodeoxycholic acid exerts its protective effect against
mitochondria-dependent programmed cell death in SH-SY5Y cells
through Akt activation (Chun and Low, 2012).
We therefore assessed the effect of DUA and ursocholanic acid
in parkin-mutant fibroblasts on Akt phosphorylation at Ser473.
There was a marked increase in the pAktSer473:Akt protein ratio
by 400% after treatment with DUA and 305% after treatment
with ursocholanic acid (P50.05) in parkin-mutant fibroblasts
compared with the ratio in untreated parkin-mutant fibroblasts
(Fig. 5A). Interestingly, this change was only evident in parkinmutant
fibroblasts, the pAktSer473:Akt ratio in control fibroblasts
remained constant after drug treatment. We next aimed to confirm
that both ursocholanic acid and DUA are exerting their mitochondrial
rescue effect through activation of the Akt pathway
rather than Akt activation merely being associated with the
rescue effect of our top compounds. As predicted, pretreatment
with either Akt inhibitor LY29400 (a phosphatidylinositol 3-kinase
inhibitor) or triciribine (a selective inhibitor of cellular phosphorylation/
activation of Akt) abolished the rescue effect of ursocholanic
acid and DUA on cellular ATP levels in parkin-mutant fibroblasts
(Fig. 5B).
Neither DUA nor ursocholanic acid are FDA-licensed drugs; little
information is available on their bioavailability and safety in humans.
In contrast, the chemically closely related bile acid ursodeoxycholic
acid has been in clinical use as treatment for primary biliary cirrhosis
for 430 years. Its clinical pharmacokinetics are well characterized
(Ward et al., 1984). The chemically closely related ursolic acid is a
naturally occurring compound present in many plants. Based on their
structural similarities, we hypothesized that both ursolic acid and
ursodeoxycholic acid may have a similar mitochondrial rescue
effect as DUA and ursocholanic acid. Indeed, both ursolic acid and
ursodeoxycholic acid normalized intracellular ATP levels similar to the
effect observed for DUA and ursocholanic acid (Fig. 6).
Effect in Parkin-deficient neuronal
model system
We next assessed the rescue effect of ursocholanic acid and ursodeoxycholic
acid in a neuronal cell culture model. Small interfering
RNA mediated knockdown of parkin resulted in a reduction of Parkin
protein levels by 80% in cortical mouse neurons as shown by western
blotting and a decrease in cellular ATP levels by 40%. Treatment with
10pM ursocholanic acid or 10pM ursodeoxycholic acid rescued the
cellular ATP loss in these Parkin-deficient neurons (Fig. 7). Thus,
ursocholanic acid and ursodeoxycholic acid have a rescue effect on
mitochondrial dysfunction not only in parkin-mutant fibroblasts but
also in parkin-deficient neurons.
Rescue effect in LRRK2G2019S mutant
patient tissue
We finally determined whether ursocholanic acid and the chemically
related and FDA-licensed drug ursodeoxycholic acid also
have a mitochondrial rescue effect in other forms of familial
Figure 1 This flowchart shows an overview of the screening strategy used. Each part of the screen is depicted as is the number of positive
hit compounds that were taken to the next stage of the screen.
4 | Brain 2013: Page 4 of 13 H. Mortiboys et al.
