Relaxin as a natural agent for vascular health

Abstract

Hypertension, atherothrombosis, myocardial infarction, stroke, peripheral vascular disease, and renal failure are the main manifestations of cardiovascular disease (CVD), the leading cause of death and disability in developed countries. Continuing insight into the pathophysiology of CVD can allow identification of effective therapeutic strategies to reduce the occurrence of death and/or severe disabilities. In this context, a healthy endothelium is deemed crucial to proper functioning and maintenance of anatomical integrity of the vascular system in many organs. Of note, epidemiologic studies indicate that the incidence of CVD in women is very low until menopause and increases sharply thereafter. The loss of protection against CVD in post-menopausal women has been chiefly attributed to ovarian steroid deficiency. However, besides steroids, the ovary also produces the peptide hormone relaxin (RLX), which provides potent vasoactive effects which render it the most likely candidate as the elusive physiological shield against CVD in fertile women. In particular, RLX has a specific relaxant effect on peripheral and coronary vasculature, exerted by the stimulation of endogenous nitric oxide (NO) generation by cells of the vascular wall, and can induce angiogenesis. Moreover, RLX inhibits the activation of inflammatory leukocytes and platelets, which play a key role in CVD. Experimental studies performed in vascular and blood cell in vitro and in animal models of vascular dysfunction, as well as pioneer clinical observations, have provided evidence that RLX can prevent and/or improve CVD, thus offering background to clinical trials aimed at exploring the broad therapeutic potential of human recombinant RLX as a new cardiovascular drug.

Keywords: blood vessels; cardiovascular disease; endothelial cells; nitric oxide; relaxin; vascular smooth muscle.

Figure 1

The endothelial functions.

Figure 2

Schematic diagram highlighting the role of the endothelium in the pathophysiology of vascular dysfunction and the targets for RLX action, which include i) up-regulation of NOS II and endogenous NO production in endothelial and vascular smooth muscle cells, leading to vascular relaxation; reduced expression of endothelial cell adhesion molecules; reduced adhesion and activation of neutrophils, leading to diminished oxidative stress and tissue injury; reduced platelet activation; angiogenesis.