Cholinergic Regulation of Neuroinflammation: Microglia, Immunometabolism, and Therapeutic Frontiers

Cholinergic signaling is increasingly recognized as a master regulator of neuroinflammation, with microglia positioned as the central cellular hub through which acetylcholine and its receptors shape inflammatory outcomes in the brain. A comprehensive review published in Frontiers in Immunology synthesizes current evidence across three interconnected domains: microglial biology, immunometabolism, and neuromodulation, proposing an updated framework for understanding how the cholinergic anti-inflammatory pathway operates within the central nervous system (CNS).

The review challenges the classical view that the cholinergic anti-inflammatory pathway functions primarily through peripheral vagus nerve-mediated reflexes. Instead, the authors argue that within the CNS, cholinergic signaling engages resident immune cells—particularly microglia—through a distributed neuroimmune network that extends well beyond the well-studied α7 nicotinic acetylcholine receptor (search)Search target (α7nAChR).

Microglia as the Cellular Hub

Microglia express multiple cholinergic receptor subtypes, with α7nAChR being the most extensively characterized for its anti-inflammatory effects. Activation of α7nAChR on microglia has been linked to reduced pro-inflammatory cytokine release, diminished NLRP3 inflammasome activation, and attenuated oxidative stress. However, the review emphasizes that microglial receptor expression is dynamic rather than static—aging, neurodegeneration, ischemia, and systemic inflammation can all alter the abundance and functional reactivity of cholinergic receptors.

"Cholinergic signaling is unlikely to produce consistent anti-inflammatory effects in all microglial states," the authors note. "Its impact may depend on receptor availability, intracellular signal bias, local metabolic conditions and the surrounding cytokine environment."

Beyond α7nAChR, emerging evidence implicates other nicotinic receptor subtypes—including α4β2 and α9-containing nAChRs—as well as muscarinic acetylcholine receptors in modulating microglial behavior. The α4β2 subtype has been shown to suppress neuroinflammation via the JAK2-STAT3 signaling pathway in ischemic models, while α9-containing nAChRs differentially modulate autoimmune neuroinflammation in experimental autoimmune encephalomyelitis.

Immunometabolism: The Missing Link

A central thesis of the review is that immunometabolism provides the mechanistic bridge between cholinergic signaling and the diverse inflammatory outcomes observed across neurological diseases. Microglial inflammatory activation is closely tied to metabolic remodeling—including shifts toward glycolysis, mitochondrial dysfunction, and altered lipid processing.

The review identifies three key metabolic checkpoints: the balance between glycolysis and oxidative phosphorylation, mitochondrial quality control, and lipid metabolism. Cholinergic signaling may counteract pathological glycolytic transitions, preserve mitochondrial integrity, and reduce oxidative stress. However, the authors caution that direct evidence for cholinergic regulation of central metabolic sensors—AMPK, mTOR, and HIF-1α—in microglia remains largely correlative or inferred from peripheral immune cell studies.

"The conceptual framework that links cholinergic input to microglial metabolism through AMPK, mTOR, and HIF-1α is compelling," the review states. "But when it comes to microglia, this idea remains largely hypothetical."

Lipid droplet-accumulating microglia (LDAM) have emerged as a distinct metabolic phenotype with translational relevance. These cells exhibit impaired phagocytosis, elevated oxidative stress, and dysregulated lipid metabolism, and are found in aging brains and across neurodegenerative conditions. In Alzheimer's disease (search)Search disease, amyloid-β exposure directly drives lipid droplet formation through the enzyme DGAT2, and pharmacological targeting of DGAT2 restores microglial phagocytic function and reduces plaque pathology.

Disease-Specific Evidence

The review evaluates cholinergic neuroimmune regulation across five major neurological contexts:

In Alzheimer's disease (search)Search disease, loss of basal forebrain cholinergic neurons coexists with persistent microglial activation and metabolic decline. The review highlights bidirectional interplay between cholinergic signaling and genetic risk factors such as TREM2 (search)Search target and APOE4 (search)Search target. APOE4—the strongest genetic risk factor for late-onset Alzheimer's—disrupts lipid balance in microglia and promotes a pro-inflammatory metabolic state, while also altering microglial responses to cholinergic input.

In Parkinson's disease (search)Search disease, cholinergic dysfunction contributes to both motor and non-motor symptoms, while α-synuclein-driven innate immune activation engages microglial inflammatory responses. Experimental evidence suggests that α7nAChR targeting may reduce innate immune injury, though effects likely vary by disease stage.

In stroke (search)Search disease, cholinergic stimulation or α7nAChR activation has been shown to reduce infarction-related inflammation and improve functional recovery in some models. However, the review emphasizes the critical importance of timing: anti-inflammatory effects beneficial in the acute phase may impair repair if sustained into the subacute or recovery phases.

In multiple sclerosis (search)Search disease, cholinergic pathways intersect with glial activation, blood-brain barrier dysfunction, and remyelination. Both muscarinic and non-α7 nicotinic receptor subtypes contribute to modulating neuroinflammation in experimental models.

In delirium and perioperative brain dysfunction, the "cholinergic deficiency hypothesis" intersects with systemic inflammation-induced microglial metabolic changes, including glycolytic reprogramming and mitochondrial dysfunction.

Therapeutic Translation and Challenges

The review outlines several translational strategies, including acetylcholinesterase inhibitors (search)Search drug, selective nicotinic receptor targeting, muscarinic pathway modulation, vagus nerve stimulation (VNS), and non-invasive neuromodulation such as transcutaneous auricular VNS.

However, clinical translation has faced substantial hurdles. Several α7nAChR-selective agonists—including GTS-21, MEM3454, and encenicline—have been tested in early-phase trials for cognitive impairment, but anti-inflammatory outcomes have rarely been included as endpoints. A randomized placebo-controlled trial of the α7nAChR positive allosteric modulator AVL-3288 in mild Alzheimer's disease (search)Search disease found no effect on neuroinflammatory biomarkers despite good target engagement in preclinical models.

Clinical evidence for anti-inflammatory effects of cholinesterase inhibitors remains limited and inconsistent. While some studies have reported reductions in pro-inflammatory cytokines such as IL-1β and TNF-α, others have found no significant changes. For delirium, prospective trials of donepezil and rivastigmine have largely failed to show consistent preventive or therapeutic benefits.

"Simply increasing the availability of endogenous acetylcholine is unlikely to be enough to achieve robust control of neuroinflammation by itself," the authors conclude. "Patient selection and the timing of the intervention are equally critical."

The review calls for biomarker-guided precision approaches that combine autonomic, glial, inflammatory, imaging, transcriptomic, and metabolomic readouts to identify patients most likely to benefit from cholinergic interventions. It also emphasizes that both aging and sex are major determinants of microglial heterogeneity and responsiveness to cholinergic signals, and should be systematically incorporated into future experimental design and clinical trial stratification.