title: Cytochalasin-induced actin disruption of polarized enterocytes can augment internalization of bacteria.
abstract: Cytochalasin-induced actin disruption has often been associated with decreased bacterial internalization by cultured epithelial cells, although polarized enterocytes have not been systematically studied. In assays using confluent polarized HT-29 enterocytes, cytochalasin D appeared to increase internalization of wild-type Salmonella typhimurium, Proteus mirabilis, and Escherichia coli. HeLa and HEp-2 epithelial cells, as well as HT-29 and Caco-2 enterocytes, were used to clarify this unexpected observation. Resulting data showed that cytochalasin D was associated with increased internalization of S. typhimurium and P. mirabilis by both HT-29 and Caco-2 enterocytes and with increased internalization of E. coli by HT-29 enterocytes; with either HeLa or HEp-2 cells, cytochalasin was associated with no change or a decrease in internalization of these same bacterial strains. Cytochalasin caused decreased internalization of Listeria monocytogenes by HT-29, Caco-2, HeLa, and HEp-2 cells, indicating that cytochalasin did not consistently augment bacterial internalization by polarized enterocytes. Fluorescein-labeled phalloidin confirmed marked disruption of filamentous actin in cytochalasin-treated HT-29, Caco-2, HeLa, and HEp-2 cells. Cytochalasin had no noticeable effect on epithelial viability but caused distorted apical microvilli, cell rounding, and separation of adjacent enterocytes in confluent cultures (with a corresponding decrease in transepithelial electrical resistance). Scanning electron microscopy showed that cytochalasin-induced enhanced bacterial internalization was associated with preferential bacterial adherence on the exposed enterocyte lateral surface. Colchicine, used to disrupt microtubules, had no noticeable effect on bacterial internalization by HT-29 or Caco-2 enterocytes. These data indicated that for HT-29 and Caco-2 enterocytes, cytochalasin-induced disruption of filamentous actin might augment internalization of some bacterial species by a mechanism that appeared to involve exposure of the enterocyte lateral surface.
authors.affiliation: Department of Laboratory Medicine, University of Minnesota, Minneapolis, Minnesota 55455-0385, USA. wells002@maron.tc.umn.edu
authors.forename: C L
authors.initials: CL
authors.lastname: Wells
authors.forename: E M
authors.initials: EM
authors.lastname: van de Westerlo
authors.forename: R P
authors.initials: RP
authors.lastname: Jechorek
authors.forename: H M
authors.initials: HM
authors.lastname: Haines
authors.forename: S L
authors.initials: SL
authors.lastname: Erlandsen
mesh_terms: D000199:Actins / Q000187:drug effects*; D001692:Biological Transport; D018938:Caco-2 Cells; D002450:Cell Communication; D016764:Cell Polarity; D002470:Cell Survival / Q000187:drug effects; D003078:Colchicine / Q000494:pharmacology; D015638:Cytochalasin D / Q000494:pharmacology*; D017097:Electric Impedance; D004755:Enterobacteriaceae; D004847:Epithelial Cells / Q000187:drug effects / Q000382:microbiology* / Q000648:ultrastructure; D019073:HT29 Cells; D006367:HeLa Cells; D006801:Humans; D007413:Intestinal Mucosa / Q000187:drug effects / Q000382:microbiology* / Q000648:ultrastructure; D008089:Listeria monocytogenes
chemical_list: D000199:Actins; D015638:Cytochalasin D; D003078:Colchicine