Capsaicin, The Vanilloid Receptor TRPV1 Agonist in Neuroprotection: Mechanisms Involved and Significance

Hot peppers, also called chilli, chilli pepper, or paprika of the plant genus Capsicum (family Solanaceae), are one of the most used vegetables and spices worldwide. Capsaicin (8-methyl N-vanillyl-6-noneamide) is the main pungent principle of hot green and red peppers. By acting on the capsaicin receptor or transient receptor potential cation channel vanilloid subfamily member 1 (TRPV1), capsaicin selectively stimulates and in high doses defunctionalizes capsaicin-sensitive chemonociceptors with C and Aδ afferent fibers. This channel, which is involved in a wide range of neuronal processes, is expressed in peripheral and central branches of capsaicin-sensitive nociceptive neurons, sensory ganglia, the spinal cord, and different brain regions in neuronal cell bodies, dendrites, astrocytes, and pericytes. Several experimental and clinical studies provided evidence that capsaicin protected against ischaemic or excitotoxic cerebral neuronal injury and may lower the risk of cerebral stroke. By preventing neuronal death, memory impairment and inhibiting the amyloidogenic process, capsaicin may also be beneficial in neurodegenerative disorders such as Parkinson's or Alzheimer's diseases. Capsaicin given in systemic inflammation/sepsis exerted beneficial antioxidant and anti-inflammatory effects while defunctionalization of capsaicin-sensitive vagal afferents has been demonstrated to increase brain oxidative stress. Capsaicin may act in the periphery via the vagal sensory fibers expressing TRPV1 receptors to reduce immune oxidative and inflammatory signalling to the brain. Capsaicin given in small doses has also been reported to inhibit the experimentally-induced epileptic seizures. The aim of this review is to provide a concise account on the most recent findings related to this topic. We attempted to delineate such mechanisms by which capsaicin exerts its neuronal protective effects. We also aimed to provide the reader with the current knowledge on the mechanism of action of capsaicin on sensory receptors.

Protective effect of hot peppers against amyloid β peptide and brain injury in AlCl3-induced Alzheimer's disease in rats

Objectives

This study investigated the therapeutic effect of red hot pepper (Capsicum annuum) methanolic extract in induced Alzheimer's disease using AlCl₃ in male rats.

Materials and Methods

Rats were injected with AlCl₃ intraperitoneally (IP) daily for two months. Starting from the 2nd month of AlCl₃, rats received, in addition, IP treatments with Capsicum extract (25 and 50 mg/kg) or saline. Other groups received only saline or Capsicum extract at 50 mg/kg for two months. Brain levels of reduced glutathione (GSH), nitric oxide (NO), and malondialdehyde (MDA) were determined. Additionally, paraoxonase-1 (PON-1) activity, interleukin-6 (IL-6), Aβ-peptide, and acetylcholinesterase (AChE) concentrations in the brain were measured. Behavioral testing included wire-hanging tests for neuromuscular strength and memory tests such as Y-maze and Morris water maze. Histopathology of the brain was also done.

Results

Compared with saline-treated rats, AlCl₃ caused significant elevation of brain oxidative stress as GSH level and PON-1 activity were depleted along with MDA and NO level elevation in the brain. There were also significant increases in brain Aβ-peptide, IL-6, and AChE levels. Behavioral testing indicated that AlCl₃ decreased neuromuscular strength and impaired memory performance. Capsicum extract given to AlCl₃-treated rats significantly alleviated oxidative stress and decreased Aβ-peptide and IL-6 in the brain. It also improved grip strength and memory functioning and prevented neuronal degeneration in the cerebral cortex, hippocampus, and substantia nigra of AlCl₃-treated rats.

Conclusion

Short-term administration of ASA (50 mg/kg) has adverse effects on male reproductive function in mice. Co-administration of melatonin protects against ASA-induced impairment of male reproductive function by preventing the reduction in serum TAC and testosterone levels seen with ASA treatment alone.

Inhibition of aluminum chloride-induced amyloid Aβ peptide accumulation and brain neurodegeneration by Bougainvillea spectabilis flower decoction

OBJECTIVES

To investigate the potential therapeutic effect of Bougainvillea spectabilis flower decoction on aluminum chloride (AlCl₃)-induced neurotoxicity.

MATERIALS AND METHODS

Rats received daily intraperitoneal injections of AlCl₃ at 10 mg/kg for two months and were treated with B. spectabilis decoction at 50 or 100 mg/kg or saline during the 2^nd month of the study. The control group received saline. Brain malondialdehyde (MDA), nitric oxide (NO), reduced glutathione (GSH), acetylcholinesterase (AChE), amyloid Aβ peptide, and interleukin-6 (IL-6) concentrations and paraoxonase-1 (PON-1) activity were determined and brain histology was done. Behavioral and neurological testing included Morris water maze (WMZ), Y maze, and wire hanging.

RESULTS

Compared with saline controls, AlCl₃ significantly increased brain MDA and NO along with decreased GSH and PON-1 activity. It also increased AChE, IL-6, and amyloid Aβ concentrations. AlCl₃ impaired motor strength and memory performance and caused brain neurodegeneration. B. spectabilis decoction given at 50 or 100 mg/kg protected against the biochemical and histopathological alterations evoked by AlCl₃ by alleviating the increase in MDA and NO, and decrease in GSH and PON-1 activity. B. spectabilis decoction showed no significant effect on AChE but markedly decreased IL-6 and amyloid Aβ in the brain of AlCl₃-treated rats. It also restored memory performance and motor strength, and protected against AlCl₃-induced neurodegeneration.

CONCLUSION

These results suggest that B. spectabilis flower decoction might prove of value in the treatment of Alzheimer's disease.

