2. 生猪健康养殖协同创新中心, 武汉 430070
2. Cooperative Innovation Center for Sustainable Pig Production, Wuhan 430070, China
肠道不仅是营养物质消化吸收的场所，而且是机体最大的免疫器官，维持肠道的结构完整和功能健全是生猪健康养殖的前提和基本保障[1-2]。但是，在养猪生产中，猪常常会遭受断奶、运输、冷热应激或饲料真菌毒素等非感染因素的影响；或者受到各类病原，如猪流行性腹泻病毒(porcine epidemic diarrhea virus，PEDV)等病毒以及大肠杆菌等细菌的感染[3-5]。这些因素损伤肠道后导致严重的肠道疾病，降低生产性能和效益，成为养猪业健康发展的重要限制因素之一。
在养猪生产中，猪受到上述应激后，都会迅速诱发猪肠道产生炎性细胞因子以激活肠道免疫，从而清除病原和毒素；同时，还会激活肠道的损伤修复系统，诱导肠道干细胞的定型分化来促进肠道修复[6-8]。然而，过度的炎性反应导致大量炎性细胞因子的产生或释放，并诱发产生过量的自由基，造成肠道上皮的严重损伤。最严重的肠道病毒，如PEDV等病毒感染，会引起肠道上皮脱落和坏死，引发严重的坏死性肠炎以致死亡[9]；一些常见的病原菌，如产肠毒素大肠杆菌(enterotoxigenic Escherichia coli，ETEC)以及呕吐毒素(deoxynivalenol，DON)等真菌毒素破坏了肠黏膜，不仅产生严重的腹泻等症状，降低生长速度或形成僵猪；而且导致细菌等进入血液引发系统性慢性炎症[10-11]，严重降低饲料效率和生产性能[12]。尽管病毒、细菌和饲料真菌毒素等诱导肠道炎性反应产生的具体机制各异，但其共同特点是炎性反应启动后会被放大，从而产生或释放大量的炎性细胞因子和活性氧(reactive oxygen species，ROS)等自由基[13-14]，对肠道造成严重的损伤。因此，控制肠道的过度炎症，维持肠道上皮屏障的结构和功能的正常是猪营养调控的重要目标。
目前，已经阐明了主要的炎性反应启动信号是位于猪肠道上皮屏障中的模式识别受体信号[15]，以及上皮屏障、生物屏障中的ROS信号等[16]；而过度炎性反应的主体则是免疫屏障中的巨噬细胞[17]。最新的研究发现，细胞程序性死亡(programmed cell death，PCD)在肠道炎症的发生和发展中扮演关键角色[18]。本文重点综述了PCD在肠道炎症发生中的作用，以及饲料成分对肠道PCD调控和对肠道炎性反应影响的研究进展。
1 肠道炎症的作用及过度肠道炎症的危害炎症是机体稳态维持的调控手段之一，在稳态情况下，肠道内的促炎细胞因子和抑炎细胞因子处于动态平衡，控制共生菌稳定的同时也不影响肠道细胞的正常功能。健康的肠道是指在病原菌、食物抗原和毒素存在的情况下，肠道处于一种持续的、可控的炎症状态[19]。常规饲养条件下的猪与无菌猪相比，肠道内促炎细胞因子的表达水平显著上升，免疫细胞浸润增加[20]，这种可控的炎症能够促进肠道的消化、吸收等功能。然而，当肠道炎症发生过度、促炎细胞因子数量过多时，肠道的形态和功能等会遭到破坏[21-22]。因此，控制过度的肠道炎症对于维持猪的肠道稳态十分重要。
固有层中的免疫细胞是促炎细胞因子的主要来源，在肠道炎症发生过度中占据重要地位[23]。肠道上皮位于固有层之上，上皮屏障的稳定能够抑制固有层中免疫细胞的过度激活，从而防止肠道炎症的恶化。在肠道感染过程中，肠上皮细胞的凋亡程度显著增加，隐窝底部的潘氏细胞发生坏死性凋亡，这些死亡细胞释放的损伤相关分子模式(damage-associated molecular patterns，DAMPs)激活了固有层中的免疫细胞[24]；此外，肠道感染会导致肠上皮细胞之间的紧密连接破坏，肠腔中的病原菌、毒素等直接进入固有层，它们携带的病原相关分子模式(pathogen-associated molecular patterns，PAMPs)可直接激活免疫细胞[25]。因此，肠上皮作为隔离机体与肠腔的屏障，它的稳定对于防止过度炎症的发生具有重要意义。
2 PCD与肠道炎性反应肠道稳态的维持不仅需要各种细胞的正常工作，还取决于老旧细胞或具有潜在威胁的细胞的处理，而PCD就是机体处理这一类细胞的方法。PCD包括自噬、凋亡、坏死性凋亡和细胞焦亡等，其中，适度的自噬和凋亡被认为是抗炎的死亡方式，而坏死性凋亡和细胞焦亡因其释放大量的促炎物质被认为是促炎的死亡方式[18]。
2.1 细胞凋亡细胞凋亡可分为外源性凋亡和内源性凋亡。外源性凋亡由细胞膜上的死亡受体驱动，胞内部分的死亡受体招募并激活半胱天冬蛋白酶(cysteinyl aspartate specific proteinase，Caspase)-8，激活的Caspase-8能够直接水解凋亡执行蛋白Caspase-3和Caspase-7[26]。内源性凋亡由线粒体驱动，当细胞出现内质网应激、生长因子缺乏或DNA损伤时，经过一系列信号转导，细胞内的Caspase-9被激活，激活的Caspase-9随后水解Caspase-3和Caspase-7；Caspase-3和Caspase-7能够酶切细胞内的蛋白，导致细胞膜空泡化、DNA剪切和膜磷脂破坏[27]。细胞凋亡最终导致凋亡小体的产生，从而防止细胞内容物泄漏到健康的肠道组织中引起炎症。在肠上皮中，发生生理性凋亡的细胞会逐渐迁移到绒毛顶端，随后脱落到肠腔中，并且隐窝中的干细胞也会发生细胞凋亡[18]，这种凋亡细胞数量少，并且会被吞噬细胞清除，不会产生DAMPs。然而，在肠道稳态破坏的情况下，肠上皮大量的细胞发生凋亡，吞噬细胞不能完全清除这些凋亡细胞，由此产生了大量的DAMPs，从而引发肠道炎症。
养猪生产中的致病因素与肠道细胞凋亡水平的增加息息相关。研究发现，DON处理导致猪小肠上皮细胞系(IPEC-J2细胞)的凋亡率显著增加[28-29]，还会导致IPEC-1细胞中Caspase-3和Caspase-8的表达水平升高[30]。此外，1×109 CFU大肠杆菌攻毒同样提高了Caspase-3的表达水平，加剧了IPEC-J2细胞的凋亡[31]。这些研究表明，DON和ETEC等致病因素能够增加肠道上皮的凋亡，而过度的细胞凋亡也可能是引起肠道炎症的原因之一。
2.2 自噬自噬是一种应对细胞应激的自我保护现象，而如果细胞应激是不可逆的，细胞就会死亡。自噬能够帮助细胞清除错误折叠的蛋白、受损或老化的细胞器等，维持细胞内稳态以起到保护细胞的作用；当细胞发生自噬时，细胞质内容物被隔离形成自噬小体，随后自噬小体与溶酶体合并降解其中的内容物[32]。自噬导致的细胞死亡是一种独特的死亡途径，它不需要Caspase，也不具有凋亡、坏死性凋亡或焦亡的细胞形态学特征[33]。自噬性细胞死亡的特点是细胞内出现大的囊泡和膜泡，细胞器被降解[34]。
在IPEC-J2细胞中，镉能够诱导细胞自噬基因Beclin1和自噬相关蛋白5(autophagy related protein 5，ATG5)的表达，提高微管相关蛋白轻链3(microtubule-associated protein 1 light chain 3，LC3)-Ⅱ/LC3-Ⅰ的比例，细胞自噬水平升高[35]。DON能够诱导IPEC-J2细胞中ATG5和LC3-Ⅱ的蛋白表达水平，激活细胞自噬[36]。此外，低剂量DON联合大肠杆菌处理也能够显著增强IPEC-J2细胞的自噬，并且与正常细胞相比，DON联合大肠杆菌处理提高了LC3B敲除的IPEC-J2细胞中闭锁小带蛋白-1(zonula occludens protein-1，ZO-1)和闭合蛋白(Occludin)的蛋白表达水平，降低了核苷酸结合寡聚化结构域样受体蛋白3(nucleotide-binding oligomerization domain-like receptor protein 3，NLRP3)炎症小体组分的蛋白表达水平，表明过度激活的自噬可能对细胞是有害的[37]。因此，结合之前的研究发现，过度或不足的自噬水平都会对细胞造成不利影响[38]，适度的自噬可能是保护肠道的方法之一。
