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There is a growing recognition of the complex interplay between renal cell cancer (RCC), kidney function, mechanical reduction of nephron mass, and systemic agents targeting the cancer. Earlier detection of RCC and rising life expectancy of cancer survivors places a greater emphasis on preservation of renal function after cancer resection and during systemic therapy. Unique adverse effects associated with RCC drugs not only help reveal cancer pathophysiology but also expand our knowledge of normal cell signaling and metabolism. In this review, we outline our current understanding of RCC biology and treatment, their bidirectional relationship with kidney function, and unmet research needs in this field.

Clinical studies have established the role of cigarette smoking as a risk factor in the progression of chronic kidney disease (CKD). We have shown that nicotine promotes mesangial cell proliferation and hypertrophy via nonneuronal nicotinic acetylcholine receptors (nAChRs). The α7-nAChR is one of the most important subunits of the nAChRs. These studies were designed to test the hypothesis that nicotine worsens renal injury in rats with 5/6 nephrectomy (5/6Nx) and that the α7-nAChR subunit is required for these effects. We studied five different groups: Sham, 5/6Nx, 5/6Nx + nicotine (Nic; 100 μg/ml dry wt), 5/6Nx + Nic + α7-nAChR blocker methyllicaconitine (MLA; 3 mg·kg−1·day−1sq), and Sham + Nic. Blood pressure was measured by the tail-cuff method, and urine was collected for proteinuria. After 12 wk, the rats were euthanized and kidneys were collected. We observed expression of the α7-nAChR in the proximal and distal tubules. The administration of nicotine induced a small increase in blood pressure and resulted in cotinine levels similar to those found in the plasma of smokers. In 5/6Nx rats, the administration of nicotine significantly increased urinary protein excretion (onefold), worsened the glomerular injury score and increased fibronectin (∼ 50%), NADPH oxidase 4 (NOX4; ∼100%), and transforming growth factor-β expression (∼200%). The administration of nicotine to sham rats increased total proteinuria but not albuminuria, suggesting direct effects on tubular protein reabsorption. These effects were prevented by MLA, demonstrating a critical role for the α7-nAChR as a mediator of the effects of nicotine in the progression of CKD.

Angiotensin II (ANG II) produced as result of activation of the renin-angiotensin system (RAS) plays a critical role in the pathogenesis of chronic kidney disease via its hemodynamic effects on the renal microcirculation as well as by its nonhemodynamic actions including the production of extracellular matrix proteins such as fibronectin, a multifunctional extracellular matrix protein that plays a major role in cell adhesion and migration as well as in the development of glomerulosclerosis. ETS-1 is an important transcription factor essential for normal kidney development and glomerular integrity. We previously showed that ANG II increases ETS-1 expression and is required for fibronectin production in mesangial cells. In these studies, we determined that ANG II induces phosphorylation of ETS-1 via activation of the type 1 ANG II receptor and that Erk1/2 and Akt/PKB phosphorylation are required for these effects. In addition, we characterized the role of ETS-1 on the transcriptional activation of fibronectin production in mesangial cells. We determined that ETS-1 directly activates the fibronectin promoter and by utilizing gel shift assays and chromatin immunoprecipitation assays identified two different ETS-1 binding sites that promote the transcriptional activation of fibronectin in response to ANG II. In addition, we identified the essential role of CREB and its coactivator p300 on the transcriptional activation of fibronectin by ETS-1. These studies unveil novel mechanisms involved in RAS-induced production of the extracellular matrix protein fibronectin in mesangial cells and establish the role of the transcription factor ETS-1 as a direct mediator of these effects.

