Phospholipids in signal transduction of mesangial cells.

Glomerular mesangial cells respond to a variety of hormones, cytokines, and autacoids with an immediate hydrolysis of membrane phospholipids, including phosphatidylinositol, phosphatidylcholine, and phosphatidylethanolamine. Phospholipid metabolites such as inositol phosphates and diacylglycerol serve as initiating signals for subsequent intracellular events, including release of intracellular Ca2+ stores, increased conductance of the plasma membrane to various ions, changes of intracellular pH, and protein phosphorylation. The resting functional responses, including cell contraction and proliferation, are in turn regulated by simultaneous release of bioactive lipids such as eicosanoids and platelet-activating factor, which recognize receptors on both intrinsic glomerular cells and circulating, blood-borne cells. Through this complex signaling network, phospholipid metabolism plays a central regulatory role in mesangial functions in physiological conditions as well as in inflammatory or metabolic derangements of the kidney glomerulus.