TSLP promote M2 macrophages polarization and cardiac healing after myocardial infarction

The Role of M1 and M2 Myocardial Macrophages in Promoting Proliferation and Healing via Activating Epithelial-to-Mesenchymal Transition

(1) Background: The activation of sequential processes for the formation of permanent fibrotic tissue following myocardial infarction (MI) is pivotal for optimal healing of heart tissue. M1 and M2 macrophages are known to play essential roles in wound healing by the activation of cardiac fibroblasts after an episode of MI. However, the molecular and cellular mechanisms mediated by these macrophages in cellular proliferation, fibrosis, and wound healing remain unclear. (2) Methods: In the present study, we aimed to explore the mechanisms by which M1 and M2 macrophages contribute to cellular proliferation, fibrosis, and wound healing. Using both in vivo and cellular models, we examined the remodeling effects of M1 and M2 macrophages on infarcted cardiac fibroblasts and their role in promoting cardiac healing post-MI. (3) Results: Our findings indicate that M1 macrophages induce a proliferative effect on infarcted cardiac fibroblasts by exerting an anti-apoptotic effect, thereby preventing cell death. Moreover, M1 macrophages were found to activate the mechanism of epithelial-to-mesenchymal transition (EMT), resulting in wound healing and inducing the fibrotic process. The present findings suggest that M1 macrophages play a crucial role in promoting cardiac remodeling post-MI, as they activate the EMT pathway and contribute to increased collagen production and fibrotic changes. (4) Conclusions: The present study provides insights into molecular and cellular mechanisms mediated by M1 and M2 macrophages in cellular proliferation, fibrosis, and wound healing post-MI. Our findings highlight the critical role of M1 macrophages in promoting cardiac remodeling by activating the EMT pathway. Understanding these mechanisms can potentially result in the development of targeted therapies aimed at enhancing the healing process and improving outcomes following MI.

Study on Maslinic Acid Inhibiting Cardiomyocyte Pyrolysis by Regulating TLR4/NFκB/NLRP3 Signaling Pathway

Background: The paper aimed to investigate the effects of Maslinic acid on myocardial injury caused by ischemia and hypoxia after acute myocardial infarction, and to explore the mechanism of Maslinic acid inhibiting local inflammation and myocardial cell pyrolysis, slowing down the synthesis of extracellular matrix, improving myocardial fibrosis and remodeling ventricle. Materials and Methods: Wistar rats with acute myocardial infarction were used. The serum levels of TNF-α, IL-1β, CRP, and LDH were detected by ELISA. The expressions of inflammation-related proteins such as TLR4, NFκB, NLRP3, IL-10, and TGF-β in myocardial infarction were detected by Western-blot. TUNEL method was employed to detect myocardial cell pyrolysis. Masson staining was used to detect myocardial fibrosis. Immunohistochemical method was applied to detect the expressions of CD206 and CD11C to understand the polarization of macrophages. Results: Maslinic acid can inhibit the levels of inflammatory factors such as CRP, TNF-α and IL-1β, and reduce the expression of myocardial TLR4, NFκB, NLRP3 and other inflammation-related proteins after myocardial infarction. The release of LDH is significantly reduced. The expression of TUNEL positive cells in myocardium is obviously reduced after myocardial infarction. Maslinic acid can increase the expression of CD206-positive cells and reduce the expression of CD11C-positive cells, thus regulate and promote polarization into M2 macrophages. Conclusion: Maslinic acid may inhibit myocardial cell pyrolysis and inflammatory response by regulating the TLR4/NFκB/NLRP3 signaling pathway. Maslinic acid can improve myocardial fibrosis by inhibiting myocardial cell pyrolysis and regulating the polarization of macrophages.

Elevated Plasma Thymic Stromal Lymphopoietin After Acute Myocardial Infarction

Background

Thymic stromal lymphopoietin (TSLP), a distant paralog of the cytokine IL-7, has been shown to be associated with atherosclerosis. However, the effect of plasma TSLP level after acute myocardial infarction (AMI) remains largely unclear. Thus, we aimed to assess the relationship between the concentration of TSLP at admission and the risk of major adverse cardiovascular events (MACE) in AMI patients.

Methods

A total of 175 patients with AMI and 145 unstable angina (UA) controls were recruited in the present study. The clinical characteristics were collected, and MACE was recorded during hospitalization and the follow-up period after discharge.

