Accumulation of exogenous amyloid-beta peptide in hippocampal mitochondria causes their dysfunction: a protective...

Area of Science:

• Neuroscience
• Cell Biology
• Biochemistry

Background:

• Amyloid-beta (Aβ) pathology is a hallmark of Alzheimer's disease (AD).
• Mitochondrial dysfunction, characterized by reduced energy production and increased reactive oxygen species (ROS), is linked to Aβ pathology.
• Aβ monomers and oligomers have been observed within mitochondria in AD models and human brains.

Purpose of the Study:

• To investigate the hypothesis that extracellular Aβ aggregate internalization causes mitochondrial damage.
• To elucidate the effects of Aβ on mitochondrial function and cellular integrity.
• To evaluate the therapeutic potential of melatonin in mitigating Aβ-induced mitochondrial dysfunction.

Main Methods:

• Injection of fibrillar Aβ into the hippocampus of a mouse model.
• Microscopic analysis to track Aβ entry into cells and mitochondria.
• Assessment of mitochondrial function, including ionic gradients, oxidative stress, respiratory control ratio, and ATPase activity.
• Administration of melatonin and evaluation of its effects.

Main Results:

• Fibrillar Aβ injection led to severe axonal damage and cellular Aβ uptake.
• Aβ was found within mitochondria, disrupting the inner mitochondrial membrane's ionic gradient.
• Significant increases in oxidative stress and disruption of subcellular structures were observed.
• Mitochondrial respiratory control ratio and ATPase activity were significantly reduced.
• Oral melatonin administration decreased oxidative stress, improved mitochondrial respiration, and restored energy balance.

Conclusions:

• Internalization of extracellular Aβ aggregates is a primary driver of mitochondrial damage in the context of AD pathology.
• Aβ accumulation within mitochondria disrupts key functions, leading to cellular dysfunction and neurodegeneration.
• Melatonin demonstrates neuroprotective effects by reducing oxidative stress and improving mitochondrial bioenergetics, suggesting its therapeutic potential for AD.