The apoptosis and GLP-1 hyposecretion induced by LPS via RIP/ROS/mTOR pathway in GLUTag cells

Biochimie. 2019 Jul;162:229-238. doi: 10.1016/j.biochi.2019.04.001. Epub 2019 Apr 4.

Abstract

Lipopolysaccharide (LPS) as a component of the outer structure of cell wall of gram-negative bacteria, could induce apoptosis in the intestinal endocrine cell line STC-1. However, the signaling cascades involved in this process have not been elucidated. Hence, we investigated the mechanism of cell apoptosis and hyposecretion of glucagon-like peptide 1 (GLP-1) induced by LPS in the GLUTag enteroendocrine cell line. LPS decreased the cell viability of GLUTag cells, up-regulated the TNF-α level, induced the apoptosis and down-regulated the mRNA and protein levels of GLP-1. In addition, TNF-α promoted LPS-induced apoptosis of GLUTag cells through mediating the formation of the RIP1/RIP3 necrosome. RIP1 and RIP3 knockdown increased cell viability, the mRNA and protein levels of GLP-1 and the mTOR signaling pathway-related proteins (p-mTOR and p-S6), and decreased the relative caspase 3/7 activity, cell apoptosis and ROS production. Further studies showed that ROS inhibited the mTOR signaling pathway. Moreover, the antioxidant N-acetyl-l-cysteine increased cell viability, GLP-1 expressions and the mTOR signaling pathway-related proteins, and inhibited the ROS production. However, the mTOR specific inhibitor (Rapa) reversed all these above effects. Taken together, our result revealed that LPS induced the apoptosis of GLUTag cells and GLP-1 hyposecretion through the RIP/ROS/mTOR pathway.

Keywords: Glucagon-like peptide 1; Lipopolysaccharide; Murine L cell apoptosis; RIP/ROS pathway; mTOR pathway.

MeSH terms

  • Acetylcysteine / chemistry
  • Animals
  • Apoptosis / drug effects*
  • Caspase 3 / metabolism
  • Caspase 7 / metabolism
  • Cell Line
  • Cell Survival / drug effects*
  • GTPase-Activating Proteins / metabolism
  • Glucagon-Like Peptide-1 Receptor / metabolism*
  • Lipopolysaccharides / toxicity*
  • Reactive Oxygen Species / metabolism
  • Receptor-Interacting Protein Serine-Threonine Kinases / metabolism
  • Signal Transduction / drug effects*
  • TOR Serine-Threonine Kinases / metabolism
  • Tumor Necrosis Factor-alpha / metabolism*

Substances

  • GTPase-Activating Proteins
  • Glp1r protein, mouse
  • Glucagon-Like Peptide-1 Receptor
  • Lipopolysaccharides
  • Ralbp1 protein, mouse
  • Reactive Oxygen Species
  • Tumor Necrosis Factor-alpha
  • TOR Serine-Threonine Kinases
  • mTOR protein, mouse
  • Receptor-Interacting Protein Serine-Threonine Kinases
  • Ripk3 protein, mouse
  • Casp3 protein, mouse
  • Casp7 protein, mouse
  • Caspase 3
  • Caspase 7
  • Acetylcysteine