Adjuvant-induced Polyarthritis Research Articles

Alpha-tocopherol-loaded polycaprolactone nanoparticles improve the inflammation and systemic oxidative stress of arthritic rats

Background and aimThe present study investigated the effects of orally administered α-tocopherol-loaded polycaprolactone nanoparticles on the articular inflammation and systemic oxidative status of middle-aged Holtzman rats with Freund's adjuvant-induced polyarthritis, a model for rheumatoid arthritis. Intraperitoneally administered free α-tocopherol provided the reference for comparison. Experimental procedureTwo protocols of treatment were followed: intraperitoneal administration of free α-tocopherol (100 mg/kg i.p.) or oral administration of free and nanoencapsulated α-tocopherol (100 mg/kg p.o.). Animals were treated during 18 days after arthritis induction. ResultsFree (i.p.) and encapsulated α-tocopherol decreased the hind paws edema, the leukocytes infiltration into femorotibial joints and the mRNA expression of pro-inflammatory cytokines in the tibial anterior muscle of arthritic rats, but the encapsulated compound was more effective. Free (i.p.) and encapsulated α-tocopherol decreased the high levels of reactive oxygen species in the brain and liver, but only the encapsulated compound decreased the levels of protein carbonyl groups in these organs. Both free (i.p.) and encapsulated α-tocopherol increased the α-tocopherol levels and the ratio of reduced to oxidized glutathione in these organs. ConclusionBoth intraperitoneally administered free α-tocopherol and orally administered encapsulated α-tocopherol effectively improved inflammation and systemic oxidative stress in middle-aged arthritic rats. However, the encapsulated form should be preferred because the oral administration route does not be linked to the evident discomfort that is caused in general by injectable medicaments. Consequently, α-tocopherol-loaded polycaprolactone nanoparticles may be a promising adjuvant to the most current approaches aiming at rheumatoid arthritis therapy.

Chemical characterization and anti-arthritic appraisal of Monotheca buxifolia methanolic extract in Complete Freund's Adjuvant-induced arthritis in Wistar rats.

The current study was designed to evaluate the anti-oxidant and anti-arthritic potential of a traditionally used herb, Monotheca buxifolia. The M. buxifolia methanolic extract (MBME) was prepared from the aerial parts of the plant followed by chemical characterization with GC-MS. The anti-oxidant potential of the MBME was demonstrated by DPPH scavenging activity. The effects of MBME on protein denaturation and membrane stabilization were determined by inhibition of egg albumin denaturation and RBC membrane stabilization assays, respectively. The in vivo anti-arthritic potential of the MBME at 50, 100, and 150mg/kg/day was evaluated in Complete Freund's Adjuvant-induced polyarthritis in Wistar rats treated for 21days. Phytochemicals, such as linolenic acid methyl ester, n-hexadecanoic acid, vitamin E, α-amyrin, and β-amyrin were detected in the GC-MS analysis. The plant extract exhibited a 55.20 ± 0.69% scavenging of free radicals at 100µg/ml concentration. It significantly (p < 0.05) stabilized human RBC membrane (65.06 ± 0.22%) and inhibited protein denaturation (70.53 ± 0.34%) at 100mg/ml concentration. The diclofenac sodium (DS) and MBME at 150,100, and 50mg/kg reduced the paw edema, restored the body weight, and altered blood parameters including CRP. The MBME significantly reduced the MDA and increased the SOD, CAT, and GSH levels in liver tissue homogenate in treated rats. The serum concentration of TNF-α and PGE2 was remarkably (p < 0.01-< 0.0001) restored by the DS and MBME dose dependently. The histopathological study showed that MBME 150mg/kg commendably restored the ankle joint inflammation, bone erosion, and cartilage damage in polyarthritic rats. It was concluded that the anti-oxidant, anti-inflammatory and anti-arthritic effects of MBME might be attributed to phenols, flavonoids, triterpenoids, vitamin E, phytol, and other fatty acids. This study showed the anti-arthritic potential of Monotheca buxifolia and thus validates its traditional claim.

