Modulation of neurogenic inflammation: novel approaches to inflammatory disease

Cancer-nervous system crosstalk: from biological mechanism to therapeutic opportunities

A growing body of research suggests a bidirectional interaction between cancer and the nervous system. Neural cells exert their effects on tumors by secreting neurotransmitters and cell adhesion molecules, which interact with specific receptors on tumor cells to modulate their behavior. Conversely, tumor-secreted factors, particularly including inflammatory factors, can alter neural activity and increase neuronal excitability, potentially contributing to neurological manifestations such as epilepsy. The immune system also serves as a crucial intermediary in the indirect communication between cancer and the nervous system. These insights have opened promising avenues for novel therapeutic strategies targeting both tumors and their associated neurological complications. In this review, we have synthesized the key biological mechanisms underlying cancer-nervous system interactions that have emerged over the past decade. We outline the molecular and cellular pathways mediating this cross-talk and explore the clinical implications of targeting the nervous system to suppress tumor growth and metastasis, mitigate neurological complications arising from cancer progression, and modulate the immune response through neural regulation in the context of cancer therapy.

Impact of chronic opioid use on acute health care utilization in children with IBD and arthritis: a retrospective cohort study

BACKGROUND

Opioid use is non-trivial in children with inflammatory bowel disease (IBD) and arthritis, and options are limited for pain management. We aimed to determine the impacts of chronic opioid use on acute care utilization in children with both IBD and arthritis in United States.

METHODS

Participants less than 18 years of age with IBD and arthritis, with at least one year of continuous enrollment (no interruption of insurance for at least 1 year) and at least one pharmacy claim in the Truven Health MarketScan Claims and Encounter Database, were included in the study. The primary exposure was chronic opioid use. Chronic opioid users were matched to non-exposed controls. The primary outcome was acute healthcare utilization (total number of emergency department visits and hospitalizations within 12-24 months after the index date). The association between acute care utilization and chronic opioid use was assessed using a multivariable negative binomial regression model.

RESULTS

480 children with IBD and arthritis met inclusion criteria, out of which 59 (12.3%) met the criteria for chronic opioid exposure, and 46 of them had at least one year of follow-up. IRR (incidence rate ratio) of acute healthcare use for patients exposed to chronic opioid use was 1.7 higher than controls. Additionally, public insurance and having a chronic pain condition were independently and significantly associated with greater acute healthcare use.

CONCLUSION

Chronic opioid use was significantly associated with greater acute health care utilization in children with IBD and arthritis than matched unexposed controls. Future investigation is warranted to determine if preferential use of non-opioid therapy for pain control can reduce acute healthcare costs in this population.

Carcinogenesis and Metastasis: Focus on TRPV1-Positive Neurons and Immune Cells

Both sensory neurons and immune cells, albeit at markedly different levels, express the vanilloid (capsaicin) receptor, Transient Receptor Potential, Vanilloid-1 (TRPV1). Activation of TRPV1 channels in sensory afferent nerve fibers induces local effector functions by releasing neuropeptides (most notably, substance P) which, in turn, trigger neurogenic inflammation. There is good evidence that chronic activation or inactivation of this inflammatory pathway can modify tumor growth and metastasis. TRPV1 expression was also demonstrated in a variety of mammalian immune cells, including lymphocytes, dendritic cells, macrophages and neutrophils. Therefore, the effects of TRPV1 agonists and antagonists may vary depending on the prominent cell type(s) activated and/or inhibited. Therefore, a comprehensive understanding of TRPV1 activity on immune cells and nerve endings in distinct locations is necessary to predict the outcome of therapies targeting TRPV1 channels. Here, we review the neuro-immune modulation of cancer growth and metastasis, with focus on the consequences of TRPV1 activation in nerve fibers and immune cells. Lastly, the potential use of TRPV1 modulators in cancer therapy is discussed.

Opioid Use Among Patients With Inflammatory Bowel Disease: A Systematic Review and Meta-analysis

BACKGROUND AND AIMS

Despite reported adverse effects of opioids in patients with inflammatory bowel disease (IBD), the burden of opioid use in this population appears to be high. We performed a systematic review and meta-analysis of prior studies to determine the prevalence of opioid use among patients with IBD as well as risk factors and outcomes associated with opioid use in this population.

METHODS

We conducted a systematic search of MEDLINE, Embase, Web of Science, and the Cochrane Library through November of 2019. Primary outcomes included the prevalence of opioid use and demographic and clinical variables associated with opioid use in patients with IBD. Quality was assessed using the Newcastle-Ottawa scale. We used random-effect meta-analysis to estimate pooled relative risks (RRs) and 95% CIs.

RESULTS

Of 780 citations identified, 31 were included in our study. The prevalence of opioid use was 21% (95% CI, 13%-30%) in the outpatient setting. Likewise, 62% (95% CI, 25%-92%) of patients received opioids while hospitalized for IBD. Opioid use was associated with female sex (RR 1.20; 95% CI 1.03-1.40), depression (1.99; 95% CI 1.80-2.19), substance abuse (4.67; 95% CI 2.87-7.60), prior gastrointestinal surgery (2.33; 95% CI 1.66-3.26), biologic use (1.36; 95% CI 1.06-1.74), and steroid use (1.41; 95% CI 1.04-1.91). Based on the systematic review, opioid use also appeared to be associated with increased IBD activity, healthcare use, infection, and mortality.

CONCLUSION

In a systematic review and meta-analysis, we found that 21% of outpatients with IBD (and 62% of hospitalized patients) are opioid users; use is associated with more severe IBD and increased healthcare use. Further studies are required to determine whether opioids are the cause or an effect of these associations. Nonetheless, urgent interventions are needed to reduce opioid use, improve disease-related outcomes and reduce healthcare costs.

Novelty in Inflammation and Immunomodulation in Migraine

BACKGROUND

Migraine is a diffuse and disabling disease. Its pathophysiology is complex and involves both central and peripheral dysfunctions.

OBJECTIVE

This review will discuss the pathogenesis of migraine from the origin of the neuro-inflammatory theory, to the modern pathophysiological model and the latest therapies.

METHODS

PUBMED and EMBASE (up to May 2019) were searched for: migraine, inflammation, immunomodulation. An additional search was carried out from the bibliography of previous review articles.

RESULTS

Migraine was thought to be mainly a vascular disorder, according to the so-called "vascular theory". Based on animal models, a new hypothesis called "the neuro-inflammatory" was conceived at the end of the 20th century. The growing knowledge about the trigeminovascular system and its role in the inflammatory-pain pathway, allowed to identify other specific neurotransmitters, such as the Calcitonin Gene-Related Peptide and Pituitary Adenylate Cyclase-Activating Peptide. Evidence was provided that the inflammatory-pain system could become sensitised and, due to this sensitisation, the pain could also perpetuate, even in the absence of any triggers of the migraine attack. At last, brain immune cells modification during cortical spreading depression in migraine was demonstrated, along with the existence and function of the glymphatic system. The better comprehension of the immune system abnormalities allowed the development of new immunomodulating drugs: the monoclonal antibodies against the CGRP or the CGRP receptor. Moreover, new insights into the molecular mechanism of CGRP, and the function of C-fibres and Aδ-fibres, highlighted the mechanism of action of Botulinum Toxin type A in the treatment of chronic migraine.

