ADP is a vasodilator component from Lasiodora sp. mygalomorph spider venom

Taxonomic revision and cladistic analysis of Lasiodora C. L. Koch, 1850 (Araneae, Theraphosidae) with notes on related genera

The genus Lasiodora C. L. Koch, 1850 is revised and morphological cladistic analyses carried out including all of its species, as well as most of those of the related genera Vitalius Lucas, Silva & Bertani, 1993, Nhandu Lucas, 1983, Pterinopelma Pocock, 1901, Proshapalopus Mello-Leito, 1923, Eupalaestrus Pocock, 1901, Lasiocyano Galleti-Lima, Hamilton, Borges & Guadanucci, 2023, Parvicarina Galleti-Lima, Hamilton, Borges & Guadanucci, 2023, and Tekoapora Galleti-Lima, Hamilton, Borges & Guadanucci, 2023. A matrix with 50 terminal taxa, 2 continuous and 48 discrete characters was analyzed with TNT 1.5. The result shows a monophyletic Lasiodora as sister group of Nhandu, and Vitalius is the sister group of this clade. Lasiodora comprises 7 species: Lasiodora klugi (C. L. Koch, 1841) (type species), L. benedeni Bertkau, 1880, L. parahybana Mello-Leito, 1917, L. subcanens Mello-Leito, 1921, L. camurujipe n. sp., L. sertaneja n. sp., and L. franciscana n. sp. Lasiodora itabunae Mello-Leito, 1921 is considered a junior synonym of L. klugi. Lasiodora differens Chamberlin, 1917, L. curtior Chamberlin, 1917, L. mariannae Mello-Leito, 1921, L. difficilis Mello-Leito, 1921, L. erythrocythara Mello-Leito, 1921, and Acanthoscurria cristata Mello-Leito, 1923 are considered junior synonyms of L. benedeni. Lasiodora acanthognatha Mello-Leito, 1921 is considered junior synonym of L. parahybana. Lasiodora dulcicola Mello-Leito, 1921 is considered junior synonym of L. subcanens. Nhandu sylviae Sherwood, Gabriel & Brescovit, 2023 is considered junior synonym of Vitalius sorocabae Mello-Leito, 1923. The holotype of Crypsidromus isabellinus Ausserer, 1871 (type species of the genus) was reanalyzed and is considered the senior synonym of Proshapalopus anomalus Mello-Leito, 1923 (type species of the genus). Thus, the genus Crypsidromus Ausserer, 1871 is considered valid, removed from the synonymy with Lasiodora, and Proshapalopus is considered a junior synonym of Crypsidromus. The new combination C. multicuspidatus (Mello-Leito, 1929) n. comb. is established. Crypsidromus bolivianus Simon, 1892 is considered a junior synonym of Acanthoscurria insubtilis Simon, 1892. Five species from Costa Rica described in Crypsidromus are transferred back from Lasiodora: Crypsidromus brevibulbus Valerio, 1980 comb. rev., C. carinatus Valerio, 1980 comb. rev., C. icecu Valerio, 1980 comb. rev., C. puriscal Valerio, 1980 comb. rev., C. rubitarsus Valerio, 1980 comb. rev. Lasiodora lakoi Mello-Leito, 1943 is transferred to Megaphobema, making the new combination Megaphobema lakoi (Mello-Leito, 1943) n. comb. Lasiodora spinipes Ausserer, 1871 is transferred to Theraphosa, making the new combination Theraphosa spinipes (Ausserer, 1871) n. comb. Nhandu chromatus Schmidt, 2004 is transferred to Vitalius making the new combination Vitalius chromatus (Schmidt, 2004) n. comb. Lasiodora sternalis is transferred to Acanthoscurria making the new combination Acanthoscurria sternalis (Mello-Leito, 1923). Due to the homonymy with Acanthoscurria sternalis Pocock, 1903, the new name Acanthoscurria melloleitaoi nom. nov. is proposed. The following species are considered nomina dubia: Lasiodora saeva (Walckenaer, 1837), Lasiodora striatipes (Ausserer, 1871), Lasiodora moreni (Holmberg, 1876), Crypsidromus fallax Bertkau, 1880, Trechona pantherina Keyserling, 1891, Lasiodora bahiensis Strand, 1907, Lasiodora citharacantha Mello-Leito, 1921, Lasiodora cryptostigma Mello-Leito, 1921, Lasiodora dolichosterna Mello-Leito, 1921, Lasiodora fracta Mello-Leito, 1921, and Lasiodora pleoplectra Mello-Leito, 1921. A discussion on the relationship of Lasiodora, Nhandu, Vitalius, Pterinopelma and Crypsidromus as well maps with the distributions of all Lasiodora species are provided.

