Endogenous nitric oxide increases prostaglandin biosynthesis in carrageenin rat paw oedema

The edematogenic effect of Micrurus lemniscatus venom is dependent on venom phospholipase A2 activity and modulated by non-neurogenic factors

Coral snakes mainly cause neurotoxic symptoms in human envenomation, but experimental studies have already demonstrated several pharmacological activities in addition to these effects. This investigation was carried out with the aim of evaluating (1) non-neurogenic mechanisms involved in the inflammatory response induced by Micrurus lemniscatus venom (MLV) in rat hind paws, (2) participation of PLA₂ in this response, and (3) neutralizing efficiency of commercial anti-elapid antivenom on edema. MLV promoted a rapid, significant increase in vascular permeability, influx of leukocytes, and disorganization of collagen bundles, as demonstrated by histological analysis. Several pretreatments were applied to establish the involvement of inflammatory mediators in MLV-induced edema (5 µg/paw). Treatment of animals with chlorpromazine reduced MLV-induced edema, indicating participation of TNF-α. However, the inefficiency of other pharmacological treatments suggests that eicosanoids, leukotrienes, and nitric oxide have no role in this type of edema formation. In contrast, PAF negatively modulates this venom-induced effect. MLV was recognized by anti-elapid serum, but this antivenom did not neutralize edema formation. Chemical modification of MLV with p-bromophenacyl bromide abrogated the phospholipase activity and markedly reduced edema, demonstrating PLA₂ participation in MLV-induced edema. In conclusion, the non-neurogenic inflammatory profile of MLV is characterized by TNF-α-mediated edema, participation of PLA₂ activity, and down-regulation by PAF. MLV induces an influx of leukocytes and destruction of collagen fibers at the site of its injection.

Pro- and anti-inflammatory bioactive lipids imbalance contributes to the pathobiology of autoimmune diseases

Autoimmune diseases are driven by T_H17 cells that secrete pro-inflammatory cytokines, especially IL-17. Under normal physiological conditions, autoreactive T cells are suppressed by TGF-β and IL-10 secreted by microglia and dendritic cells. When this balance is upset due to injury, infection and other causes, leukocyte recruitment and macrophage activation occurs resulting in secretion of pro-inflammatory IL-6, TNF-α, IL-17 and PGE2, LTs (leukotrienes) accompanied by a deficiency of anti-inflammatory LXA4, resolvins, protecting, and maresins. PGE2 facilitates T_H1 cell differentiation and promotes immune-mediated inflammation through T_H17 expansion. There is evidence to suggest that autoimmune diseases can be suppressed by anti-inflammatory bioactive lipids LXA4, resolvins, protecting, and maresins. These results imply that systemic and/or local application of LXA4, resolvins, protecting, and maresins and administration of their precursors AA/EPA/DHA could form a potential therapeutic approach in the prevention and treatment of autoimmune diseases.

Regulatory Role of Nitric Oxide in Cutaneous Inflammation

Nitric oxide (NO), a signaling molecule, regulates biological functions in multiple organs/tissues, including the epidermis, where it impacts permeability barrier homeostasis, wound healing, and antimicrobial defense. In addition, NO participates in cutaneous inflammation, where it exhibits pro-inflammatory properties via the cyclooxygenase/prostaglandin pathway, migration of inflammatory cells, and cytokine production. Yet, NO can also inhibit cutaneous inflammation through inhibition of T cell proliferation and leukocyte migration/infiltration, enhancement of T cell apoptosis, as well as through down-regulation of cytokine production. Topical applications of NO-releasing products can alleviate atopic dermatitis in humans and in murine disease models. The underlying mechanisms of these discrepant effects of NO on cutaneous inflammation remain unknown. In this review, we briefly review the regulatory role of NO in cutaneous inflammation and its potential, underlying mechanisms.

Bioactive Lipids in Age-Related Disorders

Our own studies and those of others have shown that defects in essential fatty acid (EFA) metabolism occurs in age-related disorders such as obesity, type 2 diabetes mellitus, hypertension, atherosclerosis, coronary heart disease, immune dysfunction and cancer. It has been noted that in all these disorders there could occur a defect in the activities of desaturases, cyclo-oxygenase (COX), and lipoxygenase (LOX) enzymes leading to a decrease in the formation of their long-chain products gamma-linolenic acid (GLA), arachidonic acid, eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA) and docosahexaenoic acid (DHA). This leads to an increase in the production of pro-inflammatory prostaglandin E2 (PGE2), thromboxanes (TXs), and leukotrienes (LTs) and a decrease in anti-inflammatory lipoxin A4, resolvins, protectins and maresins. All these bioactive molecules are termed as bioactive lipids (BALs). This imbalance in the metabolites of EFAs leads to low-grade systemic inflammation and at times acute inflammatory events at specific local sites that trigger the development of various age-related disorders such as obesity, type 2 diabetes mellitus, hypertension, coronary heart disease, atherosclerosis, and immune dysfunction as seen in rheumatoid arthritis, lupus, nephritis and other localized inflammatory conditions. This evidence implies that methods designed to restore BALs to normal can prevent age-related disorders and enhance longevity and health.

Anti-Inflammatory and Anti-Angiogenesis Effects of Verapamil on Rat Air Pouch Inflammation Model

Purpose: In the present study, the effects of verapamil on inflammation and angiogenesis in air pouch model were studied.

Methods: To create a model of inflammation in the rats, on days 1 and 3 sterile air, and on the sixth day, carrageenan was injected into the pouch subcutaneously. Normal saline as control, diclofenac sodium and dexamethasone as standards and verapamil (0.05, 0.1 and 0.2mg/rat) was injected into the pouch simultaneously with carrageenan and as well as 24 and 48 hours later. After 72 hours, volume of exudate, the leukocytes count, concentration of VEGF and IL-1ß, granulomatous tissue weight, histopathological changes and angiogenesis were considered.

