Induction of kidney injury molecule-1 in homozygous Ren2 rats is attenuated by blockade of the renin-angiotensin system or p38 MAP kinase

Effects of Mineralocorticoid Receptor Blockade and Statins on Kidney Injury Marker 1 (KIM-1) in Female Rats Receiving L-NAME and Angiotensin II

Kidney injury molecule-1 (KIM-1) is a biomarker of renal injury and a predictor of cardiovascular disease. Aldosterone, via activation of the mineralocorticoid receptor, is linked to cardiac and renal injury. However, the impact of mineralocorticoid receptor activation and blockade on KIM-1 is uncertain. We investigated whether renal KIM-1 is increased in a cardiorenal injury model induced by L-NAME/ANG II, and whether mineralocorticoid receptor blockade prevents the increase in KIM-1. Since statin use is associated with lower aldosterone, we also investigated whether administering eiSther a lipophilic statin (simvastatin) or a hydrophilic statin (pravastatin) prevents the increase in renal KIM-1. Female Wistar rats (8-10 week old), consuming a high salt diet (1.6% Na+), were randomized to the following conditions for 14 days: control; L-NAME (0.2 mg/mL in drinking water)/ANG II (225 ug/kg/day on days 12-14); L-NAME/ANG II + eplerenone (100 mg/kg/day p.o.); L-NAME/ANG II + pravastatin (20 mg/kg/day p.o.); L-NAME/ANG II + simvastatin (20 mg/kg/day p.o.). Groups treated with L-NAME/ANG II had significantly higher blood pressure, plasma and urine aldosterone, cardiac injury/stroke composite score, and renal KIM-1 than the control group. Both eplerenone and simvastatin reduced 24-h urinary KIM-1 (p = 0.0046, p = 0.031, respectively) and renal KIM-1 immunostaining (p = 0.004, p = 0.037, respectively). Eplerenone also reduced renal KIM-1 mRNA expression (p = 0.012) and cardiac injury/stroke composite score (p = 0.04). Pravastatin did not affect these damage markers. The 24-h urinary KIM-1, renal KIM-1 immunostaining, and renal KIM-1 mRNA expression correlated with cardiac injury/stroke composite score (p < 0.0001, Spearman ranked correlation = 0.69, 0.66, 0.59, respectively). In conclusion, L-NAME/ANG II increases renal KIM-1 and both eplerenone and simvastatin blunt this increase in renal KIM-1.

Renoprotective Effect of Intraoperative Dexmedetomidine in Renal Transplantation

BACKGROUND

Renal dysfunction after kidney transplantation may be influenced by many reasons. This study was designed to evaluate whether the administration of dexmedetomidine (Dex) could ameliorate renal function and prognosis after kidney transplantation.

METHODS

A total of 65 patients were divided into Dex group (n = 33) and Con group (Con, n = 32). Dex group intravenously received an initial loading dose of 0.6 μg/kg Dex for 15 min before anaesthesia induction, followed by a rate of 0.4 μg/kg/h until 30 min after kidney reperfusion. By contrast, Con group received saline. The concentration of urinary kidney injury molecule-1 (KIM-1), serum creatinine (Cr), blood urea, urine output, β2 microglobulin (β2-MG), Cystatin C (CysC), and estimated glomerular filtration rate (eGFR) was recorded and compared between two groups during the course of the hospitalization or follow-up. Mean arterial pressure (MAP) and heart rate (HR), vasoactive drugs, and anaesthetics were recorded during the operation. Pain degree was evaluated using a visual analogue scale (VAS) after operation. Delayed graft function (DGF), graft loss, length of hospital stay, and mortality were compared between groups.

RESULTS

The concentration of KIM-1 in Dex group was lower than Con group at 2 h (P = 0.018), 24 h (P = 0.013), 48 h (P < 0.01), and 72 h (P < 0.01) after reperfusion. MAP of Dex group after tracheal intubation (P = 0.012) and incision (P = 0.018) and HR after intubation (P = 0.021) were lower than that of Con group. The dosage of sufentanil during operation in Dex group was less than Con group (P = 0.039). Patients that used atropine in Dex group were more than Con group (P = 0.027). Patients who received Dex presented with lower VAS scores at 6 h (P = 0.01) and 12 h (P = 0.002) after operation. Concentration of serum Cr and blood urea had no significant differences between groups before operation and on postoperative day 1 to 6. Urine output was recorded for 6 days after operation and had no differences between groups. Also, no differences were identified between two groups in urea, Cr, β2-MG, CysC, and eGFR in the first 3 months after operation. Incidence of DGF after operation was detected no difference between groups, while length of hospital stay in Dex group was less than Con group (P = 0.012).

CONCLUSION

Dex can decrease kidney injury marker level, attenuate perioperative stress, relieve the dosage of sufentanil and postoperative pain, and reduce length of hospital stay. However, Dex is not associated with changes in prognosis in the first 3 months after transplantation.

Temporal changes in soluble angiotensin-converting enzyme 2 associated with metabolic health, body composition, and proteome dynamics during a weight loss diet intervention: a randomized trial with implications for the COVID-19 pandemic

BACKGROUND

Angiotensin-converting enzyme 2 (ACE2) serves protective functions in metabolic, cardiovascular, renal, and pulmonary diseases and is linked to COVID-19 pathology. The correlates of temporal changes in soluble ACE2 (sACE2) remain understudied.

OBJECTIVES

We explored the associations of sACE2 with metabolic health and proteome dynamics during a weight loss diet intervention.

METHODS

We analyzed 457 healthy individuals (mean ± SD age: 39.8 ± 6.6 y) with BMI 28-40 kg/m2 in the DIETFITS (Diet Intervention Examining the Factors Interacting with Treatment Success) study. Biochemical markers of metabolic health and 236 proteins were measured by Olink CVDII, CVDIII, and Inflammation I arrays at baseline and at 6 mo during the dietary intervention. We determined clinical and routine biochemical correlates of the diet-induced change in sACE2 (ΔsACE2) using stepwise linear regression. We combined feature selection models and multivariable-adjusted linear regression to identify protein dynamics associated with ΔsACE2.

RESULTS

sACE2 decreased on average at 6 mo during the diet intervention. Stronger decline in sACE2 during the diet intervention was independently associated with female sex, lower HOMA-IR and LDL cholesterol at baseline, and a stronger decline in HOMA-IR, triglycerides, HDL cholesterol, and fat mass. Participants with decreasing HOMA-IR (OR: 1.97; 95% CI: 1.28, 3.03) and triglycerides (OR: 2.71; 95% CI: 1.72, 4.26) had significantly higher odds for a decrease in sACE2 during the diet intervention than those without (P ≤ 0.0073). Feature selection models linked ΔsACE2 to changes in α-1-microglobulin/bikunin precursor, E-selectin, hydroxyacid oxidase 1, kidney injury molecule 1, tyrosine-protein kinase Mer, placental growth factor, thrombomodulin, and TNF receptor superfamily member 10B. ΔsACE2 remained associated with these protein changes in multivariable-adjusted linear regression.

CONCLUSIONS

Decrease in sACE2 during a weight loss diet intervention was associated with improvements in metabolic health, fat mass, and markers of angiotensin peptide metabolism, hepatic and vascular injury, renal function, chronic inflammation, and oxidative stress. Our findings may improve the risk stratification, prevention, and management of cardiometabolic complications.This trial was registered at clinicaltrials.gov as NCT01826591.

Predictive Nephrotoxicity Profiling of a Novel Antifungal Small Molecule in Comparison to Amphotericin B and Voriconazole

BACKGROUND AND PURPOSE

Candida albicans is the major fungal species associated with superficial mucosal infections such as oral candidiasis as well as systemic mycoses with high morbidity and mortality. On top of the rising drug resistance, currently available antifungal agents have significant adverse effects. Nephrotoxicity is the major treatment complication associated with antifungal agents.Recently, we discovered a novel antifungal small molecule SM21 with promising antifungal activity. The present study aimed to comparatively evaluate the in vivo and in vitro nephrotoxicity of SM21 comparing with Amphotericin B and voriconazole.

EXPERIMENTAL APPROACH

Nephrotoxicity of SM21 and its analogue were comparatively evaluated with Amphotericin B (AmB) and voriconazole. Immortalized human kidney proximal tubule epithelial cells (HK-2) were used for in vitro analysis of nephrotoxicity using cytotoxicity assays and qPCR gene expression analysis (Kim-1/HAVcr-1, CASP3). Sprague Dawley (SD) rat model was used to evaluate the nephrotoxicity in vivo using classical (SCr and BUN) and next-generation kidney injury urinary biomarkers (Kim-1, CLU, ALB, NGAL, β2M, and Cys C) alongside histopathological and immunohistochemical standards.

KEY RESULTS

AmB treatment showed a stronger cytotoxic impact on HK-2 viability and gene expression of cell death markers (Kim-1/HAVcr-1, CASP3) compared with SM21 and SM21 analogue in vitro (P < 0.01). In vivo data further demonstrated that SM21 did not significantly increase classical as well as novel nephrotoxic biomarkers, and minimal renal tubular necrosis and abnormalities were observed (15 mg kg-1 BW/day).

