The Role of Hydrogen Sulfide in the Development of Tolerance and Dependence to Morphine in Mice.

OBJECTIVE: Hydrogen sulfide is an endogenous gaseous mediator that has been indicated to have a role in pain mechanisms. In this study, we aimed to detect brain and spinal cord hydrogen sulfide levels during different phases of tolerance and dependence to morphine and to determine the effects of inhibition of endogenous hydrogen sulfide production on the development of tolerance and dependence. METHODS: Morphine tolerance and dependence was developed by subcutaneous injection of morphine (10 mg/kg) twice daily for 12 days. Physical dependence was determined by counting the jumps for 20 min, which is a withdrawal symptom occurring after a single dose of naloxone (5 mg/kg) administered intraperitoneally (i.p.). Propargylglycine (30 mg/kg, i.p.), a cystathionine-γ-lyase inhibitor, and hydroxylamine (12.5 mg/kg, i.p.), a cystathionine-ß-synthase inhibitor, were used as hydrogen sulfide synthase inhibitors. The tail-flick and hot-plate tests were used to determine the loss of antinociceptive effects of morphine and development of tolerance. RESULTS: It was found that chronic and acute uses of both propargylglycine and hydroxylamine prevented the development of tolerance to morphine, whereas they had no effect on morphine dependence. Chronic and acute administrations of hydrogen sulfide synthase inhibitors did not exert any difference in hydrogen sulfide levels in brain and spinal cords of both morphine-tolerant and -dependent animals. CONCLUSION: It has been concluded that hydrogen sulfide synthase inhibitors may have utility in preventing morphine tolerance.

Endocannabinoid and N-acylethanolamide levels in rat brain and spinal cord following systemic dipyrone and paracetamol administration.

The cannabinoid system has been suspected to play a role in the mechanisms of action of dipyrone and paracetamol. Our purpose was to measure the local endocannabinoid and N-acylethanolamide levels in the brain and spinal cord of rats following dipyrone and paracetamol administration. Nociception was assessed 1, 5, and 12 h following drug injections in Wistar rats, using tail-flick and hot-plate tests. The antinociceptive effects of dipyrone (150, 300, and 600 mg/kg, i.p.) and paracetamol (30, 100, and 300 mg/kg, i.p.) were observed. After administration of the highest doses of dipyrone and paracetamol, endocannabinoid (N-arachidonoylethanolamide (AEA), 2-arachidonoylglycerol (2-AG)) and N-acylethanolamide (palmitoylethanolamide (PEA), oleoylethanolamide (OEA)) levels were measured in the periaqueductal gray (PAG), rostral ventromedial medulla (RVM), and spinal cords of rats using tandem mass spectrometry with liquid chromatography. Increased 2-AG levels were observed in the PAG and the RVM 12 h after paracetamol injection; dipyrone exerted no action on 2-AG levels. Analgesic administrations led to a reduction in AEA levels in the RVM and spinal cord; similar decreases in PEA and OEA levels were observed in the RVM and the spinal cord. Dipyrone and paracetamol administrations appear to exert complicated effects on endocannabinoid and N-acylethanolamide levels in rats.

Methylene blue increases contralateral testicular ischaemia-reperfusion injury after unilateral testicular torsion.