2.3 坏死性凋亡坏死性凋亡与凋亡的信号通路存在一定的重叠。经典的坏死性凋亡是由肿瘤坏死因子受体(tumor necrosis factor receptor，TNFR)介导的，它既是凋亡的上游信号，也是坏死性凋亡的上游信号。TNFR的激活促进了细胞内TNFR复合物Ⅰ的组装。当TNFR复合物Ⅰ驱动的核因子-κB(nuclear factor kappa B，NF-κB)信号通路被阻断时，胞浆内TNFR复合物Ⅱ通过激活Caspase-8二聚体发挥促凋亡功能，此时细胞发生凋亡[39]。如果Caspase-8或其衔接蛋白Fas相关死亡结构域(Fas-associating protein with a novel death domain，FADD)受损时，受体互作蛋白激酶(receptor-interacting protein kinase，RIP)1和RIP3发生互作后，就会激活形成坏死小体，这导致坏死性凋亡执行蛋白混合系激酶区域样蛋白(mixed-lineage kinase domain-like protein，MLKL)寡聚化，易位到细胞膜并在细胞膜上打孔[40]，由此细胞就从凋亡转向坏死性凋亡。除此之外，坏死性凋亡还能够由Toll样受体(Toll-like receptor，TLR)3和4的配体、病毒及干扰素等激活[41]。虽然这些信号引起坏死性凋亡的机制各异，但最后都汇聚到RIP3和MLKL的激活这一事件。坏死性凋亡的发生通常伴随着大量的DAMPs的释放，如ATP、线粒体DNA和高迁移率族蛋白B1 (high mobility group protein B1，HMGB1)等，这些物质能够在固有层中激活免疫细胞，释放大量促炎细胞因子，起到炎症放大的作用。
坏死性凋亡的发生同样威胁着猪肠道的健康。研究表明，DON处理的IPEC-1细胞中HMGB1和磷酸化MLKL的表达水平显著升高，表明DON引起了细胞坏死性凋亡的发生[30]。脂多糖(lipopolysaccharide，LPS)是革兰氏阴性菌表面的抗原，对仔猪进行LPS腹腔注射后激活了肠道坏死性凋亡的发生，而坏死性凋亡的程序性坏死特异性抑制剂Necrostatin-1(Nec-1)处理则显著改善了LPS诱导的肠道损伤[42]。除了上述致病性的因素，还存在其他因素也会导致肠道健康受损。研究发现，硒缺乏降低了肠道绒毛高度/隐窝深度，并且还会导致IPEC-J2细胞和回肠中坏死性凋亡的发生[43]。镉暴露导致IPEC-J2细胞和猪小肠中RIP1、RIP3和MLKL的mRNA和蛋白表达水平显著升高[44]。炎性细胞因子肿瘤坏死因子-α(tumor necrosis factor-α，TNF-α)处理导致IPEC-1细胞中TNFR1和HMGB1的表达水平显著升高[45]。
2.4 细胞焦亡细胞焦亡是由激活的炎症小体驱动的一种程序性死亡形式，常见的炎症小体包括经典的NLRP3、NLR家族含CARD结构蛋白4(NLR family CARD domain-containing protein 4，NLRC4)炎症小体和Caspase-4/5/11介导的非经典炎症小体[18]。经典的炎症小体是由模式识别受体、衔接蛋白凋亡相关斑点样蛋白(apoptosis-associated speck-like protein containing a CARD，ASC)和Caspase构成。核苷酸结合寡聚化结构域(NOD)样受体家族由DAMPs或PAMPs激活，随后导致Caspase-1的自我水解激活，激活的Caspase-1能够剪切焦亡执行蛋白Gasdermin D(GSDMD)和前体炎性细胞因子白细胞介素-1β前体(pro-interleukin-1β，pro-IL-1β)和白细胞介素-18前体(pro-interleukin-18，pro-IL-18)，成熟的GSDMD寡聚体随后迁移到细胞膜上进行打孔，白细胞介素-1β(interleukin-1β，IL-1β)和白细胞介素-18(interleukin-18，IL-18)从孔中流出到细胞外。例如，当肠上皮细胞感染鼠伤寒沙门氏菌时，NLRC4炎症小体被激活，导致肠上皮细胞发生焦亡[46]。对于非经典炎症小体，细胞内的LPS能够通过激活Caspase-4/5/11来引发细胞焦亡[47]。细胞焦亡过程伴随着大量促炎细胞因子的释放，这些细胞因子在体内不断累积导致过度的肠道炎症，因此焦亡可能是过度炎症的直接结果。
在猪的不同肠段中，炎症小体的组分NLRP3、ASC和Caspase-1均有表达，其中以空肠中表达水平最高，并且在大肠杆菌感染后，猪空肠中IL-1β含量显著升高[48]。DON处理的的IPEC-J2细胞中剪切的(cleaved)-Caspase-1蛋白表达水平显著提高，并且DON联合大肠杆菌攻毒能够加剧猪空肠中NLRP3炎症小体的激活[37]。此外，LPS刺激猪单核巨噬细胞同样能够引起NLRP3炎症小体的激活[49]。这些研究表明，NLRP3炎症小体介导的细胞焦亡在猪肠道感染中发挥重要作用。然而，对猪的NLRC4基因进行测序后发现，与人的NLRC4基因相比，猪NLRC4基因中有外显子的缺失，并且猪不表达NLRC4基因，这表明在肠道炎症中，NLRC4炎症小体可能不参与细胞焦亡过程[50]。
3 饲料成分调控PCD缓解肠道炎症众多研究表明，功能性氨基酸、脂肪酸、植物提取物、益生菌、生物活性肽等饲料成分，可以通过调控PCD来缓解多种因素引起的肠道炎症，增加肠道屏障功能，从而提高畜禽养殖业生产效益。
3.1 功能性氨基酸功能性氨基酸是指可以参与调节动物机体关键代谢途径的氨基酸，具有改善动物健康状况，促进生长、发育、繁殖等的作用[51]。常见的功能性氨基酸包括谷氨酰胺、精氨酸、色氨酸和支链氨基酸等[51-52]。功能性氨基酸可通过抑制多种因素引起的肠道细胞过度凋亡，从而维持肠道正常的形态结构和功能。比如，在仔猪饲粮中添加0.5%或1.0%的精氨酸至断奶后18 d，可以缓解仔猪LPS诱导的肠道损伤，并且该作用部分是通过减少小肠绒毛细胞凋亡来实现的[53]。饲粮添加0.2%丝氨酸4周，可降低断奶仔猪空肠凋亡细胞数量，抑制Caspase-3和B细胞淋巴瘤相关X蛋白(B-cell lymphoma-2-associated X protein，Bax)基因表达，促进B淋巴细胞瘤-2L1(B-cell lymphoma-2L1，Bcl-2L1)基因表达，从而增强肠道屏障功能；并且可以缓解断奶应激引起的肠道炎症和系统性氧化应激[54]。14~25日龄仔猪饲粮中添加500 mg/kg N-乙酰半胱氨酸，可通过抑制空肠凋亡相关因子及其下游的Caspase-3和Caspase-8基因的表达，从而抑制断奶应激引起的空肠细胞过度凋亡，维持空肠形态结构[55]。小鼠连续6 d灌胃5 g/kg BW甘氨酸，可以降低空肠和结肠脱氧核糖核苷酸末端转移酶介导的缺口末端标记(terminal-deoxynucleotidyl transferase mediated nick end labeling，TUNEL)阳性细胞(凋亡细胞)数量以及空肠cleaved Caspase-3蛋白表达水平，并且降低了空肠和回肠炎性细胞因子表达水平，缓解了小鼠腹腔注射LPS诱导的肠道损伤[56]。最近的研究还发现，仔猪饲粮连续14 d添加0.2%或0.4%色氨酸，可通过抑制Caspase-3激活来缓解LPS刺激引起的仔猪回肠上皮细胞过度凋亡[57]。
也有研究发现，功能性氨基酸可通过抑制肠道细胞焦亡来缓解肠道炎症。Liu等[57]研究发现，仔猪饲粮添加0.2%或0.4%色氨酸至断奶35日龄，可通过抑制Caspase-1、NLRP3和GSDMD蛋白的表达来抑制LPS刺激引起的回肠上皮细胞焦亡，从而缓解LPS刺激引起的内质网应激。
功能性氨基酸也可以通过调控自噬来影响肠道炎症进程。培养基缺乏非必需氨基酸的情况下，可以诱导IPEC-1细胞LC3-Ⅰ转变为LC3-Ⅱ，并破坏细胞屏障功能[58]。值得注意的是，培养基缺乏L-谷氨酰胺的情况下，可以通过抑制哺乳动物雷帕霉素靶蛋白(mammalian target of rapamycin，mTOR)和丝裂原活化蛋白激酶(mitogen activated protein kinase，MAPK)/细胞外信号调节蛋白激酶(extracellular signals regulate protein kinases，ERK)通路来诱导IPEC-1细胞自噬，并干扰氨基酸代谢，从而抑制蛋白合成和细胞增殖[59]。Zhang等[60]研究发现，饲粮连续21 d添加N-氨基甲酰谷氨酸(0.1%)或L-精氨酸(0.1%)可增加宫内生长迟缓(intrauterine growth retardation，IUGR)羔羊十二指肠屏障功能和线粒体功能，缓解肠道炎症并抑制线粒体自噬。此外，仔猪连续2 d灌胃50 mg/kg BW的N-乙酰半胱氨酸，可以改善饲喂含有β-伴大豆球蛋白液态饲粮仔猪肠道代谢和吸收功能，缓解腹泻并抑制空肠黏膜细胞自噬[61]。