Ameliorative effect of morin, a plant flavonoid against Freund's complete adjuvant-induced polyarthritis in rats

Background: Rheumatoid arthritis is a chronic relapsing autoimmune disorder with multifactorial etiology and prognosis. Morin [2-(2,4-dihydroxyphenyl)-3,5,7-trihydroxy-4H-1-benzopyran-4-one], a plant flavonoid reported having antioxidant and anti-inflammatory potential. Objective: The aim is to study the anti-arthritic activity of the morin against adjuvant-induced polyarthritis in rats. Materials and Methods: Polyarthritis was induced in female Wistar rats (150–180 g) using Freund's complete adjuvant (FCA) in the tail. Leflunomide (10 mg/kg, as a standard) and morin (10, 30 and 100 mg/kg) were administered orally daily for 28 days. Results: Treatment with morin (30 and 100 mg/kg) showed statistically significant inhibition (P Abbreviations used: AIA: Adjuvant-induced arthritis, ALT: Alanine transaminase, ALP: Alkaline phosphatase, AST: Aspartate aminotransferase, BSL: Blood glucose level, CRP: C-reactive protein, ESR: Erythrocyte sedimentation rate, FCA: Freund's complete adjuvant, HO: Heme oxygenase, HDL: High-density lipoprotein, IL-1β: Interleukin-1 beta, LDL: Low-density lipoprotein, MDA: Malondialdehyde, NO: Nitric oxide, Nrf2: Nuclear factor-like 2, ROS: Reactive oxygen species, GSH: Reduced glutathione, RT-PCR: Reverse transcription-polymerase chain reaction, SOD: Superoxide dismutase, TC: Total cholesterol, TGF-β: Transforming growth factor-beta, TG: Triglyceride, TNF-α: Tumor necrosis factor-alpha, VLDL: Very low-density lipoprotein.

Transdermal anti-inflammatory activity of bilayer film containing olive compound hydroxytyrosol: physical assessment, in vivo dermal safety and efficacy study in Freund’s adjuvant-induced arthritic rat model

Previous studies have shown that hydroxytyrosol (HT) can be a potential alternative therapeutic agent for the treatment of rheumatoid arthritis (RA). However, HT is extensively metabolized following oral administration, which leads to formulating HT in a topical vehicle to prolong drug action as well as to provide a localized effect. Hidrox-6 is a freeze-dried powder derived from fresh olives and contains a high amount of HT (∼3%) and other polyphenols. Alginate bilayer films containing 5% and 10% Hidrox-6 were formulated. The films were characterized with respect to their physical, morphology, rheological properties; drug content uniformity; and in vitro drug release. Acute dermal irritancy tests and a skin sensitization study were carried out in rats. An efficacy study of the bilayer films for RA was conducted using Freund’s adjuvant-induced polyarthritis rats. Animal data showed that the bilayer film formulations did not cause skin irritancy. The efficacy in vivo results showed that the Hidrox-6 bilayer films lowered the arthritic scores, paw and ankle circumference, serum IL-6 level and cumulative histological scores compared with those measured for controls. The topical Hidrox-6 bilayer films improve synovitis and inflammatory symptoms in RA and can be a potential alternative to oral RA therapy.

Prophylactic and therapeutic effects of Mytilus edulis fatty acids on adjuvant-induced arthritis in male Wistar rats

Lipid-rich fractions from the flesh tissue of Mytilus edulis were obtained by solvent extraction and chromatographic separation, and tested for anti-inflammatory (AI) activity in vitro and in vivo. Inhibition of leukotriene production by isolated human neutrophils in response to calcium ionophore stimulation in the presence of exogenous arachidonic acid substrate was demonstrated for the hydrolysed triglyceride fraction of the crude lipid extract. This fraction was subsequently tested for in vivo AI activity using the mycobacterial adjuvant-induced polyarthritis rat model. The hydrolysed triglyceride fraction showed significant AI activity when dosed therapeutically (10 mg/kg BW/day, p.o., for 6 days from the onset of arthritis), decreasing body weight loss by 55% and hind paw swelling by 65% compared to the arthritic control. The (non-hydrolysed) crude lipid extract was effective when dosed prophylactically (30 mg/kg BW/day, p.o., for 16 days starting on day −2 of arthritigen inoculation). Structural analysis by GC and GC–MS revealed in the extracts an abundance of EPA (20:5n-3) and DHA (22:6n-3) (37% of total fatty acids), along with a small quantity of a rare anti-inflammatory n-3 analogue of arachidonic acid, namely 7, 11, 14, 17-eicosatetraenoic acid (20:4n-3).

