Celecoxib inhibits acute edema and inflammatory biomarkers through peroxisome proliferator-activated receptor-γ in rats.

OBJECTIVES: Celecoxib (CLX), a selective cyclooxygenase-II (COX-2) inhibitor, has been used for management of several inflammatory disorders. The present study aimed to explore the role of peroxisome proliferator-activated receptor-gamma (PPARγ) in CLX induced anti-inflammatory response in rats. MATERIALS AND METHODS: Carrageenan-induced paw edema was used as an acute inflammation model. Rats were treated with various intra-peritoneal (IP) doses of CLX (0.3-30 mg/kg) and pioglitazone (PGL; PPARγ agonist, 1-20 mg/kg) alone or in combination. Amounts of PPARγ, COX-2, and prostaglandin E2 (PGE2) in paw tissue, and extents of TNF-α and IL-10 in serum were measured. Moreover, levels of oxidative stress parameters as malondialdehyde (MDA), glutathione (GSH), glutathione peroxidase (GPx) activity in the cortex, hippocampus, and paw tissues were also determined. RESULTS: CLX and PGL dose-dependent administration (IP), alone or in combination reduced carrageenan-induced paw edema. Further, both agents, alone or in combination, reduced either the amounts of COX-2, PGE2, and MDA in the inflamed paw, and the levels of TNF-α in serum which were elevated by carrageenan. Both drugs also increased both levels of PPARγ, GSH, GPx activity in paws, and serum levels of IL-10 that were decreased by carrageenan. Intraplantar injection of GW-9662 (IPL), a selective PPARγ antagonist, inhibited all biochemical modifications caused by both single and combined drug treatments. CONCLUSION: CLX produced its anti-inflammatory effects probably through PPARγ receptor activation. Besides, increased anti-inflammatory effects of CLX with PGL suggest that their combination might be applied for the clinical management of inflammation especially in patients suffering from diabetes.

Venlafaxine inhibits naloxone-precipitated morphine withdrawal symptoms: Role of inflammatory cytokines and nitric oxide.

Opioid-induced neuroinflammation plays a role in the development of opioid physical dependence. Moreover, nitric oxide (NO) has been implicated in several oxidative and inflammatory pathologies. Here, we sought to determine whether treatment with venlafaxine during the development of morphine dependence could inhibit naloxone-precipitated withdrawal symptoms. The involvement of neuro-inflammation related cytokines, oxidative stress, and L-arginine (L-arg)-NO pathway in these effects were also investigated. Mice received morphine (50 mg/kg/daily; s.c.), plus venlafaxine (5 and 40 mg/kg, i.p.) once a day for 3 consecutive days. In order to evaluate the possible role of L-arg-NO on the effects caused by venlafaxine, animals received L-arg, L-NAME or aminoguanidine with venlafaxine (40 mg/kg, i.p.) 30 min before each morphine injection for 3 consecutive days. On 4th day of experiment, behavioral signs of morphine-induced physical dependence were evaluated after i.p. naloxone injection. Then, brain levels of tissue necrosis factor-alpha (TNF-α), interleukin-1-beta (IL-1ß), interleukin-6 (IL-6), interleukin-10 (IL-10), brain-derived neurotrophic factor (BDNF), NO and oxidative stress factors including; total thiol, malondialdehyde (MDA) contents and glutathione peroxidase (GPx) activity were determined. Co-administration of venlafaxine (40 mg/kg) with morphine not only inhibited the naloxone-precipitated withdrawal signs including jumping and weight loss, but also reduced the up-regulation of TNF-α, IL-1ß, IL-6, NO and MDA contents in mice brain tissue. However, repeated administration of venlafaxine inhibited the decrease in the brain levels of BDNF, total thiol and GPx. Pre-administration of L-NAME and aminoguanidine improved, while L-arg antagonized the venlafaxine-induced effects. These results provide evidences that venlafaxine could be used as a candidate drug to inhibit morphine withdrawal through the involvement of inflammatory cytokines and l-arginine-NO in mice.

Fluoxetine increases analgesic effects of morphine, prevents development of morphine tolerance and dependence through the modulation of L-type calcium channels expression in mice.

