Epithelial permeability induced by neutrophil transmigration is potentiated by hypoxia: Role of intracellular cAMP

Abstract

Mucosal tissues, such as the lung and intestine, are primary targets for ischemic damage. Under these conditions, neutrophil (polymorphonuclear leukocyte; PMN) infiltration into the protective epithelium has been implicated as a pathophysiologic mediator. Because PMN transepithelial migration results in increased paracellular permeability, and because our previous data revealed that epithelial hypoxia enhances PMN transmigration, we hypothesized that macromolecular permeability may be altered in epithelium exposed to hypoxia and reoxygenation (H/R) in the presence of PMNs. Human intestinal epithelia (T84) were grown on permeable supports, exposed to cellular hypoxia (pO2 20 torr) for 0-72 hr, and examined for increases in PMN-evoked permeability by using standard flux assays. Increasing epithelial hypoxia potentiated PMN-induced permeability of labeled paracellular tracers (size range 3-500 kD). Such increases were blocked by monoclonal antibody (mAb) to the PMN integrin CD11b (82 +/- 1% decreased compared with control mAb) and were partially blocked by anti-CD47 mAb (51 +/- 1%). Assessment of barrier recovery revealed that monolayers exposed to H/R were significantly diminished in their ability to reseal following PMN transmigration (recovery of 36 +/- 6% in H/R vs. 94 +/- 2% in normoxic controls). Because intracellular cyclic AMP (cAMP) has been demonstrated to regulate epithelial permeability, and because PMN-derived compound(s), (i.e., 5'-adenosine monophosphate; AMP) elevate epithelial cAMP, we examined the impact of hypoxia on epithelial cAMP responses. These experiments revealed that hypoxic epithelia were diminished in their ability to generate cAMP, and pharmacologic elevation (8-bromo-cAMP) of intracellular cAMP in hypoxic cells normalized both PMN-induced permeability changes and restoration of barrier function. These results support a role for PMN in increased intestinal permeability associated with reperfusion injury and imply a substantial role for cAMP signaling in maintenance of permeability during PMN transmigration.

Improving effect of Sivelestat on lipopolysaccharide‐induced lung injury in rats

“…Meanwhile, it is known that the MPO activity was markedly relevant to tissue neutrophil accumulation . The endothelial permeability thus increases due to the structure damage of the endothelial cells as well as to the enzymatic cleavage of adherent junction proteins , which eventually results in the transmigration of leukocytes across the endothelial lining into the surrounding tissues and the loss of fluid into extravascular space leading to severe hypoxemia and life‐threatening edema in the lung .…”

Regulation of endothelial and epithelial barrier functions by peptide hormones of the adrenomedullin family

“…74,118,119 ADM-induced elevation of cAMP has also been reported in epithelial cells, but in these studies a direct effect of ADM-induced barrier function has not been investigated. 120,121 Nevertheless, many other studies have shown that increased cAMP concentrations can improve epithelial barriers, [122][123][124] suggesting that ADM-induced cAMP would contribute to epithelial barrier protection. By contrast, a recent study suggests that ADM may stabilize the epithelial barrier via cAMP-independent mechanisms.…”

Heat shock protein 90β inhibits apoptosis of intestinal epithelial cells induced by hypoxia through stabilizing phosphorylated Akt

“…Due to high blood flow under normal conditions, the intestine is particularly susceptible to ischemia and resultant tissue hypoxia (6). It has been shown that ischemia/reperfusion triggers apoptosis in rat intestinal epithelial cells (7).…”