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Transcriptomic analysis reveals retinal neuromodulation by sitagliptin in an experimental model of diabetic retinopathy

ABSTRACT: The aim of the study was to explore the effect of topically administered sitagliptin, an inhibitor of the enzyme dipeptidyl peptidase-4, on the retinal expression patterns of an experimental model of DR. Background: Synaptic dysfunction and neuronal damage have been extensively associated with diabetic retinopathy (DR). Our group evidenced that chronic hyperglycemia reduces the retinal expression of presynaptic proteins, which are crucial for a proper synaptic function. The aim of the study was to explore the effect of topically administered sitagliptin, an inhibitor of the en-zyme dipeptidyl peptidase-4, on the retinal expression patterns of an experimental model of DR. Methods: Transcriptome analysis was performed comparing the retinas of 10 diabetic (db/db) mice randomly treated with sitagliptin eye drops (10 mg/mL) twice daily, and the reti-nas of 10 additional db/db mice that received vehicle eye drops. 10 non diabetic mice (db/+) were used as control group. Gene Ontology (GO) and Reactome databases were used to assess the Gene Set Enrichment Analysis (GSEA) in order to explore the most enriched biological pathways among groups. The most differentiated genes of these pathways were validated through quantitative RT-PCR. Results: Transcriptome analysis revealed that sitagliptin eye drops have a significant effect on retinal expression patterns and that neurotransmission was the most enriched biological process. Our study evidenced enriched pathways that contain genes involved in membrane trafficking, transmission across chemical synapses, vesi-cle-mediated transport, neurotransmitter receptors and postsynaptic signal transmission with negative regulation of signaling as a consequence of neuroprotector treatment with sitagliptin. This improves the modulation of macromolecule biosynthetic process with positive regulation of cell communication which provides beneficial effects for neuronal metabolism. Conclu-sions: This study suggests that topical administration of sitagliptin ameliorates the abnormali-ties on presynaptic and postsynaptic signal transmission during experimental DR, and that this improvement is one of the main mechanisms behind the previously demonstrated beneficial effects.

ORGANISM(S): Mus musculus

PROVIDER: GSE219084 | GEO | 2023/01/11

REPOSITORIES: GEO

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Project description:Diabetic retinopathy (DR), the leading cause of blindness in working-age adults, is thought to be primarily a microvascular complication of diabetes. Müller cells, the major macroglia of the retina, are important for maintaining a healthy and functional retina and play a critical role in several pathological events during DR disease progression as they are a central element of the retinal neurovascular unit. Here, we aim to improve our understanding of Müller cell-specific signaling pathways that are altered during disease progression in order to develop novel gene therapy strategies targeting Müller cells in DR. To achieve this, we used a multi-omics approach on purified Müller cells from 6-month-old control and diabetic db/db mice, including (i) RNA-seq followed by oPOSSUM-3 transcription factor (TF) binding site cluster analysis, (ii) glial chromatin landscape analysis by ATAC-seq, and (iii) Müller cell proteomics by MS/MS mass spectrometry. This led to the identification of the glucocorticoid receptor (GR, gene ID: Nr3c1) as the most promising candidate. Its transcripts and protein were most highly expressed in Müller cells and significantly reduced in cells from diabetic mice, its target gene cluster was downregulated in Müller cells from diabetic animals, and importantly, it was identified as a potential master regulator not only by oPOSSUM analysis based on differentially expressed mRNA in Müller cells, but also validated by the ATAC-seq approach. Next, we investigated the effect of GR modulation in an in vitro cortisol-stimulated retinal explant model. Cortisol not only increased GR phosphorylation levels, but also induced changes in the expression of known downstream GR target genes. Finally, we evaluated whether AAV-mediated GR overexpression in Müller cells improves retinal functionality and found moderate functional improvements in electroretinogram recordings. Although synthetic and topical glucocorticoids are widely used in ophthalmology with undeniable beneficial effects, our study provides valuable new insights into the role of GR signaling and glial alterations in the diabetic retina and thus supports the therapeutic concept of locally enhancing the GR signaling axis. However, our finding of reduced GR levels in Müller cells of the diabetic retina suggests that therapeutic approaches should aim at increasing the expression of the receptor rather than adding more ligands. This may result in optimized local efficacy with fewer systemic unwarranted side effects.

Project description:Diabetic retinopathy (DR), a leading cause of irreversible vision loss in the working-age population, is an inflammatory, neuro-vascular complication of diabetes with poorly understood mechanism. N6-methyladenosine (m6A) modification plays crucial roles in biological and pathological events, while its role in DR remain elusive. Herein, we identified the pathological involvement of m6A demethylase FTO in DR. FTO expression was elevated in proliferative membranes of DR patients, endothelial cells (EC) under diabetic stress, and retinal vessels of diabetic murine models. FTO overexpression in EC promoted EC cycle progression and tip cell formation to facilitate angiogenesis in vitro, in mice and in zebrafish. FTO also regulated EC-pericyte crosstalk to trigger diabetes-induced microvascular leakage, and mediated EC-microglia crosstalk to induce retinal inflammation and subsequent neurodegeneration in vivo and in vitro. Mechanistically, FTO regulated EC features depending on its demethylation activity via modulating CDK2 mRNA stability with YTHDF2 as the reader. Moreover, FTO up-regulation in EC under diabetic conditions was driven by lactic acid mediated histone lactylation. FB23-2, which inhibits FTO’s m6A demethylase activity, suppressed diabetes associated endothelial phenotypes in vitro and in vivo. Noteworthy, we developed a novel macrophage membrane coated and PLGA-Dil based nanoplatform encapsulating FB23-2 for systemic administration, and confirmed its targeting and therapeutic efficacy in mice. Collectively, our study demonstrated an FTO-mediated regulatory network that coordinates EC biology and retinal homeostasis in DR, providing a promising nanotherapeutic approach for DR treatment. Diabetic retinopathy (DR), a leading cause of irreversible vision loss in the working-age population, is an inflammatory, neuro-vascular complication of diabetes with poorly understood mechanism. N6-methyladenosine (m6A) modification plays crucial roles in biological and pathological events, while its role in DR remain elusive. Herein, we identified the pathological involvement of m6A demethylase FTO in DR. FTO expression was elevated in proliferative membranes of DR patients, endothelial cells (EC) under diabetic stress, and retinal vessels of diabetic murine models. FTO overexpression in EC promoted EC cycle progression and tip cell formation to facilitate angiogenesis in vitro, in mice and in zebrafish. FTO also regulated EC-pericyte crosstalk to trigger diabetes-induced microvascular leakage, and mediated EC-microglia crosstalk to induce retinal inflammation and subsequent neurodegeneration in vivo and in vitro. Mechanistically, FTO regulated EC features depending on its demethylation activity via modulating CDK2 mRNA stability with YTHDF2 as the reader. Moreover, FTO up-regulation in EC under diabetic conditions was driven by lactic acid mediated histone lactylation. FB23-2, which inhibits FTO’s m6A demethylase activity, suppressed diabetes associated endothelial phenotypes in vitro and in vivo. Noteworthy, we developed a novel macrophage membrane coated and PLGA-Dil based nanoplatform encapsulating FB23-2 for systemic administration, and confirmed its targeting and therapeutic efficacy in mice. Collectively, our study demonstrated an FTO-mediated regulatory network that coordinates EC biology and retinal homeostasis in DR, providing a promising nanotherapeutic approach for DR treatment.

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Transcriptomic analysis reveals retinal neuromodulation by sitagliptin in an experimental model of diabetic retinopathy

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