Endothelial cells overexpressing CXCR1/2 are renoprotective in rats with acute kidney injury.

Inflammation that develops with the release of chemokines and cytokines during acute kidney injury (AKI) has been shown to participate in functional renal recovery. Although a major research focus has been on the role of macrophages, the family of C-X-C motif chemokines that promote neutrophil adherence and activation also increases with kidney ischemia-reperfusion (I/R) injury. This study tested the hypothesis that intravenous delivery of endothelial cells (ECs) that overexpress (C-X-C motif) chemokine receptors 1 and 2 (CXCR1 and CXCR2, respectively) improves outcomes in kidney I/R injury. Overexpression of CXCR1/2 enhanced homing of endothelial cells to I/R-injured kidneys and limited interstitial fibrosis, capillary rarefaction, and tissue injury biomarkers (serum creatinine concentration and urinary kidney injury molecule-1) following AKI and also reduced expression of P-selectin and the rodent (C-X-C motif) chemokine cytokine-induced neutrophil chemoattractant (CINC)-2ß as well as the number of myeloperoxidase-positive cells in the postischemic kidney. The serum chemokine/cytokine profile, including CINC-1, showed similar reductions. These findings were not observed in rats given endothelial cells transduced with an empty adenoviral vector (null-ECs) or a vehicle alone. These data indicate that extrarenal endothelial cells that overexpress CXCR1 and CXCR2, but not null-ECs or vehicle alone, reduce I/R kidney injury and preserve kidney function in a rat model of AKI.NEW & NOTEWORTHY Inflammation facilitates kidney ischemia-reperfusion (I/R) injury. Endothelial cells (ECs) that were modified to overexpress (C-X-C motif) chemokine receptor (CXCR)1/2 (CXCR1/2-ECs) were injected immediately following kidney I/R injury. The interaction of CXCR1/2-ECs, but not ECs transduced with an empty adenoviral vector, with injured kidney tissue preserved kidney function and reduced production of inflammatory markers, capillary rarefaction, and interstitial fibrosis. The study highlights a functional role for the C-X-C chemokine pathway in kidney damage following I/R injury.

Matrix metalloproteinase-9 regulates afferent arteriolar remodeling and function in hypertension-induced kidney disease.

This study tested if matrix metalloproteinase (MMP)-9 promoted microvascular pathology that initiates hypertensive (HT) kidney disease in salt-sensitive (SS) Dahl rats. SS rats lacking Mmp9 (Mmp9-/-) and littermate control SS rats were studied after one week on a normotensive 0.3% sodium chloride (Pre-HT SS and Pre-HT Mmp9-/-) or a hypertension-inducing diet containing 4.0% sodium chloride (HT SS and HT Mmp9-/-). Telemetry-monitored blood pressure of both the HT SS and HT Mmp9-/- rats increased and did not differ. Kidney microvessel transforming growth factor-beta 1 (Tgfb1) mRNA did not differ between Pre-HT SS and Pre-HT Mmp9-/- rats, but with hypertension and expression of Mmp9 and Tgfb1 increased in HT SS rats, along with phospho-Smad2 labeling of nuclei of vascular smooth muscle cells, and with peri-arteriolar fibronectin deposition. Loss of MMP-9 prevented hypertension-induced phenotypic transformation of microvascular smooth muscle cells and the expected increased microvascular expression of pro-inflammatory molecules. Loss of MMP-9 in vascular smooth muscle cells in vitro prevented cyclic strain-induced production of active TGF-ß1 and phospho-Smad2/3 stimulation. Afferent arteriolar autoregulation was impaired in HT SS rats but not in HT Mmp9-/- rats or the HT SS rats treated with doxycycline, an MMP inhibitor. HT SS but not HT Mmp9-/- rats showed decreased glomerular Wilms Tumor 1 protein-positive cells (a marker of podocytes) along with increased urinary podocin and nephrin mRNA excretion, all indicative of glomerular damage. Thus, our findings support an active role for MMP-9 in a hypertension-induced kidney microvascular remodeling process that promotes glomerular epithelial cell injury in SS rats.

Aristolochic acid-induced nephropathy is attenuated in mice lacking the neutral amino acid transporter B0AT1 (Slc6a19).

