Abstract
Several studies showed that hydroxyethyl starch (HES), a synthetic colloid used in volume replacement therapies, interferes with leukocyte-endothelium interactions. Although still unclear, the mechanism seems to involve the inhibition of neutrophils’ integrin. With the aim to provide direct evidence of the binding of HES to neutrophils and to investigate the influence of HES on neutrophil chemotaxis, we isolated and treated the cells with different concentrations of fluorescein-conjugated HES (HES-FITC), with or without different stimuli (N-Formylmethionine-leucyl-phenylalanine, fMLP, or IL-8). HES internalization was evaluated by trypan blue quenching and ammonium chloride treatment. Chemotaxis was evaluated by under-agarose assay after pretreatment of the cells with HES or a balanced saline solution. The integrin interacting with HES was identified by using specific blocking antibodies. Our results showed that HES-FITC binds to the plasma membrane of neutrophils without being internalized. Additionally, the cell-associated fluorescence increased after stimulation of neutrophils with fMLP (p < 0.01) but not IL-8. HES treatment impaired the chemotaxis only towards fMLP, event mainly ascribed to the inhibition of CD-11b (Mac-1 integrin) activity. Therefore, the observed effect mediated by HES should be taken into account during volume replacement therapies. Thus, HES treatment could be advantageous in clinical conditions where a low activation/recruitment of neutrophils may be beneficial, but may be harmful when unimpaired immune functions are mandatory.
Highlights
Fluid resuscitation with colloid and crystalloid solutions is one of the main interventions in the management of critically ill patients
To evaluate the binding of hydroxyethyl starch (HES) to neutrophils, cells were treated with different concentrations of HES labeled with fluorescein isothiocyanate (FITC) and the fluorescence intensity was read with a microplate reader
Since HES can be synthesized starting from different raw materials, with various molar substitution and C2/C6 ratios [18], we further tested whether HES from these two sources showed the same binding affinity for neutrophils
Summary
Fluid resuscitation with colloid and crystalloid solutions is one of the main interventions in the management of critically ill patients. A wealth of evidence indicates that HES is able to modulate several leukocyte functions such as degranulation [6], oxidative burst [7,8,9,10] and neutrophil–endothelium interaction [11]. This last aspect is of particular relevance, considering the role of leukocytes in inducing microvascular permeability and endothelial damage [12,13]. We evaluated the influence of HES on the chemotaxis of neutrophils in response to IL-8 and fMLP, in order to estimate the impact of HES-containing volume replacement solutions on neutrophils’ activity during in vitro simulated inflammatory conditions
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