PI3K/AKT signaling activation by roflumilast ameliorates rotenone-induced Parkinson's disease in rats

Parkinson's disease (PD) is the second most common progressive age-related neurodegenerative disorder. Paramount evidence shed light on the role of PI3K/AKT signaling activation in the treatment of neurodegenerative disorders. PI3K/AKT signaling can be activated via cAMP-dependent pathways achieved by phosphodiesterase 4 (PDE4) inhibition. Roflumilast is a well-known PDE4 inhibitor that is currently used in the treatment of chronic obstructive pulmonary disease. Furthermore, roflumilast has been proposed as a favorable candidate for the treatment of neurological disorders. The current study aimed to unravel the neuroprotective role of roflumilast in the rotenone model of PD in rats. Ninety male rats were allocated into six groups as follows: control, rotenone (1.5 mg/kg/48 h, s.c.), L-dopa (22.5 mg/kg, p.o), and roflumilast (0.2, 0.4 or 0.8 mg/kg, p.o). All treatments were administrated for 21 days 1 h after rotenone injection. Rats treated with roflumilast showed an improvement in motor activity and coordination as well as preservation of dopaminergic neurons in the striatum. Moreover, roflumilast increased cAMP level and activated the PI3K/AKT axis via stimulation of CREB/BDNF/TrkB and SIRT1/PTP1B/IGF1 signaling cascades. Roflumilast also caused an upsurge in mTOR and Nrf2, halted GSK-3β and NF-ĸB, and suppressed FoxO1 and caspase-3. Our study revealed that roflumilast exerted neuroprotective effects in rotenone-induced neurotoxicity in rats. These neuroprotective effects were mediated via the crosstalk between CREB/BDNF/TrkB and SIRT1/PTP1B/IGF1 signaling pathways which activates PI3K/AKT trajectory. Therefore, PDE4 inhibition is likely to offer a reliable persuasive avenue in curing PD via PI3K/AKT signaling activation.

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.

Cardioprotection by methylene Blue Against Epinephrine-Induced Cardiac Arrhythmias and Myocardial Injury

Methylene blue is used in the treatment of vasoplegic syndrome after cardiac surgery, anaphylaxis, and septic shock refractory to epinephrine and fluid resuscitation. In this study, we investigated the potential protective effect of methylene blue on the development of cardiac arrhythmias after injection of epinephrine in rats. Methylene blue was given intraperitoneally at doses of 50 or 100 mg/kg. Cardiac arrhythmia was then induced with 10 μg/kg of epinephrine intravenously. In untreated, control rats, epinephrine caused bradycardia (96.48 ± 1.06 vs. 365.03 ± 0.68 beats/min), increased PR interval (0.54 ± 0.04 vs. 0.039 ± 0.004), RR interval (0.64 ± 0.003 vs. 0.16 ± 0.004 sec), shortened QTc interval (0.067 ± 0.05 vs. 0.1 ± 0.004 sec), increased QRS duration (0.048 ± 0.005 vs. 0.028 ± 0.002 sec), decreased R wave amplitude (0.3 ± 0.03 vs. 0.49 ± 0.04 mv), decreased the height of the ST segment (-0.0696 ± 0.004 vs. -0.0054 ± 0.003 mv), and caused ventricular extrasystoles (7.92 ± 0.56 vs. 0.5 ± 0.5). Methylene blue given at 50 or 100 mg/kg increased the heart rate, decreased RR interval, QRS duration and the drop in the ST height, increased duration of QTc interval and R wave amplitude and decreased the number of extrasystoles. The histological study showed that methylene blue protected against myocardial structural disorganization, cellular damage, necrosis, and haemorrhage between muscle fibres induced by epinephrine injection. We conclude that methylene blue dose-dependently prevented epinephrine-induced arrhythmias and cardiac muscle injury.

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.

Identification of biomarkers for the detection of subtle brain injury after cannabis and/or tramadol administration

Background

There is a need to identify biomarkers which could indicate the occurrence of brain injury in drug abuse.

Objectives

We aimed to investigate ubiquitin-C-terminal hydrolase-1 (UCH-L1), a neuronal cell body injury marker, the glial protein S-100 beta (S100β), and the glial fibrillary acidic protein (GFAP) as putative markers for neuronal injury due to cannabis, tramadol, or their combined use.

Materials and methods

Rats were treated with cannabis and/or tramadol subcutaneously daily for 6 weeks and UCH-L1, S100β, and GFAP were immunoassayed in the brain and serum.

Results

The results are as follows: (i) either cannabis or tramadol increased UCH-L1 and GFAP in the brain, (ii) serum UCH-L1 and GFAP increased by the highest dose of cannabis or tramadol, (iii) there was no additive effect for cannabis and tramadol on UCH-L1 or GFAP level in the brain or serum, (iv) S100β decreased in the brain by 5–20 mg/kg of cannabis and in the serum following 20 mg/kg of cannabis, and (v) S100β levels increased in the brain after 20 mg/kg of tramadol but decreased the brain and serum after both cannabis and tramadol. Cytoplasmic vacuolations, apoptotic cells, and gliosis were observed in the brain tissue of cannabis and/or tramadol-treated rats.

