A cyclic azapeptide ligand of the scavenger receptor CD36/SR-B2 reduces the atherosclerotic lesion progression and enhances plaque stability in apolipoprotein E-deficient mice

Atherosclerosis is a chronic inflammatory disease of the arterial walls that develops at predisposed sites. As a major risk factor for adverse cardiovascular pathology, atherosclerosis can progress to myocardial infarction and stroke, due to the rupture of unstable atherosclerotic lesions. Macrophage uptake of modified lipoproteins and metabolic dysfunction contributes significantly to the initiation and development of atherosclerotic lesions. The cluster of differentiation 36 receptor [CD36 (SR-B2)] plays a key role in atherosclerotic lesion progression and acts as an efferocytic molecule in the resolution of advanced plaque. In previous studies, linear azapeptide CD36 ligands were shown to exhibit anti-atherosclerotic properties. In the present study, a novel potent and selective macrocyclic azapeptide CD36 ligand, MPE-298, has proven effective in protecting against atherosclerosis progression. Features of greater plaque stability were observed after 8 weeks of daily injections with the cyclic azapeptide in apolipoprotein E-deficient mice fed a high-fat high-cholesterol diet.

Abstract 004: Pro-angiogenic Effects Of The Thrombospondin-1 Inhibitor Lskl In Preeclampsia Models

Introduction: Preeclampsia (PE) is characterized by high blood pressure, proteinuria and/or multi-organ damage, reaching 10% of all pregnancies globally. To date, no medication can treat PE. We recently identified an upregulation of the antiangiogenic protein Thrombospondin-1 (THBS1) in human and experimental PE. THBS1 is a main activator of latent TGF-β. We postulate that THBS1-mediated TGF-β activation can contribute to impair placental angiogenesis during PE. In this study, we aim to test the effects of LSKL, an inhibitor of TGF-β activation by THBS1, on angiogenesis in placentas of a mouse model of PE and in human placental endothelial cells exposed to PE-like conditions.

Methods: Heterozygous female mice overexpressing human angiotensinogen and renin (PE) or C57BL/6 (control) were treated with LSKL or control peptide SLLK (280 μM, sc) at gestational day (GD) 14.5 (n=3 pregnant mouse/group). Placentas (n=4-9/pregnancy) were collected at GD 18.5. Placental expressions of TGF-β1, β2, total/phospho SMAD2 were assessed by western blot and angiogenesis by immunohistochemistry. Endothelial cells were extracted by magnetic sorting from human placentas (n=4) of healthy pregnancies. Cells were treated with LSKL or SLLK (30 μM) under hypoxia (0.5% vs. 8% O 2 ) or thrombin (10 u/mL). THBS1 expression in cells was assessed by immunofluorescence. Cell angiogenesis was quantified by the number of closed tubes formed on matrigel (per 15,000 cells, 4h).

Results: LSKL treatment reduced the expression of TGF-β2 (P<0.01) and phospho-SMAD2 (P<0.05) and significantly improved angiogenesis (P<0.05) in placentas of PE mouse versus control. In cells, both thrombin (P<0.05) and hypoxia (P<0.05) significantly increased THBS1 expression. Thrombin (P<0.01) and hypoxia (P<0.05) significantly impaired cell angiogenesis on matrigel (P<0.01), which was prevented by LSKL treatment (P<0.01). LSKL similarly reduced TGB-β2 (p<0.05) and phospho-SMAD2 (P<0.05) expressions in endothelial cells under thrombin and hypoxia cell exposure.

Conclusion: Our results describe a significant pro-angiogenic effect of LSKL treatment by regulating THBS1 and TGF-β2 mechanisms in an experimental model of PE and in human placental endothelial cells exposed to PE-like conditions.

Atheroprotective and atheroregressive potential of azapeptide derivatives of GHRP-6 as selective CD36 ligands in apolipoprotein E-deficient mice

BACKGROUND AND AIMS

Scavenger receptor class B member 3, also known as cluster of differentiation-36 (CD36) receptor, is involved in the uptake and accumulation of modified lipoprotein in macrophages, driving atherosclerosis progression. Azapeptide analogs of growth hormone-releasing peptide-6 (GHRP-6) have been developed as selective CD36 ligands and evaluated for their anti-atherosclerotic properties in apoe^-/- mice.

METHODS

From 4 to 19 weeks of age, male apoe^-/- mice were fed a high fat high cholesterol (HFHC) diet, then switched to normal chow and treated daily with 300 nmol/kg of MPE-001 ([aza-Tyr⁴]-GHRP-6) or MPE-003 ([aza-(N,N-diallylaminobut-2-ynyl)Gly⁴]-GHRP-6) for 9 weeks. In another protocol, mice were fed a HFHC diet throughout the study.

RESULTS

Azapeptides decreased lesion progression in the aortic arch and reduced aortic sinus lesion areas below pre-existing lesions levels in apoe^-/- mice which were switched to chow diet. In mice fed a HFHC throughout the study, azapeptides reduced lesion progression in the aortic vessel and sinus. The anti-atherosclerotic effect of azapeptides was associated with a reduced ratio of iNOS⁺/CD206⁺ macrophages within lesions, and lowered plasma inflammatory cytokine levels. Monocytes from azapeptide-treated mice showed altered mitochondrial oxygen consumption rates, consistent with an M2-like phenotype. These effects were dependent on CD36, and not observed in apoe^-/-cd36^-/- mice.

CONCLUSIONS

Azapeptides MPE-001 and MPE-003 diminished aortic lesion progression and reduced, below pre-existing levels, lesions in the aortic sinus of atherosclerotic mice. A relative increase of M2-like macrophages was observed in lesions, associated with reduced systemic inflammation. Development of CD36-selective azapeptide ligands merits consideration for treating atherosclerotic disease.