猪源黏膜乳杆菌和色氨酸调节幼龄小鼠胃肠免疫稳态与功能发育的机制

Mechanisms of Regulatory Role of Porcine Limosilactobacillus mucosae and Tryptophan on Gastrointestinal Immune Homeostasis and Function Development of Young Mice

本试验旨在研究猪源黏膜乳杆菌(Limosilactobacillus mucosae)与色氨酸单独或联合处理调节幼龄小鼠胃肠5-羟色胺受体(HTR)与免疫功能发育的规律与机制。试验选取32只3周龄雄性C57BL/6小鼠,随机分为对照组、色氨酸组、黏膜乳杆菌组和黏膜乳杆菌+色氨酸组,每组8个重复,每个重复1只。黏膜乳杆菌组和黏膜乳杆菌+色氨酸组小鼠每隔1 d灌胃100μL/(只·d)的黏膜乳杆菌活菌悬液(1×10^(8) CFU/mL),其余组灌胃等量磷酸盐缓冲液;色氨酸组和黏膜乳杆菌+色氨酸组小鼠通过饮水添加0.15 mg/(g BW·d)的色氨酸(0.5 mg/mL色氨酸饮水),其余组饮水中添加0.44 mg/mL的丙氨酸作为等氮处理。试验期14 d。结果表明:1)黏膜乳杆菌+色氨酸处理2周后,可显著提高小鼠体重和小肠长度(P<0.05);2)黏膜乳杆菌或与色氨酸联用可调节胃肠5-羟色胺(5-HT)代谢稳态,并差异化调节HTR在胃肠的表达,显著上调HTR4和HTR7在胃中的表达(P<0.05);3)黏膜乳杆菌或与色氨酸联用可促进胃和空肠中M2型巨噬细胞的极化、上调Wnt3a表达并差异化调节转化生长因子-β(TGF-β)亚型在胃肠的表达;4)黏膜乳杆菌或与色氨酸联用可显著提高结肠中吲哚浓度(P<0.05),但显著降低小肠和结肠中5-HT浓度(P<0.05)。以上结果表明,猪源黏膜乳杆菌和色氨酸联合使用可通过调节胃肠5-HT代谢与HTR的表达、上调M2型巨噬细胞极化和胃肠TGF-β亚型表达并激活Wnt信号促进幼龄小鼠胃肠发育和生长。

The aim of this experiment was to investigate the regulation and mechanism of the gastrointestinal 5-hydroxytryptamine receptor(HTR)and immune function development of young mice treated with Limosilactobacillus mucosae and tryptophan alone or in combination.Thirty-two 3-week-old male C57BL/6 mice were randomly divided into control group,tryptophan group,Limosilactobacillus mucosae group and Limosilactobacillus mucosae+tryptophan group with 8 replicates per group and 1 mouse per replicate.Mice in Limosilactobacillus mucosae group and Limosilactobacillus mucosae+tryptophan group were given 100μL/(mouse·d)Limosilactobacillus mucosae live bacterial suspension(1×10^(8)CFU/mL)every other day,and those in the other groups were given the same amount of phosphate buffer solution;while mice in the tryptophan group and Limosilactobacillus mucosae+tryptophan group were added 0.15 mg/(g BW·d)tryptophan in drinking water(0.5 mg/mL tryptophan in drinking water),and 0.44 mg/mL alanine was added in drinking water of the other groups as iso-nitrogen treatment.The experiment lasted for 14 days.The results showed as follows:1)after 2 weeks of treatment with Limosilactobacillus mucosae and tryptophan,the body weight and small intestine length of mice were significantly increased(P<0.05);2)Limosilactobacillus mucosae or combined with tryptophan could regulate the metabolic homeostasis of 5-hydroxytryptamine(5-HT)in gastrointestinal tract,differentiated the expression of HTR in gastrointestinal tract,and significantly up-regulated the expression of HTR4 and HTR7 in the stomach(P<0.05);3)Limosilactobacillus mucosae or combined with tryptophan could promote the polarization of M2-type macrophages in stomach and jejunum,up-regulate the expression of Wnt3a,and differentially regulate the expression of transforming growth factor-β(TGF-β)subtypes in gastrointestinal tract;4)Limosilactobacillus mucosae or combined with tryptophan significantly increased the indole concentration in colon(P<0.05),but significantly decreased the 5-HT concentration in small intestine and colon(P<0.05).These results indicate that the combination of porcine Limosilactobacillus mucosae and tryptophan can promote gastrointestinal development and growth of young mice by regulating gastrointestinal 5-HT metabolism and HTR expression,up-regulating M2-type macrophage polarization and gastrointestinal TGF-βsubtype expression,and activating Wnt signaling.