Acanthocytosis and brain damage in area postrema and choroid plexus: Description of novel signs of Loxosceles apachea envenomation in rats

Loxocelism is a neglected medical problem that depends on its severity, can cause a cutaneous or viscero-cutaneous syndrome. This syndrome is characterized by hemostatic effects and necrosis, and the severity of the loxoscelism depends on the amount of venom injected, the zone of inoculation, and the species. In the Chihuahuan desert, the most abundant species is L. apachea. Its venom and biological effects are understudied, including neurological effects. Thus, our aim is to explore the effect of this regional species of medical interest in the United States-Mexico border community, using rat blood and central nervous system (CNS), particularly, two brain structures involved in brain homeostasis, Area postrema (AP) and Choroid plexus (PC). L. apachea specimens were collected and venom was obtained. Different venom concentrations (0, 0.178 and 0.87 μg/g) were inoculated into Sprague-Dawley rats (intraperitoneal injection). Subsequently, blood was extracted and stained with Wright staining; coronal sections of AP were obtained and stained with Hematoxylin-Eosin (HE) staining and laminin γ immunolabelling, the same was done with CP sections. Blood, AP and CP were observed under the microscope and abnormalities in erythrocytes and fluctuation in leukocyte types were described and quantified in blood. Capillaries were also quantified in AP and damage was described in CP. L. apachea venom produced a segmented neutrophil increment (neutrophilia), lymphocyte diminishment (leukopenia) and erythrocytes presented membrane abnormalities (acanthocytosis). Extravasated erythrocytes were observed in HE stained sections from both, AP and CP, which suggest that near to this section a hemorrhage is present; through immunohistofluorescence, a diminishment of laminin γ was observed in AP endothelial cells and in CP ependymal cells when these structures were exposed to L. apachea venom. In conclusion, L. apachea venom produced leukopenia, netrophilia and acanthocytosis in rat peripheral blood, and also generated hemorrhages on AP and CP through degradation of laminin γ.

Age-Related Modulations of AQP4 and Caveolin-1 in the Hippocampus Predispose the Toxic Effect of Phoneutria nigriventer Spider Venom

We have previously demonstrated that Phoneutria nigriventer venom (PNV) causes blood–brain barrier (BBB) breakdown, swelling of astrocytes end-feet and fluid permeation into brain interstitium in rats. Caveolae and water channels respond to BBB alterations by co-participation in shear stress response and edema formation/resolution. Herein, we showed post-natal developmental-related changes of two BBB-associated transporter proteins: the endothelial caveolin-1 (Cav-1), the major scaffolding protein from caveolae frame, and the astroglial aquaporin-4 (AQP4), the main water channel protein expressed in astrocytic peri-vascular end-feet processes, in the hippocampus of rats intraperitoneally-administered PNV. Western blotting protein levels; immunohistochemistry (IHC) protein distribution in CA1, CA2, and CA3 subfields; and gene expression by Real Time-Polymerase Chain Reaction (qPCR) were assessed in post-natal Day 14 (P14) and 8–10-week-old rats over critical periods of envenomation. The intensity and duration of the toxic manifestations indicate P14 neonate rats more vulnerable to PNV than adults. Histologically, the capillaries of P14 and 8–10-week-old rats treated with PNV showed perivascular edema, while controls did not. The intensity of the toxic manifestations in P14 decreases temporally (2 > 5 > 24 h), while inversely the expression of AQP4 and Cav-1 peaked at 24 h when clinically PNV-treated animals do not differ from saline controls. IHC of AQP4 revealed that hippocampal CA1 showed the least expression at 2 h when toxic manifestation was maximal. Subfield IHC quantification revealed that in P14 rats Cav-1 peaked at 24 h when toxic manifestations were absent, whereas in 8–10-week-old rats Cav-1 peaked at 2 h when toxic signs were highest, and progressively attenuated such increases until 24 h, remaining though significantly above baseline. Considering astrocyte-endothelial physical and functional interactions, we hypothesize that age-related modulations of AQP4 and Cav-1 might be linked both to changes in functional properties of astrocytes during post-natal development and in the BBB breakdown induced by the venom of P. nigriventer.