Results: Verapamil significantly reduced leukocyte accumulation in all doses, but effect of 0.1mg/rat was more significant (P<0.001). The exudate volume and granulomatous tissue weight was reduced with all doses, especially 0.1mg/rat (P<0.01). Doses 0.05, 0.1 and 0.2mg/rat of verapamil compared with the control group (carrageenan) led to a reduction in the amount of hemoglobin in the tissue as the angiogenesis indicator (P<0.001, P<0.01 and P<0.05, respectively). VEGF level of exudate was reduced by doses of 0.05 and 0.1mg/rat (P<0.05). In addition, IL-1β concentration was lowered by 0.1mg/rat of verapamil (P<0.05). Histopathological changes, severity of granulomatous inflammation, granulomatous tissue cell density and angiogenesis in verapamil group were markedly lower compared to carrageenan group.

Conclusion: Verapamil has significant anti-inflammatory and anti-angiogenesis effects in the air pouch model probably due to attenuation effects of verapamil on IL-1β and VEGF.

Structural analysis of Centrolobium tomentosum seed lectin with inflammatory activity

A glycosylated lectin (CTL) with specificity for mannose and glucose has been detected and purified from seeds of Centrolobium tomentosum, a legume plant from Dalbergieae tribe. It was isolated by mannose-sepharose affinity chromatography. The primary structure was determined by tandem mass spectrometry and consists of 245 amino acids, similar to other Dalbergieae lectins. CTL structures were solved from two crystal forms, a monoclinic and a tetragonal, diffracted at 2.25 and 1.9 Å, respectively. The carbohydrate recognition domain (CRD), metal-binding site and glycosylation site were characterized, and the structural basis for mannose/glucose-binding was elucidated. The lectin adopts the canonical dimeric organization of legume lectins. CTL showed acute inflammatory effect in paw edema model. The protein was subjected to ligand screening (dimannosides and trimannoside) by molecular docking, and interactions were compared with similar lectins possessing the same ligand specificity. This is the first crystal structure of mannose/glucose native seed lectin with proinflammatory activity isolated from the Centrolobium genus.

Metabolic Connection of Inflammatory Pain: Pivotal Role of a Pyruvate Dehydrogenase Kinase-Pyruvate Dehydrogenase-Lactic Acid Axis

Pyruvate dehydrogenase kinases (PDK1-4) are mitochondrial metabolic regulators that serve as decision makers via modulation of pyruvate dehydrogenase (PDH) activity to convert pyruvate either aerobically to acetyl-CoA or anaerobically to lactate. Metabolic dysregulation and inflammatory processes are two sides of the same coin in several pathophysiological conditions. The lactic acid surge associated with the metabolic shift has been implicated in diverse painful states. In this study, we investigated the role of PDK-PDH-lactic acid axis in the pathogenesis of chronic inflammatory pain. Deficiency of Pdk2 and/or Pdk4 in mice attenuated complete Freund's adjuvant (CFA)-induced pain hypersensitivities. Likewise, Pdk2/4 deficiency attenuated the localized lactic acid surge along with hallmarks of peripheral and central inflammation following intraplantar administration of CFA. In vitro studies supported the role of PDK2/4 as promoters of classical proinflammatory activation of macrophages. Moreover, the pharmacological inhibition of PDKs or lactic acid production diminished CFA-induced inflammation and pain hypersensitivities. Thus, a PDK-PDH-lactic acid axis seems to mediate inflammation-driven chronic pain, establishing a connection between metabolism and inflammatory pain.

SIGNIFICANCE STATEMENT

The mitochondrial pyruvate dehydrogenase (PDH) kinases (PDKs) and their substrate PDH orchestrate the conversion of pyruvate either aerobically to acetyl-CoA or anaerobically to lactate. Lactate, the predominant end product of glycolysis, has recently been identified as a signaling molecule for neuron-glia interactions and neuronal plasticity. Pathological metabolic shift and subsequent lactic acid production are thought to play an important role in diverse painful states; however, their contribution to inflammation-driven pain is still to be comprehended. Here, we report that the PDK-PDH-lactic acid axis constitutes a key component of inflammatory pain pathogenesis. Our findings establish an unanticipated link between metabolism and inflammatory pain. This study unlocks a previously ill-explored research avenue for the metabolic control of inflammatory pain pathogenesis.

In vivo anti-inflammatory and antiarthritic activities of aqueous extracts from Thymelaea hirsuta

Background:

The aerial parts of Thymelaea hirsuta (TH) are used as a decoction in the treatment of different pathologies in folk medicine in Morocco.

Objective:

The aqueous extracts were evaluated for its anti-inflammatory activity and in inhibition of adjuvant induction arthritis in male Wistar rats.

Materials and Methods:

The anti-inflammatory activity was carried out using carrageenan-induced rat paw edema model, and the antiarthritic activity was carried out using complete Freund's adjuvant-induced arthritis model.

Results:

The plant extract (500 mg/kg body weight) exhibited significant activity in acute inflammation produced 60% of inhibition after 4 h as compared with that of the standard anti-inflammatory drug, the diclofenac (100 mg/kg) which showed 40% of inhibition. In arthritis model, the extract produced 85% inhibition after 18 days when compared with the diclofenac (10 mg/kg; 72%).

Conclusion:

These results indicate that the aqueous extract of TH had an anti-inflammatory activity and inhibited the induction of adjuvant arthritis in male Wistar rats.

Antinociceptive Activity and Redox Profile of the Monoterpenes (+)-Camphene, p-Cymene, and Geranyl Acetate in Experimental Models

Objective. To evaluate antinocicpetive and redox properties of the monoterpenes (+)-camphene, p-cymene, and geranyl acetate in in vivo and in vitro experimental models. Methods. Evaluation of the in vitro antioxidant activity of (+)-camphene, p-cymene, and geranyl acetate using different free radical-generating systems and evaluation of antinociceptive actions by acetic acid-induced writhing and formalin-induced nociception tests in mice. Results. p-Cymene has the strongest antinociceptive effect, but (+)-camphene and geranyl acetate also present significant activity at high doses (200 mg/kg). (+)-Camphene had the strongest antioxidant effect in vitro at TBARS and TRAP/TAR assays and also had the highest scavenging activities against different free radicals, such as hydroxyl and superoxide radicals. Sodium nitroprussiate-derived NO production was enhanced by (+)-camphene. Geranyl acetate and p-cymene also presented some antioxidant effects, but with a varying profile according the free radical-generating system studied. Conclusion. (+)-Camphene, p-cymene, and geranyl acetate may present pharmacological properties related to inflammation and pain-related processes, being potentially useful for development of new therapeutic strategies, with limited possibilities for p-cymene and geranyl acetate.

