| First Author | Naidu S | Year | 2008 |
| Journal | J Immunol | Volume | 181 |
| Issue | 6 | Pages | 4113-23 |
| PubMed ID | 18768868 | Mgi Jnum | J:139091 |
| Mgi Id | MGI:3807313 | Doi | 10.4049/jimmunol.181.6.4113 |
| Citation | Naidu S, et al. (2008) An atypical NF-kappaB-regulated pathway mediates phorbol ester-dependent heme oxygenase-1 gene activation in monocytes. J Immunol 181(6):4113-23 |
| abstractText | Heme oxygenase (HO)-1 catalyzes the rate-limiting step of heme degradation and plays an important anti-inflammatory role via its enzymatic products carbon monoxide and biliverdin. In this study it is reported that the HO-1 gene is transcriptionally induced by the phorbol ester PMA in cell cultures of monocytic cells with a regulatory pattern that is different from that of LPS-dependent HO-1 induction in these cells. Activation of HO-1 by PMA was mediated via a newly identified kappaB element of the proximal rat HO-1 gene promoter region (-284 to -275). This HO-kappaB element was a nuclear target for the NF-kappaB subunit p65/RelA as determined by nuclear binding assays and transfection experiments with luciferase reporter gene constructs in RAW264.7 monocytes. Moreover, PMA-dependent induction of endogenous HO-1 gene expression and promoter activity was abrogated in embryonic fibroblasts from p65(-/-) mice. PMA-dependent HO-1 gene activation was reduced by an overexpressed dominant negative mutant of IkappaBalpha, but not by dominant negative IkappaB kinase-2, suggesting that the classical NF-kappaB pathway was not involved in this regulation. The antioxidant N-acetylcysteine and inhibitors of p38 MAPK or serine/threonine kinase CK2 blocked PMA-dependent HO-1 gene activation. Finally, it is demonstrated by luciferase assays with a Gal4-CHOP fusion protein that the activation of p38 MAPK by PMA was independent of CK2. Taken together, induction of HO-1 gene expression by PMA is regulated via an IkappaB kinase-independent, atypical NF-kappaB pathway that is mediated via the activation of p38 MAPK and CK2. |
