Evaluation of Cisplatin-Induced Acute Kidney Injury in Patients Co-Prescribed Serotonin Receptor Antagonists: A Retrospective Analysis.

BACKGROUND: Cisplatin is an effective first line therapy for a variety of cancers. Cisplatin is highly emetogenic and resulting volume depletion can contribute to acute kidney injury (AKI). Anti-emetic drugs such as 5-hydroxytryptamine type 3 receptor antagonists (5-HT3RAs) are commonly prescribed to prevent this complication. Preclinical studies suggest first generation 5-HT3RAs may alter the renal clearance and increase cisplatin toxicity. This retrospective study evaluated whether different 5-HT3RAs modify the risk of AKI in patients receiving cisplatin. METHODS: Patients with cancer who received cisplatin between January 1, 2010 and December 31, 2016 were included. Patients over 18 years old with available data for baseline and post-treatment serum creatinine, cisplatin cumulative dose, and administration of 5-HT3RAs including first generation (ondansetron, granisetron, and ramosetron) and second generation (palonosetron) were analyzed. AKI defined as 1.5x increase in serum creatinine. Fisher's exact and Wilcoxon rank-sum tests were used to assess univariable associations between baseline covariates and AKI, and logistic regression for multivariable associations with AKI. RESULTS: Of 8703 patients identified with cisplatin exposure, 6889 were included. A total of 3881 (56.3%) patients received at least one 5-HT3RA, including palonosetron (3750, 54.4%), ondansetron (1399, 20.3%) and granisetron (11, 0.2%). AKI developed in 1666 (24.2%) patients following cisplatin. Patients who received any 5-HT3RAs were less likely to experience AKI as compared to patients that did not (22.6% vs 26.2%, p=0.001). Older age, male gender, African ethnicity, and cumulative cisplatin dose were univariately associated with higher risk for AKI (P<0.001). After adjusting for these variables, use of any of these antiemetic drugs was protective for AKI (OR 0.84, 95% CI: 0.75, 0.94; P= 0.003) with no difference detected between type of 5-HT3RA. CONCLUSION: Nephrotoxicity continues to be a concern following cisplatin therapy. Given its emetogenic nature, use of antiemetic drugs such as 5-HT3RAs can lessen emesis and lower risk of kidney injury. This retrospective analysis supports use of any 5-HT3RAs to lower risk of AKI.

Regulation of renal calbindin expression during cisplatin-induced kidney injury.

Since the discovery of calbindin release into the urine during renal injury, there has been growing interest in the utility of this protein as a biomarker of nephrotoxicity. However, little is known about the intrarenal regulation of the release and expression of this calcium-regulating protein during kidney injury. We sought to characterize the time-dependent expression and excretion of the protein calbindin in the distal tubule in comparison to kidney injury molecule-1 (Kim-1), a protein in the proximal tubule, in mice treated with cisplatin. Urine, blood, and kidneys were collected from male C57BL/6 mice treated with vehicle or cisplatin (20 mg/kg ip). Urinary concentrations of calbindin and Kim-1 were elevated by 11.6-fold and 2.5-fold, respectively, within 2 days after cisplatin. Circulating creatinine and blood urea nitrogen levels increased in cisplatin-treated mice by 3 days, confirming the development of acute kidney injury. Time-dependent decreases in intrarenal calbindin protein were observed on Days 3 and 4 and a 200-fold upregulation of calbindin (CALB1) and KIM-1 messenger RNAs (mRNAs) was observed on Day 3. These data suggest that early loss of calbindin protein into the urine along with declines in renal calbindin levels initiates a compensatory induction of mRNA expression at later time points (Days 3 and 4). Understanding the regulation of calbindin during cisplatin nephrotoxicity further enhances its utility as a potential urinary biomarker of kidney damage. The results of the current study support the combined use of a proximal (Kim-1) and distal tubule (calbindin) marker to phenotype acute kidney injury secondary to cisplatin administration.

Endogenous markers of kidney function and renal drug clearance processes of filtration, secretion, and reabsorption.

