Modulation of transient receptor potential (TRP) channels by plant derived substances used in over-the-counter cough and cold remedies

Stinson, Rebecca J.; Morice, Alyn H.; Sadofsky, Laura R.

Abstract

Background: Upper respiratory tract infections (URTIs) impact all age groups and have a significant economic and social burden on society, worldwide. Most URTIs are mild and self-limiting, but due to the wide range of possible causative agents, including Rhinovirus (hRV), Adenovirus, Respiratory Syncytial Virus (RSV), Coronavirus and Influenza, there is no single and effective treatment. Over-the-counter (OTC) remedies, including traditional medicines and those containing plant derived substances, help to alleviate symptoms including inflammation, pain, fever and cough. Purpose: This systematic review focuses on the role of the major plant derived substances in several OTC remedies used to treat cold symptoms, with a particular focus on the transient receptor potential (TRP) channels involved in pain and cough. Methods: Literature searches were done using Pubmed and Web of Science, with no date limitations, using the principles of the PRISMA statement. The search terms used were ‘TRP channel AND plant compound’, ‘cough AND plant compound’, ‘cough AND TRP channels AND plant compound’, ‘cough AND P2X3 AND plant compound’ and ‘P2X3 AND plant compound’ where plant compound represents menthol or camphor or eucalyptus or turpentine or thymol. Results: The literature reviewed showed that menthol activates TRPM8 and may inhibit respiratory reflexes reducing irritation and cough. Menthol has a bimodal action on TRPA1, but inhibition may have an analgesic effect. Eucalyptus also activates TRPM8 and inhibits TRPA1 whilst down regulating P2X3, aiding in the reduction of cough, pain and airway irritation. Camphor inhibits TRPA1 and the activation of TRPM8 may add to the effects of menthol. Activation of TRPV1 by camphor, may also have an analgesic effect. Conclusions: The literature suggests that these plant derived substances have multifaceted actions and can interact with the TRP ‘cough’ receptors. The plant derived substances used in cough and cold medicines have the potential to target multiple symptoms experienced during a cold.

Citation

Stinson, R. J., Morice, A. H., & Sadofsky, L. R. (2023). Modulation of transient receptor potential (TRP) channels by plant derived substances used in over-the-counter cough and cold remedies. Respiratory Research, 24(1), Article 45. https://doi.org/10.1186/s12931-023-02347-z

• Journal Article Type: Review
• Acceptance Date: Jan 27, 2023
• Online Publication Date: Feb 8, 2023
• Publication Date: Dec 1, 2023
• Deposit Date: Feb 9, 2023
• Publicly Available Date: Feb 9, 2023
• Journal: Respiratory Research
• Print ISSN: 1465-9921
• Electronic ISSN: 1465-993X
• Publisher: BioMed Central
• Peer Reviewed: Peer Reviewed
• Volume: 24
• Issue: 1
• Article Number: 45
• DOI: https://doi.org/10.1186/s12931-023-02347-z
• Keywords: Menthol; Camphor; Eucalyptus; Thymol; TRP channels; Cough; Cold; Over-the-counter therapies
• Public URL: https://hull-repository.worktribe.com/output/4193656
• Additional Information: Received: 6 October 2022; Accepted: 27 January 2023; First Online: 8 February 2023; : ; : Not applicable.; : Not applicable.; : LS received funding from Procter & Gamble to support this work.