Copper-Induced Microglial Activation Involves PKC/NOX/PARP-1/TRPM2 Signaling Pathway

Area of Science:

• Neuroscience
• Cell Biology
• Toxicology

Background:

• Copper (Cu²⁺) is essential for brain function but toxic at high levels, causing oxidative stress.
• Microglial activation is critical in neuroinflammation, and the TRPM2 channel is implicated in oxidative stress responses.
• Mechanisms linking copper, TRPM2 channels, and microglial activation are not fully understood.

Purpose of the Study:

• To investigate the signaling pathways of TRPM2 channel and microglial activation induced by Cu²⁺.
• To elucidate the roles of reactive oxygen species (ROS), Poly(ADP-ribose) polymerase 1 (PARP-1), protein kinase C (PKC), and NADPH oxidase (NOX) in this process.

Main Methods:

• Treatment of microglial cells with varying concentrations of Cu²⁺.
• Measurement of intracellular calcium concentration ([Ca²⁺]_i) and cell morphology.
• Utilized TRPM2 inhibitors (2-APB, ACA), PARP-1 inhibitors (PJ-34, DPQ), PKC inhibitors, and NOX inhibitors.

Main Results:

• Cu²⁺ exposure increased [Ca²⁺]_i and induced microglial activation, effects blocked by TRPM2 inhibitors.
• PARP-1 activation was essential for Cu²⁺-induced increases in [Ca²⁺]_i and morphological changes.
• Cu²⁺-induced ROS production was mediated by PKC and NOX, and inhibiting these pathways attenuated Ca²⁺ influx and microglial activation.

Conclusions:

• PKC and NOX mediate ROS production, leading to PARP-1-dependent TRPM2 channel activation.
• This cascade results in a Ca²⁺ response responsible for Cu²⁺-induced microglial activation.
• Findings reveal a novel signaling pathway in copper-mediated neuroinflammation.