CGRP and substance P create a feedback loop between nerves and immune cells that drives arthritis pain and inflammation | Research

The takeaway

Neuroimmune crosstalk in arthritis involves sensory nerves releasing CGRP and substance P to modulate macrophages, while macrophage-derived IL-1β, IL-6, and TNF-α sensitize nociceptors—creating a self-perpetuating cycle of pain and inflammation.

Bidirectional nerve-immune loop
CGRP/substance P from nerves modulate macrophages while macrophage cytokines sensitize nerves—creating a self-perpetuating cycle that dual-target therapies could break

What the researchers found

Sensory nerves release CGRP and SP → modulate macrophages and immune cells. Macrophage IL-1β, IL-6, TNF-α → sensitize nociceptors. CCL2 → engages neuronal receptors for excitability. Sympathetic signaling → immune modulation. Synovial remodeling: nerve sprouting + immune infiltration.

Why it matters

Arthritis pain is often undertreated because current therapies target either inflammation or pain but not both. Understanding the neuroimmune feedback loop reveals dual-target therapeutic opportunities using neuropeptide-targeting drugs.

How the study worked

Narrative review of neuroimmune interactions in arthritis, integrating synovial biology, neuropeptide signaling, and macrophage-neuron crosstalk.

What this study cannot tell us

Narrative review. Most mechanistic data from animal models. Clinical evidence for neuropeptide-targeted arthritis therapy is limited.

How to read the evidence

Narrative review integrating mechanistic and clinical evidence. Strong biological framework for therapeutic development.

When this study was published

Published in 2025.

The bigger picture

Anti-CGRP drugs (developed for migraine) and NK1 antagonists (developed for nausea) could be repurposed for arthritis pain by disrupting the neuroimmune feedback loop. This represents a novel therapeutic paradigm for chronic joint disease.

Questions still open

Could anti-CGRP or anti-substance P drugs reduce arthritis pain and inflammation simultaneously?
Does nerve sprouting in the synovium predict arthritis pain severity?
Would combining neuropeptide blockers with anti-inflammatory therapy improve arthritis outcomes?

Common questions

Why is arthritis pain so hard to treat?

Arthritis pain persists because nerves and immune cells in the joint talk to each other in a feedback loop. Immune cells release chemicals that make nerves more sensitive to pain, while activated nerves release peptides (CGRP, substance P) that fuel more inflammation. This cycle is hard to break by targeting only one side.

Could migraine drugs help arthritis?

Possibly. Anti-CGRP drugs used for migraines could potentially break the neuroimmune feedback loop in arthritis by blocking CGRP released from nerve fibers in the joint. Similarly, substance P blockers (like aprepitant, used for nausea) could reduce both pain and inflammation in joints.

Read the original research

Neuroimmune interactions in arthritis: linking pain sensitisation and inflammation.

Journal of bone and mineral metabolism

View on PubMed ↗Publisher’s paper ↗

Citation

Sow, Tammie Tao Min; Hasegawa, Tetsuo. (2025). Neuroimmune interactions in arthritis: linking pain sensitisation and inflammation.. Journal of bone and mineral metabolism. https://doi.org/10.1007/s00774-025-01678-9