Enhancement of brown fat thermogenesis using chenodeoxycholic acid in mice.

OBJECTIVE: Besides their role in lipid absorption, bile acids (BAs) can act as signalling molecules. Cholic acid was shown to counteract obesity and associated metabolic disorders in high-fat-diet (cHF)-fed mice while enhancing energy expenditure through induction of mitochondrial uncoupling protein 1 (UCP1) and activation of non-shivering thermogenesis in brown adipose tissue (BAT). In this study, the effects of another natural BA, chenodeoxycholic acid (CDCA), on dietary obesity, UCP1 in both interscapular BAT and in white adipose tissue (brite cells in WAT), were characterized in dietary-obese mice. RESEARCH DESIGN: To induce obesity and associated metabolic disorders, male 2-month-old C57BL/6J mice were fed cHF (35% lipid wt wt(-1), mainly corn oil) for 4 months. Mice were then fed either (i) for 8 weeks with cHF or with cHF with two different doses (0.5%, 1%; wt wt(-1)) of CDCA (8-week reversion); or (ii) for 3 weeks with cHF or with cHF with 1% CDCA, or pair-fed (PF) to match calorie intake of the CDCA mice fed ad libitum; mice on standard chow diet were also used (3-week reversion). RESULTS: In the 8-week reversion, the CDCA intervention resulted in a dose-dependent reduction of obesity, dyslipidaemia and glucose intolerance, which could be largely explained by a transient decrease in food intake. The 3-week reversion revealed mild CDCA-dependent and food intake-independent induction of UCP1-mediated thermogenesis in interscapular BAT, negligible increase of UCP1 in subcutaneous WAT and a shift from carbohydrate to lipid oxidation. CONCLUSIONS: CDCA could reverse obesity in cHF-fed mice, mainly in response to the reduction in food intake, an effect probably occuring but neglected in previous studies using cholic acid. Nevertheless, CDCA-dependent and food intake-independent induction of UCP1 in BAT (but not in WAT) could contribute to the reduction in adiposity and to the stabilization of the lean phenotype.

Evaluation of olive oil mill wastewater toxicity on the mitochondrial bioenergetics after treatment with Candida oleophila.

In a previous work the ability of Candida oleophila to use phenolic compounds as sole carbon and energy source at high concentrations without an additional carbon source was reported. C. oleophila grown in bioreactor batch cultures in a diluted and sterilized olive oil mill wastewater (OMW) caused a significant decrease in the total tannins content but no significant alteration was observed in phenolic acid and fatty acid content. Both treated and untreated OMWs were tested to evaluate the capacity in interfering with mitochondrial bioenergetics. Mitochondrial respiration was not affected by treated OMW on the range of used concentrations, contrary to the untreated OMW. Furthermore, mitochondrial membrane potential and respiratory complexes were always significantly less affected by treated OMW in comparison with untreated OMW. However, supplementary treatment should be applied before OMW could be considered non-toxic.

Mitochondrial bioenergetics is affected by the herbicide paraquat.

The potential toxicity of the herbicide paraquat (1,1-dimethyl-4,4'-bipyridylium dichloride) was tested in bioenergetic functions of isolated rat liver mitochondria. Paraquat increases the rate of State 4 respiration, doubling at 10 mM, indicating uncoupling effects. Additionally, State 3 respiration is depressed by about 15%, at 10 mM paraquat, whereas uncoupled respiration in the presence of CCCP is depressed by about 30%. Furthermore, paraquat partially inhibits the ATPase activity through a direct effect on this enzyme complex. However, at high concentrations (5-10 mM), the ATPase activity is stimulated, probably as consequence of the described uncoupling effect. Depression of respiratory activity is mediated through partial inhibitions of mitochondrial complexes III and IV. Paraquat depresses delta psi as a function of herbicide concentration. In addition, the depolarization induced by ADP is decreased and repolarization is biphasic suggesting a double effect. Repolarization resumes at a level consistently higher than the initial level before ADP addition, for paraquat concentrations up to 10 mM. This particular effect is clear at 1 mM paraquat and tends to fade out with increasing concentrations of the herbicide.

Cardioselective and cumulative oxidation of mitochondrial DNA following subchronic doxorubicin administration.