Evaluation of anti-nociceptive, anti-inflammatory and antipyretic potential of Mikania cordata (Burm. f.) Robinson in experimental animal model

Mikania cordata is widely used for the treatment of cuts, wounds, and dengue fever in Bangladesh. In the present study, essential oil (12.5, 25 and 50 mg/kg) and two extracts, viz., chloroform and ethyl acetate extracts (200, 400, 800 mg/kg b.w.) were tested for peripheral and central anti-nociceptive activity by acetic acid-induced writhing and hot plate method, respectively. Carrageenan-induced rat paw edema assay and yeast-induced hyperthermia assay were also carried out to evaluate anti-inflammatory and antipyretic properties of oil and extracts, respectively at aforesaid doses. The essential oil (50 mg/kg), chloroform extract (800 mg/kg) and ethyl acetate extract (800 mg/kg) showed potent peripheral anti-nociceptive activity having 47.33%, 29.33% and 16.65% of writhing inhibition, respectively, comparable with standard diclofenac (52.0%). Essential oil (50 mg/kg), chloroform extract (800 mg/kg) and ethyl acetate extract (800 mg/kg) presented promising central anti-nociceptive activity as well having 95.86%, 79.18% and 42.37% elongation of reaction time, respectively, at 90 min after administration of essential oil, ethyl acetate extract and 60 min after administration of chloroform extract. In anti-inflammatory activity screening, the essential oil (50 mg/kg) produced the highest 72.80% edema inhibition at 4 h after administration of carrageenan which was comparable with that of standard phenylbutazoe (87.87%). On the other hand, chloroform extract (800 mg/kg) and ethyl acetate extract (800 mg/kg) showed up to 34.31% and 15.27% of edema inhibition, respectively, at 4 h after administration of carrageenan. In antipyretic assay, the essential oil and chloroform extract displayed a strong antipyretic effect in yeast-induced rats, whereas the ethyl acetate extract had no antipyretic activity. The present study revealed anti-nociceptive, anti-inflammatory and antipyretic potential of M. cordata which could be the therapeutic option against fever, inflammations as well as painful conditions and confirmed the traditional use of M. cordata.

Cough and airway disease: The role of ion channels

Cough is the most common reason for patients to visit a primary care physician, yet it remains an unmet medical need. It can be idiopathic in nature but can also be a troublesome symptom across chronic lung diseases such as asthma, COPD and idiopathic pulmonary fibrosis (IPF). Chronic cough affects up to 12% of the population and yet there are no safe and effective therapies. The cough reflex is regulated by vagal, sensory afferent nerves which innervate the airway. The Transient Receptor Potential (TRP) family of ion channels are expressed on sensory nerve terminals, and when activated can evoke cough. This review focuses on the role of 4 TRP channels; TRP Vannilloid 1 (TRPV1), TRP Ankyrin 1 (TRPA1), TRP Vannilloid 4 (TRPV4) and TRP Melastatin 8 (TRPM8) and the purinergic P2X3 receptor and their possible role in chronic cough. We conclude that these ion channels, given their expression profile and their role in the activation of sensory afferents and the cough reflex, may represent excellent therapeutic targets for the treatment of respiratory symptoms in chronic lung disease.

Predictors of Chronic Opioid Use in Newly Diagnosed Crohn's Disease

BACKGROUND AND AIMS

Patients with Crohn's disease (CD) are often prescribed opioids chronically to manage pain associated with their disease. However, little evidence exists to support this practice. Here, we examine newly diagnosed patients with CD with and without chronic opioid use (COU) and sought to identify predictors and consequences of COU.

METHODS

A nationally representative administrative health care claims that data set identified newly diagnosed patients with CD. Their data were examined during the periods 6 months before and 2 years after diagnosis. Multivariable logistic regression was used to assess predictors of COU at diagnosis.

RESULTS

The final study cohort consisted of 47,164 patients with CD. Of them, 3.8% were identified with new COU. Chronic opioid users were more likely women, older, and likely who had more surgeries, endoscopies, admissions, and medication usage compared with other patients. Features detected before CD diagnosis that correlated with COU after diagnosis included previous opioid use (odds ratio [OR] = 6.6), chronic pain (OR = 1.36), arthritis (OR = 1.95), and mental disorders (OR = 1.58). Interestingly, emergency department visits before CD Dx increased the risk of COU (OR = 1.11), whereas endoscopy reduced COU risk (OR = 0.88).

CONCLUSIONS

This study presents a nationally representative assessment of COU in newly diagnosed patients with CD. The results may be used to determine the impact of COU in this population and to alert clinicians to those patients with CD at high risk of COU. Chronic opioids are consistently associated with indicators of more severe disease; however, additional research is needed to determine whether COU drives disease severity or vice versa.

Extracellular Adenosine 5'-Triphosphate in Obstructive Airway Diseases

In recent years, numerous studies have generated data supporting the hypothesis that extracellular adenosine 5'-triphosphate (ATP) plays a major role in obstructive airway diseases. Studies in animal models and human subjects have shown that increased amounts of extracellular ATP are found in the lungs of patients with COPD and asthma and that ATP has effects on multiple cell types in the lungs, resulting in increased inflammation, induction of bronchoconstriction, and cough. These effects of ATP are mediated by cell surface P2 purinergic receptors and involve other endogenous inflammatory agents. Recent clinical trials reported promising treatment with P2X3R antagonists for the alleviation of chronic cough. The purpose of this review was to describe these studies and outline some of the remaining questions, as well as the potential clinical implications, associated with the pharmacologic manipulation of ATP signaling in the lungs.

Neuroimmunity: Physiology and Pathology

Evolution has yielded multiple complex and complementary mechanisms to detect environmental danger and protect tissues from damage. The nervous system rapidly processes information and coordinates complex defense behaviors, and the immune system eliminates diverse threats by virtue of mobile, specialized cell populations. The two systems are tightly integrated, cooperating in local and systemic reflexes that restore homeostasis in response to tissue injury and infection. They further share a broad common language of cytokines, growth factors, and neuropeptides that enables bidirectional communication. However, this reciprocal cross talk permits amplification of maladaptive feedforward inflammatory loops that contribute to the development of allergy, autoimmunity, itch, and pain. Appreciating the immune and nervous systems as a holistic, coordinated defense system provides both new insights into inflammation and exciting opportunities for managing acute and chronic inflammatory diseases.

Volatile oils: Potential agents for the treatment of respiratory infections

Due to presence of secondary bioactive metabolites, natural compounds are considered a major source of new active molecules that can be developed as new drugs. Infectious diseases, and mainly the common respiratory infections, are major challenges to the current chemotherapy systems and, therefore, there is a requirement to find new compounds with therapeutic potential. The volatile natural compounds and essential oils are the main treasure agents in the natural compounds with antibiotic potential. The present chapter reviews natural traditional remedies used in the treatment of respiratory infections with the emphasis on antibacterial, antiviral, and antiinflammation activities of the volatile natural compounds (essential oils, etc.), and provides a brief view in some of structural activity relationships between antibacterial potencies and chemical structures of the essential oil’s constituents.

Irrigation with bupivacaine at the surgical bed for postoperative pain relief after laparoscopic cholecystectomy

PURPOSE

The aim of this study was to evaluate the effect of bupivacaine irrigated at the surgical bed on postoperative pain relief in laparoscopic cholecystectomy patients.

