A Diagnostic Approach for Rodent Progressive Cardiomyopathy and Like Lesions in Toxicology Studies up to 28 Days in the Sprague Dawley Rat (Part 2 of 2).

To test the diagnostic approach described in part 1 of this article, 2 exercises were completed by pathologists from multiple companies/agencies. Pathologist's examination of whole slide image (WSI) heart sections from rats using personal diagnostic approaches (exercise #1) corroborated conclusions from study #1. Using the diagnostic approach described in part 1, these pathologists examined the same WSI heart sections (exercise #2) to determine whether that approach increased consistency of diagnosis of rodent progressive cardiomyopathy (PCM) lesions. In exercise #2, there was improved consistency of categorization of small borderline morphologies and mild lesions, but a decrement in consistency of categorizing minimal lesions. Exercises 1 and 2 suggest the described diagnostic approach is representative of that in use by the majority of toxicologic pathologists across companies/agencies and that application by all may improve diagnostic consistency of PCM/like lesions. Additionally, a criterion of approximately 5% heart section involvement is suggested for separating mild from moderate or greater severity. While evidence is not absolute, until further investigation shows otherwise, microscopic changes resembling PCM, but located in the epicardial and subepicardial region of the right ventricle, may be considered as part of the spectrum of PCM.

A Diagnostic Approach for Rodent Progressive Cardiomyopathy and Like Lesions in Toxicology Studies up to 28 Days in the Sprague Dawley Rat (Part 1 of 2).

Spontaneous rodent progressive cardiomyopathy (PCM) in the Sprague Dawley rat may confound identification and/or interpretation of potential test article (TA)-related cardiotoxicity. Pathologists apply diagnostic term(s) and thresholds for diagnosing and assigning severity grades for PCM and/or PCM-like (PCM/like) lesions consistently within a study, which is necessary to identify and interpret TA-related findings. Due to differences in training and/or experiences, diagnostic terms and thresholds may vary between pathologists. Harmonized terminology and thresholds across studies will generate better historical control data, will likely enhance interpretation of study data, and may further enhance our understanding of the spontaneous change. An assessment of the diagnostic approaches of a group of 37 pathologists identified an approach that is relatively easily applied; and if adopted, it could enhance diagnostic consistency across studies. This approach uses the single "slash" term "necrosis/inflammatory cell infiltrate (NICI)" as the diagnosis for the spectrum of lesions seen in younger rats, uses no threshold for diagnosis (e.g., diagnose all lesions clearly identifiable as PCM/like), and uses aggregate lesion size of approximately ≥45% of the field of view (FOV) using a 10×/22 eyepiece and the 40× objective or approximately ≥100% of the FOV using the 60× objective as the criterion separating minimal from mild severities.

Evaluation of Pepsinogen I as a Biomarker of Drug-induced Gastric Mucosal Injury in Cynomolgus Monkeys.

Gastric mucosal injury is frequently observed in nonclinical studies of nonhuman primates. Because microscopic evaluation of stomach is generally a terminal procedure, our objective was to determine whether serum pepsinogen I (PG I) could serve as a noninvasive biomarker for detection of gastric mucosal injury in monkey. Serum PG I was measured using a commercial human immunoassay in cynomolgus monkeys ( n = 166) prior to dosing and/or terminally in 11 studies of up to 1 month duration. Mean ( SD) PG I values (ug/L) for monkeys with ( n = 59) and without ( n = 100) gastric mucosal degeneration were 101 (215) and 28 (12.6), respectively. For monkeys with baseline and terminal PG I data, mean ( SD) fold change (ratio of terminal to baseline PG I) for monkeys with ( n = 57) and without ( n = 76) glandular degeneration were 4.1 (11.3) and 1 (0.28). Receiver operating characteristic area under the curve (AUC) data demonstrated moderate diagnostic accuracy for serum PG I for glandular degeneration, AUC ( SE) 0.789 (0.04), with improved diagnostic accuracy as a fold change of baseline, AUC ( SE) 0.816 (0.04), consistent with the large interindividual but low intraindividual variability of serum PG I values in control monkeys. These data demonstrate that serum PG I is a useful biomarker of drug-induced gastric mucosal injury in the cynomolgus monkey.