We recently reported the preferential accumulation of 8-hydroxydeoxyguanosine (8OHdG) adducts in cardiac mitochondrial DNA (mtDNA) following acute intoxication of rats with doxorubicin (C.M. Palmeira et al., Biochim. Biophys. Acta, 1321 (1997) 101-106). The concentration of 8OHdG adducts decreased to control values within 2 weeks. Since conventional antineoplastic therapy entails repeated administration of small doses of doxorubicin, it was of interest to characterize the kinetics for the accumulation and repair of 8OHdG adducts in the various DNA fractions. Weekly injections of doxorubicin (2 mg/kg, i.p.) to adult male Sprague-Dawley rats caused a cumulative dose-dependent increase in the concentration of 8OHdG adducts in both mtDNA and nuclear DNA (nDNA) from heart and liver. Following six weekly injections, the concentration of 8OHdG in cardiac mtDNA was 50% higher than liver mtDNA and twice that of cardiac nDNA. In contrast to the rapid repair of 8OHdG observed during the first days following an acute intoxicating dose of doxorubicin, the concentration of 8OHdG adducts remained constant between 1 and 5 weeks following the last injection. This was true for all DNA fractions examined. The cardioselective accumulation and persistence of 8OHdG adducts to mtDNA is consistent with the implication of mitochondrial dysfunction in the cumulative and irreversible cardiotoxicity observed clinically in patients receiving doxorubicin cancer chemotherapy.

Preferential oxidation of cardiac mitochondrial DNA following acute intoxication with doxorubicin.

The purpose of this investigation was to determine whether acute doxorubicin intoxication causes a preferential accumulation of 8-hydroxydeoxyguanosine (8OHdG) adducts to mitochondrial DNA (mtDNA) as opposed to nuclear DNA (nDNA), particularly in cardiac tissue. Adult male rats received a single i.p. bolus of doxorubicin (15 mg/kg) and were killed 1-14 days later. Acute intoxication with doxorubicin caused a 2-fold greater increase in 8OHdG adducts to mtDNA compared to nDNA, the concentration of adducts to both nDNA and mtDNA being 20%-40% greater for heart as opposed to liver. For both tissues, the relative abundance of adducts was highest at the earliest time-point examined (24 h) and decreased to control values by 2 weeks. The temporal dilution of 8OHdG adducts was not the result of cell hyperplasia and was only partially due to amplification of the mitochondrial genome, most probably via an increase in DNA copy number rather than a stimulation of mitochondrial biogenesis.

Impairment of mitochondrial energy metabolism of two marine fish by in vitro mercuric chloride exposure.

The goal of this work was to understand the extent of mercury toxic effects in liver metabolism under an episode of acute contamination. Hence, the effects of in vitro mercuric chloride in liver mitochondria were assessed in two commercial marine fish: Senegalese sole (Solea senegalensis) and gilthead seabream (Sparus aurata). Liver mitochondria were exposed to 0.2mgL(-1) of mercury, the average concentration found in fish inhabiting contaminated areas. Mercuric chloride depressed mitochondrial respiration state 3 and the maximal oxygen consumption in the presence of FCCP indicating inhibitory effects on the oxidative phosphorylation and on the electron transport chain, respectively. The inhibition of F1Fo-ATPase and succinate-dehydrogenase activities also corroborated the ability of mercury to inhibit ADP phosphorylation and the electron transport chain. This study brings new understanding on the mercury levels able to impair fish mitochondrial function, reinforcing the need for further assessing bioenergetics as a proxy for fish health status.

Higher efficiency of the liver phosphorylative system in diabetic Goto-Kakizaki (GK) rats.

Liver mitochondrial bioenergetics of Goto-Kakizaki (GK) rats (a model of non-insulin dependent diabetes mellitus) reveals a Delta Psi upon energization with succinate significantly increased relatively to control animals. The repolarization rate following ADP phosphorylation is also significantly increased in GK mitochondria in parallel with increased ATPase activity. The increase in the repolarization rate and ATPase activity is presumably related to an improved efficiency of F(0)F(1)-ATPase, either from a better phosphorylative energy coupling or as a consequence of an enlarged number of catalytic units. Titrations with oligomycin indicate that diabetic GK liver mitochondria require excess oligomycin pulses to completely abolish phosphorylation, relative to control mitochondria. Therefore, accepting that the number of operational ATP synthase units is inversely proportional to the amount of added oligomycin, it is concluded that liver mitochondria of diabetic GK rats are provided with extra catalytic units relative to control mitochondria of normal rats. Other tissues (kidney, brain and skeletal muscle) were evaluated for the same bioenergetic parameters, confirming that this feature is exclusive to liver from diabetic GK rats.