Discovery of Novel Therapies for Rheumatic Diseases and Associated Pain Requires Suitable and Relevant Disease Models: a Comparison of Monoarthritis and Polyarthritis Efficacy Models.

BioTechniquesVol. 45, No. 4 Application Forum - Sponsored PaperOpen AccessDiscovery of novel therapies for rheumatic diseases and associated pain requires suitable and relevant disease models: a comparison of monoarthritis and polyarthritis efficacy models.MD Biosciences Inc.MD Biosciences Inc.MD Biosciences Inc., 1000 Westgate Dr, St Paul, MN, 55114Search for more papers by this authorPublished Online:16 May 2018https://doi.org/10.2144/000112997AboutSectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinkedInRedditEmail IntroductionChronic pain associated with rheumatic diseases such as rheumatoid arthritis (RA) and osteoarthritis (OA) affects millions of people every year. This pain subsequently affects almost every aspect of a person's life and has a substantial impact on economics such as health insurance, lost wages, reduced productivity and increased incidence of depression and suicide. These facts highlight the need for relevant disease models to assess new therapies for both inflammation and pain associated with the disease.Polyarthritis vs Monoarthritis Disease ModelsComplete Freund's Adjuvant (CFA) has been widely used for the induction of rheumatoid arthritis in rats. Injection of the CFA in the tail base results in a chronic arthritis involving multiple joints (adjuvant induced arthritis). While using end readouts such as clinical signs, scores, body weights, response to mechanical and thermal stimuli, and a record of the spontaneous pain (footprint of pain) allows evaluation of a proposed therapy, there are many disadvantages to the experimental polyarthritis model. The adjuvant, when injected into the tail base, promotes a widespread systemic disease that results in severe discomfort and stress on the animals.By injecting the CFA intrarticular and periarticular into a rat or mouse joint, you achieve a localized, less severe monoarthritis within a few days. The disease represents many of the features of rheumatoid arthritis such as pannus formation, without complicating factors such as poor animal mobility, altered weight gain, systemic disease, and severe disease such as joint ankylosis. Other advantages to the monoarthritis model is that arthritis can be induced in various species and strains that allow for genetic background studies (e.g. transgenic mice), the uninjured joint acts as a control reducing the number of animals required per study, and the injection technique can be applied to other RA models allowing the local administration of test compound when required. The addition of pain measurements to the clinical readouts also allows for therapeutic evaluation of analgesia in rats (Figure 1).Figure 1. Response to mechanical pain (force required to move paw) and response to thermal pain (time to remove paw) in the CFA-induced Monoarthritis model in rats.Visit MD Biosciences Website for More Information on These Arthritis Research Tools:Collagen induced arthritis (CIA), Collagen antibody induced arthritis (CAIA)Adjuvant-induced polyarthritis and monoarthritis and associated painCollagen reagents, adjuvants and related ELISAsArthritoMab™ Antibody CocktailAggrecan AntibodiesMD Biosciences, Inc.Email: info-us@mdbiosciences.comWeb site: www.mdbiosciences.comPhone (US/Canada): 888-USMDBIOFiguresReferencesRelatedDetails Vol. 45, No. 4 Follow us on social media for the latest updates Metrics Downloaded 147 times History Published online 16 May 2018 Published in print October 2008 Information© 2008 Future Science LtdPDF download

Blockade of the chemokine receptor CXCR2 ameliorates adjuvant‐induced arthritis in rats

