"Several years ago it was recognized that the cGAS-STING system was a key part of the inflammation seen in microglial cells in the aging brain (and in the brains of people with neurodegenerative diseases). And this new paper has tracked down further details: the reason this inflammatory pathway has been set off is the leakage of DNA from damaged mitochondria in those microglial cells."

https://www.science.org/content/blog-post/aging-brain-misplaced-dna-blame