METHODS

This study included 60 patients undergoing elective laparoscopic cholecystectomy who were prospectively randomized into 2 groups. The placebo group (n=30) received 20cc saline without bupivacaine, installed into the gallbladder bed. The bupivacaine group (n=30) received 20cc of 0.5% bupivacaine in at the same surgical site. Pain was assessed at 0, 6, 12, and 24 hours by using a visual analog scale (VAS).

RESULTS

A significant difference (P=.018) was observed in pain levels between both groups at 6 hours postoperatively. The average analgesic requirement was lower in the bupivacaine group, but this did not reach statistical significance.

CONCLUSIONS

In our study, the use of bupivacaine irrigated over the surgical bed was an effective method for reducing pain during the first postoperative hours after laparoscopic cholecystectomy.

Episiotomy pain relief: Use of Lavender oil essence in primiparous Iranian women

INTRODUCTION

Post-episiotomy discomfort and its consequences can affect maternal quality of life and mental health as well as the mother and baby relationship. Complementary medicine is increasingly used and Lavender oil is frequently prescribed due to its antiseptic and healing properties.

METHOD

This clinical trial involved 60 qualified primiparous women admitted for labor in Kamali Hospital in Karaj, Iran. They were randomly categorized into two groups: case (using Lavender oil) and control (usual hospital protocol). Participants pain and discomfort were recorded using a Visual Analogue Scale (VAS) and a Redness, Edema, Ecchymosis, Discharge Scale (REEDA). Pain was evaluated at 4 h, 12 h and 5 days following episiotomy. Collected data was analyzed in SPSS 14 using an independent t-test and chi-square.

RESULTS

There was a statistical difference in pain intensity scores between the 2 groups after 4 h (p = 0.002, and 5 days (p = 0.000) after episiotomy. However, differences in pain intensity between the two groups, at 12 h post-surgery, were not significant (p = 0.066). The REEDA score was significantly lower in the experimental group (Lavender oil group) 5 days after episiotomy (p = 0.000).

CONCLUSION

According to these findings, use of Lavender oil essence can be effective in reducing perineal discomfort following episiotomy. It is suggested that Lavender oil essence may be preferably to the use of Betadine for episiotomy wound care.

Neurogenic inflammation in lung disease: burnt out?

Neurogenic inflammation results from activation of sensory nerves which, acting in an 'efferent' manner, release sensory neuropeptides to induce a wide variety of physiological and immunological responses. This process is easy to demonstrate experimentally in the airways of small laboratory animal species but in human airways is equivocal and, at best, minor compared with cholinergic neural control. Nevertheless, sensory neuropeptides (calcitonin gene-related peptide and the tachykinins, substance P and neurokinin A) induce airway responses in both laboratory animals and humans which suggest a potential for sensory-efferent control of human airways. In addition, there is indirect evidence for an increased 'expression' of sensory nerves and tachykinin receptors in asthma and bronchitis, which indicates that neurogenic inflammation contributes to pathophysiology of these airway conditions. In contrast, clinical trials using different classes of drugs to inhibit sensory nerve responses have failed to resolve whether neurogenic inflammation is involved in asthma, although there are concerns about the relevance of some of these studies. In contrast to their involvement in airway neurogenic inflammation, sensory nerves may be important in initiating protective reflexes, including coughing and sneezing, acting via their afferent pathways. Thus, although flickering, the concept of neurogenic inflammation in lung disease is not yet burnt out. However, it needs the rekindling of interest which re-evaluation as a protective process may bring, together with data from more appropriate clinical studies in asthma and chronic bronchitis.

Capsaicin delays regeneration of the neuromuscular junction of rat extensor digitorum longus muscle after ischemia

Trauma or the tourniquet used in orthopedic surgery is often associated with ischemia-reperfusion (I/R) injury with a consequent decrease of muscle power. To explore whether components of the neuromuscular junction (NMJ) are involved in this muscle dysfunction, NMJs were ultrastructurally characterized in the extensor digitorum longus muscle of rats at reperfusion times of 1, 24, 72, and 168 h after a 120-min arterial occlusion. Disorganization of the presynaptic membrane and mitochondrial injury was noted at 1 h, followed by fragmentation and partial engulfment of nerve terminals by Schwann cells at 24 and 72 h. The magnitude of degenerative changes declined at 168 h, suggesting the commencement of regeneration. The postsynaptic membrane remained intact throughout the whole period. In our previous study, deafferentation with pretreatment of the sciatic nerve with capsaicin, which reduces neurogenic inflammation and has a selective effect on nociceptive fibers, improved functional recovery of the muscle after I/R. The present results document a significantly delayed structural regeneration of the motor nerve terminals after combined capsaicin and I/R treatment. Since capsaicin treatment alone had no discernible effect on the structure of NMJs, the findings point to a possibly indirect effect of capsaicin on the motor nerves, which may predispose them to increased susceptibility unmasked only by a subsequent injury. The mismatch between the enhanced functional improvement of the muscle and delayed regeneration of the nerve after capsaicin pretreatment questions the efficient use of such deafferentation to protect the integrity of neuromuscular junctions in I/R injury.

An Investigation of the Analgesic and Anti-Inflammatory Effects of Nigella sativa Seed Polyphenols

Extracts obtained from the seeds of Nigella sativa are used as a spice or remedy for the treatment of various inflammatory diseases. The purpose of this study was to examine the analgesic and anti-inflammatory effects of its polyphenols. N. sativa seed polyphenols were prepared, and analgesic and anti-inflammatory effects were studied in mice and rats using the acetic acid-induced writhing, formalin, light tail flick, carrageenan-induced paw edema, and croton oil-induced ear edema tests. In the acetic acid-induced writhing test, oral administration of N. sativa polyphenols (NSP) decreased the number of abdominal constrictions. Both oral and intraperitoneal administration of NSP significantly suppressed in a dose-dependent manner the nociceptive response in the early and late phases of the formalin test, and the effect on the late phase was more pronounced. Pretreatment with naloxone failed to reverse the analgesic activity of NSP in this test. NSP did not produce a significant analgesia in the light tail flick test in mice. Oral administration of NSP did not produce a significant reduction in carrageenan-induced paw edema. However, when injected intraperitoneally, NSP inhibited paw edema in a dosedependent manner. NSP when applied topically failed to reduce croton oil-induced ear edema. These results suggest that NSP have analgesic and anti-inflammatory effects. The lack of analgesic effect of NSP in the light tail flick test and also the failure of naloxone to reverse the analgesia in the formalin test reveal that mechanisms other than stimulation of opioid receptors are involved.

Urgosedin Inhibits Hypotension, Hypoglycemia, and Pro-Inflammatory Mediators Induced by Lipopolysaccharide

Urgosedin is a newly synthesized compound especially with serotonergic and alpha-adrenergic blocking actions. In rat isolated thoracic aorta, urgosedin competitively antagonized norepinephrine-, clonidine-, and serotonin-induced vasocontractions in a concentration-dependent manner. In radioligand binding experiments, urgosedin had significant binding affinities on alpha1/alpha2, 5-HT1A, 5-HT1B and 5-HT2A receptors. Intravenous injection of lipopolysaccharide (LPS) produced a biphasic hypotension in normotensive rats. Although intravenous injection of urgosedin caused minor depressor actions in the normotensive Wistar rat, urgosedin significantly attenuated the secondary prolonged hypotension produced by LPS. The plasma levels of cytokines (IL-1beta, IL-6, TNF-alpha, and IFN-gamma) and hypoglycemia induced by LPS were also reduced by urgosedin. Moreover, the acute survival rates (350 minutes) of endotoxic shock increased from 0% (LPS group) to 100% in the groups pretreated with urgosedin. In RAW264.7 cells, urgosedin inhibited LPS-induced inducible nitric oxide synthase (iNOS) expression. In conclusion, our data suggest that urgosedin was a newly potent serotonergic and mild alpha-adrenergic blocking agent. Its prevention of LPS-induced hypotension and hypoglycemia might partially mediate through its inhibition activities on the iNOS expression and cytokines formation. Urgosedin might be an effective pharmacological agent against LPS-induced hypotension, hypoglycemia, and the formation of pro-inflammatory mediators.

