UP-REGULATION OF INOS MESSENGER-RNA EXPRESSION AND INCREASED PRODUCTION OF NO IN HUMAN MONOBLAST CELL-LINE, U937 TRANSFECTED BY HTLV-I TAX GENE

We investigated the mRNA expression of inducible nitric oxide synthase (iNOS) and the production of nitric oxide (NO) in human T cell lympho tropic virus type I (HTLV-I) p40(tax)-transfected U937 cells, a human monoblast cell line. Transfection of HTLV-I p40(tax) U937 cells induce d up-regulation of iNOS mRNA expression and subsequent NO production. Furthermore, interferon gamma (IFN-gamma) stimulation of HTLV-I p40(ta x)-transfected U937 cells enhanced iNOS mRNA expression and NO product ion. The kinetics of iNOS mRNA expression and NO production indicated maximal effect at 24 and 48 hours, respectively, after culture with or without IFN-gamma. These findings suggest that HTLV-I p40(tax) can ac t as a transactivator of NO production in cells of Mo/M phi lineage. T o what extent this mechanism may be involved in the pathogenesis of HT LV-I-associated diseases warrants further investigation.