Fatty acid ethyl ester synthase inhibition ameliorates ethanol-induced Ca²⁺-dependent mitochondrial dysfunction and acute pancreatitis

Abstract

ObjectiveNon-oxidative metabolism of ethanol (NOME) produces fatty acid ethyl esters (FAEEs) via carboxylester lipase (CEL) and other enzyme action implicated in mitochondrial injury and acute pancreatitis (AP). This study investigated the relative importance of oxidative and non-oxidative pathways in mitochondrial dysfunction, pancreatic damage and development of alcoholic AP, and whether deleterious effects of NOME are preventable.DesignIntracellular calcium ([Ca2+]C), NAD(P)H, mitochondrial membrane potential and activation of apoptotic and necrotic cell death pathways were examined in isolated pancreatic acinar cells in response to ethanol and/or palmitoleic acid (POA) in the presence or absence of 4-methylpyrazole (4-MP) to inhibit oxidative metabolism. A novel in vivo model of alcoholic AP induced by intraperitoneal administration of ethanol and POA was developed to assess the effects of manipulating alcohol metabolism.ResultsInhibition of OME with 4-MP converted predominantly transient [Ca2+]C rises induced by low ethanol/POA combination to sustained elevations, with concurrent mitochondrial depolarisation, fall of NAD(P)H and cellular necrosis in vitro. All effects were prevented by 3-benzyl-6-chloro-2-pyrone (3-BCP), a CEL inhibitor. 3-BCP also significantly inhibited rises of pancreatic FAEE in vivo and ameliorated acute pancreatic damage and inflammation induced by administration of ethanol and POA to mice.ConclusionsA combination of low ethanol and fatty acid that did not exert deleterious effects per se became toxic when oxidative metabolism was inhibited. The in vitro and in vivo damage was markedly inhibited by blockade of CEL, indicating the potential for development of specific therapy for treatment of alcoholic AP via inhibition of FAEE generation.

Fatty Acid Ethyl Esters Are Less Toxic Than Their Parent Fatty Acids Generated during Acute Pancreatitis

“…22 These recent findings published by Criddle et al 22 partly differ from our current work and their earlier studies. 17,21 In our current work, similar to their 2006 study, we note FAEEs to be less toxic than the parent FAs.…”

“…In addition, in contrast to their 2006 study which showed FAEE cytotoxicity depends on their conversion to FAs 21 ; their 2014 study 22 showed this to depend on the conversion of POA to POAEE. This increase in cytosolic calcium and severity of pancreatitis were significantly reduced with the agent 3-benzyl-6-chloro-2-pyrone (3-BCP), a generic serine protease inhibitor, 68,69 which they proposed Figure 5 Triolein administration causes a worse cytokine response and inflammation compared with OAEE.…”

“…In 2014, 22 Criddle et al 17 in contrast to their 2004 study noted that POA in most cases did not induce a sustained increase in cytosolic calcium. In addition, in contrast to their 2006 study which showed FAEE cytotoxicity depends on their conversion to FAs 21 ; their 2014 study 22 showed this to depend on the conversion of POA to POAEE.…”

“…iii) As we note, FAEEs do cause cell death and pancreatitis, but it is substantially milder than from the parent FAs. iv) The pattern of necrosis noted by intraperitoneal administration of FAEEs or FAs þ ethanol 22 shows this to be localized to the edges of the lobules, with relative sparing of acinar cells in the center, Figure 6 Triolein causes worse systemic injury compared with OAEE. A: Presence of TUNEL þ cells (inset, black arrows) in lungs are significantly higher in the GTO group than the OAEE group.…”

CFTR: A new horizon in the pathomechanism and treatment of pancreatitis

“…smoking, diet) must also be responsible for the induction of the disease. Furthermore, the importance of nonoxidative ethanol metabolites such as fatty acid ethyl esters as well as cytotoxic fatty acids in acute pancreatitis is now being increasingly recognized [52].…”