The kidneys are responsible for maintaining physiologic homeostasis. The kidneys clear a variety of drugs and other substances through passive (filtration) and active processes that utilize transport proteins. Renal clearance is comprised of the processes of glomerular filtration, tubular secretion, and tubular reabsorption. Endogenous biomarkers, such as creatinine and cystatin C, are routinely used to estimate renal clearance. Understanding the contributing components of renal function and clearance, through the use of biomarkers, is necessary in elucidating the renal pharmacology of drugs and other substances. While exogenous markers of kidney function have been known for decades, several complexities have limited their usage. Several endogenous markers are being evaluated and hold promise to elucidate the individual components of kidney function that represent filtration, secretion, and reabsorption.

Influence of vitamin D treatment on functional expression of drug disposition pathways in human kidney proximal tubule cells during simulated uremia.

Effects of cholecalciferol (VitD3) and calcitriol (1,25-VitD3), on the expression and function of major vitamin D metabolizing enzymes (cytochrome P450 [CYP]2R1, CYP24A1) and select drug transport pathways (ABCB1/P-gp, SLCO4C1/OATP4C1) were evaluated in human kidney proximal tubule epithelial cells (hPTECs) under normal and uraemic serum conditions.hPTECs were incubated with 10% normal or uraemic serum for 24 h followed by treatment with 2% ethanol vehicle, or 100 and 240 nM doses of VitD3, or 1,25-VitD3 for 6 days. The effects of treatment on mRNA and protein expression and functional activity of select CYP enzymes and transporters were assessedUnder uraemic serum, treatment with 1,25-VitD3 resulted in increased mRNA but decreased protein expression of CYP2R1. Activity of CYP2R1 was not influenced by serum or VitD analogues. CYP24A1 expression was increased with 1,25-VitD3 under normal as well as uraemic serum, although to a lesser extent. ABCB1/P-gp mRNA expression increased under normal and uraemic serum, with exposure to 1,25-VitD3. SLCO4C1/OATP4C1 exhibited increased mRNA but decreased protein expression, under uraemic serum + 1,25-VitD3. Functional assessments of transport showed no changes regardless of exposure to serum or 1,25-VitD3.Key findings indicate that uraemic serum and VitD treatment led to differential effects on the functional expression of CYPs and transporters in hPTECs.

Time-dependent changes in kidney injury biomarkers in patients receiving multiple cycles of cisplatin chemotherapy.

Proteins secreted into urine following tubular injury are being increasingly used as biomarkers of clinical and subclinical nephrotoxicity. In the present study, we sought to characterize the time-dependent urinary excretion of three promising biomarkers, kidney injury molecule-1 (KIM-1), calbindin, and trefoil factor 3 (TFF3), during two different chemotherapy cycles in 27 patients with solid tumors prescribed the anticancer drug cisplatin (≥25 mg/m2). Urinary biomarkers were evaluated at Days 3 and 10 during an initial and a subsequent cycle of cisplatin chemotherapy. Longitudinal analyses compared the mean difference estimations for biomarker concentrations during and across the initial and subsequent cycles of cisplatin treatment. Traditional biomarkers including serum creatinine, estimated glomerular filtration rate, and blood urea nitrogen were unchanged during and across both cycles of cisplatin therapy. In response to the initial cycle, urinary KIM-1 concentrations increased from baseline and remained elevated through a subsequent cycle of cisplatin chemotherapy. By comparison, urinary levels of calbindin were elevated 10 days after the initial cisplatin treatment, but largely unchanged by cisplatin exposure in a subsequent cycle. Early elevations in urinary TFF3 at 3 days after cisplatin administration were observed consistently in both the initial and subsequent cycle of cisplatin treatment. In conclusion, the longitudinal assessment of biomarker performance in the same cohort of oncology patients reveals different patterns of urinary excretion between initial and subsequent cycles of cisplatin-containing chemotherapy. These data add novel cycle-dependent insight to the growing literature addressing the ability of urinary biomarkers to detect subclinical renal injury in patients receiving cisplatin.

The effect of MEK1/2 inhibitors on cisplatin-induced acute kidney injury (AKI) and cancer growth in mice.