Downloaded from http://brain.oxfordjournals.org/ at Serials Department on September 9, 2013
Table 1 Positive hits of the primary screen, and results from stage 1 and 2 of the drug screen
Drug name Stage 1 Stage 2
Cell
free
Toxicity EC50
MMP
ATP
recovery
Dose
response
curve
EC50
ATP
Podophyllotoxin acetate 3 3 Ambiguous X X X
2,6-Dimethoxyquinone 3 3 1 mM X X X
Ginkgolic acid 3 3 1.6mM 3 3 250nM
2’,Beta-dihydroxychalcone 3 3 200nM 3 3 250nM
Gatifloxacin 3 3 100nM 3 3 250nM
Amlodipine besylate 3 3 1 mM 3 3 250nM
Simvastatin 3 3 1 mM X X X
Hydroquinone 3 3 1 mM X X X
7-Methoxychromone 3 3 100nM X X X
Perindopril erbumine 3 3 12 mM 3 3 150nM
Ceftibuten 3 3 1 mM 3 3 250nM
Cefdinir 3 3 25 mM 3 3 350nM
3Alpha-hydroxy-3-deoxyangolensic acid methyl ester 3 3 100nM 3 3 150nM
Dibenzothiophene 3 3 600nM X X X
Clonidine hydrochloride 3 3 1 mM X X X
Desipramine hydrochloride 3 X X X X X
Ginkgolide a 3 3 100nM 3 3 150nM
Sericetin 3 3 158nM 3 3 150nM
Friedelin 3 3 1 mM 3 3 150nM
3Beta,7beta-diacetoxydeoxodeacetoxydeoxydihydrogedunin 3 3 240nM X X X
Oleanolic acid acetate 3 X X X X X
Pristimerol diacetate 3 3 631 mM 3 3 125nM
Khellin 3 3 6 mM 3 3 250nM
Khivorin 3 3 6 mM X X X
Allopurinol 3 3 1 mM X X X
Menthone 3 X 7mM X X X
Acetylcholine 3 X 60 mM X X X
Probenecid 3 X 13 mM X X X
Enalapril maleate 3 X 2mM X X X
Acivicin 3 X 31mM X X X
Ephedrine (1 R,2S) hydrochloride 3 3 Ambiguous 3 X X
Propylthiouracil 3 3 Ambiguous 3 X X
Clobetasol propionate 3 3 10 mM 3 3 1 mM
Santonin 3 3 125nM X X X
Ursocholanic acid 3 3 1 mM 3 3 350nM
Methylergonovine maleate 3 3 Ambiguous 3 X X
Androsterone sodium sulfate 3 3 5mM 3 3 350nM
Dehydro (11,12)ursolic acid lactone (no longer available) 3 3 100 mM 3 3 350nM
Cholest-5-en-3-one 3 3 1 mM 3 X X
Fluorometholone 3 3 350nM 3 X X
Prazosin hydrochloride 3 3 250nM 3 3 150nM
Narasin 3 X X X X X
Cedryl acetate 3 X X X X X
N-benzyltropan-4-ol X 3 X X X X
Naproxol X 3 X X X X
Hydroxychloroquine sulphate 3 3 1.2mM 3 3 1 mM
11-Oxoursolic acid acetate (no longer available) 3 3 0.1nM 3 3 150nM
Prednisolone 3 3 446mM 3 3 350nM
Ebselen 3 3 100nM 3 3 1 mM
Racephedrine hydrochloride 3 3 5 mM X X X
Snap (S-nitroso-N-acetylpenicillamine) 3 3 200nM X X X
3-Amino-beta-pinene 3 3 10 mM 3 3 1 mM
Benzalkonium chloride 3 3 12.5nM 3 3 1 mM
Melezitose 3 3 1 mM 3 3 1 mM
(continued)
Ursocholanic acid in familial PD Brain 2013: Page 5 of 13 | 5
Downloaded from http://brain.oxfordjournals.org/ at Serials Department on September 9, 2013
Parkinson’s disease. We therefore investigated the effect of these
compounds on cellular ATP levels in LRRK2G2019S mutant patient
tissue. Treatment of LRRK2G2019S mutant fibroblasts from three
different patients with Parkinson’s disease carrying this mutation
with 10nM of ursocholanic acid or ursodeoxycholic acid for 24 h
resulted in complete rescue of cellular ATP levels (Fig. 8), similar to
the effect observed in parkin-mutant patient tissue. Therefore, the
beneficial effect of these compounds does not appear to be limited
to parkin-associated Parkinson’s disease.
