Panoply™ Human TLR7 Over-expressing Stable Cell Line

Rosacea is a chronic inflammatory skin disease caused by impaired skin barrier function and innate/adaptive immune dysregulation. Toll-like receptors (TLRs) can sense damaged skin and initiate downstream inflammatory and immune responses, but their role in rosacea remains unclear. Here, researchers used RNA sequencing analysis to discover that the TLR signaling pathway is the most enriched signaling pathway in rosacea lesions, with TLR7 being particularly prominent and positively correlated with the severity of inflammation. In an LL37-induced rosacea-like mouse model, silencing TLR7 prevented the development of rosacea-like skin inflammation. Specifically, researchers demonstrated that overexpression of TLR7 in keratinocytes activates the rapamycin-sensitive mTOR complex 1 (mTORC1) pathway via the NFκB signaling pathway. Ultimately, the TLR7/NFκB/mTORC1 axis promotes the production of cytokines and chemokines, leading to the migration and infiltration of CD4+ T cells into rosacea lesions. These studies reveal the crucial role of TLR7 in the pathogenesis of rosacea and suggest that it may be a potential target for the treatment of rosacea.

Here, researchers performed RNA-sequencing from TLR7-overexpressing HaCaT keratinocytes with or without R848 (a specific ligand of TLR7) treatment and identified 1,501 differentially expressed genes (DEGs) between two groups. Gene set enrichment analysis (GSEA) showed that the NFκB signaling pathway ranked among the top two (Figure 1A and B). To determine whether TLR7 regulates NFκB, researchers used immunoblotting to examine the phosphorylation level of p65/NFκB (p-p65) in TLR7-overexpressing human keratinocytes. The results showed that R848 activation of TLR7 significantly enhanced the activation of the NFκB signaling pathway (Figure 1C). However, after TLR7 overactivation, the non-canonical NFκB pathway (P100/P52) could not be activated. Furthermore, R848 stimulation upregulated NFκB family transcription factors (including NFKB1, NFKB2, RELA, and RELB) (Figure 1D). To further verify the role of TLR7 in regulating the NFκB signaling pathway in rosacea, researchers performed immunofluorescence staining on mouse skin lesions and found that the antimicrobial peptide LL37 increased p-p65 expression in the epidermis, a phenomenon not observed in Tlr7 siRNA-treated mice (Figure 1E and F). This evidence suggests that TLR7 activation in keratinocytes can activate the NFκB signaling pathway in rosacea.

Figure 1. Stimulation of TLR7 activates NFκB signaling in keratinocytes. (Huang Y, et al., 2023)