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Selenium (Se) deficiency can seriously affect the small intestine of swine, and cause diarrhea in swine. However, the specific mechanism of Se deficiency-induced swine diarrhea has rarely been reported. Here, to explore the damage of Se deficiency on the calcium homeostasis and autophagy mechanism of swine, in vivo and in vitro models of swine intestinal Se deficiency were established. Twenty-four pure line castrated male Yorkshire pigs (45 d old, 12.50 ± 1.32 kg, 12 full-sibling pairs) were divided into 2 equal groups and fed Se-deficient diet (0.007 mg Se/kg) as the Se-deficiency group, or fed Se-adequate diet (0.3 mg Se/kg) as the control group for 16 weeks. The intestinal porcine enterocyte cell line (IPEC-J2) was divided into 2 groups, and cultured by Se-deficient medium as the Se-deficient group, or cultured by normal medium as the control group. Morphological observations showed that compared with the control group, intestinal cells in the Se-deficiency group were significantly damaged, and autophagosomes increased. Autophagy staining and cytoplasmic calcium staining results showed that in the Se-deficiency group, autophagy increased and calcium homeostasis was destroyed. According to the reactive oxygen species (ROS) staining results, the percentage of ROS in the Se-deficiency group was higher than that in the control group in the in vitro model. Compared with the control group, the protein and mRNA expressions of autophagy-calcium-related genes including Beclin 1 , microtubule-associated proteins 1A ( LC3-1 ), microtubule-associated proteins 1B ( LC3-2 ), autophagy-related protein 5 ( ATG5 ), autophagy-related protein 12 ( ATG12 ), autophagy-related protein 16 ( ATG16 ), mammalian target of rapamycin ( mTOR ), calmodulin-dependent protein kinase kinase β ( CAMKK-β ), adenosine 5′-monophosphate-activated protein kinase ( AMPK ), sarco(endo)plasmic reticulum Ca 2+ -ATPase ( SERCA ), and calpain in the Se-deficiency group were significantly increased which was consistent in vivo and in vitro ( P < 0.05). Altogether, our results indicated that Se deficiency could destroy the calcium homeostasis of the swine small intestine to trigger cell autophagy and oxidative stress, which was helpful to explain the mechanism of Se deficiency-induced diarrhea in swine.

Selenium (Se) plays a crucial role in intestinal health. However, the specific mechanism by which deficiency of Se causes intestinal damage remains unclear. This study was to explore whether Se deficiency can cause ER stress and induce apoptosis in swine small intestine. We established the Se deficiency swine model in vivo and the intestinal epithelial (IPEC-J2) cell Se deficiency model in vitro. The results of morphological observation showed that Se deficiency caused structural damage in intestinal villi and the decrease of goblet cell structure. The apoptotic characteristics such as nucleolar condensation, mitochondrial swelling, and apoptotic bodies were observed in the IPEC-J2 cells. The results of acridine orange/ethidium bromide and mitochondrial membrane potential fluorescence staining in vitro showed that there were more apoptotic cells in the Se-deficiency group than that in the control group. The protein and/or mRNA expression levels of Bax, Bcl-2, caspase 3, caspase 8, caspase 9, cytc, PERK, ATF6, IRE, XBP1, CHOP, GRP78, which are related to ER stress-apoptosis pathway, were significantly increased in the Se-deficient group which compared with the control group in vivo and in vitro were consistent. These results indicated that Se deficiency induced ER stress and increased the apoptosis in swine small intestine and IPEC-J2 cells and then caused the damage in swine small intestinal tissue. Besides, the results of gene expressions in our experiment proved that ER stress induced by Se deficiency promoted

Background:Selenium deficiency can seriously affect the intestinal status of swine, and cause diarrhea in swine. However, the specific mechanism of selenium intestinal injury caused by selenium deficiency is rarely reported.Methods:Here, to explore the damage of selenium deficiency on the calcium homeostasis and autophagy mechanism of swine, in vivo and in vitro models of swine intestinal selenium deficiency were established. The intestinal model of swine intestine was established by feeding different selenium concentrations. Besides, selenium-deficient medium and normal medium were used to culture IPEC-J2 cells to establish in vitro models. Morphological observation and cell staining were used to determine the way of intestinal injury, and gene expression was quantitatively detected by qPCR and WB.Results:Morphological observations showed that compared with the control group, intestinal cells in the Se-deficiency group were significantly damaged, and autophagosomes increased. MDC staining and cytoplasmic calcium staining results showed that in the Se-deficiency group, autophagy increased and calcium homeostasis was destroyed. Also, according to the ROS test results, the percentage of ROS in the Se-deficiency group is higher than the control group in the in vitro model. Compared with the control group, the protein and mRNA expressions of autophagy and calcium-related genes (Beclin1, LC3-1, LC3-2, ATG5, ATG12, ATG16, mTOR, CAMKK-β, AMPK, SERCA, calpain) in the Se-deficiency group were significantly increased which was consistent in vivo and in vitro. Under the influence of selenium deficiency, the mRNA expression level of selenoproteins decreased significantly, and the steady-state content of some elements was also destroyed. Conclusion:Altogether, our results indicated that selenium deficiency could destroy the calcium homeostasis and antioxidant homeostasis of swine intestine to trigger cell autophagy. Moreover, selenium deficiency reduces the overall expression of selenoproteins and affects the content of elements in the intestine.

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