Discussion
The strong evidence of mitochondrial dysfunction in both sporadic
and familial Parkinson’s disease suggests targeting mitochondria as
a promising strategy for disease-modifying therapy in Parkinson’s
disease (Meissner et al., 2011; Schapira, 2012). We had previously
demonstrated a complete rescue of mitochondrial dysfunction in
parkin-mutant patient tissue using the glutathione precursor
Table 1 Continued
Drug name Stage 1 Stage 2
Cell
free
Toxicity EC50
MMP
ATP
recovery
Dose
response
curve
EC50
ATP
3-Oxoursan (28-13)olide 3 3 1 mM X X X
Budesonide 3 3 390nM 3 3 1 mM
Prednisolone acetate 3 3 150nM 3 3 1 mM
Furegrelate sodium 3 3 3.9nM X X X
Tamoxifen citrate 3 3 1nM 3 3 1 mM
6,7-Dichloro-3-hydroxy-2-quinoxalinecarboxylic acid 3 3 Ambiguous 3 X X
This table details the positive hits of the primary screen and the results from each part of stage 1 and stage 2 of the drug screen. 3 indicates that the compound fulfilled the
necessary criteria and went through this particular stage; X indicates it did not and was therefore not taken any further. ‘Cell free’ indicates whether the compound reacted
with the fluorescent dye tetramethylrhodamine methyl ester (TMRM) in a cell free assay. The ‘Tox’ column provides information on possible toxicity of the respective
compound. ‘EC50 MMP’ indicates the EC50 concentration of the compounds in the mitochondrial membrane potential assay. ‘ATP recovery’ indicates if the compounds
were also effective in recovering the ATP levels in parkin-mutant fibroblasts. ‘Dose response curve’ indicates whether the compounds displayed a known characterised dose
response curve shape. ‘EC50 ATP’ provides information about the EC50 of the compounds in the cellular ATP assay.
Table 2 Top 15 hits that rescued the mitochondrial membrane potential and cellular ATP levels in all four patients and had
drug-like dose response curves
Drug name Compound origin Steroid like
structure
Additional comments
Gatifloxacin Synthetic X Antibiotic with negative effect on glucose homeostasis and
neurological function in vivo
Amlodipine besylate Synthetic X Ca-antagonist, concerns about side-effect profile (including
oedema, insomnia, dizziness, depression)
3Alpha-hydroxy-3-deoxyangolensic
acid methyl ester
Natural X No information on use in humans or rodents
Ginkgolide a Natural X Previous studies have given inconsistent results for
neuroprotective effect of ginkgo in neurodegenerative
disease and related model systems
Pristimerol diacetate Semi synthetic X No information on use in humans or rodents
Ephedrine (1R,2S) hydrochloride Natural X Sympatomimetic amine, intolerance and drug interaction
likely in Parkinson’s disease
Ursocholanic acid Natural 3 Taken forward
Androsterone sodium sulphate Semi synthetic 3 Steroid, excluded due to likelihood of side effects on long
term treatment
Dehydro (11,12)ursolic acid lactone Natural 3 Taken forward
Cholest-5-en-3-one Semi synthetic 3 cholesterol, excluded due to likelihood of side effects on
long term treatment
Hydroxychloroquine sulphate Synthetic X Inhibitory effect on mitophagy
11-Oxoursolic acid acetate Natural 3 Unable to obtain more of the compound
Budesonide Semi synthetic 3 Steroid with high-first pass effect, excluded due to likelihood
of limited biological availability
Prednisolone acetate Semi synthetic 3 Steroid, excluded due to likelihood of side effects on long
term treatment
Tamoxifen citrate Synthetic X Can cause cognitive impairment and other major side effects
Additional information is provided on origin of compound, the presence of a steroid-like structure as well as justification for not taking the majority of these compounds
forward. The two compounds taken forward are the chemically related substances ursocholanic acid and dehydro (11,12) ursolic acid lactone. Additional information on
those compounds that have been excluded from further analysis is provided in the Supplementary material.
6 | Brain 2013: Page 6 of 13 H. Mortiboys et al.
