Prenatal exposure to benzo(a)pyrene impairs later-life cortical neuronal function.

Prenatal exposure to environmental contaminants, such as benzo(a)pyrene [B(a)P] has been shown to impair brain development. The overarching hypothesis of our work is that glutamate receptor subunit expression is crucial for cortical evoked responses and that prenatal B(a)P exposure modulates the temporal developmental expression of glutamatergic receptor subunits in the somatosensory cortex. To characterize prenatal B(a)P exposure on the development of cortical function, pregnant Long Evans rats were exposed to low-level B(a)P (300 microg/kg BW) by oral gavage on gestational days 14-17. At this exposure dose, there was no significant effect of B(a)P on (1) the number of pups born per litter, (2) the pre-weaning growth curves and (3) initial and final brain to body weight ratios. Control and B(a)P-exposed offspring were profiled for B(a)P metabolites in plasma and whole brain during the pre-weaning period. No detectable levels of metabolites were found in the control offspring. However, a time-dependent decrease in total metabolite concentration was observed in B(a)P-exposed offspring. On PND100-120, cerebrocortical mRNA expression was determined for the glutamatergic NMDA receptor subunit (NR2B) in control and B(a)P-exposed offspring. Neural activity was also recorded from neurons in primary somatic sensory (barrel) cortex. Semiquantitative PCR from B(a)P-exposed offspring revealed a significant 50% reduction in NR2B mRNA expression in B(a)P-exposed offspring relative to controls. Recordings from B(a)P-exposed offspring revealed that N-methyl-d-aspartate (NMDA) receptor-dependent neuronal activity in barrel cortex evoked by whisker stimulation was also significantly reduced (70%) as compared to controls. Analysis showed that the greatest deficit in cortical neuronal responses occurred in the shorter latency epochs from 5 to 20 ms post-stimulus. The results suggest that in utero exposure to benzo(a)pyrene results in diminished mRNA expression of the NMDA NR2B receptor subunit to result in late life deficits in cortical neuronal activity in the offspring. The findings from this study lead to a strong prediction that in utero exposure to benzo(a)pyrene at a time when synapses are first formed and adjusted in strength by activity in the sensory pathways will produce a strong negative effect on brain function in offspring progeny.

N-demethyl-clarithromycin induced HeLa apoptosis through regulating Akt and ERK activity / 中国药理学通报

Aim To study the mechanisms of N-demethyl-clarithromycin-induced apoptosis in human cervical cancer cell line HeLa. Methods MTT, photomicroscopical observation, DNA agarose gel electrophoresis, LDH release and Western blot were used for apoptosis assay. Results N-demethyl-clarithromycin inhibited growth of HeLa in a time-dependent manner. Apoptotic bodies were found with Hoechst 33258 staining after treatment with 60 ?mol?L-1 N-demethyl-clarithromycin. DNA fragmentation was observed in N-demethyl-clarithromycin treated HeLa cells. The Akt inhibitor and the ERK inhibitor (PD98059) increased cell death. The expression of anti-apoptotic protein Akt, phosphorylated-Akt, ERK and phosphorylated-ERK decreased. Conclusion N-demethyl-clarithromycin induces HeLa apoptosis through Akt and ERK expression and phosphorylation.