Degenerative process and cell death in salivary glands of Rhipicephalus sanguineus (Latreille, 1806) (Acari: Ixodidae) semi‐engorged female exposed to the acaricide permethrin

Abstract

Ticks are ectoparasites of great medical and veterinary importance around the world and synthetic chemicals such as permethrin have been used for their control. This study provides a cytochemistry analysis of both degenerative and cell death processes in salivary glands of the brown dog tick Rhipicephalus sanguineus semi-engorged females exposed to 206, 1,031, and 2,062 ppm of permethrin. The results presented herein demonstrate that permethrin is a potent chemical acaricide that would act on the glandular tissue's morphophysiology in this tick species by eliciting severe changes in the acinus shape, intense vacuolation of the acinar cells' cytoplasm, marked glandular tissue disorganization, culminating in an advanced degenerative stage with consequent formation of many apoptotic bodies (cell death). In addition, permethrin induced major changes in the acinar cells' nucleus, such as a change both in its shape and size, chromatin marginalization, nuclear fragmentation, and appearance of picnotic nuclei, especially when the highest concentrations of the product were used. Thus, permethrin induced early degeneration of this tissue characterized by significant changes in the structure of acinar cells and production of enzymes related to the cell death process, in addition to interfering directly in the genetic material of these cells.

Morpho-ultrastructural alterations in the salivary glands of semi-engorged Riphicephalus sanguineus s.l. females subjected to permethrin

“…The ultrastructural data regarding the salivary glands of the females from the control group corroborate light microscopy analyses by Nodari et al [16][17][18] , who demonstrated that in this group the acini were intact, maintaining original shape; i.e., rounded, and presenting intact cells. The acini I cells presented a well-defined basal membrane labyrinth, as described in literature [22], with randomly distributed mitochondria throughout the cytoplasm and the presence of lipid inclusions (drops).…”

“…The RNA molecules would also be used in the synthesis of acid phosphatase [29], corroborating Nodari et al [18], who reported intense staining of this enzyme in the acinar cells of female R. sanguineus s. l. salivary glands subjected to these concentrations of permethrin. The presence of this enzyme would be directly associated with the degenerative process of the tissue [18,29], once the increase in the level of activity of the acid hydrolases (acid phosphatase) is a characteristic of autophagic cell death [34,35,[37][38][39][40][41][42].…”

“…Thus, considering the similarities between the nuclear [18] and nucleolar alterations found in this study, it can be inferred that the salivary glands of semi-engorged R. sanguineus s. l. females subjected to different concentrations of permethrin would also be undergoing the process described by Kerr et al [31]; i.e., apoptotic death.…”

“…Considering this, the present study had the objective to cytochemically analyze the alterations in the nucleolar structure and in the ultrastructure of the salivary gland cells of R. sanguineus s. l. semi-engorged females subjected to different concentrations of permethrin (206, 1031 and 2062 ppm). Studies by Nodari et al [16][17][18] have demonstrated that this pyrethroid would accelerate the degeneration of the glandular tissue in this species.…”

“…Studies on tick salivary glands degeneration [11][12][13], mainly addressing the influence of synthetic acaricides on the morphophysiology [14][15][16][17][18] and ultrastructure, are scarce in the literature. Considering this, the present study had the objective to cytochemically analyze the alterations in the nucleolar structure and in the ultrastructure of the salivary gland cells of R. sanguineus s. l. semi-engorged females subjected to different concentrations of permethrin (206, 1031 and 2062 ppm).…”