Ultrastructural changes in endothelial cells of cerebral microvessels after exposure to nitric oxide donor

It has been largely accepted that nitric oxide (NO) plays an important role in cerebral vasomotor control. NO has also been proposed to be a significant chemical in the process of endothelial cell injuries in various pathological conditions. Although the toxic effect of high concentrations of NO has been shown, only a few ultrastructural studies have been reported. The purpose of this study is to demonstrate physiological and pathological changes in cerebral microvessels after exposure to a high dose of NO donor. Glyceryl trinitrate, a NO donating chemical, was administered intravenously (10 mg/kg) to experimental rats. The vasomotor response was monitored by in vivo fluorescein videomicroscopy and ultrastructural changes were studied using transmission electron microscopy. The result showed long-lasting vasodilatation of pial microvessels. The greatest response was observed in microvessels with baseline diameter of less than 10 μm compared with microvessels of a larger diameter (P = 0.003). Exposure to NO donor produced considerable changes in the ultrastructure of cerebral microvessels. Such morphological changes were characterized by increased pinocytosis, increased microvillous formation, mitochondrial swelling, doming of the endothelial surface, swelling of the perivascular astrocytic foot plate and partial separation of endothelial cells from the adjacent brain tissue. These results confirm the cytotoxic effect of NO on cerebral endothelial cell and further elaborate the role of this substance in endothelial cell injury observed in various conditions.     

Aerosol gemcitabine inhibits the growth of primary osteosarcoma and osteosarcoma lung metastases

Osteosacarcoma (OS) lung metastases are often resistant to chemotherapy. Most anticancer drugs are administered systemically. In many cases this is followed by dose-dependent toxicity, which may not allow the achievement of therapeutic levels in lungs to eradicate metastases. We determined the efficacy of gemcitabine (GCB) by administering it directly to the lungs via aerosol and studied the role of the Fas pathway in response to the therapy. We used 2 osteosarcoma lung metastases animal models: human LM7 cells that form lung metastases in mice following intravenous injection and murine LM8 cells, which grows subcutaneously in mice and spontaneously metastasize to the lung. Treatment was initiated when the presence of lung metastases had been established. Aerosol GCB inhibited the growth of lung metastases in mice. Intraperitoneal GCB administration at similar dosage had no effect on lung metastases. Besides its direct effect on lung metastases, aerosol GCB suppressed the growth of subcutaneous LM8 tumor. Histopathological examination of mice receiving aerosol GCB showed no evidence of toxicity. Lungs are distinguished from other tissues by the constitutive expression of FasL. Since exposure of tumor cells to GCB upregulated Fas expression, we hypothesized that the susceptibility of the tumor cells to ligand-induced cell death by resident lung cells may be increased. Therefore, the Fas pathway may contribute to the therapeutic effect of aerosol GCB.     

Some environmental and hygienic aspects of preschool children's health in an industrial town

The results of a medical genetic study of the spread of congenital morphogenetic types (CMGT) among 3-7-year-old children living in Magnitogorsk whose territory is highly polluted with chemical compounds are presented. In Magnitogorsk, the mean of CMGT cases per child is 2.89, which is much greater than the respective values for environmentally favorable cities and towns in Russia. The most common signs are as follows: diastema (137.79 cases per 1000 children), clinodactyly (135.98 per 1000), epicanthus (122.44 per 1000), and wide umbilical ring (110.71 per 1000).     

Distribution of camptothecin after delivery as a liposome aerosol or following intramuscular injection in mice

