Clara cell secretory protein increases phagocytic and decreases oxidative activity of neutrophils.

The research investigates the role of a protein, Clara cell secretory protein (CCSP), in influencing the activity of neutrophils, a type of white blood cell, in horses experiencing recurrent airway obstruction. The study found that CCSP reduced the neutrophils’ destructive oxidative activity and promoted their pathogen-removing phagocytic activity.

Objective of the Research

• The main objective of the study was to investigate the molecular and functional interactions between the Clara cell secretory protein (CCSP) and neutrophils. These neutrophils were derived from both healthy animals and those suffering from recurrent airway obstruction—a condition similar to asthma in humans—either during a period of remission or during an exacerbation of the disease.

Methodology and Findings

• Neutrophils gathered from both the bronchoalveolar region (a part of the respiratory tract) and the blood were evaluated using immuno-cytochemistry and immuno-electron microscopy to detect the presence of CCSP. These procedures allowed the researchers to visualize the cellular and molecular structures associated with the protein.
• The blood neutrophils’ oxidative burst (a process where the neutrophils produce reactive oxygen species to kill pathogens) and their phagocytic activity (the process of engulfing and consuming bacteria or other particles) were measured in the presence of various concentrations of recombinant equine CCSP, a lab-created version of the protein.
• It was found that the neutrophils in the horses with exacerbated lung inflammation housed a significantly larger amount of CCSP compared to the control group. However, blood neutrophils from both groups did not contain CCSP in notable quantities.
• Upon further observation with immuno-electron microscopy, the CCSP was seen localizing within both the cytoplasm and the nucleus of the neutrophils.
• The incubation of blood neutrophils with CCSP led to a significant decrease in their oxidative burst activity and an increase in their capability to perform phagocytosis. Both changes were statistically significant with P values less than 0.001, indicating the results are unlikely due to chance.

Implications

• These findings show that CCSP can enter neutrophils during active lung inflammation and change the functions of these neutrophils. Its presence in the nucleus hints at a potential transcriptional role, suggesting that CCSP might be influencing the genetic activity within the neutrophils.
• The reduced oxidative activity and enhanced phagocytic properties in the presence of CCSP could potentially alleviate the airway inflammation seen in conditions like recurrent airway obstruction in horses by moderating neutrophil activities.
• The study opens avenues for further research into the application of these findings in managing and treating recurrent airway obstruction and other similar respiratory illnesses in not just horses, but potentially in humans as well.