Here, we aimed to investigate the effects of fluoxetine on morphine-induced analgesia, as well as preventive effects of it on morphine induced tolerance and dependence in mice. We also elucidate the involvement of L-type Ca2+ channels in these phenomena. To induce morphine tolerance, mice were treated with morphine (50 mg/kg) for 3 consecutive days. To evaluate the involvement of the calcium channel in the effects of fluoxetine (5, 20 mg/kg), combination ineffective doses of the two L-type calcium channel blockers, nimodipine (5 mg/kg) or diltiazem (20 mg/kg) with flouxetine were used with each morphine dose. Nociceptive behavior was evaluated using hot-plate test, while physical dependence assessed by naloxone-precipitated withdrawal on the fourth day of experiment. The expression of Cav1.2 and Cav1.3 subunits of the L-type calcium channels in cortex and mesolimbic tissues were measured using western immunoassay. Results showed that co-administration of fluoxetine (20 mg/kg) with morphine increased its acute analgesia effect and prevented the induction of morphine antinociceptive tolerance and physical dependence in mice. Moreover, these effects was potentiated by pre-treatment with diltiazem or nimodipine. Results also showed up-regulation of the Cav1.3 and Cav1.2 expression in the cerebral cortex and mesolimbic regions through the development of morphine dependence. Moreover, chronic administration of fluoxetine with morphine reduced the observed up-regulation of Cav1.3 and Cav1.2 expression in cortex and mesolimbic tissues. Our data indicated that co-administering of fluoxetine with morphine could potentiate the antinociceptive effect of morphine, prevent morphine analgesia tolerance and attenuated the morphine withdrawal signs during induction phases. Moreover, we also pointed out for the first time the role of L-type Ca2+ channel channels in the modulatory effects of fluoxetine on the morphine-related effects.

Venlafaxine prevents morphine antinociceptive tolerance: The role of neuroinflammation and the l-arginine-nitric oxide pathway.

Opioid-induced neuroinflammation and the nitric oxide (NO) signal-transduction pathway are involved in the development of opioid analgesic tolerance. The antidepressant venlafaxine (VLF) modulates NO in nervous tissues, and so we investigated its effect on induced tolerance to morphine, neuroinflammation, and oxidative stress in mice. Tolerance to the analgesic effects of morphine were induced by injecting mice with morphine (50 mg/kg) once a day for three consecutive days; the effect of co-administration of VLF (5 or 40 mg/kg) with morphine was similarly tested in a separate group. To determine if the NO precursor l-arginine hydrochloride (l-arg) or NO are involved in the effects rendered by VLF, animals were pre-treated with l-arg (200 mg/kg), or the NO synthesis inhibitors N(ω)-nitro-l-arginine methyl ester (L-NAME; 30 mg/kg) or aminoguanidine hydrochloride (AG; 100 mg/kg), along with VLF (40 mg/kg) for three days before receiving morphine for another three days. Nociception was assessed with a hot-plate test on the fourth day, and the concentration of tumor necrosis factor alpha (TNF-α), interleukin-1beta (IL-1ß), interleukin-6 (IL-6), interleukin-10, brain-derived neurotrophic factor, NO, and oxidative stress factors such as total thiol, malondialdehyde content, and glutathione peroxidase (GPx) activity in the brain was also determined. Co-administration of VLF with morphine attenuated morphine-induced analgesic tolerance and prevented the upregulation of proinflammatory cytokines (TNF-α, IL-1ß, and IL-6), NO, and malondialdehyde in brains of mice with induced morphine tolerance; chronic VLF administration inhibited this decrease in brain-derived neurotrophic factor, total thiol, and GPx levels. Moreover, repeated administration of l-arg before receipt of VLF antagonized the effects induced by VLF, while L-NAME and AG potentiated these effects. VLF attenuates morphine-induced analgesic tolerance, at least partly because of its anti-inflammatory and antioxidative properties. VLF also appears to suppress the development of morphine-induced analgesic tolerance through an l-arg-NO-mediated mechanism.

Local antinociceptive action of fluoxetine in the rat formalin assay: role of l-arginine/nitric oxide/cGMP/KATP channel pathway.

