Suppression of inflammatory arthritis by the parasitic worm product ES-62 is associated with epigenetic changes in synovial fibroblasts

Abstract

ES-62 is the major secreted protein of the parasitic filarial nematode, Acanthocheilonema viteae. The molecule exists as a large tetramer (MW, ~240kD), which possesses immunomodulatory properties by virtue of multiple phosphorylcholine (PC) moieties attached to N-type glycans. By suppressing inflammatory immune responses, ES-62 can prevent disease development in certain mouse models of allergic and autoimmune conditions, including joint pathology in collagen-induced arthritis (CIA), a model of rheumatoid arthritis (RA). Such protection is associated with functional suppression of “pathogenic” hyper-responsive synovial fibroblasts (SFs), which exhibit an aggressive inflammatory and bone-damaging phenotype induced by their epigenetic rewiring in response to the inflammatory microenvironment of the arthritic joint. Critically, exposure to ES-62 in vivo induces a stably-imprinted CIA-SF phenotype that exhibits functional responses more typical of healthy, Naïve-SFs. Consistent with this, ES-62 “rewiring” of SFs away from the hyper-responsive phenotype is associated with suppression of ERK activation, STAT3 activation and miR-155 upregulation, signals widely associated with SF pathogenesis. Surprisingly however, DNA methylome analysis of Naïve-, CIA- and ES-62-CIA-SF cohorts reveals that rather than simply preventing pathogenic rewiring of SFs, ES-62 induces further changes in DNA methylation under the inflammatory conditions pertaining in the inflamed joint, including targeting genes associated with ciliogenesis, to programme a novel “resolving” CIA-SF phenotype. In addition to introducing a previously unsuspected aspect of ES-62’s mechanism of action, such unique behaviour signposts the potential for developing DNA methylation signatures predictive of pathogenesis and its resolution and hence, candidate mechanisms by which novel therapeutic interventions could prevent SFs from perpetuating joint inflammation and destruction in RA. Pertinent to these translational aspects of ES-62-behavior, small molecule analogues (SMAs) based on ES-62’s active PC-moieties mimic the rewiring of SFs as well as the protection against joint disease in CIA afforded by the parasitic worm product.

Cytohesin-2/ARNO: A Novel Bridge Between Cell Migration and Immunoregulation in Synovial Fibroblasts

“…We chose the Collagen-Induced Arthritis (CIA) model, as it shares hallmarks of human disease relevant for this study, such as the SF activation. As expected from previous studies ( 38 ), CIA SFs showed elevated cytokine production compared to naïve cells, corroborating their inflammatory phenotype. ARNO knock-down in such CIA cells reduced the IL-1β-dependent release of IL-6, CCL2 and MMP3, the latter also in a significant manner in these in vivo activated cells.…”

“…To obtain further mechanistic insight, we investigated potential signaling pathways regulated by ARNO ( Figure 4 ). Thus, we explored the role of ARNO in the IL-1β STAT3 signalling pathway, as this can play key roles in both acute and chronic inflammatory responses upon IL-1β stimulation in SFs ( 38 ). We also evaluated the p38 MAPK pathway, as it has been shown to be important for RA pathogenesis and IL-1β signalling ( 39 ) and also for ARNO signaling in relation to MMP expression ( 31 ).…”

“…Regulation of the RANKL/OPG axis by SFs has been shown to depend on the combined effects of inflammatory cytokines ( 50 ). Therefore, we repeated the experiment using fibroblasts from arthritic CIA mice, which have become epigenetically modified in vivo as a result of their chronic exposure to multiple cytokines and proinflammatory mediators ( 38 , 51 ). Reflecting their imprinted pathogenic status, such CIA SFs showed a stronger induction of ARNO expression than naïve cells in response to IL-1β.…”

“…Interestingly, this effect was greatly enhanced in SFs expanded from mice undergoing experimental Collagen-Induced Arthritis. This can be a consequence of the SFs epigenetically rewiring, by which cells adopt an inflammatory phenotype that is maintained in vivo and ex vivo ( 38 , 60 ). Reflecting this transformation, ARNO appeared to be involved in MMP3 production only in CIA SFs, but not in healthy cells.…”

The parasitic worm product ES-62 protects the osteoimmunology axis in a mouse model of obesity-accelerated ageing

“…Alternatively, and consistent with our wealth of data suggesting that ES-62 acts to resolve chronic inflammation rather than suppressing steady-state or “emergency” responses, it is possible that ES-62 only targets “hyper-responsive” cells, the cross-talk between signals generated by ES-62 and the pathogenic microenvironment generating a unique, modulated phenotype. Supporting this idea, whilst ES-62 similarly has little or no effect on the functionality of fibroblasts in the synovial joints of healthy mice, it induces a stable epigenetically rewired, inflammation-resolving/tissue repair phenotype of synovial fibroblast in mice undergoing collagen-induced arthritis (CIA; a model of rheumatoid arthritis), that is distinct from that found in naïve animals ( 65 ). Interestingly, IL-1β signalling, a key factor in driving the pathogenic transformation of synovial fibroblasts in CIA and rheumatoid arthritis that is targeted by ES-62 ( 65 ), is crucial to the pro-inflammatory training of both BM and migratory “surveillance” haemopoietic stem and progenitor cells (HSCPs) and their resultant accumulation and differentiation into adipose tissue-resident myeloid cells that perpetuates the inflammatory osteoimmunology cycle in obesity ( 24 , 66 – 68 ).…”