Sensory and signaling mechanisms of bradykinin, eicosanoids, platelet-activating factor, and nitric oxide in peripheral nociceptors

Peripheral mediators can contribute to the development and maintenance of inflammatory and neuropathic pain and its concomitants (hyperalgesia and allodynia) via two mechanisms. Activation or excitation by these substances of nociceptive nerve endings or fibers implicates generation of action potentials which then travel to the central nervous system and may induce pain sensation. Sensitization of nociceptors refers to their increased responsiveness to either thermal, mechanical, or chemical stimuli that may be translated to corresponding hyperalgesias. This review aims to give an account of the excitatory and sensitizing actions of inflammatory mediators including bradykinin, prostaglandins, thromboxanes, leukotrienes, platelet-activating factor, and nitric oxide on nociceptive primary afferent neurons. Manifestations, receptor molecules, and intracellular signaling mechanisms of the effects of these mediators are discussed in detail. With regard to signaling, most data reported have been obtained from transfected nonneuronal cells and somata of cultured sensory neurons as these structures are more accessible to direct study of sensory and signal transduction. The peripheral processes of sensory neurons, where painful stimuli actually affect the nociceptors in vivo, show marked differences with respect to biophysics, ultrastructure, and equipment with receptors and ion channels compared with cellular models. Therefore, an effort was made to highlight signaling mechanisms for which supporting data from molecular, cellular, and behavioral models are consistent with findings that reflect properties of peripheral nociceptive nerve endings. Identified molecular elements of these signaling pathways may serve as validated targets for development of novel types of analgesic drugs.

In vivo and in vitro anti-inflammatory and anti-nociceptive activities of lovastatin in rodents

Statins are among the most prescribed drugs in recent clinical practice. They are also known for their pleiotropic actions, which are independent of their lipid-lowering properties. The effect of lovastatin was investigated against carrageenan-induced paw edema in male Wistar rats (200-250 g) and on leukocyte migration, as measured by carrageenan-induced peritonitis in male Swiss mice (20-25 g), which are models of acute inflammation. Lovastatin (administered 1 h prior to carrageenan), at oral doses of 2, 5, and 10 mg/kg, markedly attenuated paw edema formation in rats at the 4th hour after carrageenan injection (25, 43, and 37% inhibition, respectively). Inhibitions of 20, 45 and 80% were observed in the leukocyte migration, as evaluated by carrageenan-induced peritonitis in mice with lovastatin doses of 0.5, 1 and 5 mg/kg, as compared to controls. Furthermore, lovastatin (administered 1 h before initiation) reduced the nociceptive effect of the formalin test in mice, at both phases, at doses of 2, 5, and 10 mg/kg: first phase (51, 65, and 70%, respectively) and second phase (73, 57, and 66% inhibition of licking time, respectively). The anti-nociceptive activity of lovastatin was inhibited by naloxone (3 mg/kg, sc). Lovastatin (0.01, 0.1, and 1 µg/mL) inhibited by 23, 79, and 86%, respectively, the release of myeloperoxidase from human neutrophils. Leukocyte (predominantly neutrophils) infiltration was almost completely reduced by lovastatin treatment, as observed in the model of acute paw edema with hematoxylin and eosin staining. In addition, lovastatin decreased the number of cells expressing tumor necrosis factor-α (TNF-α) and the inducible form of nitric oxide synthase (iNOS) activity. Therefore, the alterations in leukocyte activity and cytokine release could contribute to the anti-inflammatory activity of lovastatin.

Diazepam decreases leukocyte-endothelium interactions in situ

High doses of diazepam reduce the inflammatory paw edema in rats. This effect was attributed to an action of diazepam on the Translocator Protein (TSPO). We evaluated the effects of diazepam (10 mg/kg, intraperitoneally) on leukocyte rolling and migration. In carrageenan-induced acute inflammation, diazepam decreased the interaction of leukocytes with endothelial cells (rolling) and the number of leukocytes in the mesentery (migration). RU486 (antagonist of glucocorticoid receptors) reduced the effects of diazepam on leukocyte rolling and migration, suggesting a participation of endogenous corticosteroids. We also showed that the effects of diazepam on leukocyte-endothelium interactions are mediated by nitric oxide (NO), since prior treatment with l-arginine (precursor of NO) partially precludes the inhibitory effects of diazepam; conversely, pretreatment with L-NAME (false substrate of the NO synthase) somewhat potentiates the effects of diazepam. The pathways that underlie the effects of diazepam remain to be further elucidated, but we believe that both local and systemic mechanisms may overlap to explain the influence of diazepam on leukocyte-endothelium interactions.

Anti-inflammatory effects of low molecular weight heparin derivative in a rat model of carrageenan-induced pleurisy

Low molecular weight heparin derivatives are characterized by low anti-coagulant activity and marked anti-inflammatory effects that allow for these molecules to be viewed as a new class of non-steroidal anti-inflammatory drugs (NSAIDs). We show here that K5NOSepiLMW, an O-sulphated heparin-like semi-synthetic polymer of the D-glucuronic acid-N-acetyleparoson disaccharide unit with low molecular weight, has marked anti-inflammatory effects in a rat model of acute inflammation, the carrageenan-induced pleurisy, commonly used to test NSAID efficacy. A 30-min. pre-treatment with K5NOSepiLMW (0.1, 0.5 and 1 mg/kg b.wt., given intrapleurally) attenuated the recruitment of leucocytes in the lung tissue and the pleural exudate, inhibited the induction of inducible nitric oxide synthase and cyclooxygenase-2 (COX-2), thereby abating the generation of nitric oxide and pro-inflammatory prostaglandins such as PgE(2) and PGF(1alpha), reduced the inflammation-induced nitroxidative lung tissue injury, as shown by tissue thiobarbituric acid-reactive substances and nitrotyrosine, and blunted the local generation of cytokines such as interleukin-1beta and tumour necrosis factor-alpha. All these parameters were markedly increased by intrapleural carrageenan in the absence of any pre-treatment. The anti-inflammatory action of K5NOSepiLMW is specific, as judged by the lack of therapeutic effects of B4/110, a biologically inactive cognate polysaccharide, given in the place of the authentic molecule. Moreover, K5NOSepiLMW showed similar effects as celecoxib (1 mg/kg b.wt), a COX-2 inhibitor and well-known NSAID. This study provides further insight into the mechanisms underlying the beneficial effects of heparin derivatives in inflammation and identifies K5NOSepiLMW as a novel, promising anti-inflammatory drug.