Greater involvement of neurokinins found in Guinea pig models of severe asthma compared with mild asthma

BACKGROUND

Involvement of neurokinins in asthma has been previously pointed out by several reports. However, the relationship between neurokinins and the severity of asthma has remained unclear. We developed a model of mild asthma (model I) and severe asthma (model II) in guinea pigs, and investigated the function of neurokinins in both models.

METHODS

In models I and II, systemically sensitized guinea pigs were made to inhale ovalbumin once and three times, respectively. Substance P (SP) and neurokinin A (NKA) concentrations in the bronchoalveolar lavage fluid (BALF) were measured in models I and II. Then, the effects of a capsaicin pretreatment, which depletes neurokinins, in both animal models on airway narrowing induced by the last ovalbumin inhalation, airway hyperresponsiveness to inhaled methacholine, and eosinophil accumulation in BALF, were investigated.

RESULTS

SP concentration tended to increase and the NKA concentration increased significantly in model II, but not in model I. Capsaicin pretreatment significantly inhibited the late bronchial response that was observed 2-6 h after the last ovalbumin inhalation, airway hyperresponsiveness and eosinophil accumulation in model II. On the other hand, it had no effects on the responses in model I.

CONCLUSION

It is suggested that the more severe the disease, the greater the involvement of neurokinins.

Pharmacologic treatment of chronic obstructive pulmonary disease: past, present, and future

Pharmacologic treatment of chronic obstructive pulmonary disease (COPD) has evolved considerably during the past several decades. Initial treatment of the disease was accomplished primarily through antibiotics, mucolytic agents, and nonselective sympathomimetic agents. Up-to-date treatment guidelines stratified according to strength of evidence are published in the National Heart, Lung, and Blood Institute-World Health Organization workshop report on the Global Strategy for the Diagnosis, Management, and Prevention of Chronic Obstructive Pulmonary Disease. Current drug therapy for stable COPD focuses primarily on bronchodilation through inhaled beta2-agonists and anticholinergic agents, immunization, and elimination of smoking as a risk factor. Although many pharmacologic agents are available to treat COPD, no drug has demonstrated effectiveness in halting progression of the disease. Rather, the goal of drug therapy at this time is to maintain control of symptoms and prevent COPD exacerbations. Compared with asthma, research into treatment for COPD has been minimal. However, a long-acting anticholinergic agent, tiotropium, has received approval status by the United States Food and Drug Administration. The drug has been shown to improve spirometric parameters, quality of life, and utilization of health care resources. In addition, several new targets for the treatment of COPD are being studied, and a few agents, including some that theoretically may slow functional decline in patients with COPD, are in development.

Anti-inflammatory and analgesic properties of the leaf extracts and essential oil of Lavandula angustifolia Mill

Extracts obtained from the leaves of Lavandula angustifolia Mill. (Lamiaceae) are used in Iranian folk medicine as remedies for the treatment of various inflammatory diseases. For evaluation of its probable analgesic and anti-inflammatory effects, hydroalcoholic extract, polyphenolic fraction and essential oil of the leaves of the herb were prepared and their analgesic effects were studied in mice using formalin and acetic acid-induced writhing tests. Carrageenan test in rats was used for assessment of anti-inflammatory activity of above-mentioned fractions. Results showed that while the hydroalcoholic extract (400-1600 mg/kg, p.o.) inhibited only the second phase of formalin test, the polyphenolic fraction (800 and 1600 mg/kg, p.o.) and essential oil (100 and 200 mg/kg, p.o.) suppressed both phases. In acetic acid-induced writhing test, polyphenolic fraction (400 and 800 mg/kg, p.o.) and essential oil (100 and 200 mg/kg, p.o.) reduced the number of abdominal constrictions. Essential oil at a dose of 200mg/kg also inhibited carrageenan-induced paw edema. Results of the present study confirm the traditional use of Lavandula angustifolia for the treatment of painful and inflammatory conditions and calls for further investigations to determine the active chemical constituent(s).

Peripheral opioidergic regulation of the tracheobronchial mucociliary transport system

We hypothesized that, in the airway mucosa, opioids are inhibitory neural modulators that cause an increase in net water absorption in the airway mucosa (as in the gut). Changes in bidirectional water fluxes across ovine tracheal mucosa in response to basolateral application of the opioid peptides beta-endorphin, dynorphin A-(1-8), and [d-Ala(2), d-Leu(5)]-enkephalin (DADLE) were measured. beta-Endorphin and dynorphin A-(1-8) decreased luminal-to-basolateral water fluxes, and dynorphin A-(1-8) and DADLE increased basolateral-to-luminal water flux. These responses were electroneutral. In seven beagle dogs, administration of aerosolized beta-endorphin (1 mg) to the tracheobronchial airways decreased the clearance of radiotagged particles from the bronchi in 1 h from 34.7 to 22.0% (P < 0.001). Naloxone abrogated the beta-endorphin-induced changes in vitro and in vivo. Contrary to our hypothesis, the opioid-induced changes in water fluxes would all lead to a predictable increase in airway surface fluid. The beta-endorphin-induced increases in airway fluid together with reduced bronchial mucociliary clearance may produce procongestive responses when opioids are administered as antitussives.

The effects of sympathectomy on capsaicin-evoked fos expression of spinal dorsal horn GABAergic neurons

Electrophysiological studies have suggested that activity of spinal GABAergic interneurons can be enhanced following intradermal injection of capsaicin (CAP). This activity is proposed to be involved in the generation of dorsal root reflexes (DRRs) that contribute to neurogenic inflammation. We have recently reported that NMDA or non-NMDA antagonists by intrathecal pretreatment attenuate the increased Fos expression in spinal dorsal horn GABAergic neurons after intradermal injection of CAP in rats. Sympathetic efferents have been suggested to modulate inflammatory pain possibly by interactions with primary afferent terminals. In electrophysiological studies by our group, enhancement of the CAP-induced DRRs could be prevented by surgical sympathectomy and blocked by intraarterial pretreatment of the foot with alpha(1)- but not by alpha(2)-adrenoceptor antagonists. In order to determine morphologically if surgical sympathectomy changes the expression of Fos in GABAergic neurons in the lumbosacral spinal cord induced by CAP injection, further experiments were performed using immunofluorescence double-labeling staining at 30 min following CAP or vehicle injection into the glabrous skin of one hind paw of anesthetized rats both in sham-operated and sympathectomized animals. Our results showed that the proportion of Fos-positive GABAergic neuronal profiles was significantly increased following CAP injection (48.8+/-4.76%) compared to vehicle injection (23.8+/-5.1%) in laminae I-V on the ipsilateral side (P<0.05). However, when sympathetic efferents were removed surgically 7-10 days prior to the experiment (n=6), only 32.07+/-9.03% of GABA-immunoreactive neuronal profiles were stained for Fos following CAP injection, a significant reduction in the CAP-evoked Fos-staining of GABAergic neurons after surgical sympathectomy. These findings support our previous electrophysiological studies that GABAergic neurons take part in nociceptive processing within the spinal dorsal horn and suggest that sympathetic efferents may affect nociceptive transduction in the periphery.

