Acetone Vehicle Research Articles

Sex Differences in Temporal Regulation of Piezo1 in Resiquimod Accelerated Systemic Lupus

Lupus disproportionally affects women (9:1), particularly women of color, but men with this disease often have more pronounced symptoms than their female counterparts. Individuals with lupus are anywhere from two to fifty times as likely to experience a cardiovascular (CV) event than the rest of the population. Though such complications are widely known, the mechanisms these disease processes are unknown. One well established pathogenesis of many CV diseases stems from an alteration of mechanical forces. The cation channel, Piezo1, is a mechanosensitive channel and is known to play a critical role in CV diseases like heart failure. Therefore, we hypothesized that inducing lupus-associated cardiac pathology in a lupus-prone mouse model would increase the expression of Piezo1. To investigate this, lupus-prone female and male B6.Nba2 mice aged 10-14 weeks were subjected to Resiquimod (R848; a TLR7/8 agonist;100μg/30μl) treatment or acetone vehicle twice a week for four weeks. Echocardiograms were performed every four weeks. Mice were sacrificed and their tissues harvested at 4- and 16-weeks after the start of R848 treatment. Piezo1 levels were subsequently analyzed in the heart by real time quantitative polymerase chain reaction (RTqPCR), immunoblot, and immunofluorescent staining. By echocardiography, female mice treated with R848 showed an increase in left ventricle (LV) wall thickness was seen at four weeks, followed by an increase in internal diameters over the following 12 weeks, culminating in cardiac dysfunction by 16 weeks via significantly decreased ejection fraction (EF; p<0.05) Interestingly, males showed no such cardiac dysfunction at any timepoint. By RTqPCR, female Piezo1 levels were higher overall than their male counterparts (p<0.05). Cardiac Piezo1 gene expression at 4 weeks was shown to be decreased in the R848-treated groups of both sexes. At 16 weeks, this trend was reversed in both male and female mice, showing R848-treatment induced an an upregulation of cardiac Piezo1 compared to each sex’s respective vehicle controls. Interestingly, while Piezo1 protein expression followed the same 4-week trend of downregulation in R848-treated mice regardless of sex, protein expression in the female R848-treated heart continued in a trending increase at the 16-week timepoint, while the male R848 heart showed unchanged. We found that this increase in cardiac Piezo1 in female, R848-treated is significantly correlated with higher left ventricular internal diameters (both LV-EDV (p<0.05) and -ESV (p<0.01)). This data demonstrates a sex difference phenotype in lupus-associated murine cardiac dysfunction, potentially through a Piezo1-mediated pathway. Further investigation is warranted to elucidate the Piezo1-dependent mechanisms involved in lupus-associated cardiovascular disease. Veterans Affairs Biomedical Laboratory Research & Development Career Development Award (CDA-2) 1IK2BX005605-01 to J.P.V.B, Medical University of South Carolina College of Medicine Program Project Grant to and J.P.V.B., and Medical University of South Carolina Core Centers for Clinical Research Project Award P30AR072582 to M.A.C and J.P.V.B. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

A comparative study of the in vitro dermal absorption of radiolabeled benzophenone through human skin

Octocrylene is a common sun filter ingredient used to protect the skin from damaging UV rays. Benzophenone is an impurity found in formulations containing octocrylene. [14C]-Benzophenone was spiked (0.1 g/L) into 2 commercial sunscreen formulations; Neutrogena® Beach Defense Sunscreen Spray Broad Spectrum SPF 70 Aerosol, Neutrogena® Ultra Sheer Body Mist Sunscreen Broad Spectrum SPF 30 Aerosol, and an acetone vehicle. The formulations were applied (ca 2 μL/cm2) to dermatomed human skin mounted in static diffusion cells in vitro. Receptor fluid was collected up to 24 h post dose. All samples were analyzed by liquid scintillation counting. The dermal delivery of [14C]-Benzophenone was 10.02, 9.04 and 5.19% for the 3 formulations. However, the [14C]-Benzophenone mass balances were low; 81.5, 85.3 and 8.02%, respectively. A volatility test was performed replacing skin with aluminum foil for the sunscreen formulations only. The [14C]-Benzophenone mass balance at dosing was 99% but fell to 56.9 and 60.6% at 24 h post dose, confirming the losses were due to [14C]-Benzophenone volatility. A conservative dermal absorption value of 12.42% was proposed to cover [14C]-Benzophenone containing formulations.

