Pathophysiological basis of acute inflammatory hyperaemia in the rat knee: roles of cyclo-oxygenase-1 and -2

Platelet Factor 4 Attenuates Experimental Acute Liver Injury in Mice

Platelet factor 4 (PF4) is a pleiotropic inflammatory chemokine, which has been implicated in various inflammatory disorders including liver fibrosis. However, its role in acute liver diseases has not yet been elucidated. Here we describe an unexpected, anti-inflammatory role of PF4. Serum concentrations of PF4 were measured in patients and mice with acute liver diseases. Acute liver injury in mice was induced either by carbon tetrachloride or by D-galactosamine hydrochloride and lipopolysaccharide. Serum levels of PF4 were decreased in patients and mice with acute liver diseases. PF4^-/- mice displayed increased liver damage in both models compared to control which was associated with increased apoptosis of hepatocytes and an enhanced pro-inflammatory response of liver macrophages. In this experimental setting, PF4^-/- mice were unable to generate activated Protein C (APC), a protein with anti-inflammatory activities on monocytes/macrophages. In vitro, PF4 limited the activation of liver resident macrophages. Hence, the systemic application of PF4 led to a strong amelioration of experimental liver injury. Along with reduced liver injury, PF4 improved the severity of the pro-inflammatory response of liver macrophages and induced increased levels of APC. PF4 has a yet unidentified direct anti-inflammatory effect in two models of acute liver injury. Thus, attenuation of acute liver injury by systemic administration of PF4 might offer a novel therapeutic approach for acute liver diseases.

Validation of therapeutic anti-inflammatory potential of Arjuna Ksheera Paka - A traditional Ayurvedic formulation of Terminalia arjuna

Arjuna Ksheera Paka (AKP), a traditional Ayurvedic formulation of Terminalia arjuna (T. arjuna) bark powder is used for its cardioprotective effects. However, its anti-inflammatory efficacy remained unexplored. In the present study, AKP was prepared in cow milk (as per standard Ayurvedic procedure) and compared with standard hydroalcoholic extract (HA) of T. arjuna. The extracts were analyzed for gross phytoconstituents levels, and their antioxidant activity was assayed by DPPH free radical scavenging activity and inhibition of lipid peroxidation. The in vivo anti-inflammatory activity of AKP and HA was studied in carrageenan-induced hind paw biphasic edema in C57BL/6 mice (at 200, 400 and 800 mg/kg BW). The percentage extraction yield of AKP was two folds higher than HA implying that the phytoconstituents in AKP were diluted by a factor of 0.5. The total polyphenol content of HA was (3.8 times) higher than AKP and the antioxidant activity of HA was also higher compared to AKP. Both the extracts, however, showed significant (p < 0.05) anti-inflammatory activity in reducing paw edema in mice. The efficacy of HA was more than AKP at early phase of inflammation, whereas, in the late phase of inflammation AKP was more efficacious and equipotent to HA. Thus, regardless of low in vitro antioxidant activity, AKP exhibited potential in vivo anti-inflammatory activity. The higher efficacy of AKP could be due to the presence of milk solids. These milk solids may act as adjuvants to T. arjuna's phytoconstituents, contributing to their sustained bioavailability, leading to higher in vivo anti-inflammatory efficacy at lower drug concentrations.

Carvedilol can attenuate histamine-induced paw edema and formaldehyde-induced arthritis in rats without risk of gastric irritation

BACKGROUND AND AIM

Rheumatoid arthritis treatment aims to control joint damage and any associated complications such as cardiovascular disease. Most anti-inflammatory drugs have a high tendency to cause gastro-intestinal irritation. The present study is designed to investigate the anti-inflammatory effect of carvedilol and to study its effect on gastric mucosa.

