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Open AccessArticle

In Vivo Autophagy Up-Regulation of Small Intestine Enterocytes in Chinese Soft-Shelled Turtles during Hibernation

MOE Joint International Research Laboratory of Animal Health and Food safety, College of Veterinary Medicine, Nanjing Agricultural University, Nanjing 210095, China
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Biomolecules 2019, 9(11), 682; https://doi.org/10.3390/biom9110682
Received: 18 September 2019 / Revised: 26 October 2019 / Accepted: 28 October 2019 / Published: 1 November 2019
Many studies have focused on how autophagy plays an important role in intestinal homeostasis under pathological conditions. However, its role in the intestine during hibernation remains unclear. In the current study, we characterized in vivo up-regulation of autophagy in enterocytes of the small intestine of Chinese soft-shelled turtles during hibernation. Autophagy-specific markers were used to confirm the existence of autophagy in enterocytes through immunohistochemistry (IHC), immunofluorescence (IF), and immunoblotting. IHC staining indicated strong, positive immunoreactivity of the autophagy-related gene (ATG7), microtubule-associated protein light chain (LC3), and lysosomal-associated membrane protein 1 (LAMP1) within the mucosal surface during hibernation and poor expression during nonhibernation. IF staining results showed the opposite tendency for ATG7, LC3, and sequestosome 1 (p62). During hibernation ATG7 and LC3 showed strong, positive immunosignaling within the mucosal surface, while p62 showed strong, positive immunosignaling during nonhibernation. Similar findings were confirmed by immunoblotting. Moreover, the ultrastructural components of autophagy in enterocytes were revealed by transmission electron microscopy (TEM). During hibernation, the cumulative formation of phagophores and autophagosomes were closely associated with well-developed rough endoplasmic reticulum in enterocytes. These autophagosomes overlapped with lysosomes, multivesicular bodies, and degraded mitochondria to facilitate the formation of autophagolysosome, amphisomes, and mitophagy in enterocytes. Immunoblotting showed the expression level of PTEN-induced kinase 1 (PINK1), and adenosine monophosphate-activated protein kinase (AMPK) was enhanced during hibernation. Furthermore, the exosome secretion pathway of early–late endosomes and multivesicular bodies were closely linked with autophagosomes in enterocytes during hibernation. These findings suggest that the entrance into hibernation is a main challenge for reptiles to maintain homeostasis and cellular quality control in the intestine. View Full-Text
Keywords: enterocytes; autophagy; autophagosome; ATG7; LC3; p62; hibernation; Chinese soft-shelled turtle enterocytes; autophagy; autophagosome; ATG7; LC3; p62; hibernation; Chinese soft-shelled turtle
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Vistro, W.A.; Zhang, Y.; Bai, X.; Yang, P.; Huang, Y.; Qu, W.; Baloch, A.S.; Wu, R.; Tarique, I.; Chen, Q. In Vivo Autophagy Up-Regulation of Small Intestine Enterocytes in Chinese Soft-Shelled Turtles during Hibernation. Biomolecules 2019, 9, 682.

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