[Mechanism of Yiguanjian in treating dry eye through regulating macrophage polarization]

This study investigated the therapeutic effects of Yiguanjian on dry eye in rats and explored its underlying mechanism in regulating macrophage polarization. A rat model of dry eye was established by topical instillation of 0.2% benzalkonium chloride solution. After successful modeling, the rats were treated continuously for 4 weeks. Dry eye phenotypes were evaluated by the tear secretion test and corneal fluorescein staining. HE staining was performed to assess pathological changes in the cornea and lacrimal gland. PAS staining was employed to count conjunctival goblet cells. TUNEL staining was conducted to evaluate apoptosis. ELISA was employed to measure the levels of interleukin(IL)-1β, IL-6, IL-10, and tumor necrosis factor-α(TNF-α) in the lacrimal gland. Immunofluorescence assay was performed to detect the expression of phosphorylated nuclear factor-κB p65(p-NF-κB p65) in the cornea and to assess changes in the proportions of M1 and M2 macrophages in the lacrimal gland. RT-qPCR was employed to determine the mRNA levels of Toll-like receptor 4(TLR4) and myeloid differentiation factor 88(MyD88). Western blot analysis was performed to quantify the protein levels of TLR4, MyD88, inducible nitric oxide synthase(iNOS), cluster of differentiation 206(CD206), arginase-Ⅰ(Arg-Ⅰ), and NF-κB pathway-related proteins. The results showed that Yiguanjian increased tear secretion, alleviated corneal injury and the pathological changes in the cornea and lacrimal gland, increased conjunctival goblet cell number(P<0.05), and reduced the apoptotic rate(P<0.01) in the rat model of dry eye. In addition, Yiguanjian lowered the levels of IL-1β, IL-6, and TNF-α while increasing the level of IL-10 in the lacrimal gland(P<0.01), and it reduced the expression of p-NF-κB p65 in the corneal tissue(P<0.01), downregulated the expression of TLR4, MyD88, iNOS, and NF-κB pathway-related proteins(P<0.05), and upregulated the expression of CD206 and Arg-Ⅰ(P<0.05). Meanwhile, Yiguanjian decreased the proportion of M1 macrophages(P<0.05) and increased the proportion of M2 macrophages(P<0.01). These findings indicate that Yiguanjian can alleviate ocular surface injury and lacrimal gland inflammation in the rat model of dry eye by inhibiting TLR4/MyD88/NF-κB signaling pathway activation and promoting macrophage polarization from the M1 to the M2 phenotype.