Pharmacological HIF-1 stabilization promotes intestinal epithelial healing through regulation of α-integrin expression and function

Intestinal epithelia are critical for maintaining gastrointestinal homeostasis. Epithelial barrier injury, causing inflammation and vascular damage, results in inflammatory hypoxia, and thus, healing occurs in an oxygen-restricted environment. The transcription factor hypoxia-inducible factor (HIF)-1 regulates genes important for cell survival and repair, including the cell adhesion protein beta 1-integrin. Integrins function as alpha beta-dimers, and alpha-integrin-matrix binding is critical for cell migration. We hypothesized that HIF-1 stabilization accelerates epithelial migration through integrin-dependent pathways. We aimed to examine functional and post-translational activity of alpha-integrins during HIF-1-mediated intestinal epithelial healing. Wound healing was assessed in T84 monolayers over 24 h with/without prolyl-hydroxylase inhibitor (PHDi) (GB-004), which stabilizes HIF-1. Gene and protein expression were measured by RT-PCR and immunoblot, and alpha-integrin localization was assessed by immunofluorescence. alpha-integrin function was assessed by antibody-mediated blockade, and integrin alpha 6 regulation was determined by HIF-1 alpha chromatin immunoprecipitation. Models of mucosal wounding and 2,4,6-trinitrobenzenesulfonic acid (TNBS)-induced colitis were used to examine integrin expression and localization in vivo. PHDi treatment accelerated wound closure and migration within 12 h, associated with increased integrin alpha 2 and alpha 6 protein, but not alpha 3. Functional blockade of integrins alpha 2 and alpha 6 inhibited PHDi-mediated accelerated wound closure. HIF-1 bound directly to the integrin alpha 6 promoter. PHDi treatment accelerated mucosal healing, which was associated with increased alpha 6 immunohistochemical staining in wound-associated epithelium and wound-adjacent tissue. PHDi treatment increased alpha 6 protein levels in colonocytes of TNBS mice and induced alpha 6 staining in regenerating crypts and reepithelialized inflammatory lesions. Together, these data demonstrate a role for HIF-1 in regulating both integrin alpha 2 and alpha 6 responses during intestinal epithelial healing. NEW & NOTEWORTHY HIF-1 plays an important role in epithelial restitution, selectively inducing integrins alpha 6 and alpha 2 to promote migration and proliferation, respectively. HIF-stabilizing prolyl-hydroxylase inhibitors accelerate intestinal mucosal healing by inducing epithelial integrin expression.

Automated summary

HIF-1 plays a crucial role in intestinal epithelial restitution by selectively inducing integrins alpha 6 and alpha 2 to promote migration and proliferation. Treatment with HIF-stabilizing prolyl-hydroxylase inhibitors accelerates intestinal mucosal healing by inducing epithelial integrin expression.