Hypertonic saline alteration of the PMN cytoskeleton: Implications for signal transduction and the cytotoxic response

Background: Recognition that hypertonic saline (HTS) modulates the inflammatory response has renewed interest in this agent for postinjury resuscitation, Changes in extracellular tonicity alter cell shape and are accompanied by cytoskeletal reorganization. Recent evidence suggests that cytoskeletal reorganization is critical for receptor-mediated signal transduction, We hypothesized that HTS-induced changes in the cytoskeleton interfere with cytotoxic signal transduction. Methods: Isolated neutrophils (PMNs) were incubated in HTS (Na+ = 180 mmol/L) and activated with N-formyl-methionyl-leucyl-phenylalanine (receptor-mediated) or phorbol myristate (receptor independent). Actin polymerization was assessed by digital image microscopy and flow cytometry, PMN superoxide anion (O-2(-)) production and p38 MAPK activation was measured by reduction of cytochrome c and Western blot, Pretreatment with cytochalasin B was used to disrupt HTS-induced actin reorganization. Results: HTS inhibited receptor-mediated cytoskeletal reorganization and attenuated p38 MAPK activation and O-2(-) production, HTS had no effect on receptor-independent O-2(-) production, Cytoskeletal disruption (cytochalasin B) prevented HTS attenuation of receptor-mediated p38 MAPK activation. Conclusion: HTS attenuates the PMN cytotoxic response by interfering with intracellular signal transduction. Changes in the actin cytoskeleton appear to modulate receptor-mediated p38 MAPK signaling.