Effects of oral dosing paradigms (gavage versus diet) on pharmacokinetics and pharmacodynamics

Interspecies scaling of toxicity reference values in human health versus ecological risk assessments: A critical review

Risk assessments that focus on anthropogenic chemicals in environmental media-whether considering human health or ecological effects-often rely on toxicity data from experimentally studied species to estimate safe exposures for species that lack similar data. Current default extrapolation approaches used in both human health risk assessments and ecological risk assessments (ERAs) account for differences in body weight between the test organisms and the species of interest, but the two default approaches differ in important ways. Human health risk assessments currently employ a default based on body weight raised to the three-quarters power. Ecological risk assessments for wildlife (i.e., mammals and birds) are typically based directly on body weight, as measured in the test organism and receptor species. This review describes differences in the experimental data underlying these default practices and discusses the many factors that affect interspecies variability in chemical exposures. The interplay of these different factors can lead to substantial departures from default expectations. Alternative methodologies for conducting more accurate interspecies extrapolations in ERAs for wildlife are discussed, including tissue-based toxicity reference values, physiologically based toxicokinetic and/or toxicodynamic modeling, chemical read-across, and a system of categorical defaults based on route of exposure and toxic mode of action. Integr Environ Assess Manag 2024;20:749-764. © 2023 SETAC.

Toxicological effects assessment for wildlife in the 21st century: Review of current methods and recommendations for a path forward

Model species (e.g., granivorous gamebirds, waterfowl, passerines, domesticated rodents) have been used for decades in guideline laboratory tests to generate survival, growth, and reproductive data for prospective ecological risk assessments (ERAs) for birds and mammals, while officially adopted risk assessment schemes for amphibians and reptiles do not exist. There are recognized shortcomings of current in vivo methods as well as uncertainty around the extent to which species with different life histories (e.g., terrestrial amphibians, reptiles, bats) than these commonly used models are protected by existing ERA frameworks. Approaches other than validating additional animal models for testing are being developed, but the incorporation of such new approach methodologies (NAMs) into risk assessment frameworks will require robust validations against in vivo responses. This takes time, and the ability to extrapolate findings from nonanimal studies to organism- and population-level effects in terrestrial wildlife remains weak. Failure to adequately anticipate and predict hazards could have economic and potentially even legal consequences for regulators and product registrants. In order to be able to use fewer animals or replace them altogether in the long term, vertebrate use and whole organism data will be needed to provide data for NAM validation in the short term. Therefore, it is worth investing resources for potential updates to existing standard test guidelines used in the laboratory as well as addressing the need for clear guidance on the conduct of field studies. Herein, we review the potential for improving standard in vivo test methods and for advancing the use of field studies in wildlife risk assessment, as these tools will be needed in the foreseeable future. Integr Environ Assess Manag 2024;20:699-724. © 2023 His Majesty the King in Right of Canada and The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC). Reproduced with the permission of the Minister of Environment and Climate Change Canada. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.

Oral intake of bucillamine, carvedilol, metformin, or phenformin does not protect against UVR-induced squamous cell carcinomas in hairless mice

Squamous cell carcinoma represents the second most common type of keratinocyte carcinoma with ultraviolet radiation (UVR) making up the primary risk factor. Oral photoprotection aims to reduce incidence rates through oral intake of photoprotective compounds. Recently, drug repurposing has gained traction as an interesting source of chemoprevention. Because of their reported photoprotective properties, we investigated the potential of bucillamine, carvedilol, metformin, and phenformin as photoprotective compounds following oral intake in UVR-exposed hairless mice. Tumour development was observed in all groups in response to UVR, with only the positive control (Nicotinamide) demonstrating a reduction in tumour incidence (23.8%). No change in tumour development was observed in the four repurposed drug groups compared to the UV control group, whereas nicotinamide significantly reduced carcinogenesis (P = 0.00012). Metformin treatment significantly reduced UVR-induced erythema (P = 0.012), bucillamine and phenformin increased dorsal pigmentation (P = 0.0013, and P = 0.0005), but no other photoprotective effect was observed across the repurposed groups. This study demonstrates that oral supplementation with bucillamine, carvedilol, metformin, or phenformin does not affect UVR-induced carcinogenesis in hairless mice.

