Expression and genotype-dependent catalytic activity of N-acetyltransferase 2 (NAT2) in human peripheral blood mononuclear cells and its modulation by Sirtuin 1

N-acetyltransferase 2 (NAT2) catalyzes the biotransformation of numerous arylamine and hydrazine drugs and carcinogens. Genetic polymorphisms of NAT2 modify drug efficacy and toxicity and susceptibility to diseases such as cancer and type 2 diabetes. Expression of NAT2 has been documented in the liver and gastrointestinal tract but not in other tissues. Deacetylation of cytosolic proteins by sirtuins is a post-translational modification important in regulatory networks of diverse cellular processes. The aim of the present study was to investigate NAT2 expression in peripheral blood mononuclear cells (PBMC) and the effects of NAT2 genotype and Sirtuin 1 (SIRT1). Both NAT2 and SIRT1 proteins were expressed on PBMC. Their expression was more prevalent on CD3+ compared to CD19+ and CD56+ cell populations. N-acetylation capacity of PBMC exhibited a NAT2 gene-dose response toward the N-acetylation of isoniazid. Subjects with rapid NAT2 genotype showed an apparent V-max of 42.1 +/- 2.4; intermediate NAT2 genotypes an apparent V-max of 22.6 +/- 2.2; and slow acetylator NAT2 genotypes an apparent V-max of 19.9 +/- 1.7 nM acetyl-isoniazid/24 h/million cells. The N-acetylation capacity of NAT2 in the presence of SIRT1 enhancer was significantly decreased (p < 0.001), conversely, the transient silencing of SIRT1 resulted in an increase of N-acetylation capacity (p < 0.001). These findings are the first report of NAT2 genotype-dependent expression on PBMC and post-translational modification by SIRT1. These findings constitute a substantial advance in our understanding of human N-acetyltransferase expression and a new much less invasive method for measurement of human NAT2 expression and phenotype.