Synaptic Membrane Synthesis in Rats Depends on Dietary Sufficiency of Vitamin C, Vitamin E, and Selenium: Relevance for Alzheimer's Disease.

Chronic consumption of a diet enriched with nutritional precursors of phospholipids, including uridine and the polyunsaturated fatty acids, docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), was shown previously to enhance levels of brain phospholipids and synaptic proteins in rodents. Vitamin C, vitamin E, and selenium may directly affect the breakdown or synthesis of membrane phospholipids. The present study investigated the necessity of antioxidants for the effectiveness of supplementation with uridine plus DHA and EPA (as fish oil) in rats. Rats were randomized to four treatment groups and received, for 6 weeks, one of four experimental diets, i.e., a diet low in antioxidants, a diet high in antioxidants, a diet low in antioxidants supplemented with DHA+EPA+uridine, or a diet high in antioxidants supplemented with DHA+EPA+uridine. On completion of dietary treatment, rats were sacrificed, and brain levels of phospholipids, synaptic proteins, and two enzymes involved in phospholipid synthesis (choline-phosphate cytidylyltransferase, PCYT1A, and choline/ethanolamine phosphotransferase, CEPT1) were analyzed. Levels of phospholipids, the pre- and post-synaptic proteins Synapsin-1 and PSD95, and the enzymes PCYT1A and CEPT1 were significantly enhanced by combined supplementation of DHA+EPA+uridine and antioxidants and not enhanced by supplementation of DHA+EPA+uridine with insufficient antioxidant levels. Our data suggest that dietary vitamin C, vitamin E, and selenium are essential for the phospholipid precursors' effects on increasing levels of membrane phospholipids and synaptic proteins, the indirect indicators of synaptogenesis. Their concomitant supply may be relevant in Alzheimer's disease patients, because the disease is characterized by synapse loss and lower plasma and brain levels of phospholipid precursors and antioxidants.

Regenerative effects of peptide nanofibers in an experimental model of Parkinson's disease.

Parkinson's disease (PD) is characterized by progressive degeneration of dopaminergic nigrostriatal neurons and reduction in striatal dopamine levels. Although there are few treatment options for PD such as Levodopa, they are used just to relieve and modify the symptoms. There are no therapies available for PD to slow down the degeneration process in the brain and recover the lost function. In this study, we used extracellular matrix (ECM) mimetic peptide amphiphile (PA) nanofibers as a potential therapeutic approach in a PD rat model. We demonstrated the effect of heparan sulfate mimetic and laminin mimetic PA nanofibers on reducing striatal injury and enhancing functional recovery after unilateral striatal injection of 6-hydroxydopamine (6-OHDA). The bioactive self-assembled PA nanofibers significantly reduced forelimb asymmetry, contralateral forelimb akinesia and d-amphetamine-induced rotational behavior in cylinder, stepping and rotation tests, respectively, in 6-OHDA-lesioned rats after 6 weeks. The behavioral improvement with PA nanofiber administration was associated with enhanced striatal dopamine and tyrosine hydroxylase content as well as reduced cleaved-Caspase-3 levels. Histological assessment also showed that PA nanofiber injection to the striatum resulted in better tissue integrity compared to control groups. In addition, PA nanofibers reduced the progressive cell loss in SH-SY5Y cells caused by 6-OHDA treatment. These data showed that the bioactive peptide nanofibers improve neurochemical and behavioral consequences of Parkinsonism in rats and provide a promising new strategy for treatment of PD. STATEMENT OF SIGNIFICANCE: Biomimetic nanomaterials bearing natural bioactive signals which are derived from extracellular matrix components like laminin and heparan sulfates provide promising therapeutic strategies for regeneration of the nervous system. However, no research has been reported exploring the use of biomimetic materials against degeneration in Parkinson's disease. In this work, we investigated potential therapeutic effects of heparan sulfate and laminin mimetic PA nanofibers on reduction of striatal injury in experimental Parkinson's disease model. PA nanofibers enhanced functional recovery associated with enhanced striatal dopamine and tyrosine hydroxylase content as well as reduced cleaved-Caspase-3 levels. Overall, this study shows the improvement in consequences of Parkinsonism in rats and provides a new platform for treatment of Parkinson's disease.

CDP-choline modulates matrix metalloproteinases in rat sciatic injury.

