鼠李糖乳杆菌调节大肠杆菌感染引发的奶牛乳腺ASC依赖及非依赖炎性体应答机理

Cow mastitis seriously affects the yield and quality of milk. Escherichia coli (E. coli) are the most commonpathogenic bacteria of mastitis. Lactobacillus rhamnosus GR-1 (LGR-1) represents a novel alternative to antibiotics for controlling E. coli-induced mastitis, which may be closely related with regulating inflammasome activation, especially the inflammatory response due to apoptosis-associated speck-like protein containing a CARD (ASC)-dependent inflammasome activation and damage of mammary epithelium due to ASC-independent inflammasome activation. In the present study, an E. coli model of bovine mastitis, as well as an ASC-deficient mouse model and in vitro primary bovine mammary epithelial cell (BMEC) model of E. coli infection will be established. The aim of the study, therefore, is to reveal the molecular mechanism of LGR-1 regulating ASC-dependent/independent inflammasome activation via: (1) analyzing the expression and location of NLRP3, NLRC4 and NLRP1b inflammasomes in mammary glands; (2) evaluating the effect of LGR-1 on inflammasome responses and NF-κB activation; and (3) assessing whether LGR-1 inhibites E. coli-induced cell pyroptosis and ameliorates the injury in mammary glands via regulating ASC-independent inflammasome activation in the ASC-deficient BMEC and mouse models during E. coli infection. The study can provide new insights into rational use of probiotics in preventing pathogenic infection of the bovine or human mammary glands.

奶牛乳房炎严重影响奶产量和质量，大肠杆菌（E.coli）是引起乳房炎的常见致病菌。鼠李糖乳酸杆菌（LGR-1）作为潜在的抗生素替代品用于奶牛大肠杆菌性乳房炎防治，这可能与其影响大肠杆菌感染引发的含CARD结构域的凋亡相关斑点样蛋白（ASC）依赖及非依赖炎性体激活，减轻炎性反应及乳腺损伤密切相关。本项目拟通过建立ASC缺失的奶牛及鼠大肠杆菌性乳房炎模型，并结合原代乳腺上皮细胞体外模型，旨在:（1）分析NLRP3、NLRC4及NLRP1炎性体在奶牛乳腺中的表达、定位及动态变化；（2）探讨LGR-1是否影响E.coli引起的ASC依赖炎性体激活及NF-κB活化；和（3）研究LGR-1是否通过调节ASC非依赖的炎性体应答，阻止细胞焦亡，减轻组织损伤。研究将揭示LGR-1调节大肠杆菌引发的奶牛乳腺ASC依赖及非依赖炎性体应答机理，为合理利用益生菌防治奶牛及人类乳腺感染性疾病提供科学依据。

奶牛乳房炎一直是困扰奶牛养殖业和乳品行业的重大难题。大肠杆菌（E.coli）是引起乳房炎的主要致病菌之一，常引起临床型乳房炎，导致奶牛产奶量下降和奶牛淘汰，造成严重的经济损失。我们前期研究表明鼠李糖乳杆菌（LGR-1）作为潜在的抗生素替代品可用于奶牛大肠杆菌性乳房炎防治，这可能与其影响大肠杆菌感染引发的含CARD结构域的凋亡相关斑点样蛋白（ASC）依赖及非依赖炎性体激活，减轻炎性反应及乳腺损伤密切相关。本项目建立了大肠杆菌诱导的乳房炎细胞模型和动物模型，探讨了：（1）大肠杆菌激活炎性体诱导乳房炎性反应的作用机制；（2）LGR-1在E.coli引起的ASC依赖炎性体激活及NF-κB活化的作用；（3）LGR-1通过调节ASC非依赖的炎性体应答，阻止细胞焦亡，减轻大肠杆菌性乳房炎作用机制；（4）大麦虫血淋巴通过调节ASC非依赖的炎性体应答，阻止细胞焦亡，减轻大肠杆菌性乳房炎作用机制；我们的研究为合理利用益生菌防治乳房炎提供重要科学依据，也为新型替抗产品奠定了一定基础。