Anti-inflammatory effects of low molecular weight heparin derivative in a rat model of carrageenan-induced pleurisy

Low molecular weight heparin derivatives are characterized by low anti-coagulant activity and marked anti-inflammatory effects that allow for these molecules to be viewed as a new class of non-steroidal anti-inflammatory drugs (NSAIDs). We show here that K5NOSepiLMW, an O-sulphated heparin-like semi-synthetic polymer of the D-glucuronic acid-N-acetyleparoson disaccharide unit with low molecular weight, has marked anti-inflammatory effects in a rat model of acute inflammation, the carrageenan-induced pleurisy, commonly used to test NSAID efficacy. A 30-min. pre-treatment with K5NOSepiLMW (0.1, 0.5 and 1 mg/kg b.wt., given intrapleurally) attenuated the recruitment of leucocytes in the lung tissue and the pleural exudate, inhibited the induction of inducible nitric oxide synthase and cyclooxygenase-2 (COX-2), thereby abating the generation of nitric oxide and pro-inflammatory prostaglandins such as PgE(2) and PGF(1alpha), reduced the inflammation-induced nitroxidative lung tissue injury, as shown by tissue thiobarbituric acid-reactive substances and nitrotyrosine, and blunted the local generation of cytokines such as interleukin-1beta and tumour necrosis factor-alpha. All these parameters were markedly increased by intrapleural carrageenan in the absence of any pre-treatment. The anti-inflammatory action of K5NOSepiLMW is specific, as judged by the lack of therapeutic effects of B4/110, a biologically inactive cognate polysaccharide, given in the place of the authentic molecule. Moreover, K5NOSepiLMW showed similar effects as celecoxib (1 mg/kg b.wt), a COX-2 inhibitor and well-known NSAID. This study provides further insight into the mechanisms underlying the beneficial effects of heparin derivatives in inflammation and identifies K5NOSepiLMW as a novel, promising anti-inflammatory drug.

Maternal and fetal circulating sKL and ET-1 levels as function of normal labor at term

OBJECTIVES

To determine whether labor is associated with alterations of the levels of soluble c-kit ligand (sKL) and endothelin-1 (ET-1) in maternal plasma and umbilical cord blood.

METHODS

The sKL and ET-1 levels were investigated in umbilical cord and maternal plasma on the day of delivery in 18 pregnant women with vaginal delivery during labor, 18 non-pregnant women and 9 pregnant women before cesarean delivery, using an ELISA assay.

RESULTS

Umbilical cord plasma sKL levels were significantly higher than the maternal plasma in both types of delivery (p = 0.0001, p < 0.0001, respectively). However, maternal plasma ET-1 levels in the presence of labor were significantly higher than the cesarean delivery group (p < 0.0001). No difference was noted for sKL and ET-1 in umbilical cord vessels of both groups. Furthermore, a highly significant inverse correlation was documented between the individual levels of cord plasma ET-1 and the levels of cord plasma sKL (r = -0.6269, p = 0.0054).

CONCLUSIONS

The sKL levels found in umbilical cord plasma are consistent with the pleiotropic effects of sKL in facilitating the transition of the fetus to the neonatal stage. The reduced ET-1 maternal plasma levels, compared to non-pregnant women, probably are indicative of a putative mechanism for embryo protection from vasoconstriction sequelae. This assumption is strengthened by the corresponding ET-1 levels in umbilical cord plasma.

HPLC and anti-inflammatory studies of the flavonoid rich chloroform extract fraction of Orthosiphon stamineus leaves

The aim of the present study was to verify the anti-inflammatory activity of Orthosiphon stamineus leaf extracts and to identify the active compound(s) contributing to its anti-inflammatory activity using a developed HPLC method. Active chloroform extract of O. stamineus was fractionated into three fractions using a dry flash column chromatography method. These three fractions were investigated for anti-peritoneal capillary permeability, in vitro nitric oxide scavenging activity, anti-inflammatory and nitric oxide (NO) inhibition using carrageenan-induced hind paw edema method. The flavonoid rich chloroform extract fraction (CF2) [containing sinensetin (2.86% w/w), eupatorin (5.05% w/w) and 3’-hydroxy-5,6,7,4’-tetramethoxyflavone (1.101% w/w)], significantly reduced rat hind paw edema, NO and decreased dye leakage to peritoneal cavity at p < 0.05. IC₅₀ of in vitro NO scavenging of CF2 was 0.3 mg/mL. These results suggest that the anti-inflammatory properties of these CF2 may possibly be due to the presence of flavonoid compounds capable of affecting the NO pathway.

Hind limb ischemic preconditioning induces an anti-inflammatory response by remote organs in rats

Ischemic preconditioning (IPC), a strategy used to attenuate ischemia-reperfusion injury, consists of brief ischemic periods, each followed by reperfusion, prior to a sustained ischemic insult. The purpose of the present study was to evaluate the local and systemic anti-inflammatory effects of hind limb IPC in male Wistar rat (200-250 g) models of acute inflammation. IPC was induced with right hind limb ischemia for 10 min by placing an elastic rubber band tourniquet on the proximal part of the limb followed by 30 min of reperfusion. Groups (N = 6-8) were submitted to right or left paw edema (PE) with carrageenan (100 microg) or Dextran (200 microg), hemorrhagic cystitis with ifosfamide (200 mg/kg, ip) or gastric injury (GI) with indomethacin (20 mg/kg, vo). Controls received similar treatments, without IPC (Sham-IPC). PE is reported as variation of paw volume (mL), vesical edema (VE) as vesical wet weight (mg), vascular permeability (VP) with Evans blue extravasation (microg), GI with the gastric lesion index (GLI; total length of all erosions, mm), and neutrophil migration (NM) from myeloperoxidase activity. The statistical significance (P < 0.05) was determined by ANOVA, followed by the Tukey test. Carrageenan or Dextran-induced PE and VP in either paw were reduced by IPC (42-58.7%). IPC inhibited VE (38.8%) and VP (54%) in ifosfamide-induced hemorrhagic cystitis. GI and NM induced by indomethacin were inhibited by IPC (GLI: 90.3%; NM: 64%). This study shows for the first time that IPC produces local and systemic anti-inflammatory effects in models of acute inflammation other than ischemia-reperfusion injury.