The effect of low dose amphetamine in rotenone-induced toxicity in a mice model of Parkinson's disease

OBJECTIVES

The effects of low dose amphetamine on oxidative stress and rotenone-induced neurotoxicity and liver injury were examined in vivo in a mice model of Parkinson's disease.

MATERIALS AND METHODS

Male mice were treated with rotenone (1.5 mg/kg, every other day for two weeks, subcutaneously). Mice received either the vehicle or amphetamine intraperitoneally at doses of 0.5, 1.0, or 2.0 mg/kg. Oxidative stress was assessed by measurement of the lipid peroxidation product malondialdehyde (MDA), nitric oxide (NO), total anti-oxidant capacity (TAC), and paraoxonase-1 (PON-1) activity in the brain and liver. In addition, brain concentrations of nuclear factor kappa B (NF-κB) and tyrosine hydroxylase were determined and histopathology and Bax/Bcl-2 immunohistochemistry were performed.

RESULTS

The levels of lipid peroxidation and NO were increased and TAC and PON-1 were decreased significantly compared with vehicle-injected control mice. There were also significantly increased NF-κB and decreased tyrosine hydroxylase in the brain following rotenone administration. These changes were significantly attenuated by amphetamine. Rotenone caused neurodegenerative changes in the substantia nigra, cerebral cortex, and hippocampus. The liver showed degenerative changes in hepatocytes and infiltration of Kupffer cells. Bax/Bcl2 ratio was significantly increased in brain and liver tissues. Amphetamine prevented these histopathological changes and the increase in apoptosis evoked by rotenone.

CONCLUSION

These results suggest that low dose amphetamine exerts anti-oxidant and anti-apoptotic effects, protects against rotenone-induced neurodegeneration, and could prevent neuronal cell degeneration in Parkinson's disease.

Correction to: Capsaicin Exerts Anti-convulsant and Neuroprotective Effects in Pentylenetetrazole-Induced Seizures

The original version of this article unfortunately contains an error in the Y axis units in Fig. 1b, c (the symbol µ is not clear: µmol/g.tissue). This has been corrected by publishing this erratum.

Nitric oxide synthase inhibitors protect against brain and liver damage caused by acute malathion intoxication

OBJECTIVE

To investigate the effect of N^G-nitro-l-arginine methyl ester (l-NAME), a non-selective nitric oxide synthase (NOS) inhibitor, and 7-nitroindazole (7-NI), a selective neuronal NOS inhibitor, on oxidative stress and tissue damage in brain and liver and on DNA damage of peripheral blood lymphocytes in malathion intoxicated rats.

METHODS

Malathion (150 mg/kg) was given intraperitoneally (i.p.) along with l-NAME or 7-NI (10 or 20 mg/kg, i.p.) and rats were euthanized 4 h later. The lipid peroxidation product malondialdehyde (MDA), nitric oxide (nitrite), reduced glutathione (GSH) concentrations and paraoxonase-1 (PON-1) activity were measured in both brain and liver. Moreover, the activities of glutathione peroxidase (GPx) acetylcholinesterase (AChE), and butyrylcholinesterase (BChE), total antioxidant capacity (TAC), glucose concentrations were determined in brain. Liver enzyme determination, Comet assay, histopathological examination of brain and liver sections and inducible nitric oxide synthase (iNOS) immunohistochemistry were also performed.

RESULTS

(i) Rats treated with only malathion exhibited increased nitric oxide and lipid peroxidation (malondialdehyde) accompanied with a decrease in GSH content, and PON-1 activity in brain and liver. Glutathione peroxidase activity, TAC, glucose concentrations, AChE and BChE activities were decreased in brain. There were also raised liver aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activities and increased DNA damage of peripheral blood lymphocytes (Comet assay). Malathion caused marked histopathological changes and increased the expression of iNOS in brain and liver tissues. (ii) In brain of malathion-intoxicated rats, l-NAME or 7-NI resulted in decreased nitrite and MDA contents while increasing TAC and PON1 activity. Reduced GSH and GPx activity showed an increase by l-NAME. AChE activity increased by 20 mg/kg l-NAME and 10 mg/kg 7-NI. AChE activity decreased by the higher dose of 7-NI while either dose of 7-NI resulted in decreased BChE activity. (iii) In liver of malathion-intoxicated rats, decreased MDA content was observed after l-NAME or 7-NI. Nitrite level was unchanged by l-NAME but increased after 7-NI which also resulted in decreased GSH concentration and PON1 activity. Either inhibitor resulted in decreased liver ALT activity. (iv) DNA damage of peripheral blood lymphocytes was markedly inhibited by l-NAME or 7-NI treatment. (v) iNOS expression in brain and liver decreased by l-NAME or 7-NI. (vi) More marked improvement of the histopathological alterations induced by malathion in brain and liver was observed after 7-NI compared with l-NAME.

CONCLUSIONS

In malathion intoxicated rats, the neuronal NOS inhibitor 7-NI and to much less extent l-NAME were able to protect the brain and liver tissue integrity along with improvement in oxidative stress parameters. The decrease in DNA damage of peripheral blood lymphocytes by NOS inhibitors also suggests the involvement of nitric oxide in this process.

Bougainvillea spectabilis flowers extract protects against the rotenone-induced toxicity

OBJECTIVE

To investigate the effect of two extracts of Bougainvillea spectabilis (B. spectabilis) flowers with yellow and pink/purple on brain oxidative stress and neuronal damage caused in rats by systemic rotenone injection.

