Double-stranded RNA-dependent protein kinase is not required for double-stranded RNA-induced nitric oxide synthase expression or nuclear factor-kappaB activation by islets.
Environmental factors, such as viral infection, have been implicated in the destruction of beta-cells during the development of autoimmune diabetes. Double-stranded RNA (dsRNA), produced during viral replication, is an active component of a viral infection that stimulates antiviral responses in infected cells. Previous studies have shown that treatment of rat islets with dsRNA in combination with gamma-interferon (IFN-gamma) results in a nitric oxide-dependent inhibition of glucose-stimulated insulin secretion. This study examines the role of nuclear factor-kappaB (NF-kappaB) and the dsRNA-dependent protein kinase (PKR) in dsRNA + IFN-gamma-induced nitric oxide synthase (iNOS) expression and nitric oxide production by rat, mouse, and human islets. Treatment of rat and human islets with dsRNA in the form of polyinosinic-polycytidylic acid (poly IC) and IFN-gamma resulted in iNOS expression and nitric oxide production. Inhibitors of NF-kappaB activation-the proteasome inhibitor MG-132 and the antioxidant pyrrolidine-dithiocarbamate (PDTC)-prevented poly IC + IFN-gamma-induced iNOS expression and nitric oxide production. Incubation of rat islets for 3 h or human islets for 2 h with poly IC alone or poly IC + IFN-gamma resulted in NF-kappaB nuclear translocation and degradation of the NF-kappaB inhibitor protein, IkappaB, events that are prevented by MG-132. PKR has been shown to participate in dsRNA-induced NF-kappaB activation in a number of cell types, including mouse embryonic fibroblasts. However, poly IC stimulated NF-kappaB nuclear translocation and IkappaB degradation to similar levels in islets isolated from mice devoid of PKR (PKR-/-) and wild-type mice (PKR+/+). Furthermore, the genetic absence of PKR did not affect dsRNA + IFN-gamma-induced iNOS expression, nitric oxide production, or the inhibitory actions of these agents on glucose-stimulated insulin secretion. These results suggest that 1) NF-KB activation is required for dsRNA + IFN-gamma-induced iNOS expression, 2) PKR is not required for either dsRNA-induced NF-kappaB activation or dsRNA + IFN-y-induced iNOS expression by islets, and 3) PKR is not required for dsRNA + IFN-gamma-induced inhibition of glucose-stimulated insulin secretion by islets.
Blair
L A
LA
Edward A. Doisy Department of Biochemistry and Molecular Biology, St Louis University School of Medicine, Missouri 63104, USA.
Heitmeier
M R
MR
Scarim
A L
AL
Maggi
L B
LB
Corbett
J A
JA
D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004338:Drug Combinations; D004790:Enzyme Induction / Q000502:physiology; D005260:Female; D005947:Glucose / Q000494:pharmacology; D006801:Humans; D007328:Insulin / Q000378:metabolism; D000078790:Insulin Secretion; D007371:Interferon-gamma / Q000494:pharmacology; D007515:Islets of Langerhans / Q000187:drug effects / Q000502:physiology*; D007976:Leupeptins / Q000494:pharmacology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D016328:NF-kappa B / Q000502:physiology*; D019001:Nitric Oxide Synthase / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II; D009573:Nitrites / Q000378:metabolism; D011070:Poly I-C / Q000494:pharmacology; D011759:Pyrrolidines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013859:Thiocarbamates / Q000494:pharmacology; D019892:eIF-2 Kinase / Q000172:deficiency / Q000502:physiology*
D000975:Antioxidants; D015853:Cysteine Proteinase Inhibitors; D004338:Drug Combinations; D007328:Insulin; D007976:Leupeptins; D016328:NF-kappa B; D009573:Nitrites; D011759:Pyrrolidines; D013859:Thiocarbamates; C020972:pyrrolidine dithiocarbamic acid; D007371:Interferon-gamma; C496319:NOS2 protein, human; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse; C496318:Nos2 protein, rat; D019892:eIF-2 Kinase; D005947:Glucose; D011070:Poly I-C; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde