Researchers at the University of California San Diego (UCSD) have identified a pathway connecting the brain and the immune system that contributes to heart attack damage. Published in the journal Cell, the study proposes a 'triple node' approach involving the heart, brain, and neuroimmune systems, challenging traditional views that often focus on the heart in isolation. Experiments in mice demonstrated that disabling specific components of this circuit significantly reduced damage and improved cardiac function following experimentally induced heart attacks.
The study proposes a 'triple node' approach involving the heart, brain, and neuroimmune systems, challenging traditional views that often focus on the heart in isolation.
Discovery of the Heart-Brain-Immune Loop
The research indicates that during a heart attack, sensory neurons transmit information from the heart to the brain. Assistant Professor Vineet Augustine, a neuroscientist and lead author of the study, noted that the brain perceives a heart attack as an injury, subsequently triggering an immune response.
This immune response, in the absence of pathogens, may inadvertently exacerbate the damage to heart tissue.
Postdoctoral Scholar Saurabh Yadav, also a lead author, stated that blocking this heart-brain-neuroimmune system prevented the spread of injury in laboratory animals. The interdisciplinary project involved neurobiologists, cardiologists, and immunologists, utilizing advanced genetic and neuroscience tools. This included heart surgery on mice, real-time physiological measurements, and echocardiography, to map these complex connections.
Experimental Findings and Mechanism
During the study, researchers observed that certain vagal neurons, specifically TRPV1 expressing neurons, "wrap around the injury site" in mice during a heart attack. These TRPV1 neurons were found to transmit signals from the heart to the hypothalamus, a deep-brain structure.
Other cells within the hypothalamus then relay these signals to a different cluster of nerve cells that project back to the heart. These returning nerve cells release an immune protein that promotes inflammation.
Experiments investigated whether blocking communication through these nerve cells could mitigate heart attack severity. Disabling this group of TRPV1 nerve cells led to notable improvements in the heart's pumping efficiency and electrical signals associated with contraction. The UCSD team reported that blocking any of the three junctures within this identified heart-brain-immune loop alleviated heart attack complications in the mice.
Disabling this group of TRPV1 nerve cells led to notable improvements in the heart's pumping efficiency and electrical signals associated with contraction.
Implications for Treatment and Future Research
This research suggests that manipulating the immune system or blocking specific neural pathways could offer novel therapeutic approaches for heart attack patients. Augustine highlighted that current heart attack treatments are often invasive and primarily focused on cardiac repair.
The findings point toward potential non-invasive methods to minimize the immune system's inadvertent damaging effects post-heart attack. Ongoing research in Augustine's laboratory aims to further investigate the mechanisms and functions of these three-node connections.
Background on Neuroimmune Links
Links between the nervous and immune systems have been a focus of research for several decades. The vagus nerve, a large nerve bundle, plays a role in transmitting signals between the brain and various organs, regulating essential functions such as breathing, blood pressure, and digestion.
Previous findings include:
- In 2000, researchers at the Feinstein Institutes for Medical Research observed that electrical stimulation of the vagus nerve reduced the production of an immune protein linked to inflammation.
- In July, an implantable vagus nerve stimulator developed by SetPoint Medical received FDA approval for treating rheumatoid arthritis, an autoimmune disease.
Earlier research has also established connections between the cardiovascular, nervous, and immune systems. For example, sudden cardiac deaths reportedly increased during the 1994 Northridge earthquake and during high-stakes sporting events. Dr. Kalyanam Shivkumar, a UCLA cardiac electrophysiologist, has noted that these stress-induced "fight-or-flight" signals, while beneficial in emergencies, can trigger harmful inflammation long-term, potentially contributing to heart swelling, arrhythmias, and heart failure.