The present study was conducted to evaluate the local antinociceptive actions of fluoxetine, a selective serotonin reuptake inhibitor, and the possible involvement of the l-arginine/NO/cGMP/KATP channel pathway in this effect using the formalin test in rats. To elucidate the underlying mechanisms, animals were pre-treated with l-NAME, aminoguanidine, methylene blue, glibenclamide, l-arginine, sodium nitroprusside, or diazoxide. Local ipsilateral, but not contralateral, administration of fluoxetine (10-300 µg/paw) dose-dependently suppressed flinching number during both early and late phases of the test, and this was comparable with morphine also given peripherally. Pre-treatment with l-NAME, aminoguanidine, methylene blue, or glibenclamide dose-dependently prevented fluoxetine (100 µg/paw)-induced antinociception in the late phase. In contrast, administration of l-arginine, sodium nitroprusside, and diazoxide significantly enhanced the antinociception caused by fluoxetine in the late phase of the test. However, these treatments had no significant effect on the antinociceptive response of fluoxetine in the early phase of the formalin test. Our data demonstrate that local peripheral antinociception of fluoxetine during the late phase of the formalin test could be due to activation of l-arginine/NO/cGMP/KATP channel pathway. The peripheral action of fluoxetine raises the possibility that topical application of this drug (e.g., as a cream, ointment, or jelly) may be a useful method for relieving the inflammatory pain states.

Venlafaxine Attenuates the Development of Morphine Tolerance and Dependence: Role of L-Arginine/Nitric Oxide/cGMP Pathway.

BACKGROUND: Severe pain reduces quality of life of patients with various diseases, often because chronic morphine therapy results in reduced analgesic effectiveness, or tolerance, leading to escalating doses and distressing adverse effects. Nitric oxide (NO) plays a role in morphine tolerance and dependence. OBJECTIVE: Venlafaxine, an antidepressant, is known to modulate nitric oxide (NO) pathway in nervous tissues. In the present study, the effect of systemic venlafaxine (VLF) on the development of morphine tolerance and dependence, acute morphine-induced antinociception, and the probable involvement of the L-arginine/NO/cGMP pathway in these effects were investigated in mice. METHODS: Animals developed tolerance to the antinociceptive effect of morphine (50 mg/kg, s.c. daily) for 3 consecutive days. NO modulators like L-NAME (NO synthase inhibitor) and L-Arginine (L-Arg, substrate for NO synthase), sildenafil (cGMP-PDE inhibitor) alone or in combination with venlafaxine were used. RESULTS: The results showed that i.p. administration of VLF (5-40 mg/kg) produced antinociceptive effect in a dose-dependent way. Pretreatment with L-Arg (200 mg/kg, i.p.) reversed the antinociception and L-NAME (30 mg/kg, i.p.) and sildenafil (10 mg/kg, i.p.) potentiated the antinociceptive effect. Moreover, co-administration of VLF in non-effective dose (5 mg/kg) with morphine, potentiated acute morphine-induced analgesia (5 mg/kg, s.c.). This effect was antagonized by L-arginine (200 mg/kg, i.p.) and potentiated by L-NAME (30 mg/kg, i.p.) and sildenafil (10 mg/kg, i.p.). On the other hand, VLF was prevented the development of morphine antinociceptive tolerance and dependence. These effects were antagonized by L-arginine (200 mg/kg, i.p.) and potentiated by L-NAME (30 mg/kg, i.p.) and sildenafil (10 mg/kg, i.p.). CONCLUSION: Our data suggest that the combination of VLF with morphine may be a relevant therapeutic implication to manage pain even when tolerance to morphine exists. Moreover, our data demonstrates the involvement of L-Arg/NO/cGMP pathway in the prevention of morphine tolerance and dependence by venlafaxine.

Systemic and local anti-nociceptive effects of simvastatin in the rat formalin assay: Role of peroxisome proliferator-activated receptor γ and nitric oxide.

This study aimed to determine the potential systemic and local anti-nociceptive effects of simvastatin (SIM) and the possible role of peroxisome proliferator-activated receptor gamma (PPARγ) and nitric oxide (NO) pathways using a formalin assay in rats. After allocation, rats were intraplantarly (i.pl.) treated with formalin solution (2.5%) and the flinching behaviors were recorded for 5 min (phase 1) and 15-60 min (phase 2). SIM was given intraperitoneally (i.p.) and i.pl. 30 and 20 min before test, respectively. Intraperitoneal administration of SIM attenuated the flinching number during both phases of the test. This effect of i.p. SIM was significantly reduced by L -NAME (NO synthase blocker, i.p.), but was augmented by L -arginine (NO precursor, i.p.) during both phases of the formalin assay. Moreover, the antinociception caused by i.p. SIM was blocked by GW-9662 (PPARγ antagonist) at dose 2 mg/kg (i.p.). In another experiment, concurrent ip administration of non-effective dose of simvastatin (5 mg/kg) with pioglitazone (PPARγ agonist; 10, 20 mg/kg) produced antinociception. However, pre-treatment with i.p. GW-9662 inhibited the enhanced antinociceptive effect of pioglitazone on SIM during the phase 2 of formalin assay. Results also showed that i.pl. SIM alone had no anti-nociceptive effects. However, significant anti-nociception was observed when SIM (i.pl.) co-administered with non-effective dose of pioglitazone. Moreover, the enhanced effect was antagonized by pre-treatment with i.pl. GW-9662. Our data suggest that SIM produced antinociception through systemic but not local route of administration in rats. Moreover, the antinociceptive effect of SIM is partly mediated through PPARγ receptors and NO pathway. © 2017 Wiley Periodicals, Inc.