In a clinically-relevant model of 4 week, low-dose cisplatin-induced AKI, mice were injected subcutaneously with non small cell lung cancer (NSCLC) cells that harbor an activating Kirsten rat sarcoma viral oncogene homolog (KRAS)G12V mutation. Phospho extracellular signal-regulated kinase1/2 (pERK1/2) expression in kidney and tumors was decreased by the MEK1/2 inhibitors, U0126 and trametinib, that potently inhibit pERK1/2. U0126 resulted in a significant improvement in kidney function, acute tubular necrosis (ATN) and tubular cell apoptosis in mice with AKI. Genes that were significantly decreased by U0126 were heat shock protein 1, cyclin-dependent kinase 4 (CDK4) and stratifin (14-3-3σ). U0126 resulted in a significant decrease in tumor weight and volume and significantly increased the chemotherapeutic effect of cisplatin. Trametinib, a MEK1/2 inhibitor that is FDA-approved for the treatment of cancer, did not result in functional protection against AKI or worse AKI, but dramatically decreased tumor growth more than cisplatin. Smaller tumors in cisplatin or MEK1/2 inhibitor-treated mice were not related to changes in microtubule-associated proteins 1A/1B light chain 3B (LC3-II), p62, cleaved caspase-3, granzyme B, or programmed death-ligand 1 (PD-L1). In summary, despite ERK inhibition by both U0126 and trametinib, only U0126 protected against AKI suggesting that the protection against AKI by U0126 was due to an off-target effect independent of ERK inhibition. The effect of U0126 to decrease AKI may be mediated by inhibition of heat shock protein 1, CDK4 or stratifin (14-3-3σ). Trametinib was more effective than cisplatin in decreasing tumor growth, but unlike cisplatin, trametinib did not cause AKI.

Rituximab Exhibits Altered Pharmacokinetics in Patients With Membranous Nephropathy.

BACKGROUND: Rituximab (RTX) is a chimeric monoclonal anti-CD20 antibody used off-label in the treatment of membranous nephropathy (MN). Unfortunately, limited information is available on the pharmacokinetics of therapeutic proteins such as RTX in patients with glomerular kidney diseases. OBJECTIVE: The current study evaluated RTX pharmacokinetics in patients with MN (n = 20) who received 4 RTX weekly intravenous infusions (375 mg/m2) over a month, with a repeat of the identical treatment at 6 months. Baseline patient characteristics were gender (17 male/3 female), age (49 ± 13 years), and body surface area (2.2 ± 0.24 m2). METHODS: Compartmental pharmacokinetic analyses were conducted using Phoenix, and comparisons of these parameters were made between the MN patients and published data from 2 reference populations without kidney diseases (follicular lymphoma and autoimmune disorders). RESULTS: Patients with MN exhibited a shorter half-life, reduced volume of central compartment, decreased area under the serum concentration-time curve (exposure), and increased RTX clearance from the central compartment versus previous reports in the reference patient populations. CONCLUSIONS AND RELEVANCE: These results suggest that shorter half-life and lower exposures to RTX in patients with MN may necessitate higher doses and/or changes to dosing frequency to optimize the relationships between serum concentrations and therapeutic effects.

Pharmacokinetic determinants of cisplatin-induced subclinical kidney injury in oncology patients.

PURPOSE: The ability to predict and detect clinical and subclinical nephrotoxicity early in the course of therapy has the potential to improve long-term outcomes in cancer patients receiving cisplatin chemotherapy. Pharmacokinetic parameters could serve as predictors of cisplatin-induced nephrotoxicity. METHODS: Participants [n = 13] were treated with a 1-h cisplatin infusion [30-75 mg/m2]. Blood was collected pre-dose and up to 6 h post-dose. Urinary biomarkers [KIM-1, calbindin, clusterin, GST-pi, ß2M, albumin, NGAL, osteopontin, clusterin, MCP-1, cystatin C, and TFF3] were measured at baseline, days 3 and 10. Total and unbound platinum concentrations were measured using ICP/MS. Noncompartmental analysis was performed, and correlation and regression analyses evaluated the relationships between platinum pharmacokinetics and nephrotoxicity. RESULTS: Peak platinum urinary concentrations correlated with urinary levels of KIM-1, calbindin, clusterin, GST-pi, ß2M, albumin, NGAL, osteopontin, clusterin, cystatin C, and TFF3 at day 10. Unbound platinum plasma concentrations at 2 h also correlated with urinary clusterin, ß2M, cystatin C, NGAL, osteopontin, and TFF3 at day 3. Regression analyses suggested 2-h total plasma platinum concentrations greater than 2000 ng/ml, and peak urinary platinum concentrations above 24,000 ng/ml may serve as potential approximations for elevated risk of nephrotoxicity. Platinum area under the plasma concentration time curve was associated with serum creatinine and estimated glomerular filtration rate. CONCLUSIONS: Peak plasma and urinary platinum concentrations and pharmacokinetic parameters were associated with risk of subclinical cisplatin-induced kidney injury as assessed using novel urinary biomarkers. Future studies will examine these relationships in larger clinical populations of cisplatin-induced acute kidney injury.