3.2 脂肪酸脂肪酸根据含有的碳原子数可以分为短链脂肪酸、中链脂肪酸和长链脂肪酸。短链脂肪酸为含有1~6个碳原子的脂肪酸，包括直链脂肪酸(主要为酸、丙酸和丁酸)和支链脂肪酸(包括异丁酸和异戊酸)。直链脂肪酸主要由肠道微生物分解宿主肠腔中消化酶不能消化的碳水化合物产生，而支链脂肪酸则由肠道微生物分解含氮物质(主要为支链氨基酸)生成。中链脂肪酸为含有6~12个碳原子的脂肪酸，主要包括己酸(C6 ∶ 0)、辛酸(C8 ∶ 0)、癸酸(C10 ∶ 0)和十二烷酸(C12 ∶ 0)。长链脂肪酸含有的碳原子数大于12，如棕榈酸(C16 ∶ 0)、硬脂酸(C18 ∶ 0)、花生四烯酸(C20 ∶ 4)、二十二碳六烯酸(C22 ∶ 6)等。首先，短链脂肪酸可通过调控细胞凋亡来影响肠道炎症。组蛋白去乙酰化酶(histone deacetylase，HDAC)1可与T细胞中的Fas启动子结合，而丁酸通过抑制HDAC1活性来诱导T细胞中的Fas启动子超乙酰化和Fas基因表达，从而通过诱导T细胞凋亡来缓解结肠炎[62]。
此外，短链脂肪酸还被证明可以通过诱导自噬来缓解多种因素引起的肠道炎症和肠道损伤。饮水添加2%的丁酸钠4周，可通过低氧诱导因子-1α(hypoxia inducible factor-1α，HIF-1α)上调自噬，缓解小鼠葡聚糖硫酸钠(dextran sulphate sodium，DSS)诱导的结肠炎症[63]。丁酸钠可通过激活腺苷酸活化蛋白激酶(AMP-activated protein kinase，AMPK)信号通路诱导线粒体自噬，缓解IPEC-J2细胞过氧化氢(hydrogen peroxide，H2O2)诱导的氧化应激、炎症、细胞屏障功能和线粒体功能障碍[64]。此外，在21~35日龄断奶仔猪饲粮添加0.75 g/kg的三丁酸甘油酯，可以缓解仔猪敌草快腹腔滴注引起的氧化应激、肠道炎症和肠道损伤，改善线粒体功能，并诱导线粒体自噬，从而提高仔猪的生长性能[65]。值得注意的是，约氏乳杆菌CJ21和枯草芽孢杆菌BS15混合益生菌通过促进丁酸的产生来诱导结肠上皮细胞自噬，进而抑制婴儿沙门氏菌在断奶仔猪结肠上皮细胞内增殖[66]。
也有研究发现，短链脂肪酸和中链脂肪酸可以抑制肠上皮细胞焦亡和坏死性凋亡。乙酸、丙酸和丁酸可通过抑制HDAC活性来抑制NLRP3炎性小体激活，促进紧密连接蛋白表达，缓解LPS诱导的人结肠上皮细胞(Caco-2)屏障功能障碍[67]。另外，二十碳五烯酸和花生四烯酸可以缓解IPEC-1细胞ETEC k88诱导的炎症和细胞屏障功能损伤，部分是通过抑制NLRP3炎性小体介导的细胞焦亡以及受体互作蛋白激酶3(receptor-interacting protein kinase 3，RIPK3)介导的坏死性凋亡实现[68]。
3.3 植物提取物植物提取物是来源于植物的多酚、生物碱、精油、有机酸、多糖和色素，具有抗氧化、抗炎、抗菌、调节胃肠道功能和促生长的作用[69-70]。多种植物提取物被证明可以通过抑制肠道细胞过度凋亡来增加肠道屏障功能、抑制肠道炎症。在断奶仔猪饲粮中连续14 d添加100 mg/kg褐藻寡糖，可通过上调B淋巴细胞瘤-2(B-cell lymphoma-2，Bcl-2)基因以及下调Bax、Caspase-3和Caspase-9基因抑制小肠上皮凋亡，增加肠道屏障功能，从而增加断奶14 d仔猪平均体重[71]。此外，在断奶14 d内的仔猪饲粮中添加0.1%绿原酸，可降低空肠晚期凋亡细胞占总凋亡细胞百分比以及十二指肠和空肠Bax与Bcl-2基因比值，从而缓解断奶应激引起的仔猪小肠上皮细胞过度凋亡[72]。落新妇苷通过增强抗氧化酶活性和屏障功能相关基因表达，降低炎症和凋亡相关基因表达，从而缓解DON引起的IPEC-J2细胞氧化应激、炎症、过度细胞凋亡和细胞屏障功能障碍[73]。山奈酚则可通过上调细胞周期(G1/S-特异性周期蛋白-D1、细胞周期素依赖性激酶4和E2F转录因子1)和抗氧化系统(谷胱甘肽还原酶、谷胱甘肽s转移酶α4和血红素加氧酶-1)相关基因表达，增加紧密连接蛋白[ZO-1、闭锁小带蛋白-2(zonula occludens protein-2，ZO-2)、Occludin和封闭蛋白-4(Claudin-4)]、抗氧化转录因子核因子E2相关因子2(nuclear factor E2-related factor 2，Nrf2)蛋白丰度，并通过增加Bcl-2与Bax蛋白丰度比值，缓解敌草快诱导的IPEC-1细胞过度凋亡、氧化应激、细胞周期阻滞和细胞屏障功能障碍[74]。另外，槲皮素通过抑制细胞过度凋亡和氧化应激，促进细胞增殖，从而缓解H2O2诱导的IPEC-J2细胞损伤[75]。松果菊苷是从管花肉苁蓉中分离、纯化的一种苯乙醇苷类化合物，可通过抑制mTOR/信号转导及转录激活蛋白3(signal transducer and activator of transcription 3，STAT3)通路来抑制大鼠小肠上皮细胞(IEC-6细胞)LPS诱导的炎症和细胞凋亡[76]。姜黄素可以剂量依赖性地抑制人结肠上皮细胞(HT29细胞)干扰素-γ(interferon-γ，IFN-γ)诱导的细胞凋亡，这可能与姜黄素抑制白细胞介素-7(interleukin-7，IL-7)的表达有关[77]。
特定的植物提取物也可以通过调控肠道细胞自噬来发挥抑炎作用。小鼠连续7 d灌胃2 mg/kg BW雷公藤红素，可以通过抑制磷酸肌醇-3-激酶(phosphoinositide-3-kinase，PI3K)/蛋白激酶B(protein kinase B，Akt)/mTOR信号通路上调结肠组织自噬，降低结肠组织髓过氧化物酶(myeloperoxidase，MPO)活性，抑制促炎细胞因子表达和中性粒细胞浸润，从而缓解白细胞介素-10(interleukin-10，IL-10)缺陷小鼠自发性结肠炎[78]。小檗碱通过激活AMPK/mTOR信号通路来激活自噬，缓解小鼠单核巨噬细胞(J774A.1细胞)氧化型低密度脂蛋白诱导的炎症[79]。Cao等[80]研究发现，断奶仔猪饲粮连续14 d添加100 mg/kg的白藜芦醇，可以缓解仔猪敌草快腹腔滴注引起的肠道损伤、氧化应激和线粒体损伤，并诱导线粒体自噬。
特定的植物提取物还可以通过抑制NLRP3炎性小体激活来缓解肠道炎症和肠道损伤。小鼠连续7 d灌胃3、10、30 mg/kg BW羟基积雪草酸，可以抑制结肠NLRP3炎性小体激活、炎性细胞因子表达以及线粒体ROS产生，缓解小鼠DSS引起的结肠炎[81]。豆蔻素作为芳香烃受体配体可通过芳香烃受体(aryl hydrocarbon receptor，AhR)/Nrf2/Nrf2调控的抗氧化因子醌氧化还原酶1(quinine oxidoreductase 1，NQO1)通路抑制NLRP3炎性小体激活和炎性细胞因子表达，小鼠连续7或10 d灌胃15、30、60 mg/kg BW豆蔻素，可以分别缓解2, 4, 6-三硝基苯磺酸(2, 4, 6-trinitro-benzenesulfonic acid，TNBS)和DSS诱导的结肠炎和结肠损伤[82]。血根碱通过抑制结肠促炎细胞因子表达、阻断NLRP3-Caspase-1/IL-1β信号通路以及改善结肠菌群稳态，缓解小鼠DSS诱导的结肠炎[83]。
