Endogenous production of nitric oxide by iNOS in human cells restricts inflammatory activation and cholesterol/fatty acid biosynthesis

Nitric oxide (NO) is a bioactive gas that is known to control many physiological processes. In human parenchymal cells, the function of iNOS-derived NO is incompletely understood. Here, we used RNA-seq to examine the role of iNOS-derived NO in the control of gene expression in a human lung epithelial cell line treated with inflammatory cytokines. iNOS-derived NO restricted the expression of genes involved in immune signaling, including the immune-related genes CXCL9 and E-selectin that were not previously known to be inhibited by iNOS. We also determined that iNOS-derived NO inhibits the expression of genes needed for cholesterol/fatty acid biosynthesis in response to cytokine stimulation, a process not previously known to be affected by NO. These findings establish the regulation of immune activation and cholesterol/fatty acid biosynthesis as main functions of iNOS in human parenchymal cells. Overall design: Our aim is to understand how iNOS-derived NO impacts cytokine-induced gene expression in A549 cells. To achieve this, cells were untreated, treated with 1400W (a selective iNOS inhibitor) alone, treated with cytokines or treated with cytokines and 1400W in quadruplicates for 16 hours. Our main findings were established by comparing cytokine-treated and cytokine+1400W-treated cells.