Assessment of TNFα contribution to the functional up-regulation of kinin B1 receptors in the mouse paw after treatment with LPS

Role of Endothelial Kinin B1 Receptor on the Membrane Potential of Transgenic Rat Aorta

The kinin receptors are classically involved in inflammation, pain and sepsis. The effects of the kinin B1 receptor agonist des-Arg9-bradykinin (DBK) and lipopolysaccharide (LPS) were investigated by comparing the membrane potential responses of aortic rings from transgenic rats overexpressing the kinin B1 receptor (B1R) in the endothelium (TGR(Tie2B1)) and Sprague Dawley (SD) rats. No difference in the resting membrane potential in the aorta’s smooth muscle from the transgenic and SD rats was observed. The aorta rings from SD rats hyperpolarized only to LPS but not to DBK, whereas the aorta rings from TGR(Tie2B1) responded by the administration of both drugs. DBK and LPS responses were inhibited by the B1 receptor antagonist R715 and by iberiotoxin in both cases. Thapsigargin induced a hyperpolarization in the smooth muscle of SD rats that was not reversed by R715, but was reversed by iberiotoxin and this hyperpolarization was further augmented by DBK administration. These results show that the model of overexpression of vascular B1 receptors in the TGR(Tie2B1) rats represent a good model to study the role of functional B1 receptors in the absence of any pathological stimulus. The data also show that KCa channels are the final mediators of the hyperpolarizing responses to DBK and LPS. In addition, we suggest an interaction between the B1R and TLR4, since the hyperpolarization induced by LPS could be abolished in the presence of R715.

Sesquiterpenes from Essential Oils and Anti-Inflammatory Activity

This review is aimed at presenting relevant information on the therapeutic potential of essential oil sesquiterpenes with anti-inflammatory activity. The data reviewed provide a basis for seeking new anti-inflammatory drugs from natural products that do not exhibit the undesirable side effects often displayed by anti-inflammatory drugs. In this review the experimental models, possible mechanisms of action, and chemical structures of 12 sesquiterpenes are presented.

Sensory and signaling mechanisms of bradykinin, eicosanoids, platelet-activating factor, and nitric oxide in peripheral nociceptors

Peripheral mediators can contribute to the development and maintenance of inflammatory and neuropathic pain and its concomitants (hyperalgesia and allodynia) via two mechanisms. Activation or excitation by these substances of nociceptive nerve endings or fibers implicates generation of action potentials which then travel to the central nervous system and may induce pain sensation. Sensitization of nociceptors refers to their increased responsiveness to either thermal, mechanical, or chemical stimuli that may be translated to corresponding hyperalgesias. This review aims to give an account of the excitatory and sensitizing actions of inflammatory mediators including bradykinin, prostaglandins, thromboxanes, leukotrienes, platelet-activating factor, and nitric oxide on nociceptive primary afferent neurons. Manifestations, receptor molecules, and intracellular signaling mechanisms of the effects of these mediators are discussed in detail. With regard to signaling, most data reported have been obtained from transfected nonneuronal cells and somata of cultured sensory neurons as these structures are more accessible to direct study of sensory and signal transduction. The peripheral processes of sensory neurons, where painful stimuli actually affect the nociceptors in vivo, show marked differences with respect to biophysics, ultrastructure, and equipment with receptors and ion channels compared with cellular models. Therefore, an effort was made to highlight signaling mechanisms for which supporting data from molecular, cellular, and behavioral models are consistent with findings that reflect properties of peripheral nociceptive nerve endings. Identified molecular elements of these signaling pathways may serve as validated targets for development of novel types of analgesic drugs.

The relevance of kinin B1 receptor upregulation in a mouse model of colitis

BACKGROUND AND PURPOSE

Kinins are implicated in many pathophysiological conditions, and recent evidence has suggested their involvement in colitis. This study assessed the role of the kinin B1 receptors in a mouse model of colitis.

EXPERIMENTAL APPROACH

Colitis was induced in mice by 2,4,6-trinitrobenzene sulphonic acid (TNBS), and tissue damage and myeloperoxidase activity were assessed. B1 receptor induction was analysed by organ bath studies, binding assay and reverse transcription PCR.

