Nanoparticulate anatase TiO 2 (TiO 2 NPs) upregulates the expression of silkworm ( Bombyx mori ) neuropeptide receptor and promotes silkworm feeding, growth, and silking

Bombyx mori orphan G protein-coupled receptor, BNGR-A4, is the specific receptor of B. mori neuropeptide F (BmNPFR, neuropeptide F designated NPF). BmNPFR binds specifically and efficiently to B. mori neuropeptides BmNPF1a and BmNPF1b, which activates the ERK1/2 signaling pathway to regulate B. mori food intake and growth. Titanium dioxide nanoparticles (TiO 2 NPs) can promote B. mori growth. However, whether the mechanisms of TiO 2 NPs’ effects are correlated with BmNPFR remains unknown. In this study, the effects of TiO 2 NPs (5 mg/L) feeding and BmNPFR-dsRNA injection on B. mori food intake and growth were investigated; after TiO 2 NPs treatments, B. mori food intake, body weight, and cocoon shell weight were 5.82%, 4.64%, and 9.30% higher, respectively, than those of controls. The food intake, body weight, and cocoon shell weight of the BmNPFR-dsRNA injection group were reduced by 8.05%, 6.28%, and 6.98%, respectively, compared to the control. After TiO 2 NPs treatment for 72 h, the transcriptional levels of BmNPFR, BmNPF1a, and BmNPF1b in the midgut were 1.58, 1.43, and 1.34-folds, respectively, of those of the control, but 1.99, 2.26, and 2.19-folds, respectively, of the BmNPFR-dsRNA injection group; the phosphorylation level of MAPK was 24.03% higher than the control, while the phosphorylation level of BmNPFR-dsRNA injection group was 71.00% of control. The results indicated that TiO 2 NPs affect B. mori feeding and growth through increasing the expression of BmNPFR. This study helps clarify the roles of BmNPF/BmNPFR system in TiO 2 NPs’ effects on B. mori feeding, growth, and development.