Hamster Cheek Pouch Research Articles

E. coli lipopolysaccharide attenuates adenosine A1 receptor-mediated increase in plasma exudation from the hamster cheek pouch

To determine whether exposure to E. coli lipopolysaccharide (LPS) modulates adenosine A(1) receptor-induced increase in plasma exudation from the intact hamster cheek pouch microcirculation. Using intravital microscopy, we found that suffusion of R(-)-N(6)-(2-phenylisopropyl)-adenosine (R(-)-PIA) (1.0 and 10.0 nM), a selective adenosine A(1) receptor agonist, onto the intact cheek pouch elicited significant, concentration-dependent leaky site formation and increase in clearance of fluorescein thioisocyanate-dextran (mol mass, 70 kDa) from post-capillary venules (p < 0.05). These responses were significantly attenuated by pre-treatment of hamsters with LPS (p < 0.05). By contrast, LPS had no significant effects on CGS-21680-, a selective adenosine A(2A) receptor agonist, bradykinin- and substance P-induced increases in plasma exudation from the cheek pouch. These data indicate that LPS attenuates adenosine A(1) receptor-induced increase in plasma exudation in vivo in a specific fashion. We suggest that this phenomenon represents an endogenous anti-inflammatory cue to avoid excessive inflammation during Gram-negative bacterial infections.

In Vivo Simultaneous Morphological and Biochemical Optical Imaging of Oral Epithelial Cancer

Early detection of cancer is key to reducing morbidity and mortality. Morphological and chemical biomarkers presage the transition from normal to cancerous tissue. We have developed a noninvasive imaging system incorporating optical coherence tomography (OCT) and fluorescence lifetime imaging microscopy (FLIM) into a single optical system for the first time, in order to acquire both sets of biomarkers. OCT can provide morphological images of tissue with high resolution, while FLIM can provide biochemical tissue maps. Coregistered OCT volumes and FLIM images have been acquired simultaneously in an in vivo hamster cheek pouch model of oral cancer. The OCT images indicate morphological biomarkers for cancer including thickening of the epithelial layer and loss of the layered structure. The FLIM images indicate chemical biomarkers including increased nicotinamide adenine dinucleotide and reduced collagen emission. While both sets of biomarkers can differentiate normal and cancerous tissue, we believe their combination will enable the discrimination of benign lesions possessing some of the indicated biomarkers, e.g., scarring or inflammation.

Effects of low‐level laser therapy on collagen expression and neutrophil infiltrate in 5‐fluorouracil‐induced oral mucositis in hamsters

Several studies have suggested that low-level laser therapy (LLLT) can ameliorate oral mucositis; however, the mechanisms involved are not well understood. The aim of this study was to investigate the mechanisms of action of LLLT on chemotherapy-induced oral mucositis, as related to effects on collagen expression and inflammation. A hamster cheek pouch model of oral mucositis was used with all animals receiving intraperitoneal 5-fluorouracil, followed by surface irritation. Animals were randomly allocated into three groups, and treated with an InGaAIP diode laser at a wavelength of 660 nm and output power of 35 or 100 mW laser, or no laser. Clinical severity of mucositis was assessed at four time-points by a blinded examiner. Buccal pouch tissue was harvested from a subgroup of animals in each group at four time-points. Collagen was qualitatively and quantitatively evaluated after picrosirius staining. The density of the neutrophil infiltrate was also scored. Peak clinical severity of mucositis was reduced in the 35 mW laser group as compared to the 100 mW and control groups. The reduced peak clinical severity of mucositis in the 35 mW laser group was accompanied by a decrease in the number of neutrophils and an increase in the proportion of mature collagen as compared to the other two groups. The total quantity of collagen was significantly higher in the control (no laser) group at the day 11 time-point, as compared to the 35 mW laser group, consistent with a more prolonged inflammatory response in the control group. This study supports two mechanisms of action for LLLT in reducing mucositis severity. The increase in collagen organization in response to the 35 mW laser indicates that LLLT promotes wound healing. In addition, LLLT also appears to have an anti-inflammatory effect, as evidenced by the reduction in neutrophil infiltrate.

A dual-modality optical coherence tomography and fluorescence lifetime imaging microscopy system for simultaneous morphological and biochemical tissue characterization.

