Bradykinin is involved in hyperalgesia induced by Bothrops jararaca venom

Molecular Aspects Involved in the Mechanisms of Bothrops jararaca Venom-Induced Hyperalgesia: Participation of NK1 Receptor and Glial Cells

Accidents caused by Bothrops jararaca (Bj) snakes result in several local and systemic manifestations, with pain being a fundamental characteristic. The inflammatory process responsible for hyperalgesia induced by Bj venom (Bjv) has been studied; however, the specific roles played by the peripheral and central nervous systems in this phenomenon remain unclear. To clarify this, we induced hyperalgesia in rats using Bjv and collected tissues from dorsal root ganglia (DRGs) and spinal cord (SC) at 2 and 4 h post-induction. Samples were labeled for Iba-1 (macrophage and microglia), GFAP (satellite cells and astrocytes), EGR1 (neurons), and NK1 receptors. Additionally, we investigated the impact of minocycline, an inhibitor of microglia, and GR82334 antagonist on Bjv-induced hyperalgesia. Our findings reveal an increase in Iba1 in DRG at 2 h and EGR1 at 4 h. In the SC, markers for microglia, astrocytes, neurons, and NK1 receptors exhibited increased expression after 2 h, with EGR1 continuing to rise at 4 h. Minocycline and GR82334 inhibited venom-induced hyperalgesia, highlighting the crucial roles of microglia and NK1 receptors in this phenomenon. Our results suggest that the hyperalgesic effects of Bjv involve the participation of microglial and astrocytic cells, in addition to the activation of NK1 receptors.

Inflammatory mediators in the pronociceptive effects induced by Bothrops leucurus snake venom: The role of biogenic amines, nitric oxide, and eicosanoids

Bothrops leucurus is the major causative agent of venomous snakebites in Northeastern Brazil. Severe pain is the most frequent symptom in these envenomings, with an important inflammatory component. This work characterized the pronociceptive effects evoked by B. leucurus venom (BLV) in mice and the role of inflammatory mediators in these responses. The nociceptive behaviors were quantified by the modified formalin test. The mechanical hyperalgesia was assessed by the digital von Frey test. Pharmacological assays were performed with different antagonists and synthesis inhibitors to investigate the involvement of inflammatory mediators in both nociceptive events. BLV (1-15 μg/paw) injection in mice evoked intense and dose-dependent nociceptive behaviors that lasted for up to 1 h. BLV (10 μg/paw) also caused sustained mechanical hyperalgesia. Histamine and serotonin played a role in the nociception, but not in the BLV-induced mechanical hyperalgesia. Nitric oxide contributed to both responses, but only to the late stages of mechanical hyperalgesia. Eicosanoids were also present in both nociceptive responses. Prostanoid synthesis by COX-1 seemed to be more relevant for the nociception, whereas COX-2 had a more prominent role in the mechanical hyperalgesia. Leukotrienes were the most relevant mediators of BLV-induced mechanical hyperalgesia, hence inhibiting lipoxygenase pathway could be an efficient therapeutic strategy for pain management during envenoming. Our behavioral data demonstrates that BLV promotes nociceptive transmission mediated by biogenic amines, nitric oxide and eicosanoids, and nociceptor sensitization through nitric oxide and eicosanoids. Moreover, phospholipases A₂ (PLA₂), an important class of toxins present in bothropic venoms, appear to play an important role in the nociceptive and hypernociceptive response induced by BLV.

