Nitric oxide in afferent arterioles after uninephrectomy depends on extracellular L-arginine.

Uninephrectomy (UNX) causes hyperperfusion of the contralateral remaining kidney via increased nitric oxide (NO) synthesis. Although the exact mechanism remains largely unknown, we hypothesize that this would be localized to the afferent arteriole and that it depends on cellular uptake of l-arginine. The experiments were performed in rats 2 days (early) or 6 wk (late) after UNX and compared with controls (Sham) to study acute and chronic effects on NO metabolism. Renal blood flow was increased after UNX (21 ± 2 ml·min(-1)·kg(-1) in sham, 30 ± 3 in early, and 26 ± 1 in late, P < 0.05). NO inhibition with N(ω)-nitro-L-arginine methyl ester hydrochloride (L-NAME) caused a greater increase in renal vascular resistance in early UNX compared with Sham and late UNX (138 ± 24 vs. 88 ± 10, and 84 ± 7%, P < 0.01). The lower limit of autoregulation was increased both in early and late UNX compared with Sham (P < 0.05). L-NAME did not affect the ANG II-induced contraction of isolated afferent arterioles (AA) from Sham. AA from early UNX displayed a more pronounced contraction in response to L-NAME (-57 ± 7 vs. -16 ± 7%, P < 0.05) and in the absence of L-arginine (-41 ± 4%, P < 0.05) compared with both late UNX and Sham. mRNA expression of endothelial NO synthase was reduced, whereas protein expression was unchanged. Cationic amino acid transporter-1 and -2 mRNA was increased, while protein was unaffected in isolated preglomerular resistance vessels. In conclusion, NO-dependent hyperperfusion of the remaining kidney in early UNX is associated with increased NO release from the afferent arteriole, which is highly dependent on extracellular L-arginine availability.

Collagen-binding proteins in age-dependent changes in renal collagen turnover: microarray analysis of mRNA expression.

Aging is associated with progressive structural and functional deterioration of the kidney. Among the morphological changes associated with renal aging is an accumulation of extracellular matrix (ECM) in the glomeruli and tubuloinsterstitium, which may ultimately lead to the development of renal fibrosis. The mechanisms governing the regulation of ECM metabolism during renal aging are only incompletely defined. We present data from a genome-wide mRNA expression study on renal tissue from 90 wk old male Wistar rats and 10 wk old controls using Illumina BeadArray cDNA microarray. Regulation of candidate gene products was verified by real-time PCR. Morphological changes were evaluated by routine histological methods. Activated fibroblasts were identified by their expression of alpha-smooth muscle actin and collagen I. Morphological analysis demonstrated an expansion of the tubulointerstitial compartment with increased amounts of fibrous collagen but no overt glomerular or tubular damage in the aged rats. Activated fibroblasts were readily detectable in the adventitial layer of large renal vessels in controls and were not found in the old animals. In agreement with this finding, gene expression analysis revealed significant downregulation of collagen I mRNA along with numerous other ECM components. Concomitantly, collagen-stabilizing proteins were induced, whereas matrix metalloproteinase 9, an enzyme involved in collagen breakdown, was reduced. In conclusion, our results suggest that ECM expansion during renal aging results from an augmented stabilization in conjunction with a reduced breakdown of collagen fibers. Collagen stabilizing proteins may be essential for the control of renal ECM turnover and the pathogenesis of kidney fibrosis.

Long-term risk of ESRD in IgAN; validation of Japanese prognostic model in a Norwegian cohort.

BACKGROUND: Recently, a Japanese model used to predict 10-year risk of end-stage renal disease (ESRD) in IgA nephropathy (IgAN) patients was published. We tested the applicability of the Japanese model in predicting 10- to 20-year risk of ESRD and all-cause mortality in a cohort of Norwegian IgAN patients. METHODS: A cohort of IgAN patients (1988-2004) were identified in the Norwegian Kidney Biopsy Registry (NKBR) and ESRD or death during follow-up through 2008 was identified through record linkage with the Norwegian Renal Registry (ESRD) and the Norwegian Population Registry (deaths). Data from the NKBR were used to classify patients into nine different prognostic groups (0-1, 1-5, 5-10, 10-20, 20-30, 30-50, 50-70, 70-90 and >90% risk of ESRD) according to the Japanese prognostic model. The predicted risk was compared to the measured risk of ESRD in the different prognostic groups. RESULTS: In eight of the nine risk groups, representing 597/633 (94%) of the patients in our cohort, the observed 10-year risk was within or close to the expected 10-year risk of ESRD. ESRD occurring after >10 years of observation was most frequent in the groups with 5-30% expected risk at 10 years of follow-up. A close association between risk of ESRD and risk of death prior to ESRD was observed. CONCLUSIONS: The Japanese prognostic model is applicable to predict 10-year risk of ESRD in Norwegian IgAN patients. A new finding in the present study is that the model can also be used to predict which patients have the highest risk of developing ESRD after 10-20 years of follow-up as well as all-cause mortality risk.