Epidemiological studies have established the role of cigarette smoking as a risk factor in the progression of chronic kidney disease, including diabetic nephropathy. We have previously reported that nicotine promotes mesangial cell proliferation and hypertrophy via activation of nonneuronal nicotinic acetylcholine receptors and that nicotine worsens renal injury in a model of acute glomerulonephritis (Jaimes E, Tian RX, Raij L. Am J Physiol Heart Circ Physiol292: H76–H82, 2007; Jaimes EA, Tian RX, Joshi M, Raij L. Am J Nephrol29: 319–326, 2009). These studies were designed to test the hypothesis that nicotine worsens renal injury in db/dbmice, a well-established model of diabetic nephropathy, and that reactive oxygen species play an important as mediators of these effects. For these studies, nicotine (100 μg/ml) was administered in the drinking water to control and db/dbmice for 10 wk. Blood pressure was measured by the tail-cuff method, and urine was collected for proteinuria. At death, kidneys were collected for histology and molecular biology. The administration of nicotine did not result in significant changes in blood pressure or blood glucose and resulted in cotinine levels similar to those found in the plasma of smokers. In diabetic mice, the administration of nicotine significantly increased urinary protein excretion (1-fold), glomerular hypertrophy, and mesangial area (∼20%). These changes were accompanied by significant increases in NADPH oxidase 4 (∼30%) and increased nitrotyrosine and Akt expression. In vitro, we determined that nicotine has additive effects to high glucose on reactive oxygen species generation and Akt phosphorylation in human mesangial cells. These findings unveil novel mechanisms that may result in the development of novel strategies in the treatment and prevention of diabetic nephropathy in smokers.

Glomerular endothelial cells (GEC) are strategically situated within the capillary loop and adjacent to the glomerular mesangium. GEC serve as targets of metabolic, biochemical, and hemodynamic signals that regulate the glomerular microcirculation. Unequivocally, hyperglycemia, hypertension, and the local renin-angiotensin system partake in the initiation and progression of diabetic nephropathy (DN). Whether free fatty acids (FFA) and reactive oxygen species (ROS) that have been associated with the endothelial dysfunction of diabetic macrovascular disease also contribute to DN is not known. Since endothelial cells from different organs and from different species may display different phenotypes, we employed human GEC to investigate the effect of high glucose (22.5 mmol/l), FFA (800 μmol/l), and angiotensin II (ANG II; 10−7mol/l) on the genesis of ROS and their effects on endothelial nitric oxide synthase (eNOS), cyclooxygenase-2 (COX-2), and the synthesis of prostaglandins (PGs). We demonstrated that high glucose but not high FFA increased the expression of a dysfunctional eNOS as well as increased ROS from NADPH oxidase (100%) and likely from uncoupled eNOS. ANG II also induced ROS from NADPH oxidase. High glucose and ANG II upregulated (100%) COX-2 via ROS and significantly increased the synthesis of prostacyclin (PGI2) by 300%. In contrast, FFA did not upregulate COX-2 but increased PGI2(500%). These novel studies are the first in human GEC that characterize the differential role of FFA, hyperglycemia, and ANG II on the genesis of ROS, COX-2, and PGs and their interplay in the early stages of hyperglcyemia.

Clinical and experimental studies have provided evidence suggesting that statins exert renoprotective effects. To investigate the mechanisms by which statins may exert renoprotection, we utilized the hypertensive Dahl salt-sensitive (DS) rat model, which manifests cardiovascular and renal injury linked to increased angiotensin II-dependent activation of NADPH oxidase and decreased nitric oxide (NO) bioavailability. DS rats given high salt diet (4% NaCl) for 10 wk exhibited hypertension [systolic blood pressure (SBP) 200 ± 8 vs. 150 ± 2 mmHg in normal salt diet (0.5% NaCl), P< 0.05], glomerulosclerosis, and proteinuria (158%). This was associated with increased renal oxidative stress demonstrated by urinary 8-F2α-isoprostane excretion and NADPH oxidase activity, increased protein expression of transforming growth factor (TGF)-β (63%) and fibronectin (181%), increased mRNA expression of the proinflammatory molecules monocyte chemoattractant protein-1 (MCP-1) and lectin-like oxidized LDL receptor-1 (LOX-1), as well as downregulation of endothelial NO synthase (eNOS) activity (−44%) and protein expression. Return to normal salt had no effect on SBP or any of the measured parameters. Atorvastatin (30 mg·kg−1·day−1) significantly attenuated proteinuria and glomerulosclerosis and normalized renal oxidative stress, TGF-β1, fibronectin, MCP-1 and LOX-1 expression, and eNOS activity and expression. Atorvastatin-treated rats showed a modest reduction in SBP that remained in the hypertensive range (174 ± 8 mmHg). Atorvastatin combined with removal of high salt normalized SBP and proteinuria. These findings suggest that statins mitigate hypertensive renal injury by restoring the balance among NO, TGF-β1, and oxidative stress and explain the added renoprotective effects observed in clinical studies using statins in addition to inhibitors of the renin-angiotensin system.