Investigation of inflammatory mechanisms induced by croton oil in mouse ear

Croton oil is liquid at room temperature, with a pale-yellow color and spicy odor. It is commonly used in combination with phenol as a chemical peeling agent in dermatology, which reveals its caustic exfoliating effects. Topical use of croton oil at a high dose produces skin irritation, inflammation, swelling, pain, and even tumors. Therefore, croton oil has been widely used for inflammation, pain, and tumor related research, with different animal models having been established. However, mechanistic studies through which croton oil induces skin swelling, injury and activates tissue repair/regeneration are limited. The present study used croton oil to induce mouse ear edema and examined tissue responses 4 h after exposure. To this end, croton oil was applied to the ventral side of mouse ears, followed by tissue collection. Samples were analyzed by hematoxylin and eosin (H&E) staining, toluidine blue staining, and immunohistochemistry staining for myeloperoxidase (MPO) and matrix metalloproteinase-9 (MMP-9). Western blotting and ELISA were also carried out for MMP-9 together with unbiased proteomic analysis using mass-spectrometry. Results from our study demonstrated that as soon as 4 h of exposure to 2.5 % croton oil, the expression levels of MPO and MMP-9 in the dermis significantly increased compared to acetone-treated (vehicle) control ears, as did other inflammatory reactions such as swelling and neutrophil aggregation and infiltration. Subsequently, proteomic analysis confirmed that croton oil treatment resulted in significant upregulation of proteins such as myeloperoxidase (MPO), matrix metalloproteinase-9 (MMP-9), and matrix metalloproteinase-8 (MMP-8) in the ear skin. Interestingly, mouse ears treated with acetone vehicle showed differential expression of 2,478 proteins relative to naïve tissues; among those differentially expressed in acetone-treated samples were members of the phosphatidylinositol-glycan biosynthesis class N, T and U proteins (PIGN, PIGT, and PIGU). Overall, this work confirms the presence of neutrophil-derived MPO and MMP-9 and extends the body of knowledge to show that MMP-8 is also present during croton oil-mediated skin inflammation in the mouse ear; moreover, we find that acetone vehicle is not inert and has effects on the skin that should be considered moving forward.

In silico predictions of absorption of MDI substances after dermal or inhalation exposures to support a category based read-across assessment

Methylenediphenyl diisocyanate (MDI) substances used polyurethane production can range from their simplest monomeric forms (e.g., 4,4′-MDI) to mixtures of the monomers with various homologues, homopolymer, and prepolymer derivatives. The relative dermal or inhalation absorption of 39 constituents of these substances in human were predicted using the GastroPlus® program.Predicted dermal uptake and absorption of the three MDI monomers from an acetone vehicle was 84–86% and 1.4–1.5%, respectively, with lower uptake and absorption predicted for the higher MW analogs. Lower absorption was predicted from exposures in a more lipophilic vehicle (1-octanol).Modeled inhalation exposures afforded the highest pulmonary absorption for the MDI monomers (38–54%), with 3–27% for the MW range of 381–751, and <0.1% for the remaining, higher MW derivatives. Predicted oral absorption, representing mucociliary transport, ranged from 5 to 10% for the MDI monomers, 10–25% for constituents of MW 381–751, and ≤3% for constituents with MW > 900.These in silico evaluations should be useful in category-based, worst-case, Read-Across assessments for MDI monomers and modified MDI substances for potential systemic effects. Predictions of appreciable mucociliary transport may also be useful to address data gaps in oral toxicity testing for this category of compounds.

Acetone Ingestion Mimics a Fasting State to Improve Glucose Tolerance in a Mouse Model of Gestational Hyperglycemia.

Gestational diabetes mellitus results, in part, from a sub-optimal β-cell mass (BCM) during pregnancy. Artemisinins were reported to increase BCM in models of diabetes by α- to β-cell conversion leading to enhanced glucose tolerance. We used a mouse model of gestational glucose intolerance to compare the effects of an artemisinin (artesunate) on glycemia of pregnant mice with vehicle treatment (acetone) or no treatment. Animals were treated daily from gestational days (GD) 0.5 to 6.5. An intraperitoneal glucose tolerance test was performed prior to euthanasia at GD18.5 or post-partum. Glucose tolerance was significantly improved in both pregnant and non-pregnant mice with both artesunate and vehicle-alone treatment, suggesting the outcome was primarily due to the acetone vehicle. In non-pregnant, acetone-treated animals, improved glucose tolerance was associated with a higher BCM and a significant increase in bihormonal insulin and glucagon-containing pancreatic islet cells, suggesting α- to β-cell conversion. BCM did not differ with treatment during pregnancy or post-partum. However, placental weight was higher in acetone-treated animals and was associated with an upregulation of apelinergic genes. Acetone-treated animals had reduced weight gain during treatment despite comparable food consumption to non-treated mice, suggesting transient effects on nutrient uptake. The mean duodenal and ileum villus height was reduced following exposure to acetone. We conclude that acetone treatment may mimic transient fasting, resulting in a subsequent improvement in glucose tolerance during pregnancy.

Modulation of brain serotonin by benzyl butyl phthalate in Fundulus heteroclitus (mummichog).