Most pathological conditions elicit changes in the tissue optical response that may be interrogated by one or more optical imaging modalities. Any single modality typically only furnishes an incomplete picture of the tissue optical response, hence an approach that integrates complementary optical imaging modalities is needed for a more comprehensive non-destructive and minimally-invasive tissue characterization. We have developed a dual-modality system, incorporating optical coherence tomography (OCT) and fluorescence lifetime imaging microscopy (FLIM), that is capable of simultaneously characterizing the 3-D tissue morphology and its biochemical composition. The Fourier domain OCT subsystem, at an 830 nm center wavelength, provided high-resolution morphological volumetric tissue images with an axial and lateral resolution of 7.3 and 13.4 µm, respectively. The multispectral FLIM subsystem, based on a direct pulse-recording approach (upon 355 nm laser excitation), provided two-dimensional superficial maps of the tissue autofluorescence intensity and lifetime at three customizable emission bands with 100 µm lateral resolution. Both subsystems share the same excitation/illumination optical path and are simultaneously raster scanned on the sample to generate coregistered OCT volumes and FLIM images. The developed OCT/FLIM system was capable of a maximum A-line rate of 59 KHz for OCT and a pixel rate of up to 30 KHz for FLIM. The dual-modality system was validated with standard fluorophore solutions and subsequently applied to the characterization of two biological tissue types: postmortem human coronary atherosclerotic plaques, and in vivo normal and cancerous hamster cheek pouch epithelial tissue.

Serum amyloid P ameliorates radiation-induced oral mucositis and fibrosis

PurposeTo evaluate the effect of the anti-fibrotic protein serum amyloid P (SAP) on radiation-induced oral mucositis (OM) and fibrosis in a hamster cheek-pouch model.Experimental DesignHamsters received a single dose of radiation (40 Gy) to the left everted cheek pouch to induce significant OM. The protective therapeutic potential of SAP was evaluated using varying dosing regimens. The extent of OM was measured using a validated six-point scoring scheme ranging from 0 (normal tissue, no mucositis) to 5 (complete ulceration). Fibrotic remodeling was also visualized histologically and quantified at later time points using collagen gene expression.ResultsSAP treatment attenuated the profile of radiation-induced oral mucositis by delaying the time of onset, reducing the peak value, and enhancing the resolution of injury. The peak mucositis score was reduced by approximately 0.5 grade in SAP-treated animals. The number of animal days with a score of ≥ 3 was reduced by 48% in the SAP-treated group, compared with the saline control group (P < 0.01). SAP also inhibited the extent of tissue remodeling and decreased radiation-induced increases in myofibroblast number. Attenuated collagen deposition and gene expression was also observed in the cheek pouches of hamsters treated with SAP at both 16 and 28 days post-radiation.ConclusionsSAP treatment significantly attenuated radiation-induced injury. In particular, SAP attenuated the severity of OM and inhibited pathogenic remodeling. This suggests that SAP may be a useful therapy for the palliation of side effects observed during treatment for head and neck cancer.

Screening of virulence gene in golden hamster cheek pouch mucosa carcinomatous change induced by 9,10-dimethylene-1,2-benzanthracene

To examine and analyze the global gene expression at the different stages of golden hamster cheek pouch mucosa carcinomatous change induced by 9,10-dimethylene-1,2 benzanthracene (DMBA). The model of golden hamster cheek pouch squamous cell carcinoma was induced by DMBA. The RNA of normal mucosa, precancerous lesions and squamous cell carcinoma of fresh tissue of golden hamsters was extracted and purified and the cRNA labeled by fluorescent Cy3 synthesized, which respectively hybridized with the agilent rat cDNA microarray containing 41 000 genes-expressed sequence tags, scanning with Agilent G2565AA fluorescence scanner. The Ratio>or=2 and Ratio<or=0.5 were used to determine the threshold value of the differences gene expression and analyze the relevant biological information of the three different stages of cancer. The Venn diagram by Gene Spring 10.0 analysis software was then used to select the genes of continuing expression in the three different stages of cancer. Meanwhile, RT-PCR was used to confirm the correctness of the results of the gene chip. A total of 5255 differentially expressed genes were detected during the process from normal mucosa to the squamous cell carcinoma, of which 2896 was up-regulated and 2359 down-regulated. There were 22 genes that showed continues abnormal expression through the three different stages of carcinomatous change, including 3 up-regulated, 19 down-regulated. The RT-PCR results of Eaf-2 and Ecg-2 were consistent with the gene chip. The development of oral mucosal squamous cell carcinoma involved a number of abnormal genes. The genes showing continues abnormal expression at different stages of carcinomatous change may be the important pathogenetic ones.

