Lysophosphatidic acid receptors LPA1 and LPA3 promote CXCL12-mediated smooth muscle progenitor cell recruitment in neointima formation.

RATIONALE: The chemokine CXCL12 (CXC motif ligand 12) and its receptor CXCR 4 (CXC motif receptor 4) direct the recruitment of smooth muscle progenitor cells (SPCs) in neointima formation after vascular injury. Lysophosphatidic acid (LPA) induces CXCL12 and neointimal accumulation of smooth muscle cells (SMCs) in uninjured arteries. Thus, we hypothesize that LPA may regulate CXCL12-mediated vascular remodelling. OBJECTIVES: We evaluated the role of LPA receptors in initiating CXCL12-dependent vascular repair by SPCs. METHODS AND RESULTS: Wire-induced carotid injury was performed in apolipoprotein E(-/-) mice on western-type diet. LPA receptor expression was studied by immunostaining and quantitative RT-PCR. LPA receptors LPA(1) and LPA(3) were detected in the media of uninjured arteries and in the injury-induced neointima. LPA(3) mRNA was upregulated and LPA(1) mRNA downregulated at one week after injury. The LPA(1/3) antagonist Ki16425 inhibited neointima formation by 71% and reduced both relative neointimal SMCs and the macrophage content. Additionally, neointimal hypoxia-inducible factor-1alpha and CXCL12 expression, the injury-induced peripheral stem cell antigen-1 (Sca-1)(+)/Lin(-) SPC mobilization, and the neointimal recruitment of Sca-1(+)SMCs were inhibited by Ki16425. In wild type mice, LPA20:4 increased CXCL12 and hypoxia-inducible factor-1alpha expression in carotid arteries as early as 1 day following short-term endoluminal incubation. LPA20:4-induced SPC mobilization and neointima formation were blocked by Ki16425, LPA(1)- and LPA(3)-specific small interfering (si)RNA, and the CXCR4 antagonist POL5551. Ki16425 reduced LPA20:4-mediated neointimal recruitment of SPC as demonstrated by 2-photon microscopy in bone marrow chimeric mice after repopulation with SM22-LacZ transgenic, hematopoietic cells. Moreover, POL5551 decreased the neointimal accumulation of CXCR4(+) SMCs. CONCLUSIONS: LPA(1) and LPA(3) promote neointima formation through activation of CXCL12-mediated mobilization and recruitment of SPCs.

Discovery of novel, highly potent and selective beta-hairpin mimetic CXCR4 inhibitors with excellent anti-HIV activity and pharmacokinetic profiles.

Novel highly potent CXCR4 inhibitors with good pharmacokinetic properties were designed and optimized starting from the naturally occurring beta-hairpin peptide polyphemusin II. The design involved incorporating important residues from polyphemusin II into a macrocyclic template-bound beta-hairpin mimetic. Using a parallel synthesis approach, the potency and ADME properties of the mimetics were optimized in iterative cycles, resulting in the CXCR4 inhibitors POL2438 and POL3026. The inhibitory potencies of these compounds were confirmed in a series of HIV-1 invasion assays in vitro. POL3026 showed excellent plasma stability, high selectivity for CXCR4, favorable pharmacokinetic properties in the dog, and thus has the potential to become a therapeutic compound for application in the treatment of HIV infections (as an entry inhibitor), cancer (for angiogenesis suppression and inhibition of metastasis), inflammation, and in stem cell transplant therapy.

Development of a Hypusine Reagent for Peptide Synthesis.

The synthesis of a reagent that enables the incorporation of the unusual amino acid (2S,9R)-hypusine (Hpu) into peptide sequences is described. The reagent, (2S,9R)-11-[(benzyloxycarbonyl)amino]-7-(carbobenzyloxy)-2-[(9-fluorenylmethoxycarbonyl)amino]-9-(tetrahydropyran-2-yloxy)-7-azaundecanoic acid, is utilized in the synthesis of a hexapeptide containing the primary pentapeptide sequence of the eukaryotic initiation factor eIF-5A, L-Cys-L-Thr-Gly-Hpu-L-His-Gly. The reagent is shown to be effective for both solution phase and Merrifield resin synthesis.