Tumor necrosis factor expression is ameliorated after exposure to an acidic environment.
BACKGROUND
It has been well established that laparoscopic surgery presents several clinical benefits, including reduced pain and a shorter hospital stay. These effects have been associated with a decrease in the inflammatory response. Previous studies have demonstrated that reduced inflammation after laparoscopic surgery is the product of carbon dioxide insufflation, which decreases peritoneal pH. The objective of this study was to investigate the cellular and molecular mechanisms responsible for the reduced response after exposure to acidic environments.


METHODS
A murine macrophage line (J744) was incubated in culture medium at pH 6.0 or pH 7.4 for 3 h at 37°C. Then, cells were stimulated with lipopolysaccharide (LPS) at pH 7.4, the expression of TNF-α (qRT-PCR or enzyme-linked immunosorbent assay (ELISA) and intracellular pH were measured. In addition, CD14 and Toll-like receptor 4 expression and NF-κB nuclear translocation were analyzed.


RESULTS
A significant decrease in LPS-induced TNF-α expression levels was observed in cells pre-incubated at pH 6.0 in comparison with cells at neutral pH conditions. This decrease in TNF-α levels was not associated with a reduction in cell surface expression of CD14 and Toll-like receptor 4. Exposure to an extracellular acidic environment resulted in a reduction of IκB phosphorylation and NF-κB nuclear translocation, secondary to a significant drop in cytosolic pH.


CONCLUSIONS
These observations provide a potential mechanism for the reduced expression of TNF-α after exposure to low extracellular pH, which may be related to acidification after CO(2) insufflation during laparoscopic surgery. In addition, extracellular acidic pH environments could emerge as an important regulator of macrophage function.
Grabowski
Julia
J
University of California San Diego, School of Medicine, Department of Surgery, La Jolla, California 92093-0739, USA.
Vazquez
Daniel E
DE
Costantini
Todd
T
Cauvi
David M
DM
Charles
Wisler
W
Bickler
Stephen
S
Talamini
Mark A
MA
Vega
Virginia L
VL
Coimbra
Raul
R
De Maio
Antonio
A
D000818:Animals; D002460:Cell Line; D006863:Hydrogen-Ion Concentration; D018950:Lipopolysaccharide Receptors / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008264:Macrophages / Q000187:drug effects* / Q000378:metabolism*; D051379:Mice; D023421:Models, Animal; D016328:NF-kappa B / Q000378:metabolism; D051197:Toll-Like Receptor 4 / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*
D018950:Lipopolysaccharide Receptors; D008070:Lipopolysaccharides; D016328:NF-kappa B; C493487:Tlr4 protein, mouse; D051197:Toll-Like Receptor 4; D014409:Tumor Necrosis Factor-alpha