EXPERIMENTAL APPROACH

Lornoxicam (1.3mg/kg) or carvedilol (10mg/kg) was administrated orally 1h before histamine injection into animals of a histamine-induced paw edema model and orally daily for 11days into animals of a formaldehyde-induced arthritis model. Tumor necrosis factor-α and prostaglandin E₂ were measured in animals of the formaldehyde-induced arthritis model. The effect of lornoxicam and carvedilol on gastric mucosa was assessed in normal rats and after induction of cold stress ulcer.

RESULTS

Carvedilol succeeded in reducing hind paw edema in both histamine-induced paw edema and formaldehyde-induced arthritis and in reducing the elevated level of tumor necrosis factor-α and prostaglandin E₂ nearly with near equal efficacy compared with lornoxicam. Carvedilol did not show any ulcerative effect on the gastric mucosa of normal rats, and its use was associated with an improvement of both the gross and histopathological pictures of gastric ulcers in animals of the cold stress ulcer model compared with lornoxicam treated rats.

CONCLUSION

The current findings support the use of carvedilol both in the management of inflammation as well as the prevention of cardiovascular complications in rheumatoid arthritis patients. The use of carvedilol was not associated with any gastro-intestinal tract irritation.

2-Pentadecyl-2-Oxazoline, the Oxazoline of Pea, Modulates Carrageenan-Induced Acute Inflammation

N-acylethanolamines (NAEs) involve a family of lipid molecules existent in animal and plant, with N-palmitoylethanolamide (PEA) that arouses great attention owing to its anti-inflammatory, analgesic and neuroprotective activities. Because PEA is produced on demand and exerts pleiotropic effects, the modulation of specific amidases for NAEs (and in particular NAE-hydrolyzing acid amidase NAAA, which is more selective for PEA) could be a condition to preserve its levels. Here we investigate the effect of 2-Pentadecyl-2-oxazoline (PEA-OXA) the oxazoline of PEA, on human recombinant NAAA in vitro and in an established model of Carrageenan (CAR)-induced rat paw inflammation. PEA-OXA dose-dependently significantly inhibited recombinant NAAA and, orally administered to rats (10 mg/kg), limiting histological damage, thermal hyperalgesia and the increase of infiltrating inflammatory cells after CAR injection in the rat right hindpaw, compared to ultramicronized PEA given orally at the same dose (10 mg/kg). These effects were accompanied by elevation of paw PEA levels. Moreover, PEA-OXA markedly reduced neutrophil infiltration and pro-inflammatory cytokine release and prevented CAR-induced IκB-α degradation, nuclear translocation of NF-κB p65, the increase of inducible nitric oxide synthase, cyclooxygenase-2, intercellular adhesion molecule-1, and mast cell activation. Experiments in PPAR-α knockout mice showed that the anti-inflammatory effects of PEA-OXA were not dependent on the presence of PPAR-α receptors. In conclusion, NAAA modulators as PEA-OXA could help to maximize the tissue availability of PEA by increasing its levels and anti-inflammatory effects.

Anti inflammatory activity of Myrica nagi Linn. Bark

The present study evaluated the anti inflammatory activity of ethyl acetate and aqueous extracts of bark of M. nagi using carrageenan and histamine induced rat paw edema. Adult Wistar albino rats were subjected to carrageenan and histamine induced rat paw edema tests. In carrageenan induced rat paw edema the effects of ethyl acetate and aqueous extract at 100 and 200 mg/kg showed % inhibition of edema 27% and 22% respectively than the standard drug aspirin (28%). These ethyl acetate and aqueous extract extracts also showed % inhibition of edema 25% and 18% respectively than the standard drug (27%) when rats challenged with histamine induced rat paw edema. Future research should focus on the identification and the anti inflammatory activity of the constituents from this plant.