Cry1Ab-expressing rice did not influence expression of fecundity-related genes in the wolf spider Pardosa pseudoannulata

The impact of Bacillus thuringiensis (Bt) toxin proteins on non-target predatory arthropods is not well understood at the cellular and molecular levels. Here, we investigated the potential effects of Cry1Ab expressing rice on fecundity of the wolf spider, Pardosa pseudoannulata, and some of the underlying molecular mechanisms. The results indicated that brown planthoppers (BPHs) reared on Cry1Ab-expressing rice accumulated the Cry toxin and that reproductive parameters (pre-oviposition period, post-oviposition stage, number of eggs, and egg hatching rate) of the spiders that consumed BPHs reared on Bt rice were not different from those that consumed BPHs reared on the non-Bt control rice. The accumulated Cry1Ab did not influence several vitellin (Vt) parameters, including stored energy and amino acid composition, during one generation. We considered the possibility that the Cry toxins exert their influence on beneficial predators via more subtle effects detectable at the molecular level in terms of gene expression. This led us to transcriptome analysis to detect differentially expressed genes in the ovaries of spiders exposed to dietary Cry1Ab and their counterpart control spiders. Eight genes, associated with vitellogenesis, vitellogenin receptor activity, and vitellin membrane formation were not differentially expressed between ovaries from the treated and control spiders, confirmed by qPCR analysis. We infer that dietary Cry1Ab expressing rice does not influence fecundity, nor expression levels of Vt-associated genes in P. pseudoannulata.

Peptidomics of Acanthoscurria gomesiana spider venom reveals new toxins with potential antimicrobial activity

Acanthoscurria gomesiana is a Brazilian spider from the Theraphosidae family inhabiting regions of Southeastern Brazil. Potent antimicrobial peptides as gomesin and acanthoscurrin have been discovered from the spider hemolymph in previous works. Spider venoms are also recognized as sources of biologically active peptides, however the venom peptidome of A. gomesiana remained unexplored to date. In this work, a MS-based workflow was applied to the investigation of the spider venom peptidome. Data-independent and data-dependent LC-MS/MS acquisitions of intact peptides and of peptides submitted to multiple enzyme digestions, followed by automated chromatographic alignment, de novo analysis, database and homology searches with manual validations showed that the venom is composed by <165 features, with masses ranging from 0.4-15.8kDa. From digestions, 135 peptides were identified from 17 proteins, including three new mature peptides: U1-TRTX-Agm1a, U1-TRTX-Agm2a and U1-TRTX-Agm3a, containing 3, 4 and 3 disulfide bonds, respectively. The toxins U1-TRTX-Agm1a differed by only one amino acid from U1-TRTX-Ap1a from A. paulensis and U1-TRTX-Agm2a was derived from the genicutoxin-D1 precursor from A. geniculata. These toxins have potential applications as antimicrobial agents, as the peptide fraction of A. gomesiana showed activity against Escherichia coli, Enterobacter cloacae and Candida albicans strains. MS data are available via ProteomeXchange Consortium with identifier PXD003884.

BIOLOGICAL SIGNIFICANCE

Biological fluids of the Acanthoscurria gomesiana spider are sources of active molecules, as is the case of antimicrobial peptides and acylpolyamines found in the hemolymphs. The venom is also a potential source of toxins with pharmacological and biotechnological applications. However, to our knowledge no A. gomesiana venom toxin structure has been determined to date. Using a combination of high resolution mass spectrometry, transcriptomics and bioinformatics, we employed a workflow to fully sequence, determine the number of disulfide bonds of mature peptides and we found new potential antimicrobial peptides. This workflow is suitable for complete peptide toxin sequencing when handling limited amount of venom samples and can accelerate the discovery of peptides with potential biotechnological applications.

Generalized vasculitic exanthem following Loxosceles reclusa envenomation

Brown recluse spider bites (BRSB) cause a myriad of reactions ranging from local necrosis to potentially lethal systemic involvement. Envenomation may induce a generalized exanthem known clinically but not described histologically. We report a 49-year-old female who developed a generalized exanthem 24 hours after BRSB. The histopathology demonstrated a necrotizing vasculitis similar to that seen at an envenomation site but without epidermal necrosis. Loxoscelism should be considered in patients residing in endemic areas who present with a vasculitic exanthem.

Epidemiological and clinical manifestations of patients hospitalized with brown recluse spider bite

BACKGROUND

Necrotic arachnidism represents a common health problem and standard treatments are usually safe and effective.

OBJECTIVE

The aim of this study was to review documented Loxosceles species spider envenomations and identify the natural history of affected patients.

