Protective Effect of NO2-OA on Oxidative Stress, Gliosis, and Pro-Angiogenic Response in Müller Glial Cells.

Inflammation and oxidative and nitrosative stress are involved in the pathogenesis of proliferative retinopathies (PR). In PR, a loss of balance between pro-angiogenic and anti-angiogenic factors favors the secretion of vascular endothelial growth factor (VEGF). This vascular change results in alterations in the blood-retinal barrier, with extravasation of plasma proteins such as α2-macroglobulin (α2M) and gliosis in Müller glial cells (MGCs, such as MIO-M1). It is well known that MGCs play important roles in healthy and sick retinas, including in PR. Nitro-fatty acids are electrophilic lipid mediators with anti-inflammatory and cytoprotective properties. Our aim was to investigate whether nitro-oleic acid (NO2-OA) is beneficial against oxidative stress, gliosis, and the pro-angiogenic response in MGCs. Pure synthetic NO2-OA increased HO-1 expression in a time- and concentration-dependent manner, which was abrogated by the Nrf2 inhibitor trigonelline. In response to phorbol 12-myristate 13-acetate (PMA) and lipopolysaccharide (LPS), NO2-OA prevented the ROS increase and reduced the gliosis induced by α2M. Finally, when hypoxic MGCs were incubated with NO2-OA, the increase in VEGF mRNA expression was not affected, but under hypoxia and inflammation (IL-1ß), NO2-OA significantly reduced VEGF mRNA levels. Furthermore, NO2-OA inhibited endothelial cell (BAEC) tubulogenesis. Our results highlight NO2-OA's protective effect on oxidative damage, gliosis; and the exacerbated pro-angiogenic response in MGCs.

Studying molecular signaling in major angiogenic diseases.

The growth of blood vessels from already existing vasculature is angiogenesis and it is one of the fundamental processes in fetal development, tissue damage or repair, and the reproductive cycle. In a healthy person, angiogenesis is regulated by the balance between pro- and anti-angiogenic factors. However, when the balance is disturbed, it results in various diseases or disorders. The angiogenesis pathway is a sequential cascade and differs based on the stimuli. Therefore, targeting one of the factors involved in the process can help us find a therapeutic strategy to treat irregular angiogenesis. In the past three decades of cancer research, angiogenesis has been at its peak, where an anti-angiogenic agent inhibiting vascular endothelial growth factor acts as a promising substance to treat cancer. In addition, cancer can be assessed based on the expression of angiogenic factors and its response to therapies. Angiogenesis is important for all tissues, which might be normal or pathologically changed and occur through ages. In clinical therapeutics, target therapy focusing on discovery of novel anti-angiogenic agents like bevacizumab, cetuximab, sunitinib, imatinib, lenvatinib, thalidomide, everolimus etc., to block or inhibit the angiogenesis pathway is well explored in recent times. In this review, we will discuss about the molecular signaling pathways involved in major angiogenic diseases in detail.

Targeting HGF/c-Met Axis Decreases Circulating Regulatory T Cells Accumulation in Gastric Cancer Patients.

Elucidating mechanisms involved in tumor-induced immunosuppression is of great interest since it could help to improve cancer immunotherapy efficacy. Here we show that Hepatocyte Growth Factor (HGF), a pro-tumoral and proangiogenic factor, and its receptor c-Met are involved in regulatory T cells (Treg) accumulation in the peripheral blood of gastric cancer (GC) patients. We observed that c-Met is expressed on circulating monocytes from GC patients. The elevated expression on monocytes is associated with clinical parameters linked to an aggressive disease phenotype and correlates with a worse prognosis. Monocyte-derived dendritic cells from GC patients differentiated in the presence of HGF adopt a regulatory phenotype with a lower expression of co-stimulatory molecules, impaired maturation capacities, and an increased ability to produce interleukin-10 and to induce Treg differentiation in vitro. In the MEGA-ACCORD20-PRODIGE17 trial, GC patients received an anti-HGF antibody treatment (rilotumumab), which had been described to have an anti-angiogenic activity by decreasing proliferation of endothelial cells and tube formation. Rilotumumab decreased circulating Treg in GC patients. Thus, we identified that HGF indirectly triggers Treg accumulation via c-Met-expressing monocytes in the peripheral blood of GC patients. Our study provides arguments for potential alternative use of HGF/c-Met targeted therapies based on their immunomodulatory properties which could lead to the development of new therapeutic associations in cancer patients, for example with immune checkpoint inhibitors.

Serum-Derived Small Extracellular Vesicles From Diabetic Mice Impair Angiogenic Property of Microvascular Endothelial Cells: Role of EZH2.

Background Impaired angiogenic abilities of the microvascular endothelial cell (MVEC) play a crucial role in diabetes mellitus-impaired ischemic tissue repair. However, the underlying mechanisms of diabetes mellitus-impaired MVEC function remain unclear. We studied the role of serum-derived small extracellular vesicles (ssEVs) in diabetes mellitus-impaired MVEC function. Methods and Results ssEVs were isolated from 8-week-old male db/db and db/+ mice by ultracentrifugation and size/number were determined by the Nano-sight tracking system. Diabetic ssEVs significantly impaired tube formation and migration abilities of human MVECs. Furthermore, local transplantation of diabetic ssEVs strikingly reduced blood perfusion and capillary/arteriole density in ischemic hind limb of wildtype C57BL/6J mice. Diabetic ssEVs decreased secretion/expression of several pro-angiogenic factors in human MVECs. Mechanistically, expression of enhancer of zest homolog 2 (EZH2), the major methyltransferase responsible for catalyzing H3K27me3 (a transcription repressive maker), and H3K27me3 was increased in MVECs from db/db mice. Diabetic ssEVs increased EZH2 and H3K27me3 expression/activity in human MVECs. Expression of EZH2 mRNA was increased in diabetic ssEVs. EZH2-specific inhibitor significantly reversed diabetic ssEVs-enhanced expression of EZH2 and H3K27me3, impaired expression of angiogenic factors, and improved blood perfusion and vessel density in ischemic hind limb of C57BL/6J mice. Finally, EZH2 inactivation repressed diabetic ssEVs-induced H3K27me3 expression at promoter of pro-angiogenic genes. Conclusions Diabetic ssEVs impair the angiogenic property of MVECs via, at least partially, transferring EZH2 mRNA to MVECs, thus inducing the epigenetic mechanism involving EZH2-enhanced expression of H3K27me3 and consequent silencing of pro-angiogenic genes. Our findings unravel the cellular mechanism and expand the scope of bloodborne substances that impair MVEC function in diabetes mellitus.

Clinical implications of placenta-derived angiogenic/anti-angiogenic biomarkers in pre-eclampsia.

Pre-eclampsia (PE) is a devastating systemic disease which results in maternal hypertension with multi-organ failure due to angiogenic imbalance, characterized by lack of circulating pro-angiogenic factors and excess of anti-angiogenic factors. These factors are crucial for understanding the pathophysiology of PE since they serve as a critical link from placental dysfunction to the clinical syndrome of systemic endothelial dysfunction in the disease. Moreover, utilizing these angiogenic/anti-angiogenic biomarkers can be helpful in risk stratifying and the early detection of PE, which allows for timely intervention to improve maternal and neonatal outcomes. In this review, we summarize updated perspectives of the angiogenic imbalance in PE with detailed characterization of key factors involved in the pathogenesis and how the developed biomarkers can be used in clinical settings as diagnostic tools and as possible therapeutic targets of PE.