Hepatotoxic effect of cyclosporin A in the mitochondrial respiratory chain

Knockout of cyclophilin D in Ppif⁻/⁻ mice increases stability of brain mitochondria against Ca²⁺ stress

The mitochondrial peptidyl prolyl isomerase cyclophilin D (CypD) activates permeability transition (PT). To study the role of CypD in this process we compared the functions of brain mitochondria isolated from wild type (BMWT) and CypD knockout (Ppif(-/-)) mice (BMKO) with and without CypD inhibitor Cyclosporin A (CsA) under normal and Ca(2+) stress conditions. Our data demonstrate that BMKO are characterized by higher rates of glutamate/malate-dependent oxidative phosphorylation, higher membrane potential and higher resistance to detrimental Ca(2+) effects than BMWT. Under the elevated Ca(2+) and correspondingly decreased membrane potential the dose response in BMKO shifts to higher Ca(2+) concentrations as compared to BMWT. However, significantly high Ca(2+) levels result in complete loss of membrane potential in BMKO, too. CsA diminishes the loss of membrane potential in BMWT but has no protecting effect in BMKO. The results are in line with the assumption that PT is regulated by CypD under the control of matrix Ca(2+). Due to missing of CypD the BMKO can favor PT only at high Ca(2+) concentrations. It is concluded that CypD sensitizes the brain mitochondria to PT, and its inhibition by CsA or CypD absence improves the complex I-related mitochondrial function and increases mitochondria stability against Ca(2+) stress.

On the performance of trimetazidine and vitamin e as pharmacoprotection agents in cyclosporin a-induced toxicity

The immunosuppressant drug cyclosporin A (CyA) has been used in diseases with immunological basis and in transplant patients. Nephrotoxicity and hepatotoxicity are the main adverse effects of this drug. To find a protective drug against those effects we assayed the cardioprotector Trimetazidine (TMZ) and vitamin E, used as nutritional supplements to alleviate oxidative stress. Six groups of eight male Wistar rats each were prepared (groups A-F): A, control; B, vitamin E (10 mg/Kg/day); C, TMZ (20 mg/Kg/day); D, 25 mg/Kg/day CyA; E, CyA and vitamin E (25 mg/Kg/day CyA + 10 mg/Kg/day Vit E); F, TMZ for 20 days (20 mg/kg/day); and then CyA (25 mg/kg/day) and TMZ (20 mg/Kg/day). The experiment lasted 120 days. The exposure of rats to CyA promoted nephrotoxicity and hepatotoxicity with an increase in serum urea, creatinine, and glutamate dehydrogenase (GLDH). Structural and ultrastructural studies of liver and kidney were performed. Group D showed adverse effects induced by CyA since statistically significant differences were found with respect to the control group (A). Vitamin E (E) showed no protective effect. Pretreatment with TMZ (F) attenuated the adverse effects of CyA. We conclude that CyA-induced nephrotoxicity and hepatotoxicity are attenuated by the cytoprotective effect of TMZ. TMZ inhibits the reabsorption and, consequently, the accumulation of CyA in the cell. The antioxidant capacity of vitamin E did not improve the effect of CyA.

Mitochondrial electron transport chain deficiency, cardiomyopathy, and long-term cardiac transplant outcome

Organ transplantation in multisystemic mitochondrial cytopathies is usually not performed because of perceived untoward complications. We report three patients with demonstrated oxidative phosphorylation defects and dilated cardiomyopathy who underwent cardiac transplant. All three patients tolerated immunosuppression medications and have had an excellent long-term outcome. Our results suggest that with proper patient selection in this population, cardiac transplantation is feasible and can have good outcomes.

Attenuation of gentamicin-induced nephrotoxicity: trimetazidine versus N-acetyl cysteine

Gentamicin (G) is a highly nephrotoxic aminoglucoside. It was used to experimentally induce nephrotoxicity in male Wistar rats. To find a drug capable of protecting the nephron we assayed a cardioprotector (trimetazidine, TMZ) and a hepatoprotector (N-acetyl cysteine, NAC). The rats were divided into six groups (n = 8): (A) control without drugs; (B) treated with 50 mg kg(-1) per day (i.p.) of G for 7 days; (C) diet supplemented with 20 mg kg(-1) per day of TMZ for 7 days; (D) treated with 10 mg kg(-1) per day (i.p.) of NAC for 7 days; (E) pretreated for 7 days with 20 mg kg(-1) per day of TMZ and during the following 7 days with G + TMZ; (F) pretreated for 7 days with 10 mg kg(-1) per day (i.p.) of NAC and during the following 7 days with G + NAC. Urea and creatinine as well as the excretion of urinary gamma-glutamyl transpeptidase (GGT(u)) and urinary N-acetyl-glucosaminidase (NAG(u)) were determined and structural and ultrastructural studies were carried out. Group B was used as a G-induced nephrotoxicity control. Pretreatment with TMZ (E) showed a protector effect against induced nephrotoxicity, with no biochemical or functional changes nor alterations in histoarchitecture or ultrastructure. Pretreatment with NAC (F) showed no protector effect against G-induced nephrotoxicity since no statistically significant differences were found with respect to the control group with G. We conclude that G-induced nephrotoxicity is attenuated by the cytoprotective effect of TMZ. We may infer that TMZ inhibits the reabsorption and consequently the accumulation of G in the proximal tubule cell.