CONCLUSIONS AND IMPLICATIONS

SM21 had a significantly better safety profile in terms of nephrotoxicity with no major tubular epithelial abnormalities observed in kidney cells and no augmentation of kidney injury biomarkers compared to AmB. Kim-1 and CLU were the most sensitive biomarkers for detection of AmB-induced kidney damage. Future clinical trials should consider inclusion of these novel biomarkers as early indicators of acute kidney injury in antifungal-induced nephrotoxicity.

Effects of TORC1 Inhibition during the Early and Established Phases of Polycystic Kidney Disease

The disease-modifying effects of target of rapamycin complex 1 (TORC1) inhibitors during different stages of polycystic kidney disease (PKD) are not well defined. In this study, male Lewis Polycystic Kidney Disease (LPK) rats (a genetic ortholog of human NPHP9, phenotypically characterised by diffuse distal nephron cystic growth) and Lewis controls received either vehicle (V) or sirolimus (S, 0.2 mg/kg by intraperitoneal injection 5 days per week) during the early (postnatal weeks 3 to 10) or late stages of disease (weeks 10 to 20). In early-stage disease, sirolimus reduced kidney enlargement (by 63%), slowed the rate of increase in total kidney volume (TKV) in serial MRI by 78.2% (LPK+V: 132.3±59.7 vs. LPK+S: 28.8±12.0% per week) but only partly reduced the percentage renal cyst area (by 19%) and did not affect the decline in endogenous creatinine clearance (CrCl) in LPK rats. In late-stage disease, sirolimus reduced kidney enlargement (by 22%) and the rate of increase in TKV by 71.8% (LPK+V: 13.1±6.6 vs. LPK+S: 3.7±3.7% per week) but the percentage renal cyst area was unaltered, and the CrCl only marginally better. Sirolimus reduced renal TORC1 activation but not TORC2, NF-κB DNA binding activity, CCL2 or TNFα expression, and abnormalities in cilia ultrastructure, hypertension and cardiac disease were also not improved. Thus, the relative treatment efficacy of TORC1 inhibition on kidney enlargement was consistent at all disease stages, but the absolute effect was determined by the timing of drug initiation. Furthermore, cystic microarchitecture, renal function and cardiac disease remain abnormal with TORC1 inhibition, indicating that additional approaches to normalise cellular dedifferentiation, inflammation and hypertension are required to completely arrest the progression of PKDs.

Aldosterone induces NRK-52E cell apoptosis in acute kidney injury via rno-miR-203 hypermethylation and Kim-1 upregulation

Acute kidney injury (AKI) is characterized by an acute reduction in kidney function as identified by an increase in serum creatinine levels and reduction in urine output. Kidney injury molecule-1 (Kim-1) is a hallmark of kidney diseases, since it is typically non-detectable in the non-injured kidney, but upregulated and excreted in the urine during AKI. Aldosterone (Aldo) is a mediator of the renin-angiotensin-Aldo system with a pivotal role in the regulation of salt and extracellular fluid metabolism. In the present study, mice subjected to renal ischemia/reperfusion-induced AKI were investigated. The mice exhibited elevated levels of Aldo and angiotensin II, together with increased Kim-1 expression levels in renal tissue. Treatment of the mice with the Aldo receptor antagonist spironolactone decreased Kim-1 expression levels. These results suggest that Aldo may be associated with the expression of Kim-1 during AKI. However, the molecular mechanism underlying the role of Aldo in Kim-1 expression is unclear, and thus was investigated using NRK-52E cells. Aldo was found to induce the apoptosis of NRK-52E cells via the hypermethylation of rno-microRNA (miR)-203 and upregulation of Kim-1. In addition, luciferase reporter assays demonstrated that Kim-1 was a target gene of rno-miR-203 in NRK-52E cells. Furthermore, Aldo-induced NRK-52E cell apoptosis was reduced by treatment with pre-miR-203 and spironolactone to a greater extent when compared with either alone. The results may provide a promising diagnostic marker or novel therapeutic target for AKI.

Constitutive renal Rel/nuclear factor-κB expression in Lewis polycystic kidney disease rats

AIM: To determine the temporal expression and pattern of Rel/nuclear factor (NF)-κB proteins in renal tissue in polycystic kidney disease (PKD).

METHODS: The renal expression of Rel/NF-κB proteins was determined by immunohistochemistry, immunofluorescence and immunoblot analysis in Lewis polycystic kidney rats (LPK, a genetic ortholog of human nephronopthsis-9) from postnatal weeks 3 to 20. At each timepoint, renal disease progression and the mRNA expression of NF-κB-dependent genes (TNFα and CCL2) were determined. NF-κB was also histologically assessed in human PKD tissue.

RESULTS: Progressive kidney enlargement in LPK rats was accompanied by increased renal cell proliferation and interstitial monocyte accumulation (peaking at weeks 3 and 10 respectively), and progressive interstitial fibrosis (with α smooth muscle actin and Sirius Red deposition significantly increased compared to Lewis kidneys from weeks 3 to 6 onwards). Rel/NF-κB proteins (phosphorylated-p105, p65, p50, c-Rel and RelB) were expressed in cystic epithelial cells (CECs) of LPK kidneys as early as postnatal week 3 and sustained until late-stage disease at week 20. From weeks 10 to 20, nuclear p65, p50, RelB and cytoplasmic IκBα protein levels, and TNFα and CCL2 expression, were upregulated in LPK compared to Lewis kidneys. NF-κB proteins were consistently expressed in CECs of human PKD. The DNA damage marker γ-H2AX was also identified in the CECs of LPK and human polycystic kidneys.

CONCLUSION: Several NF-κB proteins are consistently expressed in CECs in human and experimental PKD. These data suggest that the upregulation of both the canonical and non-canonical pathways of NF-κB signaling may be a constitutive and early pathological feature of cystic renal diseases.

Kidney Injury Molecule-1 Is Specifically Expressed in Cystically-Transformed Proximal Tubules of the PKD/Mhm (cy/+) Rat Model of Polycystic Kidney Disease

Expression of kidney injury molecule-1 (Kim-1) is rapidly upregulated following tubular injury, constituting a biomarker for acute kidney damage. We examined the renal localization of Kim-1 expression in PKD/Mhm (polycystic kidney disease, Mannheim) (cy/+) rats (cy: mutated allel, +: wild type allel), an established model for autosomal dominant polycystic kidney disease, with chronic, mainly proximal tubulointerstitial alterations. For immunohistochemistry or Western blot analysis, kidneys of male adult heterozygously-affected (cy/+) and unaffected (+/+) littermates were perfusion-fixed or directly removed. Kim-1 expression was determined using peroxidase- or fluorescence-linked immunohistochemistry (alone or in combination with markers for tubule segments or differentiation). Compared to (+/+), only in (cy/+) kidneys, a chronic expression of Kim-1 could be detected by Western blot analysis, which was histologically confined to an apical cellular localization in areas of cystically-transformed proximal tubules with varying size and morphology, but not in distal tubular segments. Kim-1 was expressed by cystic epithelia exhibiting varying extents of dedifferentiation, as shown by double labeling with aquaporin-1, vimentin or osteopontin, yielding partial cellular coexpression. In this model, in contrast to other known molecules indicating renal injury and/or repair mechanisms, the chronic renal expression of Kim-1 is strictly confined to proximal cysts. Its exact role in interfering with tubulo-interstitial alterations in polycystic kidney disease warrants future investigations.

Mammalian Target of Rapamycin Mediates Kidney Injury Molecule 1-Dependent Tubule Injury in a Surrogate Model

Kidney injury molecule 1 (KIM-1), an epithelial phagocytic receptor, is markedly upregulated in the proximal tubule in various forms of acute and chronic kidney injury in humans and many other species. Whereas acute expression of KIM-1 has adaptive anti-inflammatory effects, chronic expression may be maladaptive in mice. Here, we characterized the zebrafish Kim family, consisting of Kim-1, Kim-3, and Kim-4. Kim-1 was markedly upregulated in kidney after gentamicin-induced injury and had conserved phagocytic activity in zebrafish. Both constitutive and tamoxifen-induced expression of Kim-1 in zebrafish kidney tubules resulted in loss of the tubule brush border, reduced GFR, pericardial edema, and increased mortality. Kim-1-induced kidney injury was associated with reduction of growth of adult fish. Kim-1 expression led to activation of the mammalian target of rapamycin (mTOR) pathway, and inhibition of this pathway with rapamycin increased survival. mTOR pathway inhibition in KIM-1-overexpressing transgenic mice also significantly ameliorated serum creatinine level, proteinuria, tubular injury, and kidney inflammation. In conclusion, persistent Kim-1 expression results in chronic kidney damage in zebrafish through a mechanism involving mTOR. This observation predicted the role of the mTOR pathway and the therapeutic efficacy of mTOR-targeted agents in KIM-1-mediated kidney injury and fibrosis in mice, demonstrating the utility of the Kim-1 renal tubule zebrafish models.

Kidney injury molecule-1 and the loss of kidney function in diabetic nephropathy: a likely causal link in patients with type 1 diabetes

OBJECTIVE

We evaluated the predictive value and clinical benefit of urinary kidney injury molecule (KIM)-1 for progression of diabetic nephropathy (DN) in type 1 diabetes. We also investigated its causal role for the decrease of estimated glomerular filtration rate (eGFR) by a Mendelian randomization (MR) approach.

