Poly(ADP-ribose) polymerase gene disruption conferred mice resistant to streptozotocin-induced diabetes

Abstract

Streptozotocin (STZ), a glucose analogue known to induce diabetes in experimental animals, causes DNA strand breaks and subsequent activation of poly(ADPribose) polymerase (Parp). Because Parp uses NAD as a substrate, extensive DNA damage will result in reduction of cellular NAD level. In fact, STZ induces NAD depletion and cell death in isolated pancreatic islets in vitro. Activation of Parp therefore is thought to play an important role in STZ-induced diabetes. In the present study, we established Parp-deficient (Parp ؊/؊ ) mice by disrupting Parp exon 1 by using the homologous recombination technique. These mice were used to examine the possible involvement of Parp in STZ-induced ␤-cell damage in vivo. The wild-type (Parp ؉/؉ ) mice showed significant increases in blood glucose concentration from 129 mg͞dl to 218, 370, 477, and 452 mg͞dl on experimental days 1, 7, 21, and 60, respectively, after a single injection of 180 mg STZ͞kg body weight. In contrast, the concentration of blood glucose in Parp ؊/؊ mice remained normal up to day 7, slightly increased on day 21, but returned to normal levels on day 60. STZ injection caused extensive necrosis in the islets of Parp ؉/؉ mice on day 1, with subsequent progressive islet atrophy and loss of functional ␤ cells from day 7. In contrast, the extent of islet ␤-cell death and dysfunction was markedly less in Parp ؊/؊ mice. Our findings clearly implicate Parp activation in islet ␤-cell damage and glucose intolerance induced by STZ in vivo.Various types of DNA damage produced by many environmental chemicals or reactive oxygen species generated by inflammatory reactions contribute to insulin-dependent diabetes mellitus (IDDM) through the induction of ␤-cell death in pancreatic islets (1-3). Acute exposure to streptozotocin [2-deoxy-2-(3-methyl-3-nitrosourea)l-D-glucopyranose, STZ] induces massive ␤-cell death and diabetes mellitus in experimental animals (4, 5). STZ also causes a rapid depletion of cellular NAD in islets (6-9), but this depletion is prevented by injection of nicotinamide immediately before or soon after the administration of STZ (10). Okamoto and colleagues (2, 11) demonstrated that STZ induces DNA strand breaks and activation of poly(ADP-ribose) polymerase (Parp) with subsequent reduction of NAD levels in the isolated pancreatic islets in vitro. These findings suggest the involvement of Parp as a key molecule in STZ-induced ␤-cell death and diabetes through extensive poly(ADP-ribose) formation and NAD depletion, leading to reduction of ATP level and cell death. In agreement with this hypothesis, Parp inhibitors such as 3-aminobenzamide or nicotinamide prevent the depletion of NAD and induction of STZ-induced ␤-cell death (12, 13). However, because Parp inhibitors possess other effects, such as scavenging hydrogen peroxide (14), it is not clear whether and how Parp activity contributes to ␤-cell death and the development of diabetes in vivo. Thus, engineering of a Parp-deficient animal model would be useful for investigating the role of Parp in S...

Genetic control of non obese diabetic mice susceptibility to high-dose streptozotocin-induced diabetes

“…Whereas PARP-1 activation and subsequent NAD + depletion have been implicated as a major mechanism of HDS-induced pancreatic beta-cell destruction [27,28,29], we did not detect any linkage of NOD HDSsusceptiblity to the D1Mit36 (92.3 cM) and D1Mit407 (101.5 cM) markers surrounding the corresponding gene at 98.6 cM in chromosome 1. This result is not really surprising since our previous studies showed that, in the NOD mouse, PARP-1 activation was not required for HDS-induced diabetes [6].…”

The mechanisms of alloxan- and streptozotocin-induced diabetes

“…Also, mice deficient in PARP are resistant to beta cell death mediated by streptozotocin, in spite of DNA fragmentation. The absence of PARP prevents the depletion of the cofactor NAD + and the subsequent loss of ATP [84,[88][89][90] and thus cell death.…”

Streptozotocin Upregulates GAD67 Expression in MIN6N8a Mouse Beta Cells

“…The whole cell extracts or nuclear extracts were prepared [34] and then the proteins were fractionated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The proteins were electrotransferred into Immobilon-P (Millipore Co, Bedford, MA, USA).…”

“…Damage to DNA by STZ (due to the DNA alkylating activity of its methyl nitrosourea moiety [30]) depletes NAD+, which in turn inhibits insulin biosynthesis and secretion and leads to beta cell death through energy depletion [32]. This conclusion is further supported by the observations that the mice deficient in poly (ADP-ribose) polymerase (PARP) are resistant to STZ-mediated beta-cell death [33][34][35].…”