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Because of the less-than-robust response to therapy and impact on choice of optimal chemotherapy and prognosis, chronic kidney disease has drawn attention in the treatment of multiple myeloma, a malignant hematologic disorder that can produce significant amounts of monoclonal immunoglobulin free light chains (FLCs). These low-molecular-weight proteins are relatively freely filtered through the glomerulus and are reabsorbed by the proximal tubule. The present study demonstrated that during the process of metabolism of immunoglobulin FLCs, ROS activated the STAT1 pathway in proximal tubule epithelium. STAT1 activation served as the seminal signaling molecule that produced the proinflammatory molecule IL-1[beta], as well as the profibrotic agent TGF-[beta] by this portion of the nephron. These effects occurred in vivo and were produced specifically by the generation of hydrogen peroxide by the [V.sub.L] domain of the light chain. To the extent that the experiments reflect the human condition, these studies offer insights into the pathogenesis of progressive kidney failure in the setting of lymphoproliferative disorders, such as multiple myeloma, that feature increased circulating levels of monoclonal immunoglobulin fragments that require metabolism by the kidney., Introduction Multiple myeloma, a malignant plasma cell disorder, has an incidence rate of approximately 1.1% among all malignancies and constitutes 12%-13% of hematologic malignancies in the United States (1). Nearly [...]

A common renal complication of multiple myeloma is 'myeloma kidney,' a condition also known as cast nephropathy. The renal lesions (casts) are directly related to the production of monoclonal immunoglobulin free light chains (FLCs), which coprecipitate with Tamm-Horsfall glycoprotein (THP) in the lumen of the distal nephron, obstructing tubular fluid flow. Here, we report that analysis of the binding interaction between FLCs and THP demonstrates that the secondary structure and key amino acid residues on the complementarity-determining region 3 (CDR3) of FLCs are critically important determinants of the molecular interaction with THP. The findings permitted development of a cyclized competitor peptide that demonstrated strong inhibitory capability in the binding of FLCs to THP in vitro. When used in a rodent model of cast nephropathy, this cyclized peptide construct served as an effective inhibitor of intraluminal cast formation and prevented the functional manifestations of acute kidney injury in vivo. These experiments provide proof of concept that intraluminal cast formation is integrally involved in the pathogenesis of acute kidney injury from cast nephropathy. Further, the data support a clinically relevant approach to the management of renal failure in the setting of multiple myeloma., Introduction One of the functions of the kidney is to filter and metabolize low molecular weight proteins that include immunoglobulin free light chains (FLCs). Polyclonal FLCs are secreted normally in [...]

Sanders PW. Vascular consequences of dietary salt intake. Am J Physiol Renal Physiol 297: F237-F243, 2009. First published April 1, 2009; doi: 10.1152/ajprenal.00027.2009.-Animal and human studies support an untoward effect of excess dietary NaCl (salt) intake on cardiovascular and renal function and life span. Recent work has promoted the concept that the endothelium, in particular, reacts to changes in dietary salt intake through a complex series of events that are independent of blood pressure and the renin-angiotensin-aldosterone axis. The cellular signaling events culminate in the intravascular production of transforming growth factor-[beta] (TGF-[beta]) and nitric oxide in response to increased salt intake. Plasticity of the endothelium is integral in the vascular remodeling consequences associated with excess salt intake, because nitric oxide serves as a negative regulator of TGF-[beta] production. Impairment of nitric oxide production, such as occurs with endothelial dysfunction in a variety of disease states, results in unopposed excess vascular TGF-[beta] production, which promotes reduced vascular compliance and augmented peripheral arterial constriction and hypertension. Persistent alterations in vascular function promote the increase in cardiovascular events and reductions in renal function that reduce life span during increased salt intake. transforming growth factor-[beta]; nitric oxide; vascular remodeling; arterial compliance

