TLR8 aggravates skin inflammation and fibrosis by activating skin fibroblasts in systemic sclerosis

Xiangzhen Kong; Shuai Jiang; Qiuyu He; Xiangguang Shi; Weilin Pu; Yan Huang; Yanyun Ma; Qingmei Liu; Dayan Sun; Delin Huang; Fei Wu; Pengcheng Li; Wenzhen Tu; Yinhuan Zhao; Lei Wang; Yuanyuan Chen; Wenyu Wu; Yulong Tang; Xiansheng Zhao; Qing Zhu; Jian Gao; Weihong Xu; Xiaochuan Shui; Feng Qian; Jiucun Wang

doi:10.1093/rheumatology/kead456

TLR8 aggravates skin inflammation and fibrosis by activating skin fibroblasts in systemic sclerosis

Rheumatology (Oxford). 2023 Sep 4:kead456. doi: 10.1093/rheumatology/kead456. Online ahead of print.

Authors

Xiangzhen Kong¹, Shuai Jiang², Qiuyu He¹, Xiangguang Shi³, Weilin Pu⁴, Yan Huang¹, Yanyun Ma^{5

6}, Qingmei Liu³, Dayan Sun⁷, Delin Huang¹, Fei Wu¹, Pengcheng Li⁸, Wenzhen Tu⁹, Yinhuan Zhao⁹, Lei Wang⁹, Yuanyuan Chen⁹, Wenyu Wu³, Yulong Tang¹, Xiansheng Zhao¹⁰, Qing Zhu¹¹, Jian Gao^{1

12}, Weihong Xu¹³, Xiaochuan Shui¹⁴, Feng Qian¹², Jiucun Wang^{1

15

16}

Affiliations

¹ State Key Laboratory of Genetic Engineering, Collaborative Innovation Center for Genetics and Development, School of Life Sciences, and Human Phenome Institute, Fudan University, Shanghai, China.
² Department of General Surgery, Shanghai Pudong Hospital, Fudan University Pudong Medical Center, Shanghai Key Laboratory of Vascular Lesions Regulation and Remodeling, Shanghai, China.
³ Department of Dermatology, Huashan Hospital and State Key Laboratory of Genetic Engineering, School of Life Sciences, Fudan University, Shanghai, China.
⁴ Greater Bay Area Institute of Precision Medicine (Guangzhou), School of Life Sciences, Fudan University, Guangzhou, China.
⁵ Institute for Six-sector Economy, Fudan University, Shanghai, China.
⁶ Ministry of Education Key Laboratory of Contemporary Anthropology, School of Life Sciences, Fudan University, Shanghai, China.
⁷ Department of Neonatal Surgery, National Center for Children's Health, Beijing Children's Hospital, Capital Medical University, Beijing, China.
⁸ Department of Pancreatic Surgery, Fudan University Cancer Hospital, Shanghai, China.
⁹ Division of Rheumatology, Shanghai Integrated Traditional Chinese and Western Medicine Hospital, Shanghai, China.
¹⁰ Department of Dermatology, Huashan Hospital, Fudan University, Shanghai, China.
¹¹ Division of Gastroenterology and Hepatology, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China.
¹² Ministry of Education Key Laboratory of Contemporary Anthropology, Zhangjiang Fudan International Innovation Center, Human Phenome Institute and School of Life Sciences, Fudan University, Shanghai, China.
¹³ Laboratory Department of Tongren Hospital Affiliated to Medical College of Shanghai Jiaotong University, Shanghai, China.
¹⁴ Xiangyang Central Hospital, Affiliated Hospital of Hubei University of Arts and Science, Xiangyang, China.
¹⁵ Research Unit of Dissecting the Population Genetics and Developing New Technologies for Treatment and Prevention of Skin Phenotypes and Dermatological Diseases (2019RU058), Chinese Academy of Medical Sciences, Beijing, China.
¹⁶ Institute of Rheumatology, Immunology, and Allergy, Fudan University, Shanghai, China.

PMID: 37665747
DOI: 10.1093/rheumatology/kead456

Abstract

Objectives: Innate immunity significantly contributes to systemic sclerosis (SSc) pathogenesis. TLR8 is an important innate immune mediator that is implicated in autoimmunity and fibrosis. However, the expression, mechanism of action, and pathogenic role of TLR8 in SSc remain unclear. The aim of this study was to explore the roles and underlying mechanisms of TLR8 in SSc.

Methods: The expression of TLR8 was analyzed based on a public dataset and then verified in skin tissues and skin fibroblasts of SSc patients. The role of TLR8 in inflammation and fibrosis was investigated using a TLR8-overexpression vector, activator (VTX-2337), inhibitor (cu-cpt-8m), and TLR8 siRNA in skin fibroblasts. The pathogenic role of TLR8 in skin inflammation and fibrosis was further validated in a bleomycin (BLM)-induced mouse skin inflammation and fibrosis model.

Results: TLR8 levels were significantly elevated in SSc skin tissues and myofibroblasts, along with significant activation of the TLR8 pathway. In vitro studies showed that overexpression or activation of TLR8 by a recombinant plasmid or VTX-2337 upregulated IL-6, IL-1β, COL I, COL III, and α-SMA in skin fibroblasts. Consistently, both TLR8-siRNA and cu-cpt-8m reversed the phenotypes observed in TLR8-activating fibroblasts. Mechanistically, TLR8 induces skin fibrosis and inflammation in a manner dependent on the MAPK, NF-κB, and SMAD2/3 pathways. Subcutaneous injection of cu-cpt-8m significantly alleviated BLM-induced skin inflammation and fibrosis in vivo.

Conclusion: TLR8 might be a promising therapeutic target to improve the treatment strategy for SSc skin inflammation and fibrosis.

Keywords: TLR8; fibrosis; inflammation; skin fibroblasts; systemic sclerosis.