Regulation of Chemokine Expression by NaCl Occurs Independently of Cystic Fibrosis Transmembrane Conductance Regulator in Macrophages

Abstract

Chronic pulmonary inflammation and infection are the leading causes of morbidity and mortality in cystic fibrosis (CF). While the effect of mutation of the cystic fibrosis transmembrane conductance regulator (CFTR) on airways remains controversial, some groups have demonstrated increases in Na(+) and Cl(-) in CF airway surface liquid compared to normal airways. We investigated the consequences of NaCl on pro-inflammatory chemokine and cytokine production by macrophages. Stimulation of mouse macrophages with increasing amounts of NaCl induced macrophage inflammatory protein-2 (MIP-2) and tumor necrosis factor-alpha (TNF-alpha) production. Further, co-incubation of macrophages with NaCl in the presence of either lipopolysaccharide (LPS) or TNF-alpha synergistically increased MIP-2 production. Both the NaCl and NaCl plus LPS responses were partially dependent on endogenous production and autocrine signaling by TNF-alpha. To investigate the role of CFTR in MIP-2 production, we compared the responses of wild-type and DeltaF508 CF mouse macrophages to NaCl and LPS. The responses of macrophages from both strains were indistinguishable. In addition, CFTR mRNA was not expressed in macrophages. Taken together, these findings suggest that NaCl stimulates MIP-2 production by macrophages through a mechanism that is partially dependent on TNF-alpha but independent of macrophage CFTR expression.

Alterations in Ceramide Concentration and pH Determine the Release of Reactive Oxygen Species by Cftr-Deficient Macrophages on Infection

“…This impairment in ROS release by Cftr-deficient macrophages also decreases the bactericidal capability of these cells against P. aeruginosa. In contrast, Cftr deficiency did not affect the cytokine release response by these lung macrophages, a finding that is consistent with those of previous studies showing that Cftr is not involved in the production of cytokines (KC and MIP2) by LPSstimulated macrophages (30). This situation is in marked contrast to that in Cftr-deficient epithelial cells, which show a marked increase in the constitutive release of proinflammatory cytokines, such as IL-1 and IL-8 (5, 31, 32). )…”

Salt-Dependent Chemotaxis of Macrophages

“…Since other chemokines or chemotactically active factors might play important roles in this system, we assessed the role of the transcription factor tonicity-responsive enhancer binding protein (TonEBP), which protects cells from osmotic stress [10], [11], [12], [13] and which previously had been shown to control the transcription of chemokine genes, too [9], [14]. We thus investigated a possible role of TonEBP in salt-dependent chemotaxis using RAW264.7 macrophages with a stable TonEBP overexpression as described previously [2].…”

Elementary immunology: Na+ as a regulator of immunity

“…Studies have shown that increases in the NaCl concentration to osmolalities of approximately 500–630 mOsm/kg were sufficient to promote the release of tumor necrosis factor (TNF) [34, 35] and chemokine (C-X-C motif) ligand 2 (CXCL2; macrophage inflammatory protein-2) [34] from macrophages in the absence of any additional inflammatory priming. Ip and Medzhitov reported that an increase in the NaCl concentration by 100 mM to a total osmolality of approximately 500 mOsm/kg in lipopolysaccharide (LPS)-treated cells promoted caspase-1-dependent IL-1β- and IL-1α-release from macrophages [36], while an increase of 40 mM NaCl compared to standard cell culture conditions alone were not sufficient to promote the release of IL-1 in LPS-treated cells [37].…”