Antinociceptive and anti‐inflammatory properties of 7‐hydroxycoumarin in experimental animal models: potential therapeutic for the control of inflammatory chronic pain

Objectives In the present study we investigated the antinociceptive, anti‐inflammatory and antipyretic effects of 7‐hydroxycoumarin (7‐HC) in animal models. Methods The effects of oral 7‐HC were tested against acetic acid‐induced writhing, formalin test, tail flick test, complete Freund's adjuvant (CFA)‐induced hypernociception, carrageenan‐induced paw oedema, lipopolysaccharide‐induced fever and the rota rod test. Key findings 7‐HC (3–60 mg/kg) produced a dose‐related antinociception against acetic acid‐induced writhing in mice and in the formalin test. In contrast, treatment with 7‐HC did not prevent thermal nociception in the tail flick test. A single treatment with 7‐HC, 60 mg/kg, produced a long‐lasting antinociceptive effect against CFA‐induced hypernociception, a chronic inflammatory pain stimulus. Notably, at 60 mg/kg per day over 4 days the administration of 7‐HC produced a continuous antinociceptive effect against CFA‐induced hypernociception. 7‐HC (30–120 mg/kg) produced anti‐inflammatory and antipyretic effects against carrageenan‐induced inflammation and lipopolysaccharide‐induced fever, respectively. Moreover, 7‐HC was found to be safe with respect to ulcer induction. In the rota rod test, 7‐HC‐treated mice did not show any motor performance alterations. Conclusions The prolonged antinociceptive and anti‐inflammatory effects of 7‐HC, in association with its low ulcerogenic activity, indicate that this molecule might be a good candidate for development of new drugs for the control of chronic inflammatory pain and fever.     

皮内注药对急性内脏炎症痛大鼠抗伤害作用的研究

目的在动物模型上研究皮内注药对内脏炎症痛的抗伤害作用及对其机制进行初步探讨。方法大鼠乙状结肠壁粘膜下定量注射福尔马林(5%,0.1 m l)制作急性内脏炎症痛模型,观察大鼠行为学表现并进行评分。分别在实验区(直肠、乙状结肠相应的脊神经体表分布区)及实验区外(远离直肠、乙状结肠相应的脊神经体表分布区)皮内多点注射0.125%、0.25%利多卡因或生理盐水,进行疼痛学评分;在利多卡因皮内注射组,采用高效液相色谱法测定血浆利多卡因浓度。结果福尔马林注射组同皮内注药组在第一个时间段内疼痛分数差异无显著性(P>0.05)。在实验区皮内注射0.25%利多卡因和生理盐水均能减轻内脏痛反应(P<0.01),而0.125%利多卡因皮内注射对疼痛分数同福尔马林致炎组相比差异无显著性(P>0.05);在实验区外唯有0.25%利多卡因皮内注射有抗伤害效应。皮内注射0.25%利多卡因的血浆浓度高于0.125%利多卡因组(P<0.01)。结论在内脏致痛器官的脊神经体表分布区皮内注射可降低动物的痛行为学评分,其作用可能与药物经皮内吸收入血和局部刺激激活末梢感受器有关。     

