The defense mechanism of surfactant protein (SP-A, SP-D) against urinary tract infection

SP-D在正常人膀胱黏膜中表达，其mRNA在UPEC感染模型小鼠膀胱中表达升高。分离的J96-SP-D复合物显示出细菌对5637细胞（人膀胱细胞系）的粘附减少，以及upec诱导的细胞毒性。此外，SP-D与UPK1a结合，抑制FimH蛋白受体结合域与UPK1a的结合。用SP-D对5637细胞进行预孵育，然后清洗细胞，可以显著降低细菌对细胞的粘附和upec诱导的细胞损伤。我们认为SP-D可以保护尿路上皮膀胱细胞免受UPEC感染。

SP-D was expressed in normal human bladder mucosa and its mRNA was increased in the bladder of the UPEC infection model in mice. Isolated J96-SP-D complex exhibited decreased bacterial adherence to 5637 cells, the human bladder cell line, and the UPEC-induced cytotoxicity. In addition, SP-D bound to UPK1a and inhibited the binding of receptor-binding domain of FimH protein to UPK1a. Pre-incubation of the 5637 cells with SP-D and then washing the cells significantly decreased bacterial adherence to the cells and UPEC-induced cell injury. We conclude that SP-D protects the urothelial bladder cells against UPEC infection.