FK506 suppresses hypoxia­induced inflammation and protects tight junction function via the CaN­NFATc1 signaling pathway in retinal microvascular epithelial cells.

The present study aimed to identify whether FK506 suppresses hypoxia­induced inflammation and protects tight junction function via the calcineurin­nuclear factor of activated T­cells 1 (CaN­NFATc1) signaling pathway in mouse retinal microvascular endothelial cells (mRMECs). The mRMECs were treated with FK506 at different concentrations following the induction of hypoxia. Trans­epithelial electrical resistance (TEER) and cell permeability were examined to measure the integrity of the tight junctions. The concentrations of inflammatory cytokines were measured using reverse transcription­quantitative polymerase chain reaction analysis and enzyme­linked immunosorbent assays. The protein expression levels of zonula occludens­1 (ZO­1) and nuclear factor of activated T­cell 1 (NFATc1) were identified using immunofluorescent microscopy and western blot analysis. The TEER value was decreased following hypoxia, but increased following treatment with FK506 (1 and 10 µM) for 24 and 48 h. The protein expression of ZO­1 was also increased following FK506 treatment for 24 h at 1 and 10 µM. By contrast, following treatment with FK506 (1 and 10 µM) for 24 and 48 h, the elevated cell permeability in the hypoxia group was significantly downregulated. Similarly, the concentrations of inflammatory cytokines, including cyclooxygenase­2, inducible nitric oxide synthase, monocyte chemoattractant protein­1, interleukin­6, intercellular adhesion molecule­1 and vascular cell adhesion molecule­1, were downregulated following treatment with FK506 for 24 h at 1 and 10 µM. Following treatment with FK506, the level of total NFATc1 was downregulated and the level of phosphorylated NFATc1 was upregulated. Taken together, FK506 suppressed injury to the tight junctions and downregulated the expression of inflammatory cytokines in hypoxia­induced mRMECs via the CaN­NFATc1 signaling pathway. This suggests a potentially effective therapy for hypoxia­induced retinal microangiopathy.