B0AT1 (Slc6a19) mediates absorption of neutral amino acids in the small intestine and in the kidneys, where it is primarily expressed in early proximal tubules (S1-S2). To determine the role of B0AT1 in nephropathy induced by aristolochic acid (AA), which targets the proximal tubule, littermate female B0AT1-deficient (Slc6a19-/-), heterozygous (Slc6a19+/-), and wild-type (WT) mice were administered AA (10 mg/kg ip) or vehicle every 3 days for 3 wk, and analyses were performed after the last injection or 3 wk later. Vehicle-treated mice lacking Slc6a19 showed normal body and kidney weight and plasma creatinine versus WT mice. The urinary glucose-to-creatinine ratio (UGCR) and urinary albumin-to-creatinine ratio (UACR) were two to four times higher in vehicle-treated Slc6a19-/- versus WT mice, associated with lesser expression of early proximal transporters Na+-glucose cotransporter 2 and megalin, respectively. AA caused tubular injury independently of B0AT1, including robust increases in cortical mRNA expression of p53, p21, and hepatitis A virus cellular receptor 1 (Havcr1), downregulation of related proximal tubule amino acid transporters B0AT2 (Slc6a15), B0AT3 (Slc6a18), and Slc7a9, and modest histological tubular damage and a rise in plasma creatinine. Absence of B0AT1, however, attenuated AA-induced cortical upregulation of mRNA markers of senescence (p16), inflammation [lipocalin 2 (Lcn2), C-C motif chemokine ligand 2 (Ccl2), and C-C motif chemokine receptor 2 (Ccr2)], and fibrosis [tissue inhibitor of metallopeptidase 1 (Timp1), transforming growth factor-ß1 (Tgfb1), and collagen type I-α1 (Col1a1)], associated with lesser fibrosis staining, lesser suppression of proximal tubular organic anion transporter 1, restoration of Na+-glucose cotransporter 2 expression, and prevention of the AA-induced fivefold increase in the urinary albumin-to-creatinine ratio observed in WT mice. The data suggest that proximal tubular B0AT1 is important for the physiology of renal glucose and albumin retention but potentially deleterious for the kidney response following AA-induced kidney injury.NEW & NOTEWORTHY Based on insights from studies manipulating glucose transport, the hypothesis has been proposed that inhibiting intestinal uptake or renal reabsorption of energy substrates has unique therapeutic potential to improve metabolic disease and kidney outcome in response to injury. The present study takes this idea to B0AT1, the major transporter for neutral amino acids in the intestine and kidney, and shows that its absence attenuates aristolochic acid-induced nephropathy.

Clinicopathologic predictors of renal outcomes in light chain cast nephropathy: a multicenter retrospective study.

Light chain cast nephropathy (LCCN) in multiple myeloma often leads to severe and poorly reversible acute kidney injury. Severe renal impairment influences the allocation of chemotherapy and its tolerability; it also affects patient survival. Whether renal biopsy findings add to the clinical assessment in predicting renal and patient outcomes in LCCN is uncertain. We retrospectively reviewed clinical presentation, chemotherapy regimens, hematologic response, and renal and patient outcomes in 178 patients with biopsy-proven LCCN from 10 centers in Europe and North America. A detailed pathology review, including assessment of the extent of cast formation, was performed to study correlations with initial presentation and outcomes. Patients presented with a mean estimated glomerular filtration rate (eGFR) of 13 ± 11 mL/min/1.73 m2, and 82% had stage 3 acute kidney injury. The mean number of casts was 3.2/mm2 in the cortex. Tubulointerstitial lesions were frequent: acute tubular injury (94%), tubulitis (82%), tubular rupture (62%), giant cell reaction (60%), and cortical and medullary inflammation (95% and 75%, respectively). Medullary inflammation, giant cell reaction, and the extent of cast formation correlated with eGFR value at LCCN diagnosis. During a median follow-up of 22 months, mean eGFR increased to 43 ± 30 mL/min/1.73 m2. Age, ß2-microglobulin, best hematologic response, number of cortical casts per square millimeter, and degree of interstitial fibrosis/tubular atrophy (IFTA) were independently associated with a higher eGFR during follow-up. This eGFR value correlated with overall survival, independently of the hematologic response. This study shows that extent of cast formation and IFTA in LCCN predicts the quality of renal response, which, in turn, is associated with overall survival.