Chemokine receptors CXCR1 and CXCR2 may mediate influx of neutrophils in models of acute and chronic inflammation. The potential benefits of oral administration of a CXCR1/2 inhibitor, DF 2162, in adjuvant-induced polyarthritis (AIA) were investigated. A model of AIA in rats was used to compare the therapeutic effects of the treatment with DF2162, anti-TNF or anti-CINC-1 antibodies on joint inflammation and local production of cytokines and chemokines. DF2162 prevented chemotaxis of rat and human neutrophils induced by chemokines acting on CXCR1/2. DF2162 was orally bioavailable and metabolized to two major metabolites. Only metabolite 1 retained CXCR1/2 blocking activity. Treatment with DF2162 (15 mg kg(-1), twice daily) or metabolite 1, but not metabolite 2, starting on day 10 after arthritis induction diminished histological score, the increase in paw volume, neutrophil influx and local production of TNF, IL-1beta, CCL2 and CCL5. The effects of DF2162 were similar to those of anti-TNF, and more effective than those of anti-CINC-1, antibodies. DF2162 prevented disease progression even when started 13 days after arthritis induction. DF 2162, a novel orally-active non-competitive allosteric inhibitor of CXCR1 and CXCR2, significantly ameliorates AIA in rats, an effect quantitatively and qualitatively similar to those of anti-TNF antibody treatment. These findings highlight the contribution of CXCR2 in the pathophysiology of AIA and suggest that blockade of CXCR1/2 may be a valid therapeutic target for further studies aiming at the development of new drugs for treatment of rheumatoid arthritis.

Antiinflammatory role of endomorphins in osteoarthritis, rheumatoid arthritis, and adjuvant‐induced polyarthritis

Pain sensitization and the related secretion of neuropeptides from sensory nerve terminals are proinflammatory in osteoarthritis (OA), rheumatoid arthritis (RA), and adjuvant-induced polyarthritis. In contrast, endogenous opioids such as the recently discovered endomorphins (EMs) are antiinflammatory. However, the role of endogenous EMs such as EM-1 and EM-2 has never been investigated in OA and RA. We established a highly sensitive radioimmunoassay to detect EM-1 and EM-2. In patients with RA and patients with OA, immunohistochemistry for EM-1 and EM-2 was performed, and double-staining was used to identify EM-positive cells. The effects of EM-1 and EM-2 on the secretion of interleukin-6 (IL-6) and IL-8 from human synovial tissue were studied by tissue superfusion, and the therapeutic effects of EM-1 were tested in a rat model of adjuvant-induced polyarthritis. EM-positive cells were located in the sublining area and vessel walls but were particularly evident in the highly inflamed lining area. Human macrophages, T cells, and fibroblasts stained positive for EMs. The synovial density of EM-positive cells was higher in patients with OA than in those with RA. EM-1 inhibited synovial secretion of IL-6 in patients with RA and secretion of IL-8 in patients with RA and those with OA (maximum 10(-10)M). EM-2 inhibited IL-8 secretion only from RA tissue (maximum 10(-10)M). In rats with adjuvant-induced polyarthritis, thymus, spleen, and synovial tissue contained significantly more EM-1 than was observed in controls. Rats with adjuvant-induced polyarthritis benefited from EM-1 treatment. EM-1 had antiinflammatory effects in patients with OA or RA and in a model of adjuvant-induced polyarthritis. Local enhancement of EM-1 might be an interesting therapeutic option in different forms of arthritis.

Anti-Inflammatory Effects of 4-Phenyl-3-butenoic Acid and 5-(Acetylamino)-4-oxo-6-phenyl-2-hexenoic Acid Methyl Ester, Potential Inhibitors of Neuropeptide Bioactivation

Substance P (SP) and calcitonin gene-related peptide (CGRP) are well established mediators of inflammation. Therefore, inhibition of the biosynthesis of these neuropeptides is an attractive potential strategy for pharmacological intervention against a number of inflammatory diseases. The final step in the biosynthesis of SP and CGRP is the conversion of their glycine-extended precursors to the active amidated peptide, and this process is catalyzed by sequential action of the enzymes peptidylglycine alpha-monooxygenase (PAM) and peptidylamidoglycolate lyase. We have demonstrated previously that 4-phenyl-3-butenoic acid (PBA) is a PAM inhibitor, and we have also shown that in vivo inhibition of serum PAM by PBA correlates with this compound's ability to inhibit carrageenan-induced edema in the rat. Here we demonstrate the ability of PBA to inhibit all three phases of adjuvant-induced polyarthritis (AIP) in rats; this represents the first time that an amidation inhibitor has been shown to be active in a model of chronic inflammation. We recently introduced 5-(acetylamino)-4-oxo-6-phenyl-2-hexenoic acid (AOPHA) as one of a new series of mechanism-based amidation inhibitors. We now report for the first time that AOPHA and its methyl ester (AOPHA-Me) are active inhibitors of serum PAM in vivo, and we show that AOPHA-Me correspondingly inhibits carrageenan-induced edema in rats in a dose-dependent manner. Neither PBA nor AOPHA-Me exhibits significant cyclooxygenase (COX) inhibition in vitro; thus, the anti-inflammatory activities of PBA and AOPHA-Me are apparently not a consequence of COX inhibition. We discuss possible pharmacological mechanisms that may account for the activities of these new anti-inflammatory compounds.

