Identification of putative gene based markers of renal toxicity

Urinary kidney biomarkers for early detection of nephrotoxicity in clinical drug development

Early detection of drug-induced kidney injury is vital in drug development. Generally accepted biomarkers such as creatinine and blood urea nitrogen (BUN) lack sensitivity and early injury responses are missed. Many new biomarkers to detect nephrotoxicity for pre-clinical utilization have been described and their use is adopted in regulatory guidelines. However, guidance on appropriate biomarkers for clinical trials is minimal. We provide an overview of potentially useful kidney biomarkers that can be used in clinical trials. This includes guidance to select biomarkers suitable to capture specific characteristics of the (expected) kidney injury. We conclude that measurement of urinary kidney injury marker-1 (KIM-1) serves many purposes and is often an appropriate choice. Cystatin C captures effects on glomerular filtration rate (GFR), but this marker should preferably be combined with more specific markers to localize the origin of the observed effect. Untoward effects on tubules can be captured relatively well with several markers. Direct detection of glomerular injury is currently impossible since specific biomarkers are lacking. Indirect assessment of toxic effects on glomeruli is possible by using carefully selected panels of other injury markers. We conclude that it is possible to obtain appropriate information on nephrotoxicity in clinical drug development by using carefully selected panels of injury markers and suggest that identification and validation of specific glomerular biomarkers could be of great value.

Mitochondrial dysfunction and oxidative damage in the liver and kidney of rats following exposure to copper nanoparticles for five consecutive days

Mitochondrial dysfunction and oxidative damage may be the initial events of copper nanoparticle (CuNP)-induced hepato and nephrotoxicity.

Recent Successes in the Identification, Development, and Qualification of Translational Biomarkers

The development of novel safety or efficacy biomarkers has increasingly been used to improve safety monitoring and minimize attrition during drug development; however, for new biomarkers, the failure rate can equal or exceed that of new chemical entities. Drug-induced kidney injury is recognized to occur throughout the drug development process, with histopathology considered to be the gold standard for preclinical toxicologic screening. Renal biomarkers used clinically are primarily biomarkers of renal function and are considered insensitive for the detection of drug-induced kidney injury during first-in-man studies, particularly for compounds known to induce renal injury in preclinical species. Recent efforts by public–private partnerships have led to unprecedented success in the identification, development, and qualification of several new translatable biomarkers of kidney injury in the rat. To optimize the chance of success in current and future biomarker efforts in preclinical species and man, selection and development of biomarkers should emphasize biological considerations including marker variability and biology in both health and disease. The research to support the qualification of novel renal safety markers for routine use in the clinical setting is currently underway, and results from this work are greatly anticipated.

Use of urinary renal biomarkers to evaluate the nephrotoxic effects of melamine or cyanuric acid in non-pregnant and pregnant rats

Although traditional assessments of renal damage detect loss of kidney function, urinary renal biomarkers are proposed to indicate early changes in renal integrity. The recent adulteration of infant formula and other milk-based foods with melamine revealed a link between melamine ingestion and nephropathy. Thus, the effects of melamine and related analogs (e.g., cyanuric acid) should be assessed in other potentially sensitive groups. We evaluated whether urinary Kim-1, clusterin, and osteopontin could detect the effects of high doses of melamine or cyanuric acid in pregnant and non-pregnant female rats gavaged with 1000 mg/kg bw/day for 10 days. We demonstrate that these biomarkers can differentiate the severity of effects induced by melamine or cyanuric acid. All melamine-treated animals experienced adverse effects; however, pregnant rats were most sensitive as indicated by increased SCr, BUN, and kidney weights, decreased body weight, and presence of renal crystals. These effects coincided with elevated urinary biomarker levels as early as day 2 of exposure. One cyanuric acid-treated rat displayed effects similar to melamine, including increased urinary biomarker levels. This work illustrates that these biomarkers can detect early effects of melamine or cyanuric acid crystal-induced nephropathy and further supports the use of urinary protein immunoassays as a powerful, non-invasive method to assess nephrotoxicity.

Evaluation of the usefulness of novel biomarkers for drug-induced acute kidney injury in beagle dogs

As kidney is a major target organ affected by drug toxicity, early detection of renal injury is critical in preclinical drug development. In past decades, a series of novel biomarkers of drug-induced nephrotoxicity were discovered and verified in rats. However, limited data regarding the performance of novel biomarkers in non-rodent species are publicly available. To increase the applicability of these biomarkers, we evaluated the performance of 4 urinary biomarkers including neutrophil gelatinase-associated lipocalin (NGAL), clusterin, total protein, and N-acetyl-β-D-glucosaminidase (NAG), relative to histopathology and traditional clinical chemistry in beagle dogs with acute kidney injury (AKI) induced by gentamicin. The results showed that urinary NGAL and clusterin levels were significantly elevated in dogs on days 1 and 3 after administration of gentamicin, respectively. Gene expression analysis further provided mechanistic evidence to support that NGAL and clusterin are potential biomarkers for the early assessment of drug-induced renal damage. Furthermore, the high area (both AUCs=1.000) under receiver operator characteristics (ROC) curve also indicated that NGAL and clusterin were the most sensitive biomarkers for detection of gentamicin-induced renal proximal tubular toxicity. Our results also suggested that NAG may be used in routine toxicity testing due to its sensitivity and robustness for detection of tissue injury. The present data will provide insights into the preclinical use of these biomarkers for detection of drug-induced AKI in non-rodent species.

