LPS induce HO-1 in adrenocortical cells

ASTORT F.; MARTINEZ CALEJMAN C; MERCAU M.; REPETTO E.M.; ARIAS P.; CYMERYNG C. B.

Miami Beach, EEUU

Congreso; Heme oxygenases in Biology and Medicine - 6th Internacional Congress; 2009

Previous experiments from our laboratory, demonstrating increases in HO-1 mRNA, protein, and activity levels in the adrenal cortex of LPS-treated rats led us to hypothesize that HO-1 activity is involved in the modulation of steroid production stimulated by LPS. As direct effects of LPS on adrenocortical cells have not been addressed, the aim of the present study was to analyze the mechanism of HO-1 induction by LPS in adrenocortical cells (Y1).           The expression of the LPS receptor TLR-4 (RT-PCR) was detected in Y1 cells, its mRNA levels being unaffected by LPS treatment (10 µg/ml for 24 h). HO-1 mRNA and protein (western blot) levels were increased by LPS in a dose dependent way. HO-1 promoter activity was studied with a luciferase reporter plasmid containing 4 kb from the murine promoter of HO-1 [pGL2(-4)HO-1] and NFkB activity was evaluated using a reporter plasmid containing an NFkB response element [pKb/LUC]. LPS-dependent activation of pKb/LUC and pGL2(-4)HO-1 were prevented by co-incubation with the IKK inhibitor, PS-1145. This inhibitor also blocked the LPS dependent increase in steroid production in Y1 cells.           In summary, LPS-dependent HO-1 transcription in adrenocortical cells probably involves NFkB activation, as PS-1145 prevented the activation of both HO-1 and Kb/LUC. Increased HO-1 activity may play two important roles: on the one hand, HO-1 could act as an antioxidant enzyme protecting the cells from oxidative stress arising after LPS stimulation; on the other, HO-1 activity could locally modulate steroidogenesis.