Activation of PI3Kγ/Akt pathway increases cardiomyocyte HMGB1 expression in diabetic environment.
BACKGROUND
The high mobility group box 1 (HMGB1) protein mediates the cardiomyocyte-cardiac fibroblast interaction that contributes to induction of myocardial fibrosis in diabetes mellitus (DM). In the present study, we aim to investigate the intracellular signaling pathway that leads to cardiomyocyte HMGB1 expression under a diabetic environment.


RESULTS
HMGB1 expression is increased in high concentration of glucose (HG)-conditioned cardiomyocytes. Challenging cardiomyocytes with HG also increased PI3Kγ and Akt phosphorylation. Inhibition of PI3Kγ (CRISPR/Cas9 knockout plasmid or AS605240) prevented HG-induced Akt phosphorylation and HMGB1 expression by the cardiomyocytes. In addition, inhibition of Akt (Akt1/2/3 siRNA or A6730) attenuated HG-induced HMGB1 production. Finally, challenging cardiomyocytes with HG resulted in increased reactive oxygen species (ROS) production. Treatment of cardiomyocytes with an antioxidant (Mitotempo) abolished HG-induced PI3Kγ and Akt activation, as well as HMGB1 production.


METHODS
Isolated rat cardiomyocytes were cultured with a high concentration of glucose. Cardiomyocyte phosphatidylinositol 3-kinase gamma (PI3Kγ) and Akt were determined by Western blot. Cardiomyocyte HMGB1 production was evaluated with Western blot and enzyme-linked immunosorbent assay (ELISA), while cardiomyocyte oxidative stress was determined with a DCFDA fluorescence probe.


CONCLUSIONS
Our results suggest that the cardiomyocytes incur an oxidative stress under diabetic condition, which subsequently activates the PI3Kγ/Akt cell-signaling pathway and further increases HMGB1 expression.
Division of Cardiology, Department of Medicine, The Affiliated People's Hospital of Jiangsu University, Zhenjiang, Jiangsu, 212002, China.
Jia
J
Song
Division of Cardiology, Department of Medicine, The Affiliated People's Hospital of Jiangsu University, Zhenjiang, Jiangsu, 212002, China.
Qian
Q
Liu
Division of Cardiology, Department of Medicine, The Affiliated People's Hospital of Jiangsu University, Zhenjiang, Jiangsu, 212002, China.
Han
H
Tang
Division of Cardiology, Department of Medicine, The Affiliated People's Hospital of Jiangsu University, Zhenjiang, Jiangsu, 212002, China.|Critical Illness Research, Lawson Health Research Institute, London, Ontario, N6A 4G5, Canada.
Aibin
A
Tao
Division of Cardiology, Department of Medicine, The Affiliated People's Hospital of Jiangsu University, Zhenjiang, Jiangsu, 212002, China.
Hao
H
Wang
Critical Illness Research, Lawson Health Research Institute, London, Ontario, N6A 4G5, Canada.
Raymond
R
Kao
Division of Cardiology, Department of Medicine, The Affiliated People's Hospital of Jiangsu University, Zhenjiang, Jiangsu, 212002, China.|Critical Illness Research, Lawson Health Research Institute, London, Ontario, N6A 4G5, Canada.|Departments of Medicine, Pathology and Laboratory Medicine, Schulich School of Medicine and Dentistry, Western University, London, Ontario, N6A 4G5, Canada.
Tao
T
Rui
D000818:Animals; D064113:CRISPR-Cas Systems; D002478:Cells, Cultured; D060833:Cellular Microenvironment; D058544:Class Ib Phosphatidylinositol 3-Kinase / Q000235:genetics / Q000378:metabolism*; D058065:Diabetic Cardiomyopathies / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D005947:Glucose / Q000378:metabolism*; D024243:HMGB1 Protein / Q000378:metabolism*; D032383:Myocytes, Cardiac / Q000201:enzymology* / Q000473:pathology; D018384:Oxidative Stress; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction; D013997:Time Factors; D014162:Transfection; D015854:Up-Regulation
D024243:HMGB1 Protein; C104200:Hbp1 protein, rat; D017382:Reactive Oxygen Species; D058544:Class Ib Phosphatidylinositol 3-Kinase; C546765:Pik3cg protein, rat; C494920:Akt1 protein, rat; C494923:Akt2 protein, rat; C111490:Akt3 protein, rat; D051057:Proto-Oncogene Proteins c-akt; D005947:Glucose
Akt; HMGB1; PI3Kγ; cardiomyocyte; diabetes mellitus