Pharmacological evidence for systemic and peripheral antinociceptive activities of pioglitazone in the rat formalin test: Role of PPARγ and nitric oxide.

Nitric oxide (NO) is involved in numerous physiological processes of the central and peripheral nervous system. This study aimed to evaluate the involvement of PPARγ and NO pathway in the systemic and peripheral antinociceptive effect pioglitazone (Pio) using formalin test in rats. After allocation, rats were injected with 2.5% formalin solution and the flinching behaviors were recorded for 5min (phase 1) and 15-60min (phase 2). Pioglitazone was administered intraperitoneally (i.p.) at doses (10-50mg/kg) and intraplantarly (i.pl.) at doses (10-30µg/paw) 60 and 20min before test, respectively. To investigate the mechanism involved, rats were given GW-9662 (a PPARγ antagonist), L-NAME (NO synthase inhibitor), L-arginine (NO precursor), or l-NAME+GW-9662 along with pioglitazone. Results showed that both of i.p. and i.pl. routes of pioglitazone administration produced antinociception in both phases of formalin-induced pain. Antinociception caused by i.p. and i.pl. pioglitazone was blocked by GW-9662 at doses 2mg/kg (i.p.) and 3µg/paw (i.pl.) in both phases of the test, respectively. The antinociceptive effects of i.p. and i.pl. pioglitazone were significantly reduced by l-arginine, but were augmented by l-NAME in second phase of test. However, pre-treatment with GW-9662 inhibited the enhanced antinociceptive effect of l-NAME on pioglitazone in second phase of formalin test during i.p. and i.pl. administration. Furthermore, the antinociceptive effect of systemic pioglitazone was antagonized by i.pl. administration of GW-9662 (3µg/paw). Our data suggest that local and systemic antinociceptive activity of pioglitazone is mediated partly through PPARγ in collaboration with NO pathway. Moreover, the cumulative results suggest a close link of interaction between PPARγ and NO.

Potentiation of indomethacin-induced anti-inflammatory response by pioglitazone in carrageenan-induced acute inflammation in rats: Role of PPARγ receptors.

This study aimed to assess the interaction between anti-inflammatory effects of pioglitazone (peroxysome proliferator activated receptor-gamma (PPARγ) agonist, PGL), and indomethacin (cyclooxygenase (COX) inhibitor, IND) and to evaluate the possible underlying mechanisms. Paw edema induced by carrageenan was used to induce inflammation. Different doses of IND (0.3-10mg/kg) and PGL (1-20mg/kg) alone or in combination were administered intraperitoneally to rats. Paw tissue levels of PPARγ, COX-2, and prostaglandin E2 and serum levels of TNF-α and IL-10 were also estimated. Doses of IND and PGL showed a statistically significant anti-inflammatory effect. Combination of a non-effective dose of IND (0.3mg/kg) with increasing doses of PGL (1-10mg/kg) resulted in potentiated anti-inflammation and vise versa. IND, PGL and the combination were able to reduce the COX-2, PGE2 contents and TNF-α level. Moreover, all these treatments caused elevation in PPARγ levels and IL-10 levels. However, when the rats were pre-treated with GW-9662 (a selective PPARγ antagonist), all the anti-inflammation and alterations in the biochemical factors were antagonized. These results showed that PGL markedly enhanced the anti-inflammatory activity of IND and this effect mediated partly at least, through PPARγ. Possible mechanisms of the interaction were that PGL stimulates the PPARγ and inhibits COX-2 by those cytokines that trigger the PPARγ and also inhibit COX-2. This study suggests that combination therapy with pioglitazone and indomethacin may provide an alternative for the clinical control of inflammation especially in patients with diabetes.

Beneficial effects of ellagic acid against animal models of scopolamine- and diazepam-induced cognitive impairments.

