Innocent Ejike Nwankwo

Effect of permethrin plus antioxidants on locomotor activity and striatum in adolescent rats

Pyrethroids are important insecticides used largely because of their high activity as an insecticide and their low mammalian toxicity. Some studies have demonstrated that these products show neurotoxic effects on the mammalian central nervous system. The aim of the present study was to investigate the propensity of permethrin to induce oxidative stress in adolescent rats and its possible attenuation by Vitamin E alone or+Coenzyme Q(10). Data indicated that adolescent rats exposed to permethrin exhibited alteration in the locomotor activity and plasma membrane fluidity of striatum. Vitamin E+Q(10) and Vitamin E alone supplementation reversed the negative effect on central nervous system. Permethrin alteration of striatum plasma membrane fluidity was restored by Vitamin E+Q(10). Data obtained from red blood cells showed that permethrin did not induce any modification of plasma membrane fluidity in adolescent rats, whereas antioxidants supplementation induced pro-oxidant effect. In summary some differences between antioxidant treatments were observed at striatum level: Coenzyme Q(10)+Vitamin E maintains plasma membrane fluidity, while Vitamin E is more effective to preserve GSH level.

Astrogliosis in the brain of obese Zucker rat: A model of metabolic syndrome

Metabolic syndrome (MetS) is a disorder characterized primarily by the development of insulin resistance. Insulin resistance and subsequent hyperinsulinemia, originating from abdominal obesity, increases the risk of cerebrovascular and cardiovascular disease and all-cause mortality. Obesity is probably a risk factor for Alzheimers disease and vascular dementia and is associated with impaired cognitive function. The obese Zucker rat (OZR) represents a model of type 2 diabetes exhibiting a moderate degree of arterial hypertension and of increased oxidative stress. To clarify the possible relationships between MetS and brain damage, the present study has investigated brain microanatomy in OZRs compared with their littermate controls lean Zucker rats (LZRs). Male OZRs and LZRs of 12 weeks of age were used. Their brain was processed for immunochemical and immunohistochemical analysis of glial fibrillary acidic protein (GFAP). In frontal and parietal cortex of OZRs a significant increase in the number of GFAP immunoreactive astrocytes was observed. Similar findings were found in the hippocampus, where an increased number of GFAP immunoreactive astrocytes were detected in the CA1 and CA3 subfields and dentate gyrus of OZRs compared to the LZRs. These findings indicating the occurrence of brain injury accompanied by astrogliosis in OZRs suggest that these rats, developed as an animal model of type 2 diabetes, may also represent a model for assessing the influence of MetS on brain. The identification of neurodegenerative changes in OZRs may represent the first step for better characterizing neuronal involvement in this model of MetS and possible treatment for countering it.

Intranasal Drug Delivery to the Central Nervous System: Present Status and Future Outlook

Pharmacological treatment of disorders affecting the central nervous system (CNS) is a complex task. Different parameters may negatively influence effective targeting of the CNS and drug compliance, for example, poor brain-blood barrier (BBB) permeability, patient forgetfulness or neglect, and lack of collaboration between caregivers and patients. Pharmaceutical science is constantly looking for new administration strategies for efficient drug delivery to the CNS that could obviate these problems. Drugs can reach the brain through the skin, nasal cavity and oral cavity, and while effective transport of drugs from skin and nasal cavity to the CNS has been documented, these studies did not stimulate the introduction of a substantial number of new drug formulations to treat CNS disorders. Nasal drug delivery, generally used to administer locally acting molecules, is not common for systemic administration, although the possibility and importance of such systemic administration is suggested by several studies. This paper reviewed different anatomical and pharmaceutical factors related to drug administration through the nasal route, and explored whether nasal delivery of selected CNS drugs could improve their pharmacokinetics and patient compliance. This route offers attractive advantages, and pharmaceutical scientists and anatomists should collaborate to improve CNS drug compliance and to increase the number of compounds that can be administered intranasally.

