Effect of some statin group of drugs on the phase profile of liposomal membrane – a fluorescence anisotropy study

Abstract

Using the fluorescent probe 1,6-diphenyl-1,3,5-hexatriene, we have investigated the effect of some statin group of drugs, widely used in hyperlipidemia, on the phase transition of model membranes such as dipalmitoyl phosphatidylcholine (DPPC) liposomes. The nature of the changes in the fluorescence anisotropy values suggested that the drugs simvastatin and mevastatin fluidized the membrane both before and after the phase transition temperature (T _m), whereas atorvastatin fluidized the membrane below T _m but rigidified the same above T _m, i.e., introduced an intermediate fluid condition within the lipid matrix. We have calculated the changes in van’t Hoff enthalpy values associated with the phase transitions due to chain melting in all the cases, and observed that the values of enthalpy decreased with increase in drug concentrations. In order to get a better insight, the fraction of motionally restricted lipid molecules was determined.

Keywords:

• statins
• fluorescence anisotropy
• 1,6-diphenylhexatriene
• phase transition temperature
• van’t Hoff enthalpy
• motionally restricted lipid molecules

Acknowledgement

This work was financially supported by Defence Research Development Organization, Government of India.