Predictiveness of the Human-CYP3A4-Transgenic Mouse Model (Cyp3aXAV) for Human Drug Exposure of CYP3A4-Metabolized Drugs

The extrapolation of drug exposure between species remains a challenging step in drug development, contributing to the low success rate of drug approval. As a consequence, extrapolation of toxicology from animal models to humans to evaluate safe, first-in-human (FIH) doses requires high safety margins. We hypothesized that a human-CYP3A4-expressing transgenic (Cyp3aXAV) mouse is a more predictive model for human drug exposure of CYP3A4-metabolized small-molecule drugs. Population pharmacokinetic models based on wild-type (WT) and Cyp3aXAV mouse pharmacokinetic data of oral lorlatinib, brigatinib, ribociclib and fisogatinib were allometrically scaled and compared to human exposure. Extrapolation of the Cyp3aXAV mouse model closely predicted the observed human exposure for lorlatinib and brigatinib with a 1.1-fold and 1.0-fold difference, respectively, compared to a 2.1-fold and 1.9-fold deviation for WT-based extrapolations of lorlatinib and brigatinib, respectively. For ribociclib, the extrapolated WT mouse model gave better predictions with a 1.0-fold deviation compared to a 0.3-fold deviation for the extrapolated Cyp3aXAV mouse model. Due to the lack of a human population pharmacokinetic model for fisogatinib, only median maximum concentration ratios were calculated, resulting in ratios of 1.0 and 0.6 for WT and Cyp3aXAV mice extrapolations, respectively. The more accurate predictions of human exposure in preclinical research based on the Cyp3aXAV mouse model can ultimately result in FIH doses associated with improved safety and efficacy and in higher success rates in drug development.

Alleviation of a polyglucosan storage disorder by enhancement of autophagic glycogen catabolism

This work employs adult polyglucosan body disease (APBD) models to explore the efficacy and mechanism of action of the polyglucosan-reducing compound 144DG11. APBD is a glycogen storage disorder (GSD) caused by glycogen branching enzyme (GBE) deficiency causing accumulation of poorly branched glycogen inclusions called polyglucosans. 144DG11 improved survival and motor parameters in a GBE knockin (Gbeys/ys ) APBD mouse model. 144DG11 reduced polyglucosan and glycogen in brain, liver, heart, and peripheral nerve. Indirect calorimetry experiments revealed that 144DG11 increases carbohydrate burn at the expense of fat burn, suggesting metabolic mobilization of pathogenic polyglucosan. At the cellular level, 144DG11 increased glycolytic, mitochondrial, and total ATP production. The molecular target of 144DG11 is the lysosomal membrane protein LAMP1, whose interaction with the compound, similar to LAMP1 knockdown, enhanced autolysosomal degradation of glycogen and lysosomal acidification. 144DG11 also enhanced mitochondrial activity and modulated lysosomal features as revealed by bioenergetic, image-based phenotyping and proteomics analyses. As an effective lysosomal targeting therapy in a GSD model, 144DG11 could be developed into a safe and efficacious glycogen and lysosomal storage disease therapy.

Evaluation of toxic effects induced by repeated exposure to Cylindrospermopsin in rats using a 28-day feeding study

Cylindrospermopsin (CYN) is a toxin with a world-wide increasing occurrence. It can induce toxic effects both in humans and the environment, and toxicity studies are needed to complete its toxicological profile. In this sense, in vivo oral toxicity studies with pure CYN are scarce. The aim of this work was to perform a repeated dose 28-day oral study in rats following the OECD guideline 407 to provide information on health hazard likely to arise from this kind of exposure. Male and female Sprague-Dawley rats were dosed with 18.75, 37.5 and 75 μg CYN/kg b.w./day. After the study period, no clinical signs or mortality and no significant differences in final body weight, body weight gain and total feed intake in both sexes were observed. Only in females some biochemical parameters (triglycerides (TRIG) levels and aspartate aminotransferase (AST) activity) as well as changes in the weight of organs (absolute liver weight values, relative kidney/body weight ratios or relative liver weight/brain weight ratios) were altered, but without toxicological relevance. Histopathological analysis revealed a very mild affectation of liver and kidney in rats. These results suggest the need to perform longer oral toxicity studies to define the potential consequences of long term CYN exposure.