Anti-arthritic Effects of Ephedra sinica STAPF Herb-Acupuncture: Inhibition of Lipopolysaccharide-Induced Inflammation and Adjuvant-Induced Polyarthritis

Anti-inflammatory and anti-arthritic effects of water distillates of Ephedra sinica STAPF (ES), in herb-acupuncture, on the inflammatory responses of arthritis was investigated using phorbol 12-myristate 13-acetate (PMA)/lipopolysaccharide (LPS)-induced human macrophage and adjuvant-induced arthritic rat. The luciferase reporter vectors driven by the tumor necrosis factor (TNF)-alpha and cyclooxygenase-2 promoters were transiently transfected into U937 cells, which were then differentiated and stimulated by PMA and LPS, respectively, to develop an in vitro anti-inflammation assay system. The luciferase activities, observed in the activated U937 cells, were significantly inhibited by ES herb-acupuncture, compared to those of PD98509 and berberine. To evaluate ES herb-acupuncture as a novel anti-arthritic therapy, a polyarthritic rat model was developed using heat-killed Mycobacterium tuberculosis, and 50 mul of ES distillate was subcutaneously injected into the ST36 acupoint on each knee joint. While the articular indexes of arthritic rats were evidently decreased by ES herb-acupuncture, their body weights did not regain their initial levels. This may be due to the accelerating effects of ES on weight-loss and fat consumption. The mRNA expressions of TNF-alpha and interleukin (IL)-6 genes, which were closely stimulated in the arthritic rat joints, were found to be restored to the normal levels through the ES treatment. In the case of IL-1beta, the recovery was not significant but substantial. The anti-arthritic effect of ES herb-acupuncture was not found in the ES-treated/non-acupoint group. In conclusion, the ES herb-acupuncture into the ST36 acupoint was found to be effective in alleviating the inflammatory response and thus arthritic symptoms in adjuvant-induced arthritic rats.

Anti-inflammatory activity of Indian black tea (Sikkim variety)

In this study, the anti-inflammatory (in reference to the cardinal signs of inflammation) and other related pharmacological activities of the hot water extract of black tea ( Camellia sinensis, Sikkim variety) were evaluated along with certain standard drugs. The extract showed significant inhibitory activity against carrageenin, histamine, serotonin and prostaglandin-induced pedal inflammation. The extract inhibited exudative inflammation. The tea extract also inhibited cotton pellet-induced granuloma formation and adjuvant-induced polyarthritis. Black tea extract showed significant inhibition against glucose oxidase-mediated inflammation. The present observations establish the efficacy of this particular variety of black tea, both in the exudative and proliferative forms and as well in the chronic phase of inflammation.

Anti-inflammatory activity of ‘TAF’ an active fraction from the plant Barleria prionitis Linn.

‘TAF’ fraction from the methanol–water extract of Barleria prionitis Linn. was evaluated for anti-inflammatory and anti-arthritic activities against different acute and chronic animal test models. It exhibited significant anti-inflammatory activity against different inflammagens like carrageenan, histamine and dextran. The anti-inflammatory activity in adrenalectomised rats was maintained showing that the effect of fraction ‘TAF’ is not activated by the pituitary–adrenal axis. Significant anti-arthritic activity was observed in adjuvant-induced polyarthritis test in rats. ‘TAF’ also showed inhibition of vascular permeability and leucocytes migration in vivo into the site of inflammatory insult. Ibuprofen (Cadilla India Ltd., Mumbai) was used as a standard reference drug. The oral (p.o.) LD 50 was more than 3000 mg/kg, with no signs of abnormalities or any mortality observed for 15 days after single-dose drug administration. The intraperitoneal (i.p.) LD 50 was found to be 2530 mg/kg (±87 mg/kg S.E.) [Proceedings of Society of Experimental Biological Medicine 57 (1944) 261].