RESEARCH DESIGN AND METHODS

We followed 1,573 patients with type 1 diabetes for 6 years. KIM-1 was measured at baseline and normalized with urinary creatinine. KIM-1 predictive value was evaluated by Cox regression, while its added predictive benefit was evaluated using a panel of statistical indexes. The causality for the loss of renal function was evaluated with MR, utilizing the top signal from our genome-wide association study (GWAS) as the instrumental variable.

RESULTS

KIM-1 was not an independent predictor of progression of DN when adjusted for albumin excretion rate (AER) and added no prognostic benefit to AER or eGFR. In multiple regressions, KIM-1 was associated with lower eGFR independently of diabetes duration (β = -4.066; P < 0.0001) but not of AER. In our GWAS, rs2036402 in the KIM1 gene was strongly associated with KIM-1 (β = -0.51; P = 6.5 × 10(-38)). In the MR, KIM-1 was associated with lower eGFR, independently of diabetes duration and AER (β = -5.044; P = 0.040), suggesting a causal relationship.

CONCLUSIONS

KIM-1 did not predict progression to end-stage renal disease independently of AER and added no prognostic benefit to current biomarkers. Nevertheless, the MR showed that the inverse association of increased KIM-1 levels with lower eGFR is likely to represent a causal link.

Early biomarkers of renal injury and protective effect of erythropoietin on kidneys of asphyxiated newborn rats

BACKGROUND

The aims of this study were to determine which of the two biomarkers of renal injury, kidney injury molecule-1 or cystatin C, is more sensitive and to evaluate whether erythropoietin protects kidneys injured by perinatal asphyxia.

METHODS

Animals were split into three groups designated as follows: AE, pups that survived perinatal asphyxia and subsequently received 2.5 μg (0.1 ml) of darbepoetin-α (i.p.); A, the pups that survived perinatal asphyxia and received 0.1 ml of 0.9% NaCl; and C, control group. The pups were killed at different ages of life (6 h, 24 h, 48 h, 7 d, and 14 d of age; 10 rats in each subgroup). Immunohistopathological evaluation of kidneys was performed.

RESULTS

At 48 h and on days 7 and 14, absolute injury scores were significantly lower in group AE as measured by both biomarkers. Cystatin C expression was the most intensive 6 h after the hypoxic event (average value of absolute injury score was 2.82) and declined over time. Expression of kidney injury molecule-1 was less intensive, with the average value of absolute injury score being 2.02 at 6 h and 2.105 at 24 h; the peak value (2.155) was recorded 48 h after the hypoxic event.

CONCLUSION

Erythropoietin has a protective effect on hypoxic kidneys. Cystatin C is more sensitive as an early biomarker of acute kidney injury in comparison with kidney injury molecule-1.

Effects of rebamipide on nephrotoxicity associated with selected NSAIDs in rats

Use of nonsteroidal anti-inflammatory drugs (NSAIDs) is primarily limited by renal and gastrointestinal adverse effects. Rebamipide suppresses gastric mucosal injury when administered with NSAIDs. This study aimed to determine rebamipide's influence upon renal effects following concomitant use with celecoxib or diclofenac. On day 0, rats were randomly divided into 6 groups (n≥6). On days 1 and 2, three groups received placebo and three groups were administered rebamipide (30 mg/kg) twice daily. On day 3, the rats treated with placebo received another dose of placebo and ten minutes later a single dose of celecoxib (40 mg/kg), diclofenac (10mg/kg), or placebo, respectively. The rats treated with rebamipide received one more dose of rebamipide and ten minutes later one single dose of celecoxib, diclofenac, or placebo, respectively. Urine and blood samples were collected on days 0, 2, and 3. Sodium and potassium excretion rates decreased significantly in the rats treated with celecoxib, diclofenac, rebamipide plus celecoxib, or rebamipide plus diclofenac on day 3. Blood urea nitrogen (BUN) levels significantly increased in placebo plus diclofenac and rebamipide plus diclofenac groups on day 3. Comparing the two groups, the levels of BUN was significantly higher in the rebamipide plus diclofenac group compared to that of placebo plus diclofenac group. Concomitant administration of rebamipide with either NSAID caused a rise in concentrations of urinary kidney injury molecule-1. Histopathological evaluations revealed an intensified NSAID-induced tubular necrosis by rebamipide. Based upon the results obtained, concomitant administration of rebamipide with NSAIDs enhances the effect of NSAIDs on tubular injury.

Urine kidney injury molecule-1: a potential non-invasive biomarker for patients with renal cell carcinoma

BACKGROUND

KIM-1 staining is upregulated in proximal tubule-derived renal cell carcinoma (RCC) including clear renal cell carcinoma and papillary renal cell carcinoma, but not in chromophobe RCC (distal tubular tumor). This study was designed to prospectively examine urine KIM-1 level before and 1 month after removal of renal tumors.

PATIENTS AND DESIGN

A total of 19 patients were eventually enrolled in the study based on pre-operative imaging studies. Pre-operative and follow-up (1 month) urine KIM-1 levels were measured. The urine KIM-1 levels (uKIM-1) were then normalized to urine creatinine levels (uCr). Renal tumors were also stained for KIM-1 using immunohistochemical techniques.

RESULTS

The KIM-1-negative staining group included 7 cases, and the KIM-1-positive group consisted of 12 cases. The percentage of KIM-1-positive staining RCC cells ranged from 10 to 100 %, and the staining intensity ranged from 1+ to 3+. In both groups, serum creatinine levels were both significantly elevated after nephrectomy. In the KIM-1-negative group, uKIM-1/uCr remained at a similar level before (0.37 ± 0.1 ng/mg Cr) and after nephrectomy (0.32 ± 0.01 ng/mg Cr). However, in the KIM-1-positive group, elevated uKIM-1/uCr at 1.20 ± 0.31 ng/mg Cr was significantly reduced to 0.36 ± 0.1 ng/mg Cr, which was similar to the pre-operative uKIM-1/uCr (0.37 ± 0.1 ng/mg Cr) in the KIM-1-negative group.

CONCLUSION

Our small but prospective study showed significant reduction in uKIM-1/uCr after nephrectomy in the KIM-1 positive group, suggesting that urine KIM-1 may serve as a surrogate biomarker for kidney cancer and a non-invasive pre-operative measure to evaluate the malignant potential of renal masses.

Effect of treatment on urinary kidney injury molecule-1 in IgA nephropathy

Background

Kidney injury molecule-1 (KIM-1) is a biomarker useful for detecting early tubular damage and has been recently reported as a useful marker for evaluating kidney injury in IgA nephropathy (IgAN). We therefore investigated whether treatment decreases urinary KIM-1 excretion in IgAN.

Methods

We prospectively enrolled 37 patients with biopsy-proven IgAN. Urinary KIM-1 was assessed before and after treatment, which included low salt diet, blood pressure control, pharmacotherapy with angiotensin receptor blockers and/or angiotensin converting enzyme inhibitors, and immunosuppressive agents as necessary. The median treatment duration was 24 months.

Results

Urinary KIM-1/creatinine (Cr) was significantly decreased in patients with IgAN after treatment compared to baseline (P < 0.0001, 1.16 [0.51-1.83] vs 0.26 [0.12-0.65] ng/mg). There was a decrease in the amount of proteinuria after treatment, but it was not statistically significant (P = 0.052, 748.1 [405-1569.7] vs 569.2 [252.2-1114] g/d). Estimated glomerular filtration rate (eGFR) did not change with treatment (P = 0.599, 79.28 ± 30.56 vs 80.98 ± 32.37 ml/min/1.73 m²). Urinary KIM-1 was not correlated with proteinuria baseline or follow up (pre-: R = - 0.100, P = 0.577, post-: R = 0.001, P = 0.993). In patients with higher baseline urinary KIM-1, both urinary KIM-1 level and proteinuria were significantly decreased following treatment.

Conclusions

Treatment decreases urinary KIM-1/Cr in patients with IgAN. It also reduces proteinuria in patients with higher baseline urinary KIM-1. These results suggest a potential role for urinary KIM-1 as a biomarker for predicting treatment response in IgAN, however, further study is needed to verify this.

Tissue expression and correlation of a panel of urinary biomarkers following cisplatin-induced kidney injury

In recent years, there has been considerable activity to identify urinary biomarkers of nephrotoxicity as noninvasive measurements with greater sensitivity and specificity than traditional biomarkers, such as serum creatinine and blood urea nitrogen. Our study aimed to use cisplatin-treated rats to evaluate the use of immunohistochemistry directed at multiple urinary biomarkers in kidney tissue. Tissue levels were compared to urinary levels of these biomarkers to demonstrate tissue specificity and sensitivity. These techniques could also be used in studies where urine samples are not available, such as retrospective studies in drug safety testing, to demonstrate the potential utility of using these biomarkers in future preclinical or clinical studies. All of the biomarkers investigated showed either an increase (kidney injury molecule [KIM-1], osteopontin [OPN], and, clusterin) or a decrease (alpha-glutathione S-transferase and trefoil factor 3) except beta 2 microglobulin (β2MG) that showed no significant changes 5 days after 1.0 mg/kg or 2.5 mg/kg cisplatin treatment. All of the biomarkers except β2MG showed utility as tissue biomarkers, but KIM-1 and OPN expression correlated closely with urinary biomarker measurements and reflect tissue damage. Future studies are needed to determine the wider application of these two markers for detecting renal toxicity following administration of other nephrotoxicants.