Maladaptive activation of the renin-angiotensin system (RAS) has been shown to play a critical role in the pathogenesis of chronic kidney disease. Reactive oxygen species (ROS) are critical signals for many of the nonhemodynamic effects of angiotensin II (ANG II). We have demonstrated that ANG II increases mesangial and cortical cyclooxygenase-2 (COX-2) expression and activity via NADPH oxidase-derived ROS. The transcription factor ETS-1 (E26 transformation-specific sequence) has been identified as a critical regulator of growth-related responses and inflammation. The present studies were designed to determine: 1) whether ANG II induces ETS-1 expression in vitro in cultured rat mesangial cells and in vivo in rats infused with ANG II; and 2) whether ROS and COX-2 are mediators of ETS-1 induction in response to ANG II. Mesangial cells stimulated with ANG II (10−7M) exhibited a significant increase in ETS-1 expression that was prevented by the angiotensin type 1 receptor blocker candesartan. NADPH oxidase inhibition with dyphenilene iodinium or apocynin also prevented ETS-1 induction, establishing the role of ROS as mediators of ETS-1 expression in response to ANG II. COX-2 inhibition prevented ETS-1 expression in response to ANG II, suggesting that COX-2 is required for ETS-1 induction. By utilizing short interfering RNAs against ETS-1, we have also determined that ETS-1 is required to induce the production of fibronectin in response to ANG II. Furthermore, rats infused with ANG II manifested increased glomerular expression of ETS-1. These studies unveil novel pathways that may play an important role in the pathogenesis of renal injury when RAS is activated.

Salt-sensitive (SS) hypertension is a vascular diathesis characterized by reduced cardiovascular and renal nitric oxide bioavailability and local upregulation of ANG II. We have demonstrated that rats infused with ANG II manifest increased cortical cyclooxygenase (COX)-2 expression and activity via NADPH oxidase-derived reactive oxygen species (ROS). In the present studies we used Dahl salt-sensitive (DS) rats to test the hypothesis that hypertensive SS rats have increased cortical COX-2 upregulation, which is mediated by ANG II and ROS. DS rats were placed on either a normal-salt diet (0.5% NaCl) or a high-salt diet (4% NaCl) for 6 wk and treated with either the ANG II type 1 (AT1) receptor blocker candesartan (Can, 10 mg·kg−1·day−1) or the SOD mimetic tempol (1 mmol/l). Hypertensive SS rats had a twofold increase in the cortical expression of COX-2 as assessed by Western blot. These changes in COX-2 expression were accompanied by a 10-fold increase in COX-2 mRNA expression and a 2-fold increase in the urinary excretion of PGE2. Treatment with either the AT1receptor blocker Can or the SOD mimetic tempol did not reduce blood pressure but resulted in significant reductions in the cortical expression of COX-2 and the urinary excretion of PGE2. In conclusion, we have demonstrated that local activation of the renin-angiotensin system, via increased ROS generation, mediates COX-2 upregulation in hypertensive SS rats. These studies unveil novel mechanistic pathways that may play a role in the pathogenesis of hypertensive renal injury.