CLX (celecoxib), a selective COX-2 (cyclo-oxygenase-2) inhibitor, has numerous pleiotropic effects on the body that may be independent of its COX-2 inhibitory activity. The cancer chemopreventive ability of CLX, particularly in CRC (colorectal cancer), has been shown in epidemiological studies. Here we have, for the first time, examined the biophysical effects of CLX on the cellular membranes of COX-2 expressing (HT29) and COX-2 non-expressing (SW620) cell lines using ATR-FTIR (attenuated total reflectance–Fourier transform IR) spectroscopy and SL-ESR (spin label–ESR) spectroscopy. Our results show that CLX treatment decreased lipid fluidity in the cancer cell lines irrespective of COX-2 expression status. As metastatic cells have higher membrane fluidity, we examined the effect of CLX on the metastatic potential of these cells. The CLX treatment efficiently decreased the proliferation, anchorage-independent growth, ability to close a scratch wound and migration and invasion of the CRC cell lines through Matrigel. We propose that one of the ways by which CLX exerts its anti-tumorigenic effects is via alterations in cellular membrane fluidity which has a notable impact on the cells' metastatic potential.

CLX (celecoxib) is a highly hydrophobic non-steroidal anti-inflammatory drug with high plasma protein binding. We describe here the encapsulation of CLX in MLVs (multilamellar vesicles) composed of DSPC (1,2-distearoyl- sn -glycero-3-phosphocholine) and variable amounts of cholesterol. The effects of cholesterol content on liposome size, percentage drug loading and in vitro drug release profiles were investigated. Differential scanning calorimetry and FTIR (Fourier-transform infrared) spectroscopy were used to determine molecular interactions between CLX, cholesterol and DSPC. The phase transition temperature ( T m ) of vesicles was reduced in a synergistic manner in the presence of both CLX and cholesterol. Encapsulation efficiency, loading and release of CLX decreased with increasing cholesterol content. FTIR results indicated that this decrease was due to a competition between CLX and cholesterol for the co-operativity region of the phospholipids. In the presence of cholesterol, CLX was pushed further into the hydrophobic core of the bilayer. However, MLVs prepared with DSPC only (without cholesterol) exhibited the lowest ability for drug retention after 72 h. Our results indicated that CLX, without the requirement of modifications to enhance solubilization, can be encapsulated and released from liposomal formulations. This method of drug delivery may be used to circumvent the low bioavailability and systemic side effects of oral CLX formulations.

Statins are commonly used drugs in the treatment of hypercholesterolaemia. There are many adverse effects of statins on skeletal muscle, but the underlying mechanisms remain unclear. In the present study, the effects of low dose (20 mg/kg) simvastatin, a lipophilic statin, on rat EDL muscle (extensor digitorum longus muscle) were investigated at the molecular level using FTIR (Fourier-transform infrared) spectroscopy. FTIR spectroscopy allows us rapid and sensitive determination of functional groups belonging to proteins, lipids, carbohydrates and nucleic acids simultaneously. The results revealed that simvastatin treatment induces a significant decrease in lipid, nucleic acid, protein and glycogen content. A significant increase in the lipid/protein and nucleic acid/protein ratios was also obtained with simvastatin treatment. Furthermore, an increase in lipid order and membrane fluidity was detected. A decrease in the bandwidth of the amide I band and shifting of the position of this band to higher frequency values in treated muscle indicates structural changes in proteins. Detailed secondary structure analysis of the amide I band revealed a significant increase in antiparallel and aggregated β-sheet, random coil structure and a significant decrease in β-sheet structure, which indicates protein denaturation.

Tamoxifen (TAM) is a non-steroidal antiestrogen drug, which is widely used to prevent and treat breast, liver, pancreas and brain cancers. The present work investigates, in detail, the concentration dependent behavior of TAM (varying from 1 mol% to 45 mol%) on membrane fluidity. The differential scanning calorimetry (DSC) studies showed that tamoxifen eliminates the pre-transition and decreases the main phase transition to lower temperatures. Using visible spectroscopy at 440 nm and Fourier transform infrared (FTIR) spectroscopy it was found that membrane dynamics decreases for 1 and 3 mol% tamoxifen in both the gel and liquid crystalline phases. Above these concentrations up to 18–24 mol%, it increases and reaches its maximum values. As tamoxifen concentration was further increased, the membrane dynamics is found to be gradually decreased, although TAM still has fluidifying effect in comparison to pure phospholipid membrane. These findings are important for the effective use of tamoxifen in the cancer therapy to eliminate its dose dependent side effects reported in the literature.

There are contradictory results in the literature relating to the effect oftamoxifen on membrane fluidity. The present work investigates the effect oftamoxifen on membrane dynamics to find out whether the concentration oftamoxifen can be one of the factors in this discrepancy. Turbidity(absorbance at 440 nm) and Fourier transform infrared spectroscopicstudies reveal that tamoxifen causes opposite effects on membranefluidity at low (1 mol.%) and high (30 mol.%) tamoxifen concentrations. Lowtamoxifen concentrations increase the absorbance in the gel and liquidcrystalline phase, whereas high tamoxifen concentrations decrease theabsorbance in gel and liquid crystalline phase, whereas tamoxifenconcentrations decrease the absorbance. Observations on both phasesshow that the bandwidth of the CH2 stretching bands decreases with1 mol.% tamoxifen and increases with 30 mol.% tamoxifen present, indicatinga decrease in membrane fluidity at low tamoxifen concentrations and anincrease in fluidity at high tamoxifen concentrations. It is seen that theapparent discrepancy in the literature on the effect of tamoxifen onmembrane fluidity mainly arises from the tamoxifen concentration used andthe confusion on the concept of lipid fluidity and lipid order.

The effect of α-tocopherol on the frequency of the CH 2 stretching bands of infrared spectra of dipalmitoylphosphotidylcholine multibilayers has been investigated, both in H 2 O and 2 H 2 O buffer, to determine the reason for the discrepancy in the literature between the results of different spectroscopic techniques relating to the effect of α-tocopherol on membrane order in the gel phase. In contrast to previous FTIR studies, the present FTIR results indicate that αT increases the frequencies of the CH 2 stretching bands in the gel phase, which implies an increase in the number of gauche conformers (increase in disordering), which is in agreement with other ESR and NMR spectroscopic studies.

Binary and tertiary mixture of α-tocophenol, cholesterol and dimyristoylphosphatidylcholine in the form of multilamellar liposomes were investigated by Fourier Transform Infrared and visible spectroscopy. Results of the FTIR and turbidity experiments indicate that α T decreases or diminishes the effect of cholesterol on the frequency and the bandwidth of the C-H stretching, CH 2 scissoring and C=O stretching bands in FTIR spectra and the turbidity measurements (recorded as absorbance values at 440 nm) in phospholipid model membranes.