GBP5 exacerbates rosacea‐like skin inflammation by skewing macrophage polarization towards M1 phenotype through the NF‐κB signalling pathway

Abstract Background Rosacea is a chronic inflammatory skin disease with increased macrophage infiltration. However, the molecular mechanism remains unclear. Objectives To determine the significance of macrophage infiltration, and the correlation between Guanylate‐binding protein 5 (GBP5) and polarization of macrophages in rosacea‐like inflammation. Methods Here we tested the hypothesis that Guanylate‐binding protein 5 (GBP5) aggravates rosacea‐like skin inflammation by promoting the polarization of the M1 macrophages through the NF‐κB signalling pathway. We depleted macrophage by injecting clodronate‐containing liposomes. We next explored the association between GBP5 and macrophage in rosacea tissue through transcriptome analysis and immunofluorescence analysis. We evaluated the severity of rosacea‐like skin inflammation when BALB/c mice were injected with GBP5 siRNA intradermally daily for three consecutive days. At last, to study the causality of knocking down GBP5‐blunted M1 macrophage polarization, THP‐1 cell was treated with GBP5 siRNA. Results Macrophage depletion ameliorated rosacea‐like skin inflammation in mice, implying the important role of macrophages in rosacea. Based on the transcriptome analysis, Guanylate‐binding protein 5 (GBP5) was identified as hub gene that was associated with macrophage infiltration in rosacea. Next, we found that GBP5 expression was significantly upregulated in rosacea tissues and positively correlated with macrophage infiltration, the immunofluorescence analysis revealed the co‐localization between GBP5 and macrophages. In vivo, silencing of GBP5 attenuated rosacea‐like skin inflammation in the LL‐37‐induced mouse model and suppressed the expression of M1 signature genes such as IL‐6, iNOS and TNF‐a. In vitro, knocking down GBP5 significantly blunted the polarization of the M1 macrophages partly by repressing the activation of the NF‐κB signalling pathways. Conclusions Together, our study revealed the important role of macrophages in rosacea and identified GBP5 as a key regulator of rosacea by inducing M1 macrophage polarization via NF‐κB signalling pathways.