Protective effect of carvedilol on chenodeoxycholate induction of the permeability transition pore.

Intracellular accumulation of toxic, hydrophobic bile acids has been proposed as one of the putative final common pathways leading to cholestatic liver injury. Furthermore, bile acids have been proposed as a causative factor for hepatic cardiomyopathy. Hepatic tissue concentrations of chenodeoxycholic acid (CDCA) during cholestasis are greater than those of other toxic bile acids. In the presence of calcium and phosphate, CDCA induced the permeability transition pore (PTP) in freshly isolated rat liver mitochondria. In this study, we evaluated the effects of carvedilol, a multirole cardioprotective compound, on CDCA-induced PTP. Mitochondrial membrane potential, osmotic swelling, and calcium fluxes were monitored. CDCA-induced PTP, characterized by membrane depolarization, release of matrix calcium, and osmotic swelling, was prevented by carvedilol. Under the same conditions, its hydroxylated analog BM-910228 did not reveal any protective effect. This finding reinforces carvedilol's therapeutic interest, because it may potentially prevent mitochondrial dysfunction associated with cardiomyopathy in the pathophysiology of cholestatic liver disease

Alterations of liver mitochondrial bioenergetics in diabetic Goto-Kakizaki rats.

Respiratory indexes and the transmembrane electrical potential (delta psi) were evaluated in mitochondrial preparations from 6-month-old Goto-Kakizaki (GK) and Wistar rats in the presence of glutamate + malate and succinate. We found that in diabetic GK mitochondria, flavin adenine dinucleotide (FAD)-linked respiratory indexes (respiratory control ratio [RCR] and adenosine diphosphate [ADP] to oxygen ratio [ADP/O]) are increased and uncoupled respiration is largely enhanced, indicating increased respiratory chain activity in GK rats. Delta psi development in GK mitochondrial preparations, energized using glutamate + malate or succinate as substrates, and the repolarization rate upon phosphorylation of the added ADP were significantly higher in GK mitochondrial preparations. These results indicate an enhanced activity of the phosphorylation system, confirmed by evaluating delta psi development when the mitochondria are energized by adenosine triphosphate (ATP). Moreover, recovery of the potential upon a phosphorylative cycle is increased in GK mitochondria, reflecting a more efficient coupling between the phosphorylative and oxidative system. Contrasting with results obtained for alloxan- or streptozotocin-induced diabetic rats, this study clearly demonstrates no impairment of mitochondrial bioenergetics in diabetic GK rats. On the contrary, at this age, we observed a higher efficiency of the phosphorylation system as compared with Wistar rats.

Acrylic acid induces the glutathione-independent mitochondrial permeability transition in vitro.

Acrylic acid (AA) is used widely in the synthesis of esters essential in the production of paints, adhesives, plastics, and coatings. The minimal systemic toxicity of AA is attributed to its rapid oxidation to acetyl-CoA and CO2 via the vitamin B12-independent beta-oxidation pathway. This oxidation is localized to the mitochondria and preliminary evidence suggests a possible inhibition of mitochondrial metabolism by acrylic acid. The purpose of this investigation was to evaluate whether AA interferes with mitochondrial bioenergetics in vitro. Incubation of isolated rat liver mitochondrial with AA resulted in a dose-dependent induction of the mitochondrial permeability transition (MPT). This was evidenced by an increased sensitivity to calcium-induced stimulation of state 4 oxygen consumption, depolarization of membrane potential, and swelling, all of which were prevented by preincubating the mitochondrial with cyclosporine A, a potent and specific inhibitor of the mitochondrial permeability transition pore. Both N-ethylmaleimide (NEM) and dithiothreitol (DTT) showed only partial protection against induction of the MPT by AA. Associated with the induction of the MPT by AA was the loss of mitochondrial glutathione (GSH), which was due to efflux from the matrix rather than oxidation to GSSG. Cyclosporine A, by inhibiting the permeability transition, prevented the AA-induced loss of mitochondrial GSH. In conclusion, AA increases the sensitivity of isolated mitochondria in vitro to the calcium-dependent induction of the MPT. Although the molecular mechanism has yet to be defined, it does not appear to be related to the oxidation of critical thiols.

Bile acids affect liver mitochondrial bioenergetics: possible relevance for cholestasis therapy.