Peanut butter as an alternative dose delivery method to prevent strain-dependent orogastric gavage-induced stress in mouse teratogenicity studies

INTRODUCTION

Animal-based studies are essential for assessing toxicity to environmental pollutants, especially when the potential targets are specific developmental time points, teratogenic, or multi-organ systems that cannot be modeled in vitro. Orogastric gavage is a widely used technique for exposure because of its increased accuracy of dose administration over free feeding. However, repeated use of this method has been reported to cause physiological stress on the exposed animals that could interfere with interpretation of results. Previous studies have shown that genetic background also contributes to the level of stress and can affect individual response.

METHODS

To evaluate the impact of stress on repeated orogastric gavage, we exposed C67BL/6J and 129S1/SvImJ inbred mouse strains to 2,3,7,8 tetrachlorodibenzo-p-dioxin (TCDD), a potent xenobiotic that has been extensively studied in vivo. Pregnant females were dosed for ten days after mating using orogastric gavage with olive oil as vehicle or through diet using peanut butter as vehicle. Serum corticosterone levels, body weight, and reproduction endpoints were measured to evaluate levels of stress induced by the dosing technique.

RESULTS

The levels of stress caused by orogastric gavage was strongly dependent on strain background and on the phenotypic endpoint. Orogastric gavage-induced stress was more detrimental in 129S1/SvlmJ pregnant female mice than in C57BL/6J.

CONCLUSION

These results show that administration of xenobiotics via controlled diet can improve the reproducibility and rigor of exposure studies requiring orogastric delivery.

Cyclooxygenase activity mediates colorectal cancer cell resistance to the omega-3 polyunsaturated fatty acid eicosapentaenoic acid

Purpose

The naturally-occurring omega-3 polyunsaturated fatty acid eicosapentaenoic acid (EPA) is safe, well-tolerated and inexpensive, making it an attractive anti-cancer intervention. However, EPA has only modest anti-colorectal cancer (CRC) activity, when used alone. Both cyclooxygenase (COX) isoforms metabolise EPA and are over-expressed in CRC cells. We investigated whether COX inhibition increases the sensitivity of CRC cells to growth inhibition by EPA.

Methods

A panel of 18 human and mouse CRC cell lines was used to characterize the differential sensitivity of CRC cells to the growth inhibitory effects of EPA. The effect of CRISPR-Cas9 genetic deletion and pharmacological inhibition of COX-1 and COX-2 on the anti-cancer activity of EPA was determined using in vitro and in vivo models.

Results

Genetic ablation of both COX isoforms increased sensitivity of CT26 mouse CRC cells to growth inhibition by EPA in vitro and in vivo. The non-selective COX inhibitor aspirin and the selective COX-2 inhibitor celecoxib increased sensitivity of several human and mouse CRC cell lines to EPA in vitro. However, in a MC38 mouse CRC cell tumour model, with dosing that mirrored low-dose aspirin use in humans, thereby producing significant platelet COX-1 inhibition, there was ineffective intra-tumoral COX-2 inhibition by aspirin and no effect on EPA sensitivity of MC38 cell tumours.

Conclusion

Cyclooxygenase inhibition by non-steroidal anti-inflammatory drugs represents a therapeutic opportunity to augment the modest anti-CRC activity of EPA. However, intra-tumoral COX inhibition is likely to be critical for this drug-nutrient interaction and careful tissue pharmacodynamic profiling is required in subsequent pre-clinical and human studies.

