PhytoScience - Science
Tylenol and Antibiotics Cause Liver Failure
Study Title:
Drug-induced liver injury in 2007.
Study Abstract:
PURPOSE OF REVIEW: To summarize the pertinent literature on the causes, epidemiology, prevalence, clinical features, evaluation and mechanisms of drug-induced liver injury reported during 2007. RECENT FINDINGS: Although the frequency of drug-induced liver injury remains low, new data from the Centers for Disease Control and Prevention confirm that of the approximately 1600 new acute liver failure cases annually, acetaminophen hepatotoxicity accounts for 41%; among children with acute liver failure, acetaminophen was the second most common cause. Antimicrobials lead the list of non-acetaminophen causes of drug-induced liver injury. In Asia, herbal compounds are the most common causes of the condition. Pravastatin was shown to be safe in patients with nonalcoholic fatty liver disease or chronic hepatitis C. The US Food and Drug Administration issued a draft guidance document on the premarketing clinical evaluation and stopping rules of drug-induced liver injury signals, including Hy’s Law cases in clinical trials. SUMMARY: The year 2007 brought with it several reminders of the importance of drug-induced liver injury in the clinical trial as well as the clinical practice setting. There is additional evidence that statin drugs may be used safely in patients with chronic liver disease. Comments received by the US Food and Drug Administration to finalize their guidance document are eagerly awaited.
Study Information:
Norris W, Paredes AH, Lewis JH. Drug-induced liver injury in 2007. Curr Opin Gastroenterol. 2008 May 24(3):287-97.
Hepatology Section, Division of Gastroenterology, Georgetown University Hospital, Georgetown University Medical Center, Washington, DC 20007, USA.
Silymarin Reduces Tylenol Liver Toxicity
Study Title:
Acetaminophen-induced toxicity to human epidermoid cell line A431 and hepatoblastoma cell line Hep G2, in vitro, is diminished by silymarin.
Study Abstract:
The increase in cellular and mitochondrial glutathione disulfide (GSSG) levels and the GSSG:GSH ratio after acetaminophen (AAP) overdose suggest the involvement of an oxidant stress in the pathophysiology. However, the initial severe depletion of hepatocellular glutathione makes quantitative assessment of the oxidant stress difficult. Therefore, we tested the hypothesis that oxidant stress precedes the onset of cell injury in a cell culture model using 2’,7’-dichlorofluorescein (DCF) fluorescence as a marker for intracellular oxidant stress. Cultured primary murine hepatocytes were exposed to 5 mM AAP. DCF fluorescence, XTT reduction, lactate dehydrogenase (LDH) release, and trypan blue uptake were determined from 0 to 12 h. After glutathione depletion at 3 h, DCF fluorescence increased by 16-fold and was maintained at that level up to 12 h. At 1.5 h after AAP, a significant decrease of the cellular XTT reduction capacity was observed, which continued to decline until 9 h. Cell necrosis (LDH release, trypan blue uptake) was detectable in 20% of cells at 6 h, with a significant further increase at later time points. Pretreatment with 20 mM N-acetylcysteine (NAC) 1 h before AAP enhanced cellular glutathione content, prevented or attenuated the AAP-induced decrease of GSH levels and XTT reduction capacity, respectively, and reduced the loss of cell viability. Additionally, treatment with NAC 2 h after AAP exposure prevented further deterioration of XTT reduction at 3 h and later, and attenuated cell necrosis. Thus, AAP-induced oxidant stress precedes cell necrosis and, in cultured hepatocytes, the oxidant stress is involved in the propagation of cell injury.
Study Information:
Shear NH, Malkiewicz IM, Klein D, Koren G, Randor S, Neuman MG. Acetaminophen-induced toxicity to human epidermoid cell line A431 and hepatoblastoma cell line Hep G2, in vitro, is diminished by silymarin. Skin Pharmacol. 1995 August 8(6):279-91.
Division of Dermatology, Sunnybrook Health Science Centre, Ont., Canada.
Prior Taking of Lipoic Acid Protects Against Tylenol-Induced Liver Damage
Study Title:
The potential protective role of alpha-lipoic acid against acetaminophen-induced hepatic and renal damage.