Effects of hyaluronan on carrageenan-induced synovitis in rat TMJ

Nitric oxide is one of many proinflammatory mediators that are involved in temporomandibular joint (TMJ) inflammatory disorder and is synthesized by inducible nitric oxide synthase (iNOS). iNOS is transcriptionally regulated by nuclear factor-κB (NF-κB) in cases of inflammation, proliferation, and apoptosis. It has also been reported that nitric oxide is positively regulated by carrageenan and negatively regulated by hyaluronan in the knee joint. The aim of this study was to histologically evaluate how inflammation and cell proliferation of the synovial membrane are affected by the exogenous administration of carrageenan and hyaluronan in the rat TMJ by investigating iNOS, NF-κB, and anti proliferating cell nuclear antigen (PCNA) immunoreactivity. As results, immunoreactive cells to iNOS, NF-κB, and PCNA were normally localized only in the synovial membrane of wild type TMJs. The numbers of immunoreactive cells were extensively larger in the carrageenan-injected synovial membranes exhibiting excessive folding, and smaller in the hyaluronan-injected synovial membranes showing a few folds. These results indicate that a carrageenan injection induced inflammation and cell proliferation especially in the synovial membrane and that hyaluronan relieved the inflammation by decreasing inflammatory molecules in the synovial membrane.

Can L(+)-lactate be used as a marker of experimentally induced inflammation in rats?

OBJECTIVE

The purpose of this study was to investigate if L(+)-lactate (lactate) can be used as a marker of progression of joint inflammation in comparison with a reference marker, prostaglandin E2 (PGE(2)), and to analyse implications for drug treatments.

MATERIALS AND METHODS

The assessment of the inflammation time course and the treatment efficacy studies were performed on two occasions. At specific time points, synovial fluid was extracted from Sprague-Dawley rats (n = 87) challenged with either carrageenan (Cg) or Freund's complete adjuvant (FCA) or from six non-inflamed rats. Naproxen (7.5 or 30 micromol/kg) or rofecoxib (30 micromol/kg) was administered per os 2 h post Cg or at 48 h post FCA. Levels of PGE(2) and lactate were assessed either by immuno-assay or by colorimetric assay.

RESULTS

Increased levels of both markers were detected following Cg or FCA injection. Pharmacological treatments resulted in lower concentrations of PGE(2) whereas levels of lactate remained unaffected compared to the vehicle-treated group.

CONCLUSION

Our results suggest that lactate may be useful as an additional biomarker of inflammatory processes, especially for monitoring the non-cox-inhibitor sensitive cascade.

Angiotensin II type 1 receptor as a novel therapeutic target in rheumatoid arthritis: in vivo analyses in rodent models of arthritis and ex vivo analyses in human inflammatory synovitis

OBJECTIVE

Angiotensin II (Ang II) is known to have proinflammatory actions, and Ang II type 1 (AT(1)) receptors are up-regulated in the rheumatoid synovium, suggesting that this receptor could be a therapeutic target. The purpose of this study was to investigate the antiinflammatory potential of the selective AT(1) receptor antagonist losartan, which is currently used for the treatment of cardiovascular disease.

METHODS

Dose-ranging studies of losartan (1-50 mg/kg) were initially conducted in a rat model of acute (carrageenan/kaolin) arthritis, with subsequent evaluation in a rat model of adjuvant-induced arthritis (Freund's complete adjuvant). Losartan (10(-10) to 10(-6)M) was further tested ex vivo in human inflammatory synovitis, using collagenase-digested synovium.

RESULTS

Western blot and immunohistochemical analyses both revealed a substantial increase in AT(1) receptor protein content in synovium from acutely and chronically inflamed rat knee joints. Similarly, synovial Ang I/II protein content was elevated during inflammation. Losartan inhibited acute joint inflammation in a dose-dependent manner, with 15 mg/kg being the optimal dose (and used in subsequent studies). Both prophylactic and therapeutic administration of 15 mg/kg of losartan substantially reduced knee joint swelling in rats with adjuvant monarthritis (> or =50%; P < 0.0001). Losartan also suppressed tumor necrosis factor alpha generation from inflamed human synovium in a dose-dependent manner (P < 0.05).