Electronic supplementary material

The online version of this article (10.1007/s00280-020-04157-2) contains supplementary material, which is available to authorized users.

New use for an old drug: COX-independent anti-inflammatory effects of sulindac in models of cystic fibrosis

Background and Purpose

Pulmonary disease is the main cause of morbidity and mortality in cystic fibrosis (CF) patients due to exacerbated inflammation. To date, the only anti‐inflammatory drug available to CF patients is high‐dose ibuprofen, which can slow pulmonary disease progression, but whose cyclooxygenase‐dependent digestive adverse effects limit its clinical use. Here we have tested sulindac, another non‐steroidal anti‐inflammatory drug with an undefined anti‐inflammatory effect in CF airway epithelial cells.

Experimental Approach

Using in vitro and in vivo models, we NF‐κB activity and IL‐8 secretion. In HeLa‐F508del cells, we performed luciferase reporter gene assays in order to measure i) IL‐8 promoter activity, and ii) the activity of synthetic promoter containing NF‐κB responsive elements. We quantified IL‐8 secretion in airway epithelial CFBE cells cultured at an air‐liquid interface and in a mouse model of CF.

Key Results

Sulindac inhibited the transcriptional activity of NF‐κB and decreased IL‐8 transcription and secretion in TNF‐α stimulated CF cells via a cyclooxygenase‐independent mechanism. This effect was confirmed in vivo in a mouse model of CF induced by intra‐tracheal instillation of LPS, with a significant decrease of the induction of mRNA for MIP‐2, following treatment with sulindac.

Conclusion and Implications

Overall, sulindac decrease lung inflammation by a mechanism independent of cycolooxygenase. This drug could be beneficially employed in CF.

Novel synthetic pyridyl analogues of CDDO-Imidazolide are useful new tools in cancer prevention

Two new analogues of CDDO-Imidazolide (CDDO-Im), namely 1-[2-Cyano-3,12-dioxooleana-1,9(11)-dien-28-oyl]-4(-pyridin-2-yl)-1H-imidazole ("CDDO-2P-Im") and 1-[2-Cyano-3,12-dioxooleana-1,9(11)-dien-28-oyl]-4(-pyridin-3-yl)-1H-imidazole ("CDDO-3P-Im") have been synthesized and tested for their potential use as chemopreventive drugs. At nanomolar concentrations, they were equipotent to CDDO-Im for inducing differentiation and apoptosis in U937 leukemia cells. As inflammation and oxidative stress contribute to carcinogenesis, we also assessed their cytoprotective potential. The new compounds suppressed inducible nitric oxide synthase (iNOS) expression in RAW264.7 macrophage-like cells and significantly elevated heme oxygenase-1 (HO-1) and quinone reductase (NQO1) mRNA and protein levels in various mouse tissues in vivo. Most importantly, pharmacokinetic studies performed in vitro in human plasma and in vivo showed that each new analogue was more stable than CDDO-Im. Much higher concentrations of the new derivatives were found in mouse liver, lung, pancreas and kidney after gavage in contrast to CDDO-Im. Because of their better bioavailability and their excellent anti-inflammatory profile in vitro, CDDO-2P-Im and CDDO-3P-Im were tested for prevention in a highly relevant mouse lung cancer model, in which A/J mice develop lung carcinomas after injection of vinyl carbamate, a potent carcinogen. CDDO-2P-Im and CDDO-3P-Im were as effective as CDDO-Im for reducing the size and the severity of the lung tumors.

