Antinociceptive effect of certain dimethoxy flavones in mice

Effects of 1-methyl-1, 2, 3, 4-tetrahydroisoquinoline on a diabetic neuropathic pain model

Background: Neuropathy is a prevalent and debilitating complication of poorly managed diabetes, contributing towards poor quality of life, amputation risk, and increased mortality. The available therapies for diabetic neuropathic pain (DPN) have limitations in terms of efficacy, tolerability and patient compliance. Dysfunction in the peripheral and central monoaminergic system has been evidenced in various types of neuropathic and acute pain. The objective of the present study was to investigate 1-methyl 1, 2, 3, 4-tetrahydroisoquinoline (1MeTIQ), an endogenous amine found in human brain with a known neuroprotective profile, in a model of streptozotocin (STZ) induced neuropathic pain. Methods: Diabetic neuropathy in male BALB/c mice was induced by intraperitoneal injection of a single dose of STZ (200 mg/kg). Upon development of DPN after 4 weeks, mice were investigated for mechanical allodynia (von Frey filament pressure test) and thermal hyperalgesia (tail immersion test). Ondansetron (1.0 mg/kg i.p.), naloxone (3.0 mg/kg i.p.) and yohimbine (2.0 mg/kg i.p.) were used to elucidate the possible mechanism involved. Postmortem frontal cortical, striatal and hippocampal tissues were dissected and evaluated for changes in levels of dopamine, noradrenaline and serotonin using High-Performance Liquid Chromatography (HPLC) with UV detection. Results: Acute administration of 1MeTIQ (15-45 mg/kg i.p.) reversed streptozotocin-induced diabetic neuropathic static mechanical allodynia (von Frey filament pressure test) and thermal hyperalgesia (tail immersion test), these outcomes being comparable to standard gabapentin. Furthermore, HPLC analysis revealed that STZ-diabetic mice expressed lower concentrations of serotonin in all three brain regions examined, while dopamine was diminished in the striatum and 1MeTIQ reversed all these neurotransmitter modifications. These findings suggest that the antihyperalgesic/antiallodynic activity of 1MeTIQ may be mediated in part via supraspinal opioidergic and monoaminergic modulation since they were naloxone, yohimbine and ondansetron reversible. Conclusion: It was also concluded that acute treatment with 1MeTIQ ameliorated STZ-induced mechanical allodynia and thermal hyperalgesia and restored brain regionally altered serotonin and dopamine concentrations which signify a potential for 1MeTIQ in the management of DPN.

Anti-neuropathic effect of 7,3'-dihydroxyflavone in paclitaxel induced peripheral neuropathy in mice involving GABAA, KATP channel and adenosine receptors

Peripheral neuropathy induced by chemotherapeutic agents is the most common dose-limiting adverse effect observed in patients during and after treatment of malignancies. Many flavones have been reported to ameliorate neuropathy of different origin in experimental animals and their possible mode of action explored. The present study aims to investigate 7,3'-dihydroxyflavone for its anti-neuropathic effect against paclitaxel induced peripheral neuropathy in mice by employing behavioural tests such as mechanical allodynia, cold allodynia and thermal hyperalgesia. The possible involvement of GABA_A, K_ATP channels and adenosine receptors in the anti-neuropathic effect of 7,3'-dihydroxyflavone was also studied by employing suitable interacting drugs. Treatment with 7,3'-dihydroxyflavone (50, 100 or 200 mg/kg, s.c) significantly and dose-dependently reduced the paw withdrawal response score in both mechanical and cold allodynia and also increased the tail flick response time in thermal hyperalgesia due to paclitaxel-induced neuropathy. Pre-treatment with glibenclamide (10 mg/kg, i.p), caffeine (50 mg/kg, i.p) or bicuculline (2 mg/kg, i.p) significantly reversed the anti-neuropathic effect of 7,3'-dihydroxyflavone in behavioral tests. In conclusion, the present investigation identified 7,3'-dihydroxyflavone as a potential candidate with anti-neuropathic effect against paclitaxel induced peripheral neuropathy involving K_ATP channels, adenosine and GABA_A receptors.

Flavonoid-Like Components of Peanut Stem and Leaf Extract Promote Sleep by Decreasing Neuronal Excitability

SCOPE

Peanut stem and leaf (PSL), a traditional Chinese medicine, is widely used as a dietary supplement to improve sleep quality; however, the underlying mechanism is unclear. Here, the study aims to determine whether active compounds in PSL extract exert their effects by mediating neuronal excitability.