Effects of photobiomodulation therapy on the local experimental envenoming by Bothrops leucurus snake

Bothrops leucurus is the major causative agent of snakebites in Brazil's Northeast. The systemic effects of its venom are effectively neutralized by antivenom therapy, preventing bitten patients' death. However, antivenom fails in neutralizing local effects that include intense pain, edema, bleeding, and myonecrosis. Such effects can lead to irreversible sequels, representing a clinically relevant issue for which there is no current effective treatment. Herein, the effects of photobiomodulation therapy (PBMT) were tested in the local actions induced by B. leucurus venom (BLV) in mice (n = 123 animals in 20 experimental groups). A continuous emission AlGaAs semiconductor diode laser was used in two wavelengths (660 or 780 nm). Mechanical nociceptive thresholds were assessed with the electronic von Frey apparatus. Local edema was determined by measuring the increase in paw thickness. Hemorrhage was quantified by digital measurement of the bleeding area. Myotoxicity was evaluated by serum creatine kinase (CK) activity and histopathological analysis. PBMT promoted anti-hypernociception in BLV-injected mice; irradiation with the 660 nm laser resulted in faster effect onset than the 780 nm laser. Both laser protocols reduced paw edema formation, whether irradiation was performed immediately or half an hour after venom injection. BLV-induced hemorrhage was not altered by PBMT. Laser irradiation delayed, but did not prevent myotoxicity caused by BLV, as shown by a late increase in CK activity and histopathological alterations. PBMT was effective in the control of some of the major local effects of BLV refractory to antivenom. It is a potential complementary therapy that could be used in bothropic envenoming, minimizing the morbidity of these snakebite accidents.

Tabebuia aurea decreases hyperalgesia and neuronal injury induced by snake venom

ETHNOPHARMACOLOGICAL RELEVANCE

Tabebuia aurea (Silva Manso) Benth. & Hook. f. ex S. Moore is used as anti-inflammatory, analgesic and antiophidic in traditional medicine, though its pharmacological proprieties are still underexplored. In the bothropic envenoming, pain is a key symptom drove by an intense local inflammatory and neurotoxic event. The antivenom serum therapy is still the main treatment despite its poor local effects against pain and tissue injury. Furthermore, it is limited to ambulatorial niches, giving space for the search of new and more inclusive pharmacological approaches.

AIM OF THE STUDY

evaluation of Tabebuia aurea hydroethanolic extract (HEETa) in hyperalgesia and neuronal injury induced by Bothrops mattogrossensis venom (VBm).

MATERIALS AND METHODS

Stem barks from Tabebuia aurea were extracted with ethanol and water (7:3, v/v) to yield the extract HEETa. Then, HEETa was analyzed by LC-DAD-MS and its constituents were identified. Snake venoms were extracted from adult specimens of Bothrops mattogrossensis, lyophilized and kept at -20 °C until use. Male Swiss mice, weighting 20-25 g, were used to hyperalgesia (electronic von Frey), motor impairment (Rotarod test) and tissue injury evaluation (histopatology and ATF-3 immunohistochemistry). Therefore, three experimental groups were formed: VBm (1 pg, 1 ng, 0.3 μg, 1 μg, 3 and 6 μg/paw), HEETa orally (180, 540, 720, 810 or 1080 mg/kg; 10 mL/kg, 30 min prior VBm inoculation) and VBm neutralized (VBm: HEETa, 1:100 parts, respectively). In all set of experiments a control (saline group) was used. First, we made a dose-time-response course curve of VBm's induced hyperalgesia. Next, VBm maximum hyperalgesic dose was employed to perform HEETa orally dose-time-response course curve and analyses of VBm neutralized. Paw tissues for histopathology and DRGs were collected from animals inoculated with VBm maximum dose and treated with HEETa antihyperalgesic effective dose or neutralized VBm. Paws were extract two or 72 h after VBm inoculation and DRGs, in the maximum expected time expression of ATF-3 (72 h).

