Evidence brief: Integrated in silico and in vivo larvicidal evaluation of compounds targeting juvenile hormone for malaria vector control

Abstract

Malaria remains a major global health challenge, particularly in sub-Saharan Africa, where it is a leading cause of morbidity and mortality. Inhibition of the mosquito juvenile hormone binding protein (MJHBP) is essential for developing selective and effective insecticides against malaria vectors. We performed virtual screening on 2,874 compounds from Agrochemical Insecticides Library using Python-based workflow in RDKit and Pandas libraries. The resultant compounds were subjected to molecular docking study against MJHBP (pdb:5V13). Further evaluation was performed through molecular mechanics generalized Born surface area (MM-GBSA) analysis, insecticide-likeness assessment, toxicity and environmental hazard predictions and Density Functional Theory (DFT) studies. The top-ranked compounds, together with the co-crystallized ligand, were subsequently subjected to molecular dynamics (MD) simulations. The molecular docking and MM-GBSA analyses identified fifteen lead compounds as potent inhibitors, exhibiting binding affinities ranging from –49.84 kcal/mol to –89.51 kcal/mol, values comparable to that of the co-crystallized ligand (–75.83 kcal/mol). The DFT results of the analysed compounds indicated that the top candidates, based on docking scores and binding energies, possessed lower HOMO-LUMO energy gap values, 1.52 eV for F3023-0929 and 2.36 eV for F2708-0061, compared to the co-crystallized ligand, which had a gap of 3.43 eV. All the top compounds displayed significant insecticidal potential with minimal environmental hazards. The stability of the most promising compounds (F2708-0061 and F3023-0929), identified based on binding free energy, was further corroborated through MD simulation. Further in vivo experiments revealed that F3023-0929 and F2708-0061 exhibited potent larvicidal activity, with LC₅₀ values of 37.75 ppm and 33.49 ppm, respectively, thereby supporting their potential as promising insecticidal candidates for mosquito control.

1. Introduction

Malaria continues to pose a significant public health challenge globally and especially in sub-Saharan Africa, where it remains a leading cause of morbidity and mortality [1]. The primary vectors of this disease are female Anopheles mosquitoes, which transmit the Plasmodium pathogen responsible for the illness [2]. In this regard, malaria transmission rates are better reduced by mosquito control which involves vector elimination and minimizing human-vector contact. Traditional control strategies, such as insecticide-treated nets (ITNs) and indoor residual spraying (IRS), have been instrumental in reducing transmission rates [3]. However, the effectiveness of these interventions is increasingly undermined by the development of insecticide resistance among mosquito populations [4]. Studies have documented significant resistance to pyrethroids, organophosphates, carbamates and organochlorines, the primary insecticides used in ITNs and IRS, leading to decreased mortality rates in mosquito populations and compromised control efforts [5,6]. This necessitates the discovery of new effective chemical compounds for vector control.

Pyrethroids and organochlorines cause a knockdown effect on mosquitoes by disrupting the insect’s voltage-gated sodium channels in neuronal membranes while carbamates and organophosphate work by inhibiting acetylcholinesterase (AChE) enzyme, preventing breakdown of the neurotransmitter acetylcholine, which leads to the death of the insect [5]. The growing resistance to these insecticides points to likely alterations of these molecular targets, and hence identifying and developing novel chemical compounds that target new bilogical pathways is necessary [7]. Juvenile hormone binding protein (JHBP) is one of those potential targets being considered for insecticide development. The juvenile hormone system plays a pivotal role in mosquito development which includes, regulating metamorphosis, reproduction, and physiological adaptations [8]. In mosquitoes, the binding of juvenile hormone to its receptor proteins is crucial for maintaining the larval stage and preventing premature pupation. Interfering with this hormone signaling mechanism can lead to developmental abnormalities and mortality [9]. Thus, targeting the mosquito juvenile hormone binding protein (MJHBP), which mediates juvenile hormone action, offers a promising avenue for developing specific and effective insecticides.