Galectin 3 secretion in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a complex and fatal disorder characterized by an unrelenting increase in pulmonary arterial pressure. Excessive proliferation of pulmonary artery smooth muscle cells (PASMC) leads to increased vascular resistance and eventually right ventricular failure and death. Our lab has hypothesized that circulating Galectin-3 (Gal-3), a readily secreted b-galactoside-binding lectin protein, previously investigated as a biomarker of PAH, has a key role in the pathology of PAH. Co-culture experiments as well as recombinant protein supplementation show that soluble GAL-3 is biologically active and induces SMC growth and proliferation(P<.05). Inversely, inhibition of GAL-3 using blocking antibodies prevents this SMC proliferation. (p<.05) To test our hypothesis in-vivo we injected GAL-3 KO mice with a liver specific AAV overexpressing GAL-3 or GFP (control) and exposed them to sugen/hypoxia to induce PAH. Surprisingly our initial findings indicate no protection with liver GAL-3 overexpression compared to GFP transduced mice. Contrary to our hypothesis, while liver overexpression of GAL-3 was robustly increased, there was no evidence of GAL3 in the lungs or plasma of GAL3KO mice indicating it may not be robustly secreted from the hepatocyte, unlike what was observed in other cell types. This lack of circulating Gal-3 generated by liver overexpression revealed a knowledge gap in the mechanism of Gal-3 secretion into the circulation. To address this we have generated at a number of mutant forms of GAL3 that alter motifs proposed to be relevant to Gal-3 secretion. R186S prevents binding to the all but 1 of the 176 of GAL-3 binding glycans however this appears to have no impact on its uptake in GAL-3 KO cells. Similarly, L131A/L203A GAL-3 which prevents the oligomerization of GAL-3 by preventing interaction of the carbohydrate recognition domain with its n terminal binding domain (responsible for oligomerization) also maintains its ability to interact with these cells. These changes did not interfere with its secretion into the media. However, these interactions do appear to be altered somewhat, when a cell surface biotinylation assay is performed there is significantly less R185S on the cell surface compared to WT GAL-3. Our findings suggest that ECs and SMCs can secrete GAL-3 and exert pathological actions such as increasing proliferation in vitro. Our blocking antibody further suggests that this secreted GAL-3 is capable of regulating SMC proliferation and provides evidence for possible treatment of PAH. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.