Activation of an H2O2-generating NADH Oxidase in Human Lung Fibroblasts by Transforming Growth Factor β1

The signaling pathways involved in the long-term metabolic effects of angiotensin II (Ang II) in vascular smooth muscle cells are incompletely understood but include the generation of molecules likely to affect oxidase activity. We examined the ability of Ang II to stimulate superoxide anion formation and investigated the identity of the oxidases responsible for its production. Treatment of vascular smooth muscle cells with Ang II for 4 to 6 hours caused a 2.7 +/- 0.4-fold increase in intracellular superoxide anion formation as detected by lucigenin assay. This superoxide appeared to result from activation of both the NADPH and NADH oxidases. NADPH oxidase activity increased from 3.23 +/- 0.61 to 11.80 +/- 1.72 nmol O2-/min per milligram protein after 4 hours of Ang II, whereas NADH oxidase activity increased from 16.76 +/- 2.13 to 45.00 +/- 4.57 nmol O2-/min per milligram protein. The NADPH oxidase activity was stimulated by exogenous phosphatidic and arachidonic acids and was partially inhibited by the specific inhibitor diphenylene iodinium. NADH oxidase activity was increased by arachidonic and linoleic acids, was insensitive to exogenous phosphatidic acid, and was inhibited by high concentrations of quinacrine. Both of these oxidases appear to reside in the plasma membrane, on the basis of migration of the activity after cellular fractionation and their apparent insensitivity to the mitochondrial poison KCN. These observations suggest that Ang II specifically activates enzyme systems that promote superoxide generation and raise the possibility that these pathways function as second messengers for long-term responses, such as hypertrophy or hyperplasia.

Glomerulonephritis is an inflammation of the kidney characterized by the accumulation of extracellular matrix within the damaged glomeruli, impaired filtration and proteinuria. In its progressive form, the disease destroys kidney function leading to uraemia and death, unless dialysis therapy or kidney transplantation is available. The pathogenesis of glomerulonephritis is incompletely understood, but the eliciting factor is thought often to be an immunological injury to mesangial and/or other resident cells in the glomeruli. We have used an animal model of acute mesangial proliferative glomerulonephritis to show that this disease is associated with increased production and activity of transforming growth factor beta 1 (TGF-beta 1), an inducer of extracellular matrix production. Here we report that administration of anti-TGF-beta 1 at the time of induction of the glomerular disease suppresses the increased production of extracellular matrix and dramatically attenuates histological manifestations of the disease. These results provide direct evidence for a causal role of TGF-beta 1 in the pathogenesis of the experimental disease and suggest a new approach to the therapy of glomerulonephritis.