Kidney toxicity accounts for a significant percentage of morbidity and drug candidate failure. Serum creatinine (SCr) and blood urea nitrogen (BUN) have been used to monitor kidney dysfunction for over a century but these markers are insensitive and non-specific. In multi-site preclinical rat toxicology studies the diagnostic performance of urinary kidney injury molecule-1 (Kim-1) was compared to traditional biomarkers as predictors of kidney tubular histopathologic changes, currently considered the “gold standard” of nephrotoxicity. In multiple models of kidney injury, urinary Kim-1 significantly outperformed SCr and BUN. The area under the receiver operating characteristic curve for Kim-1 was between 0.91 and 0.99 as compared to 0.79 to 0.9 for BUN and 0.73 to 0.85 for SCr. Thus urinary Kim-1 is the first injury biomarker of kidney toxicity qualified by the FDA and EMEA and is expected to significantly improve kidney safety monitoring.

These results demonstrate that tissue-specific miRNAs may serve as diagnostically sensitive plasma biomarkers of tissue injury.

The capacities of urinary trefoil factor 3 (TFF3) and urinary albumin to detect acute renal tubular injury have never been evaluated with sufficient statistical rigor to permit their use in regulated drug development instead of the current preclinical biomarkers serum creatinine (SCr) and blood urea nitrogen (BUN). Working with rats, we found that urinary TFF3 protein levels were markedly reduced, and urinary albumin were markedly increased in response to renal tubular injury. Urinary TFF3 levels did not respond to nonrenal toxicants, and urinary albumin faithfully reflected alterations in renal function. In situ hybridization localized TFF3 expression in tubules of the outer stripe of the outer medulla. Albumin outperformed either SCr or BUN for detecting kidney tubule injury and TFF3 augmented the potential of BUN and SCr to detect kidney damage. Use of urinary TFF3 and albumin will enable more sensitive and robust diagnosis of acute renal tubular injury than traditional biomarkers.

The Predictive Safety Testing Consortium's first regulatory submission to qualify kidney safety biomarkers revealed two deficiencies. To address the need for biomarkers that monitor recovery from agent-induced renal damage, we scored changes in the levels of urinary biomarkers in rats during recovery from renal injury induced by exposure to carbapenem A or gentamicin. All biomarkers responded to histologic tubular toxicities to varied degrees and with different kinetics. After a recovery period, all biomarkers returned to levels approaching those observed in uninjured animals. We next addressed the need for a serum biomarker that reflects general kidney function regardless of the exact site of renal injury. Our assay for serum cystatin C is more sensitive and specific than serum creatinine (SCr) or blood urea nitrogen (BUN) in monitoring generalized renal function after exposure of rats to eight nephrotoxicants and two hepatotoxicants. This sensitive serum biomarker will enable testing of renal function in animal studies that do not involve urine collection.

Novel urinary kidney safety biomarkers have been identified recently that may outperform or add value to the conventional renal function biomarkers, blood urea nitrogen (BUN) and serum creatinine (SCr). To assess the relative performance of the growing list of novel biomarkers, a comprehensive evaluation was conducted for 12 urinary biomarkers in 22 rat studies including 12 kidney toxicants and 10 compounds with toxicities observed in organs other than kidney. The kidney toxicity studies included kidney tubular toxicants and glomerular toxicants. The 12 urinary biomarkers evaluated included Kim-1, clusterin, osteopontin, osteoactivin, albumin, lipocalin-2, GST-α, β2-microglobulin, cystatin C, retinol binding protein 4, total protein, and N-acetyl-β-D-glucosaminidase. Receiver operator characteristic (ROC) curves were generated for each biomarker and for BUN and SCr to compare the relative performance of the 12 biomarkers in individual animals against the microscopic histomorphologic changes observed in the kidney. Among the kidney toxicity biomarkers analyzed, Kim-1, clusterin, and albumin showed the highest overall performance for detecting drug-induced renal tubular injury in the rat in a sensitive and specific manner, whereas albumin showed the highest performance in detecting drug-induced glomerular injury. Although most of the evaluated kidney biomarkers were more sensitive in detecting kidney toxicity compared with BUN and SCr, all biomarkers demonstrated some lack of specificity, most notably NGAL and osteopontin, illustrating the need for caution when interpreting urinary biomarker increases in rat samples when organ toxicity is unknown.