Antinociceptive and anti-inflammatory effects of Satureja hortensis L. extracts and essential oil

Satureja hortensis L. (Lamiaceae) is a medicinal plant used in Iranian folk medicine as muscle and bone pain reliever. In the present study, hydroalcoholic extract, polyphenolic fraction and essential oil of the aerial parts of the herb were prepared and evaluated for the analgesic activity using light tail flick, formalin and acetic acid-induced writhing in mice. Also, the anti-inflammatory effects of the above-mentioned preparations were assessed using carrageenan-induced paw edema in rats. Results showed that in the light tail flick test neither the essential oil nor the extracts could exert any significant effect. The hydroalcoholic extract (2000 mg/kg, p.o.) and the essential oil (200 mg/kg, p.o.) inhibited the mice writhing responses caused by acetic acid. In formalin test, hydroalcoholic extract (500-2000 mg/kg, p.o.), polyphenolic fraction (250-1000 mg/kg, p.o.) and the essential oil (50-200 mg/kg, p.o.) showed analgesic activity and pretreatment with naloxone (1 mg/kg, i.p.) or caffeine (20 mg/kg, i.p.) failed to reverse this antinociceptive activity. Polyphenolic fraction (1000 mg/kg, p.o.) and the essential oil (200 mg/kg) reduced edema caused by carrageenan. These results suggest that S. hortensis L. has antinociceptive and anti-inflammatory effects and probably mechanism(s) other than involvement of opioid and adenosine receptors mediate(s) the antinociception.

Acupuncture modulation of capsaicin-induced inflammation: effect of intraperitoneal and local administration of naloxone in rats. A blinded controlled study

OBJECTIVE

It is believed that acupunctural stimulation induces an analgesic response mainly through a central mechanism: that is, through an increase in the production of opioid peptides and their release at different levels in the nervous system. We sought to establish whether the modulating effect of acupuncture on experimental neurogenic edema can be attributed to a central mechanism only or whether a peripheral mechanism could also exist. Intraperitoneal administration was compared to local administration in the same paw in rats that were injected with capsaicin and in the same dermatome of the acupunctural stimulation.

MATERIALS AND METHODS

Experimentation was conducted on 105 male Sprague-Dawley rats weighing 180-220 g, divided into 7 groups as follows: group 1, control; groups 2-4 (15 animals), stimulated with manual acupuncture; group 3 also treated with intraperitoneal naloxone 1 mg/kg; group 4 also treated locally with naloxone (20 microg); groups 5-7 (15 animals), stimulated with 5 Hz and 5 mA electroacupuncture (EAP); group 6 also treated with intraperitoneal naloxone, 1 mg/kg, group 7 also treated locally with naloxone (20 microg).

RESULTS

The results indicate that the administration of 1 mg/kg of naloxone intraperitoneally can inhibit the modulating effect of acupunctural stimulation. Equally effective in inhibiting the modulating effect of acupunctural stimulation, although not having a systemic effect, is a 20-microg dose of naloxone administered peripherally on the site of edema induction.

CONCLUSION

It is possible to conclude that both systemic and peripheral mechanisms seem to be implicated in the modulating effect of acupuncture on the neurogenic inflammation mechanism.

Proteinases and proteinase-activated receptor 2: a possible role to promote visceral hyperalgesia in rats

BACKGROUND & AIMS

PAR-2s are highly expressed throughout the gastrointestinal tract. These receptors are cleaved by trypsin and mast cell tryptase and can be activated by peptides corresponding to the tethered ligand of the receptor (SLIGRL-NH2 for rat). The aim of this study was to determine whether colonic administration of PAR-2 agonists affects visceral sensitivity to rectal distention in conscious rats.

METHODS

Abdominal contractions (a criteria of visceral pain) were recorded in rats equipped with intramuscular electrodes. Rectal distention was performed at various times after intracolonic infusion of SLIGRL-NH2 and trypsin. Inflammation parameters and permeability were followed in the colon after the intracolonic injections. Fos expression at a spinal level (L4-L6) was also studied 2 hours after intracolonic injection of SLIGRL-NH2.

RESULTS

Rectal distention significantly increased abdominal contractions starting at the RD volume of 0.8 mL. Intracolonic injection of SLIGRL-NH2 (200 microg/rat) and trypsin (200 U/rat), but not vehicle, LRGILS-NH2 (control peptide), boiled trypsin, or SLIGRL-NH2 injected IP, significantly increased (P < 0.05) abdominal contractions for high volumes of distention, 10- and 24-hour postinfusion. SLIGRL-NH2-induced hyperalgesia was inhibited by a NK1 receptor antagonist (SR 140333) but not by indomethacin. Intracolonic injection of SLIGRL-NH2 elevated spinal Fos expression and caused increased intestinal permeability but did not cause detectable inflammation.

CONCLUSIONS

Intracolonic infusion of subinflammatory doses of PAR-2 agonists activated spinal afferent neurons and produced a delayed rectal hyperalgesia that involves changes in intestinal permeability and the activation of NK1 receptors. These results identify a possible role for proteinases and PAR-2 in the genesis of visceral hyperalgesia.

NMDA or non-NMDA receptor antagonists attenuate increased Fos expression in spinal dorsal horn GABAergic neurons after intradermal injection of capsaicin in rats

GABAergic neurons play an important role in the generation of primary afferent depolarization, which results in presynaptic inhibition and, if large enough, triggers dorsal root reflexes. Recent electrophysiological studies by our group have suggested that increased excitation of spinal GABAergic neurons by activation of N-methyl-D-aspartate (NMDA) and non-NMDA receptors following intradermal injection of capsaicin results in the generation of DRRs that contribute to neurogenic inflammation. The present study was to determine if changes in the expression of Fos protein occur in GABAergic neurons in the lumbosacral spinal cord following injection of capsaicin into the glabrous skin of one hind paw of anesthetized rats and if pretreatment with an NMDA receptor antagonist, D-(-)-2-amino-7-phosphonoheptanoic acid (AP7) or a non-NMDA receptor antagonist, 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) blocks Fos expression in these neurons. The experiments used western blots and immunofluorescence double labeling staining following capsaicin or vehicle injection. Western blots showed that Fos protein was increased on the ipsilateral side in spinal cord tissue 0.5 h after capsaicin injection. Pretreatment with AP7 or CNQX caused a decrease in capsaicin-induced Fos expression. Immunofluorescence double labeling showed that the proportion of Fos-positive GABAergic neuronal profiles was significantly increased following capsaicin injection (48.8+/-4.8%) compared to the vehicle injection (23.8+/-5.1%) in superficial laminae on the ipsilateral side in lumbosacral spinal cord (P<0.05). However, when the spinal cord was pretreated with AP7 (5 microg) or CNQX (0.2 microg), only 9.1+/-0.6% or 7.1+/-0.8% of GABA-immunoreactive neuronal profiles were stained for Fos following capsaicin injection. The blockade of the capsaicin-evoked Fos staining was dose-dependent. These findings suggest that GABAergic neurons take part in dorsal horn circuits that modulate nociceptive information and that the function of GABAergic neurons following capsaicin injection is partially mediated by NMDA and non-NMDA receptors.