Conclusions

These results suggest that changes in UCH-L1, GFAP, or S100β are likely to reflect neurotoxicity and serum levels could be used to detect neuronal damage in chronic users.

Neuroprotective Effects of Low Dose Anandamide in Pentylenetetrazole-Induced Kindling in Rats

Anandamide (N-arachidonoylethanolamine) is an endogenous cannabinoid receptor CB1 ligand that exhibits neuroprotective effects in the brain. In this study, the effect of exogenously given anandamide on pentylenetetrazole (PTZ)-induced chemical kindling oxidative stress and brain damage in rats was studied. Rats were intraperitoneally (i.p.) injected with 35 mg/kg PTZ once every 48 hours for 12 times to induce seizures. Anandamide was i.p. given. 30 min prior to PTZ injection at 100 or 200 mg/kg. Injections of PTZ induced significant increase in brain lipid peroxidation (malondialdehyde: MDA), and nitric oxide associated with marked decrease in brain reduced glutathione (GSH). There were also significant decrements in acetylcholinesterase (AChE) concentration, butyrylcholinesterase (BChE) and paraoxonase-1 (PON-1) activities in brain tissue of PTZ injected rats. Meanwhile, there was no significant effect for PTZ on the concentration of brain neutrophil elastase. Anandamide administered at 100 and 200 mg/kg significantly decreased MDA and increased GSH contents and at 200 mg/kg significantly decreased nitric oxide in brain of PTZ-treated rats. The drug also caused significant increments in AChE concentration and PON-1 activity but had no significant effect on BChE or neutrophil elastase in rats treated with PTZ. Anandamide given at the dose of 200mg/kg significantly decreased the mean seizure scores over the study period by 22.3% and the frequency of myoclonic jerks and rearing (stage 3) by 56.7% compared with the vehicle-treated group. Anandamide given at 100 and 200 mg/kg completely inhibited the development of generalized tonic-clonic seizures (stage 5). It is concluded that in the PTZ-induced seizures, the cannabinoid receptor CB1 agonist anandamide decreases brain oxidative stress, neuronal injury, and exerts an antiepileptic activity.

Modulation of gastric acid secretion by cannabinoids in rats

The current study aimed to evaluate the role of cannabinoid receptors in the regulation of gastric acid secretion and oxidative stress in gastric mucosa. To fulfill this aim, gastric acid secretion stimulated with histamine (5 mg/kg, subcutaneous [SC]), 2-deoxy- d-glucose (D-G) (200 mg/kg, intravenous) or -carbachol (4 μg/kg, SC) in the 4-hour pylorus-ligated rats. The CB1R agonist ( N-arachidonoyl dopamine, 1 mg/kg, SC) inhibited gastric acid secretion stimulated by D-G and carbachol but not in histamine, reduced pepsin content, and increased mucin secretion. Furthermore, it decreased malondialdehyde (MDA) and nitric oxide (NO) contents with an increase in glutathione (GSH) and paraoxonase 1 (PON-1). Meanwhile, CB2R antagonist (AM630, 1 mg/kg, SC) inhibited gastric acid secretion stimulated by D-G and reduced MDA and NO contents with an increase in GSH and PON-1. Meanwhile, CB1R antagonist rimonabant or CB2R agonist GW 405833 had no effect on stimulated gastric acid secretion. Therefore, both CB1R agonist and CB2R antagonist may exert antisecretory and antioxidant potential in the stomach.

Grape Seed Extract Alone or Combined with Atropine in Treatment of Malathion Induced Neuro- and Genotoxicity

The aim of this study was to investigate the effect of treatment with grape seed extract (GSE) on the neurotoxic and genotoxic effects of acute malathion exposure. Rats received malathion (150 mg/kg by i.p. injection) for two successive days alone or combined with GSE at doses of 150 or 300 mg/kg, orally or with GSE at 300 mg/kg and atropine at a dose of 2 mg/kg, i.p. Malondialdehyde (MDA), reduced glutathione (GSH), nitric oxide, paraoxonase (PON1) were determined in cortex, striatum, and rest of brain tissue (subcortex). Interleukin-1β (IL-1β), and butyrylcholinesterase (BChE) activities were determined in brain regions. Cytogenetic analyses for chromosomal aberrations in somatic and germ cells, micronucleus test, Comet assay, DNA fragmentation of liver cells and histopathological examination of brain and liver sections were also performed. Malathion resulted in an increase in MDA, nitric oxide; a decrease in GSH and PON1 activity in different brain regions. IL-1β increased, while BChE activity decreased in brain after the administration of malathion. The insecticide also caused marked structural and numerical chromosomal aberrations and increased liver DNA fragmentation. The Comet assay showed a significant increase in DNA damage of peripheral blood lymphocytes. These effects of malathion were alleviated with the administration of GSE alone or combined with atropine. Addition of atropine to treatment with GSE was associated with significant decrease in MDA, BChE and chromosomal aberrations compared with GSE only treatment. Our data indicate that GSE protects against malathion neurotoxic and genotoxic effects, most likely through reducing brain oxidative stress and inflammatory response.

