D29-13 Eld607 Attenuates Pulmonary Fibrosis By Suppressing Orai1-mediated Ca²+ Signaling

Abstract Rationale Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive lung disease of unknown cause in older adults, characterized by excessive extracellular matrix (ECM) accumulation, increased α-smooth muscle actin (α-SMA) expression, collagen deposition, worsening dyspnea, declining lung function, and poor prognosis. Although antifibrotic drugs are available, their clinical efficacy remains limited. Fibroblast functions, including proliferation, protein secretion, and contraction, are highly regulated by intracellular Ca²+ signaling. The plasma membrane Ca2+ channel Orai1 likely mediates Ca²+ signaling in fibroblasts. The novel immunomodulator ELD607 inhibits SOCE by selectively internalizing Orai1. We hypothesize that inhibition of Orai1 by ELD607 will reverse TGF-β-induced ECM production and fibrosis in bleomycin-exposed mice and may be a novel therapy for IPF. Methods We used immunocytochemistry to investigate ELD607’s effect on TGF-β-induced αSMA production in lung fibroblasts. Fluo-4 was used to measure cytoplasmic Ca²+. Cell contractility was assessed after TGF-β-induction and ELD607 post-treatment. Finally, pSMAD2/3 localization was examined to investigate ELD607’s impact on TGF-β signaling. In C57BL/6 mice, intranasal ELD607 (1 mg/kg) was administered daily for 10 days, starting 14 days after intratracheal bleomycin (1.5 U/kg). Results There was an ∼85% reversal of αSMA formation in fibroblasts after both pre- and post- treatment with ELD607. ELD607 inhibited TGF-β stimulated Ca²+ influx in fibroblasts. ELD607 inhibited TGF-β-induced nuclear localization of pSMAD2/3 by ∼60%, normalizing it to vehicle levels. TGF-β-induced αSMA cell contractility was significantly reduced in the presence of ELD607. In mice, daily intranasal ELD607 administration significantly reduced lung damage and collagen deposition, as demonstrated by a ∼60% reduction in the Ashcroft score (H 0.022) and an ∼82% reduction in Masson’s Trichrome staining (p 0.0001) compared to bleomycin-treated mouse lungs. Conclusions Our data indicate a hitherto unrecognized role for Orai1/Ca2+ signaling in the initiation of fibrosis. Further, our data suggest that inhibition of Orai1 with inhaled ELD607 may be a novel therapeutic approach to reverse fibrosis in IPF patients. This abstract is funded by: NIH