Can we target tubular damage to prevent renal function decline in diabetes?

The glomerulus has been at the center of attention as the primary site of injury in diabetic nephropathy (DN). Although there is no question that there are changes seen in the glomerulus, it is also well known that tubulointerstitial changes are a prominent component of the disease, especially in patients with type 2 diabetes. The level of albuminuria and DN disease progression best correlate with tubular degeneration and interstitial fibrosis. Nephrotoxicity studies in animals reveal that albuminuria is a highly sensitive marker of early tubular toxicity even in the absence of glomerular pathology. Urinary biomarker data in human beings support the view that proximal tubule injury contributes in a primary way, rather than in a secondary manner, to the development of early DN. I present a model in which very specific injury to the proximal tubule in vivo in the mouse results in severe inflammation, loss of blood vessels, interstitial fibrosis, and glomerulosclerosis. Increased glucose levels, free glycation adducts, reactive oxygen species, and oxidized lipids result in toxicity to tubule epithelia. This results in loss of cells with a stimulus to repair the epithelium. However, because of sublethal injury there is cell-cycle arrest in epithelial cells attempting to replace damaged cells. This leads to epithelial secretion of both profibrogenic growth factors, collagens, and factors that cause pericytes to proliferate and differentiate into myofibroblasts, leading to endothelial destabilization and capillary rarefaction. Local ischemia ensues with further injury to the tubules, more profibrogenic mediators, matrix protein deposition, fibrosis, and glomerulosclerosis.

Kidney injury molecule-1: more than just an injury marker of tubular epithelial cells?

Regardless of the original causes and etiology, the progression to renal function declines follows a final common pathway associated with tubulointerstitial injury, in which the proximal tubular epithelial cells (PTEC) are instrumental. Kidney injury molecule-1 (KIM-1) is an emerging biomarker, and its expression and release are induced in PTEC upon injury. KIM-1 plays the role as a double-edged sword and implicates in the process of kidney injury and healing. Expression of KIM-1 is also associated with tubulointerstitial inflammation and fibrosis. More importantly, KIM-1 expressing PTEC play the role as the residential phagocytes, contribute to the removal of apoptotic cells and facilitate the regeneration of injured tubules. The precise mechanism of KIM-1 and its sheded ectodomain on restoration of tubular integrity after injury is not fully understood. Other than PTEC, macrophages (Mø) also implicate in tubular repair. Understanding the crosstalk between Mø and the injured PTEC is essential for designing appropriate methods for controlling the sophisticated machinery in tubular regeneration and healing. This article will review the current findings of KIM-1, beginning with its basic structure, utility as a biomarker, and possible functions, with focus on the role of KIM-1 in regeneration and healing of injured PTEC.

KIM-1 expression predicts renal outcomes in IgA nephropathy

BACKGROUND

Kidney injury molecule-1 (KIM-1) is a sensitive biomarker for proximal tubular injury. Recently, a few studies have shown that urinary KIM-1 has clinical implications in IgA nephropathy (IgAN). We performed this study to determine whether tissue KIM-1 has clinical implications for predicting long-term outcome and whether urinary KIM-1 is correlated with tissue KIM-1 and kidney injury in IgAN patients.

METHODS

We assessed the prognostic prediction capability of tissue KIM-1 expression in 69 adult patients with IgAN retrospectively. Renal biopsies from all patients were scored by a pathologist who was blinded to the clinical data for the pathologic variables. The primary outcome was the composite of a 50 % reduction in eGFR or end-stage renal disease. Tissue KIM-1 expression was assessed semiquantitatively by counting the stained tubules per 100× power field; 0 tubule indicates grade 0; 1-5 tubules, grade 1; 6-10 tubules, grade 2; and more than 10 tubules, grade 3. Comparing urinary KIM-1 and tissue KIM-1 expression, 50 consecutive IgAN patients were prospectively enrolled to measure urinary KIM-1 levels and examine their biopsy specimens by KIM-1 immunohistochemistry.

RESULTS

Univariate analysis showed that tissue KIM-1 expression was associated with the renal outcome in IgAN. Multivariate regression analysis, as the relationship of tissue KIM-1 with prognosis, was consistent. Proteinuria at biopsy and tissue KIM-1 grade 3 were shown to have a prognostic value. The concentration of urinary KIM-1/Cr in patients with IgAN was significantly higher than that in the normal controls.

CONCLUSION

Tissue KIM-1 expression is an independent predictor of adverse renal outcomes in IgA nephropathy patients.

Osteopontin and symmetric dimethylarginine plasma levels in solitary functioning kidney in children

AIM

The present study aimed to examine whether plasma osteopontin (pOPN) and symmetric dimethylarginine (pSDMA) are useful biomarkers of renal dysfunction in children with solitary functioning kidney (SFK).

METHODS

We measured circulating pOPN and pSDMA in 51 patients with SFK and no other urinary defects. Patients were subdivided into two groups: primary SFK (pSFK) - unilateral renal agenesis (URA), and secondary SFK (sSFK) - unilateral nephrectomy. The control group (C) contained 21 healthy children, with mean age 9.92 ± 4.85 years. Immunoenzymatic ELISA commercial kits were used to measure pOPN and pSDMA concentrations.

RESULTS

Plasma osteopontin and pSDMA levels in children with SFK were higher than those in healthy participants (p < 0.05). There was no difference in pOPN and pSDMA concentrations between patients with pSFK and those with sSFK (p > 0.05). Receiver operator characteristic analyses performed to define the diagnostic efficiency of serum creatinine, pOPN and pSDMA in identifying children with C(cr)  < 90 mL/min/1.73 m(2) among all examined children revealed no differences between all three AUCs (p > 0.05).

CONCLUSION

Increased pOPN and pSDMA levels were observed in children with SFK. Both pOPN and pSDMA correlated with eGFR; however, the sensitivity and specificity of those markers were not better than those of creatinine.

Indomethacin reduces glomerular and tubular damage markers but not renal inflammation in chronic kidney disease patients: a post-hoc analysis

Under specific conditions non-steroidal anti-inflammatory drugs (NSAIDs) may be used to lower therapy-resistant proteinuria. The potentially beneficial anti-proteinuric, tubulo-protective, and anti-inflammatory effects of NSAIDs may be offset by an increased risk of (renal) side effects. We investigated the effect of indomethacin on urinary markers of glomerular and tubular damage and renal inflammation. We performed a post-hoc analysis of a prospective open-label crossover study in chronic kidney disease patients (n = 12) with mild renal function impairment and stable residual proteinuria of 4.7±4.1 g/d. After a wash-out period of six wks without any RAAS blocking agents or other therapy to lower proteinuria (untreated proteinuria (UP)), patients subsequently received indomethacin 75 mg BID for 4 wks (NSAID). Healthy subjects (n = 10) screened for kidney donation served as controls. Urine and plasma levels of total IgG, IgG4, KIM-1, beta-2-microglobulin, H-FABP, MCP-1 and NGAL were determined using ELISA. Following NSAID treatment, 24 h -urinary excretion of glomerular and proximal tubular damage markers was reduced in comparison with the period without anti-proteinuric treatment (total IgG: UP 131[38–513] vs NSAID 38[17–218] mg/24 h, p<0.01; IgG4: 50[16–68] vs 10[1–38] mg/24 h, p<0.001; beta-2-microglobulin: 200[55–404] vs 50[28–110] ug/24 h, p = 0.03; KIM-1: 9[5]–[14] vs 5[2]–[9] ug/24 h, p = 0.01). Fractional excretions of these damage markers were also reduced by NSAID. The distal tubular marker H-FABP showed a trend to reduction following NSAID treatment. Surprisingly, NSAID treatment did not reduce urinary excretion of the inflammation markers MCP-1 and NGAL, but did reduce plasma MCP-1 levels, resulting in an increased fractional MCP-1 excretion. In conclusion, the anti-proteinuric effect of indomethacin is associated with reduced urinary excretion of glomerular and tubular damage markers, but not with reduced excretion of renal inflammation markers. Future studies should address whether the short term glomerulo- and tubulo-protective effects as observed outweigh the possible side-effects of NSAID treatment on the long term.

