Effects of destruxins on free calcium and hydrogen ions in insect hemocytes

• Published in: Insect science 2014-02, Vol.21 (1), p.31-38
• Main Authors: Chen, Xiu‐Run, Hu, Qiong‐Bo, Yu, Xiao‐Qiang, Ren, Shun‐Xiang
• Format: Article
• Language: English
• Subjects: Animals; Biological Transport - drug effects; Bombyx mori; calcium; Calcium - metabolism; Cell Line; confocal laser scanning microscopy; Depsipeptides - metabolism; Depsipeptides - pharmacology; destruxin; entomopathogenic fungi; hemocytes; Hemocytes - drug effects; Hemocytes - metabolism; hydrogen; Hydrogen - metabolism; hydrogen ions; insect immunity; Insect Proteins - metabolism; Insecta - drug effects; Insecta - metabolism; Insecta - microbiology; insects; ions; Ions - metabolism; mechanism of action; Metarhizium - chemistry; Metarhizium - metabolism; Metarhizium anisopliae; Mycotoxins - metabolism; Mycotoxins - pharmacology; protons; Spodoptera litura; 昆虫; 氢离子; 游离钙离子; 激光共聚焦显微镜; 细胞内; 血细胞; 金龟子绿僵菌; 霉菌毒素
• ISSN: 1672-9609; 1744-7917
• DOI: 10.1111/1744-7917.12028

Destruxins, cyclohexadepsipeptidic mycotoxins isolated from the entomopathogenic fungus Metarhizium anisopliae, inhibit innate insect immunity. However, their mechanism of action remains unclear. In this study, the effects of destruxins on changes in free calcium and hydrogen ions in the hemocytes of Exolontha serrulata, Bombyx mori and the Spodoptera litura SL‐1 cell line were detected using laser scanning confocal microscopy (LSCM). An instant Ca²⁺ influx of hemocytes induced by destruxins A and B (DA and DB) was recorded. The DA/DB‐dependent Ca²⁺ influx was not influenced by the Ca²⁺ channel inhibitors 2‐aminoethoxydiphenyl borane (2‐APB) and U73122. It also had an apparently different LSCM profile from that of the ionomycin‐dependent Ca²⁺ influx. However, the instant Ca²⁺ influx was not seen in the SL‐1 cells; on the contrary, a slow, moderate enhancement of intracellular Ca²⁺ was observed. Meanwhile, an instant intracellular free H⁺ decrease aroused by DA and DB was found. DB at 20 μmol/L and DA at 690 μmol/L significantly reduced intracellular free H⁺ levels. Furthermore, the vacuolar H⁺‐ATPase (V‐ATPase) inhibitor bafilomycin A1 had obvious effects on the decreases of intracellular free H⁺ in hemocytes. These results suggest that the mechanism of DA/DB‐dependent Ca²⁺ influx is perhaps not related to Ca²⁺ channels and ionophores; rather, the intracellular free H⁺ decrease might be due to V‐ATPase inhibition.