Endocrine-disrupting chemicals have been known to alter important animal behaviors by modulating serotonin (5-hydroxytryptamine, 5-HT) and dopamine. F. heteroclitus (mummichog) brain serotonin and dopamine levels were quantified by enzyme-linked immunosorbent assay (ELISA) following a 28-day exposure regimen involving daily doses of either 0.1 mg l-1 benzyl butyl phthalate (BBP) dissolved in acetone or acetone alone (0.1 mg l-1). No differences in mean brain mass or total protein homogenate were induced by exposure to the acetone vehicle or BBP in acetone. The acetone vehicle had no effect on dopamine, serotonin, or tyrosine hydroxylase levels, but acetone did decrease tryptophan hydroxylase levels (p = 0.011). Exposure to BBP in acetone decreased dopamine (p = 0.024), increased serotonin (p < 0.001), reduced tryptophan hydroxylase as compared to the acetone vehicle alone (p < 0.001), and had no significant effect on tyrosine hydroxylase levels. This study is the first to report modulation of F. heteroclitus brain serotonin and its enzyme tryptophan hydroxylase following sub-lethal exposure to BBP in an acetone vehicle. In addition, modulation of brain dopamine in F. heteroclitus, sans simultaneous modulation of tyrosine hydroxylase, was also observed. These findings support the use of F. heteroclitus for assessing sub-lethal BBP exposure.

Channa striatus cream down-regulates tumour necrosis factor (TNF)-alpha gene expression and alleviates chronic-like dermatitis in mouse model

Ethnopharmacological relevanceHaruan, Channa striatus, is a freshwater fish which has been well-known locally to accelerate wound healing during post-operative and post-partum periods. The fish extract also has potent anti-inflammatory and analgesic properties. Aim of the studyTo assess topical anti-inflammatory effect of Haruan cream on 12-0-tetradecanoylphorbol-13-acetate (TPA)-induced chronic-like dermatitis in mice. Materials and methodsMale ICR mice were randomized into six groups of five mice each: acetone (vehicle), TPA alone (negative control), three Haruan treatment groups (Haruan 1%, Haruan 5% and Haruan 10%) and hydrocortisone 1% (positive control). Briefly, both surfaces of mouse ears were applied with TPA (2.5μg/20μl acetone) for five times on alternate days and with Haruan or hydrocortisone 1% cream for the last three days. Mouse ear thickness was measured 24h after final treatment with the cream and the ears were harvested for further histological analysis and gene expression studies of TNF-α by real-time reverse transcriptase-polymerase chain reaction (RT-qPCR). ResultsTopical application of Haruan cream had reduced the mouse ear thickness 18.1–28%) with comparable effect to the positive control. In addition, histopathological comparison had shown evident reduction in various parameters of cutaneous inflammation including dermal oedema, inflammatory cells infiltration and proliferation of epidermal keratinocytes. Furthermore, TPA application had resulted in the up-regulation of TNF-α gene expression by 353-fold, which was subsequently down-regulated by the Haruan cream (34- to 112-fold). ConclusionHaruan is an effective topical anti-inflammatory agent in this mouse model of chronic-like dermatitis, thus suggesting its potential as a non-steroidal treatment option for chronic inflammatory dermatoses.

A Role for Regulatory T Cells in a Murine Model of Epicutaneous Toluene Diisocyanate Sensitization.

Toluene diisocyanate (TDI) is a leading cause of chemical-induced occupational asthma which impacts workers in a variety of industries worldwide. Recently, the robust regulatory potential of regulatory T cells (Tregs) has become apparent, including their functional role in the regulation of allergic disease; however, their function in TDI-induced sensitization has not been explored. To elucidate the kinetics, phenotype, and function of Tregs during TDI sensitization, BALB/c mice were dermally exposed (on each ear) to a single application of TDI (0.5-4% v/v) or acetone vehicle and endpoints were evaluated via RT-PCR and flow cytometry. The draining lymph node (dLN) Treg population expanded significantly 4, 7, and 9 days after single 4% TDI exposure. This population was identified using a variety of surface and intracellular markers and was found to be phenotypically heterogeneous based on increased expression of markers including CD103, CCR6, CTLA4, ICOS, and Neuropilin-1 during TDI sensitization. Tregs isolated from TDI-sensitized mice were significantly more suppressive compared with their control counterparts, further supporting a functional role for Tregs during TDI sensitization. Last, Tregs were depleted prior to TDI sensitization and an intensified sensitization response was observed. Collectively, these data indicate that Tregs exhibit a functional role during TDI sensitization. Because the role of Tregs in TDI sensitization has not been previously elucidated, these data contribute to the understanding of the immunologic mechanisms of chemical induced allergic disease.