Neurogenic inflammation in the context of migraine

Despite considerable research into the pathogenesis of idiopathic headaches, such as migraine, the pathophysiological mechanisms underlying them remain poorly understood. Although it is well established that the trigeminal nerve becomes activated during migraine, the consequences of this activation remain controversial. One theory, based on preclinical observations, is that activation of trigeminal sensory fibers leads to a painful neurogenic inflammation within the meningeal (dural) vasculature mediated by neuropeptide release from trigeminal sensory fibres and characterized by plasma protein extravasation, vasodilation, and mast cell degranulation. Effective antimigraine agents such as ergots, triptans, opioids, and valproate inhibit preclinical neurogenic dural extravasation, suggesting that this activity may be a predictor of potential clinical efficacy of novel agents. However, several clinical trials with other agents that inhibit this process preclinically have failed to show efficacy in the acute treatment of migraine in man. Alternatively, it has been proposed that painful neurogenic vasodilation of meningeal blood vessels could be a key component of the inflammatory process during migraine headache. This view is supported by the observation that jugular plasma levels of the potent vasodilator, calcitonin gene-related peptide (CGRP) are elevated during the headache and normalized by successful sumatriptan treatment. Preclinically, activation of trigeminal sensory fibers evokes a CGRP-mediated neurogenic dural vasodilation, which is blocked by dihydroergotamine, triptans, and opioids but unaffected by NK1 receptor antagonists that failed in clinical trials. These observations suggest that CGRP release with associated neurogenic dural vasodilation may be important in the generation of migraine pain, a theory that would ultimately be tested by the clinical testing of a CGRP receptor antagonist.

The effect of unilateral sympathectomy and cavity preparation on peptidergic nerves and immune cells in rat dental pulp

Recent evidence suggests interactions between primary afferent nociceptors and postganglionic sympathetic efferents in the pathogenesis of inflammation. The effect of unilateral removal of the superior cervical ganglion on the innervation pattern of nerve fibers immunoreactive (IR) to calcitonin gene-related peptide (CGRP), substance P (SP), and neuropeptide Y (NPY), as well as the occurrence of immune cells in the injured and uninjured rat molar pulp, was investigated. Light microscopic immunocytochemistry demonstrated that the molar pulps contralateral to the sympathectomy contained a NPY-IR nerve fiber network more dense and heavily stained than unoperated control rats. The NPY-IR fibers showed, however, no sprouting after deep cavity preparation. There was no compensatory increase in CGRP- and SP-IR nerve fibers in the dental pulp after unilateral sympathectomy, although a significant increase in cells IR to CGRP and SP was found in the ipsilateral trigeminal ganglion. Unilateral sympathectomy induced a significant increase in immune cell density both in the inflamed and in the uninflamed dental pulp bilaterally. Our results demonstrate, for the first time, a trophic effect of the sympathetic nerves on immune cells in the dental pulp, indicating that an imbalance of sympathetic nerves may induce inflammation and pain in teeth.

Inhibition of synovial plasma extravasation by preemptive administration of an antiinflammatory irrigation solution in the rat knee

Inflammation and hyperalgesia during surgical procedures are caused by the local release of multiple inflammatory mediators. We used a rat knee joint model of acute inflammation (synovial plasma extravasation) to determine whether preemptive intraarticular irrigation of the antiinflammatory drugs ketoprofen, amitriptyline, or oxymetazoline, alone or in combination, can reduce inflammatory soup-induced plasma extravasation. These three drugs were selected because of their abilities to collectively inhibit the inflammatory effects of biogenic amines, eicosanoid production, and the release of neuropeptides from C-fiber terminals. Synovial perfusion of each one of the three drugs 10 min before, and then in combination with, the inflammatory soup (bradykinin, 5-hydroxytryptamine, and mustard oil) did not reduce plasma extravasation. Similarly, two-drug combinations did not significantly reduce inflammatory soup-induced plasma extravasation. The combination of all three drugs (amitriptyline, ketoprofen, and oxymetazoline) produced a dramatic inhibition of plasma extravasation and was more effective than any of the two-drug combinations. A comparison between the preemptive (10 min before inflammatory soup perfusion) and postinflammatory administration (10 min after inflammatory soup perfusion) showed that the postinflammatory administration of the three-drug solution lost all ability to inhibit inflammatory soup-induced plasma extravasation. We conclude that acute synovial inflammation, which is induced and maintained by multiple mediators, can be substantially inhibited only by the preemptive administration of a drug combination that targets multiple inflammatory mediators.

IMPLICATIONS

Preemptive, intraarticular irrigation of a combination of multiple antiinflammatory drugs is a novel and potentially effective method for reducing the synovial inflammatory response, such as that during arthroscopy. In this study, a three-drug combination infusion was statistically superior to one- or two-drug infusions in a rat model.

NK1 receptor stimulation causes contraction and inositol phosphate increase in medium-size human isolated bronchi

Although contraction of human isolated bronchi is mediated mainly by tachykinin NK2 receptors, NK1 receptors, via prostanoid release, contract small-size (approximately 1 mm in diameter) bronchi. Here, we have investigated the presence and biological responses of NK1 receptors in medium-size (2-5 mm in diameter) human isolated bronchi. Specific staining was seen in bronchial sections with an antibody directed against the human NK1 receptor. The selective NK1 receptor agonist, [Sar(9), Met(O2)(11)]SP, contracted about 60% of human isolated bronchial rings. This effect was reduced by two different NK1 receptor antagonists, CP-99,994 and SR 140333. Contraction induced by [Sar(9), Met(O2)(11)]SP was independent of acetylcholine and histamine release and epithelium removal, and was not affected by nitric oxide synthase and cyclooxygenase (COX) inhibition. [Sar(9), Met(O2)(11)]SP increased inositol phosphate (IP) levels, and SR 140333 blocked this increase, in segments of medium- and small-size (approximately 1 mm in diameter) human bronchi. COX inhibition blocked the IP increase induced by [Sar(9), Met(O2)(11)]SP in small-size, but not in medium-size, bronchi. NK1 receptors mediated bronchoconstriction in a large proportion of medium-size human bronchi. Unlike small-size bronchi this effect is independent of prostanoid release, and the results are suggestive of a direct activation of smooth muscle receptors and IP release.

Immunologically induced histamine release from rat peritoneal mast cells is enhanced by low levels of substance P

Although direct activation of mast cells by high concentrations (>10(-6) M) of substance P is well established, the effect of sub-micromolar concentrations of the neuropeptide on mast cell activation has not been reported. We hence investigated if substance P would modulate immunologic activation of mast cells by studying the effect of the neuropeptide on anti-rat immunologlobulin E antibody (anti-IgE)-induced histamine release from purified rat peritoneal mast cells. We observed that substance P could dose-dependently potentiate anti-IgE-induced histamine release from rat peritoneal mast cells at concentrations (3x10(-9) M to 3x10(-7) M) which alone induced insignificant or low level of histamine release. While the potentiating effect of substance P was not suppressed by any of the non-peptide tachykinin receptor antagonists CP99994 ((2S,3S)-3-(2-methoxybenzylamino)-2-phenylpiperidine), SR48968 ((S)-N-methyl-N-(4-acetylamino-4-phenylpiperidino)-2-(3,4-dichlorophenyl) butyl-benzamide) and SR142801 ((S)-(N)-(1-[3-(1-benzoyl-3(3,4-dichlorophenyl)piperidine-3-yl)propyl]-4-phenylpiperidin-4-yl)-N-methyl-acetamide), it was mimicked by compound 48/80 and suppressed by benzalkonium chloride. Hence, substance P enhanced anti-IgE-induced histamine release through a similar receptor-independent mechanism as the direct mast cell activating action of polybasic compounds. Since high concentrations of substance P required for directly activating mast cells may not be achievable physiologically, the enhancing actions of the neuropeptide on the immunologic activation of mast cells may be more clinically relevant in the pathogenesis of various inflammatory conditions.

