Firm neutrophil (PMN)-endothelial (EC) adhesion is crucial to the PMN-mediated hyperinflammation observed in acute lung injury. Hypertonic saline (HTS) used for resuscitation of hemorrhagic shock has been associated with a decreased incidence of PMN-mediated lung injury/acute respiratory distress syndrome. We hypothesize that physiologically accessible hypertonic incubation (170mM vs. 140mM, osmolarity ranging from 360-300 mOsm/L) inhibits pro-inflammatory activation of human pulmonary microvascular endothelial cells (HMVECs). Pro-inflammatory activation of HMVECs was investigated in response to TNFα including IL-8 release, ICAM-1 surface expression, PMN adhesion, and signaling mechanisms under both isotonic (control) and hypertonic conditions. Hyperosmolarity alone had no effect on either basal IL-8 release or ICAM-1 surface expression, but did lead to concentration-dependent decreases in TNFα–induced IL-8 release, ICAM-1 surface expression, and PMN:HMVEC adhesion. Conversely, HTS activated p38 mitogen-activated protein kinase (MAPK) and enhanced TNFα activation of p38 MAPK. Despite this basal activation, hyperosmolar incubation attenuated TNFα stimulated IL-8 release and ICAM-1 surface expression and subsequent PMN adherence, while p38 MAPK inhibition did not further influence the effects of hyperosmolar conditions on ICAM-1 surface expression. In addition, TNFα induced NF-kB DNA binding, but HTS conditions attenuated this by 31% (p<0.01). In conclusion, HTS reduces PMN:HMVEC adhesion as well as TNFα-induced pro-inflammatory activation of primary HMVECs via attenuation of NF-kB signaling.

Initiating prehospital resuscitation with plasma in patients with trauma-associated hemorrhagic shock will result in more rapid and durable clot formation and, thus, the need for fewer packed cell infusions, less frequent use of cryoprecipitate, and more ventilator-free hospital days compared with those of patients randomized to standard crystalloid field resuscitation.

Background Arachidonic acid (AA, and its leukotriene derivatives e.g.: LTB4) is an inflammatory mediator in post-shock mesenteric lymph that appears to act as an agonist on G-protein coupled receptors (GPCRs). These mediators prime neutrophils (PMNs) for an increased production of superoxide, implicated in the development of ALI. Hypertonic saline (HTS) has also been shown to have immunomodulatory effects such as attenuation of PMN priming by precluding appropriate clathrin-mediated endocytosis of activated GPCRs, thereby potentially attenuating ALI. We hypothesize that HTS inhibits priming of the PMN oxidase by these lipid mediators. Methods After PMNs were isolated from healthy donors, incubation was done in either isotonic buffer (control) or HTS (180 mmol/L) for 5 minutes at 37°C. The PMNs were then primed for 10 minutes with AA [5 μM] or 5 minutes with LTB4 [1 μM] and the oxidase was activated with 200 ng/ml of phorbol 12-myristate 13-acetate (PMA), a non-GPCR activator, and superoxide anion generation was measured via reduction of cytochrome c. Results Both AA [5 μM] and LTB4 [1 μM] significantly primed the PMA activated respiratory burst (p<0.05, ANOVA, Newman-Keuls, n=4). HTS inhibited both AA and LTB4 priming of the respiratory burst. Conclusions These data indicate that HTS reduces the cytotoxicity of PMNs stimulated by these lipid mediators in vitro and further support the immunomodulatory effects of HTS.

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