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  1. Ooi YL, Khang TF, Naidu M, Fong KC
    Eye (Lond), 2013 Mar;27(3):425-31.
    PMID: 23196646 DOI: 10.1038/eye.2012.260
    To compare the potential retinal toxicity of two commercially Brilliant blue G dyes (Brilliant Peel and Ocublue Plus) and Indocyanine green (ICG) at usual clinical concentration.
    Matched MeSH terms: Retinal Ganglion Cells/drug effects
  2. Fazel MF, Abu IF, Mohamad MHN, Agarwal R, Iezhitsa I, Bakar NS, et al.
    PLoS One, 2020;15(7):e0236450.
    PMID: 32706792 DOI: 10.1371/journal.pone.0236450
    Retinal ganglion cell (RGC) loss and optic neuropathy, both hallmarks of glaucoma, have been shown to involve N-methyl-D-aspartate receptor (NMDAR)-mediated excitotoxicity. This study investigated the neuroprotective effects of Philanthotoxin (PhTX)-343 in NMDA-induced retinal injury to alleviate ensuing visual impairments. Sprague-Dawley rats were divided into three; Group I was intravitreally injected with phosphate buffer saline as the control, Group II was injected with NMDA (160 nM) to induce retinal excitotoxic injury, while Group III was injected with PhTX-343 (160 nM) 24 h prior to excitotoxicity induction with NMDA. Rats were subjected to visual behaviour tests seven days post-treatment and subsequently euthanized. Rat retinas and optic nerves were subjected to H&E and toluidine blue staining, respectively. Histological assessments showed that NMDA exposure resulted in significant loss of retinal cell nuclei and thinning of ganglion cell layer (GCL). PhTX-343 pre-treatment prevented NMDA-induced changes where the RGC layer morphology is similar to the control. The numbers of nuclei in the NMDA group were markedly lower compared to the control (p<0.05). PhTX-343 group had significantly higher numbers of nuclei within 100 μm length and 100 μm2 area of GCL (2.9- and 1.7-fold, respectively) compared to NMDA group (p<0.05). PhTX-343 group also displayed lesser optic nerve fibres degeneration compared to NMDA group which showed vacuolation in all sections. In the visual behaviour test, the NMDA group recorded higher total distance travelled, and lower total immobile time and episodes compared to the control and PhTX-343 groups (p<0.05). Object recognition tests showed that the rats in PhTX-343 group could recognize objects better, whereas the same objects were identified as novel by NMDA rats despite multiple exposures (p<0.05). Visual performances in the PhTX-343 group were all comparable with the control (p>0.05). These findings suggested that PhTX-343 inhibit retinal cell loss, optic nerve damage, and visual impairments in NMDA-induced rats.
    Matched MeSH terms: Retinal Ganglion Cells/drug effects*
  3. Arfuzir NN, Lambuk L, Jafri AJ, Agarwal R, Iezhitsa I, Sidek S, et al.
    Neuroscience, 2016 06 14;325:153-64.
    PMID: 27012609 DOI: 10.1016/j.neuroscience.2016.03.041
    Vascular dysregulation has long been recognized as an important pathophysiological factor underlying the development of glaucomatous neuropathy. Endothelin-1 (ET1) has been shown to be a key player due to its potent vasoconstrictive properties that result in retinal ischemia and oxidative stress leading to retinal ganglion cell (RGC) apoptosis and optic nerve (ON) damage. In this study we investigated the protective effects of magnesium acetyltaurate (MgAT) against retinal cell apoptosis and ON damage. MgAT was administered intravitreally prior to, along with or after administration of ET1. Seven days post-injection, animals were euthanized and retinae were subjected to morphometric analysis, TUNEL and caspase-3 staining. ON sections were stained with toluidine blue and were graded for neurodegenerative effects. Oxidative stress was also estimated in isolated retinae. Pre-treatment with MgAT significantly lowered ET1-induced retinal cell apoptosis as measured by retinal morphometry and TUNEL staining. This group of animals also showed significantly lesser caspase-3 activation and significantly reduced retinal oxidative stress compared to the animals that received intravitreal injection of only ET1. Additionally, the axonal degeneration in ON was markedly reduced in MgAT pretreated animals. The animals that received MgAT co- or post-treatment with ET1 also showed improvement in all parameters; however, the effects were not as significant as observed in MgAT pretreated animals. The current study showed that the intravitreal pre-treatment with MgAT reduces caspase-3 activation and prevents retinal cell apoptosis and axon loss in ON induced by ET1. This protective effect of ET1 was associated with reduced retinal oxidative stress.
    Matched MeSH terms: Retinal Ganglion Cells/drug effects
  4. Nor Arfuzir NN, Agarwal R, Iezhitsa I, Agarwal P, Sidek S, Spasov A, et al.
    Curr. Eye Res., 2018 08;43(8):1032-1040.
    PMID: 29676937 DOI: 10.1080/02713683.2018.1467933
    PURPOSE: Retinal ganglion cell apoptosis in glaucoma is associated with elevated levels of endothelin-1 (ET1), a potent vasoconstrictor. ET1-induced retinal ischemia leads to altered expression of nitric oxide synthase (NOS) isoforms leading to increased formation of nitric oxide (NO) and retinal nitrosative stress. Since magnesium (Mg) is known to improve endothelial functions and reduce oxidative stress and taurine (TAU) possesses potent antioxidant properties, we investigated the protective effects of magnesium acetyltaurate (MgAT) against ET1-induced nitrosative stress and retinal damage in rats. We also compared the effects of MgAT with that of TAU alone.

