The HIF-1α/p53/miRNA-34a/Klotho axis in retinal pigment epithelial cells promotes subretinal fibrosis and exacerbates choroidal neovascularization.

Wet age-related macular degeneration (wAMD), characterized by choroidal neovascularization (CNV), is a leading cause of irreversible vision loss among elderly people in developed nations. Subretinal fibrosis, mediated by epithelial-mesenchymal transition (EMT) of retinal pigment epithelium (RPE) cells, leads to unsuccessful anti-vascular endothelial growth factor (VEGF) agent treatments in CNV patients. Under hypoxic conditions, hypoxia-inducible factor-1α (HIF-1α) increases the stability and activation of p53, which activates microRNA-34a (miRNA-34a) transcription to promote fibrosis. Additionally, Klotho is a target gene of miRNA-34a that inhibits fibrosis. This study aimed to explore the role of the HIF-1α/p53/miRNA-34a/Klotho axis in subretinal fibrosis and CNV. Hypoxia-induced HIF-1α promoted p53 stability, phosphorylation and nuclear translocation in ARPE-19 cells (a human RPE cell line). HIF-1α-dependent p53 activation up-regulated miRNA-34a expression in ARPE-19 cells following hypoxia. Moreover, hypoxia-induced p53-dependent miRNA-34a inhibited the expression of Klotho in ARPE-19 cells. Additionally, the HIF-1α/p53/miRNA-34a/Klotho axis facilitated hypoxia-induced EMT in ARPE-19 cells. In vivo, blockade of the HIF-1α/p53/miRNA-34a/Klotho axis alleviated the formation of mouse laser-induced CNV and subretinal fibrosis. In short, the HIF-1α/p53/miRNA-34a/Klotho axis in RPE cells promoted subretinal fibrosis, thus aggravating the formation of CNV.

Quantitative study of peripapillary retinal nerve fiber layer thickness and peripapillary vessel density in patients with different stages of Parkinson's disease.

AIM: To observe the changes in the thickness of peripapillary retinal nerve fiber layer (pRNFL) and peripapillary vessel density (pVD) in patients with different stages of Parkinson's disease (PD). METHODS: Totally 47 patients (47 eyes) with primary PD were divided into the mild group and the moderate-to-severe group according to Hoehn & Yahr (H&Y) stage. Among them, there were 27 cases (27 eyes) in mild group and 20 cases (20 eyes) in moderate-to-severe group. And 20 cases (20 eyes) who were included in the control group were healthy people who came to our hospital for health screening at the same time. All participants underwent optical coherence tomography angiography (OCTA) examinations. The pRNFL thickness, total vessel density (tVD) and capillary vessel density (cVD) of the optic disc in average, superior half, inferior half, superior nasal (SN), nasal superior (NS), nasal inferior (NI), inferior nasal (IN), inferior temporal (IT), temporal inferior (TI), temporal superior (TS), and superior temporal (ST) were measured. One-way ANOVA was used to compare the differences of optic disc parameters among the three groups, and Pearson and Spearman correlations were used to analyze the correlation between pRNFL, pVD and the disease duration, H&Y stage and UPDRS-III score in patients with PD, respectively. RESULTS: There were significant differences in pRNFL thickness in average, superior half, inferior half, SN, NS, IN, IT and ST quadrants among the three groups (P<0.05). In PD group, the pRNFL thickness in average, superior half, inferior half, NS and IT quadrants were negatively correlated with H&Y stage and UPDRS-III score, respectively (P<0.05). There were statistically significant differences in the cVD of whole image, inferior half, NI and TS quadrants, the tVD of the whole image, inferior half, and peripapillary among the three groups (P<0.05). In PD group, the tVD of whole image and the cVD of NI and TS quadrants were negatively correlated with the H&Y stage, respectively (P<0.05); the cVD of TS quadrant was negatively correlated with UPDRS-III score (P<0.05). CONCLUSION: The thickness of pRNFL in PD patients is significantly decreased, and it is negatively correlated with H&Y stage and UPDRS-III score. With the increase of the severity of the disease, the pVD parameters in PD patients increase at first in the mild group, and then decrease in the moderate-to-severe group, and negatively correlate with H&Y stage and UPDRS-III score.

