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标题: Effect of aldosterone on renal transforming growth factor- [打印本页]

作者: 轻羽    时间: 2009-4-22 08:13     标题: Effect of aldosterone on renal transforming growth factor-

作者:Irmantas Juknevicius, Yoav Segal, Stefan Kren, Rutha Lee, and Thomas H. Hostetter作者单位:Division of Renal Diseases and Hypertension, Department of Medicine, University of Minnesota, Minneapolis, Minnesota 55455; and National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892 7 s: y8 ?. e2 I. a+ `7 h
                  
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          【摘要】
$ q4 r$ ~# B! B3 f6 r" c& B! A      Aldosterone participates in the pathophysiology of several models of progressive chronic renal disease. Because of the causal connection between transforming growth factor- 1 (TGF- ) and scarring in many such models, we hypothesized that aldosterone could evoke TGF- in the kidney. Aldosterone infusion for 3 days in otherwise normal rats caused a more than twofold increase in TGF- excretion without changes in systolic pressure or evidence of kidney damage. Concurrent treatment with amiloride did not alter this effect, indicating that aldosterone's stimulation of TGF- was independent of its regulation of sodium or potassium transport. However, concurrent treatment with spironolactone did block the increase in TGF-, indicating that the effect depends on the mineralocorticoid receptor. Renal mRNA for serum glucocorticoid kinase rose, but no change in TGF- message occurred, suggesting posttranscriptional enhancement of renal TGF-. In summary, aldosterone provokes renal TGF-, and this action may contribute to aldosterone's fibrotic propensity. % Q- K# D& }0 g* c9 q: G& i
          【关键词】 aldosterone transforming growth factor kidney( O2 V6 _3 q. N8 K
                  ALDOSTERONE AND ANG II perpetuate injury in many chronic renal diseases ( 6 ). Aldosterone also generates fibrosis in the heart, and in vitro studies have confirmed that this pathology derives at least in part from nonhemodymic actions of the steroid ( 20, 22, 26 ). Several plausible pathways for tissue injury and remodeling by aldosterone have been proposed in addition to its potential toxicity as a hypertensive agent ( 4, 20, 22 ). Transforming growth factor- 1 (TGF- ) 1 has a well-established role in a wide range of chronic renal injuries ( 1, 3, 12, 18, 23, 27 ). ANG II likely effects some of its deleterious actions through the agency of TGF- because ANG II stimulates TGF- synthesis in vitro ( 8, 27 ). Because of the increasingly recognized connection between aldosterone and progressive kidney disease, we questioned whether the mineralocorticoid might, like ANG II, induce TGF-. Renal TGF- expression is elevated in mineralocorticoid-salt hypertension ( 9 ). Also, its expression rises in the remnant kidney model, a phenomenon that also appears to depend at least in part on aldosterone ( 5 ). However, in these two models, the rats had substantial renal injury, and the TGF- may have represented a late or nonspecific response only very indirectly related to the mineralocorticoid. For this reason, we examined the renal TGF- response to aldosterone in normal rats before injury or hypertension supervened.
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MATERIALS AND METHODS
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/ a6 F- [) M0 y# ]. cMale Sprague-Dawley rats weighing between 250 and 300 g were used for these studies. They had free access to standard rat chow (24% protein and 29% sodium; Teklad Premier Laboratory Diets, Madison, WI) and tap water. Under methohexitol anesthsesia, osmotically driven minipumps (Alzet) were implanted subcutaneously. Aldosterone was infused at 80 µg·kg -1 ·day -1. Some of the controls had implantation of a pump with saline added to the infusion chamber. Other controls underwent only anesthesia and a sham incision. One group of rats received amiloride dissolved in DMSO and further diluted in olive oil at 3 mg·kg -1 ·day -1 subcutaneously. Another group of rats received spironolactone in powdered chow of the same composition mixed to deliver 400 mg·kg -1 ·day -1. Between the 2nd and 3rd day after the procedure, urine was collected for 24 h. On the 3rd day, systolic blood pressures were measured in the awake state by tail cuff. Later on the 3rd day, the animals were killed, and trunk blood and kidneys were obtained for analyses. The kidneys were divided into cortex and medulla. The studies were approved by Research Animal Resources of the University of Minnesota. The National Institutes of Health Guide for the Care and Use of Laboratory Animals was followed.( D6 k0 w9 L) I

