calpastatin and Aortic-Aneurysm

Aneurysms of the ascending aorta are an outstanding challenge to clinicians as they may persist asymptomatic until they present with dissection or rupture. Intensive research is performed to reveal the molecular mechanisms causing aneurysm formation. Calpains are ubiquitous non-lysosomal cysteine proteases which are classically activated by calcium signaling. The two major forms of the calpain-family are calpain-I and calpain-II. Calpastatin specifically inhibits the proteolytic activity of calpain-I and -II. Recently it has been demonstrated in aneurysm tissues from ascending aortas obtained from Marfan syndrome patients that calpain-II expression is increased and calpastatin expression is decreased. Thus, we were interested in the probable role of calpains in aneurysms of ascending aorta in non-Marfan patients. Therefore, ascending aortic samples of dilated and non-dilated aortas were analyzed according to their calpain-I, -II and calpastatin content as well as the expression levels of MMPs and elastin as well as the infiltration of inflammatory cells. We have found significant differences in calpain-I and calpastatin protein expression and serum levels in patients with aneurysm of the ascending aorta. Furthermore, MMP-1 and MMP-3 expression levels correlate with calpain-I protein levels. Due to our findings we conclude that calpain-1 seems to be related to fibrotic alteration in aortic aneurysm tissue in our experimental group. The change in calpain-1 modulates the structure of aortic tissue causing alteration in elastin structure, thus enabling macrophage infiltration and elevation of MMP levels. Circulating levels of calpain-1 may be used as a prognostic marker in the future if further correlation analyses are done.

Topics: Aged; Aorta; Aortic Aneurysm; Calcium-Binding Proteins; Calpain; Elastin; Enzyme-Linked Immunosorbent Assay; Female; Humans; Immunohistochemistry; Male; Metalloproteases; Middle Aged; Polymerase Chain Reaction

Marfan syndrome (MFS) is a heritable disorder of connective tissue, affecting principally skeletal, ocular, and cardiovascular systems. The most life-threatening manifestations are aortic aneurysm and dissection. We investigated changes in the proteome of aortic media in patients with and without MFS to gain insight into molecular mechanisms leading to aortic dilatation.. Aortic samples were collected from 46 patients. Twenty-two patients suffered from MFS, 9 patients had bicuspid aortic valve, and 15 patients without connective tissue disorder served as controls. Aortic media was isolated and its proteome was analyzed in 12 patients with the use of 2-dimensional difference gel electrophoresis and mass spectrometry. We found higher amounts of filamin A C-terminal fragment, calponin 1, vinculin, microfibril-associated glycoprotein 4, and myosin-10 heavy chain in aortic media of MFS aneurysm samples than in controls. Regulation of filamin A C-terminal fragmentation was validated in all patient samples by immunoblotting. Cleavage of filamin A and the calpain substrate spectrin was increased in the MFS and bicuspid aortic valve groups. Extent of cleavage correlated positively with calpain 2 expression and negatively with the expression of its endogenous inhibitor calpastatin.. Our observation demonstrates for the first time upregulation of the C-terminal fragment of filamin A in dilated aortic media of MFS and bicuspid aortic valve patients. In addition, our results present evidence that the cleavage of filamin A is highly likely the result of the protease calpain. Increased calpain activity might explain, at least in part, histological alterations in dilated aorta.

Topics: Adult; Aorta; Aortic Aneurysm; Calcium-Binding Proteins; Calpain; Contractile Proteins; Enzyme Activation; Female; Filamins; Humans; Male; Marfan Syndrome; Microfilament Proteins; Middle Aged; Protein Structure, Tertiary; Proteomics; Spectrin; Tunica Media