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Background and Purpose: Many cancer cells depend on anti-apoptotic B-cell lymphoma 2 (Bcl-2) proteins for their survival. Bcl-2 antagonism through Bcl-2 homology 3 (BH3) mimetics has emerged as a novel anti-cancer therapy. ABT-199 (Venetoclax), a recently developed BH3 mimetic that selectively inhibits Bcl-2, was introduced into the clinic for treatment of relapsed chronic lymphocytic leukaemia. Early generations of Bcl-2 inhibitors evoked sustained Ca2+ responses in pancreatic acinar cells (PACs) inducing cell death. Therefore, BH3 mimetics could potentially be toxic for the pancreas when used to treat cancer. Although ABT-199 was shown to kill Bcl-2-dependent cancer cells without affecting intracellular Ca2+ signalling, its effects on PACs have not yet been determined. Hence, it is essential and timely to assess whether this recently approved anti-leukaemic drug might potentially have pancreatotoxic effects.Experimental Approach: Single-cell Ca2+ measurements and cell death analysis were performed on isolated mouse PACs.Key Results: Inhibition of Bcl-2 via ABT-199 did not elicit intracellular Ca2+ signalling on its own or potentiate Ca2+ signalling induced by physiological/pathophysiological stimuli in PACs. Although ABT-199 did not affect cell death in PACs, under conditions that killed ABT-199-sensitive cancer cells, cytosolic Ca2+ extrusion was slightly enhanced in the presence of ABT-199. In contrast, inhibition of Bcl-xL potentiated pathophysiological Ca2+ responses in PACs, without exacerbating cell death.Conclusion and Implications: Our results demonstrate that apart from having a modest effect on cytosolic Ca2+ extrusion, ABT-199 does not substantially alter intracellular Ca2+ homeostasis in normal PACs and should be safe for the pancreas during cancer treatment.Linked Articles: This article is part of a themed section on Mitochondrial Pharmacology: Featured Mechanisms and Approaches for Therapy Translation. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.22/issuetoc. [ABSTRACT FROM AUTHOR]

ABSTRACT [ABSTRACT FROM AUTHOR]

Alcohol-related acute pancreatitis can be mediated by a combination of alcohol and fatty acids (fatty acid ethyl esters) and is initiated by a sustained elevation of the Ca2+ concentration inside pancreatic acinar cells ([Ca2+]i), due to excessive release of Ca2+ stored inside the cells followed by Ca2+ entry from the interstitial fluid. The sustained [Ca2+]i elevation activates intracellular digestive proenzymes resulting in necrosis and inflammation. We tested the hypothesis that pharmacological blockade of store-operated or Ca2+ release-activated Ca2+ channels (CRAC) would prevent sustained elevation of [Ca2+]i and therefore protease activation and necrosis. In isolated mouse pancreatic acinar cells, CRAC channels were activated by blocking Ca2+ ATPase pumps in the endoplasmic reticulum with thapsigargin in the absence of external Ca2+. Ca2+ entry then occurred upon admission of Ca2+ to the extracellular solution. The CRAC channel blocker developed by GlaxoSmithKline, GSK-7975A, inhibited store-operated Ca2+ entry in a concentration-dependent manner within the range of 1 to 50 μM (IC50 = 3.4 μM), but had little or no effect on the physiological Ca2+ spiking evoked by acetylcholine or cholecystokinin. Palmitoleic acid ethyl ester (100 μM), an important mediator of alcohol-related pancreatitis, evoked a sustained elevation of [Ca2+]i, which was markedly reduced by CRAC blockade. Importantly, the palmitoleic acid ethyl ester-induced trypsin and protease activity as well as necrosis were almost abolished by blocking CRAC channels. There is currently no specific treatment of pancreatitis, but our data show that pharmacological CRAC blockade is highly effective against toxic [Ca2+]i elevation, necrosis, and trypsin/protease activity and therefore has potential to effectively treat pancreatitis. [ABSTRACT FROM AUTHOR]

BH3 mimetics are small-molecule inhibitors of B-cell lymphoma-2 (Bcl-2) and Bcl-xL, which disrupt the heterodimerisation of anti- and pro-apoptotic Bcl-2 family members sensitising cells to apoptotic death. These compounds have been developed as anti-cancer agents to counteract increased levels of Bcl-2 proteins often present in cancer cells. Application of a chemotherapeutic drug supported with a BH3 mimetic has the potential to overcome drug resistance in cancers overexpressing anti-apoptotic Bcl-2 proteins and thus increase the success rate of the treatment. We have previously shown that the BH3 mimetics, BH3I-2' and HA14-1, induce Ca 2+ release from intracellular stores followed by a sustained elevation of the cytosolic Ca 2+ concentration. Here we demonstrate that loss of Bax, but not Bcl-2 or Bak, inhibits this sustained Ca 2+ elevation. What is more, in the absence of Bax, thapsigargin-elicited responses were decreased; and in two-photon-permeabilised bax -/- cells, Ca 2+ loss from the ER was reduced compared to WT cells. The Ca 2+ -like peptides, CALP-1 and CALP-3, which activate EF hand motifs of Ca 2+ -binding proteins, significantly reduced excessive Ca 2+ signals and necrosis caused by two BH3 mimetics: BH3I-2' and gossypol. In the presence of CALP-1, cell death was shifted from necrotic towards apoptotic, whereas CALP-3 increased the proportion of live cells. Importantly, neither of the CALPs markedly affected physiological Ca 2+ signals elicited by ACh, or cholecystokinin. In conclusion, the reduction in passive ER Ca 2+ leak in bax -/- cells as well as the fact that BH3 mimetics trigger substantial Ca 2+ signals by liberating Bax, indicate that Bax may regulate Ca 2+ leak channels in the ER. This study also demonstrates proof-of-principle that pre-activation of EF hand Ca 2+ -binding sites by CALPs can be used to ameliorate excessive Ca 2+ signals caused by BH3 mimetics and shift necrotic death towards apoptosis.