There is a growing interest in leveraging the brain’s natural waste-clearing mechanisms to potentially slow or alleviate the progression of Alzheimer’s disease. Recent research has unveiled a novel method that has demonstrated success in clearing toxic protein aggregates associated with Alzheimer’s in the brains of mice. This technique not only reduced these detrimental clumps but also enhanced the animals’ performance in memory and learning assessments.
The approach centers on inhibiting a receptor known as DDR2, a target more commonly explored in the context of lung health. According to Jia Li from Guangzhou Medical University in China, blocking the DDR2 pathway could theoretically decrease the production of amyloid-beta protein while simultaneously bolstering the clearance of these protein wastes. “We are hoping it can finally reverse Alzheimer’s,” Li stated.
Understanding Alzheimer’s Pathogenesis and Emerging Therapies
The accumulation of misfolded proteins, forming amyloid plaques and tau tangles, is widely recognized as a primary driver of Alzheimer’s disease. While existing medications can eliminate amyloid clumps, their impact on alleviating Alzheimer’s symptoms has been limited. Consequently, research efforts are increasingly shifting towards alternative strategies, including enhancing the glymphatic system, which is responsible for removing waste products from the brain.
Li and his team are building upon this understanding by focusing on a specific receptor embedded within cell membranes. This receptor, identified as DDR2 (discoidin domain receptor 2), appears to play a role in amplifying glymphatic activity among its various functions. Jin Su, a member of Li’s research group also affiliated with Guangzhou Medical University, is independently investigating DDR2 in relation to pulmonary fibrosis. This lung condition arises from the dysfunction of the extracellular matrix, the protein network surrounding cells. This dysfunction leads to an excessive deposition of collagen, a structural protein, which in turn restricts the oxygen supply available to cells.
Evidence suggests a connection between the malfunction of the extracellular matrix and the deposition of amyloid and tau proteins in Alzheimer’s disease, presenting similar detrimental effects. Li noted that this oxygen deprivation could be a contributing factor to cognitive impairments affecting thinking and memory.
Investigating DDR2’s Role in Alzheimer’s Disease
To explore DDR2’s potential involvement, the researchers undertook an initial examination of human tissue databases. They discovered that DDR2 is rarely present in healthy brain tissue. However, upon analyzing samples from individuals diagnosed with Alzheimer’s disease, a significant abundance of DDR2 was detected. Jin Su emphasized, “We are the first to confirm that DDR2 is found in high abundance in Alzheimer’s brain tissue.”
Through a series of experiments involving human and non-human primate cells, alongside mouse models of Alzheimer’s, the research team has developed a hypothesis that DDR2 regulates the cellular dysfunction implicated in the disease’s symptomatology. Their findings indicate that three specific cell types appear to increase their membrane expression of DDR2 during the progression of Alzheimer’s disease. These include reactive astrocytes, which are found surrounding amyloid-beta clumps; perivascular fibroblasts, whose activity changes prior to the onset of Alzheimer’s; and choroid plexus epithelial cells, which are crucial for the production of cerebrospinal fluid, a key component of the glymphatic system.
Potential Therapeutic Implications and Future Directions
Shiju Gu from Harvard University suggests that these findings imply that targeting DDR2 could offer a multi-faceted approach to addressing various aspects of Alzheimer’s disease. However, acknowledging the complexity of the condition, Gu expressed a note of caution, stating, “I will put a big question mark here in terms of reversing Alzheimer’s.”
Subsequently, the researchers developed a monoclonal antibody designed to target and neutralize DDR2 receptors. In an Alzheimer’s mouse model, this intervention led to improvements in both spatial learning and memory. Brain imaging revealed a reduction in DDR2 levels, a decrease in amyloid plaques, and a strengthened glymphatic system. Gu commented, “The mouse results are overall encouraging and, within the limits of a mouse model, fairly impressive. It reiterates the significance of glymphatic function and brain fluid dynamics in brain health. This suggests DDR2 is a legitimate target for potential Alzheimer’s treatment.”
César Cunha of the Novo Nordisk Foundation Center for Basic Metabolic Research in Denmark commended the researchers for moving beyond merely targeting amyloid plaques. However, he pointed out that the mouse model used represented a relatively uncommon form of inherited Alzheimer’s, which typically manifests earlier than the more prevalent late-onset form. Therefore, the effectiveness of the antibody in common late-onset Alzheimer’s remains uncertain.
Despite this, Su maintains that DDR2 upregulation has been observed in individuals with both familial and late-onset Alzheimer’s, suggesting broader therapeutic applicability. She also noted that DDR2 expression appears to be influenced by aging and hypoxia, both known risk factors for late-onset Alzheimer’s.
The research team is currently conducting a clinical trial employing a tracer to monitor DDR2 levels in the brains of individuals with Alzheimer’s. This will help determine the optimal sites for antibody administration, according to Li. They are also working on developing a smaller antibody fragment engineered to more effectively penetrate the blood-brain barrier.