Enhanced expression of haem oxygenase-1 by nitric oxide and antiinflammatory drugs in NIH 3T3 fibroblasts

1 Haem oxygenase-l (HO-1) can exert protective effects against oxidative st ress and inflammation. Fibroblasts participate in inflammatory responses wh ere they produce high levels of prostaglandins (PGs) and nitric oxide (NO). However, little is known of the presence of HO-1 in these cells and the po ssible interactions among these pathways. Incubation of cells with NO donor s, spermine nonoate (SPNO) and S-nitroso-N-acetylpenicillamine (SNAP), indu ced a dose- and time-dependent expression of HO-1 protein. 2 NO donors increased basal PGE(2) release although they reduced PGE, accum ulated in the medium and cyclo-oxygenase (COX) activity when cells were sti mulated with lipopolysaccharide (LPS). COX-2 protein was weakly induced by SPNO in basal conditions and in the presence of LPS a synergy for HO-1 and COX-2 protein expression was observed. 3 Our results indicate that reactive oxygen species participate in the indu ctive effect of NO donors or LPS on HO-1 expression, whereas endogenous NO production may play a role in the mechanism of the synergy exhibited by SPN O and LPS on HO-1 and COX-2 expression. In this system, zinc protoporphyrin IX did not affect nitrite levels but reduced COX activity. 4 The selective COX-2 inhibitors SC58125 and NS398 as well as the non-selec tive COX inhibitor, indomethacin, strongly reduced PGE(2) synthesis and sho wed a synergy with NO donors in HO-1 and COX-2 induction. Addition of PGE(2 ) had no effect, suggesting a mechanism independent of PGs formation. 5 In inflammatory conditions a number of factors could cooperate to induce HO-1 and COX-2, with a positive regulation by COX inhibitors.