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Background & Aims: Epiplakin is a member of the plakin protein family and exclusively expressed in epithelial tissues where it binds to keratins. Epiplakin-deficient (Eppk1(-/-)) mice displayed no obvious spontaneous phenotype, but their keratinocytes showed a faster keratin network breakdown in response to stress. The role of epiplakin in the stressed liver remained to be elucidated., Methods: Wild-type (WT) and Eppk1(-/-) mice were subjected to common bile duct ligation (CBDL) or fed with a 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC)-containing diet. The importance of epiplakin during keratin reorganization was assessed in primary hepatocytes., Results: Our experiments revealed that epiplakin is expressed in hepatocytes and cholangiocytes, and binds to keratin 8 (K8) and K18 via multiple domains. In several liver stress models epiplakin and K8 genes displayed identical expression patterns and transgenic K8 overexpression resulted in elevated hepatic epiplakin levels. After CBDL and DDC treatment, Eppk1(-/-) mice developed a more pronounced liver injury and their livers contained larger amounts of hepatocellular keratin granules, indicating impaired disease-induced keratin network reorganization. In line with these findings, primary Eppk1(-/-) hepatocytes showed increased formation of keratin aggregates after treatment with the phosphatase inhibitor okadaic acid, a phenotype which was rescued by the chemical chaperone trimethylamine N-oxide (TMAO). Finally, transfection experiments revealed that Eppk1(-/-) primary hepatocytes were less able to tolerate forced K8 overexpression and that TMAO treatment rescued this phenotype., Conclusion: Our data indicate that epiplakin plays a protective role during experimental liver injuries by chaperoning disease-induced keratin reorganization., (Copyright © 2015 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.)

Aim: To investigate the role of major non-protein and protein sulfhydryls and disulfides in chemically induced gastric hemorrhagic mucosal lesions (HML) and the mechanism of gastroprotective effect of sucralfate., Methods: Rats were given 1 mL of 75% ethanol, 25% NaCl, 0.6 mol/L HCl, 0.2 mol/L NaOH or 1% ammonia solutions intragastrically (i.g.) and sacrificed 1, 3, 6 or 12 min later. Total (reduced and oxidized) glutathione (GSH + GSSG), glutathione disulfide (GSSG), protein free sulfhydryls (PSH), protein-glutathione mixed disulfides (PSSG) and protein cystine disulfides (PSSP) were measured in gastric mucosa and liver., Results: Reduced glutathione (GSH) was depleted in the gastric mucosa after ethanol, HCl or NaCl exposure, while oxidized glutathione (GSSG) concentrations increased, except by HCl and NaOH exposure. Decreased levels of PSH after exposure to ethanol were observed, NaCl or NaOH while the total protein disulfides were increased. Ratios of reduced to oxidized glutathione or sulfhydrils to disulfides were decreased by all chemicals. No changes in thiol homeostasis were detected in the liver after i.g. abbreviation should be spelled out the first time here administration of ethanol. Sucralfate increased the concentrations of GSH and PSH and prevented the ethanol-induced changes in gastric mucosal thiol concentrations., Conclusion: Our modified methods are now suitable for direct measurements of major protein and non-protein thiols/disulfides in the gastric mucosa or liver. A common element in the pathogenesis of chemically induced HML and in the mechanism of gastroprotective drugs seems to be the decreased ratios of reduced and oxidized glutathione as well as protein sulfhydryls and disulfides.

