Comparative effect of Phoneutria nigriventer spider venom and capsaicin on the rat paw oedema

Potamotrygon motoro stingray venom induces both neurogenic and inflammatory pain behavior in rodents

Freshwater stingray accidents cause an immediate, intense, and unrelieved pain which is followed by edema, erythema and necrosis formation. Treatment for stingray envenomation is based on administration of analgesic, antipyretic and anti-inflammatory drugs. Concerning pain control, it is prescribed to immerse punctured limb on hot water to alleviate pain. There are no studies demonstrating specific targets on which stingray venom acts to promote pain. Therefore, the aim of this work was to investigate some mechanisms of Potamotrygon motoro venom (PmV) that contribute to nociception induction. Evaluating spontaneous pain behavior in mice injected i.pl. with PmV, it was seen that PmV induced both neurogenic and inflammatory pain. PmV also induced hyperalgesia in both mice and rats, evaluated through electronic von Frey and rat paw pressure test, respectively. Partial inhibition of hyperalgesia was observed in mice treated with cromolyn or promethazine, which indicated that mast cell and histamine via H1 receptor participate in the inflammatory pain. To search for some targets involved in PmVinduced hyperalgesia, the participation of TRPV1, calcium channels, neurokinins, CGRP, and norepinephrine, was evaluated in rats. It was seen that PmV-induced hyperalgesia occurs with the participation of neurokinins, mainly via NK1 receptor, CGRP, and calcium influx, through both P/Q and L-type voltage-dependent calcium channels, besides TRPV1 activation. The data presented herein indicate that PmV causes hyperalgesia in rodents which is dependent on the participation of several neuroinflammatory mediators.

Capsaicin and Its Role in Chronic Diseases

A significant number of experimental and clinical studies published in peer-reviewed journals have demonstrated promising pharmacological properties of capsaicin in relieving signs and symptoms of non-communicable diseases (chronic diseases). This chapter provides an overview made from basic and clinical research studies of the potential therapeutic effects of capsaicin, loaded in different application forms, such as solution and cream, on chronic diseases (e.g. arthritis, chronic pain, functional gastrointestinal disorders and cancer). In addition to the anti-inflammatory and analgesic properties of capsaicin largely recognized via, mainly, interaction with the TRPV1, the effects of capsaicin on different cell signalling pathways will be further discussed here. The analgesic, anti-inflammatory or apoptotic effects of capsaicin show promising results in arthritis, neuropathic pain, gastrointestinal disorders or cancer, since evidence demonstrates that the oral or local application of capsaicin reduce inflammation and pain in rheumatoid arthritis, promotes gastric protection against ulcer and induces apoptosis of the tumour cells. Sadly, these results have been paralleled by conflicting studies, which indicate that high concentrations of capsaicin are likely to evoke deleterious effects, thus suggesting that capsaicin activates different pathways at different concentrations in both human and rodent tissues. Thus, to establish effective capsaicin doses for chronic conditions, which can be benefited from capsaicin therapeutic effects, is a real challenge that must be pursued.

Neurokinin-1 receptor antagonist orvepitant is an effective inhibitor of itch-associated response in a Mongolian gerbil model of scratching behaviour

Data suggest that substance P could play an important role in pruritus, and therefore, blockade of the neurokinin (NK)-1 receptor might be antipruritic. Thus, we explored in the Mongolian gerbil the effect on scratching behaviour, induced by intra-dermal injection of the NK-1 receptor-specific agonist GR73632, of oral administration of the NK-1 receptor antagonist orvepitant. Orvepitant at all doses tested (0.1-10 mg/kg p.o.) produced a profound inhibition of GR73632 (30 nmol i.d.) induced hindlimb scratching; the minimum effective dose of orvepitant in this model was identified as ≤0.1 mg/kg. The data generated supported the proposition that the antipruritic potential of orvepitant should be evaluated in clinical trials.

Mechanisms involved in the nociception triggered by the venom of the armed spider Phoneutria nigriventer

BACKGROUND

The frequency of accidental spider bites in Brazil is growing, and poisoning due to bites from the spider genus Phoneutria nigriventer is the second most frequent source of such accidents. Intense local pain is the major symptom reported after bites of P. nigriventer, although the mechanisms involved are still poorly understood. Therefore, the aim of this study was to identify the mechanisms involved in nociception triggered by the venom of Phoneutria nigriventer (PNV).

