Tissue cytokine accumulation following administration of liposome-encapsulated hemoglobin in mice

Background: Liposome-encapsulated hemoglobin (LEH) is an experimental red cell substitute which is being developed as an artificial oxygen-carrying resuscitative fluid. This particulate hemoglobin carrier has been shown to accumulate in organs of the reticuloendothelial system, particularly the liver and spleen. Previous investigations have demonstrated that injection of LEH in mice does not illicit serum TNF-alpha but can inhibit LPS-stimulated TNF-alpha production in naive cultured alveolar macrophages. Materials and Methods: We have measured the kinetics of tissue-specific accumulation of inflammatory (TNF-alpha, IL-1 beta) and regulatory cytokines (1L-4, n-10) over the course of 24 h after an injection of 10% blood volume in the tail vein of mice by ELISA. Serum, liver, and spleen were collected from sacrificed animals at 1, 2, 4, 8, and 24 h after LEH injection. Results: Tissue-associated cytokines were observed in the absence of significant changes in serum levels. Liver-associated IL-1 beta was observed to increase significantly over sham or vehicle injected animals at 1 h (413 +/- 57 pg/ml, p < 0.05) and 2 h (455 +/- 40 pg/ml, p < 0.05) following LEH administration and decreased below baseline at 4 h. Liver-associated n-10 was significantly increased over sham animals at all time points following LEH injection and increased to maximal levels at 4 h (1,382+/-256 pg/ml, p<0.05). IL-10 was also observed in spleen and serum at significantly increased levels over sham animals. Conclusion: These results indicate that LEH elicits local inflammatory cytokine production in organs of the reticuloendothelial system which may be a consequence of accumulation in tissue-resident phagocytes.