Corticosterone affects the differentiation of a neuronal cerebral cortex-derived cell line through modulation of the nicotinic acetylcholine receptor.

Chronic exposure to stress hormones has an impact on brain structures relevant to cognition. Nicotinic acetylcholine receptors (AChRs) are involved in numerous cognitive processes including learning and memory formation. In order to better understand the molecular mechanisms of chronic stress-triggered mental disease, the effect of corticosterone (CORT) on the biology of AChRs was studied in the neuronal cell line CNh. We found that chronic treatment with CORT reduced the expression levels of the α7-type neuronal AChR and, to a lesser extent, of α4-AChR. CORT also delayed the acquisition of the mature cell phenotype in CNh cells. Chronic nicotine treatment affected the differentiation of CNh cells and exerted a synergistic effect with CORT, suggesting that AChR could participate in signaling pathways that control the cell cycle. Overexpression of α7-AChR-GFP abolished the CORT effects on the cell cycle and the specific α7-AChR inhibitor, methyllycaconitine, mimicked the proliferative action exerted by CORT. Whole-cell voltage-clamp recordings showed a significant decrease in nicotine-evoked currents in CORT-treated cells. Taken together, these observations indicate that AChRs, and the α7-AChR in particular, could act as modulators of the differentiation of CNh cells and that CORT could impair the acquisition of a mature phenotype by affecting the function of this AChR subtype.

Osmotic stress sensitizes naturally resistant cells to TNF-alpha-induced apoptosis.

Most cells are naturally resistant to TNF-alpha-induced cell death and become sensitized when NF-kappaB transactivation is blocked or in the presence of protein synthesis inhibitors that prevent the expression of anti-apoptotic genes. In this report we analyzed the role of osmotic stress on TNF-alpha-induced cell death. We found that it sensitizes the naturally resistant HeLa cells to TNF-alpha-induced apoptosis, with the involvement of an increase in the activity of several kinases, the inhibition of Bcl-2 expression, and a late increase on NF-kappaB activation. Cell death occurs regardless of the enhanced NF-kappaB activity, whose inhibition produces an increase in apoptosis. The inhibition of p38 kinase, also involved in NF-kappaB activation, significantly increases the effect of osmotic stress on TNF-alpha-induced cell death.