METHODS

Rotenone 1.5 mg/kg was given three times per week alone or in combination with B. spectabilis flowers extracts (25 mg or 50 mg) via the subcutaneous route for 2 weeks. Brain concentrations of the lipid peroxidation marker malondialdehyde (MDA), reduced glutathione, nitric oxide (nitrite), the pro-inflammatory cytokine interleukin-1beta (Il-1β) as well as butyrylcholinesterase, and paraoxonase-1 (PON-1) activities, were determined. Histopathology and caspase-3 immunohistochemistry were also performed.

RESULTS

Rotenone resulted in significant increases of brain MDA (the product of lipid peroxidation), and nitric oxide content along with decreased brain reduced glutathione. There were also marked and significant inhibition of brain PON-1 and BChE activities and increased Il-1β in brain of rotenone-treated rats. B. spectabilis flowers extract itself resulted in brain oxidative stress increasing both lipid peroxidation and nitrite content whilst inhibiting PON-1 activity. The yellow flowers extract inhibited BChE activity and increased brain Il-1β. When given to rotenone-treated rats, B. spectabilis extracts, however, decreased lipid peroxidation while their low administered doses increased brain GSH. Brain nitrite decreased by the pink extract but showed further increase by the yellow extract. Either extract, however, caused further inhibition of PON-1 activity while the yellow extract resulted in further inhibition of BChE activity. Histopathological studies indicated that both extracts protected against brain, liver and kidney damage caused by the toxicant.

CONCLUSIONS

These data indicate that B. spectabilis flowers extracts exert protective effect against the toxic effects of rotenone on brain, liver and kidney. B. spectabilis flowers extracts decreased brain lipid peroxidation and prevented neuronal death due to rotenone and might thus prove the value in treatment of Parkinson's disease.

Acetylcholinesterase, butyrylcholinesterase and paraoxonase 1 activities in rats treated with cannabis, tramadol or both

OBJECTIVE

To investigate the effect of Cannabis sativa resin and/or tramadol, two commonly drugs of abuse on acetylcholinesterase and butyrylcholinesterase activities as a possible cholinergic biomarkers of neurotoxicity induced by these agents.

METHODS

Rats were treated with cannabis resin (5, 10 or 20 mg/kg) (equivalent to the active constituent Δ⁹-tetrahydrocannabinol), tramadol (5, 10 and 20 mg/kg) or tramadol (10 mg/kg) combined with cannabis resin (5, 10 and 20 mg/kg) subcutaneously daily for 6 weeks. Acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) activities were measured in brain and serum. We also measured the activity of paraoxonase-1 (PON1) in serum of rats treated with these agents.

RESULTS

(i) AChE activity in brain increased after 10-20 mg/kg cannabis resin (by 16.3-36.5%). AChE activity in brain did not change after treatment with 5-20 mg/kg tramadol. The administration of both cannabis resin (5, 10 or 20 mg/kg) and tramadol (10 mg/kg) resulted in decreased brain AChE activity by 14.1%, 12.9% and 13.6%, respectively; (ii) BChE activity in serum was markedly and dose-dependently inhibited by cannabis resin (by 60.9-76.9%). BChE activity also decreased by 17.6-36.5% by 10-20 mg/kg tramadol and by 57.2-63.9% by the cannabis resin/tramadol combined treatment; (iii) Cannabis resin at doses of 20 mg/kg increased serum PON1 activity by 25.7%. In contrast, tramadol given at 5, 10 and 20 mg/kg resulted in a dose-dependent decrease in serum PON1 activity by 19%, 36.7%, and 46.1%, respectively. Meanwhile, treatment with cannabis resin plus tramadol resulted in 40.2%, 35.8%, 30.7% inhibition of PON1 activity compared to the saline group.

CONCLUSIONS

These data suggest that cannabis resin exerts different effects on AChE and BChE activities which could contribute to the memory problems and the decline in cognitive function in chronic users.

Gastric acid inhibitory and gastric protective effects of Cannabis and cannabinoids

Cannabis sativa has long been known for its psychotropic effect. Only recently with the discovery of the cannabinoid receptors, their endogenous legends and the enzymes responsible for their synthesis and degradation, the role of this 'endocannabinoid system' in different pathophysiologic processes is beginning to be delineated. There is evidence that CB1 receptor stimulation with synthetic cannabinoids or Cannabis sativa extracts rich in Δ(9)-tetrahydrocannabinol inhibit gastric acid secretion in humans and experimental animals. This is specially seen when gastric acid secretion is stimulated by pentagastrin, carbachol or 2-deoxy-d-glucose. Cannabis and/or cannabinoids protect the gastric mucosa against noxious challenge with non-steroidal anti-inflammatory drugs, ethanol as well as against stress-induced mucosal damage. Cannabis/cannabinoids might protect the gastric mucosa by virtue of its antisecretory, antioxidant, anti-inflammatory, and vasodilator properties.

Prevalence, clinical features and treatment of depression in Parkinson’s disease: An update

