Temporal study of acetaminophen (APAP) and S-adenosyl-L-methionine (SAMe) effects on subcellular hepatic SAMe levels and methionine adenosyltransferase (MAT) expression and activity

Methionine Cycle Rewiring by Targeting miR-873-5p Modulates Ammonia Metabolism to Protect the Liver from Acetaminophen

Drug-induced liver injury (DILI) development is commonly associated with acetaminophen (APAP) overdose, where glutathione scavenging leads to mitochondrial dysfunction and hepatocyte death. DILI is a severe disorder without effective late-stage treatment, since N-acetyl cysteine must be administered 8 h after overdose to be efficient. Ammonia homeostasis is altered during liver diseases and, during DILI, it is accompanied by decreased glycine N-methyltransferase (GNMT) expression and S-adenosylmethionine (AdoMet) levels that suggest a reduced methionine cycle. Anti-miR-873-5p treatment prevents cell death in primary hepatocytes and the appearance of necrotic areas in liver from APAP-administered mice. In our study, we demonstrate a GNMT and methionine cycle activity restoration by the anti-miR-873-5p that reduces mitochondrial dysfunction and oxidative stress. The lack of hyperammoniemia caused by the therapy results in a decreased urea cycle, enhancing the synthesis of polyamines from ornithine and AdoMet and thus impacting the observed recovery of mitochondria and hepatocyte proliferation for regeneration. In summary, anti-miR-873-5p appears to be an effective therapy against APAP-induced liver injury, where the restoration of GNMT and the methionine cycle may prevent mitochondrial dysfunction while activating hepatocyte proliferative response.

Perinatal Acetaminophen Exposure and Childhood Attention-Deficit/Hyperactivity Disorder (ADHD): Exploring the Role of Umbilical Cord Plasma Metabolites in Oxidative Stress Pathways

Oxidative stress mechanisms may explain associations between perinatal acetaminophen exposure and childhood attention-deficit hyperactivity disorder (ADHD). We investigated whether the changes in umbilical cord plasma amino acids needed to synthesize the antioxidant glutathione and in the oxidative stress biomarker 8-hydroxy-deoxyguanosine may explain the association between cord plasma acetaminophen and ADHD in the Boston Birth Cohort (BBC). Mother–child dyads were followed at the Boston Medical Center between 1998 and 2018. Cord plasma analytes were measured from archived samples collected at birth. Physician diagnoses of childhood ADHD were obtained from medical records. The final sample consisted of 568 participants (child mean age [SD]: 9.3 [3.5] years, 315 (52.8%) male, 248 (43.7%) ADHD, 320 (56.3%) neurotypical development). Cord unmetabolized acetaminophen was positively correlated with methionine (R = 0.33, p < 0.001), serine (R = 0.30, p < 0.001), glycine (R = 0.34, p < 0.001), and glutamate (R = 0.16, p < 0.001). Children with cord acetaminophen levels >50th percentile appeared to have higher risk of ADHD for each increase in cord 8-hydroxy-deoxyguanosine level. Adjusting for covariates, increasing cord methionine, glycine, serine, and 8-hydroxy-deoxyguanosine were associated with significantly higher odds for childhood ADHD. Cord methionine statistically mediated 22.1% (natural indirect effect logOR = 0.167, SE = 0.071, p = 0.019) and glycine mediated 22.0% (natural indirect effect logOR = 0.166, SE = 0.078, p = 0.032) of the association between cord acetaminophen >50th percentile with ADHD. Our findings provide some clues, but additional investigation into oxidative stress pathways and the association of acetaminophen exposure and childhood ADHD is warranted.