Psychophysical Measurements of Itch and Nociceptive Sensations in an Experimental Model of Allergic Contact Dermatitis

Allergic contact dermatitis (ACD) is a common condition that can significantly affect the quality of life. Contact with allergens results in delayed hypersensitivity reactions involving T lymphocytes, with associated skin inflammation and spontaneous itch and nociceptive sensations. However, psychophysical studies of these sensations are lacking. In the present study, we sensitized 8 healthy volunteers to squaric acid dibutyl ester (SADBE). Two weeks later, 1 volar forearm was challenged with SADBE, and the other with acetone vehicle control. Subsequently, participants rated the maximal perceived intensity of spontaneous itch, pricking/stinging, and burning every 6 to 12 hours for 1 week, using the generalized Labeled Magnitude Scale. In the laboratory, they judged stimulus-evoked sensations within and outside the chemically treated area. The SADBE- but not the acetone-treated skin resulted in 1) localized inflammation, with spontaneous itch and nociceptive sensations peaking at 24 to 48 hours after challenge, 2) alloknesis, hyperknesis, and hyperalgesia to mechanical stimuli that were reduced or eliminated by anesthetic cooling of the SADBE-treated area and restored on rewarming, suggesting that sensations and dysesthesias are dependent on ongoing peripheral neural activity, and 3) enhanced itch to intradermal injection of histamine, BAM8-22, or β-alanine. This experimental model of T-cell-mediated inflammation may prove useful in evaluating potential treatments of itch from ACD. PerspectiveIn a model of allergic contact dermatitis, experimentally applied in humans, psychophysical measurements were obtained of persistent, spontaneous itch and enhanced stimulus-evoked itch and pain sensations. These sensory measurements will be useful in the identification of the neural mechanisms underlying inflammatory itch and pain.

Abstract B43: Dose-response on the chemopreventive effects of sarcophine-diol on UVB-induced skin tumor development in SKH-1 hairless mice.

Abstract Sarcophine-diol (SD) is a lactone ring-opened analogue of sarcophine. It has shown chemopreventive effects on chemically-induced skin tumor development in female CD-1 mice, as well as in a UVB-induced skin tumor development model in hairless SKH-1 mice at a dose of 30 μg SD applied topically and 180 mJ/cm2 UVB. The objective of this study was to determine the dose-response on the chemopreventive effects of SD on SKH-1 hairless mice when exposed to a UVB radiation dose of 30 mJ/cm2. This UVB dose better represents chronic human skin exposure to sunlight leading to skin cancer than previous studies applying much higher UVB doses. Carcinogenesis was initiated and promoted by UVB radiation. Female hairless SKH-1 mice were divided into 5 groups. The control group was topically treated with 200 μL of acetone (vehicle), and the SD treatment groups were topically treated with SD (30 μg, 45 μg, and 60 μg dissolved in 200 μL of acetone) 1 hour before UVB radiation (30 mJ/cm2). The last group of animals received 60 μg SD/200 μl acetone without UVB exposure. These treatments were continued for 27 weeks. Tumor multiplicity and tumor volumes were recorded on a weekly basis for 27 weeks. Weight gain and any signs of toxicity were closely monitored as well. Histological characteristics and the proliferating cell nuclear antigen (PCNA) were evaluated in the mice skin collected at the end of the experiment. The dose-response study proved a modest increase in chemopreventive effects with the increase in SD dose, reflected in reduced tumor multiplicities and tumor volumes. SD also reduced the number of cells positively stained with PCNA proliferation marker in mice skin. The study also showed that SD applications without UVB exposure had no effect on the structure of mice skin. The results from this study suggest that broader range doses of SD are necessary to improve the chemopreventive effects. Citation Format: Ruth F. Guillermo, Xiaoying Zhang, Radhey S. Kaushik, David Zeman, Safwat A. Ahmed, Sherief Khalifa, Hesham Fahmy, Chandradhar Dwivedi. Dose-response on the chemo-preventive effects of sarcophine-diol on UVB-induced skin tumor development in SKH-1 hairless mice. [abstract]. In: Proceedings of the Eleventh Annual AACR International Conference on Frontiers in Cancer Prevention Research; 2012 Oct 16-19; Anaheim, CA. Philadelphia (PA): AACR; Cancer Prev Res 2012;5(11 Suppl):Abstract nr B43.

Dose-Response on the Chemopreventive Effects of Sarcophine-Diol on UVB-Induced Skin Tumor Development in SKH-1 Hairless Mice