METHODS AND RESULTS

Aqueous PSL extract (500 mg kg^-1 BW) increases the duration of total sleep (TS), slow wave sleep (SWS) and rapid eye movement sleep (REMS) in BALB/c mice after 7 and 14 continuous days of intragastric administration. Two PSL extract components with flavonoid-like structures: 4',7-di-O-methylnaringenin (DMN, 61 µg kg^-1 BW) and 2'-O-methylisoliquiritigenin (MIL, 12 µg kg^-1 BW), show similar effects on sleep in BALB/c mice. Moreover, incubation with DMN (50 µM) and MIL (50 µM) acutely reduces voltage-gated sodium and potassium currents and suppresses the firing of evoked action potential in mouse cortical neurons, indicating the inhibition on neuronal excitability. Meanwhile, RNA-seq analysis predicts the potential regulation of voltage-gated channels, which is according with the molecular docking simulation that both MIL and DMN can bind to voltage gated sodium channels 1.2 (Na_v 1.2).

CONCLUSIONS

DMN and MIL are the active ingredients of PSL that improve sleep quality, suggesting that PSL promotes sleep by regulating the excitability of neurons.

PA-Int5: An isatin-thiosemicarbazone derivative that exhibits anti-nociceptive and anti-inflammatory effects in Swiss mice

Pain and inflammation are symptoms of various diseases, and they can be modulated by different pathways, thus highlighting the importance of investigating the therapeutic effects of novel compounds. Previous studies have shown that isatin-thiosemicarbazone exhibits antitumor, antifungal antibacterial and other biological properties. Based on the wide range of biological effects of these compounds, the aim of the present study was to investigate the central nervous system (CNS) performance, and the anti-nociceptive and anti-inflammatory activity of (Z)-2-(5-nitro-2-oxoindolin-3-ilidene)-N-hydroazinecarbothioamide (PA-Int5) in treated mice. Three doses of PA-Int5 were tested orally (1.0, 2.5 and 5.0 mg/kg) in the nociceptive and inflammatory animal models. Additionally, the potential sedative effects of PA-Int5 (5 mg/kg, oral gavage) were investigated using an open field and rotarod tests, to exclude any possible unspecific effects of the nociceptive assays. Anti-nociceptive activity was assessed using the acetic acid-induced abdominal contortion and formalin tests, whereas anti-inflammatory activity was assessed using a carrageenan-induced paw edema and zymosan-induced air-pouch models. PA-Int5 (5 mg/kg) induced anti-nociceptive activity in the abdominal contortion model. In the formalin test, PA-Int5 (at 2.5 and 5 mg/kg) reduced nociception in the second phase. At the higher dose tested, PA-Int5 did not affect spontaneous locomotion or motor coordination. The data revealed that at all doses tested, the compound significantly reduced paw edema following carrageenan administration. In the zymosan-induced air-pouch model, PA-Int5 potently inhibited leukocyte migration and protein levels at the site of inflammation. When combined, the results revealed, for the first time, that PA-Int5 exhibited anti-nociceptive and anti-inflammatory activities, and highlights its potential, as well that of other derivatives, as novel candidates for pain relief.

5-O-methylcneorumchromone K Exerts Antinociceptive Effects in Mice via Interaction with GABAA Receptors

The proper pharmacological control of pain is a continuous challenge for patients and health care providers. Even the most widely used medications for pain treatment are still ineffective or unsafe for some patients, especially for those who suffer from chronic pain. Substances containing the chromone scaffold have shown a variety of biological activities, including analgesic effects. This work presents for the first time the centrally mediated antinociceptive activity of 5-O-methylcneorumchromone K (5-CK). Cold plate and tail flick tests in mice showed that the 5-CK-induced antinociception was dose-dependent, longer-lasting, and more efficacious than that induced by morphine. The 5-CK-induced antinociception was not reversed by the opioid antagonist naloxone. Topological descriptors (fingerprints) were employed to narrow the antagonist selection to further investigate 5-CK's mechanism of action. Next, based on the results of fingerprints analysis, functional antagonist assays were conducted on nociceptive tests. The effect of 5-CK was completely reversed in both cold plate and tail-flick tests by GABA_A receptor antagonist bicuculline, but not by atropine or glibenclamide. Molecular docking studies suggest that 5-CK binds to the orthosteric binding site, with a similar binding profile to that observed for bicuculline and GABA. These results evidence that 5-CK has a centrally mediated antinociceptive effect, probably involving the activation of GABAergic pathways.

