Involvement of spinal neurokinins, excitatory amino acids, proinflammatory cytokines, nitric oxide and prostanoids in pain facilitation induced by Phoneutria nigriventer spider venom

Thermoregulation Effects of Phoneutria nigriventer Isolated Toxins in Rats

Body temperature is primarily regulated by the hypothalamus, ensuring proper metabolic function. Envenomation by Phoneutria nigriventer can cause symptoms such as hypothermia, hyperthermia, sweating, and shivering, all related to thermoregulation. This study aims to analyze and identify components of the venom that affect thermoregulation and to evaluate possible mechanisms. Rats were used for thermoregulation analysis, venom fractionation by gel filtration and reverse-phase chromatography (C18), and sequencing by Edman degradation. The venom exhibited hypothermic effects in rats, while its fractions demonstrated both hypothermic (pool II) and hyperthermic (pool III) effects. Further separations of the pools with C18 identified specific peaks responsible for these effects. However, as the peaks were further purified, their effects became less significant. Tests on U87 human glioblastoma cells showed no toxicity. Sequencing of the most active peaks revealed masses similar to those of the Tachykinin and Ctenotoxin families, both known to act on the nervous system. The study concludes that molecules derived from venom can act synergistically or antagonistically. Additionally, toxins that affect thermoregulation are poorly studied and require further characterization. These toxins could potentially serve as sources for the development of new thermoregulatory drugs.

Spider-Venom Peptides: Structure, Bioactivity, Strategy, and Research Applications

Spiders (Araneae), having thrived for over 300 million years, exhibit remarkable diversity, with 47,000 described species and an estimated 150,000 species in existence. Evolving with intricate venom, spiders are nature's skilled predators. While only a small fraction of spiders pose a threat to humans, their venoms contain complex compounds, holding promise as drug leads. Spider venoms primarily serve to immobilize prey, achieved through neurotoxins targeting ion channels. Peptides constitute a major part of these venoms, displaying diverse pharmacological activities, and making them appealing for drug development. Moreover, spider-venom peptides have emerged as valuable tools for exploring human disease mechanisms. This review focuses on the roles of spider-venom peptides in spider survival strategies and their dual significance as pharmaceutical research tools. By integrating recent discoveries, it provides a comprehensive overview of these peptides, their targets, bioactivities, and their relevance in spider survival and medical research.

Assessment of local pain and analgesia in envenoming by wandering spiders (Phoneutria spp.)

Phoneutrism (bites by wandering spiders of the genus Phoneutria) frequently results in local pain. We describe a retrospective cohort study of a case series of phoneutrism admitted to our Emergency Department (ED), in which we used the Numeric Pain Rating Scale (NPRS 0-10) to assess the intensity of local pain upon admission, and recorded the analgesic measures used to control this pain. Other criteria for inclusion were: (1) An age ≥8 years, (2) Treatment exclusively at our ED, and (3) Visualization or photographing the spider at the time of the bite and/or bringing the spider for identification. The patients were classified into three groups based on the intensity of pain at admission: group 1 - mild or no pain (NPRS: 0-3), group 2 - moderate pain (NPRS: 4-6), and group 3 - intense or severe pain (NPRS: 7-10). Fifty-two patients fulfilled the inclusion criteria (n = 11, 14 and 27 in groups 1, 2, and 3, respectively), with a median age of 37 years. The median NPRS upon admission was 7 (interquartile range: 5-8). In patients with an NPRS <7 (groups 1 and 2), only dipyrone was used to alleviate the pain, with six cases in group 1 requiring no analgesia. Most of the cases in group 3 (19/27) were treated with a local anesthetic infiltration (2% lidocaine), in association with analgesics given i.v. in 16 cases (dipyrone, 14; tramadol, 2); additional analgesic treatment was required in seven cases, six of which were treated with tramadol i.v. The median time spent in the ED was 18, 58 and 120 min for groups 1, 2 and 3, respectively. These findings show that most cases of envenoming by Phoneturia spp. involved intense local pain (NPRS ≥7), with local anesthetics being used only in these cases, often in association with dipyrone i.v.

