Protective role of nuclear factor kappa B against nitric oxide-induced apoptosis in J774 macrophages

We investigated the role of constitutive transcription factor nuclear facto r kappaB (NF-kappaB) in nitric oxide (NO)-mediated apoptosis in J774 macrop hages, Our results show that NF-kappaB is present in untreated J774 cells i n a form constitutively active. Incubation of cells with sodium nitroprussi de (SNP) and S-nitroso-gluthatione (GSNO), two NO-generating compounds, cau sed: (a) inhibition of constitutive NF-kappaB/DNA binding activity; (b) dec rease of cell viability; (c) DNA fragmentation; (d) ApopTag positivity. Pyr rolidine dithiocarbamate (PDTC) and N-alpha -para-tosyl-L-lysine chlorometh yl ketone (TLCK), two inhibitors of NF-kappaB activation, showed the same e ffects of both NO-generating compounds. Furthermore, SNP and GSNO as well a s PDTC and TLCK significantly increased the cytoplasmic level of I kappaB a lpha. All together these results demonstrate that constitutive NF-kappaB pr otects J774 macrophages from NO-induced apoptosis, Moreover, these findings show, for the first time, that NO-generating compounds may induce apoptosi s in J774 macrophages by down-regulating constitutive NF-kappaB/DNA binding activity and suggest a novel mechanism by which NO induces apoptosis.