CONCLUSION

Targeting the angiotensin pathway, particularly AT(1) receptors, could have significant therapeutic potential. Randomized placebo-controlled trials are now warranted to establish the extent to which angiotensin receptor blockers may provide antiinflammatory benefits.

Anti-inflammatory and gastrointestinal effects of a novel diclofenac derivative

S-diclofenac (2-[(2,6-dichlorophenyl)amino]benzeneacetic acid 4-(3H-1,2,dithiol-3-thione-5-yl)phenyl ester; ACS 15) is a novel molecule comprising a hydrogen sulfide (H2S)-releasing dithiol-thione moiety attached by an ester linkage to diclofenac. S-diclofenac administration inhibited lipopolysaccharide-induced inflammation (as evidenced by reduced lung and liver myeloperoxidase activity) and caused significantly less gastric toxicity than diclofenac. S-diclofenac did not affect blood pressure or heart rate of the anesthetized rat. S-diclofenac administration downregulated expression of genes encoding enzymes which synthesize nitric oxide, prostanoids, and H2S; reduced plasma IL-1beta/TNF-alpha; and elevated plasma IL-10. Reduced liver NF-kappaB p65 and AP-1/c-fos DNA-binding activity was also observed. These effects were mimicked in large part by a combination of diclofenac plus an H2S-releasing moiety (ADT-OH). Incubation of S-diclofenac (100 microM) with rat plasma or liver homogenate caused a time-dependent release of H2S, which was inhibited by sodium fluoride (10 mM). Administration of S-diclofenac (47.2 micromol/kg, i.p.) to conscious rats significantly increased plasma H2S concentration (at 45 min and 6 h). We propose that H2S release from S-diclofenac in vivo contributes to the observed effects.

A Sensitive Gait Parameter for Quantification of Arthritis in Rats

Quantification of arthritis is helpful for investigating pain mechanisms of arthritis and for developing new drugs. We assessed and identified a feasible parameter for quantification of rat arthritis using a novel gait analyzing system. Knee-joint injection with small doses of lambda-carrageenan decreased swing time ratio (STR, swing time of the non-treated hindlimb/swing time of the lambda-carrageenan-injected hindlimb) in a dose-dependent manner. Intraperitoneal treatment with indomethacin restored the decreased STR dose-dependently. The arthritis could not be accurately quantified by swing time and swelling, common indices of arthritis. These results show that STR is a sensitive, reliable parameter for quantification of arthritis.

Sex differences in inflammation and inflammatory pain in cyclooxygenase-deficient mice

There are two cyclooxygenase (COX) genes encoding characterized enzymes, COX-1 and COX-2. Nonsteroidal anti-inflammatory drugs are commonly used as analgesics in inflammatory arthritis, and these often inhibit both cyclooxygenases. Recently, inhibitors of COX-2 have been used in the treatment of inflammatory arthritis, as this isoform is thought to be critical in inflammation and pain. The objective of this study was to determine the effect of COX-1 or COX-2 gene disruption on the development of chronic Freund’s adjuvant-induced arthritis and inflammatory pain in male and female mice. The effect of COX-1 or COX-2 gene disruption on inflammatory hyperalgesia, allodynia, inflammatory edema, and arthritic joint destruction was studied. COX-2 knockout mice (COX-2 −/−) showed reduced edema and joint destruction in female, but not male, animals. In addition, neither male nor female COX-2 −/− mice developed thermal hyperalgesia or mechanical allodynia, either ipsilateral or contralateral to the inflammation. COX-1 gene disruption also reduced inflammatory edema and joint destruction in female, but not male mice, although females of both COX −/− lines did show some bony destruction. There was no difference in ipsilateral allodynia between COX-1 knockout and wild-type animals, but female COX-1 −/− mice showed reduced contralateral allodynia compared with male COX-1 −/− or wild-type mice. These data show that the gene products of both COX genes contribute to pain and local inflammation in inflammatory arthritis. There are sex differences in some of these effects, and this suggests that the effects of COX inhibitors may be sex dependent.

