INTESTINAL CYTOSKELETON DEGRADATION PRECEDES TIGHT JUNCTION LOSS FOLLOWING HEMORRHAGIC SHOCK


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Abstract

Hemorrhagic shock (HS) leads to intestinal barrier loss, causing systemic inflammation, which in turn can ultimately lead to multiorgan dysfunction syndrome. Barrier function is based on tight junctions (TJs) between intact epithelial cells. These TJs are anchored in the cell via the filamentous actin (F-actin) cytoskeleton. We hypothesize that HS causes hypoperfusion, leading to loss of F-actin, via activation of actin-depolymerizing factor/cofilin (AC), and consequently TJ loss. This study is aimed at unraveling the changes in cytoskeleton and TJ integrity after HS in organs commonly affected in multiorgan dysfunction syndrome (liver, kidney, and intestine) and to elucidate the events preceding cytoskeleton loss. Adult rats were subjected to a nonlethal HS and sacrificed, along with unshocked controls, at 15, 30, 60, and 90 min after induction of shock. Cytoskeleton, TJ integrity loss, and its consequences were studied by assessment of globular actin, F-actin, AC, zonula occludens protein 1, claudin 3, and bacterial translocation. In the liver and kidney, TJ and the F-actin cytoskeleton remained intact at all time points studied. However, in the intestine, significant loss of F-actin and increase of globular actin was seen from 15 min after shock. This change preceded statistically significant loss of the TJ proteins claudin 3 and zonula occludens protein 1, which were observed starting at 60 min after induction of shock (P < 0.05 vs. controls). Early after induction of shock (15 and 30 min) the nonactive AC (phosphorylated AC) in the intestine was significantly decreased (by 21% and 27%, P < 0.05 vs. control), whereas total AC remained constant, reflecting an increase in activated AC in the intestine from 15 min after shock. Bacterial translocation to mesenteric lymph nodes, liver, and spleen was present from 30 min after shock. This study shows for the first time that HS results in AC activation, selective intestinal actin cytoskeleton disruption, and TJ loss very early after the onset of shock. Loss of this intestinal barrier results in translocation of toxins and bacteria, which enhances inflammation and leads to infections.

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