Breaking New Ground: Immune System Discovery Offers Potential Solution to Alzheimer’s

A groundbreaking study has shed new light on the relationship between the immune system and Alzheimer’s disease. Researchers at the University of Virginia School of Medicine have discovered that an immune molecule called STING plays a crucial role in driving the formation of amyloid plaques and tau tangles, hallmarks of Alzheimer’s.

The study found that blocking STING activity in lab mice protected them from mental decline, suggesting a promising new target for developing treatments. This breakthrough has far-reaching implications for understanding and treating not only Alzheimer’s but also other neurodegenerative diseases like Parkinson’s disease, amyotrophic lateral sclerosis (ALS), and dementia.

“The findings demonstrate that the DNA damage that naturally accumulates during aging triggers STING-mediated brain inflammation and neuronal damage in Alzheimer’s disease,” said researcher John Lukens, PhD. “These results help to explain why aging is associated with increased Alzheimer’s risk and uncover a novel pathway to target in the treatment of neurodegenerative diseases.”

The study, published in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association, involved a team of researchers from UVA’s Department of Neuroscience and Center for Brain Immunology and Glia (BIG Center). They found that removing STING dampened microglial activation around amyloid plaques, protected nearby neurons from damage, and improved memory function in Alzheimer’s model mice.

The discovery of STING as a key player in the development of neurodegenerative diseases opens new doors for research into potential treatments. While much more work is needed to translate these findings into effective therapies, this breakthrough has sparked hope among researchers and patients alike.

“Our hope is that this work moves us close to finding safer and more effective ways to protect the aging brain,” said Lukens. “Shedding light on how STING contributes to that damage may help us target similar molecules and ultimately develop effective disease-modifying treatments.”

The APOE gene is a major genetic risk factor for Alzheimer’s disease, with three different versions: APOE2, APOE3, and APOE4. While APOE4 increases the risk of developing Alzheimer’s, APOE2 is associated with a lower risk. However, how these isoforms lead to strikingly different risk profiles is poorly understood.

A recent study published in Nature Communications offers clues into how APOE isoforms differentially affect human microglia function in Alzheimer’s disease. The study, led by Dr. Sarah Marzi and Dr. Kitty Murphy at the UK Dementia Research Institute at King’s College London and the Department of Basic and Clinical Neuroscience, underscores the need for new targeted interventions based on APOE genotypes.

The researchers developed a human “xenotransplantation model,” where human microglia were grown from stem cells, manipulated to express different APOE versions, then transplanted into the brains of mice that had developed a buildup of amyloid plaques. The microglia were then isolated and analyzed for their gene expression (using transcriptomics) and chromatin accessibility.

The study uncovered widespread changes to the transcriptomic and chromatin landscape of microglia, dependent on the APOE isoform expressed. The largest differences were observed when comparing the APOE2 and APOE4 microglia.

In APOE4 microglia, researchers saw an increase in the production of cytokines, signaling molecules involved in immune regulation. They also observed diminished capacity for the microglia to migrate and shift into protective states. Furthermore, the microglia became less effective in phagocytosis, a process by which they digest and clear up particles such as debris and pathogens.

Conversely, APOE2 microglia showed increased expression of various genes that increase microglia proliferation and migration, and a decreased inflammatory immune response. Additionally, APOE2 microglia showed increased DNA-binding of the vitamin D receptor. Low levels of vitamin D have been associated with a higher incidence of Alzheimer’s.

The study highlights that microglia responses to amyloid pathology differ significantly across APOE versions. This finding underscores that considering the interplay between genetic risk factors and microglial states is critical in disease progression. The study also highlights the potential role of the vitamin D receptor, providing new avenues for therapeutic exploration.

Dr. Sarah Marzi, Senior Lecturer in Neuroscience at King’s College London and lead author of the study, said: “Our findings emphasize that there is a complex interplay between genetic, epigenetic, and environmental factors that influence microglial responses in Alzheimer’s disease. We found remarkable differences when comparing microglia expressing different isoforms of the same gene. Our research suggests that microglia expressing the risk-increasing APOE4 variant are not as effective at mounting protective microglial functions, including cell migration, phagocytosis and anti-inflammatory signaling. This underscores the need for targeted interventions based on APOE genotype.”

The study conducted by researchers at University College London (UCL) has revealed a striking connection between worsening symptoms of depression in middle-aged adults and the onset of physical pain later on. The research, published in the journal eClinicalMedicine, analyzed data from 3,668 adults aged over 50 who experienced moderate to severe pain, compared with a matched group who did not experience such pain.

The findings indicate that depressive symptoms rapidly worsened in the eight years prior to the onset of pain, peaking at the moment when pain began and remaining high afterward. In contrast, depressive symptoms were less severe, less prevalent, and relatively constant among those without pain. This trend was observed for loneliness as well, which increased before and after the onset of pain but remained low and stable in the non-pain group.

The researchers suggested that early mental health interventions might help prevent or reduce later aches and pains by addressing factors such as stress, inflammation, immune responses, and autonomic nervous system dysregulation. They also highlighted the importance of considering pain not just from a biological perspective but also taking into account social determinants of health and community support programs.

The study found that individuals with less education and wealth were more likely to experience a sharp increase in depressive symptoms before experiencing pain. This finding underscored the need for prioritizing vulnerable populations with fewer socioeconomic resources, providing them with accessible mental health and community support programs.

While social isolation showed little difference between the pain and non-pain groups, loneliness was a significant predictor of later pain. The researchers suggested that the quality of relationships might matter more than quantity or levels of social interaction in mitigating against pain and depression.

The study had some limitations, including an overwhelmingly white participant population reflecting England’s age group demographics. Future research should investigate whether results are similar for younger groups and those with more racial and ethnic diversity.

In conclusion, the UCL researchers’ findings suggest that early mental health interventions might help prevent or reduce later aches and pains in middle-aged adults by addressing factors such as depression, loneliness, stress, inflammation, immune responses, and autonomic nervous system dysregulation.