Pain-related toxins in scorpion and spider venoms: a face to face with ion channels

Pain is a common symptom induced during envenomation by spiders and scorpions. Toxins isolated from their venom have become essential tools for studying the functioning and physiopathological role of ion channels, as they modulate their activity. In particular, toxins that induce pain relief effects can serve as a molecular basis for the development of future analgesics in humans. This review provides a summary of the different scorpion and spider toxins that directly interact with pain-related ion channels, with inhibitory or stimulatory effects. Some of these toxins were shown to affect pain modalities in different animal models providing information on the role played by these channels in the pain process. The close interaction of certain gating-modifier toxins with membrane phospholipids close to ion channels is examined along with molecular approaches to improve selectivity, affinity or bioavailability in vivo for therapeutic purposes.

Analgesic and Anti-Inflammatory Activities of Sophocarpine from Sophora viciifolia Hance

Sophora viciifolia Hance is an edible plant used in traditional Chinese medicine. Sophocarpine, a tetracyclic quinolizidine alkaloid, is one of the most abundant active ingredients in Sophora viciifolia Hance. Here, we study the analgesic and anti-inflammatory effects, as well as the acute toxicity of sophocarpine from Sophora viciifolia Hance in mice. Sophocarpine (20, 40, and 80 mg/kgbw) significantly prolonged the delay period before a hot plate reaction occurred (all P < 0.05), and the delay before a tail-flick response was induced by a warm bath (P < 0.05; P < 0.01). Sophocarpine (40, 80 mg/kg) resulted in dose-dependent inhibition of the writhing reaction induced by acetic acid in mice (P < 0.05; P < 0.001, respectively). Sophocarpine (80 mg/kg) reduced the total duration of a formalin-induced pain response (P < 0.05). Sophocarpine prolonged the foot-licking latency of mice after the hot plate reaction, and this effect was antagonized by calcium chloride and enhanced by verapamil. Sophocarpine (20, 40, and 80 mg/kg) significantly inhibited xylene-induced ear edema (P < 0.01; P < 0.001; P < 0.001, respectively) and the penetration of acetic acid-induced dye into the peritoneal cavity (P < 0.01; P < 0.01; P < 0.001, respectively). It also reduced the levels of proinflammatory cytokine interleukin (IL)-1β, IL-6, and prostaglandin E2 (P < 0.05, P < 0.01, P < 0.001) and those of serum nitric oxide (P < 0.05). The results of this study suggest that sophocarpine possesses certain analgesic and anti-inflammatory activities, which may be related to calcium and inhibition of the secretion of inflammatory factors.

Pro-inflammatory response induced by the venom of Parachartergus fraternus wasp

The sting of different wasp species triggers local and systemic reactions in victims that can lead to death. Parachartergus fraternus is responsible for frequent accidents in Latin America; however, few studies have been conducted on this insect and its venom. In this study, the inflammatory process induced by the venom of the P. fraternus wasp (Pfv; 100, 200, and 400 μg/kg) was characterized. Mice were used to assess paw edema, vascular permeability, mast cell degranulation, leukocyte influx, nitric oxide (NO) production, expression of inflammatory genes, and histopathological changes. Pfv triggered edema formation with a peak dose of 200 μg/kg at 10 min. There was an increase in permeability in all periods and doses evaluated, with no differences between them. The 200 μg/kg dose induced mast cell degranulation in all periods, with a peak at 15 min. This same dose induced leukocyte influx with a predominance of mononuclear cells and triggered a peak in NO production in the 12th hour. The increase in COX-2, iNOS, and IFN-γ mRNA expression occurred after 1 and 6 h, and there was an increase in IL-10 expression after 48 h. In addition, Pfv triggered edema and induced an influx of macrophages and mast cells into the injection site. Therefore, Pfv induces an inflammatory process from the first 5 min of inoculation that can persist for up to 48 h.

Measuring Earwax Cortisol Concentration using a non-stressful sampling method

BACKGROUND

"Short-term" samples are not the most appropriate for reflecting chronic cortisol concentration. Although hair is used for reflecting the systemic level of this hormone, its use as a "long-term" measure appears clinically problematic. Local and systemic stress and non-stress related factors may release cortisol that is accumulated in hair. Non-stressful earwax sampling methods may provide a more accurate specimen to measure chronic cortisol concentration.

METHODS

Earwax from both ears of 37 controls were extracted using a clinical procedure commonly associated with local pain. One month later, earwax from the left ear side was extracted using the same procedure, and earwax from the right ear side was more comfortably obtained, using a novel earwax self-sampling device. Participants also provided one centimetre of hair that represented the retrospective month of cortisol output, and one serum sample that reflected the effect of systemic stressors on cortisol levels. Earwax (ECC), Hair (HCC) and Serum (SCC) Cortisol Concentration were correlated and compared. Confounders' effect on cortisol levels were studied.

