Novel protective mechanisms for S-adenosyl-L-methionine against acetaminophen hepatotoxicity: improvement of key antioxidant enzymatic function

Acetaminophen (APAP) overdose leads to severe hepatotoxicity, increased oxidative stress and mitochondrial dysfunction. S-adenosyl-L-methionine (SAMe) protects against APAP toxicity at a mmol/kg equivalent dose to N-acetylcysteine (NAC). SAMe acts as a principle biological methyl donor and participates in polyamine synthesis which increase cell growth and has a role in mitochondrial protection. The purpose of the current study tested the hypothesis that SAMe protects against APAP toxicity by maintaining critical antioxidant enzymes and markers of oxidative stress. Male C57Bl/6 mice were treated with vehicle (Veh; water 15 ml/kg, ip), SAMe (1.25 mmol/kg, ip), APAP (250 mg/kg, ip), and SAMe+APAP (SAMe given 1 h following APAP). Liver was collected 2 and 4 h following APAP administration; mitochondrial swelling as well as hepatic catalase, glutathione peroxidase (GPx), glutathione reductase, and both Mn- and Cu/Zn-superoxide dismutase (SOD) enzyme activity were evaluated. Mitochondrial protein carbonyl, 3-nitrotyrosine cytochrome c leakage were analyzed by Western blot. SAMe significantly increased SOD, GPx, and glutathione reductase activity at 4 h following APAP overdose. SAMe greatly reduced markers of oxidative stress and cytochrome C leakage following APAP overdose. Our studies also demonstrate that a 1.25 mmol/kg dose of SAMe does not inhibit CYP 2E1 enzyme activity. The current study identifies a plausible mechanism for the decreased oxidative stress observed when SAMe is given following APAP.     

The role of catechol-O-methyltransferase in catechol-enhanced erythroid differentiation of K562 cells

Catechol is widely used in pharmaceutical and chemical industries. Catechol is also one of phenolic metabolites of benzene in vivo. Our previous study showed that catechol improved erythroid differentiation potency of K562 cells, which was associated with decreased DNA methylation in erythroid specific genes. Catechol is a substrate for the catechol-O-methyltransferase (COMT)-mediated methylation. In the present study, the role of COMT in catechol-enhanced erythroid differentiation of K562 cells was investigated. Benzidine staining showed that exposure to catechol enhanced hemin-induced hemoglobin accumulation and induced mRNA expression of erythroid specific genes in K562 cells. Treatment with catechol caused a time- and concentration-dependent increase in guaiacol concentration in the medium of cultured K562 cells. When COMT expression was knocked down by COMT shRNA expression in K562 cells, the production of guaiacol significantly reduced, and the sensitivity of K562 cells to cytotoxicity of catechol significantly increased. Knockdown of COMT expression by COMT shRNA expression also eliminated catechol-enhanced erythroid differentiation of K562 cells. In addition, the pre-treatment with methyl donor S-adenosyl-l-methionine or its demethylated product S-adenosyl-l-homocysteine induced a significant increase in hemin-induced Hb synthesis in K562 cells and the mRNA expression of erythroid specific genes. These findings indicated that O-methylation catalyzed by COMT acted as detoxication of catechol and involved in catechol-enhanced erythroid differentiation of K562 cells, and the production of S-adenosyl-l-homocysteine partly explained catechol-enhanced erythroid differentiation.     

S-adenosyl-L-methionine co-administration prevents the ethanol-elicited dissociation of hepatic mitochondrial ribosomes in male rats

Background:  Chronic ethanol feeding to male rats has been shown to result in decreased mitochondrial translation, depressed respiratory complex levels and mitochondrial respiration rates. In addition, ethanol consumption has been shown to result in an increased dissociation of mitoribosomes. S-adenosyl-L-methionine (SAM) is required for the assembly and subsequent stability of mitoribosomes and is depleted during chronic ethanol feeding. The ability of dietary SAM co-administration to prevent these ethanol-elicited lesions was investigated.
Methods:  Male Sprague-Dawley rats were fed a nutritionally adequate liquid diet with ethanol comprising 36% of the calories according to a pair-fed design for 28 days. For some animals, SAM was supplemented in the diet at 200 mg/l. Liver mitochondria were prepared and mitoribosomes isolated. Respiration rates, ATP levels, respiratory complex levels, and the extent of mitoribosome dissociation were determined.
Results:  Twenty-eight days of ethanol feeding were found to result in decreased SAM content, depressed respiration, and increased mitoribosome dissociation. No changes in mitochondrial protein content; levels of respiratory complexes I, III, and V; complex I activities; and ATP levels were detected. Co-administration of SAM in the diet was found to prevent ethanol-induced SAM depletion, respiration decreases and mitoribosome dissociation.
Conclusions:  Taken together, these findings suggest (1) that mitoribosome dissociation precedes respiratory complex depressions in alcoholic animals and (2) that dietary supplementation of SAM prevents some of the early mitochondrial lesions associated with chronic ethanol consumption.     

