Reevaluating the Brain’s Role in Heart Attacks
Researchers are encouraging a new perspective on the brain’s involvement in heart attacks, focusing on the interactions between the heart, brain, and immune system that can exacerbate heart damage following a myocardial infarction in mice. Findings released in Cell on January 27, indicate that these incidents may extend beyond simply being cardiovascular issues.
The study highlights a brain-immune network that heightens cardiovascular complications during a heart attack. Scientists discovered neurons in the vagus nerve that transmit signals from the heart to the brain, which subsequently trigger immune and inflammatory responses, resulting in extensive heart damage. By blocking this communication pathway, researchers observed improved recovery outcomes in mice, opening avenues for potential new treatments.
“The heart doesn’t function in a vacuum. The nervous system communicates with it, and the immune system does too,” comments Vineet Augustine, a neuroscientist at the University of California, San Diego, and co-author of the study. He sees this as progress towards integrating multiple systems, a framework that could also apply to other diseases.
Cameron McAlpine, who examines immune interactions within the cardiovascular and nervous systems at the Icahn School of Medicine at Mount Sinai, suggests that the significance of this axis in heart attack dynamics has been acknowledged for decades. “It looks like this connection is pivotal,” he states.
Understanding the Brain-Heart Connection
Heart attacks occur when blood flow is obstructed to the heart muscle, causing tissue damage and initiating cellular and molecular changes. “A heart attack is akin to an earthquake,” Augustine explains. “It has a focal point from which damage radiates outward.” Once it begins to spread, a major portion of the tissue can perish.
Prior studies have indicated that the vagus nerve, crucial for connecting the brain to various organs, sends signals to the brain post-heart attack. “The nervous system governs all the standard functions of the heart,” remarks Kalyanam Shivkumar, a cardiologist at UCLA.
These signals from the heart to the brain activate the sympathetic nervous system, often referred to as the body’s ‘fight or flight’ response. This heightened sympathetic state leads to inflammation in heart tissues, which can severely compromise cardiac function and potentially result in heart failure. “The core issue stems from signals traveling from the heart to the brain,” Shivkumar notes, though the specific cells and pathways involved have been less understood.
To explore this further, Augustine and colleagues induced heart attacks in mice by permanently occluding a heart artery. They aimed to observe how nerve connections between the heart and vagus nerve shift after such an event. What they found was that sensory neurons in the vagus nerve forming new connections around the injured heart tissues heightened detection of harmful stimuli.
By blocking these neurons, researchers found reduced damage and inflammation, stabilizing heart rate and rhythm. “These neurons communicate directly with the injured area,” indicates Augustine. Silencing them can significantly minimize additional damage and keep the injury localized.