Sarcophine-diol (SD) is a lactone ring-opened analogue of sarcophine. It has shown chemopreventive effects on chemically-induced skin tumor development in female CD-1 mice, as well as in a UVB-induced skin tumor development model in hairless SKH-1 mice at a dose of 30 μg SD applied topically and 180 mJ/cm2 UVB. The objective of this study was to determine the dose-response on the chemopreventive effects of SD on SKH-1 hairless mice when exposed to a UVB radiation dose of 30 mJ/cm2. This UVB dose better represents chronic human skin exposure to sunlight leading to skin cancer than previous studies applying much higher UVB doses. Carcinogenesis was initiated and promoted by UVB radiation. Female hairless SKH-1 mice were divided into five groups. The control group was topically treated with 200 μL of acetone (vehicle), and the SD treatment groups were topically treated with SD (30 μg, 45 μg, and 60 μg dissolved in 200 μL of acetone) 1 h before UVB radiation (30 mJ/cm2). The last group of animals received 60 μg SD/200 μL acetone without UVB exposure. These treatments were continued for 27 weeks. Tumor multiplicity and tumor volumes were recorded on a weekly basis for 27 weeks. Weight gain and any signs of toxicity were also closely monitored. Histological characteristics and the proliferating cell nuclear antigen (PCNA) were evaluated in the mice skin collected at the end of the experiment. The dose-response study proved a modest increase in chemopreventive effects with the increase in SD dose. SD reduced the number of cells positively stained with PCNA proliferation marker in mice skin. The study also showed that SD application without UVB exposure has no effect on the structure of skin. The results from this study suggest that broader range doses of SD are necessary to improve the chemopreventive effects.

Acute Treatment with Kerosene Damages the Dermal Barrier and Alters the Distribution of Topically Applied Benzo(a)pyrene in Mice

The dermal route is important in many occupational exposures. Some materials may reduce the barrier function of the skin to enhance absorption and effect on internal organs. We have reported previously that kerosene cleaning following treatment with used engine oil increased DNA adduct levels in the lungs of mice compared with animals treated with used oil alone. To investigate what other physiological parameters might be affected by kerosene, we conducted in vitro and in vivo measurements of skin barrier function. We also topically applied 3H-BAP(100 nM in 25 μL acetone) and washed half the mice with 25 μL kerosene 1 hr after carcinogen application. Groups of four mice were euthanized from 1 to 72 hr after treatment. Skin, lungs, and livers were harvested from each animal and stored separately. Kerosene application reduced the barrier function of the skin in vitro beyond the effect of the acetone vehicle and the vehicle plus BAP. In vivo studies indicated that kerosene treatment reduced the barrier function at 4 and 8 hr post application and that the barrier function recovered at 24 hr after a single treatment. The fraction of the radiolabel remaining in the skin of animals treated with 3H-BAP and washed with kerosene was significantly less than those not washed, beginning at 24 hr (p< 0.05). Fractional distribution to the lungs and livers of these animals became significantly elevated at this time. Kerosene treatment compromises dermal barrier function and the ability of the skin to retain water, enhances carcinogen absorption, and alters organ distribution. This appears to contribute to the increase in BAP DNA adducts we reported earlier.

Urethral carcinoma and hyperplasia in male and female B6C3F1 mice treated with 3,3',4,4'-tetrachloroazobenzene (TCAB).

B6C3F1 mice chronically exposed to 3,3',4,4'-tetrachloroazobenzene (TCAB), a contaminant of dichloroaniline-derived herbicides, developed a number of neoplastic and nonneoplastic lesions, including carcinoma of the urinary tract. Groups of fifty male and fifty female B6C3F1 mice were exposed by gavage to TCAB at dose levels of 0, 3, 10, and 30 mg/kg five days a week for two years. Control animals received corn oil:acetone (99:1) vehicle. Decreased survival of male mice in the mid-dose group and of male and female mice in the high-dose groups was related mainly to the occurrence of urethral transitional cell (urothelial) carcinoma and resulting urinary obstruction. Increased urethral transitional cell carcinomas were seen in all treated male groups in a dose-related manner as well as in the females treated with 30 mg/kg TCAB. Administration of TCAB was also associated with increased transitional cell hyperplasia of the urethra. Most nonneoplastic lesions of the urogenital tract were considered secondary to local invasion and urinary obstruction by the urethral transitional cell carcinomas. The mechanism of tumor induction is uncertain, but the high frequency of tumors in the proximal urethra of male mice suggests that the neoplasms result from the exposure of a susceptible population of urothelial cells to a carcinogenic metabolite of TCAB.

Abstract A96: Melanoma chemoprevention using topical PBISe

Abstract Despite public awareness and availability of sunscreen, incidence and mortality rates for malignant melanoma continue to increase every year. Novel strategies are required to prevent melanoma development as the causes for ∼60% of cases remaining unknown. While sunscreen is effective at protecting skin from UV radiation induced damage, inhibiting melanocytic lesion development using body creams or sunscreens containing chemopreventive agents could be a novel approach to fight this disease. Hence, the chemopreventive efficacy of PBISe, a selenium containing isosteric analogue of PBIT, has been examined in laboratory generated skin reconstructs and melanoma tumor xenograft models. The data demonstrate that PBISe treated skin reconstructs containing melanocytic lesion cells had 60–70% smaller tumor lesions compared to control treated skins. Furthermore, mice topically treated with PBISe had ∼50% fewer tumors compared to PBIT or acetone vehicle treated control groups. Mechanistically, PBISe elevated MAP kinase pathway activity as indicated by increased pErk1/2 levels to amounts that induced cellular senescence. Furthermore, PBISe treatment down-regulated cyclin-D1, upregulated the expression of cell cycle inhibitors p21 and p27 as well as apoptotic markers cleaved caspase-3 and PARP to inhibit cell proliferation and induce apoptosis. In conclusion, the results demonstrate the potential utility of topical PBISe application for preventing melanoma leision development. Citation Information: Mol Cancer Ther 2009;8(12 Suppl):A96.