鞘内注射右美托咪定对瑞芬太尼诱发的大鼠术后痛觉过敏的影响

目的研究鞘内注射右美托咪定(DEX)对瑞芬太尼诱发的大鼠切口痛痛觉过敏的作用。方法雄性SD大鼠60只,随机分为5组,每组12只:对照组(C组)、切口痛组(I组)、瑞芬太尼+切口痛组(R组)、DEX(0.1μg/kg)+瑞芬太尼+切口痛组(D1组)及DEX(1μg/kg)+瑞芬太尼+切口痛组(D2组)。除C组外均在七氟醚麻醉下建立大鼠切口痛模型,D1、D2组术前1 h鞘内注射相应剂量的DEX 10μL,其余组注射10μL生理盐水;R组和D1、D2组术前30 min开始泵注瑞芬太尼1μg/(kg·min)持续120 min,其余组泵注等体积生理盐水。于术前24 h,停药后1、3、6、24、48 h(T0^T5时点)分别检测机械缩足阈值(PMWT)和热缩足反射潜伏期(PWL)。结果 I组在T1T5时点)分别检测机械缩足阈值(PMWT)和热缩足反射潜伏期(PWL)。结果 I组在T1^T4时点的PMWT及T1T4时点的PMWT及T1^T5时点的PWL均显著低于C组;R组在T2T5时点的PWL均显著低于C组;R组在T2^T5时点的PMWT及在T1T5时点的PMWT及在T1^T4时点的PWL较I组显著降低;而D1、D2组在T1T4时点的PWL较I组显著降低;而D1、D2组在T1^T5时点的PMWT、PWL明显高于R组,差异有统计学意义(P<0.05);D2组大鼠的PMWT在T1T5时点的PMWT、PWL明显高于R组,差异有统计学意义(P<0.05);D2组大鼠的PMWT在T1^T3时点显著高于D1组,在T2T3时点显著高于D1组,在T2^T4时点的PWL高于D1组,差异有统计学意义(P<0.01),其余时点无显著差异。结论大鼠术后痛觉过敏模型中,瑞芬太尼可诱发切口周围组织的痛觉过敏;鞘内注射DEX可以预防瑞芬太尼诱发的痛觉过敏,且与剂量相关。     

Cerebrolysin improves peripheral inflammatory pain: Sex differences in two models of acute and chronic mechanical hypersensitivity

Chronic inflammatory pain is a major health problem worldwide with high prevalence in women. Cerebrolysin is a multimodal neuropeptide preparation that crosses the blood brain barrier and displays neuroprotective properties in aging and disease. Previously, we showed that cerebrolysin reduced mechanical allodynia in a model of persistent inflammation and pain. We aim to build upon the findings of our previous study by investigating the response to acute administration of cerebrolysin in two models of peripheral inflammation and assessing sex differences. We utilized the complete Freund's adjuvant (CFA) that produces maximal oedema and mechanical allodynia within days and carrageenan that produces similar effects within hours. Cerebrolysin reversed the mechanical allodynia in both sexes in CFA-treated rats. On the other hand, in rats treated with carrageenan, cerebrolysin was only effective in reducing mechanical allodynia in female rats. In conclusion, the present study shows that cerebrolysin effects may be sex-specific depending on different mechanisms that are at play in these two models of peripheral inflammatory pain. Further investigations are required to determine the factors contributing to sex differences.     

Role of complement C5a in mechanical inflammatory hypernociception: potential use of C5a receptor antagonists to control inflammatory pain

BACKGROUND AND PURPOSE: C5a, a complement activation product, exhibits a broad spectrum of inflammatory activities particularly neutrophil chemoattraction. Herein, the role of C5a in the genesis of inflammatory hypernociception was investigated in rats and mice using the specific C5a receptor antagonist PMX53 (AcF-[OP(D-Cha)WR]). EXPERIMENTAL APPROACH: Mechanical hypernociception was evaluated with a modification of the Randall-Selitto test in rats and electronic pressure meter paw test in mice. Cytokines were measured by ELISA and neutrophil migration was determined by myeloperoxidase activity. KEY RESULTS: Local pretreatment of rats with PMX53 (60-180 microg per paw) inhibited zymosan-, carrageenan-, lipopolysaccharide (LPS)- and antigen-induced hypernociception. These effects were associated with C5a receptor blockade since PMX53 also inhibited the hypernociception induced by zymosan-activated serum and C5a but not by the direct-acting hypernociceptive mediators, prostaglandin E(2) and dopamine. Underlying the C5a hypernociceptive mechanisms, PMX53 did not alter the cytokine release induced by inflammatory stimuli. However, PMX53 inhibited cytokine-induced hypernociception. PMX53 also inhibited the recruitment of neutrophils induced by zymosan but not by carrageenan or LPS, indicating an involvement of neutrophils in the hypernociceptive effect of C5a. Furthermore, the C5a-induced hypernociception was reduced in neutrophil-depleted rats. Extending these findings in rats, blocking C5a receptors also reduced zymosan-induced joint hypernociception in mice. CONCLUSIONS AND IMPLICATIONS: These results suggest that C5a is an important inflammatory hypernociceptive mediator, acting by a mechanism independent of hypernociceptive cytokine release, but dependent on the presence of neutrophils. Therefore, we suggest that inhibiting the action of C5a has therapeutic potential in the control of inflammatory pain.     