RESULTS

The highest levels of cortisol concentration were found in serum, and the lowest in hair (p < 0.01). Left-ECC was larger than Right-ECC (p = 0.03). Right-ECC was the only sample unaffected by confounders (all p > 0.05). A Pearson correlation showed that Right-ECC and HCC samples were moderately correlated between them (r = 0.39; p = 0.03).

CONCLUSIONS

The self-sampling device did not increase cortisol locally. It provided the cortisol level that was least likely to be affected by confounding factors over the previous month. ECC using the novel device might constitute another accurate, but more suitable and affordable specimen for measuring chronic cortisol concentration.

Pain modulatory properties of Phoneutria nigriventer crude venom and derived peptides: A double-edged sword

Phoneutria nigriventer venom (PNV) is a complex mixture of toxins exerting multiple pharmacological effects that ultimately result in severe local pain at the site of the bite. It has been proposed that the PNV-induced pain is mediated by both peripheral and central mechanisms. The nociception triggered by PNV is peripherally mediated by the activation of B₂, 5-HT₄, NMDA, AMPA, NK₁, and NK₂ receptors, as well as TTXS-Na⁺, ASIC, and TRPV1 channels. The activation of tachykinin, glutamate and CGRP receptors along with the production of inflammatory mediators are, at least partially, responsible for the central component of pain. Despite its well established pro-nociceptive properties, PNV contains some toxins with antinociceptive activity, which have been studied in the last few years. The toxins ω-CNTX-Pn4a, ω-CNTX-Pn2a, ω-CNTX-Pn3a, κ-CNTX-Pn1a, U₇-CNTX-Pn1a, δ-CNTX-Pn1a, and Γ-CNTX-Pn1a from PNV, as well as the semi-synthetic peptide PnPP-19 have been tested in different experimental models of pain showing consistent antinociceptive properties. This review aims to discuss the pro- and antinociceptive actions of PNV and its toxins, highlighting possible mechanisms involved in these apparently dualistic properties.

Infrared thermography to diagnose and manage venomous animal bites and stings

INTRODUCTION

Infrared imaging (IR) is a noninvasive technique that quantifies body surface temperature, producing a digital color image. IR has been used to study diseases in which skin temperature can reflect the presence of inflammation.

METHODS

This was an observational pilot study of eight patients envenomed by snakes, spiders, and scorpions. All patients were examined using a thermal camera.

RESULTS

In all cases, we obtained infrared images that corroborated clinical findings indicating localized effects of venom, specifically inflammation.

CONCLUSIONS

IR has potential for use as a research, diagnostic, and monitoring tool for localized effects of animal venoms.

Spinal astrocytic activation contributes to mechanical allodynia in a rat model of cyclophosphamide-induced cystitis

BACKGROUND

Previous studies have demonstrated that glial cells play an important role in the generation and maintenance of neuropathic pain. Activated glial cells produce numerous mediators such as proinflammatory cytokines that facilitate neuronal activity and synaptic plasticity. Similarly, bladder pain syndrome/interstitial cystitis shares many characteristics of neuropathic pain. However, related report on the involvement of spinal glia in bladder pain syndrome/interstitial cystitis-associated pathological pain and the underlying mechanisms are still lacking. The present study investigated spinal glial activation and underlying molecular mechanisms in a rat model of bladder pain syndrome/interstitial cystitis.

RESULTS

A rat model of bladder pain syndrome/interstitial cystitis was established via systemic injection with cyclophosphamide. Mechanical allodynia was tested with von Frey monofilaments and up-down method. Moreover, Western blots and double immunofluorescence were used to detect the expression and location of glial fibrillary acidic protein, OX42/Iba1, P-P38, NeuN, interleukin (IL)-1β, phosphorylation of N-methyl-D-aspartate receptor 1 (P-NR1), and IL-1 receptor I (IL-1RI) in the L6-S1 spinal cord. We found that glial fibrillary acidic protein rather than OX42/Iba1 or P-P38 was significantly increased in the spinal cord of cyclophosphamide-induced cystitis. L-alpha-aminoadipate but not minocycline markedly attenuated the allodynia. Furthermore, we found that spinal IL-1β was dramatically increased in cyclophosphamide-induced cystitis, and activated astrocytes were the only source of IL-1β release, which contributed to allodynia in cystitis rats. Besides, spinal P-NR1 was statistically increased in cyclophosphamide-induced cystitis and only localized in IL-1RI positive neurons in spinal dorsal horn. Additionally, NR antagonist significantly attenuated the cystitis-induced pain. Interestingly, the time course of the P-NR1 expression paralleled to that of IL-1β or glial fibrillary acidic protein.

