Human peritoneal mesothelial cells produce nitric oxide: Induction by cytokines

Objective: To investigate the induction of nitric oxide synthase type II (i NOS) in human peritoneal mesothelial cells (HPMC) using cytokines and bacte rial lipopolysaccharide (LPS). Design: Confluent monolayers of HPMC were exposed to cytokines [tumor necro sis factor alpha (TNF alpha), interleukin-1beta (IL-1 beta), interferon gam ma (IFN gamma)]or LPS, individually or in various double and triple combina tions, for 24 - 72 hours. Concentrations of nitrate and nitrite in the medi a were quantified using the Griess reaction and used as indirect indices of nitric oxide (NO) production. The expression of iNOS was assessed using re verse transcriptase-polymerase chain reaction (RT-PCR) and Western blot. Results: Neither single cytokines nor LPS was able to induce iNOS mRNA or N O production. Both double combinations of TNF alpha + IFN gamma and IL-1 be ta + IFN gamma were able to induce iNOS mRNA expression, but only TNF alpha + IFN gamma induced significant NO production. The triple combination of T NF alpha + IFN gamma + IL-1 beta induced even more NO production than TNF a lpha + IFN gamma. There was no constitutive NO synthase type III (eNOS) exp ression in HPMC. Conclusions: Certain combinations of cytokines could stimulate cultured HPM C to produce NO, and HPMC might be a source of intraperitoneal NO productio n during peritonitis.