Investigation of anti‐inflammatory,nitric oxide donating,vasorelaxation and ulcerogenic activities of 1, 3‐diphenylprop‐2‐en‐1‐one derivatives in animal models

The main aim of this work is to find out novel chemical moieties with potent anti‐inflammatory and vasorelaxant activities with reduced gastric toxicities. For fulfilling the above aim, here we investigated novel chalcones (1, 3‐diphenylprop‐2‐en‐1‐one derivatives) with nitric oxide (NO) and hydrogen sulphide (H₂S) donating potency for anti‐inflammatory activity by carrageenan‐induced rat paw oedema. These molecules then further evaluated for in‐vitro NO‐releasing potency and vasorelaxation effect on isolated adult goat aortic tissue. The promising molecules were further screened for ulcerogenic activity in the rat model. The tested compounds produced % inhibition in paw oedema ranging from 29.16% to 79.69% and standard drug Diclofenac sodium produced 85.30% reduction in paw oedema after 5 hours. Out of this dataset, compounds AI1, AI7, Ca1, B2, B10, D2, and E8 showed 73.01%, 79.69%, 75.02%, 75.46%, 74.35%, 73.9% and 74.35% reduction in paw oedema respectively, which is approximately 80%–90% to that of standard Diclofenac sodium. The compound Ca1 was found to release 0.870 ± 0.025 mol/mol of NO and standard Glyceryl trinitrate (GTN) was found to release 0.983 ± 0.063 mol/mol of NO. The compound Ca1 produced 950.2 μmol/L of EC₅₀ whereas standard GTN produced 975.8 μmol/L of EC₅₀ for aortic smooth relaxation. The compounds Ca1 produced 0.1117 of ulcer index which is far less than that of standard Diclofenac sodium (1.148). The potent lead molecules were further evaluated to understand the mechanism of vasorelaxation by using specific antagonists or blockers of NO and H₂S.     

The role of alpha5 nicotinic acetylcholine receptors in mouse models of chronic inflammatory and neuropathic pain

The aim of the present study was to determine the impact of α₅ nicotinic acetylcholine receptor (nAChR) subunit deletion in the mouse on the development and intensity of nociceptive behavior in various chronic pain models.The role of α₅-containing nAChRs was explored in mouse models of chronic pain, including peripheral neuropathy (chronic constriction nerve injury, CCI), tonic inflammatory pain (the formalin test) and short and long-term inflammatory pain (complete Freund's adjuvant, CFA and carrageenan tests) in α₅ knock-out (KO) and wild-type (WT) mice.The results showed that paw-licking time was decreased in the formalin test, and the hyperalgesic and allodynic responses to carrageenan and CFA injections were also reduced. In addition, paw edema in formalin-, carrageenan- or CFA-treated mice were attenuated in α₅-KO mice significantly. Furthermore, tumor necrosis factor-alpha (TNF-α) levels of carrageenan-treated paws were lower in α₅-KO mice. The antinociceptive effects of nicotine and sazetidine-A but not varenicline were α₅-dependent in the formalin test. Both hyperalgesia and allodynia observed in the CCI test were reduced in α₅-KO mice. Nicotine reversal of mechanical allodynia in the CCI test was mediated through α₅-nAChRs at spinal and peripheral sites.In summary, our results highlight the involvement of the α₅ nAChR subunit in the development of hyperalgesia, allodynia and inflammation associated with chronic neuropathic and inflammatory pain models. They also suggest the importance of α₅-nAChRs as a target for the treatment of chronic pain.     