Downloaded from http://brain.oxfordjournals.org/ at Serials Department on September 9, 2013
L-2-oxothiazolidine-4-carboxylic acid (OTCA) and also a mild partial
rescue effect on mitochondrial function after rapamycin treatment
(Mortiboys et al., 2008; Tain et al., 2009). Based on these
‘proof of principle’ data, we have now undertaken the first drug
screen in Parkinson’s disease patient tissue and identified a group
of chemically-related compounds with marked rescue effect on
mitochondrial function. Our data are in keeping with previous
studies that reported a protective effect of the taurine conjugate
of ursodeoxycholic acid (TUDCA) against mitochondrial toxins in
parkin-deficient Caenorhabditis elegans (Ved et al., 2005).
Recently, an Akt-mediated, partial neuroprotective effect of
TUDCA on MPTP-induced dopaminergic cell death has been
observed in a mouse model of Parkinson’s disease (Castro-
Caldas et al., 2012). Our data strongly suggest a class effect for
bile acids and their derivates such as DUA, ursocholanic acid and
ursodeoxycholic acid and the natural pentacyclic triterpenoid
Figure 2 Rescue of mitochondrial function in parkin-mutant fibroblasts by treatment with 100nM ursocholanic acid (UCA) for 24 h.
(A) Mitochondrial membrane potential and (B) cellular ATP levels are decreased in untreated fibroblasts of patients with parkin mutations
compared with untreated controls (P50.05), treatment with ursocholanic acid results in normalization of mitochondrial membrane
potential and ATP levels (P50.05). (C) Mitochondrial membrane potential and (D) cellular ATP levels after treatment with increasing
concentrations of ursocholanic acid for 24 h, reflecting a sigmoidal dose response curve. (E and F) Activity of each of the individual
respiratory chain enzymes are increased by treatment with ursocholanic acid in both control and parkin-mutant fibroblasts. Data presented
are corrected to protein levels *P50.05, **P50.01, ***P50.001.
Ursocholanic acid in familial PD Brain 2013: Page 7 of 13 | 7
Downloaded from http://brain.oxfordjournals.org/ at Serials Department on September 9, 2013
ursolic acid. The bioavailability of ursolic acid and its dose-dependent
increase in brain tissue of mice has been well characterized
(Yin et al., 2012). A beneficial effect of both ursolic acid and
ursodeoxycholic acid or TUDCA has also been described in different
in vitro and in vivo model systems for other
neurodegenerative conditions, including Alzheimer’s disease,
Huntington’s disease and stroke (Keene et al., 2002; Rodrigues
et al., 2003; Ramalho et al., 2008; Wilkinson et al., 2011).
Of note, 7 of 15 of the compounds that rescued both the mitochondrial
membrane potential and cellular ATP levels as well as
Figure 3 Inhibition or knockdown of the glucocorticoid receptor abolishes the rescue effect of ursocholanic acid (UCA) and DUA in
parkin-mutant fibroblasts. (A) Cellular ATP levels are reduced in parkin-mutant patient fibroblasts (black bars) compared with controls
(white bars) and recovered to normal levels after treatment with 100nM ursocholanic acid or DUA for 24 h. This rescue effect is completely
abolished by pretreatment with 1 mM RU486 (glucocorticoid receptor antagonist) for 4 h. (B) Cellular ATP levels are reduced in
parkin mutant patient fibroblasts transfected with either scramble small interfering RNA (dark grey bars) or glucocorticoid receptor small
interfering RNA (black bars) compared with control fibroblasts transfected with scramble small interfering RNA (white bars) or glucocorticoid
receptor small interfering RNA (light grey bars) *P50.05. Treatment with 100nM ursocholanic acid or DUA completely rescues
this defect in parkin mutant fibroblasts transfected with scramble small interfering RNA (white and dark grey bars) but not in parkin
mutant fibroblasts transfected with glucocorticoid receptor small interfering RNA treatment with ursocholanic acid and DUA (black bars)
compared with controls also transfected with glucocorticoid receptor small interfering RNA (light grey bars). DMSO = dimethylsulphoxide.
