Sublethal concentration of λ-cyhalothrin inhibits insulin-like peptides and leads to reproductive toxicity in Chrysoperla sinica.

Insulin-like peptides (ILPs) act as crucial reproductive neuropeptides in insects, regulating insect reproduction through the insulin signaling pathway (ISP). Our previous studies have found that the sublethal concentrations (LC₁ and LC₁₀) of lambda-cyhalothrin (λCy) could induce severe reproductive toxicity in the lacewing, Chrysoperla sinica (Tjeder), but the toxicological mechanism remains unclear. This study discovered that λCy could inhibit CsILP transcription, leading to a decrease in insulin content and downregulation of C. sinica insulin receptor (CsInR) and C. sinica forkhead box O (CsFOXO) expression in ISP. Interference with CsILP expression resulted in downregulation of C. sinica vitellogenin (CsVg) and decreasing fecundity, while exogenous injection of bovine insulin promoted upregulation of CsVg expression and facilitated reproduction in female adults of C. sinica. Meanwhile, interference with FOXO of ILP downstream transcription factor could lead to downregulation of CsVg, hindering ovarian development and resulting in a decrease in egg production. However, exogenous injection of bovine insulin could remedy the effects caused by FOXO interference. In addition, ILP mediates juvenile hormone and 20-hydroxyecdysone biosynthesis by acting on their synthetic regulatory enzymes and influences the signal transduction of the 2 reproductive endocrine hormones, thereby regulating the reproductive endocrine environment in C. sinica. In conclusion, λCy inhibits CsILP expression, leading to disorder of ISP, leading to the reduced fecundity of C. sinica.