Vascular EC-SOD limits the accumulation, proinflammatory profibrotic reprogramming, and hyaluronan binding of...

Dysregulated redox signaling contributes to pulmonary hypertension (PH) and vascular depletion of the redox enzyme extracellular superoxide dismutase (EC-SOD) from smooth muscle cells [EC-SOD SMC knockout (KO)] worsens chronic hypoxic PH. Given the important role of macrophages in PH, this study aimed to determine if interstitial macrophages (IMs) and their interactions with hyaluronan (HA), a component of extracellular matrix (ECM), are modulated by vascular EC-SOD. Floxed wild-type, EC-SOD SMC KO, and SOD mimetic- or vehicle-treated mice were exposed to hypobaric hypoxia [∼10% fraction of inspired oxygen ([Formula: see text])], for 4, 14, or 21 days. Using flow cytometry, we demonstrated that the transient increase in IMs at day 4 was exacerbated in EC-SOD SMC KO mice and prevented with SOD mimetic pretreatment. Highlighting the importance of targeting vascular oxidative stress in the early response to hypoxia, pretreatment with a single dose of EC-SOD mimetic decreased right ventricular systolic pressure, right ventricular hypertrophy, and small vessel muscularization at day 21. To assess IM phenotypic reprogramming in hypoxia, RNA-seq was performed on flow-sorted IMs revealing baseline proinflammatory activation and enhanced activation of vascular and ECM remodeling pathways in response to hypoxia in EC-SOD SMC KO IMs compared with controls. To further investigate the ECM remodeling response, we quantified IMs expressing the lymphatic vessel endothelial hyaluronan receptor 1 (Lyve1), and IM-hyaluronan binding. Lyve1⁺ IMs and Lyve1⁺ HA⁺ IMs were increased in response to hypoxia in EC-SOD SMC KO mice and accumulated in the perivascular space of the lung. In conclusion, vascular EC-SOD limits IM accumulation and proinflammatory profibrotic IM signaling, including perivascular accumulation of Lyve1⁺ IMs and their binding to hyaluronan.NEW & NOTEWORTHY Expression of the redox enzyme EC-SOD limits PH severity. Using vascular-selective EC-SOD depletion and SOD mimetic treatment in chronic hypoxic PH, we demonstrated that EC-SOD limits the hypoxia-induced accumulation of IMs. IMs from mice with low vascular EC-SOD were proinflammatory at baseline and enhanced ECM remodeling pathway activation in response to hypoxia. We identified Lyve1⁺ IMs as a perivascular, ECM-interacting subset that accumulate in hypoxia and could contribute to vascular remodeling in PH.