Figure 4 Structures of the top two compounds identified from the original drug screen, namely (A) dehydro (11,12) ursolic acid lactone and
(C) ursocholanic acid and two further compounds which are structurally similar, namely (B) ursolic acid and (D) ursodeoxycholic acid. The
structural similarities are highlighted in red. The structures are represented in standard chemical format displaying the 3D orientation of
groups. Where no group is specified a methyl group is attached. Hydrogens are only shown if they affect the 3D orientation of the molecule.
8 | Brain 2013: Page 8 of 13 H. Mortiboys et al.
Downloaded from http://brain.oxfordjournals.org/ at Serials Department on September 9, 2013
having drug-like dose response curves had a steroid-like structure.
Lim et al. (2012) reported independently a neuroprotective effect
of the chemically closely related sterol biosynthesis intermediate
lanosterol. Both ursolic acid and lanosterol induce mild mitochondrial
uncoupling that has been proposed as a promising strategy
for disease modification in Parkinson’s disease (Liobikas et al.,
2011; Ho et al., 2012; Lim et al., 2012).
The inhibition of the mitochondrial rescue effect of DUA and
ursocholanic acid after pretreatment with RU486 is in keeping
with previous observations on glucocorticoid receptor-mediated
biological activity of ursolic acid or ursodeoxycholic acid (Tanaka
and Makino, 1992; Sharma et al., 2011). However, genome-wide
gene expression studies did not reveal any relevant and consistent
changes in parkin-mutant fibroblasts after treatment with ursolic
acid or DUA (data not shown). In particular, there was no effect
on messenger RNA levels of mitochondrial master regulators such
as PGC1alpha (now known as PPARGC1A) or mitochondrial
uncoupling proteins. The biological function of glucocorticoids
encompasses both genomic and non-genomic effects, including
direct binding to the mitochondrial membrane, which can lead
to partial uncoupling of oxidative phosphorylation (Haller et al.,
2008).
We appreciate that our work largely focused on assessing the
effect of compounds in parkin-mutant Parkinson’s disease patient
tissue. However, the beneficial effect of the lead compound, ursocholanic
acid and the chemically related licensed drug ursodeoxycholic
acid were also clearly apparent in LRRK2G2019S mutant
fibroblasts. Ten per cent of all sporadic and 30% of familial
Parkinson’s disease can be due to the LRRK2G2019S mutation in
Ashkenazi Jewish patients with Parkinson’s disease (Ozelius et al.,
2006). The prevalence may be even higher in other populations
(Lesage et al., 2006). The mitochondrial phenotype is generally
accepted to be correct for PARK2 but additional work is needed to
determine whether rescue of mitochondrial function will result in
at least partial rescue of neuronal dysfunction and cell loss in
LRRK2G2019S-mutant model systems. If this was to be the case,
then our lead compounds or structurally related drugs may already
have a beneficial effect in a significant number of patients with
Parkinson’s disease even if their effect was limited to parkin- and
LRRK2G2019S mutant patients with Parkinson’s disease only.
Mitochondrial dysfunction was first implicated in the pathogenesis
of Parkinson’s disease when drug abusers developed parkinsonism
after accidental exposure to the complex I inhibitor MPTP
(Abou-Sleiman et al., 2006; Schapira, 2008). Subsequently, several
groups reported independently decreased complex I activity in
Parkinson’s disease (Mizuno et al., 1989; Parker et al., 1989;
Schapira et al., 1989). It is now widely accepted that mitochondrial
dysfunction and impaired morphology play a crucial role in
the pathogenesis of early-onset Parkinson’s disease due to mutations
in parkin (PARK2), PINK1 or DJ1 (PARK7) (Cookson and
Bandmann, 2010). Mitochondrial dysfunction has also been
observed in patient tissue (see above) or model systems of lateonset
Parkinson’s disease due to mutations in LRRK2 or alpha
synuclein (SNCA) (Loeb et al., 2010; Hindle et al., 2013). Akt, a
protein kinase with multiple targets, is activated by successive
phosphorylation at two sites. Failure of Akt signalling has been
described as the ‘common core’ underlying neuronal degeneration
and cell death in both familial and sporadic Parkinson’s disease
(Greene et al., 2011). Akt phosphorylation is reduced in dopaminergic
neurons of sporadic Parkinson’s disease (Malagelada et al.,
2008; Timmons et al., 2009). Both increased expression of alpha
synuclein (SNCA) and SNCA mutations lead to reduced Akt
Figure 5 The rescue effect of ursocholanic acid and DUA is Akt
mediated. (A) pAktSer473 protein levels as a ratio to total Akt
protein levels as measured by ELISA. pAktSer473 levels are
increased in parkin-mutant patient cells after treatment with
both ursocholanic acid (grey bars) and DUA (black bars)
(***P50.001, *P50.05). (B and C) Cellular ATP levels in
control fibroblasts (white bars) and parkin-mutant fibroblasts
(black bars). Pretreatment with the phosphatidylinositol
3-kinases (PI 3-kinase) inhibitor LY29400 or triciribine, which
selectively inhibit the cellular phosphorylation/activation of Akt,
abolish the rescue effect of both ursocholanic acid (B) and DUA
(C) (*P50.05). DMSO = dimethylsulphoxide.