Protection by Neostigmine and Atropine Against Brain and Liver Injury Induced by Acute Malathion Exposure

We examined the effect of treatment with neostigmine alone or with atropine on brain oxidative stress and on brain and liver tissue damage following acute malathion toxicity. Rats were intraperitoneally treated with malathion 150 mg/kg along with neostigmine (200 or 400 μg/kg) or neostigmine (200 μg/kg) + atropine (1 mg/kg) and euthanized 4 h later. Results indicated that compared with the saline group, malathion resulted in (i) higher brain malondialdehyde (MDA) and nitric oxide (46.4% and 86.2%); (ii) decreased brain reduced glutathione (GSH) (67.6%); (iii) decreased brain paraoxonase-1 (PON1), acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) activities (31.2%, 21.6% and 60%); (iv) decreased brain glucose (-38.1%); (v) neuronal degeneration in cortex and hippocampus and markedly increased glial fibrillary acidic protein (GFAP) immunostaining in the hippocampus; (v) hydropic and fatty degeneration in liver. Rats treated with malathion along with neostigmine or neostigmine + atropine showed no change in brain MDA but decreased nitric oxide (-34.2%-48%). GSH increased after neostigmine 200 μg/kg or neostigmine + atropine (35.8% and 41%). PON1 activity increased (42%-35.2%) and glucose concentrations increased (91.5%-81.5%) by 400 μg/kg neostigmine or neostigmine + atropine. Brain AChE activity remained unchanged but BChE activity showed 18.3% increment after 400 μg/kg neostigmine. Rats treated with 400 μg/kg neostigmine or neostigmine + atropine had normal neuronal appearance in cortex and hippocampus and weak GFAP expression in hippocampus. Liver damage was prevented by neostigmine + atropine. These results suggest that treatment with neostigmine + atropine afforded protection against the deleterious effects of acute malathion on the brain and liver.

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.

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.

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.

One-pot three-component synthesis of novel heterocyclic steroids as a central antioxidant and anti-inflammatory agents

Oxidative stress and inflammation have been implicated in several neurodegenerative and developmental brain disorders. The present work was devoted to the design and synthesis of novel steroid derivatives bearing promising heterocyclic moiety that would act to reduce neuro-inflammation and oxidative stress in brain. The novel heterocyclic steroids were synthesized and their chemical structures were confirmed by studying their analytical and spectral data. The tested compounds were assayed in the model of neuro-inflammation produced in rats by cerebral lipopolysaccharide injection. The intracerebral administration of bacterial endotoxin resulted in cerebral inflammatory state evidenced by increased malondialdehyde (MDA), decreased reduced glutathione (GSH) level, increased nitric oxide as well as increased acetylcholinesterase (AChE) activity in the brain. Compounds 6, 10, 8b and 13a markedly increased reduced glutathione. Malondialadehyde and nitric oxide levels were reduced to normal values after treatment with all tested compounds. AChE activity was normalized by compound 8b and reduced to below normal values by compounds 10 and 14a. These results are exciting in that these agents might be useful candidates in treatment of cerebral inflammation.

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.

Synthesis of modified steroids as a novel class of non-ulcerogenic, anti-inflammatory and anti-nociceptive agents

The identification of compounds able to treat both pain and inflammation with limited side effects is one of the prominent goals in biomedical research. This study aimed at the synthesis of new modified steroids with structures justifying non-ulcerogenic, anti-inflammatory and anti-nociceptive activities. The steroid derivatives were synthesized via straightforward and efficient methods and their structures were established based on the analytical and spectral data. The in vivo anti-inflammatory, anti-nociceptive and anti-ulcerogenic activities of some of these compounds were studied. The newly synthesized compounds 8b, 19b, 24 and 31a showed anti-inflammatory, anti-nociceptive and anti-ulcerogenic activity with various intensities. Oedema was significantly reduced by either dose 25 or 50 mg/kg of all tested compounds at 3 and 4 h post-carrageenan. Compound 19b was the most effective in alleviating thermal pain. The analgesic activity of either dose of the compounds 8b, 24, 31a as well as the high dose 19b was significantly higher than that for indomethacin (IND). Gastric mucosal lesions caused in the rats by the administration of 96% EtOH and IND were inhibited by all tested compounds administered at (50 mg/kg) dose in the study.

Structure-based design of benzimidazole sugar conjugates: synthesis, SAR and in vivo anti-inflammatory and analgesic activities

A series of 2-methyl-N-substituted-benzimidazoles, bearing hydroxypyrrolidinon-5-yl or hydroxypyrrolidin-2-yl, 2,3:5,6-di-O-isopropylidene-alpha-D-mannofuranoside, 2,3,5,6-tetrahydroxy-alpha-D-mannofuranoside, 1:2,5:6-di-O-isopropylidene-alpha-D-gluco-furanose,3-O-benzyl-6,7-dideoxy-1:2-O-isopropylidene-alpha-D-xylo-heptofuranos-5-ulose, 3-O-benzyl-6,7-dideoxy-1,2-dihydroxy-alpha-D-xylo-heptofuranos-5-ulose, 1,2,5,6-tetrahydroxy-alpha-D-glucofuranose sugar moieties, were obtained in good yields from 2-methyl N-(trichloroacetamidomethyl)benzimidazole as a donor and carbohydrate residues as acceptor precursors in the presence of catalytic amount of trimethylsilyl trifluoromethanesulfonate (TMSOTf) as Lewis acid. Compounds 6, 7, 10, 13, 15, and 16 showed significant anti-inflammatory and analgesic activities.

