Azithromycin alleviates the severity of rheumatoid arthritis via targeting UPR component GRP78

Abstract

Background and Purpose: Azithromycin (AZM) is a macrolide antibiotic with well-described anti-inflammatory properties. This study aimed to substantiate its treatment potential in rheumatoid arthritis (RA). Experimental Approach: Gene expression profiles were collected by RNA-sequencing and the effects of AZM were assessed in functional assays. In vitro and vivo assays for examining the blockade of glucose-regulated protein 78 (GRP78) actions by AZM: assays for defining the anti-inflammatory activity of AZM using fibroblast-like synoviocytes (FLSs) from RA patients as well as collagen-induced arthritis (CIA) in DBA/1 mice. Identification and characterization of the binding of AZM to GRP78 using drug affability responsive target stability assay, proteomics and cellular thermal shift assay. Detect AZM inhibition of GRP78 and dependence of AZM’s anti-arthritis activity on GRP78. Key Results: AZM reduced pro-inflammatory factor production, cell migration, invasion and chemo-attractive potential, enhanced apoptosis, thereby reducing the deleterious inflammatory response of RA FLSs in vitro. AZM ameliorated the severity of CIA lesions. Transcriptional analyses implied that AZM treatment causes impairments in signaling cascades associated with cholesterol and lipid biosynthetic process. GRP78 was isolated as a novel target of AZM. AZM-mediated activation of unfolded protein response (UPR) via inhibiting GRP78 activity is required not only for inducing the expression of C/EBP-homologous protein (CHOP), but also for activation of sterol-regulatory element binding protein (SREBP) and its targeted genes involved in cholesterol and lipid biosynthetic process. Further, deletion of GRP78 abolished AZM’s anti-arthritis activity. Conclusion and Implications: These findings confirmed that AZM is an anti-arthritis therapeutic drug for RA treatment.