Design and Synthesis of Novel Peptidomimetic Inhibitors of TLR4 (Toll-like receptor 4), as a Potential Cardio-Protective Agents

Myocardial ischemia (MI) is the leading cause of death in the USA and other developed countries. Similarly, sepsis is one of the most common complications after surgery, and is the main cause of death in non-coronary adult intensive care units. These conditions consist of two components: the first is a direct, depressive influence on the cardiovascular system, and the second is the involvement of the systemic immune system in the heart as a response to inflammation caused by sepsis or MI. The mechanism that leads to the release of pro-inflammatory cytokines also includes the activation of TLR4. This protein is a pattern recognition receptor that specifically mediates cellular responses generated after binding to the receptor bacterial lipopolysaccharide (LPS). TLR4 also responds to endogenous factors produced during different stress stimuli or with cell damage. These responses support TLR4`s role in the inflammatory response to ischemic injury. The goal of presented here research is to find a novel drug candidates which will be able to inhibit TLR4’s activity and as a result of this to suppress the negative effects of sepsis and MI.

We used known peptide (IVFAEMOCG) which binds to the TIR domain of the receptor and inhibit the TLR4’s activation. This peptide mimics a sequence of TLR4 downstream target (TRAM adaptor), binding to TRAM and interrupts the physiological interaction between the TLR4 TIR domain and the adaptor molecule. Based on sequence of the peptide, we synthesized its peptidomimetic derivatives.

Out of the first set of 7 peptidomimetics, LT51-54 exhibited a significant protective effect in cardiomyocytes. Based on their structures, another 23 molecules were designed, synthesized, and tested in-vitro. The most active compounds were: LT58, LT59, LT61, and LT62.