Is Iba-1 protein expression a sensitive marker for microglia activation in experimental diabetic retinopathy?

AIM: To investigate the changes of Iba-1 and other potential markers for microglia activation in experimental diabetic retinopathy (DR). METHODS: Male Sprague-Dawley rats were rendered diabetes via intraperitoneal injection of streptozotocin. The retinas were harvested at 1 to 24wk after diabetes onset. Hypoxia-treated mouse microglial cell line (BV2 cells) was employed as the in vitro model to mimic diabetic condition. The expressions of Iba-1, CD11b, ICAM-1 as well as the inflammatory factors were examined with real-time polymerase chain reaction, Western blot and immunofluorescence both in vivo and in vitro. RESULTS: Compared with age-matched normal control, the number of microglia (Iba-1 positive immunostaining) in diabetic rat retinas was increased from 1 to 24wk of diabetes, which was most obvious at 12wk of diabetes. Iba-1 protein expression detected by Western blot was increased slightly in diabetic rat retinas compared with that in age-matched normal control; however, there was statistically significant between two groups only at 2wk after diabetes onset. The mRNA expression of Iba-1 was decreased significantly at 2 and 4wk of diabetic rat retinas, and remained unchanged at 8 and 12wk of diabetes. In BV2 cells, there was no significant change for the Iba-1 protein expression between normoxia and hypoxia groups; however, its mRNA level was decreased significantly under hypoxia. To further characterize microglial activation, F4/80, CD11b and inflammatory factors were detected both in vivo and in vitro. Compared with normal control, the expressions of F4/80 and CD11b as well as the inflammatory factors, such as ICAM-1, iNOS, COX2, IL-1ß and IL-6, were increased significantly both in vivo and in vitro. CONCLUSION: Iba-1 protein expression might not be a sensitive marker to evaluate the activation of microglia in experimental DR. However, Iba-1 immunostaining, in combination with other markers like CD11b and ICAM-1, could be well reflect the activation of microglia. Thus, it is of great importance to explore other potential marker to evaluate the activation of microglia.

MLN4924 inhibits hedgehog signaling pathway and activates autophagy to alleviate mouse laser-induced choroidal neovascularization lesion.

Neovascular age-related macular degeneration (nAMD), featured as choroidal neovascularization (CNV), can cause blindness in the elderly population. MLN4924, a highly selective small-molecule inhibitor of NEDD8 (neuronal precursor cell-expressed developmentally down-regulated protein 8)-activating enzyme (NAE), inhibits the proliferation, angiogenesis and inflammation of multiple cancers via up-regulating hedgehog pathway-regulated autophagy. MLN4924 intraperitoneal injection mitigated the leakage, area and volume of mouse laser-induced CNV lesion. Additionally, compared to CNV 7 d group, MLN4924 treated mouse retina-retinal pigment epithelium (RPE)-choroid complex showed decreased expression of hedgehog pathway-associated molecules patched 1 (PTCH1), smoothened (SMO), GLI family zinc finger 1 (GLI1) and GLI family zinc finger 2 (GLI2) with increased expression of autophagy-associated molecules sequestosome 1 (p62) and LC microtubule-associated protein 1 light chain 3 (LC3). Meanwhile, human choroidal endothelial cells (HCECs) exposed to hypoxia condition also showed decreased expression of hedgehog pathway-associated molecules and increased expression of autophagy-associated molecules. Compared to hypoxia + MLN4924 group, SMO agonist SAG up-regulated hedgehog pathway and down-regulated autophagy, whereas autophagy inhibitor PIK-III inhibited autophagy with no effect on hedgehog pathway, indicating that MLN4924 facilitated autophagy of HCECs via hindering hedgehog pathway under hypoxia condition. Finally, MLN4924 inhibited proliferation, migration and tube formation of HCECs via boosting hedgehog pathway-regulated autophagy. In summary, MLN4924 relieved the formation of mouse laser-induced CNV lesion might via up-regulating hedgehog pathway-regulated autophagy. The results provide a potential interfering strategy for nAMD targeting the autophagy of choroidal endothelial cells.