Analysis of mechanisms causing renal scars in pyelonephritis

肾疤痕被认为是慢性肾盂肾炎的终末期。在大鼠实验性肾盂肾炎模型中，甘露糖敏感(MR)纤毛菌株引起严重的肾瘢痕形成，而甘露糖抗性(MS)或非纤毛菌株不引起严重的瘢痕形成，超氧化物歧化酶处理可抑制这种瘢痕形成。比较了细菌与人多形核白细胞(PMN)相互作用的能力。MS菌毛菌株刺激PMN产生超氧阴离子的能力是MR菌种和非菌毛菌株的两倍。MS菌毛由几个亚基组成；一个主要亚基和其他次要亚基。粘附素是一种较小的亚基，负责甘露糖与真核细胞的敏感黏附。为了研究粘附素在肾脏瘢痕形成中的作用，我们构建了粘附素缺陷突变体，该突变体具有菌毛结构，但不能凝集豚鼠红细胞。重组载体pSH2携带合成和表达功能性MS菌毛的基因组信息。含有MS菌毛粘附素基因缺失的突变体pYMZ84不能凝集豚鼠红细胞，即使表达菌毛的细菌在形态和抗原性上与携带完整MS菌毛基因的pSH2产生的菌毛没有区别。携带pYMZ84的大肠杆菌不会引起大鼠肾脏的瘢痕形成，而携带pSH2的大肠杆菌则会造成严重的肾脏瘢痕。与非粘附素突变型和突变型中性粒细胞相比，经MS-纤毛菌刺激后，PMN的化学发光峰显着升高，且大部分氧化爆发发生在5min内。这些数据表明，MS菌毛使细菌在几分钟内引起PMN的大量氧化爆发，并导致感染器官的组织损伤，MS菌毛的粘附素在这一过程中起着核心作用。

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.