Effects of bacterial lipopolysaccharide on ciclooxygenase activity and expression levels and steroid production in adrenal y1 cells: possible involvement of NF-kB signaling

MARTINEZ CALEJMAN C; ASTORT F; DI GRUCCIO JM; REPETTO EM; MERCAU M; ARIAS P; PIGNATARO OP; CYMERYNG CB

Rio de Janeiro, Brasil

Congreso; 13th International Congress of Endocrinology – ICE 2008; 2008

International Society of Endocrinology (ISE)

Although the increase in glucocorticoid secretion by the adrenal cortex during the inflammatory response to systemic lipopolysaccharide (LPS) administration has been mainly attributed to effects at higher levels of the hypotalamic-pituitary-adrenal (HPA) axis, increasing evidence supports a direct effect of LPS on adrenocortical cells. In this sense, the aim of this study was to analyze the effects of LPS on steroid production by adrenal Y1 cells, as well as the signaling/transduction mechanisms involved. According to our results, this murine adrenal cell line expresses Toll-like 4 receptors, demonstrated by RT-PCR. When  Y1 cells were transfected with a luciferase reporter plasmid containing an NFkB response element, LPS stimulation (10 µg/ml)  resulted in a significant increase in luciferase activity (C: 0,88 ± 0,10; LPS: 2,00 ± 0,09; p<0,0001, n= 3), showing the activation of this signaling pathway. LPS treatment resulted in a significant increase in progesterone production; this effect was blocked by an inhibitor of IKK activity (C: 46,32 ± 2,31;  LPS:  92,98 ± 7,4;  IKK-Inh:  46,94 ± 2,7; LPS + IKK-Inh: 66,99 ± 4 ng/ml;  C vs LPS p< 0.001;  LPS vs LPS + IKK-Inh, p< 0,01). As detected by western blotting, ciclooxygenase-2 (COX-2) expression levels were also increased by LPS.  LPS-stimulated progesterone production was significantly inhibited by two non specific COX inhibitors (indomethacin and diclofenac) and one specific COX-2 inhibitor (parecoxib). In conclusion, our results demonstrate a direct stimulatory effect of LPS on steroid production by adrenal cells. This effect is probably initiated by the interaction of LPS with a Toll-like 4 receptor at the plasma membrane, followed by the nuclear translocation of NFkB and the induction of specific genes. Among them, an increase in the expression levels of COX-2 was also demonstrated. Finally, increased production of arachidonic acid derivatives would result in augmented steroidogenesis.