CONCLUSIONS

Our results demonstrated that astrocytic activation but not microglial activation contributed to the allodynia in cyclophosphamide-induced cystitis and IL-1β released from astrocytes might bind to its endogenous receptor on the neurons inducing the phosphorylation of NR1 subunit, leading to sensory neuronal hyperexcitability and pathological pain.

Analysis of Protein Composition and Bioactivity of Neoponera villosa Venom (Hymenoptera: Formicidae)

Ants cause a series of accidents involving humans. Such accidents generate different reactions in the body, ranging from a mild irritation at the bite site to anaphylactic shock, and these reactions depend on the mechanism of action of the venom. The study of animal venom is a science known as venomics. Through venomics, the composition of the venom of several ant species has already been characterized and their biological activities described. Thus, the aim of this study was to evaluate the protein composition and biological activities (hemolytic and immunostimulatory) of the venom of Neoponera villosa (N. villosa), an ant widely distributed in South America. The protein composition was evaluated by proteomic techniques, such as two-dimensional electrophoresis. To assess the biological activity, hemolysis assay was carried out and cytokines were quantified after exposure of macrophages to the venom. The venom of N. villosa has a profile composed of 145 proteins, including structural and metabolic components (e.g., tubulin and ATPase), allergenic and immunomodulatory proteins (arginine kinase and heat shock proteins (HSPs)), protective proteins of venom (superoxide dismutase (SOD) and catalase) and tissue degradation proteins (hyaluronidase and phospholipase A2). The venom was able to induce hemolysis in human erythrocytes and also induced release of both pro-inflammatory cytokines, as the anti-inflammatory cytokine release by murine macrophages. These results allow better understanding of the composition and complexity of N. villosa venom in the human body, as well as the possible mechanisms of action after the bite.

Pharmacological Characterization of the Edema Caused by Vitalius dubius (Theraphosidae, Mygalomorphae) Spider Venom in Rats

Bites by tarantulas (Theraphosidae, Mygalomorphae) in humans can result in mild clinical manifestations such as local pain, erythema, and edema. Vitalius dubius is a medium-sized, nonaggressive theraphosid found in southeastern Brazil. In this work, we investigated the mediators involved in the plasma extravasation caused by V. dubius venom in rats. The venom caused dose-dependent (0.1-100 μg/site) edema in rat dorsal skin. This edema was significantly inhibited by ((S)1-{2-[3(3-4-dichlorophenyl)-1-(3-iso-propoxyphenylacetyl)piperidine-3-yl]ethyl}-4-phenyl-1-azoniabicyclo[2.2.2]octone, chloride) (SR140333, a neurokinin NK1 receptor antagonist), indomethacin [a nonselective cyclooxygenase (COX) inhibitor], cyproheptadine (a serotonin 5-hydroxytryptamine1/2 and histamine H1 receptor antagonist), and N(ω)-nitro-L-arginine methyl ester (a nitric oxide synthase inhibitor). In contrast, mepyramine (a histamine H1 receptor antagonist), D-Arg-[Hyp(3),Thi(5),D-Tic(7),Oic(8)-]-BK (JE 049, a bradykinin B2 receptor antagonist), and ((S)-N-methyl-N-[4-(4-acetylamino-4-phenylpiperidino)-2-(3,4-di-chlorophenyl)butyl]benzamide) (SR48968, a neurokinin NK2 receptor antagonist) had no effect on the venom-induced increase in vascular permeability. In rat hind paws, the venom-induced edema was attenuated by ketoprofen (a nonselective COX inhibitor) administered 15 minutes postvenom. Preincubation of venom with commercial antiarachnid antivenom attenuated the venom-induced edema. These results suggest that the enhanced vascular permeability evoked by V. dubius venom involves serotonin, COX products, neurokinin NK1 receptors, and nitric oxide formation. The attenuation of hind paw edema by ketoprofen suggests that COX inhibitors could be useful in treating the local inflammatory response to bites by these spiders.

