Yingqin Ni

Neuroprotective effect of transcorneal electrical stimulation on light-induced photoreceptor degeneration ☆

Direct electrical stimulation of neural tissues is a strategic approach to treat injured axons by accelerating their outgrowth [Al-Majed, A.A., Neumann, C.M., Brushart, T.M., Gordon, T., 2000. Brief electrical stimulation promotes the speed and accuracy of motor axonal regeneration. J. Neurosci. 20, 2602-2608] and promoting their regeneration [Geremia, N.M., Gordon, T., Brushart, T.M., Al-Majed, A.A., Verge, V.M.K., 2007. Electrical stimulation promotes sensory neuron regeneration and growth-associated gene expression. Exp. Neurol. 205, 347-359]. Recently, transcorneal electrical stimulation (TCES), a novel less invasive method, has been shown to rescue axotomized and damaged retinal ganglion cells [Morimoto, T., Miyoshi, T., Matsuda, S., Tano, Y., Fujikado, T., Fukuda, Y., 2005. Transcorneal electrical stimulation rescues axotomized retinal ganglion cells by activating endogenous retinal IGF-1 system. Invest. Ophthalmol. Vis. Sci. 46(6), 2147-2155]. Here, we investigated the neuroprotection of TCES on light-induced photoreceptor degeneration and the underlying mechanism. Adult male Sprague-Dawley (SD) rats received TCES before (pre-TCES) or after (post-TCES) intense light exposure. After fourteen days of light exposure, retinal histology and electroretinography were performed to evaluate the neuroprotective effect of TCES. The mRNA and protein levels of apoptotic-associated genes including Bcl-2, Bax, Caspase-3 as well as ciliary neurotrophic factor (CNTF) and brain-derived neurotrophic factor (BDNF) in the retinas were determined by real-time PCR and Western blot analysis. The localization of these gene products in the retinas was examined by immunohistochemistry. Both pre- and post-TCES ameliorated the progressive photoreceptor degeneration. The degree of rescue depended on the strength of the electric charge. Post-TCES showed a relatively better and longer-term protective effect than pre-TCES. Real-time PCR and Western blot analysis revealed an upregulation of Bcl-2, CNTF, and BDNF and a downregulation of Bax in the retinas after TCES. Immunohistochemical studies showed that Bcl-2 and CNTF were selectively upregulated in Müller cells. These findings provide a new therapeutic method to prevent or delay photoreceptor degeneration through activating the intrinsic survival system.

Neuroprotective Effects of Naloxone against Light-Induced Photoreceptor Degeneration through Inhibiting Retinal Microglial Activation

PURPOSE To determine the role of microglial activation in light-induced photoreceptor degeneration and the neuroprotective effects of naloxone as a novel microglial inhibitor. METHODS Sprague-Dawley rats were exposed to intense blue light for 24 hours. Daily intraperitoneal injection of naloxone or PBS as a control was given 2 days before exposure to light and was continued for 2 weeks. Apoptotic cells were detected by the TUNEL assay, and anti-OX42 antibody was used to label retinal microglia. Western blot was applied to evaluate the retinal interleukin (IL)-1beta protein levels. Retinal histologic examination and electroretinography (ERG) were also performed to evaluate the effects of naloxone on light-induced photoreceptor degeneration. RESULTS TUNEL-positive cells were noted in the outer nuclear layer (ONL) of the retina as early as 2 hours and peaked at 24 hours after exposure to light. OX42-positive microglia occurred in the ONL and subretinal space at 6 hours, peaked at 3 days, and changed morphologically from the resting ramified to the activated amoeboid. Expression of IL-1beta protein was also significantly increased at 3 days. Compared with the control, the number of microglia in the outer retina was significantly decreased in the naloxone-treated group at 3 days, and the thickness of ONL and the amplitudes of dark-adapted a- and b-waves were also well preserved at 14 days. CONCLUSIONS The activation and migration of microglia and the expression of neurotoxic factor (IL-1beta) coincide with photoreceptor apoptosis, suggesting that activated microglia play a major role in light-induced photoreceptor degeneration. Inhibiting microglial activation by naloxone significantly reduces this degeneration.