METHODOLOGY/PRINCIPAL FINDINGS

Twenty microliters of PNV or PBS was injected into the mouse paw (intraplantar, i.pl.). The time spent licking the injected paw was considered indicative of the level of nociception. I.pl. injection of PNV produced spontaneous nociception, which was reduced by arachnid antivenin (ArAv), local anaesthetics, opioids, acetaminophen and dipyrone, but not indomethacin. Boiling or dialysing the venom reduced the nociception induced by the venom. PNV-induced nociception is not dependent on glutamate or histamine receptors or on mast cell degranulation, but it is mediated by the stimulation of sensory fibres that contain serotonin 4 (5-HT4) and vanilloid receptors (TRPV1). We detected a kallikrein-like kinin-generating enzyme activity in tissue treated with PNV, which also contributes to nociception. Inhibition of enzymatic activity or administration of a receptor antagonist for kinin B2 was able to inhibit the nociception induced by PNV. PNV nociception was also reduced by the blockade of tetrodotoxin-sensitive Na(+) channels, acid-sensitive ion channels (ASIC) and TRPV1 receptors.

CONCLUSION/SIGNIFICANCE

Results suggest that both low- and high-molecular-weight toxins of PNV produce spontaneous nociception through direct or indirect action of kinin B2, TRPV1, 5-HT4 or ASIC receptors and voltage-dependent sodium channels present in sensory neurons but not in mast cells. Understanding the mechanisms involved in nociception caused by PNV are of interest not only for better treating poisoning by P. nigriventer but also appreciating the diversity of targets triggered by PNV toxins.

Synthesis and pharmacological characterization of a novel nitric oxide-releasing diclofenac derivative containing a benzofuroxan moiety

1-oxy-benzo[1,2,5]oxadiazol-5-ylmethyl [2-(2,6-dichloro-phenylamino)-phenyl]-acetate, a new diclofenac derivative bearing a benzofuroxan heterocyclic moiety in its structure, was prepared by the reaction of sodium diclofenac and 5-bromomethyl-benzo[1,2,5]oxadiazole 1-oxide. Pharmacological characterization of this modified diclofenac maintained the anti-inflammatory activity similar to its parent compound assayed in vitro and in vivo. The ulcerogenic properties of native diclofenac were not observed with this modified compound, despite the inhibition of prostaglandin E2 gastric content. The better gastric tolerability seems to be related to nitric oxide release ability.

Role of sensory innervation in the rat pulmonary neutrophil recruitment induced by staphylococcal enterotoxins type A and B

Rat airways exposure to Staphylococcal enterotoxin A (SEA) and B (SEB) induces marked neutrophil influx. Since sensory neuropeptides play important roles in cell infiltration, in this study we have investigated its contribution in triggering SEA- and SEB-induced pulmonary neutrophil infiltration. Male Wistar rats were exposed intratracheally with SEA (3 ng/trachea) or SEB (250 ng/trachea). Animals received different in vivo pretreatments, after which the neutrophil counts and levels of substance P and IL-1 in bronchoalveolar lavage fluid were evaluated. Alveolar macrophages and peritoneal mast cells were incubated with SEA and SEB to determine the IL-1 and TNF-alpha levels. Capsaicin pretreatment significantly reduced SEA- and SEB-induced neutrophil influx in bronchoalveolar lavage fluid, but this treatment was more effective to reduce SEA responses. Treatments with SR140333 (tachykinin NK(1) receptor antagonist) and SR48968 (tachykinin NK(2) receptor antagonist) decreased SEA-induced neutrophil influx, whereas SEB-induced responses were inhibited by SR140333 only. Cyproheptadine (histamine/5-hydroxytriptamine receptor antagonist) and MD 7222 (5-HT(3) receptor antagonist) reduced SEA- and SEB-induced neutrophil influx. The substance P and IL-1 levels in bronchoalveolar lavage fluid of SEA-exposed rats were significantly higher than SEB. In addition, SEA (but not SEB) significantly released mast cell TNF-alpha. Increased production of TNF-alpha and IL-1 in alveolar macrophages was observed in response to SEA and SEB. In conclusion, sensory neuropeptides contribute significantly to SEA- and SEB-induced pulmonary neutrophil recruitment, but SEA requires in a higher extent the airways sensory innervation, and participation of mast cells and alveolar macrophage products.

