Expression of the aryl hydrocarbon receptor pathway and cyclooxygenase-2 in dog tumors.

In humans, the aryl hydrocarbon receptor (AHR) gene battery constitutes a set of contaminant-responsive genes, which have been recently shown to be involved in the regulation of several patho-physiological conditions, including tumorigenesis. As the domestic dog represents a valuable animal model in comparative oncology, mRNA levels of cytochromes P450 1A1, 1A2 and 1B1 (CYP1A1, 1A2 and 1B1), AHR, AHR nuclear translocator (ARNT), AHR repressor (AHRR, whose partial sequence was here obtained) and cyclooxygenase-2 (COX2) were measured in dog control tissues (liver, skin, mammary gland and bone), in 47 mast cell tumors (MCTs), 32 mammary tumors (MTs), 5 osteosarcoma (OSA) and related surgical margins. Target genes were constitutively expressed in the dog, confirming the available human data. Furthermore, their pattern of expression in tumor biopsies was comparable to that already described in a variety of human cancers; in particular, both AHR and COX2 genes were up-regulated and positively correlated, while CYP1A1 and CYP1A2 mRNAs were generally poorly expressed. This work demonstrated for the first time that target mRNAs are expressed in neoplastic tissues of dogs, thereby increasing the knowledge about dog cancer biology and confirming this species as an useful animal model for comparative studies on human oncology.

A cell-based approach for the early assessment of the phospholipidogenic potential in pharmaceutical research and drug development.

Phospholipidosis is a term commonly used to indicate a phospholipid storage disorder; in affected cells, phospholipids accumulate in lysosomes that acquire a multilamellar morphological appearance. Cationic amphiphilic drugs (CADs) are suggested to induce phospholipidosis by direct interaction of xenobiotics with intracellular phospholipids or by the action of xenobiotics on the synthesis and metabolism of phospholipids. To date, electron microscopy (EM) represents the most reliable and the preferred method for the demonstration of phospholipidotic cell damage. Nevertheless, EM has a low throughput, it is expensive, and it is not suitable for screening purposes. We discuss here the assessment of the the phospholipidogenic potential of drugs using a cell culture-based model. In this test, intracellular phospholipids of treated U-937 cells (a human monocyte-derived cell line) were measured using the fluorescent probe Nile red. Eleven CADs reported to induce phospholipidosis in vivo and eight nonphospholipidogenic drugs were tested. Results obtained with the U-937 model confirmed the phospholipidogenic potential of drugs tested as described in the literature. Results have also been correlated with data obtained with a physical-chemical model (chromatographic hydrophobicity index measurement). Good correlation was obtained, confirming that the physical-chemical properties of CADs play a crucial role in the development of phospholipidosis. This work demonstrates that the U-937 model is a rapid and sensitive method for the determination of phospholipidosis-mediated cell damage. The specificity and the predictive potency observed make this method suitable for screening purposes in pharmaceutical development.

Successful xenografting of cryopreserved primary pancreatic cancers.

In order to assess the suitability of cryopreserved neoplastic tissues for xenografting into nude (nu/nu) mice, we compared the take rate in 28 samples of pancreatic ductal carcinoma. Eleven fresh samples were implanted in nu/nu mice, and 17 were frozen in cryopreserving solution and implanted at a later time. All samples were examined for the presence of neoplastic tissue in cryostat sections. A total of 15 tumors grew in the animals; five from the freshly implanted samples and ten from those cryopreserved. Ten xenografted tumors were characterized for alterations in p53, K-ras, and p16 genes, which were found in six, eight, and nine cases, respectively. Our results demonstrate that the take rate for xenografting is comparable between cryopreserved and fresh tissue samples. The procedure allows for the exchange of tumor material between institutions and permits the establishment of centralized facilities for the storage of an array of different primary tumor samples suitable for the production of in vivo models of cancers.

The calcium-channel blocker lacidipine reduces the development of atherosclerotic lesions in the apoE-deficient mouse.