3.4 益生菌饲粮中添加益生菌对畜禽肠道健康有显著的影响[84]，使用的益生菌包括乳杆菌、双歧杆菌、肠球菌、芽孢杆菌等[85]。鼠李糖乳杆菌、丁酸梭菌、双歧杆菌等直接饲喂微生物被证明可通过抑制肠道细胞凋亡来缓解多种因素引起的肠道损伤。鼠李糖乳杆菌RC007可以抑制DON诱导的仔猪空肠外植体炎性细胞因子的表达，并可能通过抑制MAPK信号通路来抑制细胞凋亡，降低DON的肠道毒性[86]。Yang等[87]利用肉仔鸡进行试验发现，植物乳杆菌JM113可通过降低空肠组织Bax与Bcl-2基因比值以及抑制炎性细胞因子表达，激活mTOR信号通路，从而缓解肉仔鸡DON诱导的肠道损伤。丁酸梭菌可通过直接抑制肠出血性大肠杆菌黏附于鸡胚肠上皮细胞，以及间接抑制Caspase-9和Caspase-3的激活来抑制鸡胚肠上皮细胞凋亡，从而缓解肠出血性大肠杆菌诱导的肠道损伤[88]。酪丁酸梭菌通过抑制MAPK和c-Jun氨基末端激酶(c-Jun N-terminal kinase，JNK)信号通路抑制LPS诱导的细胞凋亡，从而维持IPEC-J2细胞的细胞屏障功能[89]。Tang等[90]研究发现，解淀粉芽孢杆菌SC06通过Akt-叉头转录因子(FOXO)通路诱导自噬，缓解敌草快诱导的IPEC-J2细胞氧化应激、细胞凋亡和细胞损伤。此外，早产大鼠的坏死性小肠结肠炎模型中的研究发现，双歧杆菌通过激活TLR2来增加环氧化酶-2(cyclooxgenase-2，COX-2)和前列腺素E2(prostaglandin E2，PGE2)表达，从而通过抑制回肠上皮细胞凋亡来缓解的肠道损伤[91]。
近年来的研究发现，一些益生菌还可以通过抑制肠道细胞焦亡来缓解肠道炎症。饲粮添加丁酸梭菌可以缓解断奶仔猪ETEC引起的肠道屏障功能障碍和肠道炎症，并抑制NLRP3炎性小体激活[92]。约氏乳杆菌L531可通过抑制NLRC4、NLRP3炎性小体激活以及NF-κB信号通路激活来缓解断奶仔猪婴儿沙门氏杆菌感染诱导的肠道炎症[93]。鼠李糖乳杆菌GG则可通过抑制NF-κB信号通路以及NLRP6炎性小体激活，缓解断奶仔猪沙门氏菌单相变异菌株感染引起的肠道炎症和肠道损伤[94]。固有层中的巨噬细胞也参与肠道稳态的维持，副干酪乳杆菌通过诱导巨噬细胞产生IL-10来抑制NLRP3炎性小体激活，进而抑制巨噬细胞激活Caspase-1以及分泌IL-1β[95]。约氏乳杆菌L531通过抑制TLR4/NF-κB/NLRP3炎性小体信号通路，缓解IPEC-J2细胞鼠伤寒沙门氏菌感染诱导的炎症和细胞屏障功能障碍[96]。
此外，一些益生菌也可通过多种信号通路调控自噬，缓解肠道炎症和肠道损伤。其中，部分研究表明，双歧杆菌等益生菌通过促进自噬抑制了肠道炎性反应和损伤。例如，双歧杆菌培养液上清可以抑制大鼠回肠上皮细胞(IEC-18)LPS诱导的自噬，增加IEC-18的细胞屏障功能[97]。约氏乳杆菌L531可通过NF-κB-Sequestosome-1(SQSTM1)通路来诱导线粒体自噬，缓解断奶仔猪婴儿沙门氏菌感染诱导的线粒体损伤[93]。干酪乳杆菌ATCC 393合成的硒纳米颗粒通过调控mTOR/磷酸酯酶与张力蛋白同源物(PTEN)诱导假定激酶1(PINK1)介导的线粒体自噬，有效缓解IPEC-J2细胞H2O2诱导的氧化应激和细胞屏障功能障碍[98]。但也有一些研究发现，部分益生菌对肠道屏障功能的维护作用伴随着自噬发生的降低。罗伊氏乳杆菌ZJ617可通过mTOR通路增加机体抗氧化能力和小肠紧密连接蛋白表达，抑制小肠细胞自噬，从而缓解小鼠LPS诱导的肠道屏障功能障碍[99]。鼠李糖乳杆菌GG可以促进表皮生长因子受体(epidermal growth factor receptor，EGFR)介导的Akt激活来抑制婴儿沙门氏菌感染诱导的断奶仔猪回肠上皮细胞自噬，维持肠道屏障功能[100]。
3.5 生物活性肽在蛋白质分子结构中加密了许多具有独特生物学活性的肽段。这些肽段在母蛋白序列中无生物活性，经胃肠道消化或者食品加工后这些肽段被释放出来，并在体内显示出多种生理功能，因此被称之为生物活性肽[101]。生物活性肽通常包含2~30个氨基酸残基，具有抗氧化、抑菌、免疫调节、降血压、降糖、降胆固醇等多种生理功能[102-104]。本实验室前期研究发现，生物活性三肽(bioactive tripeptide，BTP)可以通过调控细胞焦亡和自噬来缓解肠道炎症；小鼠连续7 d灌胃300 mg/kg BW的BTP，可以抑制鼠伤寒沙门氏菌感染引起的NLRC4炎性激活，并缓解小鼠的鼠伤寒沙门氏菌感染引起肠道炎症和肠道损伤[25]。另外，小鼠连续7 d灌胃50、100、150 mg/kg BW的BTP，可通过增加AMPK磷酸化来抑制ROS的产生，从而通过抑制NLRP3炎性小体激活来缓解小鼠DSS诱导的结肠炎[105]。本实验室相关研究还发现，BTP可以通过诱导转录因子核受体77(Nur77)向线粒体易位，进而通过诱导自噬来抑制炎症和氧化应激[106]。
4 小结肠道过度炎性反应引起肠道结构和功能的损害，控制过度炎性反应已成为动物营养调控的重要目标。在感染和应激等状态下，肠道上皮细胞和固有层细胞发生的PCD在炎性反应的发生和发展中发挥了重要作用。目前，已有众多研究表明，多种饲料成分对肠道过度炎性反应的控制与PCD的调控有关，但是仅有少数研究证明了调控作用是直接通过影响PCD发生的。由于不同类型的PCD在炎性反应中主要发挥的作用不同，不同类型的细胞中主要发生的PCD类型也不同。因此，未来仍需鉴定出调控肠道PCD，从而抑制肠道过度炎性反应的关键靶点，并针对性地研发出靶向调控的应用调控手段，为实现肠道过度炎性反应的控制提供新产品和新技术。
| [1] |
WEISS U. Intestinal networks in health and disease[J]. Nature, 2011, 474(7351): 297. DOI:10.1038/474297a |
| [2] |
ADEWOLE D I, KIM I H, NYACHOTI C M. Gut health of pigs: challenge models and response criteria with a critical analysis of the effectiveness of selected feed additives—a review[J]. Asian-Australasian Journal of Animal Sciences, 2016, 29(7): 909-924. |
| [3] |
TANG F, WANG J F, LI D Z, et al. Comparative genomic analysis of 127 Escherichia coli strains isolated from domestic animals with diarrhea in China[J]. BMC Genomics, 2019, 20(1): 212. DOI:10.1186/s12864-019-5588-2 |
| [4] |
ZHANG H L, HAN F F, YAN X G, et al. Prevalence and phylogenetic analysis of spike gene of porcine epidemic diarrhea virus in Henan province, China in 2015-2019[J]. Infection, Genetics and Evolution, 2021, 88: 104709. DOI:10.1016/j.meegid.2021.104709 |
| [5] |
YANG C K, CHENG Y H, TSAI W T, et al. Prevalence of mycotoxins in feed and feed ingredients between 2015 and 2017 in Taiwan[J]. Environmental Science and Pollution Research International, 2019, 26(23): 23798-23806. DOI:10.1007/s11356-019-05659-0 |
| [6] |
LEBERT D C, HUTTENLOCHER A. Inflammation and wound repair[J]. Seminars in Immunology, 2014, 26(4): 315-320. DOI:10.1016/j.smim.2014.04.007 |
| [7] |
SOMMER K, WIENDL M, MVLLER T M, et al. Intestinal mucosal wound healing and barrier integrity in IBD-crosstalk and trafficking of cellular players[J]. Frontiers in Medicine, 2021, 8: 643973. DOI:10.3389/fmed.2021.643973 |
