IL-15 mediates antigen-induced neutrophil migration by triggering IL-18 production

Quercetin reduces inflammatory pain: inhibition of oxidative stress and cytokine production

Quercetin (1) is known to have both antioxidant and antinociceptive effects. However, the mechanism involved in its antinociceptive effect is not fully elucidated. Cytokines and reactive oxygen species have been implicated in the cascade of events resulting in inflammatory pain. Therefore, we evaluated the antinociceptive mechanism of 1 focusing on the role of cytokines and oxidative stress. Intraperitoneal and oral treatments with 1 dose-dependently inhibited inflammatory nociception induced by acetic acid and phenyl-p-benzoquinone and also the second phase of formalin- and carrageenin-induced mechanical hypernociception. Compound 1 also inhibited the hypernociception induced by cytokines (e.g., TNFalpha and CXCL1), but not by inflammatory mediators that directly sensitize the nociceptor such as PGE2 and dopamine. On the other hand, 1 reduced carrageenin-induced IL-1beta production as well as carrageenin-induced decrease of reduced glutathione (GSH) levels. These results suggest that 1 exerts its analgesic effect by inhibiting pro-nociceptive cytokine production and the oxidative imbalance mediation of inflammatory pain.

Expression and activity of COX-1 and 2 and 5-LOX in joint tissues from dogs with naturally occurring coxofemoral joint osteoarthritis

Understanding the neurobiology of pain in naturally occurring models of osteoarthritis (OA) may improve the understanding of human OA pain. Both COX and LOX have been associated with joint pain. This study evaluated COX-1, COX-2, and 5-LOX expression and activity in a naturally occurring canine model of secondary OA. Hip joint capsule with synovial tissue (HJC) and femoral head subchondral bone (FH) was collected from normal dogs and dogs undergoing total hip replacement for coxofemoral joint OA. Tissues were analyzed for COX-1, COX-2, and LOX protein, and PGE(2) and LTB(4). Significantly more COX-2 protein was present in OA HJC than normal joints (p = 0.0009). There was no significant difference in COX-1 or LOX protein, although LOX protein was increased (p = 0.069). PGE(2) concentration in normal and OA HJC was similar (p = 1.0). LTB(4) concentration in OA HJC was significantly greater than normal HJC (p = 0.028). Significantly more COX-1 (p = 0.0098), COX-2 (p = 0.0028), and LOX (p = 0.0095) protein was present in OA FH tissue compared to normal FH tissue. There were no differences in PGE(2) or LTB(4) concentration in normal and OA FH tissue (p = 0.77 and p = 0.11). Together, these data suggest both COX-2 and 5-LOX are appropriate targets for the management of pain associated with naturally occurring OA.

Fructose-1,6-bisphosphate reduces inflammatory pain-like behaviour in mice: role of adenosine acting on A1 receptors

BACKGROUND AND PURPOSE

D-Fructose-1,6-bisphosphate (FBP) is an intermediate in the glycolytic pathway, exerting pharmacological actions on inflammation by inhibiting cytokine production or interfering with adenosine production. Here, the possible antinociceptive effect of FBP and its mechanism of action in the carrageenin paw inflammation model in mice were addressed, focusing on the two mechanisms described above.

EXPERIMENTAL APPROACH

Mechanical hyperalgesia (decrease in the nociceptive threshold) was evaluated by the electronic pressure-metre test; cytokine levels were measured by elisa and adenosine was determined by high performance liquid chromatography.

KEY RESULTS

Pretreatment of mice with FBP reduced hyperalgesia induced by intraplantar injection of carrageenin (up to 54%), tumour necrosis factor alpha (40%), interleukin-1 beta (46%), CXCL1 (33%), prostaglandin E(2) (41%) or dopamine (55%). However, FBP treatment did not alter carrageenin-induced cytokine (tumour necrosis factor alpha and interleukin-1 beta) or chemokine (CXCL1) production. On the other hand, the antinociceptive effect of FBP was prevented by systemic and intraplantar treatment with an adenosine A(1) receptor antagonist (8-cyclopentyl-1,3-dipropylxanthine), suggesting that the FBP effect is mediated by peripheral adenosine acting on A(1) receptors. Giving FBP to mice increased adenosine levels in plasma, and adenosine treatment of paw inflammation presented a similar antinociceptive mechanism to that of FBP.

