Substance P and CGRP Drive the Severe Cough of Pulmonary Fibrosis | Research

The takeaway

Increased expression of substance P, NK1R, and CGRP in lung tissue correlated directly with heightened cough sensitivity in a guinea pig model of idiopathic pulmonary fibrosis.

Direct cough correlation
Substance P, CGRP, TRPA1, and TRPV1 levels all positively correlated with cough sensitivity — the more neuropeptide, the worse the cough

What the researchers found

Bleomycin-induced pulmonary fibrosis in guinea pigs caused significantly increased expression of substance P, NK1R, CGRP, TRPA1, and TRPV1 in cough reflex pathways, all positively correlated with enhanced cough sensitivity to capsaicin challenge.

Why it matters

Cough in IPF has no effective treatment. Identifying substance P, CGRP, and TRP channels as drivers opens the door to targeting these neuropeptides — potentially using existing drugs like NK1R antagonists or anti-CGRP antibodies — for a currently untreatable symptom.

The numbers in context

TRPA1/TRPV1 upregulated in ganglia; SP/NK1R/CGRP upregulated in lung; positive correlation with cough sensitivity; NGF/NKA/NKB/BDNF also measured

How the study worked

Animal study. Bleomycin-induced pulmonary fibrosis guinea pig model. Cough sensitivity to capsaicin measured. Neuropeptide expression (SP, NK1R, CGRP) by immunohistochemistry and RT-qPCR. TRP channel expression by Western blot and RT-qPCR. Neurogenic factor concentrations by ELISA.

Who was studied

Male guinea pigs with bleomycin-induced pulmonary fibrosis

What this study cannot tell us

Guinea pig model — may not fully replicate human IPF cough. Bleomycin-induced fibrosis differs from naturally occurring IPF. Correlation between neuropeptides and cough doesn't prove causation. Small animal numbers likely.

How to read the evidence

Moderate evidence: well-designed animal study with multiple measurement methods and consistent correlations, but limited to guinea pig model.

When this study was published

Published 2021. Research on neuropeptide-mediated cough continues, with anti-CGRP and anti-substance P approaches being explored.

The bigger picture

This connects neuropeptide biology to a devastating respiratory symptom. If substance P and CGRP drive fibrosis-related cough, existing anti-CGRP migraine drugs or NK1R antagonists could be repurposed — creating a therapeutic pathway where none currently exists.

Questions still open

Would anti-CGRP antibodies used for migraine also reduce cough in IPF patients?
Could NK1R antagonists like aprepitant provide cough relief in pulmonary fibrosis?
Do human IPF patients have similarly elevated substance P and CGRP in their lungs?

Common questions

Why do pulmonary fibrosis patients cough so much?

This study suggests that fibrotic lungs produce elevated levels of neuropeptides substance P and CGRP, which sensitize cough nerves (through TRPA1 and TRPV1 channels). This creates a vicious cycle of neurogenic inflammation and heightened cough sensitivity.

Could migraine drugs help with IPF cough?

Potentially. Anti-CGRP antibodies used for migraine target the same neuropeptide (CGRP) found elevated in fibrotic lungs. If human IPF cough is also CGRP-driven, these drugs might provide relief — though this hypothesis needs clinical testing.

Read the original research

Increased expression of transient receptor potential channels and neurogenic factors associates with cough severity in a guinea pig model.

BMC pulmonary medicine, 21(1), 187

View on PubMed ↗Publisher’s paper ↗

Citation

Guan, Mengyue; Ying, Sun; Wang, Yuguang. (2021). Increased expression of transient receptor potential channels and neurogenic factors associates with cough severity in a guinea pig model.. BMC pulmonary medicine, 21(1), 187. https://doi.org/10.1186/s12890-021-01556-w