METHODS

A retrospective single-centre study included 52 patients with necrotic arachnidism hospitalized in the dermatology department between 1997 and 2004. We examined the relationship between the epidemiological, clinical and laboratory parameters and degree of lesion severity, length of hospitalization and time to complete healing.

RESULTS

The bites occurred predominantly in rural areas, 67% between April and August. Only 35% of the patients sought medical care within 24 h post bite. Most bites were of the extremities (67%). Time to complete healing ranged from 14 days to more than 8 weeks (mean, 4.8 weeks). A marked relationship was found between age, comorbidities, lesion severity and time to complete healing (P < 0.01). Duration of hospitalization was significantly longer in patients with severe thigh lesions (P < 0.02).

CONCLUSIONS

Loxosceles species spider bites frequently induce necrotic, slowly healing ulcers on the fatty areas of the body. Early, appropriate systemic therapy may provide clinical benefit.

Verified bites by yellow sac spiders (genus Cheiracanthium) in the United States and Australia: where is the necrosis?

Spiders of the genus Cheiracanthium are frequently reported in review articles and medical references to be a definitive cause of dermonecrosis or necrotic arachnidism in humans. We provide 20 cases of verified bites by Cheiracanthium spiders from the United States and Australia, none with necrosis. A review of the international literature on 39 verified Cheiracanthium bites found only one case of mild necrosis in the European species C. punctorium. The basis for the suggestion that this spider genus causes dermonecrosis seems to be mostly inference from venom experiments in rabbits and guinea pigs, circumstantial spider involvement in human skin lesions, and repetitive citation of non-definitive reports in the medical literature. We discuss factors that lead to the erroneous elevation of virtually innocuous spiders to that of significant medical concern, which is a recurring problem in the medical community.

Host selection by a kleptobiotic spider

Why do kleptobiotic spiders of the genus Argyrodes seem to be associated with spiders of the genus Nephila worldwide? Observations following introduction of experimental insect prey of different sizes and weights on to host webs revealed that: (1) small prey are more effectively retained on the web of Nephila clavipes than on the web of another common host, Leucauge venusta. (2) N. clavipes did not consume small prey that accumulated on the web whereas larger, heavier prey were enveloped and stored. (3) We observed clear partitioning of prey items between N. clavipes and Argyrodes spp.; diet selection by Argyrodes did not overlap with that of N. clavipes but closely overlapped with that of L. venusta. (4) L. venusta responds very quickly to prey impact whereas N. clavipes is slower, offering a temporal window of opportunity for Argyrodes foraging. (5) The ability of L. venusta to detect and respond to small items also means that it acts aggressively to Argyrodes spp., whereas N. clavipes does not. Consequently, food-acquisition behaviours of Argyrodes were clearly less risky with N. clavipes compared with L. venusta. We conclude that when a kleptobiotic organism has a choice of various host species, it will opt for the least risky host that presents the highest rate of availability of food items. The fact that Nephila species present such characteristics explains the worldwide association with Argyrodes kleptobiotic spiders.

Diagnoses of brown recluse spider bites (loxoscelism) greatly outnumber actual verifications of the spider in four western American states

We attempt to demonstrate that physicians overdiagnose loxoscelism (colloquially known as 'brown recluse spider bites') by comparing the numbers of such diagnoses to the historically known numbers of Loxosceles spiders from the same areas in four western American states. The medical community from non-endemic Loxosceles areas often makes loxoscelism diagnoses solely on the basis of dermonecrotic lesions where Loxosceles spiders are rare or non-existent. If these diagnoses were correct then Loxosceles populations should be evident, specimens should readily be collected over the years and there should be a reasonable correlation between diagnoses and spider specimens. In 41 months of data collection, we were informed of 216 loxoscelism diagnoses from California, Oregon, Washington and Colorado. In contrast, from these four states, we can only find historical evidence of 35 brown recluse or Mediterranean recluse spiders. There is no consistency between localities of known Loxosceles populations and loxoscelism diagnoses. There are many conditions of diverse etiology that manifest in dermonecrosis. In the western United States, physician familiarity with these conditions will lead to more accurate diagnoses and subsequent proper remedy.

Latrodectism: a prospective cohort study of bites by formally identified redback spiders

OBJECTIVE

To determine the spectrum of severity and early diagnostic predictors of redback spider bites (Latrodectus hasselti), and to examine the effect of intramuscular redback antivenom.

