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Molecular and Cellular Biology, August 2001, p. 5605-5613, Vol. 21, No. 16
Department of Diabetes and Endocrinology,
Princess Alexandra Hospital, Woolloongabba, Brisbane 4102, Australia,1 and CRC Carcinogenesis
Group, Paterson Institute for Cancer Research, Christie Hospital (NHS)
Trust, Manchester, M20 4BX,2 and
Department of Clinical Biochemistry, Manchester Royal
Infirmary, Manchester M13 9WL,3 United Kingdom
Received 15 December 2000/Returned for modification 23 March
2001/Accepted 8 May 2001
Type 1 diabetes is thought to occur as a result of the loss of
insulin-producing pancreatic
0270-7306/01/$04.00+0 DOI: 10.1128/MCB.21.16.5605-5613.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Increased Susceptibility to Streptozotocin-Induced
-Cell
Apoptosis and Delayed Autoimmune Diabetes in
Alkylpurine- DNA-N-Glycosylase-Deficient Mice
cells by an environmentally triggered
autoimmune reaction. In rodent models of diabetes, streptozotocin (STZ), a genotoxic methylating agent that is targeted to the
cells,
is used to trigger the initial cell death. High single doses of STZ
cause extensive
-cell necrosis, while multiple low doses induce
limited apoptosis, which elicits an autoimmune reaction that
eliminates the remaining cells. We now show that in mice lacking the
DNA repair enzyme alkylpurine-DNA-N-glycosylase (APNG),
-cell necrosis was markedly attenuated after a single dose of STZ.
This is most probably due to the reduction in the frequency of base
excision repair-induced strand breaks and the consequent activation of
poly(ADP-ribose) polymerase (PARP), which results in catastrophic ATP
depletion and cell necrosis. Indeed, PARP activity was not induced in
APNG
/
islet cells following treatment with STZ in
vitro. However, 48 h after STZ treatment, there was a peak of
apoptosis in the
cells of APNG
/
mice.
Apoptosis was not observed in PARP-inhibited APNG+/+ mice,
suggesting that apoptotic pathways are activated in the absence
of significant numbers of DNA strand breaks. Interestingly, STZ-treated
APNG
/
mice succumbed to diabetes 8 months after
treatment, in contrast to previous work with PARP inhibitors, where a
high incidence of
-cell tumors was observed. In the
multiple-low-dose model, STZ induced diabetes in both
APNG
/
and APNG+/+ mice; however, the
initial peak of apoptosis was 2.5-fold greater in the
APNG
/
mice. We conclude that APNG substrates are
diabetogenic but by different mechanisms according to the status of
APNG activity.
*
Corresponding author. Mailing address: CRC
Carcinogenesis Group, Paterson Institute for Cancer Research, Christie
Hospital (NHS) Trust, Manchester M20 4BX, United Kingdom. Phone:
44-161-446-3124. Fax: 44-161-446-3109. E-mail:
relder{at}picr.man.ac.uk.
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