Influência da dopamina na resposta imune celular de Rhipicephalus microplus inoculados com Metarhizium anisopliae

Abstract

Currently, the control of Rhipicephalus microplus widely performed through the use of chemical acaricides, but the misuse of these products contributes to the development ticks’ populations more resistant, contamination of animal products, and the environment by their residues. In this situation, biological control by entomopathogenic fungi is a promising alternative that can be used in integrated management to control ticks. Metarhizium spp. is one of the fungi used with recognized performance in the biological control of arthropods. In response to fungal infection, arthropods activate tick immune responses against pathogens. However, a greater understanding is needed of the role of the R. microplus immune system and its defense mechanisms against a fungal infection is needed to advance in the development of more effective control against the parasite. Dopamine (DA) is a biogenic monoamine that interconnects the nervous and immune systems, reported to modulate the phagocytosis of insect hemocytes. The present study evaluated the effect of DA in the cellular immune response and survival of R. microplus inoculated with M. anisopliae blastospores. The following groups were formed: C (untreated group), P (ticks inoculated with phosphate buffer solution), D (ticks inoculated with 3μL of 1.025 ng μL-1 DA), M [ticks inoculated with M. anisopliae (3μL; 106

blastospores mL-1

)], and DM [ticks inoculated with DA (3μL; 1.025

ng μL-1 ) and after 20 min, M. anisopliae (3μL; 106

blastospores mL-1 And only C, P, and D for the phagocytosis assay. By analyzing the effects of exogenous DA inoculation: it increased the survival of females after being inoculated with dopamine in association with the fungus 72h after treatment; increased the number of circulating hemocytes in the group inoculated with DA followed or not by fungal infection 24h after inoculation; did not influence the phagocytic index of hemocytes of ticks challenged with M. anisopliae; influenced the activity of phenoloxidase in hemolymph where ticks inoculated with DA and the fungus or exclusively with AD was higher than in untreated or only ticks inoculated with the fungus, 72 h after treatment; it was possible to detect it in hemocytes of ticks treated and not treated with fungus. The analysis of the immune response of R. microplus challenged with entomopathogenic fungi contributes to the advancement and development of new effective biological control strategies. Our study demonstrated for the first time the immune system of R. Microplus being modulated by the action of exogenous DA