Abstract 1968: Mutagenesis and carcinogenesis induced by dibenzo[a,l]pyrene in the mouse oral cavity: A potential new model for oral cancer

Abstract The annual incidence of cancer of the oral cavity and pharynx in the US is about 30,000 cases, similar to that for leukemia and pancreas, and resulting in a 5 yr survival rate of about 50%. Current models utilizing 4-nitroquinoline-N-oxide in rats and mice or 7,12-dimethylbenzanthracene in the hamster cheek pouch, suffer from relevancy of these synthetic carcinogens and/or the target site. One 2-year feeding study reported that dietary administration of the tobacco smoke carcinogen, benzo(a)pyrene (BaP) leads to tumors at several sites including tongue, but only at very high doses, and mainly in forestomach (Culp, S.J., et al., Carcinogenesis, 9, 117-124, 1998). Here as a potential new model, we investigated whether the more powerful tobacco smoke carcinogen, dibenzo[a,l]pyrene (DB[a,l]P) is mutagenic and carcinogenic in the oral cavity of the B6C3F1 lacI and B6C3F1 mouse resp. upon topical application. Four groups of B6C3F1 lacI mice (6/group) received DB[a,l]P (12, 6, and 3 nmol) or vehicle 3x per week. B6C3F1 mice (20/group) received the same treatment, with an additional 24 nmol group. At 38 weeks the lacI mice were euthanized and DNA was isolated from tongue and upper oral mucosa. For the 12 nmol dose group, the mutant fraction (MF) in the cII gene in upper mucosa and tongue increased about 2-fold relative to that in vehicle-alone (5.2 +/- 0.8 and 4.6 +/- 1.2 vs 2.7 +/- 1.3 and 2.6 +/- 1.2) resp. in units of mutants/105 pfu. The increases were statistically significant (ρ = 0.023 and 0.016) for upper mucosa and tongue resp. The MF's at lower doses were non-significantly elevated. The mutational profile in the DB[a,l]P-induced mutants was compared with that induced by BaP in upper mucosa. BaP was previously shown to be mutagenic in many tissues including oral tissues when administered by gavage (Guttenplan, J.B, et al., Mutation Res., 559,199-210, 2004). Only 4% of BaP-induced mutations were at AT base pairs vs. 31% for DB[a,l]P; consistent with a report of the comparative mutational profile of BaP and DB[a,l]P in lung (Leavitt, S.A., et al., Mutagenesis 23, 445-450, 2008). The fraction of mutations at AT base pairs for DB[a,l]P is very similar to that observed in p53 mutations in the human oral cavity. One yr after the start of treatments, B6C3F1 mice were euthanized and oral squamous cell carcinomas (OSCC) were found in 31% of the high-dose group. Tumors were located in several sites in the oral cavity, although not in tongue. Immunohistochemical analyses revealed that p53 protein was overexpressed in malignant tissues, but not controls. The facts that DB[a,l]P induces mutations and tumors in the oral cavity, and has a mutational profile in oral tissue similar to that found in p53 in human OSCC, indicate DB[a,l]P administration to the mouse oral cavity will likely provide the basis for a new and more relevant model for cancer of the oral cavity than existing models. Supported by NCI grant no. R01 CA 100924 Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1968.

The vasodilatory peptide maxadilan increases vascular permeability due to activation of leukocytes in postcapillary venules