Liver microsomal enzyme activities and glutathione (GSH) contents of fasted male rats pretreated with phenobarbital (PBT) or vehicle controls were measured during and after exposure to trichloroethylene (TRI) (1% x 2 hr). TRI caused morphologic liver injury only in the pbt animals. Cytochrome P-450 and b5 contents were diminished by the end of the first hr of TRI exposure and NADH-cytochrome c reduction increased three-fold by eight hr in the PBT animals. The only change in vehicle animals exposed to TRI was a decrease in NADPH-cytochrome c reductase activity by eight hr. Hepatic GSH contents of vehicle animals, constant during TRI exposure, rose with time. In contrast, in PBT animals, hepatic GSH contents decreased during TRI exposure and then rebounded. Decreases in GSH were most profound in the microsomal fraction. When fed animals with approximately two-fold higher hepatic GSH levels than fasted animals were exposed to TRI, they had shorter anesthesia recovery times and less liver injury, although excreting similar or slightly more trichlorinated metabolite into their urine in 24 hr than their fasted counterparts. We suggest that the hepatoxic effects of trichloroethylene are caused by inadequate detoxification of its reactive intermediates.

In young female rats, thymectomy causes RER alterations and a slight increase in SER. PCN augments SER in the hepatocytes of both intact and thymectomized rats. Thymectomy prolongs zoxazolamine paralysis and PCN treatment decreases the duration of zoxazolamine paralysis both in intact and operated rats.

Vinyl chloride, an occupational carcinogen, produces acute liver injury in rats pretreated with phenobarbital or Aroclor 1254. Injury appears related to morphologic changes in the endoplasmic reticulum. The degree of injury, as indicated by elevation of serum enzymes derived from the liver, correlates with the magnitude of induction of cytochrome P-450 and its reduction by NADPH. Hepatic injury following 1,1-dichloroethylene exposure differs strikingly from that caused by vinyl chloride and appears to involve plasma membranes, mitochondria, and chromatin and spares endoplasmic reticulum. Induction of cytochrome P-450 appears to protect against 1,1-dichloroethylene but not vinyl chloride.

Zoxazolamine paralysis, hexobarbital anesthesia and digitoxin convulsions were diminished in rats by 3 days of pretreatment with pregnenolone-16alpha-carbonitrile (PCN). Simultaneous injection of dl-ethionine did not block this effect of PCN. Dl-Ethionine decreased, while PCN or PCN + ethionene increased, zoxazolamine metabolism by the 9,000g supernatant fraction of the liver. Dl-ethionine neutralized the influence of PCN and phenobarbital on zoxazolamine metabolism in rats that were pretreated with PCN or phenobarbital for 1 day, and it inhibited the action of phenobarbital on hexobarbital anesthesia. PCN augmented the liver weight of animals given dl-ehtionine whereas dl-ethionine in itself did not. PCN produced SER proliferation in hepatocytes and dl-ethionine caused lipid accumulation, SER proliferation and myelin-figure formation. When administered conjointly, these compounds had an additive effect on the liver cell ultrastructure.

A single injection of vinblastine given i.v. to rats lead to the disappearance of microtubules, development of crystalline inclusions, dilation of Golgi sacculi, formation of multivesicular bodies and cytosegresomes as well as accumulation of lysosomes in the cytoplasm of liver cells. The endoplasmic reticulum and mitochondria do not seem to be affected. The question of whether or not these fine structural alterations are causally related has yet to be elucidated.

In female rats, pregnenolone-16alpha-carbonitrile [PCN (a known microsomal enzyme inducer)] augmented liver weight and significantly increased hepatic protein, total lipid, phospholipid and ATP concentrations. These changes were correlated with hepatic drug-metabolizing enzyme induction. PCN did not alter body weight, or water, ash, triglyceride and cholesterol levels in the liver, but caused a mild reduction of hepatic glycogen.

Ischemia and anoxia are associated with decreased concentrations of cellular antioxidants. The hypothesis that recirculation of oxygenated blood to previously ischemic tissue may result in enhanced free-radical reactions leading to lipid peroxidation and tissue damage was investigated. Elevated hepatic conjugated diene concentrations were detected 60 min after treatment of rats with carbon tetrachloride, a positive control, but were not found after 90 min ischemia or at 5 or 60 min after reperfusion of ischemic tissue. These findings suggest that lipid peroxidation may not be an early event in ischemia-induced necrosis but do not rule out a role of other free-radical reactions in the pathogenesis of ischemic necrosis.