Emerging biomarkers and metabolomics for assessing toxic nephropathy and acute kidney injury (AKI) in neonatology

Identification of novel drug-induced toxic nephropathy and acute kidney injury (AKI) biomarkers has been designated as a top priority by the American Society of Nephrology. Increasing knowledge in the science of biology and medicine is leading to the discovery of still more new biomarkers and of their roles in molecular pathways triggered by physiological and pathological conditions. Concomitantly, the development of the so-called "omics" allows the progressive clinical utilization of a multitude of information, from those related to the human genome (genomics) and proteome (proteomics), including the emerging epigenomics, to those related to metabolites (metabolomics). In preterm newborns, one of the most important factors causing the pathogenesis and the progression of AKI is the interaction between the individual genetic code, the environment, the gestational age, and the disease. By analyzing a small urine sample, metabolomics allows to identify instantly any change in phenotype, including changes due to genetic modifications. The role of liquid chromatography-mass spectrometry (LC-MS), proton nuclear magnetic resonance (1H NMR), and other emerging technologies is strategic, contributing basically to the sudden development of new biochemical and molecular tests. Urine neutrophil gelatinase-associated lipocalin (uNGAL) and kidney injury molecule-1 (KIM-1) are closely correlated with the severity of kidney injury, representing noninvasive sensitive surrogate biomarkers for diagnosing, monitoring, and quantifying kidney damage. To become routine tests, uNGAL and KIM-1 should be carefully tested in multicenter clinical trials and should be measured in biological fluids by robust, standardized analytical methods.

Therapeutic translation in acute kidney injury: the epithelial/endothelial axis

Acute kidney injury (AKI) remains a major clinical event with rising incidence, severity, and cost; it now has a morbidity and mortality exceeding acute myocardial infarction. There is also a documented conversion to and acceleration of chronic kidney disease to end-stage renal disease. The multifactorial nature of AKI etiologies and pathophysiology and the lack of diagnostic techniques have hindered translation of preclinical success. An evolving understanding of epithelial, endothelial, and inflammatory cell interactions and individualization of care will result in the eventual development of effective therapeutic strategies. This review focuses on epithelial and endothelial injury mediators, interactions, and targets for therapy.

Normal Ranges and Variability of Novel Urinary Renal Biomarkers in Sprague-Dawley Rats

Differences were examined between male and female Sprague-Dawley rats in basal levels of a wide range of urinary biomarkers, including 7 recently qualified biomarkers. The data were generated from urine samples collected on 3 occasions from untreated rats included in a study of the effect of gentamicin nephrotoxicity on urinary renal biomarkers, reported in a companion article in this journal (Gautier et al. 2014). The performance of multiple assays (9 singleplex assays and 2 multiplex platforms from Rules Based Medicine [RBM] and Meso Scale Discovery [MSD]) was evaluated, and normal ranges and variability estimates were derived. While variability was generally greater on the RBM platform than other assays, the more striking difference in the results from different assays was in magnitude. Where differences were observed between assays for an individual biomarker, they were seen in both sexes and consistent across samples collected at different time points. Differences of up to 15-fold were observed for some biomarker values between assays indicating that results generated using different assays should not be compared. For 8 biomarkers, there was compelling evidence for a sex difference. Baseline values in males were significantly higher than in females for total protein, β2-microglobulin, clusterin, cystatin-C, glutathione-S-transferase (GST-α), tissue inhibitor of metalloproteinases (TIMP-1), and vascular endothelial growth factor (VEGF); female values were significantly higher than that of males for albumin. The largest sex differences (male greater than female by 2- to 11-fold) were seen with β2-microglobulin, GST-α, and TIMP-1. These data add substantially to the limited body of knowledge in this area and provide a useful framework for evaluation of the potential relevance of sex differences in the diagnostic performance of these biomarkers.

Kidney injury molecule-1 expression in IgA nephropathy and its correlation with hypoxia and tubulointerstitial inflammation

Tubulointerstitial injury plays an important role in the development and progression of chronic kidney disease (CKD). Kidney injury molecule (KIM)-1 is induced in damaged proximal tubules in both acute renal injury and CKD. However, the dynamics of KIM-1 in CKD and effects of KIM-1 expression on disease progression are unknown. Here, we aimed to determine the associations between tubular KIM-1 expression levels, renal function, and inflammation in CKD. The relationships between levels of KIM-1 and clinicopathological parameters were analyzed in patients with progressive and nonprogressive IgA nephropathy. KIM-1 expression was increased in patients with IgA nephropathy, and its expression was significantly correlated with the decrease of renal function. KIM-1 was particularly evident at the site with reduced capillary density, and KIM-1-positive tubules were surrounded by infiltrates of inflammatory cells. Using in vitro cell models, we showed that cellular stressors, including hypoxia, induced KIM-1 expression. KIM-1-expressing cells produced more chemokines/cytokines when cultured under hypoxic conditions. Furthermore, we showed that tubular cells with KIM-1 expression can regulate the immune response of inflammatory cells through the secretion of chemotactic factors. These data suggest that KIM-1-expressing epithelial cells may play a role in the pathogenesis of tubulointerstitial inflammation during chronic renal injury through the secretion of chemokines/cytokines.

