Mycoplasma leachii causes polyarthritis in calves via the blood route but is not associated with pneumonia

Mycoplasma leachii was initially isolated from arthritic calves in South Queensland, Australia, and its ability to cause clinical polyarthritis in calves was demonstrated by experimental infection. However, the source of M. leachii infection in calves and its means of spreading are not well known. In this study, one-month-old calves were inoculated with cultures of M. leachii or joint fluid (collected from M. leachii-infected calves) through the intraarticular, intravenous, intratracheal, intranasal or oral routes. Multidisciplinary procedures, including clinical assessment, etiology assessment, pathology and immunohistochemistry (IHC), were used to evaluate the pathogenicity of M. leachii in calves and to elucidate the transmission route of M. leachii infection in calves. The results showed that all calves inoculated intraarticularly with cultured GN407 or joint fluid and two-thirds of the calves inoculated intravenously with joint fluid developed severe polyarthritis, and the M. leachii antigen was detected in the joints of all infected calves by IHC and PCR. In contrast, calves inoculated with cultured M. leachii or joint fluid through the intratracheal, intranasal or oral routes did not show any M. leachii infection in the clinical assessment, etiology assessment, or pathology and IHC results. These results indicated that polyarthritis caused by M. leachii in calves is transmitted via the blood route; however, this disease is not transmitted through the respiratory or digestive routes. In addition, the M. leachii antigen was not detected in the lungs of all the inoculated calves using IHC and PCR, indicating that M. leachii is not associated with pneumonia, even in the calves inoculated through the respiratory duct. These findings are important information for the prevention and control of calf polyarthritis caused by M. leachii.     

CpG-DNA对金黄色葡萄球菌诱导的乳腺炎大鼠的保护研究

【目的】建立金黄色葡萄球菌（Staphylococcus aureus）感染的大鼠乳腺炎模型，并观察CpG-DNA对乳腺的保护作用。【方法】18只雌鼠分3组(n=6)，产后72h分别灌注磷酸盐缓冲液（phosphate buffer solution，PBS）（C组）、2×105CFU•ml-1（L组）和2×1012CFU•ml-1 (H组)金葡菌到第四对乳腺内，24 h处死。L组乳腺病变轻微，H组腺泡结构破坏严重，并有大量嗜中性粒细胞（polymorphonuclear neutrophils，PMN）浸润；H组乳腺组织TNF-α、IL-6水平显著上升。选择2×1012CFU•ml-1为诱发剂量观察CpG-DNA对乳腺的保护作用：72只雌鼠分成对照和试验组(n=36)，对照组产后0 h肌注PBS；试验组肌注CpG-DNA，72 h后灌注金葡菌到第四对乳腺内。分别于灌注前（定义为0 h），灌注后8、16、24、48和72 h（n=6）处死。【结果】感染初期试验组乳腺腺泡内PMN较对照组浸润迅速。试验组乳腺组织白细胞介素-6（interleukine-6，IL-6）在16、24和48 h显著高于对照组。CpG-DNA能显著提高0、24和72 h乳腺组织肿瘤坏死因子-α（tumor necrosis factor-α，TNF-α）水平。试验组8、16和72 h的乳腺组织金葡菌数显著低于对照组。CpG-DNA能显著提高乳腺组织中其特异性受体TLR-9（toll-like receptor-9）mRNA表达水平。【结论】CpG-DNA对金葡菌感染诱发大鼠乳腺炎的乳腺有保护作用。     