Effects of caffeine on brain antioxidant status and mitochondrial respiration in acetaminophen-intoxicated mice

Hepatic encephalopathy is a pathophysiological complication of acute liver failure, which may be triggered by hepatotoxic drugs such as acetaminophen (APAP). Although APAP is safe in therapeutic concentration, APAP overdose may induce neurotoxicity, which is mainly associated with oxidative stress. Caffeine is a compound widely found in numerous natural beverages. However, the neuroprotective effect of caffeine remains unclear during APAP intoxication. The present study aimed to investigate the possible modulatory effects of caffeine on brain after APAP intoxication. Mice received intraperitoneal injections of APAP (250 mg/kg) and/or caffeine (20 mg/kg) and, 4 h after APAP administration, samples of brain and blood were collected for the biochemical analysis. APAP enhanced the transaminase activity levels in plasma, increased oxidative stress biomarkers (lipid peroxidation and reactive oxygen species), promoted an imbalance in endogenous antioxidant system in brain homogenate and increased the mortality. In contrast, APAP did not induce dysfunction of the mitochondrial bioenergetics. Co-treatment with caffeine modulated the biomarkers of oxidative stress as well as antioxidant system in brain. Besides, survival assays demonstrated that caffeine protective effects could be dose- and time-dependent. In addition, caffeine promoted an increase of mitochondrial bioenergetics response in brain by the enhancement of the oxidative phosphorylation, which could promote a better energy supply necessary for brain recovery. In conclusion, caffeine prevented APAP-induced biochemical alterations in brain and reduced lethality in APAP-intoxicated mice, these effects may relate to the preservation of the cellular antioxidant status, and these therapeutic properties could be useful in the treatment of hepatic encephalopathy induced by APAP intoxication.

Induction of Mkp-1 and Nuclear Translocation of Nrf2 by Limonoids from Khaya grandifoliola C.DC Protect L-02 Hepatocytes against Acetaminophen-Induced Hepatotoxicity

Drug-induced liver injury (DILI) is a major clinical problem where natural compounds hold promise for its abrogation. Khaya grandifoliola (Meliaceae) is used in Cameroonian traditional medicine for the treatment of liver related diseases and has been studied for its hepatoprotective properties. Till date, reports showing the hepatoprotective molecular mechanism of the plant are lacking. The aim of this study was therefore to identify compounds from the plant bearing hepatoprotective activity and the related molecular mechanism by assessing their effects against acetaminophen (APAP)-induced hepatotoxicity in normal human liver L-02 cells line. The cells were exposed to APAP (10 mM) or co-treated with phytochemical compounds (40 μM) over a period of 36 h and, biochemical and molecular parameters assessed. Three known limonoids namely 17-epi-methyl-6-hydroxylangolensate, 7-deacetoxy-7-oxogedunin and deacetoxy-7R-hydroxygedunin were identified. The results of cells viability and membrane integrity, reactive oxygen species generation and lipid membrane peroxidation assays, cellular glutathione content determination as well as expression of cytochrome P450 2E1 demonstrated the protective action of the limonoids. Immunoblotting analysis revealed that limonoids inhibited APAP-induced c-Jun N-terminal Kinase phosphorylation (p-JNK), mitochondrial translocation of p-JNK and Bcl₂-associated X Protein, and the release of Apoptosis-inducing Factor into the cytosol. Interestingly, limonoids increased the expression of Mitogen-activated Protein Kinase Phosphatase (Mkp)-1, an endogenous inhibitor of JNK phosphorylation and, induced the nuclear translocation of Nuclear Factor Erythroid 2-related Factor-2 (Nrf2) and decreased the expression of Kelch-like ECH-associated Protein-1. The limonoids also reversed the APAP-induced decreased mRNA levels of Catalase, Superoxide Dismutase-1, Glutathione-S-Transferase and Methionine Adenosyltransferase-1A. The obtained results suggest that the isolated limonoids protect L-02 hepatocytes against APAP-induced hepatotoxicity mainly through increase expression of Mkp-1 and nuclear translocation of Nrf2. Thus, these compounds are in part responsible of the hepatoprotective activity of K. grandifoliola and further analysis including in vivo and toxicological studies are needed to select the most potent compound that may be useful as therapeutic agents against DILI.

