PIMT prevents the apoptosis of endothelial cells in response to glycated low density lipoproteins and protective effects of grape seed procyanidin B2.
BACKGROUND
The development of diabetic angiopathy is associated with profound vascular endothelial cells (VEC) dysfunction and apoptosis. Glycated low density lipoproteins (gly-LDL) continuously produced in the setting of diabetic patients play an important role in causing VEC dysfunction and apoptosis. However, the underlying molecular mechanism remains largely elusive. Protein L-isoaspartyl methyltransferase (PIMT) is a widely expressed protein repair enzyme by multiple cell types of arterial wall including VEC. Our previous proteomic studies showed that the expression of PIMT was significantly decreased in the aorta of diabetic rats as compared with control rats and treatment with grape seed procyanidin extracts significantly increased the PIMT expression in diabetic rats. We hypothesized that PIMT plays a critical role in gly-LDL induced VEC apoptosis; grape seed procyanidin B2 (GSPB2) protect against gly-LDL induced VEC apoptosis through PIMT regulation.


RESULTS
HUVEC transfected negative control and PIMT siRNA were treated with or without GSPB2 (10 µmol/L) for 48 h. Moreover, HUVEC of PIMT overexpression were stimulated by gly-LDL (50 µg/ml) in the presence or absence of GSPB2 (10 µmol/L) for 48 h. Our results showed that gly-LDL downregulated PIMT expression and PIMT overexpression or GSPB2 significantly attenuated gly-LDL induced VEC apoptosis. PIMT siRNA increased VEC apoptosis with up-regulation of p53, cytochrome c release, caspase-9 and caspase-3 activation. Mechanistically, overexpression of PIMT or GSPB2 increased the phosphorylation of ERK1/2 and GSK3β in the gly-LDL induced VEC.


CONCLUSIONS
In summary, our study identified PIMT as a key player responsible for gly-LDL induced VEC apoptosis and GSPB2 protect against gly-LDL induced VEC apoptosis by PIMT up-regulation. Targeting PIMT including use of GSPB2 could be turned into clinical application in the fighting against diabetic vascular complications.
Key Laboratory of Cardiovascular Proteomics of Shandong Province, Department of Geriatric Endocrinology, Qi-Lu Hospital of Shandong University, Jinan, China.
Xiao-li
XL
Li
Bao-ying
BY
Li
Mei
M
Cheng
Fei
F
Yu
Wen-bin
WB
Yin
Qian
Q
Cai
Zhen
Z
Zhang
Jian-hua
JH
Zhang
Jun-fu
JF
Wang
Rui-hai
RH
Zhou
Hai-qing
HQ
Gao
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D044946:Biflavonoids / Q000494:pharmacology*; D053148:Caspase 3 / Q000378:metabolism; D053453:Caspase 9 / Q000378:metabolism; D002392:Catechin / Q000494:pharmacology*; D002470:Cell Survival / Q000187:drug effects; D045304:Cytochromes c / Q000378:metabolism; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005947:Glucose / Q000494:pharmacology; D017127:Glycation End Products, Advanced; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism; D000071679:Glycogen Synthase Kinase 3 beta; D056604:Grape Seed Extract / Q000494:pharmacology*; D061307:Human Umbilical Vein Endothelial Cells / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology*; D006801:Humans; D020287:In Situ Nick-End Labeling; D008077:Lipoproteins, LDL / Q000494:pharmacology*; D010766:Phosphorylation / Q000187:drug effects; D010957:Plasmids / Q000378:metabolism; D044945:Proanthocyanidins / Q000494:pharmacology*; D020011:Protective Agents / Q000494:pharmacology*; D026601:Protein D-Aspartate-L-Isoaspartate Methyltransferase / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000378:metabolism; D051381:Rats; D014161:Transduction, Genetic; D014162:Transfection; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D000093844:Glycated Proteins
D044946:Biflavonoids; D053148:Caspase 3; D053453:Caspase 9; D002392:Catechin; D045304:Cytochromes c; D048049:Extracellular Signal-Regulated MAP Kinases; D005947:Glucose; D017127:Glycation End Products, Advanced; D038362:Glycogen Synthase Kinase 3; D000071679:Glycogen Synthase Kinase 3 beta; D056604:Grape Seed Extract; D008077:Lipoproteins, LDL; D044945:Proanthocyanidins; D020011:Protective Agents; D026601:Protein D-Aspartate-L-Isoaspartate Methyltransferase; D034741:RNA, Small Interfering; D016159:Tumor Suppressor Protein p53; C511402:Grape Seed Proanthocyanidins; C031797:glycated lipoproteins, LDL; D000093844:Glycated Proteins; C479580:procyanidin B2; C000605506:GSK3B protein, human; C000605508:Gsk3b protein, rat