Identifying the stability of housekeeping genes to be used for the quantitative real-time PCR normalization in retinal tissue of streptozotocin-induced diabetic rats

AIM:To investigate the stability of the seven housekeeping genes:beta-actin(ActB),glyceraldehyde-3-phosphate dehydrogenase(GAPDH),18s ribosomal unit 5(18s),cyclophilin A(CycA),hypoxanthine-guanine phosphoribosyl transferase(HPRT),ribosomal protein large P0(36B4)and terminal uridylyl transferase 1(U6)in the diabetic retinal tissue of rat model.METHODS:The expression of these seven genes in rat retinal tissues was determined using real-time quantitative reverse transcription polymerase chain reaction(RT-qPCR)in two groups;normal control rats and streptozotocininduced diabetic rats.The stability analysis of gene expression was investigated using geNorm,NormFinder,BestKeeper,and comparative delta-Ct(ΔCt)algorithms.RESULTS:The 36B4 gene was stably expressed in the retinal tissues of normal control animals;however,it was less stable in diabetic retinas.The 18s gene was expressed consistently in both normal control and diabetic rats’retinal tissue.That this gene was the best reference for data normalisation in RT-qPCR studies that used the retinal tissue of streptozotocin-induced diabetic rats.Furthermore,there was no ideal gene stably expressed for use in all experimental settings.CONCLUSION:Identifying relevant genes is a need for achieving RT-qPCR validity and reliability and must be appropriately achieved based on a specific experimental setting.

Neuroprotective effects of exogenous brain-derived neurotrophic factor on amyloid-beta 1-40-induced retinal degeneration

Amyloid-beta(Aβ)-related alterations,similar to those found in the brains of patients with Alzheimer's disease,have been observed in the retina of patients with glaucoma.Decreased levels of brain-derived neurotrophic factor(BDNF)are believed to be associated with the neurotoxic effects of Aβpeptide.To investigate the mechanism underlying the neuroprotective effects of BDNF on Aβ_(1-40)-induced retinal injury in Sprague-Dawley rats,we treated rats by intravitreal administration of phosphate-buffered saline(control),Aβ_(1-40)(5 nM),or Aβ_(1-40)(5 nM)combined with BDNF(1μg/mL).We found that intravitreal administration of Aβ_(1-40)induced retinal ganglion cell apoptosis.Fluoro-Gold staining showed a significantly lower number of retinal ganglion cells in the Aβ_(1-40)group than in the control and BDNF groups.In the Aβ_(1-40)group,low number of RGCs was associated with increased caspase-3 expression and reduced TrkB and ERK1/2 expression.BDNF abolished Aβ_(1-40)-induced increase in the expression of caspase-3 at the gene and protein levels in the retina and upregulated TrkB and ERK1/2 expression.These findings suggest that treatment with BDNF prevents RGC apoptosis induced by Aβ_(1-40)by activating the BDNF-TrkB signaling pathway in rats.

Magnesium acetyltaurate prevents retinal damage and visual impairment in rats through suppression of NMDA-induced upregulation of NF-κB,p53 and AP-1(c-Jun/c-Fos)

