Effect of progesterone on DPPC membrane: Evidence for lateral phase separation and inverse action in lipid dynamics

Effects of the non-steroidal anti-inflammatory drug celecoxib on cholesterol containing distearoyl phosphatidylcholine membranes

“…This kind of disconcerted behavior has been previously reported for interactions of model membranes with melatonin [26], progesterone [17], vitamin D 2 [15], vitamin E [30] and cholesterol [29]. This controversial effect of high celecoxib concentrations on membrane order and dynamics may reflect the presence of more than one phase in the bilayer [30].…”

“…This band arises from the stretching vibrations of ester carbonyl groups of phospholipids and is conformationally sensitive to the level of hydration at the membrane interface [17,26]. Therefore any effect seen in the spectra of this region (C=O stretching) can be attributed to an interaction of celecoxib or cholesterol with the polar/apolar interfacial region of the membrane.…”

“…An increase in the bandwidth is an indication of an increase in the dynamics and therefore the fluidity of the membrane system [4,17,18,25,26]. In the interpretation of the results in FTIR spectra, extra care was taken in distinguishing between structural parameters (frequency) describing molecular order and dynamical parameters (bandwidth) describing molecular mobility, as suggested previously by us and others [26,29].…”

“…MLVs were prepared according to the procedure reported previously [17,26]. Briefly, 5 mg of DSPC and 0.82 mg cholesterol (to have a DSPC:Chol molar ratio of 3:1) was dissolved in 150 µl chloroform and excess chloroform was evaporated by using a gentle stream of nitrogen.…”

“…Therefore, it is not clear whether CLX exerts its function through a direct interaction with membrane bound enzymes or whether its interaction with cellular membranes alters the activity of these enzymes. Amphipathic and lipophilic compounds are not only able to alter the phase transition, fluidity and order of the membrane lipids but also membrane function which is achieved by influencing the activity of integral membrane proteins [16,17,19,20]. CLX, being a lipophilic compound, is also a potential modulator of membrane lipid structure and dynamics and understanding these interactions at molecular level will provide further understanding of its mechanism of action.…”