Aluminum Exposure Impairs Electrochemically Measured Vesicular Storage and Exocytosis via Iron Homeostasis Dysregulation.

Widespread human exposure to aluminum (Al) has raised increasing concerns about its effects on neuronal functions since Al3+ can cross the blood-brain barrier and accumulate in neuronal cells, especially considering its ionic similarity to ferric iron (Fe3+), a metal strongly associated with neurodegenerative diseases. In this study, we demonstrate that Al3+ affects vesicles in an iron-status-dependent manner in pheochromocytoma (PC12) cells, causing distinct changes under iron-normal, deficient, and overloaded conditions. Al3+ competes with Fe3+ for transferrin binding and enters cells via transferrin receptor (TfR)-mediated endocytosis, ultimately leading to cellular iron deficiency. This disruption alters dopamine-related proteins and molecular pathways, impairing exocytotic dynamics and reducing the average vesicular transmitter storage. When iron level is overloaded, TfR expression is downregulated to avoid Al3+ affecting vesicles. However, supplementation with ferric ammonium citrate (FAC) fails to reverse Al3+-induced iron deficiency due to Al3+ simultaneously upregulating TfR, allowing excess Fe3+ to further decrease neurotransmitter release. Furthermore, deferoxamine (DFOM), an Fe chelator, destabilizes exocytotic fusion pores, suggesting a potential drawback of chelation therapy. These findings highlight iron dysregulation as a key pathway through which Al3+ impairs vesicular function, providing a new insight into how metal ion interactions modulate neurotransmission.