Efferocytosis, a process whereby dying cells are engulfed and destroyed by other cells, is crucial in the recovery from pneumonia. However, this cellular cleaning is not as effective in smokers and people with a low body weight, according to new research.
The study, “Recovery from pneumonia requires efferocytosis which is impaired in smokers and those with low body mass index and enhanced by statins,” published in the journal Thorax, suggests that keeping an eye on patients’ nutritional state might improve their speed of recovery.
While most patients recover rather well from pneumonia, some continue having symptoms for a long time. Scientists know that a crucial process of the recovery is the clearance of dead and dying immune cells that have finished their work in the infected lung. The process is taken care of by another class of immune cells called macrophages, and although the process has been studied in mice, scientists have not looked at patients recovering from pneumonia.
Researchers at the University of Liverpool in England enrolled 22 patients with pneumonia admitted to the hospital. After one month, patients were examined with bronchoscopy, and researchers collected cells from the patients’ lungs using bronchoalveolar washing. The recovered macrophages were then analyzed for their ability to clear dead cells.
Researchers noted that the clearance ability of the cells seemed to be better as symptoms improved, but the finding was not statistically significant. They also analyzed a range of other factors, finding that age did not impact the process, nor did use of corticosteroid drugs or antibiotics often used in pneumonia.
However, smoking, either currently or in the past, slowed the process down. The research team also discovered that the process was less effective in people with a low body mass index (BMI), but increased as people gained weight. Also, people who were treated with statins had higher rates of cell clearance.
The findings are not entirely surprising since earlier studies have shown that statins affect two enzymes that are involved in protein clearance pathways, increasing the rate of efferocytosis. Researchers were, however, not aware of the impact of BMI on the clearance process, and the study suggests that adequate nutrition might be a key factor in improving recovery after pneumonia.