Anti-inflammatory and antinociceptive effects of the isatin derivative (Z)-2-(5-chloro-2-oxoindolin-3-ylidene)-N-phenyl-hydrazinecarbothioamide in mice

Several isatin derivatives have shown important biological activities, which have attracted interest from researchers. For this reason, the present study aimed to evaluate the anti-inflammatory and antinociceptive effects of the isatin derivative (Z)-2-(5-chloro-2-oxoindolin-3-ylidene)-N-phenyl-hydrazinecarbothioamide (COPHCT) in mice. Three doses of this compound were tested: 1.0, 2.5, and 5.0 mg/kg. The anti-inflammatory activity was assessed using the carrageenan-induced paw edema model and the zymosan-induced air pouch model. The evaluation of the antinociceptive effect was performed through the formalin test and the acetic acid-induced abdominal writhing test. The paw edema assay demonstrated that all doses of the compound showed a significant reduction of the edema in the second hour evaluated, but a better response was observed in the fourth hour. The zymosan-induced air pouch model indicated that the compound, in all doses, significantly reduced leukocyte migration and total protein concentration levels. In the formalin test, the doses 1.0, 2.5, and 5.0 mg/kg of COPHCT showed activity only in the second phase, with reduction in paw pain time of 73.61, 79.46, and 73.85%, respectively. The number of abdominal writhings decreased with the increasing dose, but only 5.0 mg/kg COPHCT exhibited a significant response, with a reduction of 24.88%. These results demonstrated the ability of this compound to interfere in the anti-inflammatory activity of edema, vascular permeability, and cell migration. In addition, its possible antinociceptive effect may be related to the dose used.

Antinociceptive effect of flavonol and a few structurally related dimethoxy flavonols in mice

Previous reports suggest flavonoids as potent analgesic compounds. Based on these observations, the present study investigated the antinociceptive action of flavonol, 3', 4'-dimethoxy flavonol, 6, 3'-dimethoxy flavonol, 7, 2'-dimethoxy flavonol, and 7, 3'-dimethoxy flavonol and the possible mechanisms involved in these effects. The antinociceptive effect of the investigated compounds in doses of 25, 50, 100, and 200 mg/kg was evaluated in male Swiss albino mice using the acetic acid test, formalin-induced nociception, and hot water tail immersion test. The role of opioid, tryptaminergic, adrenergic, dopaminergic, GABAergic, and K⁺_ATP channels in producing the antinociceptive effect was also studied using appropriate interacting agents. Treatment with flavonol and dimethoxy flavonols resulted in a significant reduction in the number of abdominal constrictions in the acetic acid test, a significant inhibition of the paw-licking/biting response time in both the phases of formalin nociception and also a significant increase in mean reaction time in the hot water tail immersion test. These observations revealed the antinociceptive effect of dimethoxy flavonols. The role of opioid, serotonergic (5HT₃), and dopaminergic system was identified in the antinociceptive effect of flavonol and all dimethoxy derivatives investigated. In addition, the role of GABAergic, K⁺_ATP channel, and α-2 adrenergic mechanisms were also observed in the antinociceptive action of some of the investigated compounds. The present study identified the antinociceptive effect of flavonol and dimethoxy flavonols in mice acting through different neuronal pathways.

Effect of flavonol and its dimethoxy derivatives on paclitaxel-induced peripheral neuropathy in mice

Background:

Peripheral neuropathy is the dose limiting side effect of many anticancer drugs. Flavonoids exhibit good antinociceptive effect in animal models. Their efficacy against different types of nociception has been documented. The present study investigated the effect of flavonol (3-hydroxy flavone), 3′,4′-dimethoxy flavonol, 6,3′-dimethoxy flavonol, 7,2′-dimethoxy flavonol and 7,3′-dimethoxy flavonol against paclitaxel-induced peripheral neuropathy in mice.

Methods:

A single dose of paclitaxel (10 mg/kg, i.p.) was administered to induce peripheral neuropathy in mice and the manifestations of peripheral neuropathy such as tactile allodynia, cold allodynia and thermal hyperalgesia were assessed 24 h later by employing Von Frey hair aesthesiometer test, acetone bubble test and hot water tail immersion test, respectively. The test compounds were prepared as a suspension in 0.5% carboxymethyl cellulose and were administered s.c. in various doses (25, 50, 100 and 200 mg/kg). The above behavioral responses were assessed prior to and 30 min after drug treatment. In addition, the effect of test compounds on proinflammatory cytokines like tumor necrosis factor-alpha (TNF-α), interleukin-1-beta (IL-1β) and free radicals was investigated by using suitable in vitro assays.

Results:

A dose-dependent attenuation of tactile allodynia, cold allodynia and thermal hyperalgesia was evidenced in mice treated with flavonol derivatives. The test compounds inhibited TNF-α, IL-1β and free radicals in a concentration-dependent manner.