Preeclampsia and the risk of end-stage renal disease.

BACKGROUND: It is unknown whether preeclampsia is a risk marker for subsequent end-stage renal disease (ESRD). METHODS: We linked data from the Medical Birth Registry of Norway, which contains data on all births in Norway since 1967, with data from the Norwegian Renal Registry, which contains data on all patients receiving a diagnosis of end-stage renal disease (ESRD) since 1980, to assess the association between preeclampsia in one or more pregnancies and the subsequent development of ESRD. The study population consisted of women who had had a first singleton birth between 1967 and 1991; we included data from up to three pregnancies. RESULTS: ESRD developed in 477 of 570,433 women a mean (+/-SD) of 17+/-9 years after the first pregnancy (overall rate, 3.7 per 100,000 women per year). Among women who had been pregnant one or more times, preeclampsia during the first pregnancy was associated with a relative risk of ESRD of 4.7 (95% confidence interval [CI], 3.6 to 6.1). Among women who had been pregnant two or more times, preeclampsia during the first pregnancy was associated with a relative risk of ESRD of 3.2 (95% CI, 2.2 to 4.9), preeclampsia during the second pregnancy with a relative risk of 6.7 (95% CI, 4.3 to 10.6), and preeclampsia during both pregnancies with a relative risk of 6.4 (95% CI, 3.0 to 13.5). Among women who had been pregnant three or more times, preeclampsia during one pregnancy was associated with a relative risk of ESRD of 6.3 (95% CI, 4.1 to 9.9), and preeclampsia during two or three pregnancies was associated with a relative risk of 15.5 (95% CI, 7.8 to 30.8). Having a low-birth-weight or preterm infant increased the relative risk of ESRD. The results were similar after adjustment for possible confounders and after exclusion of women who had kidney disease, rheumatic disease, essential hypertension, or diabetes mellitus before pregnancy. CONCLUSIONS: Although the absolute risk of ESRD in women who have had preeclampsia is low, preeclampsia is a marker for an increased risk of subsequent ESRD.

Pre-transplant course and risk of kidney transplant failure in IgA nephropathy patients.

BACKGROUND: There is lack of knowledge to what degree clinical/morphological presentation and course of IgA nephropathy (IgAN) prior to end-stage renal disease are risk factors for graft loss after kidney transplantation. MATERIAL AND METHODS: Patients with IgAN between 1988 and 2006 (registered in the Norwegian Kidney Biopsy Registry) who later received a kidney transplant (registered in the Norwegian Renal Registry) were included. The cohort was followed up regarding death-censored graft loss throughout 2008. Graft survival with a rapid progressive (RP) vs. a slow progressive (SP) course of pre-Tx IgAN (annual GFR > or <30 mL/min/1.73 m(2) ) was studied. RESULTS: Among 106 included patients, there were 14 graft losses giving a graft loss rate of 1.9/100 patient years. Follow-up until the first kidney transplant was 6.9 ± 4.4 (range 0.1-19) yr. Patients with pre-Tx RP had a higher graft loss rate compared with SP patients (6.3 vs.1.3/100 patient years, p < 0.001). Graft loss rate with living-related donor (LRD) was similar to unrelated donor (UD) grafts. Most RP patients had received LRD grafts, and in SP patients, graft survival with LRD grafts was better than UD grafts (0.3 vs.2.1/100 patient years, p = 0.055). CONCLUSIONS: A rapid pre-transplant course is a strong risk factor for transplant failure in patients with IgAN.

Losartan increases NO release in afferent arterioles during regression of L-NAME-induced renal damage.