It has been pointed out that intracellular accumulation of bile acids cause hepatocyte injury in cholestatic disease process. This study was aimed to test if cytotoxicity of these compounds is mediated through mitochondria dysfunction. Bile acids effects on isolated rat liver mitochondrial were analyzed by monitoring changes in membrane potential and mitochondrial respiration, as well as alterations in H(+) membrane permeability and mitochondrial permeability transition pore induction. Increasing concentrations of the bile acids litocholic (LCA), deoxycholic (DCA), ursodeoxycholic (UDCA), chenodeoxycholic (CDCA), glycochenodeoxycholic (GCDC), or taurochenodeoxycholic (TCDC) decrease transmembrane potential (delta psi) developed upon succinate energization. These compounds also decreased state 3 respiration and enhanced state 4. We have also demonstrated that the observed concentration-dependent stimulation of state 4 by LCA, DCA, CDCA, TCDC, and GCDC, is associated with an enhanced permeability of mitochondria to H(+). Addition of LCA, DCA, CDCA, TCDC, GCDC, and UDCA to mitochondria energized with succinate resulted in a dose-dependent membrane depolarization and stimulation of mitochondrial permeability transition. Tauroursodeoxycholate (TUDC) elicited no significant effect on succinate-supported mitochondrial bioenergetics. In contrast, in the presence of glycoursodeoxycholic (GUDC), delta psi increases as a function of bile salt concentration. The results of this investigation demonstrate that at toxicologically relevant concentrations, most but not all bile acids alter mitochondrial bioenergetics, so impairment of mitochondrial function can be clinically relevant for patients with cholestasis.

Membrane lipid peroxidation induces changes in gamma-[3H]aminobutyric acid transport and calcium uptake by synaptosomes.

In the present study, we analyze the effect of Fe2+/ascorbate-induced lipid peroxidation on Ca(2+)-dependent and Ca(2+)-independent release and on the uptake of gamma-[3H]aminobutyric acid (GABA) by sheep brain synaptosomes. In addition, we study the effect of lipid peroxidation on the levels of cytosolic calcium and on the uptake of calcium (45Ca2+). After membrane lipid peroxidation, a decrease in the uptake of GABA is observed. After ascorbate/Fe(2+)-induced membrane lipid peroxidation, a significant decrease in [3H]GABA release in response to K(+)-depolarization occurs, in the absence and in the presence of Ca2+. The influx of 45Ca2+ induced by K(+)-depolarization is significantly depressed under peroxidative conditions, while basal calcium uptake is inhibited to a much lesser degree. The levels of free ionic calcium [Ca2+]i, as determined by the fluorescent dye Indo-1, are increased after synaptosomes were submitted to the ascorbate/Fe2+ oxidative stress. It is concluded that membrane lipid peroxidation induces a decrease in Ca(2+)-dependent and Ca(2+)-independent efflux of accumulated [3H]GABA in response to elevated K+ pulses (60 mM) and in the depolarization-induced calcium influx, while free ionic calcium levels increase. The Ca(2+)-dependent efflux is interpreted to reflect stimulus-secretion coupling process and the Ca(2+)-independent efflux may reflect membrane transport processes. Thus, the results suggest a possible relationship between a reduced calcium movement across the membrane, the decrease in neurotransmitters uptake and release and oxidative stress.

Inhibitory effect of carvedilol in the high-conductance state of the mitochondrial permeability transition pore.

The mitochondrial permeability transition is a widely studied, but poorly understood, phenomenon in mitochondrial bioenergetics. It has been recognised that this phenomenon is related to the opening of a protein pore in the inner mitochondrial membrane, and that opening of this pore is the cause of some forms of mitochondrial dysfunction. In this work, we propose that carvedilol, a multi-role cardioprotective compound, may act as an inhibitor of the high-conductance state of the mitochondrial permeability transition pore, a conclusion supported by the finding that carvedilol provides differential protection against mitochondrial swelling in sucrose and KCl-based media, and that it is unable to protect against calcium-induced depolarisation of the mitochondrial membrane. We also show that carvedilol inhibits the oxidation of mitochondrial thiol groups and that, beyond causing a slight depression of the membrane potential, it has no inhibitory effect on mitochondrial calcium uptake.A decrease in the number of oxidised protein thiol groups may be the main mechanism responsible for this selective inhibition of the permeability transition pore in heart mitochondria. These effects may be important for the role of carvedilol in some cardiac pathologies.

Continuous monitoring of mitochondrial membrane potential in hepatocyte cell suspensions.