Conclusions:

These results revealed that flavonol and its dimethoxy derivatives ameliorated the manifestations of paclitaxel-induced peripheral neuropathy in mice. The inhibition of proinflammatory cytokines and free radicals could contribute to this beneficial effect.

Sedative-hypnotic like effect of 5-methoxyflavone in mice and investigation on possible mechanisms by in vivo and in silico methods

Flavonoids have been shown to possess central nervous system (CNS) depressant effect mediated through the ionotropic GABA_A receptors. In the present study, 5-methoxyflavone was evaluated for sedative-hypnotic like activity in mice and the mechanisms involved by employing a battery of tests including molecular docking studies. In the open field test, 5-methoxyflavone in various doses (50, 100 and 150 mg/kg, i.p) exhibited a significant and dose-dependent reduction in the spontaneous locomotor activity (F (530) = 87.17 P < 0.001). Pretreatment with 5-methoxyflavone decreased the latency to sleep induction after pentobarbitone or ether administration and also significantly increased the duration of sleep (p < 0.001). A significant and dose-dependent myorelaxant effect was observed with 5-methoxyflavone in the inclined plane, horizontal wire test and rota rod test. Pretreatment with picrotoxin, bicuculline, glycine, caffeine or NMDA either decreased or completely abolished the hypnotic effect of 5-methoxyflavone in mice. The above results revealed the involvement of GABA_A, adenosine, glycine and NMDA receptors in the hypnotic effect of 5-methoxyflavone. The results of in silico studies indicated that, 5-methoxyflavone exhibits good binding affinity towards these receptors by H-bond interactions. In conclusion, the present study identified a novel and potential sedative-hypnotic like effect of 5-methoxyflavone involving multiple mechanisms.

Polymethoxyflavones from Nicotiana plumbaginifolia (Solanaceae) Exert Antinociceptive and Neuropharmacological Effects in Mice

Polymethoxylavones (PMFs) are known to exhibit significant anti-inflammatory and neuroprotective properties. Nicotiana plumbaginifolia, an annual Bangladeshi herb, is rich in polymethoxyflavones that possess significant analgesic and anxiolytic activities. The present study aimed to determine the antinociceptive and neuropharmacological activities of polyoxygenated flavonoids namely- 3,3′,5,6,7,8-hexamethoxy-4′,5′-methylenedioxyflavone (1), 3,3′,4′,5′,5,6,7,8-octamethoxyflavone (exoticin) (2), 6,7,4′,5′-dimethylenedioxy-3,5,3′-trimethoxyflavone (3), and 3,3′,4′,5,5′,8-hexamethoxy-6,7-methylenedioxyflavone (4), isolated and identified from N. plumbaginifolia. Antinociceptive activity was assessed using the acetic-acid induced writhing, hot plate, tail immersion, formalin and carrageenan-induced paw edema tests, whereas neuropharmacological effects were evaluated in the hole cross, open field and elevated plus maze test. Oral treatment of compounds 1, 3, and 4 (12.5–25 mg/kg b.w.) exhibited dose-dependent and significant (p < 0.01) antinociceptive activity in the acetic-acid, formalin, carrageenan, and thermal (hot plate)-induced pain models. The association of ATP-sensitive K⁺ channel and opioid systems in their antinociceptive effect was obvious from the antagonist effect of glibenclamide and naloxone, respectively. These findings suggested central and peripheral antinociceptive activities of the compounds. Compound 1, 3, and 4 (12.5 mg/kg b.w.) demonstrated significant (p < 0.05) anxiolytic-like activity in the elevated plus-maze test, while the involvement of GABA_A receptor in the action of compound 3 and 4 was evident from the reversal effects of flumazenil. In addition, compounds 1 and 4 (12.5–25 mg/kg b.w) exhibited anxiolytic activity without altering the locomotor responses. The present study suggested that the polymethoxyflavones (1–4) from N. Plumbaginifolia could be considered as suitable candidates for the development of analgesic and anxiolytic agents.

