Sublethal hemorrhagic shock reduces tumor necrosis factor alpha-producing capacity in different cell compartments

Hemorrhagic shock results in a severe impairment of the immune response. Im munological alterations after hemorrhagic shock thus appear to be responsib le for reduced resistance to infectious agents commonly observed after shoc k and severe injury. In the present study we examined the TNF-alpha -produc ing capacity of immune cells derived from different organs after sublethal shock in rats. Hemorrhagic shock was established by pressure controlled ble eding to a mean arterial pressure of 35 mm Hg for 35-40 min and consecutive resuscitation in male Sprague-Dawley rats. Twenty four hours after shock, TNF-alpha production in response to lipopolysaccharide (LPS, Salmonella fri edenau) stimulation was measured in isolated spleen, bone marrow and blood cells. TNF-alpha production could be induced by stimulation with 1 ng/ml, i n blood, spleen and bone marrow cells collected from sham-operated animals. A maximal stimulation was observed in all cell types after stimulation wit h 10 ng/ml LPS and could not be further increased with LPS doses of 100 ng/ ml. Hemorrhagic shock of 35 mm Hg for 35-40 min, with consecutive resuscita tion did not result in mortality, in contrast to a 4 hours lasting hemorrha gic shock resulting in 80% mortality. Blood, spleen or bone marrow cells, h arvested from animals 24 hours after sublethal hemorrhagic shock, showed a significantly reduced TNF-alpha production in all cell populations after LP S stimulation. Serum collected from animals 2 hours after sublethal hemorrh agic shock contained an activity not present either before or 24 hours afte r shock, that downregulated LPS-indueed TNF-alpha. production in rat whole blood cultures and the murine macrophage cell line J774. The inhibitory act ivity present in serum, 2 hours after shock is not IL-10 since this mediato r was not detectable in any serum sample. However, in the serum samples wit h TNF-alpha -inhibitory activity, elevated levels of PGE(2) metabolites wer e found, which suggests the involvement of prostaglandins in trauma-induced immunosuppression. Altered TNF-alpha expression might be partially explain ed by an inhibitory activity in the serum already present 2 hours after sho ck. Since adequate, but not overwhelming TNF-alpha production is essential for host response, the altered cytokine formation might explain local and s ystemic susceptibility to infections after hemorrhagic shock.