QUANTITATIVE CHARACTERIZATION OF A REPEATED ACUTE JOINT INFLAMMATION MODEL IN RATS

1. Chronic pain owing to arthritis is a major clinical problem worldwide. To study the underlying pathological mechanisms of chronic pain and the effectiveness of different treatments, a number of experimental models have been developed over the years. 2. We introduced a new subchronic inflammatory model by repeated unilateral administration of carrageenan into the ankle joint of rats, and investigated the degree and the time-course of the oedema, and thermal and mechanical hyperalgesia. 3. Carrageenan (450 microg) was injected on three occasions (on days 1, 4 and 7), and the resulting oedema, thermal hyperalgesia (paw withdrawal test) and weight load were characterized in voluntarily walking rats daily for 15 days. The effect of diclofenac sodium (3 mg/kg orally daily for 15 days) was also determined. 4. Repetitive administration of carrageenan caused fluctuating oedema and pain responses, which did not normalize within 3 days. Exacerbated inflammatory oedema was observed after the second and third injections. Oedema and a decreased weight load of the inflamed paw were observed throughout the investigation period, and paw withdrawal thresholds to noxious thermal stimuli returned to baseline pre-carrageenan values from Day 13. 5. Oral diclofenac (3 mg/kg daily for 15 days) significantly decreased oedema within a few days (Day 3), whereas its anti-allodynic effect developed only several days later (Day 9). However, diclofenac at the applied dose did not influence the thermal hyperalgesia. 6. The results suggest that the repeated administration of carrageenan might be a suitable model for determining the effects of long-lasting treatment.

Diazepam effects on carrageenan-induced inflammatory paw edema in rats: Role of nitric oxide

High doses of diazepam (10.0-20.0 mg/kg) were shown to reduce the volume of acute inflammatory paw edema in rats as a response to carrageenan administration. This effect was attributed to an action of diazepam on the peripheral-type benzodiazepine receptor (PBR) present in the adrenal and/or immune/inflammatory cells. The present study was undertaken to analyze the involvement of nitric oxide (NO) on the effects of diazepam on carrageenan-induced paw edema in rats (CIPE) and to look for the presence of PBR and inducible/constitutive NO synthases (NOS) on slices taken from the inflamed paws of diazepam-treated rats. For that, an acute inhibition of NO biosynthesis was achieved using 50.0 mg/kg No mega-nitro-L-arginine (L-NAME), L-arginine (300.0 mg/kg), the true precursor of NO, and D-arginine (300.0 mg/kg), its false substrate, were also used. The following results were obtained: (1) diazepam (10.0 and 20.0 mg/kg) decreased CIPE values in a dose- and time-dependent way; (2) diazepam effects on CIPE were increased by L-NAME pretreatment; (3) treatment with L-arginine but not with D-arginine reverted at least in part the decrements of CIPE values observed after diazepam administration; (4) PBR were found in endothelial and inflammatory cells that migrated to the inflammatory site at the rat paw; (5) confocal microscopy showed the presence of both PBR and NOS in endothelial and inflammatory cells taken from inflamed paw tissues of rats treated with diazepam a finding not observed in tissues provided from rats treated with diazepam's control solution. These results suggest an important role for NO on the effects of diazepam on CIPE. Most probably, these effects reflect a direct action of diazepam on PBR present in the endothelium of the microvascular ambient and/or on immune/inflammatory cells. An action like that would lead, among other factors, to a decrease in NO, generated by NO synthase, and thus in the mechanisms responsible for CIPE.

Effects of Anacardium occidentale stem bark extract on in vivo inflammatory models

The methanol extract of Anacardium occidentale stem bark was evaluated for activities against the lipopolysaccharide (LPS)-induced septic shock, as well as LPS-induced microvascular permeability in mice. Pre-treatment with Anacardium occidentale extract (25-200 mg/kg) caused a dose-dependent and significant (p < 0.05) reduction in the elevated levels of alanine and aspartate aminotransferases in the sera of D-galactosamine-primed mice injected with LPS. The highest dose of the extract studied (200 mg/kg) produced a 100% protection against death from sepsis. Pentoxifylline (100 mg/kg) and L-NAME (5 mg/kg) offered 100% protection against LPS-induced septic shock, and produced marked reduction in elevated levels of transferases. A dose-related inhibition of LPS-induced microvascular permability in mice was also produced by pentoxifylline, L-NAME and the extract.

Effect of methylguanidine in carrageenan-induced acute inflammation in the rats

In vitro and in vivo studies have demonstrated that methylguanidine, an inhibitor of nitric oxide synthase (NOS), is also able to reduce tumour necrosis factor-alpha (TNF-alpha) release. In the present study, we evaluated the anti-inflammatory potential of methylguanidine treatment in two models of acute inflammation (carrageenan-induced paw edema and pleurisy) where oxyradical, nitric oxide (NO) and prostaglandins play a crucial role in the inflammatory processes. Our data show that methylguanidine, given intraperitoneally at the dose of 30 mg/kg, inhibits the inflammatory response reducing significantly (P<0.05) paw swelling, pleural exudates formation, mononuclear cell infiltration and histological injury. Furthermore, our data suggests that there is a significant (P<0.05) reduction in the activity and expression both of the inducible NOS (iNOS) and of cyclooxygenase-2 in lung tissue of pleurisy model. Methylguanidine is also able to reduce the appearance of nitrotyrosine and of the nuclear enzyme poly(adenosine diphosphate [ADP]-ribose) synthase immunoreactivity in the inflamed lung tissues. Treatment with aminoguanidine, the reference drug, significantly reduced all the evaluated pro-inflammatory parameters in carrageenan-treated rats. Taken together, the present results demonstrate that methylguanidine exerts potent anti-inflammatory effects that could be, in part, related to an inhibition of the expression/activity of the iNOS and cyclooxygenase-2 and, another part, may be related to a reduction of TNF-alpha release.