Inhibition of nitric oxide synthesis (NOS) induces hypertension and heavy proteinuria. Renal structure and function have shown striking improvement after interventions targeting ANG II or endothelin (ET) receptors in rats recovering after long-term NOS inhibition. To search for mechanisms underlying losartan-assisted regression of renal disease in rodents, we measured NO release and contractility to ET in afferent arterioles (AAs) from Sprague-Dawley rats recovering for 2 wk after 4 wk of N(G)-nitro-L-arginine methyl ester treatment. Losartan administration during the recovery period decreased blood pressure (113 ± 4 vs. 146 ± 5 mmHg, P < 0.01), reduced protein/creatinine ratio more (proteinuria decrease: Δ1,836 ± 214 vs. Δ1,024 ± 180 mg/mmol, P < 0.01), and normalized microvascular hypertrophy (AA media/lumen ratio: 1.74 ± 0.05 vs. 2.09 ± 0.08, P < 0.05) compared with no treatment. In diaminofluorescein-FM-loaded AAs from losartan-treated animals, NO release (% of baseline) was increased compared with untreated animals after stimulation with 10(-7) M ACh (118 ± 4 vs. 90 ± 7%, t = 560 s, P < 0.001) and 10(-9) M ET (123 ± 4 vs. 101 ± 5%, t = 560 s, P < 0.001). There was also a blunted contractile response to 10(-7) M ET in AAs from losartan-treated animals compared with untreated animals (Δ4.01 ± 2.9 vs. Δ14.6 ± 1.7 µm, P < 0.01), which disappeared after acute NOS inhibition (Δ10.7 ± 3.7 vs. Δ12.5 ± 2.9 µm, not significant). Contractile dose responses to ET (10(-9), 10(-8), 10(-7) M) were enhanced by NOS inhibition and blunted by exogenous NO (10(-2) mM S-nitroso-N-acetyl-penicillamine) in losartan-treated but not in untreated vessels. Reducing blood pressure similar to losartan with hydralazine did not improve AA hypertrophy, ET-induced contractility, ET-induced NO release, and NO sensitivity. In conclusion, blockade of the local action of ANG II improved endothelial function in AAs, a mechanism that is likely to contribute to the beneficial effects of AT(1a)R antagonism during the recovery of renal function after long-term NOS inhibition in rats.

Previous preeclampsia and risk for progression of biopsy-verified kidney disease to end-stage renal disease.

BACKGROUND: A recent study has shown that preeclampsia is an important risk marker for end-stage renal disease (ESRD), but the underlying mechanisms are unclear. The present study investigated whether previous preeclampsia was associated with progression of established kidney disease. Material and methods. Data from the Norwegian Kidney Biopsy Registry and the Medical Birth Registry of Norway were linked. We included women who, after their last pregnancy, had had a representative kidney biopsy in 1988-2005. Women were followed up for the development of ESRD using data from the Norwegian Renal Registry. Baseline was set at the time of biopsy and Cox regression statistics were performed. RESULTS: Of the 582 included women, 76 developed ESRD 3.9 ± 3.4 years (range, 0.08-16 years) after diagnosis. Mean age at first birth was 24.0 ± 4.8 years and at the time of diagnosis 41.3 ± 9.7 years. Women with clinically diagnosed preeclampsia in their first pregnancy had a relative risk of ESRD of 1.2 (95% CI, 0.63-2.4) and women with preterm birth had a relative risk of 2.1 (95% CI, 1.2-3.9). After extensive adjustments for clinical and histopathological variables at the time of diagnosis, the relative risks were 1.1 (95% CI, 0.50-2.6) and 2.4 (95% CI, 1.2-4.6), respectively. Compared to women with a first term birth without preeclampsia, women with term preeclampsia were diagnosed at a younger age (36 vs 42 years) and women with preterm birth without preeclampsia had a lower estimated glomerular filtration rate at diagnosis (48 vs 64 ml/min/1.73 m(2)). CONCLUSION: In women with kidney disease diagnosed at kidney biopsy, previous preeclampsia does not seem to be a risk marker for progression to ESRD.

Are adverse pregnancy outcomes risk factors for development of end-stage renal disease in women with diabetes?

BACKGROUND: It is unknown whether adverse pregnancy-related outcomes in women with pregestational diabetes are associated with later development of end-stage renal disease (ESRD) or death. METHODS: We linked data from the Medical Birth Registry of Norway with data from the Norwegian Renal Registry and the Norwegian Cause of Death Registry. Data from up to three pregnancies for women with a first singleton delivery from 1967 to 1994 were included and analysed in a cohort design using Cox regression. RESULTS: Altogether, 639,018 women were included in the analyses, among whom 2204 women had diabetes mellitus before pregnancy. Their first pregnancy was complicated by pre-eclampsia in 13.2%, low birth weight offspring (<2.5 kg) in 11.0% and preterm birth in 25.1%, and their risk of ESRD and death in the follow-up period of up to 37 years was markedly higher. In women with pregestational diabetes, pre-eclampsia and preterm birth were associated with significantly increased risks of ESRD and death in women with only one pregnancy, but not in women with two or more pregnancies. CONCLUSIONS: In women with pregestational diabetes, pre-eclampsia and preterm birth were associated with long-term increased risk of ESRD and death, but only in women who had only one pregnancy.

