Adaptive Remodeling of an In Vitro Gut–Vascular Barrier Model Composed of Rat Intestinal Microvascular Endothelial Cells Under Cobalt Chloride-Induced Chemical Hypoxia

The gut–vascular barrier (GVB) serves as a critical defense against bacterial translocation, yet its adaptive response to hypoxic stress remains poorly defined. Here, we investigated how cobalt chloride-induced chemical hypoxia (500 μM CoCl2) affects rat intestinal microvascular endothelial cells (RIMVECs) and the in vitro RIMVEC monolayer model, combining Evans blue (EB)–albumin efflux assays, Western blotting, immunofluorescence, and migration assays. Under the conditions tested, short-term CoCl2 exposure (SC, 6 h) enhanced the integrity of the RIMVEC monolayer, whereas prolonged CoCl2 exposure (PC, 24 h) disrupted the barrier. SC-mediated protection was associated with HIF-1α activation, altered expression of tight junction proteins (ZO-1, Occludin, and Claudin-1), cytoskeletal stabilization, and enhanced endothelial migration. In contrast, PC induced tight junction disassembly and cytoskeletal remodeling under sustained HIF-1α signaling. Silencing HIF-1α attenuated these effects, supporting a role for HIF-1α in the RIMVEC monolayer. Notably, prior SC attenuated subsequent inflammatory RIMVEC monolayer damage. Collectively, these findings indicate that chemical hypoxia can exert an HIF-1α-associated, duration-dependent effect on the RIMVEC monolayer and suggest that modulating hypoxia duration may offer a potential strategy for GVB-related disorders.