Tomorou attenuates progression of rheumatoid arthritis through alteration in ULK-1 independent autophagy pathway in collagen induced arthritis mice model

Abstract

Rheumatoid arthritis (RA) is a multifactorial disease which is complicated by apoptosis resistance. Autophagy is one of the key mechanisms which are involved in the development of resistance to apoptosis as well as to the standard therapies against RA. Aberration in autophagy and apoptosis homeostasis results in the development of oxidative stress thus complicates the pathogenesis of RA. In the given study, tomorou, an indigenous herb of Hunza-Nagar Valley, has been evaluated for its pro-apoptotic, anti-inflammatory, and anti-rheumatic activity. Several major classes of bioactive phytochemicals including steroids, terpenoids, phenols, flavonoids, and essential oils have been detected in the aqueous and ethyl acetate extracts of tomorou through phytochemical analysis. Plant extracts depicted enhanced free radical scavenging activity through di-phenyl-2-picryl hydrazyl hydrate (DPPH) assay and ameliorated the symptoms of arthritis in collagen induced arthritic (CIA) mice model. Moreover, the 6 week extract treatment resulted in the reduction of IL-6 serum levels thus making it an effective anti-inflammatory agent. Upregulation of microtubule-associated proteins light chain 3b (LC3b) and downregulation of UNC51-like kinase 1 (ULK-1) in arthritic mice proposed a ULK-1 independent non-canonical autophagy pathway. Treatment with extracts upregulated the expression of caspase 3 which in turn inhibited the activity of LC3b thus altering the autophagy pathway. However, ULK-1 expression was restored to normal in aqueous extract treated group whereas it was upregulated in ethyl acetate extract treated group. On the other hand, a novel LC3b-independent autophagy pathway was observed in mice treated with ethyl acetate extract due to ULK-1 upregulation. Despite of significantly high IL-6 levels, the arthritic symptoms waned off which suggested the participation of IL-6 in LC3b-independent autophagy pathway in the extract prepared in ethyl acetate. Conclusively, the study established pro-apoptotic, antioxidant, anti-inflammatory and anti-rheumatic activity of tomorou and suggested an intricate autophagy pathway shift.