高盐喂食对Dahl盐敏感大鼠肾小管上皮向间质转化和肾脏纤维化的影响

The impact of high-salt intake on tubular epithelial-to-mesenchymal transition and renal fibrosis in Dahl salt-sensitive rats

目的探讨高盐喂食对Dahl盐敏感大鼠肾小管上皮向间质转化（EMT）和肾脏纤维化的影响。方法 7～8周龄雄性Dahl盐敏感大鼠（SS,n=24）及SS-13BN大鼠（13BN,n=12）,高盐（8%NaCl）、低盐（0.3%NaCl）喂食干预4周与8周,测量血压、血尿生化指标;采用Masson染色评估肾脏纤维化程度;免疫组化和实时定量聚合酶链反应（PCR）分别检测肾小管上皮标志E-钙黏蛋白（E-cadherin）和间质细胞标志α平滑肌肌动蛋白（α-SMA）mRNA和蛋白的表达情况。结果 1与基线期比较,SS和13BN大鼠高盐干预4周后收缩压增高,SS大鼠增高幅度更为明显[SS：（184.4±4.5）比（139.0±0.3）mm Hg;13BN：（156.3±2.1）比（139.8±1.2）mm Hg];8周高盐干预时血压显著高于4周[（227.1±3.6）比（184.4±4.5）mm Hg,P〈0.01]。24周高盐负荷后,两种大鼠肾脏出现明显的胶原纤维沉积,且SS高盐组明显多于13BN高盐组[肾小球：（9.8±1.9）%比（8.7±0.4）%;肾间质：（9.1±0.2）%比（6.7±0.3）%]。8周时,SS高盐组肾小球和间质胶原沉积较4周进一步加重[肾小球：（15.4±0.9）%比（9.8±1.9）%;肾间质：（13.9±0.4）%比（9.1±0.2）%]。34周和8周高盐干预后,与SS低盐组相比,SS高盐组肾脏E-cadherin表达均减少,α-SMA表达增加。4肾脏纤维化程度与肾小管EMT的发生相关（E-cadherin：r=-0.720,α-SMA：r=0.848;均P〈0.01）。结论高盐喂食可诱导Dahl盐敏感大鼠肾小管上皮细胞EMT的发生,促进肾脏纤维化。

Objective To investigate the impact of high-salt intake on epithelial-to-mesenchymal transition （EMT） and renal fibrosis in Dahl salt-sensitive （SS} rats. Methods Twenty-four male SS and twelve eonsomic SS-13BN （13BN） rats were randomized to low-salt or high-salt diets for 4 and 8 weeks, respectively. After the intervention, systolic blood pressure （SBP） and biochemical markers in blood and urine were measured, and renal fibrosis was evaluated by Masson staining. The mRNA and protein expression levels of E-cadherin and alpha smooth muscle ac- tin （a-SMA） were assessed by immunohistochemistry and real-time polymerase chain reaction（PCR）. Results Compared with baseline levels, the high-salt diet groups showed significantly higher blood pressure, the increase be- ing more obvious in the SS high-sah diet group [SS： （184.4±4.5） vs （139.0±0.3）ram Hg; 13BN： （156.3v2. 1） vs （139.8± 1.2）mm Hg]. SS rats had significantly increased SBP after 8 weeks of high-salt diets relative to 4 weeks [（227.1±3.6） vs （184.4±4.5）mm Hg, P〈0.01]. After 4 weeks of salt loading, Masson staining of col lagen in kidneys was more pronounced in rats with high-sah diets than with normal diets. Under high-sah feeding, SS rats showed higher glomerular and interstitial fibrosis than 13BN rats [glomeruli： （9.8 ± 1.9）% vs （8.7 ± 0.4）% ; interstitium ： （ 9.1 ± 0.2 ） % vs （ 6.7 ± 0.3 ） % ]. SS rats with high-salt diets had more collagen deposition in the glomeruli and interstitium at 8 weeks than at 4 weeks [glomeruli： （15.4±0.9） % vs （9.8±1.9）% ; interstiti- urn： （13.9 ± 0.4 ）% vs （9.1±0.2）%]. High-salt feeding induced tubular EMT as identified by reduced expression of E cadherin and increased expression of a SMA in SS rats after 4 and 8 weeks of high-salt feeding. Renal interstitial fibrosis was correlated negatively with E-cadherin, but positively with a-SMA （r=- 0. 720 for E-cadher- in; r=0. 848 for a-SMA;both P〈0.01）. Conclusion High-salt intake might induce tubular EMT and facilitate renal fibrosis in salt-sensitive rats.