BACKGROUND: Lacidipine is a widely used calcium-channel blocker, which has both long-lasting antihypertensive activity and also antioxidant properties. Previous studies have demonstrated the ability of lacidipine to reduce the development of atherosclerotic lesions in several animal models. OBJECTIVE: The present study investigated the antiatherosclerotic potential of lacidipine in the apoE-deficient mouse, an experimental model of atherosclerosis showing progressively complex and widespread lesions which closely resemble the inflammatory-fibrous plaques seen in humans. METHODS: Lacidipine was administered daily by gavage for 10 weeks at dose levels of 0 (control), 0.3, 1.0 and 3.0 mg/kg. RESULTS: Lacidipine administration reduces the extension of atherosclerotic lesions in the aorta of the apoE-deficient mouse without affecting plasma lipid levels. We also show that apoE-deficient mice have four-fold higher values of the proatherogenic peptide, endothelin, compared with the wild-type C57BL/6 mouse and that lacidipine administration reduced, in a dose-dependent manner, the concentrations of plasma endothelin. CONCLUSION: Lacidipine has anti-atherogenic effects in the apoE-deficient mouse, and reduces plasma endothelin concentrations.

Anti-atherosclerotic activity of the calcium antagonist lacidipine in cholesterol-fed hamsters.

We have investigated the activity of the calcium antagonist lacidipine in male hamsters fed an atherogenic diet containing 2% cholesterol and 5% butter. Animals were examined at 14, 20 and 24 weeks of treatment. At 14 weeks, in hamsters fed the atherogenic diet and without lacidipine treatment, there were significant increases in serum levels of total cholesterol, triglycerides and lipoproteins; these values were approximately similar at week 24. Lacidipine treatment at 0.3, 1.0 and 3.0 mg/kg/d did not affect levels of serum cholesterol, triglycerides and lipoproteins. At 24 weeks, in hyperlipidemic hamsters fed the atherogenic diet, the area of the fatty streak in the aortic arch covered a mean area of 375 +/- 145 micron2 x 100, which accounted for 2.7% of the total surface area of the aortic arch. In hamsters fed the atherogenic diet and treated with lacidipine at 0.3, 1.0 and 3.0 mg/kg, at 24 weeks, the surface area of the aortic arch lesion was significantly reduced by 41 to 71%. In the thoracic aorta at 24 weeks, in lacidipine-treated animals, both the incidence and degree of severity of the lesions was reduced, the area of the fatty streak being lowered by 78 to 97% in comparison with non-lacidipine-treated control animals. Ultrastructural examination demonstrated that the early changes in the aorta in hamsters fed the atherogenic diet involved the intima and smooth muscle cells; lacidipine treatment reduced the severity of the intimal lesions significantly. With SEM, lacidipine administration was seen to reduce endothelial irregularity and the presence of crater-like lesions. At TEM, treatment with lacidipine reduced the number of foam cells and the presence of liposomes in the subendothelium. This investigation demonstrates that in the hyperlipidemic hamster, lacidipine treatment decreases atheromatous lesions without lowering serum lipids. It is suggested that lacidipine influences the atherogenic process by an unusual mechanism which may be related to a combination of both the long-lasting calcium antagonism of the drug and significant antioxidant activity.

Comparison between MRI, microbiology and histology in evaluation of antibiotics in a murine model of thigh infection.

Although in vivo magnetic resonance imaging (MRI) is rapidly becoming a recognised tool in experimental pharmacological research, at the best of our knowledge, scarce application in the field of antibacterial drug research has been reported so far. In this last field, animal models of bacterial infections are used to test the efficacy of novel compounds. In this paper we have explored the potential usefulness of MRI in monitoring the chronological evolution of experimental bacterial infections and the effect of different therapeutic treatments. A murine model of thigh infection induced by Staphylococcus aureus has been used and the efficacy of vancomycin and imipenem/cilastatin has been tested. Three groups of infected animals were studied by microbiology, histology and MRI methods. The results obtained show that in vivo MRI data are highly consistent with microbiological and histological data, allowing, similarly to these commonly used techniques, the efficacy of different antibacterial treatments to be quantified. Our findings suggest that MRI could be used to assess the efficacy of new chemical entities in antibacterial pharmacological research. The advantages of MRI, as a non invasive technique, in comparison with commonly used microbiological and histological methods are discussed.

