Protective effects of glucose-6-phosphate dehydrogenase on neurotoxicity of aluminium applied into the CA1 sector of rat hippocampus.

BACKGROUND & OBJECTIVES: Aluminum (Al) toxicity is closely linked to the pathogenesis of Alzheimer's disease (AD). This experimental study was aimed to investigate the active avoidance behaviour of rats after intrahippocampal injection of Al, and biochemical and immunohistochemical changes in three bilateral brain structures namely, forebrain cortex (FBCx), hippocampus and basal forebrain (BF). METHODS: Seven days after intra-hippocampal (CA1 sector) injection of AlCl3 into adult male Wistar rats they were subjected to two-way active avoidance (AA) tests over five consecutive days. Control rats were treated with 0.9% w/v saline. The animals were decapitated on the day 12 post-injection. The activities of acetylcholinesterase (AChE) and glucose-6-phosphate dehydrogenase (G6PDH) were measured in the FBCx, hippocampus and BF. Immunohistochemical staining was performed for transferrin receptors, amyloid ß and tau protein. RESULTS: The activities of both AChE and G6PDH were found to be decreased bilaterally in the FBCx, hippocampus and basal forebrain compared to those of control rats. The number of correct AA responses was reduced by AlCl3 treatment. G6PDH administered prior to AlCl 3 resulted in a reversal of the effects of AlCl3 on both biochemical and behavioural parameters. Strong immunohistochemical staining of transferrin receptors was found bilaterally in the FBCx and the hippocampus in all three study groups. In addition, very strong amyloid ß staining was detected bilaterally in all structures in AlCl3-treated rats but was moderate in G6PDH/AlCl3-treated rats. Strong tau staining was noted bilaterally in AlCl3-treated rats. In contrast, tau staining was only moderate in G6PDH/AlCl3-treated rats. INTERPRETATION & CONCLUSIONS: Our findings indicated that the G6PDH alleviated the signs of behavioural and biochemical effects of AlCl3-treatment suggesting its involvement in the pathogenesis of Al neurotoxicity and its potential therapeutic benefit. The present model could serve as a useful tool in AD investigations.

Intermittent theta burst stimulation attenuates oxidative stress and reactive astrogliosis in the streptozotocin-induced model of Alzheimer's disease-like pathology.

Introduction: Intracerebroventricularly (icv) injected streptozotocin (STZ) is a widely used model for sporadic Alzheimer's disease (sAD)-like pathology, marked by oxidative stress-mediated pathological progression. Intermittent theta burst stimulation (iTBS) is a noninvasive technique for brain activity stimulation with the ability to induce long-term potentiation-like plasticity and represents a promising treatment for several neurological diseases, including AD. The present study aims to investigate the effect of the iTBS protocol on the animal model of STZ-induced sAD-like pathology in the context of antioxidant, anti-inflammatory, and anti-amyloidogenic effects in the cortex, striatum, hippocampus, and cerebellum. Methods: Male Wistar rats were divided into four experimental groups: control (icv normal saline solution), STZ (icv STZ-3 mg/kg), STZ + iTBS (STZ rats subjected to iTBS protocol), and STZ + Placebo (STZ animals subjected to placebo iTBS noise artifact). Biochemical assays and immunofluorescence microscopy were used to evaluate functional and structural changes. Results: The icv STZ administration induces oxidative stress and attenuates antioxidative capacity in all examined brain regions. iTBS treatment significantly reduced oxidative and nitrosative stress parameters. Also, iTBS decreased Aß-1-42 and APP levels. The iTBS enhances antioxidative capacity reported as elevated activity of its enzymatic and non-enzymatic components. In addition, iTBS elevated BDNF expression and attenuated STZ-induced astrogliosis confirmed by decreased GFAP+/VIM+/C3+ cell reactivity in the hippocampus. Discussion: Our results provide experimental evidence for the beneficial effects of the applied iTBS protocol in attenuating oxidative stress, increasing antioxidant capacity and decreasing reactive astrogliosis in STZ-administrated rats.

The effect of inhibition of nitric oxide synthase on aluminium-induced toxicity in the rat brain.

The goal of the present study was to examine the effectiveness of a non-specific nitric oxide synthase (NOS) inhibitor N-nitro-L-arginine methyl ester (L-NAME) to modulate the toxicity of aluminium chloride (AlCl3). Rats were killed at 3 h and at 30 days after treatments and the striatum was removed. Nitrite, superoxide, superoxide dismutase activity, malondialdehyde and reduced glutathione were determined. AlCl3 exposure promoted oxidative stress in the striatum. The biochemical changes observed in neuronal tissues show that aluminium acts as pro-oxidant, while the NOS inhibitor exerts antioxidant action in AlCl3-treated rats. We conclude that L-NAME can efficiently protect neuronal tissue from AlCl3-induced toxicity.

Nitric oxide synthase inhibitors partially inhibit oxidative stress development in the rat brain during sepsis provoked by cecal ligation and puncture.