Parkinson’s disease (PD) is one of the most prevalent neurodegenerative diseases which typically affects individuals over 65 years. Although the symptomatology is predominantly motor, neuropsychiatric manifestations, e.g., depression, apathy, anxiety, and cognitive impairment occur in the course of the illness and can have a great impact on the quality of life in these patients. Parkinson’s disease is commonly comorbid with depression with prevalence rates of depression, generally higher than those reported in general population. Depression in PD is frequently underestimated and consequently undertreated, which have significant effects on the quality of life in these patients. The neurobiology of depression in PD is complex and involves alterations in dopaminergic, serotonergic, noradrenergic and possibly other neurotransmitter systems which are affected in the course of the disease. The tricyclic antidepressants and the selective serotonin reuptake inhibitors are the two classes of antidepressant drugs used for depressive symptoms in PD. Several published studies suggested that both classes are of comparable efficacy. Other serotonergic antidepressants, e.g., nefazodone and trazodone have also been of benefit. Meanwhile, there are limited data available on other drugs but these suggest a benefit from the serotonin and noradrenaline reuptake inhibitors such as mirtazapine, venlafaxine, atomoxetine and duloxetine. Some of the drugs used in symptomatic treatment of PD, e.g., the irreversible selective inhibitors of the enzyme monoamine oxidase-B, rasagiline and selegiline as well as the dopamine receptor agonist pramipexole are likely to have direct antidepressant activity independent of their motor improving action. This would make these drugs an attractive option in depressed subjects with PD. The aim of this review is to provide an updated data on the prevalence, clinical features of depression in subjects with PD. The effects of antiparkinsonian and antidepressant drugs on depressive symptoms in these patients are also discussed.

Drug therapy for Parkinson’s disease: An update

Parkinson’s disease (PD) is the most common neurodegenerative movement disorder, affecting about 1% of the population above the age of 65. PD is characterized by a selective degeneration of the dopaminergic neurons of the substantia nigra pars compacta. This results in a marked loss of striatal dopamine and the development of the characteristic features of the disease, i.e., bradykinesia, rest tremor, rigidity, gait abnormalities and postural instability. Other types of neurons/neurotransmitters are also involved in PD, including cholinergic, serotonergic, glutamatergic, adenosine, and GABAergic neurotransmission which might have relevance to the motor, non-motor, neuropsychiatric and cognitive disturbances that occur in the course of the disease. The treatment of PD relies on replacement therapy with levodopa (L-dopa), the precursor of dopamine, in combination with a peripheral decarboxylase inhibitor (carbidopa or benserazide). The effect of L-dopa, however, declines over time together with the development of motor complications especially dyskinesia in a significant proportion of patients within 5 years of therapy. Other drugs include dopamine-receptor-agonists, catechol-O-methyltransferase inhibitors, monoamine oxidase type B (MAO-B) inhibitors, anticholinergics and adjuvant therapy with the antiviral drug and the N-methyl-D-aspartate glutamate receptor antagonist amantadine. Although, these medications can result in substantial improvements in parkinsonian symptoms, especially during the early stages of the disease, they are often not successful in advanced disease. Moreover, dopaminergic cell death continues over time, emphasizing the need for neuroprotective or neuroregenerative therapies. In recent years, research has focused on non-dopaminergic approach such as the use of A_2A receptor antagonists: istradefylline and preladenant or the calcium channel antagonist isradipine. Safinamide is a selective and reversible inhibitor of MAO-B, a glutamate receptor inhibitor as well as sodium and calcium channel blocker. Minocycline and pioglitazone are other agents which have been shown to prevent dopaminergic nigral cell loss in animal models of PD. There is also an evidence to suggest a benefit from iron chelation therapy with deferiprone and from the use of antioxidants or mitochondrial function enhancers such as creatine, alpha-lipoic acid, l-carnitine, and coenzyme Q10.

Citric acid effects on brain and liver oxidative stress in lipopolysaccharide-treated mice

Citric acid is a weak organic acid found in the greatest amounts in citrus fruits. This study examined the effect of citric acid on endotoxin-induced oxidative stress of the brain and liver. Mice were challenged with a single intraperitoneal dose of lipopolysaccharide (LPS; 200 μg/kg). Citric acid was given orally at 1, 2, or 4 g/kg at time of endotoxin injection and mice were euthanized 4 h later. LPS induced oxidative stress in the brain and liver tissue, resulting in marked increase in lipid peroxidation (malondialdehyde [MDA]) and nitrite, while significantly decreasing reduced glutathione, glutathione peroxidase (GPx), and paraoxonase 1 (PON1) activity. Tumor necrosis factor-alpha (TNF-α) showed a pronounced increase in brain tissue after endotoxin injection. The administration of citric acid (1-2 g/kg) attenuated LPS-induced elevations in brain MDA, nitrite, TNF-α, GPx, and PON1 activity. In the liver, nitrite was decreased by 1 g/kg citric acid. GPx activity was increased, while PON1 activity was decreased by citric acid. The LPS-induced liver injury, DNA fragmentation, serum transaminase elevations, caspase-3, and inducible nitric oxide synthase expression were attenuated by 1-2 g/kg citric acid. DNA fragmentation, however, increased after 4 g/kg citric acid. Thus in this model of systemic inflammation, citric acid (1-2 g/kg) decreased brain lipid peroxidation and inflammation, liver damage, and DNA fragmentation.

Brain and liver oxidative stress after sertraline and haloperidol treatment in mice

BACKGROUND

Haloperidol is a classic antipsychotic drug known for its propensity to cause extrapyramidal side effects. Sertraline is an antidepressant drug which has been reported to cause extrapyramidal symptoms. We aimed to see whether treatment with sertraline would worsen the effect of haloperidol on oxidative stress in the brains of mice.

METHODS

Sertraline (10 or 20 mg/kg), haloperidol (2 mg/kg), haloperidol combined with sertraline or saline was administered daily via the subcutaneous route and mice were euthanized 10 days later when biochemical assays were carried out. Malondialdehyde (MDA), reduced glutathione (GSH), nitric oxide (nitrite) levels, total antioxidant capacity (TAC), acetylcholinesterase (AChE), catalase and paraoxonase 1 (PON1) activities were determined in the brain and liver.

