Epithelial exposure to hypoxia modulates neutrophil transepithelial migration.
Polymorphonuclear leukocytes (PMN) are central to the pathogenesis of a number of intestinal diseases. PMN-induced damage to the protective epithelium occurs in hemorrhagic shock, necrotizing enterocolitis and conditions resulting in intestinal reperfusion injury. In such diseases, tissue hypoxia has been implicated as a pathophysiologic mediator. Thus, we hypothesized that exposure of intestinal epithelia to hypoxia may modulate PMN-epithelial interactions. In this study, T84 cell monolayers, a human intestinal crypt cell line, and isolated human PMN were used to examine the influence of hypoxia/reoxygenation (H/R) on PMN transepithelial migration. Confluent T84 cell monolayers were exposed to hypoxia (range 2-21% O2 for 0-72 h) and reoxygenated with buffer containing PMN. Transmigration of PMN (basolateral to apical orientation) was driven by a transepithelial gradient of the chemotactic peptide tMLP. In response to hypoxia/reoxygenation (H/R), transmigration into, and across epithelial monolayer was increased in a dose- (EC50 approximately 7% O2) and time-dependent fashion (3.5 +/- 0.3-fold increase at 2% O2 for 48 h, P < 0.001). Such conditions of H/R were not toxic to epithelia and did not influence epithelial barrier function. The influence of H/R on PMN transmigration was protein synthesis-dependent (> 80% decreased in the presence of cycloheximide) and could be inhibited by addition of functionally inhibitory antibodies to the PMN beta 2 integrin CD11b/18 (> 80% attenuated) and to CD47 (> 90% decreased compared to control). Hypoxia induced epithelial production and basolateral release of the PMN activating chemokine interleukin-8 (IL-8, nearly sixfold increase over normoxic control) which remained avidly associated with the epithelial matrix. Treatment of epithelial cells with IL-8 antisense oligonucleotides resulted in decreased monolayer-associated PMN but did not influence PMN transmigration, suggesting that epithelial IL-8 production may serve as a recruitment signal for PMN to the basal surface of polarized epithelia. The present observations indicate that H/R provides a relevant stimulus for novel biochemical crosstalk between epithelia and PMN.
Colgan
S P
SP
Center for Experimental Therapeutics and Reperfusion Injury, Brigham and Women's Hospital, Boston, Massachusetts, USA.
Dzus
A L
AL
Parkos
C A
CA
D000818:Animals; D015703:Antigens, CD / Q000378:metabolism; D018821:CD18 Antigens / Q000378:metabolism; D051928:CD47 Antigen; D002352:Carrier Proteins / Q000378:metabolism; D002465:Cell Movement; D002478:Cells, Cultured; D004847:Epithelial Cells; D006801:Humans; D016209:Interleukin-8 / Q000378:metabolism; D051379:Mice; D008954:Models, Biological; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000378:metabolism; D009504:Neutrophils / Q000166:cytology*; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D010100:Oxygen / Q000378:metabolism*
D015703:Antigens, CD; D018821:CD18 Antigens; D051928:CD47 Antigen; C497894:CD47 protein, human; D002352:Carrier Proteins; C497895:Cd47 protein, mouse; D016209:Interleukin-8; D016376:Oligonucleotides, Antisense; D009240:N-Formylmethionine Leucyl-Phenylalanine; D010100:Oxygen