eNOS uncoupling in the cerebellum after BBB disruption by exposure to Phoneutria nigriventer spider venom

Numerous studies have shown that the venom of Phoneutria nigriventer (PNV) armed-spider causes excitotoxic signals and blood-brain barrier breakdown (BBBb) in rats. Nitric oxide (NO) is a signaling molecule which has a role in endothelium homeostasis and vascular health. The present study investigated the relevance of endothelial NO synthase (eNOS) uncoupling to clinical neurotoxic evolution induced by PNV. eNOS immunoblotting of cerebellum lysates processed through low-temperature SDS-PAGE revealed significant increased monomerization of the enzyme at critical periods of severe envenoming (1-2 h), whereas eNOS dimerization reversal paralleled to amelioration of animals condition (5-72 h). Moreover, eNOS uncoupling was accompanied by increased expression in calcium-sensing calmodulin protein and calcium-binding calbindin-D28 protein in cerebellar neurons. It is known that greater eNOS monomers than dimers implies the inability of eNOS to produce NO leading to superoxide production and endothelial/vascular barrier dysfunction. We suggest that transient eNOS deactivation and disturbances in calcium handling reduce NO production and enhance production of free radicals thus contributing to endothelial dysfunction in the cerebellum of envenomed rats. In addition, eNOS uncoupling compromises the enzyme capacity to respond to shear stress contributing to perivascular edema and it is one of the mechanisms involved in the BBBb promoted by PNV.

Spinal astrocytic activation contributes to mechanical allodynia in a rat chemotherapy-induced neuropathic pain model

Chemotherapy-induced neuropathic pain (CNP) is the major dose-limiting factor in cancer chemotherapy. However, the neural mechanisms underlying CNP remain enigmatic. Accumulating evidence implicates the involvement of spinal glia in some neuropathic pain models. In this study, using a vincristine-evoked CNP rat model with obvious mechanical allodynia, we found that spinal astrocyte rather than microglia was dramatically activated. The mechanical allodynia was dose-dependently attenuated by intrathecal administratration of L-α-aminoadipate (astrocytic specific inhibitor); whereas minocycline (microglial specific inhibitor) had no such effect, indicating that spinal astrocytic activation contributes to allodynia in CNP rat. Furthermore, oxidative stress mediated the development of spinal astrocytic activation, and activated astrocytes dramatically increased interleukin-1β expression which induced N-methyl-D-aspartic acid receptor (NMDAR) phosphorylation in spinal neurons to strengthen pain transmission. Taken together, our findings suggest that spinal activated astrocytes may be a crucial component of the pathophysiology of CNP and “Astrocyte-Cytokine-NMDAR-neuron” pathway may be one detailed neural mechanisms underlying CNP. Thus, inhibiting spinal astrocytic activation may represent a novel therapeutic strategy for treating CNP.

Spinal astrocytic activation is involved in a virally-induced rat model of neuropathic pain

Postherpetic neuralgia (PHN), the most common complication of herpes zoster (HZ), plays a major role in decreased life quality of HZ patients. However, the neural mechanisms underlying PHN remain unclear. Here, using a PHN rat model at 2 weeks after varicella zoster virus infection, we found that spinal astrocytes were dramatically activated. The mechanical allodynia and spinal central sensitization were significantly attenuated by intrathecally injected L-α-aminoadipate (astrocytic specific inhibitor) whereas minocycline (microglial specific inhibitor) had no effect, which indicated that spinal astrocyte but not microglia contributed to the chronic pain in PHN rat. Further study was taken to investigate the molecular mechanism of astrocyte-incudced allodynia in PHN rat at post-infection 2 weeks. Results showed that nitric oxide (NO) produced by inducible nitric oxide synthase mediated the development of spinal astrocytic activation, and activated astrocytes dramatically increased interleukin-1β expression which induced N-methyl-D-aspartic acid receptor (NMDAR) phosphorylation in spinal dorsal horn neurons to strengthen pain transmission. Taken together, these results suggest that spinal activated astrocytes may be one of the most important factors in the pathophysiology of PHN and “NO-Astrocyte-Cytokine-NMDAR-Neuron” pathway may be the detailed neural mechanisms underlying PHN. Thus, inhibiting spinal astrocytic activation may represent a novel therapeutic strategy for clinical management of PHN.