Effects of biphenyldimethyl-dicarboxylate administration alone or combined with silymarin in the CCL4 model of liver fibrosis in rats

The effect of biphenyldimethyldicarboxylate (DDB), a synthetic compound, in use for the treatment of chronic hepatitis was studied on hepatic injury caused in rats by administration of carbon tetrachloride (CCl₄). Starting at time of administration of the first dose of CCl₄, rats received DDB at four dose levels (3, 15, 75 or 375 mg/kg), silymarin (22 mg/kg), a combination of DDB (75 mg/kg) and silymarin (22 mg/kg) or saline (control) once orally daily for 30 days. The administration of DDB in CCl₄-treated rats at 75 or 375 mg/kg resulted in 61.2-76.2% decrease in alanine aminotransferase (ALT) and 46.9-60.8% decrease in aspartate aminotransferase (AST), respectively compared with the CCl₄ control group. Silymarin treatment resulted in 34.6 and 30% decrease in ALT and AST, while DDB (75 mg/kg) combined with silymarin (22 mg/kg) resulted in 58.2 and 31% decrease in ALT and AST, respectively. Serum creatinine increased by 50% by DDB at 375 mg/kg. After treatment with DDB at 75 or 375 mg/kg or DDB combined with silymarin, the development of liver necrosis and fibrosis caused by CCl₄ was markedly reduced, while after DDB combined with silymarin no DNA aneuploid cells could be observed. The decrease in glycogen and protein contents in hepatocytes caused by CCl₄ was markedly prevented by co-treatment with DDB at 75 or 375 mg/kg or DDB combined with silymarin. It is concluded that in the model of hepatic injury caused by chronic administration of CCl₄ in rats, the synthetic compound DDB, limits hepatocellular injury and exerts antifibrotic effect. Better improvement in protein, DNA, mucopolysaccharide content was seen after both DDB and silymarin compared to DDB alone. It is suggested, therefore, that DDB alone or in combination with silymarin might prove of benefit in the therapy of chronic liver disease. Monitoring of kidney functions in patients taking DDB is warranted.

Molecular pharmacological approach to drug actions on the afferent and efferent fibres of the vagal nerve involved in gastric mucosal protection in rats

BACKGROUND

Gastric mucosal protection is associated with the actions of anti-ulcer drugs or agents affecting on the afferent and/or efferent nerve fibres of the vagal nerve.

AIMS

1. To identify the dose-response curves of drugs (compounds) on the afferent vanilloid-receptor (capsaicin or resiniferatoxin-sensitive) and on efferent secretion (atropine, pirenzepine, cimetidine, ranitidine, famotidine, omeprazole, esomeprazole) basal gastric acid and stimulated gastric secretion in relation to the chemically-induced gastric mucosal damage in rats; 2. To determine the ED50 (pD2) and pA2 on the calculation of affinity and intrinsic affinity curves for these agonists/antagonists, as an indication of relative potency of effects.

MATERIALS AND METHODS

The observations were carried out in rats (30 different models).

RESULTS

The ED50 values for affinities of capsaicin, resiniferatoxin were obtained in nmol/kg b.w. range, whereas the values were in the nmol/kg to micromol/kg b.w. ranges for effects on the gastric basal, stimulated (bethanechol, pentagastrin, histamine) gastric secretion, and the gastric mucosal damage-produced by different ulcerogenic agents (ethanol, HCl, aspirin, indomethacin).

CONCLUSION

From the observations, that agents acting on vanilloid (capsaicin) receptors were the most potent inhibitors of acid secretion and gastric lesions from necrotizing agents, suggests that the capsaicin sensitive afferent nerves have a primary place in the efferent regulated events leading to initiation of gastric mucosal damage.

Evaluation of the anti-inflammatory and anti-nociceptive activities of novel synthesized melatonin analogues

This study aimed at evaluation of the reactivity of melatonin (1) towards various chemical reagents to produce new melatonin analogues containing heterocyclic moieties which would provide basic pharmacological activities. The pyrrolo[1,2-a]indole derivatives 3, 5, 12, 14 and pyrido[1,2-a]indole derivatives 9a, b were synthesized via straightforward and efficient methods and their structures were established based on the analytical and spectral data. Also, this work was extended to study the potential role of the novel synthesized melatonin analogues 3, 5, 9a and 12 as anti-inflammatory and anti-nociceptive agents in comparison with melatonin. After s.c. administration all compounds induced significant anti-inflammatory activity, inhibiting the paw oedema response compared with the control group at all time points in the test. Compound 5 has the strongest anti-inflammatory activity which exceeds that of the parent reference, melatonin, followed by compounds 9a and 12, at the first 2h of administration. Effect of melatonin analogues on thermal pain, acetic acid-induced writhing and gastric lesions caused by indomethacin was also investigated. Compounds 5 and 12 were more potent as anti-nociceptive drugs; they are more potent in this respect than melatonin.

