MicroRNA-145-5p targeting of TRIM2 mediates the apoptosis of retinal ganglion cells via the PI3K/AKT signaling pathway in glaucoma.

BACKGROUND: There is accumulating evidence to suggest that microRNAs (miRNAs) are associated with the progressive optic neuropathy including glaucoma. Apoptosis of retinal ganglion cells (RGCs) is a hallmark of glaucoma. The present study focused on the effects of miR-145-5p on RGC apoptosis in glaucoma. METHODS: We established a glaucoma rat model by intraocular injection of N-methyl-d-aspartic acid (NMDA). RGCs were isolated from newborn rats and treated with NMDA. Hematoxylin and eosin staining was performed to detect morphological changes in the retinas of rats. The expression of miR-145-5p and tripartite motif-containing 2 (TRIM2) in RGCs was measured by RT-qPCR. The viability of RGCs was measured by MTT assay. Flow cytometry analysis and TUNEL assays were conducted to assess the apoptosis of RGCs. The interaction between miR-145-5p and TRIM2 was investigated using a luciferase reporter assay. RESULTS: Rats injected with NMDA showed a thinner ganglion cell layer (GCL) and inner plexiform layer (IPL) as well as increased expression of miR-145-5p. Silencing of miR-145-5p significantly increased the GCL and IPL in the glaucoma rat model. Moreover, miR-145-5p expression was upregulated in RGCs ex vivo in response to NMDA. Silencing of miR-145-5p promoted cell viability and suppressed apoptosis in NMDA-treated RGCs. Mechanistically, miR-145-5p targeted the TRIM2 3' untranslated region to suppress its expression. TRIM2 was upregulated in NMDA-treated RGCs and protected RGCs against NMDA-induced apoptosis. Furthermore, miR-145-5p suppressed the PI3K/AKT pathway by downregulating TRIM2 in NMDA-treated RGCs. CONCLUSIONS: Suppression of miR-145-5p inhibited the apoptosis of RGCs via TRIM2-mediated activation of the PI3K/AKT signaling pathway in NMDA-induced glaucoma.

Intravitreal injection of soluble erythropoietin receptor exacerbates photoreceptor cell apoptosis in a rat model of retinal detachment.

PURPOSE: To evaluate the effects of intravitreal injection of soluble erythropoietin (EPO) receptor (sEPOR) on photoreceptor cell apoptosis in an animal model of retinal detachment (RD). METHODS: Various dosages of sEPOR (2, 20, or 200 ng) were injected into the vitreous cavities of normal rats. Three days after injection, retinal function was measured by flash electroretinography (ERG). On day 7, histopathology and retinal morphology were examined by light and transmission electron microscopy (TEM), respectively. Rat models of RD were successfully established by injection of 1.4% sodium hyaluronate into the subretinal space, followed by immediate injection of phosphate-buffered saline (PBS) or sEPOR into the vitreous cavity. On day 3, photoreceptor cell apoptosis was evaluated using terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL), and caspase-3 activity assayed by Western blotting and immunofluorescence. Light microscopic examination of retinal histopathology was used to determine the thickness of the outer nuclear layer (ONL) 14 days after establishment of RD. RESULTS: There were no significant differences in the latency and amplitude of maximal a, b and oscillatory potential (OP) wave responses by flash ERG before or 3 days after sEPOR injection (p > 0.05). Retinal tissues showed no obvious pathological changes by either light or transmission electron microscopy. Both Western blotting and immunofluorescence indicated consistent sEPOR enhanced caspase-3 activation aggravated apoptosis of photoreceptor cells in RD rat retinas. On day 14, RD ONLs were thinner, according to increasing dosages of sEPOR. CONCLUSION: Intravitreal injection of sEPOR exacerbates photoreceptor cell apoptosis in RD models via activation of caspase-3.

Effects of supplemental erythropoietin on its receptor expression and signal transduction pathways in rat model of retinal detachment.

PURPOSE: The aim of this study was to investigate the effects of supplemental erythropoietin (EPO) on its receptor (EPOR) and signal transduction pathways in rat model of retinal detachment (RD). METHODS: To investigate the effect of EPO on EPOR expression in RD rats 100, 200 or 400 ng EPO was injected into the vitreous cavity immediately after RD model was induced. Western blot and immunohistochemistry analyses were performed to measure EPOR expression. To investigate the effect of EPO on signal transduction pathways in RD rats single dose of 400 ng EPO was injected into the vitreous cavity immediately after RD model was induced. The total and phosphorylated levels of JAK2, Akt, ERK-1/2, STAT5 and NF-κB were assessed by western blot. RESULTS: Western blot analysis showed that, compared with the normal control group, EPOR expression in the neurosensory retina was significantly increased in experimental RD groups (P < 0.05), but the differences were not significant between experimental RD groups (P > 0.05). Immunohistochemical examination indicated that EPOR staining on retinas became strongly positive 3 days after RD, with no significant difference in staining intensities between the treatment groups. Phosphorylated levels of JAK2, Akt, ERK-1/2, STAT5, and NF-κB were enhanced 3 days after RD, but only JAK2, Akt, and ERK-1/2 phosphorylation was further enhanced by 400 ng EPO treatment (P < 0.05). CONCLUSIONS: Supplementary EPO cannot affect EPOR expression in detached retina, but EPO may activate both PI-3K/Akt and MAPK/ERK-1/2 signal transduction pathways in RD model.