Digoxin disrupts the inflammatory response in experimental pneumococcal pneumonia

Area of Science:

• Immunology
• Pharmacology
• Microbiology

Background:

• Cardiac glycosides like digoxin are used to treat heart conditions.
• The impact of digoxin on pulmonary antibacterial mechanisms is not well understood.
• Streptococcus pneumoniae is a common cause of bacterial pneumonia.

Purpose of the Study:

• To investigate the effects of digoxin on pulmonary antibacterial mechanisms against Streptococcus pneumoniae.
• To determine if digoxin influences the host's ability to clear pneumococcal infections in the lungs.

Main Methods:

• Normal CD-1 mice were administered digoxin.
• Mice were intratracheally inoculated with Streptococcus pneumoniae.
• Pulmonary clearance of viable pneumococci and immune cell recruitment (granulocytes and macrophages) were assessed.
• In vitro pneumococcidal activity of alveolar macrophages was evaluated.

Main Results:

• Digoxin treatment significantly reduced mouse survival rates compared to controls.
• Digoxin impaired the clearance of viable pneumococci from the lungs.
• A marked attenuation in the recruitment of granulocytes and macrophages into bronchoalveolar spaces was observed in digoxin-treated mice.
• Digoxin did not affect the in vitro killing of pneumococci by alveolar macrophages at clinically relevant concentrations.

Conclusions:

• Digoxin disrupts host defense against Streptococcus pneumoniae by impeding the inflammatory response in the lungs.
• The cardiac glycoside interferes with the recruitment of immune cells necessary for clearing bacterial infections.
• Digoxin's negative impact on pulmonary antibacterial mechanisms warrants further investigation, especially in patients with pneumonia.