Angiogenic microenvironment augments impaired endothelial responses under diabetic conditions

Serum Exosomal Circular RNA Expression Profile and Regulative Role in Proliferative Diabetic Retinopathy

BACKGROUND

Proliferative diabetic retinopathy (PDR), as one of the main microvascular complications of diabetes mellitus, seriously threatens the visual function of the working-age population; yet, the underlying pathogenesis is still poorly understood. This study aimed to identify the distinct exosomal circular RNA (circRNA) expression in PDR serum and preliminarily explore the potential pro-angiogenic mechanism of specific exosomal circRNAs.

METHODS

We collected serum samples from 10 patients with PDR and 10 patients with age-matched senile cataract to detect the exosomal differentially expressed genes (DEGs) of circRNAs via high-throughput sequencing, followed by validation with quantitative real-time PCR (qRT-PCR). Next, bioinformatics analyses including competitive endogenous RNA (ceRNA) network, protein-protein interaction network (PPI), and functional enrichment analyses were performed. In addition, the potential function of circFndc3b (hsa_circ_0006156) derived from high-glucose-induced endothelial cells was analyzed in human retinal vascular endothelial cells (HRVECs).

RESULTS

In total, 26 circRNAs, 106 microRNAs (miRNAs), and 2,264 messenger RNAs (mRNAs) were identified as differentially expressed in PDR serum exosomes compared with cataract serum exosomes (fold change > 1, P < 0.05). A circRNA-miRNA-mRNA ceRNA network was established. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis revealed that the mRNAs were mainly enriched in the PI3K-Akt signaling pathway, MAPK signaling pathway, Wnt signaling pathway, and VEGF signaling pathway. The PPI network and module analysis identified 10 hub genes, including RhoA, Cdc42, and RASA1. Finally, circFndc3b and exosomes derived from high-glucose-induced endothelial cells were identified with the capability to facilitate angiogenesis in vitro.

CONCLUSION

Aberrant profiling of exosomal circRNAs in PDR serum was identified. CircFndc3b derived from high-glucose-induced endothelial cells may play an important role in the angiogenesis of PDR.

Long non-coding RNAs in diabetic wound healing: Current research and clinical relevance

Diabetic wounds are a protracted complication of diabetes mainly characterised by chronic inflammation, obstruction of epithelialization, damaged blood vessels and collagen production (maturation), as well as neuropathy. As a non‐coding RNA (ncRNA) that lack coding potential, long non‐coding RNAs (lncRNAs) have recently been reported to play a salient role in diabetic wound healing. Here, this review summarises the roles of lncRNAs in the pathology and treatments of diabetic wounds, providing references for its potential clinical diagnostic criteria or therapeutic targets in the future.

TGR5 receptor activation attenuates diabetic retinopathy through suppression of RhoA/ROCK signaling

Diabetic retinopathy (DR) is a common microvascular complication of diabetes mellitus. Abnormal energy metabolism in microvascular endothelium is involved in the progression of diabetic retinopathy. Bile Acid G-Protein-Coupled Membrane Receptor (TGR5) has emerged as a novel regulator of metabolic disorders. However, the role of TGR5 in diabetes mellitus-induced microvascular dysfunction in retinas is largely unknown. Herein, enzyme-linked immunosorbent assay was used for analyzing bile acid (BA) profiles in diabetic rat retinas and retinal microvascular endothelial cells (RMECs) cultured in high glucose medium. The effects of TGR5 agonist on streptozotocin (STZ)-induced diabetic retinopathy were evaluated by HE staining, TUNEL staining, retinal trypsin digestion, and vascular permeability assay. A pharmacological inhibitor of RhoA was used to study the role of TGR5 on the regulation of Rho/Rho-associated coiled-coil containing protein kinase (ROCK) and western blot, immunofluorescence and siRNA silencing were performed to study the related signaling pathways. Here we show that bile acids were downregulated during DR progression in the diabetic rat retinas and RMECs cultured in high glucose medium. The TGR5 agonist obviously ameliorated diabetes-induced retinal microvascular dysfunction in vivo, and inhibited the effect of TNF-α on endothelial cell proliferation, migration, and permeability in vitro. In contrast, knockdown of TGR5 by siRNA aggravated TNF-α-induced actin polymerization and endothelial permeability. Mechanistically, the effects of TGR5 on the improvement of endothelial function was due to its regulatory role on the ROCK signaling pathway. An inhibitor of RhoA significantly reversed the loss of tight junction protein under TNF-α stimulation. Taken together, our findings suggest that insufficient BA signaling plays an important pathogenic role in the development of DR. Upregulation or activation of TGR5 may inhibit RhoA/ROCK-dependent actin remodeling and represent an important therapeutic intervention for DR.