Brain Activity of Thioctic Acid Enantiomers: In Vitro and in Vivo Studies in an Animal Model of Cerebrovascular Injury

Oxidative stress is an imbalance between the production of free radicals and antioxidant defense mechanisms, potentially leading to tissue damage. Oxidative stress has a key role in the development of cerebrovascular and/or neurodegenerative diseases. This phenomenon is mainly mediated by an enhanced superoxide production by the vascular endothelium with its consequent dysfunction. Thioctic, also known as alpha-lipoic acid (1,2-dithiolane-3-pentanoic acid), is a naturally occurring antioxidant that neutralizes free radicals in the fatty and watery regions of cells. Both the reduced and oxidized forms of the compound possess antioxidant ability. Thioctic acid has two optical isomers designated as (+)- and (−)-thioctic acid. Naturally occurring thioctic acid is the (+)-thioctic acid form, but the synthetic compound largely used in the market for stability reasons is a mixture of (+)- and (−)-thioctic acid. The present study was designed to compare the antioxidant activity of the two enantiomers versus the racemic form of thioctic acid on hydrogen peroxide-induced apoptosis in a rat pheochromocytoma PC12 cell line. Cell viability was evaluated by MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay and free oxygen radical species (ROS) production was assessed by flow cytometry. Antioxidant activity of the two enantiomers and the racemic form of thioctic acid was also evaluated in spontaneously hypertensive rats (SHR) used as an in vivo model of increased oxidative stress. A 3-h exposure of PC12 cells to hydrogen peroxide (H2O2) significantly decreased cell viability and increased levels of intracellular ROS production. Pre-treatment with racemic thioctic acid or (+)-enantiomer significantly inhibited H2O2-induced decrease in cell viability from the concentration of 50 μmol/L and 20 μmol/L, respectively. Racemic thioctic acid and (+)-salt decreased levels of intracellular ROS, which were unaffected by (−)-thioctic acid. In the brain of SHR, the occurrence of astrogliosis and neuronal damage, with a decreased expression of neurofilament 200 kDa were observed. Treatment of SHR for 30 days with (+)-thioctic acid reduced the size of astrocytes and increased the neurofilament immunoreaction. The above findings could contribute to clarify the role played by thioctic acid in central nervous system injury related to oxidative stress. The more pronounced effect of (+)-thioctic acid observed in this study may have practical therapeutic implications worthy of being investigated in further preclinical and clinical studies.

Effects of Cholinergic Enhancing Drugs on Cholinergic Transporters in the Brain and Peripheral Blood Lymphocytes of Spontaneously Hypertensive Rats

Cholinergic hypofunction is a trait of Alzheimers disease and vascular dementia and countering it is one of the main therapeutic strategies available for these disorders. Cholinergic transporters control cellular mechanisms of acetylcholine (ACh) synthesis and release at presynaptic terminals. This study has assessed the influence of 4 week treatment with two different cholinergic enhancing drugs, the cholinergic precursor choline alphoscerate (alpha-glyceryl-phosphorylcholine) or the acetylcholinesterase (AChE) inhibitor galantamine on high affinity choline uptake transporter (CHT) and vesicular ACh transporter (VAChT) expression in the brain of spontaneously hypertensive rats (SHR). SHR represent an animal model of cerebrovascular injury characterized by cholinergic hypofunction. Analysis was performed by immunochemistry, ELISA and immunohistochemistry on frontal cortex, striatum and hippocampus. Immunochemical and ELISA analysis was extended to peripheral blood lymphocytes (PBL), used as a peripheral reference of changes of brain cholinergic markers. An increased expression of VAChT and CHT was observed in brain areas investigated and in PBL of SHR. The similar trend for cholinergic transporters observed in brain and PBL suggests these cells may represent a marker of brain cholinergic transporters. Treatment with choline alphoscerate increased CHT and to a greater extent VAChT expression. Treatment with galantamine countered the increase of CHT and VAChT. The different activity of the cholinergic precursor and of the AChE inhibitor on parameters investigated is likely related to their mechanism of action. Choline alphoscerate increases ACh synthesis and release. This requires an augmentation of systems regulating neurotransmitter uptake and storage. The effect of choline alphoscerate on CHT and VAChT observed in this study suggests an improved synaptic efficiency elicited by the compound. The AChE inhibitor slows-down ACh degradation in the synaptic cleft. A greater availability of neurotransmitter elicited by galantamine counters the enhanced activity of cholinergic transporters compensating cholinergic deficits. Differences in the activity of the cholinergic precursor and AChE inhibitor investigated on CHT and VAChT suggests that association between choline alphoscerate and AChE/cholinesterase inhibitors may represent a strategy for potentiating deficient cholinergic neurotransmission worthwhile of being investigated in clinical trials.