Vasodilator activity of Poecilotheria ornata venom involves activation of the NO/cGMP pathway and inhibition of calcium influx to vascular smooth muscle cells

Tarantula venoms may be a natural source of new vasodilator components useful in pharmacological research. Moreover, biological function data of the venoms are important to enhance the knowledge about the biodiversity and evolution of these species. The present study aims to describe the vasodilatory activity induced by the venom of Poecilotheria ornata on isolated rat aortic rings. This venom induced a vasodilator activity that was significantly reduced after incubation with L-NAME or ODQ. Measurements of nitrite concentrations on rat aorta homogenates showed that the venom significantly increased the basal levels. Moreover, the venom attenuates the contraction induced by calcium. These results suggest that P. ornata venom contains a mixture of vasodilator components that act through the activation of the nitric oxide/cGMP pathway, as well as, through an endothelium-independent mechanism that involves the calcium influx into vascular smooth muscle cells.

A subfraction obtained from the venom of the tarantula Poecilotheria regalis contains inhibitor cystine knot peptides and induces relaxation of rat aorta by inhibiting L-type voltage-gated calcium channels

Venoms from tarantulas contain low molecular weight vasodilatory compounds whose biological action is conceived as part of the envenomation strategy due to its propagative effects. However, some properties of venom-induced vasodilation do not match those described by such compounds, suggesting that other toxins may cooperate with these ones to produce the observed biological effect. Owing to the distribution and function of voltage-gated ion channels in blood vessels, disulfide-rich peptides isolated from venoms of tarantulas could be conceived into potential vasodilatory compounds. However, only two peptides isolated from spider venoms have been investigated so far. This study describes for the first time a subfraction containing inhibitor cystine knot peptides, PrFr-I, obtained from the venom of the tarantula Poecilotheria regalis. This subfraction induced sustained vasodilation in rat aortic rings independent of vascular endothelium and endothelial ion channels. Furthermore, PrFr-I decreased calcium-induced contraction of rat aortic segments and reduced extracellular calcium influx to chromaffin cells by the blockade of L-type voltage-gated calcium channels. This mechanism was unrelated to the activation of potassium channels from vascular smooth muscle, since vasodilation was not affected in the presence of TEA, and PrFr-I did not modify the conductance of the voltage-gated potassium channel K_v10.1. This work proposes a new envenomating function of peptides from venoms of tarantulas, and establishes a new mechanism for venom-induced vasodilation.

Brazilian Theraphosidae: a toxicological point of view

The Theraphosidae family includes the largest number of species of the Mygalomorphae infraorder, with hundreds of species currently catalogued. However, there is a huge lack on physiologic and even ecologic information available, especially in Brazil, which is the most biodiverse country in the world. Over the years, spiders have been presented as a source of multiple biologically active compounds with basic roles, such as primary defense against pathogenic microorganisms or modulation of metabolic pathways and as specialized hunters. Spider venoms also evolved in order to enable the capture of prey by interaction with a diversity of molecular targets of interest, raising their pharmaceutical potential for the development of new drugs. Among the activities found in compounds isolated from venoms and hemocytes of Brazilian Theraphosidae there are antimicrobial, antifungal, antiparasitic and antitumoral, as well as properties related to proteinase action and neuromuscular blockage modulated by ionic voltage-gated channel interaction. These characteristics are present in different species from multiple genera, which is strong evidence of the important role in spider survival. The present review aims to compile the main results of studies from the last decades on Brazilian Theraphosidae with special focus on results obtained with the crude venom or compounds isolated from both venom and hemocytes, and their physiological and chemical characterization.

Small Molecules in the Venom of the Scorpion Hormurus waigiensis

Despite scorpion stings posing a significant public health issue in particular regions of the world, certain aspects of scorpion venom chemistry remain poorly described. Although there has been extensive research into the identity and activity of scorpion venom peptides, non-peptide small molecules present in the venom have received comparatively little attention. Small molecules can have important functions within venoms; for example, in some spider species the main toxic components of the venom are acylpolyamines. Other molecules can have auxiliary effects that facilitate envenomation, such as purines with hypotensive properties utilised by snakes. In this study, we investigated some non-peptide small molecule constituents of Hormurus waigiensis venom using LC/MS, reversed-phase HPLC, and NMR spectroscopy. We identified adenosine, adenosine monophosphate (AMP), and citric acid within the venom, with low quantities of the amino acids glutamic acid and aspartic acid also being present. Purine nucleosides such as adenosine play important auxiliary functions in snake venoms when injected alongside other venom toxins, and they may have a similar role within H. waigiensis venom. Further research on these and other small molecules in scorpion venoms may elucidate their roles in prey capture and predator defence, and gaining a greater understanding of how scorpion venom components act in combination could allow for the development of improved first aid.

