The effect of Panton Valentin Leukocidin (PVL) on the airway smooth muscle viability

摘要

Methicillin-resistant Staphylococcus aureus (MRSA) is recognized as a worldwide pathogen, and the incidence of community-acquired infections (CA-MRSA) is increased. A virulence factor has been found in most CA-MRSA infections, the Panton-Valentin leukocidin (PVL), which causes polymorphonuclear leukocytes lysis and acute uncontrolled inflammation and tissue injury. In this study we investigated the effect of bacterial supernatant of PVL positive or negative strains on airway smooth muscle obtained from rabbit trachea. MRSA that carry the PVL-gene, confirmed by PCR, is cultured on GP agar and colonies were transferred into casein casein yeast extract medium. The culture supernatants were removed after centrifugation and the presence of PVL was confirmed using an immunochromatographic test. Rabbit tracheal ASMC were isolated and incubated with PVL positive or negative bacterial supernatant (1:20 - 1:2000) for 1 - 3 days. The effect of PVL on the ASMC morphology or viability was estimated using microscope observations or indirect immunofluores- cence with anti-Smooth muscle α-actin antibody and Dapi for DNA staining, and Trypan blue staining, respectively. ASMC incubated with PVL exhibit increased cell size, granular cytoplasm, and ruptured nuclei. Furthermore, PVL reduces cell number mainly in ASMC incubated in the presence of 10% FBS, therefore actively proliferating cells. These results show that apart from the known effect of PVL on immune cells and inflammation process, PVL has a direct toxic effect on airway smooth muscle cells.