CdSe magic-sized quantum dots incorporated in biomembrane models at the air-water interface composed of components of tumorigenic and non-tumorigenic cells.

Cadmium selenide (CdSe) magic-sized quantum dots (MSQDs) are semiconductor nanocrystals with stable luminescence that are feasible for biomedical applications, especially for in vivo and in vitro imaging of tumor cells. In this work, we investigated the specific interaction of CdSe MSQDs with tumorigenic and non-tumorigenic cells using Langmuir monolayers and Langmuir-Blodgett (LB) films of lipids as membrane models for diagnosis of cancerous cells. Surface pressure-area isotherms and polarization modulation reflection-absorption spectroscopy (PM-IRRAS) showed an intrinsic interaction between the quantum dots, inserted in the aqueous subphase, and Langmuir monolayers constituted either of selected lipids or of tumorigenic and non-tumorigenic cell extracts. The films were transferred to solid supports to obtain microscopic images, providing information on their morphology. Similarity between films with different compositions representing cell membranes, with or without the quantum dots, was evaluated by atomic force microscopy (AFM) and confocal microscopy. This study demonstrates that the affinity of quantum dots for models representing cancer cells permits the use of these systems as devices for cancer diagnosis.

Putative role of heparan sulfate proteoglycan expression and shedding on the proliferation and survival of cells after photodynamic therapy.

INTRODUCTION: Photodynamic therapy is based on the selective retention of a photosensitizer by highly proliferating cells and its activation with light at the appropriate wavelength. This combination generates reactive oxygen species that ultimately kill the cells. Some cells, however, may survive photodynamic therapy and the interaction of these cells with the extracellular matrix has profound effect in tumor biology. The knowledge of photodynamic therapy action on the extracellular matrix has not been fully explored. It has been focused mainly on integrins, matrix metalloproteinases and on growth factors and immunological mediators. Other important molecules involved in the regulation of many cell processes are the glycosaminoglycans, polymers of disaccharide units, present on the cell surface and in the extracellular matrix. In most cases, the glycosaminoglycans occur as proteoglycans. AIMS: The purpose of the present investigation is to evaluate heparan sulfate proteoglycan expression and shedding, and its relation to the survival of the remaining cells, after a liposomal-AlClPc based photodynamic treatment. MATERIALS: A wild-type endothelial cell derived from rabbit aorta and its counterpart transfected with EJ-ras oncogene were used. RESULTS: Both cell lines presented augmented heparan sulfate proteoglycan syndecan-4 mRNA expression, augmented synthesis of heparan sulfate chains and increased shedding. Also, the formation of stress fibers on the border of the cells and the arrest in G(1) phase of the cell cycle was observed. CONCLUSIONS: These results show that surviving cells after photodynamic therapy exhibit changes in their morphology and cell processes that differ from that of non-treated cells, and these changes are probably hindering the cells from resuming normal proliferation.

Heparan sulfate and control of endothelial cell proliferation: increased synthesis during the S phase of the cell cycle and inhibition of thymidine incorporation induced by ortho-nitrophenyl-beta-D-xylose.

The effect of xylosides on the synthesis of [35S]-sulfated glycosaminoglycans by endothelial cells in culture was investigated. Ortho-nitrophenyl-beta-D-xylose (10(-3)M) produces a dramatic enhancement on the synthesis of heparan sulfate and chondroitin sulfate secreted to the medium (20- and 100-fold, respectively). Para-nitrophenylxyloside, at the same concentration, produces an enhancement of only 37- and 3-fold of chondroitin sulfate and heparan sulfate, respectively. These differences of action seem to be related with the higher lipophilic character of ortho-nitrophenyl-xyloside. A lower enhancement of the synthesis of the two glycosaminoglycans is also observed with 2-naphtol beta-D-xylose and cis/trans-decahydro-2-naphtol beta-D-xylose. Besides stimulating the synthesis, O-nitrophenyl-beta-D-xylose as PMA [J. Cell. Biochem. 70 (1998) 563] also inhibits [3H]-thymidine incorporation by quiescent endothelial cells stimulated for growth by fetal calf serum (FCS). The combination of xylosides with PMA produced some cumulative effect. PMA stimulates the synthesis of heparan sulfate mainly at G1 phase whereas the highest enhancement of synthesis produced by the xylosides is in the S phase of the endothelial cell cycle.

