The Regulatory Pathways of Nitric Oxide Production in Glomeruli Podocytes

Abstract

Nitric Oxide (NO) is a major paracrine and autocrine signaling molecule. In the kidney, it can be released by the glomerulus and regulates microvascular hemodynamics in concert with antagonistic vasoactive substances such as angiotensin II (Ang II). Strong changes in glomerular NO production, which can be triggered by inflammation, oxidative stress or other factors, can lead to glomerular epithelial cells (podocytes) damage and subsequent alteration of glomerular filtration rate resulting in severe proteinuria. Because NO production is primarily Ca2+-dependent, we focused on the studies of the role of Ca2+ handling and NO production in response to different paracrine factors in the podocytes. The podocytes of freshly isolated glomeruli from the kidneys of Dahl salt-sensitive rats were labeled with a combination of NO and intracellular Ca2+ ionophores (DAF-FM and Fura Red, respectively) to monitor changes in fluorescence with the use of confocal microscopy. Paracrine molecules (ATP, Ang II, ET-1 and H2O2) were applied to the glomeruli to determine the effects on Ca2+ handling and NO release. To determine the specificity of the responses, control experiments were performed using a NO production blocker, L-NAME, which resulted in an attenuation of NO production. Both Ang II and H2O2 significantly increase NO production. In contrast, ATP and ET-1 have not affected NO level in glomeruli. These effects seemed to be localized to the podocyte foot processes, where they may be involved in altering glomerular permeability.