Chronic pain increases brainstem proneurotensin/neuromedin-N mRNA expression: a hybridization-histochemical and immunohistochemical study using three different rat models for chronic nociception

The role of neurotensin in the central nervous system is poorly understood. Exogenous neurotensin has potent antinociceptive effects when injected into the midbrain periaqueductal gray (PAG). Although it is present in terminals, fibers and perikarya within the PAG and other midbrain regions known for their antinociceptive circuits, it is not known whether endogenous neurotensin modulates nociception. We examined the midbrain in three different rat models for nociception to learn whether acute or chronic pain altered neuronal levels of the proneurotensin/neuromedin N mRNA (neurotensin mRNA). The models were: adjuvant-induced polyarthritis, adjuvant-induced unilateral paw inflammation, and unilateral peripheral mononeuropathy caused by ligation of the sciatic nerve. Behavioral observations confirmed that the expected symptoms developed as previously described. Within each of the three experimental models, we performed in situ hybridization histochemistry on coronal sections from three midbrain levels that included the rostral one-third of the PAG, the middle one-third of the PAG, and the caudal one-third of the PAG. At the level of the rostral PAG, we found that neither chronic nor acute nociception altered the frequencies or distributions of neurons containing neurotensin mRNA. In contrast, at the levels of the mid- and caudal one third of the PAG, the early effects of the nociceptive lesions differed from the chronic effects. During the acute phase of each model, increases in either the frequency or field area of neurons that were hybridization-positive for neurotensin mRNA were confined to the ventromedial PAG and the dorsal raphe nucleus. As the nociceptive stimuli became chronic, the early increases in neurotensin mRNA-containing neurons at the level of the middle third of the ventral PAG were diminished but remained above control levels, while increases in neurotensin mRNA began to occur in the midbrain tegmentum lateral to the PAG. The most striking increases in neurotensin mRNA expression were observed 16-17 days after the onset of nociceptive stimuli. At the level of the mid-PAG and caudal PAG, increased hybridization signal intensities and neuron frequencies occurred within the nucleus cuneiformis and the lateral tegmental nuclei, including the pedunculopontine and microcellular tegmental nuclei, as well as the deep mesencephalic nuclei. Hybridization-positive neurons in the tegmental nuclei were not observed at early stages of lesion development, but were a consistent feature of caudal midbrains after nociception became chronic.(ABSTRACT TRUNCATED AT 400 WORDS)

Therapeutic Efficacy in Experimental Polyarthritis of Viral-Driven Enkephalin Overproduction in Sensory Neurons

Rheumatoid arthritis is characterized by erosive inflammation of the joints, new bone proliferation, and ankylosis, leading to severely reduced locomotion and intense chronic pain. In a model of this disease, adjuvant-induced polyarthritis in the rat, neurons involved in pain transmission and control undergo plastic changes, especially at the spinal level. These changes affect notably neurons that contain opioids, such as enkephalins deriving from preproenkephalin A (PA) precursor protein. Using recombinant herpes simplex virus containing rat PA cDNA, we enhanced enkephalin synthesis in sensory neurons of polyarthritic rats. This treatment markedly improved locomotion and reduced hyperalgesia. Furthermore, the progression of bone destruction slowed down, which is the most difficult target to reach in the treatment of patients suffering from arthritis. These data demonstrate the therapeutic efficacy of enkephalin overproduction in a model of systemic inflammatory and painful chronic disorder.

Concerning the anti-arthritic action of cetyl myristoleate in rats: An interim report

The proposed arthro-preventive action of cetyl myristoleate, an OTC product sold as a nutritional supplement, could not be confirmed, using an almost identical bioassay (adjuvant-induced polyarthritis in rats) as that described in the original report (Diehl and May, 1994) with the same, and 3 other, dosing schedules.