Acute Kidney Injury Biomarkers Predict an Increase in Serum Milrinone Concentration Earlier Than Serum Creatinine-Defined Acute Kidney Injury in Infants After Cardiac Surgery.

BACKGROUND: Milrinone, an inotropic agent used ubiquitously in children after cardiac surgery, accumulates in acute kidney injury (AKI). We assessed if urinary AKI biomarkers are predictive of an increase in milrinone concentrations in infants after cardiac surgery. METHODS: Multicenter prospective pilot study of infants undergoing cardiac surgery. Urinary AKI biomarkers were measured in the urine at specific time intervals after cardiopulmonary bypass initiation. AKI was defined using the Kidney Disease: Improving Global Outcomes serum creatinine criteria. Serum milrinone concentrations were measured at specific intervals after drug initiation, dose changes, and termination. Excessive milrinone activity was defined as a 20% increase in serum concentration between 6 and 36 hours after initiation. The temporal relationship between urinary AKI biomarker concentrations and a 20% increase in milrinone concentration was assessed. RESULTS: AKI occurred in 31 (33%) of infants. Milrinone clearance was lower in patients with AKI (4.2 versus 5.6 L/h/70 kg; P = 0.02). Excessive milrinone activity was associated with development of serum creatinine-defined AKI [odds ratio (OR) 3.0; 95% confidence interval (CI), 1.21-7.39; P = 0.02]. Both tissue inhibitor metalloproteinase type 2 and insulin-like growth factor-binding protein type 7 (TIMP-2*IGFBP-7) ≥0.78 at 12 hours (OR 2.72; 95% CI, 1.01-7.38; P = 0.04) and kidney injury molecule 1 (KIM-1) ≥529.57 at 24 hours (OR 2.76; 95% CI, 1.06-7.17; P = 0.04) predicted excessive milrinone activity before a diagnosis of AKI. CONCLUSIONS: In this pilot study, urine TIMP-2*IGFBP-7 and KIM-1 were predictive of AKI and excessive milrinone activity. Future studies that include a pharmacodynamics assessment of patient hemodynamics, excessive milrinone activity, and AKI biomarker concentrations may be warranted to integrate this concept into clinical practice.

Urinary protein biomarkers of kidney injury in patients receiving cisplatin chemotherapy.

Despite recent progress in the development of novel approaches to treat cancer, traditional antineoplastic drugs, such as cisplatin, remain a mainstay of regimens targeting solid tumors. Use of cisplatin is limited by acute kidney injury, which occurs in approximately 30% of patients. Current clinical measures, such as serum creatinine and estimated glomerular filtration rate, are inadequate in their ability to detect acute kidney injury, particularly when there is only a moderate degree of injury. Thus, there is an urgent need for improved diagnostic biomarkers to predict nephrotoxicity. There is also interest by the U.S. Food and Drug Administration to validate and implement new biomarkers to identify clinical and subclinical acute kidney injury in patients during the drug approval process. This minireview provides an overview of the current literature regarding the utility of urinary proteins (albumin, beta-2-microglobulin, N-acetyl-D-glucosaminidase, kidney injury molecule-1, neutrophil gelatinase-associated lipocalin, and cystatin C) as biomarkers for cisplatin-induced AKI. Many of the well-studied urinary proteins (KIM-1, NGAL, B2M, albumin) as well as emerging biomarkers (calbindin, monocyte chemotactic protein-1, and trefoil factor 3) display distinct patterns of time-dependent excretion after cisplatin administration. Implementation of these biomarker proteins in the oncology clinic has been hampered by a lack of validation studies. To address these issues, large head-to-head studies are needed to fully characterize time-dependent responses and establish accurate cutoff values and ranges, particularly in cancer patients. Impact statement There is growing interest in using urinary protein biomarkers to detect acute kidney injury in oncology patients prescribed the nephrotoxic anticancer drug cisplatin. We aim to synthesize and organize the existing literature on biomarkers examined clinically in patients receiving cisplatin-containing chemotherapy regimens. This minireview highlights several proteins (kidney injury molecule-1, beta-2-microglobulin, neutrophil gelatinase-associated lipocalin, calbindin, monocyte chemotactic protein-1, trefoil factor 3) with the greatest promise for detecting cisplatin-induced acute kidney injury in humans. A comprehensive review of the existing literature may aid in the design of larger studies needed to implement the clinical use of these urinary proteins as biomarkers of kidney injury.

