Parkinson’s disease has long been described through a familiar biological storyline: abnormal accumulation of alpha-synuclein, progressive loss of dopamine-producing neurons in the substantia nigra, and the resulting movement symptoms of tremor, rigidity and slowness. A new perspective in npj Parkinson’s Disease argues that this single-pathology framework may be too narrow for a disorder that varies dramatically from one patient to another. In “Rethinking single-pathology therapies by targeting inflammation and co-pathologies in Parkinson’s disease,” J.M. Webster and A.S. Harms call for a broader therapeutic strategy—one that treats neuroinflammation and the additional disease processes that often accompany alpha-synuclein pathology rather than attempting to eliminate one molecular target in isolation.
The argument arrives at a moment when Parkinson’s research is confronting a difficult reality: therapies that improve symptoms have transformed clinical care, but treatments that reliably slow or stop neurodegeneration remain elusive. Levodopa and related dopaminergic drugs can restore signaling in damaged motor circuits, yet they do not remove the underlying causes of neuronal injury. Experimental approaches aimed at alpha-synuclein have generated intense interest, including antibodies, vaccines, aggregation inhibitors and gene-based technologies. However, the authors’ central premise is that alpha-synuclein may be only one component of a complex biological network. If inflammation, mitochondrial dysfunction, impaired protein clearance, vascular changes or other misfolded proteins are simultaneously damaging the brain, attacking alpha-synuclein alone may leave major drivers of disease untouched.
Alpha-synuclein is a neuronal protein involved in synaptic function, but under pathological conditions it can misfold, aggregate and spread through interconnected regions of the nervous system. These abnormal assemblies are associated with Lewy bodies and Lewy neurites, microscopic structures found in Parkinson’s disease and related disorders. Yet the presence of alpha-synuclein does not fully explain clinical diversity. Some people develop predominantly tremor-related disease, while others experience early gait impairment, cognitive decline, sleep disturbance, autonomic dysfunction or psychiatric symptoms. The timing and severity of these features can differ widely, suggesting that additional biological processes influence which neural systems become vulnerable and how quickly damage progresses.
Inflammation is one of the most important candidates in this wider model. The brain’s resident immune cells, known as microglia, constantly survey neural tissue and respond to injury or abnormal proteins. In a healthy state, this response can help remove debris and restore balance. When activation becomes persistent, however, microglia may release inflammatory mediators, reactive oxygen species and other signals capable of injuring neurons. Astrocytes, which support neurons and regulate the chemical environment of the brain, can also shift into reactive states that alter metabolism, synaptic signaling and immune communication. Rather than viewing inflammation as a secondary consequence of neuronal death, the paper emphasizes the possibility that it can become an active amplifier of degeneration.
The biological connection between alpha-synuclein and inflammation is particularly important. Misfolded alpha-synuclein can stimulate innate immune receptors on microglia and other cells, while inflammatory conditions may make neurons more vulnerable to the protein’s toxic effects. This creates a feedback loop: abnormal protein accumulation activates immune pathways, inflammation increases cellular stress, and stressed neurons become less capable of maintaining protein quality control and energy production. Mitochondria, the organelles that generate most of a cell’s energy, are especially sensitive to this combination of stressors. Damage to mitochondrial function can increase oxidative stress, impair axonal transport and weaken the neuron’s ability to survive. A therapy that suppresses one component of this cycle may therefore produce limited benefits if the rest of the network remains active.
The concept of co-pathology expands the problem beyond alpha-synuclein. Many people with Parkinson’s disease show biological evidence of additional abnormalities, including amyloid-beta plaques, tau-related changes, vascular injury or alterations associated with the immune system and lysosomal function. These features do not occur in every patient, and their effects can depend on age, genetics, disease stage and the regions of the brain involved. A person whose cognitive symptoms are influenced by amyloid or tau pathology may respond differently from someone whose disease is dominated by motor-circuit degeneration and inflammation. The authors’ framework therefore supports more precise biological classification, rather than treating Parkinson’s disease as a single uniform condition.
