Inhibition of p38 Mitogen-Activated Protein Kinase Enhances the Apoptosis Induced by Oxidized Low-Density Lipoprotein in Endothelial Progenitor Cells

Abstract

Oxidized low-density lipoprotein (oxLDL) is an important risk factor in the development of atherosclerosis. oxLDL has been shown to decrease endothelial progenitor cell (EPC) number by inducing apoptosis. p38 mitogen-activated protein kinase (MAPK) was shown to be activated by oxLDL and participated in the regulation of EPC number and function. However, the role of p38 remains unknown. Here, we show that oxLDL-induced p38 phosphorylation in EPCs is time and dose dependent. Treatment with antioxidant N-acetyl cysteine restored oxLDL-induced p38 phosphorylation to basal levels. LOX-1-blocking antibody also significantly decreased oxLDL-induced p38 phosphorylation. Interestingly, TUNEL staining showed that pretreatment with the p38 inhibitor SB203580 further increased oxLDL-induced apoptosis in EPCs. In accordance with these findings, pretreatment with SB203580 further attenuated Akt phosphorylation in EPCs challenged with oxLDL, indicating an interaction between Akt and p38 MAPK pathways. In agreement, inhibition of p38 MAPK further attenuated Akt phosphorylation and increased apoptosis in EPCs isolated from hypercholesterolemic ApoE-/- mice. In conclusion, p38 MAPK serves as an anti-apoptotic pathway by supporting Akt activity when EPCs are challenged with oxLDL.

Calcitonin gene-related peptide promotes proliferation and inhibits apoptosis in endothelial progenitor cells via inhibiting MAPK signaling

“…These findings suggest that CGRP is highly associated with CRLR and MAPK signalling during proliferation and SD-induced apoptosis in EPCs. Several reports have been published regarding the regulation of proliferation and apoptosis by MAPK signalling in other cell types [ 25 – 28 , 31 ], although the pathways controlling apoptosis activation and inhibition are inconsistent. p38 functions in an anti-apoptotic pathway, and the p38 pathway inhibitor SB203580 further increased oxidized low-density lipoprotein (oxLDL)-induced apoptosis in EPCs [ 25 ].…”

“…MAPKs (mitogen-activated protein kinases) are ancient and central signal transducers that include three subgroups: extracellular signal regulated kinase (ERK), c-Jun N-terminal kinase (JNK), and p38 signalling families [ 24 ]. MAPKs regulate a variety of cellular processes, including EPC apoptosis [ 25 ] and proliferation [ 26 – 28 ], and each MAPK family contributes distinctly to pro- and anti-apoptotic pathways in other cells [ 29 , 30 ]. Activation of p38 MAPKs increases the number of circulating EPCs [ 25 ]; however, p38 activation but not ERK activation contributes to reducing the number of EPCs ex vivo [ 31 ].…”

“…MAPKs regulate a variety of cellular processes, including EPC apoptosis [ 25 ] and proliferation [ 26 – 28 ], and each MAPK family contributes distinctly to pro- and anti-apoptotic pathways in other cells [ 29 , 30 ]. Activation of p38 MAPKs increases the number of circulating EPCs [ 25 ]; however, p38 activation but not ERK activation contributes to reducing the number of EPCs ex vivo [ 31 ]. EPC proliferation may be regulated by ERK phosphorylation, as evidenced by the significant inhibition of EPC proliferation induced by a selective ERK kinase inhibitor [ 27 ].…”

Store-operated calcium entry-activated autophagy protects EPC proliferation via the CAMKK2-MTOR pathway in ox-LDL exposure

“…Previous studies have focused on ox-LDL-induced apoptosis in VSMCs, [38][39][40] endothelial cells [41][42][43][44] and EPCs. 45 The differences in oxidative status, concentration and the treatment time of ox-LDL as well as cell species might account for the different effects of our ] i measurement. Ox-LDL (60 mg/ml) was added to the medium without calcium, followed by adding back 2 mM Ca (Cells were isolated from 3 rats for one experiment and 3 independent experiments were performed, western blot results were normalized to the controls (given as one-fold), mean C SD, Ã P < 0.05, ÃÃ P < 0.01).…”

Involvement of endothelial nitric oxide synthase pathway in IGF‑1 protects endothelial progenitor cells against injury from oxidized LDLs

“…The purity of the LDLs was assessed by agarose gel electrophoresis and the protein concentration was determined by the modified Lowry method (26). The LDL particles were dialyzed by semi-permeable membrane (3500D) for 24 h with 0.01 M PBS (pH 7.4) at 4˚C to remove EDTA, then oxidized by exposure to CuSO 4 (10 mM CuSO 4 , 24 h at 37˚C) (27). EDTA was added and the LDL particles were dialyzed by semi-permeable membrane (3500D) for 24 h with PBS to terminate the oxidization at 4˚C.…”