1. Testicular ischaemia-reperfusion injury is commonly seen in childhood. Infertility occurs in 25% of patients after unilateral testicular ischaemia. It is has been reported that methylene blue has a positive effect in the reparation of ischaemia-reperfusion injury in different tissues. Therefore, we hypothesized that methylene blue may prevent the hazardous effects of ischaemia-reperfusion injury in testicular tissue after unilateral testicular torsion. 2. Thirty-two prepubertal Wistar-albino rats were divided into four groups. Testicular torsion was created by rotating the right testis 720 degrees in a clockwise direction for 5 h in all groups except for Group C, which was the sham control group. In Group T, bilateral orchiectomy was performed following the torsion period. In Group TD, both testes were removed 5 days after the torsion period. In Group MB, methylene blue (1 mg/kg, i.p.) was administered 40 min before detorsion and once daily over 5 days; then, both testes were harvested. Tissue levels of malondialdehyde (MDA), serum levels of creatine kinase (CK), mean testicular biopsy score (MTBS) and mean seminifer tubule diameter (MSTD) were determined. 3. There was a significant difference in MTBS between Groups T and TD (P < 0.05) in both ipsilateral and contralateral testes. In the contralateral testis, treatment with methylene blue decreased MTBS and MSTD (P < 0.05) and increased MDA levels (P < 0.05). In Group T, mean serum CK concentrations were higher than in any of the other groups (P < 0.05). 4. After 5 h of unilateral testicular torsion and a 5 day reperfusion period, serious tissue damage occurred on both the ipsilateral and contralateral sides. Serum CK concentrations may be an indicator for ischaemia, but not for ischaemia-reperfusion injury. Contrary to our hypothesis, methylene blue increased contralateral testicular damage after unilateral testicular torsion and exacerbated oxidative events.

Effect of curcumin on ipsilateral and contralateral testes after unilateral testicular torsion in a rat model.

OBJECTIVE: The aim of the study was to determine the protective effect of curcumin on testicular ischemia-reperfusion (I/R) injury. MATERIALS AND METHODS: 32 male rats were divided into four groups (n = 8): group 1: control; group 2: ischemia; group 3: I/R, and group 4: I/R+CUR. Curcumin (150 mg/kg, p.o.) was administered before 30 min of reperfusion in group 4. Malondialdehyde (MDA) levels, Johnsen's testicular biopsy scores, and mean seminiferous tubule diameter measurements were evaluated in testes. In addition, endothelial nitric oxide synthase (eNOS) and inducible nitric oxide synthase (iNOS) expressions were evaluated immunohistochemically. RESULTS: MDA levels in control groups were significantly lower than other groups in ipsilateral and contralateral testes. Johnsen's scores in the control group were significantly higher than in other groups. MDA levels and Johnsen's scores in the I/R+CUR group were similar to the ischemia and I/R groups in ipsilateral and contralateral testes. The immunoreactivity of iNOS and eNOS were increased in I/R ipsilateral testicular groups. After I/R, iNOS and eNOS expression increased slightly in contralateral groups. Additionally, the curcumin treatment decreased iNOS and eNOS immunoreactivity in ipsilateral and contralateral testes. CONCLUSION: The results suggest that curcumin did not protect the unilateral nor contralateral testes. This observation may depend on inhibition of iNOS and eNOS due to inhibition of the antioxidant, anti-inflammatory effects of nitric oxide.

Antihyperalgesic, but not antiallodynic, effect of melatonin in nerve-injured neuropathic mice: Possible involvements of the L-arginine-NO pathway and opioid system.

The present study was undertaken to determine the effects of intracerebroventricular (i.c.v.) and intraperitoneal (i.p.) melatonin on mechanical allodynia and thermal hyperalgesia in mice with partial tight ligation of the sciatic nerve, and how the nitric oxide (NO) precursor l-arginine and the opiate antagonist naloxone influence this effect. A plantar analgesic meter was used to assess thermal hyperalgesia, and nerve injury-induced mechanical hyperalgesia was assessed with von Frey filaments. 1-5 weeks following the surgery, marked mechanical allodynia and thermal hyperalgesia developed in neuropathic mice. Intracerebroventricular and intraperitoneal melatonin, with its higher doses, produced a blockade of thermal hyperalgesia, but not mechanical allodynia. Administration of both l-arginine and naloxone, at doses which produced no effect on their own, partially reversed antihyperalgesic effect of melatonin. These results suggest that although it has different effects on neuropathic pain-related behaviors, melatonin may have clinical utility in neuropathic pain therapy in the future. It is also concluded that l-arginine-NO pathway and opioidergic system are involved in the antihyperalgesic effect of melatonin in nerve-injured mice.

