Meeting Abstract
Exposure to chemotherapeutic agents has been linked to the increased risk of type 2 diabetes (T2D), a metabolic disease defined as both the peripheral insulin resistance and impaired glucose-stimulated insulin secretion (GSIS) from pancreatic beta cells. Using clonal rat pancreatic &beta-cell line, INS-1 832/13 cells, we investigated the effects of the chemotherapeutic drug doxorubicin on pancreatic &beta-cell survival and function. We analyzed the effects of time- and dose-dependency of doxorubicin exposure on insulin secretion, cellular viability and toxicity. Toxicity (measured as leakage of intracellular protease and cell titer blue reduction) and apoptosis (measured as caspase 3/7 enzymatic activity) were both significantly increased after 6 h of doxorubicin exposure; glucose utilization was also impaired. Oxidative stress did not play a major role in the induction of toxicity, as doxorubicin failed to undergo redox cycling and appreciably increase hydrogen peroxide levels in INS-1 832/13 cells. Doxorubicin was reduced in vitro by cytoplasmic fractions in a NAD(P)H-dependent manner, indicative of bioreductive metabolism of this compound. In live INS-1 832/13 cells, doxorubicin caused a significant decrease in the total NAD+ pool, consistent with the activation of the poly-ADP ribose polymerase (PARP) pathway, which consumes NAD+ to repair DNA damage and leads to programmed cell death if activated in excess. Treatment of INS-1 832/13 cells with the PARP inhibitor MK-4827 ameliorated doxorubicin-dependent reductions in cell viability and NAD+ pool. These data suggest that PARP activation rather than oxidative stress induction is the major mechanism of doxorubicin toxicity in pancreatic &beta-cells.