卡介菌多糖核酸对内毒素诱发的实验性山羊乳腺炎乳腺组织的保护研究

【目的】本试验通过卡介菌多糖核酸对内毒素诱发的实验性山羊乳腺炎乳腺组织的保护研究，探讨灌注免疫增强剂BCG-PSN对乳腺组织的影响，研究调动乳腺自身的防御功能，以防治乳腺炎的发生。【方法】选取泌乳初期健康睢宁白山羊6只，左乳区经过乳头管灌注卡介菌多糖核酸5 ml，右乳区灌入5 ml注射用生理盐水作为对照，连灌6 d。第7天按50 µg•kg-1体重分别向左、右乳区灌注大肠杆菌内毒素。灌注前及灌注后0、1、2、3、4、5、6、7、8、9、24 h观察山羊整体及乳房局部变化。灌注24 h后，处死动物，取乳腺组织，部分Bouin氏液固定、部分液氮保存。【结果】临床症状及病理切片观察均显示，山羊表现典型的急性乳腺炎症状。与灌注生理盐水对照相比，乳腺灌注卡介菌多糖核酸能显著降低乳腺组织中部分炎症相关因子的含量及其基因表达水平。其中N-乙酰-β-D-氨基葡萄糖苷酶（NAGase）、髓过氧化物酶（MPO）、碱性磷酸酶（AKP）、诱导型一氧化氮合成酶（iNOS）活性显著降低（P<0.05）；IL-1β、TNF-α的含量及其mRNA表达水平均显著降低（P<0.05），IL-6的含量显著降低（P<0.05），其mRNA表达水平有所降低但差异不显著（P>0.05）。【结论】灌注卡介菌多糖核酸可以抑制乳腺组织内IL-1β、TNF-α等炎性细胞因子及和炎症相关酶的过度释放、减轻炎症因子对乳腺上皮细胞的损伤，对内毒素诱发的山羊实验性乳腺炎有较强的保护作用。     

临床型奶牛乳房炎乳腺组织的比较蛋白质组研究

 【目的】采用比较蛋白质组学技术分析、检测了临床健康与乳房炎奶牛乳腺组织中的差异表达蛋白,以寻找药物治疗目标,探讨奶牛乳房炎的发生机理。【方法】采用二维凝胶电泳分离临床健康与乳房炎奶牛的乳腺组织蛋白,考马斯亮蓝染色,PDQuest7.4软件自动匹配检测差异表达蛋白斑点,高效液相色谱串联离子阱质谱分析鉴定。【结果】凝胶图谱中检测出15个差异蛋白斑点,串联质谱分析后有12个蛋白斑点可搜索到相应的结果,对应于10种蛋白质,主要涉及结合、运输和催化活性等分子功能,参与细胞、代谢及生物调节等生理过程。【结论】临床健康与乳房炎奶牛的乳腺组织中蛋白的表达模式存在差异,表达差异蛋白与奶牛乳房炎的发生相关,对其分析有利于探索机体的生理病理状态,还可为揭示奶牛乳房炎的发生机理提供直接依据。     

胞壁酰二肽对体外奶牛乳腺上皮细胞生长及胞内NOD2 mRNA表达的影响

【目的】奶牛乳房炎是奶牛养殖业中最为常见,同时也是带来经济损失最为严重的疾病之一,其主要病因是细菌感染。奶牛乳腺的固有免疫是抵抗病原菌入侵的第一道防线。NOD2是机体固有免疫模式识别受体核苷酸结合寡聚域(nucleotide-binding oligomerization domain,NOD)蛋白家族中的重要一员,通过识别其特异性配体胞壁酰二肽(muramyl dipeptide,MDP)——一种广泛存在于革兰氏阳性菌和革兰氏阴性菌细胞壁中的成分,而参与抵抗多种病原菌入侵。奶牛乳腺上皮细胞(bovine mammary epithelial cells,BMEC)除泌乳以外,还是奶牛乳腺的免疫屏障。本试验欲探究MDP对BMEC体外生长状态及胞内NOD2表达量的影响。【方法】选取健康泌乳中期荷斯坦奶牛乳腺腺泡为组织原材料,采用胶原酶Ⅰ消化法结合梯度浓度胰蛋白酶纯化法分离BMEC;使用上皮细胞特异性表达的角蛋白-18(cytokeratin-18,CK-18)及成纤维细胞特异性表达的波形蛋白(Vimentin)抗体,通过免疫荧光技术对纯化后获得的细胞进行鉴定;将BMEC设为6个处理组,分别添加浓度为0(空白对照组)、1、5、10、15及20μg·mL~(-1)的MDP,24 h后显微镜下观察细胞状态,同时提取细胞RNA并反转录为cDNA,采用实时荧光定量PCR方法检测BMEC中NOD2的表达量。【结果】(1)胶原酶Ⅰ消化法结合梯度浓度胰蛋白酶纯化法分离得到的细胞CK-18免疫荧光结果为阳性,而Vimentin反应为阴性;细胞生长状态良好。(2)空白对照组、1、5及10μg·mL~(-1) MDP刺激组的BMEC生长状态良好,无任何肉眼可见变化;15μg·mL~(-1) MDP刺激组可见少量的BMEC脱落;而20μg·mL~(-1)MDP刺激组可见大量BMEC脱落,漂浮,且即使仍贴壁的细胞,其形态也发生了变化。(3)与空白对照组相比,各刺激组细胞NOD2 mRNA的表达量与MDP的刺激浓度呈正相关,即刺激时间为24 h时,随着MDP浓度的增加,BMEC中NOD2受体mRNA的表达量逐渐增加(P0.05)。【结论】成功获得了纯度较好的BMEC,该细胞生长状态良好,可以用于后续试验;虽然BMEC中NOD2受体mRNA的表达量与MDP的刺激浓度呈正相关,但在保持BMEC生长状态正常的前提下,MDP体外刺激浓度应控制在10μg·mL~(-1)以下。这些结果提示我们:当病原菌入侵乳腺时,BMEC可以通过NOD2受体途径参与免疫防御反应,但这种防御能力受细菌数量或毒力强度的影响。即在一定的细菌数量或毒力范围内,随着细菌数量的增加或毒力的增强,奶牛乳腺的免疫防御反应也增强,进而清除外来病原菌;而当细菌数量或毒力强度超过一定范围时,乳腺组织受到严重损伤,免疫防御屏障也随之崩溃,奶牛乳腺局部甚至全身将呈现出明显的临床症状。     