Clinical and preclinical studies have demonstrated an important effect of arterial pathobiology on the progressive loss of renal function that occurs in chronic kidney disease. Chronic kidney disease, in turn, promotes alterations in vascular function. A modulating role for dietary salt has been suggested, with the amount of salt intake regulating endothelial cell production of transforming growth factor-[beta]1 (TGF-[beta]1), a fibrogenic growth factor that promotes arteriosclerosis and glomerulosclerosis. The purpose of the present studies was to determine how the interaction between dietary salt intake and vasculature promoted the production of TGF-[beta]1 in rats. Two different vascular tissues, aortic rings and glomeruli, were chosen for study. Dietary salt induced, in a dosedependent fashion, activation of proline-rich tyrosine kinase-2 (Pyk2) and further identified c-Src as an important binding partner of Pyk2 in these tissues. Use of pharmacological inhibitors and dominant negative strategies confirmed that dietary salt induced complex formation of Pyk2 and c-Src with downstream activation of p38 and p42/44 mitogen-activated protein kinases and generation of TGF-[beta]1. The experiments defined the molecular signaling events that promoted the production of TGF-[beta]1, a key growth factor involved in the vascular response to increased salt intake. proline-rich tyrosine kinase-2; c-Src; aorta; glomerulus; endothelium

The kidney is capable of regeneration following injury, particularly following acute insults. Although the mechanisms underlying cellular regeneration are incompletely understood, emerging evidence suggests a role for cells of renal origin in the repair and replacement of damaged renal tubule cells. The overall hypothesis of this study is that native kidney cells that reside in a niche in the kidney provide robust contribution to the repair of kidney tubules following injury. To test this hypothesis, we utilized a model of renal ischemia-reperfusion injury that results in extensive morphological changes, particularly in the outer medulla. Renal tissue obtained from mice constitutively expressing Escherichia coli [beta]-galactosidase (ROSA26) was dissected from the cortex, outer medulla, or papilla and implanted under the renal capsule of the injured mice. Mice were allowed to recover for 7 days. Sections through the injured kidney demonstrated the presence of implantderived cells in renal tubules in the outer medulla. The implanted renal region that exhibited the most robust response was the papilla, whereas tissue pieces from the cortex and outer medulla showed less contribution to recipient renal tubules. These results provide proofof-principle evidence that renal-derived reparative cells reside in all regions of the kidney, perhaps more predominantly in the renal papilla. A greater understanding of the cell biology of renal repair by native kidney cells will provide further insight into the design of novel therapies in acute kidney injury, and the subcapsular implant technique described in this study may offer unique advantages to evaluate renal repair mechanisms. epithelial repair; ischemia-reperfusion injury; progenitor cells

Accurate determination of renal function in mice is a major impediment to the use of murine models in acute kidney injury. The purpose of this study was to determine whether early changes in renal function could be detected using dynamic gamma camera imaging in a mouse model of ischemia-reperfusion (I/R) injury. C57BL/6 mice (n = 5/group) underwent a right nephrectomy, followed by either 30 min of I/R injury or sham surgery of the remaining kidney. Dynamic renal studies (21 min, 10 s/frame) were conducted before surgery (baseline) and at 5, 24, and 48 h by injection of [sup.99m]Tc-mercaptoacetyltriglycine (MAG3; ~1.0 mCi/mouse) via the tail vein. The percentage of injected dose (%ID) in the kidney was calculated for each 10-s interval after MAG3 injection, using standard region of interest analyses. A defect in renal function in I/R-treated mice was detected as early as 5 h after surgery compared with sham-treated mice, identified by the increased %ID (at peak) in the I/R-treated kidneys at 100 s (P < 0.01) that remained significantly higher than sham-treated mice for the duration of the scan until 600 s (P < 0.05). At 48 h, the renal scan demonstrated functional renal recovery of the I/R mice and was comparable to sham-treated mice. Our study shows that using dynamic imaging, renal dysfunction can be detected and quantified reliably as early as 5 h after I/R insult, allowing for evaluation of early treatment interventions. acute kidney injury; nuclear imaging; mice models of acute renal failure

