Modification of Tumor Necrosis Factor-α and C-C Motif Chemokine Ligand 18 Secretion by Monocytes Derived from Patients with Diabetic Foot Syndrome.

Background: This study involves the investigation of spontaneous and induced secretion of the pro-inflammatory cytokine tumor necrosis factor-α (TNF-α) and the anti-inflammatory chemokine C-C motif chemokine ligand 18 (CCL18) by monocytes isolated from blood of patients with long-term type 2 diabetes mellitus (T2DM), both with or without foot ulcers. Methods: A total of 121 patients with T2DM (79 without diabetic foot syndrome (DFS) and 42 patients with DFS) were included. Cluster of Differentiation 14 (CD14+) monocytes were isolated from patients' blood and stimulated by interferon-γ (IFN-γ) and interleukin-4 (IL-4) for induction of pro- and anti-inflammatory monocyte activation, respectively. The concentrations of TNF-α and CCL18 in the culture medium were measured using ELISA on day 1 and day 6 after cell stimulation. Results: We found a correlation between glycated hemoglobin (HbA1c) and stimulated secretion levels of TNF-α (r = 0.726, p = 0.027) and CCL18 (r = -0.949, p = 0.051) in patients with DFS. There was an increase of pro- and anti-inflammatory activation of monocytes in all patients with different durations of DFS (p < 0.05). However, no stimulation of anti-inflammatory activation was detected in patients with DFS lasting more than 6 months (p = 0.033). Conclusions: Our study showed an increase in pro-inflammatory secretion and a decrease in anti-inflammatory secretion by monocytes isolated from blood of patients with T2DM depending on HbA1c levels and duration of the inflammatory process. These findings allow us to assume that monocytes isolated from T2DM patients are characterized by a biased ability to respond towards pro-inflammatory stimulation, contributing to the chronic wound process.

Tumor Necrosis Factor-α and C-C Motif Chemokine Ligand 18 Associate with Atherosclerotic Lipid Accumulation In situ and In vitro.

Atherosclerosis is regarded as a chronic inflammatory disease associated with changes in the innate immune system functioning and cytokine disturbances. Local inflammation in the arterial wall is an important component in the development and growth of atherosclerotic plaques. Inside the lesions, both pro- and antiinflammatory cytokines were detected, highlighting the complexity of the atherosclerotic process. However, little is known about the expression of these signaling molecules in early human atherosclerotic lesions. In this study, we explored localization of a pro-inflammatory cytokine, tumor necrosis factor-α (TNFα), and anti-inflammatory chemokine, C-C motif chemokine ligand 18 (CCL18), in the arterial wall of human aorta. We noticed differences in the intensity of staining for TNFα and CCL18 in atherosclerotic lesions and grossly normal areas, as well as differences in their localization. While CCL18 prevailed in the areas close to the aortic lumen, TNFα was localized in deeper layers of the intima. We next studied the expression of TNFα and CCL18 mRNA in lesions corresponding to different stages of atherosclerosis progression and found that it was maximal in lipofibrous plaques that are most enriched in lipids. To test the hypothesis that cytokine expression can be associated with lipid accumulation, we studied the TNFα and CCL18 expression profiles in primary human monocyte-derived macrophages after inducing lipid accumulation by incubating cultured cells with atherogenic LDL. We found that intracellular cholesterol accumulation was associated with upregulation of both TNFα and CCL18, confirming our hypothesis. These results encourage further investigation of cytokine expression in human atherosclerotic lesions and its role in the atherosclerosis progression.

Macrophages and Their Contribution to the Development of Atherosclerosis.

Atherosclerosis can be regarded as chronic inflammatory disease driven by lipid accumulation in the arterial wall. Macrophages play a key role in the development of local inflammatory response and atherosclerotic lesion growth. Atherosclerotic plaque is a complex microenvironment, in which different subsets of macrophages coexist executing distinct, although in some cases overlapping functions. According to the classical simplified nomenclature, lesion macrophages can belong to pro-inflammatory or anti-inflammatory or alternatively activated types. While the former promote the inflammatory response and participate in lipid accumulation, the latter are responsible for the inflammation resolution and plaque stabilisation. Atherosclerotic lesion dynamics depends therefore on the balance between these macrophages populations. The diverse functions of macrophages make them an attractive therapeutic target for the development of novel anti-atherosclerotic treatments. In this chapter, we discuss different types of macrophages and their roles in atherosclerotic lesion dynamics and describe the results of several experiments studying macrophage polarisation in atherosclerosis.

Use of Primary Macrophages for Searching Novel Immunocorrectors.

In this mini-review, the role of macrophage phenotypes in atherogenesis is considered. Recent studies on distribution of M1 and M2 macrophages in different types of atherosclerotic lesions indicate that macrophages exhibit a high degree of plasticity of phenotype in response to various conditions in microenvironment. The effect of the accumulation of cholesterol, a key event in atherogenesis, on the macrophage phenotype is also discussed. The article presents the results of transcriptome analysis of cholesterol-loaded macrophages revealing genes involved in immune response whose expression rate has changed the most. It turned out that the interaction of macrophages with modified LDL leads to higher expression levels of pro-inflammatory marker TNF-α and antiinflammatory marker CCL18. Phenotypic profile of macrophage activation could be a good target for testing of novel anti-atherogenic immunocorrectors. A number of anti-atherogenic drugs were tested as potential immunocorrectors using primary macrophage-based model.

Phenomenon of individual difference in human monocyte activation.

Macrophages play an important role in the pathogenesis of atherosclerosis, including the early pre-clinical stages of the disease development. We have explored the possibility that the disease onset could be associated with altered monocyte/macrophage response to activating pro- and anti-inflammatory stimuli. We evaluated the susceptibility of circulating monocytes from healthy individuals and patients with asymptomatic carotid atherosclerosis to M1 and M2 activation. The obtained data indicated the existence of a remarkable individual difference in susceptibility to activation among monocytes isolated from the blood of different subjects, regardless of the presence or absence of atherosclerosis. The identified differences in susceptibility to activation between monocytes may explain the individual peculiarities of the immune response in different subjects.

Macrophage phenotypic plasticity in atherosclerosis: The associated features and the peculiarities of the expression of inflammatory genes.

Macrophages are essential players in induction and progression of atherosclerotic inflammation. The complexity of macrophage phenotypes was observed in human plaques and atherosclerotic lesions in mouse models of atherosclerosis. Plaque macrophages were shown to exhibit a phenotypic range that is intermediate between two extremes, M1 (pro-inflammatory) and M2 (anti-inflammatory). Indeed, in atherosclerosis, macrophages demonstrate phenotypic plasticity to rapidly adjust to changing microenvironmental conditions. In the plaque, serum lipids, serum lipoproteins and various pro- or anti-inflammatory stimuli such as cytokines, chemokines and small bioactive molecules could greatly influence the macrophage phenotype inducing switch towards more proinflammatory or anti-inflammatory properties. Dynamic plasticity of macrophages is achieved by up-regulation and down-regulation of an overlapping set of transcription factors that drive macrophage polarization. Understanding of mechanisms of macrophage plasticity and resolving functional characteristics of distinct macrophage phenotypes should help in the development of new strategies for treatment of chronic inflammation in atherosclerosis and other cardiovascular diseases.