TITLE:
Membrane and Subcellular Muscle Injury Are Induced by Single or Multiple Exposure to Cigarette Smoke
AUTHORS:
Ana Maria Fleig-Mayer, Alba Ramirez-Sarmiento, Amanda Iglesias, Montserrat Morlá, Carlos Coronell, Diego Rodríguez, Simona Pichinni, Josep Lloreta, Piergiorgio Zuccaro, Xavier Busquets, Joaquim Gea, Jose R. Jardim, Mauricio Orozco-Levi
KEYWORDS:
Skeletal Muscle, Muscle Injury, Muscle Regeneration, Quadriceps, Cigarette Smoking
JOURNAL NAME:
Open Journal of Pathology,
Vol.4 No.3,
July
21,
2014
ABSTRACT: Cigarette smoking is
the main cause of chronic obstructive pulmonary disease (COPD). Diaphragm
injury is observed in patients with COPD. However, the potential role of
smoking in triggering or perpetuating muscle injury is unknown. The present
study was aimed at evaluating the potential role of commercial tobacco smoke as
a direct cause of skeletal muscle injury in experimental conditions. Seventy
Wistar rats (170 - 250 g) were assigned to smoking (n = 49) or non-smoking (n =
21) groups. The smoking groups were submitted to a single or multiple (i.e., five or thirty) daily sessions of
cigarette smoking in an inhalatory chamber (time length: 2 h each session). The
level of exposure was constant and assessed by CO concentrations (50 ppm) and
serum cotinine analysis. Animals
submitted to a single smoke exposure and the corresponding controls were euthanized
in groups at 0 h, 2 h, 4 h, 24 h or 48 h after completing the exposure. Animals
submitted to multiple exposures were euthanized at 0 h after smoking. Samples
from vastus lateralis muscle were obtained and processed for assessing
cell injury and selected protein expression. Monoclonal anti-albumin antibodies
were used to identify muscle fibers with sarcolemmal (membrane) injury.
Subcellular muscle injury was assessed using transmission electron microscopy
(EM). MyoD, myogenin and α-tubulin
were immunodetected using western blot techniques. Exposure to cigarette smoke
associated with significant membrane damage (mean relative difference (MRD)
with controls: +181%, p = 0.004) and sarcomere disruptions (MRD: +226%, p = 0.001).
Expression of MyoD and myogenin (normalized to α-tubulin) were significantly increased at 4 h and remained
increased at 48 h post-exposure. We conclude that not only a single but also
consecutive exposure to tobacco smoke have acute deleterious effects on
peripheral muscle structure. A rapid induction of subrogate markers of skeletal
muscle stress and repair processes associates to sarcolemmal and sarcomere
damage.