Anti-inflammatory, antinociceptive, and gastric effects of Hypericum perforatum in rats

The pharmacological activity of Hypericum perforatum was assessed using models of inflammation, nociception, and gastric mucosal injury in rats. H. perforatum was given systemically as well as orally. When administered systemically, H. perforatum (50–300 mg/kg, s.c.) produced a dose-related and significant inhibition of the edematogenic response to s.p. injection of carrageenan. The percentages of maximal inhibition by the above doses were 53.7, 61.3, and 75.3%, respectively (compared to 90% after 50 mg/kg fluoxetine and 60.7% after 72 mg/kg etodolac). In tests of nociception, H. perforatum, administered orally, displayed antinociceptive activity in the tail electric stimulation and hot plate tests. The antinociceptive activity was observed with 25 mg/kg and a maximal increase in hot plate latency by 50% (compared to 73.2 and 77.8% increases by 5 or 10 mg/kg fluoxetine, respectively). In contrast, the acetic acid–induced (0.6%, i.p.) writhing was significantly reduced by fluoxetine or etodolac, but not H. perforatum. Also, the nociceptive response caused by i.p. injection of capsaicin (1.6 μg/paw) was unaffected by H. perforatum, but reduced by fluoxetine. Injection of H. perforatum (50, 125, or 250 mg/kg, s.c.) to pylorus-ligated rats, decreased gastric acid secretion, but increased indomethacin-induced gastric mucosal lesions dose dependently. These results demonstrate that H. perforatum exhibits antiedematogenic and antinociceptive properties, which may be of value for the management of inflammatory painful conditions. The agent, however, causes gastric irritation and may aggravate that of NSAIDs.

Antinociceptive and behavioral effects of ribavirin in mice

The antinociceptive effect of ribavirin, an antiviral drug, was studied after systemic injection using several pain tests in mice. In the hot-plate test of thermal pain, capsaicin-induced chemogenic pain, formalin test and abdominal stretching assay induced by the i.p. injection of 0.6% acetic acid, ribavirin produced a dose-related reduction in nociceptive responses. The visceral antinociceptive effect of ribavirin was unaffected by co-treatment with yohimbine, atropine or theophylline, but partially reversed by naloxone. Antinociception by ribavirin was augmented by treatment with prazosin, doxazosin, propranolol, guanethidine, glibenclamide, baclofen, indomethacin or cysteamine. Further, the ribavirin induced antinociception was enhanced by D2 receptor antagonists haloperidol, sulpiride, clozapine or domperidone and by the dopamine D2 receptor agonist bromocryptine. Ribavirin did not exhibit depression-like effect, nor it influenced the effect of amitriptyline in the forced swimming test. It did not impair cognitive performance in the Morris water Maze test. The present data demonstrate that ribavirin administered via systemic route possesses visceral and thermal anti-nociceptive properties. The ribavirin analgesic effect was partially reversed by naloxone, an opioid antagonist.

Effect of rosiglitazone and nateglinide on serum glucose and lipid profile alone or in combination with the biguanide metformin in diabetic rats

This study was designed to investigate the effect of 1 month treatment with nateglinide, rosiglitazone, metformin and their different combinations on streptozotocin (STZ) diabetic rats.

METHODS

Diabetes was induced by a single intraperitoneal injection of STZ at a dose 55 mg kg(-1). The plasma glucose, total lipid, cholesterol, triglyceride and protein components were measured before and 15 and 30 days after the administration of the antidiabetic agents.

RESULTS

After the treatment, a significant reduction was observed in fasting blood glucose levels in all groups. Rosiglitazone or metformin were found to exhibit a hypolipidaemic effect in diabetic rats when administered alone or in combination. In comparison, nateglinide, when used alone, resulted in a significant increase in cholesterol and total lipid levels. This effect was masked when nateglinide was administered concurrently with metformin and hypolipidaemic effect was noticed.

CONCLUSIONS

Results from this study suggest that compared with nateglinide, rosiglitazone has a more favorable effect on the lipid profile in STZ-induced diabetes in rats.

