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Sautin, Yuri Y., James M. Crawford, and Stanislav I. Svetlov. Enhancement of survival by LPA via Erk1/Erk2 and PI 3-kinase/Akt pathways in a murine hepatocyte cell line. Am J Physiol Cell Physiol 281: C2010--C2019, 2001. First published September 5, 2001; 10.1152/ajpcell.00077.2001.--Protective mechanisms for lysophosphatidic acid (LPA) against cell death caused by Clostridium difficile toxin, or tumor necrosis factor-[alpha] (TNF-[alpha]) plus D-galactosamine, were investigated in a murine hepatocyte cell line AML12 expressing Edg2 LPA receptor. In these models of hepatocellular injury, LPA prevented hepatocyte damage, suppressed apoptosis, and enhanced cell survival in a dose-dependent fashion. The protective effects of LPA were abolished by wortmannin and LY-294002, specific inhibitors of phosphatidylinositol 3-phosphate kinase (PI 3-kinase), and by PD-98059 and U-0126, inhibitors of MEK1/MEK2. In nontreated hepatocytes, LPA elicited a gradual and sustained increase in phosphorylation of Erk1/Erk2 over 180 min of stimulation and downstream phosphorylation of p90RSK and transcription factor Elk-1. In C. difficile toxin-treated cells, LPA-induced phosphorylation of Erk1/Erk2 was rapid but transient, while p90RSK and Elk-1 phosphorylation did not change significantly. LPA stimulated phosphorylation of Akt in a timedependent manner in both intact and toxin-treated AML12 hepatocytes. Wortmannin and LY-294002 abolished phosphorylation of Akt, further supporting activation of PI 3-kinase/Akt as a signaling pathway, which mediates hepatocyte protection by LPA. Taken together, these results demonstrate that LPA prevents cell apoptosis induced by C. difficile toxin and TNF-[alpha]/ D-galactosamine in the AML12 murine hepatocyte cell line. Cell protection by LPA involves activation of the mitogen-activated protein kinase Erk1/Erk2 cascade and PI 3-kinase-dependent phosphorylation of Akt. lysophosphatidic acid; phosphatidylinositol-3-phosphate kinase; Clostridium difficile; mitogen-activated protein kinase Received 15 February 200; accepted in final form 27 August 2001

The characterization and partial purification of secretory platelet-activating factor (PAF)-acetylhydrolase of the rat hepatobiliary system were conducted. The objective is to show that both rat hepatocytes and Kupffer cells secrete constitutive pPAF-AH (plasma-type platelet-activating factor-acetylhydrolase) in cultured mediums. Results demonstrate that rat bile contains substantial amounts of PAF-AH exhibiting pPAF-AH properties.

Ecstasy use is a growing problem in the United States. Techniques to demonstrate and characterize the toxicity associated with its use have been limited and employed infrequently. In this study, we compare the deleterious effects of ecstasy use in rats with that of methamphet-amine and traumatic brain injury. Specifically, we investigate the degradation of structural proteins αII-spectrin and tau by the pro-necrotic calpain and pro-apoptotic caspase systems. Ecstasy-induced neurotoxicity is shown after 24 hours, although to a much lesser extent than that of metham-phetamine or traumatic brain injury. Neurotoxicity is still evident after 72 hours. Furthermore, apoptosis of the liver is seen 72 hours after ecstasy use. Use of protease inhibitors may be useful in preventing ecstasy-induced toxicity. [ABSTRACT FROM AUTHOR]

The biological roles of phospholipid growth factors lysophosphatidic acid (LPA) and sphingosine-1-phosphate (S1P) have been broadly investigated. The cellular effects of LPA and S1P are mediated predominantly via endothelial differentiation gene (EDG) receptors. Yet, the biological significance of LPA, S1P and their EDG receptors in cells of the liver remains unclear. Recent data demonstrate the presence of EDG2 and EDG4 mRNA for LPA receptor in a murine hepatocyte cell line transformed with human TGF-α, and in primary mouse hepatocytes. EDG2 receptor protein is expressed in mouse liver, where it appears to be located in nonparenchymal cells. Moreover, we have obtained data suggesting that proliferation of small hepatocyte-progenitors and stem (oval) cells during liver injury is associated with the expression of EDG2 and EDG4 receptors. LPA, and possibly S1P, appear to be essential factors that control proliferation and motility of hepatic stellate cells (HSC) and hepatoma cells. It is proposed that LPA, S1P and their respective EDG receptors play important roles in pathophysiology of chronic liver injury and fibrogenesis. The underlying mechanisms recruited by LPA and S1P in pathogenesis of liver injury remain to be investigated. [Copyright &y& Elsevier]

Liver and kidney damage associated with polytrauma, endotoxic shock/sepsis, and organ transplantation, are among the leading causes of the multiple organ failure. Development of novel sensitive biomarkers that detect early stages of liver and kidney injury is vital for the effective diagnostics and treatment of these life-threatening conditions. Previously, we identified several hepatic proteins, including Argininosuccinate Synthase (ASS) and sulfotransferases which were degraded in the liver and rapidly released into circulation during Ischemia/Reperfusion (I/R) injury. Here we compared sensitivity and specificity of the newly developed sandwich ELISA assays for ASS and the sulfotransferase isoform SULT2A1 with the standard clinical liver and kidney tests Alanine Aminotransferase (ALT) and Aspartate Transaminase (AST) in various pre-clinical models of acute injury. Our data suggest that ASS and SULT2A1 have superior characteristics for liver and kidney health assessment in endotoxemia, Ischemia/Reperfusion (I/R), chemical and drug-induced liver injury and may be of high potential value for clinical applications.