Abstract Body: Pulmonary arterial hypertension (PAH) is a disease where chronic high pulmonary arterial pressure causes inflammation, remodeling, and dysfunctions of lung endothelial/smooth muscle cells, and right ventricle (RV) cardiomyocytes. Pathogenesis is caused by a mixture of genetic, epigenetic, and environmental factors. Our clinical studies found PAH patients had elevated cadmium (Cd) and antimony (Sb) levels in the blood and/or urine, which correlated with increased severity of PAH parameters. Thus, we hypothesize that environmental factors, specifically chronic heavy metal exposure, could contribute to PAH pathogenesis either directly or indirectly.
We tested if Cd could induce PAH or worsen PAH parameters in the mouse SU5416 and hypoxia (SuHx) PAH model. Forty male C57/6J mice were initially split in 2 groups: control and 5ppm Cd in drinking water (n=20/each) for 8 weeks (wks). Diastolic and systolic functions were evaluated with echocardiography (echo) at baseline, and 8ks. Then, half of these mice were subject to PAH induction, netting 4 subgroups (n=10/group): CTRL, Cd, PAH, and Cd+PAH. Echo was performed again 4 wks post-PAH induction, followed by RV systolic pressure (RVSP) measurement (n=3/group). The remaining 7 mice/group were euthanized for heart/lung histopathology focusing on fibrosis and hypertrophy, and protein western blot analyses. GraphPad Prism 8 software was used for statistical analysis with normality checked. When data did not follow normality, the non-parametric equivalence was used. Two-way and one-way ANOVA with Tukey were performed for echo/RVSP and histological/biochemical analyses respectively, with a p-value<0.05 being significant.
Results showed 12-wks Cd exposure alone caused: (1) significantly increased RV systolic function indicating systolic stimulation, and (2) significantly increased collagen contents in both ventricles and LV cardiomyocyte area when compared to CTRL. Twelve-wks Cd+PAH group demonstrated (1) significantly decreased RV cardiac output and RVSP measurements indicating RV failure; (2) no further RV changes in collagen contents or hypertrophy; (3) LV western blot analysis revealed significant upregulation of antioxidant proteins, including catalase and superoxide dismutase 2, when compared to PAH group. Further mechanistic experiments are being conducted, including whether Sb has similar results as Cd.