RESULTS

Sertraline monotherapy did not alter GSH, MDA, TAC or nitrite in the brain. Haloperidol decreased GSH and TAC and increased MDA and nitrite. The combined treatment with sertraline and haloperidol resulted in increased MDA, but to a lesser extent than haloperidol monotherapy. A significant increase in GSH and TAC and decreased nitrite was observed after the combination treatment was compared with haloperidol monotherapy. Catalase activity decreased with sertraline or haloperidol treatment. PON1 activity decreased with sertraline and haloperidol monotherapy and showed a further decrease with the combination therapy compared with haloperidol monotherapy. AChE activity decreased after haloperidol and increased with the combination treatment compared with haloperidol monotherapy. In the liver, GSH was unaltered after sertraline, haloperidol or their combination. MDA increased with sertraline, haloperidol and their combination. TAC decreased after combination therapy. Nitric oxide increased after sertraline, haloperidol or their combination. PON1 activity decreased with sertraline, haloperidol and with sertraline-haloperidol co-treatment.

CONCLUSIONS

Sertraline did not worsen brain oxidative stress-induced with haloperidol, however, liver peroxidation increased. Sertraline decreased catalase and PON1 activity which might expose the brain to further oxidative insults.

Effects of afferent and efferent denervation of vagal nerve on endotoxin-induced oxidative stress in rats

This study investigated the role of vagal innervation in oxidative stress after systemic administration of lipopolysaccharide (LPS) endotoxin. Control rats and rats subjected to bilateral subdiaphragmatic vagotomy, perivagal capsaicin application (5 mg/ml) or cholinergic receptor blockade with subcutaneous atropine (1 mg/kg), were intraperitoneally injected with 300 μg/kg of LPS and euthanized 4 h later. Results indicated that; (1) surgical vagotomy and sensory denervation by perivagal capsaicin increased brain oxidative stress and decreased reduced glutathione in basal condition (saline-treated rats) and following endotoxin challenge; (2) oxidative stress decreased after cholinergic blockade with atropine in endotoxemic rats; (3) nitric oxide decreased by abdominal vagotomy, sensory deafferentation and cholinergic blockade after endotoxin injection; (4) liver lipid peroxidation decreased after surgical vagotomy and cholinergic blockade but increased after sensory deafferentation; (5) liver reduced glutathione decreased following vagotomy and sensory denervation in basal state and by cholinergic blockade in basal state and during endotoxemia; (6) nitric oxide increased by vagotomy in basal state and by sensory denervation and cholinergic blockade in basal state and during endotoxemia; (7) liver histological damage increased by subdiaphragmatic vagotomy, sensory denervation or cholinergic blockade. These findings suggest that: (1) sensory fibers (signals from the periphery) running in the vagus nerves are important in maintaining the redox status of the brain; (2) capsaicin vagal sensory nerves are likely to maintain nitric oxide tone in basal conditions; (3) the vagus nerve modulates liver redox status and nitric oxide release, (4) the vagus nerve mediates protective role in the liver with both cholinergic and capsaicin-sensitive mechanisms being involved.

Cannabis-induced impairment of learning and memory: effect of different nootropic drugs

Cannabis sativa preparations are the most commonly used illicit drugs worldwide. The present study aimed to investigate the effect of Cannabis sativa extract in the working memory version of the Morris water maze (MWM; Morris, 1984[43]) test and determine the effect of standard memory enhancing drugs. Cannabis sativa was given at doses of 5, 10 or 20 mg/kg (expressed as Δ(9)-tetrahydrocannabinol) alone or co-administered with donepezil (1 mg/kg), piracetam (150 mg/ kg), vinpocetine (1.5 mg/kg) or ginkgo biloba (25 mg/kg) once daily subcutaneously (s.c.) for one month. Mice were examined three times weekly for their ability to locate a submerged platform. Mice were euthanized 30 days after starting cannabis injection when biochemical assays were carried out. Malondialdehyde (MDA), reduced glutathione (GSH), nitric oxide, glucose and brain monoamines were determined. Cannabis resulted in a significant increase in the time taken to locate the platform and enhanced the memory impairment produced by scopolamine. This effect of cannabis decreased by memory enhancing drugs with piracetam resulting in the most-shorter latency compared with the cannabis. Biochemically, cannabis altered the oxidative status of the brain with decreased MDA, increased GSH, but decreased nitric oxide and glucose. In cannabis-treated rats, the level of GSH in brain was increased after vinpocetine and donepezil and was markedly elevated after Ginkgo biloba. Piracetam restored the decrease in glucose and nitric oxide by cannabis. Cannabis caused dose-dependent increases of brain serotonin, noradrenaline and dopamine. After cannabis treatment, noradrenaline is restored to its normal value by donepezil, vinpocetine or Ginkgo biloba, but increased by piracetam. The level of dopamine was significantly reduced by piracetam, vinpocetine or Ginkgo biloba. These data indicate that cannabis administration is associated with impaired memory performance which is likely to involve decreased brain glucose availability as well as alterations in brain monoamine neurotransmitter levels. Piracetam is more effective in ameliorating the cognitive impairments than other nootropics by alleviating the alterations in glucose, nitric oxide and dopamine in brain.

The effect of antidepressant drugs on thioacetamide-induced oxidative stress

OBJECTIVE

The aim of the present study was to investigate the effect of the serotonin selective reuptake inhibitors (SSRIs) fluoxetine and sertraline and the tricyclic drug imipramine on oxidative stress in the brain and liver caused by thioacetamide in rats.

MATERIALS AND METHODS

Drugs were administered orally once daily at doses of 10 and 20 mg/kg for two weeks prior to intraperitoneal injection of thioacetamide (300 mg/kg). Rats were euthanized 24 h after thioacetamide. Reduced glutathione (GSH), malondialdehyde (MDA) and nitric oxide were measured in brain and liver. Alanine aminotransferase (ALT), aspartate aminotransferase (AST), and alkaline phosphatase (ALP) were measured in serum and histopathological evaluation of liver injury was performed.