Such precision would require a new generation of biomarkers capable of measuring several disease mechanisms at once. Researchers are already investigating cerebrospinal-fluid assays, blood-based markers, neuroimaging techniques, genetic profiles and digital measurements derived from movement, speech and sleep. Biomarkers of alpha-synuclein aggregation could potentially be combined with indicators of immune activation, neuronal injury, lysosomal dysfunction or vascular damage. Advanced imaging may help reveal changes in dopamine terminals, microglial activity and brain connectivity, while wearable devices can track subtle fluctuations in gait and motor performance over time. The goal would be to identify biologically meaningful subtypes and match each patient with a treatment combination designed for the mechanisms most active in that individual.
This strategy could involve combining disease-modifying therapies rather than searching for a single universal drug. One treatment might reduce alpha-synuclein production or aggregation, another could restrain damaging inflammatory signaling, and a third might improve lysosomal or mitochondrial function. In patients with prominent co-pathologies, therapies directed at amyloid, tau or vascular risk might become relevant as well. Such combinations would be scientifically and clinically challenging. The treatments could interact in unexpected ways, immune suppression could create safety risks, and trials would need to determine whether a biological change actually translates into slower disability. Nevertheless, the paper’s message is that the complexity of Parkinson’s disease should be reflected in the design of therapies and clinical studies.
The authors’ proposal also challenges how success is measured. Conventional Parkinson’s trials often focus on motor scales, medication requirements or short-term changes in symptoms. Those outcomes remain essential, but they may not capture whether a treatment is altering the underlying disease process. A therapy that reduces inflammation might not immediately improve tremor, while a treatment that targets co-pathology could first influence cognition, sleep or autonomic function. Future trials may need longer follow-up periods, molecular biomarker panels and outcome measures tailored to distinct disease subtypes. Adaptive trial designs could allow investigators to test several mechanisms simultaneously and modify treatment assignments as biological data accumulate.
The broader significance of the perspective is its rejection of a one-size-fits-all explanation for Parkinson’s disease. Alpha-synuclein remains a central target, but Webster and Harms argue that it should be studied within the larger ecosystem of immune responses, cellular stress, aging, genetics and coexisting neuropathologies. This does not guarantee that combination therapies will succeed, nor does it diminish the value of research focused on alpha-synuclein. Instead, it reframes the question: the most effective future treatment may not be the drug that neutralizes one pathological hallmark, but a carefully matched intervention that interrupts several reinforcing processes before neuronal damage becomes irreversible. For patients and researchers, that shift could mark a move from treating Parkinson’s as a single molecular disease toward treating it as a biologically diverse collection of interacting disorders.
Subject of Research: Parkinson’s disease, neuroinflammation, alpha-synuclein pathology and co-pathologies
Article Title: Rethinking single-pathology therapies by targeting inflammation and co-pathologies in Parkinson’s disease
Article References: Webster, J.M., Harms, A.S. “Rethinking single-pathology therapies by targeting inflammation and co-pathologies in Parkinson’s disease.” npj Parkinson’s Disease (2026). https://doi.org/10.1038/s41531-026-01502-9
Image Credits: AI Generated
DOI: 10.1038/s41531-026-01502-9
Keywords: Parkinson’s disease, neuroinflammation, alpha-synuclein, co-pathology, microglia, astrocytes, neurodegeneration, precision medicine, disease-modifying therapy, biomarkers
Tags: alpha-synuclein aggregationco-pathologies in Parkinson’scomplex biological networks in neurodegenerative diseasescomprehensive Parkinson’s disease managementdisease-modifying Parkinson’s treatmentsinflammation and neurodegenerationinnovative approaches to Parkinson’slimitations of dopamine replacement therapymitochondrial dysfunction in Parkinson’smulti-target Parkinson’s therapiesneurodegeneration treatment strategiesParkinson’s disease neuroinflammation
