Extracellular Superoxide Dismutase Regulates Early Vascular Hyaluronan Remodeling in Hypoxic Pulmonary Hypertension

Victor Tseng,Clare Prohaska,Eva Nozik-Grayck,Vincent Hascall,Kevin Ni,Barbara Triggs-Raine,C Michael Hart,Laura Hernandez-Lagunas,Irina Petrache,Hanan Elajaili,Ronald Midura,Valbona Cali,Ayed Allawzi

doi:10.1038/s41598-019-57147-7

Abstract

Chronic hypoxia leads to pathologic remodeling of the pulmonary vasculature and pulmonary hypertension (PH). The antioxidant enzyme extracellular superoxide dismutase (SOD3) protects against hypoxia-induced PH. Hyaluronan (HA), a ubiquitous glycosaminoglycan of the lung extracellular matrix, is rapidly recycled at sites of vessel injury and repair. We investigated the hypothesis that SOD3 preserves HA homeostasis by inhibiting oxidative and enzymatic hyaluronidase-mediated HA breakdown. In SOD3-deficient mice, hypoxia increased lung hyaluronidase expression and activity, hyaluronan fragmentation, and effacement of HA from the vessel wall of small pulmonary arteries. Hyaluronan fragmentation corresponded to hypoxic induction of the cell surface hyaluronidase-2 (Hyal2), which was localized in the vascular media. Human pulmonary artery smooth muscle cells (HPASMCs) demonstrated hypoxic induction of Hyal2 and SOD-suppressible hyaluronidase activity, congruent to our observations in vivo. Fragmentation of homeostatic high molecular weight HA promoted HPASMC proliferation in vitro, whereas pharmacologic inhibition of hyaluronidase activity prevented hypoxia- and oxidant-induced proliferation. Hypoxia initiates SOD3-dependent alterations in the structure and regulation of hyaluronan in the pulmonary vascular extracellular matrix. These changes occurred soon after hypoxia exposure, prior to appearance of PH, and may contribute to the early pathogenesis of this disease.

Highlights

One facet of this disease is the presence of high oxidative stress within the vessel wall and perivascular matrix[3]
pulmonary hypertension (PH) was evaluated by measurement of right ventricular systolic pressures (RVSP) and RV hypertrophy (RVH) by Fulton’s Index
Between 14 and 35 days of chronic hypoxia, Right ventricular systolic pressure (RVSP) and RVH did not worsen further in WT mice, whereas both indices continued to progress in SOD3KO mice (Fig. 1A,B)

Summary

Introduction

One facet of this disease is the presence of high oxidative stress within the vessel wall and perivascular matrix[3]. There is a critical gap in our understanding of how the extracellular oxidative environment can lead to irreversible pulmonary vascular remodeling in chronic hypoxia. To understand the regulation of HA fragmentation in the lung, we studied how SOD3 protects against HA breakdown in a mouse model of chronic hypoxia. SOD3 is required to prevent HA fragmentation by ROS in vitro[25], and protects against lysis and shedding of HA and HS side chains into the airspaces in an inhalational asbestos model of acute lung injury and fibrosis[26,27]. Chronic hypoxia is a more muted process, with a lesser rate of oxidative stress accumulation and inflammation compared to these chemically-induced lung injuries. We utilized mouse strains deficient in SOD3, exposed to chronic hypoxia, followed by quantitative, structural, and histologic characterization of lung HA

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