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

Luis Fernando Díaz-Peña; Torres-Ortiz Daniela; Manuel B Aguilar; Enoch Luis; Fernando Lazcano-Pérez; Roberto Arreguín-Espinosa; Arturo Hernandez-Cruz; César Ibarra-Alvarado; Alejandro García-Arredondo

doi:10.1016/j.toxcx.2023.100151

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

Toxicon X. 2023 Feb 17:18:100151. doi: 10.1016/j.toxcx.2023.100151. eCollection 2023 Jun.

Affiliations

¹ Posgrado en Ciencias Químico Biológicas, Facultad de Química, Universidad Autónoma de Querétaro, Centro Universitario S/N, 76010, Querétaro, Querétaro, Mexico.
² Laboratorio de Neurofarmacología Marina, Instituto de Neurobiología, Universidad Nacional Autónoma de México, Juriquilla, Querétaro, 76230, Mexico.
³ Cátedras CONACYT, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Circuito Exterior s/n, 04510, Ciudad de México, Mexico.
⁴ Laboratorio Nacional de Canalopatías, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Circuito Exterior s/n, Ciudad de México, Mexico.
⁵ Laboratorio de Química de Biomacromoléculas, Instituto de Química, Universidad Nacional Autónoma de México, Ciudad de México, 04510, Mexico.
⁶ Departamento de Neurociencia Cognitiva, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Circuito Exterior s/n, Ciudad de México, Mexico.
⁷ Departamento de Investigación Química y Farmacológica de Productos Naturales, Facultad de Química, Universidad Autónoma de Querétaro, Centro Universitario S/N, 76010, Querétaro, Querétaro, Mexico.

Abstract

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.

Keywords: ACh, acetylcholine; ADP, adenosine diphosphate; Cav, voltage-gated calcium channel; DMEM, Dulbecco's modified eagle's medium; DRP, disulfide-rich peptide; EC50, half maximal effective concentration; Emax, maximum effect; FBS, fetal bovine serum; HPLC, high-performance liquid chromatography; ICK peptide; ICK, inhibitor cystine knot; IKCa, intermediate conductance calcium-activated potassium channel; Kv, voltage-gated potassium channel; L-type calcium voltage-gated calcium; LC-MS/MS, liquid chromatography-tandem mass spectrometer; MALDI, matrix-assisted desorption ionization; Nav, voltage-gated sodium channel; Phe, phenylephrine; Poecilotheria regalis, venom; RP, reverse phase; Rat aorta; SEM, standard error of the mean; SKCa, small conductance calcium-activated potassium channel; SNP, sodium nitroprusside; TEA, tetraethylammonium; TOF, time of flight; TRP, transient receptor potential; Vasodilation; Vh, holding-voltage; endothelium-intact (E+), endothelium-denuded (E−).