Expression of Transient Receptor Potential Ankyrin 1 (TRPA1) and Its Role in Insulin Release from Rat Pancreatic Beta Cells

Abstract

ObjectiveSeveral transient receptor potential (TRP) channels are expressed in pancreatic beta cells and have been proposed to be involved in insulin secretion. However, the endogenous ligands for these channels are far from clear. Here, we demonstrate the expression of the transient receptor potential ankyrin 1 (TRPA1) ion channel in the pancreatic beta cells and its role in insulin release. TRPA1 is an attractive candidate for inducing insulin release because it is calcium permeable and is activated by molecules that are produced during oxidative glycolysis.MethodsImmunohistochemistry, RT-PCR, and Western blot techniques were used to determine the expression of TRPA1 channel. Ca2+ fluorescence imaging and electrophysiology (voltage- and current-clamp) techniques were used to study the channel properties. TRPA1-mediated insulin release was determined using ELISA.ResultsTRPA1 is abundantly expressed in a rat pancreatic beta cell line and freshly isolated rat pancreatic beta cells, but not in pancreatic alpha cells. Activation of TRPA1 by allyl isothiocyanate (AITC), hydrogen peroxide (H2O2), 4-hydroxynonenal (4-HNE), and cyclopentenone prostaglandins (PGJ2) and a novel agonist methylglyoxal (MG) induces membrane current, depolarization, and Ca2+ influx leading to generation of action potentials in a pancreatic beta cell line and primary cultured pancreatic beta cells. Activation of TRPA1 by agonists stimulates insulin release in pancreatic beta cells that can be inhibited by TRPA1 antagonists such as HC030031 or AP-18 and by RNA interference. TRPA1-mediated insulin release is also observed in conditions of voltage-gated Na+ and Ca2+ channel blockade as well as ATP sensitive potassium (KATP) channel activation.ConclusionsWe propose that endogenous and exogenous ligands of TRPA1 cause Ca2+ influx and induce basal insulin release and that TRPA1-mediated depolarization acts synergistically with KATP channel blockade to facilitate insulin release.

Streptozotocin Stimulates the Ion Channel TRPA1 Directly

“…We first monitored blood glucose levels of wild type and Trpa1 Ϫ/Ϫ mice injected intraperitoneally with STZ (180 mg/kg) to determine whether TRPA1 influenced STZ-mediated induction of diabetes (29). STZ (180 mg/kg) induced hyperglycemia of similar severity, onset, and duration in mice of the two genotypes ( Fig.…”

Embryonic thermosensitive TRPA1 determines transgenerational diapause phenotype of the silkworm,Bombyx mori

“…These TRPAs are part of the system of transduction, integration, and rapid response to heat and chemical stimuli (23,27,28,(36)(37)(38). Recent in vitro and in vivo studies have provided evidence that both TRPA1 and TRPV3 channels are expressed in nonneural cells, including skin epithelial cells in vertebrates (39)(40)(41). Furthermore, it has been proposed that TRPV3 in the skin may release diffusible molecules, such as adenosine triphosphate, which would then mediate thermotransduction in skin (41).…”

Effects of methylglyoxal on human cardiac fibroblast: roles of transient receptor potential ankyrin 1 (TRPA1) channels

“…Therefore, to investigate whether TRPA1 can function in cardiac fibroblasts, the [Ca 2ϩ ] i measurement using fura-2 AM was applied. The effects of a dicarbonyl compound MG, an agent to activate TRPA1 (13,26,53) Figure 3B showed the concentration-dependent effects of MG on [Ca 2ϩ ] i . The increased value in F340/F380 measured at the peak level or 2 min after the application of MG with reference to F340/F380 at the resting state was plotted against each concentration of MG.…”