重组溶葡萄球菌酶对金葡菌诱导试验性小鼠乳腺炎的防治研究

试验采用重组溶葡萄球菌酶探讨了对小鼠试验性乳腺炎的治疗效果.利用微量肉汤稀释法测定了重组溶葡萄球菌酶时乳源金黄色葡萄球菌(Staphylococcus aureus)的最小抑菌浓度(MIC)和最小杀菌浓度(MBC).将18只泌乳8～10 d的BALB/C母鼠随机分成正常组、阳性对照组和试验组.阳性时照组和试验组母鼠经第4对、第5对乳腺乳头管注入50μL 2.0x105CFU的细菌悬液.试验组攻菌出现症状后,每个乳腺经乳头管注入1 U·mL-1的重组溶葡萄球菌酶稀释液50μL,间隔12 h 1次.观察小鼠的临床症状,测定体温、血常规等指标.接菌66h后,颈静脉放血处死小鼠,取小鼠乳腺进行细菌计数和病理组织切片制作.结果显示,重组溶葡萄球菌酶对金黄色葡萄球菌的MIC值为0.001 U·mL-1,MBC值为0.063U·mL-1.病理组织观察显示,正常组的腺泡结构完整,而阳性对照组的乳腺组织局部被破坏,间质增宽,炎性细胞浸润严重,试验组的组织结构基本正常,有轻度充血.说明重组溶葡萄球菌酶能有效地减少细菌感染,降低组织的损伤程度,对乳腺有一定地保护作用.     

奶牛乳房炎乳腺膜蛋白的比较蛋白质组学研究

【目的】通过分析临床健康和乳房炎奶牛乳腺组织膜蛋白的差异表达,以期在蛋白质水平探索奶牛乳房炎的发生机理。【方法】采用二维凝胶电泳技术分离了临床健康和乳房炎奶牛的乳腺组织膜蛋白,经考马斯亮蓝染色后PDQuest 7.4软件匹配、检测凝胶中差异表达的蛋白点,对12个差异蛋白点采用高效液相色谱串联离子阱质谱分析,SEQUEST软件搜索NCBInr数据库。半定量RT-PCR分析差异表达蛋白的mRNA水平。【结果】12个差异蛋白点鉴定为11种蛋白质,其中9个蛋白点在临床型乳房炎奶牛乳腺组织膜蛋白中表达量上调而3个蛋白点表达量下调,主要涉及细胞膜骨架系统、信号转导、物质结合和传递等生物学功能。半定量RT-PCR分析表明,乳房炎奶牛乳腺组织中钙粒蛋白B的mRNA表达水平是健康奶牛的1.6倍。【结论】推测这些差异蛋白的表达变化与奶牛乳房炎发生相关,为从蛋白质水平揭示奶牛乳房炎的发生机理以及发现潜在的治疗目标蛋白提供了理论依据。     

