Uridine treatment protects against neonatal brain damage and long-term cognitive deficits caused by hyperoxia.

Exposure to excessive oxygen in survivors of preterm birth is one of the factors that underlie the adverse neurological outcome in later life. Various pathological changes including enhanced apoptotic activity, oxidative stress and inflammation as well as decreased neuronal survival has been demonstrated in animal models of neonatal hyperoxia. The aim of the present study was to investigate the effect of administering uridine, an anti-apoptotic agent, on cellular, molecular and behavioral consequences of hyperoxia-induced brain damage in a neonatal rat model. For five days from birth, rat pups were either subjected continuously to room air (21% oxygen) or hyperoxia (80% oxygen) and received daily intraperitoneal (i.p.) injections of saline (0.9% NaCl) or uridine (500mg/kg). Two-thirds of all pups were sacrificed on postnatal day 5 (P5) in order to investigate apoptotic cell death, myelination and number of surviving neurons. One-thirds of pups were raised through P40 in order to evaluate early reflexes, sensorimotor coordination and cognitive functions followed by investigation of neuron count and myelination. We show that uridine treatment reduces apoptotic cell death and hypomyelination while increasing the number of surviving neurons in hyperoxic pups on P5. In addition, uridine enhances learning and memory performances in periadolescent rats on P40. These data suggest that uridine administered during the course of hyperoxic insult enhances cognitive functions at periadolescent period probably by reducing apoptotic cell death and preventing hypomyelination during the neonatal period in a rat model of hyperoxia-induced brain injury.

Long-term cognitive effects of uridine treatment in a neonatal rat model of hypoxic-ischemic encephalopathy.

Hypoxic-ischemic encephalopathy (HIE), is the most common brain disorder in neonates during the perinatal period, which, to date, can only be managed to some extent by hypothermia. Uridine is the principal circulating pyrimidine in humans which is utilized as a precursor for membrane phospholipid biosynthesis. Uridine has recently been shown to provide clinical benefit in treatment of Alzheimer's disease due to its involvement in increasing number of brain synapses along with other phospholipid precursors. We previously showed that uridine treatment ameliorated brain damage by reducing apoptosis in a rat model of neonatal HIE. The aim of the present study was to investigate the effects of uridine administration on cognitive functions during periadolescent period in rats subjected to hypoxic-ischemic (HI) brain damage in neonatal period. Male newborn rats were subjected to HI insult on postnatal day 7 (P7) and were injected intraperitoneally with either saline or uridine (500mg/kg) for three consecutive days. Part of pups in each group were sacrificed on P10 to collect brain samples for active Caspase-3 analyses and the remaining pups were raised through P40 to evaluate early reflexes, sensorimotor coordination and learning and memory functions by Negative Geotaxis (NG), Beam Walking (BW) and Morris Water Maze (MWM) tasks, respectively. Confirming our previous findings, we showed that uridine administration reduced apoptotic cell damage on P10. No significant difference was observed between uridine and saline groups in early reflexes or sensorimotor coordination. On the other hand, rats receiving uridine displayed improved learning and memory in MWM during periadolescent period. We conclude that uridine treatment improves learning and memory in the long term by, probably, reducing apoptotic cell death in early newborn period. This is the first study to show beneficial cognitive effects of uridine in rats with brain damage.

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.

Neuroprotective effects of uridine in a rat model of neonatal hypoxic-ischemic encephalopathy.

Neonatal hypoxic-ischemic encephalopathy (HIE) is a major cause of neurological disability requiring newer therapeutic strategies. Uridine is the principal circulating pyrimidine in humans and a substrate for nucleotides and membrane phospholipids. The objective of this study was to investigate the effects of uridine in a neonatal rat model of HIE. Rat pups subjected to hypoxic-ischemic insult on postnatal day 7 were injected intraperitoneally with either saline or uridine (100, 300 or 500mg/kg) for three consecutive days and brains were collected for evaluation of brain infarct volume and apoptosis. Compared with Control group, uridine at 300 and 500mg/kg doses significantly reduced percent infarct volume, TUNEL(+) cell ratio and active Caspase-3 immunoreactivity in the cortex, as well as in CA1 and CA3 regions of the hippocampus. Uridine (300 and 500mg/kg) also decreased active Caspase-3 expression in the ipsilateral hemisphere. These data indicate that uridine dose-dependently reduces brain injury in a rat model of neonatal HIE by decreasing apoptosis.

Neuroprotective effects of melatonin administered alone or in combination with topiramate in neonatal hypoxic-ischemic rat model.