Cell therapy with human renal cell cultures containing erythropoietin-positive cells improves chronic kidney injury

New therapeutic strategies for chronic kidney disease (CKD) are necessary to offset the rising incidence of CKD and donor shortage. Erythropoietin (EPO), a cytokine produced by fibroblast-like cells in the kidney, has recently emerged as a renoprotective factor with anti-inflammatory, antioxidant properties. This study (a) determined whether human renal cultures (human primary kidney cells [hPKC]) can be enriched in EPO-positive cells (hPKC(F+)) by using magnetic-bead sorting; (b) characterized hPKC(F+) following cell separation; and (c) established that intrarenal delivery of enriched hPKC(F+) cells would be more beneficial in treatment of renal injury, inflammation, and oxidative stress than unsorted hPKC cultures in a chronic kidney injury model. Fluorescence-activated cell sorting analysis revealed higher expression of EPO (36%) and CD73 (27%) in hPKC(F+) as compared with hPKC. After induction of renal injury, intrarenal delivery of hPKC(F+) or hPKC significantly reduced serum creatinine, interstitial fibrosis in the medulla, and abundance of CD68-positive cells in the cortex and medulla (p < .05). However, only hPKC(F+) attenuated interstitial fibrosis in the renal cortex and decreased urinary albumin (3.5-fold) and urinary tubular injury marker kidney injury molecule 1 (16-fold). hPKC(F+) also significantly reduced levels of renal cortical monocyte chemotactic protein 1 (1.8-fold) and oxidative DNA marker 8-hydroxy-deoxyguanosine (8-OHdG) (2.4-fold). After 12 weeks, we detected few injected cells, which were localized mostly to the cortical interstitium. Although cell therapy with either hPKC(F+) or hPKC improved renal function, the hPKC(F+) subpopulation provides greater renoprotection, perhaps through attenuation of inflammation and oxidative stress. We conclude that hPKC(F+) may be used as components of cell-based therapies for degenerative kidney diseases.

Renal effects of long-term darbepoetin alpha treatment in hypertensive TGR(mRen2)27 rats

INTRODUCTION

Erytropoietin (EPO) has cytoprotective and angiogenic properties and has a beneficial effect in ischaemic conditions. Since the development of renal interstitial abnormalities are often associated with ischaemia, we studied the effects of the long-acting EPO analogue darbepoetin alpha (DA) on kidney damage in TGR(mRen2)27 (Ren2) rats.

MATERIALS AND METHODS

Ren2 rats were randomised to DA or vehicle (VEH) or to DA + angiotensin converting enzyme inhibitor (ACEi) or VEH + ACEi. Sprague Dawley (SD) rats served as controls. Blood pressure was measured weekly and 24-h urine was collected to measure proteinuria. Blood samples were collected for creatinine and haematocrit. Kidneys were studied for inflammation and pre-fibrosis. Renal mRNA expression was studied for EPO, EPO-receptor, collagen-3α1 and kidney injury molecule-1 (KIM-1).

RESULTS

DA had no effect on SBP, serum creatinine and proteinuria. Interstitial and glomerular α-SMA expression was significantly increased in Ren2. ACEi but not DA improved the increased renal inflammatory and pro-fibrotic profile in Ren2 rats. DA on top of ACEi further reduced glomerular α-SMA and KIM-1 expression.

CONCLUSION

Long-term DA treatment has no beneficial effects on renal structural and functional changes in TGR(mRen2)27 rats in the time frame studied and the dose provided.

Glomerular expression of kidney injury molecule-1 and podocytopenia in diabetic glomerulopathy

BACKGROUND/AIMS

Studies have shown that kidney injury molecule-1 (KIM-1) is upregulated in damaged renal proximal tubules. In this study, we examined KIM-1 expression in glomerular epithelial cells in diabetic glomerulopathy.

METHODS

Renal histology, immunostaining and Western blot for protein level, and real-time PCR for mRNA expression of KIM-1 and podocyte markers were evaluated in untreated or losartan-treated Zucker lean (Fa/+) and Zucker diabetic fatty (Fa/Fa) rats.

RESULTS

The diabetic rats showed an increased glomerular expression of KIM-1. KIM-1 staining was localized primarily in the hyperplastic parietal epithelium of Bowman's capsule in the early stages of diabetes with subsequent increase in KIM-1-positive cells in the glomerular tuft in the more advanced stages. The increase in glomerular KIM-1 was associated with a decrease in podocytes in Fa/Fa rats. Antiproteinuric treatment with losartan attenuated podocytopenia and decreased renal expression of KIM-1 in treated diabetic rats. In an in vitro study, albumin overload increased KIM-1 protein in the primary cultures of rat glomerular epithelial cells.

CONCLUSION

These results show that glomerular KIM-1 expression was increased, in proportion to the extent of proteinuria and podocytopenia in the diabetic animals, supporting that KIM-1 could be used as a potential biomarker for glomerular injury in proteinuric kidney disease.

Angiotensin II activation of mTOR results in tubulointerstitial fibrosis through loss of N-cadherin

BACKGROUND/AIMS

Angiotensin (Ang) II contributes to tubulointerstitial fibrosis. Recent data highlight mammalian target of rapamycin (mTOR)/S6 kinase 1 (S6K1) signaling in tubulointerstitial fibrosis; however, the mechanisms remain unclear. Thereby, we investigated the role of Ang II on mTOR/S6K1-dependent proximal tubule (PT) injury, remodeling, and fibrosis.

METHODS

We utilized young transgenic Ren2 rats (R2-T) and Sprague-Dawley rats (SD-T) treated with the Ang type 1 receptor (AT(1)R) blocker telmisartan (2 mg · kg(-1) · day(-1)) or vehicle (R2-C; SD-C) for 3 weeks to examine PT structure and function.

RESULTS

Ren2 rats displayed increased systolic blood pressure, proteinuria and increased PT oxidant stress and remodeling. There were parallel increases in kidney injury molecule-1 and reductions in neprilysin and megalin with associated ultrastructural findings of decreased clathrin-coated pits, endosomes, and vacuoles. Ren2 rats displayed increased Serine(2448) phosphorylation of mTOR and downstream S6K1, in concert with ultrastructural basement membrane thickening, tubulointerstitial fibrosis and loss of the adhesion molecule N-cadherin. Telmisartan treatment attenuated proteinuria as well as the biochemical and tubulointerstitial structural abnormalities seen in the Ren2 rats.

CONCLUSIONS

Our observations suggest that Ang II activation of the AT(1)R contributes to PT brush border injury and remodeling, in part, due to enhanced mTOR/S6K1 signaling which promotes tubulointerstitial fibrosis through loss of N-cadherin.

High urinary excretion of kidney injury molecule-1 is an independent predictor of end-stage renal disease in patients with IgA nephropathy

BACKGROUND

The variable course of immunoglobulin A nephropathy (IgAN) warrants accurate tools for the prediction of progression. Urinary kidney injury molecule-1 (KIM-1) and neutrophil gelatinase-associated lipocalin (NGAL) are markers for the detection of early tubular damage caused by various renal conditions. We evaluated the prognostic value of these markers in patients with IgAN.

METHODS

We included patients (n = 65, 72% male, age 43 ± 13 years) with biopsy-proven IgAN, who were evaluated for proteinuria. Urinary KIM-1 and NGAL were measured by enzyme-linked immunosorbent assay. We analysed data using Cox regression for the outcome end-stage renal disease (ESRD).

RESULTS

Median serum creatinine was 142 μmol/L and proteinuria 2.2 g/day. During follow-up (median 75 months), 23 patients (35%) developed ESRD. In patients with IgAN median urinary KIM-1 excretion was 1.7 ng/min and NGAL excretion was 47 ng/min, both significantly higher than in healthy controls. KIM-1 and NGAL were correlated with proteinuria (r = 0.40 and 0.34, respectively, P < 0.01) and each other (r = 0.53, P < 0.01) but not with estimated glomerular filtration rate (eGFR). Interestingly, KIM-1 was not significantly correlated with the excretion of α(1)-microglobulin (α(1)m) and β(2)-microglobulin (β(2)m), known markers of tubular injury. Univariate analysis showed that baseline serum creatinine and urinary excretion of total protein, α(1)m, β(2)m, immunoglobulin G, KIM-1 and NGAL were significantly associated with ESRD. By multivariate analysis, serum creatinine and KIM-1 excretion proved to be significant independent predictors of ESRD.

CONCLUSION

KIM-1 and NGAL excretion are increased in patients with IgAN and correlate with proteinuria but not with eGFR. Baseline serum creatinine and urinary KIM-1, but not proteinuria, are independent predictors of ESRD.

Long-term effects of neonatal treatment with dexamethasone, L-carnitine, and combinations thereof in rats

Because L-carnitine (L-CAR) is a potential substitute for neonatal dexamethasone (DEX) with respect to the prevention of long-term side effects, rats were treated on d 1, 2, and 3 after birth with saline, DEX, L-CAR, half the dose of DEX, and L-CAR + half DEX. DEX led to growth retardation, increased mortality, and severe kidney damage at 50 wk of age. L-CAR had no negative effects on growth, kidney function at 50 wk, and survival at 101 wk. Growth retardation was induced transiently by half DEX and permanently by L-CAR + half DEX, slightly reduced kidney function but no reduced life span was found in both these groups. Except for the DEX group, blood glucose levels were normal at 50 wk in all groups. A serendipitous finding was that L-CAR treatment caused one-third less food intake; however, these rats maintained normal body weight. In conclusion, L-CAR, a lower dose of DEX, and their combination caused less negative effects in later life. Because L-CAR + half DEX had a negative effect on growth, attention to monitor L-CAR levels during DEX treatment of preterm newborns seems to be justified. The finding that neonatal L-CAR caused reduced food intake in later life warrants further investigation.

