Selective deletion of zinc transporter 3 in amacrine cells promotes retinal ganglion cell survival and optic nerve regeneration after injury

Vision depends on accurate signal conduction from the retina to the brain through the optic nerve,an important part of the central nervous system that consists of bundles of axons originating from retinal ganglion cells.The mammalian optic nerve,an important part of the central nervous system,cannot regenerate once it is injured,leading to permanent vision loss.To date,there is no clinical treatment that can regenerate the optic nerve and restore vision.Our previous study found that the mobile zinc(Zn^(2+))level increased rapidly after optic nerve injury in the retina,specifically in the vesicles of the inner plexiform layer.Furthermore,chelating Zn^(2+)significantly promoted axonal regeneration with a long-term effect.In this study,we conditionally knocked out zinc transporter 3(ZnT3)in amacrine cells or retinal ganglion cells to construct two transgenic mouse lines(VGAT^(Cre)ZnT3^(fl/fl)and VGLUT2^(Cre)ZnT3^(fl/fl),respectively).We obtained direct evidence that the rapidly increased mobile Zn^(2+)in response to injury was from amacrine cells.We also found that selective deletion of ZnT3 in amacrine cells promoted retinal ganglion cell survival and axonal regeneration after optic nerve crush injury,improved retinal ganglion cell function,and promoted vision recovery.Sequencing analysis of reginal ganglion cells revealed that inhibiting the release of presynaptic Zn^(2+)affected the transcription of key genes related to the survival of retinal ganglion cells in postsynaptic neurons,regulated the synaptic connection between amacrine cells and retinal ganglion cells,and affected the fate of retinal ganglion cells.These results suggest that amacrine cells release Zn^(2+)to trigger transcriptomic changes related to neuronal growth and survival in reginal ganglion cells,thereby influencing the synaptic plasticity of retinal networks.These results make the theory of zinc-dependent retinal ganglion cell death more accurate and complete and provide new insights into the complex interactions between retinal cell networks.

Autophagy inhibitor 3-methyladenine regulatesthe expression of LC3, Beclin-1 and ZnTs in ratcerebral cortex following recurrent neonatal seizures

BACKGROUND： Autophagy is a homeostatic process for intracellular recycling of bulk proteins and aging organelles. Increased autophagy has now been reported in experimental models of traumatic brain injury, stroke and excitotoxicity, and in patients with Alzheimer＇s disease and critical illness. The role of autophagy in developmental epilepsy, however, is unknown. The present study was to investigate the effects of recurrent neonatal seizure, in the presence and absence of autophagy inhibitor 3-methyladenine （3-MA）, on the acute phase gene expression of ZnTs, LC3 and Beclin-1 in rat cerebral cortex and the interaction among them.METHODS： Thirty-six Sprague-Dawley neonatal rats at postnatal day 6（P6） were randomly divided into three groups： a recurrent-seizures group （RS, n=12）, a 3-MA treated-seizure group （3-MA group, each rat pretreated with 3-methyladenine before seizures, 100nmol/μl/day, i.p., n=12） and a control group （n=12）. At 1.5 and 6 hours after the last seizures, the mRNA levels of ZnT1-ZnT3, microtubule-associated protein 1A/1B light chain 3 （LC3） and beclin-1 were detected using the real-time RT-PCR method. The LC3 protein level was examined by Western blotting.RESULTS： The levels of LC3, beclin-1 and ZnT-2 transcripts in the RS group elevated signi？ cantly at 1.5 and 6 hours after the last seizures compared with those in the control and 3-MA groups. At the interval of 1.5 hours, the mRNA level of ZnT-1 increased signi？ cantly after the last seizure compared with that in the control group. There was no signi？ cant difference in the transcript levels of ZnT-3 among the three groups. Linear correlation analysis showed that the expression of the ？ ve genes in the control group exhibited a signi？ cant inter-relationship. In the 3-MA group, however, the inter-relationship was only found between beclin-1 and ZnT-1. In the RS group, the inter-relationship was not observed.CONCLUSIONS： The autophagy/lysosomal pathway is immediately activated along with the elevated expression of ZnT1 and ZnT2 in the cerebral cortex after recurrent seizures. 3-MA is involved in the regulation of the autophagy/lysosomal pathway and ZnTs by down-regulating the expression of LC3 and beclin-1.