RESULTS

From HEETa extract, glycosylated iridoids were identified, such as catalpol, minecoside, verminoside and specioside. VBm induced a time and dose dependent hyperalgesia with its highest effect seen with 3 µg/paw, 2 h after venom inoculation. HEETa effective dose (720 mg/kg) decreased significantly VBm induced hyperalgesia (3 µg/paw) with no motor impairment and signs of acute toxicity. HEETa antihyperalgesic action starts 1.5 h after VBm inoculation and lasted up until 2 h after VBm. Hyperalgesia wasn't reduced by VBm: HEETa neutralization. Histopathology revealed a large hemorragic field 2 h after VBm inoculation and an intense inflammatory infiltrate of polymorphonuclear cells at 72 h. Both HEETa orally and VBm: HEETa groups had a reduced inflammation at 72 h after VBm. Also, the venom significantly induced ATF-3 expression (35.37 ± 3.25%) compared with saline group (4.18 ± 0.68%) which was reduced in HEETa orally (25.87 ± 2.57%) and VBm: HEETa (19.84 ± 2.15%) groups.

CONCLUSION

HEETa reduced the hyperalgesia and neuronal injury induced by VBm. These effects could be related to iridoid glycosides detected in HEETa and their intrinsic reported mechanism.

Pain-like behaviors and local mechanisms involved in the nociception experimentally induced by Latrodectus curacaviensis spider venom

The present study was undertaken to characterize the behavioral manifestations of nociception and the local mechanisms involved with the nociceptive response elicited by Latrodectus curacaviensis venom (LCV) in mice. After the intraplantar LCV inoculation, spontaneous nociception, mechanical and thermal nociceptive thresholds, motor performance, edema and cytokine levels were evaluated using von Frey filaments, hot/cold plate, rota-rod, plethismometer and ELISA, respectively. Analysis of LCV was performed by SDS-PAGE and chromatography. Intraplantar injection of LCV (1-100 ng/paw) induced intense and heat-sensitive spontaneous nociception, mediated by serotonin and bradykinin receptors, TRPV1 channels, as well as by transient local inflammation. LCV (0.1-10 ng/paw) induced mechanical allodynia, which was reduced by the local pretreatment with H1 receptor or TRPV1 antagonists. Corroborating the TRPV1 involvement, in thermal nociception assays, LCV induced a similar response to that of capsaicin, a TRPV1 agonist, facilitating the response to noxious hot stimuli and inhibiting the response to cold noxious stimulation. LCV promoted mast cell degranulation, increased IL-1β paw levels, but did not produce a relevant edematogenic effect. Analysis of LCV components showed a predominance of high molecular weight proteins. This work provides the first mechanistic hypothesis to explain the local pain induced by LCV, the most frequent clinical symptom of human envenomation.

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.

Secreted Phospholipases A₂ from Animal Venoms in Pain and Analgesia

Animal venoms comprise a complex mixture of components that affect several biological systems. Based on the high selectivity for their molecular targets, these components are also a rich source of potential therapeutic agents. Among the main components of animal venoms are the secreted phospholipases A₂ (sPLA₂s). These PLA₂ belong to distinct PLA₂s groups. For example, snake venom sPLA₂s from Elapidae and Viperidae families, the most important families when considering envenomation, belong, respectively, to the IA and IIA/IIB groups, whereas bee venom PLA₂ belongs to group III of sPLA₂s. It is well known that PLA₂, due to its hydrolytic activity on phospholipids, takes part in many pathophysiological processes, including inflammation and pain. Therefore, secreted PLA₂s obtained from animal venoms have been widely used as tools to (a) modulate inflammation and pain, uncovering molecular targets that are implicated in the control of inflammatory (including painful) and neurodegenerative diseases; (b) shed light on the pathophysiology of inflammation and pain observed in human envenomation by poisonous animals; and, (c) characterize molecular mechanisms involved in inflammatory diseases. The present review summarizes the knowledge on the nociceptive and antinociceptive actions of sPLA₂s from animal venoms, particularly snake venoms.

