EXPRESSION OF HEME OXYGENASE AND INDUCIBLE NITRIC-OXIDE SYNTHASE MESSENGER-RNA IN HUMAN BRAIN-TUMORS

Heme oxygenase-1, a key enzyme in heme catabolism, and inducible nitri c oxide synthase (iNOS) are responsible for production of carbon monox ide and nitric oxide (NO), respectively. Expression of each enzyme has been shown to be modulated by heme and NO, raising a possibility for the coordinated regulation of the two enzymes. We therefore analyzed t he expression levels of both mRNA in humans using brain tumors. Either heme oxygenase-l or iNOS mRNA was expressed at higher levels in brain tumors compared to the brain tissue, but their expression levels were not apparently correlated. Tn the brain tumor cell lines, treatment w ith cytokines increased the expression of iNOS mRNA but not heme oxyge nase 1 mRNA, whereas treatment with an NO donor increased the expressi on of heme oxygenase-l mRNA but not MOS mRNA. These results suggest th e separate regulation of expression of both enzyme mRNA in humans. (C) 1996 Academic Press, Inc.