16, 17 SAH is the substrate for the bidirectional enzyme SAH hydrolase (SAHH) (Supporting Material Fig.). Cu may regulate methionine metabolism through its known

inhibitory effect on SAHH with consequent increase in SAH, the principal inhibitor of transmethylation reactions.12, 13, 18 Cu binds noncompetitively to the SAHH enzyme and reduces its activity by releasing NAD+ cofactors.19 The regulatory role of increased Cu in down-regulation of SAHH activity, with consequent elevation of its substrate SAH and its potential secondary epigenetic effects on gene expression, suggest that methionine metabolism could be the missing link between Cu accumulation and hepatocyte damage in WD. Of note, there has been a growing interest in SAHH due to its relationship with SAH levels ABT-263 and gene expression in hepatic steatosis20 and human SAHH deficiency.21 We hypothesized that by regulating Sahh expression, Cu and its associated hepatic inflammation initiate alterations in methionine metabolism that affect DNA methylation status and potentially the expression of selected genes central to endoplasmic reticulum (ER) stress and

lipid metabolism in WD. To test this hypothesis, we modulated Cu levels and inflammation by administering the Cu chelator penicillamine (PCA) and hepatic methylation status by administering the methyl donor betaine in the tx-j mouse model of WD. CPT1A, carnitine palmitoyltransferase 1A; Cu, copper; DNMT, DNA Talazoparib supplier methyltransferase; ER, endoplasmic reticulum; GRP78, glucose-regulated protein 78; PCA, penicillamine; PPARα, peroxisome proliferator-activated receptor alpha; SAH, S-adenosylhomocysteine; SAHH, S-adenosylhomocysteine hydrolase; SAM, S-adenosylmethionine;

SREBP1c, sterol regulatory element-binding protein 1c; TNF-α, tumor necrosis factor alpha; WD, Wilson’s disease. We used the C3HeB/FeJ-Atp7btx-J/J mouse (tx-j) model of WD with its background strain C3HeB/FeJ (C3H) as a control. The tx-j mouse model has a G712D missense mutation predicted to be in the second transmembrane region of the Atp7B gene, which results in a phenotypic disorder similar to WD.22 Mice in the baseline and PCA experiments were obtained from many the Jackson Laboratory (Bar Harbor, ME), whereas mice in the betaine experiments were obtained from our in-house UC Davis colony that was developed from C3H breeder pairs and homozygous-affected tx-j breeder pairs purchased from the Jackson Laboratory. At 24 weeks of age, seven males from each strain were taken for harvest of blood and tissues and served as control groups for mice in PCA and betaine studies. From age 12 to 24 weeks, a subgroup of seven male tx-j mice received treatment with oral PCA (Sigma Aldrich, St. Louis, MO) that was dissolved in deionized water at 100 mg/kg bodyweight/day, a dose shown to reduce hepatic Cu concentration in a rat model of WD.23 PCA was not administered to control mice since Cu deficiency could independently modify lipid24 and methionine metabolism.