DESIGN AND SETTING

Prospective cohort study of calls to New South Wales, Queensland and Western Australian poisons information centres and presentations to Royal Prince Alfred Hospital and Royal Darwin Hospital emergency departments.

PATIENTS

68 people with definite redback spider bites in which the spider was immediately collected and expertly identified (1 February 1999 to 30 April 2002).

INTERVENTIONS

Intramuscular redback spider antivenom in a smaller cohort of hospitalised patients.

MAIN OUTCOME MEASURES

Pain severity and duration, local effects and systemic envenomation (effects, prevalence, and persistence > 24 hours).

RESULTS

The median duration of effects was 48 hours (interquartile range, 24-96 hours). Pain occurred after all bites and was severe in 42 (62%). Forty-five patients (66%) had pain lasting longer than 24 hours, and 22 (32%) were unable to sleep because of pain. Systemic effects occurred in 24 (35%). Increasing pain over one hour occurred in 37 cases (54%), and local/regional diaphoresis in 23 (34%); both these features were highly predictive of L. hasselti bites compared with bites of other spiders. One of six patients treated with intramuscular antivenom (17%) had no pain at 24 hours, compared with two of 17 untreated patients (12%) (difference, 5%; 95% CI, -36% to +64%; P = 0.95). There was no difference in duration of systemic effects with antivenom administration.

CONCLUSIONS

Most redback spider bites cause severe and persistent effects. Intramuscular antivenom appears to be less effective than previously thought and its use by this route needs review.

Brown recluse spiders: a review to help guide physicians in nonendemic areas

The brown recluse spider (Loxosceles reclusa) exists in significant populations mainly in the midwestern United States. Although bites can cause significant harm, envenomation is infrequent, and cases are usually clinically insignificant. Proper knowledge of the spider's habitat and lifestyle as well as the signs and symptoms of loxoscelism are needed to assess clinical cases adequately. Loxoscelism can masquerade as many serious pathologies, and vice versa, so it is important for the clinician to explore all possibilities in the differential diagnosis thoroughly. Treatments are controversial, and no conclusive test for envenomation is currently available. This review provides information to help physicians, especially in nonendemic areas, include or exclude brown recluse bite in the clinical diagnosis and provide proper care.

Distribution of the medically-implicated hobo spider (Araneae: Agelenidae) and a benign congener, Tegenaria duellica, in the United States and Canada

The hobo spider, Tegenaria agrestis (Walckenaer), and the related Tegenaria duellica Simon are very similar European spiders that have become well established in the northwestern United States and British Columbia. The hobo spider is considered to be medically important; T. duellica is considered harmless but is often misidentified as the hobo spider. The current distribution of the hobo spider includes southern British Columbia, Washington, Oregon, Idaho, northern Utah, the western half of Montana, western Wyoming, and two small, isolated populations in Colorado. T. duellica is found mostly west of the Cascade and Coastal mountain ranges from southern British Columbia to central Oregon. In large human population centers where both species are sympatric, T. duellica is usually more common than the hobo spider. Data from a total of 1,232 hobo spiders and 395 T. duellica are included in this study.

Molecular cloning and expression of a functional dermonecrotic and haemolytic factor from Loxosceles laeta venom

The bite of spiders of the genus Loxosceles can induce a variety of biological effects, including dermonecrosis and complement-dependent haemolysis. The aim of this study was to generate recombinant proteins from the Loxosceles spider gland to facilitate structural and functional studies in the mechanisms of loxoscelism. Using "Expressed Sequencing Tag" strategy of aleatory clones from, L. laeta venom gland cDNA library we have identified clones containing inserts coding for proteins with significant similarity with previously obtained N-terminus of sphingomyelinases from Loxosceles intermedia venom [1]. Clone H17 was expressed as a fusion protein containing a 6x His-tag at its N-terminus and yielded a 33kDa protein. The recombinant protein was endowed with all biological properties ascribed to the whole L. laeta venom and sphingomyelinases from L. intermedia, including dermonecrotic and complement-dependent haemolytic activities. Antiserum raised against the recombinant protein recognised a 32-kDa protein in crude L. laeta venom and was able to block the dermonecrotic reaction caused by whole L. laeta venom. This study demonstrates conclusively that the sphingomyelinase activity in the whole venom is responsible for the major pathological effects of Loxosceles spider envenomation.