Wild‐type amyloid beta 1‐40 peptide induces vascular smooth muscle cell death independently from matrix metalloprotease activity

Abstract

SummaryCerebral amyloid angiopathy (CAA) is an important cause of intracerebral hemorrhages in the elderly, characterized by amyloid-b (Ab) peptide accumulating in central nervous system blood vessels. Within the vessel walls, Ab-peptide deposits [composed mainly of wild-type (WT) Ab 1-40 peptide in sporadic forms] induce impaired adhesion of vascular smooth muscle cells (VSMCs) to the extracellular matrix (ECM) associated with their degeneration. This process often results in a loss of blood vessel wall integrity and ultimately translates into cerebral ischemia and microhemorrhages, both clinical features of CAA. In this study, we decipher the molecular mechanism of matrix metalloprotease (MMP)-2 activation in WT-Ab 1-40 -treated VSMC and provide evidence that MMP activity, although playing a critical role in cell detachment disrupting ECM components, is not involved in the WT-Ab 1-40 -induced degeneration of VSMCs. Indeed, whereas this peptide clearly induced VSMC apoptosis, neither preventing MMP-2 activity nor hampering the expression of membrane type1-MMP, or preventing tissue inhibitors of MMPs-2 (TIMP-2) recruitment (two proteins evidenced here as involved in MMP-2 activation), reduced the number of dead cells. Even the use of broad-range MMP inhibitors (GM6001 and Batimastat) did not affect WT-Ab 1-40 -induced cell apoptosis. Our results, in contrast to those obtained using the Ab 1-40 Dutch variant suggesting a link between MMP-2 activity, VSMC mortality and degradation of specific matrix components, indicate that the ontogenesis of the Dutch familial and sporadic forms of CAAs is different. ECM degradation and VSMC degeneration would be tightly connected in the Dutch familial form while being two independent processes in sporadic forms of CAA.

β‐amyloid context intensifies vascular smooth muscle cells induced inflammatory response and de‐differentiation

“…Immunocytochemistry was performed as described by Blaise et al, (2012). After treatment, cells were washed, fixed, permeabilized and incubated with primary antibodies (anti-a-actin or -SM22).…”

“…Rat VSMCs were isolated as described by Blaise et al, (2012). Experiments were performed on cells at passages from 2 to 6 for VSMCs or from 3 to 13 for bEnd.3 cells.…”

“…Gelatin zymography of conditioned media samples was performed as described by Blaise et al, (2012). PGE 2 secretion was evaluated with an enzyme immunoassay kit from Cayman Chemical SPI-BIO (Massy, France).…”

“…Protein extraction, Western blot and detection signal procedures were as described by Blaise et al, (2012). Antibodies are given in Table 2.…”

“…RT-PCR assays were performed as described by Blaise et al, (2012);. The forward and reverse primer sequences used to amplify the cDNA are given in Table 1.…”