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Aims In obesity, infiltration of adipose tissue by proinflammatory immune cells causes chronic low-grade inflammation. We investigated the chemokine profiles of human visceral adipocytes by the reverse transcription polymerase chain reaction and the effect of human neutrophil elastase (HNE) on monocyte chemoattractant protein-1 (MCP-1) mRNA and protein levels. Main methods Human adipocytes were obtained from cryopreserved omental preadipocytes of subjects with a body mass index (BMI) < 30 kg/m 2 or > 30 kg/m 2 and were cultured to assess chemokine production. Key findings Chemokine responses associated with obesity-related inflammation were well preserved in cultured human adipocytes derived from cryopreserved preadipocytes. Visceral adipocytes from subjects with a BMI > 30 kg/m 2 expressed mRNA for MCP-1, regulated on activation, normal T cell expressed and secreted (RANTES), epithelial cell-derived neutrophil-activating peptide-78 (ENA-78), interleukin-8 (IL-8), lymphotactin-β, and fractalkine. Although visceral adipocytes from subjects with a BMI < 30 kg/m 2 also expressed MCP-1, RANTES, ENA-78, and IL-8 mRNA, neither lymphotactin-β nor fraktalkine mRNA was detected. Interestingly, expression of MCP-1 mRNA was decreased significantly after exposure to HNE (85 × 10 3 μM/L), suggesting the induction of nuclear factor-kappa B repressing factor. Significance Adipocytes from subjects with a BMI > 30 kg/m 2 or < 30 kg/m 2 have different chemokine profiles. Only adipocytes from subjects with a BMI > 30 kg/m 2 express lymphotactin-β and fractalkine mRNA. Differential chemokine profiles of visceral adipocytes contribute to infiltration of adipose tissue by adaptive immune cells. Neutrophil activation is involved in induction of nuclear factor-kappa B repressing factor, resulting in regulation of immune cell trafficking. [ABSTRACT FROM AUTHOR]

Neutrophil extracellular traps (NETs) have an important role in antimicrobial innate immunity and release substances that may modulate the immune response. We investigated the effects of soluble factors from NETs and neutrophil granule proteins on human monocyte function by using the Transwell system to prevent cell–cell contact. NET formation was induced by exposing human neutrophils to phorbol myristate acetate (PMA). When monocytes were incubated with PMA alone, expression of interleukin (IL)-4, IL-6, IL-8, and tumor necrosis factor (TNF)-alpha mRNA was upregulated, but IL-10, IL-12, and interferon (IFN)-gamma mRNA were not detected. Incubation of monocytes with NETs enhanced the expression of IL-10 and IFN-gamma mRNA, but not IL-12 mRNA. Myeloperoxidase stimulated IFN-gamma production by monocytes in a dose-dependent manner. Both a nuclear factor-kappaB inhibitor (PDTC) and an intracellular calcium antagonist (TMB-8) prevented upregulation of IFN-gamma production. Neither a combined p38alpha and p38beta inhibitor (SB203580) nor an extracellular signal-regulated kinase inhibitor (PD98059) suppressed IFN-gamma production. Interestingly, a combined p38gamma and p38delta inhibitor (BIRB796) significantly decreased IFN-gamma production. These findings suggest that myeloperoxidase induces IFN-gamma production by monocytes via p38gamma/delta mitogen-activated protein kinase. [ABSTRACT FROM AUTHOR]

Chronic inflammation is often linked to the presence of type 2-polarized macrophages, which are induced by the T helper type 2 cytokines interleukin-4 and interleukin-13 (IL-13). IL-13 is a key mediator of tissue fibrosis caused by T helper type 2-based inflammation. Human neutrophil elastase (HNE) plays a pivotal role in the pathogenesis of pulmonary fibrosis. This study investigated the priming effect of granulocyte–macrophage colony-stimulating factor (GM-CSF) on IL-13 expression by macrophages stimulated with HNE. Adherent macrophages were obtained from primary cultures of human mononuclear cells. Expression of IL-13 mRNA and protein by GM-CSF-dependent macrophages was investigated after stimulation with HNE, using the polymerase chain reaction and enzyme-linked immunosorbent assay. GM-CSF had a priming effect on IL-13 mRNA and protein expression by macrophages stimulated with HNE, while this effect was not observed for various other cytokines. GM-CSF-dependent macrophages showed a significant increase in the expression of protease activated receptor-2 (PAR-2) mRNA and protein. The response of IL-13 mRNA to HNE was significantly decreased by pretreatment with alpha1-antitrypsin, a PAR-2 antibody (SAM11), or a PAR-2 antagonist (ENMD-1068). These findings suggest that stimulation with HNE can induce IL-13 production by macrophages, especially GM-CSF-dependent macrophages. Accordingly, neutrophil elastase may have a key role in fibrosis associated with chronic inflammation. [ABSTRACT FROM AUTHOR]