Unaltered hepatic oxidative phosphorylation and mitochondrial permeability transition in wistar rats treated with nimesulide: Relevance for nimesulide toxicity characterization

Sea lamprey cardiac mitochondrial bioenergetics after exposure to TFM and its metabolites

Population control of invasive sea lamprey relies heavily on lampricide treatment of infested streams. The lampricide 3-trifluoromethyl-4-nitrophenol (TFM) is thought to impair mitochondrial ATP production through uncoupling oxidative phosphorylation. However, the effect of TFM on the entire electron transport chain (complexes I to V) in the mitochondria is not clear. In addition, TFM is reduced in phase I metabolism by sea lamprey at higher levels than in other fish species. The effects of these TFM reductive metabolites on mitochondria have not been explored. In this study, we sought to examine the effects of TFM and its reductive metabolite amino-TFM (TFMa) on cardiac mitochondrial oxygen consumption and membrane potential to delineate potential mechanisms for toxicity. To determine if molecules with similar structure also exhibit similar effects on mitochondria, we used 4-nitro-3-methylphenol (NMP) and its reductive metabolites 4-amino-3-methylphenol (NMPa) and 4-nitroso-3-methylphenol (NMPn) for comparisons. We found that mitochondrial bioenergetics was heavily affected with increasing concentrations of TFM, NMP, and NMPa when complexes I and II of the electron transport chain were examined, indicating that the toxic action of these compounds was exerted not only by uncoupling complex V, but also affecting complexes I and II.

Nimesulide-induced fatal acute liver failure in an elderly woman with metastatic biliary adenocarcinoma. A case report

CONTEXT

Nimesulide is a selective inhibitor of the enzyme cyclooxygenase 2. Although considered to be a safe drug, cases of acute hepatitis and fulminant liver failure have been reported in Europe, the United States and South America, especially among elderly female patients. Until now, there had not been any reports in the literature relating to Brazilian subjects.

CASE REPORT

An 81-year old female who had been using nimesulide therapy for six days presented hematemesis and epistaxis two days before hospitalization. Clinical examination showed an extensive coagulation disorder, diffuse hematomas, hypotension and tachypnea. Laboratory tests revealed abnormalities in coagulation tests; leukocytosis; reduced platelet, hemoglobin and red blood cell counts; and elevated direct bilirubin, serum aspartate transaminase (AST), gamma-glutamyl transpeptidase (GGT), alkaline phosphatase and renal function biomarkers. Hepatitis B and C tests were not reactive. Carcinoembryonic antigen (CEA), CA-19-9 and CA-125 levels were increased by, respectively, 1,000, 10,000 and 13 fold, whereas the alpha-fetoprotein level was normal, thus indicating a malignant tumor in the bile duct that did not originate from the liver. Thirty-six hours after hospitalization, the patient's condition worsened, leading to death. The necropsy findings included acute hepatitis with hepatocellular collapse, as well as metastasis of a carcinoma, probably from the bile duct.

CONCLUSION

Despite the carcinoma presented by the patient, nimesulide use may have contributed towards the fatal acute liver failure. Until this issue has been clarified, caution is required in prescribing nimesulide for liver disease patients.

Protective effects of Hammada scoparia flavonoid-enriched fraction on liver injury induced by warm ischemia/reperfusion

CONTEXT

Hepatic ischemia/reperfusion injury (IRI) is a major cause of liver damage during liver surgery and transplantation. Plants have historically been used in treating liver damage, and Hammada scoparia (Pomel) (Chenopodiaceae) has been reported to possess a broad spectrum of pharmacological and therapeutic activities.

OBJECTIVE

In this study, a flavonoid-enriched fraction was used before the warm ischemia (WI) process as pharmacological preconditioning and in combination with technical postconditioning to evaluate their protective effects.

MATERIALS AND METHODS

The rats were divided into five groups: a sham group; a control group (Control-IR) that was submitted to 60 min WI; a Pharmacological Preconditioning group (PreC-IR) that received flavonoid-enriched fraction (200 mg/kg body weight); a Postconditioning group (PostC) and a PreC + PostC group.

