Natural Compound Pinocembrin Relieves Hip Fracture Pain by Blocking Substance P Signaling in Aged Rats | Research

The takeaway

Pinocembrin alleviated hip fracture pain in aged rats by suppressing substance P and its receptor Tacr1 in the spinal cord, reducing both pain signaling and vascular inflammation.

Substance P and Tacr1 reversed by treatment
Pinocembrin suppressed the upregulated substance P neuropeptide signaling pathway in the spinal cord that drives hip fracture pain and vascular changes in aged rats

What the researchers found

PCN treatment reduced pain and inflammation in aged rats with hip fractures, reversing substance P signaling.

Why it matters

This research highlights a potential new treatment for managing pain in older adults with hip fractures, a common and debilitating injury. Understanding how PCN works could lead to better pain management strategies.

How the study worked

Aged rats with hip fractures were treated with either a vehicle or 80 mg/kg/day of PCN for two weeks, and various pain and inflammation markers were measured.

What this study cannot tell us

The study was conducted in aged rats, and results may not directly translate to humans. Further research is needed to confirm the findings in clinical settings.

How to read the evidence

This is a preclinical study in aged rats with hip fractures — a relevant animal model for the clinical condition. The mechanistic confirmation using both pinocembrin and a specific receptor antagonist strengthens the evidence, though translation to humans remains to be established.

When this study was published

Published in 2022 in the Journal of Neurophysiology, this study addresses an ongoing clinical need for non-opioid pain management in elderly hip fracture patients.

The bigger picture

Hip fracture pain management in elderly patients is a significant clinical challenge — opioids carry high risks of delirium, falls, and respiratory depression in this population. Identifying that substance P signaling drives both pain and vascular changes after hip fracture provides two therapeutic avenues: natural compounds like pinocembrin that suppress substance P production, and specific NK1 receptor antagonists that block its action. Both approaches could potentially offer non-opioid pain management for one of the most common orthopedic injuries in the elderly.

Questions still open

Could pinocembrin or NK1 receptor antagonists reduce opioid requirements after hip fracture surgery in elderly patients?
Does the substance P-mediated vascular component (warmth, swelling) contribute to delayed healing after hip fracture?
Would combining pinocembrin with standard fracture pain management produce additive or synergistic analgesic effects?

Common questions

Why is hip fracture pain so difficult to manage in elderly patients?

Hip fracture pain is intense and involves both bone damage and significant soft tissue inflammation. In elderly patients, the standard pain medications — particularly opioids — carry high risks of confusion (delirium), further falls, respiratory depression, and constipation. This creates an urgent need for non-opioid pain alternatives, which is why understanding the substance P pathway is clinically important.

What is pinocembrin?

Pinocembrin is a natural flavonoid compound found in honey, propolis, and certain plants. It has known anti-inflammatory and neuroprotective properties. This study shows it can reduce pain signaling through the substance P neuropeptide pathway, adding analgesic activity to its known biological effects. It is not currently available as a pharmaceutical drug.

Read the original research

Pinocembrin relieves hip fracture-induced pain by repressing spinal substance P signaling in aged rats.

Journal of neurophysiology, 127(2), 397-404

View on PubMed ↗Publisher’s paper ↗

Citation

Xing, Baorui; Feng, Nana; Zhang, Juan; Li, Yunmei; Hou, Xiuxiu; Wu, Hao; Liu, Wendong; Han, Guangpu. (2022). Pinocembrin relieves hip fracture-induced pain by repressing spinal substance P signaling in aged rats.. Journal of neurophysiology, 127(2), 397-404. https://doi.org/10.1152/jn.00517.2021