Antinociceptive efficacy of verticinone in murine models of inflammatory pain and paclitaxel induced neuropathic pain

Verticinone, an isosteroidal alkaloid separated from Bulbus Fritillaria (Chinese name "Bei-mu"), was evaluated for its analgesic activities in murine models of inflammatory and neuropathic pain. It was shown that oral administarion of verticinone could significantly inhibit acetic acid-induced writhing response in a dose-dependent way, and the writhing inhibition of 3 mg/kg verticinone was 66.2%, which was approximately higher than that of 200 mg/kg aspirin. In the formalin test, a high dose of (3 mg/kg) verticinone could inhibit the nociceptive response of both phases, but the lower dose (1.5 mg/kg) could only inhibit the second phase response, which suggested that verticinone might exert its analgesic effect through both central and peripheral mechanisms. In addition, in formalin and acetic acid tests, the spontaneous locomotive activities of the mice treated with verticinone were transiently greatly decreased when compared with the vehicle group. In the rat model of paclitaxel induced neuropathic pain, in contrast to the declined analgesic effect of morphine after repeated administration with the same dose, a relatively constant analgesic effect of verticinone was observed. These investigations suggested that verticinone could exert a good antinociceptive effect on inflammatory pain and cancer-related neuropathic pain probably through both peripheral and central mechanisms, and it might be partly involved with some sedation effects. Verticinone is expected to become a potentially novel sedative-analgesic agent without producing tolerance and dependence, but further studies are still urgently needed to elucidate the precise mechanisms and activities of it.     

Thiazolyl‐N‐substituted amides: A group of effective anti‐inflammatory agents with potential for local anesthetic properties. Synthesis,biological evaluation,and a QSAR approach

A series of thiazolyl‐N‐substituted amides were synthesized and tested for anti‐inflammatory activity. Their R_M values were determined as an expression of their lipophilicity. Theoretical calculation of their lipophilicity, as clog P and log D_7.4 was also performed. The effect of the synthesized compounds on inflammation, using the carrageenan‐induced mouse paw edema model was studied. In general, the studied compounds were found to be potent anti‐inflammatory agents (23.2–72.1%). Anti‐inflammatory activity was influenced by some structural characteristics of the synthesized compounds. An attempt was made to correlate their biological activity with some physicochemical parameters using a quantitative structure–activity relationship approach (QSAR). A parabolic dependence of activity from clog D_7.4 and a linear dependence from surface tension were found. The anti‐inflammatory activity of the thiazolyl‐amides were found to a great extent to be under pharmacokinetic control. Drug Dev. Res. 48:53–60, 1999. © 1999 Wiley‐Liss, Inc.     

Discovery of Novel 1,2,4‐Triazol‐5‐Ones as Tumor Necrosis Factor‐Alpha Inhibitors for the Treatment of Neuropathic Pain

In this work, synthetic integration of substituted semicarbazides and various aliphatic, aryl and heteroaryl acids into 1,2,4‐triazol‐5‐ones was accomplished. Following the assessment of neurotoxicity and peripheral analgesic activity, the compounds were evaluated in two peripheral models of neuropathic pain, the chronic constriction injury and partial sciatic nerve ligation to assess their antihyperalgesic and antiallodynic potential. ED₅₀ studies undertaken for selected compounds exhibiting promising efficacies ( 1c , 3c and 4a ) revealed values ranging from 13.21 to 39.85 mg/kg in four behavioral assays of hyperalgesia and allodynia (spontaneous pain, tactile allodynia, cold allodynia, and mechanical hyperalgesia). Mechanistic studies revealed that the compounds suppressed the inflammatory component of the neuropathic pain inhibiting tumor necrosis factor‐alpha and preventing oxidative and nitrosative stress.     

Antinociceptive effects of NCX-701 (nitro-paracetamol) in neuropathic rats: enhancement of antinociception by co-administration with gabapentin

Background and purpose:

Neuropathic pain is characterized by a poor response to classic analgesics. In the present study, we have assessed the antinociceptive activity of NCX-701 (nitro-paracetamol) in neuropathic rats, after systemic and intrathecal (i.t.) administration. In addition, we analysed the possible benefit of the combination of NCX-701 and gabapentin, a well-known potent analgesic, in the treatment of neuropathic pain

Experimental approach:

The antinociceptive effects of i.v. and i.t. NCX-701 and paracetamol were studied in spinal cord neuronal responses from neuropathic adult male Wistar rats, using the recording of single motor units technique. The effect of i.v. and i.t. NCX-701 in combination with i.v. gabapentin was studied by isobolographic analysis.

