Activation of the eIF2 alpha-ATF4 Pathway by Chronic Paracetamol Treatment Is Prevented by Dietary Supplementation with Cysteine

Chronic treatment with acetaminophen (APAP) induces cysteine (Cys) and glutathione (GSH) deficiency which leads to adverse metabolic effects including muscle atrophy. Mammalian cells respond to essential amino acid deprivation through the phosphorylation of the eukaryotic translation initiation factor 2 alpha (eIF2 alpha). Phosphorylated eIF2 alpha leads to the recruitment of activating transcription factor 4 (ATF4) to specific CCAAT/enhancer-binding protein-ATF response element (CARE) located in the promoters of target genes. Our purpose was to study the activation of the eIF2 alpha-ATF4 pathway in response to APAP-induced Cys deficiency, as well as the potential contribution of the eIF2 alpha kinase GCN2 and the effect of dietary supplementation with Cys. Our results showed that chronic treatment with APAP activated both GCN2 and PERK eIF2 alpha kinases and downstream target genes in the liver. Activation of the eIF2 alpha-ATF4 pathway in skeletal muscle was accompanied by muscle atrophy even in the absence of GCN2. The dietary supplementation with cysteine reversed APAP-induced decreases in plasma-free Cys, liver GSH, muscle mass, and muscle GSH. Our new findings demonstrate that dietary Cys supplementation also reversed the APAP-induced activation of GCN2 and PERK and downstream ATF4-target genes in the liver.