Chronic kidney disease in the Dahl/Rapp salt-sensitive (S) rat is related to an arteriolopathic process that occurs following the onset of hypertension and involves vascular smooth muscle cell (VSMC) hyperplasia and luminal constriction. Because previous studies have shown that activation of the epidermal growth factor receptor (EGFR) produces a mitogenic stimulus in VSMC and the EGFR participates integrally in the vasoconstrictor responses of renal arterioles, the present study analyzed the expression of EGFR in these animals. Compared with Sprague-Dawley (SD) rats, renal cortical expression of EGFR was increased in both prehypertensive and hypertensive S rats. Immunohistochemistry using a polyclonal antibody to EGFR demonstrated that EGFR expression was prominent in the renal vasculature, particularly in the media of afferent and efferent arterioles and the aorta of S rats. When examined, primary cultures of VSMC from S rats showed increased expression of EGFR, compared with VSMC from SD and Dahl/Rapp salt-resistant rats. Following addition of EGF, autophosphorylation of the EGFR was enhanced in cells from S rats, as was the downstream signaling events that included activation of p42/44 MAPK and Akt pathways. Thus in vivo and in vitro studies demonstrated augmented expression and functional activity of the EGFR in S rats. vascular smooth muscle; chronic kidney disease

The Dahl/Rapp salt-sensitive (S) rat is a model of salt-sensitive hypertension and hypertensive renal disease. This study explored the role of vascular remodeling in the development of renal failure in S rats. Groups of S and Sprague-Dawley rats were given 0.3 and 8.0% NaCl diets for up to 21 days and evidence of smooth muscle proliferation identified using immunohistochemistry that showed nuclear accumulation of proliferating cell nuclear antigen and 5-bromo-2'-deoxy-uridine. Compared with the other three groups, S rats on 8.0% NaCl diet showed increased nuclear labeling of cells of the aorta and arteries and arterioles of the kidney by the end of the first week of study. Progressive luminal narrowing of the interlobular arteries and preglomerular arterioles occurred in S rats over the 3 wk on the 8.0% NaCl diet. Accumulation of pimonidazole adducts and nuclear accumulation of hypoxia-inducible factor-1[alpha] (HIF-1[alpha]) were used as markers of tissue hypoxia. By the end of the second week of study, pimonidazole levels increased in S rats on 8.0% NaCl diet and deposition was apparent in tubular cells in the cortex and medulla. At the completion of the experiment, HIF-1[alpha] levels were increased in nuclear extracts from the cortex and medulla of S rats on this diet, compared with the other three groups of rats. The data demonstrated a disorder of the vascular remodeling process with proliferation of vascular smooth muscle cells temporally followed by development of tissue hypoxia in the hypertensive nephropathy of S rats on 8.0% NaCl diet. salt-sensitive hypertension; kidney disease; hypoxia; hypoxia-inducible factor-1; pimonidazole

Ying, Wei-Zhong, and Paul W. Sanders. The interrelationship between TGF-[[beta].sub.1] and nitric oxide is altered in saltsensitive hypertension. Am J Physiol Renal Physiol 285: F902-F908, 2003. First published July 15, 2003; 10.1152/ ajprenal.00177.2003.-The study of salt-sensitive hypertension has been facilitated by development of genetic models, especially the Dahl/Rapp salt-sensitive (S) rat. S rats rapidly become hypertensive after initiation of a diet containing 8.0% NaCl and subsequently develop arteriolonephrosclerosis and renal failure, whereas the salt-resistant (R) strain remains normotensive on the same diet. The purpose of the present study was to use these strains to demonstrate the interactions between transforming growth factor-[[beta].sub.1] (TGF-[[beta].sub.1]) and nitric oxide (NO). Young, male S and R rats were fed for 4 days diets that contained either 0.3 or 8.0% NaC1. An increase in dietary salt increased kinase activities of both p38 MAPK and p42/44 MAPK in cytoplasmic extracts from aortic rings and isolated glomeruli from both strains. Inhibition of either pathway with PD-098059 or SB-203580 decreased production of TGF-[[beta].sub.1] and nitrate plus nitrite (NOx). In both strains, production of active TGF-[[beta].sub.1] and N[O.sub.x] linearly correlated. Incubation of aortic rings and isolated glomeruli with the NO donor NOR3 decreased TGF-[[beta].sub.1] levels, whereas the NO synthase inhibitor [N.sup.[omega]]-nitro-a-arginine methyl ester increased production. The inhibitory effect of NO on production of TGF-[[beta].sub.1] was reduced in preparations from S rats. Although a close interrelationship existed between TGF-[[beta].sub.1] and NO in both strains, production of TGF-[[beta].sub.1] was increased in prehypertensive S rats and was further exaggerated with the. increase in dietary salt intake. Augmented vascular and glomerular production of TGF-[beta].sub.1] and diminished NO may contribute to the development of hypertensive nephrosclerosis in S rats. dietary salt; transforming growth factor-[[beta].sub.1]; salt sensitivity; Dahl/Rapp rat

