A novel neuroprotective role of a small peptide from flesh fly, 5-S-GAD in the rat retina in vivo

Abstract

N--Alanyl-5-S-glutathionyl-3,4-dihydroxyphenylalanine(5-S-GAD), an antibacterial substance isolated from flesh fly, has been described as having multipotential biological activities toward various tissues. However, there has been no report testing its action on neural cells. In the present study, we investigate whether 5-S-GAD is neurotoxic or neuroprotective to the rat retina. 5-S-GAD at high doses (more than 200 pmol) induced apoptosis of retinal neurons 7 days after intraocular injection. NMDA (50-100 nmol)induced loss of retinal ganglion cells (RGCs) and thinning of the inner retina 7 days after injection. 5-S-GAD at low doses (2-20 pmol) significantly attenuated the loss of RGCs and the thinning of inner retina induced by NMDA in a dose-dependent manner. To understand the protective mechanism of 5-S-GAD, we investigated the influence of 5-S-GAD on the cell survival molecules, phospho-Akt and Bcl-2. 5-S-GAD (2-20 pmol) rapidly increased phospho-Akt expression 1-7 days and Bcl-2 expression 3-7 days after injection. The cellular localization of this increase was both in bipolar cells and RGCs. This neurosurvival effect of 5-S-GAD was further tested using another toxic model of optic nerve injury. 5-S-GAD significantly blocked the apoptosis of RGCs 7 days after optic nerve crush. These resultsshow that 5-S-GAD (2-20 pmol) protects against the NMDA-and optic nerve crush-induced apoptosis of RGCs. The neuroprotective action of 5-S-GAD in the retina might be mediated by the cell survival phopho-Akt/Bcl-2 system and offers a therapeutic option to rescue RGCs from various types of excitotoxic disease, such as glaucoma. Running title: Neuroprotection by 5-S-GAD

Requirement of Retinoic Acid Receptor β for Genipin Derivative-Induced Optic Nerve Regeneration in Adult Rat Retina

“…After lateral canthotomy of rats, the conjunctiva was incised laterally to the cornea, the retractor bulbi muscle was separated, and the optic nerve exposed under the binocular-operating microscope. Optic nerve was crushed 2 mm behind the eye with angled jeweler’s forceps (Dumont # 5) for 10 sec, avoiding injury to the ophthalmic artery as previously described [20]. Rats were housed in clear plastic cages and maintained under the 12 h light/dark cycles at 23°C.…”

Protective action of nipradilol mediated through S-nitrosylation of Keap1 and HO-1 induction in retinal ganglion cells

“…The volume of injection was set at 5 μl of total volume after removal of the same volume of vitreous fluid. The optic nerve was crushed 1 mm away from the eyeball with forceps as described previously (Koriyama et al, 2008).…”

5-S-GAD Attenuates Fe2+-Induced Lipid Peroxidation and Cell Death in a Neuronal Cell Model

“…5-S-GAD was first found to inhibit tyrosine phosphorylation of proteins such as v-Src (Hijikata et al 1997). Recently, we reported that 5-S-GAD protected against cell death of rat retinal ganglion cells after treatment with N-methyl-Daspartate and optic nerve injury in vivo, and hydrogen peroxide in vitro (Koriyama et al 2008(Koriyama et al , 2009). Akiyama et al (2009) reported that 5-S-GAD delayed the development of cataracts induced by diamide, galactose, and steroid in chick embryos, rats, and cultured lenses.…”

“…We have recently reported that 5-S-GAD protects retinal ganglion cells from excitotoxic or oxidative stress-induced damage (Koriyama et al 2008(Koriyama et al , 2009.…”