Nitric oxide modulates the expression of matricellular genes involved in fibrosis in renal glomerular mesangial cells

By means of their proliferative and secretory potential glomerular
mesangial cells are thought to be important mediators of glomerular
inflammation and fibrosis. Recent studies have established a direct
role for NO in the regulation of gene expression in different cell
types including mesangial cells. Representational difference
analysis was used to investigate changes in gene expression
elicited by the treatment of S-Nitroso-L-glutathione in rat
mesangial cells. We identified 7 upregulated and 11 downregulated
genes. Four out of 11 downregulated genes, connective tissue growth
factor, thrombospondin-1, collagen type I alpha 1 and collagen type
I alpha 2, are matricellular genes linked to inflammation and
fibrosis of different organs including the kidney. Results were
verified by using Northern blot analysis, quantitative real time
PCR and protein analysis methods in human mesangial cells treated
with a series of NO donors. We validated our findings by inducing
endogenous NO production by cytokine stimulation. Real time PCR
analysis showed that two additional matrix related genes, biglycan
and collagen type IV alpha 2 are also downregulated by NO.
Connective tissue growth factor promoter studies in mesangial cells
demonstrated that NO acts at the transcriptional level to suppress
gene expression. These results reveal a complex role of NO in
regulating gene expression in mesangial cells and suggest an
antifibrotic potential for NO.