The emerging role of irisin in experimentally induced arthritis: a recent update involving HMGB1/MCP1/Chitotriosidase I-mediated necroptosis.

Objectives: Necroptosis is a tightly adjusted inflammatory necrotizing cell death signaling pathway that participates in pathogenesis of discrete diseases as rheumatoid arthritis (RA). Irisin is a myokine with immuno-modulatory effect. Evaluation of irisin efficiency as a novel therapeutic agent in experimentally induced RA via modulating immuno-inflammatory, necroptotic molecular and biochemical signaling pathways.

Methods: RA was induced in 30 female Wister albino rats by a single subcutaneous injection of collagen-II with incomplete Freund's adjuvant (CII-IFA) followed by booster immunization dose 10 days later. After 14 days of the injection, arthritis chronic phase was precipitated. 15 rats were treated by S.C irisin injection daily for 4 weeks. Joint tissue homogenate RIPK-3, MLKL, HMGB1, MCP1, IL-6, CHIT1, MDA, and PN levels were assessed calorimetrically. However, TNF-α mRNA expression level was evaluated by the qrt-PCR technique.

Results: The results showed that irisin significantly decreases the level of all assessed biochemical parameters, except MDA, which was significantly increased in comparison with the correspondent values in the arthritic group with no treatment (ttt).

Conclusions: Irisin exhibits therapeutic anti-inflammatory and antioxidant effects via modulating immuno-inflammatory, necroptotic molecular, and biochemical signaling pathways in experimentally induced RA in rats.

Abbreviations: RA: rheumatoid arthritis; RIPK3: receptor-interacting protein kinase 1; MLKL: mixed lineage kinase domain-like protein; HMGB1: High-mobility group protein box 1; MCP1: Monocyte chemoattractant protein 1; IL-6: Interleukin 6; CHIT1: Chitotriosidase; MDA: Malondialdehyde; PN: Peroxynitrite; TNF-α: Tumor Necrosis Factor; qrt-PCR: quantitative real-time reverse transcription PCR; CII-IFA: collagen-II with incomplete Freund's adjuvant; ttt: treatmentNote: gene (NCBI GenBank Nucleotide accession # NM_012675.3); The housekeeping gene (NCBI GenBank Nucleotide accession # NM_017008.4).