We report a simple fluorometric method for the continuous monitoring of mitochondrial membrane potential and cell viability in suspensions of hepatocytes exposed in vitro to cytotoxic agents. Suspensions of freshly isolated hepatocytes (10(6) cells/mL) preloaded with rhodamine 123 (Rh 123, 100 mumol/L) are transferred to a thermostatically controlled mixed cuvette to which the desired cytotoxic agent is added. Rh 123 is a cationic fluorophore that is actively accumulated by cells in direct proportion to the mitochondrial membrane potential. Cell viability was estimated by monitoring propidium iodide (PI) fluorescence. Exposure of cell suspensions to the mitochondrial uncoupling agent FCCP caused an immediate and titratable increase in Rh 123 fluorescence. Subsequent treatment with digitonin did not change Rh 123 fluorescence, suggeseting that Rh 123 equilibrates rapidly across the intact cell membrane. Likewise, treatment of hepatocyte suspensions with inhibitors of mitochondrial respiration (rotenone, cyanide, or menadione) caused an immediate increase in Rh 123 fluorescence. This was accompanied by a progressive increase in PI fluorescence, suggesting a causal relationship between mitochondrial depolarization and cell injury. In contrast, 1,4-benzoquinone caused a time-dependent and linear increase in PI fluorescence that paralleled changes in Rh 123 fluorescence. Comparing the time courses for changes in PI and Rh 123 fluorescence suggests that for benzoquinone, the depolarization of the mitochondria is a consequence rather than a cause of the cell injury. This modified procedure provides a simple and specific technique for continuously monitoring mitochondrial membrane potential and cell viability in suspensions of freshly isolated hepatocytes. The advantage is that there is no need to separate cells from the incubation medium, making it possible to record real-time changes in mitochondrial membrane potential and cell viability throughout the in vitro exposure period.

Carvedilol reduces mitochondrial damage induced by hypoxanthine/xanthine oxidase: relevance to hypoxia/reoxygenation injury.

The cardioprotective properties of new pharmaceuticals such as carvedilol might be explained by enhanced mitochondrial protection. The aim of this work was to determine the role of carvedilol in the protection of heart mitochondria from oxidative damage induced by hypoxanthine/xanthine oxidase, a known source of oxidative stress in the vascular system. Carvedilol reduced oxidative-stress-induced mitochondrial injury, as seen by the delay in the loss of the mitochondrial transmembranar potential (Delta Psi), the decrease in mitochondrial swelling, and the increase in mitochondrial calcium uptake. Carvedilol improved the mitochondrial respiratory activity in state III and offered an overall protection in the respiratory control and in the P/O ratios in mitochondria under oxidative stress. The data indicated that carvedilol was able to partly protect heart mitochondria from oxidative stress-induced damage. Our results suggest that mitochondria can be important targets for some cardioprotective pharmaceuticals.

Decreased susceptibility to lipid peroxidation of Goto-Kakizaki rats: relationship to mitochondrial antioxidant capacity.

The respiratory function and the antioxidant capacity of liver mitochondrial preparations isolated from Goto-Kakizaki non-insulin dependent diabetic rats and from Wistar control rats, with the age of 6 months, were compared. It was found that Goto-Kakizaki mitochondrial preparations presented a higher coupling between oxidative and phosphorylative systems, compared to non-diabetic preparations. Goto-Kakizaki mitochondria presented a lower susceptibility to lipid peroxidation induced by ADP/Fe2+, as evaluated by the formation of thiobarbituric acid substances. The decreased susceptibility to peroxidation in diabetic rats was correlated with an increase in mitochondrial vitamin E (alpha-tocopherol) content and GSH/GSSG ratio. Moreover, the glutathione reductase activity was significantly increased, whereas the glutathione peroxidase was decreased. Superoxide dismutase activity was unchanged in diabetic rats. Fatty acid analyses showed that the content in polyunsaturated fatty acids of Goto-Kakizaki mitochondrial membranes was significantly higher compared to controls. These results indicate that the lower susceptibility to lipid peroxidation of mitochondria from diabetic rats was related to their antioxidant defense systems, and may correspond to an adaptative response of the cells against oxidative stress in the early phase of diabetes.

Carvedilol in heart mitochondria: protonophore or opener of the mitochondrial K(ATP) channels?

