Cyclic AMP-guanine exchange factor activation inhibits JNK-dependent lipopolysaccharide-induced apoptosis in rat hepatocytes

Abstract

Lipopolysaccharide (LPS) is known to damage hepatocytes by cytokines released from activated Kupffer cells, but the ancillary role of LPS as a direct hepatotoxin is less well characterized. The aim of this study was to determine the direct effect of LPS on hepatocyte viability and the underlying signaling mechanism. Rat hepatocyte cultures treated overnight with LPS (500 ng/mL) induced apoptosis as monitored morphologically (Hoechst 33258) and biochemically (cleavage of caspase 3 and 9 and the appearance of cytochrome C in the cytoplasm). LPS-induced apoptosis was additive to that induced by glycochenodeoxycholate or Fas ligand, was associated with activation of c-Jun N-terminal kinase B (JNK) and p38 mitogen-activated protein kinases (MAPK), and inhibition of protein kinase (AKT). Inhibition of JNK by SP600125, but not of p38 MAPK by SB203580 attenuated LPS-induced apoptosis, indicating JNK dependency. CPT-2-Me-cAMP, an activator of cAMP-GEF, decreased apoptosis due to LPS alone or in combination with glycochenodeoxycholate or Fas ligand. CPT-2-Me-cAMP also prevented LPS-induced activation of JNK and inhibition of AKT Taken together, these results suggest that LPS can induce hepatocyte apoptosis directly in vitro in a JNK-dependent manner and activation of cAMP-GEF protects against the LPS-induced apoptosis most likely by reversing the effect of LPS on JNK and AKT

The effects of ursodeoxycholic acid on sepsis-induced cholestasis management in an animal model

“…The primary suggested mechanism underlying hepatocyte death is LPS-induced apoptosis. 23 In our study, LPS-induced hepatocyte death was evident via the higher percentage of apoptosis compared to the control group; UDCA resulted in a lower percentage of apoptosis comparable to that of the control group, suggesting a positive effect of UDCA in minimizing or preventing hepatocellular damage and death. The effect of UDCA on apoptosis inhibition has been reportedly mediated by the upregulation of various anti-apoptotic proteins, such as FLICE-inhibitory protein, myeloid leukaemia sequence-1 protein, and cellular inhibitor of apoptosis-2 protein.…”

Intracellular cAMP Sensor EPAC: Physiology, Pathophysiology, and Therapeutics Development

“…GSK inhibition prevents bile acid-induced phosphorylation of proapoptotic JNK and thus protects hepatocytes against bile acid-induced apoptosis (481). Furthermore, lipopolysaccharide (LPS) has been demonstrated to induce hepatocyte apoptosis through the activation of JNK and inhibition of Akt, whereas EPAC activation reverses the LPS-mediated activation of JNK and Akt to prevent LPS-induced apoptosis (836). Therefore, these studies suggest EPAC signaling may be implicated in a general cytoprotective role in liver cells.…”

Quantitative proteomic analysis of hepatocyte-secreted extracellular vesicles reveals candidate markers for liver toxicity

“…In the current report, we identified novel putative markers for liver injury in an in vitro model. We used two well-known hepatotoxins, galactosamine (galN), which causes liver injury resembling acute viral hepatitis [33], and Escherichia coli -derived lipopolysaccharide (LPS) promoting liver inflammation and damage [34–38]. Finally, by using an animal model for acute liver injury, we showed that similar protein alterations can be detected in the EVs isolated from sera.…”