Kidney injury molecule-1: a translational journey

Kidney injury molecule-1 (KIM-1, also named TIM-1 and HAVCR-1) was identified as the most highly upregulated protein in the proximal tubule of the kidney after injury. This protein is present with injury in multiple species including man, and also after a large number of acute and chronic insults to the kidney. It is a type-1 membrane protein whose ectodomain is released into the lumen of the tubule. The ectodomain is heavily glycosylated and stable and appears in the urine after injury. It has been qualified by the United States Food and Drug Administration and the European Medicines Agency for preclinical assessment of nephrotoxicity and on a case-by-case basis for clinical evaluation. As a biomarker in humans, its utility has been demonstrated in acute and chronic injury and in renal cell carcinoma, a condition similar to injury, where there is dedifferentiation of the epithelial cell. KIM-1 is a phosphatidylserine receptor which recognizes apoptotic cells directing them to lysosomes. It also serves as a receptor for oxidized lipoproteins and hence is important for uptake of components of the tubular lumen which may be immunomodulatory and/or toxic to the cell. KIM-1 is unique in being the first molecule, not also present on myeloid cells, that transforms kidney proximal epithelial cells into semi-professional phagocytes. Data suggest that KIM-1 expression is protective during early injury, whereas in chronic disease states, prolonged KIM-1 expression may be maladaptive and may represent a target for therapy of chronic kidney disease.

Time-series pattern of gene expression profile in gentamycin-induced nephrotoxicity

There have been many studies investigating the genomic biomarker and/or molecular mechanism of nephrotoxicity using microarray. However, most of these researches were carried out by studying gene expression changes at one specific time point. As gene expression varies with time and disease stage, the current study investigated the time-series pattern of gene expression in a rat model using a typical nephrotoxic compound. Rats were administrated with 80 mg/kg gentamycin or saline by intramuscular injection for 14 consecutive days followed by a 28-d recovery. Rats were scarified on D2, D4, D8, D15 and Recovery Day (R29), when kidneys were obtained for whole-genome microarray analysis and histological examination. Urine was collected at each necropsy for kidney injury molecular-1 (KIM-1) analysis. The KIM-1 detection and histological examination confirmed the nephrotoxicity. After differentially expression genes (DEGs) identification, there were 4360 and 4323 regulated genes for females and males, respectively. However, few overlapping expression genes co-regluated at each time point were found. By principle component analysis (PCA) and hierarchical cluster, the gene expression patterns were observed to be apparently associated with the disease stage. GO Annotation showed (1) immune response and related process, response to wounding, cell locomotion on D2; (2) cell death and apoptosis was also noted on D4; (3) processes of organic acid or carboxylic acid, apoptosis or cell death on D8 and D15; (4) processes of cell cycle, mitosis, division cell cycle on R29. In conclusion, the authors mapped the time-series gene expression patterns at the initiation, development and recovery stage of gentamycin-induced nephrotoxicity.

A bioinformatics approach identifies signal transducer and activator of transcription-3 and checkpoint kinase 1 as upstream regulators of kidney injury molecule-1 after kidney injury

Kidney injury molecule-1 (KIM-1)/T cell Ig and mucin domain-containing protein-1 (TIM-1) is upregulated more than other proteins after AKI, and it is highly expressed in renal damage of various etiologies. In this capacity, KIM-1/TIM-1 acts as a phosphatidylserine receptor on the surface of injured proximal tubular epithelial cells, mediating phagocytosis of apoptotic cells, and it may also act as a costimulatory molecule for immune cells. Despite recognition of KIM-1 as an important therapeutic target for kidney disease, the regulators of KIM-1 transcription in the kidney remain unknown. Using a bioinformatics approach, we identified upstream regulators of KIM-1 after AKI. In response to tubular injury in rat and human kidneys or oxidant stress in human proximal tubular epithelial cells (HPTECs), KIM-1 expression increased significantly in a manner that corresponded temporally and regionally with increased phosphorylation of checkpoint kinase 1 (Chk1) and STAT3. Both ischemic and oxidant stress resulted in a dramatic increase in reactive oxygen species that phosphorylated and activated Chk1, which subsequently bound to STAT3, phosphorylating it at S727. Furthermore, STAT3 bound to the KIM-1 promoter after ischemic and oxidant stress, and pharmacological or genetic induction of STAT3 in HPTECs increased KIM-1 mRNA and protein levels. Conversely, inhibition of STAT3 using siRNAs or dominant negative mutants reduced KIM-1 expression in a kidney cancer cell line (769-P) that expresses high basal levels of KIM-1. These observations highlight Chk1 and STAT3 as critical upstream regulators of KIM-1 expression after AKI and may suggest novel approaches for therapeutic intervention.

Genomic and proteomic analyses of 1,3-dinitrobenzene-induced testicular toxicity in Sprague-Dawley rats

1,3-Dinitrobenzene (DNB) is an industrial intermediate and testicular toxicant that has been shown to target Sertoli cells. The mechanism of action of DNB in the testis, however, is unclear. To investigate global alterations in gene or protein expression during testicular toxicity, testes from rats treated orally with DNB were subjected to microarray and two-dimensional gel electrophoresis (2-DE) analyses. Histopathological abnormalities were detected in the testes of the DNB-treated rats. Microarray analysis revealed that, during early testicular toxicity, several genes involved in apoptosis, germ cell/Sertoli cell junction, and tight junction signaling pathways were differentially expressed. Based on 2-DE analysis, 36 protein spots showing significantly different expression during early testicular toxicity were selected and identified. Network analysis of the identified proteins revealed that these proteins are associated with cellular development or reproductive system diseases. Collectively, these data will help clarify the molecular mechanism underlying testicular toxicity in DNB-exposed rats.