Neurogenic inflammation in the airways

Release of neuropeptides, including tachykinins and calcitonin gene-related peptide, from sensory nerves via an axon or local reflex may have inflammatory effects in the airways. This neurogenic inflammation may be initiated by activation of sensory nerves by inflammatory mediators and irritants. Neurogenic inflammation is well developed in rodents and may contribute to the inflammatory response to allergens, infections and irritants in animal models. However, the role of neurogenic inflammation in airway inflammatory diseases, such as asthma and COPD is still uncertain as there is little direct evidence for the involvement of sensory neuropeptides in human airways. Initial clinical studies using strategies to block neurogenic inflammation have not been encouraging, but it is important to study more severe forms of airway disease in more prolonged studies in the future to explore the role of neurogenic inflammation.

Differential role of neurokinin receptors in human lymphocyte and monocyte chemotaxis

The precise nature of neurokin receptor involvement in human immune cell chemotaxis is unclear. This study therefore sought to directly compare the chemotactic effects of neurokinins on human T lymphocytes and monocytes. Substance P was found to have a similar dose-dependent chemotactic action on T lymphocyte and monocyte populations. In contrast, T lymphocytes were found to be more responsive than monocytes both to the highly selective NK-1 agonist, [Sar(9)Met O(2)(11)]-substance P, and also to the NK-2 selective agonist, beta-alanine neurokinin A((4-10)). Consistent with these findings, substance P-induced chemotaxis of both T lymphocyte and monocytes was attenuated by the selective NK-1 antagonist LY303870. However, the selective NK-2 antagonist MEN 10,376 was only effective in inhibiting the T lymphocyte response. The study confirms that neurokinins have chemotactic actions on immune cells and indicates important functional differences between human T lymphocyte and monocyte responses. This provides a potential mechanism by which the nervous system can selectively influence cellular recruitment in inflammatory disease.

Effect of triterpenoids on the inflammation induced by protein kinase C activators, neuronally acting irritants and other agents

In order to establish the mode of the anti-inflammatory activity of triterpenoids, 11 naturally occurring compounds were assayed on mouse ear oedema induced by the protein kinase C activators, mezerein, 12-O-tetradecanoylphorbol-13-acetate (TPA), two 12-deoxyphorbol-13-monoesters (13-tetradecanoate (DPT) and 13-phenylacetate (DPP)) and bryostatin 1, and by resiniferatoxin, xylene and arachidonic acid. The effects on bradykinin-induced paw oedema and on the rat skin inflammation caused by hydrogen peroxide were also examined. The oedema induced by mezerein and DPT was reduced to different extents by the triterpenoids administered epicutaneously (0.5 mg per ear). Against DPT-induced oedema, lupane and oleanane derivatives were the most effective compounds. Oleananes and lupanes possessing a carboxyl group were active against bryostatin 1-induced oedema. Most of the triterpenoids were ineffective against the neurogenic inflammation caused by resiniferatoxin and xylene. Many triterpenoids, especially oleanane and lupane alcoholic derivatives, were active against the plantar oedema induced by bradykinin and on the intradermal inflammation induced by hydrogen peroxide. In conclusion, the anti-inflammatory activity of triterpenoids may depend on inhibition of protein kinase C, without any involvement of neurogenic inflammatory mechanisms.

Novel approaches and targets for treatment of chronic obstructive pulmonary disease

There is a driving need to develop new and effective treatments for COPD. Bronchodilators are now the mainstay of symptomatic therapy and a new long-acting anticholinergic bronchodilator, tiotropium bromide, is now in advanced clinical trials as a once daily dry powder inhaler. Several inflammatory mediators are involved in the chronic neutrophilic inflammation that typifies COPD, including leukotriene B(4) and interleukin 8, for which specific receptor antagonists have been developed. Since the inflammatory process in COPD is essentially steroid resistant, new antiinflammatory treatments are needed. Drugs that may be effective include phosphodiesterase 4 inhibitors, NF-kappaB inhibitors, and interleukin 10. Inhibition of proteases is another approach and inhibitors of neutrophil elastase, cathepsins, and matrix metalloproteases are now in clinical development. Supply of endogenous antiproteases, such as alpha(1)-antitrypsin and secretory leukocyte protease inhibitors as recombinant proteins or by gene transfer, is also being explored. In future drugs that may stimulate alveolar repair might be developed, including retinoid receptor agonists and hepatic growth factor. Future directions will include earlier detection of disease, gene profiling to identify which smokers are at risk of COPD, and the development of noninvasive surrogate markers to monitor disease activity in order to monitor new therapies. Identification of genes that confer a risk for COPD in smokers may identify novel targets for drug development. Barnes PJ. Novel approaches and targets for treatment of chronic obstructive pulmonary disease.

The effect of a sciatic nerve block on the development of inflammation in carrageenan injected rats

Neurogenic inflammation may participate in postoperative inflammatory pain. We evaluated, in the rat, the influence of a short and prolonged sciatic nerve block on carrageenan-induced inflammation, the time course of which may be compared to postoperative inflammation. A catheter was placed on the right sciatic nerve and injected with 0.5% bupivacaine with epinephrine (0.2 mL): one injection in the Short Block Group, and four injections performed at 90-min intervals in the Prolonged Block Group. In all groups, the two hind paws were then injected with carrageenan. The development of inflammation was evaluated in both hind paws by measurement of paw circumference (PC) before, and 1, 2, 3, 4, 6, and 24 h after carrageenan injection. Temperature of both hind paws was evaluated at the same time points. The vocalization threshold to paw pressure test (VTPP) of both hind paws was evaluated at 6, 8, 10, 12, and 24 h after carrageenan injection. The left hind paw was used for the Control Group. A Sham Group had a catheter placed on the sciatic nerve and injected with normal saline. Inflammation developed in the Control Group with a maximum increase of PC (32%) and temperature (14%) 4 h after carrageenan injection and a maximal reduction of VTPP (44%) at 6 h, reflecting mechanical allodynia. A similar evolution was observed in the Sham Group. In the Short Block Group, the nerve block did not influence the PC, the paw temperature, or the VTPP when compared with the Control Group. In the Prolonged Block Group, when compared with the Control Group, the increased PC was reduced throughout the 24 h (P < 0.0001). The maximal increase in PC at 4 h was limited to 23%, as compared with the precarrageenan value. This effect on PC did not persist at 24 h. Paw temperature was increased (P = 0.07) throughout the study in the Prolonged Block Group, as compared with the Control Group. The VTPP reduction was still limited in the Prolonged Block Group at 24 h, as compared with the Control Group (P < 0.0001). We conclude that a prolonged sciatic nerve block limits carrageenan-induced increase in PC and, subsequently, mechanical allodynia at 24 h in rats.

