Artificial colloids influence survival rate of human monocytes

Introduction

Monocytes are within the first line of an organisms immune defense. However in the course of sepsis they undergo apoptotic cell death [1,2]. It is unclear whether this serves to protect the organism from a hyperreactive inflammatory response or is a sign for immune dysfunction.

The artificial colloids hydroxyethylstarch (HES), dextran (DEX) and gelatine (GEL) are essential in perioperative volume replacement as well as in the treatment of trauma shock and sepsis. In this study we investigated whether artificial colloids influence survival or apoptosis of human monocytes in vitro.

Methods

Monocytes were isolated from buffy coats of healthy donors by gradient centrifugation and adherence to plastic culture dishes. They were incubated for 8 h with HES, DEX and GEL at 10 to 40 mg/ml. Staurosporine was added to induce cell death. Alive, apoptotic and necrotic cells were identified by Annexin V/Propidium Iodide staining and 10 000 cells were analysed by flow cytometry. Presence of apoptotic cell death was confirmed by electron microscopy, TUNEL, and cell death detection ELISA. Regression analysis of colloid concentration against cell status was performed. Slope values were tested with Students' t-test against 0. Significance was assumed for P < 0.05.

Results

All artificial colloids reduced the fraction of viable cells in a concentration dependent manner. This effect was significant with DEX. Apoptotic cells, which were calculated as a fraction of dead cells were reduced with DEX more than with HES, but increased significantly with GEL.

Incubation with staurosporine reduced cell viability and increased the fraction of apoptotic cells. Neither colloid nor concentration had additional influence. Only the results for HES are shown.

Conclusion

DEX, HES, and GEL promote monocyte death in vitro. This effect is concentration dependent, but most obvious beyond concentrations found in clinical practice. Cell viability is reduced most by DEX, whereas GEL seems to delay the course of cell death, as apoptotic cells undergo secondary necrosis in vitro. Staurosporine induced cell death is not blocked.

Table 1