2.4　Nitric Oxide(NO)Measurement

Biologically produced NO is rapidly oxidized to nitrite and nitrate in aqueous solutions.47)In this study，NO production was measured as nitrite concentration in cell-free culture supernatants using the NO detection kit(Jiancheng Bioengineering Institute，Nanjing，China)by colorimetric assay.After 48h treatment，100μL of culture supernatant was collected for examining the NO concentration.The absorbance was measured at 540nm by using a spectrophotometer(UV-1800，Shimadzu，Japan).NO concentration was calculated using the absorbance by the formula described in the instruction.(https://www.daowen.com)