Testicular torsion, oxidative stress and the role of antioxidant therapy.

Testicular torsion is a urological syndrome caused mainly by a twist in the spermatic cord. It constitutes a surgical emergency and affects newborns, children and adolescent boys. The torsion must be treated promptly to avoid loss of function of ipsilateral and contralateral testis. This syndrome often leads to infertility of the ipsilateral (torted) and contralateral (not torted) testis,but the mechanisms of cellular injury remain still incompletely understood. The primary pathophysiologic event in testicular torsion is ischemia followed by reperfusion; thus, testicular torsion/detorsion is an ischemia/reperfusion (I/R) injury to the testis. Testicular torsion and detorsion causes morphological and biochemical changes by both ischemia and reperfusion of the tissues. These I/R injury is associated with overgeneration of reactive oxygen species (ROS) and reactive nitrogen species (RNS), and also with a common mechanism to other organs such as brain, heart and kidneys. Although the results are not conclusive and the molecular mechanism by which antioxidants control male fertility have not yet been clearly identified, several antioxidant enzymes and antioxidant drugs have been studied to prevent such I/R injury in testis. As a result, antioxidant therapy may represent a new non-hormonal option within a broader therapeutic strategy in men with ROS-mediated infertility such as testicular torsion.

Gastroprotective effect of L-carnitine on indomethacin-induced gastric mucosal injury in rats: a preliminary study.

BACKGROUND: Numerous studies have shown that use of nonsteroidal anti-inflammatory drugs (NSAIDs) is associated with various gastric mucosal lesions, collectively referred to as NSAID gastropathy, but the detailed mechanism is still not properly understood. L-carnitine, a vitamin-like substance, is a naturally occurring enzymatic antioxidant with a potent free oxygen radical quencher and scavenger capacity; it protects the biological membranes against lipid peroxidation. It has recently been shown that L-carnitine has a gastroprotective effect on gastric mucosa. To our knowledge, the role of L-carnitine on NSAIDs-induced gastric mucosal injury is undefined. AIM: The aim of the present study was to determine the gastroprotective effect of L-carnitine on indomethacin-induced gastric mucosal lesions in the rat stomachs. MATERIAL AND METHODS: In our study, gastric mucosal injury was induced by the intragastric administration of indomethacin (30 mg/kg). L-carnitine (10, 50, 100 mg/kg) was given to rats by gavage 30 min before the indomethacin administration. The animals were killed 3 h after administration of indomethacin. The stomach of each animal was removed. Mucosal damage was evaluated with macroscopic study and histopathologically. RESULTS: The intragastric administration of indomethacin induced hyperemia and hemorrhagic erosions in the rat stomachs. L-carnitine significantly prevented gastric ulcerogenesis induced by indomethacin and decreased the ulcer index macroscopically and histopathologically. CONCLUSION: L-carnitine decreases indomethacin-induced gastric mucosal injury and this gastroprotective effect may be attributed to its well-known antioxidant effect.

Oxidative stress, male infertility and the role of carnitines.

Oxidative stress has been shown to be a major cause of male infertility; a large proportion of infertile men have elevated levels of seminal reactive oxygen species (ROS). High concentrations of ROS cause sperm pathology such as ATP depletion leading to insufficient axonemal phosphorylation, lipid peroxidation and loss of motility and viability. L-carnitine, a naturally occurring enzymatic antioxidant, is a necessary factor in the utilization of long chain fatty acids to produce energy. Furthermore, it plays a pivotal role in the maturation of spermatozoa within the male reproductive tract. Epididymal plasma contains the highest levels of L-carnitine found in the human body, and initiation of sperm motility occurs in parallel to L-carnitine increase in the epididymal lumen. It is known that L-carnitine prevents the formation of ROS, scavenges free radicals and protects cells from peroxidative stress. Moreover, it plays a key role in sperm metabolism by providing readily available energy for use by spermatozoa, which positively affects sperm motility, maturation and the spermatogenic process. L-carnitine and its derivatives have been proposed recently for treatment of male infertility, and a number of controlled and uncontrolled human and animal studies have been conducted to indicate their possible application. As a result, antioxidant therapy with carnitines may represent a new nonhormonal option within a broader therapeutic strategy in men with ROS-mediated infertility.

