Involvement of TRPM2 and L-type Ca²⁺ channels in Ca²⁺ entry and cell death induced by hydrogen peroxide in rat β-cell line RIN-5F

Abstract

-Ca 2+ overload is one of the mechanisms for H 2 O 2 -induced cell death in rat pancreatic β-cell line RIN-5F cells. RIN-5F cells express TRPM2, which is a Ca 2+ -permeable channel activated by H 2 O 2 , and voltage-dependent L-type Ca 2+ channels, both of which induce Ca 2+ entry by H 2 O 2 . This study examined the contribution of these channels to H 2 O 2 -induced Ca 2+ entry and cell death in RIN-5F cells. Cytosolic Ca 2+ concentration was measured using fura-2 as a Ca 2+ indicator. Cell death was estimated by trypan blue exclusion. Pre-treatment with poly(ADP-ribose) polymerase (PARP) inhibitors, which inhibit TRPM2 activation, strongly reduced Ca 2+ entry by H 2 O 2 . The PARP inhibitors used had no effect on the Ca 2+ elevation by voltage-dependent L-type Ca 2+ channels. On the other hand, pre-treatment with L-type Ca 2+ channel blockers, which did not affect TRPM2 activation, partly reduced H 2 O 2 -induced Ca 2+ entry. Treatment with PARP inhibitors but not L-type Ca 2+ channel blockers, around the early phase in H 2 O 2 -induced Ca 2+ elevation, also reduced the late phase. Moreover, H 2 O 2 -induced RIN-5F cell death was strongly attenuated by PARP inhibitors, in compared to L-type Ca 2+ channel blockers. Our results suggest that TRPM2 channels rather than L-type Ca 2+ channels primarily contribute to H 2 O 2 -induced Ca 2+ entry and cell death.

TRPM2 promotes the proliferation and invasion of pancreatic ductal adenocarcinoma

“…The TRPM2 gene encodes a tetrameric cation channel that is permeable to sodium, calcium and potassium, and is activated by free intracellular adenosine 5′-diphosphate (ADP)-ribose ( 15 , 16 ). The encoded protein, also activated by oxidative stress, may induce susceptibility to cell death ( 17 , 18 ). According to previous studies, TRPM2 may induce apoptosis in different types of cancer ( 19 , 20 ).…”

TRPM2 channel-mediated cell death: An important mechanism linking oxidative stress-inducing pathological factors to associated pathological conditions

“…As discussed above, the activity of nuclear PARP, particularly PARP-1, is crucial for the induction of ADPR generation and subsequent TRPM2 channel activation by ROS and other OS-inducing pathological stimuli. PARP inhibitors have been used in many studies as an alternative or additional means to prevent OS-induced TRPM2-mediated effects [ 36 , 39 , 48 , 74 , 75 , 82 , [121] , [122] , [123] , [124] , [125] , [126] ], including cell death. Example PARP inhibitors include SB-750139, N-(6-oxo-5,6-dihydro-phenanthridin-2-yl)-N,N-dimethylacetamide (PJ34), 3-aminobenzamide (3-AB) and 3,4-dihydro-5-[4-(1-piperidinyl)butoxy]-1(2H)-isoquinolinone (DPQ).…”

“…The TRPM2 channel is widely distributed throughout the body and is highly sensitive to activation by OS-inducing stimuli [ [31] , [32] , [33] ]. A large number of studies have been carried out over the past decades that provide compelling evidence to show that the TRPM2 channel is a key mechanism mediating OS-induced alteration in intracellular Ca 2+ and Zn 2+ homeostasis to disrupt various cellular functions and further support a significant role for aberrant TRPM2 channel activity in diverse OS-associated pathologies [ [34] , [35] , [36] , [37] , [38] , [39] , [40] , [41] , [42] , [43] , [44] , [45] , [46] , [47] , [48] ]. A well-established mechanism, among others, by which the TRPM2 channel contributes to these pathological processes, is to mediate OS-induced cell death.…”

Molecular Regulations and Functions of the Transient Receptor Potential Channels of the Islets of Langerhans and Insulinoma Cells

“…Oxidative stress increases the concentration of ADPR and Ca 2+ in the cytoplasm, which synergize to activate TRPM2 and increase Ca 2+ influx [29,62]. In rat insulinoma cell lines, H 2 O 2 and TNFα cause cell death, which can be inhibited by treatment with antisense-TRPM2 [30,34,63].…”