IL-15 mediates immune inflammatory hypernociception by triggering a sequential release of IFN-gamma, endothelin, and prostaglandin

Interleukin-15 inhibits smooth muscle cell proliferation and hyaluronan production in rat ductus arteriosus

Neointimal cushion formation (NCF) is an important vascular remodeling for anatomical closure of the ductus arteriosus (DA). Inflammatory responses to vascular injury or atherosclerosis are known to be associated with the pathogenesis of NCF. We found that the expression of interleukin (IL)-15 mRNA was significantly higher in rat DA than in the aorta. IL-15 immunoreactivity was detected predominantly in the internal elastic laminae (IEL) and to a lesser extent in smooth muscle cells (SMCs) in rat DA. Prostaglandin E (PGE) increased the expression of IL-15 mRNA in cultured DA SMCs. IL-15 significantly attenuated the platelet-derived growth factor (PDGF)-BB-mediated SMC proliferation, but did not change SMC migration. IL-15 significantly attenuated PGE1-induced hyaluronic acid (HA) production in a dose-dependent manner, which is a potent stimulator of NCF. Accordingly, IL-15 might have an inhibitory effect on the physiologic vascular remodeling processes in closing the DA.

Antigen-induced inflammatory mechanical hypernociception in mice is mediated by IL-18

There is pre-clinical evidence that therapies targeting IL-18 might be beneficial in controlling arthropathies, which are accompanied by hypernociception (nociceptor sensitization). In the present study, we addressed the hypernociceptive role of IL-18 in a model of antigen-induced inflammation in mice and its mechanisms. In naïve mice, the intraplantar injection of IL-18 induced dose- and time-dependent mechanical hypernociception, which was inhibited in IFN-gamma deficient (-/-) mice, and by the pre-treatment with bosentan (dual endothelin [ET] receptor antagonist), BQ123 (ET(A) receptor antagonist) or indomethacin (cyclooxygenase inhibitor). IL-18 hypernociception was unaffected in TNFR1(-/-) mice or by the pre-treatment with sIL-15Ralpha (soluble form of IL-15 receptor), BQ788 (ET(B) receptor antagonist) or guanethidine (sympathetic blocker). The ovalbumin (OVA) challenge-induced mechanical hypernociception in immunized mice was inhibited by the pre-treatment with anti-IL-18 antibody or in IL-18(-/-) mice. Furthermore, IL-18 induced significant IFN-gamma production in the paw skin of naïve mice. The OVA challenge-induced IFN-gamma and ET-1 productions were inhibited in IL-18(-/-) immunized mice, as well as ET-1 production in IFN-gamma(-/-) immunized mice. In addition, significant PGE2 production was detected after IL-18 or ET-1 (via ET(A) receptors) injection in naïve mice. Taken together with previous data, these results suggest that IL-18 plays a significant role in antigen-induced inflammatory hypernociception via the production of IFN-gamma, ET-1 and PGE2. Thus, IL-18 and IL-18-downstream mediators demonstrated herein might constitute targets to inhibit antigen-induced inflammatory pain.

Anti-inflammatory and analgesic effects of the sesquiterpene lactone budlein A in mice: inhibition of cytokine production-dependent mechanism

The anti-inflammatory activities of some medicinal plants are attributed to their contents of sesquiterpene lactones. In the present study, the anti-inflammatory and anti-nociceptive activity of a sesquiterpene lactone isolated from Viguiera robusta, budlein A in mice was investigated. The treatment with budlein A dose--(1.0-10.0 mg/kg, p.o., respectively) dependently inhibited the carrageenan-induced: i. neutrophil migration to the peritoneal cavity (2-52%), ii. neutrophil migration to the paw skin tissue (32-74%), iii. paw oedema (13-74%) and iv. mechanical hypernociception (2-58%) as well as the acetic acid-induced writhings (0-66%). Additionally, budlein A (10.0 mg/kg) treatment inhibited the mechanical hypernociception-induced by tumour necrosis factor (TNF-alpha, 36%), Keratinocyte-derived chemokine (KC, 37%) and Interleukin-1beta (IL-1beta, 28%), but not of prostaglandin E(2) or dopamine. Budlein A also inhibited the carrageenan-induced release of TNF-alpha (52%), KC (70%) and IL-1beta (59%). Furthermore, an 8 days treatment with budlein A inhibited Complete Freund's adjuvant (10 microl/paw)-induced hypernociception, paw oedema and paw skin myeloperoxidase activity increase while not affecting the motor performance or myeloperoxidase activity in the stomach. Concluding, the present data suggest that budlein A presents anti-inflammatory and antinociceptive property in mice by a mechanism dependent on inhibition of cytokines production. It supports the potential beneficial effect of orally administered budlein A in inflammatory diseases involving cytokine-mediated nociception, oedema and neutrophil migration.

Toll-like receptor 2 and 4 combination engagement upregulate IL-15 synergistically in human rheumatoid synovial fibroblasts

Toll-like receptors (TLRs) are pattern-recognition receptors that connect innate and adaptive immunity. Interleukin-15 (IL-15) is a proinflammatory, innate response cytokine that mediates pleiotropic effector functions in inflammatory synovitis of rheumatoid arthritis (RA). The aim of this study was to clarify whether stimulation of TLR2 and TLR4 by their specific ligands induces the production of IL-15 in fibroblast-like synoviocytes (FLS) from RA patients. FLS were isolated from RA synovial tissues and stimulated with the TLR2 ligand bacterial peptidoglycan (PGN) and the TLR4 ligand lipopolysaccharide (LPS). IL-15 in the culture supernatants was measured by ELISA, and mRNA levels were assessed by RT-PCR and real time PCR. The expression of TLR2, TLR4, and IL-15 in the RA synovium was quantified by immunohistochemistry and compared with values obtained in osteoarthritis synovium. IL-15 production increased in culture supernatants of RA FLS stimulated with PGN or PGN plus LPS, and this was upregulated at the transcriptional level. In contrast, LPS did not increase the level of IL-15 although it augmented the stimulatory effect of PGN on IL-15 production. Inhibition of nuclear factor (NF)-kappaB with a specific inhibitor abrogated the stimulatory effect of PGN or PGN plus LPS on IL-15. Neutralization of TLR2 with a blocking monoclonal antibody significantly reduced IL-15 production (P<0.05), reflecting the functional relevance of TLR2 activation in the induction of IL-15 production. These data suggest that TLR2 activation in RA FLS by microbial constituents is involved in the induction of IL-15 and that TLR2 promotes inflammation through NF-kappaB. TLR4 augmented the stimulatory effect of TLR2 on IL-15, possibly contributing to the maintenance of synovitis in patients with RA.