Up-regulated TLR4 in cardiomyocytes exacerbates heart failure after long-term myocardial infarction.
It remains unclear whether and how cardiomyocytes contribute to the inflammation in chronic heart failure (CHF). We recently reviewed the capacity of cardiomyocytes to initiate inflammation, by means of expressing certain immune receptors such as toll-like receptors (TLRs) that respond to pathogen- and damage-associated molecular patterns (PAMP and DAMP). Previous studies observed TLR4-mediated inflammation within days of myocardial infarction (MI). This study examined TLR4 expression and function in cardiomyocytes of failing hearts after 4 weeks of MI in rats. The increases of TLR4 mRNA and proteins, as well as inflammatory cytokine production, were observed in both the infarct and remote myocardium. Enhanced immunostaining for TLR4 was observed in cardiomyocytes but not infiltrating leucocytes. The injection of lentivirus shRNA against TLR4 into the infarcted heart decreased inflammatory cytokine production and improved heart function in vivo. Accordingly, in cardiomyocytes isolated from CHF hearts, increases of TLR4 mRNA and proteins were detected. More robust binding of TLR4 with lipopolysaccharide (LPS), a PAMP ligand for TLR4, and heat shock protein 60 (HSP60), a DAMP ligand for TLR4, was observed in CHF cardiomyocytes under a confocal microscope. The maximum binding capacity (Bmax ) of TLR4 was increased for LPS and HSP60, whereas the binding affinity (Kd) was not significantly changed. Furthermore, both LPS and HSP60 induced more robust production of inflammatory cytokines in CHF cardiomyocytes, which was reduced by TLR4-blocking antibodies. We conclude that the expression, ligand-binding capacity and pro-inflammatory function of cardiomyocyte TLR4 are up-regulated after long-term MI, which promote inflammation and exacerbate heart failure.
Department of Physiology and Key Lab of Ministry of Education in Fertility Preservation and Maintenance, Ningxia Medical University, Yinchuan, China.
Li
L
Liu
Department of Ultrasonography, Changhai Hospital, Shanghai, China.
Yin
Y
Wang
Department of General Internal Medicine, Branch of 411 Hospital of People's Liberation Army, Shanghai, China.
Zhi-Yong
ZY
Cao
Department of Physiology and Key Lab of Ministry of Education in Fertility Preservation and Maintenance, Ningxia Medical University, Yinchuan, China.
Meng-Meng
MM
Wang
Department of Physiology and Key Lab of Ministry of Education in Fertility Preservation and Maintenance, Ningxia Medical University, Yinchuan, China.
Xue-Mei
XM
Liu
Department of Physiology and Key Lab of Ministry of Education in Fertility Preservation and Maintenance, Ningxia Medical University, Yinchuan, China.
Ting
T
Gao
Department of Physiology and Key Lab of Ministry of Education in Fertility Preservation and Maintenance, Ningxia Medical University, Yinchuan, China.
Qi-Kuan
QK
Hu
Department of Physiology and Key Lab of Ministry of Education in Fertility Preservation and Maintenance, Ningxia Medical University, Yinchuan, China.|Department of Physiology, Second Military Medical University, Shanghai, China.
Wen-Jun
WJ
Yuan
Department of Physiology, Second Military Medical University, Shanghai, China.|Key Laboratory of Arrhythmias of the Ministry of Education of China, Shanghai East Hospital, Tongji University School of Medicine, Shanghai, China.
Li
L
Lin
D000818:Animals; D015153:Blotting, Western; D002478:Cells, Cultured; D018834:Chaperonin 60 / Q000378:metabolism; D002908:Chronic Disease; D006333:Heart Failure / Q000235:genetics / Q000378:metabolism*; D007249:Inflammation / Q000235:genetics / Q000378:metabolism; D015850:Interleukin-6 / Q000235:genetics / Q000378:metabolism; D008070:Lipopolysaccharides / Q000378:metabolism; D008297:Male; D018613:Microscopy, Confocal; D024101:Mitochondrial Proteins / Q000378:metabolism; D009203:Myocardial Infarction / Q000235:genetics / Q000378:metabolism*; D009206:Myocardium / Q000378:metabolism / Q000473:pathology; D032383:Myocytes, Cardiac / Q000378:metabolism*; D011485:Protein Binding; D034622:RNA Interference; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000378:metabolism; D015854:Up-Regulation
D018834:Chaperonin 60; C557067:Hspd1 protein, rat; D015850:Interleukin-6; D008070:Lipopolysaccharides; D024101:Mitochondrial Proteins; D051197:Toll-Like Receptor 4; D014409:Tumor Necrosis Factor-alpha
cardiomyocyte; heart failure; inflammation; toll-like receptor