PURPOSE: The objective of this study was to compare the effects of two neuroprotective agents; melatonin, a free radical scavenger and topiramate, AMPA/kainate receptor antagonist, administered alone or in combination in neonatal hypoxic-ischemic model. METHODS: After being anesthetized, 7-day-old pups underwent ischemia followed by exposure to hypoxia. The pups were divided into 4 groups in order to receive the vehicle, melatonin, topiramate and combination of topiramate and melatonin. These were administered intraperitoneally for three times; the first before ischemia, the second after hypoxia and the third 24 hours after the second dose. After sacrification, infarct volume and apoptosis were evaluated. RESULTS: Percent infarcted brain volume was significantly reduced in rats which received drugs compared with those which received the vehicle. The number of TUNEL positive cells per unit area in hippocampus and cortex were markedly reduced in drug treated groups compared with control group. No significant differences were found regarding percent infarcted brain volume and number of TUNEL positive cells among drug-treated groups. CONCLUSIONS: Melatonin and topiramate, administered either alone or in combination significantly reduced the percent infarcted brain volume and number of TUNEL positive cells suggesting that these agents may confer benefit in treatment of infants with hypoxic-ischemic encephalopathy.

Citicoline and postconditioning provides neuroprotection in a rat model of ischemic spinal cord injury.

BACKGROUND: Ischemic spinal cord injury is a chain of events caused by the reduction and/or cessation of spinal cord blood flow, which results in neuronal degeneration and loss. Ischemic postconditioning is defined as a series of intermittent interruptions of blood flow in the early phase of reperfusion and has been shown to reduce the infarct size in cerebral ischemia. Our study aimed to characterize the relationship between the neuronal injury-decreasing effects of citicoline and ischemic postconditioning, which were proven to be effective against the apoptotic process. METHOD: Spinal cord ischemia was produced in rats using an intrathoracic approach to implement the synchronous arcus aorta and subclavian artery clipping method. In our study, 42 male Sprague-Dawley rats (309 +/- 27 g) were used. Animals were divided into sham operated, spinal ischemia, citicoline, postconditioning, and postconditioning citicoline groups. Postconditioning was generated by six cycles of 1 min occlusion/5 min reperfusion. A 600 mmol/kg dose of citicoline was given intraperitoneally before ischemia in the citicoline and postconditioning citicoline groups. All rats were sacrificed 96 h after reperfusion. For immunohistochemical analysis, bcl-2, caspase 3, caspase 9, and bax immune staining were performed. Caspase 3, caspase 9, bax, and bcl-2 were used as apoptotic and antiapoptotic markers, respectively. FINDINGS: The blood pressure values obtained at the onset of reperfusion were significantly lower than the preischemic values. A difference in immunohistochemical scoring was detected between the caspase 3, caspase 9, bax, and bcl-2 groups. When comparisons between the ischemia (groups 2, 3, 4, and 5) and sham groups (group 1) were performed, a significant increase in caspase 3, caspase 9, bax, and bcl-2 was detected. When comparing the subgroups, the average score of caspase 9 was found to be significantly higher in ischemia group 2. The average score of bcl-2 was also found to be significantly higher in postconditioning and citicoline group 5. CONCLUSIONS: It is thus thought that combining citicoline with postconditioning provides protection by inhibiting the caspase pathway and by increasing the antiapoptotic proteins.

Neuroprotective effects of postconditioning on lipid peroxidation and apoptosis after focal cerebral ischemia/reperfusion injury in rats.

AIM: Apoptosis after cerebral ischemia/reperfusion (I/R) injury leads to the process of cell death. The deal therapeutic approach would target the apoptosis after I/R. Ischemic postconditioning is a recently discovered neuroprotective strategy that involves the application of brief mechanical reperfusion with a specific algorithm at the onset of reperfusion following an ischemic period. MATERIAL AND METHODS: Transient MCAo was performed on male SD (275+/-25 g) rats with intraluminal thread insertion for 2 hrs. Rats (n:36) were treated with postconditioning after 60 minutes of occlusion. The postconditioning algorithm was 30 secs of brief reperfusion followed by 30 secs of MCAo and this cycle was repeated 3 times at the onset of reperfusion. RESULTS: After I/R injury, % change of the malonyldialdehyde (MDA) levels in the cortex, which is an index of lipid peroxidation, was found significantly higher in the I/R group. On the other hand postconditioning upregulated Bcl-2 and Bax translocation to the mitochondria, and caspase-3 activity and also reduced oxidative stress levels. CONCLUSION: These findings indicated this neuroprotective effect is most likely achieved by antiapoptotic mechanisms through caspase pathways.

Investigation of neuroprotective effects of cyclooxygenase inhibitors in the 6-hydroxydopamine induced rat Parkinson model.