Acute Alpha-Naphthylisothiocyanate-induced Liver Toxicity in Germfree and Conventional Male Rats.

Differences in the responses of conventional and germfree male Sprague-Dawley rats to acute injury induced by alpha-naphthylisothiocyanate (ANIT), a well-characterized biliary epithelial toxicant, were evaluated. Conventional and germfree rats were dosed once orally with 50 mg/kg of ANIT or corn oil alone and serially sacrificed daily for the next 3 days. Germfree rats treated with ANIT tended to have greater increases in virtually all liver and biliary-related analytes compared with conventional rats treated with ANIT; however, significant differences were found only in a few of these analytes including increased bile acids on day 3, total bilirubin on day 4, glutamate dehydrogenase (GLDH) on day 3, and reduced paraoxonase 1 (PON1) on days 2 and 3. Histologic differences between the conventional and germfree rats were modest, but most pronounced on day 2 (24-hr post dosing). Based on subjective scoring, biliary necrosis, neutrophilic cholangitis, and portal tract edema were more severe in germfree rats at 24 hr post dosing compared with conventional rats. Biliary epithelial replication did not differ between treated groups, however. Overall, germfree rats had a modestly greater level of biliary tract injury based on subjective histologic scoring and clinical chemistry measurements following an acute exposure to the well-characterized biliary toxin, ANIT; however, the difference between the ANIT-treated germfree and conventional groups was modest and most evident only within the first day following exposure. These findings suggest that the microbiome did not significantly affect ANIT-induced acute biliary tract injury in the conditions of this study.

Lapatinib Plasma and Tumor Concentrations and Effects on HER Receptor Phosphorylation in Tumor.

PURPOSE: The paradigm shift in cancer treatment from cytotoxic drugs to tumor targeted therapies poses new challenges, including optimization of dose and schedule based on a biologically effective dose, rather than the historical maximum tolerated dose. Optimal dosing is currently determined using concentrations of tyrosine kinase inhibitors in plasma as a surrogate for tumor concentrations. To examine this plasma-tumor relationship, we explored the association between lapatinib levels in tumor and plasma in mice and humans, and those effects on phosphorylation of human epidermal growth factor receptors (HER) in human tumors. EXPERIMENTAL DESIGN: Mice bearing BT474 HER2+ human breast cancer xenografts were dosed once or twice daily (BID) with lapatinib. Drug concentrations were measured in blood, tumor, liver, and kidney. In a randomized phase I clinical trial, 28 treatment-naïve female patients with early stage HER2+ breast cancer received lapatinib 1000 or 1500 mg once daily (QD) or 500 mg BID before evaluating steady-state lapatinib levels in plasma and tumor. RESULTS: In mice, lapatinib levels were 4-fold higher in tumor than blood with a 4-fold longer half-life. Tumor concentrations exceeded the in vitro IC90 (~ 900 nM or 500 ng/mL) for inhibition of HER2 phosphorylation throughout the 12-hour dosing interval. In patients, tumor levels were 6- and 10-fold higher with QD and BID dosing, respectively, compared to plasma trough levels. The relationship between tumor and plasma concentration was complex, indicating multiple determinants. HER receptor phosphorylation varied depending upon lapatinib tumor concentrations, suggestive of changes in the repertoire of HER homo- and heterodimers. CONCLUSION: Plasma lapatinib concentrations underestimated tumor drug levels, suggesting that optimal dosing should be focused on the site of action to avoid to inappropriate dose escalation. Larger clinical trials are required to determine optimal dose and schedule to achieve tumor concentrations that maximally inhibit HER receptors. CLINICAL TRIAL REGISTRATION: NCT00359190.

Lack of association of ABCB4 insertion mutation with gallbladder mucoceles in dogs.

