The role of 5-hydroxymethylcytosine in mitochondria after ischemic stroke

Area of Science:

• Epigenetics
• Mitochondrial Biology
• Neuroscience

Background:

• 5-Hydroxymethylcytosine (5hmC) is an epigenetic mark found in DNA, RNA, and mtDNA, implicated in various diseases.
• Tet enzymes regulate 5hmC levels and are involved in gene expression.
• The role of 5hmC in mitochondrial DNA (mtDNA) following acute brain injury remains underexplored.

Purpose of the Study:

• To investigate the dynamic changes in mtDNA 5hmC levels after acute brain ischemia in mice.
• To explore the relationship between mtDNA 5hmC, mitochondrial gene expression, and ATP production post-ischemia.
• To identify the role of Tet enzymes, specifically Tet2, in regulating mtDNA 5hmC during ischemic injury.

Main Methods:

• Quantification of mtDNA 5hmC and 5-methylcytosine (5mC) levels at different time points after inducing acute brain ischemia in male and female mice.
• Measurement of mitochondrial Tet2 expression.
• Assessment of mitochondrial ATP production and mRNA levels of mitochondrial genes.

Main Results:

• mtDNA 5hmC abundance significantly increased at 1 day and peaked at 2 days post-ischemia, while mtDNA 5mC remained unchanged.
• Increased mitochondrial Tet2 expression correlated with the rise in mtDNA 5hmC.
• Inhibition of Tet2 reduced mtDNA 5hmC levels and concurrently increased mitochondrial ATP production.
• Elevated mtDNA 5hmC levels were associated with increased mRNA expression of mitochondrial genes following ischemia/reperfusion injury.

Conclusions:

• Acute brain ischemia induces a significant increase in mtDNA 5hmC, primarily mediated by Tet2.
• mtDNA 5hmC plays a role in regulating mitochondrial gene expression and influences cellular ATP levels.
• These findings highlight a novel epigenetic mechanism in mitochondria responding to ischemic stress, with potential implications for understanding and treating related diseases.