Pharmacokinetic evaluation of the equivalency of gavage, dietary, and drinking water exposure to manganese in F344 rats

Concerns exist as to whether individuals may be at greater risk for neurotoxicity following increased manganese (Mn) oral intake. The goals of this study were to determine the equivalence of 3 methods of oral exposure and the rate (mg Mn/kg/day) of exposure. Adult male rats were allocated to control diet (10 ppm), high manganese diet (200 ppm), manganese-supplemented drinking water, and manganese gavage treatment groups. Animals in the drinking water and gavage groups were given the 10 ppm manganese diet and supplemented with manganese chloride (MnCl(2)) in drinking water or once-daily gavage to provide a daily manganese intake equivalent to that seen in the high-manganese diet group. No statistically significant difference in body weight gain or terminal body weights was seen. Rats were anesthetized following 7 and 61 exposure days, and samples of bile and blood were collected. Rats were then euthanized and striatum, olfactory bulb, frontal cortex, cerebellum, liver, spleen, and femur samples were collected for chemical analysis. Hematocrit was unaffected by manganese exposure. Liver and bile manganese concentrations were elevated in all treatment groups on day 61 (relative to controls). Increased cerebellum manganese concentrations were seen in animals from the high-manganese diet group (day 61, relative to controls). Increased (relative to all treatment groups) femur, striatum, cerebellum, frontal cortex, and olfactory bulb manganese concentrations were also seen following gavage suggesting that dose rate is an important factor in the pharmacokinetics of oral manganese. These data will be used to refine physiologically based pharmacokinetic models, extending their utility for manganese risk assessment by including multiple dietary exposures.

Should oral gavage be abandoned in toxicity testing of endocrine disruptors?

For decades, hazard assessments for environmental chemicals have used intra-gastric gavage to assess the effects of 'oral' exposures. It is now widely used--and in some cases required--by US federal agencies to assess potential toxicity of endocrine disrupting chemicals (EDCs). In this review we enumerate several reasons why gavage is not appropriate for the assessment of EDCs using bisphenol A (BPA) as a main example. First, whereas human dietary exposures interact with the oral mucosa, gavage exposures avoid these interactions, leading to dramatic differences in absorption, bioavailability and metabolism with implications for toxicokinetic assumptions and models. Additionally, there are well acknowledged complications associated with gavage, such as perforation of the esophagus that diminish its value in toxicological experiments. Finally, the gavage protocol itself can induce stress responses by the endocrine system and confound the assessment of EDCs. These serious flaws have not been taken into account in interpreting results of EDC research. We propose the exploration of alternatives to mimic human exposures when there are multiple exposure routes/sources and when exposures are chronic. We conclude that gavage may be preferred over other routes for some environmental chemicals in some circumstances, but it does not appropriately model human dietary exposures for many chemicals. Because it avoids exposure pathways, is stressful, and thus interferes with endocrine responses, gavage should be abandoned as the default route of administration for hazard assessments of EDCs.

Vascular and cardiac effects of grape powder in the spontaneously hypertensive rat

BACKGROUND

We previously reported that resveratrol, a polyphenol found in red grapes, attenuated changes in small artery geometry and stiffness, as well as cardiac hypertrophy and cardiac function in the spontaneously hypertensive rat (SHR). However, in addition to resveratrol, grapes contain a variety of bioactive polyphenols such as catechins, anthocyanins, and flavonoids. Therefore, we investigated the effects of grape consumption in SHR.

METHODS

Wistar-Kyoto (WKY) rats and SHR were treated with freeze-dried grape powder for 10 weeks. Dilatory, geometry, and stiffness properties of mesenteric small arteries were assessed by pressurized myography. Left ventricular mass index and cardiac function were assessed by two-dimensional guided M-mode and pulse-wave Doppler echocardiography.

RESULTS

Elevated blood pressure in SHR was associated with remodeling and impaired endothelium-dependent relaxation of small arteries. Augmented left ventricular mass index (reflecting hypertrophy) and diminished cardiac function were also evident in SHR. Although grape treatment failed to affect cardiac dysfunction, it elicited a significant reduction in blood pressure, improved arterial relaxation, increased vascular compliance, and attenuated cardiac hypertrophy.

CONCLUSIONS

Treatment with whole grape powder conferred mild vascular and cardiac benefits in SHR. Therefore, dietary grape consumption may be a feasible and salutary adjunct to pharmacological treatment of human hypertension.