Spinal Substance P Receptor Expression and Internalization in Acute, Short-Term, and Long-Term Inflammatory Pain States

Inflammatory pain involves the sensitization of both primary afferent and spinal cord neurons. To explore the neurochemical changes that contribute to inflammatory pain, we have examined the expression and ligand-induced internalization of the substance P receptor (SPR) in the spinal cord in acute, short-term, and long-term inflammatory pain states. These inflammatory models included unilateral injection of formalin (8-60 min), carrageenan (3 hr), and complete Freund's adjuvant (CFA; 3 d) into the rat hindpaw as well as adjuvant-induced polyarthritis (21 d). In acute inflammatory pain there is ongoing release of substance P (SP) as measured by SPR internalization in lamina I neurons at both 8 and 60 min after formalin injection. Although there is no tonic release of SP in short-term inflammatory pain, at 3 hr after carrageenan injection, SP is released in response to both noxious and non-noxious somatosensory stimulation with SPR internalization being observed in neurons located in both laminae I and III-IV. In long-term inflammatory pain models (CFA and polyarthritis) the same pattern of SP release and SPR activation occurs as is observed in short-term inflammation with the addition that there is a significant upregulation of the SPR in lamina I neurons. These results suggest that SPR internalization might serve as a marker of the contribution of ongoing primary afferent input in acute and persistent pain states. These stereotypical neurochemical changes suggest that there are unique neurochemical signatures for acute, short-term, and long-term inflammatory pain.

Inhibition by leukotriene inhibitors, and calcium and platelet-activating factor antagonists, of acute gastric and intestinal damage in arthritic rats and in cholinomimetic-treated mice.

The leukotrienes, platelet activating factor and intracellular calcium have been implicated in the development of gastro-intestinal lesions induced by non-steroidal anti-inflammatory drugs (NSAIDs) but the relative significance of these inflammatory mediators in lesion formation has not been established in sensitive and specific models of gastro-intestinal ulceration. In the present study the effects of drugs affecting 5-lipoxygenase activity, the actions of platelet activating factor and intracellular calcium on the development of gastric and intestinal ulceration induced by NSAIDs were investigated in highly sensitive models of ulcerogenicity induced by treatment with either the cholinomimetic, acetyl-beta-methyl choline chloride, in mice (gastric mucosal lesions) or adjuvant-induced polyarthritis in rats (gastric and intestinal mucosal lesions) as well as in normal mice (intestinal mucosal lesions). The 5-lipoxygenase inhibitors, such as MK-886 (3-[1-(4-chlorobenzyl)-3-t-butyl-thio-5-isopropylindol-2-yl]-2,2-+ ++dimethylpropanoic acid), given at doses shown to reduce the indomethacin-induced increase in mucosal leukotriene B4 concentrations were found to partially prevent the development of gastric and intestinal lesion induced by indomethacin and gastric lesions from aspirin, but the same doses of MK-886 did not affect gastric lesions from diclofenac. Pretreatment with these inhibitors at both 3-5 h and 0-0.25 h was required to achieve protection against gastric mucosal damage from indomethacin. Immediate prior administration of platelet activating factor antagonists (e.g. WEB-2086) with the 5-lipoxygenase inhibitors did not affect gastric or intestinal lesions induced by indomethacin. The calcium antagonist, verapamil, was slightly protective against gastric and intestinal lesions induced by indomethacin. Gastric lesions were further prevented by combinations of a single dose of verapamil with a platelet activating factor antagonist but not combined with a 5-lipoxygenase inhibitor; other combinations of verapamil with lipoxygenase inhibitors or platelet-activating factor antagonists being without inhibitory effects on gastric or intestinal lesions compared with the drugs alone. These results show that 5-lipoxygenase products and intracellular calcium play a major role in acute gastric and intestinal damage by the NSAIDs, but platelet-activating factor has little or no appreciable involvement.

Polyarthritis-associated changes in the opioid control of spinal CGRP release in the rat

