BH3 mimetic-elicited Ca2+ signals in pancreatic acinar cells are dependent on Bax and can be reduced by Ca2+-like peptides

Abstract

BH3 mimetics are small-molecule inhibitors of B-cell lymphoma-2 (Bcl-2) and Bcl-xL, which disrupt the heterodimerisation of antiand pro-apoptotic Bcl-2 family members sensitising cells to apoptotic death. These compounds have been developed as anticancer 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.

ABT‐199 (Venetoclax), a BH3‐mimetic Bcl‐2 inhibitor, does not cause Ca2+‐signalling dysregulation or toxicity in pancreatic acinar cells

“…PAC isolation was performed as described previously (Ferdek et al, ). The isolation and the experimental work was carried out in NaHEPES buffer.…”

“…Because of the non‐equal numbers cells recorded in the viewing fields, n may vary between treatment groups in the given experimental setting. Quantitative analysis of Ca 2+ responses was performed as described previously (Ferdek et al, ). Briefly, areas under the individual traces were calculated according to the formula: Σ(F/F 0 −F 0 ) × Δt, where F is the recorded fluorescence, F 0 is the baseline fluorescence and Δt is the time interval.…”

“…For instance, HA14‐1 also inhibits the Ca 2+ ‐pump activity of the sarco/endoplasmic reticulum Ca ATPase (SERCA), provoking cell death in part by depleting the ER Ca 2+ ‐store (Hermanson et al, ; Akl et al, ). Moreover, both HA14‐1 and BH3I‐2′ were found to have pancreatotoxic effects (Gerasimenko et al, ; Ferdek et al, ). These effects were mediated directly by pathological Ca 2+ responses in pancreatic acinar cells (PACs), the secretory epithelium that produces and releases digestive enzymes in the pancreas (Gerasimenko et al, ).…”

“…Given that several of the early BH3 mimetics have been shown to alter intracellular Ca 2+ signalling, particularly in the pancreas (Gerasimenko et al, ; Ferdek et al, ), it became essential and timely to determine whether or not the recently approved anti‐leukaemic drug ABT‐199 and other inhibitors such as selective Bcl‐xL antagonist A‐1155463 and Bcl‐2/Bcl‐xL inhibitor ABT‐737 show effects that might potentially be pancreatotoxic. Although ABT‐199 was shown not to dysregulate intracellular Ca 2+ signalling upon acute application in the Bcl‐2‐dependent diffuse large Bcl (DLBCL) cell lines (Vervloessem et al, , ), data on healthy primary cells are very limited.…”

On BH3 Mimetics and Ca2+ Signaling

“…Similar effects of Ca 21 deregulation by HA14-1 were also demonstrated in platelets, HeLa and HEK-293T cells [Akl et al, 2013]. A recent study has shed new light on this phenomenon by showing that Ca 21 responses induced in pancreatic acinar cells by HA14-1, BH3I-2 0 and gossypol were largely diminished in the absence of Bax, but not Bak or Bcl-2 [Ferdek et al, 2017], suggesting a regulatory role for Bax in Ca 21 release from the intracellular stores ( Fig. 1).…”