AT(1) receptor activation regulates the mRNA expression of CAT1, CAT2, arginase-1, and DDAH2 in preglomerular vessels from angiotensin II hypertensive rats.

Previously, we found increased expression of l-arginine metabolizing enzymes in both kidneys from two-kidney, one-clip (2K1C) hypertensive rats (Helle F, Hultstrom M, Skogstrand T, Palm F, Iversen BM. Am J Physiol Renal Physiol 296: F78-F86, 2009). In the present study, we investigate whether AT(1) receptor activation can induce the changes observed in 2K1C. Four groups of rats were infused with 80 ng/min ANG II or saline for 14 days and/or given 60 mg x kg(-1) x day(-1) losartan. Gene expression was studied in isolated preglomerular vessels by RT-PCR. Dose-responses to ANG II were studied in isolated preglomerular vessels with and without acute NOS inhibition [10(-4) mol/l N(G)-nitro-l-arginine methyl ester (l-NAME)]. Expressions of endothelial nitric oxide synthase (eNOS), caveolin-1, and arginase-2 were not changed by ANG II infusion. CAT1 (0.3 8 +/- 0.07 to 0.73 +/- 0.12, P < 0.05), CAT2 (1.14 +/- 0.29 to 2.74 +/- 0.48), DDAH2 (1.09 +/- 0.27 to 2.3 +/- 0.46), and arginase-1 (1.08 +/- 0.17 to 1.82 +/- 0.22) were increased in ANG II-infused rats. This was prevented by losartan treatment, which reduced the expression of eNOS (0.97 +/- 0.26 to 0.37 +/- 0.11 in controls; 0.8 +/- 0.16 to 0.36 +/- 0.1 in ANG II-infused rats) and caveolin-1 (2.49 +/- 0.59 to 0.82 +/- 0.24 in controls and 2.59 +/- 0.61 to 1.1 +/- 0.25 in ANG II-infused rats). ANG II (10(-10) mol/l) caused vessels from ANG II-infused animals to contract to 53 +/- 15% of baseline diameter and 90 +/- 5% of baseline diameter in controls (P < 0.05) and was further enhanced by l-NAME to 4 +/- 4% of baseline diameter (P < 0.05). In vivo losartan treatment reduced the reactivity of isolated vessels to 91 +/- 2% of baseline in response to 10(-7) mol/l ANG II compared with 82 +/- 3% in controls (P < 0.05) and prevented the increased responsiveness caused by ANG II infusion. In conclusion, CAT1, CAT2, DDAH2, and arginase-1 expression in renal resistance vessels is regulated through the AT(1) receptor. This finding may be of direct importance for NOS and the regulation of preglomerular vascular function.

Low birth weight increases risk for end-stage renal disease.

Case-control studies have shown an association between low birth weight and risk for renal failure. The Medical Birth Registry of Norway, which comprises data on all births in Norway since 1967, and the Norwegian Renal Registry, which comprises data on all patients who have developed ESRD in Norway since 1980, were used to examine whether birth-related variables were associated with risk for ESRD. Of the 2,183,317 children born between 1967 and 2004, 526 were found in the ESRD registry. Compared with birth weight in the 10th to 90th percentiles, births <10th percentile had a relative risk (RR) for ESRD of 1.7 (95% confidence interval 1.4 to 2.2; P < 0.001). Births with a weight for gestational age <10th percentile had an RR of 1.5 (95% confidence interval 1.2 to 1.9; P = 0.002). These associations were virtually identical after adjustment for birth-related confounders such as congenital malformations, multiple delivery, maternal age at birth, and maternal preeclampsia. Low birth weight was more strongly associated with development of ESRD during the first 14 years of life than after age 15. Low birth weight and low birth weight for gestational age were similarly associated with multiple causes of ESRD. In conclusion, in this cohort study with a maximum follow-up of 38 years, low birth weight and intrauterine growth restriction were associated with increased risk for ESRD.

Upregulation of tissue inhibitor of metalloproteases-1 (TIMP-1) and procollagen-N-peptidase in hypertension-induced renal damage.

