Open AccessMoraxella catarrhalis is internalized in respiratory epithelial cells by a trigger‐like mechanism and initiates a TLR2‐ and partly NOD1‐dependent inflammatory immune response
Author(s) -
Slevogt Hortense,
Seybold Joachim,
Tiwari Krish.,
Hocke Andreas C.,
Jonatat Carola,
Dietel Solveig,
Hippenstiel Stefan,
Singer Bernhard B.,
Bachmann Sebastian,
Suttorp Norbert,
Opitz Bastian
Publication year - 2007
Publication title -
cellular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.542
H-Index - 138
eISSN - 1462-5822
pISSN - 1462-5814
DOI - 10.1111/j.1462-5822.2006.00821.x
Subject(s) - biology , moraxella catarrhalis , nod1 , respiratory epithelium , microbiology and biotechnology , tlr2 , intracellular parasite , innate immune system , intracellular , immunology , immune system , epithelium , nod2 , haemophilus influenzae , genetics , antibiotics
Summary Moraxella catarrhalis is an important pathogen in patients with chronic obstructive lung disease (COPD). While M. catarrhalis has been categorized as an extracellular bacterium so far, the potential to invade human respiratory epithelium has not yet been explored. Our results obtained by electron and confocal microscopy demonstrated a considerable potential of M. catarrhalis to invade bronchial epithelial (BEAS‐2B) cells, type II pneumocytes (A549) and primary small airway epithelial cells (SAEC). Moraxella invasion was dependent on cellular microfilament as well as on bacterial viability, and characterized by macropinocytosis leading to the formation of lamellipodia and engulfment of the invading organism into macropinosomes, thus indicating a trigger‐like uptake mechanism. In addition, the cells examined expressed TLR2 as well as NOD1, a recently found cytosolic protein implicated in the intracellular recognition of bacterial cell wall components. Importantly, inhibition of TLR2 or NOD1 expression by RNAi significantly reduced the M. catarrhalis ‐induced IL‐8 secretion. The role of TLR2 and NOD1 was further confirmed by overexpression assays in HEK293 cells. Overall, M. catarrhalis may employ lung epithelial cell invasion to colonize and to infect the respiratory tract, nonetheless, the bacteria are recognized by cell surface TLR2 and the intracellular surveillance molecule NOD1.