    METHODS: Sprague Dawley rats were intravitreally injected with ET1. MgAT and TAU were administered as pre-, co-, or posttreatment. Subsequently, the expression of NOS isoforms was detected in retina by immunohistochemistry, retinal nitrotyrosine level was estimated using ELISA, and retinal cell apoptosis was detected by TUNEL staining.

    RESULTS: Intravitreal ET1 caused a significant increase in the expressions of nNOS and iNOS while eNOS expression was significantly reduced compared to vehicle treated group. Administration of both MgAT and TAU restored the altered levels of NOS isoform expression, reduced retinal nitrosative stress and retinal cell apoptosis. The effect of MgAT, however, was greater than that of TAU alone.

    CONCLUSIONS: MgAT and TAU prevent ET1-induced retinal cell apoptosis by reducing retinal nitrosative stress in Sprague Dawley rats. Addition of TAU to Mg seems to enhance the efficacy of TAU compared to when given alone. Moreover, the pretreatment with MgAT/TAU showed higher efficacy compared to co- or posttreatment.

    Matched MeSH terms: Retinal Ganglion Cells/drug effects
  5. Nor Arfuzir NN, Agarwal R, Iezhitsa I, Agarwal P, Ismail NM
    Exp Eye Res, 2020 05;194:107996.
    PMID: 32156652 DOI: 10.1016/j.exer.2020.107996
    Endothelin-1 (ET-1), a potent vasoconstrictor, plays a significant role in the pathophysiology of ocular conditions like glaucoma. Glaucoma is characterized by apoptotic loss of retinal ganglion cells (RGCs) and loss of visual fields and is a leading cause of irreversible blindness. In glaucomatous eyes, retinal ischemia causes release of pro-inflammatory mediators such as interleukin (IL)-1β, IL-6 and tumor necrosis factor (TNF)-α and promotes activation of transcription factors such as nuclear factor kappa B (NFKB) and c-Jun. Magnesium acetyltaurate (MgAT) has previously been shown to protect against ET-1 induced retinal and optic nerve damage. Current study investigated the mechanisms underlying these effects of MgAT, which so far remain unknown. Sprague dawley rats were intravitreally injected with ET-1 with or without pretreatment with MgAT. Seven days post-injection, retinal expression of IL-1β, IL-6, TNF-α, NFKB and c-Jun protein and genes was determined using multiplex assay, Western blot and PCR. Animals were subjected to retrograde labeling of RGCs to determine the extent of RGC survival. RGC survival was also examined using Brn3A staining. Furthermore, visual functions of rats were determined using Morris water maze. It was observed that pre-treatment with MgAT protects against ET-1 induced increase in the retinal expression of IL-1β, IL-6 and TNF-α proteins and genes. It also protected against ET-1 induced activation of NFKB and c-Jun. These effects of MgAT were associated with greater RGC survival and preservation of visual functions in rats. In conclusion, MgAT prevents ET-1 induced RGC loss and loss of visual functions by suppressing neuroinflammatory reaction in rat retinas.
    Matched MeSH terms: Retinal Ganglion Cells/drug effects*
  6. Razali N, Agarwal R, Agarwal P, Tripathy M, Kapitonova MY, Kutty MK, et al.
    Exp Eye Res, 2016 Feb;143:9-16.
    PMID: 26424219 DOI: 10.1016/j.exer.2015.09.014
    Steroid-induced hypertension and glaucoma is associated with increased extracellular meshwork (ECM) deposition in trabecular meshwork (TM). Previous studies have shown that single drop application of trans-resveratrol lowers IOP in steroid-induced ocular hypertensive (SIOH) rats. This IOP lowering is attributed to activation of adenosine A1 receptors, which may lead to increased matrix metalloproteinase (MMP)-2 activity. This study evaluated the effect of repeated topical application of trans-resveratrol for 21 days in SIOH animals on IOP, changes in MMP-2 level in aqueous humor, trabecular meshwork and retinal morphology and retinal redox status. We observed that treatment with trans-resveratrol results in significant and sustained IOP reduction in SIOH rats. This IOP reduction is associated with significantly higher aqueous humor total MMP-2 level; significantly reduced TM thickness and increased number of TM cells. Treatment with trans-resveratrol also significantly increased ganglion cell layer (GCL) thickness, the linear cell density in the GCL and inner retina thickness; and significantly reduced retinal oxidative stress compared to the SIOH vehicle-treated group. In conclusion, repeated dose topical application of trans-resveratrol produces sustained IOP lowering effect, which is associated with increased level of aqueous humor MMP-2, normalization of TM and retinal morphology and restoration of retinal redox status.