The etiology of canine gallbladder mucocele (GBM) has not yet been identified. However, several studies have linked GBM in dogs to particular breeds (Shetland Sheepdogs are commonly implicated), concurrent endocrine disease (hyperadrenocorticism and/or hypothyroidism), and a mutation in the canine ABCB4 gene (ABCB4 1583_1584G), particularly in Shetland Sheepdogs. The current study assessed ABCB4 1583_1584G, in a wider sample of dogs with GBM compared with age and breed-matched controls. ABCB4 1583_1584G was identified in 4 of 8 Shetland Sheepdogs and 13 of 28 other breeds with GBM. ABCB4 1583_1584G was also detected in 9 of 12 Shetland Sheepdogs and 23 of 37 other breeds that did not have GBM. No statistically significant association existed between ABCB4 1583_1584G and the presence of GBM for all dogs combined or for Shetland Sheepdogs alone. In contrast to previously reported findings, the current study did not identify a strong association between ABCB4 1583_1584G and GBM in Shetland Sheepdogs or other breeds.

Effects of Kupffer cell depletion on acute alpha-naphthylisothiocyanate-induced liver toxicity in male mice.

Depletion of Kupffer cells, known to modulate chemical-induced hepatocellular injury, has not been studied with regard to biliary epithelial injury. Here, the authors investigated the effect of Kupffer cell depletion by clodronate on the toxicity of alpha-naphthylisothiocyanate (ANIT), known to injure biliary epithelium as well as hepatocytes. Up to 99% depletion of Kupffer cells occurred in ANIT and liposome-encapsulated clodronate-treated mice. The effect of Kupffer cell depletion was most evident one day following ANIT treatment. Histologically, there was a modest increase in neutrophil infiltration of the bile ducts, hepatocytic necrosis, and microvesicular vacuolization in the ANIT and clodronate-treated mice, but differences between other groups did not persist. Clinical pathology analytes related to the biliary or hepatocellular injury were significantly elevated in ANIT and clodronate-treated mice compared to mice given clodronate only. This was also true for mice given ANIT and empty liposomes in the case of the biliary analytes. However, group means were typically higher for the ANIT and clodronate-treated group than others on the first 2 days following ANIT injection. These findings suggest that Kupffer cell reduction increases hepatobiliary damage due to ANIT treatment.

Effect of estrous cycle phase on clinical pathology values in beagle dogs.

BACKGROUND: In dogs, the diestrus phase is considerably longer than in most domestic animals, and is characterized by high circulating progesterone concentrations that may influence clinical pathology values. OBJECTIVE: The objective of this retrospective study was to investigate differences in clinical pathology data in dogs in diestrus compared with data from dogs in all other phases of the estrous cycle. METHODS: Phase of the estrous cycle was determined by histologic evaluation of reproductive tissues from 86 control female Beagles that had participated in 23 toxicity studies. Serum biochemical, hematologic, and urinalysis values from dogs in diestrus were compared with data from dogs in all other estrous cycle phases using a 2-tailed t-test. RESULTS: In Beagles in diestrus (n = 38), serum cholesterol concentrations and eosinophil counts were 35% (P < .0001) and 45.8% (P = .0035) higher, respectively, than for Beagles in all other phases of the estrous cycle (n = 48). Furthermore, Beagles in diestrus had 14% lower AST activity (P = .0011), 1% lower chloride concentration (P = .0224), 7.8% lower hemoglobin concentration (P < .0001), 7.8% lower RBC count (P < .0001), and 7.6% lower hematocrit (P < .0001) compared with female dogs in all other phases of the estrous cycle. Urine values did not differ significantly between groups. CONCLUSIONS: Differences in clinical pathology values between dogs in different phases of the estrous cycle could potentially confound interpretation of data in toxicity studies, which often have small group sizes. Interpretation of clinical pathology data in female dogs should be performed with due consideration given to the phase of the estrous cycle.

An initial characterization of N-terminal-proatrial natriuretic peptide in serum of Sprague Dawley rats.

In the clinical setting, natriuretic peptides (NPs) have proven to be reliable noninvasive markers for diagnostic, prognostic, and therapeutic monitoring of heart failure. Given their proven utility in humans, NPs are potential candidates for translational biomarkers during drug development to detect drug-induced hemodynamic stress resulting in cardiac hypertrophy in preclinical species. We evaluated the intra- and interassay precision and the stability of serum N-terminal-proatrial natriuretic peptide (NT-proANP) using a commercially available enzyme-linked immunoassay (EIA). We then measured NT-proANP concentrations in 532 serum samples from 337 male Crl:CD(SD) rats with or without pressure-induced cardiac hypertrophy. Additionally, we established a reference range using samples from control animals across multiple studies. The data demonstrate that the NT-proANP EIA is a robust and reproducible assay for the measurement of NT-proANP. The noninvasive translational utility, minimal sample volume requirement, and the lack of existing hypertrophic biomarkers in the male rat make NT-proANP an excellent candidate for further interrogation as a biomarker of cardiac hypertrophy in preclinical toxicology investigations.