大肠杆菌内毒素诱导奶山羊急性乳房炎试验

试验研究了大肠杆菌内毒素乳房灌注在奶山羊引起的临床反应。结果表明，大肠杆菌内毒素注入杂种奶山羊乳池内能诱导出典型的急性乳房炎局部症状和全身症状：乳房肿胀，发热疼痛，体温升高，产奶量下降等。超声波图象说明，水肿是急性乳房肿胀的主要原因。随着局部炎症消失，乳腺组织能迅速达到临床上的完全康复。     

绵阳市奶牛乳房炎的调查与分析

采用临床调查、BMT法和苛性钠法对绵阳市6个不同规模奶牛场的乳房炎进行了检测。结果表明，临床型乳房炎的发病率为2％～11．67％（平均发病率为6．08％），隐性乳房炎的感染率为41．67％～86．40％（平均感染率为55．00％）。用SPSS统计软件对奶牛乳房炎各乳区之间的相关性及BMT和苛性钠两种检测方法的差异性进行了方差分析。结果表明，奶牛乳房炎各乳区之间的感染率差异不显著（P〉0．05），乳房炎的发生与乳区之间无明显相关性；BMT和NaOH两种方法对乳房炎检测的结果之间差异不显著（P〉0．05），表明这两种方法都可用于隐性乳房炎的检测。     

内毒素对山羊乳腺组织中与乳腺炎相关的酶和细胞因子的影响

8只泌乳期的健康睢宁白山羊,产后72 h分别用内毒素和灭菌生理盐水经乳头管灌注左右侧乳房.灌注前及灌注后0、1、2、3、4、5、6、7、8、9、24 h观察山羊整体及乳房局部变化.灌注24 h后,处死动物,取乳腺组织,部分用Bou in氏液固定,部分用液氮保存.临床症状及病理切片观察均显示,山羊表现典型的急性乳腺炎症状.检测两侧乳腺组织中部分与乳腺炎症相关因子的含量及其基因表达水平的结果表明:与灌注生理盐水对照相比,灌注内毒素侧乳腺组织中N-乙酰-β-D氨-基葡萄糖苷酶(NAGase)、髓过氧化物酶(MPO)、诱导型一氧化氮合成酶(iNOS)的活性及IL-1β、IL-6的含量极显著升高(P<0.01),TNFα-含量显著升高(P<0.05);相同条件下对2种处理组织样中3种细胞因子mRNA表达水平进行PCR扩增,灌注内毒素侧能检到明显的目的条带,对照侧未见明显的目的条带.     

Polysaccharide Nucleic Acid of Bacillus Calmette Guerin Modulates Th1/ Th2 Cytokine Gene Expression in Lipopolysaccharide-lnduced Mastitis in Rats

The aim of this study was to evaluate, in rats, the changes in the T helper type 1（Th1）/Th2 radio in mammary glands after an intramammary infusion of lipopolysaccharide （LPS） and to characterize the moderating effects of the polysaccharide nucleic acid of Bacillus Calmette Guerin （BCG-PSN） on the mammary gland. In the control group, the levels of IL-2 and INF-7 mRNA expression increased, whereas IL-4 mRNA expression decreased after LPS challenge. As a consequence, the INF-γ/IL-4 mRNA ratio was significantly higher at 3, 6, and 9 h post-infusion （PI） compared to the control value （0 h; P〈0.01）. BCG-PSN increased mRNA expression of both INF-γ and IL-4 before infusion of LPS. LPS challenge significantly the reduced Th1/Th2 cytokine ratio due to Thl cytokine IFN-γ suppression and Th2 cytokine IL-4 upregulation compared with the control group. A significant reduction of N-acetyl-β-D-glucosaminidase （NAGase） was observed at 24 h PI in the BCG-PSN treatment group compared to the control group （P〈 0.05）. Thus, it was demonstrated that level of BCG-PSN might change the Th1/Th2 ratio mainly by enhancing the Th2 immune response. This is the first report of a Th1/Th2 change induced by coliform mastitis and characterization of the effect of BCG-PSN on mammary gland inflammation. This study makes a better understanding of the mechanisms of coliform mastitis and provides a putative novel strategy for the prevention and/or treatment of mastitis.     

