Pneumonia, a widespread respiratory infection, is increasingly recognized for its potential to trigger severe and lasting heart problems. New research from the university of Alabama at Birmingham identifies a specific bacterial enzyme, zmpB, as a key factor in this hazardous connection, offering a deeper understanding of why some pneumonia patients experience cardiac events. The study, published in Cell Reports, could pave the way for improved risk assessment and targeted therapies to protect the cardiovascular health of those affected by this common illness.
Pneumonia, a leading cause of death worldwide, may trigger severe heart complications in some patients, according to a new study identifying a bacterial enzyme potentially responsible for this dangerous link. Understanding why certain pneumonia cases lead to heart problems is crucial for improving patient outcomes and reducing mortality.
Each year, pneumonia results in over 1.2 million emergency room visits and more than 41,000 deaths among adults in the United States. Globally, the disease claims the lives of over one million children under five annually. While traditionally viewed as a respiratory illness, pneumonia can also lead to life-threatening cardiac issues such as heart failure, irregular heartbeats, and even heart attacks.
Researchers at the University of Alabama Birmingham (UAB) have pinpointed an enzyme called zmpB, produced by Streptococcus pneumoniae – the most common cause of community-acquired pneumonia – as a potential key factor in the development of these heart complications. The study, published Thursday in Cell Reports, offers new insights into why some patients experience cardiac events during or after a pneumonia infection.
“Approximately one in five patients hospitalized with pneumonia suffers a life-threatening cardiac event,” explained Carlos J. Orihuela, professor of microbiology at UAB, according to a UAB news release. “Even years after the infection, these patients remain at least twice as likely to develop heart failure.”
The research team utilized whole-genome bacterial association studies (bGWAS), mouse models, and human cardiac organoids to investigate the connection between S. pneumoniae and heart damage. Their findings confirmed that the bacteria can directly injure the heart and demonstrated that zmpB promotes bacterial invasion of heart tissue.
Enzymes play a critical role in bacterial survival and replication, and can sometimes facilitate attacks on host tissues. Identifying zmpB as a contributing factor opens the door to potential new targets for vaccines or therapeutic interventions.
By analyzing hundreds of bacterial strains isolated from patients who developed heart complications and comparing them to strains from patients who only experienced pneumonia, researchers identified a clear pattern. Patients with heart failure were more frequently infected with strains of S. pneumoniae containing the zmpB gene, specifically those with a distinct genetic feature: FIVAR domains.
These FIVAR domains are segments of the protein that help the bacteria invade and survive within heart cells, leading to localized infections. The study also revealed a correlation between the number of FIVAR domains associated with the gene and the severity of cardiac damage. The findings suggest that these domains play a crucial role in the bacteria’s ability to harm the heart.
Experiments on mice showed that those infected with a standard strain of pneumonia developed numerous microlesions and cellular damage in their heart tissue. In contrast, mice infected with a strain genetically modified to lack the zmpB gene exhibited fewer microlesions and minimal heart cell damage.
To further assess the relevance to humans, researchers used human cardiac organoids – heart cells grown from stem cells in a laboratory setting. These organoids were exposed to different conditions, including infection with pneumococcal strains with and without the zmpB gene, and varying forms of the zmpB enzyme.
Organoids infected with strains expressing zmpB with FIVAR domains allowed for bacterial attachment and invasion of heart cells. However, strains with zmpB lacking FIVAR domains caused less cellular destruction and reduced bacterial penetration into the cells.
The researchers noted that mouse models demonstrated a dependence of heart damage on zmpB expression by the bacterial strain, while organoid experiments indicated that proteins with FIVAR domains facilitate bacterial invasion and damage to heart cells. These results underscore the enzyme’s role in the progression of cardiac complications.
The UAB research team believes that understanding these “molecular fingerprints” could lead to more effective protection of patients against heart damage during pneumonia or a reduction in the severity of the illness. The findings could guide future vaccination strategies and therapeutic approaches.
While further research is needed before these findings can be applied clinically, researchers suggest that a simple genetic test could potentially identify high-risk bacterial strains, allowing for closer cardiac monitoring or targeted treatments to prevent heart damage in pneumonia patients.
Experts emphasize the importance of this research, noting that it clarifies the role of an enzyme in S. pneumoniae whose biological function was previously poorly understood and explains the mechanism by which certain bacterial strains cause severe complications. This discovery opens a potential pathway toward preventative measures.