Renoprotective effect of Stat1 deletion in murine aristolochic acid nephropathy.

Injured tubule epithelium stimulates a profibrotic milieu that accelerates loss of function in chronic kidney disease (CKD). This study tested the role of signal transducer and activator of transcription 1 (STAT1) in the progressive loss of kidney function in aristolochic acid (AA) nephropathy, a model of CKD. Mean serum creatinine concentration increased in wild-type (WT) littermates treated with AA, whereas Stat1-/- mice were protected. Focal increases in the apical expression of kidney injury molecule (KIM)-1 were observed in the proximal tubules of WT mice with AA treatment but were absent in Stat1-/- mice in the treatment group as well as in both control groups. A composite injury score, an indicator of proximal tubule injury, was reduced in Stat1-/- mice treated with AA. Increased expression of integrin-ß6 and phosphorylated Smad2/3 in proximal tubules as well as interstitial collagen and fibronectin were observed in WT mice following AA treatment but were all decreased in AA-treated Stat1-/- mice. The data indicated that STAT1 activation facilitated the development of progressive kidney injury and interstitial fibrosis in AA nephropathy.

Restoration of afferent arteriolar autoregulatory behavior in ischemia-reperfusion injury in rat kidneys.

Renal autoregulation is critical in maintaining stable renal blood flow (RBF) and glomerular filtration rate (GFR). Renal ischemia-reperfusion (IR)-induced kidney injury is characterized by reduced RBF and GFR. The mechanisms contributing to renal microvascular dysfunction in IR have not been fully determined. We hypothesized that increased reactive oxygen species (ROS) contributed to impaired renal autoregulatory capability in IR rats. Afferent arteriolar autoregulatory behavior was assessed using the blood-perfused juxtamedullary nephron preparation. IR was induced by 60 min of bilateral renal artery occlusion followed by 24 h of reperfusion. Afferent arterioles from sham rats exhibited normal autoregulatory behavior. Stepwise increases in perfusion pressure caused pressure-dependent vasoconstriction to 65 ± 3% of baseline diameter (13.2 ± 0.4 µm) at 170 mmHg. In contrast, pressure-mediated vasoconstriction was markedly attenuated in IR rats. Baseline diameter averaged 11.7 ± 0.5 µm and remained between 90% and 101% of baseline over 65-170 mmHg, indicating impaired autoregulatory function. Acute antioxidant administration (tempol or apocynin) to IR kidneys for 20 min increased baseline diameter and improved autoregulatory capability, such that the pressure-diameter profiles were indistinguishable from those of sham kidneys. Furthermore, the addition of polyethylene glycol superoxide dismutase or polyethylene glycol-catalase to the perfusate blood also restored afferent arteriolar autoregulatory responsiveness in IR rats, indicating the involvement of superoxide and/or hydrogen peroxide. IR elevated mRNA expression of NADPH oxidase subunits and monocyte chemoattractant protein-1 in renal tissue homogenates, and this was prevented by tempol pretreatment. These results suggest that ROS accumulation, likely involving superoxide and/or hydrogen peroxide, impairs renal autoregulation in IR rats in a reversible fashion.NEW & NOTEWORTHY Renal ischemia-reperfusion (IR) leads to renal microvascular dysfunction manifested by impaired afferent arteriolar autoregulatory efficiency. Acute administration of scavengers of reactive oxygen species, polyethylene glycol-superoxide dismutase, or polyethylene glycol-catalase following renal IR restored afferent arteriolar autoregulatory capability in IR rats, indicating that renal IR led to reversible impairment of afferent arteriolar autoregulatory capability. Intervention with antioxidant treatment following IR may improve outcomes in patients by preserving renovascular autoregulatory function and potentially preventing the progression to chronic kidney disease after acute kidney injury.

UAB-UCSD O'Brien Center for Acute Kidney Injury Research.