Electrical stimulation ameliorates light-induced photoreceptor degeneration in vitro via suppressing the proinflammatory effect of microglia and enhancing the neurotrophic potential of Müller cells.

Many types of electrical stimulation (ES) devices have been shown to promote the survival of degenerated neural cells, such as dopaminergic neurons in the medial forebrain bundle-transected rats, ischemic-injured cortical neurons and inner-and outer-nuclear-layer cells in degenerated retina. Using a rat photic injury model, our lab previously proved the neuroprotective effect of transcorneal electrical stimulation (TCES) on apoptotic photoreceptor cells. To delineate the mechanisms that might underlie this process, the effects of ES on light-damaged photoreceptor degeneration-induced microglia and Müller cell activation were investigated in the present in vitro study. Our data showed that ES (3 ms, 20 Hz, 300-1600 μA) increased survival among light-reared cone-derived cells (661W) cultured alongside microglia or Müller cells analyzed by LDH and TUNEL assays. The degree of rescue was found to depend on the different intensities of the ES current. The immunocytochemistry revealed that ES significantly decreased the numbers of activated microglia cells with ameboid shapes and increased the numbers of reactive gliotic Müller cells with larger soma when they were co-cultured with light-damaged 661W cells. Real-time RT-PCR and Western blotting indicated that ES which was applied to different co-cultures and 661W cell-conditioned media (661WCM)-treated glia cultures had a prominent inhibitive effect on the secretion of interleukin (IL)-1β and tumor necrosis factor (TNF)-α in microglia and a positive regulative effect on the production of brain-derived neurotrophic factor (BDNF) and ciliary neurotrophic factor (CNTF) in Müller cells. The death rate of light-exposed 661W cells cultured with microglia was decreased significantly by the addition of neutralizing antibodies against IL-1β and TNF-α. On the other hand, the death rate of light-exposed 661W cells cultured with Müller cells was prominently increased when the co-culture was incubated in the presence of neutralizing antibody against BDNF while anti-CNTF neutralizing antibody did not induce additional exacerbation of the cell death among those 661W cells. These findings indicate the feasibility of using ES to create a nurturing environment for light-damaged photoreceptor cells. This environment is characterized by diminished microglial activation and fortified Müller cells reactive gliosis, which may have great potential in ameliorating photoreceptor damage. In this way, ES was here determined to be a novel, potent therapeutic option for delaying the progression of photoreceptor degeneration in patients suffering from retinitis pigmentosa (RP).

Müller cells upregulate the expression of SAP97 in light-injured rat retina

SAP97 is thought to play key roles in synapse assembly and synaptic plasticity. This study was carried out to determine whether it is involved in the Müller cell response to blue light injury. In light-injured rats, obvious intracellular edema in the outer retina was observed by transmission electron microscopy. The immunostaining of SAP97 was upregulated and concentrated in the Müller cell processes after photic injury, which was similar to the changes of AQP4 and the inwardly rectifying potassium channel, Kir4.1. Western blots showed that SAP97 and AQP4 protein levels were both increased on the third day after light exposure when compared with the control group (P<0.05). The upregulation of SAP97 coincides with the redistribution of AQP4 and Kir4.1 in blue light-injured rat retina.

Generation and characterization of immortalized rat retinal microglial cell lines.

Retinal microglia play an important role as resident immunocompetent and phagocytic cells in the event of injury and disease. Retinal microglia and microglia precursor transplantation show a rescue effect in ischemic retina and retinal degeneration. However, studies of retinal microglia have been hampered by the difficulty of obtaining sufficient numbers of microglia. One way to circumvent this difficulty is to establish permanent retinal microglia cell lines. In the present study, we report the generation of immortalized retinal microglia, T‐MG cells, from postnatal day 3 rat retinal tissue using a lentiviral vector encoding SV40 large T antigen. The T‐MG cells exhibited cell‐type‐specific antigens for monocyte/macrophage lineage cells, including CD11b (OX42), ED1 (OX6), and Iba1, and actively phagocytosed latex beads. In addition to primary retinal microglia, T‐MG cells also have the ability to recruit into chemokines. Treatment of T‐MG cells with lipopolysaccharide (LPS) led to increased levels of tumor necrosis factor‐α, interleukin‐1β, and inducible nitric oxide synthase. Genome‐wide microarray analysis showed a less than 1% difference in the genes between the T‐MG cells and the control primary retinal microglia. The T‐MG cells exhibited properties similar to those of the primary retinal microglia and should have considerable utility as an in vitro model for the study of retinal microglia in health and as a curative therapy and an in vivo model for the study of retinal microglia in disease.