The effects of a high-salt diet on the expression of nitric oxide synthase (NOS3) and elaboration of nitric oxide (NO) in rat kidney glomeruli are investigated by monitoring the level of NOS3 mRNA expression and calcium-dependent NO production. Results reveal that a high salt load increases the elaboration of NOS3 mRNA and enhances NO production. This effect is mediated by transforming growth factor-beta1.

Transforming growth factors (TGF) affect renal function and promote glomerulosclerosis. The mechanism of dietary salt modulation of the synthesis and secretion of TGF-beta in the rat kidney is investigated by monitoring the renal excretion of TGF-beta1 in the presence of an elevated salt diet. Results reveal that the enhancement of TGF synthesis brought about by dietary salt is mediated via a potassium channel sensitive to tetraethylammonium.

Primary cultures of rat mesangial cells were exposed to glomerulopathic light chain produced alterations in Ca2+ homeostasis to determine the effects of immunoglobulins on the mechanisms cellular homeostasis. Pretreatment of primary cultures of rat mesangial cells with glumerulopathic light chain reduced calcium transients in response to surface receptor agonists. Furthermore, the effects of monoclonal light chains on intracellular calcium homeostasis involved the inhibition of calcium influx and calcium release from intracellular stores.

Ying, Wei-Zhong, and Paul W. Sanders. Dietary salt increases endothelial nitric oxide synthase and TGF-[Beta] 1 in rat aortic endothelium. Am. J. Physiol. 277 (Heart Circ. Physiol. 46): H1293-H1298, 1999.--The amount of NaCl in the diet plays an important role in modulating nitric oxide (NO) synthesis in vivo. In the glomerulus, dietary NaCl also regulates transforming growth factor-[Beta] 1 (TGF-[Beta] 1) production. We hypothesized that dietary NaCl intake regulated expression of the endothelial isoform of nitric oxide synthase (NOS3) and TGF-[Beta] 1 in the aorta. Administration of 8.0% NaCl diet to rats for 7 days did not affect blood pressure but increased steady-state mRNA and protein levels of NOS3 in the arterial wall compared with animals on 0.3% NaCl diet. Northern analysis demonstrated increased steady-state amounts of mRNA of TGF-[Beta] 1 in aortas of rats on 8.0% NaCl diet. By ELISA, both total and active TGF-[Beta] 1 were increased in these vessel segments. Endothelial denudation of aortic rings reduced active TGF-[Beta] 1 secretion to undetectable levels. Addition of a neutralizing antibody to TGF-[Beta] to aortic ring segments attenuated NO production but not to that observed in animals on the 0.3% NaCl diet. The data showed that dietary NaCl intake modulated NOS3 and TGF-[Beta] 1 expression in the arterial wall; NOS3 expression was at least partially regulated by endothelial cell production of TGF-[Beta] 1. transforming growth factor-[Beta] 1; nitric oxide; sodium chloride; Sprague-Dawley rat