Researchers here provide evidence for natural killer cells to act to reduce inflammation in the brain. This is of interest because chronic inflammation in brain tissue, neuroinflammation, is a prominent feature of neurodegenerative diseases such as Alzheimer's disease and Parkinson's disease. If a natural mechanism that suppresses inflammation can be harnessed, it might be possible to slow or reverse neurodegenerative conditions, given that inflammation appears to play such a significant role in their progression. That said, recent work on cellular senescence in the supporting cells of brain suggests that selectively eliminating those senescent cells, and thus their inflammatory signaling, via senolytic therapies might be a more direct and near term approach than further attempts at the manipulation of mechanisms involved in the resolution of inflammation.
Natural killer (NK) cells provide the first line of defense against invasion or a virus and are equipped with activating receptors that can sense cellular stress and identify cells that have been altered due to infection. A new study highlights that NK cells act not only as efficient scavengers that attack an intruder but may be critical for regulating and restraining inflammation of brain tissue and protein clumping - hallmarks of Parkinson's and other neurodegenerative disorders. The report also found that NK cell depletion in a mouse model significantly exaggerated the disease condition. This led to the discovery that, without NK cells, the nervous system was left vulnerable to attack.
"We believe that NK cells exert protection by their ability to reduce inflammation in the brain and clear proteins that misfold and create toxic clumps. In their absence, proteins were left unchecked, and we saw a substantial decrease in viral resistant cells, confirming that NK cells are a major source of signaling proteins that boost the immune system response."
Researchers are quick to caution that the Parkinson's work was done in animal models, but are optimistic about future immunotherapy discoveries. Recent human trials that tested immunotherapies against an aggressive form of brain cancer called glioblastoma, indicating that NK cells contribute to elimination of tumor cells and release messages in support of defense of the immune system. Parkinson's is no longer considered a brain-specific disease, and researchers increasingly recognize a functional connection between the immune system and central nervous system. Researchers found that, in conditions of chronic inflammation such as Parkinson's, the blood-brain barrier becomes disrupted, allowing immune cells to channel into the brain. "Understanding how the periphery signals for NKs to patrol for infectious agents, even in the absence of disease, could lead to breakthrough treatments for Parkinson's disease."