Context In a previous study, it has been shown that ellagic acid (EA), a polyphenolic compound found in pomegranate and different berries, prevents cognitive and hippocampal long-term potentiation (LTP) impairments induced by traumatic brain injury in rats through antioxidant and anti-inflammatory mechanisms. Objective The present study was conducted to assess the potential of EA as a memory enhancer. Materials and methods The elevated plus maze (EPM) and passive avoidance (PA) paradigm were used to evaluate learning and memory parameters. Three doses (10, 30 and 100 mg/kg, i.p.) of EA were administered to animals. Memory impairment was induced by scopolamine treatment (0.4 mg/kg, i.p.) and/or diazepam (1 mg/kg, i.p.). Acquisition trials were carried out 30 min after scopolamine treatment and retention trials were performed for 5 min 24 h after the acquisition trials. Results EA at doses 30 and 100 mg/kg significantly reversed the amnesia induced by scopolamine (0.4 mg/kg, i.p.) in the EPM and PA tests in mice. Also, EA at doses 30 and 100 mg/kg significantly antagonized the amnesia induced by diazepam (1 mg/kg, i.p.) in EPM test in rats. Moreover, chronic administration of EA at dose 30 mg/kg ameliorated the memory deficit induced by diazepam (1 mg/kg, i.p.) in rats. Discussion and conclusion This study demonstrates that ellagic acid is effective in preventing scopolamine- and diazepam-induced cognitive impairments without altering the animals' locomotion. This suggests the potential of EA application as a useful memory restorative agent in the treatment of dementia seen in elderly persons.

Ellagic acid enhances the antinociceptive action of carbamazepine in the acetic acid writhing test with mice.

CONTEXT: Ellagic acid (EA) produced antinociceptive and anti-inflammatory effects through the central and peripheral sites of action. OBJECTIVE: The objective of the current study was to examine the functional interaction between ellagic acid and carbamazepine (CBZ) on pain. MATERIALS AND METHODS: Fourteen groups of mice (8-10 each) were used in this study. Pain was induced by intraperitoneal acetic acid in mice (writhing test) and the functional interaction was analyzed using the isobolographic method. EA at doses 0.3, 1, 3, and 10 mg/kg and carbamazepine at doses 3, 10, 20, and 30 mg/kg, alone and also in combination (1/2, 1/4, and 1/8 of the drug's ED50) were intraperitoneally administered 30 min before acetic acid (0.6% v/v). Then, the abdominal writhes were counted during a 25-min period. RESULTS: EA (0.3-10 mg/kg, i.p.) and CBZ (3-30 mg/kg, i.p.) inhibited the writhing response evoked by acetic acid. Fifty percent effective dose (ED50) values against this tonic pain were 1.02 mg/kg and 6.40 mg/kg for EA and CBZ, respectively. The antinociception induced by EA showed higher potency than that of carbamazepine. Co-administration of increasing fractional increments of ED50 values of EA and CBZ produced additive interaction against writhing responses, as revealed by isobolographic analysis. DISCUSSION AND CONCLUSION: These results suggest that a combination of carbamazepine and ellagic acid may be a new strategy for the management of neuropathic pain such as what occurs in trigeminal neuralgia, since the use of carbamazepine is often limited by its adverse effects and by reduction of its analgesic effect through microsomal enzyme induction.

Effect of crocin on nitric oxide synthase expression in post-ischemic isolated rat heart.

OBJECTIVE: Oxidative stress damages cells and brings about the pathogenesis of ischemia/reperfusion injury. This study was carried out to investigate the preconditioning and cardio protective potential effects of crocin and vitamin E by the eNOS and iNOS express gene in ischemia/reperfusion in rats. MATERIAL & METHODS: Male rats were divided into seven groups, namely: sham, control group and experimental groups treated with crocin(10, 20 and 40 mg/kg), vitamin E (100 mg/kg) and combination of crocin (40 mg/kg) with vitamin E (100 mg/kg) that were gavaged The heart was removed and relocated to a Langendorff apparatus and subjected to global ischemia and then the left ventricular end diastolic pressure (LVEDP) were measured as a hemodynamic parameter. Total RNA was extracted from heart frozen tissues. RT-PCR technique was performed by specific primers designed for nitric oxide gene and the results were assessed by agarose gel electrophoresis. RESULTS: Results after ischemia and reperfusion showed that crocin 40 mg/kg produced a significant improvement of LVEDP as a mechanical function (p<0.05), associated with a reduction of iNOS release (p<0.05). The eNOS mRNA levels were significantly higher in crocin-treated 40 mg/kg compared to controls treated by RT-PCR technique. The combination of crocin and vitamin E have shown more effective on the reduction of iNOS release (p<0.01). CONCLUSION: In the isolated rat heart, protective effect of crocin, may possibly be explained by regulating eNOS and iNOS expressions. The Results resultsconfirmed the hypothesis that cardioprotective effect of crocin is partly mediated by nitric oxide. This could explain the cardioprotective action of crocin following ischemia and reperfusion.