Inflammatory events induced by brown spider venom and its recombinant dermonecrotic toxin: a pharmacological investigation

Accidents involving Brown spider (Loxosceles sp.) venom produce a massive inflammatory response in injured region. This venom has a complex mixture of different toxins, and the dermonecrotic toxin is the major contributor to toxic effects. The ability of Loxosceles intermedia venom and a recombinant isoform of dermonecrotic toxin to induce edema and increase in vascular permeability was investigated. These toxins were injected into hind paws and caused a marked dose and time-dependent edema and increase in vascular permeability in mice. Furthermore, the enzymatic activity of venom toxins may be primal for these effects. A mutated recombinant isoform of dermonecrotic toxin, that has only residual enzymatic activity, was not able to induce these inflammatory events. Besides the previous heating of toxins markedly reduced the paw edema and vascular permeability showing that thermolabile constituents can trigger these effects. In addition, the ability of these venom toxins to evoke inflammatory events was partially reduced in compound 48/80-pretreated animals, suggesting that mast cells may be involved in these responses. Pretreating mice with histamine (prometazine and cetirizine) and serotonin (methysergide) receptor antagonists significantly attenuated toxins induced edema and vascular permeability. Moreover, HPLC analysis of whole venom showed the presence of histamine sufficient to induce inflammatory responses. In conclusion, these inflammatory events may result from the activation of mast cells, which in turn release bioamines and may be related to intrinsic histamine content of venom.

Role of substance P and bradykinin in acute pancreatitis induced by secretory phospholipase A2

OBJECTIVES

Secretory phospholipases A2 (sPLA2s) induce acute pancreatitis when injected into the common bile duct of rats. Substance P via neurokinin 1 (NK-1) receptors and bradykinin via B2 receptors are described to play important roles in the pathophysiology of acute pancreatitis. This study was undertaken to evaluate the role of substance P and bradykinin in the sPLA2-induced pancreatitis.

METHODS

Rats were submitted to the common bile duct injection of sPLA2 obtained from Naja mocambique mocambique venom at 300 microg/kg. At 4 hours thereafter, measurement of pancreatic plasma extravasation, pancreatic and lung myeloperoxidase (MPO), serum amylase, and serum tumor necrosis factor alpha levels were evaluated.

RESULTS

Injection of sPLA2 significantly increased all parameters evaluated. Pretreatment with either the NK-1 receptor antagonist SR140333 or the B2 receptor antagonist icatibant largely reduced the increased pancreatic plasma extravasation and circulating levels of tumor necrosis factor alpha. Both treatments partly reduced the MPO levels in the pancreas, whereas in the lungs, icatibant was more efficient to reduce the increased MPO levels. In addition, icatibant largely reduced the serum levels of amylase, whereas SR140333 had no significant effect.

CONCLUSIONS

We concluded that NK-1 and B2 receptors can regulate important steps in the local and remote inflammation during acute pancreatitis induced by sPLA2.

Neutrophil migration in mice induced by a mannose-binding lectin isolated from Annona coriacea seeds

A novel 14-kDa lectin from Annona coriacea seeds (ACLEC) with hemagglutinating activity on erythrocytes has been recently described. Since plant lectins are known to present inflammatory activity, this study aimed to investigate the leukocyte migration induced by ACLEC, and inflammatory mediators involved in this phenomenon. Male Swiss mice were intraperitoneally injected with ACLEC (3-100 microg/cavity), and at 4-96 h thereafter the leukocyte counts in peritoneal lavage fluid were evaluated. ACLEC induced a dose-dependent neutrophil accumulation, reaching maximal responses at 16 h after injection (approximately 40-fold increase for 30 microg/cavity). Significant accumulation of mononuclear cells was observed at 72 h (2.7-fold increase). The carbohydrate mannose nearly abolished the neutrophil influx, whereas sucrose, glucose and galactose had no effect. Dexamethasone, the cyclooxygenase-2 (COX-2) inhibitor celecoxib and the Platelet activating factor (PAF) receptor antagonist PCA4248 significantly reduced ACLEC-induced neutrophil influx. The tachykinin NK(1) antagonist SR140333, the tachykinin NK(2) antagonist SR48968, the non-selective NO inhibitor L-NAME, the selective inducible NOS inhibitor aminoguanidine and the lypoxygenase inhibitor AA861 all failed to modify the ACLEC-induced responses. In conclusion, ACLEC is able to attract neutrophils into the mice peritoneal cavity by mechanisms involving interactions of the lectin with cell-specific mannose recognition, leading to the release of COX-2-derived mediators and PAF.