| [8] |
XUE X, FALCON D M. The role of immune cells and cytokines in intestinal wound healing[J]. International Journal of Molecular Sciences, 2019, 20(23): 6097. DOI:10.3390/ijms20236097 |
| [9] |
JUNG K, SAIF L J, WANG Q H. Porcine epidemic diarrhea virus (PEDV): an update on etiology, transmission, pathogenesis, and prevention and control[J]. Virus Research, 2020, 286: 198045. DOI:10.1016/j.virusres.2020.198045 |
| [10] |
PARDO-CAMACHO C, GONZÁLEZ-CASTRO A M, RODIÑO-JANEIRO B K, et al. Epithelial immunity: priming defensive responses in the intestinal mucosa[J]. American Journal of Physiology.Gastrointestinal and Liver Physiology, 2018, 314(2): G247-G255. DOI:10.1152/ajpgi.00215.2016 |
| [11] |
ALLAIRE J M, CROWLEY S M, LAW H T, et al. The intestinal epithelium: central coordinator of mucosal immunity[J]. Trends in Immunology, 2018, 39(9): 677-696. DOI:10.1016/j.it.2018.04.002 |
| [12] |
PLUSKE J R, TURPIN D L, KIM J C. Gastrointestinal tract (gut) health in the young pig[J]. Animal Nutrition, 2018, 4(2): 187-196. DOI:10.1016/j.aninu.2017.12.004 |
| [13] |
YANG Q L, WANG Y X, JIA A N, et al. The crosstalk between gut bacteria and host immunity in intestinal inflammation[J]. Journal of Cellular Physiology, 2021, 236(4): 2239-2254. DOI:10.1002/jcp.30024 |
| [14] |
LEONARDI I, LI X, ILIEV I D. Macrophage interactions with fungi and bacteria in inflammatory bowel disease[J]. Current Opinion in Gastroenterology, 2018, 34(6): 392-397. DOI:10.1097/MOG.0000000000000479 |
| [15] |
UENISHI H, SHINKAI H. Porcine Toll-like receptors: the front line of pathogen monitoring and possible implications for disease resistance[J]. Developmental and Comparative Immunology, 2009, 33(3): 353-361. DOI:10.1016/j.dci.2008.06.001 |
| [16] |
BRYAN N, AHSWIN H, SMART N, et al. Reactive oxygen species (ROS)—a family of fate deciding molecules pivotal in constructive inflammation and wound healing[J]. European Cells & Materials, 2012, 24: 249-265. |
| [17] |
KRATOFIL R M, KUBES P, DENISET J F. Monocyte conversion during inflammation and injury[J]. Arteriosclerosis, Thrombosis, and Vascular Biology, 2017, 37(1): 35-42. DOI:10.1161/ATVBAHA.116.308198 |
| [18] |
PATANKAR J V, BECKER C. Cell death in the gut epithelium and implications for chronic inflammation[J]. Nature Reviews: Gastroenterology & Hepatology, 2020, 17(9): 543-556. |
| [19] |
LIU Y L. Fatty acids, inflammation and intestinal health in pigs[J]. Journal of Animal Science and Biotechnology, 2015, 6(1): 41. DOI:10.1186/s40104-015-0040-1 |
| [20] |
SHIRKEY T W, SIGGERS R H, GOLDADE B G, et al. Effects of commensal bacteria on intestinal morphology and expression of proinflammatory cytokines in the gnotobiotic pig[J]. Experimental Biology and Medicine, 2006, 231(8): 1333-1345. DOI:10.1177/153537020623100807 |
| [21] |
CHENG C S, XIA M, ZHANG X M, et al. Supplementing oregano essential oil in a reduced-protein diet improves growth performance and nutrient digestibility by modulating intestinal bacteria, intestinal morphology, and antioxidative capacity of growing-finishing pigs[J]. Animals, 2018, 8(9): 159. DOI:10.3390/ani8090159 |
| [22] |
LUO Y H, LIU L, CHEN D W, et al.Dietary supplementation of fructo-oligosaccharides alleviates enterotoxigenic E. coli-induced disruption of intestinal epithelium in a weaned piglet model[J/OL].British Journal of Nutrition: 1-9[2022-07-15].https://doi.org/10.1017/S0007114521004451.DOI: 10.1017/S0007114521004451.