AIM: Recent experimental and clinical studies on Parkinson's disease point out the pivotal role of inflammation in the pathogenesis of neurodegeneration and the possible positive effects of nonsteroidal anti-inflammatory drug therapies. Our aim in this study was to investigate the preventive effects of nonsteroidal anti-inflammatory drugs in the 6-hydroxydopamine (6-OHDA) induced rat model of Parkinson's disease. MATERIAL AND METHODS: Twenty-one female Wistar-Albino rats (200-250g) were used in this study. The rats were divided in three groups: Saline group (n: 7, 2 ml), Acetylsalicylic acid group (n: 7, 100 mg/kg), and Meloxicam group (n: 7, 50 mg/kg). An hour after administration, the rats received a unilateral intranigral injection of 6-OHDA to produce the Parkinson model lesion. Rotational tests were performed two weeks later as follow-up. Immunohistochemical tests were performed in all groups to determine the severity of the lesion in the substantia nigra. RESULTS: Administration of drugs an hour before the lesions were created did not protect the degeneration of dopaminergic neurons in the substantia nigra. CONCLUSION: Oral usage of low repeated doses of nonsteroidal anti-inflammatory drugs may possibly slow down the progression of the disease.

Neuronal protective effects of focal ischemic pre- and/or postconditioning on the model of transient focal cerebral ischemia in rats.

We investigated the neuroprotective effects of pre- and postconditioning on infarct volume in the transient middle cerebral artery occlusion (MCAo) model in rats. Thirty-two male rats were divided into occlusion, preconditioning, postconditioning and both pre- and postconditioning groups. MCAo (120 minutes) was monitored with continuous cerebral tissue oxygen (O2) pressure (PtiO2). Pre-conditioning comprised 10 minutes of MCAo, 24 hours prior to the 120 minute MCAo. The postconditioning algorithm was 30 seconds of reperfusion followed by 30 seconds of MCAo. This cycle was repeated 3 times at the onset of reperfusion. Comparison of infarct volumes showed a significant difference between the conditioned groups and occlusion group. Although there was better protection in the preconditioning group compared with the other two conditioned groups, the results did not reach statistically significant levels. The results suggest that preconditioning, postconditioning and pre/post conditioning have protective effects on cerebral ischemia.

Effects of hypoxic preconditioning in antioxidant enzyme activities in hypoxic-ischemic brain damage in immature rats.

AIM: HI (hypoxic-ischemic) brain injury is a major cause of neonatal mortality and longterm neurological morbidity. The aim of the present study was to investigate the effects of HPC (hypoxic preconditioning) on the oxidative-antioxidative status in the neonatal HI brain model. MATERIAL AND METHODS: Fifty five 7-day-old rats were placed into; Control, HPC, HPC+HI insult, and HI insult groups. HPC, The HPC+HI insult groups were subjected to hypoxia (37 degrees C, 8%O2) and the control group to normoxia for 2.5 hrs. Twenty-four hours later, the rats in the HPC+HI insult and HI insult groups were exposed to cerebral HI produced by unilateral right common carotid artery (CCA) occlusion combined with 90 min hypoxia. Four hours after recovery, the malondialdehyde (MDA) level and the activities of superoxide dismutase (SOD), and glutathione peroxidase (GPx) were determined in the brain tissues of the rats. RESULTS: The findings of the present study suggest increased lipid peroxidation and/or decreased antioxidant activity in the brain of the HI rats. CONCLUSION: The beneficial effects of HPC might not be related to the alterations in the antioxidative activity.

Effects of intranigral vs intrastriatal fetal mesencephalic neural grafts on motor behavior disorders in a rat Parkinson model.

BACKGROUND: Numerous experimental and clinical studies have shown that intrastriatal fetal mesencephalic grafts grow, survive, and reinnervate host brain tissue, resulting in partial recovery of motor deficits. In addition, pharmacological evidence indicates that these grafts increase dopamine secretion in lesioned brain. However, to date, no grafting method has completely restored the nigrostriatal pathway, and there is no consensus on optimal graft numbers or locations. This study compared outcomes with multiple striatal grafts vs a single intranigral graft in a rat model of Parkinson disease. METHODS: Forty-one female Wistar rats weighing 200 to 250 g were used. First, baseline rotational behavior testing with amphetamine injection was done to identify each animal's dominant nigrostriatal pathway (left vs right hemisphere). Some rats then received a unilateral intranigral injection of 6-hydroxydopamine (4 microL [8 microg]) to produce the Parkinson model lesion, and rotational testing was repeated. One group of the lesioned rats received a single intranigral injection of suspended fetal ventral mesencephalic cells (n = 11), and another received multiple intrastriatal grafts of the same type (n = 11). RESULTS: Both grafted groups showed significant improvement on rotational testing with amphetamine and apomorphine at 6 weeks "postgrafting" (P < .001 for "postlesioning" vs postgrafting results in each of the 2 groups); however, the animals with multiple intrastriatal grafts showed complete recovery from motor asymmetry, whereas the rats with single intranigral grafts showed only partial improvement. CONCLUSION: The findings indicate that multiple intrastriatal grafts result in significantly greater functional improvement than single intranigral grafts in this rat Parkinson model.