Pb2+ reduces PKCs and NF-kappaB in vitro

The mechanism of lead (Pb(2+))-induced neurotoxicity has not yet been fully elucidated. The purpose of this study was to examine the effects of Pb(2+) on several protein kinase C (PKC) isoforms and the nuclear factor-kappaB (NF-kappaB)-I-kappaB kinase-alpha (IKK-alpha) axis in cultured neuronal cells. Neurons were isolated from rat fetal brain at the 18th day of gestation of pregnant Sprague Dawley rats and cultured for 10 days before use. Neurons were exposed to Pb(2+) at concentrations of 10(-10), 10(-9), 10(-8), and 10(-7) mol/L for 14 h and antigens of typical PKC-alpha,beta,gamma; novel PKC (epsilon, delta), atypical PKC (lambda), NF-kappaB (p50), and IKK-alpha were enriched by immunoprecipitation and determined by western blotting. Total, calcium-dependent and independent PKC activities were also determined by counting the transferred gamma-(32) P in the substrate-histone. The results indicated that inorganic Pb(2+) significantly reduced all PKC isoforms (alpha,beta,gamma, epsilon, lambda) except delta, inhibiting the total, calcium-dependent and calcium-independent PKC activities in a dose-dependent manner. Additionally, Pb(2+) gradually reduced NF-kappaB (p50) and IKK-alpha protein levels. This suggests that Pb(2+) exhibits varying preference for individual PKC isoforms but reduces the NF-kappaB-IKK-alpha axis to a similar extent.