Identification of metabolomic biomarkers for drug-induced acute kidney injury in rats

Nephrotoxicity is a common side effect observed during both nonclinical and clinical drug development investigations. The present study aimed to identify metabolomic biomarkers that could provide early and sensitive indication of nephrotoxicity in rats. Metabolomic analyses were performed using capillary electrophoresis-time-of-flight mass spectrometry on rat plasma collected at 9 and 24 h after a single dose of 2-bromoethylamine or n-phenylanthranilic acid and at 24 h after 7 days of repeated doses of gentamicin, cyclosporine A or cisplatin. Among a total of 169 metabolites identified, 3-methylhistidine (3-MH), 3-indoxyl sulfate (3-IS) and guanidoacetate (GAA) were selected as candidate biomarkers. The biological significance and reproducibility of the observed changes were monitored over time in acute nephrotoxicity model rats treated with a single dose of cisplatin, with the glomerular filtration rate monitored by determination of creatinine clearance. Increased plasma levels of 3-MH and 3-IS were related to a decline in glomerular filtration due to a renal failure. In contrast, the decrease in plasma GAA, which is synthesized from arginine and glycine in the kidneys, was considered to reflect decreased production due to renal malfunction. Although definitive validation studies are required to confirm their usefulness and reliability, 3-MH, 3-IS and GAA may prove to be valuable plasma biomarkers for monitoring nephrotoxicity in rats.

Cell cycle arrest in a model of colistin nephrotoxicity

Colistin (polymixin E) is an antibiotic prescribed with resurging frequency for multidrug resistant gram negative bacterial infections. It is associated with nephrotoxicity in humans in up to 55% of cases. Little is known regarding genes involved in colistin nephrotoxicity. A murine model of colistin-mediated kidney injury was developed. C57/BL6 mice were administered saline or colistin at a dose of 16 mg/kg/day in 2 divided intraperitoneal doses and killed after either 3 or 15 days of colistin. After 15 days, mice exposed to colistin had elevated blood urea nitrogen (BUN), creatinine, and pathologic evidence of acute tubular necrosis and apoptosis. After 3 days, mice had neither BUN elevation nor substantial pathologic injury; however, urinary neutrophil gelatinase-associated lipocalin was elevated (P = 0.017). An Illumina gene expression array was performed on kidney RNA harvested 72 h after first colistin dose to identify differentially expressed genes early in drug treatment. Array data revealed 21 differentially expressed genes (false discovery rate < 0.1) between control and colistin-exposed mice, including LGALS3 and CCNB1. The gene signature was significantly enriched for genes involved in cell cycle proliferation. RT-PCR, immunoblot, and immunostaining validated the relevance of key genes and proteins. This murine model offers insights into the potential mechanism of colistin-mediated nephrotoxicity. Further studies will determine whether the identified genes play a causative or protective role in colistin-induced nephrotoxicity.

Blood transcriptomics: applications in toxicology

The number of new chemicals that are being synthesized each year has been steadily increasing. While chemicals are of immense benefit to mankind, many of them have a significant negative impact, primarily owing to their inherent chemistry and toxicity, on the environment as well as human health. In addition to chemical exposures, human exposures to numerous non-chemical toxic agents take place in the environment and workplace. Given that human exposure to toxic agents is often unavoidable and many of these agents are found to have detrimental human health effects, it is important to develop strategies to prevent the adverse health effects associated with toxic exposures. Early detection of adverse health effects as well as a clear understanding of the mechanisms, especially at the molecular level, underlying these effects are key elements in preventing the adverse health effects associated with human exposure to toxic agents. Recent developments in genomics, especially transcriptomics, have prompted investigations into this important area of toxicology. Previous studies conducted in our laboratory and elsewhere have demonstrated the potential application of blood gene expression profiling as a sensitive, mechanistically relevant and practical surrogate approach for the early detection of adverse health effects associated with exposure to toxic agents. The advantages of blood gene expression profiling as a surrogate approach to detect early target organ toxicity and the molecular mechanisms underlying the toxicity are illustrated and discussed using recent studies on hepatotoxicity and pulmonary toxicity. Furthermore, the important challenges this emerging field in toxicology faces are presented in this review article.

Comparison of 3 Kidney Injury Multiplex Panels in Rats

Kidney injury biomarkers have been utilized by pharmaceutical companies as a means to assess the potential of candidate drugs to induce nephrotoxicity. Multiple platforms and assay methods exist, but the comparison of these methods has not been described. Millipore’s Kidney Toxicity panel, EMD/Novagen’s Widescreen Kidney Toxicity panel, and Meso Scales Kidney Injury panel were selected based on published information. Kidney injury molecule 1, cystatin C, clusterin, and osteopontin were the 4 biomarkers common among all kits tested and the focus of this study. Rats were treated with a low and high dose of para-aminophenol, a known nephrotoxicant, and urine samples were collected and analyzed on the Bio-Plex 200 or MSD’s Sector Imager 6000, according to manufacturers specifications. Comparatively, of the 3 kits, Millipore was the most consistent in detecting elevations of 3 out of the 4 biomarkers at both dose levels and indicated time points.

Qualified kidney biomarkers and their potential significance in drug safety evaluation and prediction

The kidney is one of the major organs drug toxicity may target. Some renal safety biomarkers have been proposed to measure kidney injury and function accordingly. Despite the widespread use for diagnosis and monitoring of renal injury and function for decades, serum creatinine and blood urea nitrogen are nonspecific biomarkers with insensitive and delayed response in the clinical setting. There is an urgent need to identify and qualify novel kidney safety biomarkers that would be used to detect and predict drug-induced nephrotoxicity in preclinical toxicological studies, clinical trials and patient care in sequence. To do that, eight novel renal safety biomarkers have been well characterized and qualified for preclinical drug safety screening, and their clinical bridging validation is underway as well. Of them, some are used to detect or predict proximal tubular injury, and others are used to diagnose and monitor glomerular damage. Thus, measurement of a panel of kidney safety biomarkers in parallel would help maximally capture all potential safety signals for a more informative decision to be made in drug research and development as well as for optimal selection of the drug and its dose in clinical practice.