|
| [23] |
CAPRARA G, ALLAVENA P, ERRENI M. Intestinal macrophages at the crossroad between diet, inflammation, and cancer[J]. International Journal of Molecular Sciences, 2020, 21(14): 4825. DOI:10.3390/ijms21144825 |
| [24] |
ADOLPH T E, TOMCZAK M F, NIEDERREITER L, et al. Paneth cells as a site of origin for intestinal inflammation[J]. Nature, 2013, 503(7475): 272-276. DOI:10.1038/nature12599 |
| [25] |
CUI C B, LIU Q, DUAN B B, et al. Bioactive triple peptide inhibits inflammasome activation to alleviate Salmonella-induced intestinal inflammation in mice via modulation of host defense and bacterial virulence[J]. Food & Function, 2022, 13(6): 3512-3525. |
| [26] |
BOATRIGHT K M, SALVESEN G S. Mechanisms of caspase activation[J]. Current Opinion in Cell Biology, 2003, 15(6): 725-731. DOI:10.1016/j.ceb.2003.10.009 |
| [27] |
SHI Y G. Caspase activation: revisiting the induced proximity model[J]. Cell, 2004, 117(7): 855-858. DOI:10.1016/j.cell.2004.06.007 |
| [28] |
李若楠, 康瑞芬, 沈丹, 等. 谷氨酰胺对呕吐毒素诱导IPEC-J2细胞凋亡和炎症的影响[J]. 南京农业大学学报, 2020, 43(4): 740-747. LI R N, KANG R F, SHEN D, et al. Effects of glutamine on deoxynivalenol induced apoptosis and inflammation of IPEC-J2 cells[J]. Journal of Nanjing Agricultural University, 2020, 43(4): 740-747 (in Chinese). |
| [29] |
廖美芳, 孟英才, 詹济华, 等. 呕吐毒素对IPEC-J2细胞凋亡的影响[J]. 动物营养学报, 2018, 30(3): 1027-1034. LIAO M F, MENG Y C, ZHAN J H, et al. Effects of deoxynivalenol on apoptosis of IPEC-J2 cells[J]. Chinese Journal of Animal Nutrition, 2018, 30(3): 1027-1034 (in Chinese). DOI:10.3969/j.issn.1006-267x.2018.03.027 |
| [30] |
XIAO K, LIU C C, QIN Q, et al. EPA and DHA attenuate deoxynivalenol-induced intestinal porcine epithelial cell injury and protect barrier function integrity by inhibiting necroptosis signaling pathway[J]. The FASEB Journal, 2020, 34(2): 2483-2496. DOI:10.1096/fj.201902298R |
| [31] |
XIA P P, WU Y P, LIAN S Q, et al. Deletion of FaeG alleviated enterotoxigenic Escherichia coli F4ac-induced apoptosis in the intestine[J]. AMB Express, 2021, 11(1): 44. DOI:10.1186/s13568-021-01201-z |
| [32] |
KUMAR P, JAGTAP Y A, PATWA S M, et al. Autophagy based cellular physiological strategies target oncogenic progression[J]. Journal of Cellular Physiology, 2022, 237(1): 258-277. DOI:10.1002/jcp.30567 |
| [33] |
BEDOUI S, HEROLD M J, STRASSER A. Emerging connectivity of programmed cell death pathways and its physiological implications[J]. Nature Reviews Molecular Cell Biology, 2020, 21(11): 678-695. DOI:10.1038/s41580-020-0270-8 |
| [34] |
KROEMER G, LEVINE B. Autophagic cell death: the story of a misnomer[J]. Nature Reviews: Molecular Cell Biology, 2008, 9(12): 1004-1010. DOI:10.1038/nrm2529 |
| [35] |
CAO Z, GAO J S, HUANG W Y, et al. Curcumin mitigates deoxynivalenol-induced intestinal epithelial barrier disruption by regulating Nrf2/p53 and NF-κB/MLCK signaling in mice[J]. Food and Chemical Toxicology, 2022, 167: 113281. DOI:10.1016/j.fct.2022.113281 |
| [36] |
LIU S P, KANG W L, MAO X R, et al. Low dose of arsenic exacerbates toxicity to mice and IPEC-J2 cells exposed with deoxynivalenol: aryl hydrocarbon receptor and autophagy might be novel therapeutic targets[J]. Science of the Total Environment, 2022, 832: 155027. DOI:10.1016/j.scitotenv.2022.155027 |
| [37] |
GE L, LIU D D, MAO X R, et al. Low dose of deoxynivalenol aggravates intestinal inflammation and barrier dysfunction induced by enterotoxigenic Escherichia coli infection through activating macroautophagy/NLRP3 inflammasomes[J]. Journal of Agricultural and Food Chemistry, 2022, 70(9): 3009-3022. DOI:10.1021/acs.jafc.1c07834 |
| [38] |
YAMOTO M, LEE C, CHUSILP S, et al. The role of autophagy in intestinal epithelial injury[J]. Pediatric Surgery International, 2019, 35(12): 1389-1394. DOI:10.1007/s00383-019-04566-2 |
| [39] |
TENEV T, BIANCHI K, DARDING M, et al. The ripoptosome, a signaling platform that assembles in response to genotoxic stress and loss of IAPs[J]. Molecular Cell, 2011, 43(3): 432-448. DOI:10.1016/j.molcel.2011.06.006 |
| [40] |
HILDEBRAND J M, TANZER M C, LUCET I S, et al. Activation of the pseudokinase MLKL unleashes the four-helix bundle domain to induce membrane localization and necroptotic cell death[J]. Proceedings of the National Academy of Sciences of the United States of America, 2014, 111(42): 15072-15077. DOI:10.1073/pnas.1408987111 |
| [41] |
MARTENS S, BRIDELANCE J, ROELANDT R, et al. MLKL in cancer: more than a necroptosis regulator[J]. Cell Death and Differentiation, 2021, 28(6): 1757-1772. DOI:10.1038/s41418-021-00785-0 |
| [42] |
LIU Y L, XU Q, WANG Y, et al. Necroptosis is active and contributes to intestinal injury in a piglet model with lipopolysaccharide challenge[J]. Cell Death & Disease, 2021, 12(1): 62. |
| [43] |
ZHANG Y, ZHANG J L, BAO J, et al. Selenium deficiency induced necroptosis, Th1/Th2 imbalance, and inflammatory responses in swine ileum[J]. Journal of Cellular Physiology, 2021, 236(1): 222-234. DOI:10.1002/jcp.29836 |
| [44] |
CHEN X M, BI M Y, YANG J, et al. Cadmium exposure triggers oxidative stress, necroptosis, Th1/Th2 imbalance and promotes inflammation through the TNF-α/NF-κB pathway in swine small intestine[J]. Journal of Hazardous Materials, 2022, 421: 126704. DOI:10.1016/j.jhazmat.2021.126704 |
| [45] |
XIAO K, XU Q, LIU C C, et al. Docosahexaenoic acid alleviates cell injury and improves barrier function by suppressing necroptosis signaling in TNF-α-challenged porcine intestinal epithelial cells[J]. Innate Immunity, 2020, 26(8): 653-665. DOI:10.1177/1753425920966686 |
| [46] |
RAUCH I, DEETS K A, JI D X, et al. NAIP-NLRC4 inflammasomes coordinate intestinal epithelial cell expulsion with eicosanoid and IL-18 release via activation of caspase-1 and -8[J]. Immunity, 2017, 46(4): 649-659. DOI:10.1016/j.immuni.2017.03.016 |
| [47] |
KAYAGAKI N, WONG M T, STOWE I B, et al. Noncanonical inflammasome activation by intracellular LPS independent of TLR4[J]. Science, 2013, 341(6151): 1246-1249. DOI:10.1126/science.1240248 |
| [48] |
KERN M, ASCHENBACH J R, TEDIN K, et al. Characterization of inflammasome components in pig intestine and analysis of the influence of probiotic Enterococcus faecium during an Escherichia coli challenge[J]. Immunological Investigations, 2017, 46(7): 742-757. DOI:10.1080/08820139.2017.1360341 |
| [49] |
LIU Y, YAO W X, XU J, et al. The anti-inflammatory effects of acetaminophen and N-acetylcysteine through suppression of the NLRP3 inflammasome pathway in LPS-challenged piglet mononuclear phagocytes[J]. Innate Immunity, 2015, 21(6): 587-597. DOI:10.1177/1753425914566205 |
| [50] |
SAKUMA C, TOKI D, SHINKAI H, et al. Pig lacks functional NLRC4 and NAIP genes[J]. Immunogenetics, 2017, 69(2): 125-130. DOI:10.1007/s00251-016-0955-5 |
| [51] |
WU G Y. Functional amino acids in growth, reproduction, and health[J]. Advances in Nutrition, 2010, 1(1): 31-37. DOI:10.3945/an.110.1008 |
| [52] |
KIM S W, MATEO R D, YIN Y L, et al. Functional amino acids and fatty acids for enhancing production performance of sows and piglets[J]. Asian-Australasian Journal of Animal Sciences, 2007, 20(2): 295-306. |