Role of IgG(T) and IgGa isotypes obtained from arachnidic antivenom to neutralize toxic activities of Loxosceles gaucho, Phoneutria nigriventer and Tityus serrulatus venoms

The ability of IgG(T) and IgGa subclasses--isolated by liquid chromatography from equine arachnidic antivenom (AAV)-to neutralize toxic activities of Loxosceles gaucho, Phoneutria nigriventer and Tityus serrulatus venoms as well as to remove venom toxins from circulation was investigated. These subclasses showed similar antibody titers against L. gaucho, P. nigriventer and T. serrulatus venoms, and by immunoblotting few differences were observed in the recognition pattern of venom antigens. IgG(T) and IgGa neutralized 100% lethality induced by L. gaucho and 50% of P. nigriventer venom, but IgGa failed to neutralize T. serrulatus venom, in contrast to IgG(T). Both subclasses neutralized local reactions and dermonecrosis induced by L. gaucho venom in rabbits. In mice, IgG(T) and IgGa partially neutralized the edematogenic activity induced by P. nigriventer and T. serrulatus venoms, but only IgG(T) neutralized (ca. 81%) the nociceptive activity induced by T. serrulatus venom. Both subclasses failed to neutralize nociceptive activity induced by P. nigriventer venom. IgG(T) reduced the serum venom levels of animals injected with L. gaucho, P. nigriventer or T. serrulatus venoms, while IgGa solely reduced L. gaucho and P. nigriventer venoms levels. Our results demostrate that IgG(T) and IgGa subclasses neutralize toxic activities induced by P. nigriventer, T. serrulatus and L. gaucho venoms with different efficacies, as well as depurate these venoms from circulation.

Comparison of the partial proteomes of the venoms of Brazilian spiders of the genus Phoneutria

The proteomes of the venoms of the Brazilian wandering "armed" spiders Phoneutria nigriventer, Phoneutria reidyi, and Phoneutria keyserlingi, were compared using two-dimensional gel electrophoresis. The venom components were also fractionated using a combination of preparative reverse phase HPLC on Vydac C4, analytical RP-HPLC on Vydac C8 and C18 and cation exchange FPLC on Resource S at pH 6.1 and 4.7, or anion exchange HPLC on Synchropak AX-300 at pH 8.6. The amino acid sequences of the native and S-pyridyl-ethylated proteins and peptides derived from them by enzymatic digestion and chemical cleavages were determined using a Shimadzu PPSQ-21(A) automated protein sequencer, and by MS/MS collision induced dissociations. To date nearly 400 peptides and proteins (1.2-27 kDa) have been isolated in a pure state and, of these, more than 100 have had their complete or partial amino acid sequences determined. These sequences demonstrate, as might be expected, that the venoms of P. reidyi and P. keyserlingi (Family: Ctenidae) both contain a similar range of isoforms of the neurotoxins as those previously isolated from P. nigriventer which are active on neuronal ion (Ca(2+), Na(+) and K(+)) channels and NMDA-type glutamate receptors. In addition two new families of small (3-4 kDa) toxins, some larger protein (>10 kDa) components, and two serine proteinases of the venom of P. nigriventer are described. These enzymes may be responsible for some of the post-translational modification observed in some of the venom components.

Oedematogenic activity induced by Kunitz-type inhibitors from Dimorphandra mollis seeds