Potential new targets involved in 1,3-dinitrobenzene induced testicular toxicity

1,3-Dinitrobenzene (DNB) causes testicular injury, particularly to Sertoli cells, and induces apoptosis in the surrounding germinal cells in rodents; however, the mechanisms causing this toxicity are poorly understood. Our studies, using standard and molecular tools, were conducted to better understand the pathogenesis of the testicular effects. Four daily oral doses of 0.1-8mg/kg/day caused marked testicular lesions in rats from 4mg/kg/day. Global transcriptomics revealed cell cycle and cell death as the major biological processes affected with the expression of genes associated with cell cycle progression ("mitotic roles of polo-like kinase") being particularly altered. In a single dose time course study (4mg/kg), no adverse changes were recorded; however, in contrast to the data from the multiple dose study, plasma testosterone and testicular steroidogenesis-related gene expression were affected. These steroid hormone effects were confirmed in vitro using the H295R steroidogenesis assay. With this global approach we show that DNB not only induces apoptosis and interferes with cell cycle in the testes but that DNB can also modulate steroid hormone biosynthesis, suggesting an interference with the endocrine system. However, the contribution of the endocrine changes to the severe testicular lesions is presently unknown and requires further investigation.

Gene expression profiling of nephrotoxicity from copper nanoparticles in rats after repeated oral administration

The goal of this study was to investigate the mechanisms of nanocopper-induced nephrotoxicity by analyzing renal gene expression profiles phenotypically anchored to conventional toxicological outcomes. Male Wistar rats were given nanocopper (50, 100, 200 mg/kg) and microcopper (200 mg/kg) at different doses for 5 days. We found nanocopper can induce widespread renal proximal tubule necrosis in rat kidneys with blood urea nitrogen and creatinine increase. Whole genome transcriptome profiling of rat kidneys revealed significant alterations in the expression of many genes involved in valine, leucine, and isoleucine degradation, complement and coagulation cascades, oxidative phosphorylation, cell cycle, mitogen-activated protein kinase signaling pathway, glutathione metabolism, and others may be involved in the development of these phenotypes. Results from this study provide new insights into the nephrotoxicity of copper nano-particles and illustrate how toxicogenomic approaches are providing an unprecedented amount of mechanistic information on molecular responses to nanocopper and how they are likely to impact hazard and risk assessment.

[Kidney injury biomarkers]

Over the last few decades, prevalence of renal diseases has grown continuously in occidental societies due to life conditions (age, life style, chronic disease, etc.) or potential exposure to nephrotoxic agents (drugs and environmental chemicals). Today, the knowledge of the nephropatology mechanism is improving. Nevertheless, considering it is a complex and multifunctional structure, the clinical strategy of this issue (prognostic, diagnostic or therapy) keeps posing a major challenge for clinicians mostly because classical markers are not sensitive enough and require hours before reaching significant levels. Furthermore, most of these markers provide information on function and not on structural integrity of the tissue. Identification and development of new biomarkers share promise of improvement in the rapid diagnostic of kidney diseases and development of new cures in order to optimize the clinical strategy associated to the renal failure.

Influence of systemic administration of atelocollagen on mouse livers: an ideal biomaterial for systemic drug delivery

Atelocollagen (AC), a biomaterial with low antigenicity and high bioaffinity, has been widely used in implantable materials in clinical practice. Preclinical studies have demonstrated that AC is a potential drug carrier for local and systemic delivery of cytokines, growth factors, plasmid DNA, small interfering RNA, and microRNA. AC is also believed to have low systemic toxicity on the basis of the safety of implant usage; however, this is not enough determined. Therefore, we performed whole genome expression profiling in mouse liver after systemic administration of AC or the cationic liposome carrier DOTAP/cholesterol (LP) and compared the changes of gene expressions associated with hepatotoxicity. Microarray analysis revealed that systemic LP administration significantly increased expression of toxicity-related genes, i.e., those for lipocalin-2, cyclin-dependent kinase inhibitor 1A, serum amyloid A isoforms, chemokine ligands, and granzyme B. Alternatively, AC administration did not alter the expression of any of these genes. Further gene ontology (GO) enrichment analysis highlighted the characteristic annotations extracted from genes upregulated after LP administration, and most of them were related to toxicity annotations such as immune response, inflammatory response, and apoptosis induction. In contrast, GO enrichment analysis of genes induced after AC administration revealed that only three annotations, all of which were unrelated to toxicity. These findings indicate that AC is potentially far less hepatotoxic than LP after systemic administration, suggesting that AC may be an excellent biomaterial for nontoxic drug delivery system carriers.