Neuroprotective Activity of Thioctic Acid in Central Nervous System Lesions Consequent to Peripheral Nerve Injury

Peripheral neuropathies are heterogeneous disorders presenting often with hyperalgesia and allodynia. This study has assessed if chronic constriction injury (CCI) of sciatic nerve is accompanied by increased oxidative stress and central nervous system (CNS) changes and if these changes are sensitive to treatment with thioctic acid. Thioctic acid is a naturally occurring antioxidant existing in two optical isomers (+)- and (−)-thioctic acid and in the racemic form. It has been proposed for treating disorders associated with increased oxidative stress. Sciatic nerve CCI was made in spontaneously hypertensive rats (SHRs) and in normotensive reference cohorts. Rats were untreated or treated intraperitoneally for 14 days with (+/−)-, (+)-, or (−)-thioctic acid. Oxidative stress, astrogliosis, myelin sheets status, and neuronal injury in motor and sensory cerebrocortical areas were assessed. Increase of oxidative stress markers, astrogliosis, and neuronal damage accompanied by a decreased expression of neurofilament were observed in SHR. This phenomenon was more pronounced after CCI. Thioctic acid countered astrogliosis and neuronal damage, (+)-thioctic acid being more active than (+/−)- or (−)-enantiomers. These findings suggest a neuroprotective activity of thioctic acid on CNS lesions consequent to CCI and that the compound may represent a therapeutic option for entrapment neuropathies.

Modulation of Monoaminergic Transporters by Choline-Containing Phospholipids in Rat Brain

Choline-containing phospholipids were proposed as cognition enhancing agents, but evidence on their activity is controversial. CDP-choline (cytidine-5´-diphosphocholine, CDP) and choline alphoscerate (L-alpha-glycerylphosphorylcholine, GPC) represent the choline-containing phospholipids with larger clinical evidence in the treatment of sequelae of cerebrovascular accidents and of cognitive disorders. These compounds which display mainly a cholinergic profile interfere with phospholipids biosynthesis, brain metabolism and neurotransmitter systems. Dated preclinical studies and clinical evidence suggested that CDP-choline may have also a monoaminergic profile. The present study was designed to assess the influence of treatment for 7 days with choline-equivalent doses (CDP-choline: 325 mg/Kg/day; GPC: 150 mg/Kg/day) of these compounds on brain dopamine (DA), and serotonin (5-HT) levels and on DA plasma membrane transporter (DAT), vesicular monoamine transporters (VMAT1 and VMAT2), serotonin transporter (SERT), and norepinephrine transporter (NET) in the rat. Frontal cortex, striatum and cerebellum were investigated by HPLC with electrochemical detection, immunohistochemistry, Western blot analysis and ELISA techniques. CDP-choline did not affect DA levels, which increased after GPC administration in frontal cortex and cerebellum. GPC increased also 5-HT levels in frontal cortex and striatum. DAT was stimulated in frontal cortex and cerebellum by both CDP and GPC, whereas VMAT2, SERT, NET were unaffected. VMAT1 was not detectable. The above data indicate that CDP-choline and GPC possess a monoaminergic profile and interfere to some extent with brain monoamine transporters. This activity on a relevant drug target, good tolerability and safety of CDP-choline and GPC suggests that these compounds may merit further investigations in appropriate clinical settings.

Comparative analysis of urinary schistosomiasis among primary school children and rural farmers in Obollo-Eke, Enugu State, Nigeria: Implications for control

OBJECTIVE To determine the prevalence, sex-age related intensity of urinary schistosomiasis and to compare such parameters among rural school children and rural farmers in selected communities in Obollo-Eke located in Southeast, Nigeria. METHODS A cross-sectional survey involving 1 337 school children and farmers was conducted in Obollo-Eke community between September 2006 and July 2007. Demographic data of subjects was collected using a questionnaire prepared for this purpose. Urine samples were collected and examined for haematuria and ova of Schistosoma haematobium (S. haematobium) using Medi-test Combi 9 and sedimentation technique respectively. RESULTS The prevalence of urinary schistosomiasis based on microscopic examination of the urine sediment for the ova of S. haematobium was 17.5% while the prevalence of haematuria was 15.6%. Infection intensity varied from light to heavy. In general, the prevalence was higher among males (20.8%) than females (14.6%; P>0.05) and was slightly higher among primary school children (18.0%; n=762) than farmers (16.9%; n=575; P>0.05). The age-specific prevalence of schistosomiasis among the study subjects ranged from 8.3% to 21.2% in 0-5 years and 11-15 years age groups respectively. CONCLUSIONS Haematuria and mean egg/10 mL urine (r = 0.95; P<0.01) showed that both procedures are reliable for the diagnosis of the disease and can be used to ascertain the prevalence of the disease in any community. The comparative analysis of urinary bilharziasis among primary school children and rural farmers demonstrated that the infection is moderately high in these two risk population groups at Obollo-Eke. A robust intervention strategy is clearly needed.

