Reactive species mediate inhibition of alveolar type II sodium transport during mycoplasma infection.
BACKGROUND
Mycoplasma pneumoniae is a significant cause of pneumonia in humans.


OBJECTIVE
To determine the impact of mycoplasma infection and the host inflammatory response on alveolar type II (ATII) cell ion transport in vivo and in vitro.


METHODS
Mice were infected with M. pulmonis for measurements of alveolar fluid clearance (AFC) in vivo and isolation of ATII cells. ATII cells were infected in vivo for determination of epithelial Na+ channel (ENaC) total and cell surface protein levels by biotinylation and Western blot and in vitro for whole cell patch clamp recording and measurement of nitric oxide (NO) production by chemiluminescence.


RESULTS
Mycoplasma infection significantly inhibited AFC at 24 h and total and amiloride-sensitive AFC by 48 h postinfection (pi). In contrast, infected myeloperoxidase-deficient mice had similar basal and amiloride-sensitive AFC values to uninfected control mice at 48 h pi. Addition of forskolin restored total and amiloride-sensitive AFC to control values at 48 h pi. ATII cells isolated from infected mice demonstrated normal alpha, beta, and gamma ENaC total protein levels; however, infected whole-lung cell-surface levels of gamma ENaC were significantly decreased. Patch-clamp recordings demonstrated a significant decrease in total and amiloride-sensitive Na+ currents at 24 h pi. ATII cells demonstrated a significant increase in the production of NO at 24 h pi and inhibition of NO by ATII cells before infection reversed the decrease in total Na+ currents.


CONCLUSIONS
These data indicate that mycoplasma infection results in decreased AFC and functional ENaC via the production of reactive oxygen nitrogen intermediates.
Hickman-Davis
Judy M
JM
Department of Anesthesiology, University of Alabama at Birmingham, Birmingham, AL 35205-3703, USA.
McNicholas-Bevensee
Carmel
C
Davis
Ian C
IC
Ma
He-Ping
HP
Davis
Glenda C
GC
Bosworth
Charles A
CA
Matalon
Sadis
S
D000818:Animals; D018929:Cell Culture Techniques; D051379:Mice; D009175:Mycoplasma Infections / Q000378:metabolism*; D045803:Mycoplasma pulmonis; D018410:Pneumonia, Bacterial / Q000378:metabolism* / Q000382:microbiology; D011650:Pulmonary Alveoli / Q000378:metabolism*; D026361:Reactive Nitrogen Species / Q000502:physiology; D017382:Reactive Oxygen Species; D020545:Respiratory Mucosa / Q000378:metabolism*; D015222:Sodium Channels / Q000378:metabolism*
D026361:Reactive Nitrogen Species; D017382:Reactive Oxygen Species; D015222:Sodium Channels