Detection of antimicrobial resistance and virulence-related genes in Streptococcus uberis and Streptococcus parauberis isolated from clinical bovine mastitis cases in northwestern China

The objectives of this study were to investigate antimicrobial resistance of Streptococcus uberis and Streptococcus parauberis isolated from cows with bovine clinical mastitis in China and to examine the distribution of resistance- and virulence-related gene patterns. Antimicrobial susceptibility was determined by the E-test. Genes encoding antimicrobial resistance and invasiveness factors were examined by PCR. A total of 27 strains were obtained from 326 mastitis milk samples. Streptococcus parauberis isolates (n=11) showed high resistance to erythromycin (90.9%), followed by tetracycline (45.5%), chloramphenicol (36.4%) and clindamycin (27.3%). Streptococcus uberis isolates (n=16) were highly resistant to tetracycline (81.3%) and clindamycin (62.5%). Both species were susceptible to ampicillin. The most prevalent resistance gene in S. uberis was tetM (80.0%), followed by blaZ (62.5%) and ermB (62.5%). However, tetM, blaZ, and ermB genes were only found in 27.3, 45.5, and 27.3%, respectively, of S. parauberis. In addition, all of the isolates carried at least one selected virulence-related gene. The most prevalent virulence-associated gene pattern in the current study was sua+pauA/skc+gapC+hasC detected in 22.2% of the strains. One S. uberis strain carried 7 virulence-associated genes and belonged to the sua+pauA/skc+gapC+cfu+hasA+hasB+hasC pattern. More than 59.3% of analysed strains carried 4 to 7 virulence-related genes. Our findings demonstrated that S. parauberis and S. uberis isolated from clinical bovine mastitis cases in China exhibited diverse molecular ecology, and that the strains were highly resistant to antibiotics commonly used in the dairy cow industry. The data obtained in the current study contribute to a better understanding of the pathogenesis of bacteria in mastitis caused by these pathogens, and the findings are relevant to the development of multivalent vaccines and targeted prevention procedures.     

NH4Cl promotes apoptosis and inflammation in bovine mammary epithelial cells via the circ02771/miR-194b/TGIF1 axis

Excess ammonia (NH₃) in the circulation of dairy animals can reduce animal health and the quality of products for human consumption. To develop effective prevention and treatment methods, it is essential to examine the molecular mechanisms through which excess NH₃ may affect the mammary gland. The present study used bovine mammary epithelial cells (BMECs) to evaluate the effects of exogenous NH₄Cl on the abundance of circular RNAs (circRNAs) using high-throughput sequencing. Among the identified circRNAs, circ02771 was the most significantly upregulated by exogenous NH₄Cl (P<0.05), with a fold change of 4.12. The results of the apoptosis and proliferation assays, transmission electron microscopy, H&E staining, and immunohistochemistry revealed that circ02771 increased apoptosis and inflammation. A double luciferase reporter assay revealed that circ02771 targeted miR-194b, and the overexpression of circ02771 (pcDNA-circ02771) reduced (P<0.05) the expression of miR-194b and led to apoptosis and inflammation. Circ02771 also enhanced the expression of transforming growth factor beta-induced factor homeobox 1 (TGIF1), which is a target gene of miR-194b. Overall, this study suggests that the circ02771/miR-194b/TGIF1 axis plays a role in mediating the effects of NH₄Cl on BMECs. Therefore, this axis provides a novel target to help control hazards within the mammary gland from high circulating NH₄Cl levels.     

三种炎症因子在致炎大鼠乳腺组织中的表达

为探明在酯多糖（LPS）致炎的大鼠乳腺中,黏附因子-1（ICAM-1）、肿瘤坏死因子-α（TNF-α）、白介素-1β（IL-1β）表达分布的变化。取产后5 d乳房注射LPS致炎大鼠的乳腺组织,及LPS致伤的体外培养大鼠乳腺MVECs（Microvascular Endothelial Cells）,采用免疫组化方法检测ICAM-1、TNF-α和IL-1β的表达。结果表明：LPS处理大鼠乳腺后4~24 h内,乳腺组织切片试验和体外培养大鼠乳腺微血管内皮细胞（Rat MammaryMicrovascular Enclothelial Cells,RMMVECs）试验中ICAM-1和IL-1β的表达逐渐增强,TNF-α在乳腺组织切片试验中6 h表达显著增强,之后则逐渐减弱。在体外培养RMMVECs中-α表达逐渐增强。表达部位主要在乳腺上皮细胞和血管内皮细胞,IL-1β在腺泡腔中的白细胞中也有表达。由此可见,LPS处理大鼠乳腺后ICAM-1、TNF-α和IL-1β这三种细胞因子均参与了乳腺炎症过程中的免疫反应。     