BACKGROUND: Hypertensive renal damage starts in the juxtamedullary cortex (JMC) and gradually extends towards the outer cortex (OC). The intention of the study was to examine if the increase of fibrous tissue in the JMC of the spontaneously hypertensive rat (SHR) is dependent on an increase of collagen synthesis or a decreased collagen breakdown compared to the normotensive control (WKY). METHODS AND RESULTS: The renal damage was evaluated by light microscopy, and the amount of fibrosis was quantified using Sirius red staining. Real-time RT-PCR was used to quantify mRNA for: collagen-type-1-alpha-1 (col1a1), procollagen-n- and -c-proteinase, matrix metalloproteases, MMP-2 and MMP-9, tissue inhibitor of metalloproteases, TIMP-1 and TIMP-2. Western blot was used to quantify the proteins of MMP-2, MMP-9, TIMP-1 and TIMP-2. The relative activities of MMP-2 and MMP-9 were assayed by zymography. The JMC in SHR had an increased amount of collagen as measured by Sirius red, and a 15-fold increase in the mRNA for col1a1. The gene expression of procollagen-c-proteinase was unchanged while procollagen-n-proteinase was increased in SHR and had the highest expression in the JMC. The mRNA for MMP-2 and MMP-9 showed increased expression in SHR, but not specifically in the JMC. Protein analysis showed increased expression for MMP-2 in SHR and in the JMC. MMP-9 protein was lower in SHR. TIMP-1 was increased in SHR at both mRNA and protein level and more so in the JMC. The mRNA and protein analysis of TIMP-2 showed small differences between SHR and WKY. CONCLUSION: An imbalance of collagen metabolism featuring increased synthesis and inhibition of breakdown favours renal interstitial fibrosis in SHR.

Glomerular charge barrier and development of proteinuria in passive Heymann nephritis.

BACKGROUND/AIM: Passive Heymann nephritis (PHN) in rats is a commonly used model of membranous glomerulonephritis in man where the cause of proteinuria is not fully resolved. This study was designed to investigate the role of the glomerular charge barrier in development of PHN proteinuria. METHODS: We studied female Sprague-Dawley rats (n = 33) at days 0, 2, 5 and 14 after induction of PHN by injection of antiserum against renal tubular epithelial antigens (anti-Fx1A). Measuring clearance of chymotrypsinogen A (Chym, MW 25,000, 21 A) and similar sized anionic chymotrypsinogen (aChym), together with (51)Cr-EDTA, we hypothesized an increased sieving coefficient (theta) of aChym in the early phase of PHN due to impairment of the glomerular charge barrier. RESULTS: No proteinuria was seen at day 2 (5.8 +/- 1.4 mg/ 24 h, p > 0.05), while protein excretion increased to 23.2 +/- 2.9 mg/24 h (p < 0.05) at day 5 (84 +/- 2% albumin) and further to 544.3 +/- 51.1 mg/24 h (p < 0.01) at day 14 (60 +/- 1% albumin; p < 0.01, day 5 vs. day 14). theta aChym was similar to control at day 2 (0.49 +/- 0.03, p > 0.05), increased at day 5 to 0.62 +/- 0.02 (p < 0.01) but decreased at day 14 to 0.39 +/- 0.02 (p < 0.01). The sieving coefficient of Chym (theta Chym) was decreased at day 14 (p < 0.05). The ratio of theta aChym to theta Chym was increased at day 5 (p < 0.01) but was elsewhere similar to control. CONCLUSION: The increased ratio of theta aChym to theta Chym and selective albuminuria at day 5 indicates an initial impairment of the glomerular charge barrier in PHN.

Long-term risk of cancer in membranous nephropathy patients.

BACKGROUND: There is a well-known association between membranous nephropathy (MN) and cancer, and patients with MN usually are examined for cancer at the time of diagnosis. The long-term risk of cancer after MN is not well studied. STUDY DESIGN: Cohort study with record linkage between the Norwegian Kidney Biopsy Registry and Norwegian Cancer Registry. SETTING & PARTICIPANTS: 161 patients with MN from 1988 to 2003. PREDICTOR: Patients with MN compared with the age- and sex-adjusted general Norwegian population. OUTCOMES: Cancer diagnosis reported through 2003. RESULTS: Mean duration of follow-up was 6.2 years (range, 0.1 to 15 years). 33 patients developed cancer; including 24 patients with cancer after the diagnosis of MN. Median time from diagnosis of MN to diagnosis of cancer was 60 months (range, 0 to 157 months). Mean annual incidence ratio of cancer was 2.4/100 person-years (2.1/100 person-years in the 0- to 5-year period and 2.8/100 person-years for the 5 to 15 years after kidney biopsy). During the 0 to 15 years after the diagnosis of MN, the expected number of cancers was 10.7, resulting in a standardized incidence ratio of cancer of 2.25 (95% confidence interval, 1.44 to 3.35). In the 5 to 15 years after diagnosis, standardized incidence ratio was 2.30 (95% confidence interval, 1.19 to 4.02). Patients with MN who developed cancer were older (65 versus 52 years; P < 0.001). Patients with cancer and MN had a greater mortality rate than patients without cancer (67% versus 26%; P < 0.001). LIMITATIONS: Follow-up treatment after MN with cytotoxic and immunosuppressive medications is not known. CONCLUSIONS: An increased risk of developing cancer is observed after the diagnosis of MN, which persists for many years.

