A. Dabrowski et al., Activation of mitogen-activated protein kinases in different models of pancreatic acinar cell damage, Z GASTROENT, 38(6), 2000, pp. 469-481
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.
Aim: To determine the activity of MAPKs and the level of Bar, Bcl-2 and p53
- proteins known to be involved in the regulation of apoptosis - in pancre
atic acini subjected to stressful stimuli leading to cell death.
Methods and Results: Isolated pancreatic acini were irradiated for 30 min w
ith ultraviolet B (UV-B) or stimulated with supraphysiological concentratio
ns of cholecystokinin (CCK). As it was assessed by means of acridine orange
/ethidium bromide staining, irradiation with UV-B induced predominantly apo
ptosis while necrosis predominated in CCK-stimulated acini. The activity of
MAPK, JNK and p38MAPK was determined by means of Western-blotting, with th
e 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 le
vel 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 bo
th kinases was not affected by the pretreatment with antioxidant - N-acetyl
o-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 sig
nificant changes in Bar, Bcl-2 and p53 levels assessed by means of Western-
blotting.
Conclusion: It seems likely that a specific interaction between MAPK and p3
8MAPK signaling pathway may be involved in the determination of the cell de
ath mechanism in pancreatic acini subjected to stressful stimuli.