| [53] |
LIU Y L, HUANG J J, HOU Y Q, et al. Dietary arginine supplementation alleviates intestinal mucosal disruption induced by Escherichia coli lipopolysaccharide in weaned pigs[J]. British Journal of Nutrition, 2008, 100(3): 552-560. DOI:10.1017/S0007114508911612 |
| [54] |
ZHOU X H, ZHANG Y M, WU X, et al. Effects of dietary serine supplementation on intestinal integrity, inflammation and oxidative status in early-weaned piglets[J]. Cellular Physiology and Biochemistry, 2018, 48(3): 993-1002. DOI:10.1159/000491967 |
| [55] |
ZHU L H, CAI X, GUO Q, et al. Effect of N-acetyl cysteine on enterocyte apoptosis and intracellular signaling pathways' response to oxidative stress in weaned piglets[J]. British Journal of Nutrition, 2013, 110(11): 1938-1947. DOI:10.1017/S0007114513001608 |
| [56] |
ZHANG Y C, MU T Q, JIA H, et al. Protective effects of glycine against lipopolysaccharide-induced intestinal apoptosis and inflammation[J]. Amino Acids, 2022, 54(3): 353-364. DOI:10.1007/s00726-021-03011-w |
| [57] |
LIU G M, TAO J Y, LU J J, et al. Dietary tryptophan supplementation improves antioxidant status and alleviates inflammation, endoplasmic reticulum stress, apoptosis, and pyroptosis in the intestine of piglets after lipopolysaccharide challenge[J]. Antioxidants, 2022, 11(5): 872. DOI:10.3390/antiox11050872 |
| [58] |
YANG Y, LI W, SUN Y L, et al. Amino acid deprivation disrupts barrier function and induces protective autophagy in intestinal porcine epithelial cells[J]. Amino Acids, 2015, 47(10): 2177-2184. DOI:10.1007/s00726-014-1844-6 |
| [59] |
ZHU Y H, LIN G, DAI Z L, et al. L-glutamine deprivation induces autophagy and alters the mTOR and MAPK signaling pathways in porcine intestinal epithelial cells[J]. Amino Acids, 2015, 47(10): 2185-2197. DOI:10.1007/s00726-014-1785-0 |
| [60] |
ZHANG H, MA Y, WANG M Z, et al. Dietary supplementation of L-arginine and N-carbamylglutamate enhances duodenal barrier and mitochondrial functions and suppresses duodenal inflammation and mitophagy in suckling lambs suffering from intrauterine-growth-restriction[J]. Food & Function, 2020, 11(5): 4456-4470. |
| [61] |
WANG H Y, LI C C, PENG M, et al. N-acetylcysteine improves intestinal function and attenuates intestinal autophagy in piglets challenged with β-conglycinin[J]. Scientific Reports, 2021, 11(1): 1261. DOI:10.1038/s41598-021-80994-2 |
| [62] |
ZIMMERMAN M A, SINGH N, MARTIN P M, et al. Butyrate suppresses colonic inflammation through HDAC1-dependent Fas upregulation and Fas-mediated apoptosis of T cells[J]. American Journal of Physiology.Gastrointestinal and Liver Physiology, 2012, 302(12): G1405-G1415. DOI:10.1152/ajpgi.00543.2011 |
| [63] |
ZHOU C, LI L Z, LI T M, et al. SCFAs induce autophagy in intestinal epithelial cells and relieve colitis by stabilizing HIF-1α[J]. Journal of Molecular Medicine, 2020, 98(8): 1189-1202. DOI:10.1007/s00109-020-01947-2 |
| [64] |
LI X, WANG C C, ZHU J, et al. Sodium butyrate ameliorates oxidative stress-induced intestinal epithelium barrier injury and mitochondrial damage through AMPK-mitophagy pathway[J]. Oxidative Medicine and Cellular Longevity, 2022, 2022: 3745135. |
| [65] |
WANG C C, CAO S T, ZHANG Q H, et al. Dietary tributyrin attenuates intestinal inflammation, enhances mitochondrial function, and induces mitophagy in piglets challenged with diquat[J]. Journal of Agricultural and Food Chemistry, 2019, 67(5): 1409-1417. DOI:10.1021/acs.jafc.8b06208 |
| [66] |
CHU B X, ZHU Y H, SU J H, et al. Butyrate-mediated autophagy inhibition limits cytosolic Salmonella infantis replication in the colon of pigs treated with a mixture of Lactobacillus and Bacillus[J]. Veterinary Research, 2020, 51(1): 99. DOI:10.1186/s13567-020-00823-8 |
| [67] |
FENG Y H, WANG Y, WANG P, et al. Short-chain fatty acids manifest stimulative and protective effects on intestinal barrier function through the inhibition of NLRP3 inflammasome and autophagy[J]. Cellular Physiology and Biochemistry, 2018, 49(1): 190-205. DOI:10.1159/000492853 |
| [68] |
XIAO K, YANG Y, ZHANG Y, et al. Long-chain PUFA ameliorate enterotoxigenic Escherichia coli-induced intestinal inflammation and cell injury by modulating pyroptosis and necroptosis signaling pathways in porcine intestinal epithelial cells[J]. British Journal of Nutrition, 2022, 128(5): 835-850. DOI:10.1017/S0007114521005092 |
| [69] |
王晓杰, 黄立新, 张彩虹, 等. 植物提取物饲料添加剂的研究进展[J]. 生物质化学工程, 2018, 52(3): 50-58. WANG X J, HUANG L X, ZHANG C H, et al. Research development of botanical extract as feed additive in poultry[J]. Biomass Chemical Engineering, 2018, 52(3): 50-58 (in Chinese). DOI:10.3969/j.issn.1673-5854.2018.03.009 |
| [70] |
MOHAMMADI GHEISAR M, KIM I H. Phytobiotics in poultry and swine nutrition—a review[J]. Italian Journal of Animal Science, 2018, 17(1): 92-99. DOI:10.1080/1828051X.2017.1350120 |
| [71] |
WAN J, ZHANG J, CHEN D W, et al. Alginate oligosaccharide-induced intestinal morphology, barrier function and epithelium apoptosis modifications have beneficial effects on the growth performance of weaned pigs[J]. Journal of Animal Science and Biotechnology, 2018, 9: 58. DOI:10.1186/s40104-018-0273-x |
| [72] |
CHEN J L, XIE H M, CHEN D W, et al. Chlorogenic acid improves intestinal development via suppressing mucosa inflammation and cell apoptosis in weaned pigs[J]. ACS Omega, 2018, 3(2): 2211-2219. DOI:10.1021/acsomega.7b01971 |
| [73] |
XU X X, YAN G R, CHANG J, et al. Astilbin ameliorates deoxynivalenol-induced oxidative stress and apoptosis in intestinal porcine epithelial cells (IPEC-J2)[J]. Journal of Applied Toxicology, 2020, 40(10): 1362-1372. DOI:10.1002/jat.3989 |
| [74] |
JIN Y H, ZHAI Z A, JIA H, et al. Kaempferol attenuates diquat-induced oxidative damage and apoptosis in intestinal porcine epithelial cells[J]. Food & Function, 2021, 12(15): 6889-6899. |
| [75] |
CHEN Z G, YUAN Q L, XU G R, et al. Effects of quercetin on proliferation and H2O2-induced apoptosis of intestinal porcine enterocyte cells[J]. Molecules, 2018, 23(8): 2012. DOI:10.3390/molecules23082012 |
| [76] |
LI L, WAN G W, HAN B, et al. Echinacoside alleviated LPS-induced cell apoptosis and inflammation in rat intestine epithelial cells by inhibiting the mTOR/STAT3 pathway[J]. Biomedicine & Pharmacotherapy, 2018, 104: 622-628. |
| [77] |
LOGANES C, LEGA S, BRAMUZZO M, et al. Curcumin anti-apoptotic action in a model of intestinal epithelial inflammatory damage[J]. Nutrients, 2017, 9(6): 578. DOI:10.3390/nu9060578 |
| [78] |
ZHAO J, SUN Y, SHI P L, et al. Celastrol ameliorates experimental colitis in IL-10 deficient mice via the up-regulation of autophagy[J]. International Immunopharmacology, 2015, 26(1): 221-228. DOI:10.1016/j.intimp.2015.03.033 |
| [79] |
FAN X D, WANG J, HOU J C, et al. Berberine alleviates ox-LDL induced inflammatory factors by up-regulation of autophagy via AMPK/mTOR signaling pathway[J]. Journal of Translational Medicine, 2015, 13: 92. DOI:10.1186/s12967-015-0450-z |
| [80] |
