Activation of p38 MAPK and expression of TGF-β1 in rat colon enterocytes after whole body γ-irradiation

Abstract

Purpose: To examine the p38 mitogen-activated protein kinase (p38) phosphorylation and transforming growth factor beta 1 (TGF-β1) expression in rat colon enterocytes after irradiation and their contribution to pathology of intestinal radiation disease.

Materials and methods: Male Wistar rats were irradiated with whole body γ-radiation of 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10 Gy (⁶⁰Co, 1.44 Gy.min^–1). Samples were taken 4 and 24 h after irradiation, immunohistochemically stained, then p38 phosphorylation and TGF-β1 expression were measured in apical and cryptal enterocytes using computer image analysis. In selected groups, morphometric parameters, mitosis and apoptosis were evaluated.

Results: P38 phosphorylation integrated optical density (IOD)-based levels increased 2.4-fold (p ≤ 0.01) and 3.6 to 22.8-fold (p ≤ 0.001) in apical enterocytes 4 h after 0.5 Gy and 24 h after 3–10 Gy, respectively. TGF-β1 IOD-based expression increased 3.3- to 6.9-fold (p ≤ 0.001) and 1.6- to 4.9-fold (p ≤ 0.001) in apical cells 4 h after 0.5–2, 4, 5 Gy and 24 h after 6–10 Gy, respectively. No changes were observed in crypts.

Conclusions: We found a chronological and dose-dependent order of p38 activation and TGF-β1 expression in apical enterocytes. Transient up-regulation of p38 and TGF-β1 signalling observed 4 h after low-dose irradiation may participate in molecular mechanisms creating cellular over-expression in apical compartment, while persistent patterns measured 24 h after high-dose irradiation might provide protection of remaining cells in order to maintain tissue integrity.

Keywords::

• p38
• TGF-β1
• enterocyte
• image analysis

Acknowledgements

This work was supported by the Ministry of Defence of the Czech Republic through grant MO0FVZ0000501 (institutional support No. 9079301306023) and grant OVUOFVZ200812 – RADSPEC. We would like to thank Mrs Šárka Průchová for her skilful technical assistance.

Declaration of interest The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.