Sulodexide prevents activation of the PLA2/COX-2/VEGF inflammatory pathway in human retinal endothelial cells by blocking the effect of AGE/RAGE

Diabetic retinopathy is characterized by the breakdown of endothelial blood-retinal barrier. We tested the hypothesis that sulodexide (SDX), a highly purified glycosaminoglycan composed of 80% iduronylglycosaminoglycan sulfate and 20% dermatan sulfate, protects human retinal endothelial cells (HREC) from high glucose (HG)-induced damage, through the suppression of inflammatory ERK/cPLA2/COX-2/PGE₂ pathway, by blocking the effect of advanced glycation end-products (AGEs). HREC were treated with HG (25mM) or AGEs (glycated-BSA, 2mg/ml) for 48h, with or without SDX (60μg/ml) or aflibercept (AFL, 40μg/ml), a VEGF-trap. SDX protected HREC from HG-induced damage (MTT and LDH release) and preserved their blood-retinal barrier-like properties (Trans Endothelial Electrical Resistance and junction proteins, claudin-5, VE-cadherin and occludin, immunofluorescence and immunoblot) as well as their angiogenic potential (Tube Formation Assay). Both HG and AGEs increased phosphoERK and phospho-cPLA₂, an effect counteracted by SDX and, less efficiently, by AFL. Both HG and exogenous VEGF (80ng/ml) increased PGE₂ release, an effect partially reverted by SDX for HG and by AFL for VEGF. Analysis of NFκB activity revealed that HG increased the abundance of p65 in the nuclear fraction (nuclear translocation), an effect entirely reverted by SDX, but only partially by AFL. SDX, AFL and SDX+AFL protected HREC even when added 24h after HG. These data show that SDX protects HREC from HG damage and suggest that it counteracts the activation of ERK/cPLA2/COX-2/PGE₂ pathway by reducing AGE-related signaling and downstream NFκB activity. This mechanism, partially distinct from VEGF blockade, may contribute to the therapeutic effect of SDX.

Therapeutic ultrasound reverses peripheral ischemia in type 2 diabetic mice through PI3K-Akt-eNOS pathway

Therapeutic ultrasound (TUS) has been demonstrated to improve endothelial nitric oxide synthase (eNOS) activity, which played a crucial role in the regulation of angiogenesis. Diabetes Mellitus (DM) impairs eNOS activity. We tested the hypothesis that DM may retard unilateral hindlimb ischemia-induced angiogenesis by inhibiting eNOS in high-fat diet (HFD)/streptozocin (STZ) induced diabetic mice, and that TUS may reverse DM-related impairment of angiogenesis. C57BL/6 mice were allocated to four groups: (A) mice were fed standard diet (control); (B) mice were fed standard diet and treated with TUS (control+TUS); (C) type-2 DM mice were induced by HFD/STZ (diabetic); and (D) type-2 DM mice and treated with TUS (dabetic+TUS). All mice were surgically induced unilateral limb ischemia. The ischemic skeletal muscles in groups B and D were irradiated with extracorporeal TUS for 9 minutes/day (frequency of 1 MHz, intensity of 0.3 W/cm²) for 14 consecutive days. The result showed that TUS augmented the blood perfusion, increased capillary density accompanied by an upregulation of angiogenic factors and a downregulation of apoptotic proteins in group D relative to group C. In vitro, TUS inhibited the apoptosis, promoted tubule formation, proliferation and migration capacities, increased angiogenic factors expression and reduced apoptotic protein levels in human umbilical vein endothelial cells (HUVECs). Furthermore, TUS can robust reverse the inhibiting effect induced by high glucose (HG) on HUVECs, and these benefits could be blocked by phosphoinositide 3-kinase (PI3K) inhibitor (LY294002) or eNOS inhibitor (L-NAME). Together, TUS restored type-2 DM-mediated inhibition of ischemia-induced angiogenesis, partially via PI3K-Akt-eNOS signal pathway.