LAAE-14, a new in vitro inhibitor of intracellular calcium mobilization, modulates acute and chronic inflammation

A new lipidic acid-amido ether derivative (LAAE-14) able to reduce dose-dependently the calcium increases mediated either by calcium ionophore ionomycin, by the endoplasmic reticular Ca(2+)-ATPase inhibitor thapsigargin, or by the chemotactic tripeptide N-formyl-L-methionyl-L-leucyl-L-phenylalanine (fMLP), in human neutrophils as well as in murine peritoneal macrophages, but not ATP, has been evaluated as a potential anti-inflammatory drug. This compound attenuated leukocyte activation by means of its inhibitory effect on the respiratory burst elicited in both types of cells by 12-O-tetradecanoyl phorbol 13-acetate, by inhibition of the degranulation process induced by cytochalasin B+fMLP or cytochalasin B+platelet activating factor, as well as by reduction of leukotriene B(4) synthesis induced by the calcium ionophore A23187. In addition, in zymosan-stimulated mouse peritoneal macrophages LAAE-14 caused a potent inhibition of nitrite and prostaglandin E(2) production. This compound exerted acute and chronic anti-inflammatory effects by oral route, that may be related with several mechanisms such as attenuation of leukocyte activation, inhibition of inducible nitric oxide synthase, cyclo-oxygenase-2 and cytosolic phospholipase A(2) expression as well as reduction in tumour necrosis factor-alpha production. Its anti-inflammatory profile is clearly correlated with its behavior as inhibitor of intracellular calcium mobilization. The profile and potency of this compound may have relevance for the inhibition of the inflammatory response at different levels and may represent a new approach to the development of new anti-inflammatory drugs.

Regulation of prostaglandin generation in carrageenan-induced pleurisy by inducible nitric oxide synthase in knockout mice

In the present study, by comparing the responses in wild-type mice (iNOSWT) and mice lacking (iNOSKO) the inducible (or type 2) nitric oxide synthase (iNOS), we investigated the correlation between endogenous nitric oxide (NO) and prostaglandin (PG) generation in carrageenan-induced pleurisy. The inflammatory response in iNOSKO mice was significantly reduced in respect to iNOSWT animals, as demonstrated by the exudate volume (-63%) and numbers of infiltrating cells (-62%). The levels of NOx in the pleural exudate from carrageenan-treated mice were significantly (p < 0.01) decreased in iNOSKO mice (16 +/- 7.6 nmoles/mice) compared to iNOSWT animals (133 +/- 9 nmoles/mice). Similarly, the amounts of PGE2 in the pleural exudates of carrageenan-treated animals were significantly (p < 0.01) lower in iNOSKO compared to iNOSWT mice (120 +/- 20 pg/mice vs. 308 +/- 51 pg/mice). Also the amounts of 6-keto-PGF(1 alpha) produced by lungs from carrageenan-treated iNOSKO mice (1.01 +/- 0.10 ng/tissue mg) were significantly (p < 0.01) reduced compared to iNOSWT carrageenan-treated mice (2.1 +/- 0.09 ng/tissue mg). In conclusion our results confirm, by the use of iNOSKO mice that in carrageenan-induced pleurisy NO positively modulates PG biosynthesis.

Anti-inflammatory effects of peripheral benzodiazepine receptor ligands in two mouse models of inflammation

In vivo treatment of mice with peripheral benzodiazepine receptor ligands exerts an inhibitory effect on the inflammatory response in two models of acute inflammation. In the first model, pretreatment of the animals (24 h) with 1-(2-chlorophenyl)-N-methyl-N(1-methylpropyl)-3-isoquinoline carboxamide (PK11195) and 7-chloro-5-(4-Chlorophenyl)-1, 3-dihydro-1-methyl-2-H-1,4-benzodiazepin-2 (Ro5-4864), at different doses (0.00001-10 mg/kg, i.p.) dose dependently inhibited the formation of mouse paw oedema induced by carrageenan with mean ID(50s) of 0.009 (95% confidence limits=0.0076-0.013) and 0.04 (95% confidence limits=0.025-0.0086) mg/kg, respectively. Both ligands (0. 1 mg/kg, i.p.) inhibited in the same way the mouse paw oedema induced by carrageenan in animals with and without adrenal glands. PK11195 and Ro5-4864 (0.1 mg/kg, i.p.) inhibited the mouse paw oedema induced by several inflammatory mediators. In the second model, the pretreatment (24 h) with peripheral benzodiazepine receptor ligands (0.1 mg/kg, i.p.) exerted an inhibitory effect on neutrophil influx and produce a marked inhibition of carrageenan-produced interleukin-13 and interleukin-6 in pleural exudation. Our results extend previous findings that peripheral benzodiazepine receptor is involved in the inflammatory response, and suggest that this action may be linked to the action of different inflammatory mediators, probably mainly by the inhibition of the release of pro-inflammatory cytokines.

Linked activation of nitric oxide synthase and cyclooxygenase in peripheral monocytes of asymptomatic migraine without aura patients

Many reports indicate that nitric oxide (NO) could be involved in migraine without aura (MWA), an extremely diffuse clinical event. Since monocyte may be a relevant source of NO, we analysed monocyte activation in MWA patients, in a period in which they were free of symptoms. NO basal production by MWA peripheral monocytes was significantly higher than in healthy subjects (91.25+/-8.6 microM/10(6) cells vs. 22.6+/-3.2 microM/106 cells). Interestingly, even the release of prostaglandin E2 (PGE2), was higher in MWA patients than in healthy subjects (3137+/-320 pg/10(6) cells vs. 1531+/-220 pg/10(6) cells). The incubation of monocytes from healthy subjects and MWA patients with N-nitro-L-arginine methyl ester caused a marked decrease of both NO and PGE2 release. We hypothesise that NOS and cyclooxygenase pathways in monocytes are linked and are, in MWA patients, up-regulated, even in a symptoms-free period. NO and PGE2 hyperproduction could therefore be involved in the neurovascular modifications leading to migraine attacks.