RESULTS

The use of the flavonoid-enriched fraction was noted to significantly (p < 0.05) reduce liver injury, as evidenced by the decrease in liver transaminase activities (AST and ALT) and lactic dehydrogenase (LDH), alkaline phosphatase (ALP), and lipid peroxidation (TBARS), levels as well as the enhancement of antioxidant enzymes (catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx)) responses. The results also indicated that, compared with the separate application of pharmacological preconditioning and postconditioning, the combination of both treatments was more effective in reducing tissue oxidative stress levels through modulating SOD, GSH-PX, and CAT activities. Furthermore, the combined protocol further decreased the liver morphological score compared with solo treatment.

DISCUSSION AND CONCLUSION

Overall, the results indicate that the H. scoparia flavonoid-enriched fraction could be a promising candidate for future application as a pharmacological preconditioning agent against hepatic IRI.

Mitochondrial complex I dysfunction induced by cocaine and cocaine plus morphine in brain and liver mitochondria

Mitochondrial function and energy metabolism are affected in brains of human cocaine abusers. Cocaine is known to induce mitochondrial dysfunction in cardiac and hepatic tissues, but its effects on brain bioenergetics are less documented. Furthermore, the combination of cocaine and opioids (speedball) was also shown to induce mitochondrial dysfunction. In this work, we compared the effects of cocaine and/or morphine on the bioenergetics of isolated brain and liver mitochondria, to understand their specific effects in each tissue. Upon energization with complex I substrates, cocaine decreased state-3 respiration in brain (but not in liver) mitochondria and decreased uncoupled respiration and mitochondrial potential in both tissues, through a direct effect on complex I. Morphine presented only slight effects on brain and liver mitochondria, and the combination cocaine+morphine had similar effects to cocaine alone, except for a greater decrease in state-3 respiration. Brain and liver mitochondrial respirations were differentially affected, and liver mitochondria were more prone to proton leak caused by the drugs or their combination. This was possibly related with a different dependence on complex I in mitochondrial populations from these tissues. In summary, cocaine and cocaine+morphine induce mitochondrial complex I dysfunction in isolated brain and liver mitochondria, with specific effects in each tissue.

Flurbiprofen, a cyclooxygenase inhibitor, protects mice from hepatic ischemia/reperfusion injury by inhibiting GSK-3β signaling and mitochondrial permeability transition

Flurbiprofen acts as a nonselective inhibitor for cyclooxygenases (COX-1 and COX-2), but its impact on hepatic ischemia/reperfusion (I/R) injury remains unclear. Mice were randomized into sham, I/R and flurbiprofen (Flurb) groups. The hepatic artery and portal vein to the left and median liver lobes were occluded for 90 min and unclamped for reperfusion to establish a model of segmental (70%) warm hepatic ischemia. Pretreatment of animals with flurbiprofen prior to I/R insult significantly decreased serum alanine aminotransferase (ALT), aspartate aminotransferase (AST) and lactate dehydrogenase (LDH), and prevented hepatocytes from I/R-induced apoptosis/necrosis. Moreover, flurbiprofen dramatically inhibited mitochondrial permeability transition (MPT) pore opening, and thus prevented mitochondrial-related cell death and apoptosis. Mechanistic studies revealed that flurbiprofen markedly inhibited glycogen synthase kinase (GSK)-3β activity and increased phosphorylation of GSK-3β at Ser9, which, consequently, could modulate the adenine nucleotide translocase (ANT)-cyclophilin D (CyP-D) complex and the susceptibility to MPT induction. Therefore, administration of flurbiprofen prior to hepatic I/R ameliorates mitochondrial and hepatocellular damage through inhibition of MPT and inactivation of GSK-3β, and provides experimental evidence for clinical use of flurbiprofen to protect liver function in surgical settings in addition to its conventional use for pain relief.

