Exploring Leptin Antagonism in Ophthalmic Cell Models

Abstract

BackgroundEmerging evidence suggests that angiogenic and pro-inflammatory cytokine leptin might be implicated in ocular neovascularization. However, the potential of inhibiting leptin function in ophthalmic cells has never been explored. Here we assessed mitogenic, angiogenic, and signaling leptin activities in retinal and corneal endothelial cells and examined the capability of a specific leptin receptor (ObR) antagonist, Allo-aca, to inhibit these functions.Methods and ResultsThe experiments were carried out in monkey retinal (RF/6A) and bovine corneal (BCE) endothelial cells. Leptin at 50-250 ng/mL stimulated the growth of both cell lines in a dose-dependent manner. The maximal mitogenic response (35±7 and 27±3% in RF6A and BCE cells, respectively) was noted at 24 h of 250 ng/mL leptin treatments. Leptin-dependent proliferation was reduced to base levels with 10 and 100 nM Allo-aca in BCE and RF6A cells, respectively. In both cell lines, leptin promoted angiogenic responses, with the maximal increase in tube formation (163±10 and 133±8% in RF6A and BCE cultures, respectively) observed under a 250 ng/mL leptin treatment for 3 h. Furthermore, in both cell lines 250 ng/mL leptin modulated the activity or expression of several signaling molecules involved in proliferation, inflammatory activity and angiogenesis, such as STAT3, Akt, and ERK1/2, COX2, and NFκB. In both cell lines, leptin-induced angiogenic and signaling responses were significantly inhibited with 100 nM Allo-aca. We also found that leptin increased its own mRNA and protein expression in both cell lines, and this autocrine effect was abolished by 100-250 nM Allo-aca.ConclusionsOur data provide new insights into the role of leptin in ocular endothelial cells and represent the first original report on targeting ObR in ophthalmic cell models.

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

“…This study focuses on the angiogenic function of leptin and its involvement in ocular neovascularization. The leptin receptor (ObR) is expressed in vascular endothelial cells and studies in vitro demonstrated that leptin can induce angiogenic differentiation as well as proliferation and migration of endothelial cells, including cells of ophthalmic origin (Bouloumié et al, 1998 ; Sierra-Honigmann et al, 1998 ; Cao et al, 2001 ; Park et al, 2001 ; Anagnostoulis et al, 2008 ; Ferla et al, 2011 ; Garonna et al, 2011 ; Scolaro et al, 2013 ; Parrino et al, 2014 ; Adya et al, 2015 ). In mouse models, transgenic overexpression of the leptin gene ( ob ) potentiated ischemia-induced retinal neovascularization, while leptin deficiency due to ob inactivation, significantly reduced ocular angiogenesis, proving again the role of this cytokine in neovascularization (Suganami et al, 2004 ).…”

“…We have recently demonstrated that leptin is a potent mitogenic and angiogenic factor in retinal and corneal endothelial cells (Scolaro et al, 2013 ; Parrino et al, 2014 ). We have described that these leptin functions are associated with the modulation of the activity or expression of several signaling molecules involved in proliferation, inflammatory activity and angiogenesis, including the transcription factor STAT3, common kinases Ras, ERK1/2 and Akt, pro-inflammatory mediators and regulators COX2 and NF-κB.…”

“…Furthermore, we have found that leptin can upregulate its own mRNA and protein expression in retinal and corneal cells, suggesting the existence of leptin autocrine circuits in the eye. We have validated leptin involvement in the above processes using a selective and highly efficacious ObR antagonist Allo-aca, a leptin peptidomimetic that blocks ObR activation and biological activity at low-mid nmol//L concentrations in vitro in different cell types (Scolaro et al, 2013 ; Parrino et al, 2014 ).…”

Optimization of adiponectin‐derived peptides for inhibition of cancer cell growth and signaling

“…In many other cell lines, adiponectin reduces leptin‐induced STAT3 phosphorylation and signaling . Thus, we selected two non‐tumor cell lines that are still stimulated by leptin addition together with STAT3 activation and this growth stimulation/STAT3 activation can be reversed by concomitant addition of Allo‐aca . Adiponectin protein inhibits the proliferation of BCE cells .…”

“…24 ADP355 reduces ERK1/2 activation in BC cells 10 similar to the effect of ObR antagonist peptides in both cancer and the endothelial cell models. 24,42 Leptin added at 15 nM increased BCE and RF/6A cell proliferation at 24 h by 21% and 26%, respectively (Table II). When the cells were concomitantly treated with 15 nM leptin and 100 nM Allo-aca, the cell growth was reduced to 13% (BCE) and 16% (RF/6A) compared to untreated controls (Table II).…”