Peripheral inflammation modifies the effect of intrathecal IL-1β on spinal PGE2 production mainly through cyclooxygenase-2 activity. A spinal microdialysis study in freely moving rats

Acute inflammation induces upregulation of IL-1beta both at the site of the peripheral inflammation and in the cerebrospinal fluid (CSF). The central increase of IL-1beta mainly contributes to the development of hypersensitivity. However, the spinal mechanisms for the effects of IL-1beta in nociceptive transmission are incompletely understood. It is also unknown whether previous sensitization changes IL-1beta activity. We therefore investigated the dose-effect relationship of intrathecal (i.t.) IL-1beta on spinal PGE(2) production in the absence and presence of peripheral formalin inflammation with spinal microdialysis in freely moving rats. The possible involvement of cyclooxygenase (COX) isoforms in the IL-1beta-mediated spinal PGE(2) production on the background of peripheral formalin inflammation was further evaluated with the selective COX-1 and COX-2 inhibitors. We found that the i.t. administration of IL-1beta, with doses of 1, 2, 8, or 16 ng, increased PGE(2) levels in CSF in a dose-related fashion. This IL-1beta-evoked PGE(2) release occurred within 30min after IL-1beta administration, peaked at 30-60 min interval, and returned gradually to the baseline level within 4h. Peripheral formalin inflammation in the paw induced a more prolonged effect of spinal IL-1beta with larger PGE(2) releases in the CSF compared with the non-inflammatory state, suggesting that peripheral inflammation enhances central sensitization. The COX-2 inhibitor SC58236 (15 mg/kg) reduced the IL-1beta-mediated PGE(2) increase in CSF by 86% while the COX-1 inhibitor SC58560 (15 mg/kg) had less effect (28%). Our study suggests that mainly the COX-2 enzyme mediates the IL-1beta-induced increase in spinal PGE(2) in the presence of peripheral formalin inflammation.

Divergent roles of nitrergic and prostanoid pathways in chronic joint inflammation

BACKGROUND

Nitrergic and prostanoid pathways have both been implicated in inflammatory processes.

OBJECTIVE

To investigate their respective contributions in a rat model of chronic arthritis.

METHODS

Male Wistar rats (n = 4-6/group) received either an intra-articular injection of 2% carrageenan/4% kaolin (C/K) or intra- and periarticular injections of Freund's complete adjuvant (FCA; 10 mg/ml M tuberculosis). Joint diameter, urinary nitric oxide metabolites (NO(x)), and prostaglandin E(2) (PGE(2)) levels were measured as indices of the inflammatory process. A prophylactic and therapeutic (day 5) dose ranging study of an inducible nitric oxide synthase inhibitor, L-N-(1-iminoethyl)-lysine (L-NIL), and a cyclo-oxygenase-2 (COX-2) inhibitor, SC-236, was performed with the drugs given subcutaneously. Submaximal doses were identified and used for combination studies. Appropriate vehicle controls were included.

RESULTS

L-NIL and SC-236 dose dependently inhibited C/K induced acute joint swelling, the magnitude being greatest when they were given in combination. Both prophylactic and therapeutic administration of SC-236 in the FCA induced model of chronic arthritis produced a dose dependent reduction in all the measures assessed. However, although L-NIL demonstrated similar dose dependent inhibition of urinary NO(x) and PGE(2) levels, joint swelling was significantly exacerbated in this model. Co-administration of the inhibitors nullified the benefits of SC-236.

CONCLUSION

Whereas COX-2 derived prostaglandins are proinflammatory in both acute and chronic joint inflammation, NO seems to have divergent roles, being anti-inflammatory in chronic and proinflammatory in acute joint inflammation.