Subchronic effects of perfluorooctanesulfonate exposure on inflammation in adult male C57BL/6 mice

Previous studies indicate that exposure to perfluorooctanesulfonate (PFOS), a ubiquitous and highly persistent environmental contaminant, induces immunotoxicity in mice. However, few studies have specifically assessed the effects of PFOS on inflammation. This study utilized a standard 60-day oral exposure period to assess the effects of PFOS on the response of inflammatory cytokines [tumor necrosis factor α (TNF-α), interleukin-1 β (IL-1β), and interleukin-6 (IL-6)]. Adult male C57BL/6 mice were dosed daily by oral gavage with PFOS at 0, 0.0083, 0.0167, 0.0833, 0.4167, 0.8333 or 2.0833 mg/kg/day to yield a targeted Total Administered Dose (TAD) over 60 days of 0, 0.5, 1, 5, 25, 50, or 125 mg PFOS/kg, respectively. The percentage of peritoneal macrophages (CD11b+ cells) was significantly increased at concentrations ≥ 1 mg PFOS/kg TAD in a dose-dependent manner. Ex vivo IL-1β production by peritoneal macrophages was elevated substantially at concentrations of ≥ 5 mg PFOS/kg TAD. Moreover, PFOS exposure markedly enhanced the ex vivo production of TNF-α, IL-1β and IL-6 by peritoneal and splenic macrophages when stimulated either in vitro or in vivo with lipopolysaccharide (LPS). The serum levels of these inflammatory cytokines observed in response to in vivo stimulation with LPS were elevated substantially by exposure to PFOS. PFOS exposure elevated the expression of pro-inflammatory cytokines TNF-α, IL-1β, IL-6, and proto-oncogene, c-myc, in the spleen. These data suggest that exposure to PFOS modulates the inflammatory response, and further research is needed to determine the mechanism of action.

Sulindac and sulindac metabolites in nipple aspirate fluid and effect on drug targets in a phase I trial

Regular use of nonsteroidal anti-inflammatory drugs (NSAID) has been associated with reduced risk of breast cancer. Sulindac, a nonselective NSAID with both cyclooxygenase-2-dependent and -independent activities, is a candidate for breast chemoprevention. We conducted a phase Ib trial in 30 women at increased risk for breast cancer to evaluate the breast tissue distribution of sulindac at two dose levels (150 mg daily and 150 mg twice daily for 6 weeks), using nipple aspirate fluid (NAF) as a surrogate of breast tissue drug exposure. We also explored the effect of sulindac on drug-induced biomarkers in NAF. We show that sulindac and its metabolites partition to human breast as measured by NAF levels. Sulindac intervention did not decrease 13,14-dihydro-15-keto prostaglandin A(2), a stable derivative of prostaglandin E(2), in NAF, but exposure was associated with a significant trend towards higher levels of growth differentiation factor 15 in NAF in women receiving 150 mg twice daily (P = 0.038). These results are the first to show partitioning of sulindac and metabolites to human breast tissue and the first evidence for a potential dose-dependent effect of sulindac on growth differentiation factor 15 levels in NAF.

28-Day dietary exposure of mice to a low total dose (7 mg/kg) of perfluorooctanesulfonate (PFOS) alters neither the cellular compositions of the thymus and spleen nor humoral immune responses: does the route of administration play a pivotal role in PFOS-induced immunotoxicity?

Short-term exposure of mice to high doses of perfluorooctanesulfonate (PFOS), an ubiquitous and highly persistent environmental contaminant, induces various metabolic changes and toxic effects, including immunotoxicity. However, extrapolation of these findings to the long-term, low-dose exposures to which humans are subject is highly problematic. In this connection, recent studies have concluded that sub-chronic (28-day) exposure of mice by oral gavage to doses of PFOS that result in serum levels comparable to those found in general human populations suppress adaptive immunity. Because of the potential impact of these findings on environmental research and monitoring, we have examined here whether sub-chronic dietary exposure (a major route of human exposure) to a similarly low-dose of PFOS also suppress adaptive immune responses. Dietary treatment of male B6C3F1 mice for 28 days with a dose of PFOS that resulted in a serum concentration of 11mug/ml (ppm) significantly reduced body weight gain and increased liver mass. However, this treatment did not alter the cellular compositions of the thymus and spleen; the number of splenic cells secreting IgM antibodies against sheep red blood cell (SRBC); serum levels of IgM and IgG antibodies specifically towards SRBC; or circulating levels of IgM antibodies against the T-cell-independent antigen trinitrophenyl conjugated to lipopolysaccharide (TNP-LPS). These findings indicate that such sub-chronic dietary exposure of mice to PFOS resulting in serum levels approximately 8-85-fold greater than those observed in occupationally exposed individuals does not exert adverse effects on adaptive immunity.