Ibuprofen and Alzheimer's disease.

There is epidemiological observation that long-term treatment of patients suffering from rheumatoid arthritis with ibuprofen results in reduced risk and delayed onset of Alzheimer's disease (AD). Chronic central nervous system inflammation in AD brain is implicated in the pathology, but how ibuprofen impacts the pathogenic AD pathways is unclear. Ibuprofen, a commonly used over-the-counter nonsteroidal anti-inflammatory drug (NSAID) that is a cyclooxygenase (COX)-1 and COX-2 inhibitor as well as a peroxisome proliferator-activated receptor (PPAR) agonist, decreases the production of nitric oxide (NO), protects neurons against glutamate toxicity and decreases the production of proinflammatory cytokines. Ibuprofen crosses the blood brain barrier and suppresses neuritic plaque pathology and inflammation in AD brain. Furthermore, ibuprofen is a potent free radical scavenger, and it could reduce lipid peroxidation and free radical generation. Because of neuroprotective activity, relative safety, and its long history of use, ibuprofen is currently being developed for clinical use in AD. Ibuprofen may be a promising new therapeutic avenue for the treatment of neurodegenerative diseases such as AD.

The Protective Effect of Curcumin on Ionizing Radiation-induced Cataractogenesis in Rats.

OBJECTIVE: The aim of the study was to determine the protective effect of curcumin against ionizing radiation-induced cataract in the lens of rats. MATERIAL AND METHODS: Rats were divided into six groups. Group 1: Control, Group 2: Dimethyl sulfoxide (DMSO), Group 3: DMSO+curcumin, Group 4: Irradiation, Group 5: Irradiation+DMSO, Group 6: Irradiation+DMSO+curcumin. A 15 Gy total dose was given to 4, 5, 6 groups for radiation damage. Curcumin (100 mg/kg) was dissolved in DMSO and given by intragastric intubation for 28 days. At the end of the experiment, lenses were graded and enucleated. The lenticular activity of the antioxidant enzymes, total antioxidant and glutathione peroxidase (GSH-Px), and the malondialdehyde (MDA) were measured. RESULTS: 100% Cataract was seen in the irradiation group. Cataract rate fell to 40% and was limited at grade 1 and 2 in the curcumin group. In the irradiation group, antioxidant enzyme levels were decreased, MDA levels were increased. There was an increase in antioxidant enzyme levels and a significant decrease in MDA in the group which was given curcumin. CONCLUSION: Curcumin has antioxidant and radioprotective properties and is likely to be a valuable agent for protection against ionizing radiation. Hence, it may be used as an antioxidant and radioprotector against radiation-induced cataractogenesis.

Protective effects of L-carnitine and alpha-lipoic acid in rats with adjuvant arthritis.

