Role of PGE2 in the development of pancreatic injury induced by chronic alcohol feeding in rats

Membrane Lipid Derivatives: Roles of Arachidonic Acid and Its Metabolites in Pancreatic Physiology and Pathophysiology

One of the most important constituents of the cell membrane is arachidonic acid. Lipids forming part of the cellular membrane can be metabolized in a variety of cellular types of the body by a family of enzymes termed phospholipases: phospholipase A2, phospholipase C and phospholipase D. Phospholipase A2 is considered the most important enzyme type for the release of arachidonic acid. The latter is subsequently subjected to metabolization via different enzymes. Three enzymatic pathways, involving the enzymes cyclooxygenase, lipoxygenase and cytochrome P450, transform the lipid derivative into several bioactive compounds. Arachidonic acid itself plays a role as an intracellular signaling molecule. Additionally, its derivatives play critical roles in cell physiology and, moreover, are involved in the development of disease. Its metabolites comprise, predominantly, prostaglandins, thromboxanes, leukotrienes and hydroxyeicosatetraenoic acids. Their involvement in cellular responses leading to inflammation and/or cancer development is subject to intense study. This manuscript reviews the findings on the involvement of the membrane lipid derivative arachidonic acid and its metabolites in the development of pancreatitis, diabetes and/or pancreatic cancer.

Relationship between Hormonal Modulation and Gastroprotective Activity of Malvidin and Cyanidin Chloride: In Vivo and In Silico Approach

Peptic ulcers are lesions that affect the gastrointestinal tract and that can be triggered by external factors such as alcohol use. This study investigated the gastroprotective role of two anthocyanidins, malvidin and cyanidin chloride, in an ethanol-induced gastric ulcer model in male and female mice (ovariectomized and supplemented with 17β-estradiol or not) and aimed to evaluate the effectiveness of anthocyanidins in preventing the formation of lesions and to identify the underlying mechanisms, while considering hormonal differences. Moreover, in silico comparative analysis was performed to predict the properties and biological behaviors of the molecules. We observed that the hormonal status did not interfere with the gastroprotective action of malvidin, although antioxidant mechanisms were modulated differently depending on sex. On the other hand, cyanidin showed gastroprotective activity at different doses, demonstrating that, for the same experimental model, there is a need to adjust the effective dose depending on sex. In silico analysis showed that, despite being structurally similar, the interaction with receptors and target proteins in this study (myeloperoxidase, superoxide dismutase, catalase, and reduced glutathione) differed between the two molecules, which explains the difference observed in in vivo treatments.

Ethanol consumption as inductor of pancreatitis

Alcohol abuse is a major cause of pancreatitis, a condition that can manifest as both acute necroinflammation and chronic damage (acinar atrophy and fibrosis). Pancreatic acinar cells can metabolize ethanol via the oxidative pathway, which generates acetaldehyde and involves the enzymes alcohol dehydrogenase and possibly cytochrome P4502E1. Additionally, ethanol can be metabolized via a nonoxidative pathway involving fatty acid ethyl ester synthases. Metabolism of ethanol by acinar and other pancreatic cells and the consequent generation of toxic metabolites, are postulated to play an important role in the development of alcohol-related acute and chronic pancreatic injury. This current work will review some recent advances in the knowledge about ethanol actions on the exocrine pancreas and its relationship to inflammatory disease and cancer.

Increased calcium influx in the presence of ethanol in mouse pancreatic acinar cells

The effects of alcohol on Ca(2+) signalling remains poorly understood. Here we have investigated the effects of acute ethanol exposure on Ca(2+) influx in mouse pancreatic acinar cells. Cells were loaded with fura-2 and the changes in fluorescence were monitored by spectrofluorimetry and imaging analysis. Stimulation of cells with 20 pM cholecystokinin evoked an oscillatory pattern in [Ca(2+)](c), both in the presence and in the absence of extracellular Ca(2+). Stimulation of cells with cholecystokinin in the presence of 50 mM ethanol led to a transformation of physiological oscillations into a single transient increase in [Ca(2+)](c). This effect was observed when Ca(2+) was present in the extracellular medium, and did not appear in its absence. Addition of 1 mM CaCl(2) to the extracellular medium, following release of Ca(2+) from intracellular stores by stimulation of cells with 1 nM cholecystokinin or 1 microM thapsigargin in the absence of extracellular Ca(2+), was followed by an increase in [Ca(2+)](c). Ca(2+) influx was increased in the presence of 50 mM ethanol. The anti-oxidant cinnamtannin B-1 (10 microM) or inhibition of alcohol dehydrogenase by 4-MP (1 mM), significantly reduced Ca(2+) influx evoked by cholecystokinin in the presence of ethanol. In summary, intoxicating concentrations of ethanol may lead to over stimulation of pancreatic acinar cells by cholecystokinin. This might be partially explained by the generation of reactive oxygen species and an increased Ca(2+) entry in the presence of ethanol. Potentially ethanol might lead to Ca(2+) overload, which is a common pathological precursor that is implicated in pancreatitis.

Ethanol exerts dual effects on calcium homeostasis in CCK-8-stimulated mouse pancreatic acinar cells

Background

A significant percentage of patients with pancreatitis often presents a history of excessive alcohol consumption. Nevertheless, the patho-physiological effect of ethanol on pancreatitis remains poorly understood. In the present study, we have investigated the early effects of acute ethanol exposure on CCK-8-evoked Ca²⁺ signals in mouse pancreatic acinar cells. Changes in [Ca²⁺]_i and ROS production were analyzed employing fluorescence techniques after loading cells with fura-2 or CM-H₂DCFDA, respectively.