Comparison of pharmacokinetic and pharmacodynamic profiles of aspirin following oral gavage and diet dosing in rats

Aspirin is one of the oldest drugs and has been purported to have multiple beneficial effects, including prevention of cardiovascular disease and cancer, in addition to its original indication for treatment of inflammation, fever and pain. In cancer chemoprevention studies using animal models, two methods of aspirin administration have been employed: oral gavage and diet. The untested assumption was that exposure and the resultant pharmacological effects are similar for these two administration methods when dosing is normalized on the basis of mg/kg body weight/day. This study examined and compared time-dependent plasma and colon mucosal concentrations of aspirin metabolite salicylate (aspirin concentrations were below level of quantification), plasma thromboxane B(2) concentrations, and colon mucosal prostaglandin E(2) concentration following these two different dosing paradigms in rats. Diet dosing yielded relatively constant plasma and colon salicylate concentration vs. time profiles. On the other hand, oral gavage dosing led to a rapid peak followed by a fast decline in salicylate concentration in both plasma and colon. Nevertheless, the exposure as measured by the area under plasma or colon concentration-time curve of salicylate was linearly related to dose irrespective of the dosing method. Linear relationships were also observed between colon and plasma salicylate areas under the curve and between colon prostaglandin E(2) and plasma thromboxane B(2) areas under the curve. Therefore, more easily accessible plasma salicylate and thromboxane B(2) concentrations were representative of the salicylate exposure and prostaglandin E(2) pharmacodynamic biomarker in the target colon, respectively.

Comparing pharmacokinetic and pharmacodynamic profiles in female rats orally exposed to lovastatin by gavage versus diet

The objective of this study was to assess how the dosing method (i.e., gavage versus diet) affects the absorption and disposition of lovastatin, as well as its effect on two biological markers of exposure, such as serum levels of cholesterol and triglycerides. In preclinical safety studies the test agent is normally administered by gavage, but in chemoprevention efficacy studies the test agent is usually administered with the diet. Therefore, extrapolation of safety and efficacy data from laboratory animals to humans should consider the influence of the method of administration on the absorption, disposition and effect of the drug. Lovastatin, a blood cholesterol-lowering drug with a short elimination half-life in humans, was used to assess the influence of two different dosing methods on the drug pharmacokinetics and pharmacodynamics. Plasma and liver concentrations of lovastatin and its active metabolite lovastatin-Na were measured in female rats at sequential times after administration. Serum concentrations of triglycerides and cholesterol were measured at similar times and used as biomarkers of effect. Significant differences in pharmacokinetics and pharmacodynamics were observed after administration of lovastatin by the two oral dosing paradigms. In general, oral gavage resulted in higher peak and lower trough concentrations of lovastatin and lovastatin-Na in plasma and liver, lower area under the concentration-time curve of lovastatin-Na in plasma and liver, and less of an effect on the serum concentrations of triglycerides and cholesterol than the corresponding diet dosing. Although no inverse linear relationship was observed between pharmacokinetic and pharmacodynamic markers, in the case of serum cholesterol a visual trend could be observed which might have proven significant had data from a larger number of dose levels been available. As in our previous study with sulindac, this study illustrates potential limitations in trying to extrapolate from data obtained using different dosing schemes to potential safety and efficacy in humans.