IOxidative stress development in different brain structures and the influence of nitric oxide (NO) overproduction during sepsis was investigated using male Wistar rats. Rats were subjected to cecal ligation and puncture (CLP) or were sham-operated. To evaluate the source of NO production, 30 min before the operation septic and control animals were treated with single intraperitoneal doses of NO synthase (NOS) inhibitors: L-NAME and aminoguanidine (AG) (10, 30 or 90 mg/kg) and 7-nitroindazole (7-NI) (30 mg/kg). The concentration of GSH in the cortex, brain stem, cerebellum, striatum and hippocampus significantly decreased post CLP at both early and late stage sepsis. Lipid peroxidation also occurred in the cortex and cerebellum in late stage sepsis. Pre-treatment with a non-selective NOS inhibitor (L-NAME) and with selective inducible and neuronal NOS inhibitors (AG and 7-NI) revealed benefit effects on the GSH concentrations. Unexpectedly, NOS inhibition resulted in diverse effects on TBARS concentrations, suggesting the importance of specific quantities of NO in specific brain structures during sepsis.

Effects of L-NAME, a non-specific nitric oxide synthase inhibitor, on AlCl3-induced toxicity in the rat forebrain cortex.

The present experiments were done to determine the effectiveness of a non-specific nitric oxide synthase inhibitor, N-nitro-L-arginine methyl ester (L-NAME), on oxidative stress parameters induced by aluminium chloride (AlCl(3)) intrahippocampal injections in Wistar rats. Animals were sacrificed 3 h and 30 d after treatments, heads were immediately frozen in liquid nitrogen and forebrain cortices were removed. Crude mitochondrial fraction preparations of forebrain cortices were used for the biochemical analyses: nitrite levels, superoxide production, malondialdehyde concentrations, superoxide dismutase (SOD) activities and reduced glutathione contents. AlCl(3) injection resulted in increased nitrite concentrations, superoxide anion production, malondialdehyde concentrations and reduced glutathione contents in the forebrain cortex, suggesting that AlCl(3) exposure promoted oxidative stress in this brain structure. The biochemical changes observed in neuronal tissues showed that aluminium acted as a pro-oxidant. However, the nonspecific nitric oxide synthase (NOS) inhibitor, L-NAME, exerted anti-oxidant actions in AlCl(3)-treated animals. These results revealed that NO-mediated neurotoxicity due to intrahippocampal AlCl3 injection spread temporally and spatially to the forebrain cortex, and suggested a potentially neuroprotective effect for L-NAME.

Cytochrome c oxidase activity and nitric oxide synthase in the rat brain following aluminium intracerebral application.

In the present study we investigated the cytochrome C oxidase (CO) activity and nitric oxide synthase (NOS) isoenzyme expression after intrahippocampal AlCl3 application in selective vulnerable brain structures. A single dose of AlCl3 was applied in the CA1 sector of rats hippocampus. For biochemical analysis, the animals were killed 10 min and three days after the treatment and forebrain cortex, basal forebrain and hippocampus were removed. Activity of CO was decreased bilaterally in the AlCl3-treated groups in all examined brain structures. We also applied immunohistochemical techniques to identify changes induced by AlCl3 injection after survival periods of 10 min and three days. Both the nNOS and eNOS stains were detected in the hippocampus of controls and AlCl3-treated animals, but iNOS labelling was present in the hippocampus only three days after AlCl3 application. An increased iNOS expression three days post AlCl3 administration could be involved in the mechanism of CO activity depletion.

N-nitro-L-arginine methyl ester influence on aluminium toxicity in the brain.

We investigated the influence of a non-specific nitric oxide synthase (NOS) inhibitor, N-nitro-L-arginine methyl ester (L-NAME), on brain nitrite concentration and acetylcholine esterase activity in AlCl3-treated Wistar rats. Animals were killed 10 min, three hours, three days and 30 days after the treatment and hippocampus and basal forebrain were removed. The biochemical changes observed in neuronal tissues show the involvement of NO in the AlCl3 toxicity and cholinergic neurotransmission, and that L-NAME may have potential neuroprotective effects. Active avoidance learning was significantly impaired after AlCl3 application, while pretreatment with L-NAME prevented the behavioural deficits caused by AlCl3. We also applied immunohistochemical techniques to identify changes induced by AlCl3, L-NAME+AlCl3, as well as L-NAME injections after survival periods of three days and 30 days. Immunoreactivity of astrocytes and phagocytic microglia based on glial fibrillary acidic protein (GFAP) and a useful marker for rat macrophages (ED1), respectively, revealed a greater inflammatory response in AlCl3-injected animals compared to controls.

Nitric oxide synthase inhibitors protect cholinergic neurons against AlCl3 excitotoxicity in the rat brain.

The present experiment was carried out to determine the effectiveness of nitric oxide synthase inhibitors: 7-nitroindazole and aminoguanidine in modulating the toxicity of aluminium chloride on acetylcholine esterase activity, as well as behavioural and morphological changes of Wistar rats. For biochemical analysis the animals were killed 10 min, 3 h, 3 days and 30 days after the treatment and forebrain cortex, striatum, basal forebrain and hippocampus were removed. The biochemical changes observed in neuronal tissues show that nitric oxide synthase inhibitors exert as protective action in aluminium chloride-treated animals. In the present study, active avoidance learning was significantly impaired after aluminium chloride injection, while pretreatment with nitric oxide synthase inhibitors prevented the behavioural deficits caused between 26th and 30th day after intrahippocampal application of neurotoxin. Our data suggest that aluminium may cause learning and memory deficits, while the treatment with specific nitric oxide synthase inhibitors may prevent learning and memory deficits caused by aluminium chloride. We have also applied immunohistochemical techniques to identify neuronal- and inducible-nitric oxide synthase expression 30 days after aluminium chloride and nitric oxide synthase inhibitors injections. Our data suggest that 7-nitroindazole and aminoguanidine can be effective in the protection of toxicity induced by aluminium chloride.