During the last thirty years since the discovery of endothelin-1, the therapeutic strategy that has evolved in the clinic, mainly in the treatment of pulmonary arterial hypertension, is to block the action of the peptide either at the ETA subtype or both receptors using orally active small molecule antagonists. Recently, there has been a rapid expansion in research targeting ET receptors using chemical entities other than small molecules, particularly monoclonal antibody antagonists and selective peptide agonists and antagonists. While usually sacrificing oral bio-availability, these compounds have other therapeutic advantages with the potential to considerably expand drug targets in the endothelin pathway and extend treatment to other pathophysiological conditions. Where the small molecule approach has been retained, a novel strategy to combine two vasoconstrictor targets, the angiotensin AT1 receptor as well as the ETA receptor in the dual antagonist sparsentan has been developed. A second emerging strategy is to combine drugs that have two different targets, the ETA antagonist ambrisentan with the phosphodiesterase inhibitor tadalafil, to improve the treatment of pulmonary arterial hypertension. The solving of the crystal structure of the ETB receptor has the potential to identify allosteric binding sites for novel ligands. A further key advance is the experimental validation of a single nucleotide polymorphism that has genome wide significance in five vascular diseases and that significantly increases the amount of big endothelin-1 precursor in the plasma. This observation provides a rationale for testing this single nucleotide polymorphism to stratify patients for allocation to treatment with endothelin agents and highlights the potential to use personalized precision medicine in the endothelin field.

The CCR5 receptor and its ligands CCL3, CCL4 and CCL5 contribute to the initiation and progression of atherosclerosis. We have shown that smooth muscle CCR5 mediates vasoconstriction in human blood vessels that is antagonised by maraviroc, an anti-HIV drug. Maraviroc is reported to have low affinity for rodent CCR5. Therefore, our aim was to pharmacologically characterise vasoconstrictor responses to the selective CCR5 ligand CCL4 in the human CCR5 knock-in mouse, to determine whether human CCR5 is activated by the endogenous mouse ligand CCL4. Concentration-response curves to human CCL4, mouse CCL4 and control agonists phenylephrine and U-46619 were constructed in aorta from wild type and human CCR5 knock-in animals, set up in wire myographs. Responses were expressed as a per cent of the response to 100 mM KCl. Data were analysed to determine potency (pD2) and maximum response (EMAX %KCl). Values were expressed as mean±SEM and n-values are the number of mice. Responses to phenylephrine and U-46619 were not different between the two groups. The potency of human CCL4 was not different (knock-in pD2=9.59±0.23, n=10; wild type pD2=9.12±0.36, n=4) but the maximum response in the human CCR5 knock-in mouse aorta was significantly greater (EMAX=26.1±6.0%) than control (EMAX=8.0±2.3%) (p<0.05). Importantly, responses were obtained to the endogenous ligand, mouse CCL4, in the human knock-in animal (knock-in pD2 8.98±0.34, EMAX=16.4±5.4% n=8) as well as wild type (pD2=10.46±0.16, EMAX=14.3±8.2%, n=5). These data support the use of the human CCR5 knock-in mouse in further studies to evaluate the potential of maraviroc in atherosclerosis.

BSCR/BAS Abstracts method and electron microscopy. Monocytes were migrated to MCP-1 across CAEC incubated with neutrophil-derived microparticles using a transendothelial migration assay. Cytokine release and adhesion molecule expression by hCAEC was investigated using a cytometric bead array and fluorescent antibody binding respectively. Microparticle adhesion to hCAECs was investigated under static and flow conditions. Findings Neutrophil-derived microparticles were between 0.5 and 0.9µm. The most abundant surface markers were Annexin V with 20-30% positive microparticles, CD66c (10-15%) and CD18 (5-15%). Low levels of CD11b, CXCR2, and L-selectin were observed. More microparticles were produced in response to fMLP and aLDL compared to PBS. Microparticles bind to and induce MCP-1 release from hCAEC. Monocyte migration increased upon hCAEC incubation with neutrophil-derived microparticles and the extent of the increase was dependent on the stimulus used with aLDL>fMLP>PBS. This highlights a role for microparticles in endothelial activation. THE MAMMALIAN STE20-LIKE KINASE 2 (MST2) MODULATES PATHOLOGICAL HYPERTROPHY BY ACTIVATING THE PROTO-ONCOGENE RAF1