Results

The median value (25, 75 percentiles) of TSLP concentrations in the AMI group was higher than that in the UA group [11.18 (8.14–15.22) vs. 8.56 (5.26–11.94) pg/ml, p < 0.001, respectively]. Multivariate linear regression analysis revealed that Troponin-I (standardized β = 0.183, p = 0.004) was an independent factor for TSLP. According to the median of TSLP concentrations, all the AMI patients were divided into the high-level group (TSLP level ≥ 11.18 pg/ml, N = 91) and the low-level group (TSLP <11.18 pg/ml, N = 84). In a receiver operating characteristic curve analysis, the area under the curve for TSLP as a predictor of AMI was 0.674 with a cut-off value of 9.235 pg/ml. After a median follow-up of 14 months, Kaplan-Meier survival analysis showed no significant difference in MACE-free survival between the two groups (p = 0.648). Finally, the multivariate logistic regression analyses demonstrated that TSLP was a negative predictor of MACE in AMI patients (OR:0.778,95% CI:0.733–0.876, p = 0.032).

Conclusions

Plasma TSLP levels were elevated in patients with AMI than those in UA. The lower TSLP concentration was associated with MACE after AMI.

Macrophage Polarization in Cardiac Tissue Repair Following Myocardial Infarction

Cardiovascular disease is the leading cause of mortality and morbidity around the globe, creating a substantial socio-economic burden as a result. Myocardial infarction is a significant contributor to the detrimental impact of cardiovascular disease. The death of cardiomyocytes following myocardial infarction causes an immune response which leads to further destruction of tissue, and subsequently, results in the formation of non-contractile scar tissue. Macrophages have been recognized as important regulators and participants of inflammation and fibrosis following myocardial infarction. Macrophages are generally classified into two distinct groups, namely, classically activated, or M1 macrophages, and alternatively activated, or M2 macrophages. The phenotypic profile of cardiac macrophages, however, is much more diverse and should not be reduced to these two subsets. In this review, we describe the phenotypes and functions of macrophages which are present in the healthy, as well as the infarcted heart, and analyze them with respect to M1 and M2 polarization states. Furthermore, we discuss therapeutic strategies which utilize macrophage polarization towards an anti-inflammatory or reparative phenotype for the treatment of myocardial infarction.

Function of Macrophages in Disease: Current Understanding on Molecular Mechanisms

Tissue-resident macrophages (TRMs) are heterogeneous populations originating either from monocytes or embryonic progenitors, and distribute in lymphoid and non-lymphoid tissues. TRMs play diverse roles in many physiological processes, including metabolic function, clearance of cellular debris, and tissue remodeling and defense. Macrophages can be polarized to different functional phenotypes depending on their origin and tissue microenvironment. Specific macrophage subpopulations are associated with disease progression. In studies of fate-mapping and single-cell RNA sequencing methodologies, several critical molecules have been identified to induce the change of macrophage function. These molecules are potential markers for diagnosis and selective targets for novel macrophage-mediated treatment. In this review, we discuss some of the recent findings regarding less-known molecules and new functions of well-known molecules. Understanding the mechanisms of these molecules in macrophages has the potential to yield new macrophage-mediated treatments or diagnostic approaches to disease.

Platelets and Regulatory T Cells May Induce a Type 2 Immunity That Is Conducive to the Progression and Fibrogenesis of Endometriosis

