Mechanisms of beta-cell death in response to double-stranded (ds) RNA and interferon-gamma: dsRNA-dependent protein kinase apoptosis and nitric oxide-dependent necrosis.
Viral infection is one environmental factor that has been implicated as a precipitating event that may initiate beta-cell damage during the development of diabetes. This study examines the mechanisms by which the viral replicative intermediate, double-stranded (ds) RNA impairs beta-cell function and induces beta-cell death. The synthetic dsRNA molecule polyinosinic-polycytidylic acid (poly IC) stimulates beta-cell DNA damage and apoptosis without impairing islet secretory function. In contrast, the combination of poly IC and interferon (IFN)-gamma stimulates DNA damage, apoptosis, and necrosis of islet cells, and this damage is associated with the inhibition of glucose-stimulated insulin secretion. Nitric oxide mediates the inhibitory and destructive actions of poly IC + IFN-gamma on insulin secretion and islet cell necrosis. Inhibitors of nitric oxide synthase, aminoguanidine, and N(G)-monomethyl-L-arginine, attenuate poly IC + IFN-gamma-induced DNA damage to levels observed in response to poly IC alone, prevent islet cell necrosis, and prevent the inhibitory actions on glucose-stimulated insulin secretion. N(G)-monomethyl-L-arginine fails to prevent poly IC- and poly IC + IFN-gamma-induced islet cell apoptosis. PKR, the dsRNA-dependent protein kinase that mediates the antiviral response in infected cells, is required for poly IC- and poly IC + IFN-gamma-induced islet cell apoptosis, but not nitric oxide-mediated islet cell necrosis. Alone, poly IC fails to stimulate DNA damage in islets isolated from PKR-deficient mice; however, nitric oxide-dependent DNA damage induced by the combination of poly IC + IFN-gamma is not attenuated by the genetic absence of PKR. These findings indicate that dsRNA stimulates PKR-dependent islet cell apoptosis, an event that is associated with normal islet secretory function. In contrast, poly IC + IFN-gamma-induced inhibition of glucose-stimulated insulin secretion and islet cell necrosis are events that are mediated by islet production of nitric oxide. These findings suggest that at least one IFN-gamma-induced antiviral response (islet cell necrosis) is mediated through a PKR-independent pathway.
Scarim
A L
AL
Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, Missouri 63104, USA.
Arnush
M
M
Blair
L A
LA
Concepcion
J
J
Heitmeier
M R
MR
Scheuner
D
D
Kaufman
R J
RJ
Ryerse
J
J
Buller
R M
RM
Corbett
J A
JA
D000818:Animals; D017209:Apoptosis / Q000502:physiology; D016923:Cell Death / Q000502:physiology; D002478:Cells, Cultured; D004249:DNA Damage / Q000502:physiology; D004357:Drug Synergism; D005947:Glucose / Q000494:pharmacology; D007328:Insulin / Q000378:metabolism; D000078790:Insulin Secretion; D007371:Interferon-gamma / Q000494:pharmacology*; D007515:Islets of Langerhans / Q000378:metabolism / Q000502:physiology* / Q000648:ultrastructure; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout / Q000235:genetics; D008854:Microscopy, Electron; D009336:Necrosis; D009569:Nitric Oxide / Q000502:physiology; D011070:Poly I-C / Q000494:pharmacology*; D011494:Protein Kinases / Q000502:physiology; D012330:RNA, Double-Stranded / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D019892:eIF-2 Kinase / Q000502:physiology
D007328:Insulin; D012330:RNA, Double-Stranded; D009569:Nitric Oxide; D007371:Interferon-gamma; D011494:Protein Kinases; D019892:eIF-2 Kinase; D005947:Glucose; D011070:Poly I-C