IMPLICATIONS

Our study has shown that a prolonged (6 h) but not a short sciatic nerve block (90 min) can limit edema and related pain after carrageenan-induced inflammation in rat.

Substance P-induced vasodilatation is mediated by the neurokinin type 1 receptor but does not contribute to basal vascular tone in man

AIMS

Following intravenous administration of its prodrug, L-758,298, we assessed the pharmacodynamics of L-754,030, a novel and highly selective NK1 receptor antagonist, by examining systemic haemodynamics and the blood flow responses to intra-arterial substance P infusion.

METHODS

Sixteen healthy male volunteers participated in a double-blind, randomised, placebo controlled crossover trial of L-758 298. Forearm blood flow was measured using venous occlusion plethysmography during intrabrachial substance P infusion (0.125-128 pmol min-1 ). In part 1, eight subjects received substance P infusions before and during placebo, 0.25 mg, 1 mg or 5 mg of L-758 298. In part 2, eight subjects received substance P infusions 24 h after placebo or 1.43 mg of L-758 298.

RESULTS

L-758 298 caused dose dependent inhibition of substance P induced vasodilatation (P<0.001). Placebo adjusted differences (95% CI) in baseline forearm blood flow, mean arterial pressure and heart rate showed no relevant changes with 5 mg of L-758 298 (>1400-fold shift in substance P response): 0.00 (-0.49 to +0.49) ml 100 ml-1 min-1, 1. 0 (-3.2 to +5.2) mmHg and 1.9 (-5.9 to +9.7) beats min-1, respectively. Twenty-four hours after 1.43 mg of L-758,298, there was approximately 34-fold shift in response to substance P induced vasodilatation (P<0.008) at plasma L-754 030 concentrations of 2-3 ng ml-1. L-758 298 was generally well tolerated without serious adverse events.

CONCLUSIONS

Substance P induced forearm vasodilatation is mediated by the endothelial cell NK1 receptor in man but endogenous substance P does not appear to contribute to the maintenance of peripheral vascular tone or systemic blood pressure.

Mechanism of SNAP potentiating antiproliferative effect of calcitonin gene-related peptide in cultured vascular smooth muscle cells

We previously showed that CGRP inhibits cell proliferation which correlates with an elevation of cAMP levels in rabbit aortic vascular smooth muscle cells (VSMCs). The present study determined the effects of S-nitroso-N-acetylpenicillamine (SNAP, a nitric oxide donor) on CGRP-induced antiproliferative effects and cellular mechanism in cultured rabbit aortic VSMCs. The cells (in fifth-sixth passage) were exposed to 2.5% fetal bovine serum for 24 h in the presence or absence of SNAP, hCGRP or both.(3)H-thymidine incorporation was used to measure DNA synthesis. The results showed that SNAP (60-100 microm) significantly inhibited the proliferation and elevated cGMP levels in cultured rabbit aortic VSMCs. In combination, however, SNAP (30 microm) potentiated hCGRP (10-100 n m)-induced antiproliferation. SNAP (30 microm) and hCGRP (10-100 n m) or forskolin (10 microm), an activator of adenylate cyclase, caused more than additive cAMP elevations, but not cGMP elevations, in these cells. Quazinone, an inhibitor of cGMP-inhibited-phosphodiesterase (cGI-PDE, PDE3), or SNAP plus quazinone caused a similar potentiation as SNAP of the hCGRP-induced elevations of cAMP levels. The data indicate that SNAP-induced potentiation of CGRP's effects likely involves inhibition of cGI-PDE, thus allowing enhanced accumulation of cAMP that mediates the antiproliferative effects of hCGRP in cultured rabbit aortic VSMCs.

Pituitary adenylate cyclase-activating polypeptide and islet amyloid polypeptide in primary sensory neurons: functional implications from plasticity in expression on nerve injury and inflammation

Primary sensory neurons serve a dual role as afferent neurons, conveying sensory information from the periphery to the central nervous system, and as efferent effectors mediating, e.g., neurogenic inflammation. Neuropeptides are crucial for both these mechanisms in primary sensory neurons. In afferent functions, they act as messengers and modulators in addition to a principal transmitter; by release from peripheral terminals, they induce an efferent response, "neurogenic inflammation," which comprises vasodilatation, plasma extravasation, and recruitment of immune cells. In this article, we introduce two novel members of the sensory neuropeptide family: pituitary adenylate cyclase-activating polypeptide (PACAP) and islet amyloid polypeptide (IAPP). Whereas PACAP, a vasoactive intestinal polypeptide-resembling peptide, predominantly occurs in neuronal elements, IAPP, which is structurally related to calcitonin gene-related peptide, is most widely known as a pancreatic beta-cell peptide; as such, it has been recognized as a constituent of amyloid deposits in type 2 diabetes. In primary sensory neurons, under normal conditions, both peptides are predominantly expressed in small-sized nerve cell bodies, suggesting a role in nociception. On axotomy, the expression of PACAP is rapidly induced, whereas that of IAPP is reduced. Such a regulation of PACAP suggests that it serves a protective role during nerve injury, but that of IAPP may indicate that it is an excitatory messenger under normal conditions. In contrast, in localized adjuvant-induced inflammation, expression of both peptides is rapidly induced. For IAPP, studies in IAPP-deficient mice support the notion that IAPP is a pronociceptive peptide, because these mutant mice display a reduced nociceptive response when challenged with formalin.

Combined NK1 and NK2 tachykinin receptor antagonists: synthesis and structure-activity relationships of novel oxazolidine analogues

We report herein the synthesis and structure-activity relationships of a series of novel oxazolidine analogues with regards to NK1 and NK2 tachykinin receptor binding affinity. Among this series of oxazolidine analogues, some compounds exhibited excellent high binding affinities for both NK1 and NK2 receptors. In addition, we describe the inhibitory effect in vivo on SP-induced airway vascular hyperpermeability and NKA-induced bronchoconstriction in guinea pigs.

Effects and interactions of opioids on plasma exudation induced by cigarette smoke in guinea pig bronchi

The effects of opioids on cigarette smoke-induced plasma exudation were investigated in vivo in the main bronchi of anesthetized guinea pigs, with Evans blue dye as a plasma marker. Acute inhalation of cigarette smoke increased plasma exudation by 216% above air control values. Morphine, 0.1-10 mg/kg but not 30 mg/kg, inhibited the exudation but had no significant effect on substance P-induced exudation. Both 10 and 30 mg/kg of morphine increased exudation in air control animals, an effect inhibited by antihistamines but not by a tachykinin neurokinin type 1-receptor antagonist. Naloxone inhibited all morphine responses. Cigarette smoke-induced plasma exudation was inhibited by a mu-opioid-receptor agonist (DAMGO) but not by agonists at delta (DPDPE)- or kappa (U-50488H)-receptors. None of these agonists affected exudation in air control animals. DPDPE prevented the inhibition by DAMGO of cigarette smoke-induced plasma exudation, and the combination of DAMGO and DPDPE increased exudation in air control animals. Prevention of inhibition and the combination-induced increase were inhibited by antihistamines or the mast cell-stabilizing drug sodium cromoglycate. U-50488H did not alter the response to either DAMGO or DPDPE. We conclude that, in guinea pig main bronchi in vivo, mu-opioid-receptor agonists inhibit cigarette smoke-induced plasma exudation via a prejunctional mechanism. Plasma exudation induced by mu- and delta-receptor interactions is due to endogenous histamine release from mast cells.