Hypernociception elicited by tibio-tarsal joint flexion in mice: a novel experimental arthritis model for pharmacological screening

IL-17 mediates articular hypernociception in antigen-induced arthritis in mice

IL-17 is an important cytokine in the physiopathology of rheumatoid arthritis (RA). However, its participation in the genesis of nociception during RA remains undetermined. In this study, we evaluated the role of IL-17 in the genesis of articular nociception in a model of antigen (mBSA)-induced arthritis. We found that mBSA challenge in the femur-tibial joint of immunized mice induced a dose- and time-dependent mechanical hypernociception. The local IL-17 concentration within the mBSA-injected joints increased significantly over time. Moreover, co-treatment of mBSA challenged mice with an antibody against IL-17 inhibited hypernociception and neutrophil recruitment. In agreement, intraarticular injection of IL-17 induced hypernociception and neutrophil migration, which were reduced by the pre-treatment with fucoidin, a leukocyte adhesion inhibitor. The hypernociceptive effect of IL-17 was also reduced in TNFR1(-/-) mice and by pre-treatment with infliximab (anti-TNF antibody), a CXCR1/2 antagonist or by an IL-1 receptor antagonist. Consistent with these findings, we found that IL-17 injection into joints increased the production of TNF-alpha, IL-1beta and CXCL1/KC. Treatment with doxycycline (non-specific MMPs inhibitor), bosentan (ET(A)/ET(B) antagonist), indomethacin (COX inhibitor) or guanethidine (sympathetic blocker) inhibited IL-17-induced hypernociception. IL-17 injection also increased PGE(2) production, MMP-9 activity and COX-2, MMP-9 and PPET-1 mRNA expression in synovial membrane. These results suggest that IL-17 is a novel pro-nociceptive cytokine in mBSA-induced arthritis, whose effect depends on both neutrophil migration and various pro-inflammatory mediators, as TNF-alpha, IL-1beta, CXCR1/2 chemokines ligands, MMPs, endothelins, prostaglandins and sympathetic amines. Therefore, it is reasonable to propose IL-17 targeting therapies to control this important RA symptom.

Targeting endothelin ETA and ETB receptors inhibits antigen-induced neutrophil migration and mechanical hypernociception in mice

Endothelin may contribute to the development of inflammatory events such as leukocyte recruitment and nociception. Herein, we investigated whether endothelin-mediated mechanical hypernociception (decreased nociceptive threshold, evaluated by electronic pressure-meter) and neutrophil migration (myeloperoxidase activity) are inter-dependent in antigen challenge-induced Th1-driven hind-paw inflammation. In antigen challenge-induced inflammation, endothelin (ET) ET(A) and ET(B) receptor antagonism inhibited both hypernociception and neutrophil migration. Interestingly, ET-1 peptide-induced hypernociception was not altered by inhibiting neutrophil migration or endothelin ET(B) receptor antagonism, but rather by endothelin ET(A) receptor antagonism. Furthermore, endothelin ET(A), but not ET(B), receptor antagonism inhibited antigen-induced PGE(2) production, whereas either selective or combined blockade of endothelin ET(A) and/or ET(B) receptors reduced hypernociception and neutrophil recruitment caused by antigen challenge. Concluding, this study advances knowledge into the role for endothelin in inflammatory mechanisms and further supports the potential of endothelin receptor antagonists in controlling inflammation.

The chemokine receptors CXCR1/CXCR2 modulate antigen-induced arthritis by regulating adhesion of neutrophils to the synovial microvasculature

OBJECTIVE

The chemokine receptors CXCR1 and CXCR2 play a role in mediating neutrophil recruitment and neutrophil-dependent injury in several models of inflammation. We undertook this study to investigate the role of these receptors in mediating neutrophil adhesion, subsequent migration, and neutrophil-dependent hypernociception in a murine model of monarticular antigen-induced arthritis (AIA).