Pharmacological investigation of trimetazidine in models of inflammation, pain and gastric injury in rodents

The antinociceptive, anti-inflammatory and gastric effects of trimetazidine (2,3,4-trimethoxybenzyl-piperazine dihydrochloride), a novel anti-ischaemic compound, were evaluated in various animal models. In acute pain models, namely acetic acid-induced writhing, hot-plate assay, tail electric stimulation test, capsaicin-induced pain and the formalin test, trimetazidine (1.8-7.2 mg/kg, i.p.) showed marked antinociceptive effects. Trimetazidine did not produce any behavioural impairment as revealed by the mouse rotarod. The inhibition of writhing response by trimetazidine was reduced by yohimbine, theophylline (and to a certain extent by sulpiride) but not by prazosin, guanethidine, naloxone, atropine, propranolol, haloperidol, domperidone, clozapine, glibenclamide or caffeine. The carrageenan-evoked acute paw oedema was reduced by 19.2-21.2 and 17-18.6% by 3.6 and 7.2 mg/kg trimetazidine, respectively. The drug did not alter the oedema-suppressive effect of indomethacin or dexamethasone, but reduced that of rofecoxib. Trimetazidine at 7.2 mg/kg reduced immobility time in Porsolt's forced-swimming test by 28.9%. The acute gastric mucosal lesions evoked by indomethacin in the rat were inhibited in a dose-dependent manner by co-administration of trimetazidine. In anesthetized rats, trimetazidine potentiated the gastric acid secretory response. This study indicates that trimetazidine possesses antinociceptive and gastric protective properties. The antinociceptive properties of trimetazidine are likely to be centrally mediated, but do not involve opioid pathways.

A study of unfractionated and low molecular weight heparins in a model of cholestatic liver injury in the rat

Forty-eight rats with biliary obstruction induced by double ligation and section of the common bile duct were randomly and blindly assigned to receive subcutaneous injection of either conventional heparin sodium (1000IU kg(-1)), three already marketed low molecular weight heparin (LMWH) preparations: nadroparin (1000 anti-Xa IU kg(-1)), tinzaparin (1000 anti-Xa IU kg(-1)), enoxaparin (180 anti-Xa IU kg(-1)) or saline. Drugs were administered once a day, starting 7 days after surgery and continued for 3 weeks. At the end of the treatment period, rats were killed and analyzed for blood biochemistry and liver pathology. Liver fibrosis was assessed by image analysis. Data indicated that treatment with nadroparin decreased plasma total bilirubin, serum alkaline phosphatase (ALP) and gamma glutamyltransferase (GGT) levels by 80.3, 70.7 and 42%, compared with bile duct ligated (BDL) control values. The reduction in plasma total protein observed in BDL controls was prevented by nadroparin. Enoxaparin-treated rats showed significant reduction in plasma total bilirubin and alanine aminotransferase levels by 32.5 and 38.4% versus BDL controls. Liver necrosis evaluated histologically was significantly reduced in the nadroparin- and enoxaparin-treated rats. Morphometric analysis showed significant reduction in fibrosis on nadroparin and enoxaparin treatment: area of fibrosis: 1.66 +/- 0.17% and 14.03 +/- 1.1% versus 18.94 +/- 2.4% (P<0.05); nadroparin and enoxaparin versus BDL control. By contrast, neither conventional heparin nor tinzaparin prevented the bile duct ligation-induced liver damage as indicated by increased plasma aminotransferases, ALP and GGT concentrations and the histological evidence of necrosis. Total serum bilirubin was increased by 27.5% in rats treated with conventional heparin, while ALP and GGT levels were 38.6 and 31.4% higher after tinzaparin treatment versus BDL controls. Significant increase in the area of fibrosis was observed after tinzaparin treatment compared to BDL control group. Results suggest a beneficial effect for nadroparin and enoxaparin in the therapy of patients with obstructive jaundice or cholestatic liver disorders. The present data from bile duct ligated rats suggest an antifibrotic effect for nadroparin and enoxaparin.

Evaluation of the anti-inflammatory, anti-nociceptive and gastric effects of Ginkgo biloba in the rat

Ginkgo biloba extract (GbE) was assessed in models of acute inflammation induced by carrageenan, formalin or capsaicin in the rat, in models of nociceptive pain, such as hot-plate (55 degrees C) latency, tail-electric stimulation assay and capsaicin-induced paw licking and in the model of acute gastric damage induced by indomethacin. The agent showed marked anti-inflammatory activity in the carrageenan model of paw oedema. When given subcutaneously (s.c.) (25 and 50 mg kg(-1)) 30 min before challenge, GbE inhibited paw oedema with a maximal effect of 43.7 and 56.9%, respectively, at 2h post-carrageenan. Significant inhibition of oedema was also observed when GbE (50 mg kg(-1), s.c.) was given 30 min after carrageenan challenge. The agent was also active p.o. in acute inflammation caused by carrageenan. The administration of GbE with indomethacin, rofecoxib, celecoxib, dexamethasone or melatonin resulted in an additive effect. GbE (50 mg kg(-1), s.c.) caused significant inhibition of formalin-induced paw oedema, but did not reduce the capsaicin-induced paw oedema. In tests of nociception, GbE (25, 50 or 100 mg kg(-1)) decreased in dose-dependent manner the capsaicin-induced hind paw licking time and was similarly effective in the hot-plate assay of nociception. In contrast, when assessed in the tail-electric stimulation test, GbE was only effective in the highest dose (100 mg kg(-1)). In pylorus-ligated rats, GbE (25 or 50 mg kg(-1)) increased gastric acid secretion, but reduced gastric mucosal damage caused by IND. Results suggest that GbE may be of clinical value as an anti-inflammatory and analgesic drug alone or in conjunction with NSAIDs.