The vasodilatory peptide maxadilan (MAX) isolated from the sand fly Lutzomyia longipalpis induces plasma leakage in postcapillary venules of the hamster cheek pouch (HCP) via PAC‐1‐receptor stimulation. Here we studied arteriolar dilation, plasma leakage (FITC‐dextran 150) and accumulation of rhodamine‐labeled leukocytes in the HCP induced by topical applications of MAX 134 nM alone or combined with 8 μM M‐65, a PAC1‐receptor antagonist. Arteriolar diameter, plasma leakage (FITC‐fluorescence) and leukocyte accumulation (rhodamine‐fluorescence) was measured in digital camera images with a computer software (AxioVision 4.4). Four groups of hamsters, saline control, MAX 134 nM, MAX + M‐65 and FITC‐dextran 40 + MAX were studied. Applications of MAX and M‐65 were made topically to the HCPs in 250 μl of saline and images were recorded for 60 minutes. There was no plasma leakage increase in the saline control group but a slight increase in leukocyte accumulation. In contrast there was a lasting increase in plasma leakage (180%, P &lt; 0.05) and leukocyte accumulation (150%, P &lt; 0.05) in the MAX‐group with peak responses at 40 min and 60 min, respectively, that was inhibited by M‐65 and FITC‐dextran 40. M‐65 also inhibited arteriolar dilation while there was no significant inhibition of dilation in the FITC‐dextran 40 group. Conclusion: PAC1‐receptor activation by maxadilan causes plasma leakage and leukocyte accumulation independent of its vasodilatory effect.

Early effect of boron neutron capture therapy mediated by boronophenylalanine (BPA–BNCT) on mast cells in premalignant tissue and tumors of the hamster cheek pouch

Mast cell (MC) activation in the hamster cheek pouch cancerization model is associated with the increase in tumor cell proliferation, mediated in turn by tryptase, a protease released from mast cell granules after activation. Tryptase induces tumor cell proliferation through the activation of PAR-2 (protease activated receptor-2) on the plasma membrane of carcinoma cells. The therapeutic success of boron neutron capture therapy mediated by boronophenylalanine (BPA-BNCT) in tumor control in the hamster cheek pouch oral cancer model has been previously reported by our laboratory. Early effects of BPA-BNCT on tumors of the hamster cheek pouch include a reduction in DNA-synthesis with the concomitant decrease in the proliferation of malignant cells. The aim of the present study was to investigate the early histological changes in mast cells after BPA-BNCT in tumors and premalignant tissue of the hamster cheek pouch. Tumor-bearing pouches were treated with BPA-BNCT or beam only (neutron irradiation without prior administration of the boron compound) and sacrificed 1day after treatment. The samples were fixed in Carnoy fixative and stained with alcian blue-safranin to identify all the populations of mast cells. Total, active and inactive mast cells (MC) were counted in the connective tissue and the adventitious tissue underlying the pouch wall and at the base of the tumors in pouches treated with BPA-BNCT, in keeping with a previously described technique. BPA-BNCT induced a marked reduction in the total number of mast cells in the pouch (p<0.05). This reduction in the total number of mast cells was due to a reduction in mast cells at the base of the tumor (p<0.005) and it occurred at the expense of the active mast cells (p<0.05). A slight reduction that did not reach statistical significance also occurred in the amount of mast cells in the pouch wall (that corresponds to the premalignant tissue in tumor-bearing pouches), and in the adventitious tissue. In this case the reduction was seen in the inactive population. Both BPA-BNCT and beam only elicited a qualitative change in the secretion modality of the granule content. Although further studies are needed to evaluate the subcellular effect of BNCT on mast cell granule secretion, the reduction in cell proliferation induced by BPA-BNCT would be partially due to the decrease in total mast cells in the hamster check pouch.

Detection of vesicant-induced upper airway mucosa damage in the hamster cheek pouch model using optical coherence tomography

Hamster cheek pouches were exposed to 2-chloroethyl ethyl sulfide [CEES, half-mustard gas (HMG)] at a concentration of 0.4, 2.0, or 5.0 mg/ml for 1 or 5 min. Twenty-four hours post-HMG exposure, tissue damage was assessed by both stereomicrography and optical coherence tomography (OCT). Damage that was not visible on gross visual examination was apparent in the OCT images. Tissue changes were found to be dependent on both HMG concentration and exposure time. The submucosal and muscle layers of the cheek pouch tissue showed the greatest amount of structural alteration. Routine light microscope histology was performed to confirm the OCT observations.