    Matched MeSH terms: Retinal Ganglion Cells/drug effects
  7. Lambuk L, Jafri AJ, Arfuzir NN, Iezhitsa I, Agarwal R, Rozali KN, et al.
    Neurotox Res, 2017 01;31(1):31-45.
    PMID: 27568334 DOI: 10.1007/s12640-016-9658-9
    Glutamate excitotoxicity plays a major role in the loss of retinal ganglion cells (RGCs) in glaucoma. The toxic effects of glutamate on RGCs are mediated by the overstimulation of N-methyl-D-aspartate (NMDA) receptors. Accordingly, NMDA receptor antagonists have been suggested to inhibit excitotoxicity in RGCs and delay the progression and visual loss in glaucoma patients. The purpose of the present study was to examine the potential neuroprotective effect of Mg acetyltaurate (MgAT) on RGC death induced by NMDA. MgAT was proposed mainly due to the combination of magnesium (Mg) and taurine which may provide neuroprotection by dual mechanisms of action, i.e., inhibition of NMDA receptors and antioxidant effects. Rats were divided into 5 groups and were given intravitreal injections. Group 1 (PBS group) was injected with vehicle; group 2 (NMDA group) was injected with NMDA while groups 3 (pre-), 4 (co-), and 5 (post-) treatments were injected with MgAT, 24 h before, in combination or 24 h after NMDA injection respectively. NMDA and MgAT were injected in PBS at doses 160 and 320 nmol, respectively. Seven days after intravitreal injection, the histological changes in the retina were evaluated using hematoxylin & eosin (H&E) staining. Optic nerves were dissected and stained in Toluidine blue for grading on morphological neurodegenerative changes. The extent of apoptosis in retinal tissue was assessed by TUNEL assay and caspase-3 immunohistochemistry staining. The estimation of neurotrophic factor, oxidative stress, pro/anti-apoptotic factors and caspase-3 activity in retina was done using enzyme-linked immunosorbent assay (ELISA) technique. The retinal morphometry showed reduced thickness of ganglion cell layer (GCL) and reduction in the number of retinal cells in GCL in NMDA group compared to the MgAT-treated groups. TUNEL and caspase-3 staining showed increased number of apoptotic cells in inner retina. The results were further corroborated by the estimation of neurotrophic factor, oxidative stress, pro/anti-apoptotic factors, and caspase-3 activity in retina. In conclusion, current study revealed that intravitreal MgAT prevents retinal and optic nerve damage induced by NMDA. Overall, our data demonstrated that the pretreatment with MgAT was more effective than co- and posttreatment. This protective effect of MgAT against NMDA-induced retinal cell apoptosis could be attributed to the reduction of retinal oxidative stress and activation of BDNF-related neuroprotective mechanisms.
    Matched MeSH terms: Retinal Ganglion Cells/drug effects*
  8. Jafri AJA, Agarwal R, Iezhitsa I, Agarwal P, Spasov A, Ozerov A, et al.
    Mol. Vis., 2018;24:495-508.
    PMID: 30090013
    Purpose: Retinal nitrosative stress associated with altered expression of nitric oxide synthases (NOS) plays an important role in excitotoxic retinal ganglion cell loss in glaucoma. The present study evaluated the effects of magnesium acetyltaurate (MgAT) on changes induced by N-methyl-D-aspartate (NMDA) in the retinal expression of three NOS isoforms, retinal 3-nitrotyrosine (3-NT) levels, and the extent of retinal cell apoptosis in rats. Effects of MgAT with taurine (TAU) alone were compared to understand the benefits of a combined salt of Mg and TAU.

