| Popis: |
Gangliosides, sialylated glycosphingolipids, building components of plasma membranes of all eukaryotic cells, are involved in cell proliferation, differentiation and oncogenic transformation participating in signalling and cell-to-cell interactions. Brain ganglioside pattern is cell type specific and is altered in pathological conditions (neurodegeneration, malignancies). Moreover, changes in ganglioside content and composition in brain tumours may serve as biochemical markers in histopathological diagnosis, grading and prognosis of tumours. Ganglioside quantity and composition of gliosarcoma and meningioma was studied by: 1) spectrophotometric determination and high performance thin-layer chromatographic (HPTLC) detection followed by laser densitometric quantification ; 2) mass spectrometric analysis using nano-electrospray ionisation Fourier transform ion cyclotron resonance mass spectrometry (nano-ESI-FTICR MS) and nano-ESI quadrupole time-of-flight (QTOF) tandem MS. Gliosarcoma and meningioma had very distinct ganglioside content and composition, related to their different histopathological origin. Using HPTLC and densitometric analysis more complex ganglioside pattern was detected in gliosarcoma than in meningioma. In gliosarcoma the fractions migrating as GM3, GM2, GM1, GD2, GD1a, GD1b, GT1b and GQ1b were found ; proportions of GM2 and GD2 were higher than in normal brain tissue. In meningioma the prevalent fractions were GM3 and GD3, GM1 was less abundant, while almost no complex ganglioside structures were observed. Structural analysis by mass spectrometry confirmed the ganglioside structures visualised by HPTLC, and additionally O-acetylated GD3 species were detected in gliosarcoma. According to mass spectrometric data, all found ganglioside species are characterised by high heterogeneity of ceramide portions i.e. differing in length of fatty acids chains and/or sphingoid bases, and in some cases carrying additional hydroxylation. Results presented indicate the benefits of highly sensitive mass spectrometric methods in determination of the altered composition of brain gangliosides as well as in discovery of new structures in various types of tumours in order to provide specific biochemical markers potentially useful in diagnostics and therapy of brain tumours. |