KEY RESULTS

TNBS-induced colitis was associated with tissue damage, neutrophil infiltration and time-dependent increase of colon B1 receptor-mediated contraction, with the maximal response observed at 72 h. The upregulation of the B1 receptor at this time point was also confirmed by means of binding studies. B1 receptor mRNA levels were elevated as early as 6 h after colitis induction and remained high for up to 48 h. TNBS-evoked tissue damage and neutrophil influx were reduced by the selective B1 receptor antagonist SSR240612, and in B1 receptor knockout mice. In vivo treatment with inhibitors of protein synthesis, nuclear factor-kappaB activation, inducible nitric oxide synthase (iNOS) or tumour necrosis factor alpha (TNFalpha) significantly reduced B1 receptor agonist-induced contraction. Similar results were observed in iNOS and TNF receptor 1-knockout mice.

CONCLUSIONS AND IMPLICATIONS

These results provide convincing evidence on the role of B1 receptors in the pathogenesis of colitis. Therefore, the blockade of kinin B1 receptors might represent a new therapeutic option for treating inflammatory bowel diseases.

TNF-alpha and IL-1beta mediate inflammatory hypernociception in mice triggered by B1 but not B2 kinin receptor

Kinin receptors are involved in the genesis of inflammatory pain. However, there is controversy concerning the mechanism by which B(1) and B(2) kinin receptors mediate inflammatory hypernociception. In the present study, the role of these receptors on inflammatory hypernociception in mice was addressed. Mechanical hypernociception was detected with an electronic pressure meter paw test in mice and cytokines were measured by ELISA. It was observed that in naïve mice a B(2) (d-Arg-Hyp(3), d-Phe(7)-bradykinin) but not a B(1) kinin receptor antagonist (des-Arg(9)-[Leu(8)]-bradykinin, DALBK) inhibited bradykinin- and carrageenin-induced hypernociception. Bradykinin-induced hypernociception was inhibited by indomethacin (5 mg/kg) and guanethidine (30 mg/kg), while not affected by IL-1ra (10 mg/kg) or antibody against keratinocyte-derived chemokine (KC/CXCL-1, 500 ng/paw) or in TNFR1 knockout mice. By contrast, in previously lipopolysaccharide (LPS)-primed mouse paw, B(1) but not B(2) kinin receptor antagonist inhibited bradykinin hypernociception. Furthermore, B(1) kinin receptor agonist induced mechanical hypernociception in LPS-primed mice, which was inhibited by indomethacin, guanethidine, antiserum against TNF-alpha or IL-1ra. This was corroborated by the induction of TNF-alpha and IL-1beta release by B(1) kinin receptor agonist in LPS-primed mouse paws. Moreover, B(1) but not B(2) kinin receptor antagonist inhibited carrageenin-induced hypernociception, and TNF-alpha and IL-1beta release as well, in LPS-primed mice. These results suggest that in naïve mice the B(2) kinin receptor mediates inflammatory hypernociception dependent on prostanoids and sympathetic amines, through a cytokine-independent mechanism. On the other hand, in LPS-primed mice, the B(1) kinin receptor mediates hypernociception by a mechanism dependent on TNF-alpha and IL-1beta, which could stimulate prostanoid and sympathetic amine production.

Effect of two active compounds obtained from the essential oil of Cordia verbenacea on the acute inflammatory responses elicited by LPS in the rat paw

BACKGROUND AND PURPOSE

alpha-Humulene and trans-caryophyllene are sesquiterpene compounds identified in the essential oil of Cordia verbenacea which display topical and systemic anti-inflammatory effects in different experimental models. However, the molecular mechanisms through which they exert their anti-inflammatory activity still remain unclear. Here, we evaluate the effects of alpha-humulene and trans-caryophyllene on the acute inflammatory responses elicited by LPS.

EXPERIMENTAL APPROACH

The biological activities of alpha-humulene and trans-caryophyllene were investigated in a model of acute inflammation in rat paw, induced by LPS and characterized by paw oedema, neutrophil recruitment, cytokine production, activation of MAP kinases and NF-kappaB and up-regulated expression of kinin B(1) receptors.