Pathophysiology of vascular dysfunction in a rat model of chronic joint inflammation

The impact of chronic joint inflammation on articular vascular function in rats was investigated to address whether joint swelling and the associated vascular dysfunction are dependent upon a common prostanoid mechanism. Urinary nitrate/nitrite (NO(x)) and PGE(2) excretion, knee joint diameter and body weight were measured following induction of adjuvant-induced arthritis (AIA). Ten days postinduction of AIA, joint vascular reactivity was assessed by measuring the perfusion response using a laser Doppler imager (LDI) to topical application of acetylcholine (ACh) and sodium nitroprusside (SNP). Four groups were compared: a non-inflamed control group and three AIA groups treated i.p. with vehicle, indomethacin or SC-236 (at equimolar doses). The selective cyclooxygenase-2 (COX-2) inhibitor (SC-236) was used to differentiate between COX-1 and -2-derived prostaglandins. Urinary NO(x) and PGE(2) levels increased substantially during the early phase of AIA but decreased thereafter. Toxicity to indomethacin but not SC-236 was observed, as indicated by a marked decrease in body weight. Joint swelling was similarly attenuated by indomethacin and SC-236 (P= 0.0001 cf. vehicle-treated AIA; n= 5-6 per group), indicating that this is due to COX-2 and not COX-1 inhibition. The AIA-induced changes in urinary NO(x) and PGE(2) were corrected by both COX inhibitors. While vascular reactivity to ACh and SNP was significantly attenuated by AIA (P < 0.002; n= 5-10 per group), the perfusion responses to these vasodilating agents were similar in all three AIA groups, demonstrating that the vascular dysfunction was not corrected by inhibition of either COX-1 or COX-2 enzymes. Furthermore, the attenuation of both ACh and SNP-induced responses in AIA suggest that vascular dysfunction was not exclusively endothelial in nature. In conclusion, the joint swelling and vascular dysfunction associated with AIA appear to be mediated, at least in part, by independent mechanisms. While COX-1/COX-2 inhibition reduced joint swelling, vascular dysfunction in AIA is independent of constitutive or inducible prostanoid mechanisms, and appears not to be solely endothelial-derived, but to involve other components such as the vascular smooth muscle.

Nonsteroidal antiinflammatory drugs and a selective cyclooxygenase 2 inhibitor uncouple mitochondria in intact cells

OBJECTIVE

Uncoupling of isolated mitochondria by nonsteroidal antiinflammatory drugs (NSAIDs) has been considered relevant to the development of gastrointestinal (GI) side effects. We investigated the occurrence of NSAID-induced uncoupling of mitochondria in intact cells (rat thymocytes) compared with the effects of a selective cyclooxygenase 2 (COX-2) inhibitor.

METHODS

Oxygen consumption and mitochondrial membrane potential were simultaneously measured amperometrically and by distribution of radioactive tracer molecules, respectively, in the presence and absence of pharmacologically relevant concentrations of the NSAIDs indomethacin and diclofenac and the selective COX-2 inhibitor SC-236. Analysis of data by a technique related to top-down elasticity analysis permitted assessment of the influence of these compounds on individual components of cellular energy metabolism.

RESULTS

Indomethacin, diclofenac, and SC-236 increased proton leak in isolated mitochondria. Both diclofenac and SC-236 significantly stimulated proton leak in intact cells and simultaneously inhibited substrate oxidation and ATP turnover. Oxygen consumption rates of isolated cells remained unchanged over a wide concentration range of the drugs, despite significant effects on subsystems of cellular energy metabolism.

CONCLUSION

NSAIDs and selective COX-2 inhibitors have significant and equally directed effects on cellular energy metabolism. They both uncouple mitochondrial respiration and inhibit substrate oxidation and ATP turnover. However, the topical effect and selective COX-2 inhibition may not be sufficient to cause NSAID-like damage to the GI tract.