Inhibition of NF-kappaB by IkappaB prevents cytokine-induced NO production and promotes enterocyte apoptosis in vitro.
Nuclear factor-kappaB (N-kappaB) plays a key role in gut inflammation. NF-kappaB up-regulates proinflammatory genes encoding cytokines, adhesion molecules, and inducible nitric oxide synthase (iNOS). However, NF-kappaB has also been shown to up-regulate protective or anti-apoptotic factors. We utilized an adenoviral vector carrying a super-repressor form of the inhibitor of NF-kappaB, IkappaB, to examine the effects of NF-kappaB inhibition on cytokine-induced nitric oxide production and apoptosis in rat small intestinal epithelial cells (IEC-6). Chemical inhibitors of NF-kappaB, including pyrrolidine dithiocarbamate (PDTC), tosyl-lysine-chloromethylketone (TLCK), genistein, and N-acetyl-leu-leu-norleucinal (n-LLnL) were also utilized. Treatment of AdIkappaB-transfected cells with cytomix [1000 U/mL IFN-gamma, 1 nM IL-1beta, and 10 ng/mL tumor necrosis factor alpha (TNFalpha)] or TNFalpha-containing cytokine combinations resulted in inhibition of cytokine-induced nitrite production and a marked increase in apoptosis compared to control cells. Apoptosis occurred independently of nitric oxide (NO) production since exogenous sources of NO did not inhibit apoptosis. Inducible NOS and clAP were down-regulated in AdIkappaB-transfected cells treated with cytomix. TLCK and LLnL treatment also induced apoptosis in cytomix-treated cells, while PDTC and genistein did not. Thus, although NF-kappaB up-regulates various pro-inflammatory genes, it may also have protective or anti-apoptotic effects in enterocytes. NF-kappaB appears necessary for upregulating cIAP in IEC-6 cells upon cytokine exposure.
Potoka
D A
DA
Department of Surgery, Children's Hospital of Pittsburgh and the University of Pittsburgh School of Medicine, Pennsylvania 15213, USA.
Nadler
E P
EP
Zhou
X
X
Zhang
X R
XR
Upperman
J S
JS
Ford
H R
HR
D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D002478:Cells, Cultured; D003546:Cysteine Endopeptidases / Q000187:drug effects / Q000378:metabolism; D016207:Cytokines / Q000502:physiology*; D020895:Enterocytes / Q000166:cytology* / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D019833:Genistein / Q000494:pharmacology; D020672:I-kappa B Proteins / Q000235:genetics / Q000378:metabolism*; D007976:Leupeptins / Q000494:pharmacology; D009097:Multienzyme Complexes / Q000187:drug effects / Q000378:metabolism; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000187:drug effects / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II; D009573:Nitrites / Q000378:metabolism; D010396:Penicillamine / Q000031:analogs & derivatives / Q000494:pharmacology; D046988:Proteasome Endopeptidase Complex; D021381:Protein Transport; D011759:Pyrrolidines / Q000494:pharmacology; D051381:Rats; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D013859:Thiocarbamates / Q000494:pharmacology; D014107:Tosyllysine Chloromethyl Ketone / Q000494:pharmacology; D015854:Up-Regulation
D016207:Cytokines; D004791:Enzyme Inhibitors; D020672:I-kappa B Proteins; D007976:Leupeptins; D009097:Multienzyme Complexes; D016328:NF-kappa B; D009363:Neoplasm Proteins; D020030:Nitric Oxide Donors; D009573:Nitrites; D011759:Pyrrolidines; D011994:Recombinant Proteins; C110881:S-nitro-N-acetylpenicillamine; D013859:Thiocarbamates; C030193:immunosuppressive acidic protein; C063261:acetylleucyl-leucyl-norleucinal; D014107:Tosyllysine Chloromethyl Ketone; C020972:pyrrolidine dithiocarbamic acid; D009569:Nitric Oxide; D019833:Genistein; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496318:Nos2 protein, rat; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; D010396:Penicillamine