Regulation of prostaglandin production by inhibition of poly (ADP-ribose) synthase in carrageenan-induced pleurisy

The aim of the present study was to investigate the effect of two inhibitors (3-aminobenzamide and nicotinamide) of poly (ADP-ribose) synthetase on the production of the inflammatory mediator prostaglandins in a model of acute inflammation, carrageenan-induced pleurisy, where prostaglandins are known to play a crucial role. The results show that the poly (ADP-ribose) synthetase inhibitors, 3-aminobenzamide (2.5, 5 and 10 mg/kg) and nicotinamide (12.5, 25 and 50 mg/kg), inhibit the inflammatory response (pleural exudate formation, polymorphonuclear cell infiltration and prostaglandin production). The present results demonstrate that inhibition of poly (ADP-ribose) synthetase exerts potent anti-inflammatory effects. Part of these anti-inflammatory effects may be related to a reduction of prostaglandin production during the inflammatory process.

Pharmacological aspects of mouse hind-paw oedema induced by Lachesis muta rhombeata venom

Pharmacological aspects of mouse hind-paw oedema induced by subplantar injections of Lachesis muta rhombeata (LMR) venom were investigated. The oedema induced by subplantar injections of 10 to 50 ng/g of LMR venom is dose dependent, with onset, peak and duration at 30, 60 and 180 min, respectively. Subplantar injection of 30 ng/g of Bothrops jararaca (BJ) venom induced oedema that has the same intensity as 30 ng/g of LMR venom but lasts for more than 4 h suggesting different time course. Systemic effects or haemorrhage were not observed with doses less than 50 ng/g. Oedema is not due to the presence of oedematogenic amines since dialysis did not change the oedema induced by 30 ng/g of LMR venom. Part of the oedema induced by LMR venom is due to a thermolabile fraction since pre-heating the venom at 100 degrees C for 15 min induced a significant reduction (56.19 +/- 6.8%) of the oedematogenic activity. The oedema induced by LMR venom is possibly induced by release of a pharmacological active substance at the site of injection. Histamine, arachidonate metabolites, nitric oxide and serotonin may play important roles in the oedematogenic effect of LMR venom since pre-treatment of mice with pyrilamine, indomethacin, dexamethasone, L-NAME and methysergide induced a significant reduction (49.86 +/- 10%; 51.06 +/- 5.9%; 77.66 +/- 3.6%; 73.30 +/- 6.1% and 93.77 +/- 2.8%, respectively) of the oedema formation. The present results demonstrate that the oedema induced by LMR and BJ venoms may be triggered and maintained by different pharmacological mechanisms. Since methysergide and L-NAME were the most active inhibitors of the oedema we can suggest that a link between serotonin release by the venom and a NO synthase activation may be an important step in the oedema formation induced by LMR venom.

Relationship between nitric oxide and prostaglandins in carrageenin pleurisy

The correlation between endogenous nitric oxide (NO) generation and prostaglandin biosynthesis was studied in rat carrageenin pleurisy induced by the injection of 0.2 mL of 1% lambda-carrageenin into the pleural cavity. The pleural exudate was collected at 4 hr and the amounts of NO2- + NO3- (NOx) and prostaglandin E2 (PGE2) measured. The NOx present in the inflammatory exudate was determined by measuring the NO2- with the Griess reaction, after the reduction of NO3- to NO2- using acid-washed cadmium powder. PGE2 was measured by radioimmunoassay. The NO synthase inhibitor NG-nitro-L-arginine methyl ester (L-NAME; 1-3-10 mg/kg subcutaneously) reduced NOx by 20 +/- 7%, 41 +/- 6% and 55 +/- 9% (P < 0.01) and PGE2 by 9 +/- 6%, 41 +/- 11% and 74 +/- 9% (P < 0.001). Conversely, L-arginine (300 mg/kg SC) increasedNOx by 39 +/- 7% (P < 0.01) and PGE2 by 78 +/- 6% (P < 0.001). The NO scavenger haemoglobin (Hb), coinjected into the pleural cavity (3 mg/site) with carrageenin, produced a parallel inhibition of NOx (65 +/- 16%, P < 0.001) and PGE2 (71 +/- 18%, P < 0.001). The soluble guanylate cyclase inhibitor methylene blue (Mb; 2 mg/site) had no effect. Moreover haemoglobin, but not methylene blue, was able to significantly suppress the L-arginine-induced increase of both NOx and PGE2. In each pleural exudate, independently from the animal treatment, the amount of NOx was highly correlated to the amount of PGE2 (r = 0.93, P < 0.001). These results suggest that in rat carrageenin pleurisy the modulation of the L-arginine:NO pathway results in a parallel modulation of prostaglandin biosynthesis. The interaction between cyclooxygenase and the NO pathway may represent an important mechanism for the modulation of the inflammatory response.

Role of nitric oxide in the physiopathology of pain

Many painful disorders, including joint dysfunctions such as rheumatoid arthritis (RA) or temporomandibular joint disorders (TMD), are associated with hyperthermia of the overlying skin. The same is true of certain intractable chronic pain conditions, such as chronic orofacial pain, which may be associated with TMD. We suggest that this skin hyperthermia, caused by regional vasodilation, is induced by extravascular nitric oxide (NO). Extravascular NO can be produced in the affected joint by osteoblasts, chondrocytes, and macrophages, by mechanical stimulation of endothelial cells, or by stimulated neurons. In view of a strong correlation between pain and skin hyperthermia in these disorders, and the evidence that NO enhances the sensitivity of peripheral nociceptors, we also suggest that at least this kind of pain is associated with excessive local level of NO. This hypothesis can be verified by dynamic area telethermometry, assessing the effect of NO on the sympathetic nervous function. This mechanism, which is in line with the general role of NO as a mediator between different organ systems, also may be relevant to any pain associated with enhanced immune response. Clinical implications of the proposed mechanism are discussed.

Role of mast cell histamine in the formation of rat paw edema: a microdialysis study

We determined the endogenous histamine concentration in the subplantar space of rat hind paws using an in vivo microdialysis technique. A microdialysis probe was implanted into the rat hind paw and the histamine content in dialysates was measured by high performance liquid chromatography-fluorometry. In wild type (+/+) rats, the histamine output (basal level 25.7 +/- 0.9 pmol/ml) increased 115-, 199- and 426-fold rapidly after subplantar injection of compound 48/80 at doses of 0.5, 5 and 50 microg/paw, respectively. In genetically mast cell-deficient (Ws/Ws) rats, the basal level of histamine was one third of that obtained from +/+ rats, and was not increased by compound 48/80 injection. With this treatment, marked, dose dependent, but relatively gradual development of the paw edema was found in +/+ rats. However, no edema formation was observed in Ws/Ws rats. Histological observations showed neither mast cells nor edema to be present in the paw skin of Ws/Ws rats. These findings indicate the critical role of histamine as a trigger for the development of edema in vivo. In addition, Ws/Ws rats will provide important information as to the roles of mast cells in the inflammatory response.

