Intercellular mitochondrial transfer through nanotubules is promoted by cyclic amp (cAMP) in rat astrocytes and human glioblastoma cells

Abstract

Introduction: Tunneling nanotubes (TnTs) have been described as communications between cells, made of F-actin fibers of nanometric diameter. Mitochondria are transferred by TnTs in numerous cellular lines (1). Mitochondrial passage to tumor cells restores oxidative metabolism, decreases tumorigenic potential, as cAMP tumor cells treatment does (2). Our goal was to analyze mitochondrial trafficking through TnTs in normal and cancerous astrocytes and the effect of cAMP (which promotes astrocytes stellation). Materials & Methods: We used rat astrocytes and human glioblastoma U87 cells. Mitochondria and actin were probed with a specific-targeted green fluorescent protein and rhodamine phalloidin, respectively. Astrocytes and U87 were incubated with 8Br-cAMP (cAMP analogue). We analyzed images by confocal miscroscopy and measured width of actin connections between cells. Results: We analyzed each culture separately; astrocytes and U87 establish thick projections with mitochondria inside but treatment with cAMP promotes an increase of TnTs-like connections with mitochondria inside (control vs cAMP: astrocytes: 2.07±0.71 vs 0.85±0.21 μm, ***p<0.05, and U87: 2.69±1.40 vs.0.84±0.22 μm, *p<0.05, ±SD, ANOVA, Tukey?s test). Conclusion: cAMP promotes TnTs-like structures and mitochondrial passage within them in both normal astrocytes and glioblastoma cells; suggesting a possible role for intercellular mitochondrial transfer through TnTs induced by cAMP, in stellation process.