METHODS

AIA was induced by administration of antigen into the knee joint of previously immunized mice. Intravital microscopy studies were performed to assess leukocyte rolling and adhesion. Mechanical hypernociception was investigated using an electronic pressure meter. Neutrophil accumulation in the tissue was measured by counting neutrophils in the synovial cavity and assaying myeloperoxidase activity. Levels of tumor necrosis factor alpha (TNFalpha) and the chemokines CXCL1 and CXCL2 were quantified by enzyme-linked immunosorbent assay. Histologic analysis was performed to evaluate the severity of arthritis and leukocyte infiltration.

RESULTS

Antigen challenge in immunized mice induced production of TNFalpha, CXCL1, and CXCL2 and also resulted in neutrophil recruitment, leukocyte rolling and adhesion, and hypernociception. Treatment with reparixin or DF2162 (allosteric inhibitors of CXCR1/CXCR2) decreased neutrophil recruitment, an effect that was associated with marked inhibition of neutrophil adhesion. Drug treatment also inhibited TNFalpha production, hypernociception, and the overall severity of the disease in the tissue.

CONCLUSION

Blockade of CXCR1/CXCR2 receptors inhibits neutrophil recruitment by inhibiting the adhesion of neutrophils to synovial microvessels. As a consequence, there is decreased local cytokine production and reduced hypernociception, as well as ameloriation of overall disease in the tissue. These studies suggest a potential therapeutic role for the modulation of CXCR1/CXCR2 receptor signaling in the treatment of arthritis.

Role of IL-18 in overt pain-like behaviour in mice

There are evidences that targeting IL-18 might be beneficial to inhibit inflammatory symptoms, including hypernociception (decrease in nociceptive threshold). The mechanism of IL-18 mechanical hypernociception depends on endothelin in rats and mice. However, the role of IL-18 in overt pain-like behaviour remains undetermined. Therefore, we addressed the role of IL-18 in writhing response induced by intraperitoneal (i.p.) injection of phenyl-p-benzoquinone (PBQ) and acetic acid in mice. Firstly, it was detected that PBQ and acetic acid i.p. injection induced a dose-dependent number of writhes in Balb/c mice. Subsequently, it was observed that the PBQ - but not the acetic acid-induced writhes were diminished in IL-18 deficient ((-/-)) mice. Therefore, considering that IFN-gamma, endothelin and prostanoids mediate IL-18-induced mechanical hypernociception, we also investigated the role of these mediators in the same model of writhing response in which IL-18 participates. It was noticed that PBQ-induced writhes were diminished in IFN-gamma(-/-) mice and by the treatment with bosentan (mixed endothelin ETA/ETB receptor antagonist), BQ 123 (cyclo[DTrp-DAsp-Pro-DVal-Leu], selective endothelin ETA receptor antagonist), BQ 788 (N-cys-2,6 dimethylpiperidinocarbonyl-l-methylleucyl-d-1-methoxycarboyl-d-norleucine, selective endothelin ETB receptor antagonist) or indomethacin (cycloxigenase inhibitor). Thus, IL-18, IFN-gamma, endothelin acting on endothelin ETA and ETB receptors, and prostanoids mediate PBQ-induced writhing response in mice. To conclude, these results further advance the understanding of the physiopathology of overt pain-like behaviour, and suggest for the first time a role for IL-18 in writhing response in mice.

Treatment with DF 2162, a non-competitive allosteric inhibitor of CXCR1/2, diminishes neutrophil influx and inflammatory hypernociception in mice

BACKGROUND AND PURPOSE

Neutrophil migration into tissues is involved in the genesis of inflammatory pain. Here, we addressed the hypothesis that the effect of CXC chemokines on CXCR1/2 is important to induce neutrophil migration and inflammatory hypernociception.

EXPERIMENTAL APPROACH

Mice were treated with a non-competitive allosteric inhibitor of CXCR1/2, DF 2162, and neutrophil influx and inflammatory hypernociception were assessed by myeloperoxidase assay and electronic pressure meter test, respectively, in various models of inflammation.

