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

Background: Recognition that hypertonic saline (HTS) modulates the inflamma tory response has renewed interest in this agent for postinjury resuscitati on, 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 hy pothesized that HTS-induced changes in the cytoskeleton interfere with cyto toxic signal transduction. Methods: Isolated neutrophils (PMNs) were incubated in HTS (Na+ = 180 mmol/ L) and activated with N-formyl-methionyl-leucyl-phenylalanine (receptor-med iated) or phorbol myristate (receptor independent). Actin polymerization wa s assessed by digital image microscopy and flow cytometry, PMN superoxide a nion (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 at tenuated p38 MAPK activation and O-2(-) production, HTS had no effect on re ceptor-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 i ntracellular signal transduction. Changes in the actin cytoskeleton appear to modulate receptor-mediated p38 MAPK signaling.