Magnesium acetyltaurate(MgAT)has been shown to have a protective effect against N-methyl-D-aspartate(NMDA)-induced retinal cell apoptosis.The current study investigated the involvement of nuclear factor kappa-B(NF-κB),p53 and AP-1 family members(c-Jun/c-Fos)in neuroprotection by MgAT against NMDA-induced retinal damage.In this study,Sprague-Dawley rats were randomized to undergo intravitreal injection of vehicle,NMDA or MgAT as pre-treatment to NMDA.Seven days after injections,retinal ganglion cells survival was detected using retrograde labelling with fluorogold and BRN3A immunostaining.Functional outcome of retinal damage was assessed using electroretinography,and the mechanisms underlying antiapoptotic effect of MgAT were investigated through assessment of retinal gene expression of NF-κB,p53 and AP-1 family members(c-Jun/c-Fos)using reverse transcription-polymerase chain reaction.Retinal phospho-NF-κB,phospho-p53 and AP-1 levels were evaluated using western blot assay.Rat visual functions were evaluated using visual object recognition tests.Both retrograde labelling and BRN3A immunostaining revealed a significant increase in the number of retinal ganglion cells in rats receiving intravitreal injection of MgAT compared with the rats receiving intravitreal injection of NMDA.Electroretinography indicated that pre-treatment with MgAT partially preserved the functional activity of NMDA-exposed retinas.MgAT abolished NMDA-induced increase of retinal phospho-NF-κB,phospho-p53 and AP-1 expression and suppressed NMDA-induced transcriptional activity of NF-κB,p53 and AP-1 family members(c-Jun/c-Fos).Visual object recognition tests showed that MgAT reduced difficulties in recognizing the visual cues(i.e.objects with different shapes)after NMDA exposure,suggesting that visual functions of rats were relatively preserved by pre-treatment with MgAT.In conclusion,pre-treatment with MgAT prevents NMDA induced retinal injury by inhibiting NMDA-induced neuronal apoptosis via downregulation of transcriptional activity of NF-κB,p53 and AP-1-mediated c-Jun/c-Fos.The experiments were approved by the Animal Ethics Committee of Universiti Teknologi MARA(UiTM),Malaysia,UiTM CARE No 118/2015 on December 4,2015 and UiTM CARE No 220/7/2017 on December 8,2017 and Ethics Committee of Belgorod State National Research University,Russia,No 02/20 on January 10,2020.

Taurine protects against retinal and optic nerve damage induced by endothelin-1 in rats via antioxidant effects

Endothelin-1（ET-1）, a potent vasoconstrictor, is involved in retinal vascular dysregulation and oxidative stress in glaucomatous eyes. Taurine（TAU）, a naturally occurring free amino acid, is known for its neuroprotective and antioxidant properties. Hence, we evaluated its neuroprotective properties against ET-1 induced retinal and optic nerve damage. ET-1 was administered intravitreally to Sprague-Dawley rats and TAU was injected as pre-, co-or post-treatment. Animals were euthanized seven days post TAU injection. Retinae and optic nerve were examined for morphology, and were also processed for caspase-3 immunostaining. Retinal redox status was estimated by measuring retinal superoxide dismutase, catalase, glutathione, and malondialdehyde levels using enzyme-linked immuosorbent assay. Histopathological examination showed significantly improved retinal and optic nerve morphology in TAU-treated groups. Morphometric examination showed that TAU pre-treatment provided marked protection against ET-1 induced damage to retina and optic nerve. In accordance with the morphological observations, immunostaining for caspase showed a significantly lesser number of apoptotic retinal cells in the TAU pre-treatment group. The retinal oxidative stress was reduced in all TAU-treated groups, and particularly in the pre-treatment group. The findings suggest that treatment with TAU, particularly pre-treatment, prevents apoptosis of retinal cells induced by ET-1 and hence prevents the changes in the morphology of retina and optic nerve. The protective effect of TAU against ET-1 induced retinal and optic nerve damage is associated with reduced retinal oxidative stress.

New solutions for old challenges in glaucoma treatment:is taurine an option to consider?

Glaucoma is a range of progressive optic neuropathies characterized by progressive retinal ganglion cell loss and visual field defects.It is recognized as a leading cause of irreversible blindness affecting more than 70 million people worldwide.Currently,reduction of intraocular pressure,a widely recognized risk factor for glaucoma development,is the only pharmacological strategy for slowing down retinal ganglion cell loss and disease progression.However,retinal ganglion cell death and visual field loss have been observed in normotensive glaucoma,suggesting that the disease process is partially independent of intraocular pressure.Taurine is one of the agents that have attracted attention of researchers recently.Taurine has been shown to be involved in multiple cellular functions,including a central role as a neurotransmitter,as a trophic factor in the central nervous system development,as an osmolyte,as a neuromodulator,and as a neuroprotectant.It also plays a role in the maintenance of the structural integrity of the membranes and in the regulation of calcium transport and homeostasis.Taurine is known to prevent N-methyl-D-aspartic acid-induced excitotoxic injury to retinal ganglion cells.A recently published study clearly demonstrated that taurine prevents retinal neuronal apoptosis both in vivo and in vitro.Protective effect of taurine may be attributed to direct inhibition of apoptosis,an activation of brain derived neurotrophic factor-related neuroprotective mechanisms and reduction of retinal oxidative and nitrosative stresses.Further studies are needed to fully explore the potential of taurine as a neuroprotective agent,so that it can be applied in clinical practice,particularly for the treatment of glaucoma.The objective of current review was to summarize recent evidence on neuroprotective properties of taurine in glaucoma.

