Transient activation of protein kinase C contributes to fluoride-induced apoptosis of rat erythrocytes

Abstract

Role of PKC in fluoride-induced apoptosis of rat erythrocytes was studied in vitro and in vivo. Treatment of erythrocytes with 5mM NaF for 1–24h caused progressive accumulation of cytosolic Ca2+ and PS exposure at outer membrane surface. After 1h, these processes were suppressed by PKC inhibitors staurosporine, GF 109203X and chelerythrine, but increased by PKC activator PMA. Following 24h, NaF-induced Ca2+ uptake and PS externalization were partly prevented by PMA or staurosporine, but not by GF 109293X and chelerythrine. Application of PP inhibitor OA augmented NaF-induced cell responses within 1h, but not after 24h. Incubation of erythrocytes with 0.1–10mM NaF for 1h produced a dose-dependent PKCα translocation from cytosol to membranes with appearance of active PKM fragment. 24h NaF exposure led to complete loss of cytosolic PKCα and proteolysis of membrane PKCα. Besides, NaF weakly stimulated membrane PKCζ, although its subcellular distribution was not altered. Thus, transient PKCα activation/translocation positively contributes to NaF-induced apoptosis in vitro. Consumption of 2–20ppm fluoride by the rats for 12months also induced dose-dependent PKCα translocation to membranes and activation of membrane PKCζ, what indicates that PKC stimulation is an important physiological mechanism of fluoride toxicity.