Expression of peptide YY by human blood leukocytes

•In healthy men, peptide YY mRNA was detected in peripheral blood mononuclear cells.•Human peripheral blood mononuclear cells express peptide YY.•Peptide YY expression is down-regulated by monocyte-to-macrophage differentiation.•Peptide YY expression is down-regulated by proinflammatory stimuli.

Peptide YY is produced by L cells in the mucosa of the distal ileum, colon, and rectum and may have systemic and paracrine functions. We hypothesized that peptide YY is expressed by peripheral blood mononuclear cells. The purpose of the present study was to evaluate the expression of peptide YY mRNA and peptide by peripheral blood mononuclear cells and differentiated THP-1 cells after lipopolysaccharide treatment as an in vitro model of inflammation. Blood was drawn by venipuncture from 18- to 63-year-old healthy male blood donors (n = 63); peptide YY mRNA expression levels were detected in peripheral blood mononuclear cells from all healthy male subjects. In 3 subjects, peripheral blood mononuclear cells were cultured for 3 and 24 h and peptide YY was detected in the cell culture supernatant. In human monocytic THP-1 cells treated with phorbol-12-myristate-13-acetate to induce differentiation to macrophages, treatment with lipopolysaccharide caused down-regulation of peptide YY mRNA levels. In summary, freshly isolated peripheral blood mononuclear cells from healthy humans expressed peptide YY. In vitro data suggested that peptide YY expression is down-regulated by differentiation of monocytes to macrophages and proinflammatory stimuli.