Nihal Simsek Ozek

Structural and functional characterization of simvastatin-induced myotoxicity in different skeletal muscles.

BACKGROUND Statins are the most commonly used drugs for the treatment of hypercholesterolemia. Their most frequent side effect is myotoxicity. To date, it remains unclear whether statins preferentially induce myotoxicity in fast- or in slow-twitch muscles. Therefore, we investigated these effects on fast- (extensor digitorum longus; EDL), slow- (soleus; SOL), and mixed-twitch muscles (diaphragm; DIA) in rats by comparing their contractile and molecular structural properties. METHODS Simvastatin-induced functional changes were determined by muscle contraction measurements, and drug-induced molecular changes were investigated using Fourier transform infrared (FTIR) and attenuated total reflectance (ATR) FTIR spectroscopy. RESULTS With simvastatin administration (30 days, 50mg/kg), a depression in the force-frequency curves in all muscles was observed, indicating the impairment of muscle contractility; however, the EDL and DIA muscles were affected more severely than the SOL muscle. Spectroscopic findings also showed a decrease in protein, glycogen, nucleic acid, lipid content and an increase in lipid order and lipid dynamics in the simvastatin-treated muscles. The lipid order and dynamics directly affect membrane thickness. Therefore, the kinetics and functions of membrane ion channels were also affected, contributing to the statin-induced impairment of muscle contractility. Furthermore, a reduction in α-helix and β-sheet and an increase in random coil, aggregated and antiparallel β-sheet were observed, indicating the protein denaturation. Spectral studies showed that the extent of molecular structural alterations in the muscles following simvastatin administration was in the order EDL>DIA>SOL. CONCLUSIONS Simvastatin-induced structural and functional alterations are more profound in the fast-twitch than in the slow-twitch muscles. GENERAL SIGNIFICANCE Myotoxic effects of simvastatin are primarily observed in the fast-twitch muscles.

Low dose simvastatin induces compositional, structural and dynamic changes in rat skeletal extensor digitorum longus muscle tissue

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 beta-sheet, random coil structure and a significant decrease in beta-sheet structure, which indicates protein denaturation.

Monitoring of tryptophan as a biomarker for cancerous cells in Terahertz (THz) sensing

Tryptophan is an extremely important amino acid for a variety of biological functions in living organisms. Changes in the concentration of this amino acid can point to identification of cancerous tissues or even confirm symptoms of depression in patients. Therefore it is extremely important to identify and quantify tryptophan concentrations in human blood as well as in in-vivo diagnostic studies. Here a reflection based terahertz pulsed spectroscopy system was used to study the interaction of THz pulses with cancerous cells to gauge the possibility of using L-tryptophan as a biomarker for THz sensing of diseases. Initial measurements were performed on human colon adenocarcinoma cells and human breast cancer cells cultivated on glass slides. The glass slides utilized in the growth process limited the measurements not only to reflection based geometries but also limited the analysis of the samples in the frequency domain due to the highly absorbing nature of glass in the THz region. The useful bandwidth was limited to frequencies below 0.6THz which prohibited us from investigating the effects of L-tryptophan in these samples. Even with the limited frequency range the measurements show that there are slight differences in the transmission of the THz pulse through different samples.

Characterization of Sodium Butyrate Induced Differentiation in Colon Cancer Cells by Fourier Transform Infrared Spectroscopy and Microscopy

Colon cancer is a major cause of morbidity and mortality throughout the world.The pathogenesis of colon cancer with respect to loss of cellular differentiation has not been clearly understood. To understand this loss in colon cancer and to differentiate the cancer cells, sodium butyrate (NaB), one of the differentiation inducer, is commonly used. NaB is produced in the colonic lumen as a consequence of bacterial fermentation of complex carbohydrates and it alters colon cancer cell morphology and reduces the cell growth and motility. Although, the differentiation process of colon cancers, which are stimulated with NaB, has been resolved at genetic level, the underlying mechanisms regarding structural and functional alterations regulating the differentiation of colon cancer cells have not been well characterized. Therefore, in this study, it was aimed to explore the NaB-induced macromolecular structural and functional changes in differentiation of colon cancer cells by attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy and FTIR microspectroscopy. These changes were determined from the spectral analysis of control and NaB treated colon cancer cell spectra and their chemical maps. Based on the spectral differences, cluster analysis was applied to discriminate the groups. The spectral analysis indicated the differences in saturated and unsaturated lipids, protein and nucleic acid content between the control and NaB treated cancer cells. The variation in membrane fluidity and lipid order was also determined in the NaB treated cells. Moreover, the successful discrimination between control and treated cells was obtained. The results of this study not only shed light on better understanding the loss of differentiation mechanisms in colon cancers but also strongly support the power of ATR-FTIR spectroscopy and FTIR microscopy as novel, simple, reagent-free methods for the identification of differentiated cancer cells.