Heparins and heparinoids: occurrence, structure and mechanism of antithrombotic and hemorrhagic activities.

The correlation between structure, anticlotting, antithrombotic and hemorrhagic activities of heparin, heparan sulfate, low molecular weight heparins and heparin-like compounds from various sources that are in used in clinical practice or under development is briefly reviewed. Heparin-like molecules composed exclusively of iduronic acid 2-O-sulfate residues have weak anticlotting activities, whereas molecules that contain both iduronic acid 2-O sulfate, iduronic acid and small amounts of glucuronic acid, such as heparin, or mixed amounts of glucuronic and iduronic acids (mollusk heparins) possess high anticlotting and anti-Xa activities. These results also suggest that a proper combination of these elements might produce a strong antithrombotic agent. Heparin isolated from shrimp mimics the pharmacological activities of low molecular weight heparins. A heparan sulfate derived from bovine pancreas and a sulfated fucan from brown algae have a potent antithrombotic activity in arterial and venous thrombosis model "in vivo" with a negligible activity upon the serine-proteases of the coagulation cascade "in vitro". These and other results led to the hypothesis that antithrombotic activity of heparin and other antithrombotic agents is due at least in part by their action on endothelial cells stimulating the synthesis of an antithrombotic heparan sulfate. All the antithrombotic agents derived from heparin and other heparinoids have hemorrhagic activity. Exceptions to this are a heparan sulfate from bovine pancreas and a sulfated fucan derived from brown algae, which have no hemorrhagic activity but have high antithrombotic activities "in vivo". Once the structure of these compounds are totally defined it will be possible to design an ideal antithrombotic.

Surface chemistry and spectroscopy studies on 1,4-naphthoquinone in cell membrane models using Langmuir monolayers.

Investigating the role of drugs whose pharmaceutical activity is associated with cell membranes is fundamental to comprehending the biochemical processes that occur on membrane surfaces. In this work, we examined the action of 1,4-naphthoquinone in lipid Langmuir monolayers at the air-water interface, which served as a model for half of a membrane, and investigated the molecular interactions involved with tensiometry and vibrational spectroscopy. The surface pressure-area isotherms exhibited a noticeable shift to a lower area in relation to 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1,2-dihexadecanoyl-sn-glycero-3-phospho-l-serine (DPPS) lipid monolayers, which indicated a disruption of the monolayer structure and solubilisation of the lipids towards the aqueous subphase. To better correlate to the action of this drug in biological membrane events, cell cultures that represented tumorigenic and non-tumorigenic cells were spread onto the air-water interface, and 1,4-naphthoquinone was then incorporated. While only slight changes were observed in the non-tumorigenic cells upon drug incorporation, significant changes were observed in the tumorigenic cells, on which the organisation of the Langmuir monolayers was disrupted as evidenced by tensiometry and vibrational spectroscopy. This work then shows that this drug interacts preferentially for specific surfaces. In simplified models, it has a higher effect for the negative charged DPPS rather than the zwitterionic DPPC; and for complex cell cultures, 1,4-naphthoquinone presents a more significant effect for that representing tumorigenic cells.

Effect of carrageenans of different chemical structures in biointerfaces: a Langmuir film study.

