The multiple roles of peroxiredoxins in tick blood feeding

Hydrogen peroxide (H 2 O 2 ) and hydroxyl radicals (HO·) are generated through partial reduction of oxygen. The HO· are the most reactive and have a shorter half-life than H 2 O 2 , they are produced from comparatively stable H 2 O 2 through Fenton reaction. Although controlling HO· is important and biologically advantageous for organisms, it may be difficult. Ticks are obligate hematophagous arthropods that need blood feeding for development. Ticks feed on vertebrate blood containing high levels of iron. Ticks also concentrate iron-containing host blood, leading to high levels of iron in ticks. Host-derived iron may react with oxygen in the tick body, resulting in high concentrations of H 2 O 2 . On the other hand, ticks have antioxidant enzymes, such as peroxiredoxins (Prxs), to scavenge H 2 O 2 . Gene silencing of Prxs in ticks affects their blood feeding, oviposition, and H 2 O 2 concentration. Therefore, Prxs could play important roles in ticks’ blood feeding and oviposition through the regulation of the H 2 O 2 concentration. This review discusses the current knowledge of Prxs in hard ticks. Tick Prxs are also multifunctional molecules related to antioxidants and immunity like other organisms. In addition, tick Prxs play a role in regulating the host immune response for ticks’ survival in the host body. Tick Prx also can induce Th2 immune response in the host. Thus, this review would contribute to the further understanding of the tick’s antioxidant responses during blood feeding and the search for a candidate target for tick control.