c-Jun NH₂-terminal kinase-2 mediates osmotic stress-induced tight junction disruption in the intestinal epithelium

Abstract

Gastrointestinal epithelium faces osmotic stress, both at physiological and pathophysiological conditions. JNK activation is an immediate cellular response to osmotic stress. We investigated the effect of osmotic stress on intestinal epithelial barrier function and delineated the role of JNK2 in osmotic stress-induced tight junction (TJ) regulation in Caco-2 cell monolayers and ileum of Jnk Ϫ/Ϫ and Jnk2 Ϫ/Ϫ mice. The role of JNK activation in osmotic stress-induced TJ disruption was evaluated using JNK-specific inhibitor and antisense oligonucleotides. Furthermore, the effect of cold restraint stress in vivo on TJ integrity was determined in rats. Osmotic stress disrupted TJs and barrier function in Caco-2 cell monolayers without affecting cell viability. Osmotic stress activated JNK1 and JNK2 and the inhibition of JNK by SP600125 attenuated osmotic stress-induced TJ disruption. TJ disruption and barrier dysfunction by osmotic stress was associated with JNKdependent remodeling of actin cytoskeleton. Knockdown of JNK2 accelerated TJ assembly and attenuated osmotic stress-induced TJ disruption in Caco-2 cell monolayers. In mouse ileum in vitro, osmotic stress increased paracellular permeability, which was attenuated by SP600125. Osmotic stress disrupted actin cytoskeleton and TJs and increased paracellular permeability in the ileum of wild-type and JNK1 Ϫ/Ϫ mice, but not in JNK2 Ϫ/Ϫ mouse ileum. Cold restraint stress activated JNK in rat ileum and caused JNK-dependent remodeling of actin cytoskeleton and redistribution of occludin and zona occluden-1 from the intercellular junctions. These results reveal the role of JNK2 in the mechanism of osmotic stress-induced TJ disruption in the intestinal epithelium.

JNK Signaling: Regulation and Functions Based on Complex Protein-Protein Partnerships

“…Additionally, JNK is an important regulator of cell-cell adhesion. For example, JNK activation can lead to changes in epithelial morphology, adherens, and tight junctions (277,278). Recent studies have implicated many more JNK target proteins in these processes, including Rho-family small G-protein activators (DOCK5, DOCK7), Rab-family G-protein partners (MADD, RUSC2), vesicular transport adaptors (APBA2/MINT2), actin filament assembly proteins (Formin1, FHOD3), microtubule-associated proteins (CCSER1), and molecular motors (Myosin-9B) (80,158).…”

“…The phosphorylation of eNOS at Ser114 (lying on a loop on the heme domain, directly facing its catalytic site) potentiated its activity (358). Multiple 14-3-3 proteins (such as 14-3-3 or 14-3-3) were also described as being phosphorylated by JNK (277,278,359,360). Their case is quite unusual, as the phosphorylation site lies in a structural domain, on a short loop connecting two ␣-helices.…”

Overexpression of Hsp70 confers cytoprotection during gliadin exposure in Caco-2 cells

“…Stressful physiological and nonphysiological stimuli influence intestinal integrity (13,21,22), and by that contribute to the development of various diseases. In CD, the mechanism that allows gliadin to cross the intestinal epithelium are largely unknown.…”

“…Such cytoskeletal changes are not exclusively seen after gliadin exposure but also described for a wider range of cell stress such as heat, ischemia, high osmolarity, high glucose, or acidosis (21)(22)(23)). We and others were able to demonstrate that cells exposed to one of the latter respond with drastic alterations in the cytoskeletal network, expression of cell-cell adhesion molecules and its associated tight junctions, similar to the alterations triggered by gliadin (13,(24)(25)(26).…”

Mitochondrial Permeability Transition in Pathogenesis of Hemorrhagic Injury: Targeted Therapy with Minocycline

“…LPS and other gut-derived toxins entering the liver after H/R stimulate free radical generation and prointlammatory cytokine release by Kupffer cells to contribute to hepatic injury and increased cytokines in the blood stream [32][33][34][35]. Since JNK2 is also associated with the loss ofbarrier function of the gut [36,37), we hypothesized that }NK2 is important for promotion of liver injury after H/R. Here, we test this hypothesis and show that liver injury decreases and hepatic function improves after H/R to JNK2 deficient mice in comparison to wildtype mice.…”