Oxidative stress affects responsiveness to hypotonicity of renal cells

Oxidative stress plays a critical role in the pathophysiology of several kidney diseases and is the consequence of alterations like ischemic events. The regulatory volume decrease (RVD) is an homeostatic response essential to many cells, including renal cells, to counteract changes in the osmolarity of the external medium. The aim of the present work is to verify whether oxidative stress affects RVD in a model of renal cells (human embryonic kidney cells, HEK 293 Phoenix). To accomplish this aim, the experimental procedure consisted in: i) cell culture preparation and treatment with 200 μM H₂O₂; and ii) measurement of cell volume changes in isotonic conditions or following hypotonic stress. H₂O₂ added to the extracellular isotonic solution induced a significant reduction in cell volume, and added to the extracellular hypotonic solution dramatically impaired the expected osmotic cell swelling. Pre-incubation of cells in an extracellular isotonic solution containing H₂O₂ prevented cell from swelling after hypotonic stress application. In conclusion, H₂O₂ leads to cell shrinkage in isotonic conditions, inhibits the hypotonicity-induced cell swelling and consequently prevents RVD, hypothetically due to an activation of transport pathways determining ion loss and, in turn, water efflux. Cell shrinkage in isotonic conditions is a hallmark of apoptosis and is known as the apoptotic volume decrease.