Glutamine synthetase activity in rat urine as sensitive marker to detect S3 segment-specific injury of proximal tubule induced by xenobiotics.

The possibility of detecting segment-specific injury of the proximal tubule by means of urinary enzymes was investigated in rats. Urinary glutamine synthetase, an enzyme exclusively localized in the S3 segment, and N-acetyl-beta-D-glucosaminidase, prevalently a S1-S2, but S3 enzyme also, were determined after single treatment with 100 mg/kg body wt. of hexachloro-1:3-butadiene (HCBD; i.p.), toxic for the S3 segment, or 25 mg/kg body wt. of potassium dichromate (s.c.), toxic for the S1-S2 segments. Excretion of total urinary proteins was also measured. In addition, a dose-response relationship was determined between three doses (50, 100 and 200 mg/kg body wt.) of HCBD and glutamine synthetase activity in urine. Glutamine synthetase activity, measured according to a new assay for urine based on modification of methods developed for organs, increased in the urine only when the S3 segment of the proximal tubule was damaged, as demonstrated by histological findings of the kidneys. HCBD caused early excretion of the enzyme related to the necrosis of the S3 segment, whereas potassium dichromate caused a slight increase only when the resulting lesion to this segment (vacuolization) began to develop. On the contrary, N-acetyl-beta-D-glucosaminidase activity showed the peak of excretion 24 and 34 h after treatment with HCBD or potassium dichromate, respectively, according to the histological findings of necrosis of the S3 segment (the former) and vacuolization of the S1-S2 segments (the latter). Excretion of total urinary proteins reached the peak 24 h (HCBD) and 48 h (potassium dichromate) after treatment. HCBD at 200 mg/kg body wt, caused a peak of glutamine synthetase activity in urine 10 h after injection, whereas the peak caused by doses of 50 and 100 mg/kg body wt. occurred 24 h following treatment. The peak of enzyme activity in urine significantly increased with the dose. The results suggest that the measurement of urinary activity of S3 segment-specific enzyme as glutamine synthetase allows us to detect early S3 segment-specific injury of the proximal tubule. In addition, the method for urinary enzyme activity appears sensitive, simple and fast.

Glutamine transaminase K intranephron localization in rats determined by urinary excretion after treatment with segment-specific nephrotoxicants.

Glutamine transaminase K(GTK) excretion assessed in urine and by kidney histology was evaluated in rats after single treatment with 1.0 mg/kg i.p. of mercuric chloride, 100 mg/kg i.p. of hexachloro-1:3-butadiene (both S3, pars recta, segment-specific nephrotoxicants) and 25 mg/kg s.c. of potassium dichromate (S1-S2, pars convoluta, segment-specific nephrotoxicant). The aim was to correlate segment-specific injury and enzyme excretion in order to assess, using non-vasive methods, localization of GTK along the proximal tubule. Mercuric chloride and hexachloro-1:3-butadiene produced early focal damage in the pars recta (focal necrosis was shown 10 h after treatment, and diffuse necrosis appeared later at 34 and 24 h after treatment). Changes of the pars convoluta were occasional and delayed (72 h after treatment for both substances). On the contrary, potassium dichromate induced damage of the pars convoluta (vacuolar degeneration and focal necrosis were evident 24 h and 48 h after treatment, respectively), whereas the pars recta was affected later (focal vacuolar degeneration was observed 72 h after treatment). Increase urinary GTK excretion was early after treatment with mercuric chloride and hexachloro-1:3-butadiene (significant increase was observed within 10 h), with a peak for both substances 24 h after treatment, in agreement with the necrosis of the pars recta. Potassium dichromate induced a significant increase of enzyme excretion in urine also 24 h after injection, according to histological features showing vacuolar degeneration of the pars convoluta; the peak of excretion was reached 48 h after treatment (delay was due, probably, to s.c. administration). The results show that GTK increased in urine after treatment with S3 and S1-S2 specific nephrotoxicants; the combination of histological examination and urinary enzyme supports the evidence that the enzyme is distributed along the whole of the proximal tubule.