Key results:

The experiments showed that NCX-701, but not paracetamol, dose-dependently reduced the nociceptive responses evoked by noxious mechanical and electrical stimulation, after i.v. (ID₅₀ 542 ± 5 µmol·kg⁻¹ for noxious mechanical stimulation) or i.t. (ID₅₀ 932 ± 16 nmol·kg⁻¹) administration. The combined administration of i.v. or i.t. NCX-701 and i.v. gabapentin induced a more intense antinociceptive effect than any of the two drugs given alone. The isobolographic analysis showed a synergistic effect.

Conclusions and implications:

NCX-701 is an effective antinociceptive compound in situations of neuropathy-induced sensitization, with an action mainly located in the spinal cord. The combination of NCX-701 and gabapentin induces a synergistic enhancement of the depression of nociceptive responses evoked by natural noxious stimulation. The use of NCX-701 alone or in combination with gabapentin might open up new and promising perspectives in the treatment of neuropathic pain.     

Effect of non‐steroidal anti‐inflammatory drugs on non‐melanoma skin cancer incidence in the SKICAP‐AK trial

Recent studies link the prostaglandin metabolic pathway to skin carcinogenesis expanding possibilities that cyclooxygenase (COX) inhibitors may be utilized in non‐melanoma skin cancer (NMSC) chemoprevention. Using data from a study of the efficacy of retinol supplementation on incidence of NMSC, we sought to determine the role of non‐steroidal anti‐inflammatory drugs (NSAIDs) in NMSC development. Cox proportional hazards models describe the relationship between NSAID use and time to first squamous cell carcinoma (SCC) or basal cell carcinoma (BCC) among participants categorized by use pattern: continuous users (use for length of study duration), new users (use for less than study duration), and non‐users. For SCC and BCC, there was a statistically significant protective effect for participants who reported use for less than the study duration (HR = 0.49, 95%CI 0.28–0.87 and HR = 0.43, 95%CI 0.25–0.73, respectively). Categorical examination of NSAIDs (aspirin (ASA) vs. non‐ASA NSAIDs) showed significant effects for BCC among those using non‐ASA NSAIDs for less than the study duration (HR = 0.33, 95%CI 0.13–0.80). For SCC and BCC, NSAID use of shorter duration and potentially more recent, was more protective than longer duration of use. These results are counter to the idea that longer duration of NSAID use is more protective. Additional investigations are needed into the role NSAIDs play in the chemoprevention of NMSC. Copyright © 2009 John Wiley & Sons, Ltd.     

Involvement of spinal tyrosine kinase in inflammatory and N-methyl-D-aspartate-induced hyperalgesia in rats

Phosphorylation of a subunit of N-methyl-D-aspartate (NMDA) receptor by protein tyrosine kinase (PTK) Src or Trk is known to enhance its channel activity. We examined whether a spinally administered selective PTK inhibitor, lavendustin A, which has high affinity for Src and Trk tyrosine kinases, could influence the development and maintenance of inflammatory hyperalgesia or NMDA-induced hyperalgesia. Inflammation was induced by injection of a mixture of carrageenan and kaolin into the tail base of rats. In another group of rats, hyperalgesia was induced by intrathecal administration of NMDA. Intrathecal administration of lavendustin A (1.0 microg) or NMDA receptor antagonist, (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cycloheptane-5,10-iminemaleate, MK-801 (3.0 microg) before injection of a mixture of carrageenan and kaolin or after the development of inflammation inhibited carrageenan-kaolin-induced mechanical hyperalgesia. Intrathecal injection of 1.0 microg NMDA produced thermal and mechanical hyperalgesia. Co-administration of 1.0 microg lavendustin A with NMDA significantly reduced the duration of spontaneous pain behaviour and inhibited NMDA-induced hyperalgesia. Lavendustin A itself did not cause any sedation, motor impairment or analgesia. Our results suggest that inhibition of PTK could be therapeutically effective as an analgesic in some NMDA receptor-mediated hyperalgesic states.     

