表面活性蛋白A及D在小鼠尿路感染中的作用及机制

Innate immunity of surfactant protein A and D in urinary tract infection with uropathogenic Escherichia coli

目的研究表面活性蛋白（SP）A及sP—D在尿路感染（UTI）中的作用和机制，评价sP—A及SP—D缺失对UTI的影响。方法免疫组化评估sP—A及sP—D在野生型（wT）C57BL／6雌性小鼠肾脏内的表达及分布；Western印迹评价SP-A及sP—D双重敲除（SP—A／DKO）与wT小鼠肾脏p38磷酸化水平。应用SP-A／DKO小鼠和wT雌性小鼠构建逆行性小鼠UTI模型，小鼠分为2组：SP—A／DKO＋UTI组和wT＋UTI组，分别实验24h和48h。进行细菌培养及计数各组肾脏及尿液中的细菌含量，HE染色评价各组病理改变；免疫组化及计数肾脏及尿液内中性粒细胞的数量。体外细菌培养观察sP—A及sP—D对致尿路感染大肠杆菌（UPEC）生长的影响。结果wT小鼠肾脏内sP—A及SP—D主要分布于近曲小管及集合管。SP—A／DKO小鼠肾脏内p38磷酸化水平显著高于wT小鼠（P〈0．05）。SP—A／DKO小鼠在发生UTI时，其肾脏病理改变更重，中性粒细胞浸润更多。SP—A／DKO小鼠肾脏内及尿液内细菌量在24h及48h均显著高于wT小鼠（均P〈0．01）。体外实验显示，sP—A及sP—D均可显著抑制UPEC的生长（均P〈0．05）。结论肾脏内表达sP—A及SP—D；SP—A／DKO小鼠与wT小鼠相比，其对UTI更易感，其机制可能与UTI时炎性因子分泌不足及sP—A和sP—D对致尿路感染大肠杆菌生长的直接抑制有关。

Objective To investigate the role of surfactant protein （SP）- A and SP- D in urinary tract infection mouse model, and evaluate the effects of SP-A and SP- D absence on urinary tract infection. Methods SP-A and SP-D double knockout （SP-A/D KO） mice were made. SP-A/D KO and wild-type （WT） C57BL/6 female mice were used for this study. The expression of SP-A and SP-D in kidney was detected by immunohistochemistry （IHC）. The levels of p-p38 and p38 protein in kidneys were measured by Western blotting. Uropathogenic Escherichia coli or buffer was delivered into the bladder of female mice. At 24 and 48 h after inoculation, CFU of Escherichia coli in the kidney and urine of the treated and control mice were measured. Histological, cellular and molecular analysis were performed by several methods of H/E staining, IHC and Western blotting. The effects of SP-A and SP-D on bacterial growth were studied in vitro. Results SP-A and SP-D in kidney were located in the proximal tubules and collecting tubules. Compared with WT mice, infected SP- A/D KO mice with UPEC had higher CFU in kidneys and urine at 24 h and 48 h, increased inflammatory cells infiltrationin kidneys （P〈0.05）. Compared with WT mice, SP- A/D KO mice had higher p38 MAPK phosphorylation levels in kidneys （P 〈 0.05 ）. Growth of Escherichia coli was greatly inhibited by both SP-A and SP-D （P 〈 0.05 ）. Conclusions Both SP-A and SP-D are expressed in kidney. SP-A and SP-D can attenuate UTI induced by UPEC which may be through inhibiting bacterial growth and modulating renal inflammation.