Inhibition of Prostaglandin Transporter (PGT) Promotes Perfusion and Vascularization and Accelerates Wound Healing in Non-Diabetic and Diabetic Rats

Peripheral ischemia, resulting from diminished arterial flow and defective local vascularization, is one of the main causes of impaired wound healing in diabetes. Vasodilatory prostaglandins (PGs), including PGE₂ and PGI₂, regulate blood flow in peripheral tissues. PGs also stimulate angiogenesis by inducing vascular endothelial growth factor. However, PG levels are reduced in diabetes mainly due to enhanced degradation. We hypothesized that inhibition of the prostaglandin transporter (PGT) (SLCO2A1), which mediates the degradation of PGs, would increase blood flow and stimulate vascularization, thereby mitigating peripheral ischemia and accelerating wound healing in diabetes. Here we report that inhibiting PGT with intravenously injected PGT inhibitor, T26A, increased blood flow in ischemic hind limbs created in non-diabetic rats and streptozotocin induced diabetic rats. Systemic, or combined with topical, T26A accelerated closure of cutaneous wounds. Immunohistochemical examination revealed that inhibition of PGT enhanced vascularization (marked by larger numbers of vessels formed by CD34+ cells), and accelerated re-epithelialization of cutaneous wounds. In cultured primary human bone marrow CD34+ cells and human epidermal keratinocytes (HEKs) either inhibiting or silencing PGT increased migration in both cell lines. Thus PGT directly regulates mobilization of endothelial progenitor cells (EPCs) and HEKs, which could contribute to PGT-mediated vascularization and re-epithelialization. At the molecular level, systemic inhibition of PGT raised circulating PGE₂. Taken together, our data demonstrate that PGT modulates arterial blood flow, mobilization of EPCs and HEKs, and vascularization and epithelialization in wound healing by regulating vasodilatory and pro-angiogenic PGs.

lncRNA-MIAT regulates microvascular dysfunction by functioning as a competing endogenous RNA

RATIONALE

Pathological angiogenesis is a critical component of diseases, such as ocular disorders, cancers, and atherosclerosis. It is usually caused by the abnormal activity of biological processes, such as cell proliferation, cell motility, immune, or inflammation response. Long noncoding RNAs (lncRNAs) have emerged as critical regulators of these biological processes. However, the role of lncRNA in diabetes mellitus-induced microvascular dysfunction is largely unknown.

OBJECTIVE

To elucidate whether lncRNA-myocardial infarction-associated transcript (MIAT) is involved in diabetes mellitus-induced microvascular dysfunction.

METHODS AND RESULTS

Using quantitative polymerase chain reaction, we demonstrated increased expression of lncRNA-MIAT in diabetic retinas and endothelial cells cultured in high glucose medium. Visual electrophysiology examination, TUNEL staining, retinal trypsin digestion, vascular permeability assay, and in vitro studies revealed that MIAT knockdown obviously ameliorated diabetes mellitus-induced retinal microvascular dysfunction in vivo, and inhibited endothelial cell proliferation, migration, and tube formation in vitro. Bioinformatics analysis, luciferase assay, RNA immunoprecipitation, and in vitro studies revealed that MIAT functioned as a competing endogenous RNA, and formed a feedback loop with vascular endothelial growth factor and miR-150-5p to regulate endothelial cell function.

CONCLUSIONS

This study highlights the involvement of lncRNA-MIAT in pathological angiogenesis and facilitates the development of lncRNA-directed diagnostics and therapeutics against neovascular diseases.

Inflammation, oxidative stress, and cardiovascular disease risk factors in adults with cystic fibrosis

Cystic fibrosis (CF) represents one of a number of localized lung and non-lung diseases with an intense chronic inflammatory component associated with evidence of systemic oxidative stress. Many of these chronic inflammatory diseases are accompanied by an array of atherosclerotic processes and cardiovascular disease (CVD), another condition strongly related to inflammation and oxidative stress. As a consequence of a dramatic increase in long-lived patients with CF in recent decades, the specter of CVD must be considered in these patients who are now reaching middle age and beyond. Buttressed by recent data documenting that CF patients exhibit evidence of endothelial dysfunction, a recognized precursor of atherosclerosis and CVD, the spectrum of risk factors for CVD in CF is reviewed here. Epidemiological data further characterizing the presence and extent of atherogenic processes in CF patients would seem important to obtain. Such studies should further inform and offer mechanistic insights into how other chronic inflammatory diseases potentiate the processes leading to CVDs.