Elsevier

Free Radical Biology and Medicine

Volume 67, February 2014, Pages 265-277
Free Radical Biology and Medicine

Original Contributions
Selenoprotein S is a marker but not a regulator of endoplasmic reticulum stress in intestinal epithelial cells

https://doi.org/10.1016/j.freeradbiomed.2013.11.001Get rights and content

Abstract

Selenoproteins are candidate mediators of selenium-dependent protection against tumorigenesis and inflammation in the gut. Expression and roles of only a limited number of intestinal selenoproteins have been described so far. Selenoprotein S (SelS) has been linked to various inflammatory diseases and is suggested to be involved in endoplasmic reticulum (ER) homeostasis regulation and antioxidative protection in a cell-type-dependent manner, but its protein expression, regulation, and function in the gut are not known. We here analyzed the expression and localization of SelS in the healthy and inflamed gut and studied its regulation and function in intestinal epithelial cell lines. SelS was expressed in the intestinal epithelium of the small and large intestine and colocalized with markers of Paneth cells and macrophages. It was upregulated in inflamed ileal tissue from Crohn's disease patients and in two models of experimental colitis in mice. We detected SelS in colorectal cell lines, where it colocalized with the ER marker calnexin. SelS protein expression was unaffected by enterocytic differentiation but increased in response to selenium supplementation and after treatment with the ER stress inducer tunicamycin. On the other hand, depletion of SelS in LS174T, HT29, and Caco-2 cells by RNA interference did not cause or modulate ER stress and had no effect on hydrogen peroxide-induced cell death. In summary, we introduce SelS as a novel marker of Paneth cells and intestinal ER stress. Although it is upregulated in Crohn's disease, its role in disease etiology remains to be established.

Section snippets

Antibodies

The following primary antibodies were used in this study: mouse anti-actin, rabbit anti-active caspase-3 (BD Biosciences, San Jose, CA, USA), mouse anti-FAS (activating), mouse anti-PARP1 (Merck, Darmstadt, Germany), rabbit anti-SelS (Sigma–Aldrich, St. Louis, MO, USA), rabbit anti-calnexin, mouse anti-CHOP, rabbit anti-Ero1, rabbit anti-GRP78 (BiP), rabbit anti-inositol-requiring transmembrane kinase/endonuclease 1 (IRE1; Cell Signaling, Beverly, MA, USA), mouse anti-CD68 (Biocare Medical,

SelS protein expression in the murine and human gut

IHC analysis revealed expression of SelS in epithelial cells of the mouse small and large intestine and also in cells located in the lamina propria (LP) (Fig. 1A). The strongest immunoreactivity of SelS was seen in small intestinal crypt cells (inset of Fig. 1A), which we identified as Paneth cells by dual immunofluorescence staining of SelS and lysozyme, a Paneth cell marker. SelS was perinuclear in cells containing lysozyme granules, but was not present in the mature granules, and its

Discussion

We here show that SelS is present in the human and mouse gut, adding it to a group of selenoproteins, including GPx1–4, TrxR, SeP, and Sep15, whose intestinal expression has been shown earlier [10], [11], [12], [37]. Localization of SelS in macrophages within the LP is consistent with a previous study showing SelS in RAW264.7 macrophage cells [13]. We found particularly high expression of SelS in Paneth cells and suggest it as a novel marker of this cell type. Our IHC analysis further showed

Acknowledgments

This study was supported by the Deutsche Forschungsgemeinschaft (Bonn, Germany) (SP 1333/1-2 and GE 2328/1-2) and by the Foundation of the Royal Brisbane and Women’s Hospital (Brisbane, Australia). We thank Glynn Rees, QIMR Histology Unit, for performing the SelS/CD68 dual IF staining.

References (42)

  • B. Speckmann et al.

    Proinflammatory cytokines down-regulate intestinal selenoprotein P biosynthesis via NOS2 induction

    Free Radic. Biol. Med.

    (2010)
  • C. Hetz et al.

    Fine-tuning of the unfolded protein response: assembling the IRE1alpha interactome

    Mol. Cell

    (2009)
  • S. Florian et al.

    Loss of GPx2 increases apoptosis, mitosis, and GPx1 expression in the intestine of mice

    Free Radic. Biol. Med.

    (2010)
  • A.P. Kipp et al.

    The selenoproteins GPx2, TrxR2 and TrxR3 are regulated by Wnt signalling in the intestinal epithelium

    Biochim. Biophys. Acta

    (2012)
  • K. Wingler et al.

    Gastrointestinal glutathione peroxidase prevents transport of lipid hydroperoxides in CaCo-2 cells

    Gastroenterology

    (2000)
  • S. Du et al.

    Influence of SelS gene silence on beta-mercaptoethanol-mediated endoplasmic reticulum stress and cell apoptosis in HepG2 cells

    Biochim. Biophys. Acta

    (2010)
  • K.P. Pavlick et al.

    Role of reactive metabolites of oxygen and nitrogen in inflammatory bowel disease

    Free Radic. Biol. Med.

    (2002)
  • J.K. Hou et al.

    Dietary intake and risk of developing inflammatory bowel disease: a systematic review of the literature

    Am. J. Gastroenterol.

    (2011)
  • B. Khor et al.

    Genetics and pathogenesis of inflammatory bowel disease

    Nature

    (2011)
  • S. Krehl et al.

    Glutathione peroxidase-2 and selenium decreased inflammation and tumors in a mouse model of inflammation-associated carcinogenesis whereas sulforaphane effects differed with selenium supply

    Carcinogenesis

    (2012)
  • C.W. Barrett et al.

    Dietary selenium deficiency exacerbates DSS-induced epithelial injury and AOM/DSS-induced tumorigenesis

    PLoS One

    (2013)
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