Rat aorta relaxation induced by the venom of Poecilotheria regalis involves the activation of the NO/cGMP pathway

Spider venoms are widely recognized as a new emerging source of potential research tools, pesticides, drug leads, and therapeutic agents. Some studies suggest that these venoms may contain interesting vasodilator compounds with potential therapeutic applications. In the present study, the vasodilator activity of the venom of Poecilotheria regalis was evaluated in isolated rat aortic rings. This venom induced an endothelium-dependent vasodilation [EC₅₀ value was 5.52 (4.18-7.32) μg protein/ml with an E_max = 103.4 ± 3.8%]. While the percentage of vasodilation induced by the venom was significantly diminished in the presence of a nitric oxide synthase inhibitor (L-NAME), it remained unaltered in the presence of suramin, a P2-purinergic receptor antagonist. Moreover, the vasodilator activity of the venom was not affected after boiling bath incubation, but was significantly decreased under reducing conditions. Additionally, venom composition was analyzed by reverse-phase chromatography and MALDI-TOF mass spectrometry, and two fractions were obtained, referred to as peptidic and non-peptidic fractions. Interestingly, both fractions induced vasodilation in isolated rat aortic rings. The results of this study showed that the venom of P. regalis induces a concentration-dependent vasodilation in rat aorta that was endothelium-dependent and involves the activation of NO/cGMP pathway. These results suggest that the venom contains a combination of both peptidic and non-peptidic vasodilator components. This study provides pharmacological data that suggest that P. regalis venom may be an important source of peptidic and non-peptidic vasodilator compounds.

Vasodilator and hypotensive effects of the spider peptide Lycosin-I in vitro and in vivo

Lycosin-I, a spider peptide isolated from the venom of the spider Lycosa singoriensis, has anti-bacteria and anti-cancer properties in organisms. However, cardiovascular effects of Lycosin-I have not been studied. In this study, we investigated for the first time the vasodilator and hypotensive effects of Lycosin-I and the possible mechanisms, in order to develop a promising treatment for hypertension-related diseases. For in vitro experiments, thoracic aortas were isolated, and divided into two groups, endothelium-intact and endothelium-denuded aortic rings. Lycosin-I induced a remarkable dose-dependent relaxation in endothelium-intact aortic rings pre-treated with phenylephrine (p < 0.05), while it showed no obvious vasodilator effects in endothelium-denuded aortic rings (p > 0.05). The vasodilator effects of Lycosin-I were significantly weakened by a nitric oxide synthase (NOS) inhibitor, L-NAME (p < 0.001) and a selective inhibitor of nitric oxide (NO)-sensitive soluble guanylate cyclase (sGC), ODQ (p < 0.05), respectively. The levels of endothelial nitric oxide synthase (eNOS) phosphorylation and the NO production were significantly higher in human umbilical vascular endothelial cells pre-cultured with Lycosin-I than the control (p < 0.001), determined via western blot analysis and ozone-chemiluminescence technology. For in vivo experiments, arterial and venous catheters were inserted for mean arterial pressure (MAP) recording and drug administration in anaesthetized spontaneously hypertensive rats. Lycosin-I caused a transient drop of MAP 2 min after the administration compared with the control (p < 0.001). In conclusion, Lycosin-I has the potential to be an anti-hypertensive drug by endothelium-dependent vasodilatation, in which eNOS and NO-sensitive sGC are two main involved factors.

Overview of Antagonists Used for Determining the Mechanisms of Action Employed by Potential Vasodilators with Their Suggested Signaling Pathways

This paper is a review on the types of antagonists and the signaling mechanism pathways that have been used to determine the mechanisms of action employed for vasodilation by test compounds. Thus, we exhaustively reviewed and analyzed reports related to this topic published in PubMed between the years of 2010 till 2015. The aim of this paperis to suggest the most appropriate type of antagonists that correspond to receptors that would be involved during the mechanistic studies, as well as the latest signaling pathways trends that are being studied in order to determine the route(s) that atest compound employs for inducing vasodilation. The methods to perform the mechanism studies were included. Fundamentally, the affinity, specificity and selectivity of the antagonists to their receptors or enzymes were clearly elaborated as well as the solubility and reversibility. All the signaling pathways on the mechanisms of action involved in the vascular tone regulation have been well described in previous review articles. However, the most appropriate antagonists that should be utilized have never been suggested and elaborated before, hence the reason for this review.