In the endothelium, the single-pass membrane protein CD93, through its interaction with the extracellular matrix protein Multimerin-2, activates signaling pathways that are critical for vascular development and angiogenesis. Trafficking of adhesion molecules through endosomal compartments modulates their signaling output. However, the mechanistic basis coordinating CD93 recycling and its implications for endothelial cell (EC) function remain elusive. Human umbilical vein ECs (HUVECs) and human dermal blood ECs (HDBEC) were used in this study. Fluorescence confocal microscopy was employed to follow CD93 retrieval, recycling, and protein colocalization in spreading cells. To better define CD93 trafficking, drug treatments and transfected chimeric wild type and mutant CD93 proteins were used. The scratch assay was used to evaluate cell migration. Gene silencing strategies, flow citometry, and quantification of migratory capability were used to determine the role of Rab5c during CD93 recycling to the cell surface. Here, we identify the recycling pathway of CD93 following EC adhesion and migration. We show that the cytoplasmic domain of CD93, by its interaction with Moesin and F-actin, is instrumental for CD93 retrieval in adhering and migrating cells and that aberrant endosomal trafficking of CD93 prevents its localization at the leading edge of migration. Moreover, the small GTPase Rab5c turns out to be a key component of the molecular machinery that is able to drive CD93 recycling to the EC surface. Finally, in the Rab5c endosomal compartment CD93 forms a complex with Multimerin-2 and active β1 integrin, which is recycled back to the basolaterally-polarized cell surface by clathrin-independent endocytosis. Our findings, focusing on the pro-angiogenic receptor CD93, unveil the mechanisms of its polarized trafficking during EC adhesion and migration, opening novel therapeutic opportunities for angiogenic diseases.

Oxidative stress plays a key role in the pathophysiology of retinal diseases, including age-related macular degeneration (AMD) and diabetic retinopathy, which are the major causes of irreversible blindness in developed countries. An excess of reactive oxygen species (ROS) can directly cause functional and morphological impairments in retinal pigment epithelium (RPE), endothelial cells, and retinal ganglion cells. Antioxidants may represent a preventive/therapeutic strategy and reduce the risk of progression of AMD. Among antioxidants, N-acetyl-L-cysteine (NAC) is widely studied and has been proposed to have therapeutic benefit in treating AMD by mitigating oxidative damage in RPE. Here, we demonstrate that N-acetyl-L-cysteine ethyl ester (NACET), a lipophilic cell-permeable cysteine derivative, increases the viability in oxidative stressed RPE cells more efficiently than NAC by reacting directly and more rapidly with oxidizing agents, and that NACET, but not NAC, pretreatment predisposes RPE cells to oxidative stress resistance and increases the intracellular reduced glutathione (GSH) pool available to act as natural antioxidant defense. Moreover, we demonstrate the ability of NACET to increase GSH levels in rats’ eyes after oral administration. In conclusion, even if experiments in AMD animal models are still needed, our data suggest that NACET may play an important role in preventing and treating retinal diseases associated with oxidative stress, and may represent a valid and more efficient alternative to NAC in therapeutic protocols in which NAC has already shown promising results.

Objective. This study was aimed at assessing the long-term ocular control of adalimumab (ADA) in a large real-world population with noninfectious primary or secondary uveitis, focusing on the steroid-sparing effect and on disease-modifying antirheumatic drug (DMARD) cotreatment. Methods. In this retrospective, multicenter study, the efficacy of ADA was evaluated in terms of ocular control, changes in best-corrected visual acuity (BCVA), corticosteroid-sparing effect, and drug retention rate, overall and stratified according to DMARD cotreatment. Results. 106 patients were included. 88.7% had an associated systemic disease. After 6 and 12 months, proportions of patients with effective ocular control were 83.7% and 83.3%, respectively. At last the follow-up, 94.6% of patients had satisfactory ocular control. No difference in terms of ocular control at all time points emerged among patients starting ADA for ocular vs. systemic involvements. Patients with poor baseline BCVA remained stable or improved, while those with good BCVA hardly worsened. At 6 and 12 months, the median dose of prednisone significantly reduced to 5 mg/day (0-5) and 2.5 mg/day (0-5) (p<0.001). Over a median follow-up of 36 months, 38 subjects discontinued ADA treatment. Mild to moderate side effects were reported in 7 patients (6.6%). ADA ocular control, corticosteroid-sparing effect, and drug retention rate were not influenced by the concomitant use of DMARDs. Conclusion. The long-term ocular control of ADA in noninfectious primary or secondary uveitis is confirmed, also for BCVA preservation. Concomitant use of DMARDs does not provide additional benefits to ADA alone in terms of ocular control, steroid spare, and drug retention rate.