Matrix Metalloproteinase-2 Knockout and Heterozygote Mice Are Protected from Hydronephrosis and Kidney Fibrosis after Unilateral Ureteral Obstruction.

Matrix Metalloproteinase-2 (Mmp2) is a collagenase known to be important in the development of renal fibrosis. In unilateral ureteral obstruction (UUO) the obstructed kidney (OK) develops fibrosis, while the contralateral (CL) does not. In this study we investigated the effect of UUO on gene expression, fibrosis and pelvic remodeling in the kidneys of Mmp2 deficient mice (Mmp2-/-), heterozygous animals (Mmp2+/-) and wild-type mice (Mmp2+/+). Sham operated animals served as controls (Cntrl). UUO was prepared under isoflurane anaesthesia, and the animals were sacrificed after one week. UUO caused hydronephrosis, dilation of renal tubules, loss of parenchymal thickness, and fibrosis. Damage was most severe in Mmp2+/+ mice, while both Mmp2-/- and Mmp2+/- groups showed considerably milder hydronephrosis, no tubular necrosis, and less tubular dilation. Picrosirius red quantification of fibrous collagen showed 1.63±0.25% positivity in OK and 0.29±0.11% in CL (p<0.05) of Mmp2+/+, Mmp2-/- OK and Mmp2-/- CL exhibited only 0.49±0.09% and 0.23±0.04% (p<0.05) positivity, respectively. Mmp2+/- OK and Mmp2+/- CL showed 0.43±0.09% and 0.22±0.06% (p<0.05) positivity, respectively. Transcriptomic analysis showed that 26 genes (out of 48 examined) were differentially expressed by ANOVA (p<0.05). 25 genes were upregulated in Mmp2+/+ OK compared to Mmp2+/+ CL: Adamts1, -2, Col1a1, -2, -3a1, -4a1, -5a1, -5a2, Dcn, Fbln1, -5, Fmod, Fn1, Itga2, Loxl1, Mgp, Mmp2, -3, Nid1, Pdgfb, Spp1, Tgfb1, Timp2, Trf, Vim. In Mmp2-/- and Mmp2+/- 18 and 12 genes were expressed differentially between OK and CL, respectively. Only Mmp2 was differentially regulated when comparing Mmp2-/- OK and Mmp2+/- OK. Under stress, it appears that Mmp2+/- OK responds with less Mmp2 upregulation than Mmp2+/+ OK, suggesting that there is a threshold level of Mmp2 necessary for damage and fibrosis to occur. In conclusion, reduced Mmp2 expression during UUO protects mice against hydronephrosis and renal fibrosis.

Identification of a common molecular pathway in hypertensive renal damage: comparison of rat and human gene expression profiles.

BACKGROUND: There is a common structural progression in hypertensive renal damage with early arterial damage and fibrosis in the juxtamedullary cortex. METHOD: The present investigation identifies a common pathway using three-gene expression profiles from hypertensive rat models: 60-week-old spontaneously hypertensive rat (SHR), salt-loaded stroke-prone SHR (SHRSP), and the non-clipped kidney after 24 weeks of two-kidney, one-clip hypertension (2K1C). Kidney damage was scored using a specialized system. Gene-expression profiles were determined using microarrays and validated using a panel of 47 genes by quantitative real-time PCR. RESULTS: All groups showed kidney damage (SHRs: 0.32 ±â€Š0.09 vs. Wistar-Kyoto rats: 0.06 ±â€Š0.03; 2K1C: 0.27 ±â€Š0.13 vs. pooled controls: 0.01 ±â€Š0.01; SHRSP: 1.13 ±â€Š0.14 vs. WKY: 0.04 ±â€Š0.03; all P < 0.05). A total of 1614 genes were changed in the SHR experiment, 1323 in the SHRSP, and 576 in the 2K1C. Eighty-eight genes were similarly regulated in all three models. Gene ontology enrichment analysis identified 59 ontologies that were enriched in all three datasets. These included over-representation to extracellular matrix, response to oxidative stress, and immune system processes. Out of the 88 in-common genes, 40 could be connected in a common pathway that was compared to two gene-expression profiles from human kidneys with histologically verified fibrosis to identify a highly significant number of in-common genes that were also represented in the common genetic pathway. CONCLUSION: There is a common pathway during the development of hypertensive kidney damage in rats irrespective of model. Interestingly, large parts of this common pathway are conserved in human kidney damage, which may indicate a broader importance in the development of chronic kidney disease.

