Anti-angiogenic effects of the DPP-4 inhibitor linagliptin via inhibition of VEGFR signalling in the mouse model of oxygen-induced retinopathy
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Linagliptin has protective effects on the retinal neurovascular unit but, in proliferative retinopathy, dipeptidyl peptidase 4 (DPP-4) inhibition could be detrimental. The aim of this study was to assess the effect of linagliptin on ischaemia-induced neovascularisation of the retina.
C57BL/6J and glucagon-like peptide 1 (GLP-1) receptor (Glp1r)−/− mice were subjected to a model of oxygen-induced retinopathy (OIR). Both strains were subcutaneously treated with linagliptin from postnatal days 12 to 16. Non-injected OIR and non-exposed mice served as controls. Capillary proliferations and systemic levels of active GLP-1 were quantified. The effects of linagliptin on vascular endothelial growth factor (VEGF)-induced downstream signalling were assessed in human umbilical vein endothelial cells (HUVECs) using western blot for retinal phosphorylated extracellular signal-regulated kinase (ERK)1/2 and retinal gene expression analyses.
Linagliptin treatment led to an increase in active GLP-1 and a decreased number of neovascular nuclei in OIR mice vs controls (−30%, p < 0.05). As the reduction in neovascularisation was similar in both C57BL/6J and Glp1r−/− mice, the anti-angiogenic effects of linagliptin were independent of GLP-1R status. The expression of Vegf (also known as Vegfa) and Hif1a was increased in C57BL/6J OIR mice upon linagliptin treatment (three- vs 1.5-fold, p < 0.05, p < 0.01, respectively). In HUVECs, linagliptin inhibited VEGF-induced increases in mitogen-activated protein kinase (MAPK)/ERK (−67%, p < 0.001) and MAPK/c-Jun N-terminal kinase (JNK) (−13%, p < 0.05) pathway activities. In the retinas of C57BL/6J mice, p-ERK1/2 levels were significantly reduced upon linagliptin treatment (−47%, p < 0.05).
Systemic treatment with linagliptin demonstrated GLP-1R-independent anti-angiogenic effects mediated by an inhibition of VEGF receptor downstream signalling. The specific effects of linagliptin on diabetic retinopathy are of potential benefit for individuals with diabetes, independent of metabolic effects.
KeywordsAngiogenesis DPP-4 GLP-1 Linagliptin Oxygen-induced retinopathy Proliferative retinopathy
Dipeptidyl peptidase 4
Extracellular signal-regulated kinase
Glucagon-like peptide 1 receptor
Hypoxia-inducible factor 1α
High-mobility group box 1
Human umbilical vascular endothelial cell
c-Jun N-terminal kinase
Mitogen-activated protein kinase
Stromal cell-derived factor 1 α
Vascular endothelial growth factor
Vascular endothelial growth factor receptor
MK, ND and HPH contributed to the conception and design of this study, acquisition, analysis and interpretation of data, reviewed the literature and critically drafted and revised the manuscript. TK contributed to acquisition, analysis and interpretation of data, reviewed the literature and critically drafted and revised the manuscript. All authors approved the final version of the manuscript. MK and HPH are responsible for the integrity of the work as a whole.
This study was funded and supported by Boehringer Ingelheim. MK is an associated member of the GRK1874 DIAMICOM, funded by the Deutsche Forschungsgemeinschaft.
Duality of interest
All authors declare that there is no duality of interest associated with this manuscript. TK is a full-time employee of Boehringer Ingelheim. Boehringer Ingelheim had no influence on the conception and design of this study, or on the decision to publish the results.
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