New therapeutic approach: diphenyl diselenide reduces mitochondrial dysfunction in acetaminophen-induced acute liver failure

The acute liver failure (ALF) induced by acetaminophen (APAP) is closely related to oxidative damage and depletion of hepatic glutathione, consequently changes in cell energy metabolism and mitochondrial dysfunction have been observed after APAP overdose. Diphenyl diselenide [(PhSe)₂], a simple organoselenium compound with antioxidant properties, previously demonstrated to confer hepatoprotection. However, little is known about the protective mechanism on mitochondria. The main objective of this study was to investigate the effects (PhSe)₂ to reduce mitochondrial dysfunction and, secondly, compare in the liver homogenate the hepatoprotective effects of the (PhSe)₂ to the N-acetylcysteine (NAC) during APAP-induced ALF to validate our model. Mice were injected intraperitoneal with APAP (600 mg/kg), (PhSe)₂ (15.6 mg/kg), NAC (1200 mg/kg), APAP+(PhSe)₂ or APAP+NAC, where the (PhSe)₂ or NAC treatment were given 1 h following APAP. The liver was collected 4 h after overdose. The plasma alanine and aspartate aminotransferase activities increased after APAP administration. APAP caused a remarkable increase of oxidative stress markers (lipid peroxidation, reactive species and protein carbonylation) and decrease of the antioxidant defense in the liver homogenate and mitochondria. APAP caused a marked loss in the mitochondrial membrane potential, the mitochondrial ATPase activity, and the rate of mitochondrial oxygen consumption and increased the mitochondrial swelling. All these effects were significantly prevented by (PhSe)₂. The effectiveness of (PhSe)₂ was similar at a lower dose than NAC. In summary, (PhSe)₂ provided a significant improvement to the mitochondrial redox homeostasis and the mitochondrial bioenergetics dysfunction caused by membrane permeability transition in the hepatotoxicity APAP-induced.

Analysis of changes in hepatic gene expression in a murine model of tolerance to acetaminophen hepatotoxicity (autoprotection)

Pretreatment of mice with a low hepatotoxic dose of acetaminophen (APAP) results in resistance to a subsequent, higher dose of APAP. This mouse model, termed APAP autoprotection was used here to identify differentially expressed genes and cellular pathways that could contribute to this development of resistance to hepatotoxicity. Male C57BL/6J mice were pretreated with APAP (400mg/kg) and then challenged 48h later with 600mg APAP/kg. Livers were obtained 4 or 24h later and total hepatic RNA was isolated and hybridized to Affymetrix Mouse Genome MU430_2 GeneChip. Statistically significant genes were determined and gene expression changes were also interrogated using the Causal Reasoning Engine (CRE). Extensive literature review narrowed our focus to methionine adenosyl transferase-1 alpha (MAT1A), nuclear factor (erythroid-derived 2)-like 2 (Nrf2), flavin-containing monooxygenase 3 (Fmo3) and galectin-3 (Lgals3). Down-regulation of MAT1A could lead to decreases in S-adenosylmethionine (SAMe), which is known to protect against APAP toxicity. Nrf2 activation is expected to play a role in protective adaptation. Up-regulation of Lgals3, one of the genes supporting the Nrf2 hypothesis, can lead to suppression of apoptosis and reduced mitochondrial dysfunction. Fmo3 induction suggests the involvement of an enzyme not known to metabolize APAP in the development of tolerance to APAP toxicity. Subsequent quantitative RT-PCR and immunochemical analysis confirmed the differential expression of some of these genes in the APAP autoprotection model. In conclusion, our genomics strategy identified cellular pathways that might further explain the molecular basis for APAP autoprotection.

Wilson's disease: changes in methionine metabolism and inflammation affect global DNA methylation in early liver disease

Hepatic methionine metabolism may play an essential role in regulating methylation status and liver injury in Wilson's disease (WD) through the inhibition of S-adenosylhomocysteine hydrolase (SAHH) by copper (Cu) and the consequent accumulation of S-adenosylhomocysteine (SAH). We studied the transcript levels of selected genes related to liver injury, levels of SAHH, SAH, DNA methyltransferases genes (Dnmt1, Dnmt3a, Dnmt3b), and global DNA methylation in the tx-j mouse (tx-j), an animal model of WD. Findings were compared to those in control C3H mice, and in response to Cu chelation by penicillamine (PCA) and dietary supplementation of the methyl donor betaine to modulate inflammatory and methylation status. Transcript levels of selected genes related to endoplasmic reticulum stress, lipid synthesis, and fatty acid oxidation were down-regulated at baseline in tx-j mice, further down-regulated in response to PCA, and showed little to no response to betaine. Hepatic Sahh transcript and protein levels were reduced in tx-j mice with consequent increase of SAH levels. Hepatic Cu accumulation was associated with inflammation, as indicated by histopathology and elevated serum alanine aminotransferase (ALT) and liver tumor necrosis factor alpha (Tnf-α) levels. Dnmt3b was down-regulated in tx-j mice together with global DNA hypomethylation. PCA treatment of tx-j mice reduced Tnf-α and ALT levels, betaine treatment increased S-adenosylmethionine and up-regulated Dnmt3b levels, and both treatments restored global DNA methylation levels.

