Tacrolimus Modulates TGF-β Signaling-Related Genes and MicroRNAs in Human Retinal Pigment Epithelial Cells Activated by Lipopolysaccharide.

The retinal pigment epithelium (RPE) plays a crucial role in maintaining retinal homeostasis, and dysregulation of the transforming growth factor-beta (TGF-β) signaling pathways contributes to retinal fibrosis and inflammatory diseases, including proliferative vitreoretinopathy (PVR). Tacrolimus (FK506), an immunosuppressant, has shown potential antifibrotic properties, but its effects on TGF-β-related genes and microRNAs (miRNAs) in RPE cells remain unclear. Human RPE (H-RPE) cells were treated with lipopolysaccharide (LPS) to induce inflammation and subsequently exposed to tacrolimus. Gene and miRNA expression profiling related to TGF-β signaling pathways were conducted using microarrays, followed by Quantitative Reverse-Transcription Polymerase Chain Reaction (RT-qPCR) validation. Protein levels were assessed via enzyme-linked immunosorbent assay (ELISA), and interactions were analyzed using STRING database network analysis. Tacrolimus modulated key components of the TGF-β pathway, upregulating TGF-β2, TGF-β3, SMAD2, and SMAD4 while downregulating TGF-βR1 and SMAD7. JAK/STAT and MAPK pathways were also affected, indicating broad regulatory effects. miRNA profiling identified hsa-miR-200a-3p, hsa-miR-589-3p, hsa-miR-21, and hsa-miR-27a-5p as key regulators. STRING analysis confirmed strong functional interactions within the TGF-β network. In conclusion, tacrolimus modulates both canonical (upregulation of SMAD2/4 and downregulation of SMAD7) and non-canonical (JAK/STAT and MAPK) TGF-β signaling pathways in LPS-stimulated RPE cells. These changes collectively suggest a dual anti-inflammatory and anti-fibrotic effect. The increased TGF-β2 and decreased SMAD7 levels, alongside altered miRNA expression (e.g., downregulation of miR-200a-3p), indicate that tacrolimus may inhibit key profibrotic mechanisms underlying PVR. These findings support the potential therapeutic repurposing of tacrolimus in PVR and warrant further in vivo validation.