Direct inotropic effects of exogenous and endogenous urotensin-II: divergent actions in failing and nonfailing human myocardium.

BACKGROUND: Urotensin-II (U-II) is an endogenous peptide upregulated in failing hearts. To date, insights into the myocardial actions of U-II have been obscured by its potent vasoconstrictor effects and interspecies differences in physiological responses to U-II. METHODS AND RESULTS: We examined the direct effects of exogenous U-II on in vitro contractility in nonfailing and failing human myocardial trabeculae (n=47). Rapid cooling contractures (RCC) were used to examine sarcoplasmic reticulum Ca(2+) load. In nonfailing myocardium, exogenous U-II increased developed force (DF), rates of force generation and decline and RCC amplitude suggesting increased sarcoplasmic reticulum Ca(2+) load. In isolated myocyte suspensions from nonfailing hearts, U-II increased phospholamban phosphorylation. In failing myocardium, exogenous U-II reduced DF and rates of force generation and decline without a significant change in RCC amplitude in trabeculae or a change in phospholamban phosphorylation in myocytes. To examine the effects of endogenous U-II, we administered the peptidic U-II receptor antagonist (UT-A) GSK248451A to isolated trabeculae. UT-A induced a decrease in DF in nonfailing myocardium and an increase in DF in failing myocardium. UT-A increased RCC amplitude slightly in both nonfailing and failing myocardium. During ongoing UT-A, exogenous U-II had little effect on DF and RCC amplitude, confirming effective receptor blockade. CONCLUSIONS: U-II modulates contractility independent of vasoconstriction with opposite effects in failing and nonfailing hearts. Positive inotropic responses to UT-A alone suggests that increased endogenous U-II constrains contractility in failing hearts via an autocrine or paracrine mechanism. These findings support a potential therapeutic role for UT-A in heart failure.

Fibrates induce hepatic peroxisome and mitochondrial proliferation without overt evidence of cellular proliferation and oxidative stress in cynomolgus monkeys.

There is little primate risk factor data in the literature evaluating the relationship between proposed mechanisms of PPAR agonist-induced hepatocarcinogenesis at clinically relevant therapeutic exposures. These studies were conducted to characterize the hepatic effects of fenofibrate and ciprofibrate in the cynomolgus monkey. Male cynomolgus monkeys were given fenofibrate (250, 1250 or 2500 mg/kg/day) or ciprofibrate (3, 30, 150 or 400 mg/kg/day) for up to 15 days. The highest doses used were approximately 4 times (fenofibrate) and 9.4 times (ciprofibrate) the human therapeutic exposure for these agents based on AUC (area under the curve). For both compounds, there was a treatment-related increase in liver weight and periportal hepatocellular hypertrophy, which was related to increases in peroxisomes (up to 2.8 times controls) and mitochondria (up to 2.5 times controls). An increase in smooth endoplasmic reticulum probably contributed to the hypertrophy. There was no indication of cell proliferation as determined by the number of mitotic figures and this was confirmed by evaluating cell proliferation by immunohistochemical staining for the Ki-67 antigen. Consistent with the findings by light microscopy, there was no treatment-related effect on the level of mRNA for proteins known to be involved in the control of hepatocyte cell division or apoptosis (e.g. P21, Cyclin D1, PCNA, CDKN1A). Furthermore, there was minimal indication of oxidative stress. Thus, there was no evidence of lipofuscin accumulation, and there was no remarkable increase in the mRNA levels for most proteins known to respond to oxidative stress (e.g. catalase, glutathione peroxidase). A mild induction in the mRNA levels of cellular beta-oxidation and detoxification enzymes (e.g. acyl CoA oxidase, thioredoxin reductase) was observed. Collectively, the data from these studies suggest that the primate responds to PPARalpha agonists in a manner that is different from the rodent suggesting that the primate may be refractory to PPAR-induced hepatocarcinogenesis.