Carvedilol ([1-[carbazolyl-(4)-oxy]-3-[2-methoxyphenoxyethyl) amino]-propanol-(2)]) has been shown to protect cardiac mitochondria from oxidative stress. In this work we examined the mechanisms responsible for an observed depressive effect in the mitochondrial transmembrane potential (delta psi). Two possible mechanisms were considered: a protonophoretic activity and the opening of mitochondrial ATP-sensitive potassium channels. We show that carvedilol increases mitochondrial inner membrane permeability to protons, but not to potassium, causing an increase in state IV respiration in the presence and absence of oligomycin. By contrast, a K(ATP)-channel inhibitor, 5-hydroxydecanoic acid, did not affect carvedilol-induced depolarizations. Hence, our results suggest that carvedilol depresses mitochondrial delta psi by a weak protonophoretic mechanism.

Doxorubicin-induced persistent oxidative stress to cardiac myocytes.

We recently reported a cardioselective and cumulative oxidation of cardiac mitochondrial DNA (mtDNA) following subchronic administration of doxorubicin to rats. The mtDNA adducts persist for up to 5 weeks after cessation of doxorubicin treatment. Since the evidence suggests that this persistence of mtDNA adducts cannot be attributed to a lack of repair and replication, we investigated whether it might reflect a long-lasting stimulation of free radical-mediated adduct formation. Male Sprague-Dawley rats received weekly s.c. injections of either doxorubicin (2 mg/kg) or an equivalent volume of saline. Cardiac myocytes isolated from rats following 6 weekly injections of doxorubicin expressed a much higher rate of reactive oxygen species (ROS) formation compared to saline controls. This higher rate of ROS formation persisted for 5 weeks following the last injection. Associated with this was a persistent depression of GSH in heart tissue, while protein-thiol content was not markedly altered. These data suggest that the accumulation and persistence of oxidized mtDNA may be due, not to the stability of the adducts, but to some as yet undefined toxic lesion that causes long-lasting stimulation of ROS generation by doxorubicin. This persistent generation of ROS may contribute to the cumulative and irreversible cardiotoxicity observed clinically with the drug.

Thiols metabolism is altered by the herbicides paraquat, dinoseb and 2,4-D: a study in isolated hepatocytes.

This report is an extension and complement of a previous study reporting the effect of three herbicides (paraquat, dinoseb and 2,4-D) on cell viability, GSH oxidation, NADH and ATP depletion (Arch. Toxicol. 68:24-31, 1994). Here we report additional data and findings aimed at a better understanding of the toxicity mechanisms induced by these herbicides. Biochemical mechanisms of cytotoxicity induced by the herbicides paraquat (1,1'-dimethyl-4,4'-bipyridylium dichloride), dinoseb (2-sec-butyl-4,6-dinitrophenol) and 2,4-D (2,4-dichlorophenoxyacetic acid) were investigated in freshly isolated rat hepatocytes. Herbicide metabolism, especially paraquat and 2,4-D, rapidly depletes GSH and protein thiols. Paraquat and 2,4-D (1-10 mM) decrease the GSH/GSSG ratio, promote loss of protein thiol contents and induce lipid peroxidation. Dinoseb, the most effective cytotoxic compound under study (used in concentrations 1000-fold lower than paraquat and 2,4-D), had moderate effects upon the GSH/GSSG ratio and lipid peroxidation, causing a depletion of protein thiols of about 20%. The results indicate that the herbicides paraquat and 2,4-D are hepatotoxic and may induce cell death by decreasing cellular GSH/GSSG ratio and protein thiols, and by inducing lipid peroxidation. The cytotoxic action of dinoseb is likely to be related with the uncoupling of oxidative phosphorylation in mitochondria. Therefore, it is likely that liver damage observed during the first phase of herbicide-intoxication is related to these metabolic processes.

Chenodeoxycholate is a potent inducer of the permeability transition pore in rat liver mitochondria.

Several reports support the concept that bile acids may be cytotoxic during cholestatic disease process by causing mitochondrial dysfunction. Here we report additional data and findings aimed at a better understanding of the involvement of the permeability transition pore (PTP) opening in bile acids toxicity. The mitochondrial PTP is implicated as a mediator of cell injury and death in many situations. In the presence of calcium and phosphate, chenodeoxycholic acid (CDCA) induced a permeability transition in freshly isolated rat liver mitochondria, characterized by membrane depolarization, release of matrix calcium, and osmotic swelling. All these events were blocked by cyclosporine A (CyA) and the calcium uniporter inhibitor ruthenium red (RR). The results suggest that CDCA increases the sensitivity of isolated mitochondria in vitro to the calcium-dependent induction of the PTP.