Angiotensin II increases vesicular trafficking in brain neurons

Our previous studies have established that angiotensin (Ang) II stimulates the release, uptake, and synthesis of norepinephrine (NE) in brain neurons involving distinct signal transduction pathways. However, little is known if this NE neuromodulatory effect is a result of Ang II activation of vesicular trafficking in the catecholaminergic neurons. Thus, the aim of this study was to determine if Ang II influences movement of vesicles in live neurons. Dopamine-beta-hydroxylase (DbetaH) fused to green fluorescence protein (GFP) has been used to trace vesicular movement in live neurons by confocal microscopy. Transfection by a plasmid containing GFP-DbetaH resulted in the expression of green fluorescence, representing approximately 100 kDa GFP-DbetaH fusion protein. The fluorescence was predominantly localized in the perinuclear region of the neuronal soma, with a few neurites also depicting the fluorescence. Ang II caused a dramatic redistribution of fluorescence. The fluorescence was translocated to the neurites in a time-dependent manner. As a result, the number of neurites depicting fluorescence was significantly increased. The translocation was blocked by losartan, an Ang II type 1 receptor subtype-specific antagonist and not by PD123319, an Ang II type 2 receptor subtype antagonist. High-magnification confocal microscopic examination revealed that Ang II treatment resulted in a distal movement of certain fluorescent clusters in the neurites at an average rate of 0.84+/-0.2 micrometer/s. These observations suggest increased vesicular trafficking is a key signaling event in Ang II stimulation of NE neuromodulation.