As a model of chronic inflammatory pain, Freund's adjuvant-induced polyarthritis has been shown to be associated with marked alterations in the activity of opioid- and calcitonin gene-related peptide (CGRP)-containing neurons in the dorsal horn of the spinal cord in rats. Possible changes in the interactions between these two peptidergic systems in chronic inflammatory pain were investigated by comparing the effects of various opioid receptor ligands on the spinal outflow of CGRP-like material (CGRPLM) in polyarthritic and age-paired control rats. Intrathecal perfusion of an artificial cerebrospinal fluid in halothane-anaesthetized animals allowed the collection of CGRPLM released from the spinal cord and the application of opioid receptor ligands. The blockade of κ-opioid receptors similarly increased CGRPLM release in both groups of rats as expected of a κ-mediated tonic inhibitory control of CGRP-containing fibres in control, as well as in polyarthritic rats. In contrast, the higher increase in CGRPLM outflow due to the preferential blockade of μ opioid receptors by naloxone in polyarthritic rats as compared to non-suffering animals supports the idea of a reinforced μ opioid receptor-mediated tonic inhibitory control of CGRP-containing fibres in rats suffering from chronic pain. Even more strikingly, the differences observed in the effects of ∂-opioid receptor ligands on CGRPLM outflow suggest that ∂ receptors are functionally shifted from a participation in a phasic excitatory control in non-suffering rats to a tonic inhibitory control in polyarthritic rats. These data indicate that agonists acting at the three types of opioid receptors all exert a tonic inhibitory influence on CGRP-containing nociceptive primary afferent fibres within the spinal cord of polyarthritic rats. Such a convergence probably explains why morphine and other opioids are especially potent to reduce pain in subjects suffering from chronic inflammatory diseases.

Dimethylheptyl-THC-11 oic acid: a nonpsychoactive antiinflammatory agent with a cannabinoid template structure.

To assess the antiinflammatory activity of dimethylheptyl-THC-11 oic acid (DMH-11C), a nonpsychoactive synthetic derivative of tetrahydrocannabinol. Acute inflammation was induced by injection of interleukin-1beta and tumor necrosis factor alpha into subcutaneous air pouches formed on the backs of mice. Inflammation was quantified 6 hours later by pouch fluid leukocyte counts. Adjuvant-induced polyarthritis in rats was used as a model of chronic inflammation and joint tissue injury. Animals were either untreated, treated with safflower oil, or treated with DMH-11C in safflower oil. Arthritis was assessed by clinical observation and by histomorphologic evaluation of tibiotarsal joints. Oral administration of DMH-11C reduced the accumulation of pouch fluid leukocytes and significantly reduced the severity of adjuvant-induced polyarthritis. Histopathologic studies of tibiotarsal joints showed that DMH-11C treatment attenuated pannus formation and joint tissue injury. DMH-11C suppresses acute inflammation in the subcutaneous air pouch in mice and chronic joint inflammation characteristic of adjuvant disease in rats. These results demonstrate the potential use of this nonpsychoactive cannabinoid as an antiinflammatory agent.

Anti-inflammatory activity of a lipid fraction (lyprinol) from the NZ green-lipped mussel

A lipid-rich extract, preparared by supercritical fluid extraction of fresh stabilized mussel powder (Lyprinol), showed significant anti-inflammatory (AI) activity given therapeutically and prophylactically po to Wistar and Dark Agouti rats developing either (a) adjuvant-induced polyarthritis or (b) collagen(II)-induced autoallergic arthritis, with ED(50)</=15 mg/kg; c.f. naproxen>/=25 mg/kg or various therapeutic oils (flaxseed, evening primrose, fish)>/=1800 mg/kg given orally. Lyprinol showed little or no activity in acute irritation assays (carrageenan, kaolin, histamine) indicating it is not mimicking rapid-acting NSAIDs.Incorporating Lyprinol into arthritigenic adjuvants composed of heat-killed Mycobacterium. tuberculosis suspended in olive oil or squalane, effectively prevented arthritis development at a dose of 5 mg/rat. By contrast, 'dummy adjuvants' prepared with Mycobacterium tuberculosis and flaxseed, evening primrose or fish oils were still arthritigenic in Dark Agouti rats (doses of oil=90 mg/rat).Lyprinol subfractions inhibited leukotriene-B(4) biosynthesis by stimulated human polymorphonuclear leukocytes in vitro, and prostaglandin-E(2) production by activated human macrophages in vitro. Much of this AI activity was associated with polyunsaturated fatty acids and natural antoxidants (carotenoids, etc.).In contrast to NSAIDs, Lyprinol is non-gastrotoxic in disease-stressed rats at 300 mg/kg po and does not seem to affect platelet aggregation (human, rat). These data show Lyprinol to be a reproducible, relatively stable, source of bioactive lipids with much greater potency than plant/marine oils currently used as nutritional supplements to ameliorate signs of inflammation.