Designer Leptin Receptor Antagonist Allo-aca Inhibits VEGF Effects in Ophthalmic Neoangiogenesis Models

Abstract

Experimental and clinical data suggest that pro-angiogenic, pro-inflammatory and mitogenic cytokine leptin can be implicated in ocular neovascularization and other eye pathologies. At least in part, leptin action appears to be mediated through functional interplay with vascular endothelial growth factor (VEGF). VEGF is a potent regulator of neoangiogenesis and vascular leakage with a proven role in conditions such as proliferative diabetic retinopathy, age-related macular degeneration and diabetic macular edema. Accordingly, drugs targeting VEGF are becoming mainstream treatments for these diseases. The crosstalk between leptin and VEGF has been noted in different tissues, but its involvement in the development of eye pathologies is unclear. Leptin is coexpressed with VEGF during ocular neovascularization and can potentiate VEGF synthesis and angiogenic function. However, whether or not VEGF regulates leptin expression or signaling has never been studied. Consequently, we addressed this aspect of leptin/VEGF crosstalk in ocular models, focusing on therapeutic exploration of underlying mechanisms. Here we show, for the first time, that in retinal (RF/6A) and corneal (BCE) endothelial cells, VEGF (100 ng/mL, 24 h) stimulated leptin mRNA synthesis by 70 and 30%, respectively, and protein expression by 56 and 28%, respectively. In parallel, VEGF induced RF/6A and BCE cell growth by 33 and 20%, respectively. In addition, VEGF upregulated chemotaxis and chemokinesis in retinal cells by ~40%. VEGF-dependent proliferation and migration were significantly reduced in the presence of the leptin receptor antagonist, Allo-aca, at 100–250 nmol/L concentrations. Furthermore, Allo-aca suppressed VEGF-dependent long-term (24 h), but not acute (15 min) stimulation of the Akt and ERK1/2 signaling pathways. The efficacy of Allo-aca was validated in the rat laser-induced choroidal neovascularization model where the compound (5 μg/eye) significantly reduced pathological vascularization with the efficacy similar to that of a standard treatment (anti-VEGF antibody, 1 μg/eye). Cumulatively, our results suggest that chronic exposure to VEGF upregulates leptin expression and function. As leptin can in turn activate VEGF, the increased abundance of both cytokines could amplify pro-angiogenic and pro-inflammatory environement in the eye. Thus, combined therapies targeting ObR and VEGF should be considered in the treatment of ocular diseases.

Leptin antagonism inhibits prostate cancer xenograft growth and progression

“…In tumours with adequate tissue, enhanced cell death pathways and pro-apoptotic markers were observed with LEPR inhibition, in accordance with leptin's anti-apoptotic actions in vitro (Somasundar et al, 2004), and likely contribute Allo-aca anti-tumour action. Furthermore, Allo-aca induced anti-angiogenic properties, evidenced through reduced vascularisation and lowered abundance of angiogenic driver VEGF; this is in-keeping with previous reports of leptin and LEPR antagonist action (Coroniti et al, 2016, Cao et al, 2001, Gonzalez et al, 2006, Yang et al, 2016. Interestingly, enrichment in toxicological pathways of necrosis and altered hypoxia signalling were observed which could implicate an altered intratumoural environment mechanistically in the observed growth effects; however, these will be the subject of further future investigation.…”

Ocular macrophage origin and heterogeneity during steady state and experimental choroidal neovascularization

“…Tie2 ( TEK ) and LEPR are cell surface receptors for angiopoietin and leptin, respectively. Both macrophage-specific Tie2 knockout mice [ 29 ] and leptin receptor antagonism [ 30 ] inhibit laser-induced CNV. TEK and LEPR expression were increased by 2.1- and 2.4-fold in Mac-B (Fig.…”

Leptin signaling axis specifically associates with clinical prognosis and is multifunctional in regulating cancer progression

“…Furthermore, HIF-1α and NFκB were proposed as the major route in leptin-dependent VEGF-A induction in breast cancer [ 44 ]. The biological significance of leptin-leptin receptor axis in promoting angiogenesis was further shown by the inhibitory effect of Aca 1 treatment, a peptide leptin receptor antagonist, on endothelial cell tube formation [ 45 ], as well as by the Allo-aca (leptin receptor antagonist)-mediated reduction of pathological vascularization in rat ophthalmic neoangiogenesis model [ 46 ].…”