We have previously shown that, in bovine retina pericytes, amyloid β(1-42) and its truncated form containing amino acids 25-35, after 24 h treatment, stimulate arachidonic acid (AA) release and phosphatidylcholine hydrolysis, by activation of both cytosolic (cPLA(2)) and Ca2+- independent (iPLA,) phospholipase A,. A putative role for MAP kinases in this process emerged. Here we studied the role of the MAP-kinase family as well as both cPLA2 and iPLA, mRNA expression by a semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) in the same sublethal model of amyloid-β (Aβ) damage to pericytes in vitro. Aβ(25-35) peptide evoked AA release as well as stimulated phosphorylation of ERK1/2, p38 MAPKs and cPLA(2), but not c-Jun N-terminal kinase (JNK/SAPK). PD98059, an inhibitor of ERK-activating kinase MEK-1, and SB203580, an inhibitor of p38 protein kinase, abolished the stimulation of AA release and MAPK activities. In cells stimulated by Aβ(25-35) peptide, Western blotting and confocal microscopy analyses confirmed either an increase in the phosphorylated form of ERKs and p38 or their nuclear translocation. A complete inhibition of MAPK activation and AA release was also observed when pericytes were treated with GF109203X, a general PKC inhibitor, indicating the important role of both PKC and the two MAPKs in mediating the Aβ peptide response. Compared with samples untreated or treated with reverse Aβ(35-25) peptide, pretreatment with 50 μ M Aβ(25-35) for 24 h significantly increased the level of constitutively expressed iPLA(2) mRNA by 25%, which seems to depend on the activation of kinases. By contrast, the level of cPLA, mRNA remained unchanged. Together, these data link either the stimulation of PKC-ERK-p38 cascades or PLA(2) activity by Aβ peptide to prooxidant mechanism induced by amyloid, which may initially stimulate the cell reaction as well as metabolic repair, such as during inflammation.
|Titolo:||MAPKs mediate the activation of cytosolic phospholipase A2 by amyloid beta(25-35) peptide in bovine retina pericytes.|
|Data di pubblicazione:||2005|
|Appare nelle tipologie:||1.1 Articolo in rivista|