Shenghai Zhang

Rescue of Photoreceptors by BDNF Gene Transfer Using In Vivo Electroporation in the RCS Rat of Retinitis Pigmentosa

Purpose: To investigate the feasibility of introducing brain-derived neurotrophic factor (BDNF) gene into retinal pigment epithelial cells in vivo by electroporation and whether this method can rescue photoreceptors of retinitis pigmentosa in Royal College Surgeons (RCS) rats. Methods: The BDNF-GFP fusion eukaryotic-expressing plasmid was constructed and subretinally or intravitreously injected into the eyes of RCS rats followed by in vivo electroporation. The expression of BDNF mRNA and protein was detected by RT-PCR and Western immunoblot analysis. The number of surviving photoreceptors was counted, and the TdT-dUTP terminal nick-end labeling (TUNEL) method was used to detect the apoptotic retinal cells at different timepoints after introduction of BDNF plasmid. Results: Treated eyes showed a significantly higher rescue ratio and a lower number of TUNEL-positive photoreceptors than did the control eyes at various timepoints. Conclusion: These findings provide evidence that electroporation is an effective method for gene transfer into retinal pigment epithelial cells, and the rescue of photoreceptors can be achieved by BDNF gene transfection with electroporation.

Novel strategies to augment genetically delivered immunotoxin molecular therapy for cancer therapy

Immunotoxin therapy is a promising molecular cancer treatment strategy. Its main advantage is seletive cytotoxicity towards tumor cells and minimal toxicity in normal tissues. However, a short half-life and rapid clearance severely hampers its clinical application. We report here a novel genetic approach in which a recombinant adenovirus vector was used to deliver an immunotoxin gene e23(scFv)-PE40 targeted to the oncogene c-erbB-2 (also known as Her2/neu). This vector, when combined with a low dose of a conditionally replicative adenovirus vector (CRAd), has enhanced tumor-killing ability either alone or in combination with the chemotherapeutic agent etoposide. Our data show that low-dose CRAd facilitated the replication of replication-deficient Ad-e23(scFv)-PE40 up to 6–20 times and the transcription of e23(scFv)-PE40 gene up to 12 times. Moreover, etoposide increased the e23(scFv)-PE40 transcription up to 8.5 times. Furthermore, we show that systemic application of Ad-e23(scFv)-PE40 and enhanced expression of the immunotoxin gene was well tolerated as determined by serum biochemical markers and histological examination of most vital organs. Taken together, our data support a novel genetic immunotoxin delivery approach that may yield enhanced efficacy against a variety of Her2/neu-expressing tumors.

Enhanced transduction and improved photoreceptor survival of retinal degeneration by the combinatorial use of rAAV2 with a lower dose of adenovirus

Recombinant adeno-associated virus (rAAV) is widely used in retinal gene therapy. Enhanced rAAV transduction may be important for better therapeutic effects in some retinal gene therapies. In this study, we examined the effects of adenovirus 5 (Ad5) on retina transduction mediated by rAAV2. Our results provide the first evidence that low levels of either replication-incompetent or conditional replication-competent Ad5 significantly enhance and accelerate transgene expression in human and rat retinal cells. This effect occurs principally at the transcriptional level, rather than through enhanced viral entry or DNA replication. In in vivo analyses with the SD rat, the Balb/c mouse, and the RCS rat, strong enhancement and acceleration of transgene expression, as well as therapeutic effects, were confirmed. Low levels of Ad5 may enhance the utility of rAAV2-mediated transduction strategies in future clinical investigations.

Distinctive Gene Transduction Efficiencies of Commonly Used Viral Vectors in the Retina

The transduction efficiency and cell tropism of viral vectors rAAV2/1, rAAV2, Ad5, Ad5/F35, and Lentivirus were evaluated in retina. All viral vectors achieved efficient transduction in living rat retina. However, each vector showed distinctive efficiency in vitro especially for rAAV2/1, which displayed poor transduction in cultured retinal cells. Distinctive cell-specific GFP expression was observed in vivo and in vitro for the same viral vector. The cell-specific tropism was not strictly correlated with the correspondent distribution of viral receptors in retina. These results provided important insights into the selection of appropriate vectors when specific retinal diseases are considered for gene therapy.

