S. Kishimoto et al., The inhibitory effect of prostaglandin E-1 on oxidative stress-induced hepatocyte injury evaluated by calpain-mu activation, TRANSPLANT, 69(11), 2000, pp. 2314-2319
Background. Prostaglandin E-1 (PGE(1)) is known to inhibit ischemia-reperfu
sion injury of the liver. The calcium dependent neutral proteinase, calpain
-mu, is involved in oxidative stress-induced hepatocyte injury. We investig
ated the mechanisms of cytoprotection by PGE(1), focusing on the elevation
of intracellular calcium ([Ca2+](i)), activation of calpain-mu, and calpain
-mu-mediated activation of protein kinase C-alpha (PKC-alpha),
Methods. Cultured hepatocytes were treated with various amounts of PGE(1) (
0, 0.1, 1.0, 10, and 100 ng/ml) for 30 min and subsequently with 0.5 mM ter
t-butyl hydroperoxide (TBHP), Cell injury was evaluated by the release of l
actate dehydrogenase, Plasma membrane bleb formation was examined by phase
contrast microscopy, Activation of calpain-mu and limited degradation of PK
C-alpha was evaluated by Western blotting using antibodies that specificall
y recognize the aminoterminal regions of calpain-mu and PKC-alpha, [Ca2+](i
) was measured by confocal microscopy using Fluo-3AM.
Results, LDH release from cells treated with 10 ng/ml PGE, was significantl
y lower than from untreated cells (135+/-12 vs. 258+/-18 IU/L, respectively
; P<0.05), Morphologically, many blebs were observed in untreated cells, bu
t very few were seen in those treated with 10 ng/ml PGE(1). Western blottin
g revealed that the amount of activated calpain-mu and [Ca2+](i) increased
up to 1,300 nM at 35 min after the addition of TBHP (0.5 mmol/L) in control
experiments (without PGE(1)). PGE(1) (10 ng/ml) delayed the rise in [Ca2+]
(i) for about 30 min, but did not suppress it completely. PKC-alpha decreas
ed in experiments using PGE(1) (10 ng/ml),
Conclusion, PGE(1) exerts its cytoprotective effect in TBHP-induced hepatoc
yte injury partly by inhibiting Ca2+-calpain-mu-mediated mechanisms.