Prevention of 7-ketocholesterol-induced mitochondrial damage and cell death by calmodulin inhibition

Area of Science:

• Neuroscience
• Cell Biology
• Biochemistry

Background:

• Oxysterols, like 7-ketocholesterol, accumulate in the brain under oxidative stress and are implicated in neuronal cell death.
• Mitochondrial dysfunction and increased reactive oxygen species (ROS) are key events in oxysterol-induced neurotoxicity.

Purpose of the Study:

• To investigate the neuroprotective effects of calmodulin antagonists against 7-ketocholesterol-induced cytotoxicity in PC12 cells.
• To elucidate the role of calmodulin in the mitochondria-mediated cell death pathway and oxidative stress induced by 7-ketocholesterol.

Main Methods:

• PC12 cells were treated with 7-ketocholesterol and various calmodulin antagonists (trifluoperazine, W-7, calmidazolium).
• Assessed were nuclear damage, mitochondrial transmembrane potential, cytochrome c release, caspase-3 activation, ROS formation, and glutathione (GSH) levels.
• Antioxidants (N-Acetylcysteine, trolox, carboxy-PTIO, Mn-TBAP) were used for comparison.

Main Results:

• 7-ketocholesterol induced significant nuclear damage, decreased mitochondrial potential, cytochrome c release, caspase-3 activation, increased ROS, and GSH depletion.
• Calmodulin antagonists significantly attenuated 7-ketocholesterol's cytotoxic effects, including nuclear damage, mitochondrial permeability transition, and cell viability loss.
• Antioxidants also reduced the cytotoxic impact of 7-ketocholesterol.

Conclusions:

• Calmodulin antagonists protect PC12 cells from 7-ketocholesterol neurotoxicity by suppressing mitochondrial permeability transition and cytochrome c release.
• These protective effects are linked to reduced ROS formation and preserved GSH levels, indicating calmodulin's role in oxidative stress response.
• Calmodulin inhibition emerges as a potential therapeutic avenue against neurotoxicity mediated by oxysterols like 7-ketocholesterol.