Fenofibrate attenuates tubulointerstitial fibrosis and inflammation through suppression of nuclear factor-κB and transforming growth factor-β1/Smad3 in diabetic nephropathy

Fibrates, the ligands of peroxisome proliferator-activated receptor-alpha, have been shown to have a renal protective action in diabetic models of renal disease, but the mechanisms underlying this effect are unknown. In the present study, we sought to investigate in greater detail the effect of fenofibrate and its mechanism of action on renal inflammation and tubulointerstitial fibrosis in an animal model of type 2 diabetes mellitus. Twelve-week-old non-diabetic Zucker lean (ZL) and Zucker diabetic fatty (ZD) rats were treated with vehicle or fenofibrate for 10 weeks. mRNA and protein analyses were performed by real-time polymerase chain reaction, Western blot and immunostaining. The diabetic condition of ZD rats was associated with an increase in collagen and alpha-smooth muscle actin accumulation in the kidney, which was significantly reduced by fenofibrate. Chronic treatment of ZD rats with fenofibrate attenuated renal inflammation and tubular injury as evidenced by a decrease in mRNA and protein expression of secreted phosphoprotein-1, monocyte chemotactic protein-1 and kidney injury molecule-1 in the kidneys. Renal interstitial macrophage infiltration was also significantly reduced in the kidneys of fenofibrate-treated diabetic animals. Moreover, renal nuclear factor (NF)-kappaB DNA-binding activity, transforming growth factor (TGF)-beta1 and phospho-Smad3 proteins were significantly higher in ZD animals compared with ZL ones. This increase in NF-kappaB activity, TGF-beta1 expression and Smad3 phosphorylation was greatly attenuated by fenofibrate in the diabetic kidneys. Taken together, fenofibrate suppressed NF-kappaB and TGF-beta1/Smad3 signaling pathways and reduced renal inflammation and tubulointerstitial fibrosis in diabetic ZD animals.

Contribution of chymase-dependent angiotensin II formation to the progression of tubulointerstitial fibrosis in obstructed kidneys in hamsters

Recent studies indicate a role of chymase in the regulation of angiotensin II (AngII) formation in cardiovascular and renal tissues. We investigated a possible contribution of chymase to AngII formation and to renal fibrosis in unilateral ureteral obstruction (UUO). Eight-week-old Syrian hamsters were subjected to UUO and treated with vehicle, the specific chymase inhibitor (CI) 4-[1-(4-methyl-benzo[b]thiophen-3-ylmethyl)-1H-benzimidazol-2-ylsulfanyl]-butyric acid (50 mg/kg, twice a day, p.o.), or the selective AT(1)-receptor blocker olmesartan (10 mg/kg per day, p.o.) for 14 days. UUO-induced renal interstitial fibrosis was associated with increases in renal mRNA levels of alpha-smooth muscle actin (SMA), type I collagen, and transforming growth factor (TGF)-beta. The UUO hamsters showed markedly higher AngII contents and increased AT(1)-receptor mRNA level in the obstructed kidney than sham-operated ones. In contrast, angiotensin-converting enzyme (ACE) protein expression was significantly lower in UUO hamsters. In UUO hamsters, treatment with CI or olmesartan significantly decreased AngII levels in renal tissue and mRNA levels of alpha-SMA, type I collagen, and TGF-beta and ameliorated tubulointerstitial injury. On the other hand, neither CI nor olmesartan changed systolic blood pressure, renal ACE, and AT(1)-receptor protein levels. These data suggest that chymase-dependent intrarenal AngII formation contributes to the pathogenesis of interstitial fibrosis in obstructed kidneys of hamsters.

Novel biomarkers of acute kidney toxicity

Novel biomarkers of kidney toxicity are powerful tools not only with respect to their clinical applications but also because of their impact on drug development. These biomarkers can influence the assessment of efficacy of new drugs for kidney diseases as well as the risk management for new drugs. The science behind these novel biomarkers reflects the evolution over the past decade of genomic and proteomic platforms that have transformed the discovery and development of new biomarkers for preclinical and clinical applications in drug development. Several of these biomarkers are in use as transcriptomic biomarkers in animal models as well as translational proteomic biomarkers in animal models and in humans. Their ability to detect kidney damage earlier than is possible with currently accessible biomarkers is being given qualification through regulatory biomarker-qualification programs, which will help establish consensus for their widespread use.

Galectin-3: a novel mediator of heart failure development and progression

Galectins are a family of soluble beta-galactoside-binding lectins that play many important regulatory roles in inflammation, immunity, and cancer. Recently, a role for galectin-3 in the pathophysiology of heart failure (HF) has been suggested. Numerous studies have demonstrated the up-regulation of galectin-3 in hypertrophied hearts, its stimulatory effect on macrophage migration, fibroblast proliferation, and the development of fibrosis. The latter observation is particularly relevant as cardiac remodelling is an important determinant of the clinical outcome of HF and is linked to disease progression and poor prognosis. Because galectin-3 expression is maximal at peak fibrosis and virtually absent after recovery, routine measurement in patients with HF may prove valuable to identify those patients at highest risk for readmission or death, thus enabling physicians to tailor the level of care to individual patient needs. This review summarizes the most recent advances in galectin-3 research, with an emphasis on the role galectin-3 plays in the development and progression of HF.

Osteopontin modulates angiotensin II-induced inflammation, oxidative stress, and fibrosis of the kidney

Osteopontin, a secreted glycoprotein has been implicated in several renal pathological conditions such as those due to ureteral obstruction, ischemia, and cyclosporine toxicity. We studied its possible role in angiotensin II-mediated renal injury by infusing wild-type and osteopontin knockout mice with angiotensin II and found that it raised blood pressure and increased urinary albumin/creatinine ratios in both strains of mice. However, while wild-type mice responded to the infusion by macrophage infiltration and increased expression of alpha-smooth muscle actin, fibronectin, and transforming growth factor-beta; the osteopontin knockout mice developed none of these. Further, the knockout mice had increased expression of monocyte chemoattractant protein-1; NADPH oxidase subunits such as NOX2, gp47phox, and NOX4; and plasminogen activator inhibitor-1 compared to the wild type animals. Proximal tubule epithelial cells in culture treated with recombinant osteopontin and angiotensin II had increased alpha-smooth muscle actin and transforming growth factor-beta expression. The effect of angiotensin II was blocked by an antibody to osteopontin. In addition, osteopontin attenuated angiotensin II-induced plasminogen activator inhibitor-1 expression. These studies show that osteopontin is a promoter and an inhibitor of inflammation, oxidative stress, and fibrosis that is capable of modulating angiotensin II-induced renal damage.

Reduction of proteinuria in adriamycin-induced nephropathy is associated with reduction of renal kidney injury molecule (Kim-1) over time

Tubulointerstitial lesions are important in the progression of proteinuric renal disease. Tubular kidney injury molecule-1 (Kim-1) is induced in acute renal injury and reversible as a natural course. Kim-1 is also present in chronic renal damage; however, the dynamics of Kim-1 in chronic renal damage and effects of antiproteinuric treatment on Kim-1 are unknown. We studied Kim-1 in adriamycin nephrosis (AN) before and after renin-angiotensin system blockade. A renal biopsy was taken 6 wk after adriamycin injection to study renal damage and Kim-1 expression. Subsequently, ACE inhibition (ACEi; n = 23), angiotensin II antagonist (AT(1A); n = 23), or vehicle (n = 10) was given for 6 wk; healthy rats served as controls (CON; n = 8). In AN, renal Kim-1 mRNA was induced 26-fold vs. CON at week 6, with further increase in vehicle to week 12 (40-fold) but was reduced by ACEi and AT(1A) to 10- and 12-fold vs. CON (P < 0.05 vs. week 6). Kim-1 protein was undetectable in CON; in AN, it was present in brush border of dilated tubules in areas with adjacent interstitial lesions. Renal Kim-1 protein levels increased from weeks 6-12 in vehicle and decreased in ACEi- and AT(1A)-treated groups (P < 0.05). In vehicle, urinary Kim-1 was increased (P < 0.05 vs. CON), with a reduction by ACEi and AT(1A) (P < 0.05 vs. vehicle). Renal and urinary Kim-1 correlated with proteinuria and interstitial damage cross-sectionally. Reductions in proteinuria and renal Kim-1 correlated, which was not associated by corresponding changes in tubulointerstitial fibrosis. In conclusion, on longitudinal follow-up during antiproteinuric treatment increased renal Kim-1 expression is reversible in proportion to proteinuria reduction, likely reflecting reversibility of early tubular injury, supporting its potential as a biomarker for tubulointerstitial processes of damage and repair.

Effect of renin-angiotensin-aldosterone system inhibition, dietary sodium restriction, and/or diuretics on urinary kidney injury molecule 1 excretion in nondiabetic proteinuric kidney disease: a post hoc analysis of a randomized controlled trial

BACKGROUND

Tubulointerstitial damage plays an important role in chronic kidney disease (CKD) with proteinuria. Urinary kidney injury molecule 1 (KIM-1) reflects tubular KIM-1 and is considered a sensitive biomarker for early tubular damage. We hypothesized that a decrease in proteinuria by using therapeutic interventions is associated with decreased urinary KIM-1 levels.

STUDY DESIGN

Post hoc analysis of a randomized, double-blind, placebo-controlled, crossover trial.

SETTING & PARTICIPANTS

34 proteinuric patients without diabetes from our outpatient renal clinic.