Upregulation of SOX9 in Glial (Müller) cells in retinal light damage of rats.

Recent evidence suggests that SOX9 [sex-determining region Y (SRY) box 9], a transcription factor, plays a pivotal role in acquired diseases, revealing its importance in roles beyond development. However, whether SOX9, which is one of the key regulators of retinal Müller cell development, also participates in the pathological process of retinal degenerative diseases remains unknown. In the present study, we hypothesized that SOX9 was upregulated in Müller cells in retinal degeneration. Retinal light damage (LD) was used as a model for retinal degeneration. On day 3, 7, 14, 21, and 28 after LD in adult Sprague Dawley (SD) rats, the spatial distribution of SOX9 in the retina was observed by immunohistochemistry; the expression levels of SOX9 were measured by real-time PCR and Western blot analysis. Moreover, type 1 collagen (COL1) and cone-rod homeobox (CRX) protein levels, which are two downstream targets of SOX9, were also assessed by Western blot analysis. Colabeling for SOX9 and glutamine synthetase (GS), a specific Müller cell maker, indicated that SOX9 was expressed in the Müller cell nucleus in both control and LD groups. Significantly enhanced SOX9 expression was observed as early as day 3 after LD, and it persisted for at least 28 days. COL1 and CRX protein levels also increased after LD. Our study demonstrates the involvement of SOX9 in acquired retinal degeneration triggered by LD, which might provide novel insights into possible molecular mechanisms that would account for the involvement of Müller cells in retinal degenerative diseases.

Pediatric Infectious Endophthalmitis: A 271-case Retrospective Study at a Single Center in China

Background:Pediatric infectious endophthalmitis is a serious sight-threatening disease for children. The purpose of this study was to investigate the etiology, microbiological spectrum, and visual outcomes of infectious endophthalmitis in children at a single institution in China. Methods:It is a retrospective study of the medical records of all patients under 14 years of age with histories of infectious endophthalmitis, treated at a single institution from January 1, 2009 to January 1, 2015. The clinical characteristics, etiology, microbiological spectrum, and management, as well as the visual outcomes, were analyzed. The Kappa test and Chi-square test were used in the statistical evaluation. Results:A total of 271 children were identified, with a mean age of 5.61 ± 2.93 years (range 5 months to 14 years). Ocular trauma (94.8%) and previous ocular surgery (3.0%) were the most common etiologies. Overall, 147 (54.2%) cases had positive cultures, and 176 organisms were isolated from these patients. A single species was isolated in 120 (81.6%) cases, with multiple organisms in 27 (18.4%) cases, and the most commonly identified organisms were coagulase-negative Staphylococcus and Streptococcus species, comprising 29.5% and 26.8% of the isolates, respectively. Moreover, of 176 isolates, 142 (80.8%) were Gram-positive organisms, 23 (13.0%) were Gram-negative organisms, and 11 (6.2%) were fungi. The final visual outcomes were 20/200 or better in 66 (24.4%) eyes, counting fingers to 20/200 in 34 (12.5%), hand motions in 30 (11.1%), light perception in 33 (12.2%), no light perception in 32 (11.8%), and 9 (3.3%) eyes were enucleated or eviscerated. The visual outcomes were not available in 67 (24.7%) patients. Conclusions:Penetrating ocular trauma is the most frequent cause of pediatric endophthalmitis in China. Streptococcus and Staphylococcus species are the most commonly identified organisms in exogenous pediatric endophthalmitis whereas Fusarium species are commonly seen in endogenous endophthalmitis. In this research, in spite of aggressive management with antibiotics and vitrectomy, the visual prognosis was found to be generally poor.