Substance P directly protects heart cells from ischemia-reperfusion injury by activating the AKT survival pathway through the NK-1 receptor, reducing both cell death and tissue damage in rat heart models.
Reduced both apoptosis and necrosisSubstance P protected heart cells from both programmed cell death and traumatic cell death during oxygen deprivation, through a confirmed NK-1 receptor/AKT signaling mechanism.
What the researchers found
Substance P reduced ischemia-related lactate dehydrogenase release (a marker of cell damage) in both isolated heart preparations and hypoxic left ventricular tissue slices. It also reduced both apoptosis (programmed cell death) and necrosis (cell death from damage) in hypoxic tissue. Substance P induced AKT phosphorylation — a key step in cell survival signaling. Both the AKT inhibitor LY294002 and the NK-1 receptor antagonist L732138 blocked AKT phosphorylation and eliminated substance P's cardioprotective effect, confirming the NK-1 receptor/AKT mechanism.
Why it matters
Ischemia-reperfusion injury is a major cause of heart damage during and after heart attacks, and current therapies have limited ability to prevent it. Discovering that substance P — a peptide already present in the body — can directly protect heart cells through a well-characterized survival pathway opens a potential new therapeutic approach. The finding that this works through direct cellular effects (not just blood vessel dilation) expands our understanding of how peptides could be used in cardiac emergencies.
How the study worked
Seven-week-old male Sprague-Dawley rats were used. Researchers tested substance P's cardioprotective effects using two preparations: (1) isolated hearts subjected to ischemia-reperfusion, and (2) left ventricular tissue slice cultures exposed to short-term hypoxia without reperfusion. Cell damage was measured by lactate dehydrogenase release, and cell death was assessed for both apoptosis and necrosis. The NK-1 receptor antagonist L732138 and AKT inhibitor LY294002 were used to confirm the signaling pathway.
What this study cannot tell us
This is an animal study using isolated rat hearts and tissue slices, which may not fully replicate the complexity of human cardiac ischemia-reperfusion. The preparations lack the neurohormonal and immune responses that occur in a living organism. Dosing and timing parameters that work in isolated preparations may not translate directly to clinical use. No long-term functional outcomes were assessed.
How to read the evidence
This is a well-designed preclinical study using multiple experimental models (isolated hearts and tissue slices) with appropriate pharmacological controls (receptor antagonist and pathway inhibitor). The mechanistic evidence is convincing, but the findings are limited to animal tissue and have not been tested clinically.
When this study was published
Published in 2015, this study contributed to the growing understanding of substance P's cardiovascular roles. Research into cardioprotective peptides has continued to develop since, with some nearing clinical investigation.
The bigger picture
Cardioprotection during ischemia-reperfusion remains an unmet need in cardiac medicine. While substance P was previously known to dilate coronary arteries, this study adds a new dimension — direct cell survival signaling via AKT. This positions substance P alongside other cardioprotective peptides being investigated for use during cardiac interventions like angioplasty, where reperfusion injury is a significant clinical problem.
Questions still open
- Could substance P or NK-1 receptor agonists be administered during cardiac interventions like angioplasty to reduce reperfusion injury?
- Does endogenous substance P already play a cardioprotective role during heart attacks, and could augmenting it improve outcomes?
- How does the cardioprotective dose of substance P relate to doses that might cause unwanted side effects like pain signaling or inflammation?
Common questions
What is substance P and how does it protect the heart?
Could substance P be used to treat heart attacks?
Read the original research
Substance P induces cardioprotection in ischemia-reperfusion via activation of AKT.
American journal of physiology. Heart and circulatory physiology, 309(4), H676-84
Citation
Jubair, Shaiban; Li, Jianping; Dehlin, Heather M; Manteufel, Edward J; Goldspink, Paul H; Levick, Scott P; Janicki, Joseph S. (2015). Substance P induces cardioprotection in ischemia-reperfusion via activation of AKT.. American journal of physiology. Heart and circulatory physiology, 309(4), H676-84. https://doi.org/10.1152/ajpheart.00200.2015