Engineered probiotics can serve as therapeutics based on their ability of produce recombinant immune-stimulating properties. In this study, we built the recombinant Bacillus subtilis WB800 expressing antimicrobial peptide KR32 (WB800-KR32) using genetic engineering methods and investigated its protective effects of nuclear factor-E2-related factor 2 (Nrf2)-Kelch-like ECH-associated protein 1 (Keap1) pathway activation in intestinal oxidative disturbance induced by enterotoxigenic Escherichia coli (ETEC) K88 in weaned piglets. Twenty-eight weaned piglets were randomly distributed into four treatment groups with seven replicates fed with a basal diet. The feed of the control group (CON) was infused with normal sterilized saline; meanwhile, the ETEC, ETEC+WB800, and ETEC+WB800-KR32 groups were orally administered normal sterilized saline, 5×1010 CFU (CFU: colony forming units) WB800, and 5×1010 CFU WB800-KR32, respectively, on Days 1‒14 and all infused with ETEC K88 1×1010 CFU on Days 15‒17. The results showed that pretreatment with WB800-KR32 attenuated ETEC-induced intestinal disturbance, improved the mucosal activity of antioxidant enzyme (catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx)) and decreased the content of malondialdehyde (MDA). More importantly, WB800-KR32 downregulated genes involved in antioxidant defense (GPx and SOD1). Interestingly, WB800-KR32 upregulated the protein expression of Nrf2 and downregulated the protein expression of Keap1 in the ileum. WB800-KR32 markedly changed the richness estimators (Ace and Chao) of gut microbiota and increased the abundance of Eubacterium_rectale_ATCC_33656 in the feces. The results suggested that WB800-KR32 may alleviate ETEC-induced intestinal oxidative injury through the Nrf2-Keap1 pathway, providing a new perspective for WB800-KR32 as potential therapeutics to regulate intestinal oxidative disturbance in ETEC K88 infection.
工程益生菌具有产生重组免疫刺激物质的特性，可以作为一种治疗药物。本研究使用基因工程技术构建了表达抗菌肽KR32的重组枯草芽孢杆菌（WB800-KR32），并且探究了其在通过激活Nrf2-Keap1途径对产肠毒素大肠埃希氏菌（ETEC） K88感染断奶仔猪导致的肠道氧化态紊乱的保护作用。我们将28头断奶仔猪随机分成4组，每组7个重复，均饲喂基础日粮。对照组灌喂灭菌生理盐水；ETEC组、ETEC+WB800组和ETEC+WB800-KR32组分别在第1~14天灌喂灭菌生理盐水、5×1010 CFU WB800、5×1010 CFU WB800-KR32，在第15–17天灌喂ETEC K88 1×1010 CFU。结果表明，WB800-KR32预处理能够缓解ETEC K88导致的肠道紊乱，提高肠道粘膜抗氧化酶活性（过氧化物酶、超氧化物歧化酶和谷胱甘肽过氧化物酶），降低丙二醛含量。更重要的是，WB800-KR32预处理可上调回肠粘膜Nrf2的蛋白表达量，同时下调Keap1的蛋白表达量。此外，WB800-KR32预处理还显著改变了粪便微生物的丰度（Ace和Chao指数），并增加了Eubacterium_rectale_ ATCC_33656在粪便中的丰度。综上，WB800-KR32可能通过Nrf2-Keap1途径缓解ETEC K88导致的肠道氧化损伤，这为将WB800-KR32作为调节ETEC K88感染导致的肠道氧化失调的潜在治疗手段提供了一个新的视角。.
工程益生菌具有产生重组免疫刺激物质的特性，可以作为一种治疗药物。本研究使用基因工程技术构建了表达抗菌肽KR32的重组枯草芽孢杆菌（WB800-KR32），并且探究了其在通过激活Nrf2-Keap1途径对产肠毒素大肠埃希氏菌（ETEC） K88感染断奶仔猪导致的肠道氧化态紊乱的保护作用。我们将28头断奶仔猪随机分成4组，每组7个重复，均饲喂基础日粮。对照组灌喂灭菌生理盐水；ETEC组、ETEC+WB800组和ETEC+WB800-KR32组分别在第1~14天灌喂灭菌生理盐水、5×1010 CFU WB800、5×1010 CFU WB800-KR32，在第15–17天灌喂ETEC K88 1×1010 CFU。结果表明，WB800-KR32预处理能够缓解ETEC K88导致的肠道紊乱，提高肠道粘膜抗氧化酶活性（过氧化物酶、超氧化物歧化酶和谷胱甘肽过氧化物酶），降低丙二醛含量。更重要的是，WB800-KR32预处理可上调回肠粘膜Nrf2的蛋白表达量，同时下调Keap1的蛋白表达量。此外，WB800-KR32预处理还显著改变了粪便微生物的丰度（Ace和Chao指数），并增加了Eubacterium_rectale_ ATCC_33656在粪便中的丰度。综上，WB800-KR32可能通过Nrf2-Keap1途径缓解ETEC K88导致的肠道氧化损伤，这为将WB800-KR32作为调节ETEC K88感染导致的肠道氧化失调的潜在治疗手段提供了一个新的视角。
Keywords: Engineered probiotics; Intestine; Nuclear factor-E2-related factor 2 (Nrf2)-Kelch-like ECH-associated protein 1 (Keap1) pathway; Oxidative injury; Weaned piglets.