Interaction of Hydration, Aging, and Carbon Content of Soil on the Evaporation and Skin Bioavailability of Munition Contaminants

Water plays a key role in enhancing the permeability of human skin to many substances. To further understand its ability to potentially increase the bioavailabililty of soil contaminants, artificial sweat was applied to excised pig skin prior to dosing with munition-contaminated soils. Skin was mounted in chambers to allow simultaneous measurement of evaporation and penetration and to control air flow, which changed the dwell time of skin surface water within a l-h period post application of test materials. Additional variables included type of compound, aging of spiked soil samples, and carbon content of soil. To this end, the evaporation and skin penetration of C-14 labeled hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), 2,6-dinitrotoluene (26DNT), and 2,4,6-trinitrotoluene (TNT) were determined from two soil types, Yolo, having 1.2% carbon, and Tinker, having 9.5% carbon. RDX soil samples aged 27 mo and 62 mo were compared to freshly spiked soils samples. Similarly, 26DNT samples aged 35–36 mo and TNT samples aged 18 mo were compared to freshly spiked samples. Approximately 10 μg/cm2 of radiolabeled compound was applied in 10 mg/cm2 of soil. Radiolabel recovered from the dermis and tissue culture media (receptor fluid) was summed to determine percent absorption from the soils. Radiolabel recovered from vapor traps determined evaporation. Mean skin absorption of all compounds was higher for low-carbon soil, regardless of soil age and skin surface water as affected by air flow conditions. For 26DNT, a simultaneous increase in evaporation and penetration with conditions that favored enhanced soil hydration of freshly prepared samples was consistent with a mechanism that involved water displacement of 26DNT from its binding sites. A mean penetration of 17.5 ± 3.6% was observed for 26DNT in low-carbon soil, which approached the value previously reported for acetone vehicle (24 ± 6%). 26DNT penetration was reduced to 0.35% under dryer conditions and to 0.08% when no sweat was applied. When soil hydration conditions were not varied from cell to cell, air flow that favored a longer water dwell time increased penetration, but not evaporation, consistent with a mechanism of enhanced skin permeability from a higher hydration state of the stratum corneum. Profiles of 26DNT penetration versus air flow conditions were exponential for freshly prepared soil samples, suggesting strong and weak binding sites; corresponding profiles of 26DNT penetration from aged samples were linear, suggesting a conversion of weak to strong binding sites. Absorption and evaporation was less than 5% for TNT and less than 1% for RDX, regardless of soil type and age. Fresh preparations of RDX in Tinker soil and aged samples of TNT in Yolo soil showed a significant decrease in skin absorption with loss of surface moisture. The penetration rate of radiolabel into the receptor fluid was highest during the 1–2 h interval after dosing with 26DNT or TNT. High-performance liquid chromatography (HPLC) analysis of 26DNT in receptor fluid at maximum flux indicated no metabolism or breakdown. For TNT, however, extensive conversion to monoamino derivatives and other metabolites was observed. Relatively little radioactivity was found in the dermis after 26DNT and TNT applications, and dermal extracts were therefore not analyzed by HPLC. RDX was not sufficiently absorbed from soils to allow HPLC analysis. This study has practical significance, as the use of water for dust control at remediation sites may have the unintended effect of increasing volatilization and subsequent absorption of soil contaminants. Soil in contact with sweaty skin may give the same result. Skin absorption of 26DNT from soil was over 50-fold higher than the value for dryer skin and over 200-fold higher than the value obtained when there was no sweat application. While the hydration effect was less dramatic for RDX and TNT, soil contaminants more closely matching the physical properties of 26DNT may be similarly affected by hydration.

The Tg.AC Transgenic Mouse as a Screening Tool for Anticarcinogens: Broccoli Juice Protected Against 12-O-Tetradecanoylphorbol-13-Acetate (TPA) But Not Benzo[a]Pyrene (B[a]P)-Induced Skin Tumors