Characterization of simvastatin acid uptake by organic anion transporting polypeptide 3A1 (OATP3A1) and influence of drug-drug interaction.

Human organic anion transporting polypeptide 3A1 (OATP3A1) is predominately expressed in the heart. The ability of OATP3A1 to transport statins into cardiomyocytes is unknown, although other OATPs are known to mediate the uptake of statin drugs in liver. The pleiotropic effects and uptake of simvastatin acid were analyzed in primary human cardiomyocytes and HEK293 cells transfected with the OATP3A1 gene. Treatment with simvastatin acid reduced indoxyl sulfate-mediated reactive oxygen species and modulated OATP3A1 expression in cardiomyocytes and HEK293 cells transfected with the OATP3A1 gene. We observed a pH-dependent effect on OATP3A1 uptake, with more efficient simvastatin acid uptake at pH5.5 in HEK293 cells transfected with the OATP3A1 gene. The Michaelis-Menten constant (Km) for simvastatin acid uptake by OATP3A1 was 0.017±0.002µM and the Vmax was 0.995±0.027fmol/min/105 cells. Uptake of simvastatin acid was significantly increased by known (benzylpenicillin and estrone-3-sulfate) and potential (indoxyl sulfate and cyclosporine) substrates of OATP3A1. In conclusion, the presence of OATP3A1 in cardiomyocytes suggests that this transporter may modulate the exposure of cardiac tissue to simvastatin acid due to its enrichment in cardiomyocytes. Increases in uptake of simvastatin acid by OATP3A1 when combined with OATP substrates suggest the potential for drug-drug interactions that could influence clinical outcomes.

Pharmacogenomic Variants May Influence the Urinary Excretion of Novel Kidney Injury Biomarkers in Patients Receiving Cisplatin.

Nephrotoxicity is a dose limiting side effect associated with the use of cisplatin in the treatment of solid tumors. The degree of nephrotoxicity is dictated by the selective accumulation of cisplatin in renal tubule cells due to: (1) uptake by organic cation transporter 2 (OCT2) and copper transporter 1 (CTR1); (2) metabolism by glutathione S-transferases (GSTs) and γ-glutamyltransferase 1 (GGT1); and (3) efflux by multidrug resistance-associated protein 2 (MRP2) and multidrug and toxin extrusion protein 1 (MATE1). The purpose of this study was to determine the significance of single nucleotide polymorphisms that regulate the expression and function of transporters and metabolism genes implicated in development of acute kidney injury (AKI) in cisplatin treated patients. Changes in the kidney function were assessed using novel urinary protein biomarkers and traditional markers. Genotyping was conducted by the QuantStudio 12K Flex Real-Time PCR System using a custom open array chip with metabolism, transport, and transcription factor polymorphisms of interest to cisplatin disposition and toxicity. Traditional and novel biomarker assays for kidney toxicity were assessed for differences according to genotype by ANOVA. Allele and genotype frequencies were determined based on Caucasian population frequencies. The polymorphisms rs596881 (SLC22A2/OCT2), and rs12686377 and rs7851395 (SLC31A1/CTR1) were associated with renoprotection and maintenance of estimated glomerular filtration rate (eGFR). Polymorphisms in SLC22A2/OCT2, SLC31A1/CTRI, SLC47A1/MATE1, ABCC2/MRP2, and GSTP1 were significantly associated with increases in the urinary excretion of novel AKI biomarkers: KIM-1, TFF3, MCP1, NGAL, clusterin, cystatin C, and calbindin. Knowledge concerning which genotypes in drug transporters are associated with cisplatin-induced nephrotoxicity may help to identify at-risk patients and initiate strategies, such as using lower or fractionated cisplatin doses or avoiding cisplatin altogether, in order to prevent AKI.

