Endometritis is a common bacterial disease of dairy cows. Cathelicidins are host-defense peptides that play important roles in clearance of bacteria. However, the expression pattern of these peptides during endometritis is still unclear. We hypothesize that the levels of bovine cathelicidins increased during endometritis. This study was to investigate the changes of bovine cathelicidins during endometritis. Forty-four post-partum cows (28–35 days after calving) involved in this study were grouped according to the character of vaginal discharge (VD) into three groups. These were (1) cows with clear fluid (n = 8, healthy cows group, N); (2) cows with VD containing <50% off-white mucopurulent material (n = 20, moderate endometritis cows, M); (3) cows with VD containing > 50% yellow or white purulent material (n = 16, severe endometritis cows, S). The blood, VD, and endometrial biopsies samples were collected from each cow to assess the levels of cathelicidin 1–7. Furthermore, bovine endometrial epithelial cells (BEECs) were stimulated with different concentration of Escherichia coli (2 × 10⁶ and 2 × 10⁷ CFU/mL) to detect the cellular source of cathelicidins. Quantitative real-time PCR (RT-qPCR) was used to detect the relative mRNA expression of cathelicidins, and enzyme-linked immune sorbent assay (ELISA) method were used to measure the protein levels. The mRNA and protein levels of cathelicidin 1–7 significantly increased during bovine endometritis (both moderate and severe endometritis), while samples from severe cases showed lower levels of cathelicidins compared to moderate cases. BEECs can express cathelicidin 1–7, and E. coli triggered the release of these proteins. High concentration of E. coli decreased the mRNA and protein levels of cathelicidins. Taken together, our results supported that cathelicidins are released as host defense molecules against the bacteria during bovine endometritis, and BEECs play an active role in expression and production of cathelicidins.

子宫内膜炎是奶牛常见的细菌性疾病。Cathelicidins 是宿主防御肽，在清除细菌中起重要作用。然而，这些肽在子宫内膜炎期间的表达模式仍不清楚。我们假设在子宫内膜炎期间牛导管素的水平增加。本研究旨在探讨子宫内膜炎时牛导管素的变化。参与本研究的 44 头产后奶牛（产犊后 28-35 天）根据阴道分泌物（VD）的特征分为三组。这些是 (1) 头有清澈液体的奶牛 (n= 8，健康奶牛组，N)；(2) 含有 <50% 灰白色粘液脓性物质的 VD 奶牛（n= 20，中度子宫内膜炎奶牛，M)；(3) VD 含有> 50% 黄色或白色脓性物质的奶牛（n= 16，严重子宫内膜炎奶牛，S)。从每头奶牛收集血液、VD 和子宫内膜活检样本，以评估导管素 1-7 的水平。此外，牛子宫内膜上皮细胞 (BEECs) 受到不同浓度的刺激。大肠杆菌(2 × 10 ⁶和2 × 10 ⁷ CFU/mL) 以检测导管素的细胞来源。采用实时定量PCR（RT-qPCR）检测cathelicidins mRNA的相对表达量，采用酶联免疫吸附试验（ELISA）法检测蛋白水平。在牛子宫内膜炎（中度和重度子宫内膜炎）期间，导管素 1-7 的 mRNA 和蛋白质水平显着增加，而与中度病例相比，来自严重病例的样本显示出较低水平的导管素。BEEC 可以表达导管素 1-7，并且大肠杆菌触发这些蛋白质的释放。高浓度大肠杆菌降低导管素的 mRNA 和蛋白质水平。总之，我们的结果支持在牛子宫内膜炎期间，导管素作为宿主防御分子被释放以抵抗细菌，并​​且 BEEC 在导管素的表达和生产中发挥积极作用。