Abstract. Light microscopic and ultrastructural changes were observed in chicks challenged with North American Serpulina pilosicoli, a weakly 6-hemolytic intestinal spirochete (WBHIS) associated with human and canine intestinal spirochetosis. Chicks in control groups received trypticase soy broth or canine Serpulina innocens. The birds were necropsied at weekly intervals, and the ceca were processed for bacteriologic and pathologic examinations. No WBHIS were isolated from the ceca of chicks in the control groups, but WBHIS with genotypes similar to the parent isolates were isolated from the ceca of chicks inoculated with human and canine S. pilosicoli. Gross examination revealed no significant changes in the ceca of chicks at any time postinoculation. Light microscopic examination revealed no spirochetal attachment in the ceca of chicks in control groups. In contrast, focal to diffuse thickening of the brush border of the surface epithelium along with dilation of the crypt lumina and mild focal lamina propria heterophil infiltration were present in the ceca of chicks inoculated with human and canine S. pilosicoli. Scanning electron microscopic examination revealed focal to confluent spirochetal attachment mainly in the furrow region at the periphery of the crypt units. Transmission electron microscopic examination revealed spirochetes attached to the brush border of the cecal epithelium, causing effacement of the microvilli and disruption of the terminal web microfilaments. The cecal epithelium of chicks inoculated with the canine S. pilosicoli also had caplike elevations of the apical membrane at the point of attachment of the spirochetes together with large numbers of vesicles in the cytoplasm immediately beneath the terminal web and evidence of spirochetal invasion beyond the mucosal barrier. The changes observed suggested that the mechanism of attachment of human and canine S. pilosicoli to the cecal epithelium of chicks was analogous to but different from that described previously for other attaching and effacing gastroenteric bacterial pathogens of human beings and animals.

A significant problem faced by pharmaceutical companies today is the failure of lead compounds in the later stages of development due to unexpected toxicities. We have used two-dimensional differential in-gel electrophoresis and mass spectrometry to identify a proteomic signature associated with hepatocellular steatosis in rats after dosing with a compound in preclinical development. Liver toxicity was monitored over a 5 day dosing regime using blood biochemical parameter measurements and histopathological analysis. As early as 6 h postdosing, livers showed hepatocellular vacuolation, which increased in extent and severity over the course of the study. Alterations in plasma glucose, alanine aminotransferase, and aspartate aminotransferase were not detected until the third day of dosing and changed in magnitude up to the final day. The proteomic changes were observed at the earliest time point, and many of these could be associated with known toxicological mechanisms involved in liver steatosis. This included up-regulation of pyruvate dehydrogenase, phenylalanine hydroxylase, and 2-oxoisovalerate dehydrogenase, which are involved in acetyl-CoA production, and down-regulation of sulfite oxidase, which could play a role in triglyceride accumulation. In addition, down-regulation of the chaperone-like protein, glucose-regulated protein 78, was consistent with the decreased expression of the secretory proteins serum paraoxonase, serum albumin, and peroxiredoxin IV. The correlation of these protein changes with the clinical and histological data and their occurrence before the onset of the biochemical changes suggest that they could serve as predictive biomarkers of compounds with a propensity to induce liver steatosis.

The spirochetes inhabiting the large intestines of humans and animals consist of a diverse group of related organisms. Intestinal spirochetosis caused by Serpulina pilosicoli is a newly recognized enteric disease of human beings and animals with potential public health significance. The purpose of this study was to determine the species identity of canine intestinal spirochetes by comparing 30 isolates obtained from dogs in Australia (n = 25) and the United States (n = 5) with reference strains representing Serpulina species and Brachyspira aalborgi, by phenotypic and genetically based typing methods. All of the canine isolates were indole negative and produced a weak β-hemolysis when cultured anaerobically on agar medium containing blood. Four isolates were identified as S. pilosicoli by 16S rRNA-specific PCR assays, rRNA gene restriction fragment length polymorphism or ribotyping, and multilocus enzyme electrophoresis. The remaining 26 isolates formed a cluster related to porcineSerpulina innocens as determined by multilocus enzyme electrophoresis but had a unique ribotype pattern. The data suggested the existence of a novel Serpulina species, provisionally designated “Serpulina canis,” colonizing the intestines of dogs.