KEY RESULTS

DF 2162 inhibited neutrophil chemotaxis induced by CXCR1/2 ligands but had no effect on CXCL8 binding to neutrophils. A single mutation of the allosteric site at CXCR1 abrogated the inhibitory effect of DF 2162 on CXCL-8-induced chemotaxis. Treatment with DF 2162 prevented influx of neutrophils and inflammatory hypernociception induced by CXCL1 in a dose-dependent manner. The compound inhibited neutrophil influx and inflammatory hypernociception induced by carrageenan, lipopolysaccharide and zymosan, but not hypernociception induced by dopamine and PGE(2). DF 2162 had a synergistic effect with indomethacin or the absence of TNFR1 to abrogate carrageenan-induced hypernociception. Treatment with DF 2162 diminished neutrophil influx, oedema formation, disease score and hypernociception in collagen-induced arthritis.

CONCLUSIONS AND IMPLICATIONS

CXCR1/2 mediates neutrophil migration and is involved in the cascade of events leading to inflammatory hypernociception. In addition to modifying fundamental pathological processes, non-competitive allosteric inhibitors of CXCR1/2 may have the additional benefit of providing partial relief for pain and, hence, may be a valid therapeutic target for further studies aimed at the development of new drugs for the treatment of rheumatoid arthritis.

IL-33 mediates antigen-induced cutaneous and articular hypernociception in mice

IL-33, a new member of the IL-1 family, signals through its receptor ST2 and induces T helper 2 (Th2) cytokine synthesis and mediates inflammatory response. We have investigated the role of IL-33 in antigen-induced hypernociception. Recombinant IL-33 induced cutaneous and articular mechanical hypernociception in a time- and dose-dependent manner. The hypernociception was inhibited by soluble (s) ST2 (a decoy receptor of IL-33), IL-1 receptor antagonist (IL-1ra), bosentan [a dual endothelin (ET)(A)/ET(B) receptor antagonist], clazosentan (an ET(A) receptor antagonist), or indomethacin (a cyclooxygenase inhibitor). IL-33 induced hypernociception in IL-18(-/-) mice but not in TNFR1(-/-) or IFNgamma(-/-) mice. The IL-33-induced hypernociception was not affected by blocking IL-15 or sympathetic amines (guanethidine). Furthermore, methylated BSA (mBSA)-induced cutaneous and articular mechanical hypernociception depended on TNFR1 and IFNgamma and was blocked by sST2, IL-1ra, bosentan, clazosentan, and indomethacin. mBSA also induced significant IL-33 and ST2 mRNA expression. Importantly, we showed that mBSA induced hypernociception via the IL-33 --> TNFalpha --> IL-1beta --> IFNgamma --> ET-1 --> PGE(2) signaling cascade. These results therefore demonstrate that IL-33 is a key mediator of immune inflammatory hypernociception normally associated with a Th1 type of response, revealing a hitherto unrecognized function of IL-33 in a key immune pharmacological pathway that may be amenable to therapeutic intervention.

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

BACKGROUND AND PURPOSE

C5a, a complement activation product, exhibits a broad spectrum of inflammatory activities particularly neutrophil chemoattraction. Herein, the role of C5a in the genesis of inflammatory hypernociception was investigated in rats and mice using the specific C5a receptor antagonist PMX53 (AcF-[OP(D-Cha)WR]).

EXPERIMENTAL APPROACH

Mechanical hypernociception was evaluated with a modification of the Randall-Selitto test in rats and electronic pressure meter paw test in mice. Cytokines were measured by ELISA and neutrophil migration was determined by myeloperoxidase activity.

KEY RESULTS

Local pretreatment of rats with PMX53 (60-180 microg per paw) inhibited zymosan-, carrageenan-, lipopolysaccharide (LPS)- and antigen-induced hypernociception. These effects were associated with C5a receptor blockade since PMX53 also inhibited the hypernociception induced by zymosan-activated serum and C5a but not by the direct-acting hypernociceptive mediators, prostaglandin E(2) and dopamine. Underlying the C5a hypernociceptive mechanisms, PMX53 did not alter the cytokine release induced by inflammatory stimuli. However, PMX53 inhibited cytokine-induced hypernociception. PMX53 also inhibited the recruitment of neutrophils induced by zymosan but not by carrageenan or LPS, indicating an involvement of neutrophils in the hypernociceptive effect of C5a. Furthermore, the C5a-induced hypernociception was reduced in neutrophil-depleted rats. Extending these findings in rats, blocking C5a receptors also reduced zymosan-induced joint hypernociception in mice.