Study Abstract:
The potential protective role of alpha-lipoic acid (alpha-LA) in acetaminophen (APAP)-induced hepatotoxicity and nephrotoxicity was investigated in rats. Pretreatment of rats with alpha-LA (100mg/kg) orally protected markedly against hepatotoxicity and nephrotoxicity induced by an acute oral toxic dose of APAP (2.5 g/kg) as assessed by biochemical measurements and by histopathological examination. None of alpha-LA pretreated animals died by the acute toxic dose of APAP. Concomitantly, APAP-induced profound elevation of nitric oxide (NO) production and oxidative stress, as evidenced by increasing of lipid peroxidation level, reducing of glutathione peroxidase (GSH-Px) activity and depleting of intracellular reduced glutathione (GSH) level in liver and kidney, were suppressed by pretreatment with alpha-LA. Similarly, daily treatment of rats with a smaller dose of alpha-LA (25mg/kg) concurrently with a smaller toxic dose of APAP (750 mg/kg) for 1 week protected against APAP-induced hepatotoxicity and nephrotoxicity. This treatment also completely prevented APAP-induced mortality and markedly inhibited APAP-induced NO overproduction and oxidative stress in hepatic and renal tissues. These results provide evidence that inhibition of NO overproduction and maintenance of intracellular antioxidant status may play a pivotal role in the protective effects of alpha-LA against APAP-induced hepatic and renal damage.
Study Information:
Abdel-Zaher AO, Abdel-Hady RH, Mahmoud MM, Farrag MM. The potential protective role of alpha-lipoic acid against acetaminophen-induced hepatic and renal damage. Toxicology. 2008 January 243(3):261-70.
Department of Pharmacolog, Faculty of Medicine, Assiut University, Assiut, Egypt.
NAC Reduces Tylenol Liver Toxicity
Study Title:
Acetaminophen-induced oxidant stress and cell injury in cultured mouse hepatocytes: protection by N-acetyl cysteine.
Study Abstract:
The increase in cellular and mitochondrial glutathione disulfide (GSSG) levels and the GSSG:GSH ratio after acetaminophen (AAP) overdose suggest the involvement of an oxidant stress in the pathophysiology. However, the initial severe depletion of hepatocellular glutathione makes quantitative assessment of the oxidant stress difficult. Therefore, we tested the hypothesis that oxidant stress precedes the onset of cell injury in a cell culture model using 2’,7’-dichlorofluorescein (DCF) fluorescence as a marker for intracellular oxidant stress. Cultured primary murine hepatocytes were exposed to 5 mM AAP. DCF fluorescence, XTT reduction, lactate dehydrogenase (LDH) release, and trypan blue uptake were determined from 0 to 12 h. After glutathione depletion at 3 h, DCF fluorescence increased by 16-fold and was maintained at that level up to 12 h. At 1.5 h after AAP, a significant decrease of the cellular XTT reduction capacity was observed, which continued to decline until 9 h. Cell necrosis (LDH release, trypan blue uptake) was detectable in 20% of cells at 6 h, with a significant further increase at later time points. Pretreatment with 20 mM N-acetylcysteine (NAC) 1 h before AAP enhanced cellular glutathione content, prevented or attenuated the AAP-induced decrease of GSH levels and XTT reduction capacity, respectively, and reduced the loss of cell viability. Additionally, treatment with NAC 2 h after AAP exposure prevented further deterioration of XTT reduction at 3 h and later, and attenuated cell necrosis. Thus, AAP-induced oxidant stress precedes cell necrosis and, in cultured hepatocytes, the oxidant stress is involved in the propagation of cell injury.
Study Information:
Bajt ML, Knight TR, Lemasters JJ, Jaeschke H. Acetaminophen-induced oxidant stress and cell injury in cultured mouse hepatocytes: protection by N-acetyl cysteine. Toxicol Sci. 2004 August 80(2):343-9.
Liver Research Institute, University of Arizona, College of Medicine, Tucson, Arizona 85724, USA.