Titanium Dioxide Nanoparticles Relieve Silk Gland Damage and Increase Cocooning of Bombyx Mori under Phoxim-Induced Toxicity.

Organophosphate pesticides are applied widely in world for agricultural purposes, and their exposures often resulted in non-cocoon of Bombyx mori in China. TiO2 nanoparticles have been demonstrated to increase pesticide resistance of Bombyx mori. While the toxicity of phoxim is well documented, very limited information exists on the mechanisms of TiO2 nanoparticles improving cocooning function of Bombyx mori following exposure to phoxim. The present study was therefore undertaken to determine whether TiO2 nanoparticles attenuates silk gland injury and elevates cocooning of B. mori following exposure to phoxim. The findings suggested that phoxim exposure resulted in severe damages of the silk gland structure, significantly decreased survival of fifth-instar larvae, and cocooning in the silk gland of Bombyx mori. Furthermore, phoxim exposure significantly resulted in reductions of total protein concentrations and suppressed expressions of silk protein synthesis-related genes, including Fib-L, Fib-H, P25, Ser-2 and Ser-3, in the silk gland. TiO2 nanoparticles pretreatment, however, could significantly relieve silk gland injury and increase survival of Bombyx mori. Importantly, TiO2 nanoparticles could remarkably elevate cocooning and total protein contents, and promote expressions of Fib-L, Fib-H, P25, Ser-2 and Ser-3 in the silk gland following exposure to phoxim.