Endometriosis is a hormonal disease, as well as a chronic inflammatory disease. While various immune cells are documented to be involved in endometriosis, there is a wanton lack of a bigger picture on how these cells are coordinated to work concertedly. Since endometriotic lesions experience cyclical bleeding, they are fundamentally wounds that undergo repeated tissue injury and repair (ReTIAR). In this study, we attempted to characterize the role of platelets and regulatory T cells (Tregs) in modulating the lesional immune microenvironment and its subsequent effects on lesional progression and fibrogenesis. Through two mouse experiments, we show that, by disrupting predominantly a type 2 immune response in lesional microenvironment, both platelets and Tregs depletion decelerated lesional progression and fibrogenesis, likely through the suppression of the TGF-β1/Smad3 and PDGFR-β/PI3K/Akt signaling pathways. In particular, platelet depletion resulted in significantly reduced lesional expression of thymic stromal lymphopoietin (TSLP), leading to reduced aggregation of macrophages and alternatively activated (M2) macrophages, and of Tregs, T helper 2 (Th2) and Th17 cells but increased aggregation of Th1 cells, in lesions, which, in turn, yields retarded fibrogenesis. Similarly, Tregs depletion resulted in suppression of platelet aggregation, and reduced aggregation of M2 macrophages, Th2 and Th17 cells but increased aggregation of Th1 cells, in lesions. Thus, both platelet and Tregs depletion decelerated lesional progression and fibrogenesis by disrupting predominantly a type 2 immunity in lesional microenvironment. Taken together, this suggests that both platelets and Tregs may induce a type 2 immunity in lesional microenvironment that is conducive to lesional progression and fibrogenesis.

DEK Expression in Breast Cancer Cells Leads to the Alternative Activation of Tumor Associated Macrophages

Breast cancer (BC) is the second leading cause of cancer deaths among women. DEK is a known oncoprotein that is highly expressed in over 60% of breast cancers and is an independent marker of poor prognosis. However, the molecular mechanisms by which DEK promotes tumor progression are poorly understood. To identify novel oncogenic functions of DEK, we performed RNA-Seq analysis on isogenic Dek-knockout and complemented murine BC cells. Gene ontology analyses identified gene sets associated with immune system regulation and cytokine-mediated signaling and differential cytokine and chemokine expression was confirmed across Dek-proficient versus Dek-deficient cells. By exposing murine bone marrow-derived macrophages (BMDM) to tumor cell conditioned media (TCM) to mimic a tumor microenvironment, we showed that Dek-expressing breast cancer cells produce a cytokine milieu, including up-regulated Tslp and Ccl5 and down-regulated Cxcl1, Il-6, and GM-CSF, that drives the M2 polarization of macrophages. We validated this finding in primary murine mammary tumors and show that Dek expression in vivo is also associated with increased expression of M2 macrophage markers in murine tumors. Using TCGA data, we verified that DEK expression in primary human breast cancers correlates with the expression of several genes identified by RNA-Seq in our murine model and with M2 macrophage phenotypes. Together, our data demonstrate that by regulating the production of multiple secreted factors, DEK expression in BC cells creates a potentially immune suppressed tumor microenvironment, particularly by inducing M2 tumor associated macrophage (TAM) polarization.

Intrauterine growth restriction induces skin inflammation, increases TSLP and impairs epidermal barrier function

Intrauterine growth restriction (IUGR) and low birth weight are risk factors for childhood asthma. Atopic march describes the progression from early dermatitis to asthma during life. Since inflammatory signaling is linked to increased airway resistance and lung remodeling in rats after IUGR, we queried if these findings are related to skin inflammatory response. Firstly, we induced IUGR in Wistar rats by isocaloric protein restriction during gestation. IUGR rats showed lower body weight at postnatal day 1 (P1), catch-up growth at P21, and similar body weight like controls at P90. At P1 and P90, mRNA of inflammatory as well as fibrotic markers and number of skin immune cells (macrophages) were increased after IUGR. Skin thymic stromal lymphopoietin (TSLP) mRNA at P1 and serum TSLP at P1 and P21 were elevated in IUGR. Moreover, IUGR impaired transepidermal water loss at P21 and P90. IUGR induced higher. Secondly, the increase of TEWL after Oxazolone treatment as a model of atopic dermatitis (AD) was greater in IUGR than in Co. Our data demonstrate an early inflammatory skin response, which is linked to persistent macrophage infiltration in the skin and impaired epidermal barrier function after IUGR. These findings coupled with elevated TSLP could underlie atopic diseases in rats after IUGR. KEY MESSAGES: • The present study shows that IUGR increases macrophage infiltration and induces an inflammatory and fibrotic gene expression pattern in the skin of newborn rats. • Early postnatal inflammatory response in the skin after IUGR is followed by impaired epidermal barrier function later in life. • IUGR aggravates transepidermal water loss in an experimental atopic dermatitis model, possibly through elevated TSLP in skin and serum. • Early anti-inflammatory treatment and targeting TSLP signaling could offer novel avenues for early prevention of atopic disorders and late asthma in high-risk infants.