ATP-Mediated Compositional Change in Peripheral Myelin Membranes: A Comparative Raman Spectroscopy and Time-Of-Flight Secondary Ion Mass Spectrometry Study

Abstract

In the present paper we addressed a mechanism of the myelin reorganization initiated by extracellular ATP and adenosine in sciatic nerves of the frog Rana temporaria. In combination with Raman microspectroscopy, allowing noninvasive live-cell measurements, we employed time-of-flight secondary ion mass spectrometry (TOF-SIMS) to follow the underlying changes in chemical composition of myelin membranes triggered by the purinergic agents. The simultaneous increase in lipid ordering degree, decrease in membrane fluidity and the degree of fatty acid unsaturation were induced by both ATP and adenosine. Mass spectrometry measurements revealed that ATP administration also led to the marked elevation of membrane cholesterol and decrease of phosphotidylcholine amounts. Vesicular lipid transport pathways are considered as possible mechanisms of compositional and structural changes of myelin.

Study of myelin structure changes during the nerve fibers demyelination

“…In following experiments, the changes in conformation of myelin lipids and carotenoids (the minor membrane component) were studied during the long-lasting nerve fibers exposure with pronase E. As described in detail previously [ 14 , 15 ], the Raman spectrum of nerve fiber myelin could be characterized by the presence of a set of intensive bands, related to phospholipid fatty acids and carotenoids ( Fig 5A and 5B ). About this, we used another laser excitation wave, which made it possible to reduce the contribution of carotenoid molecules from the RS and to study only the changes in fatty acids of phospholipids.…”

“…It is known that it is possible to test the changes of myelin lipid molecules by means of RS: the relationship between RS band intensities I 1061 /I 1088 is the proportional ratio of the number of C-C bonds in the trans conformation to the number of C-C bonds in the gauche conformation; I 1270 /I 1301 is proportional to the number of double bonds of lipid fatty acids; I 1444 /I 1301 is proportional to the ordering of lipid fatty acids in the membrane. As it was previously shown, carotenoids as the part of the myelin membrane contribute to the bands at 1160 cm -1 and 1520 cm -1 , corresponding to C–C and C = C stretching modes of the polyene chain, respectively [ 12 – 15 ].…”

“…Recently, the myelin-dependent effects were shown on nerve fibers using Raman spectroscopy [ 11 – 15 ]. Carotenoids in myelin can possibly mediate the potential-induced myelin reorganization, as well as regulate the interaction of external signaling molecules with the membrane.…”

“…Carotenoids in myelin can possibly mediate the potential-induced myelin reorganization, as well as regulate the interaction of external signaling molecules with the membrane. It was shown that both lipid and carotenoid molecules are sensitive to the extracellular ATP and acetylcholine, and thus are possible mediators of the myelin membrane restructuring [ 13 – 15 ]. The aim of current investigation was to study the conformation of myelin phospholipid fatty acids and carotenoid during demyelination.…”

Metabolic imaging and secondary ion mass spectrometry to define the structure and function of liver with acute and chronic pathology

“…[11][12][13][14] By comparing the spectra of control and affected tissues, differences in the chemical composition can be revealed. 15,16 Combined with Fourier transform infrared spectroscopy, TOF-SIMS has been successfully used for fatty liver investigations of patients' liver resection specimens. The accumulation of triacylglycerols, diacylglycerols, monoacylglycerols, and fatty acids, with the apparition of myristic acid, together with a dramatic depletion of vitamin E has been observed compared with normal liver samples.…”