% i/ }3 B3 O8 M) _; vAldosterone and plasma renin activity were determined by RIA. For renin activity, the generation of ANG I was measured using a kit from New England Nuclear (Boston, MA). For aldosterone, a kit manufactured by Diagnostic Products (Los Angeles, CA) was used. TGF- was measured by immunoabsorbence using a kit from Promega (Madison, WI). Sodium and potassium were measured by flame photometry. Urinary protein was assayed by the Coomasie dye method (Bio-Rad Laboratories, Hercules, CA). For the RNase protection assays, the kidney pieces were quickly divided into cortex and papilla and frozen in liquid nitrogen. RNA was extracted from the tissues using Ultraspec RNA (Biotecx Laboratories, Houston, TX). Templates for riboprobe synthesis were amplified by PCR from a rat kidney cDNA library (BD Biosciences Clontech, Palo Alto, CA) or isolated as restriction fragments from EST clones (Research Genetics, Huntsville, AL), cloned into the vector pBC KS(-) (Stratagene, La Jolla, CA) and verified by direct sequencing. With corresponding GenBank accessions, nucleotide (nt) positions, and sizes, these templates provided riboprobes for -actin (NM_031144 .1, nt 1002-1116, 115 bases), TGF- (NM_021578 .1, nt 941-1111, 171 bases), collagen- 1 (I) (XM_213440 .2, nt 4430-4663, 234 bases), and serum glucocorticoid kinase (SGK; NM_019232 .1, nt 2422-2090, 333 bases). Riboprobes were synthesized from linearized templates using T7 polymerase in the presence of [ 32 P]UTP. RNase protection assays were carried out using the RPA III kit from Ambion (Austin, TX). The kidney RNA and the riboprobes were hybridized at 60°C overnight and then exposed to RNase. After precipitation, the hybridization products were reconstituted, loaded onto a 6% denaturing polyacrylamide gel, and electrophoresed. The phosphorimage of the gel was analyzed by densitometry. The densities were normalized to the -actin value for that sample. Yeast tRNA samples were used as negative controls.
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Statistical analysis was performed using Student's t -test for unpaired samples. The results are presented as means ± SD.
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. R: P" m# e6 w0 M3 m- P! PRESULTS
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Infusion of aldosterone for 3 days more than doubled the urinary excretion of TGF- compared with the sham controls and increased the urinary TGF- concentration ( Table 1 ). As expected, both the urinary excretion rate and the plasma level of aldosterone were higher in the rats receiving the mineralocorticoid infusion. Over this period, we observed no detectable effects of the hormone on body weight, systolic blood pressure, or urinary protein excretion. However, this same short-term administration of aldosterone did lower the plasma potassium level and suppress plasma renin activity ( Table 2 ).
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- Q$ K" T- {# B6 q* JTable 1. Effects of aldosterone infusion, O; q3 B) |7 T$ Q( ^; X) B
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Table 2. Effects of aldosterone infusion on plasma electrolytes and renin activity. G2 N2 Y2 ?) P2 Z# F1 Q& \9 H- f

+ v+ o6 i8 p9 N0 k9 r3 J5 k9 mWe questioned the roles of potassium depletion and extracellular volume expansion with consequent renin inhibition in the observed stimulation of urinary TGF-. To separate these effects, we studied separate rats simultaneously infused with aldosterone as before but also treated with the diuretic amiloride. These rats were compared with control rats receiving neither aldosterone nor amiloride ( Table 3 ). The diuretic abrogated the hypokalemia and the apparent volume expansion, as indicated by plasma renin activity. However, a similar augmentation of urinary TGF- occurred. Thus aldosterone enhances urinary TGF- independent of its actions on cation transport. In another two groups of rats, we tested the effects of the mineralocorticoid receptor blocker spironolactone over the same 3-day time period. Compared with animals receiving aldosterone alone ( n = 8), those receiving concurrent spironolactone ( n = 6) did not show reductions in serum potassium (3.4 ± 0.2 vs. 4.2 ± 0.3 meq/l, respectively, P + ^0 Q+ c7 X  W4 o3 Q
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Table 3. Effects of amiloride on aldosterone infusion; o* H5 [  F1 ~: Y% S* ?

