Nitric oxide synthase isoform expression in acute versus chronic anti-Thy 1 nephritis

Two inbred Lewis rat substrains (LEW/Moe, LEW/Maa) were identified responding differently to induction of anti-Thy 1 glomerulonephritis (aThy 1-GN). LEW/Moe rats show an acute mesangioproliferative glomerulonephritis with rapid healing of glomerular lesions within four weeks, while LEW/Maa rats develop severe glomerular injury followed by chronic glomerular sclerosis and persistent albuminuria. We investigated whether the glomerular expression pattern of nitric oxide synthase (NOS) isoforms could explain these substrain-related differences.

Rats (N = 5 to 7 per group) were investigated in a time course experiment. Severity of aThy 1-GN was determined by albuminuria measurements, glomerular matrix score and microaneurysm formation. Glomerular gene expression of NOS isoforms was determined by semiquantitative RT-PCR. Inducible NOS (iNOS) activity was determined in cultured glomeruli and peritoneal macrophages. Neuronal NOS (nNOS) protein expression was detected by Western blotting and enzyme histochemistry. Plasma renin activity (PRA) was measured by RIA.

Induction of iNOS expression and activity was found significantly increased and sustained in LEW/Maa vs. LEW/Moe rats associated with an increased number of infiltrating macrophages and with an increased capacity of iNOS-expression and iNOS-activation by isolated macrophages in LEW/Maa rats. Glomerular nNOS mRNA and nNOS protein expression were constitutively increased in LEW/Maa rats. Renal nNOS localization was restricted to the macula densa region in both substrains and associated with increased PRA in LEW/Maa rats. No difference in glomerular endothelial NOS-mRNA expression between the substrains was observed.

Increased glomerular iNOS and nNOS expression were associated with chronic anti-Thy 1 glomerulonephritis in LEW/Maa rats and may contribute to glomerular damage by separate mechanisms.