Acute kidney injury (AKI) remains a significant clinical problem through its diverse etiologies, the challenges of robust measurements of injury and recovery, and its progression to chronic kidney disease (CKD). Bridging the gap in our knowledge of this disorder requires bringing together not only the technical resources for research but also the investigators currently endeavoring to expand our knowledge and those who might bring novel ideas and expertise to this important challenge. The University of Alabama at Birmingham-University of California-San Diego O'Brien Center for Acute Kidney Injury Research brings together technical expertise and programmatic and educational efforts to advance our knowledge in these diverse issues and the required infrastructure to develop areas of novel exploration. Since its inception in 2008, this O'Brien Center has grown its impact by providing state-of-the-art resources in clinical and preclinical modeling of AKI, a bioanalytical core that facilitates measurement of critical biomarkers, including serum creatinine via LC-MS/MS among others, and a biostatistical resource that assists from design to analysis. Through these core resources and with additional educational efforts, our center has grown its investigator base to include >200 members from 51 institutions. Importantly, this center has translated its pilot and catalyst funding program with a $37 return per dollar invested. Over 500 publications have resulted from the support provided with a relative citation ratio of 2.18 ± 0.12 (iCite). Through its efforts, this disease-centric O'Brien Center is providing the infrastructure and focus to help the development of the next generation of researchers in the basic and clinical science of AKI. This center creates the promise of the application at the bedside of the advances in AKI made by current and future investigators.

Gene knockout of the Na+-glucose cotransporter SGLT2 in a murine model of acute kidney injury induced by ischemia-reperfusion.

In the early proximal tubule, Na+-glucose cotransporter 2 (SGLT2) mediates the bulk of renal glucose reabsorption. Gene deletion in mice (Sglt2-/-) was used to determine the role of SGLT2 in acute kidney injury induced by bilateral ischemia-reperfusion (IR). In Sglt2-/- and littermate wild-type mice, plasma creatinine increased similarly on day 1 after IR. This was associated with an equal increase in both genotypes in the urinary kidney injury molecule-1-to-creatinine ratio, a tubular injury marker, and similarly reduced urine osmolality and increased plasma osmolality, indicating impaired urine concentration. In both IR groups, FITC-sinistrin glomerular filtration rate was equally reduced on day 14, and plasma creatinine was similarly and incompletely restored on day 23. In Sglt2-/- mice subjected to IR, fractional urinary glucose excretion was increased on day 1 but reduced and associated with normal renal Na+-glucose cotransporter 1 (Sglt1) mRNA expression on day 23, suggesting temporary SGLT1 suppression. In wild-type mice subjected to IR, renal Sglt1 mRNA was likewise normal on day 23, whereas Sglt2 mRNA was reduced by 57%. In both genotypes, IR equally reduced urine osmolality and renal mRNA expression of the Na+-K+-2Cl- cotransporter and renin on day 23, suggesting thick ascending limb dysfunction, and similarly increased renal mRNA expression of markers of injury, inflammation, oxidative stress, and fibrosis (kidney injury molecule-1, neutrophil gelatinase-associated lipocalin, monocyte chemoattractant protein-1, transforming growth factor-ß1, NADPH oxidase-2, and collagen type 1). This was associated with equal increases in kidney histological damage scores and similar degree of capillary loss in both genotypes. The data indicate that genetic deletion of SGLT2 did not protect the kidneys in the initial injury phase or the subsequent recovery phase in a mouse model of IR-induced acute kidney injury.

Avian erythroblastosis virus E26 oncogene homolog-1 (ETS-1) plays a role in renal microvascular pathophysiology in the Dahl salt-sensitive rat.