Volume estimation of small phantoms and rat kidneys using three-dimensional ultrasonography and a position sensor.

To evaluate the accuracy of small volume estimation, both in vivo and in vitro, measurements with a three-dimensional (3D) ultrasound (US) system were carried out. A position sensor was used and the transmitting frequency was 10 MHz. Balloons with known volumes were scanned while rat kidneys were scanned in vivo and in vitro. The Archimedes' principle was used to estimate the true volume. For balloons, the 3D US system gave very good agreement with true volumes in the volume range 0.1 to 10.0 mL (r = 0.999, n = 45, mean difference +/- 2SD = 0.245 +/- 0.370 mL). For rat kidneys in vivo (volume range 0.6 to 2.7 mL) the method was less accurate (r = 0.800, n = 10, mean difference +/- 2SD = -0.288 +/- 0.676 mL). For rat kidneys in vitro (volume range 0.3 to 2.7 mL) the results showed good agreement (r = 0.981, n = 23, mean difference +/- 2SD = 0.039 +/- 0.254 mL). For balloons, kidneys in vivo and in vitro, the mean percentage error was 9.3 +/- 4.8%, -17.1 +/- 17.4%, and 4.6 +/- 11.5%, respectively. This method can estimate the volume of small phantoms and rat kidneys and opens new possibilities for volume measurements of small objects and the study of organ function in small animals. (E-mail ).

Arterial damage precedes the development of interstitial damage in the nonclipped kidney of two-kidney, one-clip hypertensive rats.

BACKGROUND: The progression of damage in the renal cortex has not been investigated in the nonclipped kidney of the two-kidney, one-clip model of renal hypertension. In other hypertensive models, damage has been found to progress from the juxtamedullary cortex (JMC) and outward, which has been attributed to early vascular effects. METHOD: The present study investigated the relation between perivascular deposition of collagen and structural damage after 16 and 24 weeks of hypertension in the nonclipped kidney in rats. RESULTS: Periarterial collagen density in the kidney was significantly increased already 16 weeks after clipping, at that time tubulointerstitial damage was not evident. After 24 weeks of clipping, periarterial collagen was further increased, and tubulointerstitial damage had developed in the JMC, whereas the outer cortex was protected. Interstitial collagen was not significantly increased in any cortex part during the course of the experiment. Collagen type I a1 mRNA was increased in the JMC after 24 weeks, and α smooth muscle actin histochemistry and collagen type I a2 in-situ hybridization identified myofibroblasts around the arteries after 16 and 24 weeks as the major source of this increase. CONCLUSION: Fibrosis in the nonclipped kidney of renal hypertensive rats starts around the juxtamedullary resistance vessels and then progresses in the JMC, whereas the outer cortex is protected. This suggests that pressure-induced injury to the vasculature attracts or activates fibroblasts in the perivascular area, which may allow damage to progress by impairing vessel function.

Afferent arteriolopathy and glomerular collapse but not segmental sclerosis induce tubular atrophy in old spontaneously hypertensive rats.

In chronic renal disease, the temporal and spatial relationship between vascular, glomerular and tubular changes is still unclear. Hypertension, an important cause of chronic renal failure, leads to afferent arteriolopathy, segmental glomerulosclerosis and tubular atrophy in the juxtamedullary cortex. We investigated the pathological changes of hypertensive renal disease in aged spontaneously hypertensive rats using a large number of serial sections, where we traced and analyzed afferent arteriole, glomerulus and proximal tubule of single nephrons. Our major finding was that both afferent arteriolopathy and glomerular capillary collapse were linked to tubular atrophy. Only nephrons with glomerular collapse (n = 13) showed tubules with reduced diameter indicating atrophy [21.66 ± 2.56 µm vs. tubules in normotensive Wistar Kyoto rats (WKY) 38.56 ± 0.56 µm, p < 0.05], as well as afferent arteriolar wall hypertrophy (diameter 32.74 ± 4.72 µm vs. afferent arterioles in WKY 19.24 ± 0.98 µm, p < 0.05). Nephrons with segmental sclerosis (n = 10) did not show tubular atrophy and tubular diameters were unchanged (35.60 ± 1.43 µm). Afferent arteriolar diameter negatively correlated with glomerular capillary volume fraction (r = -0.36) and proximal tubular diameter (r = -0.46) implying reduced glomerular and tubular flow. In line with this, chronically damaged tubules showed reduced staining for the ciliary protein inversin indicating changed ciliary signalling due to reduced urinary flow. This is the first morphological study on hypertensive renal disease making correlations between vascular, glomerular and tubular components of individual nephron units. Our data suggest that afferent arteriolopathy leads to glomerular collapse and reduced urinary flow with subsequent tubular atrophy.