Free radicals play an important role in the pathophysiology of adjuvant arthritis. The purpose of this study was to assess the efficacy of L-carnitine (LC) and alpha-lipoic acid (alpha-LA) which are known to have antioxidant effects, in the treatment of adjuvant arthritis. Arthritis model was created by the administration of complete Freund's adjuvant (CFA) in 32 of 40 male Sprague-Dawley rats. The rats were divided into five groups. Rats in Group I served as controls and received 0.1 ml kg(-1) saline. Group II received only 0.1 ml of CFA and served as the CFA-control for the other groups. Groups III-V, after being injected with CFA, were treated with LC, alpha-LA or diclofenac, respectively. Levels of malondialdehyde (MDA) and glutathione (GSH) were measured in plasma samples. Enzyme activities of superoxide dismutase (SOD) and glutathione peroxidase (GPx) were measured. The paws of rats were evaluated histopathologically to investigate the anti-inflammatory effects. TNF-alpha levels were measured for the evaluation of inflammation. In Group II plasma MDA increased, levels of glutathione decreased, enzyme activities of SOD and GPx decreased. Histopathological damage increased in the paws of the rats in this group. MDA levels decreased in Groups III-V when compared with Group II. GSH levels significantly increased in Group III and IV than Group V. SOD activity of Group IV was higher than Group III and V. TNF-alpha levels were significantly lower in Group IV and V. LC and alpha-LA seemed to have protective effects against oxidative damage in adjuvant arthritis model.

Protective effect of L-carnitine on testicular ischaemia-reperfusion injury in rats.

Testicular torsion is a urological emergency referred to as 'acute scrotum', because inappropriate treatment can lead to male subfertility and infertility. A possible cause of testicular damage is the ischaemia-reperfusion (I/R) injury attributed to oxygen free radicals. L-carnitine, a vitamin-like antioxidant, plays a pivotal role in the maturation of spermatozoa within the reproductive tract. The aim of the present paper was to determine the protective effect of L-carnitine on testicular I/R-induced injury. Thirty-two male rats were divided into 4 groups (n = 8). Testicular torsion was created by rotating the right testis 720 degrees in a clockwise direction. Group 1: sham-operated control; group 2: ischaemia; group 3: I/R; group 4: ischaemia-L-carnitine treatment-reperfusion group. L-carnitine (500 mg kg(-1), intraperitoneally) was administered before 30 min of detorsion in Group 4. After torsion (5 h) and detorsion (5 h), bilateral orchidectomy was performed. The malondialdehyde (MDA) level was evaluated in testes. Histopathologically, Johnsen's spermatogenesis criteria and mean seminiferous tubule diameter (MSTD) measurements were used. Testicular MDA levels were higher in the torsion group compared to the sham-control group (p < 0.05). Detorsion (reperfusion) caused a further increase in MDA levels (p < 0.05). Pretreatment with L-carnitine prevented a further increase in MDA levels (p < 0.05). Histologically, torsion caused some separation among germinal cells in the seminiferous tubules, which became much more prominent in the I/R group but was attenuated with L-carnitine pretreatment. In conclusion, L-carnitine pretreatment may have a protective effect in experimental testicular torsion-detorsion model in rats by its well-known antioxidant potential.

Protective effects of ibuprofen on testicular torsion/detorsion-induced ischemia/reperfusion injury in rats.

The aim of this study was to investigate the protective effect of ibuprofen on testicular torsion/detorsion-induced ischemia/reperfusion (I/R) injury. A total of 48 prepubertal male Wistar albino rats were divided into two models: early and late orchiectomy. Testicular torsion was created by rotating the right testis 720 degrees in a clockwise direction. The ischemia period was 5 h and orchiectomy was performed after 5 h of detorsion in the early orchiectomy model (EOM). In the late orchiectomy model (LOM), the ischemia period was 5 h and orchiectomy was performed after 7 days of detorsion. In the EOM, ibuprofen (70 mg/kg, po) was administrated only once, 40 min prior to detorsion. In the LOM, ibuprofen (70 mg/kg, po) was administered 40 min before detorsion, once daily for 7 days. Bilateral orchiectomy was performed in all groups to measure the tissue levels of malondialdehyde (MDA) and to microscopically investigate light and electrons. The presence of endothelial nitric oxide synthase (eNOS) activity was shown with immunohistochemical studies. Spermatogenesis and mean seminiferous tubule diameter (MSTD) were significantly decreased in ipsilateral and contralateral testis when both early and late I/R groups were compared to the sham groups. Furthermore, ibuprofen-treated animals showed an improved histological appearance in both models of testicular torsion. Ibuprofen treatment prevented lipid peroxidation resulting in decreased MDA accumulation in the testes of both models. After I/R, eNOS immunoreactivity was increased in the testicular tissues. Ibuprofen treatment decreased eNOS immunoreactivity in the germ cells of the tubules in the contralateral testes, but intense eNOS immunoreactivity was shown in the ipsilateral testes of the LOM. Electron microscopy of the testes of rats demonstrated that ibuprofen pretreatment was particularly effective in preventing the mitochondrial degeneration in both Sertoli and spermatid cells in the LOM. Because of its anti-inflammatory and antioxidant effects, ibuprofen pretreatment may have protective effects in the experimental testicular torsion/detorsion model in rats.

