Analysis of mechanisms causing renal scars in pyelonephritis

肾瘢痕被认为是慢性肾盂肾炎的终末阶段。在实验性大鼠肾盂肾炎模型中，甘露糖敏感(MR) -绒毛毒株引起严重的肾瘢痕，而甘露糖耐药（MS）或非绒毛毒株则没有，并且这种肾瘢痕通过超氧化物歧化酶处理得到抑制。比较了细菌与人多形核白细胞（pmn）相互作用的能力。ms -毛状菌比MR-毛状菌和非毛状菌产生的pmn多两倍。毛菌由几个亚基组成；一个主要的亚单位和其他次要的亚单位。其中一个次要亚基，粘附素，负责甘露糖对真核细胞的敏感粘附。为了研究粘连素在肾瘢痕形成中的作用，我们构建了具有毛状结构但不能凝集豚鼠红细胞的粘连素缺陷突变体。重组质粒pSH2携带基因组信息，用于大肠杆菌MS菌毛的合成和表达。一种含有MS毛粘连素基因缺失的突变体pYMZ84不能凝集豚鼠红细胞，尽管这种细菌在形态和抗原性上与携带MS毛粘连素完整基因的质粒pSH2所产生的毛粘连素在形态和抗原性上没有区别。携带pYMZ84的大肠杆菌不会引起肾瘢痕，而携带pSH2的大肠杆菌会引起严重的肾瘢痕。PMN在化学发光反应中表现出明显的高峰响应，且与无黏附蛋白或黏附蛋白突变菌相比，ms -毛簇菌刺激PMN后5分钟内发生氧化爆发。这些数据表明，MS菌毛赋予细菌在几分钟内引起PMNs的大量氧化爆发并导致感染器官的组织损伤，而MS菌毛的粘连素在这一过程中起核心作用。

Renal scars are thought to be the end stage of chronic pyelonephritis. In the experimental pyelonephritis model of rats, mannose sensitive (MR) -piliated strain caused severe renal scarring whereas mannose resistant (MS) - or non-piliated strain did not and this renal scarring was suppressed by treatment with superoxide dismutase. The piliation of bacteria was compared for their capacity to interact with human polymorphonuclear leukocytes (PMNs). MS-piliated strain stimulated superoxide production of PMNs two times more than MR- and non-piliated strains did. MS pili consist of several subunits ; one major subunit and other minor subunits. One of the minor subunits, adhesin, is responsible for mannose sensitive adhesion to eukaryotic cells. To investigate the role of adhesin in renal scarring, we constructed the adhesin-deficient mutant which has pilus structure but cannot agglutinate guinea pig erythrocytes. A recombinant plasmid pSH2 carries the genomic information for the synthesis and expression of functional MS pili of E.coli. A mutant, pYMZ84, containing a deletion in the adhesin gene of MS pili failed to agglutinate guinea pig erythrocytes even though the bacteria expressed pili morphologically and antigenically indistinguishable from those produced by plasmid pSH2, carrying the intact genes for the MS pili. E.coli harboring pYMZ84 did not cause renal scarring whereas E.coli harboring pSH2 caused severe renal scarring in rats. PMN showed significantly high peak response of chemiluminescence and most of oxidative burst occurred within five minutes after stimulating with MS-piliated bacteria compared with non- or adhesin mutant-piliated bacteria. These data suggest that MS pili confer the bacteria to cause large amount of oxidative burst of PMNs within a few minutes and lead to the tissue damage in the infected organ and adhesin of MS pili play a central role in this process.