Carrageenans have unique properties in the pharmaceutical and food industries that involve interactions with lipid interfaces, which may be accessed if surface chemistry techniques are employed. The interaction between three different types of carrageenans with dipalmitoylphosphatidylcholine (DPPC) was investigated using Langmuir monolayers as biointerface models. With a combination of data on Surface Pressure-Area Isotherms and Polarization Modulation Infrared Reflection-Absorption Spectroscopy (PM-IRRAS), the effect of different fractions on DPPC monolayers was compared by considering the chemical and structural differences as well as the anticoagulant activity of each fraction. Thus, a model is proposed in which carrageenans can encompass interactions that are maximized due to geometrical adaptations on behalf of the interactions between polysaccharide sulfate groups and lipid polar heads.

Toxicidade pulmonar e hepática aos vapores do metil metacrilato: um estudo experimental em ratos / Pulmonary and liver toxicity of methyl methacrylate vapors: an experimental study in rats

Methyl methacrylate (MMA) is widely used in medicine and in dentistry in dental braces and prostheses. The most important occupational exposure route of MMA is inhalation. These study aims at evaluating the MMA toxicity to the rat lung and liver related to the time of exposure. Male and female albino Wistar rats were exposed to MMA by inhalation. One group (n=36) was exposed continuously, and the other (n=36) was exposed during 8-hours/day, without water and food intake during the exposure period as to prevent the risk of water and food contamination by MMA. A control group (n=8) received water and food without MMA exposure. Rats were sacrificed 5, 8 and 10 days after exposure. Significant morphological alterations observed were pulmonary emphysema and hepatic esteatosis early detected after 5 days of MMA exposure in 26.4 percent (n=19) and 25 percent (n=18) of the animals, respectively. Pulmonary emphysema was observed in 77.7 percent (n=28) of the rats under continuous exposure, in 66.6 percent (n=24) of the 8-hours/day-exposure group, and in only one animal from the control group. Hepatic esteatosis was observed in 94.5 percent (n=34) of the continuous exposure group, and in 72.2 percent (n=26) of the rats exposured per 8-hours/day, and statistically significant differences were observed among the groups. The literature describes many pulmonary changes related to the exposure to MMA, emphysema being the main one, what is in accordance with our data. Hepatic damage has only been seen when the MMA is administered by intravenous injection. The results of this investigation show that toxicity of MMA appeared very early at the first days of inhalation of this agent. It indicates thata proper exhaustion system should be implemented prior to using MMA in order to prevent occupational related MMA injuries.

O metil metacrilato (MMA) é amplamente usado na medicina e odontologia. A principal via de exposição ocupacional é inalatória. Este trabalho visa avaliar a ação tóxica do MMA em pulmão e fígado de ratos em diferentes períodos de exposição. Ratos Wistar albinos, machos e fêmeas, foram expostos ao MMA por inalação. Um grupo (n= 36) foi exposto continuamente e outro (n=36) exposto durante oito horas diárias, sem água e ração durante a exposição, para excluir a possibilidade de contaminação da água e ração pelo MMA. Um grupo controle (n=8) recebeu água e ração e não foi exposto ao MMA. Os animais foram sacrificados com 5, 8 e 10 dias de exposição. As alterações morfológicas significativas foram enfisema pulmonar e esteatose hepática, detectados precocemente com 5 dias de exposição ao MMA, em 26,4 por cento (n=19) e 25 por cento (n=18) dos animais, respectivamente. Enfisema pulmonar foi observado em 77,7 por cento (n=28) dos animais com exposição contínua, em 66,6 por cento (n=24) dos expostos 8 horas/ dia e em 1 animal do grupo controle. Esteatose hepática foi observada em 94,5 por cento (n=34) dos animais com exposição contínua e em 72,2 por cento (n=26) dos expostos 8 horas/dia, sendo a diferença entre os grupos estaticamente significante. A principal alteração pulmonar na literatura é o enfisema, concordando com nossos achados. Alterações hepáticas somente foram observadas na administração endovenosa do MMA. Os dados do presente trabalho mostram que o efeito tóxico do MMA se manifesta precocemente nos primeiros dias de inalação deste agente, indicando que um sistema adequado de exaustão deve ser instalado antes do uso do MMA para prevenir danos ocupacionais a ele relacionados.