Dexamethasone stabilize the expanded phase of DMPC monolayer

CÁMARA, CANDELARIA I.; WILKE, NATALIA; YUDI, LIDIA M.

La Plata - Buenos Aires

Congreso; XLVIII Sociedad Argentina de Biofísica; 2018

Sociedad Argentina de Biofísica

Dexamethasone (DEX) is a synthetic glucocorticoid with a chemical structure similar to the steroids hormones. Dex is mostly used as analgesic and immunosupresant, especially in inflammation treatments (swelling, redness and paint), arthritis, skin disorder, severe allergies and asthma. Due to its hydrophobic nature and low solubility in water, DEX has toxic effects when administrated during long periods. Its toxic effects may be related with the lipophilic center, conferring a high capacity of partition in cellular membranes. In this context, the present work pretends to evaluate how DEX modifies the properties of membrane models composed of dimyristoylphosphatidylcholine (DMPC). We studied the capacity of DEX to penetrate pre-formed membranes and from these experiments we obtained the DEX concentration for saturation at 15 mN/m and the cut off value for this drug. Besides, we studied the surface tension vs mean molecular area (Langmuir isotherm) for co-spreaded DMPC:DEX mixture at several molar ratios. These monolayers were visualized with Brewster Angle Microscopy, and the effect of DEX on the phase state and the reflectivity of the monolayer was evaluated at 15°C. From the Gibbs adsorption experiments, we obtained a DEX saturation concentration of (0.22±0.08)mM when the monolayer was pre-formed at 15mN/m. DEX has a cut off value of 45mN/m, proposed higher value to that comparable to cellular membranes. This suggests that DEX can penetrate cellular bilayer. Regarding the Langmuir isotherms, a molar fraction of DEX higher than 50% stabilized the expanded phase of the DMPC monolayer blurring the LE/LC phase transition. This was in agreement with a decrease in reflectivity as DEX molar fraction increased at surface pressure higher than 30mN/m. Conclusion: Dex penetrates DMPC pre-formed monolayers up to surface pressure lower than 45 mN/m and stabilizes the expanded phase in pre-mixed monolayers.Acknowledgement: Centro de Micro y Nanoscopía de Córdoba, -CEMINCO- CONICET-Universidad Nacional de Córdoba, Córdoba, Argentina. Foncyt . CONICET.