Activation of mitogen-activated protein kinases in different models of pancreatic acinar cell damage.
Mitogen-activated protein kinase (MAPK) family members, namely MAPK, c-Jun NH2-terminal protein kinase (JNK), and p38MAPK, have been recently reported to have opposing effects on apoptosis.


OBJECTIVE
To determine the activity of MAPKs and the level of Bax, Bcl-2 and p53--proteins known to be involved in the regulation of apoptosis--in pancreatic acini subjected to stressful stimuli leading to cell death.


RESULTS
Isolated pancreatic acini were irradiated for 30 min with ultraviolet B (UV-B) or stimulated with supraphysiological concentrations of cholecystokinin (CCK). As it was assessed by means of acridine orange/ethidium bromide staining, irradiation with UV-B induced predominantly apoptosis while necrosis predominated in CCK-stimulated acini. The activity of MAPK, JNK and p38MAPK was determined by means of Western-blotting, with the use of antibodies which recognize active, dually phosphorylated enzymes. Irradiation with UV-B induced a rapid, 3-fold increase in MAPK activity. It had a maximum at 30 min and then gradually declined to reach the normal level at 120 min. Concomitantly, early activation of p38-MAPK was found at 30 min. However, unlike MAPK, p38-MAPK activity was then gradually rising to reach a maximum (5-fold increase) at 180 min. UV-B-induced activation of both kinases was not affected by the pretreatment with antioxidant--N-acetylo-L-cysteine or protein kinase C inhibitor--GF-109203X. In UV-B-irradiated cells, we did not detect any significant JNK activation as well as any significant changes in Bax, Bcl-2 and p53 levels assessed by means of Western-blotting.


CONCLUSIONS
It seems likely that a specific interaction between MAPK and p38MAPK signaling pathway may be involved in the determination of the cell death mechanism in pancreatic acini subjected to stressful stimuli.
Department of Gastroenterology, Medical School of Bialystok, Poland. adabrows@amb.ac.bialystok.pl
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Dabrowski
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Tribillo
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MI
Dabrowska
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Wereszczynska-Siemiatkowska
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Gabryelewicz
D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D016923:Cell Death / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D002766:Cholecystokinin / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects / Q000528:radiation effects; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D008297:Male; D010179:Pancreas / Q000166:cytology* / Q000187:drug effects / Q000528:radiation effects; D011518:Proto-Oncogene Proteins / Q000502:physiology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D016159:Tumor Suppressor Protein p53 / Q000502:physiology; D014466:Ultraviolet Rays; D051028:bcl-2-Associated X Protein
C494828:Bax protein, rat; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein; D002766:Cholecystokinin