Methods: Plasma, serum and lung samples from adult PAH patients who had failed treatment (i.e., required lung or heart-lung transplant), including congenital heart disease-associated PAH (APAH) and idiopathic PAH (IPAH), were obtained from the Cardiovascular Medical Research and Education Fund (CMREF). Using PAH lung protein extract, proteomic profiles were compared with 2-D DIGE, label-free mass spectrometry and MRM, identifying proteins with relative abundance changes. Using commercial ELISA assays, these proteins were evaluated in the blood of PAH patients and adult controls. Data was analyzed by either Mann-Whitney U or Kruskal-Wallis nonparametric analysis. Western blot analysis was performed on ANXA6 and DPT lung protein, with subsequent densitometric analysis.
Results: ELISA results are shown in figure 1 and table 1. There was a statistically significant difference in median S100A8 and S100A9 in aggregated PAH (combined APAH and IPAH) patients versus adult controls. There was no significant difference between ANXA6 or DPT levels in PAH patients versus adult controls. Western blot analysis showed no significant difference between ANXA6 and DPT in PAH lung.
Conclusions: There was a statistically significant difference between S100A8 and S100A9 levels in PAH patients versus controls. S100A8 and S100A9 exist as a heterodimer called calprotectin; this heterodimer is overexpressed in the lungs and is involved in modulation of inflammatory processes associated with the cardiovascular system. Although additional studies are necessary, the S100A8/A9 heterodimer is a promising prognostic biomarker of therapeutic efficacy in PAH.