Up-Regulation of Autophagy in Small Intestine Paneth Cells in Response to Total-Body gamma-Irradiation
Abstract
Macroautophagy (mAG) is a lysosomal mechanism of degradation of cell self-constituents damaged due to variety of stress factors, including ionizing irradiation. Activation of mAG requires expression of mAG protein Atg8 (LC3) and conversion of its form I (LC3-I) to form II (LC3-II), mediated by redox-sensitive Atg4 protease. We have demonstrated upregulation of this pathway in the innate host defense Paneth cells of the small intestine (SI) due to ionizing irradiation and correlation of this effect with induction of prooxidant inducible nitric oxide synthase (iNOS). CD2F1 mice were exposed to 9.25 Gy gamma -ionizing irradiation. Small intestinal specimens were collected during 7 days after ionizing irradiation. Assessment of ionizing irradiation- associated alterations in small intestinal crypt and villus cells and activation of the mAG pathway was conducted using microscopical and biochemical techniques. Analysis of iNOS protein and the associated formation of nitrites and lipid peroxidation products was performed using immunoblotting and biochemical analysis, and revealed increases in iNOS protein, nitrate levels and oxidative stress at day 1 following ionizing irradiation. Increase in immunoreactivity of LC3 protein in the crypt cells was observed at day 7 following ionizing irradiation. This effect predominantly occurred in the CD15-positive Paneth cells and was associated with accumulation of LC3-II isoform. The formation of autophagosomes in Paneth cells was confirmed by transmission electron microscopy (TEM). Up-regulation of LC3 pathway in the irradiated SI was accompanied by a decreased protein-protein interaction between LC3 and chaperone heat shock protein 70. A high-level of LC3-immunoreactivity in vacuole-shaped structures was spatially colocalized with immunoreactivity of 3-nitro-tyrosine. The observed effects were diminished in iNOS knockout B6.129P2-NOS2( exp tm1Lau) /J mice subjected to the same treatments.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 2009
- Accession Number
- ADA520842
Entities
People
- Juliann G Kiang
- Nikolai V. Gorbunov
Organizations
- Armed Forces Radiobiology Research Institute