Prior studies reported that haploinsufficiency of the transcription factor ETS-1 is renoprotective in Dahl salt-sensitive rats, but the mechanism is unclear. Here, we tested whether ETS-1 is involved in hypertension-induced renal microvascular pathology and autoregulatory impairment. Hypertension was induced in salt-sensitive rats and salt-sensitive rats that are heterozygous with 1 wild-type or reference allele of Ets1 (SSEts1+/-) by feeding a diet containing 4% sodium chloride for 1 week. Increases in blood pressure did not differ. However, phosphorylated ETS-1 increased in afferent arterioles of hypertensive salt-sensitive rats, but not in hypertensive SSEts1+/- rats. Afferent arterioles of hypertensive salt-sensitive rats showed increased monocyte chemotactic protein-1 expression and infiltration of CD68 positive monocytes/macrophages. Isolated kidney microvessels showed increased mRNA expression of vascular cell adhesion molecule, intercellular adhesion molecule, P-selectin, fibronectin, transforming growth factor-ß, and collagen I in hypertensive salt-sensitive rats compared with hypertensive SSEts1+/- rats. Using the in vitro blood-perfused juxtamedullary nephron preparation, pressure-mediated afferent arteriolar responses were significantly blunted in hypertensive salt-sensitive rats compared to hypertensive SSEts1+/- rats. Over a 65-170 mm Hg pressure range tested baseline arteriolar diameters averaged 15.1 µm and remained between 107% and 89% of baseline diameter in hypertensive salt-sensitive rats vs. 114% and 73% in hypertensive SSEts1+/- rats (significantly different). Thus, ETS-1 participates in renal arteriolar pathology and autoregulation and thereby is involved in hypertension-mediated kidney injury in salt-sensitive rats.

Novel Paradigms of Salt and Hypertension.

Salt resistance/sensitivity refers specifically to the effect of dietary sodium chloride (salt) intake on BP. Increased dietary salt intake promotes an early and uniform expansion of extracellular fluid volume and increased cardiac output. To compensate for these hemodynamic changes and maintain constant BP in salt resistance, renal and peripheral vascular resistance falls and is associated with an increase in production of nitric oxide. In contrast, the decline in peripheral vascular resistance and the increase in nitric oxide are impaired or absent in salt sensitivity, promoting an increase in BP in these individuals. Endothelial dysfunction may pose a particularly significant risk factor in the development of salt sensitivity and subsequent hypertension. Vulnerable salt-sensitive populations may have in common underlying endothelial dysfunction due to genetic or environmental influences. These individuals may be very sensitive to the hemodynamic stress of increased effective blood volume, setting in motion untoward molecular and biochemical events that lead to overproduction of TGF-ß, oxidative stress, and limited bioavailable nitric oxide. Finally, chronic high-salt ingestion produces endothelial dysfunction, even in salt-resistant subjects. Thus, the complex syndrome of salt sensitivity may be a function of the endothelium, which is integrally involved in the vascular responses to high salt intake.

Haploinsufficiency of the Transcription Factor Ets-1 Is Renoprotective in Dahl Salt-Sensitive Rats.

Studies using Dahl salt-sensitive (SS) rats identified specific quantitative trait loci that predispose animals to hypertension-associated albuminuria and kidney injury. We explored the hypothesis that kidney-specific expression of the transcription factor Ets-1, located within one of these loci on chromosome 8, mediates glomerular injury in SS hypertension. During the first week on a high-salt diet, SS rats and SS rats with only one functioning Ets-1 gene (ES rats) demonstrated similar increases in BP. However, serum creatinine concentration, albuminuria, and glomerular expression of ETS-1 and two ETS-1 targets, MCP-1 and MMP2, did not increase as substantially in ES rats as in SS rats. Mean BP subsequently increased further in SS rats and remained higher than that of ES rats for the rest of the study. After 4 weeks of high-salt intake, ES rats still showed a lower mean serum creatinine concentration and less albuminuria, as well as less histologic evidence of glomerular injury and kidney fibrosis, than SS rats did. To investigate the specific contribution of renal Ets-1, we transplanted kidneys from ES or SS rats into salt-resistant SS-Chr 13BN/McwiCrl (SS-13BN) rats. Within 10 days on a high-salt diet, BP increased similarly in ES and SS allograft recipients, becoming significantly higher than the BP of control isograft recipients. However, mean serum creatinine concentration and albuminuria remained lower in ES allograft recipients than in SS allograft recipients at 2 weeks, and ES allografts showed less glomerular injury and interstitial fibrosis. In conclusion, reduced renal expression of ETS-1 prevented hypertension-associated kidney injury in SS rats.

Family history of hematologic malignancies and risk of multiple myeloma: differences by race and clinical features.