Molecular insights into the progression of crystalline silica-induced pulmonary toxicity in rats

Identification of molecular target(s) and mechanism(s) of silica-induced pulmonary toxicity is important for the intervention and/or prevention of diseases associated with exposure to silica. Rats were exposed to crystalline silica by inhalation (15 mg m(-3), 6 h per day, 5 days) and global gene expression profile was determined in the lungs by microarray analysis at 1, 2, 4, 8 and 16 weeks following termination of silica exposure. The number of significantly differentially expressed genes (>1.5-fold change and <0.01 false discovery rate P-value) detected in the lungs during the post-exposure time intervals analyzed exhibited a steady increase in parallel with the progression of silica-induced pulmonary toxicity noticed in the rats. Quantitative real-time PCR analysis of a representative set of 10 genes confirmed the microarray findings. The number of biological functions, canonical pathways and molecular networks significantly affected by silica exposure, as identified by the bioinformatics analysis of the significantly differentially expressed genes detected during the post-exposure time intervals, also exhibited a steady increase similar to the silica-induced pulmonary toxicity. Genes involved in oxidative stress, inflammation, respiratory diseases, cancer, and tissue remodeling and fibrosis were significantly differentially expressed in the rat lungs; however, unresolved inflammation was the single most significant biological response to pulmonary exposure to silica. Excessive mucus production, as implicated by significant overexpression of the pendrin coding gene, SLC26A4, was identified as a potential novel mechanism for silica-induced pulmonary toxicity. Collectively, the findings of our study provided insights into the molecular mechanisms underlying the progression of crystalline silica-induced pulmonary toxicity in the rat. Published 2012. This article is a US Government work and is in the public domain in the USA.

Preclinical perspective of urinary biomarkers for the detection of nephrotoxicity: what we know and what we need to know

The assessment of kidney damage is a challenge and must incorporate assessment of the functional capacity of the kidney, as well as a comprehensive understanding of the kidney's role. Multiple parameters have been used for many years to measure renal functionality to assess renal damage. It is astonishing that, beside histopathology, the most common traditional parameters are serum based. However, urine is also used to obtain additional information regarding the health status of the kidneys. Since 2008, several novel urinary protein biomarkers have been qualified by the US FDA and the European Medicines Agency in conjunction with the Predictive Safety Testing Consortium in a specially developed qualification process. Subsequently, the Pharmaceuticals and Medical Devices Agency accepted the qualification of these seven urinary biomarkers. This review will give an overview of the state-of-the-art detection based on urinary biomarkers, which will enhance toxicological research in the future. In addition, the qualification process that leads to acceptance of these biomarkers will be described because of its uniqueness and importance for the field of biomarker research.

Multiwalled carbon nanotube-induced gene signatures in the mouse lung: potential predictive value for human lung cancer risk and prognosis

Concerns over the potential for multiwalled carbon nanotubes (MWCNT) to induce lung carcinogenesis have emerged. This study sought to (1) identify gene expression signatures in the mouse lungs following pharyngeal aspiration of well-dispersed MWCNT and (2) determine if these genes were associated with human lung cancer risk and progression. Genome-wide mRNA expression profiles were analyzed in mouse lungs (n = 160) exposed to 0, 10, 20, 40, or 80 μg of MWCNT by pharyngeal aspiration at 1, 7, 28, and 56 d postexposure. By using pairwise statistical analysis of microarray (SAM) and linear modeling, 24 genes were selected, which have significant changes in at least two time points, have a more than 1.5-fold change at all doses, and are significant in the linear model for the dose or the interaction of time and dose. Additionally, a 38-gene set was identified as related to cancer from 330 genes differentially expressed at d 56 postexposure in functional pathway analysis. Using the expression profiles of the cancer-related gene set in 8 mice at d 56 postexposure to 10 μg of MWCNT, a nearest centroid classification accurately predicts human lung cancer survival with a significant hazard ratio in training set (n = 256) and test set (n = 186). Furthermore, both gene signatures were associated with human lung cancer risk (n = 164) with significant odds ratios. These results may lead to development of a surveillance approach for early detection of lung cancer and prognosis associated with MWCNT in the workplace.

New perspectives for in vitro risk assessment of multiwalled carbon nanotubes: application of coculture and bioinformatics

Nanotechnology is a rapidly expanding field with wide application for industrial and medical use; therefore, understanding the toxicity of engineered nanomaterials is critical for their commercialization. While short-term in vivo studies have been performed to understand the toxicity profile of various nanomaterials, there is a current effort to shift toxicological testing from in vivo observational models to predictive and high-throughput in vitro models. However, conventional monoculture results of nanoparticle exposure are often disparate and not predictive of in vivo toxic effects. A coculture system of multiple cell types allows for cross-talk between cells and better mimics the in vivo environment. This review proposes that advanced coculture models, combined with integrated analysis of genome-wide in vivo and in vitro toxicogenomic data, may lead to development of predictive multigene expression-based models to better determine toxicity profiles of nanomaterials and consequent potential human health risk due to exposure to these compounds.

Mechanisms of crystalline silica-induced pulmonary toxicity revealed by global gene expression profiling

A proper understanding of the mechanisms underlying crystalline silica-induced pulmonary toxicity has implications in the management and potential prevention of the adverse health effects associated with silica exposure including silicosis, cancer and several auto-immune diseases. Human lung type II epithelial cells and rat lungs exposed to crystalline silica were employed as experimental models to determine global gene expression changes in order to understand the molecular mechanisms underlying silica-induced pulmonary toxicity. The differential gene expression profile induced by silica correlated with its toxicity in the A549 cells. The biological processes perturbed by silica exposure in the A549 cells and rat lungs, as identified by the bioinformatics analysis of the differentially expressed genes, demonstrated significant similarity. Functional categorization of the differentially expressed genes identified cancer, cellular movement, cellular growth and proliferation, cell death, inflammatory response, cell cycle, cellular development, and genetic disorder as top ranking biological functions perturbed by silica exposure in A549 cells and rat lungs. Results of our study, in addition to confirming several previously identified molecular targets and mechanisms involved in silica toxicity, identified novel molecular targets and mechanisms potentially involved in silica-induced pulmonary toxicity. Further investigations, including those focused on the novel molecular targets and mechanisms identified in the current study may result in better management and, possibly, reduction and/or prevention of the potential adverse health effects associated with crystalline silica exposure.