RESULTS

The administration of thioacetamide increased MDA by 151.8% and 161.2%, increased nitric oxide by 57.2% and 63.9% and decreased GSH by -40.6% and -67% in the brain and liver, respectively. Thioacetamide markedly increased serum ALT, AST and ALP by 277.8, 80.8 and 121%, respectively. In the brain, MDA was decreased in rats treated with fluoxetine or sertraline. The level of GSH increased by fluoxetine and by the higher dose of sertraline. Nitric oxide in brain was unchanged by fluoxetine, but increased after sertraline at 20 mg/kg. Brain MDA was increased by imipramine, which also decreased brain nitrite level. In the liver, fluoxetine or sertraline treatment increased GSH and nitrite levels. MDA was also increased by either drug. The drugs markedly decreased ALT, but increased ALP in serum. Meanwhile, imipramine decreased liver nitric oxide levels (at the lower dose only -32.9%), markedly increased hepatic GSH, but did not change MDA level. Serum ALT decreased by imipramine (but AST and ALP showed no change). Histopathological and histochemical examinations indicated that thioacetamide-induced liver injury was not decreased after treatment with the antidepressant drugs.

CONCLUSIONS

In thioacetamide-treated rats, pretreatment with the SSRIs drugs fluoxetine and sertraline is associated with decreased lipid peroxidation in brain; liver peroxidation, however, is increased. Imipramine displayed opposite effects. The thioacetamide-induced hepatic damage was not reduced by fluoxetine, sertraline or imipramine.  

Neuroprotective and hepatoprotective effects of micronized purified flavonoid fraction (Daflon®) in lipopolysaccharide-treated rats

Micronized purified flavonoid fraction (MPFF, Daflon®) is a phlebotonic drug widely used in chronic venous or lymphatic insufficiency. We aimed to investigate the effects of MPFF on hepatic and brain oxidative stress and on liver injury caused by lipopolysaccharide (LPS) in rats. MPFF (4.5, 9, or 18 mg/kg) or saline was administered orally for two days prior to intraperitoneal (i.p.) LPS (300 μg/kg) and at time of LPS administration. Rats were euthanized 4 h after LPS injection. The administration of LPS increased oxidative stress in brain and liver tissue. Malondialdehyde (MDA) increased by 193.5 and 191.8%, reduced glutathione (GSH) decreased by 73.8 and 70.8% and nitric oxide increased by 118.2 and 151.7% in the brain and liver, respectively. Serum paraoxonase 1 (PON1) activity decreased by 42.6%. Serum aspartate aminotransferase (AST), alanine aminotransferase (ALT) and alkaline phosphatase (ALP) were raised by 101.8, 93.6, and 223.2%, respectively. Rats treated with MPFF at 9 and 18 mg/kg showed decreased brain MDA (27.5-34%), nitrite (25.5-41%) and increased GSH (27.2-74.1%). In the liver, MDA decreased by 16.4-59.8%, nitrite decreased by 54.7-56.7%, and GSH increased by 15.2-70.5% with MPFF at 4.5, 9, or 18 mg/kg, respectively. Serum PON1 activity showed 41-65.9% increments with MPFF. Significant reductions in serum AST, ALT, and ALP were seen after treatment with MPFF. Moreover, the degree of histological damage, expression of the inducible form of nitric oxide synthase and the apoptotic enzyme caspase-3 in the liver were substantially reduced. MPFF thus prevented the increased oxidative stress and inflammation in brain and liver as well as the liver dysfunction caused by endotoxemia in the rat.

Studies on the effects of aspartame on memory and oxidative stress in brain of mice

OBJECTIVE

The dipeptide aspartame (N-L-alpha-aspartyl-Lphenylalanine, 1-methyl ester; alpha-APM) is one of the most widely used artificial sweeteners. The present study aimed to investigate the effect of repeated administration of aspartame in the working memory version of Morris water maze test, on oxidative stress and brain monoamines in brain of mice.

MATERIALS AND METHODS

Aspartame (0.625, 1.875 or 5.625 mg/kg) was administered once daily subcutaneously for 2 weeks and mice were examined four times a week for their ability to locate a submerged plate. Malondialdehyde (MDA), reduced glutathione (GSH), nitric oxide levels (the concentrations of nitrite/nitrate) and glucose were determined in brain.

RESULTS

Only at the highest dose of 5.625 mg/kg, did aspartame significantly impaired water maze performance. The mean time taken to find the escape platform (latency) over 2 weeks was significantly delayed by aspartame 5.625 mg/kg, compared with the saline-treated control group. Significant differences occurred only on the first trial to find the escape platform. Significant increase in brain MDA by 16.5% and nitric oxide by 16.2% and a decrease in GSH by 25.1% and glucose by 22.5% occurred after treatment with aspartame at 1.875 mg/kg. Aspartame administered at 5.625 mg/kg significantly increased brain MDA by 43.8%, nitric oxide by 18.6% and decreased GSH by 32.7% and glucose by 25.8%. Aspartame caused dose-dependent inhibition of brain serotonin, noradrenaline and dopamine.

CONCLUSIONS

These findings suggest impaired memory performance and increased brain oxidative stress by repeated aspartame administration. The impaired memory performance is likely to involve increased oxidative stress as well as decreased brain glucose availability.