奶牛乳腺炎病因分析及防治措施

[目的]探索奶牛乳腺炎病因及其防制措施。[方法]分析奶牛乳腺的免疫学机制,总结乳腺炎发病的原因,并提出奶牛乳腺炎的综合防制措施。[结果]奶牛乳腺存在体液免疫和细胞免疫的免疫学机制。其发病原因主要是病原微生物的感染。可采取加强卫生管理、实行干奶期治疗、疫苗免疫、选育高抗乳腺炎病的奶牛品种等方法进行防治。[结论]该研究为预防奶牛乳腺炎提供了理论依据。     

Molecular epidemiology,characterization of virulence factors and antibiotic resistance profile of Streptococcus agalactiae isolated from dairy farms in China and Pakistan

Streptococcus agalactiae is one of the most common pathogens that cause bovine mastitis worldwide. Identifying pathogen prevalence and virulence factors is critical for developing prevention and control approaches. Herein, 1 161 milk samples from various dairy farms in China (n=558) and Pakistan (n=603) were collected between 2019–2021 and were subjected to S. agalactiae isolation. Prevalence, serotyping, virulence genes, and antibiotic-resistant genes of S. agalactiae were evaluated by PCR assay. All isolates were characterized for haemolysis, biofilm production, cytotoxicity, adhesion, and invasion on bovine mammary epithelial cells. The prevalence of S. agalactiae-induced mastitis in cattle was found to be considerably higher in Pakistan than in China. Jiangsu and Sindh provinces had the highest area-wise prevalence in China and Pakistan, respectively. Serotypes Ia and II were prevalent in both countries, whereas serotype III was found only in Pakistan. Moreover, all isolates tested positive for PI-2b gene but negative for PI-1 and PI-2a genes. All isolates harboured cfb, cylE, hylB, and fbsB virulent genes, whereas many of them lacked bibA, rib and bca. However, the absence of bac and scp genes in Chinese isolates and cspA in Pakistani isolates was noted, while spb1 and lmb were not detected in isolates of both countries. Pakistani isolates, particularly serotype Ia-positive, had a considerably higher ability to produce biofilm, haemolysis, cytotoxicity, adhesion, and invasion than Chinese isolates. Most of the isolates were phenotypically resistant to tetracycline, erythromycin, and clindamycin and genotypic resistance was confirmed by the presence of ermA, ermB, tetM and tetO genes. Our study highlights the antimicrobial resistance profile and virulence-related factors contributing to the epidemiological spread of mastitis-causing S. agalactiae in China and Pakistan. The findings may facilitate future studies designed to develop improved treatment and control strategies against this pathogen.     

Prevalence and characteristics of extended spectrum β-lactamase-producing Escherichia coli from bovine mastitis cases in China

The aim of the study was to investigate the prevalence and characterization of extended-spectrum β-lactamase(ESBL)-producing Escherichia coli isolated from bovine mastitis cases in China. Chrom ID ESBL agar was used to confirm ESBL-producing E. coli. PCR and DNA sequencing were employed to characterize the genotype of ESBL-producers. Antimicrobial susceptibility was measured by disc diffusion. Overall, 73 of 318 E. coli isolates(22.96%) were identified as ESBL-producers. Of these ESBL-producing E. coli, the prevalence of blaCTX-M and bla_(TEM-1) was 97.26 and 71.23%, respectively. The predominant CTX-M-type ESBL was CTX-M-15(65.75%), followed by CTX-M-14(10.96%), CTX-M-55(9.59%), CTX-M-64(5.48%), CTX-M-65(4.11%) and CTX-M-3(1.37%). This study is the first report of CTX-M-64 and CTX-M-65 in E. coli isolated from bovine mastitis. Furthermore, 72 ESBL-producing E. coli isolates(98.63%) were found to be multidrug-resistance. This study noted high prevalence and rates of antimicrobial resistance of ESBL-producing E. coli isolates from bovine mastitis cases in China.     

