Analysis of Connexin 43 and Spermine Co-localisation in Glioblastomas

Gap junctions are channels between adjacent cells, contributing to the unhindered exchange of metabolites, second messengers, nucleotides, and other molecules. The functional status of gap junctions in brain tumours is underinvestigated. One avenue of research focuses on exploring the expression of polyamines and their co-localisation with the Connexin 43 (Cx43) in the growth zones of glioblastoma multiforme (GBM). The aim of this work was to analyse the expression of Cx43 and spermine in human GBM to reveal their roles in neuro-oncogenesis. Human GBM sample sections were used for the immunochemistry [glial fibrillary acidic protein (GFAP), Cx43, and spermine], confocal laser scanning microscopy, and electron immunohistochemistry. Immunofluorescent analysis revealed that the more extensive processes of GBM cells exhibit GFAP. All GBM samples (n = 10) exhibited positive Cx43 signals in the form of variously sized dots and lines. Cx43 formed dotted lines around cell bodies with segmented transformed nuclei, which were also present in the gliovascular complexes. Furthermore, spermine was overexpressed in all tumour samples (cytoplasm and large and thin tumour processes), including the areas of Cx43 localisation. Merging the Cx43 and spermine signals showed co-expression in the same regions: the membranes of individual cells and individual points on processes in the tumour tissue. Therefore, we established the staining of the co-localisation of Cx43 and the polyamine spermine within glioblastoma, revealing that tumour processes housing the polyamine indeed form gap junctions, suggesting their potential joint interaction. This finding indicates that glioma cells can integrate into the surrounding neural networks, potentially serving as a mechanism to release glycolysis products, relying on gap junction activity facilitated by spermine. Cx43 exhibits sensitivity to polyamines, which play a role in opening gap junctional channels. Furthermore, polyamines have been observed to eliminate the blockades caused by hydrogen ions and calcium, which is crucial for cellular physiology.