Toll-like receptor modulation in cardiovascular disease: a target for intervention?

Enhanced Platelet Toll-like Receptor 2 and 4 Expression in Acute Coronary Syndrome and Stable Angina Pectoris

Evidence is accumulating that toll-like receptors (TLR) are involved in the initiation and progression of cardiovascular disease. Enhanced expression of these receptors on monocytes has been shown in patients with acute coronary syndrome (ACS). However, expression on platelets in this group of patients has not been evaluated yet. We aimed to demonstrate the possible relationship of platelet TLR-2 and TLR-4 expressions with stable coronary artery disease and ACS pathogenesis. In this observational case-control study, 40 patients diagnosed with ACS (unstable angina pectoris, non-ST-segment elevation and ST-segment elevation ACS), 40 patients diagnosed with stable coronary artery disease, and 40 age- and gender-matched subjects with normal coronary arteries were involved. Platelet TLR-2 and TLR-4 expressions were evaluated by flow cytometry in peripheral venous blood samples obtained before coronary angiography. A total of 120 patients (60.7 ± 12.3 years, 50% men) were included. Median platelet TLR-2 and TLR-4 expressions were greater in patients with ACS compared to those with stable angina pectoris and normal coronary arteries (29.5% vs 10.5% vs 3.0%, p <0.001 and 40.5% vs 11.5% vs 3.0%, p <0.001, respectively). Median platelet TLR-2 and TLR-4 expressions were also greater in patients with stable angina pectoris compared to those with normal coronary arteries (p <0.05). In conclusion, this is the first study demonstrating enhanced TLR-2 and TLR-4 expressions on platelets in patients with ACS. These findings may suggest that platelet TLR expression as a novel potential prophylactic and therapeutic target in ACS.

Toll-like receptors: a novel target for therapeutic intervention in intestinal and hepatic ischemia-reperfusion injury?

IMPORTANCE OF THE FIELD

Toll-like receptors (TLRs) are transmembrane proteins that act mainly as sensors of microbes, orchestrating an organism's defense against infections, while they sense also host tissue injury by recognizing products of dying cells. Ischemia-reperfusion injury (IRI) represents one of these tissue damage states in which TLR-mediated mechanisms might be implicated.

AREAS COVERED IN THIS REVIEW

The most recent data on TLR signaling and the latest knowledge regarding the involvement of TLRs in the pathogenesis and progression of intestinal and hepatic IRI are presented. The potential effectiveness of TLR-modulating therapy in intestinal and liver IRI is also analyzed.

WHAT THE READER WILL GAIN

A comprehensive summary of the data suggesting TLR involvement in intestinal and hepatic IRI. Knowledge required for developing TLR modulation strategies against intestinal and hepatic IRI.

TAKE HOME MESSAGE

TLRS play a significant role in both intestinal and hepatic IRI pathophysiology. Better understanding of TLR involvement in such processes may enable the invention of novel TLR-based therapies for IRI in the intestine and liver.

Toll-like receptors in liver ischemia reperfusion injury: a novel target for therapeutic modulation?

BACKGROUND

There is increasing evidence that Toll-like receptors (TLRs) sense host tissue damage by engaging with endogenous ligands. TLRs are considered to be involved in many primarily non-immune-related diseases. Hepatic ischemia reperfusion injury (IRI) represents one of these disorders.

OBJECTIVE

To present the latest findings supporting the involvement of TLRs in liver IRI and to explore their role as potential targets for therapeutic intervention.

METHODS

A review of the literature summarizing the latest advances in TLR signaling, the role of TLRs in each hepatic cell population and the involvement of TLRs in the pathophysiology of hepatic IRI. The potential role of TLR-targeting treatment strategies in liver IRI is discussed.

CONCLUSIONS

Recent experimental evidence suggests that TLR activation on Kupffer cells provides the triggering signal for pro-inflammatory responses that lead to liver IRI. Modulating TLR signaling could have a beneficial effect in patients with liver IRI.

Toll-like receptor modulation: a novel therapeutic strategy in cardiovascular disease?