+ ~* j7 U( e; g* j; qTo further assess the mechanism of the increased TGF-, we measured its level of gene expression along with those of type 1 collagen, SGK, and -actin. The last was used as a normalizing measure in the calculations, and indeed its level did not differ between aldosterone- and nonaldosterone-infused rats ( Fig. 1 ). RNA samples extracted from cortex and medulla were analyzed separately. The only detectable change was an aldosterone-induced increase of approximately twofold in the ratio of SGK message to that of -actin in the cortex ( Table 4 ). This increase in SGK transcripts was predictable in view of the central role played by this kinase in the signal transduction pathway for aldosterone ( 17 ). The lack of an increase in TGF- message suggests that its elevation occurs through a nontranscriptional route.
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Fig. 1. Representative image of gel from RNase protection assay. SGK, serum glucocorticoid kinase; TGF-, transforming growth factor-.
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DISCUSSION1 x( a8 i8 \" b. f+ i7 ^

( G" D9 a% F- K# vAldosterone stimulated urinary TGF- excretion by a route that is independent of the steroid's effects on potassium and extracellular volume expansion and without augmentation of TGF- gene transcription. The absence of hypertension or renal injury was by design. Production of the standard mineralocorticoid-salt model of hypertension requires longer-term steroid administration, a high salt intake, and unilateral nephrectomy. In the present study, the lack of injury as gauged by proteinuria, hypertension, or collagen 1 gene expression indicates that the action of aldosterone on TGF- is a relatively direct one and not simply a late, nonspecific response to hypertensive renal injury.# D2 g: Q2 k' p+ y
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Both TGF- and the renin-angiotensin-aldosterone system (RAAS) participate in progressive renal injury ( 1, 6 ). Blockade of the RAAS at multiple sites mitigates kidney damage in experimental and clinical settings ( 6 ). TGF- causes kidney damage when overexpressed in transgenic mice, and in vitro its application to cells provokes extracellular matrix production ( 12, 13, 15, 18, 24 ). Moreover, the elevated renal levels of TGF- observed in models of progressive kidney disease fall with angiotensin-converting enzyme (ACE) inhibition or angiotensin receptor blockade ( 1, 5, 7 ). Finally, ANG II stimulates TGF- production in vivo and in vitro ( 2, 27 ). Thus one path of injury may proceed through generation of ANG II with the resultant TGF- production responsible for fibrotic consequences. However, aldosterone and ANG II mediate some of the ill effects of the RAAS in renal injury. The present results argue for an effect of aldosterone on TGF- separate from that of ANG II. That is, the augmentation of TGF- occurred despite suppression of renin activity and a likely parallel reduction in ANG II. Thus ANG II and aldosterone may each exert their injurious actions through TGF-.$ S: }: G% m! \8 Z/ [# a# k# I
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The absence of an increase in TGF- message does not preclude an increase in the protein's renal production. Increased production is likely, because an increase in release of preformed TGF- without ongoing synthesis seems unlikely to persist for even the short interval of the present protocol. Also, a nonspecific increase in urinary TGF-, perhaps resulting from a change in protein reabsorption, is inconsistent with the similar rates of total protein excretion in the infused and uninfused rats. A posttranscriptional increase in its rate of synthesis and secretion is the most probable mechanism. Indeed, such an event has been described for TGF- in several cell lines. Moreover, this mode of regulation of TGF- secretion has been best documented for retinoid and other steroid secretagogues of TGF- ( 10, 11, 25 ). Nontranscriptional control of production seems the most likely explanation for the elevation in urinary TGF- with aldosterone.
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TGF- manifests an extraordinarily wide range of actions ( 3, 16, 19 ). Renal research has largely focused on its pathological effects ( 2, 3, 12, 18, 23, 27 ). However, levels are detectable in the normal kidney, and the medulla contains a higher concentration than the kidney as a whole and comparable to that of the glomeruli ( 15 ). Regulation of renal cell proliferation may be a primary role, but the cytokine may perform other homeostatic functions. Stokes ( 21 ) discovered that TGF- antagonizes the action of mineralocorticoids on inner medullary collecting duct cells. Specifically, when such cells are grown in culture and a mineralocorticoid is applied, they develop a sodium current indicative of the stimulation of sodium transport. Addition of TGF-, at levels comparable to those in the normal medulla, blocks this mineralocorticoid-induced sodium transport. Taken with our present results, these data raise the possibility that TGF- may act as a local counterregulator to the sodium retentive actions of aldosterone. Precedents exist for such a pairing (between hormonal and paracrine/autocrine effectors in the renal medulla). For example, the opposing actions of circulating antidiuretic hormone and locally produced prostaglandin exert fine control of water reabsorption in the medulla ( 14 ). Further studies will be required to assess this hypothesized counterregulatory role of TGF-.$ T+ L* I$ K% v. u
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In summary, aldosterone increases urinary TGF- within 3 days and without hypertension or renal injury. Aldosterone may in pathological states exert profibrotic effects through this pathway., n) q8 a! t& g# {" l% \
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GRANTS
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This work was supported by National Institute of Diabetes and Digestive and Kidney Diseases Grant RO1-DK-31437.
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ACKNOWLEDGMENTS# ]0 ]/ B3 X! t3 e# S( @
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We thank Carol Thompson for secretarial help.
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作者: 命运的宠儿    时间: 2015-11-13 13:54

