Differential cytotoxicity, ER/oxidative stress, dysregulated AMPKα signaling, and mitochondrial stress by ethanol and its metabolites in human pancreatic acinar cells

• Published in: Alcoholism, clinical and experimental research Vol. 45; no. 5; pp. 961 - 978
• Main Authors: Srinivasan, Mukund P., Bhopale, Kamlesh K., Caracheo, Anna A., Kaphalia, Lata, Loganathan, Gopalakrishnan, Balamurugan, Appakalai N., Rastellini, Cristiana, Kaphalia, Bhupendra S.
• Format: Journal Article
• Language: English
• Published: England 01.05.2021
• Subjects: acetaldehyde; Acetaldehyde - pharmacology; Acetyl-CoA Carboxylase - drug effects; Acetyl-CoA Carboxylase - metabolism; Acinar Cells - drug effects; Acinar Cells - metabolism; alcoholic pancreatitis; AMP-Activated Protein Kinase Kinases - drug effects; AMP-Activated Protein Kinase Kinases - metabolism; AMP-Activated Protein Kinases - drug effects; AMP-Activated Protein Kinases - metabolism; AMPKα; Carnitine O-Palmitoyltransferase - drug effects; Carnitine O-Palmitoyltransferase - metabolism; Cell Survival - drug effects; Central Nervous System Depressants - pharmacology; Endoplasmic Reticulum Stress - drug effects; ER stress; Esters - pharmacology; Ethanol - pharmacology; fatty acid ethyl esters; human pancreatic acinar cells; Humans; Mitochondria - drug effects; Mitochondria - metabolism; Mitogen-Activated Protein Kinase 1 - drug effects; Mitogen-Activated Protein Kinase 1 - metabolism; Mitogen-Activated Protein Kinase 3 - drug effects; Mitogen-Activated Protein Kinase 3 - metabolism; Mitogen-Activated Protein Kinase 8 - drug effects; Mitogen-Activated Protein Kinase 8 - metabolism; Mitogen-Activated Protein Kinase 9 - drug effects; Mitogen-Activated Protein Kinase 9 - metabolism; Oxidative Stress - drug effects; Pancreas - cytology; human pancreatic acinar cells; ER stress; AMPKα; fatty acid ethyl esters; acetaldehyde; alcoholic pancreatitis
• ISSN: 0145-6008; 1530-0277; 1530-0277
• DOI: 10.1111/acer.14595

Background Alcoholic chronic pancreatitis (ACP) is a serious inflammatory disorder of the exocrine pancreatic gland. A previous study from this laboratory showed that ethanol (EtOH) causes cytotoxicity, dysregulates AMPKα and ER/oxidative stress signaling, and induces inflammatory responses in primary human pancreatic acinar cells (hPACs). Here we examined the differential cytotoxicity of EtOH and its oxidative (acetaldehyde) and nonoxidative (fatty acid ethyl esters; FAEEs) metabolites in hPACs was examined to understand the metabolic basis and mechanism of ACP. Methods We evaluated concentration‐dependent cytotoxicity, AMPKα inactivation, ER/oxidative stress, and inflammatory responses in hPACs by incubating them for 6 h with EtOH, acetaldehyde, or FAEEs at clinically relevant concentrations reported in alcoholic subjects using conventional methods. Cellular bioenergetics (mitochondrial stress and a real‐time ATP production rate) were determined using Seahorse XFp Extracellular Flux Analyzer in AR42J cells treated with acetaldehyde or FAEEs. Results We observed concentration‐dependent increases in LDH release, inactivation of AMPKα along with upregulation of ACC1 and FAS (key lipogenic proteins), downregulation of p‐LKB1 (an oxidative stress‐sensitive upstream kinase regulating AMPKα) and CPT1A (involved in β‐oxidation of fatty acids) in hPACs treated with EtOH, acetaldehyde, or FAEEs. Concentration‐dependent increases in oxidative stress and ER stress as measured by GRP78, unspliced XBP1, p‐eIF2α, and CHOP along with activation of p‐JNK1/2, p‐ERK1/2, and p‐P38MAPK were present in cells treated with EtOH, acetaldehyde, or FAEEs, respectively. Furthermore, a significant decrease was observed in the total ATP production rate with subsequent mitochondrial stress in AR42J cells treated with acetaldehyde and FAEEs. Conclusions EtOH and its metabolites, acetaldehyde and FAEEs, caused cytotoxicity, ER/oxidative and mitochondrial stress, and dysregulated AMPKα signaling, suggesting a key role of EtOH metabolism in the etiopathogenesis of ACP. Because oxidative EtOH metabolism is negligible in the exocrine pancreas, the pathogenesis of ACP could be attributable to the formation of FAEEs and related pancreatic acinar cell injury. To better understand the etiology of alcoholic chronic pancreatitis (ACP), we investigated the cytotoxicity of ethanol and its metabolites in primary human pancreatic acinar cells (hPACs). Ethanol, as well as its oxidative (acetaldehyde) and nonoxidative (fatty acid ethyl esters; FAEEs) metabolites, caused injury, endoplasmic reticulum/oxidative stress and dysregulated AMPKα signaling in hPACs. In view of negligible oxidative and substantial nonoxidative metabolism of ethanol in the pancreatic gland during chronic alcohol ingestion, FAEEs could significantly contribute to the etiopathogenesis of ACP.