Macrophages as a Source and Target of GDF-15.

Growth differentiation factor 15 (GDF-15) is a multifunctional cytokine that belongs to the transforming growth factor-beta (TGF-ß) superfamily. GDF-15 is involved in immune tolerance and is elevated in several acute and chronic stress conditions, often correlating with disease severity and patient prognosis in cancer172 and metabolic and cardiovascular disorders. Despite these clinical associations, the molecular mechanisms orchestrating its effects remain to be elucidated. The effects of GDF-15 are pleiotropic but cell-specific and dependent on the microenvironment. While GDF-15 expression can be stimulated by inflammatory mediators, its predominant effects were reported as anti-inflammatory and pro-fibrotic. The role of GDF-15 in the macrophage system has been increasingly investigated in recent years. Macrophages produce high levels of GDF-15 during oxidative and lysosomal stress, which can lead to fibrogenesis and angiogenesis at the tissue level. At the same time, macrophages can respond to GDF-15 by switching their phenotype to a tolerogenic one. Several GDF-15-based therapies are under development, including GDF-15 analogs/mimetics and GDF-15-targeting monoclonal antibodies. In this review, we summarize the major physiological and pathological contexts in which GDF-15 interacts with macrophages. We also discuss the major challenges and future perspectives in the therapeutic translation of GDF-15.

Dual-Specificity Phosphatases in Regulation of Tumor-Associated Macrophage Activity.

The regulation of protein kinases by dephosphorylation is a key mechanism that defines the activity of immune cells. A balanced process of the phosphorylation/dephosphorylation of key protein kinases by dual-specificity phosphatases is required for the realization of the antitumor immune response. The family of dual-specificity phosphatases is represented by several isoforms found in both resting and activated macrophages. The main substrate of dual-specificity phosphatases are three components of mitogen-activated kinase signaling cascades: the extracellular signal-regulated kinase ERK1/2, p38, and Janus kinase family. The results of the study of model tumor-associated macrophages supported the assumption of the crucial role of dual-specificity phosphatases in the formation and determination of the outcome of the immune response against tumor cells through the selective suppression of mitogen-activated kinase signaling cascades. Since mitogen-activated kinases mostly activate the production of pro-inflammatory mediators and the antitumor function of macrophages, the excess activity of dual-specificity phosphatases suppresses the ability of tumor-associated macrophages to activate the antitumor immune response. Nowadays, the fundamental research in tumor immunology is focused on the search for novel molecular targets to activate the antitumor immune response. However, to date, dual-specificity phosphatases received limited discussion as key targets of the immune system to activate the antitumor immune response. This review discusses the importance of dual-specificity phosphatases as key regulators of the tumor-associated macrophage function.

Modification of PCL Scaffolds by Reactive Magnetron Sputtering: A Possibility for Modulating Macrophage Responses.

Direct current (DC) reactive magnetron sputtering is as an efficient method for enhancing the biocompatibility of poly(ε-caprolactone) (PCL) scaffolds. However, the PCL chemical bonding state, the composition of the deposited coating, and their interaction with immune cells remain unknown. Herein, we demonstrated that the DC reactive magnetron sputtering of the titanium target in a nitrogen atmosphere leads to the formation of nitrogen-containing moieties and the titanium dioxide coating on the scaffold surface. We have provided the possible mechanism of PCL fragmentation and coating formation supported by XPS results and DFT calculations. Our preliminary biological studies suggest that DC reactive magnetron sputtering of the titanium target could be an effective tool to control macrophage functional responses toward PCL scaffolds as it allows to inhibit respiratory burst while retaining cell viability and scavenging activity.

Associations of the NRF2/KEAP1 pathway and antioxidant defense gene polymorphisms with chronic obstructive pulmonary disease.

BACKGROUND AND OBJECTIVE: Chronic obstructive pulmonary disease (COPD) is a complex chronic inflammatory disease of the respiratory system affecting primarily distal respiratory pathways and lung parenchyma. This work was designed as a case-control study aimed at investigating the association of the NRF2/KEAP1 signaling system, and antioxidant defense gene polymorphisms with COPD in population from Russia. METHODS: Ten SNPs: NFE2L2 (rs35652124), KEAP1 (rs1048290), MPO (rs2333227), PRNP (rs1799990), PTGR1 (rs2273788), HSPA1A (rs1008438), TXNRD2 (rs1139793), GSR (rs1002149), SIRT2 (rs10410544), and PTGS1 (rs1330344) were genotyped by the real-time polymerase chain reaction (TaqMan assays) in a case-control study (425 COPD patients and 457 controls, from the same region of Russia, representatives of Tatar population). Logistic regression was used to detect the association of SNPs in different models. Linear regression analyses were performed to estimate the relationship between SNPs and lung function parameters and smoking pack-years. THE RESULTS: In our population, a significant associations of KEAP1 (rs1048290) (P = 0.0015, OR = 0.72 in additive model), HSPA1A (rs1008438) (P = 0.006, OR = 2.26 in recessive model), GSR (rs1002149) (P = 0.037, OR = 1.31 in additive model) with COPD were revealed. NFE2L2 (rs35652124), PRNP (rs1799990), and HSPA1A (rs1008438) were significantly associated with COPD only in smokers. In nonsmokers, significant association was established for GSR (rs1002149). KEAP1 (rs1048290) was associated with COPD in both groups. The relationship between KEAP1 (rs1048290), NFE2L2 (rs35652124), and HSPA1A (rs1008438) and smoking pack-years was found (P = 0.005, P = 0.0028, P = 0.015). A significant genotype-dependent variation of forced vital capacity and forced expiratory volume in 1 s was observed for SIRT2 (rs10410544) (P = 0.04), NFE2L2 (rs35652124) (P = 0.028), and PRNP (rs1799990) (P = 0.044).

Development of Novel Monoclonal Antibodies for Evaluation of Transmembrane Prostate Androgen-Induced Protein 1 (TMEPAI) Expression Patterns in Gastric Cancer.

Transmembrane prostate androgen-induced protein 1 (TMEPAI) is a single-span membrane protein, functionally involved in transforming growth factor beta signaling pathway. The particular protein presented in cells in three isoforms, which differs in the length of the soluble N-terminal extracellular domain, making it challenging for the immunochemical recognition. By using quantitative real-time polymerase chain reaction, we identified significant upregulation of PMEPA1 gene expression in malignant tissues of patients with gastric adenocarcinoma. The main part of commercially available anti-TMEPAI antibodies are having polyclonal nature or not suitable for immunocytochemical localization of target protein in tissue specimens. Hence, we decide to generate a set of novel rat monoclonal antibodies (mAb) directed against conservative C-terminal cytoplasmic epitope. Immunoblotting analysis showed that monoclonal antibodies, 2E1, 6C6, and 10A7 were able to recognize specifically target protein in transiently transfected HEK293T and CHO-K1 cells. Especially established mAb, named 10A7, showed the excellent binding ability to target protein in immunohistochemistry. By using developed antibodies, we observed pronounced expression of TMEPAI in normal gastric epithelial cells while tumor cells from gastric adenomas, and adenocarcinoma samples were mostly negative for target protein expression. Also, we found that gastric epithelium cells lose the TMEPAI expression concurrently with severe dysplasia progression, which probably caused by a mechanism involving specific microRNA.