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作者: 橙味绿茶    时间: 2016-1-14 09:18

干细胞与基因技术
作者: 123456zsz    时间: 2016-1-27 16:43

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作者: 干细胞2014    时间: 2016-3-3 23:22

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作者: ines    时间: 2016-3-10 12:42

我等你哟!  
作者: 小倔驴    时间: 2016-8-29 20:27

楼主也是博士后吗  
作者: 龙水生    时间: 2016-9-3 18:27

21世纪,什么最重要——我!  
作者: 小丑的哭泣    时间: 2016-9-16 16:27

干细胞与动物克隆
作者: Kuo    时间: 2016-11-17 08:54

发贴看看自己积分  
作者: 天蓝色    时间: 2016-11-28 11:27

来上茶~~~~  
作者: 365wy    时间: 2016-12-15 12:09

人气还要再提高  
作者: IPS干细胞    时间: 2016-12-18 11:59

声明一下:本人看贴和回贴的规则,好贴必看,精华贴必回。  
作者: 苹果天堂    时间: 2016-12-25 22:54

先顶后看  
作者: aakkaa    时间: 2017-1-9 08:43

真的有么  
作者: 8666sea    时间: 2017-1-9 15:42

说的真有道理啊!
作者: mk990    时间: 2017-1-19 14:54

胚胎干细胞
作者: Diary    时间: 2017-2-14 07:57

干细胞库  
作者: 大小年    时间: 2017-3-5 08:55

发贴看看自己积分  
作者: xiao2014    时间: 2017-3-16 12:54

转基因动物
作者: pcr    时间: 2017-3-26 07:02

好啊,,不错、、、、  
作者: MIYAGI    时间: 2017-4-4 22:50

加油啊!偶一定会追随你左右,偶坚定此贴必然会起到抛砖引玉的作用~  
作者: www1202000    时间: 2017-4-5 09:35

今天临床的资料更新很多呀
作者: alwaysniu    时间: 2017-4-8 08:01

我帮你 喝喝  
作者: 再来一天    时间: 2017-4-10 15:17

希望大家都有好运  
作者: 泡泡鱼    时间: 2017-4-14 00:01

帮顶  
作者: 命运的宠儿    时间: 2017-4-30 22:33

一个人最大的破产是绝望,最大的资产是希望。  
作者: marysyq    时间: 2017-5-10 19:41

干细胞疾病模型
作者: sshang    时间: 2017-5-15 20:37

彪悍的人生不需要解释。  
作者: 某某人    时间: 2017-5-19 08:35

说的不错  
作者: xm19    时间: 2017-5-20 02:52

心脏干细胞
作者: dypnr    时间: 2017-5-22 10:55

围观来了哦  
作者: 考拉    时间: 2017-6-9 00:17

我来了~~~~~~~~~ 闪人~~~~~~~~~~~~~~~~  
作者: highlight    时间: 2017-6-12 03:38

我该不会是最后一个顶的吧  
作者: 一个平凡人    时间: 2017-7-4 01:41

有才的不在少数啊  
作者: yukun    时间: 2017-7-6 00:54

一楼的位置好啊..  
作者: 科研人    时间: 2017-7-23 12:00

不要等到人人都说你丑时才发现自己真的丑。  
作者: tuanzi    时间: 2017-7-26 02:45

我想要`~  
作者: highlight    时间: 2017-7-27 19:35

楼上的稍等啦  
作者: 舒思    时间: 2017-8-6 03:34

越办越好~~~~~~~~~`  
作者: awen    时间: 2017-8-19 16:01

既然来了,就留个脚印  
作者: Diary    时间: 2017-9-13 05:41

厉害!强~~~~没的说了!  
作者: 未必温暖    时间: 2017-10-15 16:00

帮你项项吧  