Hepatic stellate cells: a target for the treatment of liver fibrosis

Hepatic fibrosis is a wound-healing process that occurs when the liver is injured chronically. Hepatic stellate cells (HSC) are responsible for the excess production of extracellular matrix (ECM) components. The activation of HSC, a key issue in the pathogenesis of hepatic fibrosis, is mediated by various cytokines and reactive oxygen species released from the damaged hepatocytes and activated Kupffer cells. Therefore, inhibition of HSC activation and its related subsequent events, such as increased production of ECM components and enhanced proliferation, are crucial goals for intervention in the hepatic fibrogenesis cascade. This is especially true when the etiology is unknown or there is no established therapy for the cause of the chronic injury. This review explores the rationale for choosing HSC as a target for the pharmacological, molecular, and other novel therapeutics for hepatic fibrosis. One focus of this review is the inhibition of two cytokines, transforming growth factor-β and platelet-derived growth factor, which are important in hepatic fibrogenesis. A number of new agents, such as Chinese herbal recipes and herbal extracts, silymarin, S-adenosyl-l-methionine, polyenylphosphatidylcholine, and pentoxifylline are also discussed. Received: April 3, 2000 / Accepted: April 28, 2000     

Regression of gastroesophageal reflux disease symptoms using dietary supplementation with melatonin, vitamins and aminoacids: comparison with omeprazole

The prevalence of gastroesophageal reflux disease (GERD) is increasing. GERD is a chronic disease and its treatment is problematic. It may present with various symptoms including heartburn, regurgitation, dysphagia, coughing, hoarseness or chest pain. The aim of this study was to investigate if a dietary supplementation containing: melatonin, l-tryptophan, vitamin B6, folic acid, vitamin B12, methionine and betaine would help patients with GERD, and to compare the preparation with 20 mg omeprazole. Melatonin has known inhibitory activities on gastric acid secretion and nitric oxide biosynthesis. Nitric oxide has an important role in the transient lower esophageal sphincter relaxation (TLESR), which is a major mechanism of reflux in patients with GERD. Others biocompounds of the formula display anti-inflammatory and analgesic effects. A single blind randomized study was performed in which 176 patients underwent treatment using the supplement cited above (group A) and 175 received treatment of 20 mg omeprazole (group B). Symptoms were recorded in a diary and changes in severity of symptoms noted. All patients of the group A (100%) reported a complete regression of symptoms after 40 days of treatment. On the other hand, 115 subjects (65.7%) of the omeprazole reported regression of symptoms in the same period. There was statiscally significant difference between the groups (P < 0.05). This formulation promotes regression of GERD symptoms with no significant side effects.     