Cannabidiol attenuates OGD/R-induced damage by enhancing mitochondrial bioenergetics and modulating glucose metabolism via pentose-phosphate pathway in hippocampal neurons

Deficient bioenergetics and diminished redox conservation have been implicated in the development of cerebral ischemia/reperfusion injury. In this study, the mechanisms underlying the neuroprotective effects of cannabidiol (CBD), a nonpsychotropic compound derived from Cannabis sativa with FDA-approved antiepilepsy properties, were studied in vitro using an oxygen–glucose-deprivation/reperfusion (OGD/R) model in a mouse hippocampal neuronal cell line. CBD supplementation during reperfusion rescued OGD/R-induced cell death, attenuated intracellular ROS generation and lipid peroxidation, and simultaneously reversed the abnormal changes in antioxidant biomarkers. Using the Seahorse XFe24 Extracellular Flux Analyzer, we found that CBD significantly improved basal respiration, ATP-linked oxygen consumption rate, and the spare respiratory capacity, and augmented glucose consumption in OGD/R-injured neurons. The activation of glucose 6-phosphate dehydrogenase and the preservation of the NADPH/NADP+ ratio implies that the pentose-phosphate pathway is stimulated by CBD, thus protecting hippocampal neurons from OGD/R injury. This study is the first to document the neuroprotective effects of CBD against OGD/R insult, which depend in part on attenuating oxidative stress, enhancing mitochondrial bioenergetics, and modulating glucose metabolism via the pentose-phosphate pathway, thus preserving both energy and the redox balance.

Enhancement of rAAV2-Mediated Transgene Expression in Retina Cells In Vitro and In Vivo by Coadministration of Low-Dose Chemotherapeutic Drugs

PURPOSE Recombinant adeno-associated viral vector serotype 2 (rAAV2) has been used with success to deliver retina-targeted gene therapeutics in retinal degeneration. However, one of the major limitations of this approach is the vectors low transduction efficiency. This study is designed to increase AAV2 transduction efficiency in vitro and in vivo. METHODS Green fluorescence protein (GFP) or luciferase reporter gene-carried rAAV2 vectors were applied to cultured human RPE cells (ARPE-19) or animal eyes with or without chemotherapeutic agents. GFP transduction efficiency was evaluated by image, flow cytometry analysis, and Western blot. The ciliary neurotrophic factor (rAAV2-CNTF)-carried AAV2 vector was coinjected to subretinal space with or without chemotherapeutic agent. The therapeutic efficacy was evaluated by counting numbers of remaining photoreceptors in retina sections of treated or untreated eyes. RESULTS Coadministration of 0.1 μg/mL doxorubicin (DXR), 0.14 μg/mL cytarabine (Ara-C), 1 μg/mL etoposide (VP-16), or 20 μg/mL cisplatin (DDP) significantly increased rAAV2-mediated GFP and/or luciferase expression in cultured hRPE cells without any detectable toxicity. Pretreatment with DXR for 24 h prior to infection was most effective in enhancing rAAV2 transgene expression in hRPE cells. In addition, subretinal coinjection of rAAV2-CMV-ciliary neurotrophic factor (rAAV2-CNTF) and DXR into the eyes of rats with inherited retinal degeneration resulted in an approximately 2-fold increase in photoreceptor layer thickness and cellular density of the outer nuclear layer (ONL) compared to rAAV2-CNTF alone, reflecting a pronounced protection effect mediated by the enhanced expression of CNTF. CONCLUSIONS The method described here to improve rAAV2-based gene delivery is simple and feasible without any detectable toxicity. This strategy might be therapeutically exploited in the gene therapy of degenerative retinal diseases.

Involvement of the MEK-ERK/p38-CREB/c-fos signaling pathway in Kir channel inhibition-induced rat retinal Müller cell gliosis

Our previous studies have demonstrated that activation of group I metabotropic glutamate receptors downregulated Kir channels in chronic ocular hypertension (COH) rats, thus contributing to Müller cell gliosis, characterized by upregulated expression of glial fibrillary acidic protein (GFAP). In the present study, we explored possible signaling pathways linking Kir channel inhibition and GFAP upregulation. In normal retinas, intravitreal injection of BaCl2 significantly increased GFAP expression in Müller cells, which was eliminated by co-injecting mitogen-activated protein kinase (MAPK) inhibitor U0126. The protein levels of phosphorylated extracellular signal-regulated protein kinase1/2 (p-ERK1/2) and its upstream regulator, p-MEK, were significantly increased, while the levels of phosphorylated c-Jun N-terminal kinase (p-JNK) and p38 kinase (p-p38) remained unchanged. Furthermore, the protein levels of phosphorylated cAMP response element binding protein (p-CREB) and c-fos were also increased, which were blocked by co-injecting ERK inhibitor FR180204. In purified cultured rat Müller cells, BaCl2 treatment induced similar changes in these protein levels apart from p-p38 levels and the p-p38:p38 ratio showing significant upregulation. Moreover, intravitreal injection of U0126 eliminated the upregulated GFAP expression in COH retinas. Together, these results suggest that Kir channel inhibition-induced Müller cell gliosis is mediated by the MEK-ERK/p38-CREB/c-fos signaling pathway.