Role of mitochondria in nonalcoholic fatty liver disease--from origin to propagation

OBJECTIVES

Mitochondria play a major role in cell energy-generating processes and integrate several signalling pathways to control cellular life and death.

DESIGN AND METHODS

Several liver diseases are characterized by mitochondrial alterations which are directly or indirectly dependent on the activation of intracellular stress cascades or receptor-mediated pathways. This article examines the role of mitochondrial dysfunction in critical initiating or propagating events in fatty liver infiltration and nonalcoholic fatty liver disease (NAFLD). Genetic variants and the role of drug-induced toxicity have been considered.

RESULTS

Key alterations of mitochondrial physiology associated with hepatocyte fatty changes are described. The value of novel non-invasive diagnostic methods to detect mitochondrial metabolic alterations is also discussed.

CONCLUSIONS

Mitochondrial metabolic remodeling is a predominant factor in the appearance and perpetuation of hepatocyte fat accumulation. Non-invasive techniques to identify mitochondrial dysfunction and proper mitochondria protection are two necessary clinical steps for an efficient management of NAFLD.

Nimesulide-induced electrophile stress activates Nrf2 in human hepatocytes and mice but is not sufficient to induce hepatotoxicity in Nrf2-deficient mice

Nimesulide is a widely prescribed nitroaromatic sulfoanilide-type nonsteroidal anti-inflammatory drug that, despite its favorable safety profile, has been associated with rare cases of idiosyncratic drug-induced liver injury (DILI). Because reactive metabolites have been implicated in DILI, we aimed at investigating whether hepatic bioactivation of nimesulide produces a protein-reactive intermediate in hepatocytes. Also, we explored whether nimesulide can activate the transcription factor Nrf2 that would protect from drug-induced hepatocyte injury. We found that [(14)C]-nimesulide covalently bound to human liver microsomes (<50 pmol/mg under standard conditions) or immortalized human hepatocytes in a sulfaphenazole-sensitive, rifampicin-inducible manner; yet the overall extent of binding was modest. Although exposure of hepatocytes to nimesulide was not associated with increased net levels of superoxide anion, nimesulide (100 microM, 24 h) caused nuclear translocation of Nrf2 in a sulfaphenazole-sensitive manner, indicating a role of electrophilic metabolites. However, knockdown of Nrf2 with siRNA did not make the cells more sensitive to nimesulide-induced cell injury. Similarly, exposure of wild-type C57BL/6x129 Sv mice to nimesulide (100 mg/kg/day, po, for 5 days) was associated with nuclear translocation of immunoreactive Nrf2 in a small number of hepatocytes and induced >2-fold the expression levels of the Nrf2-target gene Nqo1 in wild-type but not Nrf2-null mice. Nimesulide administered to Nrf2(-/-) knockout mice did not cause increases in serum ALT activity or any apparent histopathological signs of liver injury. In conclusion, these data indicate that nimesulide is bioactivated by CYP2C to a protein-reactive electrophilic intermediate that activates the Nrf2 pathway even at nontoxic exposure levels.

Proton leak modulation in testicular mitochondria affects reactive oxygen species production and lipid peroxidation

Mitochondrial proton leak can account for almost 20% of oxygen consumption and it is generally accepted that this process contributes to basal metabolism. In order to clarify the role of basal proton leak in testicular mitochondria, we performed a comparative study with kidney and liver mitochondrial fractions. Proton leak stimulated by linoleic acid and inhibited by guanosine diphosphate (GDP) was detected, in a manner that was correlated with protein levels for uncoupling protein 2 (UCP2) in the three fractions. Modulation of proton leak had an effect on reactive oxygen species production as well as on lipid peroxidation, and this effect was also tissue-dependent. However, a possible role for the adenine nucleotide transporter (ANT) in testicular mitochondria proton leak could not be excluded. The modulation of proton leak appears as a possible and attractive target to control oxidative stress with implications for male gametogenesis.