S-腺苷蛋氨酸改善妊娠肝内胆汁淤积症患者妊娠结局的评价

目的评价S-腺苷蛋氨酸改善妊娠肝内胆汁淤积症患者妊娠结局的作用.方法计算机检索MEDLINE、EMBASE、中国循证医学数据库/Cochrane中心数据库(CEBM/CCD)、Cochrane图书馆(2003年4期)、中国医院数字图书馆和中国数字化期刊万方数据库,手工检索有关S-腺苷蛋氨酸治疗妊娠肝内胆汁淤积症的中英文随机和半随机临床对照试验,检索截止时间为2003年12月.在严格质量评价的基础上,利用RevMan 4.2 软件进行Meta分析.结果共检索到符合纳入标准的文献8篇,包括随机对照试验2篇,半随机对照试验6篇,共有研究对象424例.所有纳入研究的方法学质量均不高.Meta分析结果显示,S-腺苷蛋氨酸改善妊娠肝内胆汁淤积症患者妊娠结局的作用如下:①降低剖宫产率:与安慰剂比较差异无统计学意义[OR=1.00, 95%CI (0.23, 4.33),P=1.00];与地塞米松组及强力宁比较差异有统计学意义,其OR(95%CI)和P值分别为0.44(0.23,0.85),P= 0.01; 0.28 (0.10, 0.75), P=0.01).②延长孕周:与安慰剂比较差异无统计学意义[WMD=0.70,95%CI(=-0.69, 2.10), P=0.32];而与地塞米松、强力宁、肝益灵相比差异有统计学意义,其WMD(95%CI)值和P值分别为1.10 (0.46,1.74), P=0.000 07; 2.50 (1.86,3.14), P≤ 0.000 01; 2.20(1.61,2.79), P≤0.000 01.③增加新生儿体重:与安慰剂比较差异无统计学意义[WMD=-26.27,95%CI(=-338.35,285.82), P=0.87];与地塞米松及苦黄注射液比较差异有统计学意义,其WMD(95%CI)和P值分别为386.86 (134.41,603.31), P=0.02;410.00(321.10,498.90), P≤0.000 01.④胎儿宫内窘迫:与地塞米松和苦黄注射液比较差异无统计学意义,其OR(95%CI)和P值分别为0.47(0.14,1.16),P =0.23;0.44,(0.10,1.97),P =0.29. ⑤降低羊水粪染的发生率:与地塞米松、熊去氧胆酸和苦黄注射液相比差异无统计学意义,其OR(95%CI)和P值分别为0.46(0.21,1.02),P=0.06;0.68(0.20,2.31),P=0.53;0.82(0.24,2.81),P=0.75.⑥新生儿窒息:与地塞米松、苦黄注射液比较差异无统计学意义,其OR(95%CI)和P值分别为0.19 (0.01,4.06),P=0.29和 0.31(0.08,1.13),P=0.08;而与强力宁比较则差异有统计学意义[OR=0.09, 95%CI(0.02,0.42),P=0.002].⑦新生儿Apgar评分:与安慰剂、地塞米松和熊去氧胆酸比较差异无统计学意义,其OR(95%CI)值分别为0.25(0.02,3.04),P=0.28; 2.09(0.70,6.27),P=0.19;1.22 (0.35,4.19),P=0.75.8篇文献中有 6篇文献提到了S-腺苷蛋氨酸治疗妊娠肝内胆汁淤积症是否有副作用,其中1篇报道有轻微的胃肠道反应.结论 S-腺苷蛋氨酸用于治疗妊娠肝内胆汁淤积症可以改善某些妊娠结局,如降低剖宫产率、延长孕周、增加新生儿体重等.但其确切的疗效和安全性尚不能肯定,还需要大样本、高质量的随机对照试验加以证实.     

Catechol metabolites of zeranol and 17β-estradiol: A comparative in vitro study on the induction of oxidative DNA damage and methylation by catechol-O-methyltransferase

α-Zearalanol (α-ZAL, zeranol) is a highly estrogenic macrocyclic β-resorcylic acid lactone, which is used as a growth promotor for cattle in various countries. We have recently reported that α-ZAL and its major metabolite zearalanone (ZAN) are hydroxylated at the aromatic ring by microsomes from human liver in vitro, thereby forming two catechol metabolites each. Thus, the oxidative metabolism of α-ZAL and ZAN resembles that of the endogenous steroidal estrogens 17β-estradiol (E2) and estrone (E1), which also give rise to two catechols each. As these catechol metabolites are believed to mediate the carcinogenicity of E2 and E1 by causing oxidative DNA damage and DNA adducts, their methylation by catechol-O-methyltransferase (COMT) is an important inactivation pathway. Here we report that hepatic microsomes from five species generate catechol metabolites of α-ZAL and ZAN, the highest amounts being formed by human liver microsomes, followed by rat, mouse, steer and swine. The microsomal extracts and the individual catechols of α-ZAL, ZAN, E2 and E1 were found to induce oxidative DNA damage, as measured by the formation of 8-oxo-7,8-dihydro-2′-deoxyguanosine in a cell-free system. The ranking of pro-oxidant activity was 15-HO-ZAN > 15-HO-α-ZAL ≈ 4-HO-E2/E1 ≈ 2-HO-E2/E1 > 13-HO-ZAN > 13-HO-α-ZAL. With respect to the rate of methylation by human hepatic COMT, the ranking was 2-HO-E2/E1 >> 4-HO-E2/E1 > 15-HO-α-ZAL/ZAN >> 13-HO-α-ZAL/ZAN. Thus, some catechol metabolites of α-ZAL and ZAN are better pro-oxidants and poorer substrates of COMT than the catechols of E2 and E1. These findings warrant further investigations into the genotoxic potential of α-ZAL, which may constitute another biological activity in addition to its well-known estrogenicity.     

The antidepressant potential of oral S-adenosyl-l-methionine

S-adenosyl-l-methionine (SAMe), a naturally occurring brain metabolite, has previously been found to be effective and tolerated well in parenteral form as a treatment of major depression. To explore the antidepressant potential of oral SAMe, we conducted an open trial in 20 outpatients with major depression, including those with (n = 9) and without (n = 11) prior history of antidepressant nonresponse. The group as a whole significantly improved with oral SAMe: 7 of 11 non-treatment-resistant and 2 of 9 treatment-resistant patients experienced full antidepressant response. Side effects were mild and transient.