中文摘要：

【目的】为探讨卡介菌多糖核酸（polysaccharide nucleic acid fraction of Bacillus Calmette Guerin,BCG-PSN）对内毒素（endotoxin or lipopolysaccharide,LPS）诱发实验性动物乳腺炎的保护机制,【方法】72只清洁级SD大鼠被随机分成实验组和对照组（n=36）。确定怀孕14d起,隔日左后腿胫骨前肌肌内注射BCG-PSN（实验组）或灭菌生理盐水（对照组）0.33mL/只,连续5次;产后72h经乳头管灌注LPS10μg/侧到第4对乳腺（两侧）内。分别于灌注前（定义为0h）及灌注后3、6、9、12和24h（n=6）颈静脉放血处死动物,采集样品。【结果】组织病理学观察显示,BCG-PSN加快了LPS诱发炎症的组织修复进程,促进了炎症后期泌乳量的恢复。定量RT-PCR结果显示,BCG-PSN能降低乳腺组织中Toll样受体-4（toll-like receptor-4,TLR-4）mRNA表达水平,实验组与对照组相比,第6、9、24h差异显著。酶活性检测结果显示,诱导型一氧化氮合酶（inducible nitric oxide synthase,iNOs）活性在乳腺组织中和血清中变化规律相反;组织中酶活性,实验组和对照组分别在6、9h达到最高,血清中活性分别在6、3h最低。放射免疫检测结果显示,同对照组相比,BCG-PSN使乳腺组织中炎症相关细胞因子肿瘤坏死因子-α（tumor necrosis factor-α,TNF-α）的分泌极值降低,极值出现时间提前,而血清中未表现出明显的变化。【结论】BCG-PSN可能通过降低TLR-4的表达,抑制炎性细胞因子及酶的过度分泌,缓解LPS及相关因子（TNF-α、iNOs）对乳腺组织的损伤。

英文摘要：

Objective The aim of this study was to evaluate the polysaccharide nucleic acid fraction of Bacillus Calmette Guerin（BCG-PSN） in protection of rat mastitis induced by endotoxin（or lipopolysaccharide,LPS）.Method Seventy-two lactating SD rats were randomly divided into control and treatment groups（n=36）.BCG-PSN（treatment group,TG） or sterile pyrogen-free physiological saline solution（control group,CG） were injected at 0.33 mL into the left tibialis anterior muscle of rats 14 days after conception.The administration was repeated for five consecutive times every other day.Seventy-two hours after parturition,30 rats of each group were inoculated with 10 μg Escherichia coli LPS dissolved in 100 μL physiological saline solution into the left 4（L4） and right 4（R4） mammary glands and six as control.Just before the inoculation（control group defined as 0 h） and 3,6,9,12 and 24 h after inoculation,six rats at every time point were euthanatized and samples were collected.Results The histopathological observation indicated that treatment with BCG-PSN made a rapid renovation of mammary tissue compared with CG.Milk secretion elevated with an increasing of the luminal spaces with milk at the later stage of inflammation in TG.RT-PCR analysis showed that BCG-PSN decreased the toll-like receptor-4（TLR-4） mRNA expression level from 3 h PI and significant reduction was observed at 6 h,9 h and 24 h PI.In mammary tissue,the activity of iNOs peaked at 6 h in TG and 9 h in CG,whereas serum iNOs activity reached nadir level at 6 h and 3 h PI,respectively.Administration BCG-PSN reduced the peak level of TNF-α,in mammary tissue compared with CG,whereas no significant changes were observed in serum after LPS challenge.Conclusion These findings suggested that BCG-PSN has a general protective effect against LPS-induced local mammary injury by reducing TLR-4 mRNA expression level and further inhibiting the release of inflammatory factors（TNF-α,iNOs） that cause damage to mammary gland.