Evidence for the Involvement of Gene Regulation of Inflammatory Molecules in the Accumulation of Intracellular Cholesterol: The Mechanism of Foam Cell Formation in Atherosclerosis.

BACKGROUND: The relationship between the cellular pro-inflammatory response and intracellular lipid accumulation in atherosclerosis is not sufficiently studied. Transcriptomic analysis is one way to establish such a relationship. Previously, we identified 10 potential key genes (IL-15, CXCL8, PERK, IL-7, IL-7R, DUSP1, TIGIT, F2RL1, TSPYL2, and ANXA1) involved in cholesterol accumulation in macrophages. It should be noted that all these genes do not directly participate in cholesterol metabolism, but encode molecules related to inflammation. METHODS: In this study, we conducted a knock-down of the 10 identified key genes using siRNA to determine their possible role in cholesterol accumulation in macrophages. To assess cholesterol accumulation, human monocyte-derived macrophages (MDM) were incubated with atherogenic LDL from patients with atherosclerosis. Cholesterol content was assessed by the enzymatic method. Differentially expressed genes were identified with DESeq2 analysis. Master genes were determined by the functional analysis. RESULTS: We found that only 5 out of 10 genes (IL-15, PERK, IL-7, IL-7R, ANXA1) can affect intracellular lipid accumulation. Knock-down of the IL-15, PERK, and ANXA1 genes prevented lipid accumulation, while knock-down of the IL-7 and IL-7R genes led to increased intracellular lipid accumulation during incubation of MDM with atherogenic LDL. Seventeen overexpressed genes and 189 underexpressed genes were obtained in the DGE analysis, which allowed us to discover 20 upregulated and 86 downregulated metabolic pathways, a number of which are associated with chronic inflammation and insulin signaling. We also elucidated 13 master regulators of cholesterol accumulation that are immune response-associated genes. CONCLUSION: Thus, it was discovered that 5 inflammation-related master regulators may be involved in lipid accumulation in macrophages. Therefore, the pro-inflammatory response of macrophages may trigger foam cell formation rather than the other way around, where intracellular lipid accumulation causes an inflammatory response, as previously assumed.

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.

Heteroplasmic Variants of Mitochondrial DNA in Atherosclerotic Lesions of Human Aortic Intima.

Mitochondrial dysfunction and oxidative stress are likely involved in atherogenesis. Since the mitochondrial genome variation can alter functional activity of cells, it is necessary to assess the presence in atherosclerotic lesions of mitochondrial DNA (mtDNA) heteroplasmic mutations known to be associated with different pathological processes and ageing. In this study, mtDNA heteroplasmy and copy number (mtCN) were evaluated in the autopsy-derived samples of aortic intima differing by the type of atherosclerotic lesions. To detect mtDNA heteroplasmic variants, next generation sequencing was used, and mtCN measurement was performed by qPCR. It was shown that mtDNA heteroplasmic mutations are characteristic for particular areas of intimal tissue; in 83 intimal samples 55 heteroplasmic variants were found; mean minor allele frequencies level accounted for 0.09, with 12% mean heteroplasmy level. The mtCN variance measured in adjacent areas of intima was high, but atherosclerotic lesions and unaffected intima did not differ significantly in mtCN values. Basing on the ratio of minor and major nucleotide mtDNA variants, we can conclude that there exists the increase in the number of heteroplasmic mtDNA variants, which corresponds to the extent of atherosclerotic morphologic phenotype.