Heat shock protein 90 is downregulated in calcific aortic valve disease

Abstract

Background: Calcific aortic valve disease (CAVD) is an atheroinflammatory process; finally it leads to progressive calcification of the valve. There is no effective pharmacological treatment for CAVD and many of the underlying molecular mechanisms remain unknown. We conducted a proteomic study to reveal novel factors associated with CAVD.

Methods: We compared aortic valves from patients undergoing valvular replacement surgery due to non-calcified aortic insufficiency (control group, n = 5) to a stenotic group (n = 7) using two-dimensional difference gel electrophoresis (2D-DIGE). Protein spots were identified with mass spectrometry. Western blot and immunohistochemistry were used to validate the results in a separate patient cohort and Ingenuity Pathway Analysis (IPA) was exploited to predict the regulatory network of CAVD.

Results: We detected an upregulation of complement 9 (C9), serum amyloid P-component (APCS) and transgelin as well as downregulation of heat shock protein (HSP90), protein disulfide isomerase A3 (PDIA3), annexin A2 (ANXA2) and galectin-1 in patients with aortic valve stenosis. The decreased protein expression of HSP90 was confirmed with Western blot.

Conclusions: We describe here a novel data set of proteomic changes associated with CAVD, including downregulation of the pro-inflammatory cytosolic protein, HSP90.

Keywords: Aortic valve stenosis; Calcified aortic valve disease; Heat-shock protein; Proteomics.

Fig. 1

CAVD-related proteomic changes in human aortic valves. a Representative 2-D gel of calcified aortic valve is shown. Proteins (50 μg) were labelled with minimal DIGE and separated by IEF (pH 3–10 NL) and SDS-PAGE. b The positions of the changed spots as well as the expression profiles indicating the detected protein levels in control (C) and stenotic (AS) aortic valves are specified. HSP90, heat-shock protein 90; C9, complement 9; PDIA3, protein disulfide isomerase A3; ANXA2, annexin 2; serum amyloid P-component, APCS

Fig. 2

HSP90 expression in aortic valves. a Western blot analysis revealed decreased HSP90β protein levels in stenotic valves (AS) when compared to control valves (C). Results are mean ± SD, ** = P < 0.01. Representative Western blots are shown. Immunohistochemical stainings against HSP90α (b, d) and HSP90β (c, e) in aortic valves. VICs in aortic valve displayed cytoplasmic positivity for HSP90α (b) and HSP90β (c) stainings. Representative examples of adjacent sections of the same area of a control valve. Also the the endothelium was strongly positive for HSP90α (d) and HSP90β (e). Representative examples of adjacent sections of the same area of neovasculature in calcified valves. There was also a wide positive reaction in valve interstitial cells (VICs) and patchy positivity in inflammatory cells, mainly small lymphocytes. All pictures are at the same scale, scale bar depicts 100 μm

Fig. 3

Protein expression of annexin II and galectin-1 in aortic valves. Western blot analysis showing (a) annexin II and (b) galectin-1 in stenotic (AS) and control valves (C). Representative Western blots are shown. Results are mean ± SD

Fig. 4

The molecular network of differentially expressed proteins in CAVD generated by Ingenuity Pathway Analysis. The Ingenuity Pathway Analysis (IPA) Core Analysis-based network displays interactions between proteins that were differentially expressed in stenotic valves as compared to control valves. Up- and down-regulated proteins are in red and green, respectively. Molecules not marked with a color were not altered in the data set but they are possible connections suggested by IPA. Molecules are represented with various shapes that represent the functional class of the gene product. A solid line represents direct interactions and a dashed line represents an indirect interaction. The full names of the molecules are given in Table 3

Fig. 5

Phosphorylation of protein kinases in stenotic (AS) and control (C) valves. Western blot analysis of A) Extracellular signal regulated kinase 1/2 (ERK) 1/2), B) p38 Mitogen activated protein kinase (p38 MAPK) and C) Protein kinase B (Akt). The results in bar graphs are mean ± SD and expressed as the ratio of the phosphorylated protein kinase to total protein kinase. Representative Western blots are shown.*P < 0.05