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A Calcium Bioluminescence Assay for Functional Analysis of Mosquito Aedes aegypti and Tick Rhipicephalus microplus G Protein-coupled Receptors
Published on: April 20, 2011
Acaricidal activity of small molecule antagonists of the tick kinin receptor against Rhipicephalus microplus
Waleed M Arafa1, Kimberly H Lohmeyer2, Patricia V Pietrantonio1
1Department of Entomology, Texas A&M University, College Station, Texas, USA.
Background:
Resistance to acaricides underscores the need for tick control alternatives. We previously identified in a high-throughput screen six small molecules SACC-0412060, SACC-0412062, SACC-0412066, SACC-0064443, SACC-0428788, and SACC-0039590 as antagonists of the kinin receptor from Rhipicephalus microplus. The acaricidal activity of these molecules was investigated.
Results:
The toxicities of adjuvant/solvent combinations of a rapeseed oil methyl ester or a propylene carbonate in 5% DMSO versus 5% DMSO alone were evaluated using a larval immersion test (LIT) with the R. microplus susceptible Deutch strain, and all were non-toxic. The rapeseed oil methyl ester (1%) in 5% DMSO was adopted as the adjuvant for all molecules in bioassays. Permethrin (3.19 mM) killed all larvae. The Deutch strain mortality with SACC-0039590 and SACC-0428788 (both at 1 mM) was 100% and 73.65%, respectively, while ranged from 2.7% to 3.8% with the other small molecules. In the LIT, the LC50 of SACC-0039590 and SACC-0428788 were 60 μM, and 450 μM, respectively. For the R. microplus Arauquita pyrethroid-resistant strain in the LIT, the LC50 of SACC-0039590 and SACC-0428788 were 60 μM and 237.5 μM respectively. SACC-0039590 (N-[2-(4-chlorophenyl)ethyl]-5-methylthieno[2,3-d]pyrimidin-4-amine) and SACC-0428788 (N-[2-(4-chlorophenyl)ethyl]thieno[2,3-d]pyrimidin-4-amine) are structural analogs, the first one featuring a 5-methyl group absent in the second. For engorged Deutch females, immersion in SACC-0039590 caused dose-dependent reductions in egg mass weight (~35%) and egg hatching (21%-38.59%). Permethrin (3.19 mM) significantly reduced egg mass weight but not egg hatching.
Conclusion:
The small molecule SACC-0039590 killed susceptible and pyrethroid-resistant larvae of R. microplus and reduced the reproductive output of females. © 2025 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.
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