The Tg.AC mouse model was used to assess the utility of a short-term screening assay to evaluate compounds with suspected carcinogenic/anticarcinogenic activity. Crude broccoli juice (BROC) was evaluated for antitumorigenic effects against 12-Otetradecanoylphorbol-13-acetate (TPA) and benzo[a]pyrene (B[a]P)-induced tumors. Groups of female mice were dosed three times a week (200 μL/mouse) with one of the following: acetone vehicle control, TPA (2.5 μg/mouse), B[a]P (250 μg/mouse), BROC/TPA, or BROC/B[a]P. BROC (200 μL, 1:1 acetone) was dermally administered 1 h prior to the administration of either TPA or B[a]P to evaluate anticarcinogenic activity. Papilloma numbers were recorded weekly for each mouse. Following 13 weeks of treatment, samples from the dermal test site from all mice were examined histologically. B[a]P-induced tumors were evaluated for transgene expression by RT-PCR and immunohistochemically for cyclin D1 and p53 proteins. TPA and B[a]P induced tumors in all surviving mice. BROC showed effective antitumorigenic activity against TPA but not B[a]P. Tumor development was distinct between TPA (small, benign papillomas) and B[a]P (large, ulcerated, squamous cell carcinomas). The transgene v-Ha-ras, cyclin D1, and p53 proteins were highly expressed in B[a]P tumors where progression to malignancy was rapid (< 13 weeks). The effects induced by B[a]P appeared to cooperate with transgene expression to enhance conversion to malignancy and could serve as a phenotypic indicator for genotoxic versus nongenotoxic carcinogens. The model distinguished differences in tumor response for carcinogenic and anticarcinogenic agents. The Tg.AC mouse model offers a potentially useful screen for identifying new anticarcinogenic agents and directing future mechanistic evaluations.

Mitogen‐regulated protein/proliferin mRNA induction following single applications of tumor promoters to murine skin

Mitogen-regulated protein/proliferin (mrp/plf) gene family transcripts rise in abundance as a response to diverse chemical and physical agents that promote morphological transformation in the murine C3H/10T1/2 cultured cell model of multi-step carcinogenesis. To determine if proliferin genes respond to tumor promoters in vivo, RNA was extracted from the whole skin of SENCAR mice after single applications of 2 or 20 microg 12-O-tetradecanoylphorbol-13-acetate (TPA); 3.2 or 32 nmole), 20 or 40 mg benzoyl peroxide (BPO; 83, 165 micromole), or acetone vehicle alone (2.72 mmole). RNA samples were prepared from treated skin areas, 2-48 h after painting. Mrp/plf-mRNA was not detected in Northern blot hybridizations, but large increases in mRNAs for ornithine decarboxylase gene and mRNA (odc), v-jun oncogene-related transcription factor gene and mRNA (junB), egr1 (early growth response protein gene and mRNA) were measured relative to beta 2 microglobulin gene and mRNA (b2m) mRNA in response to TPA. BPO induced small relative changes in these mRNAs. Reverse transcriptase (RT)-polymerase chain reactions (PCR) detected fully-processed MRP/plf-mRNA 16-48 h after TPA treatments in five of six animals, and in three of six BPO-treated animals. The MRP/plf-mRNA species expressed in the skin were predominantly plf1 and mrp3 as determined by gene-specific restriction enzyme sites within the RT-PCR products. Expression was either undetectable or found at low levels in acetone-painted controls and was not detected during the anagen phase of the normal hair growth cycle in unpainted animals. These results demonstrate that mrp/plf-mRNA is differentially expressed in murine skin in response to mechanistically distinct tumor promoters and has potential utility as a short-term biomarker for tumor promoting effects in chemical carcinogenesis.

Absence of tumor promoting activity of Euphorbia milii latex on the mouse back skin

Euphorbia milii (Euphorbiaceae) is a decorative plant used in gardens and living fences. In China, it has also been employed in herbal remedies for hepatitis and abdominal edema. Since E. milii latex—lyophilized or in natura—proved to be a potent plant molluscicide, its toxicity to non-target organisms has been comprehensively studied. Concerns on a possible tumor promoting activity have discouraged its use as a locally-available alternative molluscicide in schistosomiasis control programs. Two in vitro assays (inhibition of metabolic cooperation in V79 cells and Epstein-Barr virus induction in Raji cells) had suggested that E. milii latex contained tumor-promoting substances. This study was undertaken to verify whether the latex acts as a tumor promoter in vivo as well. A single dose of the initiating agent DMBA (400 nmol) was applied on the back skin of male and female DBA/2 mice. Testing for tumor promoting activity began 10 days after initiation. Tetradecanoyl phorbol acetate (TPA) (5 nmol, positive control), lyophilized latex (20, 60 and 200 μg per mouse) or acetone (vehicle control) were applied on mouse back skin twice a week for 20 weeks. In TPA-treated mice, papillomas were firstly noted during the 11th week, and by the 17th week all animals exhibited skin tumors. No tumors developed in mice treated with the solvent alone and in those exposed to latex. Findings from the present study therefore indicated that E. milii crude latex does not act as a tumor promoting agent on the mouse back skin assay.

Suppression of the contact hypersensitivity response following topical exposure to 2-butoxyethanol in female BALB/c mice.

