RTD-1 therapeutically normalizes synovial gene signatures in rat autoimmune arthritis and suppresses proinflammatory mediators in RA synovial fibroblasts.

Prasad Tongaonkar,André J Ouellette,Percio S Gulko,Justin B Schaal,Teresina Laragione,Katie K Trinh,Vasu Punj,Dat Q Tran,Akshay Subramanian,Michael E Selsted

doi:10.1152/physiolgenomics.00066.2019

Abstract

Rhesus theta defensin-1 (RTD-1), a macrocyclic immunomodulatory host defense peptide from Old World monkeys, is therapeutic in pristane-induced arthritis (PIA) in rats, a model of rheumatoid arthritis (RA). RNA-sequence (RNA-Seq) analysis was used to interrogate the changes in gene expression in PIA rats, which identified 617 differentially expressed genes (DEGs) in PIA synovial tissue of diseased rats. Upstream regulator analysis showed upregulation of gene expression pathways regulated by TNF, IL1B, IL6, proinflammatory cytokines, and matrix metalloproteases (MMPs) involved in RA. In contrast, ligand-dependent nuclear receptors like the liver X-receptors NR1H2 and NR1H3 and peroxisome proliferator-activated receptor gamma (PPARG) were downregulated in arthritic synovia. Daily RTD-1 treatment of PIA rats for 1-5 days following disease presentation modulated 340 of the 617 disease genes, and synovial gene expression in PIA rats treated 5 days with RTD-1 closely resembled the gene signature of naive synovium. Systemic RTD-1 inhibited proinflammatory upstream regulators such as TNF, IL1, and IL6 and activated antiarthritic ligand-dependent nuclear receptor pathways, including PPARG, NR1H2, and NR1H3, that were suppressed in untreated PIA rats. RTD-1 also inhibited proinflammatory responses in IL-1β-stimulated human RA fibroblast-like synoviocytes (FLS) in vitro and diminished expression of human orthologs of disease genes that are induced in rat PIA synovium. Thus, the antiarthritic mechanisms of systemic RTD-1 include homeostatic regulation of arthritogenic gene networks in a manner that correlates temporally with clinical resolution of rat PIA.

Highlights

Rheumatoid arthritis (RA) is an autoimmune disease that afflicts ~0.5–1% of the population worldwide [29]
Principal component analysis (PCA) of the differentially expressed genes (DEGs) allowed for identification of two gene clusters that segregated with naive or pristaneinduced arthritis (PIA) rats (Fig. 2A)
RNA for sequence analysis (RNA-Seq) results were validated by qRT-PCR of up- and downregulated DEGs in PIA rat synovial tissue RNAs compared with that from naive rats (Supplementary Fig. S1)

Summary

Introduction

Rheumatoid arthritis (RA) is an autoimmune disease that afflicts ~0.5–1% of the population worldwide [29]. Pathogenesis of RA involves chronic inflammation of the synovium, joint erosion, infiltration of immune cells, and the dysregulation of immune signaling and cytokine gene expression pathways [29]. Fibroblast-like synoviocytes (FLS) play a central role in disease pathogenesis and synovial tissue infiltration by leukocytes stimulates FLS to produce inflammatory cytokines, chemokines and matrix metalloproteinases (MMPs) which mediate invasion and degradation of cartilage and bone. Dark Agouti (DA) rats injected with pristane develop chronic inflammation of joints which is pathologically similar to human RA [49, 50]. Systemic administration of rhesus ␪-defensin-1 (RTD-1) was effective in arresting and reversing joint damage in evolving and severe rat pristaneinduced arthritis (PIA) [39]

Methods

Results

Conclusion