Ursocholanic acid in familial PD Brain 2013: Page 9 of 13 | 9
Downloaded from http://brain.oxfordjournals.org/ at Serials Department on September 9, 2013
activation (Chung et al., 2011). Similarly, LRRK2 mutations (in
particular G2019S) as well as Parkin, PINK1 and DJ1 deficiency
result in decreased Akt phosphorylation (Yang et al., 2005; Fallon
et al., 2006; Murata et al., 2011; Ohta et al., 2011). In contrast,
the protective effect of beta-synuclein is mediated by increased
Akt phosphorylation and increased parkin expression normalizes
reduced Akt phosphorylation in MPTP-treated mice (Hashimoto
et al., 2004; Yasuda et al., 2011). Further work is needed to determine
whether the mitochondrial rescue effect and increased Akt
phosphorylation at Ser473 after treatment with ursocholanic acid
and DUA (as observed in our parkin-mutant fibroblast model) can
also be observed in other forms and model systems of Parkinson’s
disease.
Ursodeoxycholic acid has been licensed for the treatment of
patients with primary biliary cirrhosis since 1980. It is typically
used at a dose of 10 mg/kg of body weight per day in patients
with primary biliary cirrhosis but Parry et al. (2010) also reported
‘excellent’ safety and tolerability of ursodeoxycholic acid in
patients with motor neuron disease at 15 mg, 30mg and 50 mg/
kg per day. There was a significant correlation between serum and
CSF concentrations of ursodeoxycholic acid. There is therefore
good rationale to assume that ursodeoxycholic acid may also be
well tolerated in Parkinson’s disease and cross the blood–brain
barrier. Drug repositioning of FDA-licensed drugs such as ursodeoxycholic
acid is a promising strategy to save time and costs
but Parkinson’s disease-specific, reliable data on safety, tolerability
and CSF penetration of ursodeoxycholic acid will nevertheless be
of paramount importance before ursodeoxycholic acid can be
taken into clinical trials to assess its putative disease-modifying
effect in Parkinson’s disease.
Dopaminergic neurons derived from inducible stem cells have
already been used to assess compounds for their putative rescue
effect on crucial pathogenic mechanisms for Parkinson’s disease
and other conditions (Cooper et al., 2012). However, the inducible
stem cells-based approach, although in many ways exciting and
promising, is also costly and not without inherent problems. Our
study demonstrates that a step-wise strategy, encompassing an
initial screen in Parkinson’s disease patient fibroblasts but
Figure 6 Rescue of cellular ATP levels by 24-h treatment of parkin-mutant fibroblasts with 100nM ursocholanic acid (UCA, A), DUA
(B), ursolic acid (UA, C) and ursodeoxycholic acid (UDCA, D). Cellular ATP levels are significantly reduced in untreated parkin-mutant
patient fibroblasts (*P50.05) but significantly increased after treatment with any of these four respective drugs (*P50.05, **P50.01).
10 | Brain 2013: Page 10 of 13 H. Mortiboys et al.
