Perfluorooctane sulfonate-induced oxidative stress contributes to pancreatic β-cell apoptosis by inhibiting cyclic adenosine monophosphate pathway: Prevention by pentoxifylline

Abstract

Endocrine-disrupting chemical perfluorooctane sulfonate (PFOS) acute exposure stimulates insulin secretion from pancreatic β-cells. However, chronic exposure to PFOS on pancreatic β-cells, its role in insulin secretion, and the underlying mechanisms have not been studied. We used rat insulinoma INS-1 and human 1.1b4 islet cells to investigate the chronic effects of PFOS on glucose-stimulated insulin secretion and toxicity implicated in the downregulation of β-cell functionality. Chronic exposure of INS-1 cells or human pancreatic 1.1b4 β-cells to PFOS stimulated the small G-protein RAC1-guanosine triphosphate-dependent nicotinamide adenine dinucleotide phosphate oxidase (NOX2/gp91phox) subunit expression and activation. Upregulated NOX2/gp91phox activation led to elevated reactive oxygen species (ROS) production with a decrease in the cyclic adenosine monophosphate/protein kinase A (cAMP/PKA) pathway in both cell types. Inhibition of cAMP/PKA signaling induces β-cell mitochondrial dysfunction and endoplasmic stress via the loss of PDX1-SERCA2B and glucose-stimulated insulin release. Inhibiting RAC1-NOX2/gp91phox activation or elevating cAMP by pentoxifylline, a Food and Drug Administration-approved phosphodiesterase inhibitor, significantly reduced PFOS-induced ROS production and restored insulin secretory function of pancreatic β-cells. Enhanced secretory function in pentoxifylline-treated cells was associated with increased stability of PDX1-SERCA2B protein levels. Intriguingly, inhibition of cAMP/PKA signaling impaired pentoxifylline-induced insulin secretion caused by the activation of ROS production and mitochondrial dysfunction. Overall, our findings show that PFOS has a new and first-ever direct chronic effect on pancreatic β-cell failure through increased RAC1-NOX2/gp91phox activation and pentoxifylline-induced cAMP/PKA signaling, which inhibits PFOS-mediated mitochondrial dysfunction.

Keywords: Diabetes; Endocrine-disrupting chemicals; Insulin secretion; Oxidative stress; Pentoxifylline.