蜂胶提取物对脂多糖诱导小鼠急性乳腺炎及乳腺屏障功能的保护作用

【背景】奶牛乳腺炎是一种常见、多发的奶牛疾病,不仅危害奶牛健康,同时也造成重大经济损失。传统治疗奶牛乳腺炎的药物主要是抗生素,极易造成抗生素耐药与滥用。开发替代抗生素的方法用于奶牛乳腺炎的防治具有现实意义。蜂胶是西方蜜蜂采集植物树脂,混合自身上颚腺、蜡腺的分泌物形成的具有良好抗炎、抗菌活性的天然产物,对防治奶牛乳腺炎具有潜在开发利用价值。尽管近年来国内外有一些有关蜂胶防治乳腺炎方面的报道,但蜂胶如何影响乳血屏障功能,目前国内外尚无相关研究报道。【目的】利用细菌脂多糖（lipopolysaccharides, LPS）诱导的小鼠急性乳腺炎模型,评估中国蜂胶乙醇提取物对小鼠急性乳腺炎的保护作用及其对乳腺细胞紧密连接蛋白表达的影响,为后续利用蜂胶防治奶牛乳腺炎的深入研究奠定理论基础。【方法】采用超高效液相色谱串联三重四级杆质谱（UHPLC-QqQ-MS/MS）对中国蜂胶乙醇提取物中主要的多酚类化合物进行种类和含量测定。试验分为空白对照组、LPS模型组、中国蜂胶提取物试验组以及地塞米松阳性对照组。ICR雌性小鼠连续灌胃中国蜂胶提取物或阳性对照药物7d后,模型组、试验组和阳性对照组经第四、五对乳头管注射1 mg·kg^-1体重 LPS,建立小鼠急性乳腺炎模型,24 h后处死,收集乳腺组织样本。以苏木精-伊红（H.E）染色法、天狼星红染色法评估小鼠乳腺组织病理变化;利用酶联免疫吸附法（ELISA）测定炎症因子释放量;利用荧光定量PCR测定小鼠乳腺组织中紧密连接蛋白（Occludin、Cluadin-1、ZO-1） mRNA的表达情况;最后利用免疫组化技术研究小鼠乳腺紧密连接蛋白（Occludin和ZO-1）表达和分布情况,利用以上指标综合评判中国蜂胶乙醇提取物的抗乳腺炎活性及其对乳腺紧密连接蛋白的影响。【结果】基于UHPLC-QqQ-MS/MS,建立了中国蜂胶乙醇提取物中主要的17种多酚类化合物的精确定量方法,检测结果表明含量最高的5种化合物及其含量分别为：高良姜素（12.88±0.57 μg·mg^-1）、短叶松素3-乙酸酯（12.93±0.59 μg·mg^-1）、松属素（8.56±0.27 μg·mg^-1）和短叶松素（8.52±0.25 μg·mg^-1）。动物试验结果表明,灌胃中国蜂胶提取物能够显著缓解LPS注射导致的乳腺组织中炎性细胞浸润、缓解乳腺腺泡结构损伤;同LPS组相比,中国蜂胶提取物灌胃处理可有效抑制LPS导致的小鼠乳腺组织中炎症因子（IL-1β,IL-6和IL-10）的释放,并可提高小鼠乳腺中紧密连接蛋白的mRNA表达,缓解LPS注射所导致的乳腺上皮细胞紧密连接的破坏。【结论】中国蜂胶提取物对脂多糖诱导小鼠乳腺炎具有良好的预防效果,并可有效促进乳腺紧密连接蛋白的表达,维持乳腺中紧密连接结构完整性,保护血乳屏障,但蜂胶对紧密连接影响调控的分子机理还需进一步深入研究。     

Comparative Proteomic Analysis of Plasma from Clinical Healthy Cows and Mastitic Cows

The current research presents the protein changes in plasma from healthy dairy cows and clinical mastitic cows using two- dimensional gel electrophoresis （2-DE）. After staining with silver nitrate and Coomassie Blue, differential expression proteins were detected by PDQuest 7.4 software, and then subjected to ion trap mass spectrometer equipped with a Surveyor HPLC System, differential spots of protein were identified. Three protein spots that originated from preparation gels were identified to be two proteins. Overall, haptoglobin precursor was up-regulated in cows infected with clinical mastitis and could be a mastitis-associated diagnostic marker, whereas SCGB 2A1 （secretoglobin, family 2A, member 1） was down-regulated protein. Plasma protein expression patterns were changed when cows were infected with mammary gland inflammation; it suggests that analysis of differential expression protein might be useful to clarify the mechanisms involved in the pathophysiology, and find new diagnostic markers of mastitis and potential protein targets for treatment.