Exisulind in combination with celecoxib modulates epidermal growth factor receptor, cyclooxygenase-2, and cyclin D1 against prostate carcinogenesis: in vivo evidence

PURPOSE

Nonsteroidal anti-inflammatory drugs mediate anticancer effects by modulating cyclooxygenase-2 (COX-2)-dependent and/or COX-2-independent mechanism(s); however, the toxicity issue is a concern with single agents at higher doses. In this study, we determined the combined effect of celecoxib, a COX-2 inhibitor, along with exisulind (sulindac sulfone/Aptosyn) at low doses in prostate cancer.

EXPERIMENTAL DESIGN

We used a sequential regimen of N-methyl-N-nitrosourea + testosterone to induce prostate cancer in Wistar-Unilever rats. Following carcinogen treatment, celecoxib and exisulind individually and their combination at low doses were given in NIH-07 diet for 52 weeks. We determined the incidence of prostatic intraepithelial neoplasia, adenocarcinomas, rate of tumor cell proliferation, and apoptosis. Immunohistochemical and Western blot analysis were done to determine COX-2, epidermal growth factor receptor (EGFR), Akt, androgen receptor, and cyclin D1 expression. Serum prostaglandin E2 and tumor necrosis factor-alpha levels were determined using enzyme immunoassay/ELISA assays.

RESULTS

The rats that received celecoxib in combination with exisulind at low doses showed a significant decrease in prostatic intraepithelial neoplasia and adenocarcinomas as well as an enhanced rate of apoptosis. An overall decrease in COX-2, EGFR, Akt, androgen receptor, and cyclin D1 expression was found associated with tumor growth inhibition. Reduced serum levels of COX-2 protein, prostaglandin E2, and tumor necrosis factor-alpha indicated anti-inflammatory effects. A strong inhibition of total and phosphorylated form of EGFR (Tyr(992) and Tyr(845)) and Akt (Ser(473)) was significant in rats given with these agents in combination.

CONCLUSIONS

In this study, we show for the first time that the combination of celecoxib with exisulind at low doses could prevent prostate carcinogenesis by altering key molecular events.

Indole-3-carbinol inhibits 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone plus benzo(a)pyrene-induced lung tumorigenesis in A/J mice and modulates carcinogen-induced alterations in protein levels

We tested the chemopreventive efficacy of indole-3-carbinol (I3C), a constituent of Brassica vegetables, and its major condensation product, 3,3'-diindolylmethane (DIM), against lung tumorigenesis induced by a mixture of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and benzo[a]pyrene (BaP) in A/J mice. The mixture of NNK plus BaP (2 micromol each) was administered by gavage as eight weekly doses, whereas I3C (112 micromol/g diet) and DIM (2 and 30 micromol/g diet in experiments 1 and 2, respectively) were given in the diet for 23 weeks beginning at 50% of carcinogen treatment. I3C reduced NNK plus BaP-induced tumor multiplicity by 78% in experiment 1 and 86% in experiment 2; the respective reductions in tumor multiplicity by DIM were 5% and 66%. Using a quantitative proteomics method, isobaric tags for relative and absolute quantitation (iTRAQ) coupled with mass spectrometry, we identified and quantified at least 250 proteins in lung tissues. Of these proteins, nine showed differences in relative abundance in lung tissues of carcinogen-treated versus untreated mice: fatty acid synthase, transketolase, pulmonary surfactant-associated protein C (SP-C), L-plastin, annexin A1, and haptoglobin increased, whereas transferrin, alpha-1-antitrypsin, and apolipoprotein A-1 decreased. Supplementation of the diet of carcinogen-treated mice with I3C reduced the level of SP-C, L-plastin, annexin A1, and haptoglobin to that of untreated controls. These results were verified using immunoblotting. We show here that tumor-associated signature proteins are increased during NNK plus BaP-induced lung carcinogenesis, and I3C inhibits this effect, suggesting that the lung tumor chemopreventive activity of I3C might be related to modulation of carcinogen-induced alterations in protein levels.