Angiotensin II-induced contraction is attenuated by nitric oxide in afferent arterioles from the nonclipped kidney in 2K1C.

Two-kidney, one-clip (2K1C) is a model of renovascular hypertension where we previously found an exaggerated intracellular calcium (Ca(i)(2+)) response to ANG II in isolated afferent arterioles (AAs) from the clipped kidney (Helle F, Vagnes OB, Iversen BM. Am J Physiol Renal Physiol 291: F140-F147, 2006). To test whether nitric oxide (NO) ameliorates the exaggerated ANG II response in 2K1C, we studied ANG II (10(-7) mol/l)-induced calcium signaling and contractility with or without the NO synthase (NOS) inhibitor N(G)-nitro-l-arginine methyl ester (l-NAME). In AAs from the nonclipped kidney, l-NAME increased the ANG II-induced Ca(i)(2+) response from 0.28 +/- 0.05 to 0.55 +/- 0.09 (fura 2, 340 nm/380 nm ratio) and increased contraction from 80 +/- 6 to 60 +/- 6% of baseline (P < 0.05). In vessels from sham and clipped kidneys, l-NAME had no effect. In diaminofluorescein-FM diacetate-loaded AAs from the nonclipped kidney, ANG II increased NO-derived fluorescence to 145 +/- 34% of baseline (P < 0.05 vs. sham), but not in vessels from the sham or clipped kidney. Endothelial NOS (eNOS) mRNA and ser-1177 phosphorylation were unchanged in both kidneys from 2K1C, while eNOS protein was reduced in the clipped kidney compared with sham. Cationic amino acid transferase-1 and 2 mRNAs were increased in 2K1C, indicating increased availability of l-arginine for NO synthesis, but counteracted by decreased scavenging of the eNOS inhibitor asymmetric dimethylarginine by dimethylarginine dimethylaminohydrolase 2. In conclusion, the Ca(i)(2+) and contractile responses to ANG II are blunted by NO release in the nonclipped kidney. This may protect the nonclipped kidney from the hypertension and elevated ANG II levels in 2K1C.

Tetradecylthioacetic acid prevents the inflammatory response in two-kidney, one-clip hypertension.

ANG II promotes inflammation through nuclear factor-kappaB (NF-kappaB)-mediated induction of cytokines and reactive oxygen species (ROS). The aim of the present study was to examine the effect of tetradecylthioacetic acid (TTA), a modified fatty acid, on NF-kappaB, proinflammatory markers, ROS, and nitric oxide (NO) production in two-kidney, one-clip (2K1C) hypertension. The 2K1C TTA-treated group had lower blood pressure (128 +/- 3 mmHg) compared with 2K1C nontreated (178 +/- 5 mmHg, P < 0.001). The p50 and p65 subunits of NF-kappaB were higher in the clipped kidney (0.44 +/- 0.01 and 0.22 +/- 0.01, respectively) compared with controls (0.25 +/- 0.03 and 0.12 +/- 0.02, respectively, P < 0.001). In the 2K1C TTA-treated group, these values were similar to control levels. The same pattern of response was seen in the nonclipped kidney. In 2K1C hypertension, cytokines plasma were higher than in control: TNF-alpha was 13.5 +/- 2 pg/ml (P < 0.03), IL-1beta was 58.8 +/- 10 pg/ml (P = 0.003), IL-6 was 210 +/- 33 pg/ml (P < 0.001), and monocyte chemoattractant protein-1 was 429 +/- 21 pg/ml (P = 0.04). In the 2K1C TTA-treated group, these values were similar to controls, and the same pattern was seen in the clipped kidney. Clipping increased 8-iso-PGF-2alpha (P < 0.01) and decreased NO production (P < 0.01 vs. control) in the urine. TTA treatment normalized these values. NO production was also lower in clipped and nonclipped kidney (P < 0.001). After TTA treatment, these values were similar to controls. The results indicate that TTA has a potent anti-inflammatory effect in 2K1C by inhibition of p50/p65 NF-kappaB subunit activation, reduction of cytokines production and ROS, and enhanced NO production.