Spinal cord changes consequent to peripheral nerve injury: neuroprotective role of thioctic acid enantiomers

Peripheral neuropathies are in general characterized by hyperalgesia and allodynia with alterations of muscular sensitivity and functions. Selected antioxidants have been proposed as a potential therapeutic agents in the treatment or prevention of several pathologies related to oxidative stress. Thioctic acid is an antioxidant existing in nature and expressed in two optical isomers. (+)-Thioctic acid is the naturally occurring enantiomer, whereas the most used formulation of the compound in clinical practice, synthetic thioctic acid, is the mixture of (+) and (-)-enantiomers. The present study assessed if compression of sciatic nerve, induced by loose ligation, is accompanied by a central nervous system (CNS) changes and if thioctic acid enantiomers treatment may have a possible neuroprotective role. Loose ligation of the right sciatic nerve was performed in spontaneously hypertensive rats (SHR), used as a model of increased oxidative stress, and in normotensive Wistar-Kyoto rats (WKY) used as a control group. Animals with sciatic nerve ligation were left untreated or were treated intraperitoneally for 14 days with (+/-)-(25 and 50 mg/Kg/day), (+)-(25 mg/Kg/day), (-)-(25 mg/Kg/day) thioctic acid. Analysis, centered on injury phenomena at level of dorsal root ganglia and spinal cord, consisted in an immunochemical and immunohistochemical analysis. In the spinal cord an increase of oxidative stress markers was observed in rats after sciatic nerve ligation. It was accompanied by astrogliosis and neuronal damage without activation of apoptotic process primarily in in the dorsal horn of spinal cord. Antioxidant treatment reduced oxidative stress and astrogliosis being (+)-thioctic acid was active than (+/-)- or (-)-enantiomers. The above results demonstrated the spinal cord changes induced by peripheral nerve injury and a neuroprotective effect elicited by thioctic acid. The demonstration of a more pronounced activity of (+)-thioctic acid suggests that appropriate antioxidant strategies may represent a suitable approach in the treatment of mechanical neuropathies.

Effects of cholinergic enhancing drugs on cholinergic transporters in the brain of spontaneously hypertensive rats

Hypertension has been related to the establishment of brain damage and is the main risk factor for the development of cerebrovascular disease. Abnormal regulation of cholinergic neurotransmission might contribute to cognitive impairment associated with adult-onset dementia disorders including Alzheimer’s disease (AD) and vascular dementia (VaD). Cholinergic transporters control cellular mechanisms of acetylcholine (ACh) synthesis and release at presynaptic terminals. The high-affinity choline uptake transporter (CHT) recaptures choline deriving from acetylcholine (ACh) hydrolysis by acetylcholinesterase (AChE). Choline is resynthesized into ACh by choline acetyltransferase. The neurotransmitter is loaded into synaptic vesicles by the vesicular ACh transporter (VAChT). Abnormal regulation of cholinergic transporters might contribute to the cognitive impairments associated with neurodegenerative disorders. This study has assessed the influence of 4 week treatment with the AChE/cholinesterase (ChE) with the AChE inhibitor galantamine or with the cholinergic precursor choline alphoscerate (alpha-glyceryl-phosphorylcholine, GPC) on spontaneously hypertensive rats (SHR) used as a model of cerebrovascular injury. In these rats an obvious cholinergic hypofunction is noticeable. They could therefore represent a model for investigating the effect of drugs on cholinergic system. Wistar Kyoto (WKY) rats which belong from the normotensive phenotype opposed to SHR were investigated as well. Analysis performed by immunochemistry and ELISA included frontal cortex, striatum, hippocampus and peripheral blood lymphocytes (PBL). An increased expression of CHT and VAChT was observed in brain areas investigated and in PBL of SHR. This increase probably represents an up-regulation to counter cholinergic deficit of SHR. Treatment with galantamine countered the increase of CHT and VAChT. Treatment with GPC further increased CHT and to a greater extent VAChT. The effect of GFC is consistent with an increased synthesis of ACh it induces. This suggest that association between GPC and AChE/ChE inhibitors may represent a strategy worthwhile of being investigated in appropriate clinical trials.