Gene therapy for chronic neuropathic pain: how does it work and where do we stand today?

OBJECTIVES

Chronic neuropathic pain has been an enigma to physicians and researchers for decades. A better understanding of its pathophysiology has given us more insight into its various mechanisms and possible treatment options. We now have an understanding of the role of various ionic channels, biologically active molecules involved in pain, and also the intricate pain pathways where possible interventions might lead to substantial pain relief. The recent research on laboratory animals using virus-based vectors for gene transfer at targeted sites is very promising and may lead to additional human clinical trials. However, one needs to be aware that this "novel" approach is still in its infancy and that many of its details need to be further elucidated. The purpose of this article is to thoroughly review the current available literature and analyze the deficiencies in our current knowledge.

DESIGN

Literature review.

METHODS

After an extensive online literature search, a total of 133 articles were selected to synthesize a comprehensive review about chronic neuropathic pain and gene therapy in order to understand the concepts and mechanisms.

RESULTS

Most of the studies have shown benefits of gene therapy in animal models, and recently, phase 1 human trials using herpes simplex virus vector have started for intractable cancer pain.

CONCLUSION

Although animal data have shown safety and efficacy, and initial human trials have been promising, additional studies in humans are required to more completely understand the actual benefits and risks of using gene therapy for the treatment of chronic neuropathic pain.

Biochemistry of the envenomation response-A generator theme for interdisciplinary integration

The understanding of complex physiological processes requires information from many different areas of knowledge. To meet this interdisciplinary scenario, the ability of integrating and articulating information is demanded. The difficulty of such approach arises because, more often than not, information is fragmented through under graduation education in Health Sciences. Shifting from a fragmentary and deep view of many topics to joining them horizontally in a global view is not a trivial task for teachers to implement. To attain that objective we proposed a course herein described-Biochemistry of the envenomation response-aimed at integrating previous contents of Health Sciences courses, following international recommendations of interdisciplinary model. The contents were organized by modules with increasing topic complexity. The full understanding of the envenoming pathophysiology of each module would be attained by the integration of knowledge from different disciplines. Active-learning strategy was employed focusing concept map drawing. Evaluation was obtained by a 30-item Likert-type survey answered by ninety students; 84% of the students considered that the number of relations that they were able to establish as seen by concept maps increased throughout the course. Similarly, 98% considered that both the theme and the strategy adopted in the course contributed to develop an interdisciplinary view.

Involvement of neuronal, inducible and endothelial nitric oxide synthases in capsaicin-induced muscle hypersensitivity

Nitric oxide, which has been implicated in the development of hyperalgesia in the spinal system, has not been systematically studied in the trigeminal system, especially in the context of inflammatory muscle pain condition. In this study, we investigated the functional role of centrally released nitric oxide in the pathogenesis of orofacial muscle pain. Specifically, we examined the contribution of neuronal, inducible and endothelial nitric oxide synthases, nNOS, iNOS and eNOS, respectively, in mediating masseter hypersensitivity under acute inflammatory condition. Time-dependent changes in nNOS, iNOS and eNOS protein expression in the subnucleus caudalis (Vc) were assessed following capsaicin injection in the masseter muscle of male Sprague Dawley rats. The expression of all three nitric oxide synthases was significantly up-regulated 30-60 min following capsaicin stimulation, which paralleled the time course of the development of capsaicin-induced masseter hypersensitivity. Pretreatment with each NOS inhibitor significantly attenuated the masseter hypersensitivity. These data showed that all three NOS in the Vc are functionally important for the development of craniofacial muscle hyperalgesia and suggest that the three NOS are closely orchestrated to regulate the level of nitric oxide under normal and pathologic conditions.

Systemic envenomation caused by the wandering spider Phoneutria nigriventer, with quantification of circulating venom

INTRODUCTION

Bites by Phoneutria spp. spiders are common in Brazil, although only 0.5-1% result in severe envenomation, with most of these occurring in children. Cases of systemic envenomation in adults are very unusual, and no serum venom levels have been previously quantified in these cases.