作者: 咕咚123    时间: 2017-10-16 11:19

问渠哪得清如许,为有源头活水来。  
作者: doc2005    时间: 2017-11-2 11:19

回复一下  
作者: heart10    时间: 2017-11-7 11:43

终于看完了~~~  
作者: 20130827    时间: 2017-11-17 14:27

干细胞美容
作者: dglove    时间: 2017-12-4 13:00

昨天没来看了 ~~  
作者: 陈晴    时间: 2017-12-7 20:25

似曾相识的感觉  
作者: renee    时间: 2017-12-26 13:09

不对,就是碗是铁的,里边没饭你吃啥去?  
作者: alwaysniu    时间: 2018-1-2 12:07

不管你信不信,反正我信  
作者: 若天涯    时间: 2018-1-7 11:35

真的有么  
作者: 983abc    时间: 2018-1-8 04:50

楼主,支持!  
作者: 考拉    时间: 2018-1-12 07:50

真是有你的!  
作者: aakkaa    时间: 2018-1-22 12:58

文笔流畅,修辞得体,深得魏晋诸朝遗风,更将唐风宋骨发扬得入木三分,能在有生之年看见楼主的这个帖子。实在是我三生之幸啊。  
作者: xuguofeng    时间: 2018-2-9 18:12

看贴回复是好习惯  
作者: 安生    时间: 2018-2-25 15:28

一定要回贴,因为我是文明人哦  
作者: 我学故我思    时间: 2018-3-4 04:36

厉害!强~~~~没的说了!  
作者: 小倔驴    时间: 2018-3-25 14:27

回复一下  
作者: vsill    时间: 2018-4-26 01:34

先顶后看  
作者: 兔兔    时间: 2018-5-18 03:28

干细胞研究人员的天堂
作者: 蚂蚁    时间: 2018-5-21 22:18

世界上那些最容易的事情中,拖延时间最不费力。  
作者: 兔兔    时间: 2018-5-29 02:59

回帖是种美德.  
作者: changfeng    时间: 2018-6-13 00:43

你加油吧  
作者: 桦子    时间: 2018-7-8 06:25

每天早上起床都要看一遍“福布斯”富翁排行榜,如果上面没有我的名字,我就去上班……  
作者: mk990    时间: 2018-7-21 13:43

哈哈,有意思~顶顶 ,继续顶顶。继续顶哦  
作者: Whole    时间: 2018-7-24 03:56

发贴看看自己积分  
作者: pengzy    时间: 2018-7-25 17:17

我好想升级  
作者: MIYAGI    时间: 2018-8-1 01:27

看或者不看,贴子就在这里,不急不忙  
作者: 3344555    时间: 2018-8-2 19:45

好困啊  
作者: 泡泡鱼    时间: 2018-8-20 04:04

观看中  
作者: dogcat    时间: 2018-8-26 18:03

HOHO~~~~~~  
作者: doc2005    时间: 2018-9-12 04:39

照你这么说真的有道理哦 呵呵 不进沙子馁~~~  
作者: ines    时间: 2018-9-12 18:56

嘿...反了反了,,,,  
作者: 生物小菜鸟    时间: 2018-10-3 11:18

楼主福如东海,万寿无疆!  
作者: 海小鱼    时间: 2018-10-3 14:50

不错,支持下  
作者: frogsays    时间: 2018-10-15 19:54

我十目一行也还是看不懂啊  
作者: dypnr    时间: 2018-10-30 00:59

站个位在说  
作者: abc987    时间: 2018-11-7 22:42

我起来了 哈哈 刚才迷了会  
作者: 狂奔的蜗牛    时间: 2018-11-12 20:10

不错,看看。  
作者: 刘先生    时间: 2018-12-4 17:53

干细胞治疗  
作者: 草长莺飞    时间: 2018-12-9 16:41

希望大家都有好运  
作者: biopxl    时间: 2018-12-10 12:27

干细胞与动物克隆
作者: beautylive    时间: 2018-12-19 14:55

…没我说话的余地…飘走  




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