Synaptic Dysfunction and Neuroinflammation: Complementary Pathways Driving Cognitive Decline 

For much of the last two decades, Alzheimer’s disease biomarker research has been defined by pathology. 

Amyloid plaques and tau tangles transformed our understanding of disease biology and continue to serve as foundational biomarkers for diagnosis, patient stratification, and therapeutic development. Blood-based biomarkers such as pTau217 have accelerated this transformation further, moving Alzheimer’s research beyond specialized centers and enabling larger, more diverse clinical studies. 

As disease-modifying therapies enter clinical practice and intervention moves earlier in the disease continuum, the questions facing researchers are becoming more sophisticated. 

Increasingly, researchers need to understand: 

• Why do patients with similar pathology progress differently? 

• Which biological pathways drive cognitive decline? 

• Which pathways respond to therapy? 

• Which biomarkers provide the earliest signal of treatment effect? 

These questions require evolving beyond isolated biomarkers toward an integrated understanding of disease biology. 

At AAIC 2026, Quanterix is highlighting what we believe represents the next major evolution in Alzheimer’s biomarker research: 

The convergence of synaptic dysfunction and neuroinflammation as complementary biological pathways driving cognitive decline. 

Importantly, this shift requires biomarker portfolios capable of measuring these interconnected biological systems simultaneously, reproducibly, and at the concentrations present in blood. 

Cognitive Decline Is a Systems Failure, Not a Single Pathway Event 

Neurons do not fail in isolation, long before widespread neurodegeneration becomes apparent, subtle disruptions in synaptic communication begin to emerge. Simultaneously, astrocytes and microglia transition from homeostatic functions toward reactive and inflammatory states. Inflammation influences synaptic health, and synaptic injury amplifies inflammatory signaling. 

Together, these pathways may form a self-reinforcing biological cycle that ultimately drives neuronal dysfunction and cognitive decline. 

Understanding Alzheimer’s disease therefore requires measuring the biology occurring between pathology and clinical symptoms. 

Measuring Synaptic Biology 

Among all known pathological features of Alzheimer’s disease, synaptic loss remains one of the strongest correlates of cognitive impairment. 

This has driven growing interest in biomarkers capable of measuring different dimensions of synaptic biology. To enable researchers to investigate these questions, the Quanterix neurology portfolio includes NPTX2, a regulator of excitatory synaptic plasticity and inhibitory circuit stability that has emerged as a promising indicator of functional synaptic integrity and neuronal network health. 

Complementing this approach, the Quanterix portfolio also includes SNAP-25, providing insight into presynaptic function and neuronal communication, and PSD-95, offering a complementary view of postsynaptic architecture and signaling organization. 

Together, these biomarkers move researchers beyond the question of whether pathology exists and toward understanding how pathology affects neuronal communication, network integrity, and ultimately cognition itself. 

Rather than measuring the consequence of disease, synaptic biomarkers may allow researchers to measure the biology most closely linked to the symptoms patients experience. 

Measuring Neuroinflammation 

At the same time, our understanding of neuroinflammation has evolved dramatically. 

Astrocytes, microglia, inflammasome signaling pathways, and lipid metabolism are increasingly recognized as active participants in disease progression and therapeutic response. 

Recognizing the growing importance of inflammatory biology in Alzheimer’s disease, the Quanterix portfolio includes  GFAP, one of the most informative blood-based markers of astrocyte activation, alongside YKL-40, which provides complementary insight into chronic glial and neuroimmune activity. 

Together, these biomarkers provide researchers with a broader understanding of the neuroimmune environment and how inflammatory responses evolve across the disease continuum. 

Expanding this view further, Quanterix plans to introduce an IL-18 assay, enabling researchers to investigate inflammasome biology and innate immune activation that may precede downstream neurodegeneration and contribute directly to synaptic dysfunction. 

APOE4: Connecting the Biology 

Perhaps no factor illustrates the connection between these pathways more clearly than APOE4. 

Long recognized as the strongest genetic risk factor for late-onset Alzheimer’s disease, APOE4 is increasingly understood to influence far more than amyloid biology alone. 

APOE4 has been associated with altered microglial responses, dysregulated lipid metabolism, heightened inflammatory signaling, impaired synaptic repair, and increased neuronal vulnerability. 

In many ways, APOE4 may represent the biological bridge connecting pathology, neuroinflammation, and synaptic dysfunction. 

Recognizing the growing importance of genotype-informed biomarker strategies, Quanterix also plans to introduce an APOE4 assay, allowing researchers to investigate biological risk alongside synaptic and inflammatory biology. 

From Single Biomarkers to Biological Networks 

The implication for Alzheimer’s research is significant: 

Pathology biomarkers remain essential for identifying disease presence and underlying proteinopathy. But understanding why some individuals decline rapidly while others remain stable requires a broader biological view. 

Researchers increasingly need to answer questions such as: 

• Is pathology disrupting synaptic communication? 

• Is neuroinflammation amplifying neuronal vulnerability? 

• Are inflammatory pathways influencing therapeutic response? 

• Does APOE4 alter susceptibility to synaptic injury or immune activation? 

These questions require an integrated biomarker strategy spanning multiple biological systems. 

Why This Matters  

The Alzheimer’s field is entering a new era. 

As disease-modifying therapies become increasingly available, the conversation is shifting from: 

“Does this patient have Alzheimer’s disease?” 

to: 

“What biology is driving progression in this patient?” 

and ultimately to: 

“Which pathways should we intervene on, and how do we measure whether those interventions are working?” 

The biomarkers that define the next decade of Alzheimer’s research are unlikely to emerge from a single biological domain. They will come from understanding the interaction between pathology, synaptic dysfunction, neuroinflammation, neurodegeneration, and genetic risk. 

This is precisely where Quanterix has chosen to invest. 

Quanterix has built one of the most comprehensive blood-based neurology portfolios available today, spanning pathology, synaptic biology, neuroinflammation, and neurodegeneration. 

That portfolio already includes NPTX2, SNAP-25, PSD-95, GFAP, and YKL-40, alongside established pathology and neurodegeneration markers, with IL-18 and APOE4 coming soon as researchers increasingly investigate inflammasome biology and genotype-informed disease mechanisms. 

Combined with the analytical sensitivity of Simoa® technology and the translational expertise of Accelerator Laboratory Services, researchers can move from exploratory biology to longitudinal cohort studies and clinical development using a single biomarker ecosystem. 

That matters because the next breakthroughs in Alzheimer’s disease will come from measuring the right biology earlier, more sensitively, and across multiple interacting pathways. 

Quanterix believes the future of Alzheimer’s biomarker research is an integrated biological model of disease, and increasingly, the tools required to build that model are already here.

Written by Shana Tetrault, Ph.D. Senior Director of Product Marketing