CASE REPORT

A 52-year-old man was bitten on the neck by an adult female Phoneutria nigriventer. Immediately after the bite, there was intense local pain followed by blurred vision, profuse sweating, tremors, and an episode of vomiting; 1-2 h post bite the patient showed agitation and a blood pressure of 200/130 mmHg, and was given captopril and meperidine. Upon admission to our service 4 h post bite (time zero - T0), his blood pressure was 130/80 mmHg with a heart rate of 150 beats/min, mild tachypnea, agitation, cold extremities, profuse sweating, generalized tremors, and priapism. The patient was treated with antivenom, local anesthetic, and fluid replacement. Most of the systemic manifestations disappeared within 1 h after antivenom. Laboratory blood analyses at T0, T1, T6, T24, and T48 detected circulating venom by ELISA only at T0, before antivenom infusion (47.5 ng/mL; cut-off, 17.1 ng/mL); his serum blood sugar was 163 mg/dL at T0. The patient was discharged on the second day with a normal arterial blood pressure and a follow-up evaluation revealed no sequelae.

CONCLUSION

This is the first report of confirmed moderate/severe envenoming in an adult caused by P. nigriventer with the quantification of circulating venom.

Involvement of spinal nitric oxide (NO) in rat pain-related behaviors induced by the venom of scorpion Buthus martensi Karsch

In the present study, we investigated the role of spinal nitric oxide (NO) in rat pain-related behaviors induced by the venom of scorpion Buthus martensi Karsch (BmK). The results showed that the number of neuronal NO synthase (nNOS) positive neurons significantly increased in superficial (I-II), deep (V-VI) dorsal horn laminae and the ventral gray laminae (VII-X), but not in the nucleus proprius (III and IV) of bilateral L4-L5 lumbar spinal cord after unilateral intraplantar injection of BmK venom from 2h to 7d. This increase on the ipsilateral side to BmK venom injection was always greater than that on the contralateral side. Western blotting analysis confirmed that spinal nNOS expression was significantly up-regulated following BmK venom administration. In addition, intrathecal delivery of N(omega)-nitro-l-arginine methyl ester hydrochloride (l-NAME; a NOS inhibitor) before intraplantar injection of BmK venom by 10 min significantly attenuated spontaneous nociceptive responses and prevented the development of primary thermal hyperalgesia as well as bilateral mechanical hyperalgesia. Intrathecal injection of l-NAME could also partially inhibit BmK venom-induced c-Fos expression in lumbar spinal cord at 2 h. Thus, the results suggest that spinal NO as a critical mediator is involved in various pain-related behaviors and c-Fos expression induced by BmK venom in rats.

Role of nitric oxide/cyclic GMP/K(+) channel pathways in the antinociceptive effect caused by 2,3-bis(mesitylseleno)propenol

The present study examined the antinociceptive effects induced by 2,3-bis(mesitylseleno)propenol, a bis-selenide alkene derivate, given orally, in chemical models of pain in rats and mice. Selenide administered orally (p.o.) into the rats caused antinociception against the first and second phases of the formalin test, with mean ID(50) values of 28.17 and 39.68 mg/kg, respectively. The antinociceptive effect caused by selenide (50 mg/kg, p.o.) on the formalin test was reversed by pretreatment with N(G)-L-nitro-arginine methyl ester (L-NAME, a nitric oxide (NO) synthase inhibitor), methylene blue (a non-specific NO/guanylyl cyclase inhibitor) and glibenclamide (an ATP-sensitive K(+) channel inhibitor), but not by atropine (a muscarinic antagonist). Given orally selenide in mice produced an inhibition of glutamate-, histamine- and compound 48/80-induced nociception with mean ID(50) values of 27.58, 36.18 and 44.53 mg/kg, respectively. Moreover, oral treatment with selenide in mice decreased licking -- induced by serotonin (mean ID(50) value of >50 mg/kg). The data show that selenide exerts pronounced systemic antinociception in chemical (formalin, glutamate, histamine, compound 48/80 and serotonin-induced pain) models of nociception. Taken together, these results suggest that the antinociceptive effect of selenide on the formalin test involves the participation of nitric oxide/cyclic GMP/K(+) channel pathways in rats.