Quercetin Declines Apoptosis, Ameliorates Mitochondrial Function and Improves Retinal Ganglion Cell Survival and Function in In Vivo Model of Glaucoma in Rat and Retinal Ganglion Cell Culture In Vitro

Glaucoma is a progressive neuropathy characterized by the loss of retinal ganglion cells (RGCs). Strategies that delay or halt RGC loss have been recognized as potentially beneficial for rescuing vision in glaucoma patients. Quercetin (Qcn) is a natural and important dietary flavonoid compound, widely distributed in fruits and vegetables. Mounting evidence suggests that Qcn has numerous neuroprotective effects. However, whether Qcn exerts neuroprotective effects on RGC in glaucoma is poorly understood. In this study, we investigated the protective effect of Qcn against RGC damage in a rat chronic ocular hypertension (COHT) model in vivo and hypoxia-induced primary cultured RGC damage in vitro, and we further explored the underlying neuroprotective mechanisms. We found that Qcn not only improved RGC survival and function from a very early stage of COHT in vivo, it promoted the survival of hypoxia-treated primary cultured RGCs in vitro via ameliorating mitochondrial function and preventing mitochondria-mediated apoptosis. Our findings suggest that Qcn has direct protective effects on RGCs that are independent of lowering the intraocular pressure (IOP). Qcn may be a promising therapeutic agent for improving RGC survival and function in glaucomatous neurodegeneration.

Effects of optineurin mutants on SH-SY5Y cell survival.

Mutations in the optineurin gene (OPTN) have been found to be associated with glaucoma and amyotrophic lateral sclerosis (ALS). However, the mechanism by which this single gene mutation leads to neurodegeneration in those two diseases remains unrevealed. To study the roles of wild-type (WT) OPTN and its pathogenic mutants in neuronal survival, here we overexpressed SH-SY5Y cells with WT OPTN or its four mutants (E50K, M98K, Q398X and E478G), and detected their effects on neuronal viability under normal or oxidative stress conditions. We found that overexpression of WT OPTN or its glaucoma-linked mutants (E50K and M98K) causes little harm in SH-SY5Y cells, while ALS-associated OPTN mutants (Q398X and E478G) leads to remarkably increased oxidative status and decreased antioxidase activity, which might result in severe mitochondrial dysfunction and neuronal injury. Further investigation suggests that overexpression of WT OPTN promotes endogenous antioxidase activation in the SH-SY5Y cells under oxidative stress and increases neuronal survival. Nevertheless, this neuroprotective effect of WT OPTN is abolished by its four mutants. Our results indicate that oxidative stress may play a central role in the pathogenesis of glaucoma and ALS caused by OPTN mutation.

High Pressure-Induced mtDNA Alterations in Retinal Ganglion Cells and Subsequent Apoptosis

Purpose: Our previous study indicated that mitochondrial DNA (mtDNA) damage and mutations are crucial to the progressive loss of retinal ganglion cells (RGCs) in a glaucomatous rat model. In this study, we examined whether high pressure could directly cause mtDNA alterations and whether the latter could lead to mitochondrial dysfunction and RGC death. Methods: Primary cultured rat RGCs were exposed to 30 mm Hg of hydrostatic pressure (HP) for 12, 24, 48, 72, 96 and 120 h. mtDNA alterations and mtDNA repair/replication enzymes OGG1, MYH and polymerase gamma (POLG) expressions were also analyzed. The RGCs were then infected with a lentiviral small hairpin RNA (shRNA) expression vector targeting POLG (POLG-shRNA), and mtDNA alterations as well as mitochondrial function, including complex I/III activities and ATP production were subsequently studied at appropriate times. Finally, RGC apoptosis and the mitochondrial-apoptosis pathway-related protein cleaved caspase-3 were detected using a Terminal deoxynucleotidyl transferase dUTP nick end-labeling (TUNEL) assay and western blotting, respectively. Results: mtDNA damage was observed as early as 48 h after the exposure of RGCs to HP. At 120 h after HP, mtDNA damage and mutations significantly increased, reaching >40% and 4.8 ± 0.3-fold, respectively, compared with the control values. Twelve hours after HP, the expressions of OGG1, MYH and POLG mRNA in the RGCs were obviously increased 5.02 ± 0.6-fold (p < 0.01), 4.3 ± 0.2-fold (p < 0.05), and 0.8 ± 0.09-fold (p < 0.05). Western blot analysis showed that the protein levels of the three enzymes decreased at 72 and 120 h after HP (p < 0.05). After interference with POLG-shRNA, the mtDNA damage and mutations were significantly increased (p < 0.01), while complex I/III activities gradually decreased (p < 0.05). Corresponding decreases in membrane potential and ATP production appeared at 5 and 6 days after POLG-shRNA transfection respectively (p < 0.05). Increases in the apoptosis of RGCs and cleaved caspase-3 protein expression were observed after mtDNA damage and mutations. Conclusions: High pressures could directly cause mtDNA alterations, leading to mitochondrial dysfunction and RGC death.