Mitophagy and long-term neuronal homeostasis.

Neurons are highly polarized, post-mitotic cells that are characterized by unique morphological diversity and complexity. As highly differentiated cells that need to survive throughout organismal lifespan, neurons face exceptional energy challenges in time and space. Therefore, neurons are heavily dependent on a healthy mitochondrial network for their proper function and maintenance under both physiological and stress conditions. Multiple quality control systems have evolved to fine-tune mitochondrial number and quality, thus preserving neuronal energy homeostasis. Here, we review the contribution of mitophagy, a selective form of autophagy that targets dysfunctional or superfluous mitochondria for degradation, in maintaining nervous system homeostasis. In addition, we discuss recent evidence implicating defective or dysregulated mitophagy in the pathogenesis of neurodegenerative diseases.

LRRK2 protects immune cells against erastin-induced ferroptosis.

Ferroptosis is an iron-dependent regulated cell death pathway characterized by excessive lipid peroxidation. It is implicated in many neurodegenerative diseases, including Parkinson's Disease (PD). Mutations and increased leucine-rich repeat kinase 2 (LRRK2) kinase activity are associated with both familial and idiopathic PD pathology. Increased iron deposition was observed in the substantia nigra of LRRK2 mutation-carrying PD patients compared to healthy individuals, suggesting a potential link between LRRK2 and ferroptosis. However, the role of LRRK2 in the immune cells is still not well-understood. This study aims to investigate the effect of LRRK2 on ferroptosis-induced cell death in immune cells. We used LRRK2 parental (WT) and LRRK2 KO (KO) RAW 264.7 murine macrophages. Cells were challenged with the ferroptosis inducer, erastin, and the kinase activity was investigated using the LRRK2 kinase inhibitor, MLi2. Cell metabolism and viability analysis showed that WT cells were more resistant to ferroptosis than the KO cells. Lipid peroxidation and cellular reactive oxygen species (ROS) generation were significantly elevated in the KO cells. Furthermore, mitochondrial membrane potential and mitochondrial respiration were decreased in the KO cells after erastin treatment compared to the WT cells. Inhibition of the LRRK2 kinase function resulted in increased cell sensitivity to erastin. Cell and mitochondrial substrates utilization were altered in the KO and kinase inhibited WT cells compared to WT cells. These results indicate a protective role of LRRK2 against erastin-induced ferroptosis in RAW macrophages and point towards the importance of LRRK2 kinase function in the protective mechanism.

Mitophagy mechanisms in neuronal physiology and pathology during ageing.

Ageing in diverse species ranging from the simple nematode Caenorhabditis elegans to humans is associated with a marked decrease of neuronal function and increased susceptibility to neurodegeneration. Accumulating findings also indicate that alterations in neuronal functionality with age are associated with a decline in mitochondrial integrity and function. The rate at which a mitochondrial population is refreshed is determined by the coordination of mitochondrial biogenesis with mitophagy, a selective type of autophagy targeting damaged or superfluous mitochondria for degradation. Coupling of these opposing processes is crucial for maintaining cellular energy homeostasis, which eventually contributes to health span. Here, we focus on the role of mitophagy in nervous system function in the context of normal physiology and disease. First, we consider the progress that has been made over the last decade in elucidating the mechanisms that govern and regulate mitophagy, placing emphasis on the PINK1/Parkin-mediated mitophagy. We further discuss the contribution of mitophagy to the maintenance of neuronal homeostasis and health as well as recent findings implicating impaired mitophagy in age-related decline of the nervous system function and consequently in the pathogenesis of neurodegenerative diseases.