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.