Up-regulation Of MMP-12 Expression In Monocytes By Heat-inactivated Streptococcus Pneumoniae

Streptococcus pneumoniae is a major human pathogen, colonization of the nasopharynx by pneumococci occurs in up to 40% of the population. The bacterium is the cause of bacterial pneumonia, otitis media, bacterial meningitis and septicaemia. The Streptococcus pneumoniae causes more deaths from invasive infections than any other bacteria and is the fifth leading cause of death worldwide. In developing countries, pneumococcal pneumonia is the leading cause of death in children, resulting in about 10% mortality of all children younger than 5 years. Now, because of emergence of bacterial strains resistant to multi-antimicrobial agents, it is more and more difficult to cure the infection of Streptococcus pneumoniae. These facts mean that more emphasis should be given to the mechanisms involved in the pathogenesis of pneumococcal disease; in particular the host–bacterial interactions and the host immune defense against pneumococcal invasion.When infecting Streptococcus pneumoniae, monocytes/macrophages play an important role in cleaning the bacterium. Alveolar macrophages contribute to the early stages of innate defense against bacterium in the lung by generating antimicrobial molecules, secreting cytokines, and presenting antigens, and more important, it can clear death cells, such as apoptotic neutrophils. In animal research, depletion of alveolar macrophages produced severely inflammatory responses and increased death. Macrophages come from monocytes, thus a timely and adequate monocytes response is essential for controlling infection and terminating the inflammatory process.Several laboratories have shown that infection of Streptococcus pneumoniae shortened monocytes transit time from the bone marrow and...