The Effect of Synthetic Agonists and Antagonists of Cannabinoid Receptors on Migration of Neutrophils Elicited by Leukotriene B 4 in the Microvasculature of Hamster Cheek Pouch

The Effect of Synthetic Agonists and Antagonists of Cannabinoid Receptors on Migration of Neutrophils Elicited by Leukotriene B 4 in the Microvasculature of Hamster Cheek Pouch

Effects of propionyl-L-carnitine on ischemia–reperfusion injury in hamster cheek pouch microcirculation

Background and purpose Propionyl-l-carnitine (pLc) exerts protective effects in different experimental models of ischemia–reperfusion (I/R). The aim of the present study was to assess the effects of intravenously and topically applied pLc on microvascular permeability increase induced by I/R in the hamster cheek pouch preparation. Methods The hamster cheek pouch microcirculation was visualized by fluorescence microscopy. Microvascular permeability, leukocyte adhesion to venular walls, perfused capillary length, and capillary red blood cell velocity (VRBC) were evaluated by computer-assisted methods. E-selectin expression was assessed by in vitro analysis. Lipid peroxidation and reactive oxygen species (ROS) formation were determined by thiobarbituric acid-reactive substances (TBARS) and 2′-7′-dichlorofluorescein (DCF), respectively. Results In control animals, I/R caused a significant increase in permeability and in the leukocyte adhesion in venules. Capillary perfusion and VRBC decreased. TBARS levels and DCF fluorescence significantly increased compared with baseline. Intravenously infused pLc dose-dependently prevented leakage and leukocyte adhesion, preserved capillary perfusion, and induced vasodilation at the end of reperfusion, while ROS concentration decreased. Inhibition of nitric oxide synthase prior to pLc caused vasoconstriction and partially blunted the pLc-induced protective effects; inhibition of the endothelium-derived hyperpolarizing factor (EDHF) abolished pLc effects. Topical application of pLc on cheek pouch membrane produced the same effects as observed with intravenous administration. pLc decreased the E-selectin expression. Conclusions pLc prevents microvascular changes induced by I/R injury. The reduction of permeability increase could be mainly due to EDHF release induce vasodilatation together with NO. The reduction of E-selectin expression prevents leukocyte adhesion and permeability increase.

Chemoprevention of oral cancer in animal models, and effect on leukoplakias in human patients with ZengShengPing, a mixture of medicinal herbs

ZengShengPing (ZSP), a mixture of six medicinal herbs, has been reported to prevent esophageal squamous cell carcinoma (SCC) in human patients with dysplasia. This study was designed to investigate the chemopreventive effects of ZSP on oral cancer in animal models and human patients. In the 7,12-dimethylbenz[a]anthracene (DMBA)-induced hamster cheek pouch model, ZSP (6g/kgBW/day by gavage for 10 weeks) significantly reduced the number of visible tumor, the tumor volume, and the incidence of SCC (P<0.01). Two biomarkers associated with cell proliferation, silver stained nucleolar organizer region (AgNOR) and proliferating cell nuclear antigen (PCNA)-labeling index, were also significantly suppressed by ZSP treatment (P<0.01). In the 4-nitroquinoline 1-oxide (4NQO)-induced oro-esophageal cancer model in mice, ZSP (10% in diet) also significantly reduced the incidence of tongue SCC from 55.2% (16/29) to 22.2% (6/27) (P<0.05), and slightly reduced the incidence of esophageal SCC from 34.5% (10/29) to 22.2% (6/27). Furthermore, in a randomized clinical trial on patients with oral leukoplakia, ZSP (4 tablets, 3 times per day for 8-12months) reduced the size of oral lesion in 67.8% (40/59) patients, whereas the placebo was effective in 17% (9/53) patients (P<0.01). Such an effect was associated with significant decrease of AgNOR and PCNA-labeling index. In summary, our studies have demonstrated the chemopreventive effects of ZSP on two animal models of oral cancer, and human patients with oral leukoplakia.

Development of a model of tissue with potentially malignant disorders (PMD) in the hamster cheek pouch to explore the long- term potential therapeutic and/or toxic effects of different therapeutic modalities