Rosiglitazone, an agonist of peroxisome proliferator-activated receptor-gamma, prevents contralateral testicular ischaemia-reperfusion injury in prepubertal rats.

1. Rosiglitazone plays a positive role in the reparation of ischaemia-reperfusion (I/R) injury in different tissues. Thus, we examined its biochemical and histological effects on the contralateral testes to determine whether exogenous rosiglitazone affords any protection against testicular damage. 2. Forty-eight prepubertal male Wistar-Albino rats were divided into six groups. Testicular torsion was created by rotating the right testis 720 degrees in a clockwise direction for 5 h in all groups except group I, which was the sham-control group. In group II, bilateral orchiectomy was performed following the torsion period. After detorsion both testes were removed in the fifth hour in group III and on the seventh day in group IV. In group V, one-shot rosiglitazone (4 mg/kg) was administered 40 min before detorsion and both testes were removed following the torsion period. In group VI, rosiglitazone was administered (4 mg/kg) 40 min before detorsion and for 7 days, and then both testes were harvested. The tissue levels of malondialdehyde (MDA) were measured and mean testicular biopsy score (MTBS) and mean seminiferous tubule diameter (MSTD) were examined. Immunoexpression of endothelial nitric oxide synthase (eNOS) in testes tissues was investigated by immunohistochemical studies. 3. In the contralateral testis, the MTBS and MSTD values of group VI were significantly higher than those in group IV. Immunohistochemically, mild eNOS immunostaining was present in the germ cells of the contralateral testes in group IV after I/R. In group VI, intense eNOS immunoreactivity was seen in the contralateral testes. 4. Rosiglitazone reduces contralateral testicular damage formed after unilateral testicular torsion and alleviates the oxidative events.

L-carnitine inhibits ethanol-induced gastric mucosal injury in rats.

L-carnitine is a quaternary amine that is essential for the normal oxidation of long-chain fatty acids by mitochondria. It is known that L-carnitine and its derivatives prevent the formation of reactive oxygen species, scavenge free radicals and protect cells from peroxidative stress. Oxygen-derived free radicals and lipid peroxidation products play a critical role in the pathogenesis of ethanol-induced gastric mucosal injury. The aim of the present study was to determine the effect of L-carnitine on lipid peroxidation induced by ethanol in the rat stomach. In our study, gastric mucosal injury was induced by the intragastric administration of 1 ml of absolute ethanol. Test compounds were given to rats by gavage 30 min before the ethanol administration. The animals were killed 60 min after the administration of ethanol. The stomach of each animal was removed. Mucosal damage was evaluated by macroscopic examination, histological analysis and by measurement of lipid peroxidation and glutathione activity. The intragastric administration of ethanol induced hyperemia and hemorrhagic erosions in the rat stomachs. L-carnitine significantly prevented gastric ulcerogenesis induced by ethanol and decreased the ulcer index. Plasma and gastric lipid peroxidation that was increased significantly by ethanol was decreased after treatment with L-carnitine. Ethanol treatment decreased significantly the gastric glutathione levels, and pretreatment with L-carnitine increased them significantly. Based on these data, the beneficial effects of L-carnitine on ethanol-induced gastric mucosal injury may be attributed to its antiperoxidative effects.