Selective inhibition of l kappaB alpha phosphorylation and HIV-1 LTR-directed gene expression by novel antioxidant compounds.
Oxidative stress activates the NF-kappaB/Rel transcription factors which are involved in the activation of numerous immunoregulatory genes and the human immunodeficiency virus type 1 (HIV-1) long terminal repeat (LTR). In the present study, we examined the effects of established and novel compounds including antioxidants, ribonucleotide reductase inhibitors, and iron chelators on NF-kappaB activation and HIV LTR-mediated gene expression induced by TNF-alpha. N-Acetylcysteine (NAC), pyrrolidinedithiocarbamate (PDTC), and Trimidox (TD) at various concentrations inhibited TNF-alpha-induced NF-kappaB binding in Jurkat cells. Pretreatment of cells with these compounds prior to stimulation prevented I kappaB alpha degradation. Phosphorylation of I kappaB alpha, a prerequisite for its signal-induced degradation, was abrogated in these cells, indicating that oxidative stress is an essential step in the NF-kappaB activation pathway. On the other hand, iron chelators desferrioxamine, pyridoxal isonicotinoyl hydrazone (PIH), and salicylaldehyde isonicotinoyl hydrazone (SIH) showed no inhibition of TNF-alpha-induced NF-kappaB DNA-binding activity. Synergistic induction of HIV-1 LTR-mediated gene expression by TNF-alpha and the HIV-1 transactivator Tat in Jurkat cells was significantly suppressed in the presence of NAC and TD, but not PDTC. The inhibition of NAC and TD on LTR-directed gene expression was diminished when NF-kappaB-binding sites in the LTR were deleted, indicating that these compounds affected the NF-kappaB component of the synergism. Iron chelators PIH and SIH also showed some inhibitory effect on LTR-mediated gene activation, presumably through an NF-kappaB-independent mechanism. These experiments demonstrate that TD, at concentration 50 times lower than the effective concentration of NAC, potently inhibits NF-kappaB activity and suppresses HIV LTR expression.
Lee
R
R
Lady Davis Institute for Medical Research, Department of Microbiology, McGill University, Montreal, Quebec, Canada.
Beauparlant
P
P
Elford
H
H
Ponka
P
P
Hiscott
J
J
D000975:Antioxidants / Q000494:pharmacology*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D015967:Gene Expression Regulation, Viral / Q000187:drug effects*; D015658:HIV Infections / Q000378:metabolism / Q000821:virology*; D015497:HIV-1 / Q000187:drug effects* / Q000235:genetics*; D006801:Humans; D020672:I-kappa B Proteins; D019169:Jurkat Cells; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000235:genetics*; D012091:Repetitive Sequences, Nucleic Acid / Q000235:genetics*; D015533:Transcriptional Activation
D000975:Antioxidants; D004268:DNA-Binding Proteins; D020672:I-kappa B Proteins; D016328:NF-kappa B; C000606204:NFKBIA protein, human; D000072000:NF-KappaB Inhibitor alpha