PURPOSE: Multiple myeloma (MM) is the most common hematologic malignancy affecting Blacks in the USA, with standardized incidence rates that are twofold to threefold higher than Whites. The rationale for the disparity is unclear. METHODS: Using participants enrolled in the Molecular And Genetic Epidemiology study of myeloma (259 MM cases; 461 controls), we examined the risk of MM associated with family history of cancer, differences by race and among cases, defining clinical features. Risk estimates were calculated using odds ratios and corresponding 95% confidence intervals from logistic regression adjusted for confounders. RESULTS: Overall, MM risk in cases with relatives affected with any hematologic malignancy was significantly elevated compared to controls (OR 1.89, 95% CI 1.25-2.86). Myeloma risk associated with a family history of MM was higher than the risk associated with any hematologic malignancy (OR 3.75, 95% CI 1.75-8.05), and the effect was greater for Blacks (OR 20.9, 95% CI 2.59-168) than Whites (OR 2.04, 95% 0.83-5.04), among cases with early onset (≤60 years; OR 4.58, 95% CI 1.21-17.3) and with increasing numbers of affected relatives (p trend = 0.001). Overall, frequencies of end organ damage differed in cases with relatives affected with any hematologic malignancy and significantly more cases exhibited κ light chain restriction (OR 3.23, 95% CI 1.13-9.26). CONCLUSIONS: The excess risk of MM observed in Blacks and the variation in clinical features observed in MM patients according to family history of hematologic malignancy may be attributed to a shared germline and environmental susceptibility.

Transforming growth factor-ß mediates endothelial dysfunction in rats during high salt intake.

Endothelial dysfunction has been shown to be predictive of subsequent cardiovascular events and death. Through a mechanism that is incompletely understood, increased dietary salt intake promotes endothelial dysfunction in healthy, salt-resistant humans. The present study tested the hypothesis that dietary salt-induced transforming growth factor (TGF)-ß promoted endothelial dysfunction and salt-dependent changes in blood pressure (BP). Sprague-Dawley rats that received diets containing 0.3% NaCl [low salt (LS)] or 8.0% NaCl [high salt (HS)] were treated with vehicle or SB-525334, a specific inhibitor of TGF-ß receptor I/activin receptor-like kinase 5, beginning on day 5. BP was monitored using radiotelemetry in four groups of rats (LS, LS + SB-525334, HS, and HS + SB-525334) for up to 14 days. By day 14 of the study, mean daytime systolic BP and mean pulse pressure of the HS group treated with vehicle was greater than those in the other three groups; mean daytime systolic BP and pulse pressure of the HS + SB-525334 group did not differ from the LS and LS + SB-525334-treated groups. Whereas mean systolic BP, mean diastolic BP, and mean arterial pressure did not differ among the groups on the seventh day of the study, endothelium-dependent vasorelaxation was impaired specifically in the HS group; treatment with the activin receptor-like kinase 5 inhibitor prevented the dietary HS intake-induced increases in phospho-Smad2 (Ser(465/467)) and NADPH oxidase-4 in endothelial lysates and normalized endothelial function. These findings suggest that HS-induced endothelial dysfunction and the development of salt-dependent increases in BP were related to endothelial TGF-ß signaling.

The use of immunoglobulin light chain assays in the diagnosis of paraprotein-related kidney disease.

Kidney involvement is common in paraprotein-related diseases. A diversity of clinical presentations and histopathological features can occur secondary to tissue injury caused by precipitation or deposition of a clonal immunoglobulin, usually an immunoglobulin light chain. The paraprotein is either produced by multiple myeloma or by a clone of B-cell lineage that does not fulfill diagnostic criteria for multiple myeloma. The recent introduction of serum immunoglobulin free light chain assays, which accurately quantify both light chain isotypes to produce a ratio that indicates the presence or absence of a light chain paraprotein, is a major clinical development. However, as the interpretation of the assay can be challenging, the aim of this review is to clarify the role of serum and urinary light chain assays in the screening and diagnosis of paraprotein-related kidney disease.

Sodium and potassium regulate endothelial phospholipase C-γ and Bmx.