Downloaded from http://brain.oxfordjournals.org/ at Serials Department on September 9, 2013
subsequent confirmation of top hits in a neuronal model system
may be a less costly and more robust strategy.
Previous studies investigating the potential rescue effect of
pharmacological compounds in model systems of early onset
Parkinson’s disease have concentrated on a hypothesis-driven
approach testing individual compounds rather than assessing a
compound library in a hypothesis-free approach. Vitamin K(2)
acts as a mitochondrial electron carrier that rescues mitochondrial
dysfunction in pink1-deficient Drosophila (Vos et al., 2012).
However, it is unclear whether vitamin K(2) also rescues mitochondrial
dysfunction in Parkin deficiency. The disaccharide trehalose
increases the removal of abnormal proteins through
enhancement of autophagy. Trehalose treatment ameliorates tau
pathology but fails to revert the loss of dopaminergic neurons in a
mouse model of tauopathy with parkinsonism, overexpressing
human mutated tau protein with deletion of parkin (Rodriguez-
Navarro et al., 2010). Co-enzyme Q10 reduces the vulnerability of
inducible stem cell-derived, PINK1 mutant neural cells to the
lowest, but not to high concentrations of valinomycin and concamycin
A, rapamycin did not reduce lactate dehydrogenase release
after exposure to these toxins. In contrast, both rapamycin and
the LRRK2 inhibitor GW5074 reduced the production of mitochondrial
reactive oxygen species in PINK1 mutant neural cells
exposed to valinomycin. However, none of these compounds
were assessed for their rescue effect on baseline mitochondrial
(dys)function in PINK1 mutant model systems before toxin exposure
(Cooper et al., 2012). Future drug screens may be preceeded
by in silico screens assessing compounds for their likely effect on
enhancing the biological activity of proteins such as Parkin or
PINK1, but also on other proteins such as thioredoxin with a
reported rescue effect in Parkin-deficient Drosophila (Umeda-
Kameyama et al., 2007; Trempe et al., 2013). Other therapeutic
approaches include the overexpression of enzymes bypassing complex
I activity such as the Saccaromyces cerevisiae enzyme Ndi1p
(Vilain et al., 2012).
Acknowledgements
We would like to thank all research participants.
Funding
Financial support from Parkinson’s UK (G-0715 and G-0901) is
gratefully acknowledged.
Suppplementary material
Supplementary material is available at Brain online.
References
Abou-Sleiman PM, Muqit MM, Wood NW. Expanding insights of mitochondrial
dysfunction in Parkinson’s disease. Nat Rev Neurosci 2006;
7: 207–19.
Figure 7 Ursocholanic acid (UCA) and ursodeoxycholic acid
(UDCA) rescue effect in cortical neurons with small interfering
RNA mediated parkin knockdown. (A) Western blot showing
Parkin band at 50 kDa and actin band at 40 kDa in scramble
small interfering RNA and parkin small interfering RNA transfected
cortical neurons. (B) Parkin protein levels are reduced by
80% in parkin small interfering RNA knockdown cortical
neurons as assessed by western blotting (***P50.001).
(C) Cellular ATP levels in cortical neurons at 9 days in culture
transfected with either scramble small interfering RNA (white
bars), or parkin small interfering RNA (black bars). There is a
reduction of 43% in cellular ATP levels in the parkin small
interfering RNA transfected cells, (**P50.01), which is rescued
by treatment with 10pM ursocholanic acid or ursodeoxycholic
acid. DMSO = dimethylsulphoxide.
Figure 8 Cellular ATP levels are reduced in fibroblasts from
three LRRK2G2019S mutant patients (black bars) compared with
controls (white bars) *P50.05. There is complete recovery of
ATP to normal levels after treatment with 10nM ursocholanic
acid or 10nM ursodeoxycholic acid for 24 h.
DMSO = dimethylsulphoxide.
Ursocholanic acid in familial PD Brain 2013: Page 11 of 13 | 11
Downloaded from http://brain.oxfordjournals.org/ at Serials Department on September 9, 2013