Protective action of lacidipine in cardiac hypertrophy of the spontaneously hypertensive stroke-prone rat: an ultrastructural study.

We investigated the effect on cardiac hypertrophy of a once-daily treatment with lacidipine, at doses that do not reduce systolic blood pressure. Spontaneously hypertensive stroke-prone rats (SHR-SP) were fed a 1% NaCl enriched diet and treated daily by gastric gavage with lacidipine at doses of 0.3, 1, or 3 mg/kg/die or vehicle. At 15 weeks of age the rats were sacrificed. The heart was removed, weighed and processed for transmission electron microscopy, scanning electron microscopy and ultrastructural morphometry. Though the treatment did not reduce systolic blood pressure, heart weight and heart weight/body weight ratio were lower in the lacidipine-treated rats than in those treated with vehicle alone. Medial and subendothelial lesions were visible in coronaries of vehicle-treated SHR-SP but not in animals treated with lacidipine. In the cardiocytes of the lacidipine-treated rats, the myofibrils had a more regular arrangement and the intercalated discs did not show the irregular course and infoldings seen in the vehicle-treated rats. Morphometry showed a significantly higher density of mitochondria in the cardiocytes of lacidipine-treated SHR-SP. Scanning electron microscopy identified a decrease in the width of cardiocytes and in the number and length of lateral branches following lacidipine-treatment. The cardio-protective action of this calcium-antagonist at doses that do not reduce systolic blood pressure is attributable both to its vascular activity and to improvement in cytoplasmic organization of cardiocytes.

Lacidipine: experimental evidence of vasculoprotective properties.

Lacidipine is a second-generation 1,4-dihydropyridine calcium antagonist, whose potent and long-lasting antihypertensive properties prompted us to investigate whether its chronic administration to Dahl-S rats prevented salt-induced hypertension, vasculopathy, and accelerated mortality. These studies revealed that lacidipine proved vasoprotective when administered both prophylactically and therapeutically at doses of 0.1 and 0.3 mg/kg p.o. once a day, largely equivalent to the therapeutic doses. A generalized dose-related protection against necrotizing vasculopathy and brain damage was detected, although only the highest dose used (10 mg/kg) controlled the development of hypertension. These protective properties were further confirmed in stroke-prone spontaneously hypertensive rats, which develop accelerated mortality as a result of salt-induced cerebral apoplexy and renal lesions. All untreated controls died within 12 weeks of salt-rich diet, whereas all animals survived during the same period when treated prophylactically with lacidipine at 0.3 and 1 mg/kg p.o. once a day, although a slight reduction in systolic blood pressure was measured only with the highest dose. No cerebral lesions and a clear protection against renal damage were detected in lacidipine-treated animals. In conclusion, these findings reinforce the concept that the beneficial effects of calcium antagonists are not simply restricted to a reduction in blood pressure.

Qualitative and quantitative analysis of the progressive cerebral damage after middle cerebral artery occlusion in mice.

The middle cerebral artery occlusion (MCAO) in mice induces a focal cerebral ischaemia at the level of the tempo-parietal cortex. Histological staining and immunohistochemical markers were used to characterize the temporal progression of the cerebral infarct: both qualitative and quantitative analyses were performed at different days after the MCAO. At 3 days after MCAO, an extensive necrosis of the cerebral parenchyma was accompanied by extravasation and by massive oedema. After 7 days, GFAP marker showed a gliotic reaction with alteration of the astrocytes membrane permeability (S100 marker). Positivity for acid phosphatase staining indicated the presence of macrophages. At Day 14 and 21 following MCAO, the histological profile was essentially similar. Interestingly, at Day 7, 14 and 21, a previously unreported gliosis was observed in the subthalamic area. Quantitative analysis showed a significantly large infarct volume at Day 3 (7.88 +/- 1.95 mm3 +/- S.E.M.) compared to Day 7 (4.28 +/- 0.47 mm3 +/- S.E.M.). At Day 14 and Day 21 the infarct volumes were further decreased to 2.00 +/- 0.52 and 1.43 +/- 0.39 mm3 +/- S.E.M., respectively. These results suggest that it is important to consider the time of evaluation of cerebral ischaemia-induced cerebral infarct, especially in studies which aim to evaluate the neuroprotective effect of putative therapeutic agents.

