Role of Ca2+ release and Ca2+ entry mechanisms during pathology and the initiation of acute pancreatitis

Evans, David 2022. Role of Ca2+ release and Ca2+ entry mechanisms during pathology and the initiation of acute pancreatitis. PhD Thesis, Cardiff University. Item availability restricted.

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Abstract

Introduction – Acute pancreatitis is an inflammatory and deadly disease affecting the pancreas which is strongly associated with pathological calcium signals within pancreatic exocrine cells. These pathological global transient signals involve several mechanisms of calcium signalling including calcium release via inositol triphosphate and ryanodine receptors as well as calcium entry via store operated calcium channels. Pathological calcium signals induce necrotic effects triggered by pathological stimuli such as the bile acid, TLC-S and asparaginase, a drug commonly used to treat acute lymphoblastic leukaemia. Therefore, our goal is to investigate pathological calcium signals to prevent the development of acute pancreatitis. Previous studies have demonstrated the beneficial uses of inhibitors and compounds such as CM-4620, currently in human trials, GSK-7975A and NED-19, which are useful pharmacological tools to investigate calcium entry and NAADP�mediated calcium signalling respectively. There has been recent interest in calcium signalling regulator proteins and peptides, such as BH4-Bcl-2, and energy supplements, such as galactose which aids cell survival by reducing ATP loss, as potential therapeutic strategies. Moreover, the BH4 domain of the Bcl-2 protein has demonstrated regulation of ryanodine and inositol triphosphate receptors. This thesis focuses on the mechanisms of calcium release and entry effects of pathological stimuli within pancreatic acinar and stellate cells. Results – Using confocal microscopy techniques we have demonstrated the detrimental effects pathological agents have upon mitochondria within pancreatic acinar cells and the potential protective effects of BH4-Bcl-2 treatments upon mitochondria and cell death. The pathological increase in mitochondrial calcium reduces ATP production, increasing the likelihood of cell death and induction of acute pancreatitis. BH4-Bcl-2 demonstrated protective effects upon pathological calcium signalling and necrosis during both TLC-S and asparaginase stimulation. Furthermore, the protective effects of BH4-Bcl-2 were also granted when reducing the concentration of applied BH4-Bcl-2 peptide given in combination with galactose. Additionally, this study demonstrated reduced calcium entry due to NED-19 treatment suggesting possible linkage between calcium entry and NAADP-mediated signalling. Therefore, suggesting its potential use as a therapeutic against pathological calcium signalling reliant upon calcium entry during sustained global responses. Conclusion – Overall, this thesis provides new and additional evidence for the use of the BH4-Bcl-2 peptide to counteract pancreatic pathology at the cellular and mitochondrial level. Furthermore, it presents new arguments to use combinatory treatments in future studies. Additionally, this thesis reports inhibition of calcium entry by NED-19 that requires further investigation into NAADP-induced calcium signalling.

Item Type:	Thesis (PhD)
Date Type:	Completion
Status:	Unpublished
Schools:	Biosciences
Subjects:	Q Science > Q Science (General)
Date of First Compliant Deposit:	25 May 2022
Date of Acceptance:	25 May 2022
Last Modified:	25 May 2023 01:30
URI:	https://orca.cardiff.ac.uk/id/eprint/150015

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