Nuclear response of pancreatic islets to interleukin-1 beta.
The mechanisms by which interleukin-1 (IL-1) exerts destructive action on the pancreatic islet beta-cells remain elusive. Fragmentation of DNA leading to the activation of poly(ADP-ribose) synthetase was investigated in the present study, by assessing the nuclear response to cytokines in rat pancreatic islets. Nuclear fractions display Mg(2+)-dependent poly(ADP-ribose) synthetase activity catalyzing the incorporation of [adenine-U-14C]NAD, with Ka and Km for Mg2+ and NAD amounting to 0.86 mM and 0.43 mM, respectively. Exposure of the nuclear fraction to rIL-1 beta (10 IU/ml) provoked DNA strand breaks and increased nuclear poly(ADP-ribose) synthetase activity (148.4%, P < 0.01). In intact islets, this nuclear response was observed after 18 h culture in medium containing rIL-1 beta, with a concomitant decrease in NAD (88.5%). Brief periods of pre-incubation (90 min) with rIL-1 beta were unable to induce any nuclear activity. Under these conditions, the presence of IFN-alpha (24 U/ml) and TNF (120 U/ml) was necessary to induce a response to rIL-1 beta. Under the latter experimental conditions, a decrease in NAD content was also observed. The nuclear effects of IL-1 beta were modified by nicotinamide (10 mM), an inhibitor of poly(ADP-ribose) synthetase. It is thus conceivable that an increase in poly(ADP-ribose) synthetase activity together with DNA break is implicated in the beta cytotoxic effect of interleukin-1 beta.
Fernández-Alvarez
J
J
Endocrinology and Diabetes Unit, Hospital Clínic, University of Barcelona, Spain.
Tomás
C
C
Casamitjana
R
R
Gomis
R
R
D000225:Adenine / Q000378:metabolism; D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism*; D002478:Cells, Cultured; D003470:Culture Media; D004247:DNA / Q000378:metabolism; D004249:DNA Damage; D007375:Interleukin-1 / Q000494:pharmacology*; D007515:Islets of Langerhans / Q000648:ultrastructure*; D008274:Magnesium / Q000494:pharmacology; D008297:Male; D009243:NAD / Q000378:metabolism; D009536:Niacinamide / Q000494:pharmacology; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D011994:Recombinant Proteins / Q000494:pharmacology; D013997:Time Factors
D003470:Culture Media; D007375:Interleukin-1; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D011994:Recombinant Proteins; D009243:NAD; D009536:Niacinamide; D004247:DNA; D011065:Poly(ADP-ribose) Polymerases; D008274:Magnesium; D000225:Adenine