CAO S T, SHEN Z J, WANG C C, et al. Resveratrol improves intestinal barrier function, alleviates mitochondrial dysfunction and induces mitophagy in diquat challenged piglets[J]. Food & Function, 2019, 10(1): 344-354. |
| [81] |
GUO W J, LIU W, JIN B, et al. Asiatic acid ameliorates dextran sulfate sodium-induced murine experimental colitis via suppressing mitochondria-mediated NLRP3 inflammasome activation[J]. International Immunopharmacology, 2015, 24(2): 232-238. DOI:10.1016/j.intimp.2014.12.009 |
| [82] |
WANG K, LV Q, MIAO Y M, et al. Cardamonin, a natural flavone, alleviates inflammatory bowel disease by the inhibition of NLRP3 inflammasome activation via an AhR/Nrf2/NQO1 pathway[J]. Biochemical Pharmacology, 2018, 155: 494-509. DOI:10.1016/j.bcp.2018.07.039 |
| [83] |
LI X D, WU X, WANG Q, et al. Sanguinarine ameliorates DSS induced ulcerative colitis by inhibiting NLRP3 inflammasome activation and modulating intestinal microbiota in C57BL/6 mice[J]. Phytomedicine, 2022, 104: 154321. DOI:10.1016/j.phymed.2022.154321 |
| [84] |
佚名. 农业农村部办公厅关于印发《直接饲喂微生物和发酵制品生产菌株鉴定及其安全性评价指南》的通知(农办牧[2021]43号)[J]. 中华人民共和国农业农村部公报, 2021(11): 97-111. An on. Circular of the General Office of the Ministry of Agriculture and Rural Affairs on printing and distributing the guidelines on identification and safety evaluation of direct-fed microbials and fermented-food-derived bacterial strains ([2021]43)[J]. Gazette of the Ministry of Agriculture and Affairs of the People's Republic of China, 2021(11): 97-111 (in Chinese). |
| [85] |
BUNTYN J O, SCHMIDT T B, NISBET D J, et al. The role of direct-fed microbials in conventional livestock production[J]. Annual Review of Animal Biosciences, 2016, 4: 335-355. DOI:10.1146/annurev-animal-022114-111123 |
| [86] |
GARCÍA G R, PAYROS D, PINTON P, et al. Intestinal toxicity of deoxynivalenol is limited by Lactobacillus rhamnosus RC007 in pig jejunum explants[J]. Archives of Toxicology, 2018, 92(2): 983-993. DOI:10.1007/s00204-017-2083-x |
| [87] |
YANG X, LIANG S S, GUO F S, et al. Gut microbiota mediates the protective role of Lactobacillus plantarum in ameliorating deoxynivalenol-induced apoptosis and intestinal inflammation of broiler chickens[J]. Poultry Science, 2020, 99(5): 2395-2406. DOI:10.1016/j.psj.2019.10.034 |
| [88] |
GAO Q X, QI L L, WU T X, et al. Ability of Clostridium butyricum to inhibit Escherichia coli-induced apoptosis in chicken embryo intestinal cells[J]. Veterinary Microbiology, 2012, 160(3/4): 395-402. |
| [89] |
XIAO Z P, LIU L J, TAO W J, et al. Clostridium tyrobutyricum protect intestinal barrier function from LPS-induced apoptosis via P38/JNK signaling pathway in IPEC-J2 cells[J]. Cellular Physiology and Biochemistry, 2018, 46(5): 1779-1792. DOI:10.1159/000489364 |
| [90] |
TANG L, ZENG Z H, ZHOU Y H, et al. Bacillus amyloliquefaciens SC06 induced AKT-FOXO signaling pathway-mediated autophagy to alleviate oxidative stress in IPEC-J2 cells[J]. Antioxidants, 2021, 10(10): 1545. DOI:10.3390/antiox10101545 |
| [91] |
KHAILOVA L, MOUNT PATRICK S K, ARGANBRIGHT K M, et al. Bifidobacterium bifidum reduces apoptosis in the intestinal epithelium in necrotizing enterocolitis[J]. American Journal of Physiology: Gastrointestinal and Liver Physiology, 2010, 299(5): G1118-G1127. DOI:10.1152/ajpgi.00131.2010 |
| [92] |
LI H H, LI Y P, ZHU Q, et al. Dietary supplementation with Clostridium butyricum helps to improve the intestinal barrier function of weaned piglets challenged with enterotoxigenic Escherichia coli K88[J]. Journal of Applied Microbiology, 2018, 125(4): 964-975. DOI:10.1111/jam.13936 |
| [93] |
XIA B, YU J, HE T, et al. Lactobacillus johnsonii L531 ameliorates enteritis via elimination of damaged mitochondria and suppression of SQSTM1-dependent mitophagy in a Salmonella infantis model of piglet diarrhea[J]. The FASEB Journal, 2020, 34(2): 2821-2839. DOI:10.1096/fj.201901445RRR |
| [94] |
YU J, ZHU Y H, YANG G Y, et al. Anti-inflammatory capacity of Lactobacillus rhamnosus GG in monophasic variant Salmonella infected piglets is correlated with impeding NLRP6-mediated host inflammatory responses[J]. Veterinary Microbiology, 2017, 210: 91-100. DOI:10.1016/j.vetmic.2017.08.008 |
| [95] |
SUZUKI H, YAMAZAKI T, OHSHIO K, et al. A specific strain of lactic acid bacteria, Lactobacillus paracasei, inhibits inflammasome activation in vitro and prevents inflammation-related disorders[J]. Journal of Immunology, 2020, 205(3): 811-821. DOI:10.4049/jimmunol.1900657 |
| [96] |
CHEN S Y, LI Y N, CHU B X, et al. Lactobacillus johnsonii L531 alleviates the damage caused by Salmonella typhimurium via inhibiting TLR4, NF-κB, and NLRP3 inflammasome signaling pathways[J]. Microorganisms, 2021, 9(9): 1983. DOI:10.3390/microorganisms9091983 |
| [97] |
HAN C Q, DING Z, SHI H Y, et al. The role of probiotics in lipopolysaccharide-induced autophagy in intestinal epithelial cells[J]. Cellular Physiology and Biochemistry, 2016, 38(6): 2464-2478. DOI:10.1159/000445597 |
| [98] |
YAN S Q, QIAO L, DOU X N, et al. Biogenic selenium nanoparticles by Lactobacillus casei ATCC 393 alleviate the intestinal permeability, mitochondrial dysfunction and mitophagy induced by oxidative stress[J]. Food & Function, 2021, 12(15): 7068-7080. |
| [99] |
CUI Y J, LIU L, DOU X X, et al. Lactobacillus reuteri ZJ617 maintains intestinal integrity via regulating tight junction, autophagy and apoptosis in mice challenged with lipopolysaccharide[J]. Oncotarget, 2017, 8(44): 77489-77499. DOI:10.18632/oncotarget.20536 |
| [100] |
ZHANG W, ZHU Y H, YANG G Y, et al. Lactobacillus rhamnosus GG affects microbiota and suppresses autophagy in the intestines of pigs challenged with Salmonella infantis[J]. Frontiers in Microbiology, 2018, 8: 2705. DOI:10.3389/fmicb.2017.02705 |
| [101] |
KORHONEN H, PIHLANTO A. Food-derived bioactive peptides—opportunities for designing future foods[J]. Current Pharmaceutical Design, 2003, 9(16): 1297-1308. DOI:10.2174/1381612033454892 |
| [102] |
GIANFRANCESCHI G L, GIANFRANCESCHI G, QUASSINTI L, et al. Biochemical requirements of bioactive peptides for nutraceutical efficacy[J]. Journal of Functional Foods, 2018, 47: 252-263. DOI:10.1016/j.jff.2018.05.034 |
| [103] |
BECHAUX J, GATELLIER P, LE PAGE J F, et al. A comprehensive review of bioactive peptides obtained from animal byproducts and their applications[J]. Food & Function, 2019, 10(10): 6244-6266. |
| [104] |
DALIRI E B M, LEE B H, OH D H. Current trends and perspectives of bioactive peptides[J]. Critical Reviews in Food Science and Nutrition, 2018, 58(13): 2273-2284. DOI:10.1080/10408398.2017.1319795 |
| [105] |
DENG Z, NI J J, WU X Y, et al. GPA peptide inhibits NLRP3 inflammasome activation to ameliorate colitis through AMPK pathway[J]. Aging, 2020, 12(18): 18522-18544. DOI:10.18632/aging.103825 |
| [106] |
DENG Z, LIU Q, WANG M M, et al. GPA peptide-induced Nur77 localization at mitochondria inhibits inflammation and oxidative stress through activating autophagy in the intestine[J]. Oxidative Medicine and Cellular Longevity, 2020, 2020: 4964202. |