The effects of route of exposure, time of exposure and metabolism of 2-butoxyethanol (BE) on the contact hypersensitivity response (CHR) were evaluated in female BALB/c mice. Mice were either orally exposed to 50, 150 or 400 mg BE/kg or topically exposed to 0.25, 1.0, 4.0 or 16.0 mg BE on the ear and the oxazolone (OXA)-induced CHR evaluated by measuring ear thickness before and after OXA challenge. While no modulation was observed following oral exposure to BE, topical exposure resulted in a significant decrease in the CHR. Application of 4.0 mg BE in 4:1 acetone and olive oil (AOO) vehicle at the time of sensitization, challenge or both, decreased the CHR by 18%, 18% and 22%, respectively. A time course study of the effects of topical exposure to 4.0 mg BE/ear during the challenge phase of the CHR revealed that BE must be applied at the time of OXA challenge to significantly reduce the ear swelling response. In order to determine if metabolism of topically applied BE was required for suppression of the CHR, butoxyacetic acid (BAA), the primary metabolite of BE, was applied to the ear immediately following OXA challenge. No topical dose of BAA (2.0,4.0 and 8.0 mg BAA/ear) administered in this study altered the CHR. Blocking the metabolism of BE by oral administration of 4-methylpyrazole (MP), further reduced OXA-induced ear swelling when compared to mice exposed to BE without MP treatment. Taken together, these studies indicated that suppression of the CHR in mice following topical exposure to this glycol ether was due to the activity of BE itself and was not dependent on metabolic activation of the compound. Further studies were undertaken to identify a potential mechanism of BE-induced reduction of the CHR. Epidermal cells from untreated BALB/c mice were isolated and exposed to BE in vitro (10(-12), 10(-10), 10(-8), 10(-6) and l0(-4) M BE). In vitro exposure to BE at these concentrations did not significantly affect expression of MHC class II surface protein or protein synthesis in epidermal Langerhans cells, failing to provide in vitro evidence that BE-associated suppression of the CHR is associated with a reduction in MHC class II expression.

Role of cytochrome P450 1a1 and 1b1 in the metabolic activation of 7,12-dimethylbenz[a]anthracene and the effects of naturally occurring furanocoumarins on skin tumor initiation.

The current study was designed to determine the mechanistic basis for differences in the effects of naturally occurring furanocoumarins on skin tumor initiation by 7,12-dimethylbenz[a]anthracene (DMBA). Female SENCAR mice were pretreated topically with bergamottin, imperatorin, or isopimpinellin (100-3200 nmol), 7,8-benzoflavone (7,8-BF, 5-40 nmol, a known inhibitor of DMBA skin carcinogenesis in mice), or acetone (vehicle control) 5 min prior to topical treatment with DMBA (10 nmol). Imperatorin, isopimpinellin, and 7,8-BF, but not bergamottin, significantly blocked total DMBA-DNA adduct formation. HPLC analysis of DNA adducts revealed that bergamottin preferentially inhibited formation of anti-DMBA diol-epoxide (DMBADE) derived DNA adducts, imperatorin, and isopimpinellin inhibited both anti- and syn- derived adducts, whereas 7,8-BF showed some selectivity for reduction of syn-DMBADE-DNA adducts. Mouse embryo fibroblast C3H/10T1/2 (10T1/2) cells, and mouse hepatoma-derived 1c1c7 (Hepa-1) cells, which preferentially express P450 1b1 and P450 1a1, respectively, were co-incubated with 2 microM bergamottin, imperatorin, isopimpinellin, and 7,8-BF, and with DMBA (2 microM). Hepa-1 cells (P450 1a1) formed mainly anti-DMBADE-DNA adducts. In contrast, 10T1/2 cells (P450 1b1) formed mainly syn-DMBADE-DNA adducts. Bergamottin inhibited DMBA metabolism to DMBA-3,4-diol and blocked DNA adduct formation in Hepa-1 cells, but had little effect in 10T1/2 cells. In contrast, 7,8-BF completely blocked DMBA metabolism and DNA adduct formation in 10T1/2 cells, but had little effect in Hepa-1 cells. Imperatorin and isopimpinellin inhibited DMBA bioactivation in both cell lines. These results indicate that bergamottin is a more selective inhibitor of P450 1a1 and overall a less effective inhibitor of the metabolic activation of DMBA in mouse epidermis. In contrast, imperatorin, isopimpinellin, and especially 7,8-BF, which block metabolic activation of DMBA in mouse epidermis, appear more selective for P450 1b1. On the basis of our studies using 10T1/2 cells and Hepa-1 cells, it appears that P450 1a1 is primarily responsible for converting DMBA-3,4-diol to anti-DMBADE, whereas P450 1b1 is primarily responsible for converting DMBA-3,4-diol to syn-DMBADE. These data demonstrate the role of P450 1a1 and 1b1 in the metabolic activation of DMBA in mouse epidermis and provide a mechanistic explanation for the differential effects of naturally occurring furanocoumarins (and 7,8-BF) on polycyclic aromatic hydrocarbon skin carcinogenesis.