Phosphatidylinositide 3-kinase gamma regulates key pathologic responses to cholecystokinin in pancreatic acinar cells.
OBJECTIVE
Early events in the pancreatic acinar cell critical for development of pancreatitis include activation of the transcription factor nuclear factor kappa B (NF-kappa B), abnormal Ca(2+) responses, and trypsinogen activation. Mechanisms underlying these responses, which can be studied in isolated pancreatic acini stimulated with supraphysiologic doses of cholecystokinin (CCK-8), remain poorly understood. We here report that these responses are regulated by phosphatidylinositide 3-kinase (PI3K) gamma.


METHODS
To inactivate PI3K, we used mice deficient in the catalytic PI3K gamma subunit p110 gamma as well as the PI3K inhibitors LY294002 and wortmannin. We measured Ca(2+) responses by using Fura-2, NF-kappa B-binding activity by electromobility shift assay, I kappa B degradation by Western blotting, and trypsinogen activation by fluorogenic assay.


RESULTS
CCK-induced intracellular Ca(2+) mobilization, Ca(2+) influx, trypsinogen, and NF-kappa B activation were all diminished in pancreatic acini isolated from p110 gamma(-/-) mice. Both in mouse and rat acini, these responses were inhibited by the PI3K inhibitors. The Ca(2+) signal and trypsinogen activation were similarly reduced in acini isolated from p110 gamma(-/-) and p110 gamma(+/-) mice compared with wild-type mice. By contrast, NF-kappa B activation was inhibited in p110 gamma(-/-) acini but not in p110 gamma(+/-) acini. These differences indicate that the mechanism of NF-kappa B regulation by PI3K gamma differs from those for the Ca(2+) and trypsinogen responses. CCK-induced responses in p110 gamma(-/-) acini were all further inhibited by LY294002, indicating the involvement of other PI3K isoform(s), in addition to PI3K gamma.


CONCLUSIONS
The results show that key pathologic responses of the pancreatic acinar cell are regulated by PI3K gamma and suggest an important role for this PI3K isoform in pancreatitis.
Gukovsky
Ilya
I
Department of Medicine, VA Greater Los Angeles Healthcare Sysytem and University of California, Los Angeles, 90073, USA. igukovsk@ucla.edu
Cheng
Jason H
JH
Nam
Kyung J
KJ
Lee
Oliver T
OT
Lugea
Aurelia
A
Fischer
Lars
L
Penninger
Josef M
JM
Pandol
Stephen J
SJ
Gukovskaya
Anna S
AS
D000818:Animals; D002118:Calcium / Q000378:metabolism; D007425:Intracellular Membranes / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D016328:NF-kappa B / Q000378:metabolism; D009994:Osmolar Concentration; D010179:Pancreas / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism / Q000473:pathology*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012844:Sincalide / Q000494:pharmacology*; D014362:Trypsinogen / Q000378:metabolism
D016328:NF-kappa B; D014362:Trypsinogen; D019869:Phosphatidylinositol 3-Kinases; D012844:Sincalide; D002118:Calcium