Endogenous opiates and behavior: 2014

This paper is the thirty-seventh consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2014 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (endogenous opioids and receptors), and the roles of these opioid peptides and receptors in pain and analgesia (pain and analgesia); stress and social status (human studies); tolerance and dependence (opioid mediation of other analgesic responses); learning and memory (stress and social status); eating and drinking (stress-induced analgesia); alcohol and drugs of abuse (emotional responses in opioid-mediated behaviors); sexual activity and hormones, pregnancy, development and endocrinology (opioid involvement in stress response regulation); mental illness and mood (tolerance and dependence); seizures and neurologic disorders (learning and memory); electrical-related activity and neurophysiology (opiates and conditioned place preferences (CPP)); general activity and locomotion (eating and drinking); gastrointestinal, renal and hepatic functions (alcohol and drugs of abuse); cardiovascular responses (opiates and ethanol); respiration and thermoregulation (opiates and THC); and immunological responses (opiates and stimulants). This paper is the thirty-seventh consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2014 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (endogenous opioids and receptors), and the roles of these opioid peptides and receptors in pain and analgesia (pain and analgesia); stress and social status (human studies); tolerance and dependence (opioid mediation of other analgesic responses); learning and memory (stress and social status); eating and drinking (stress-induced analgesia); alcohol and drugs of abuse (emotional responses in opioid-mediated behaviors); sexual activity and hormones, pregnancy, development and endocrinology (opioid involvement in stress response regulation); mental illness and mood (tolerance and dependence); seizures and neurologic disorders (learning and memory); electrical-related activity and neurophysiology (opiates and conditioned place preferences (CPP)); general activity and locomotion (eating and drinking); gastrointestinal, renal and hepatic functions (alcohol and drugs of abuse); cardiovascular responses (opiates and ethanol); respiration and thermoregulation (opiates and THC); and immunological responses (opiates and stimulants).

Inhalation of Cedrus atlantica essential oil alleviates pain behavior through activation of descending pain modulation pathways in a mouse model of postoperative pain

ETHNOPHARMACOLOGICAL RELEVANCE

Cedrus atlantica essential oil (CaEO) presents analgesic and anti-inflammatory sedative properties. However, it remains unknown whether CaEO alleviates acute postoperative pain.

MATERIALS AND METHODS

Here, we investigated the effect of CaEO on postoperative pain and its mechanisms related to the descending pain control in Swiss males mice induced by a plantar incision surgery (PIS) in the hindpaw.

RESULTS

Inhalation of CaEO (5', 30' or 60') markedly reduced mechanical hypersensitivity. This effect was prevented by pre-treatment with naloxone or p-chlorophenylalanine methyl ester (PCPA, 100mg/kg, i.p.)-induced depletion of serotonin. In addition, p-alpha-methyl-para-tyrosin (AMPT, 100mg/kg, i.p.)-induced depletion of norepinephrine, intraperitoneal injection of the α2-adrenergic receptor antagonist yohimbine (0.15 mg/kg, i.p.) or haloperidol (1mg/kg, i.p.) an antagonist of dopaminergic (D1 and D2) receptors prevented the effect of CaEO on hypersensitivity.

CONCLUSIONS

These findings suggest that CaEO alleviates postoperative pain by activating the descending pain modulation pathways on the opioidergic, serotonergic, noradrenergic (α2-adrenergic) and dopaminergic (dopamine D1 and D2 receptors) systems.

Anti-inflammatory effect of certain dimethoxy flavones

OBJECTIVE

The aim of the present study was to evaluate the anti-inflammatory effect of four dimethoxy flavone derivatives; 7,2'-dimethoxy flavone, 7,3'-dimethoxy flavone, 7,4'-dimethoxy flavone and 7,8,-dimethoxy flavone and to investigate the possible cellular mechanisms involved.

MATERIALS AND METHODS

The acute anti-inflammatory effect of dimethoxy flavones was investigated by carrageenan induced hind paw oedema in rats. Further, the effect of dimethoxy flavones on certain mediators of pain and inflammation like cyclooxygenases (COX-1 and COX-2), pro-inflammatory cytokines (IL-1β and TNF-α) and free radical scavenging activity (NO and LPO) were investigated by using in vitro tests.

RESULTS

The investigated dimethoxy flavones produced a significant, dose and time dependent reduction of carrageenan induced paw oedema in rats with a maximum inhibition of 52.4% observed for 7,4'-dimethoxy flavone. Although, the test compounds inhibited both the isoforms of cyclooxygenase, a higher degree of inhibition on COX-2 was evident. A concentration dependent inhibition of other inflammatory cytokines like tumor necrosis factor-α and interleukin-1β was identified in the present study. 7,4'-dimethoxy flavone was found to be maximally effective in inhibiting nitrite ion free radical generation and 7,8-dimethoxy flavone was more active in inhibiting lipid peroxidation than the other compounds.

CONCLUSION

The results of the present study reveal the anti-inflammatory action of the investigated dimethoxy flavones. Inhibition of cyclooxygenases, cytokines and reactive oxygen species, observed in subsequent experiments may be suggested as possible mechanisms involved in the action of these compounds.