Edema and Nociception Induced by Philodryas patagoniensis Venom in Mice: A Pharmacological Evaluation with Implications for the Accident Treatment

We have investigated the mechanisms involved in the genesis of edema and nociception induced by Philodryas patagoniensis venom (PpV) injected into the footpad of mice. PpV induced dose-related edema and nociceptive effects. Pretreatment of mice with cyclooxygenase inhibitor (indomethacin), but not with cyclooxygenase 2 inhibitor (celecoxib) markedly inhibited both effects. Pretreatments with H₁ receptor antagonist (promethazine) or with dual histamine-serotonin inhibitor (cyproheptadine) failed in inhibiting both effects. In groups pretreated with captopril (angiotensin-converting enzyme inhibitor) the edema was unaltered, but nociception was clearly increased, suggesting the participation of kinins in the pathophysiology of the nociception but not of the edema-forming effect of PpV. When PpV was treated with EDTA, the nociception was similar to the one induced by untreated venom, but edema was markedly reduced. We concluded that PpV-induced edema and nociception have cyclooxygenase eicosanoids as the main mediators and no participation of vasoactive amines. Kinins seem to participate in nociception but not in edema induced by PpV. The results also suggest that metalloproteinases are the main compounds responsible for the edema, but not for the nociception induced by this venom.

JA, Zamuner SR. Analgesic Effect of Photobiomodulation on Bothrops Moojeni Venom-Induced Hyperalgesia: A Mechanism Dependent on Neuronal Inhibition, Cytokines and Kinin Receptors Modulation

Background

Envenoming induced by Bothrops snakebites is characterized by drastic local tissue damage that involves an intense inflammatory reaction and local hyperalgesia which are not neutralized by conventional antivenom treatment. Herein, the effectiveness of photobiomodulation to reduce inflammatory hyperalgesia induced by Bothrops moojeni venom (Bmv), as well as the mechanisms involved was investigated.

Methodology/Principal Findings

Bmv (1 μg) was injected through the intraplantar route in the right hind paw of mice. Mechanical hyperalgesia and allodynia were evaluated by von Frey filaments at different time points after venom injection. Low level laser therapy (LLLT) was applied at the site of Bmv injection at wavelength of red 685 nm with energy density of 2.2 J/cm² at 30 min and 3 h after venom inoculation. Neuronal activation in the dorsal horn spinal cord was determined by immunohistochemistry of Fos protein and the mRNA expression of IL-6, TNF-α, IL-10, B1 and B2 kinin receptors were evaluated by Real time-PCR 6 h after venom injection. Photobiomodulation reversed Bmv-induced mechanical hyperalgesia and allodynia and decreased Fos expression, induced by Bmv as well as the mRNA levels of IL-6, TNF-α and B1 and B2 kinin receptors. Finally, an increase on IL-10, was observed following LLLT.

Conclusion/Significance

These data demonstrate that LLLT interferes with mechanisms involved in nociception and hyperalgesia and modulates Bmv-induced nociceptive signal. The use of photobiomodulation in reducing local pain induced by Bothropic venoms should be considered as a novel therapeutic tool for the treatment of local symptoms induced after bothropic snakebites.

Envenoming caused by Bothrops snakes is characterized by drastic local tissue damage involving hemorrhage, blistering, myonecrosis, prominent inflammatory response and intense pain. The most effective treatment for Bothrops snakebites is antivenom therapy, which is very efficient in reversing systemic effects of envenomation but not the severe local effects. Thus, there exists a need to find novel complementary therapies that may further assist in the prevention or even counteract the severe local effects of bothrops snakebite. Several studies have shown the effectiveness of photobiomodulation in reducing local effects induced by Bothropic venoms, however its mechanisms still remain unknown. In this study, we analyzed the effectiveness of photobiomodulation in reducing BmV-induced mechanical allodynia and hyperalgesia as well as part of the mechanisms involved in such effect. Results demonstrate that photobiomodulation reduces venom-induced mechanical allodynia and hyperalgesia and this effect depends on a decrease of nociceptor activation at the spinal cord level and by a modulation of pro- and anti- inflammatory cytokines as well as kinin receptors at mRNA transcriptional levels. These findings make phtobiomodulation a promising candidate to be associated to antivenom therapy for the treatment of the local response induced by Bothrops venoms.