Copper supplementation in the rat: preliminary observations on the clinical, hematological and histopathological profile.

Complete toxicological examinations in female rats fed an "anti-inflammatory" 200 ppm copper-containing diet for 30 and 58 days were performed. Copper was found to accumulate in liver, kidneys and paws; however, at the hematological, clinical chemical and histopathological levels, this treatment did not seem able to induce any toxic accumulation phenomenon in the examined rats.

Lacidipine: prevention of vascular damage induced by hypertension.

Lacidipine is a long-lasting 1,4-dihydropyridine calcium antagonist that has been reported to protect salt-loaded Dahl-S rats from vascular damage and accelerated mortality when it is administered prophylactically at 0.1 and 0.3 mg/kg p.o. once a day (equivalent to the recommended dose in humans). The aim of this study was to investigate the vasoprotective properties of lacidipine in Dahl-S rats that had already developed sustained hypertension after 4 weeks of a salt-rich diet. Although none of the dosages of lacidipine (0.3, 1, and 3 mg/kg) reduced the elevated values of blood pressure, an almost complete protection from mortality was obtained. Moreover, lacidipine dose-dependently inhibited the development of macroscopic and microscopic alterations in the distal branches of mesenteric arteries and in the brain. A clear regression of vascular damage and cardiac hypertrophy was observed at the highest dose tested (3 mg/kg). These findings further support the assumption that the protective properties of lacidipine are not restricted to a reduction in blood pressure.

Vascular protection of lacidipine in salt-loaded Dahl-S rats at nonsustained antihypertensive doses.

The aim of this study was to characterize the antihypertensive and vasoprotective properties of lacidipine in salt-loaded Dahl-S rats, a suitable animal model of malignant hypertension. After 9 weeks of a high (8%) sodium chloride (NaCl) diet, 80% of the untreated Dahl-S rats died (20% survival rate) whereas a 100% survival rate was observed with chronic treatment with lacidipine at doses of 0.1 (equivalent to the recommended dose in humans), 0.3, 1, and 10 mg/kg once daily by gastric gavage. The most interesting results included the following: (a) Only the highest dose tested (10 mg/kg once daily) was able to control the increase in blood pressure, which was measured 24 h after the preceding administration of drug, yet a 100% survival rate was maintained. (b) There appeared to be prevention of brain lesions, which is very likely the cause of the survival of all of the lacidipine-treated rats in this study. (c) A clear dose-related vascular protection was observed in other tissues. In conclusion, lacidipine protects against the vascular damage and concomitant increase in mortality of salt-loaded Dahl-S rats even at doses that do not adequately control the development of hypertension.

Influence of N-allyl-normetazocine on acetylcholine release from brain slices: involvement of muscarinic receptors.

The effects of (+/-)N-allyl-normetazocine on the release of acetylcholine from different areas of guinea-pig and rat brain were investigated. 1. The drug did not modify the electrically (2 Hz) evoked tritium efflux from guinea-pig cerebral cortex, thalamus and caudate nucleus slices, preloaded with 3H-choline 0.1 mumol/l and superfused with Krebs solution containing hemicholinium-3 10 mumol/l. 2. (+/-)N-allyl-normetazocine 10 mumol/l enhanced the evoked 3H efflux from guinea-pig brain slices superfused with Krebs solution containing physostigmine 30 mumol/l or oxotremorine 0.3-1 mumol/l; the effect was naloxone-insensitive and was abolished by atropine 0.15 mumol/l, but not by pirenzepine 1 mumol/l. 3. (+/-)N-allyl-normetazocine 5 mumol/l enhanced the electrically evoked release of endogenous acetylcholine as well, in a naloxone-insensitive way. 4. Both (+/-) and (+)N-allyl-normetazocine were without effect on 3H efflux from rat caudate nucleus slices electrically stimulated at 0.2 Hz frequency, after preloading with 3H-choline and during superfusion with hemicholinium-3. 5. The results are discussed in view of the antimuscarinic properties of the drug.