BACKGROUND

Toll-like receptors (TLRs) have been recently recognised as primary receptors in the innate immune system. Apart from initiating a prompt immune response against invading pathogens, TLRs are also considered to be an important link between innate immunity, inflammation and a variety of clinical disorders, including cardiovascular diseases. TLR signalling manipulation with novel drugs could offer important opportunities for cardiovascular disease modification.

OBJECTIVE

To present the latest knowledge supporting the involvement of TLRs in the pathogenesis and progress of cardiovascular diseases and explore the role of TLRs as potential targets for therapeutic intervention in cardiovascular territory.

METHODS

A review of the literature documenting implication of TLR signalling in cardiovascular disorders. Current progress in TLR-targeting drug development and the potential role of such a treatment strategy in cardiovascular disorders are discussed.

CONCLUSIONS

A growing body of evidence supports a role for TLRs in cardiovascular disease initiation and progression. Altering TLR signalling with novel drugs could be a beneficial therapeutic strategy for patients with cardiovascular disorders.

Cardiac cachexia: a systematic overview

Cardiac cachexia as a terminal stage of chronic heart failure carries a poor prognosis. The definition of this clinical syndrome has been a matter of debate in recent years. This review describes the ongoing discussion about this issue and the complex pathophysiology of cardiac cachexia and chronic heart failure with particular focus on immunological, metabolic, and hormonal aspects at the intracellular and extracellular level. These include regulators such as neuropeptide Y, leptin, melanocortins, ghrelin, growth hormone, and insulin. The regulation of feeding is discussed as are nutritional aspects in the treatment of the disease. The mechanisms of wasting in different body compartments are described. Moreover, we discuss several therapeutic approaches. These include appetite stimulants like megestrol acetate, medroxyprogesterone acetate, and cannabinoids. Other drug classes of interest comprise angiotensin-converting enzyme inhibitors, beta-blockers, anabolic steroids, beta-adrenergic agonists, anti-inflammatory substances, statins, thalidomide, proteasome inhibitors, and pentoxifylline.

Cell-penetrating TIR BB loop decoy peptides a novel class of TLR signaling inhibitors and a tool to study topology of TIR-TIR interactions

Toll-like receptors (TLR), a family of closely related type I, transmembrane, signal transducing proteins, sense invading pathogens early in the immune response to infection and deliver intracellular signals to the cell. Both TLRs and their adapter proteins possess a conserved region, the Toll/IL-1 resistance (TIR) domain. A subregion of approximately 14 amino acids within the TIR domain, the BB loop, enables interactions between certain TLRs or between certain TLRs and their adapter molecules. Use of cell-penetrating decoy peptides composed of the sequence of the Drosophila antennapedia peptide (16 amino acids) juxtaposed to a specific TIR BB loop 14 amino acid sequences enables an evaluation of the relative efficacy of such BB loop peptides to inhibit TIR-TIR interactions and signaling. Moreover, failure of specific BB loop peptides to inhibit signaling suggests that this region of a particular TIR domain is likely to not be involved in signaling. This review discusses cell-penetrating decoy peptides as a new tool to further understanding of the molecular interactions required for TLR signaling and evaluates the potential of this approach for the creation of therapeutic agents.

Application of beta-lactamase enzyme complementation to the high-throughput screening of toll-like receptor signaling inhibitors

We describe a successful application of beta-lactamase fragment complementation to high-throughput screening (HTS) for Toll-like receptor 4 (TLR4) signaling inhibitors. We developed a stable cell line, HeLa/CL3-4, expressing MyD88/Bla(a) and TLR4/Bla(b), in which the two beta-lactamase fragments complement with each other by virtue of spontaneous MyD88-TLR4 binding via their Toll/IL-1R (TIR) domains. Inhibition of the MyD88-TLR4 binding leads to the disruption of the enzyme complementation and a loss of the lactamase activity. We used a 384-well plate format to screen 16,000 compounds using this assay and obtained 45 primary hits. After rescreening these 45 hits and eliminating compounds that directly inhibited beta-lactamase, we had five candidate inhibitors. We show that these five act as inhibitors of TLR4-MyD88 binding and are variously effective at inhibiting lipopolysaccharide-stimulated cytokine release from RAW264.7 cells. One compound is effective near 100 nM. None of the compounds showed any cytotoxicity at 20 microM.