β-伴大豆球蛋白剂量依赖性上调Hif-1α表达、线粒体自噬和NLRP3炎性小体活性、下调AhR轴诱导杂交黄颡鱼豆粕诱导型肠炎

β-conglycinin induces soybean meal-induced enteritis by dose-dependently up-regulating Hif-1α expression, mitophagy and NLRP3 inflammasomeactivity, and down-regulating AhR axis in hybrid yellow catfish

  • 摘要:
    目的 研究线粒体自噬在杂交黄颡鱼豆粕诱导型肠炎发生发展中的响应规律,初步探讨线粒体自噬在鱼类豆粕诱导型肠炎发生发展中的作用和机制。
    方法 选取初始体重为(5.11 ± 0.52)g的杂交黄颡鱼225尾,随机分为5个处理组,分别按照0、0.5、1.0、2.0、4.0 mg/kg 鱼体重的剂量后肠注射β-伴大豆球蛋白。注射24 h后取后肠组织样本,利用H.E染色、透射电镜、酶联免疫吸附、qRT-PCR等技术方法,分析后肠组织病理和细胞微结构损伤、肠道氧化应激水平、炎症水平,以及线粒体自噬、AhR轴、NLRP3、Hif-1α相关因子等的表达情况。
    结果 β-伴大豆球蛋白刺激剂量依赖性引起杂交黄颡鱼后肠组织病理学损伤,后肠肠道氧化应激水平和炎性水平显著上升,表现为黏膜褶皱长度缩短、固有层变宽、黏膜下层宽度变宽、炎性细胞浸润,后肠ROS、MDA、促炎因子il-1βtnf-α表达水平的显著上调以及抑炎因子il-10tgf-β的显著下调,以4 mg/kg处理组最为严重。透射电镜观察结果显示,β-伴大豆球蛋白刺激导致后肠上皮细胞微绒毛长度变短、疏松,细胞间缝隙变宽。同时,细胞间紧密连接蛋白Zo-1和Occludin 的表达显著下降,上皮细胞间机械屏障功能剂量依赖性受损。杂交黄颡鱼后肠上皮细胞线粒体肿胀、断裂、空泡化、线粒体嵴显著变短或消失,双层膜结构显著受损。线粒体自噬相关基因(parkinpink1bnip3fundc1)以及自噬相关基因(lc3alc3b)的mRNA表达水平显著上调,线粒体外膜电压依赖性阴离子通道蛋白VDAC1和溶酶体相关膜蛋白LAMP2的蛋白表达水平及二者共定位荧光强度显著上调。结果还显示,β-伴大豆球蛋白剂量依赖性抑制AhR轴关键因子的表达,上调Hif-1α的蛋白和mRNA表达水平,激活NLRP3炎性小体活性。
    结论 β-伴大豆球蛋白刺激剂量依赖性引起杂交黄颡鱼后肠豆粕诱导型肠炎,上皮细胞线粒体结构显著受损,线粒体自噬过度激活,后肠组织 AhR 轴关键因子的表达显著受抑制,NLRP3 轴关键因子的表达和 Hif-1α 表达显著上调。提示黄颡鱼后肠上皮细胞线粒体过度自噬可能是引起黄颡鱼豆粕诱导型肠炎的基础,Hif-1α 可能竞争性抑制 AhR 的表达,最终导致 mitophagy-NLRP3 的过度激活,加重杂交黄颡鱼后肠炎症发生。

     

    Abstract: To study the effects of mitochondrial autophagy and its mechanism in the development of soybean meal-induced enteritis in hybrid yellow catfish(Pelteobagrus fulvidraco♀×Pelteobagrus vachelli♂). A total of 225 hybrid yellow catfish with an initial body weight of (5.11 ± 0.52) g were randomly selected and divided into five treatment groups. β-conglycinin was injected at dose of 0, 0.5, 1.0, 2.0, and 4.0 mg/kg fish body weight into the hindgut of each respective group. After 24 h, hindgut samples were collected for analysis of histopathology, mitochondrial damage, intestinal oxidative stress and inflammation levels, and the expression levels of factors related to the AhR axis, NLRP3, and Hif-1α. β-conglycinin stimulation dose-dependently induced significant histopathological injury, increased intestinal oxidative stress and inflammation levels in the hindgut of hybrid yellow catfish, as evidenced by the shortened mucosal fold length, the widened lamina propria and submucosal layer, inflammatory cell infiltration, and a significant up-regulation of hindgut ROS, MDA levels. The pro-inflammatory factors of il-1β and tgf-α were significantly up-regulated, and the anti-inflammatory factors of il -10 and tgf-β were significantly down-regulated. The microvilli of hindgut epithelial cells were shortened and the intercellular junctional gaps were widen dose-dependently by β-conglycinin stimulation, accompanied by the down-regulated expressions of Zo-1 and Occludin. The intestinal barrier function was does-dependently impaired by β-conglycinin. Further more, the mitochondria in the hindgut epithelial cells exhibit swelling, fragmentation, and vacuolization, with markedly shortened or vanished cristae and severely compromised double-membrane structures. The mRNA expression levels of mitochondrial autophagy-related genes (parkin, pink1, bnip3, fundc1) and autophagy-associated genes (lc3a and lc3b) were significantly upregulated. The results of immunofluorescence showed that the protein expression levels of voltage-dependent anion channel 1 (VDAC1) and the lysosome-associated membrane protein 2 (LAMP2), as well as the intensity of their co-localization, were significantly upregulated. The AhR axis were inhibited and the axis of Hif-1α / NLRP3 were dose-dependently activted by β-conglycinin. β-conglycinin induced enteritis in hybrid yellow catfish in a dose-dependent manner, accompained with the significently damaged mitochondrial structure, the hyperactivated mitophagy of the hindgut epithelial cells, the down-regulated AhR axis and the up-regulated axis of Hif-1α / NLRP3. These fundings suggest that the hyperactivated mitophagy in the hindgut epithelial cells of yellow catfish may serve as the underlying mechanism for soybean meal-induced enteritis. Hif-1α may competitively inhibit AhR expression, ultimately leading to hyperactivation of the mitophagy-NLRP3 pathway and exacerbating hindgut inflammation in hybrid yellow catfish. The findings of this study offer a theoretical basis for identifying molecular regulatory targets to alleviated soybean meal-induced enteritis in hybrid yellow catfish.

     

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