Results

Ethanol, in the concentration range from 1 to 50 mM, evoked an oscillatory pattern in [Ca²⁺]_i. In addition, ethanol evoked reactive oxygen species generation (ROS) production. Stimulation of cells with 1 nM or 20 pM CCK-8, respectively led to a transient change and oscillations in [Ca²⁺]_i. In the presence of ethanol a transformation of 20 pM CCK-8-evoked physiological oscillations into a single transient increase in [Ca²⁺]_i in the majority of cells was observed. Whereas, in response to 1 nM CCK-8, the total Ca²⁺ mobilization was significantly increased by ethanol pre-treatment. Preincubation of cells with 1 mM 4-MP, an inhibitor of alcohol dehydrogenase, or 10 μM of the antioxidant cinnamtannin B-1, reverted the effect of ethanol on total Ca²⁺ mobilization evoked by 1 nM CCK-8. Cinnamtannin B-1 blocked ethanol-evoked ROS production.

Conclusion

ethanol may lead, either directly or through ROS generation, to an over stimulation of pancreatic acinar cells in response to CCK-8, resulting in a higher Ca²⁺ mobilization compared to normal conditions. The actions of ethanol on CCK-8-stimulation of cells create a situation potentially leading to Ca²⁺ overload, which is a common pathological precursor that mediates pancreatitis.

Ethanol impairs calcium homeostasis following CCK-8 stimulation in mouse pancreatic acinar cells

Alcohol consumption has long been associated with cell damage, and it is thought that it is involved in approximately 40% of cases of acute pancreatitis. In the present study, we have investigated the early effects of acute ethanol exposure on cholecystokinin octapeptide (CCK-8)-evoked calcium (Ca2+) signals in mouse pancreatic acinar cells. Cells were loaded with fura-2 and the changes in fluorescence were monitorized using a spectrofluorimeter. Our results show that stimulation of cells with 1 nM CCK-8 led to a transient increase in [Ca2+]c, which consisted of an initial increase followed by a decrease of [Ca2+]c toward a value close to the prestimulation level. In the presence of 50mM ethanol, CCK-8 lead to a greater Ca2+ mobilization compared to that obtained with CCK-8 alone. The peak of CCK-8-evoked Ca2+ response, the "steady-state level" reached 5 min after stimulation, the rate of decay of [Ca2+]c toward basal values and the total Ca2+ mobilization were significantly affected by ethanol pretreatment. Thapsigargin (Tps) induced an increase in [Ca2+]c due to its release from intracellular stores. After stimulation of cells with CCK-8 or Tps in the presence of 50mM ethanol, a greater [Ca2+]c peak response, a slower rate of decay of [Ca2+]c, and higher values of [Ca2+]c were observed. The effects of ethanol might result from a delayed or reduced Ca2+ extrusion from the cytosol toward the extracellular space by plasma membrane Ca2+ adenosine triphosphatase (ATPase), or into the cytosolic stores by the sarcoendoplasmic reticulum Ca2+-ATPase. Participation of mitochondria in Ca2+ handling is also demonstrated. The actions of ethanol on CCK-8 stimulation of cells create a situation potentially leading to Ca2+ overload, which is a common pathological precursor that mediates pancreatitis.

Ethanol impairs CCK-8-evoked amylase secretion through Ca2+-mediated ROS generation in mouse pancreatic acinar cells

In the present study, we have investigated the effect of ethanol on amylase release in response to cholecystokinin octapeptide (CCK-8). We have also studied the effect of ethanol on cytosolic free Ca(2+) concentration ([Ca(2+)](c)) and reactive oxygen species (ROS) production by loading of cells with fura-2 and 5-(and-6)-chloromethyl-2',7'-dichlorodihydrofluorescein diacetate, acetyl ester (CM-H(2)DCFDA), respectively. Our results show that stimulation of pancreatic acinar cells with CCK-8 induced a dose-dependent amylase secretion, resulting in a maximum at 0.3nM of 19.39+/-2.73% of the total content of amylase. Treatment of pancreatic acini with ethanol did not induce any significant effect on amylase release at a wide range of concentrations (1-50mM). In contrast, incubation of cells with 50mM ethanol clearly reduced amylase release stimulated by CCK-8. The inhibitory effect of ethanol on CCK-8-induced amylase secretion was abolished by dithiothreitol, a sulfhydryl reducing agent. Ethanol induced an increase in [Ca(2+)](c) resulting in a level higher than the prestimulation level both in the presence and in the absence of extracellular Ca(2+). Additionally, ethanol led to an increase in fluorescence of CM-H(2)DCFDA, reflecting an increase in oxidation. A decrease in oxidation was observed in the absence of extracellular Ca(2+) and in the presence of ethylene glycol-bis(2-aminoethylether)-N,N,N',N'-tetraacetic acid. Similarly, when the cells were challenged in the presence of the intracellular Ca(2+) chelator 1,2-Bis(2-amino-5-methylphenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA) and in the absence of extracellular Ca(2+), the responses to ethanol were reduced, although not completely inhibited. Taken together, our results suggest that ethanol induces generation of ROS by a Ca(2+)-dependent mechanism and reduces CCK-8-evoked amylase secretion in exocrine pancreatic cells.