Profiling of Kidney Injury Biomarkers in Patients Receiving Cisplatin: Time-dependent Changes in the Absence of Clinical Nephrotoxicity.

The success of cisplatin-containing regimens to treat solid tumors is limited, in part, by nephrotoxicity. In rodents, several urinary proteins have emerged that are sensitive indicators of cisplatin-induced kidney injury. We sought to characterize time-dependent changes in the urinary concentrations of 12 proteins, including kidney injury molecule-1 (KIM-1), calbindin, beta 2-microglobulin (ß2M), and trefoil factor 3 (TFF3) after cisplatin therapy. Urine was collected at baseline, 3 days (range, 2-5 days), and 10 days (range, 9-11 days) from 57 patients with solid tumors receiving outpatient cisplatin therapy (≥25 mg/m2 ). Serum creatinine was largely unchanged after cisplatin infusion. However, compared with baseline values, several novel biomarkers were significantly increased in the urine, including ß2M, which was threefold higher by day 3 (P < 0.0001). Urinary KIM-1 and TFF3 were elevated twofold by day 10 (P = 0.002 and P = 0.002, respectively), whereas calbindin levels were increased eightfold (P < 0.0001). We report novel time-dependent changes in the urinary excretion of noninvasive markers of subclinical kidney injury after cisplatin treatment.

Bardoxolone methyl modulates efflux transporter and detoxifying enzyme expression in cisplatin-induced kidney cell injury.

Cisplatin is prescribed for the treatment of solid tumors and elicits toxicity to kidney tubules, which limits its clinical use. Nuclear factor erythroid 2-related factor 2 (Nrf2, NFE2L2) is a critical transcription factor that has been shown to protect against kidney injury through activation of antioxidant mechanisms. We aimed to evaluate the ability of short-term treatment with the Nrf2 activator bardoxolone methyl (CDDO-Me) to protect against cisplatin-induced kidney cell toxicity. Cell viability was assessed in human kidney proximal tubule epithelial cells (hPTCs) exposed to low, intermediate, and high cisplatin concentrations in the presence and absence of CDDO-Me, administered either prior to or after cisplatin. Treatment with cisplatin alone resulted in reductions in hPTC viability, while CDDO-Me administered prior to or after cisplatin exposure yielded significantly higher cell viability (17%-71%). Gene regulation (mRNA expression) studies revealed the ability of CDDO-Me to modify protective pathways including Nrf2 induced detoxifying genes [GCLC (increased 1.9-fold), NQO1 (increased 9.3-fold)], and an efflux transporter [SLC47A1 (increased 4.5-fold)] at 12h. Protein assessments were in agreement with gene expression. Immunofluorescence revealed localization of GCLC and NQO1 to the nucleus and cytosol, respectively, with CDDO-Me administered prior to or after cisplatin exposure. The findings of enhanced cell viability and increased expression of detoxifying enzymes (GCLC and NQO1) and the multidrug and toxin extrusion protein 1 (MATE1) efflux transporter (SLC47A1) in hPTCs exposed to CDDO-Me, suggest that intermittent treatment with CDDO-Me prior to or after cisplatin exposure may be a promising approach to mitigate acute kidney injury.

Milrinone Dosing Issues in Critically Ill Children With Kidney Injury: A Review.

Milrinone is an inotropic drug used in a variety of clinical settings in adults and children. The efficacy of milrinone in pediatric low-cardiac output syndrome after cardiac surgery is reported. Its primary route of removal from the body is through the kidney as unchanged drug in the urine. Milrinone is not known to be efficiently removed by extracorporeal dialytic therapies and thus has the potential to cause serious adverse effects and potentially worsens renal function in patients experiencing acute kidney injury (AKI). AKI is an important public health issue that is associated with increased morbidity, mortality, and cost. It is a known risk factor for the development of chronic kidney disease. There are no specific therapies to mitigate AKI once it has developed, and interventions are focused on supportive care and dose adjustment of medications. Estimating glomerular filtration rate based on height and serum creatinine is the most commonly used clinical method for assessing kidney function and modification of medication doses. The purpose of this review is to discuss our current understanding of milrinone pharmacokinetics and pharmacodynamics in children with AKI and to describe the potential use of urinary biomarkers to guide therapeutic decision making for milrinone dosing.