CONCLUSION

Reduced hepatic Sahh expression was associated with increased liver SAH levels in the tx-j model of WD, with consequent global DNA hypomethylation. Increased global DNA methylation was achieved by reducing inflammation by Cu chelation or by providing methyl groups. We propose that increased SAH levels and inflammation affect widespread epigenetic regulation of gene expression in WD.

Metabolic aspects of epigenome: coupling of S-adenosylmethionine synthesis and gene regulation on chromatin by SAMIT module

Histone and DNA methyltransferases utilize S-adenosyl-L-methionine (SAM), a key intermediate of sulfur amino acid metabolism, as a donor of methyl group. SAM is biosynthesized by methionine adenosyltransferase (MAT) using two substrates, methionine and ATP. Three distinct forms of MAT (MATI, MATII and MATIII), encoded by two distinct genes (MAT1A and MAT2A), have been identified in mammals. MATII consists of α2 catalytic subunit encoded by MAT2A and β regulatory subunit encoded by MAT2B, but the physiological function of the β subunit is not clear. MafK is a member of Maf oncoproteins and functions as both transcription activator and repressor by forming diverse heterodimers to bind to DNA elements termed Maf recognition elements. Proteomics analysis of MafK-interactome revealed its interaction with both MATIIα and MATIIβ. They are recruited specifically to MafK target genes and are required for their repression by MafK and its partner Bach1. Because the catalytic activity of MATIIα is required for the MafK target gene repression, MATIIα is suggested to provide SAM locally on chromatin where it is recruited. One of the unexpected features of MATII is that MATIIα interacts with many chromatin-related proteins of diverse functions such as histone modification, chromatin remodeling, transcription regulation, and nucleo-cytoplasmic transport. MATIIα appears to generate multiple, heterogenous regulatory complexes where it provides SAM. Considering their function, the heterooligomer of MATIIα and β is named SAMIT (SAM-integrating transcription) module within their interactome where it serves SAM for nuclear methyltransferases.

The role of S-adenosyl methionine in preventing FOLFOX-induced liver toxicity: a retrospective analysis in patients affected by resected colorectal cancer treated with adjuvant FOLFOX regimen

BACKGROUND

Hepatic toxicity is often related to chemotherapy agent administration, and it represents one of the principal causes of dose reduction and chemotherapy delays or discontinuation. S-Adenosyl methionine (AdoMet) supplementation is effective in the treatment of a variety of liver injuries, but it has never been evaluated in the prevention of chemotherapy-induced liver damage.

PATIENTS AND METHODS

A total of 105 patients affected by resected colorectal cancer (CRC) were enrolled. Forty-five were treated with FOLFOX IV adjuvant regimen without administering AdoMet, 60 were treated with the same regimen plus supplementation with AdoMet. Liver enzyme levels were assessed before starting the treatment and every therapy cycle. Liver toxicity, chemotherapy course delays, discontinuations and dose reductions due to liver toxicity were recorded.

RESULTS

Aspartate aminotransferase (AST) (p < 0.001), alanine transaminase (ALT) (p = 0.003), bilirubin (p = 0.04) and gamma-glutamyltransferase (γ-GT) (p = 0.002) median level at the end of adjuvant therapy were significantly lower in patients treated with Adome. Patients supplemented with AdoMet experimented a lower grade of liver toxicity (p = 0.002) and had a reduced need of course delay (p < 0.0001) and dose reduction (p = 0.031).

CONCLUSIONS

The results of our study demonstrate a protective effect of AdoMet supplementation in patients affected by resected CRC treated with FOLFOX IV adjuvant regimen.