Studies on the glycemic and lipidemic effect of monopril and losartan in normal and diabetic rats

The effects of the angiotensin-converting enzyme (ACE) inhibitor monopril and the angiotensin II receptor blocker losartan on serum glucose, protein levels and some serum lipid components were compared in normal and diabetic rats receiving oral antidiabetic drugs 'repaglinide or gliclazide'. The two antihypertensive agents, when administered concurrently with oral hypoglycemic agents 'repaglinide or gliclazide' in normal and diabetic rats exerted a significant hypoglycemic effect. Serum protein levels were mainly unaffected by the two antihypertensive drugs. Monopril and losartan exhibit a hypolipidemic effect in normal and diabetic rats when administered in combination with oral hypoglycemic agents 'gliclazide or repaglinide'. Monopril or losartan when used alone exerted insignificant effect in high density lipoprotein (HDL) in normal rats, while in combination with gliclazide or repaglinide caused a significant increase in HDL in normal rats. Concomitantly, monopril or losartan, when administered alone or in combination with repaglinide or gliclazide in diabetic rats exerted a significant increase in serum HDL. On the other hand, all the investigated drugs showed a significant decrease in serum low density lipoprotein (LDL) in normal and diabetic rats.

Studies on the anti-inflammatory effect of fluoxetine in the rat

The anti-inflammatory activity of fluoxetine, a selective serotonin reuptake inhibitor (SSRI), was studied on the carrageenan-induced paw inflammation in the rat. Fluoxetine (10-60 mg kg(-1)) given intraperitoneally (i.p.) 30 min before carrageenan, displayed marked anti-inflammatory activity, inhibiting paw oedema by 38.6-77.7% at 2 h post-carrageenan. Fluoxetine administered at time of carrageenan injection or 30 min after carrageenan challenge, markedly inhibited the paw oedema response. Rats administered daily fluoxetine (20 mg kg(-1), i.p.) showed significantly decreased inflammatory response to subplantar carrageenan when examined on the 5th and 14th day of fluoxetine injection. Fluoxetine (10 or 20 mg kg(-1), i.p.) co-administered with indomethacin (IND) (20 mg kg(-1), i.p.), celecoxib (10 mg kg(-1), i.p.) or rofecoxib (4.5 mg kg(-1), i.p.) before carrageenan reduced the anti-oedema effect of indomethacin or celecoxib, but had additive effect to that of rofecoxib. The anti-oedema effects of fluoxetine and melatonin or the tricyclic antidepressant imipramine were additive. In contrast, administration of both fluoxetine and the heterocyclic antidepressant trazodone had no greater anti-inflammatory effect than fluoxetine alone. The anti-oedema effect of fluoxetine was partially suppressed by the opioid antagonist naloxone (4 mg kg(-1), i.p.). Fluoxetine (360 or 720 microg per paw) given into the rat paw with carrageenan reduced the oedema response by 25.4 and 35.3% 4 h post-carrageenan, respectively. It is suggested that fluoxetine alone or co-administered with either imipramine or melatonin would be of benefit in the sitting of neuropathic or inflammatory pain conditions. Both the serotonergic and the opioid systems are likely to be involved in the modulating action of fluoxetine on peripheral inflammation.

Evaluation of the anti-inflammatory and anti-nociceptive effects of different antidepressants in the rat

The present study was designed to compare the anti-inflammatory and anti-nociceptive effects of different classes of antidepressant drugs on the carrageenan paw oedema and tail-electric stimulation assays in the rat. Drugs were intraperitoneally administered 30 min prior to carrageenan or nociceptive testing. The non-selective noradrenaline (NA) and serotonin (5-HT) reuptake inhibitors imipramine, amitriptyline and clomipramine displayed anti-inflammatory activity in the carrageenan model of paw inflammation. The maximal degree of oedema inhibitions seen with these agents were 28.8, 41.5 and 46.8% for 5, 10 and 20 mg kg(-1) amitriptyline, 26.2, 38.2 and 51.4% for 3.75, 7.5 and 15 mg kg(-1) imipramine and 51.2 and 54.1% for 16 and 32 mg kg(-1) clomipramine, respectively. The heterocyclic agent trazodone significantly inhibited paw oedema by 46 and 41% at 1 and 2h after dosing at the highest dose (40 mg kg(-1)) examined. Fluoxetine, a selective 5-HT reuptake inhibitor (SSRI) caused dose-related reduction of paw oedema, with 20.7% inhibition at the dose of 10 mg kg(-1). In contrast, sertraline, another SSRI caused dose-dependent enhancement of paw oedema. All antidepressant drugs in the study showed anti-nociceptive properties in the tail-electric stimulation assay with amitriptyline and trazodone being the most effective in this respect. Taken together, data in the present study confirm anti-inflammatory and anti-nociceptive effect for some antidepressant drugs and indicate that SSRIs differently affects inflammation.