BACKGROUND: CDP-choline (cytidine-5'-diphosphocholine) improves functional recovery, promotes nerve regeneration, and decreases perineural scarring in rat peripheral nerve injury. The aim of the present study was to investigate the mechanism of action of CDP-choline with regard to matrix metalloproteinase (MMP) activity in the rat-transected sciatic nerve injury model. MATERIALS AND METHODS: Male Wistar rats were randomized into Sham, Saline, and CDP-choline groups. Rats in Sham group received Sham surgery, whereas rats in Saline and CDP-choline groups underwent right sciatic nerve transection followed by immediate primary saturation and injected intraperitoneally with 0.9% NaCl (1 mL/kg) and CDP-choline (600 µg/kg), respectively. Sciatic nerve samples were obtained 1, 3, and 7 d after the surgery and analyzed for levels and activities of MMP-2 and MMP-9, levels of tissue inhibitor of metalloproteinases-1 (TIMP-1) and TIMP-3, and axonal regeneration. RESULTS: CDP-choline treatment decreased the levels and activities of MMP-2 and MMP-9, whereas increasing levels of TIMP-1 and TIMP-3 significantly on the third and seventh day after injury compared to Saline group. In addition, CDP-choline administration resulted in new axon formation and formation and advancement of myelination on newly formed islets (compartments) of axonal regrowth. CONCLUSIONS: Our data show, for the first time, that CDP-choline modulates MMP activity and promotes the expression of TIMPs to stimulate axonal regeneration. These data help to explain one mechanism by which CDP-choline provides neuroprotection in peripheral nerve injury.

Uridine protects against hypoxic-ischemic brain injury by reducing histone deacetylase activity in neonatal rats.

PURPOSE: A significant cause of neurological disability in newborns is hypoxic-ischemic encephalopathy (HIE), a disorder which involves an enhancement in histone deacetylase (HDAC) activity among underlying pathological mechanisms. We showed recently that exogenous administration of uridine to newborn rats with HIE reduced brain injury in a dose-dependent manner. The present study was performed to investigate whether uridine modulates histone acetylation/deacetylation balance in a neonatal rat model of HIE. METHODS: Newborn rats that were subjected to hypoxic-ischemic (HI) insult on postnatal day 7 (P7) were injected intraperitoneally with either saline or uridine (500 mg/kg) for three consecutive days. One day after completion of treatment, brains of pups were collected for evaluation of brain infarct volume, apoptosis, HDAC activity and acetylated-Histone H3 (Ac-H3) and H4 (Ac-H4) protein levels. RESULTS: Results revealed that uridine administration reduced infarct volume, active Caspase-3 levels and HDAC activity while increasing the expressions of Ac-H3 and Ac-H4 proteins. CONCLUSIONS: We conclude that one mechanism by which uridine provides neuroprotection in neonatal rat HIE model involves reduction in HDAC activity.

Evidence for the existence of pyrimidinergic transmission in rat brain.

The uridine nucleotides uridine-5'-triphosphate (UTP) and uridine-5'-diphosphate (UDP) have previously been identified in media from cultured cells. However, no study to date has demonstrated their presence in brain extracellular fluid (ECF) obtained in vivo. Using a novel method, we now show that UTP and UDP, as well as uridine, are detectable in dialysates of striatal ECF obtained from freely-moving rats. Intraperitoneal (i.p.) administration of uridine or exposure of striatum to depolarizing concentrations of potassium chloride increases extracellular uridine, UTP and UDP, while tetrodotoxin (TTX) decreases their ECF levels. Uridine administration also enhances cholinergic neurotransmission which is accompanied by enhanced brain levels of diacylglycerol (DAG) and inositol trisphosphate (IP3) and blocked by suramin, but not by PPADS (pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid) or MRS2578 suggesting a possible mediation of P2Y2 receptors activated by UTP. These observations suggest that uridine, UTP and UDP may function as pyrimidinergic neurotransmitters, and that enhancement of such neurotransmission underlies pharmacologic effects of exogenous uridine on the brain.

Specific multi-nutrient enriched diet enhances hippocampal cholinergic transmission in aged rats.

Fortasyn Connect (FC) is a specific nutrient combination designed to target synaptic dysfunction in Alzheimer's disease by providing neuronal membrane precursors and other supportive nutrients. The aim of the present study was to investigate the effects of FC on hippocampal cholinergic neurotransmission in association with its effects on synaptic membrane formation in aged rats. Eighteen-month-old male Wistar rats were randomized to receive a control diet for 4 weeks or an FC-enriched diet for 4 or 6 weeks. At the end of the dietary treatments, acetylcholine (ACh) release was investigated by in vivo microdialysis in the right hippocampi. On completion of microdialysis studies, the rats were sacrificed, and the left hippocampi were obtained to determine the levels of choline, ACh, membrane phospholipids, synaptic proteins, and choline acetyltransferase. Our results revealed that supplementation with FC diet for 4 or 6 weeks, significantly enhanced basal and stimulated hippocampal ACh release and ACh tissue levels, along with levels of phospholipids. Feeding rats the FC diet for 6 weeks significantly increased the levels of choline acetyltransferase, the presynaptic marker Synapsin-1, and the postsynaptic marker PSD-95, but decreased levels of Nogo-A, a neurite outgrowth inhibitor. These data show that the FC diet enhances hippocampal cholinergic neurotransmission in aged rats and suggest that this effect is mediated by enhanced synaptic membrane formation. These data provide further insight into cellular and molecular mechanisms by which FC may support memory processes in Alzheimer's disease.