Allogeneic hematopoietic SCT as treatment option for patients with mitochondrial neurogastrointestinal encephalomyopathy (MNGIE): a consensus conference proposal for a standardized approach

Allogeneic hematopoietic SCT (HSCT) has been proposed as a treatment for patients with mitochondrial neurogastrointestinal encephalomyopathy (MNGIE). HSCT has been performed in nine patients using different protocols with varying success. Based on this preliminary experience, participants of the first consensus conference propose a common approach to allogeneic HSCT in MNGIE. Standardization of the transplant protocol and the clinical and biochemical assessments will allow evaluation of the safety and efficacy of HSCT as well as optimization of therapy for patients with MNGIE.

The elderly as a sensitive population in environmental exposures: making the case

The US population is aging. CDC has estimated that 20% of all Americans will be 65 or older by the year 2030. As a part of the aging process, the body gradually deteriorates and physiologic and metabolic limitations arise. Changes that occur in organ anatomy and function present challenges for dealing with environmental stressors of all kinds, ranging from temperature regulation to drug metabolism and excretion. The elderly are not just older adults, but rather are individuals with unique challenges and different medical needs than younger adults. The ability of the body to respond to physiological challenge presented by environmental chemicals is dependent upon the health of the organ systems that eliminate those substances from the body. Any compromise in the function of those organ systems may result in a decrease in the body's ability to protect itself from the adverse effects of xenobiotics. To investigate this issue, we performed an organ system-by-organ system review of the effects of human aging and the implications for such aging on susceptibility to drugs and xenobiotics. Birnbaum (1991) reported almost 20 years ago that it was clear that the pharmacokinetic behavior of environmental chemicals is, in many cases, altered during aging. Yet, to date, there is a paucity of data regarding recorded effects of environmental chemicals on elderly individuals. As a result, we have to rely on what is known about the effects of aging and the existing data regarding the metabolism, excretion, and adverse effects of prescription medications in that population to determine whether the elderly might be at greater risk when exposed to environmental substances. With increasing life expectancy, more and more people will confront the problems associated with advancing years. Moreover, although proper diet and exercise may lessen the immediate severity of some aspects of aging, the process will continue to gradually degrade the ability to cope with a variety of injuries and diseases. Thus, the adverse effects of long-term, low-level exposure to environmental substances will have a longer time to be manifested in a physiologically weakened elderly population. When such exposures are coupled with concurrent exposure to prescription medications, the effects could be devastating. Public health officials must be knowledgeable about the sensitivity of the growing elderly population, and ensure that the use of health guidance values (HGVs) for environmental contaminants and other substances give consideration to this physiologically compromised segment of the population.

Drug-induced liver injury through mitochondrial dysfunction: mechanisms and detection during preclinical safety studies

Mitochondrial dysfunction is a major mechanism whereby drugs can induce liver injury and other serious side effects such as lactic acidosis and rhabdomyolysis in some patients. By severely altering mitochondrial function in the liver, drugs can induce microvesicular steatosis, a potentially severe lesion that can be associated with profound hypoglycaemia and encephalopathy. They can also trigger hepatic necrosis and/or apoptosis, causing cytolytic hepatitis, which can evolve into liver failure. Milder mitochondrial dysfunction, sometimes combined with an inhibition of triglyceride egress from the liver, can induce macrovacuolar steatosis, a benign lesion in the short term. However, in the long term this lesion can evolve in some individuals towards steatohepatitis, which itself can progress to extensive fibrosis and cirrhosis. As liver injury caused by mitochondrial dysfunction can induce the premature end of clinical trials, or drug withdrawal after marketing, it should be detected during the preclinical safety studies. Several in vitro and in vivo investigations can be performed to determine if newly developed drugs disturb mitochondrial fatty acid oxidation (FAO) and the oxidative phosphorylation (OXPHOS) process, deplete hepatic mitochondrial DNA (mtDNA), or trigger the opening of the mitochondrial permeability transition (MPT) pore. As drugs can be deleterious for hepatic mitochondria in some individuals but not in others, it may also be important to use novel animal models with underlying mitochondrial and/or metabolic abnormalities. This could help us to better predict idiosyncratic liver injury caused by drug-induced mitochondrial dysfunction.