KEY RESULTS

Treatment with either alpha-humulene or trans-caryophyllene effectively reduced neutrophil migration and activation of NF-kappaB induced by LPS in the rat paw. However, only alpha-humulene significantly reduced the increase in TNF-alpha and IL-1beta levels, paw oedema and the up-regulation of B(1) receptors following treatment with LPS. Both compounds failed to interfere with the activation of the MAP kinases, ERK, p38 and JNK.

CONCLUSIONS AND IMPLICATIONS

Both alpha-humulene and trans-caryophyllene inhibit the LPS-induced NF-kappaB activation and neutrophil migration, although only alpha-humulene had the ability to prevent the production of pro-inflammatory cytokines TNF-alpha and IL-1beta and the in vivo up-regulation of kinin B(1) receptors. These data provide additional molecular and functional insights into the beneficial effects of the sesquiterpenes alpha-humulene and trans-caryophyllene isolated from the essential oil of Cordia verbenacea as agents for the management of inflammatory diseases.

Relevance of tumour necrosis factor-alpha for the inflammatory and nociceptive responses evoked by carrageenan in the mouse paw

1. The present study evaluated the participation of tumour necrosis factor-alpha (TNF-alpha) in the inflammatory and nociceptive responses evoked by carrageenan in the mouse paw. 2. The intraplantar injection of carrageenan (300 microg paw-1) induced a marked and biphasic paw oedema formation (peaks at 6 and 72 h), which was accompanied by a long-lasting mechanical allodynia (that remained elevated for up to 72 h) and a significant increase of myeloperoxidase (MPO) activity (peak at 6 h) in both Swiss and C57/BL6 mice. 3. The paw oedema, the elevation of MPO activity and to a lesser extent the mechanical allodynia elicited by carrageenan were found to be significantly reduced in TNF-alpha p55 receptor knockout mice. 4. Of interest, the systemic administration of an anti-TNF-alpha antibody produced a significant inhibition of paw oedema, mechanical allodynia and MPO activity. A noteworthy decrease in inflammatory and nociceptive responses caused by carrageenan was also observed when mice were previously treated with the preferential inhibitor of TNF-alpha synthesis, thalidomide. 5. The present results clearly indicate that the proinflammatory cytokine TNF-alpha plays a critical role in the oedema formation, as well as in the mechanical allodynia and the neutrophil migration, following carrageenan administration into the mouse paw. Intraplantar injection of carrageenan in mice could constitute a useful model for assessment of the in vivo effects of potential inhibitors of TNF-alpha-related pathways.

Long-lasting neuropathic pain induced by brachial plexus injury in mice: Role triggered by the pro-inflammatory cytokine, tumour necrosis factor α

Brachial plexus avulsion (BPA) resulted in a marked and long-lasting mechanical hypernociception (up to 80 days) in comparison to a sham-operated group, as assessed by Von Frey filaments, in both Swiss and C57/BL6 mice. In the tail-flick test, both Swiss and C57/BL6 mice submitted to BPA showed a significant thermal hypernociception, which persisted for 10 days. Both mechanical and thermal hypernociception following BPA were abolished in tumour necrosis factor alpha (TNFalpha) p55 receptor knockout mice. Moreover, the mechanical hypernociception caused by BPA was inhibited by the local application of the anti-TNFalpha (10 and 100 ng/site) antibody at the time of the surgery or by the intravenous administration (100 microg/kg) of this antibody at the time of the surgery or 4 days after the BPA. A similar inhibition of the mechanical hypernociception was observed when treating mice with the TNFalpha synthesis inhibitor thalidomide (50 mg/kg, s.c.), either at the time of the surgery or 4 days after. The results suggest that the persistent thermal, and especially the persistent mechanical, hypernociception observed following BPA in mice is largely dependent on the generation of TNFalpha. Based on these results, it is possible to suggest that therapeutic strategies for blocking TNFalpha could represent a valuable approach for the treatment of persistent neuropathic pain.