Cellular pathophysiology of ischemic acute kidney injury

Ischemic kidney injury often occurs in the context of multiple organ failure and sepsis. Here, we review the major components of this dynamic process, which involves hemodynamic alterations, inflammation, and endothelial and epithelial cell injury, followed by repair that can be adaptive and restore epithelial integrity or maladaptive, leading to chronic kidney disease. Better understanding of the cellular pathophysiological processes underlying kidney injury and repair will hopefully result in the design of more targeted therapies to prevent the injury, hasten repair, and minimize chronic progressive kidney disease.

Biomarkers for drug-induced renal damage and nephrotoxicity-an overview for applied toxicology

The detection of acute kidney injury (AKI) and the monitoring of chronic kidney disease (CKD) is becoming more important in industrialized countries. Because of the direct relation of kidney damage to the increasing age of the population, as well as the connection to other diseases like diabetes mellitus and congestive heart failure, renal diseases/failure has increased in the last decades. In addition, drug-induced kidney injury, especially of patients in intensive care units, is very often a cause of AKI. The need for diagnostic tools to identify drug-induced nephrotoxicity has been emphasized by the ICH-regulated agencies. This has lead to multiple national and international projects focusing on the identification of novel biomarkers to enhance drug development. Several parameters related to AKI or CKD are known and have been used for several decades. Most of these markers deliver information only when renal damage is well established, as is the case for serum creatinine. The field of molecular toxicology has spawned new options of the detection of nephrotoxicity. These new developments lead to the identification of urinary protein biomarkers, including Kim-1, clusterin, osteopontin or RPA-1, and other transcriptional biomarkers which enable the earlier detection of AKI and deliver further information about the area of nephron damage or the underlying mechanism. These biomarkers were mainly identified and qualified in rat but also for humans, several biomarkers have been described and now have to be validated. This review will give an overview of traditional and novel tools for the detection of renal damage.

The association between urinary kidney injury molecule 1 and urinary cadmium in elderly during long-term, low-dose cadmium exposure: a pilot study

BACKGROUND

Urinary kidney injury molecule 1 is a recently discovered early biomarker for renal damage that has been proven to be correlated to urinary cadmium in rats. However, so far the association between urinary cadmium and kidney injury molecule 1 in humans after long-term, low-dose cadmium exposure has not been studied.

METHODS

We collected urine and blood samples from 153 non-smoking men and women aged 60+, living in an area with moderate cadmium pollution from a non-ferrous metal plant for a significant period. Urinary cadmium and urinary kidney injury molecule 1 as well as other renal biomarkers (alpha1-microglobulin, beta2-microglobulin, blood urea nitrogen, urinary proteins and microalbumin) were assessed.

RESULTS

Both before (r = 0.20; p = 0.01) and after (partial r = 0.32; p < 0.0001) adjustment for creatinine, age, sex, past smoking, socio-economic status and body mass index, urinary kidney injury molecule 1 correlated with urinary cadmium concentrations. No significant association was found between the other studied renal biomarkers and urinary cadmium.

CONCLUSIONS

We showed that urinary kidney injury molecule 1 levels are positively correlated with urinary cadmium concentration in an elderly population after long-term, low-dose exposure to cadmium, while other classical markers do not show an association. Therefore, urinary kidney injury molecule 1 might be considered as a biomarker for early-stage metal-induced kidney injury by cadmium.

Fibrinogen β-derived Bβ(15-42) peptide protects against kidney ischemia/reperfusion injury

Ischemia/reperfusion (I/R) injury in the kidney is a major cause of acute kidney injury (AKI) in humans and is associated with significantly high mortality. To identify genes that modulate kidney injury and repair, we conducted genome-wide expression analysis in the rat kidneys after I/R and found that the mRNA levels of fibrinogen (Fg)α, Fgβ, and Fgγ chains significantly increase in the kidney and remain elevated throughout the regeneration process. Cellular characterization of Fgα and Fgγ chain immunoreactive proteins shows a predominant expression in renal tubular cells and the localization of immunoreactive Fgβ chain protein is primarily in the renal interstitium in healthy and regenerating kidney. We also show that urinary excretion of Fg is massively increased after kidney damage and is capable of distinguishing human patients with acute or chronic kidney injury (n = 25) from healthy volunteers (n = 25) with high sensitivity and specificity (area under the receiver operating characteristic of 0.98). Furthermore, we demonstrate that Fgβ-derived Bβ(15-42) peptide administration protects mice from I/R-induced kidney injury by aiding in epithelial cell proliferation and tissue repair. Given that kidney regeneration is a major determinant of outcome for patients with kidney damage, these results provide new opportunities for the use of Fg in diagnosis, prevention, and therapeutic interventions in kidney disease.