CONCLUSIONS AND IMPLICATIONS

These results suggest that C5a is an important inflammatory hypernociceptive mediator, acting by a mechanism independent of hypernociceptive cytokine release, but dependent on the presence of neutrophils. Therefore, we suggest that inhibiting the action of C5a has therapeutic potential in the control of inflammatory pain.

Endogenous opiates and behavior: 2006

This paper is the 29th consecutive installment of the annual review of research concerning the endogenous opioid system, now spanning 30 years of research. It summarizes papers published during 2006 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurological disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration and thermoregulation (Section 16); and immunological responses (Section 17).

Involvement of LTB4 in zymosan-induced joint nociception in mice: participation of neutrophils and PGE2

Leukotriene B4 (LTB4) mediates different inflammatory events such as neutrophil migration and pain. The present study addressed the mechanisms of LTB4-mediated joint inflammation-induced hypernociception. It was observed that zymosan-induced articular hypernociception and neutrophil migration were reduced dose-dependently by the pretreatment with MK886 (1-9 mg/kg; LT synthesis inhibitor) as well as in 5-lypoxygenase-deficient mice (5LO(-/-)) or by the selective antagonist of the LTB(4) receptor (CP105696; 3 mg/kg). Histological analysis showed reduced zymosan-induced articular inflammatory damage in 5LO(-/-) mice. The hypernociceptive role of LTB4 was confirmed further by the demonstration that joint injection of LTB4 induces a dose (8.3, 25, and 75 ng)-dependent articular hypernociception. Furthermore, zymosan induced an increase in joint LTB4 production. Investigating the mechanism underlying LTB4 mediation of zymosan-induced hypernociception, LTB4-induced hypernociception was reduced by indomethacin (5 mg/kg), MK886 (3 mg/kg), celecoxib (10 mg/kg), antineutrophil antibody (100 mug, two doses), and fucoidan (20 mg/kg) treatments as well as in 5LO(-/-) mice. The production of LTB4 induced by zymosan in the joint was reduced by the pretreatment with fucoidan or antineutrophil antibody as well as the production of PGE2 induced by LTB4. Therefore, besides reinforcing the role of endogenous LTB4 as an important mediator of inflamed joint hypernociception, these results also suggested that the mechanism of LTB4-induced articular hypernociception depends on prostanoid and neutrophil recruitment. Furthermore, the results also demonstrated clearly that LTB4-induced hypernociception depends on the additional release of endogenous LTs. Concluding, targeting LTB4 synthesis/action might constitute useful therapeutic approaches to inhibit articular inflammatory hypernociception.

Lonchocarpus sericeus lectin decreases leukocyte migration and mechanical hypernociception by inhibiting cytokine and chemokines production

In this study, we tested the potential use of a lectin from Lonchocarpus sericeus seeds (LSL), to control neutrophil migration and inflammatory hypernociception (decrease of nociceptive threshold). Pretreatment of the animals intravenously (15 min before) with LSL inhibited neutrophil migration to the peritoneal cavity in a dose-dependent fashion confirmed by an inhibition of rolling and adhesion of leukocytes by intravital microscopy. We also tested the ability of the pretreatment with LSL to inhibit neutrophil migration on immunised mice, and it was observed that a strong inhibition of neutrophil migration induced by ovoalbumin in immunized mice. Another set of experiments showed that pretreatment of the animals with LSL, inhibited the mechanical hypernociception in mice induced by the i.pl. injection of OVA in immunized mice and of carrageenan in naïve mice, but not that induced by prostaglandin E(2) (PGE(2)) or formalin. This anti-nociceptive effect correlated with an effective blockade of neutrophil influx, as assessed by the hind paw tissue myeloperoxidase levels. In addition, we measured cytokines (TNF-alpha and IL-1beta) and chemokines (MIP-1alpha [CCL3] and KC [CXCL1]) from the peritoneal exudates and i.pl. tissue. Animals treated with LSL showed inhibition of cytokines and chemokines release in a dose-dependent manner. In conclusion, we demonstrated that the inhibitory effects of LSL on neutrophil migration and mechanical inflammatory hypernocicepetion are associated with the inhibition of the production of cytokines and chemokines.