Inorganic Polyphosphates Regulate Hexokinase Activity and Reactive Oxygen Species Generation in Mitochondria of Rhipicephalus (Boophilus) microplus Embryo

Abstract

The physiological roles of polyphosphates (poly P) recently found in arthropod mitochondria remain obscure. Here, the possible involvement of poly P with reactive oxygen species generation in mitochondria of Rhipicephalus microplus embryos was investigated. Mitochondrial hexokinase and scavenger antioxidant enzymes, such as superoxide dismutase, catalase, and glutathione reductase were assayed during embryogenesis of R. microplus. The influence of poly P3 and poly P15 were analyzed during the period of higher enzymatic activity during embryogenesis. Both poly Ps inhibited hexokinase activity by up to 90% and, interestingly, the mitochondrial membrane exopolyphosphatase activity was stimulated by the hexokinase reaction product, glucose-6-phosphate. Poly P increased hydrogen peroxide generation in mitochondria in a situation where mitochondrial hexokinase is also active. The superoxide dismutase, catalase and glutathione reductase activities were higher during embryo cellularization, at the end of embryogenesis and during embryo segmentation, respectively. All of the enzymes were stimulated by poly P3. However, superoxide dismutase was not affected by poly P15, catalase activity was stimulated only at high concentrations and glutathione reductase was the only enzyme that was stimulated in the same way by both poly Ps. Altogether, our results indicate that inorganic polyphosphate and mitochondrial membrane exopolyphosphatase regulation can be correlated with the generation of reactive oxygen species in the mitochondria of R. microplus embryos.

The redox metabolic pathways function to limit Anaplasma phagocytophilum infection and multiplication while preserving fitness in tick vector cells

“…The fluorescence (excitation at 563 nm and emission at 587 nm) was measured at 15 min using a Cytation 5 Cell Imaging Multi-Mode Reader spectrofluorometer (Biotek, Winooski, VT, USA). The total H 2 O 2 released was corrected for non-specific oxidation of Amplex Red measured in the absence of horseradish peroxidase as previously described 27 , normalized by protein concentration and compared between groups by Student’s t-test with unequal variance (P < 0.05; N = 3 biological replicates).…”

“…Obligate blood-sucking ectoparasites such as ticks respond to the oxidative stress and neutralize the ROS generated from blood meal digestion to avoid tissue damage using different antioxidant defense mechanisms 24–26 . Inorganic polyphosphates regulate the generation of ROS during embryogenesis in Rhipicephalus microplus ticks by increasing the activity of superoxide dismutase, catalase and glutathione reductase, providing evidence for the function of different enzymes in mt ROS metabolism in tick embryos 27 . The role of tick mt antioxidant defense proteins in blood feeding and reproduction has also been characterized in ticks 28,29 .…”

Acaricidal Properties of the Essential Oil FromZanthoxylum caribaeumAgainstRhipicephalus microplus

“…Ticks were obtained from a colony maintained at the Faculdade de Veterinária, Universidade Federal do Rio Grande do Sul (UFRGS), Brazil, as previously described by Fraga et al (2013). R. microplus ticks from the Porto Alegre strain, free of parasites, were reared on calves obtained from a tick-free area.…”

Modulation of mitochondrial metabolism as a biochemical trait in blood feeding organisms: the redox vampire hypothesis redux

“…In the context of embryogenesis, a mitochondrial exopolyphosphatase was reportedly to act as a critical supplier of phosphate for OXPHOS (Campos et al, ). Despite exopolyphosphatase activity was directly regulated by redox balance (Campos et al, ; Costa et al, ), its reaction product polyphosphate increase both mitochondrial oxidant production, and the activity of antioxidant enzymes (Fraga et al, ) This suggests that a hormetic‐like process might be activated by polyphosphates to boost oxidant production, and ROS‐detoxification mechanisms to improve tick tolerance to redox insults. We envisage that future research on mitochondrial function in the context of blood meal in ticks would unravel not only the structural and functional consequences to this organelle, but also their contribution to energy/redox homeostasis during blood feeding.…”