Objective Given that locoregional recurrences developing from a tissue with potentially malignant disorders (PMD) in oral mucosa are a frequent cause of therapeutic failure, and that tissue with PMD is dose-limiting, the aim of the present study was to develop a model of tissue with PMD to evaluate the long- term therapeutic/toxic effects of different therapeutic modalities. Materials and methods We evaluated 5 carcinogenesis protocols based on topical application of the carcinogen dimethyl-1,2-benzanthracene in the hamster cheek pouch, twice a week for 4, 6, 7, and 8 weeks and the classical 3 times a week for 12 weeks. Results Long- term follow-up (8 months after protocol completion) was only possible with the 4- and 6-week carcinogenesis protocols. Tumour development increased progressively with time and aggressiveness of the carcinogenesis protocols. The time at which tumours developed in ≥90% of the animals was at protocol completion (T0) for the 12-week protocol, 1 month post-T0 for the 8-week protocol, 3 months post-T0 for the 7-week protocol and 4 months post-T0 for the 6-week protocol. <40% of the animals in the 4-week protocol developed tumours within the 8 months follow-up period. DNA synthesis rose as a function of time and protocol aggressiveness. Conclusions The 6-week carcinogenesis protocol was selected for long- term studies of different therapeutic modalities in tissue with PMD because it permitted long- term follow-up and guaranteed tumour development in ≥90% of the animals.

Chemoprevention of 7,12-dimethylbenz[a]anthracene (DMBA)-induced oral carcinogenesis in hamster cheek pouch by topical application of resveratrol complexed with 2-hydroxypropyl-β-cyclodextrin

Oral squamous cell carcinoma (OSCC) develops slowly and it is usually preceded by identifiable oral preneoplastic lesions (OPLs): chemoprevention could be a promising approach. Resveratrol (RV) is a plant-based agent characterized by a strong in vitro antineoplastic action, but this effect has not been clinically confirmed owing to its metabolic inactivation. In order to circumvent this limitation and to improve RV efficacy, it was locally applied and complexed with a protective and solubilising vehicle (2-hydroxypropyl-beta-cyclodextrin, HPbetaCD). The experimentation was performed in vitro on 7,12-dimethylbenz[a]anthracene-induced hamster OSCC cell line (HCPC I) and in vivo in the related animal model, by comparison of two RV-HPbetaCD formulations (cream and mouthwash) and RV alone. Vehicles and RV-formulations were free from toxicity. Antiproliferative action of RV on HCPC I was concentration- and time-dependent, and was improved in HPbetaCD-formulations. In vivo, RV prevented OPL and OSCC appearance and growth. Here, too, HPbetaCD-formulations (mainly mouthwash) demonstrated the best chemopreventive effects in terms of lesions prevalence, multiplicity, dimension, and histological signs of malignancy. HPLC detection of RV corroborated that its action is concentration-correlated and is improved by its inclusion in HPbetaCDs. In summary, our study demonstrates that RV is effective in the chemoprevention of DMBA-induced oral carcinogenesis and when it is complexed with HPbetaCDs its efficacy is significantly improved.

Of Humans and Hamsters: The Hamster Buccal Pouch Carcinogenesis Model as a Paradigm for Oral Oncogenesis and Chemoprevention

Oral squamous cell carcinoma (OSCC), a common malignancy worldwide, is an important contributor to the overall international cancer burden. Squamous cell carcinomas (SCCs) induced by 7,12-dimethylbenz[a]anthracene (DMBA) in the HBP reiterate many of the features observed in human OSCCs. The major risk factors associated with human oral cancer such as tobacco, betel quid and alcohol promote HBP carcinogenesis. SCCs induced by DMBA in the cheek pouch of Syrian hamsters are morphologically and histologically similar to human OSCC. Like human oral carcinogenesis, HBP carcinogenesis is a multistep process that involves sequential progression from hyperplasia to invasive carcinoma through varying degrees of dysplasia. In addition, HBP tumours express several biochemical and molecular markers that are also expressed in human OSCC. Multiple signaling pathways are dysfunctional in both human and hamster OSCCs. In particular, cell proliferation, apoptosis and angiogenesis are intricately interlinked in malignant transformation of the HBP mucosa by DMBA. The HBP carcinogenesis model is the best-known animal system for intervention by chemopreventive agents because of easy accessibility for examination, and follow-up of lesions. A number of synthetic and natural products have been documented to exhibit chemopreventive efficacy in the HBP model. Chemoprevention studies in the HBP model can serve as a crucial link in the potential efficacy assessment of candidate agents for oral cancer prevention and therapy.