The protective effect of erdosteine on radiocontrast induced nephrotoxicity in rats

Acute renal failure resulting from radiocontrast-induced nephrotoxicity (RIN) is suggested to occur via medullary ischemia coupled with the generation of free radicals and oxidative injury to tubular cells. The aim of the present study was to assess the effects of erdosteine on prevention of RIN. Thirty-three Wistar-albino rats were divided into five groups: control (group 1, n = 6), radiocontrast media (group 2, n = 6), erdosteine (group 3, n = 7), erdosteine four doses before radiocontrast application (group 4, n = 7) and erdosteine one dose at the same day with radiocontrast application (group 5, n = 7). RIN was induced by administration of intravenous high osmolar contrast media amidotrizoate (6 mL/kg). Total RNA was extracted from the kidney, and the expression levels of Lipocalin 2 (Lcn2) and secreted phosphoprotein 1 (Spp1) genes were evaluated by real time reverse transcription polymerase chain reaction (real-time RT-PCR). Total antioxidant status (TAS) and total oxidant status (TOS) were measured in kidney homogenates and serum samples. Serum creatinine, BUN (Blood Urea Nitrogen) and cystatin-C levels were measured from serum samples. The kidneys were evaluated histopathologically. The expression levels of Spp1 and Lcn2 genes in group 2 were significantly higher than groups 1, 3, 4, and 5. The expression levels of Spp1 and Lcn2 genes in group 4 were four and two times lower than group 5, respectively. Kidney TOS levels in group 2 were significantly higher than groups 1, 3, 4, and 5. Kidney TAS levels in group 3 were higher than group 2. Kidney oxidative stress index (OSI) levels in group 2 were significantly higher than groups 4 and 5. All rats in contrast media group developed tubular necrosis, proteinaceous casts, medullary congestion although these changes were significantly reduced in groups 4 and 5. This study demonstrated that multiple doses of erdosteine before application may have higher protective effects against RIN.

Biomarkers of acute kidney injury in children: discovery, evaluation, and clinical application

Acute kidney injury (AKI) in children is associated with increased mortality and prolonged length of hospital stay and may also be associated with long-term chronic kidney disease development. Despite encouraging results on AKI treatment in animal studies, no specific treatment has yet been successful in humans. One of the important factors contributing to this problem is the lack of an early AKI diagnostic test. Serum creatinine, the current main diagnostic test for AKI, rises late in AKI pathophysiology and is an inaccurate marker of acute changes in glomerular filtration rate. Therefore, new biomarkers of AKI are needed. With great advancements in genomics, proteomics, and metabolomics, new AKI biomarkers, mainly consisting of urinary proteins that appear in response to renal tubular cell injury, have been, and continue to be, discovered. These new biomarkers offer promise for early AKI diagnosis and for the depiction of severity of renal injury occurring with AKI. This review provides a summary of what a biomarker is, why we need new biomarkers of AKI, and how biomarkers are discovered and should be evaluated. The review also provides a summary of selected AKI biomarkers that have been studied in children.

The evolution of bioinformatics in toxicology: advancing toxicogenomics

As one reflects back through the past 50 years of scientific research, a significant accomplishment was the advance into the genomic era. Basic research scientists have uncovered the genetic code and the foundation of the most fundamental building blocks for the molecular activity that supports biological structure and function. Accompanying these structural and functional discoveries is the advance of techniques and technologies to probe molecular events, in time, across environmental and chemical exposures, within individuals, and across species. The field of toxicology has kept pace with advances in molecular study, and the past 50 years recognizes significant growth and explosive understanding of the impact of the compounds and environment to basic cellular and molecular machinery. The advancement of molecular techniques applied in a whole-genomic capacity to the study of toxicant effects, toxicogenomics, is no doubt a significant milestone for toxicological research. Toxicogenomics has also provided an avenue for advancing a joining of multidisciplinary sciences including engineering and informatics in traditional toxicological research. This review will cover the evolution of the field of toxicogenomics in the context of informatics integration its current promise, and limitations.

Emergence of biomarkers in nephropharmacology

Blood-urea nitrogen, serum creatinine and urine output have long been used as markers of kidney function despite their known limitations. In the past few years, a number of novel biomarkers have been identified in the urine and blood that can detect kidney injury early. Although, to date, none of these biomarkers are in clinical use, many have been validated as reliable and sensitive, allowing detection of kidney injury before serum creatinine levels rise and urine output drops. These markers have been evaluated in great detail in animal models and to a lesser extent in humans in postcardiopulmonary bypass and sepsis. There is relatively scarse data on the use of these biomarkers in the detection of kidney injury associated with the use of pharmacologic agents. The purpose of this article is to summarize these data and highlight the potential utility of these biomarkers in nephropharmacology.

Cross-study and cross-omics comparisons of three nephrotoxic compounds reveal mechanistic insights and new candidate biomarkers

The European InnoMed-PredTox project was a collaborative effort between 15 pharmaceutical companies, 2 small and mid-sized enterprises, and 3 universities with the goal of delivering deeper insights into the molecular mechanisms of kidney and liver toxicity and to identify mechanism-linked diagnostic or prognostic safety biomarker candidates by combining conventional toxicological parameters with "omics" data. Mechanistic toxicity studies with 16 different compounds, 2 dose levels, and 3 time points were performed in male Crl: WI(Han) rats. Three of the 16 investigated compounds, BI-3 (FP007SE), Gentamicin (FP009SF), and IMM125 (FP013NO), induced kidney proximal tubule damage (PTD). In addition to histopathology and clinical chemistry, transcriptomics microarray and proteomics 2D-DIGE analysis were performed. Data from the three PTD studies were combined for a cross-study and cross-omics meta-analysis of the target organ. The mechanistic interpretation of kidney PTD-associated deregulated transcripts revealed, in addition to previously described kidney damage transcript biomarkers such as KIM-1, CLU and TIMP-1, a number of additional deregulated pathways congruent with histopathology observations on a single animal basis, including a specific effect on the complement system. The identification of new, more specific biomarker candidates for PTD was most successful when transcriptomics data were used. Combining transcriptomics data with proteomics data added extra value.