Involvement of circulating platelets on the hyperalgesic response evoked by carrageenan and Bothrops jararaca snake venom

BACKGROUND

The role of platelets in hemostasis is well known, but few papers have reported their role in pain and edema induced by inflammatory agents.

OBJECTIVE

To evaluate the role of circulating platelets in the local injury induced by two diverse inflammatory agents, Bothrops jararaca venom (Bjv) and carrageenan.

METHODS

Rats were (i) rendered thrombocytopenic by administration of polyclonal anti-rat platelet IgG (ARPI) or busulfan, or (ii) treated with platelet inhibitors (aspirin or clopidogrel). Edema formation, local hemorrhage and the pain threshold were assessed after intraplantar injection of Bjv or carrageenan in rat hind paws. Additionally, whole platelets or platelet releasate were tested whether they directly induced hyperalgesia.

RESULTS

Platelet counts were markedly diminished in rats administered with either ARPI (± 88%) or busulfan (± 96%). Previous treatment with ARPI or busulfan slightly reduced edema induced by Bjv or carrageenan. Injection of Bjv, but not of carrageenan, induced a statistically significance increase in hemorrhage in the hind paws of thrombocytopenic rats. Remarkably, hyperalgesia evoked by Bjv or carrageenan was completely blocked in animals treated with ARPI or busulfan, or pre-treated with aspirin or clopidogrel. On the other hand, intraplantar administration of whole platelets or platelet releasate evoked hyperalgesia, which was inhibited by pre-incubation with alkaline phosphatase.

CONCLUSIONS

Thrombocytopenia or inhibition of platelet function drastically reduced hyperalgesia induced by injection of carrageenan or Bjv; moreover, platelets per se secrete phosphorylated compounds involved in pain mediation. Thus, blood platelets are crucial cells involved in the pain genesis, and their role therein has been underestimated.

Contribution of mast cells and snake venom metalloproteinases to the hyperalgesia induced by Bothrops jararaca venom in rats

Bothrops jararaca venom (Bjv) is known to induce local inflammation and severe pain. Since, mast cells are able to secrete mediators involved in algesic processes, in this study we examined the putative role of these cells in the hyperalgesia triggered by Bjv in the rat paw. We noted that treatment with mast cell stabilizer sodium cromoglicate as well as with histamine and 5-hydroxytriptamine receptor antagonists meclizine and methysergide, respectively, inhibited the Bjv-induced hyperalgesia. In addition, we showed that stimulation of isolated rat peritoneal mast cells with Bjv in vitro resulted in the release of stored and neo-generated inflammatory mediators such as histamine and leukotriene C(4), respectively. Bjv-induced histamine secretion was clearly sensitive to treatment with sodium cromoglicate and sodium nedocromil. We further observed that metalloproteinase inhibitors 1,10-phenantroline and DM43 inhibited mast cell degranulation in vitro, under conditions where inhibitors of phospholipase A(2) as well as of serine- and cysteine-proteinases were inactive. Altogether, our findings indicate that mast cells seem to contribute to the hyperalgesia caused by Bjv in the rat paw, and also provide evidence that this response might be dependent on the ability of the Bjv to activate directly mast cells.

Snake venom components enhance pain upon subcutaneous injection: an initial examination of spinal cord mediators

