cytochalasin-d and Pneumococcal-Infections

Labelled F-actin with FITC-phalloidin, we observed F-actin rearrangements by Streptococcus pneumoniae adhesion of type II pneumocytes (A549). Invasion of S. pneumoniae to A549 cells was determined by pretreating A549 cells with cytochalasin D. To investigate whether F-actin rearrangements can be blocked by Ca2+ inhibitors, A549 cells were pretreated with Ca2+ inhibitors datrollene. A549 cells were loaded with Fura-2/AM to determine the concentration of cytosolic free calcium by S. pneumoniae adhesion of A549 cells after 30,60,90 minutes respectively. Intact S. pneumoniae can promote F-actin rearrangements. Cytochalasin D is able to prevent S. pneumoniae invasion of A49 cells. S. pneumoniae adhesion of A549 cells increased cytosolic free calcium after 30, 60, 90 minuts. Ca2+ inhibitors datrollene block F-actin rearrangements dose dependently. It suggested S. pneumoniae can provoke F-actin rearrangements through Ca2+ signaling pathways, which will further lead to S. pneumoniae invasion of A49 cells.

Topics: Actins; Bacterial Adhesion; Calcium; Calcium Signaling; Cell Line; Cytochalasin D; Humans; Pneumococcal Infections; Respiratory Mucosa; Streptococcus pneumoniae

Although Streptococcus pneumoniae is the leading cause of community-acquired pneumonia in humans, the mechanism whereby the organism penetrates lung tissue is poorly understood. In the present study we have examined the capacity of pneumococci to penetrate A549 cells, a human lung alveolar carcinoma (type II pneumocyte) cell line. Not all clinical S. pneumoniae isolates initially tested were capable of penetration of the cells, as judged by resistance to extracellular antibiotics. The presence of a polysaccharide capsule also significantly reduced the capacity to both adhere to and penetrate A549 cells. Electron micrographs showed the presence of pneumococci enclosed within vacuoles of intact A549 cells, but bacteria were also seen free in the cytoplasm of damaged cells. Ongoing bacterial DNA, RNA, or protein synthesis was not essential for uptake of pneumococci by A549 cells, and uptake was not diminished by pretreatment of the pneumococci with trypsin. However, inhibition of A549 microfilament assembly with cytochalasin D abolished the phenomenon.

Topics: Bacterial Adhesion; Bacterial Capsules; Bacterial Proteins; Cells, Cultured; Chloramphenicol; Ciprofloxacin; Cytochalasin D; DNA, Bacterial; Enzyme Inhibitors; Epithelium; Humans; Microscopy, Electron; Pneumococcal Infections; Protein Synthesis Inhibitors; Pulmonary Alveoli; Rifampin; RNA, Bacterial; Streptococcus pneumoniae; Trypsin; Tumor Necrosis Factor-alpha