Effects of an ethanol extract and the diterpene,xylopic acid,of Xylopia aethiopica fruits in murine models of musculoskeletal pain

Context: Fruits of Xylopia aethiopica (Dunal) A. Rich. (Annonaceae) are used traditionally to manage arthritis, headache and other pain disorders.

Objective: The analgesic properties of the X. aethiopica ethanol fruit extract (XAE) and xylopic acid (XA) were evaluated in musculoskeletal pain models.

Materials and methods: Acute muscle pain was induced in gastrocnemius muscle of Sprague–Dawley rats with 3% carrageenan (i.m.). Rats received XAE (30–300?mg/kg), XA (10–100?mg/kg) or morphine (1–10?mg/kg) after 12?h. Effects of XAE and XA on muscle pain were assessed by measuring post-treatment grip strength of the rats. Chronic muscle pain was similarly induced, but drug treatment was on the eighth day and effects of XAE and XA assessed with Randall–Selitto test for hyperlagesia. Acute-skeletal pain was induced in knee joints of rats with 3% carrageenan-kaolin mixture and effects determined 12-h later. Similar induction protocol was used for chronic knee pain with treatment and measurement as done for chronic muscle pain.

Results: XAE and XA significantly and dose-dependently ameliorated both acute muscle (ED₅₀ mg/kg: XAE?=?22.9; XA?=?6.2) and skeletal hyperalgesia (XAE?=?39.9; XA?=?17.7) induced by 3% carrageenan. Similarly, chronic skeletal hyperalgesia was reduced by XAE and XA treatment similar to morphine (ED₅₀: XAE?=?13.0; XA?=?4.6). This reduction was also seen in chronic muscle hyperalgesia (ED₅₀: XAE?=?79.1; XA?=?42.7). XAE and XA significantly reduced the spread of hyperalgesia to contralateral limbs in both models of chronic hyperalgesia.

Conclusion: These findings establish analgesic properties of the ethanol fruit extract of X. aethiopica and xylopic acid in musculoskeletal pain.     

Antinociceptive effects of the antidepressants amitriptyline, duloxetine, mirtazapine and citalopram in animal models of acute, persistent and neuropathic pain

The effects of acute, systemic administration of amitriptyline, duloxetine and mirtazapine (antidepressant drugs that variously affect extracellular noradrenaline and serotonin levels) and the selective serotonin reuptake inhibitor (SSRI) citalopram were compared in rat models of experimental pain. None of the drugs (all 3-30 mg/kg, i.p.) affected acute nociceptive responses as measured in the tail flick test. In the hot plate test, duloxetine and mirtazapine significantly increased (P<0.05) the nociceptive response latency, whereas amitriptyline and citalopram were ineffective. In the formalin test, duloxetine and citalopram significantly attenuated, whereas amitriptyline and mirtazapine increased, second phase flinching behaviour (all P<0.05). However, amitriptyline and mirtazapine reduced second phase licking behaviour. In the chronic constriction injury model of neuropathic pain, thermal hyperalgesia of the injured hindpaw was significantly attenuated by all four drugs (P<0.05); only amitriptyline and duloxetine fully reversed thermal hypersensitivity. None of the drugs tested attenuated mechanical allodynia. In contrast amitriptyline, duloxetine and mirtazapine significantly reduced mechanical hyperalgesia (P<0.05); citalopram was ineffective. No drug-related effects on motor performance in the rotarod test were observed. These results (a) highlight the difficulty in correlating antinociceptive effects of drugs from different antidepressant classes across a range of animal pain models and (b) suggest that antidepressants that variously affect both noradrenaline and serotonin levels have more potent and efficacious antinociceptive effects than SSRIs (as exemplified by citalopram), against a range of pain-like behaviours in an animal model of neuropathic pain.