Nrf2 activators as potential modulators of injury in human kidney cells.

Cisplatin is a chemotherapeutic agent used in the treatment of solid tumors, with clinical use often complicated by kidney toxicity. Nuclear factor (erythroid-derived-2)-like 2 (Nrf2) is a transcription factor involved in kidney protectant effects. The purpose of this study was to determine whether the Nrf2 activators oltipraz, sulforaphane, and oleanolic acid could protect human kidney cells against cisplatin-induced injury and to compare the protective effects between three Nrf2 activators. Human proximal tubule cells (hPTC) and human embryonic kidney 293 cells (HEK293) were exposed to cisplatin doses in the absence and presence of Nrf2 activators. Pre- and delayed-cisplatin and Nrf2 activator exposures were also assessed. Cell viability was enhanced with Nrf2 activator exposures, with differences detected between pre- and delayed-treatments. Both sulforaphane and oltipraz increased the expression of anti-oxidant genes GCLC and NQO1. These findings suggest potential human kidney protective benefits of Nrf2 activators with planned exposures to cisplatin.

Complement Activation in Patients with Focal Segmental Glomerulosclerosis.

BACKGROUND: Recent pre-clinical studies have shown that complement activation contributes to glomerular and tubular injury in experimental FSGS. Although complement proteins are detected in the glomeruli of some patients with FSGS, it is not known whether this is due to complement activation or whether the proteins are simply trapped in sclerotic glomeruli. We measured complement activation fragments in the plasma and urine of patients with primary FSGS to determine whether complement activation is part of the disease process. STUDY DESIGN: Plasma and urine samples from patients with biopsy-proven FSGS who participated in the FSGS Clinical Trial were analyzed. SETTING AND PARTICIPANTS: We identified 19 patients for whom samples were available from weeks 0, 26, 52 and 78. The results for these FSGS patients were compared to results in samples from 10 healthy controls, 10 patients with chronic kidney disease (CKD), 20 patients with vasculitis, and 23 patients with lupus nephritis. OUTCOMES: Longitudinal control of proteinuria and estimated glomerular filtration rate (eGFR). MEASUREMENTS: Levels of the complement fragments Ba, Bb, C4a, and sC5b-9 in plasma and urine. RESULTS: Plasma and urine Ba, C4a, sC5b-9 were significantly higher in FSGS patients at the time of diagnosis than in the control groups. Plasma Ba levels inversely correlated with the eGFR at the time of diagnosis and at the end of the study. Plasma and urine Ba levels at the end of the study positively correlated with the level of proteinuria, the primary outcome of the study. LIMITATIONS: Limited number of patients with samples from all time-points. CONCLUSIONS: The complement system is activated in patients with primary FSGS, and elevated levels of plasma Ba correlate with more severe disease. Measurement of complement fragments may identify a subset of patients in whom the complement system is activated. Further investigations are needed to confirm our findings and to determine the prognostic significance of complement activation in patients with FSGS.

Quantitative profiling of human renal UDP-glucuronosyltransferases and glucuronidation activity: a comparison of normal and tumoral kidney tissues.