Purpose: The plant alkaloid camptothecin (CPT) has shown significant antitumor activity against a wide variety of human tumors xenografted in nude mice. In previous studies we have found that administration of dilauroylphosphatidylcholine (DLPC) liposome aerosols containing 9-nitrocamptothecin (9-NC) inhibits the growth of human breast, colon and lung cancer xenografts. The purpose of this study was to analyze the pharmacokinetics and tissue distribution of inhaled CPT formulated in DLPC liposomes. Methods: C57BL/6 mice with subcutaneous Lewis lung carcinoma, Swiss nu/nu mice with human lung carcinoma xenografts and BALB/c mice without tumors were used for pharmacokinetic studies of CPT administered as a liposome aerosol and BALB/c mice were given CPT intramuscularly. Results: After 30 min inhalation of CPT liposome aerosol, drug was deposited in the lungs (310 ng/g) and was followed promptly by the appearance of high concentrations in the liver (192 ng/g) and with lesser amounts appearing in other organs. Drug concentration in the brain was 61 ng/g. After intramuscular injection of CPT dissolved in DMSO, drug was released from the site of injection very slowly and accumulated mainly in the liver (136 ng/g). Only trace amounts appeared in the lungs (2–4 ng/g). These results demonstrate a prompt pulmonary and later systemic distribution of CPT following liposome aerosol administration. Conclusions: The substantial concentrations of CPT in lungs and other organs following inhalation of liposome aerosol suggest the possible benefit of it and of its more active derivative, 9-NC, in the treatment of lung, liver, kidney and brain cancer in humans. Received: 23 September 1998 / Accepted: 11 January 1999     

Centrifugation enhances integrin-mediated transduction of dendritic cells by conventional and RGD-modified adenoviral vectors

The level of antigen loading can impact on the capacity for dendritic cells (DC) to activate T cell responses. Several different approaches to adenoviral (Ad)-based transduction were therefore assessed for their effect on both transgene expression and T cell activation. While a conventional E1(-)/E3Delta Ad vector (Ad/GFP) produced a concentration-dependent expression of GFP, a modified vector expressing Arginine-Glycine-Aspartic Acid (RGD) sequence on its fiber knob (Ad-RGD/GFP) enhanced transgene expression by 9-20-fold at each MOI. The addition of centrifugal force (2000xg) during DC transduction with Ad/GFP also increased expression up to 20-fold. However, combining centrifugation with the Ad-RGD/GFP vector produced no effect on transduction rate and only a 1.5- to 2-fold increase in GFP expression, suggesting overlapping mechanisms of action. Consistent with this, exogenous RGD peptide blocked transduction regardless of the vector used, or the addition of centrifugal force, and transduction was primarily limited to DC expressing the CD51 integrin receptor. Ad vectors expressing ovalbumin (OVA) were used to assess transduced DC for their capacity to activate OVA-specific T cells. We observed a significant relationship between transgene expression and the capacity for T cell activation regardless of whether transgene expression was increased by using a higher MOI, an RGD-modified vector, or by employing centrifugal force. Furthermore, combining these approaches produced synergistic effects on T cell activation. We conclude that RGD-modified vectors and centrifugation both enhance DC transduction by increasing entry via integrin receptors and that the capacity for T cell activation can be optimized by combining approaches to achieve the highest possible level of transgene expression.     

Estrogen receptors in acoustic neurilemmomas

Acoustic neurilemmomas are more frequent, larger, and more vascular in women, and such lesions have a rapidly progressive clinical course in pregnant women; these findings suggest that the growth of these neoplasms may bear a relationship to certain hormone levels. Tissues from 8 patients with acoustic neurilemmoma (3 men and 5 women) were studied by a new fluorescent steroid histochemical technique to detect the presence of estrogen receptors in or on neoplastic cells. Estrogen receptor protein has also been found in meningioma cells in women. Neurilemmoma of the acoustic nerve is the second neoplasm of the central nervous system in which such receptors have been demonstrated.     

Radiation-induced leukemia risk among those aged 0-20 at the time of the Chernobyl accident: a case-control study in the Ukraine

A case-control study was conducted to estimate the radiation-induced acute leukemia risk for the period 1987-1997 among residents aged 0-20 at the time of the Chernobyl accident in the most radioactively contaminated territories of the Ukraine (Rivno and Zhytomir regions). Data were collected on 272 leukemia cases diagnosed between 1 January 1987 and 31 December 1997. Of these, 98 cases were verified and interviewed. Verified cases were compared to 151 randomly selected controls matched by age, gender and type of settlement. The mean value of the estimated accumulated equivalent dose to the bone marrow was 4.5 mSv, and the maximum value was 101 mSv. A statistically significant increased risk of leukemia was found among males whose estimated radiation exposure was higher than 10 mSv. This association was statistically significant for acute leukemia cases that occurred in the period 1993-1997, particularly for acute lymphoblastic leukemia. A similar association was found for acute myeloid leukemia, diagnosed in the period 1987-1992.     

