Resistin-like molecule a (RELMa) has mitogenic, angiogenic, vasoconstrictive, and chemokine-like properties and is highly relevant in lung pathology. Here, we used RELMa knockout (Retnla 2/2 ) mice to investigate the role of RELMa in pulmonary vascular remodeling after intermittent ovalbumin (OVA) challenge. We compared salineand OVA-exposed wild-type (WT) mice and found that OVA induced significant increases in right ventricular systolic pressure, cardiac hypertrophy, pulmonary vascular remodeling of intra-alveolar arteries, goblet cell hyperplasia in airway epithelium, and intensive lung inflammation, especially perivascular inflammation. Genetic ablation of Retnla prevented the OVA-induced increase in pulmonary pressure and cardiac hypertrophy seen in WT mice. Histological analysis showed that Retnla 2/2 mice exhibited less vessel muscularization, less perivascular inflammation, reduced medial thickness of intra-alveolar vessels, and fewer goblet cells in upper airway epithelium (250-600 mm) than did WT animals after OVA challenge. Gene expression profiles showed that genes associated with vascular remodeling, including those related to muscle protein, contractile fibers, and actin cytoskeleton, were expressed at a lower level in OVA-challenged Retnla 2/2 mice than in similarly treated WT mice. In addition, bronchoalveolar lavage from OVA-challenged Retnla 2/2 mice had lower levels of cytokines, such as IL-1b, -1 receptor antagonist, and -16, chemokine (C-X-C motif) ligand 1, -2, -9, -10, and -13, monocyte chemoattractant protein-1, macrophage colony-stimulating factor, TIMP metallopeptidase inhibitor-1, and triggering receptor expressed on myeloid cells-1, than did that from WT mice when analyzed by cytokine array dot blots. Retnla knockout inhibited the OVA-induced T helper 17 response but not the T helper 2 response. Altogether, our results suggest that RELMa is involved in immune response-induced pulmonary vascular remodeling and the associated increase in inflammation typically observed after OVA challenge.Keywords: resistin-like molecule a; pulmonary hypertension; vascular remodeling; inflammation; T helper 17
Clinical RelevanceWe have demonstrated that resistin-like a (RELMa) knockout mice inhibited pulmonary vascular remodeling and the increase in pulmonary pressure and cardiac hypertrophy in a model of allergen-induced pulmonary vascular remodeling. Further studies show that this prevention is associated with suppressed inflammation in the lung, involving a T helper 17 immune response. Our study reveals a novel function of RELMa on immune regulation in pulmonary hypertension and shows that it could be a novel therapeutic target for pulmonary hypertension.Resistin and resistin-like molecules (RELMs) have been identified as a family of cysteinerich small proteins that share no homology to any known hormone or cytokine (1-4). The RELM family has four murine isoforms (RELMa, RELMb, resistin, and RELMg) and two human isoforms (resistin and RELMb), all of which have a structurally conserved 10-c...