Renal metabolism by UDP-glucuronosyltransferase (UGT) enzymes is central to the clearance of many drugs. However, significant discrepancies about the relative abundance and activity of individual UGT enzymes in the normal kidney prevail among reports, whereas glucuronidation in tumoral kidney has not been examined. In this study, we performed an extensive profiling of glucuronidation metabolism in normal (n = 12) and tumor (n = 14) kidneys using targeted mass spectrometry quantification of human UGTs. We then correlated UGT protein concentrations with mRNA levels assessed by quantitative polymerase chain reaction and with conjugation activity for the major renal UGTs. Beyond the wide interindividual variability in expression levels observed among kidney samples, UGT1A9, UGT2B7, and UGT1A6 are the most abundant renal UGTs in both normal and tumoral tissues based on protein quantification. In normal kidney tissues, only UGT1A9 protein levels correlated with mRNA levels, whereas UGT1A6, UGT1A9, and UGT2B7 quantification correlated significantly with their mRNA levels in tumor kidneys. Data support that posttranscriptional regulation of UGT2B7 and UGT1A6 expression is modulating glucuronidation in the kidney. Importantly, our study reveals a significant decreased glucuronidation capacity of neoplastic kidneys versus normal kidneys that is paralleled by drastically reduced UGT1A9 and UGT2B7 mRNA and protein expression. UGT2B7 activity is the most repressed in tumors relative to normal tissues, with a 96-fold decrease in zidovudine metabolism, whereas propofol and sorafenib glucuronidation is decreased by 7.6- and 5.2-fold, respectively. Findings demonstrate that renal drug metabolism is predominantly mediated by UGT1A9 and UGT2B7 and is greatly reduced in kidney tumors.

Expression of UGT2B7 is driven by two mutually exclusive promoters and alternative splicing in human tissues: changes from prenatal life to adulthood and in kidney cancer.

OBJECTIVE: UDP-glucuronosyltransferase 2B7 (UGT2B7) plays a major detoxification role in commonly prescribed drugs and endogenous lipophilic molecules. Additional exons and multiple alternative splicing events (ASEs) at the UGT2B7 locus were recently discovered. MATERIALS AND METHODS: Novel and classical ASEs were quantified in 27 human tissues, as well as in fetal and tumoral tissues. The activity of the alternative UGT2B7 promoters was studied in cell lines. RESULTS: UGT2B7 expression is driven by an alternate promoter 1a associated with transcripts containing exon 1b, which is located ∼44 kb upstream of the known promoter 1 associated with transcripts containing exon 1 required for enzyme activity. The exon 1 was expressed most abundantly in the liver and gastrointestinal tract, whereas exon 1b was expressed predominantly in other extrahepatic tissues. Experimental evidence indicated endogenous translation that yields alternative UGT2B7s derived from the use of exon 1b are enzymatically inactive. Alternate 5' ASE predominates in fetal tissues (kidney, lung) and kidney tumor samples compared with normal adult kidney. These changes further correlate with reduced glucuronidation in neoplastic kidneys. This differential expression pattern was further confirmed using four liver and kidney cell lines and was consistent with the differential usage of alternate promoters in hepatic (promoter 1) and kidney cells (1a). CONCLUSION: UGT2B7 is characterized by two mutually exclusive exons 1, both flanked by a unique 5' promoter region. Data also indicated a switch toward functional enzyme upon maturation in the kidney and reversal of this process in neoplastic cells, considerably modifying the glucuronidation potential across human tissues and cells.

Contribution of renal and non-renal clearance on increased total clearance of adalimumab in glomerular disease.

The contribution of renal and non-renal clearance toward targeted concentrations and/or effects of therapeutic proteins in nephrotic patients are unknown. This study dissected the contribution of clearance pathways to adalimumab elimination in patients with focal segmental glomerulosclerosis (FSGS). Urine was collected from seven patients treated with adalimumab. Renal clearance (ClR ) was measured and non-renal clearance (ClNR ) was calculated as the difference between total clearance and ClR . Differences in cumulative amount in urine, ClR, and ClNR between study weeks 1 and 16 and relationships between proteinuria (protein:creatinine ratio (Up/c)), and ClR and ClNR were evaluated. Up to 13% of the adalimumab dose was lost in urine. ClNR contributed more than ClR to enhanced total clearance. There was a nonlinear relationship between Up/c and ClR (R(2) 0.7059); an increase in ClR beginning at Up/c of 12 mg/mg [slope 1.755, (C.I. -7.825 to 11.34)]. There was a linear relationship between Up/c and ClNR (R(2) 0.5039); for every one unit increase in Up/c, ClNR would increase by 3.5 mL/hr (P = 0.01). Both ClR and ClNR contribute to enhanced total clearance of adalimumab in glomerular disease secondary to FSGS. Additional research is needed to identify mechanisms for the increased ClNR pathways.