Effects of bacterial lipopolysaccharide on cyclooxygenase activity and expression levels and steroid production in adrenal Y1 cells: possible involvement of NFkB signaling

MARTINEZ CALJEMAN, CAMILA; ASTORT, FRANCISCO; DI GRUCCIO, JUAN MARTÍN; REPETTO, ESTEBAN MARTÍN; MERCAU, MARÍA; ARIAS, PABLO; PIGNATARO, OMAR PEDRO; CYMERYNG, CORA BEATRIZ

Rio de Janeiro, Brasil

Congreso; 13th International Congress of Endocrinology; 2008

International Society of Endocrinology

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 NFkappaB 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 lower than 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 lower than 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 NFkappaB 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.