Interleukin-8 favors pro-inflammatory activity of human monocytes/macrophages

Interleukin-8 (IL-8, CXCL8) belongs to major chemokines to stimulate migration of neutrophils and monocytes/macrophages (Mc/Mphs) into the inflammation sites. We studied the direct effects of IL-8 on the functionality of human Mc/Mphs in vitro. CD14-positive cells were isolated from human peripheral blood mononuclear cells (PBMCs) by positive magnetic separation and were further cultured with or without lipopolysaccharide (LPS, 1.0 μg/ml) for 24 h. We showed that upon LPS activation of Mc/Mphs, IL-8 reduced markedly both the percentages and median fluorescence intensity (MFI) of CD16 (FcγRIII)-positive cells among CD14high cells, as well as in cells that reduced the expression of СD14 during their culturing. IL-8 was also found to be capable of reducing the expression of СD124 (IL-4 receptor subunit alpha, IL-4RA), with concomitant enhancement of the expression of both CD119 (interferon-gamma receptor 1) and CD197 (CCR7) in Mph cells. In addition, IL-8 up-regulated production of IL-6 and IL-1β [but not tumor necrosis factor-α (TNF-α) and IL-10] by activated Mc/Mphs. Our results suggest the ability for IL-8 to directly favor pro-inflammatory M1-type Mph activity.