Proteinase inhibitors from plants represent a form of storage protein or may be involved in plant defense mechanisms against pests and diseases. In this study, we have investigated the oedematogenic activity of DMTI (20 kDa) and DMTI-II (23 kDa), two serine proteinases inhibitors isolated from Dimorphandra mollis (Leguminosae-Mimosoideae) seeds, belonging to the Kunitz family. Paw oedema was induced in male Wistar rats, and measured before and selected times after injection of the proteinase inhibitors. Injection of DMTI-II (3-100 microg/paw) induced a dose-dependent rat paw oedema of rapid onset and short duration, whereas DMTI (3-100 microg/paw) caused a discrete response. The histamine/5-HT receptor antagonist cyproheptadine (2 mg/kg) markedly reduced the DMTI-II-induced oedema. The bradykinin B2 receptor antagonist JE 049 (0.6 mg/kg), the tachykinin NK1 receptor antagonist SR140333 (100 microg/kg) or the NK2 receptor antagonist SR48968 (1 mg/kg) all significantly reduced the DMTI-II-induced oedema. Depletion of sensory neuropeptides by capsaicin also resulted in a significant reduction of oedema formation. In rat isolated peritoneal mast cells, DMTI-II failed to directly release histamine. In conclusion, the proteinase inhibitor DMTI-II induces rat paw oedema by triggering the formation of different inflammatory mediators and pathways, where mast cells and sensory fibers seem to play a pivotal role.

Electrospray ionization quadrupole time-of-flight and matrix-assisted laser desorption/ionization tandem time-of-flight mass spectrometric analyses to solve micro-heterogeneity in post-translationally modified peptides from Phoneutria nigriventer (Aranea, Ctenidae) venom

Previous studies of the fractionated venom of the Brazilian armed spider Phoneutria nigriventer, obtained by gel filtration, have demonstrated the presence of a fraction PhM, a pool of small peptides (up to 2000 Da) that provoke contractions in smooth muscle of guinea pig ileum. Initial attempts to sequence these peptides were largely unsuccessful because of the low purification yield and the fact that the majority seemed to be blocked at their N-termini. In the present work, analysis of this venom fraction by mass spectrometry has revealed the existence of a highly complex mixture of peptides with molecular weights corresponding to those observed for the muscle-active peptides previously described (800-1800 Da). These peptides appear to be a family of isoforms with some particular features. The amino acid sequences of 15 isoforms have been determined by tandem mass spectrometry (MS/MS) using both electrospray ionization quadrupole time-of-flight mass spectrometry (ESI-Q/ToFMS) and matrix-assisted laser desorption/ionization tandem time-of-flight mass spectrometry (MALDI-ToF/ToFMS). These molecules contain post-translational modifications such as proteolysis and C-terminal amidation, which combine to generate additional isoforms. All the isoforms sequenced in this study possess an N-terminal pyroglutamic acid residue. A search for sequence similarities with other peptides in databanks revealed that these peptides are structurally related to the tachykinins, a family of neuro-hormone peptides. The data obtained in this study will be essential for the subsequent steps of this research, the synthesis of these peptides and pharmacological characterization of their biological activity.

Characterisation of local inflammatory response induced by Thalassophryne nattereri fish venom in a mouse model of tissue injury

The Thalassophryne nattereri fish venom induces a severe burning pain, oedema, and necrosis observed both clinically and experimentally. The present study was carried out in order to describe the pattern of local acute inflammatory response after T. nattereri venom injection. Our findings show that the edematogenic response induced by T. nattereri venom in footpad of mice was dose- and time dependent, and remained significantly elevated over 48 h after injection. Analysis of footpad homogenates were tested for the presence of TNF-alpha, IL-1beta and IL-6, and demonstrated augmented levels of these cytokines. Our results showed that the injection of venom developed an inadequate cellular inflammatory response evidenced by poor infiltration of mononuclear cells, preceded by decreased number of these cells in peripheral blood. In contrast, we observed an early intense recruitment of neutrophil to peritoneal cavity, accompanied by a significant decrease in the number of mononuclear cells. A drastic increase in the total amount of cells, mainly in neutrophils, followed by mononuclear cell recruitment was observed 24 h. In addition, we also demonstrated that T. nattereri venom affects the viability of mononuclear cells (J774A1) in culture. We conclude that the scarcity of inflammatory cellular influx into local lesions (intraplantar) induced by T. nattereri venom could be a consequence of an impaired blood flow in venules at injured tissue and cytotoxic effect of the venom on inflammatory cells can contribute to this impairment.