The inhibitory effects of mercaptoalkylguanidines on cyclo-oxygenase activity

1. It has been proposed that in inflammatory conditions, in which both the inducible isoforms of nitric oxide synthase (iNOS) and cyclo-oxygenase (COX-2) are induced, inhibition of NOS also results in inhibition of arachidonic acid metabolism. In the present study we have investigated whether mercaptoalkylguanidines, a novel class of selective iNOS inhibitors, may also influence the activity of cyclo-oxygenase (COX). Therefore, the effect of mercaptoethylguanidine (MEG) and related compounds on the activity of the constitutive (COX-1) and the inducible COX (COX-2) was investigated in cells and in purified enzymes. Aminoguanidine, NG-methyl-L-arginine (L-NMA) and NG-nitro-L-arginine methyl ester (L-NAME) were also studied for comparative purposes. 2. Western blot analysis demonstrated a significant COX-1 activity in unstimulated J774 macrophages and in unstimulated human umbilical vein endothelial cells (HUVEC). Immunostimulation of the J774 macrophages by endotoxin (lipopolysaccharide of E. coli, LPS 10 micrograms ml-1) and interferon gamma (IFN gamma, 100 u ml-1) for 6 h resulted in a significant induction of COX-2, and a down-regulation of COX-1. No COX-2 immunoreactivity was detected in unstimulated HUVEC or unstimulated J774 cells. Therefore, in subsequent studies, the effect of mercaptoalkylguanidines on COX-1 activity was studied in HUVEC stimulated with arachidonic acid for 6 h, and in J774 cells stimulated with arachidonic acid for 30 min. The effect of mercaptoalkylguanidines on COX-2 activity was studied in immunostimulated J774 macrophages, both on prostaglandin production by endogenous sources, and on prostaglandin production in response to exogenous arachidonic acid stimulation. In addition, the effect of mercaptoalkylguanidines on purified COX-1 and COX-2 activities was also studied. 3. In experiments designed to measure COX-1 activity in HUVEC, the cells were stimulated by arachidonic acid (15 microM) for 6 h. This treatment induced a significant production of 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha, the stable metabolite of prostacyclin), while nitrite production was undetectable by the Griess reaction. MEG (1 microM to 3 mM) caused a dose-dependent inhibition of the accumulation of 6-keto-PGF1 alpha, with an IC50 of 20 microM. However, aminoguanidine, L-NAME or L-NMA (up to 3 mM) did not affect the production of 6-keto-PGF1 alpha in this experimental system. In experiments designed to measure COX-1 activity in J774.2 macrophages, the cells were stimulated by arachidonic acid (15 microM) for 30 min; this also induced a significant production of 6-keto-PGF1 alpha and MEG (1 microM to 3 mM), aminoguanidine (at 1 and 3 mM), but neither L-NAME nor L-NMA inhibited the production of prostaglandins. 4. In experiments designed to measure prostaglandin production by COX-2 with endogenous arachidonic acid, J774.2 cells were immunostimulated for 6 h in the absence or presence of various inhibitors. In experiments designed to measure prostaglandin production by COX-2 with exogenous arachidonic acid, J774.2 cells were immunostimulated for 6 h, followed by a replacement of the culture medium with fresh medium containing arachidonic acid and various inhibitors. Both of these treatments induced a significant production of 6-keto-PGF1 alpha. Nitrite production, an indicator of NOS activity, was moderately increased after immunostimulation. MEG (1 microM to 3 mM) caused a dose-dependent inhibition of the accumulation of COX metabolites. Similar inhibition of LPS-stimulated 6-keto PGF1 alpha production was shown by other mercaptoalkylguanidines (such as N-methyl-mercaptoethylguanidine, N,N'-dimethyl-mercaptoethylguanidine, S-methyl-mercaptoethylguanidine and guanidino-ethyldisulphide), with IC50 values ranging between 34-55 microM. However, aminoguanidine, L-NAME and L-NMA (up to 3 mM) did not affect the production of prostaglandins.5. In comparative experiments indomethacin, a non selective COX inhibitor, and NS-398, a selective COX-2 inhibitor, reduced (LPS) stimulated 6-keto-PGF1alpha production in J774 macrophages in a dose-dependent manner without affecting nitrite release. Indomethacin, but not NS-398, inhibited 6-keto-PGF1alpha production in the HUVECs. 6.The inhibitory effect of MEG was due to direct inhibition of the catalytic activity of COX as indicated in experiments with purified COX-1 and COX-2. MEG dose-dependently inhibited the purified COX-1 and COX-2 activity with IC50 values of 33microM and 36microM, respectively. Aminoguanidine (at the highest concentrations) inhibited the formation of COX-1 metabolites, without affecting COX-2 activity. High doses of L-NAME (3mM) decreased COX-1 activity only, while L-NMA (up to 3mM) had no effect on the activity of either enzyme. 7.These results suggest that MEG and related compounds are direct inhibitors of the constitutive and the inducible cyclo-oxygenases, in addition to their effects on the inducible NOS. The additional effect of mercaptoalkylguanidines on COX activity may contribute to the beneficial effects of these agents in inflammatory conditions where both iNOS and COX-2 are expressed.

Zymosan-activated plasma induces paw oedema by nitric oxide and prostaglandin production

Injection of zymosan-activated plasma into the rat paw induced oedema formation. Subplantar injection of the non isoform- selective inhibitors of nitric oxide (NO) synthase, N(G)-nitro-L-Arginine methyl ester and N(G)-methyl-L-Arginine, and of a scavenger of NO, haemoglobin, inhibited the early phase of oedema development. Inhibition of cyclooxygenase activity by indomethacin reduced the late increase in paw volume after the injection of zymosan-activated plasma. Methylene blue, an inhibitor of the soluble guanylate cyclase, had no effect. Our results suggest that in paw oedema induced by zymosan-activated plasma, the inflammatory response is dependent on NO (for the early phase) and prostaglandins (for the late phase). The effect of NO is likely to be mediated by a pathway which does not involve cyclic GMP.