TRPM8 modulation alters uptake of Transferrin-mediated Fe3+, mitochondrial Fe2+ and intracellular Ca2+-levels in microglia

Abstract

Microglia play an important role in the immunity of the central nervous system, crucial in maintaining homeostasis. However, under diseased conditions, this cell accumulates Fe^2+/3+, triggering inflammatory and neurotoxic effects that contribute to neurodegenerative disorders such as Alzheimer's and Parkinson's. Hence, the study of dysregulated microglial activation and overload of Fe^2+/3+ is crucial in the context of neurodegenerative conditions. Emerging research has identified cold-sensitive ion channels, i.e., TRPM8 in microglia, which can regulate key subcellular functions. This study explores the regulatory function of the TRPM8 in Fe^2+/3+ metabolism and its implications for potential ferroptosis in BV2 microglial cells. We used highly specific fluorescence probes, pharmacological modulators of TRPM8 and performed life cell imaging to understand the uptake of Transferrin-488, mitochondrial Fe²⁺-level, cellular Ca²⁺-levels in live BV2 cells under different experimental conditions. Our findings reveal that TRPM8 activation leads to enhanced Transferrin-488-mediated cytosolic Fe³⁺-uptake, disrupts mitochondrial superoxide levels, and promotes cell death. Interestingly, under inflammatory conditions induced by LPS treatment, TRPM8 exhibits a distinct functional role. These results position TRPM8 as an important regulator of microglial Fe^2+/3+ metabolism. This study indicates the involvement of TRPM8 in overload of Fe^2+/3+ leading to ferroptosis and potential for M1-M2 polarization in microglia. These findings impose TRPM8 as a potential therapeutic target for neurodegenerative diseases, and aging.