Snakebites are a relevant public health problem in Central and South America. Snake bite envenomations cause intense pain, not relieved by anti-venom. The fangs of many species are short, causing subcutaneous injection. Fangs of larger species inflict subcutaneous or intramuscular envenomation. To understand pain induced by subcutaneous venom, this study examined spinal mechanisms involved in pain-enhancing effects of subcutaneous Lys49 and Asp49 secretory phospholipase-A(2) (sPLA2), two components of Bothrops asper snake venom showing highly different enzymatic activities. Unilateral intraplantar sPLA2-Lys49 (catalytically inactive) or sPLA2-Asp49 (catalytically active) into rat hindpaws each induced mechanical hyperalgesia (Randall-Selitto test), whereas only catalytically active sPLA2-Asp49 caused mechanical allodynia (von Frey test). Effects induced by both sPLA2s were inhibited by intrathecal fluorocitrate, a reversible glial metabolic inhibitor. In support, immunohistochemical analysis revealed activation of dorsal horn astrocytes and microglia after intraplantar injection of either sPLA2. Spinal proinflammatory cytokines, nitric oxide, and prostanoids each appear to be involved in the pain-enhancing effects of these sPLA2s. Blockade of interleukin-1 (IL1) inhibited hyperalgesia induced by both sPLA2s, while leaving allodynia unaffected. Blockade of tumor necrosis factor reduced responses to sPLA2-Asp49. An inhibitor of neuronal nitric oxide synthase, 7-nitroindazole (7-NI), inhibited hyperalgesia induced by both sPLA2s, without interfering with allodynia induced by sPLA2-Asp49. On the other hand, L-N(6)-(1-iminoethyl)lysine (L-NI), an inhibitor of the inducible nitric oxide synthase, did not alter any sPLA2-induced effect. Lastly, celecoxib, an inhibitor of cyclooxygenase-2, attenuated sPLA2 actions. These data provide the first evidence of spinal mediators involved in pain facilitation induced by subcutaneous venoms.

Snake venom phospholipase A2s (Asp49 and Lys49) induce mechanical allodynia upon peri-sciatic administration: involvement of spinal cord glia, proinflammatory cytokines and nitric oxide

Snakebites constitute a serious public health problem in Central and South America, where species of the lancehead pit vipers (genus Bothrops) cause the majority of accidents. Bothrops envenomations are very painful, and this effect is not neutralized by antivenom treatment. Two variants of secretory phospholipases A2 (sPLA2), corresponding to Asp49 and Lys49 PLA2s, have been isolated from Bothrops asper venom. These sPLA2s induce hyperalgesia in rats following subcutaneous injection. However, venom in natural Bothrops bites is frequently delivered intramuscularly, thereby potentially reaching peripheral nerve bundles. Thus, the present series of experiments tested whether these sPLA2s could exert pain-enhancing effects following administration around healthy sciatic nerve. Both were found to produce mechanical allodynia ipsilateral to the injection site; no thermal hyperalgesia was observed. As no prior study has examined potential spinal mechanisms underlying sPLA2 actions, a series of anatomical and pharmacological studies were performed. These demonstrated that both sPLA2s produce activation of dorsal horn astrocytes and microglia that is more prominent ipsilateral to the site of injection. As proinflammatory cytokines and nitric oxide have each been previously implicated in spinally mediated pain facilitation, the effect of pharmacological blockade of these substances was tested. The results demonstrate that mechanical allodynia induced by both sPLA2s is blocked by interleukin-1 receptor antagonist, anti-rat interleukin-6 neutralizing antibody, the anti-inflammatory cytokine interleukin-10, and a nitric oxide synthesis inhibitor (L-NAME). As a variety of immune cells also produce and release sPLA2s during inflammatory states, the data may have general implications for the understanding of inflammatory pain.

The C-terminus of murine S100A9 inhibits hyperalgesia and edema induced by jararhagin

The effect of a synthetic peptide (H92-G110) identical to the C-terminus of murine S100A9 (mS100A9p) was investigated on hyperalgesia and edema induced by either jararhagin or papain in the rat paw. mS100A9p not only reverted hyperalgesia and edema induced by jararhagin, but also the highest concentration induced antinociception. Hemorrhage induced by jararhagin and its hydrolytic activity were inhibited by mS100A9p. These data suggest that mS100A9p might block jararhagin-induced hyperalgesia and edema by inhibiting jararhagin catalytic activity, since papain-induced hyperalgesia and edema were not inhibited by mS100A9p.