Crosstalk between nitric oxide synthases and cyclooxygenase 2 in the adrenal cortex of rats under lipopolysaccharide treatment

摘要

The effect of lipopolysaccharide on the modulation of steroid production by adrenal cells has been recently acknowledged. The purpose of this study was to determine the in vivo effects of LPS on adrenal cyclooxygenase 2 (COX-2) expression, analyze its crosstalk with the nitric oxide synthase (NOS) system, and assess its involvement on the modulation of glucocoiticoid production. Male Wistar rats were injected with LPS and with specific inhibitors for NOS and COX activities. PGE_2 and cortico-sterone levels were determined by RIA. Protein levels were analyzed by immunoprecipitation and western blotting. Transfection assays were performed in murine adrenocor-tical Yl cells. Results show that LPS treatment increases PGE_2 production and COX-2 protein levels in the rat adrenal cortex. Systemic inhibition of COX-2 blunted the gluco-corticoid response to ACTH, as well as the increase in NOS activity and the NOS-2 expression levels induced by LPS. Conversely, NOS inhibition prevented the LPS-dependent increase in PGE_2 production, COX-2 protein levels, and the nitrotyrosine modification of COX-2 protein. Treatment of adrenocortical cells with a NO-donor significantly potentiated the LPS-dependent increase in NFkB activity and COX-2 expression levels. In conclusion, our results show a significant crosstalk between COX-2 and NOS in the adrenal cortex upon LPS stimulation, in which each activity has a positive impact on the other. In particular, as both the activities differently affect adrenal steroid production, we hypothesize that this kind of fine modulation enables the gland to adjust steroidogenesis to prevent either an excessive or an insufficient response to the endotoxin challenge.