The anti-inflammatory effects of the phosphodiesterase inhibitor pentoxifylline in the rat

The present study aimed to evaluate the anti-inflammatory effects of pentoxifylline (PTX), a non-specific phosphodiesterase inhibitor in the rat. Acute inflammation was induced by subplantar injection of carrageenan (1%) in the rat hind paw. Results showed that intraperitoneal (i.p.) administration of PTX (36 or 72 mg kg(-1)) 30 min prior to carrageenan reduced the paw oedema response in dose-dependent manner with a maximal effect of 18.9 and 40.1%, respectively, at 2h post-carrageenan (P<0.001 and <0.001 at respective doses). Theophylline given at equimolar doses (29.9 or 45.8 mg kg(-1), i.p.) did not reduce the oedema response. With higher doses of PTX (144-300 mg kg(-1), i.p.) the anti-oedema effect of the drug was more pronounced, but mainly confined to the first 2h following carrageenan injection and decreasing rapidly thereafter. PTX (72 mg kg(-1), i.p.) given 30 min after carrageenan challenge reduced the oedema response by 24.7 and 26.2% at 1 and 2h after dosing (P<0.05 and <0.05, respectively). PTX (36 or 72 mg kg(-1), i.p.) co-administered with indomethacin (5 mg kg(-1), i.p.) 30 min before carrageenan had little modulatory effect on the anti-oedema effect of indomethacin, but the higher dose of PTX (144 mg kg(-1), i.p.) reduced the anti-inflammatory effect of indomethacin by 24% at 4h post-carrageenan. PTX (72 mg kg(-1), i.p.) enhanced the anti-oedema effect of the selective COX-2 inhibitor celecoxib (33 mg kg(-1), i.p.) by 55.1% at 4h post-carrageenan. In contrast, the higher dose of PTX (144 mg kg(-1), i.p.) reduced the anti-oedema effect of celecoxib by 46.8% at 4h post-carrageenan. PTX (36 or 72 mg kg(-1)) enhanced the anti-oedema effect of dexamethasone (0.1 mg kg(-1)) with maximal effect of 76 and 104.8% at 2h post-carrageenan (P<0.01 and <0.01 for respective doses). PTX (0.6 mg per paw) given with carrageenan into the rat hind paw reduced the oedema response with a maximal effect of 33.4% at 1h following carrageenan. PTX (0.6 mg per paw) given in the contralateral hind paw reduced the carrageenan-induced paw oedema for 1h by 32.2%. Thus, PTX, when given at doses comparable to those used in man for treatment of circulatory disorders displayed anti-inflammatory in vivo and enhanced the anti-inflammatory effect of a selective COX-2 inhibitor or dexamethasone. PTX may have therapeutic potential as anti-inflammatory agent either alone or in combination with non-steroidal anti-inflammatory drugs or with steroids. There is also an intriguing possibility for the use of topical preparations for the management of local inflammatory conditions.

Studies on the anti-inflammatory and anti-nociceptive effects of melatonin in the rat

The present study aimed to evaluate the anti-inflammatory and anti-nociceptive effects of melatonin in the rat. Acute inflammation was induced by sub-plantar injection of carrageenan (1%) in the rat hind paw. The rats received vehicle or drug 30 min before carrageenan administration and were evaluated for paw oedema at 1, 2, 3, and 4 h post-carrageenan. The induced inflammation and the formation of oedema were determined by measurement of the paw thickness. Nociception was tested by determining vocalization following electrical stimulation of the tail. Given intraperitoneally (i.p.) 30 min before carrageenan, melatonin caused significant and a dose-dependent reduction of hind paw swelling induced by carrageenan. At doses of 0.5 and 1 mg kg(-1), melatonin inhibited the carrageenan-induced oedema by 20.5 and 29.6% versus control values at 4 h post-carrageenan, respectively. Melatonin (0.5 and 1 mg kg(-1), i.p.) 30 min beforehand displayed anti-nociceptive effect in the electric stimulation of the rat tail test, increasing nociceptive thresholds to electrically-induced pain at 4 h post-treatment by 29.6 and 39.5%, respectively. Melatonin given simultaneously with the non-selective COX-1 and COX-2 inhibitor indomethacin (5 mg kg(-1), i.p.) 30 min prior to carrageenan, enhanced the anti-inflammatory effect of the latter in the carrageenan-induced paw oedema model by 23%. Melatonin (0.5 mg kg(-1), i.p.) increased the anti-nociceptive effect of indomethacin (5 mg kg(-1), i.p.). Meanwhile, the anti-inflammatory and anti-nociceptive effect of the highly selective COX-2 inhibitor rofecoxib (2.25 mg kg(-1), i.p.) was only slightly increased by melatonin administration at 0.5 mg kg(-1). Melatonin enhanced the anti-inflammatory effect of cysteamine (300 mg kg(-1), s.c.) in the carrageenan-induced paw oedema. Melatonin (20 and 40 microg per paw) given prior to carrageenan into the rat hind paw was devoid of anti-inflammatory effect. These results indicate that melatonin possesses anti-inflammatory and anti-nociceptive properties in the rat and enhance those of indomethacin. This effect is likely to be centrally mediated.