INTERVENTION

Stepwise 6-week interventions of losartan, sodium restriction (low-sodium [LS] diet), their combination, losartan plus hydrochlorothiazide (HCT), and the latter plus an LS diet.

OUTCOMES & MEASUREMENTS

Urinary excretion of KIM-1, total protein, and N-acetyl-beta-d-glucosaminidase (NAG) as a positive control for tubular injury.

RESULTS

Mean baseline urine protein level was 3.8 +/- 0.4 (SE) g/d, and KIM-1 level was 1,706 +/- 498 ng/d (increased compared with healthy controls; 74 ng/d). KIM-1 level was decreased by using placebo/LS (1,201 +/- 388 ng/d; P = 0.04), losartan/high sodium (1,184 +/- 296 ng/d; P = 0.09), losartan/LS (921 +/- 176 ng/d; P = 0.008), losartan/high sodium plus HCT (862 +/- 151 ng/d; P = 0.008) and losartan/LS plus HCT (743 +/- 170 ng/d; P = 0.001). The decrease in urinary KIM-1 levels paralleled the decrease in proteinuria (R = 0.523; P < 0.001), but not blood pressure or creatinine clearance. 16 patients reached target proteinuria with protein less than 1 g/d, whereas KIM-1 levels normalized in only 2 patients. Urinary NAG level was increased at baseline and significantly decreased during the treatment periods of combined losartan plus HCT only. The decrease in urinary NAG levels was not closely related to proteinuria.

LIMITATIONS

Post hoc analysis.

CONCLUSIONS

Urinary KIM-1 level was increased in patients with nondiabetic CKD with proteinuria and decreased in parallel with proteinuria by using losartan, sodium restriction, their combination, losartan plus HCT, and the latter plus sodium restriction. These results are consistent with the hypothesis of amelioration of proteinuria-induced tubular damage. Long-term studies are warranted to evaluate whether targeting treatment on KIM-1 can improve outcomes in patients with CKD with proteinuria.

Differential effects of sex steroids in young and aged female mRen2.Lewis rats: a model of estrogen and salt-sensitive hypertension

BACKGROUND

Male-female differences in the expression of hypertension and in end-organ damage are evident in both experimental models and human subjects, with males exhibiting a more rapid onset of cardiovascular disease and mortality than do females. The basis for these male-female differences is probably the balance of the complex effects of sex steroids (androgens, estrogen, progesterone) and their metabolites on the multiple regulatory systems that influence blood pressure (BP). A key target of estrogen and other steroids is likely to be the different components of the renin-angiotensin-aldosterone system (RAAS).

OBJECTIVE

The aim of this study was to review the current experimental evidence on the protective effects of estrogen in hypertensive models.

METHODS

The search terms estrogen , renin-aangiotensin-aldosterone system, renin receptor, salt-sensitivity, endorgan damage, hypertension, kidney, mRen2. Lewis, and injury markers were used to identify relevant publications in the PubMed database (restricted to the English language) from January 1990 to October 2007.

RESULTS

In a new congenic model that expresses the mouse renin 2 gene (mRen2. Lewis), estrogen depletion (via ovariectomy [OVX ]) in young rats was found to have a marked stimulatory effect on the progression of increased BP and cardiac dysfunction. Moreover, estrogen depletion exacerbated salt-sensitive hypertension and the extent of salt-induced cardiac and renal injury in young mRen2. Lewis rats, which probably reflected the inability to appropriately regulate various components of the RAAS. However, OVX in aged mRen2. Lewis rats conveyed renal protective effects from a high-salt diet compared with intact hypertensive littermates (64 weeks), and these effects were independent of changes in BP.

CONCLUSION

These studies in hypertensive mRen2. Lewis rats underscored the influence of ovarian hormones on BP and tissue injury, as well as the plasticity of this response, apparently due to age and salt status.

Pharmacological modulation of epithelial mesenchymal transition caused by angiotensin II. Role of ROCK and MAPK pathways

PURPOSE

Tubulointerstitial fibrosis is a final common pathway to end-stage chronic kidney diseases, which are characterized by elevated renal angiotensin II (AngII) production. This peptide participates in kidney damage inducing fibrosis and epithelial mesenchymal transition (EMT). Our aim was to describe potential therapeutic targets in AngII-induced EMT, investigating the blockade of different intracellular pathways.

METHODS

Studies were done in human tubular epithelial cells (HK2 cell line), evaluating changes in phenotype and EMT markers (Western blot and immunofluorescence).

RESULTS

Treatment of HK2 cells with AngII for 3 days caused transdifferentiation into myofibroblast-like cells. The blockade of MAPKs cascade, using specific inhibitors of p38 (SB203580), extracellular signal-regulated kinase1/2 (ERK; PD98059) and Jun N-terminal kinase (JNK) (SP600125), diminished AngII-induced EMT. The blockade of RhoA/ROCK pathway, by transfection of a RhoA dominant-negative vector or by ROCK inhibition with Y-27632 or fasudil, inhibited EMT caused by AngII. Connective tissue growth factor (CTGF) is a downstream mediator of AngII-induced EMT. MAPKs and ROCK inhibitors blocked CTGF overexpression induced by AngII. HMG-CoA reductase inhibitors, although blocked AngII-mediated kinases activation, only partially diminished EMT and did not regulate CTGF.

CONCLUSIONS

These data suggest a potential therapeutic use of kinase inhibitors in renal fibrosis.

Immunolocalization of Kim-1, RPA-1, and RPA-2 in kidney of gentamicin-, mercury-, or chromium-treated rats: relationship to renal distributions of iNOS and nitrotyrosine

Immunohistochemical studies for kidney injury molecule-1 (Kim-1), renal papillary antigen-1 (RPA-1), and renal papillary antigen-2 (RPA-2) were conducted to explore their relationship to inducible nitric oxide synthase (iNOS) and nitrotyrosine expression. Male Sprague-Dawley rats were exposed to gentamicin (100 mg/kg/day Gen, sc, for 3 days), mercury (0.25 mg Hg/kg, iv, single dose), or chromium (5 mg Cr/kg, sc, single dose) and kidney tissue was examined 24 hours or 72 hours after the last dose of the nephrotoxicant. Another group of kidneys was evaluated 24 hours after rats were administered 3 daily doses (50, 100, 150, 200, or 300 mg/kg/day) of Gen. Gen- and Cr-treated rats exhibited increased immunoreactivity of Kim-1, RPA-1, and RPA-2 largely in the S1/S2 segments and to a lesser extent in the S3 segments of the proximal tubule of the kidney, whereas Hg-treated rats showed increased immunoreactivity of Kim-1, RPA-1, and RPA-2 in the S3 segments. Up-regulation of Kim-1, RPA-1, and RPA-2 expression correlated with injured tubular epithelial cells and also correlated with immunoreactivity of iNOS and nitrotyrosine. It is possible that iNOS activation with nitrotyrosine production in injured nephron segments may be involved in the induction of Kim-1, RPA-1, and RPA-2 following exposure to nephrotoxicants.

High urinary excretion of kidney injury molecule-1 is an independent predictor of graft loss in renal transplant recipients

BACKGROUND

Chronic transplant dysfunction is characterized by renal function decline and proteinuria. Kidney injury molecule (KIM)-1, a transmembrane tubular protein with unknown function, is undetectable in normal kidneys, but markedly induced after injury. Urinary KIM-1 excretion has been quantified as biomarker of renal damage. We prospectively studied whether urinary KIM-1 predicts graft loss, independent of renal function and proteinuria.

METHODS

Renal transplant recipients (n=145) visiting our outpatient clinic between August 2001 and July 2003 collected 24-hour urine samples for assessment of baseline urinary KIM-1 excretion (microsphere-based Luminex technology), and were followed for graft loss.

RESULTS

Recipients participated at a median (interquartile range) of 6.0 (2.5-12.0) years posttransplant in baseline measurements. Follow-up beyond baseline was 4.0 (3.2-4.5) years. Urinary KIM-1 excretion was 0.72 (0.42-1.37) ng per 24 hours. Occurrence of graft loss increased over tertiles of KIM-1 excretion: 3 (6.3%), 11 (22.4%), and 17 cases (35.4%; P=0.001), respectively. High KIM-1 excretion was associated with proteinuria, low creatinine clearance, and high donor age (all P<0.01). In multivariate Cox regression analyses, prediction of graft loss by KIM-1 appeared independent of creatinine clearance, proteinuria, and donor age. Hazard ratios (95% CI) for the second and third tertile of KIM-1 excretion were 3.6 (0.9-13.5) and 5.1 (1.5-17.8) in the final model.

CONCLUSIONS

Urinary excretion of KIM-1 is an independent predictor of long-term graft loss and therefore a promising new biomarker in early prediction of graft loss.