Modulation of morphine antinociceptive tolerance and physical dependence by co-administration of simvastatin.

Statins, 3-hydroxy-3-methylglutaryl co-enzyme A (HMG-CoA) reductase inhibitors, are widely used in the management of different diseases beyond their primary indication for lowering cholesterol. Previous studies have demonstrated the neuroprotective effects of simvastatin in different animal models. In the present study, we examined the effects of simvastatin (30, 60, 100 and 300mg/kg, p.o.) on the development and expression of morphine-induced tolerance and dependence in mice. For the induction of morphine tolerance and dependence, mice were twice daily treated with morphine (10mg/kg, s.c.) for 5 consecutive days. Tolerance was evaluated by the hot-plate test and physical dependence by naloxone challenge, on the sixth day. The results showed that oral administration of simvastatin produced antinociceptive activity in a dose-dependent way. Co-administration of simvastatin with morphine did not affect the acute morphine-induced analgesia (10mg/kg, s.c.). However, repeated co-administration of simvastatin with morphine significantly attenuated the development of tolerance to the analgesic effect of morphine and inhibited the naloxone (5mg/kg, s.c.)-precipitated withdrawal signs (jumping and body weight loss). Also, simvastatin at doses of 100 and 300mg/kg attenuated the expression of morphine-induced tolerance and dependence. These data indicated that, while simvastatin can alleviate both development and expression of morphine-induced tolerance, it cannot enhance morphine-induced antinociception. Taken together, simvastatin may be used as an adjutant therapeutic agent in combination with morphine and or other opioids in patients with severe chronic pain.

A study of the mechanisms underlying the anti-inflammatory effect of ellagic acid in carrageenan-induced paw edema in rats.

OBJECTIVES: Ellagic acid (EA) has shown antinociceptive and anti-inflammatory effects. Inducible nitric oxide synthase (iNOS), cyclooxygenase 2 (COX-2) enzymes and also cytokines play a key role in many inflammatory conditions. This study was aimed to investigate the mechanisms involved in the anti-inflammatory effect of EA. MATERIALS AND METHODS: Carrageenan-induced mouse paw edema model was used for induction of inflammation. RESULTS: The results showed that intraplantar injection of carrageenan led to time-dependent development of peripheral inflammation, which resulted in a significant increase in the levels of tumor necrosis factor α (TNF-α) and interleukin 1 (IL-1) ß, nitric oxide (NO) and prostaglandin E2 (PGE2) and also iNOS and COX-2 protein expression in inflamed paw. However, systemic administration of EA (1-30 mg/kg, intraperitoneal [i.p.]) could reduce edema in a dose-dependent fashion in inflamed rat paws with ED50 value 8.41 (5.26-14.76) mg/kg. It decreased the serum concentration of NO, PGE2, aspartate aminotransferase and alanine aminotransferase, and suppress the protein expression of iNOS, COX-2 enzymes, and attenuated the formation of PGE2, TNF-α and IL-1 ß in inflamed paw tissue. We also demonstrated that EA significantly decreased the malondialdehyde (MDA) level in liver at 5 h after carrageenan injection. Moreover, histopathological studies indicated that EA significantly diminished migration of polymorphonuclear leukocytes into site of inflammation, as did indomethacin. CONCLUSIONS: Collectively, the anti-inflammatory mechanisms of EA might be related to the decrease in the level of MDA, iNOS, and COX-2 in the edema paw via the suppression of pro-inflammatory cytokines (TNFα, IL1 ß), NO and PGE2 overproduction.

Ellagic acid enhances the antinociceptive action of venlafaxine in mouse acetic acid-induced pain: An isobolographic analysis.