The amount of Na(+) and K(+) in the diet promotes significant changes in endothelial cell function. In the present study, a series of in vitro and in vivo experiments determined the role of Na(+) and K(+) in the regulation of two pleckstrin homology domain-containing intracellular signaling molecules, phospholipase C (PLC)-γ1 and epithelial and endothelial tyrosine kinase/bone marrow tyrosine kinase on chromosome X (Bmx), and agonist-generated Ca(2+) signaling in the endothelium. Extracellular K(+) concentration regulated the levels of activated PLC-γ1, Bmx, and carbachol-stimulated intracellular Ca(2+) mobilization in human endothelial cells. Additional experiments confirmed that high-conductance Ca(2+)-activated K(+) channels and phosphatidylinositol 3-kinase mediated these effects. The content of Na(+) and K(+) in the diet also regulated Bmx levels in endothelial cells and activated PLC-γ1 levels in rats in vivo. The effects of dietary K(+) on Bmx were more pronounced in rats fed a high-salt diet compared with rats fed a low-salt diet. These experiments elucidated an endothelial cell signaling mechanism regulated by electrolytes, further demonstrating an integral relationship between endothelial cell function and dietary Na(+) and K(+) content.

Nitric oxide and carbon monoxide antagonize TGF-ß through ligand-independent internalization of TßR1/ALK5.

Transforming growth factor (TGF)-ß plays a central role in vascular homeostasis and in the pathology of vascular disease. There is a growing appreciation for the role of nitric oxide (NO) and carbon monoxide (CO) as highly diffusible, bioactive signaling molecules in the vasculature. We hypothesized that both NO and CO increase endocytosis of TGF-ß receptor type 1 (TßR1) in vascular smooth muscle cells (VSMCs) through activation of dynamin-2, shielding cells from the effects of circulating TGF-ß. In this study, primary cultures of VSMCs from Sprague-Dawley rats were treated with NO-releasing molecule 3 (a NO chemical donor), CO-releasing molecule 2 (a CO chemical donor), or control. NO and CO stimulated dynamin-2 activation in VSMCs. NO and CO promoted time- and dose-dependent endocytosis of TßR1. By decreasing TßR1 surface expression through this dynamin-2-dependent process, NO and CO diminished the effects of TGF-ß on VSMCs. These findings help explain an important mechanism by which NO and CO signal in the vasculature by decreasing surface expression of TßR1 and the cellular response to TGF-ß.

Distinct populations of label-retaining cells in the adult kidney are defined temporally and exhibit divergent regional distributions.

DNA label-retention, or retention of a thymidine analog, is a characteristic of slow cycling cells and has been used to identify stem cells in several organ systems. Recent findings have demonstrated inconsistent localization of label-retaining cells (LRCs) in the kidney. Differences in the dose and timing of administration of deoxyuridine, the length of the chase period, and the species of animal used have made understanding the distinctions between these findings difficult. In the present studies, we utilized a dual loading scheme in the same animal to demonstrate that the cells labeled at different ages identified independent populations of LRC that distributed globally in an anti-parallel manner in the kidney. Loading with a DNA label in neonates identified LRC more often in the papilla, while administering the DNA label in adult mice identified LRC prominently in the cortex and the outer medulla. Furthermore, the tissue compartment distribution (epithelial-endothelial-interstitial) as well as the specific distribution within the nephron epithelia differed for these populations. These findings highlighted the complexity of the dynamics of cell proliferation in the kidney throughout the postnatal and adult period and call attention to the confusion associated with the term "label-retaining cells" for different timings of the loading and chase periods. This study indicated that the results of previous studies should be viewed as nonoverlapping and that further studies are needed to ascertain the role of each of these populations in the steady-state maintenance and injury recovery of the kidney.

Community mobility among older adults with reduced kidney function: a study of life-space.