Validation of putative genomic biomarkers of nephrotoxicity in rats

Drug-induced renal injury is a common finding in the early preclinical phase of drug development. But the specific genes responding to renal injury remain poorly defined. Identification of drug-induced gene changes is critical to provide insights into molecular mechanisms and detection of renal damage. To identify genes associated with the development of drug-induced nephrotoxicity, a literature survey was conducted and a panel of 48 genes was selected based on gene expression changes in multiple published studies. Male Sprague-Dawley rats were dosed daily for 1, 3 or 5 days to the known nephrotoxicants gentamicin, bacitracin, vancomycin and cisplatin, or the known hepatotoxicants ketoconazole, 1-naphthyl isothiocyanate and 4,4-diaminodiphenylmethane. Histopathological evaluation and clinical chemistry revealed renal proximal tubular necrosis in rats treated with the nephrotoxicants, but not from those treated with the hepatotoxicants. RNA was extracted from the kidney, and RT-PCR was performed to evaluate expression profiles of the selected genes. Among the genes examined, 24 genes are confirmed to be highly induced or repressed in rats treated with nephrotoxicants; further investigation identified that 5 of the 24 genes were also altered by hepatotoxicants. These data led to the identification of a set of genomic biomarker candidates whose expression in kidney is selectively regulated only by nephrotoxicants. Among those genes displaying the highest expression changes specifically in nephrotoxicant-treated rats were kidney injury molecule 1 (Kim1), lipocalin 2 (Lcn2), and osteopontin (Spp1). The establishment of such a genomic marker set offers a new tool in our ongoing quest to monitor nephrotoxicity.

Kidney injury molecule-1 expression in transplant biopsies is a sensitive measure of cell injury

Kidney injury molecule-1 (KIM-1) is a specific histological biomarker for diagnosing early tubular injury on renal biopsies. In this study, KIM-1 expression was quantitated in renal transplant biopsies by immunohistochemistry and correlated with renal function. None of the 25 protocol biopsies showed detectable tubular injury on histologic examination, yet 28% had focal positive KIM-1 expression. Proximal tubule KIM-1 expression was present in all biopsies from patients with histological changes showing acute tubular damage and deterioration of kidney function. In this group, higher KIM-1 staining predicted a better outcome with improved blood urea nitrogen (BUN), serum creatinine, and estimated glomerular filtration rate (eGFR) over an ensuing 18 months. KIM-1 was expressed focally in affected tubules in 92% of kidney biopsies from patients with acute cellular rejection. By contrast, there was little positive staining for Ki-67, a cell proliferation marker, in any of the groups. KIM-1 expression significantly correlated with serum creatinine and BUN, and inversely with the eGFR on the biopsy day. Our study shows that KIM-1 staining sensitively and specifically identified proximal tubular injury and correlated with the degree of renal dysfunction. KIM-1 expression is more sensitive than histology for detecting early tubular injury, and its level of expression in transplant biopsies may indicate the potential for recovery of kidney function.

Comparison of kidney injury molecule-1 and other nephrotoxicity biomarkers in urine and kidney following acute exposure to gentamicin, mercury, and chromium

Sensitive biomarkers are needed to detect kidney injury at the earliest stages. The objective of this study was to determine whether the appearance of kidney injury molecule-1 (Kim-1) protein ectodomain in urine and kidney injury molecule-1/hepatitis A viral cellular receptor-1 (Kim-1/Havcr1) gene expression in kidney tissue may be more predictive of renal injury after exposure to nephrotoxicants when compared to traditionally used biomarkers. Male Sprague-Dawley rats were injected with a range of doses of gentamicin, mercury (Hg; HgCl2), or chromium (Cr; K2Cr2O7). The results showed that increases in urinary Kim-1 and kidney Kim-1/Havcr1 gene expression paralleled the degree of severity of renal histopathology and were detected at lower doses of nephrotoxicants when compared to blood urea nitrogen (BUN), serum creatinine, and urinary N-acetyl-beta-D-glucosaminidase (NAG). In a time course study, urinary Kim-1 was elevated within 24 h after exposure to gentamicin (100 mg/kg), Hg (0.25 mg/kg), or Cr (5 mg/kg) and remained elevated through 72 h. NAG responses were nephrotoxicant dependent with elevations occurring early (gentamicin), late (Cr), or no change (Hg). At 72 h, after treatment with any of the three nephrotoxicants, there was increased Kim-1 immunoreactivity and necrosis involving approximately 50% of the proximal tubules; however, only urinary Kim-1 was significantly increased, while BUN, serum creatinine, and NAG were not different from controls. In rats treated with the hepatotoxicant galactosamine (1.1 mg/kg), serum alanine aminotransferase was increased, but no increase in urinary Kim-1 was observed. Urinary Kim-1 and kidney Kim-1/Havcr1 expression appear to be sensitive and tissue-specific biomarkers that will improve detection of early acute kidney injury following exposure to nephrotoxic chemicals and drugs.

Ovariectomy is protective against renal injury in the high-salt-fed older mRen2.Lewis rat

Studies in experimental animals and younger women suggest a protective role for estrogen; however, clinical trials may not substantiate this effect in older females. Therefore, the present study assessed the outcome of ovariectomy in older mRen2.Lewis rats subjected to a high-salt diet for 4 wk. Intact or ovariectomized (OVX, 15 wk of age) mRen2.Lewis rats were aged to 60 wk and then placed on a high-salt (HS, 8% sodium chloride) diet for 4 wk. Systolic blood pressures were similar between groups [OVX 169 ± 6 vs. Intact 182 ± 7 mmHg; P = 0.22] after the 4-wk diet; however, proteinuria [OVX 0.8 ± 0.2 vs. Intact 11.5 ± 2.6 mg/mg creatinine; P < 0.002, n = 6], renal interstitial fibrosis, glomerular sclerosis, and tubular casts were lower in OVX vs. Intact rats. Kidney injury molecule-1 mRNA, a marker of tubular damage, was 53% lower in the OVX HS group. Independent from blood pressure, OVX HS rats exhibited significantly lower cardiac (24%) and renal (32%) hypertrophy as well as lower C-reactive protein (28%). Circulating insulin-like growth factor-I (IGF-I) levels were not different between the Intact and OVX groups; however, renal cortical IGF-I mRNA and protein were attenuated in OVX rats [ P < 0.05, n = 6]. We conclude that ovariectomy in the older female mRen2.Lewis rat conveys protection against salt-dependent increase in renal injury.

Increased susceptibility of aging kidney to ischemic injury: identification of candidate genes changed during aging, but corrected by caloric restriction

Aging is associated with an increased incidence and severity of acute renal failure. However, the molecular mechanism underlying the increased susceptibility to injury remains undefined. These experiments were designed to investigate the influence of age on the response of the kidney to ischemic injury and to identify candidate genes that may mediate this response. Renal slices prepared from young (5 mo), aged ad libitum (aged-AL; 24 mo), and aged caloric-restricted (aged-CR; 24 mo) male Fischer 344 rats were subjected to ischemic stress (100% N(2)) for 0-60 min. As assessed by biochemical and histological evaluation, slices from aged-AL rats were more susceptible to injury than young counterparts. Importantly, caloric restriction attenuated the increased susceptibility to injury. In an attempt to identify the molecular pathway(s) underlying this response, microarray analysis was performed on tissue harvested from the same animals used for the viability experiments. RNA was isolated and the corresponding cDNA was hybridized to CodeLink Rat Whole Genome Bioarray slides. Subsequent gene expression analysis was performed using GeneSpring software. Using two-sample t-tests and a twofold cut-off, the expression of 92 genes was changed during aging and attenuated by caloric restriction, including claudin-7, kidney injury molecule-1 (Kim-1), and matrix metalloproteinase-7 (MMP-7). Claudin-7 gene expression peaked at 18 mo; however, increased protein expression in certain tubular epithelial cells was seen at 24 mo. Kim-1 gene expression was not elevated at 8 or 12 mo but was at 18 and 24 mo. However, changes in Kim-1 protein expression were only seen at 24 mo and corresponded to increased urinary levels. Importantly, these changes were attenuated by caloric restriction. MMP-7 gene expression was decreased at 8 mo, but an age-dependent increase was seen at 24 mo. Increased MMP-7 protein expression in tubular epithelial cells at 24 mo was correlated with the gene expression pattern. In summary, we identified genes changed by aging and changes attenuated by caloric restriction. This will facilitate investigation into the molecular mechanism mediating the age-related increase in susceptibility to injury.

Kidney injury molecule-1 is an early biomarker of cadmium nephrotoxicity

Cadmium (Cd) exposure results in injury to the proximal tubule characterized by polyuria and proteinuria. Kidney injury molecule-1 (Kim-1) is a transmembrane glycoprotein not normally detected in the mature kidney, but is upregulated and shed into the urine following nephrotoxic injury. In this study, we determine if Kim-1 might be a useful early biomarker of Cd nephrotoxicity. Male Sprague-Dawley rats were given daily injections of Cd for up to 12 weeks. Weekly urine samples were analyzed for Kim-1, protein, creatinine, metallothionein, and Clara cell protein CC-16. Significant levels of Kim-1 were detected in the urine by 6 weeks and continued to increase throughout the treatment period. This appearance of Kim-1 occurred 4-5 weeks before the onset of proteinuria, and 1-3 weeks before the appearance of metallothionein and CC-16. Higher doses of Cd gave rise to higher Kim-1 excretion. Reverse transcriptase-polymerase chain reaction (RT-PCR) expression analysis showed that Kim-1 transcript levels were increased after 6 weeks at the low dose of Cd. Immunohistochemical analysis showed that Kim-1 was present in proximal tubule cells of the Cd-treated rats. Our results suggest that Kim-1 may be a useful biomarker of early stages of Cd-induced proximal tubule injury.