BACKGROUND: Several antidepressants have been used to treat severe pain in clinics. Recently, it has been shown that ellagic acid (EA), a major constituent of pomegranate juice, produced antinociceptive and anti-inflammatory effect through the central and peripheral sites of action. MATERIALS AND METHODS: In this study, we examined the interaction between EA and venlafaxine (VLF) on pain induced by intraperitoneal acetic acid in mice using isobolographic analysis. RESULTS: EA (0.3-10mg/kg, ip) and VLF (3-60 mg/kg, ip) produced a dose-dependent inhibition of the writhing response evoked by acetic acid. Fifty percent effective dose (ED50) values against writhing behaviors were 1.02 (0.86-1.19)mg/kg and 12.37 (9.74-15.37)mg/kg for EA and VLF, respectively, and also with higher potency than that of VLF. Co-administration of increasing fractional increments of ED50 doses of EA and VLF produced synergistic interaction against writhing behaviors, as revealed by isobolographic analysis. CONCLUSION: The synergistic action of EA and VLF provides valuable tool referring to the management of visceral pain.

Involvement of L-arginine/NO/cGMP/K(ATP) channel pathway in the peripheral antinociceptive actions of ellagic acid in the rat formalin test.

The present study was conducted to evaluate the local antinociceptive actions of EA and the possible involvement of l-arginine/NO/cGMP/KATP channel pathway in this effect using formalin test in rats. To evaluate the involvement of l-arginine/NO/cGMP/KATP channel pathway in the antinociceptive action of EA, rats were pre-treated intraplantarlly with l-NAME (NOS inhibitor, 25-100µg/paw), methylene blue (guanylyl cyclase inhibitor, 100-400µg/paw), glibenclamide (ATP-sensitive K(+) channel blocker, 25-100µg/paw), l-arginine (a nitric oxide precursor, 25-100µg/paw) and sodium nitroprusside (125-500µg/paw). The local peripheral ipsilateral, but not contralateral, administration of EA into the right paw (30-300µg/paw) produced a dose-related antinociception during both early and late phases of formalin test which is comparable with morphine (25µg/paw). Moreover, local pre-treatment with l-NAME, methylene blue and glibenclamide dose-dependently prevented EA (100µg/paw)-induced antinociception in late phase. Additionally, administration of l-arginine and sodium nitroprusside significantly potentiated the antinociception induced by EA in the late phase. However, these treatments had no significant effect on antinociceptive response of EA in the early phase of the formalin test. The results of the present study showed that EA-induced local peripheral antinociception during the both phases of formalin test. Also, our data suggested the activation of the l-arginine/NO/cGMP/KATP channels pathway in EA-induced antinociception in late phase of formalin test. Topical application of EA by ointment or jelly might be a useful method to relieving the inflammatory pain states.

Ellagic acid enhances morphine analgesia and attenuates the development of morphine tolerance and dependence in mice.

According to our previous study, ellagic acid has both dose-related central and peripheral antinociceptive effect through the opioidergic and l-arginine-NO-cGMP-ATP sensitive K(+) channel pathways. In the present study, the systemic antinociceptive effects of ellagic acid in animal models of pain, and functional interactions between ellagic acid and morphine in terms of analgesia, tolerance and dependence were investigated. Ellagic acid (1-30mg/kg; i.p.) showed significant and dose-dependent antinociceptive effects in the acetic acid-induced writhing test. Intraperitoneal ellagic acid acutely interacted with morphine analgesia in a synergistic manner in this assay. Ellagic acid (1-10mg/kg; i.p.) also exerted analgesic activity in the hot-plate test. Pre-treatment with naloxone (1mg/kg; i.p.) significantly reversed ellagic acid, morphine as well as ellagic acid-morphine combination-induced antinociceptin in these two tests. More importantly, when co-administered with morphine, ellagic acid (1-10mg/kg) effectively blocked the development of tolerance to morphine analgesia in the hot-plate test. Likewise, ellagic acid dose-dependently prevented naloxone-precipitated withdrawal signs including jumping and weight loss. Ellagic acid treatment (1-30mg/kg; i.p.) had no significant effect on the locomotion activity of animals using open-field task. Therefore, these results showed that ellagic acid has notable systemic antinociceptive activity for both tonic and phasic pain models. Altogether, ellagic acid might be used in pain relief alone or in combination with opioid drugs because of enhancing morphine analgesia and preventing morphine-induced tolerance to analgesia and dependence.

Sildenafil enhances the peripheral antinociceptive effect of ellagic acid in the rat formalin test.