CONCLUSIONS AND IMPLICATIONS

In addition to anti-inflammatory action, FBP also presents an antinociceptive effect upon inflammatory hyperalgesia. Its mechanism of action seems dependent on adenosine production but not on modulation of hyperalgesic cytokine/chemokine production. In turn, adenosine acts peripherally on its A(1) receptor inhibiting hyperalgesia. FBP may have possible therapeutic applications in reducing inflammatory pain.

Aging and neutrophils: there is still much to do

Human neutrophils are activated by a wide array of compounds through their receptors. This elicits their classical functions, such as chemotaxis, phagocytosis, and the production of reactive oxygen species (ROS). Upon stimulation, neutrophils also produce lipid and immune mediators and can present antigen through the major histocompatibility complex I (MHC-I). The age-related impairment of the classical functions of neutrophils is well described, but experimental evidence showing alterations in the production of mediators and antigen presentation with aging are lacking. This review highlights the role of neutrophils in age-related pathologies such as Alzheimer's disease, atherosclerosis, cancer, and autoimmune diseases. Furthermore, we discuss how aging potentially affects the production and release of mediators by human neutrophils in ways that may contribute to the development of these pathologies.

A novel role for neutrophils as critical activators of NK cells

Neutrophils are essential players in innate immune responses to bacterial infection. Despite the striking resistance of Legionella pneumophila (Lpn) to bactericidal neutrophil function, neutrophil granulocytes are important effectors in the resolution of legionellosis. Indeed, mice depleted of neutrophils were unable to clear Lpn due to a lack of the critical cytokine IFN-gamma, which is produced by NK cells. We demonstrate that this can be ascribed to a previously unappreciated role of neutrophils as major NK cell activators. In response to Lpn infection, neutrophils activate caspase-1 and produce mature IL-18, which is indispensable for the activation of NK cells. Furthermore, we show that the IL-12p70 response in Lpn-infected neutropenic mice is also severely reduced and that the Lpn-induced IFN-gamma production by NK cells is strictly dependent on IL-12. However, since dendritic cells, and not neutrophils, are the source of Lpn-induced IL-12, its paucity is a consequence of the absence of IFN-gamma produced by NK cells rather than the absence of neutrophils per se. Therefore, neutrophil-derived IL-18, in combination with dendritic cell-produced IL-12, triggers IFN-gamma synthesis in NK cells in Lpn-infected mice. We propose a novel central role for neutrophils as essential IL-18 producers and hence NK cell "helpers" in bacterial infection.

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.

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.

Phlebotomine salivas inhibit immune inflammation-induced neutrophil migration via an autocrine DC-derived PGE2/IL-10 sequential pathway

In the present study, we investigated whether saliva from Phlebotomus papatasi and Phlebotomus duboscqi inhibited antigen-induced neutrophil migration and the mechanisms involved in these effects. The pretreatment of immunized mice with salivary gland extracts (SGE) of both phlebotomines inhibited OVA challenge-induced neutrophil migration and release of the neutrophil chemotactic mediators, MIP-1alpha, TNF-alpha, and leukotriene B4 (LTB4). Furthermore, SGE treatment enhanced the production of anti-inflammatory mediators, IL-10 and PGE2. SGE treatments failed to inhibit neutrophil migration and MIP-1alpha and LTB4 production in IL-10-/- mice, also failing in mice treated with nonselective (indomethacin) or selective (rofecoxibe) cyclooxygenase (COX) inhibitors. COX inhibition resulted in diminished SGE-induced IL-10 production, and PGE2 release triggered by SGE remained increased in IL-10-/- mice, suggesting that prostanoids are acting through an IL-10-dependent mechanism. SGE treatments in vivo reduced the OVA-induced lymphoproliferation of spleen-derived cells. Further, the in vitro incubation of bone marrow-derived dendritic cells (DC) with SGE inhibited the proliferation of CD4+T cells from OVA-immunized mice, which was reversed by indomethacin and anti-IL-10 antibody treatments. Supporting these results, SGE induced the production of PGE2 and IL-10 by DC, which were blocked by COX inhibition. These effects were associated with the reduction of DC-membrane expression of MHC-II and CD86 by SGE treatment. Altogether, the results showed that Phlebotomine saliva inhibits immune inflammation-induced neutrophil migration by an autocrine DC sequential production of PGE2/IL-10, suggesting that the saliva constituents might be promising therapeutic molecules to target immune inflammatory diseases.

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.