Unveiling the Heart's Vulnerability to Pneumonia: A Bacterial Enzyme's Role
Pneumonia, a pervasive respiratory ailment, exacts a heavy toll on global health, with over 1.2 million emergency room visits and more than 41,000 adult fatalities annually in the United States alone. The impact extends further, claiming the lives of over a million children under five worldwide each year. While the disease primarily affects the lungs, its potential to trigger life-threatening heart complications, such as heart failure, arrhythmias, or heart attacks, cannot be overlooked.
A groundbreaking study conducted by researchers from the University of Maryland School of Medicine (UMSOM) and the University of Alabama at Birmingham's Heersink School of Medicine has shed light on a bacterial enzyme that may hold the key to understanding why some individuals experience heart complications during pneumonia, while others remain unaffected. The enzyme, named zmpB, is believed to play a pivotal role in the bacteria's ability to survive, grow, and potentially attack tissues.
The research team, led by Carlos J. Orihuela, PhD, Professor of Microbiology at the University of Alabama at Birmingham, revealed that approximately one in five pneumonia patients hospitalized will suffer from severe cardiac events, with a heightened risk of heart failure even years post-hospitalization. This discovery underscores the importance of identifying the underlying causes of these complications.
The study, published in Cell Reports on December 4, focused on Streptococcus pneumoniae, the primary culprit behind community-acquired pneumonia. Through a combination of bacterial genome-wide association studies (bGWAS), mouse models, and cardiac organoids, the researchers made a significant finding: S. pneumoniae can directly damage the heart, and the zmpB enzyme facilitates the bacteria's invasion into the heart.
Adonis D'Mello, PhD, a bioinformatics analyst involved in the study, noted a striking pattern. Patients with heart failure were more frequently infected with a specific version of S. pneumoniae carrying the zmpB gene, equipped with FIVAR domains, which are specialized segments aiding in the bacteria's invasion and survival within heart cells, leading to pockets of infection. The more FIVAR domains the gene possessed, the greater the heart damage caused.
To further validate their findings, the researchers infected mice with either a regular pneumonia strain or a genetically modified strain lacking the zmpB gene. The results were striking; mice with the normal strain exhibited numerous cardiac microlesions and cell death, while those without the zmpB gene showed minimal or no such damage.
The team then exposed heart organoids, human stem cell-derived cardiac cells, to pneumococcal strains with and without the zmpB gene, as well as different versions of zmpB. The presence of zmpB with FIVAR domains resulted in successful invasion of heart cells, while those lacking FIVAR domains showed reduced heart tissue cell death and bacterial entry.
The study's findings suggest that understanding the molecular fingerprints, particularly the role of zmpB and its FIVAR domains, could pave the way for better patient protection against heart damage during pneumonia. Dr. Orihuela envisions a future where a simple genetic test could identify high-risk bacterial strains early in an infection, enabling closer cardiac monitoring or targeted treatments to prevent heart damage.
The implications of this research are far-reaching. As Mogens Kilian, a Professor Emeritus of Medical Microbiology at Aarhus University in Denmark, who was not involved in the study, noted, this research not only uncovers the function of an enigmatic enzyme in Streptococcus pneumoniae but also provides insights into the pathogenesis of severe complications associated with infections caused by certain strains of this pathogen, opening up new avenues for prevention.