BACKGROUND: Life-Space Assessment captures community mobility and social participation and quantifies the distance, frequency, and independence obtained as an older adult moves through his or her environment. Reduced estimated glomerular filtration rate (eGFR) is associated with decline in activities of daily living among older adults, but less is known about the association of eGFR with restrictions in mobility. STUDY DESIGN: Prospective observational cohort study. SETTING & PARTICIPANTS: Community-dwelling Medicare beneficiaries from the University of Alabama at Birmingham Study of Aging who had serum creatinine measured during a baseline in-home study visit and completed at least one telephone follow-up (N = 390). PREDICTOR: eGFR ≥ 60, 45-59, and <45 mL/min/1.73 m(2). OUTCOME: Life-space mobility trajectory. MEASUREMENTS: Life-space mobility was evaluated by telephone every 6 months for up to 4.5 years using the previously validated Life-Space Assessment. Scores using this tool range from 0-120 (higher scores indicate greater mobility). RESULTS: Mean age of the 390 participants was 77.6 ± 5.8 (SD) years, 41% were African American, 50.5% were women; 30.0% had eGFR of 45-59 mL/min/1.73 m(2), and 20.2% had eGFR < 45 mL/min/1.73 m(2). Age-, race-, and sex-adjusted mean baseline life-space mobility scores were 64.8(95% CI, 62.0-67.6), 63.8 (95% CI, 60.3-67.4), and 58.3 (95% CI, 53.8-62.7) among those with eGFR categories ≥ 60, 45-59, and <45 mL/min/1.73 m(2), respectively. Compared with those with eGFRs ≥ 60 mL/min/1.73 m(2), a more rapid decline in life-space mobility was found among those with eGFRs < 45 mL/min/1.73 m(2), though this did not reach statistical significance (P=0.06); a similar effect was not seen among those with eGFRs of 45-59 mL/min/1.73 m(2) (P=0.3). LIMITATIONS: Urinary albumin or longitudinal measures of eGFR were not available. CONCLUSIONS: eGFR < 45 mL/min/1.73 m(2) was associated with a trend toward a more rapid decline in life-space mobility among community-dwelling older adults. Findings should be confirmed in a larger population.

Pivotal role of apoptosis signal-regulating kinase 1 in monoclonal free light chain-mediated apoptosis.

Renal failure, a major complication associated with multiple myeloma, is usually related to deposition of monoclonal immunoglobulin free light chains (FLCs) and directly contributes to morbidity and mortality in this disease. The present study focused on the cytotoxic effects of monoclonal FLCs. Human proximal tubular epithelial cells (HK-2) were examined after incubation with two human monoclonal FLCs (termed κ2 and λ3). Incubation of HK-2 cells for 24 and 48 hours with either FLCs at 1 mg/mL promoted activation of caspase-9 and caspase-3 and increased the rate of apoptosis. Because prior studies demonstrated that FLCs generated intracellular oxidative stress, our studies focused on the redox-sensitive mitogen-activated protein kinase kinase kinase known as apoptosis signal-regulating kinase 1 (ASK1). A time-dependent increase in phosphorylation of ASK1 at T845, indicating activation of this enzyme, was observed. Small interfering RNA designed to reduce ASK1 expression in HK-2 cells successfully decreased ASK1, which was confirmed by Western blot analysis. Incubation of ASK1-depleted HK-2 cells with the two FLCs prevented the increase in apoptosis while pretreating HK-2 cell with nontargeting small interfering RNA did not prevent FLCs-mediated apoptosis. The combined data demonstrate that monoclonal FLCs activated the intrinsic apoptotic pathway in renal epithelial cells by activation of ASK1.

KDOQI US commentary on the 2012 KDIGO clinical practice guideline for management of blood pressure in CKD.

In response to the 2012 KDIGO (Kidney Disease: Improving Global Outcomes) guideline for blood pressure management in patients with chronic kidney disease not on dialysis, the National Kidney Foundation organized a group of US experts in hypertension and transplant nephrology to review the recommendations and comment on their relevancy in the context of current US clinical practice and concerns. The overriding message was the dearth of clinical trial evidence to provide strong evidence-based recommendations. For patients with CKD with normal to mildly increased albuminuria, goal blood pressure has been relaxed to ≤140/90 mm Hg for both diabetic and nondiabetic patients. In contrast, KDIGO continues to recommend goal blood pressure ≤130/80 mm Hg for patients with chronic kidney disease with moderately or severely increased albuminuria and for all renal transplant recipients regardless of the presence of proteinuria, without supporting data. The expert panel thought the KDIGO recommendations were generally reasonable but lacking in sufficient evidence support and that additional studies are greatly needed.