Background/Purpose: Systemic Sclerosis (SSc) is characterized by dysfunctional immune activation, oxidative stress, and fibrosis. In prior work, we have shown that SSc macrophages (MØs) have a pro-fibrotic immunophenotype. SSc fibroblasts and MØs engage in reciprocal mechanisms of activation, as co-cultures of SSc fibroblasts with MØs results in upregulation of ECM and inflammatory mediators. Given myeloid plasticity, we hypothesized that drug therapies that alter the SSc MØ immunophenotype would alleviate inflammation and fibrosis.

Methods: Peripheral blood monocytes were isolated and differentiated in SSc patient plasma, which we have shown in previous work confers pro-fibrotic MØ activation.  Because bardoxolone methyl (CDDO-Me), a synthetic triterpenoid derived from oleanoic acid targets multiple signaling pathways implicated in SSc pathogenesis, SSc plasma-differentiated MØs were treated in monoculture with 300nM CDDO-Me.  Prior studies in our lab demonstrate this concentration redirects MØ activation. To assess CDDO-Me-mediated effects on MØ and fibroblast cross-talk, the Transwell co-culture system was used. Mononuclear cells were separated on Ficoll-Paque Premium and enriched for CD14⁺ monocytes by magnetic bead selection. Monocyte purity was assessed at ≥95% using cytospin and flow analysis of CD14 expression. Monocyte-derived MØs were cultured in complete media with SSc patient-derived plasma and M-CSF (20ng/ml) for 4 days. Human dermal control and SSc fibroblasts were isolated from clinically affected skin of 7 individuals with SSc or 6 healthy age and gender-matched control subjects. Fibroblasts were used at passages 4–9, seeded into 24-well inserts, and incubated overnight prior establishment of co-culture. MØs and fibroblasts were co-cultured in the absence of drug treatment or 24 hrs, followed by treatment of co-cultures with 300 nM CDDO-Me for 48 hrs. SSc fibroblast and MØ activation states were interrogated using flow cytometry, qRT-PCR, ELISA, and immunoblot

Results: CDDO-Me significantly attenuated production of pro-fibrotic and and CCL2 and IL-6 in SSc MØs and induced Nrf2 signaling, as evidenced by increased expression of HMOX1 and NQO1. Surface expression of CD16, CD163, CD206, and HLA-DR, which are increased in SSc MØs, were downregulated with drug treatment. Expression of the myofibroblast marker a-SMA and fibronectin in SSc fibroblasts were decreased by CDDO-Me.

Conclusion: CDDO-Me inhibits pro-fibrotic activation of SSc plasma-differentiated MØs, resulting in decreased production of cytokines implicated in SSc pathogenesis, and significantly attenuates SSc fibroblast activation. Collectively, these results suggest CDDO-Me may have therapeutic benefits in reducing oxidative stress, inflammation, and fibrosis in SSc.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/cddo-me-attenuates-pro-fibrotic-activation-in-macrophages-and-fibroblasts-in-systemic-sclerosis/