Phoneutria nigriventer spider venom activates 5-HT4 receptors in rat-isolated vagus nerve

1. The venom of Phoneutria nigriventer spider (PNV) causes intense pain and inflammation following an attack. We have investigated the involvement of capsaicin-sensitive nerve fibres by utilizing an in vitro nerve preparation. Extracellular DC potential recordings were made from the rat-isolated vagus nerve, a preparation that is rich in capsaicin-sensitive, that is, nociceptive, C-fibres. 2. PNV (1-10 microg ml(-1)), capsaicin (0.03-0.3 microM) or 5-hydroxytriptamine (5-HT) (0.3-3 microM) induced dose-dependent depolarizations of vagus nerve fibres. Depolarizing responses to capsaicin were blocked by ruthenium red (RR, 10 microM), but responses to PNV were not. Depolarizing responses to PNV or veratridine (50 microM) were inhibited by tetrodotoxin (TTX, 10 microM), but those to capsaicin were not. This suggests that capsaicin and PNV depolarize the nerve fibres by distinct mechanisms. 3. Depolarization in response to 5-HT (3 microM) was reduced by the 5-HT(3) receptor antagonists Y25130 (0.5 micro M) and tropisetron (10 nM) or, to a lesser extent, by the 5-HT(4) receptor antagonist RS39604 (1 or 10 microM). Depolarizing responses to PNV were not affected significantly by Y25130 or tropisetron, but were blocked by RS39604. 4. These data show that 5-HT(4) receptors play a significant role in the activation of nociceptive sensory nerve fibres by PNV and suggest that this is of importance in the development of the pain and inflammation associated with bites from the P. nigriventer spider.

Peripheral tackykinin and excitatory amino acid receptors mediate hyperalgesia induced by Phoneutria nigriventer venom

The generation of hyperalgesia by Phoneutria nigriventer venom was investigated in rats using the paw pressure test, through the intraplantar injection of the venom. Hyperalgesia was significantly inhibited by N-[2-(4-chlorophenyl) ethyl]-1,3,4,5-tetrahydro-7,8-dihydroxy-2H-2-benzazepine-2-carbothioamide (capsazepine), a vanilloid receptor antagonist, by the local administration of pGlu-Ala-Asp-Pro-Asn-Lys-Phe-Tyr-Pro (spiro-gamma-lactam) Leu-Trp-NH(2) (GR82334) or of Phenyl-CO-Ala-Ala-D-Trp-Phe-D-Pro-Pro-Nle-NH(2) (GR94800), inhibitors of tachykinin NK(1) and NK(2) receptors, respectively, or by the local injection of dizocilpine (MK 801), (+/-)-2-amino-5-phosphonopentanoic acid ((+/-)-AP-5), or 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), antagonists of NMDA and non-NMDA excitatory amino acid receptors. The correlation between hyperalgesia and the inflammatory response induced by the venom was also investigated. The venom-induced edematogenic response was not modified by the pharmacological treatments. These results suggest that hyperalgesia induced by P. nigriventer venom is mediated by stimulation of capsaicin-sensitive neurons, with activation of peripheral tachykinin NK(1) and NK(2) receptors and of both the NMDA and AMPA receptors. Distinct mechanisms are involved in the development of hyperalgesia and edema induced by the venom.

Role of kinins and sensory neurons in the rat pleural leukocyte migration induced by Phoneutria nigriventer spider venom

The leukocyte migration induced by Phoneutria nigriventer spider venom (PNV) has been investigated in rats using the pleurisy model. Intrapleural injection of PNV (10-100 microg/cavity) caused a dose- and time-dependent leukocyte accumulation. The bradykinin B(2) receptor antagonist Hoe 140 (0.5 mg/kg) substantially inhibited PNV-induced cell accumulation, whereas the angiotensin-converting enzyme inhibitor captopril (2 mg/kg) potentiated by 80% this effect. The non-specific kallikrein inhibitor aprotinin and the plasma kallikrein inhibitor soybean trypsin inhibitor greatly reduced PNV-induced leukocyte migration, whereas the selective tissue kallikrein inhibitor P(ac)-F-S-R-EDDnp failed to affect PNV-induced responses. Treatment of rats with capsaicin (50 mg/kg) at the neonatal stage resulted in 67% inhibition of the PNV-induced cell migration. The neurokinin NK(1) receptor antagonist SR140333, but not the NK(2) receptor antagonist SR48968, reduced by 55% venom-induced cell accumulation. We conclude that bradykinin generation is involved in the PNV-induced pleural leukocyte migration in rats, where it can directly activate sensory nerves contributing to a neurogenic inflammatory mechanism.