OBJECTIVE: Ellagic acid (EA), a major polyphenolic compound of pomegranate juice, produces antinociceptive effects, which are mediated through opioidergic and nitric oxide-cyclic guanosine monophosphate (NO-cGMP) pathways. The present study was conducted to elucidate the peripheral antinociceptive effect of EA alone and in combination with sildenafil in the rat formalin test. MATERIALS AND METHODS: Pain was produced by intraplantar injection of formalin (2.5%) in rats and nociceptive behavior was measured as the number of flinches every 5 min in 60 min after injection. RESULTS: Local administration of EA and sildenafil dose-dependently increased the nociception threshold in both phases of the test. Moreover, sub-effective doses of sildenafil (25 or 50 mcg/paw, i.p.) significantly and dose-dependently enhanced the antinociception induced by a sub-effective dose of EA (60 mcg/paw, i.pl.) in both phases of the test. The antinociception produced by these drugs alone, or in combination, was due to a peripheral site of action, since the administration in the contralateral paw was ineffective. CONCLUSION: Our results suggest that EA has local peripheral antinociceptive activity, and enhancement of this effect with sildenafil probably occurs through the inhibition of cGMP metabolism.

Protective Effects of Crocin on Ischemia-reperfusion Induced Oxidative Stress in Comparison With Vitamin E in Isolated Rat Hearts.

BACKGROUND: Myocardial Injury caused by ischemia-reperfusion leads to cardiac dysfunction, tissue injury and metabolic changes. The production of reactive oxygen species (ROS) and lipid peroxidation are accompanied by ischemia-reperfusion injury. OBJECTIVES: The aim of this study was to assess the cardio protective potential effects of crocin in comparison with vitamin E on antioxidant capacity in ischemia-reperfusion of isolated rat hearts. MATERIALS AND METHODS: Seventy male Sprague-Dawley rats were randomly divided into seven groups, including: sham, control and experimental groups treated with different doses of crocin (10, 20 and 40 mg/kg) or vitamin E (100 mg/kg) and a combination of crocin (40 mg/kg) with vitamin E (100 mg/kg) that were administrated orally for 21 days. The heart was quickly excised, transferred to a Langendorff apparatus at constant pressure and subjected to 30 minutes of global ischemia followed by 60 minutes of reperfusion. Cardiac damage markers and antioxidant enzymes were measured. RESULTS: The results showed that superoxide dismutase and catalase enzyme activities increased and Mallon de aldehyde (MDA) decreased in animals pretreated by crocin (40 mg/kg) and vitamin E (100 mg/kg). Moreover, there was a significant improvement in post ischemic recovery of antioxidant capacity during reperfusion in rats receiving a combination of crocin (40 mg/kg) and vitamin E (100 mg/kg). CONCLUSIONS: The results demonstrated the protective role of crocin on antioxidant capacity, which may partially be related to stability or amplification of antioxidant systems. Like vitamin E, crocin may be beneficial for prevention or treatment of cardiac dysfunction and myocardial infarction in patients with ischemic heart disease.

Protective effects of crocin on hemodynamic parameters and infarct size in comparison with vitamin E after ischemia reperfusion in isolated rat hearts.

Although reperfusion is a useful method for the survival of ischemic heart, harmful effects have been observed. This study was carried out to investigate the preconditioning and cardioprotective potential effects of crocin and vitamin E on the hemodynamic and infarct size in the ischemia-reperfusion model of isolated rat hearts. Animals were divided into a control group, an ischemia-reperfusion control group and three treatment groups: crocin (10, 20, and 40 mg/kg), vitamin E (100 mg/kg), and combination (crocin 40 mg/kg with vitamin E 100 mg/kg). The hearts were excised, quickly transferred to a Langendorff apparatus, and subjected to 30 min of global ischemia followed by 60 min of reperfusion. Left ventricular developed pressure, coronary perfusion pressure, left ventricular systolic pressure, myocardial contractility, rate pressure product, coronary flow, and infarct size were assessed. The successful induction of ischemia was determined by ST elevation on the electrocardiogram.The results showed that crocin significantly improved cardiac dysfunction and also reduced infarct size in the rat hearts. However, the combination of crocin 40 mg/kg and vitamin E 100 mg/kg had an even more significantly improved effect on the hemodynamic parameters and infarct size.Therefore, it can be suggested that the protective role of crocin may be due to the stability or reinforcement of antioxidant systems, and crocin could be useful for the treatment or prevention of cardiac dysfunction.