    Methods: Excitotoxic retinal injury was induced with intravitreal injection of NMDA in Sprague-Dawley rats. All treatments were given as pre-, co-, and post-treatment with NMDA. Seven days post-injection, the retinas were processed for measurement of the expression of NOS isoforms using immunostaining and enzyme-linked immunosorbent assay (ELISA), retinal 3-NT content using ELISA, retinal histopathological changes using hematoxylin and eosin (H&E) staining, and retinal cell apoptosis using terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) staining.

    Results: As observed on immunohistochemistry, the treatment with NMDA caused a 4.53-fold increase in retinal nNOS expression compared to the PBS-treated rats (p<0.001). Among the MgAT-treated groups, only the pretreatment group showed significantly lower nNOS expression than the NMDA-treated group with a 2.00-fold reduction (p<0.001). Among the TAU-treated groups, the pre- and cotreatment groups showed 1.84- and 1.71-fold reduction in nNOS expression compared to the NMDA-treated group (p<0.001), respectively, but remained higher compared to the PBS-treated group (p<0.01). Similarly, iNOS expression in the NMDA-treated group was significantly greater than that for the PBS-treated group (2.68-fold; p<0.001). All MgAT treatment groups showed significantly lower iNOS expression than the NMDA-treated groups (3.58-, 1.51-, and 1.65-folds, respectively). However, in the MgAT co- and post-treatment groups, iNOS expression was significantly greater than in the PBS-treated group (1.77- and 1.62-folds, respectively). Pretreatment with MgAT caused 1.77-fold lower iNOS expression compared to pretreatment with TAU (p<0.05). In contrast, eNOS expression was 1.63-fold higher in the PBS-treated group than in the NMDA-treated group (p<0.001). Among all treatment groups, only pretreatment with MgAT caused restoration of retinal eNOS expression with a 1.39-fold difference from the NMDA-treated group (p<0.05). eNOS expression in the MgAT pretreatment group was also 1.34-fold higher than in the TAU pretreatment group (p<0.05). The retinal NOS expression as measured with ELISA was in accordance with that estimated with immunohistochemistry. Accordingly, among the MgAT treatment groups, only the pretreated group showed 1.47-fold lower retinal 3-NT than the NMDA-treated group, and the difference was significant (p<0.001). The H&E-stained retinal sections in all treatment groups showed statistically significantly greater numbers of retinal cell nuclei than the NMDA-treated group in the inner retina. However, the ganglion cell layer thickness in the TAU pretreatment group remained 1.23-fold lower than that in the MgAT pretreatment group (p<0.05). In line with this observation, the number of apoptotic cells as observed after TUNEL staining was 1.69-fold higher after pretreatment with TAU compared to pretreatment with MgAT (p<0.01).

    Conclusions: MgAT and TAU, particularly with pretreatment, reduce retinal cell apoptosis by reducing retinal nitrosative stress. Pretreatment with MgAT caused greater improvement in NMDA-induced changes in iNOS and eNOS expression and retinal 3-NT levels than pretreatment with TAU. The greater reduction in retinal nitrosative stress after pretreatment with MgAT was associated with lower retinal cell apoptosis and greater preservation of the ganglion cell layer thickness compared to pretreatment with TAU.

    Matched MeSH terms: Retinal Ganglion Cells/drug effects*
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