J Anesth Perioper Med. 2014;1(2):104-117. https://doi.org/10.24015/ebcmed.japm.2014.0016

Inflammation and Heart Diseases: Role of Toll-Like Receptor Signaling

Wei Chao

From the Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, USA.

Correspondence to Dr. Wei Chao at wchao@mgh.harvard.edu.

EBCMED ID: ebcmed.japm.2014.0016 DOI: 10.24015/ebcmed.japm.2014.0016


Aim of review
Heart diseases such as septic cardiomyopathy, ischemic myocardial injury and acute myocarditis pose significant perioperative risk to surgical patients and present challenges to anesthesiologists. Myocardial inflammation is a common theme of these diseases and plays an important role in their pathogeneses. Toll-like receptors (TLRs) are an important part of the innate immune system. The aim of this article is to provide a brief review on the major landmark studies of TLRs and their signaling, the complex and critical role of TLRs in severe sepsis, ischemic myocardial injury, and myocarditis. The article intends to cover animal studies defining the molecular mechanisms by which TLR signaling contributes to the pathogenesis of these heart diseases as well as the recent clinical trials targeting TLR for sepsis intervention.

Literatures were searched via PubMed with the key words TLRs, sepsis, myocardial ischemia, and myocarditis. A few previously published review articles in the relevant fields were referenced.

Recent findings
TLRs detect invading pathogens through the pathogen-associated molecular pattern (PAMP) recognition and play an essential role in the host defense. TLRs can also sense endogenous molecules with the danger-associated molecular pattern (DAMP), such as heat shock proteins (HSPs), high mobility group 1 (HMGB-1) and extracellular RNA, which are produced under various injurious conditions. Studies in the past decade have clearly established the critical role of TLR signaling in mediating cardiac inflammation in the context of severe sepsis, myocardial ischemia-reperfusion injury and acute myocarditis. A variety of microbial and non- microbial TLR ligands have been identified under these critical conditions. These ligands act through TLRs and elicit potent biochemical and inflammatory responses. By mediating the complex cardiac as well as systemic inflammation, either beneficial or deleterious in nature, TLRs play a pivotal role in the development of these cardiac diseases. Recent TLR4 antagonist (eritoran) Phase I-III clinical trials represent the latest effort targeting TLR signaling for sepsis therapeutics.

Studies of the past decade have firmly established the role of TLR signaling in cardiac inflammation and dysfunction during severe sepsis, ischemic myocardial injury, and acute myocarditis. Understanding the complex cellular and molecular pathways by which TLR signaling controls myocardial inflammation and injury provides insight into the mechanisms of these cardiac diseases and will impact on how we diagnose and treat these critical conditions in the future.

Article Type
Review Article

Declaration of Interests
No other potential conflict of interest relevant to this review was reported.

The work in our laboratory during the past decade has been supported in part by National Institutes of Health (R01-GM080906 and R01-GM097259), American Heart Association (Grant-in-Aid 0755890T), Foundation for Anesthesia Education and Research (FAER), William F. Milton Fund of Harvard University, and International Anesthesia Research Society (IARS).
I would like to thank all current and former trainees in my laboratory at Massachusetts General Hospital, Harvard Medical School for their dedication and contributions.
The following individuals have made the major contributions to our work discussed in this article: Yan Feng, Lin Zou, Yan Shen, Rui Si, Yan Li, E Wang, Ming Zhang, Yu Gong, Chan Chen, Dan Li.

This is an open-access article, published by Evidence Based Communications (EBC). This work is licensed under the Creative Commons Attribution 4.0 International License, which permits unrestricted use, distribution, and reproduction in any medium or format for any lawful purpose. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.