Specific antioxidant compounds differentially modulate cytotoxic activity of doxorubicin and cisplatin: in vitro and in vivo study

Aim

To use the antioxidant compounds (sodium selenite, selenomethionine, D-pantethine) for modulation of cytotoxic effect of doxorubicin and cisplatin toward wild type and drug-resistant mutants of several human tumor cells. Similar treatments were applied in vivo toward adult male Wistar rats.

Methods

Human tumor cells of different lines (HCT-116, Jurkat and HL-60) with various mechanisms of drug-resistance were treated with doxorubicin or cisplatin, alone or in combination with sodium selenite, selenomethionine, or D-pantethine. Cell viability, induction of apoptosis, and production of O₂^- radicals were measured. Activity of redox potential modulating enzymes was measured in the liver and blood plasma of adult male Wistar rats subjected to similar treatments.

Results

All antioxidants used in physiologically harmless concentration inhibited cytotoxic action of doxorubicin toward tumor cells sensitive to chemotherapy treatment by 15%-30%, and slightly enhanced cytotoxic effect of this medicine toward drug-resistant malignant cells. At the same time, there was no significant effect of these antioxidants on cisplatin action. Such effects were accompanied by a complete inhibition of production of superoxide radicals induced by doxorubicin. The results of in vivo study in adult male Wistar rats were in agreement with the results of in vitro study of human tumor cells.

Conclusion

Protective effect of specific antioxidant agents during cytotoxic action of doxorubicin was demonstrated in vitro in drug-sensitive human tumor cells and in adult male Wistar rats, while there was no protective effect in drug-resistant sub-lines of these tumor cells during action of doxorubicin and cisplatin.Low selectivity of action of the chemotherapeutic agents is one of their main shortcomings, leading to serious negative side effects in cancer patients. The main reason for this phenomenon is the formation of free radicals during the action of these drugs in both normal and tumor cells. Doxorubicin and cisplatin are among the most commonly used anticancer drugs. They realize the antineoplastic activity by the intercalation into DNA structure and production of the reactive oxygen species (ROS) (1-3). However, these drugs lead to severe cardio- and nephrotoxicity, which significantly limits their use for tumor treatment (4). It was shown that side effects of doxorubicin and cisplatin are mediated by hydroxyl radicals, which are formed in the presence of iron (II) from superoxide anions whose production is induced by these drugs (3,5). Numerous studies indicate that ROS-induced apoptosis of tumor cells takes place only under supraclinical doses of anthracyclines, and ROS production is not critical for realization of their anticancer activity (3). Thus, selective blocking of ROS action by specific antioxidant agents should at least partially reduce the toxicity of doxorubicin and cisplatin toward normal cells, without significant impact on the antitumor action of these drugs. Promising candidates for such role are derivatives of the pantothenic acid, since they possess significant antioxidant effect toward the mammalian cells and are able to protect the cells against toxic effects of free radicals (6). The inorganic and organic selenium derivatives (sodium selenite and selenomethionine) belong to another group of antioxidants that demonstrated a protective effect during cisplatin chemotherapy (7,8). Similar protective effects were also observed for the pantothenic acid (9). However, it remains unknown whether these antioxidants are capable of inhibiting the production of harmful ROS (including superoxide and hydroxyl radicals) due to the action of anticancer agents, and at the same time not interfering with the anti-tumor activity of these drugs. Besides, the effect of D-pantethine, selenomethionine, and sodium selenite used in combination with the anticancer drugs toward tumor cells resistant to chemotherapy has not been studied thoroughly (10).In this study, we aimed to develop new approaches for cancer chemotherapy that would eliminate negative side effects of the anticancer drugs caused by an excessive production of free radicals, which adversely affect normal tissues and organs in cancer patients. A chemotherapy regimen based on a combination of specific antioxidants (sodium selenite, selenomethionine, D-pantethine) and conventional anticancer drugs (doxorubicin, cisplatin), which are known to induce production of ROS, has been proposed. We studied the molecular mechanisms of antitumor activity of doxorubicin and cisplatin combined with the antioxidants toward tumor cell lines possessing different mechanisms of drug resistance. The results obtained in the in vitro study have been verified in experimental animals (rats).