Amelioration of the haloperidol-induced memory impairment and brain oxidative stress by cinnarizine

Haloperidol is a classic antipsychotic drug known for its propensity to cause extrapyramidal symptoms and impaired memory, owing to blockade of striatal dopamine D2 receptors. Cinnarizine is a calcium channel blocker with D2 receptor blocking properties which is widely used in treatment of vertiginous disorders. The present study aimed to see whether cinnarizine would worsen the effect of haloperidol on memory function and on oxidative stress in mice brain. Cinnarizine (5, 10 or 20 mg/kg), haloperidol, or haloperidol combined with cinnarizine was administered daily via the subcutaneous route and mice were examined on weekly basis for their ability to locate a submerged plate in the water maze test. Mice were euthanized 30 days after starting drug injection. Malondialdehyde (MDA), reduced glutathione (GSH) and nitric oxide (nitrite/nitrate) were determined in brain. Haloperidol substantially impaired water maze performance. The mean time taken to find the escape platform (latency) was significantly delayed by haloperidol (2 mg/kg, i.p.) on weeks 1-8 of the test, compared with saline control group. In contrast, those treated with haloperidol and cinnarizine showed significantly shorter latencies, which indicated that learning had occurred immediately. Haloperidol resulted in increased MDA in cortex, striatum, cerebellum and midbrain. GSH decreased in cortex, striatum and cerebellum and nitric oxide increased in cortex. Meanwhile, treatment with cinnarizine (20 mg/kg) and haloperidol resulted in significant decrease in MDA cortex, striatum, cerebellum and midbrain and an increase in GSH in cortex and striatum, compared with haloperidol group. These data suggest that cinnarizine improves the haloperidol induced brain oxidative stress and impairment of learning and memory in the water maze test in mice.

Neuroprotective effect of nitric oxide donor isosorbide-dinitrate against oxidative stress induced by ethidium bromide in rat brain

This study investigated the effect of systemic administration of isosorbide-dinitrate (ISDN) on oxidative stress and brain monoamines in a toxic model of brain demyelination evoked by intracerebral injection (i.c.i) of ethidium bromide (10 µl of 0.1 %). Rats received saline (control) or ISDN at 5 or 10 mg/kg for 10 days prior to injection of ethidium bromide. Rats were euthanized one day later, and then the levels of reduced glutathione (GSH), lipid peroxidation (malondialdehyde; MDA), nitric oxide (nitrite/nitrate), acetylcholinesterase (AChE) activity, paraoxonase activity as well as monoamine levels (serotonin, dopamine and noradrenaline) were assessed in the brain cortex in different treatment groups. The i.c.i of ethidium bromide resulted in increased oxidative stress in the cortex one day after its injection; (i) MDA increased by 36.9 %; (ii) GSH decreased by 20.8 %, while (iii) nitric oxide increased by 60.3 %; (iv) AChE and paraoxonase activities in cortex decreased by 35.9 % and 29.4 %, respectively; (v) serotonin was significantly increased. In ethidium bromide-treated rats, pretreatment with ISDN at 10 mg/kg decreased cortical MDA by 23.9 %. Reduced glutathione was increased by 25.1 % ISDN at 10 mg/kg, while nitric oxide showed a 32.8 and 41.7 % decrease after 5 and 10 mg/kg of ISDN, respectively. Acetylcholinesterase activity increased by 24.3 % by 10 mg/kg of ISDN. Paraoxonase activity showed further decrease by 72.2 and 83.8 % after treatment with 5 and 10 mg/kg of ISDN, respectively. The administration of ISDN decreased the level of serotonin and noradrenaline compared with the ethidium bromide only treated group. Overall, the present findings suggest neuroprotective effect of ISDN against oxidative stress in this model of chemical demyelination.

The effect of gabapentin on oxidative stress in a model of toxic demyelination in rat brain

BACKGROUND

Gabapentin, a structural analog of γ-aminobutyric acid (GABA), is used in the treatment of neuropathic pain in multiple sclerosis.

METHODS

This study investigated the effect of gabapentin on oxidative stress in a model of brain demyelination evoked by intracerebral injection (i.c.i) of ethidium bromide (10 μL of 0.1%). Rats received saline (control) or gabapentin at 100 or 300 mg/kg orally daily for 10 days prior to injection of ethidium bromide. Rats were euthanized 1 day later, and then the levels of reduced glutathione (GSH), glutathione peroxidase (GPx) activity, lipid peroxidation (malondialdehyde; MDA), nitrite, acetyl cholinesterase (AChE) and paraoxonase activities were assessed in the brain cortex in different treatment groups.

RESULTS

Ethidium bromide resulted in increased oxidative stress in the cortex 1 day after its injection. Malondialdehyde increased by 30.2%, whereas GSH decreased by 17.6%. GPx activity was inhibited by 78.6%. Brain nitrite increased by 55.4%, AChE activity decreased by 33.4% and paraoxonase activity decreased by 27.5%. In ethidium bromide treated rats, gabapentin administered at 300 mg/kg increased cortical MDA by 66%. GSH was unaltered by gabapentin, but GPx activity decreased by 54.3% by the higher dose of gabapentin. Nitrite decreased by 21.4% and 29.2% after 100 and 300 mg/kg of gabapentin, respectively. AChE activity increased by 28.6% and 69.3% by 100 and 300 mg/kg of gabapentin, respectively. Paraoxonase activity showed 83.3% and 73% decreases by 100 and 300 mg/kg of gabapentin, respectively.

CONCLUSIONS

These results suggest that gabapentin increases brain lipid peroxidation and decreases brain antioxidant enzymes in this model of chemical demyelination.