Dose-dependent effects of NMDA on retinal and optic nerve morphology in rats

AIM: To investigate dose-dependent effects of N-methylD-aspartate(NMDA) on retinal and optic nerve morphology in rats.METHODS: Sprague Dawley rats, 180-250 g in weight were divided into four groups. Groups 1, 2, 3 and 4 were intravitreally administered with vehicle and NMDA at the doses 80, 160 and 320 nmol respectively. Seven days after injection, rats were euthanized, and their eyes were taken for optic nerve toluidine blue and retinal hematoxylin and eosin stainings. The TUNEL assay was done for detecting apoptotic cells.RESULTS: All groups treated with NMDA showed significantly reduced ganglion cell layer(GCL) thickness within inner retina, as compared to control group. Group NMDA 160 nmol showed a significantly greater GCL thickness than the group NMDA 320 nmol. Administration of NMDA also resulted in a dose-dependent decrease in the number of nuclei both per 100 μm GCL length and per 100 μm2 of GCL. Intravitreal NMDA injection caused dosedependent damage to the optic nerve. The degeneration of nerve fibres with increased clearing of cytoplasm was observed more prominently as the NMDA dose increased. In accordance with the results of retinal morphometry analysis and optic nerve grading, TUNEL staining demonstrated NMDA-induced excitotoxic retinal injury in a dose-dependent manner.CONCLUSION: Our results demonstrate dose-dependent effects of NMDA on retinal and optic nerve morphology in rats that may be attributed to differences in the severity of excitotoxicity and oxidative stress. Our results also suggest that care should be taken while making dose selections experimentally so that the choice might best uphold study objectives.

Magnesium acethyltaurate as a potential agent for retinal and optic nerve protection in glaucoma

Glaucoma is the second leading cause of irreversible vision impairment affecting more than 70 million people worldwide with approximately 10%suffering from glaucoma-related bilateral blind（Quigley and Broman,2006）.It is a multi-factorial disease that is characterized by optic nerve damage and visual field loss.Progressive loss of retinal ganglion cells（RGCs）resulting in visual field deficits is the hallmark of glaucoma.

Glutathione (GSH) improves sperm quality and testicular morphology in streptozotocin-induced diabetic mice

Diabetes mellitus(DM)is known to cause reproductive impairment.In men,it has been linked to altered sperm quality and testicular damage.Oxidative stress(OS)plays a pivotal role in the development of DM complications.Glutathione(GSH)is a part of a nonenzymatic antioxidant defense system that protects lipid,protein,and nucleic acids from oxidative damage.However,the protective effects of exogenous GSH on the male reproductive system have not been comprehensively examined.This study determined the impact of GSH supplementation in ameliorating the adverse effect of type 1 DM on sperm quality and the seminiferous tubules of diabetic C57BL/6NTac mice.GSH at the doses of 15 mg kg^(-1)and 30 mg kg^(-1)was given intraperitoneally to mice weekly for 6 consecutive weeks.The mice were then weighed,euthanized,and had their reproductive organs excised.The diabetic(D Group)showed significant impairment of sperm quality and testicular histology compared with the nondiabetic(ND Group).Diameters of the seminiferous lumen in diabetic mice treated with 15 mg kg^(-1) GSH(DGSH15)were decreased compared with the D Group.Sperm motility was also significantly increased in the DGSH15 Group.Improvement in testicular morphology might be an early indication of the protective roles played by the exogenous GSH in protecting sperm quality from effects of untreated type 1 DM or diabetic complications.Further investigation using different doses and different routes of GSH is necessary to confirm this suggestion.