Carcinogenic Effects of MGP-7 and B[a]P on the Hamster Cheek Pouch

This study was performed to examine the carcinogenic effects of benzo[a]pyrene (B[a]P) and manufactured gas plant (MGP) residues on the hamster cheek pouch (HCP). Syrian hamsters were treated topically with a suspension of 2%, 10%, or 20% B[a]P or 50% or 100% MGP-7 (a mixture of residues from 7 MGP sites) in mineral oil for eight (short-term study) and sixteen, twenty, twenty-eight, and thirty-two weeks (long-term study). The short-term study showed that B[a]P induced p53 protein accumulation, indicative of genotoxic damage, as well as increased cell proliferation, hyperplasia, and inflammation, which is usually associated with promotional activity. In contrast, the MGP-7 presented only marginal p53 accumulation and induction of BrdU incorporation. In the long-term experiments, animals treated with 2% and 10% of B[a]P continued to show p53 protein accumulation as well as hyperplasia and increased cell proliferation and inflammation. By thirty weeks, all the animals treated with B[a]P had a 100% incidence of squamous cell carcinoma (SCC). Animals treated with 50% and 100% MGP-7 showed only weak hyperplasia and a low proliferation rate and accumulation of p53 protein through thirty-two weeks. Benzo[a]pyrene was highly carcinogenic when used at adequate doses. Manufactured gas plant residue, however, was not carcinogenic in this model.

Alcohol‐Containing Mouthwashes

Alcohol‐Containing Mouthwashes

Independent Regulation of Periarteriolar and Perivenular Nitric Oxide Mechanisms in the In Vivo Hamster Cheek Pouch Microvasculature

We tested the hypothesis that differential stimulation of nitric oxide (NO) production can be induced in pre- and postcapillary segments of the microcirculation in the hamster cheek pouch. We applied acetylcholine (ACh) or platelet-activating factor (PAF) topically and measured perivascular NO concentration ([NO]) with NO-sensitive microelectrodes in arterioles and venules of the hamster cheek pouch. We also measured NO in cultured coronary endothelial cells (CVEC) after ACh or PAF. ACh increased periarteriolar [NO] significantly in a dose-dependent manner. ACh at 1 microM increased [NO] from 438.1+/-43.4 nM at baseline to 647.9+/-66.3 nM, while 10 microM of ACh increased [NO] from baseline to 1,035.0+/-59.2 nM (P<0.05). Neither 1 nor 10 microM of ACh changed perivenular [NO] in the hamster cheek pouch. PAF, at 100 nM, increased perivenular [NO] from 326.6+/-50.8 to 622.8+/-41.5 nM. Importantly, 100 nM of PAF did not increase periarteriolar [NO]. PAF increased [NO] from 3.6+/-2.1 to 455.5+/-19.9 in CVEC, while ACh had no effect. We conclude that NO production can be stimulated in a differential manner in pre- and postcapillary segments in the hamster cheek pouch. ACh selectively stimulates the production of NO only in arterioles, while PAF stimulates the production of NO only in venules.

Effects of thalidomide on DMBA‐induced oral carcinogenesis in hamster with respect to angiogenesis

Thalidomide has been shown to have anti-angiogenic effects in pre-clinical models as well as a significant antitumor effect in hematologic tumors. However, the effects of thalidomide on oral pre-malignant lesions and oral carcinogenesis remain unexplored. The authors aimed to investigate the chemopreventive effect of thalidomide on 7,12-dimethylbenz[a]anthracene (DMBA)-induced oral carcinogenesis in hamsters with respect to angiogenesis. Seventy male Syrian golden hamsters were randomly divided into five groups, with two of 20 and three of 10. DMBA solution (0.5% in acetone) was applied topically to the left cheek pouch of male Syrian golden hamsters in group A and B, while animals in group C were painted with acetone, three times a week for 6 weeks. For the next 18 weeks, animals in group B and D received thalidomide daily (40 mg/kg body weight/day) by gavage, animals in group A and C received same volume of saline. Animals in group E received no treatment and served as blank control. At the end of the experiment, animals were killed and tissue samples were collected for examinations. Thalidomide significantly decreased the squamous cell carcinoma (SCC) incidence from 57.9 to 11.8%; angiogenesis was inhibited in dysplasia and SCC. The gene expression of vascular endothelium growth factor and tumor necrosis factor (TNF)-alpha was downregulated. Thalidomide has inhibitory effect against the malignant transformation of oral pre-cancerous lesion and angiogenesis during oral carcinogenesis. Such inhibition is related to its modulation of TNF-alpha.