The effect of different antidepressant drugs on oxidative stress after lipopolysaccharide administration in mice

This study investigated the effect of the serotonin selective reuptake inhibitors (SSRIs) fluoxetine, sertraline, fluvoxamine and the tricyclic antidepressant (TCA) impiramine on oxidative stress in brain and liver induced by lipopolysaccharide administration in mice. Each drug was administered subcutaneously at doses of 10 or 20 mg/kg, for two days prior to intraperitoneal (i.p.) administration of lipopolysaccharide E (LPS: 200 µg/kg). Mice were euthanized 4 h after administration of the lipopolysaccharide. Lipid peroxidation (malondialdehyde; MDA), reduced glutathione (GSH) and nitric oxide (nitrite/nitrate) concentrations were measured in brain and liver. Results: The administration of lipopolysaccharide increased oxidative stress in brain and liver; it increased brain MDA by 36.1 and liver MDA by 159.8 %. GSH decreased by 34.1 % and 64.8 % and nitric oxide increased by 78.7 % and 103.8 % in brain and liver, respectively. In brain, MDA decreased after the administration of sertraline and by the lower dose of fluoxetine or fluvoxamine, but increased after the higher dose of imipramine. Reduced glutathione increased after sertraline, fluvoxamine and the lower dose of fluoxetine or imipramine. Nitric oxide decreased by sertraline, fluoxetine, fluvoxamine and by the lower dose of imipramine. In the liver, all drugs decreased MDA and increased GSH level. Nitric oxide is decreased by sertraline, fluvoxamine and by the lower dose of fluoxetine or imipramine. It is concluded that, during mild systemic inflammatory illness induced by peripheral bacterial endotoxin injection, the SSRIs fluoxetine, sertraline and fluvoxamine reduced, while the TCA impiramine increased oxidative stress induced in the brain. The SSRIs as well as imipramine reduced oxidative stress due to lipopolysaccharide in liver tissue.

Modulation of lipopolysaccharide-induced oxidative stress by capsaicin

This study investigated the effect of capsaicin (the active principle of hot red pepper and a sensory excitotoxin) on oxidative stress after systemic administration of the endotoxin lipopolysaccharide (100 μg/kg, i.p.) in rats. Capsaicin (15, 150 or 1,500 μg/kg; 10, 100 or 400 μg/mL) was given via intragastric (i.g.) or intraperitoneal (i.p.) routes at time of endotoxin administration. Rats were killed 4 h later. Malondialdehyde (MDA) and reduced glutathione (GSH) were measured in brain, liver, and lungs. Alanine aminotransferase (ALT), aspartate aminotransferase, alkaline phosphatase (ALP), nitric oxide, and glucose were measured in serum. In addition, histopathological examination of liver tissue was performed. In LPS-treated rats, hepatic GSH increased significantly by 40.8% after i.p. capsaicin at 1,500 μg/kg. Liver MDA increased significantly by 32.9% after the administration of i.g. capsaicin at 1,500 μg/kg and by 27.8 and 37.6% after the administration of i.p. capsaicin at 150 and 1,500 μg/kg, respectively. In lung tissue, both MDA and GSH were decreased by capsaicin administration. MDA decreased by 19-20.8% after i.g. capsaicin and by 17.5-23.2% after i.p. capsaicin (150-1,500 μg/kg), respectively. GSH decreased by 39.3-64.3% and by 35.7-41.1% after i.g. or i.p. capsaicin (150-1,500 μg/kg), respectively. Brain GSH increased significantly after the highest dose of i.g. or i.p. capsaicin (by 20.6 and 15.9%, respectively). The increase in serum ALT and ALP after endotoxin administration was decreased by oral or i.p. capsaicin. Serum nitric oxide showed marked increase after LPS injection, but was markedly decreased after capsaicin (1,500 μg/kg, i.p.). Serum glucose increased markedly after the administration of LPS, and was normalized by capsaicin treatment. It is suggested that in the presence of mild systemic inflammation, acute capsaicin administration might alter oxidative status in some tissues and exert an anti-inflammatory effect. Capsaicin exerted protective effects in the liver and lung against the LPS-induced tissue damage.

The effects of trimetazidine on lipopolysaccharide-induced oxidative stress in mice

The effects of trimetazidine, a novel anti-ischemic agent, on the development of oxidative stress induced in mice with lipopolysaccharide endotoxin were investigated. The drug was administered orally once daily at doses of 1.8, 3.6 or 7.2 mg/kg for two days prior to intraperitoneal (i.p.) injection of lipopolysaccharide E (200 μg/kg) and at time of endotoxin administration. Mice were euthanized 4 h after administration of the lipopolysaccharide. Lipid peroxidation (malondialdehyde; MDA), reduced glutathione (GSH) and nitric oxide (nitrite/nitrate) concentrations were measured in brain and liver. The administration of lipopolysaccharide increased oxidative stress in both the brain and liver tissue. MDA increased by 33.9 and 107.1 %, GSH decreased by 23.9 and 84.3 % and nitric oxide increased 70.3 and 48.4 % in the brain and liver, respectively. Compared with the lipopolysaccharide control group, brain MDA decreased by 26.2 and 36.7 %, while GSH increased by 18.2 and 25.8 % after the administration of trimetazidine at 3.6 and 7.2 mg/kg, respectively. Brain nitric oxide decreased by 45.3, 50.8 and 57.0 % by trimetazidine at 1.8, 3.6 and 7.2 mg/kg, respectively. In the liver, MDA decreased by 18.7, 30.7 and 49.4 % and GSH increased by 150.3, 204.8 and 335.4 % following trimetazidine administration at 1.8, 3.6 and 7.2 mg/kg. Meanwhile, nitric oxide decreased by 17.3 % by 7.2 mg/kg of trimetazidine. These results indicate that administration of trimetazidine in the presence of mild systemic inflammatory response alleviates oxidative stress in the brain and liver.