Role of soluble guanylate cyclase in the trigeminal subnucleus caudalis in capsaicin-induced muscle hypersensitivity

Nitric oxide (NO) produces its effects by activating soluble guanylate cyclase (sGC). In the present study, we investigated the potential role of sGC in the subnucleus caudalis (Vc) in mediating masseter hypersensitivity under acute inflammatory condition in male Sprague-Dawley rats. First, our Western blot analysis revealed that sGC protein is reliably detected in the Vc. Subsequent immunohistochemical studies demonstrated that neuronal cell bodies in the superficial laminae of the Vc positively stained for sGC. Astrocytes in deeper lamina of the Vc also showed sGC immunoreactivity. We then tested whether intrathecal administration of sGC inhibitors, methylene blue (MB), and ODQ, in the Vc, attenuates masseter hypersensitivity induced by intramuscular injection of capsaicin. Intrathecal MB or ODQ significantly blocked the capsaicin-induced reduction of mechanical threshold to noxious stimulation of the masseter. These data indicate that the NO-sGC pathway in the Vc is involved in mediating orofacial muscle hypersensitivity under acute inflammatory conditions.

Acute blood-brain barrier permeabilization in rats after systemic Phoneutria nigriventer venom

A highly controlled transport of substances at the interface between blood and brain characterizes the blood-brain barrier (BBB), fundamental for maintenance of the homeostasis of the cerebral milieu. In this study, we investigated the time course (15 min, 1, 2, and 5 h) of BBB opening induced by intravenous (i.v.) injection of Phoneutria nigriventer spider venom (PNV) using quantitative and morphological approaches on cerebellum and hippocampus vessels for assessment of BBB permeability. The results showed vasogenic edema and tracer extravasation faster and severalfold higher in hippocampus than in cerebellum. Reactive astrocytes with swollen perivascular end-feet processes were found only in cerebellum. An immediate and total degradation of laminin in capillaries occurred resulting in the disappearance of the basement membrane. In medium-sized vessels, this effect was less prominent. The changes were transient, with cerebellum in general presenting a faster recovery. However, at 5 h laminin was overexpressed, principally in hippocampus. The rapid and abrupt shift of laminin expression in capillaries (at 15 min) coincided with the immediate and severe signs of intoxication shown by the animals, but not with the peak of leakage of vessels and vasogenic edema, which occurred later (1-2 h). The findings suggest a complex regulatory mechanism, since the extension of BBB impairment caused by PNV depends on the region of the SNC, and on the vessels types. It is suggested that the components of the BBB (gliovascular unit) have a critical role in these differences. P. nigriventer venom can be a useful tool to explore the mechanisms of BBB.

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.

How important are NK1 receptors for influencing microvascular inflammation and itch in the skin? Studies using Phoneutria nigriventer venom

Pain and itch sensations are induced by depolarization of C-fibre nerves and possibly other types of fibres. We have evidence from several species, including mice, that skin plasma extravasation induced by the Phoneutria nigriventer spider venom (PNV) is dependent on tachykinin NK(1) receptors. We have now investigated the itching measured as bouts of scratching in response to intradermal (i.d.) PNV in wildtype (NK(1)(+/+)) and NK(1) receptor knockout (NK(1)(-/-)) mice. Mice, either NK(1)(+/+) or NK(1)(-/-), were given a single i.d. injection (0.05 ml) of test agent or vehicle into the shaved dorsal skin, in the intercostal region, in a randomized way. The bouts of scratching were recorded in a blinded manner for 60 min. Oedema formation was concomitantly assessed by the extravascular accumulation of i.v. injected (125)I-albumin. The i.d. injection of either substance P (at a high dose of 100 nmol/site), or PNV (0.3-10 microg/site) induced oedema formation in NK(1)(+/+) but substantially less was observed in NK(1)(-/-) mice, as previously reported. PNV also induced scratching, but significantly less scratching was observed in NK(1)(-/-) compared with NK(1)(+/+) mice. In contrast, SP did not induce significant scratching at amounts up to 100 nmol in NK(1)(+/+) mice. Experiments with an NK(1) receptor antagonist SR140333 (at doses that blocked PNV-induced oedema) revealed that whilst a local co-injection i.d. (1 nmol) in NK(1)(+/+) mice had no effect on PNV (3 microg/site)-induced scratching (18.5+/-3.7 vs. 14.4+/-3.5 bouts, mean+/-S.E.M., n=5-7), systemic treatment with SR140333 (120 nmol/kg, i.v.) significantly inhibited scratching (14+/-3.5 vs. 3.1+/-1.2 bouts, n=4-6; P<0.05). These results indicate that NK(1) receptors are involved in mediating PNV-induced scratching and that the location of the receptors is unlikely to be skin. Thus, a distinct separation between endogenous microvascular and PNV nociceptive NK(1)-dependent effects is suggested.