NLRP3 Deficiency Reduces Macrophage Interleukin-10 Production and Enhances the Susceptibility to Doxorubicin-induced Cardiotoxicity

The vaccine adjuvant alum promotes IL-10 production that suppresses Th1 responses

The effectiveness of many vaccines licensed for clinical use relates to the induction of neutralising antibodies, facilitated by the inclusion of vaccine adjuvants, particularly alum. However, the ability of alum to preferentially promote humoral rather than cellular, particularly Th1-type responses, is not well understood. We demonstrate that alum activates immunosuppressive mechanisms following vaccination, which limit its capacity to induce Th1 responses. One of the key cytokines limiting excessive immune responses is IL-10. Injection of alum primed draining lymph node cells for enhanced IL-10 secretion ex vivo. Moreover, at the site of injection, macrophages and dendritic cells were key sources of IL-10 expression. Alum strongly enhanced the transcription and secretion of IL-10 by macrophages and dendritic cells. The absence of IL-10 signalling did not compromise alum-induced cell infiltration into the site of injection, but resulted in enhanced antigen-specific Th1 responses after vaccination. In contrast to its decisive regulatory role in regulating Th1 responses, there was no significant change in antigen-specific IgG1 antibody production following vaccination with alum in IL-10-deficient mice. Overall, these findings indicate that injection of alum promotes IL-10, which can block Th1 responses and may explain the poor efficacy of alum as an adjuvant for inducing protective Th1 immunity.

Anti-inflammatory Effects of Oct4/Sox2-overexpressing Human Adipose Tissue-derived Mesenchymal Stem Cells

BACKGROUND/AIM

The transcription factors Oct4 and Sox2 enhance the proliferation and pluripotency of human adipose tissue-derived mesenchymal stem cells (hAT-MSCs); however, the anti-inflammatory effects of Oct4- and Sox2-overexpressing hAT-MSCs (Oct4/Sox2-hAT-MSCs) are unclear. Here, we evaluated the anti-inflammatory effects of Oct4/Sox2-hAT-MSCs in vitro and in vivo.

MATERIALS AND METHODS

Supernatants from green-fluorescent protein (GFP)- and Oct4/Sox2-hAT-MSCs were used to treat lipopolysaccharide (LPS)-stimulated RAW264.7 cells and inflammatory cytokine expression was determined. In LPS-induced mice, GFP- and Oct4/Sox2-hAT-MSCs were injected intraperitoneally and survival rates, as well as sickness scores of mice, were monitored.

RESULTS

Decreased expression of pro-inflammatory cytokines was observed in Oct4/Sox2-hAT-MSC supernatant-exposed RAW264.7 cells compared to that in GFP-hAT-MSC supernatant-exposed RAW264.7 cells. The sickness score was reduced to 34.9% and the survival rate was increased by 11.1% in Oct4/Sox2-hAT-MSC-injected mice compared to that in GFP-hAT-MSC-injected mice.

CONCLUSION

Our findings provide important insights into the development of therapies utilizing Oct4/Sox2-hAT-MSCs in inflammatory diseases.

Network pharmacology exploration reveals endothelial inflammation as a common mechanism for stroke and coronary artery disease treatment of Danhong injection

Although Danhong injection (DHI) is the most widely prescribed Chinese medicine for both stroke and coronary artery disease (CAD), its underlying common molecular mechanisms remain unclear. An integrated network pharmacology and experimental verification approach was used to decipher common pharmacological mechanisms of DHI on stroke and CAD treatment. A compound-target-disease & function-pathway network was constructed and analyzed, indicating that 37 ingredients derived from DH (Salvia miltiorrhiza Bge., Flos Carthami tinctorii and DHI) modulated 68 common targets shared by stroke and CAD. In-depth network analysis results of the top diseases, functions, pathways and upstream regulators implied that a common underlying mechanism linking DHI’s role in stroke and CAD treatment was inflammatory response in the process of atherosclerosis. Experimentally, DHI exerted comprehensive anti-inflammatory effects on LPS, ox-LDL or cholesterol crystal-induced NF-κB, c-jun and p38 activation, as well as IL-1β, TNF-α, and IL-10 secretion in vascular endothelial cells. Ten of 14 predicted ingredients were verified to have significant anti-inflammatory activities on LPS-induced endothelial inflammation. DHI exerts pharmacological efficacies on both stroke and CAD through multi-ingredient, multi-target, multi-function and multi-pathway mode. Anti-endothelial inflammation therapy serves as a common underlying mechanism. This study provides a new understanding of DHI in clinical application on cardiovascular and cerebrovascular diseases.

CTRP3 protected against doxorubicin-induced cardiac dysfunction, inflammation and cell death via activation of Sirt1

BACKGROUND

Inflammation and myocytes apoptosis play critical roles in the development of doxorubicin (DOX)-induced cardiotoxicity. Our previous study found that C1q/tumour necrosis factor-related protein-3 (CTRP3) could inhibit cardiac inflammation and apoptosis of myocytes but its role in DOX-induced heart injury remains largely unknown. Our study aimed to investigate whether CTRP3 protected against DOX-induced heart injury and the underlying mechanism.

METHODS

We overexpressed CTRP3 in the hearts using an adeno-associated virus system. The mice were subjected to a single intraperitoneal injection of DOX (15mg/kg) to induce short-term model for cardiomyopathy. The morphological examination and biochemical analysis were used to evaluate the effects of CTRP3. H9C2 cells were used to verify the protective role of CTRP3 in vitro.

RESULTS

Myocardial CTRP3 protein levels were reduced in DOX-treated mice. Cardiac specific-overexpression of CTRP3 preserved heart dysfunction, and attenuated cardiac inflammation and cell loss induced by DOX in vivo and in vitro. CTRP3 could activate silent information regulator 1 (Sirt1) in vivo and in vitro. Moreover, specific inhibitor of Sirt1 and the silence of Sirt1 could abolish the protective effects of CTRP3 against DOX-induced inflammation and apoptosis.

CONCLUSION

CTRP3 protected against DOX-induced heart injury via activation of Sirt1. CTRP3 has therapeutic potential for the treatment of DOX cardiotoxicity.

Apigenin Attenuates Adriamycin-Induced Cardiomyocyte Apoptosis via the PI3K/AKT/mTOR Pathway

Treatment with Adriamycin (ADR) is one of the major causes of chemotherapy-induced cardiotoxicity and therefore is the principal limiting factor in the effectiveness of chemotherapy for cancer patients. Apigenin (API) has been shown to play a cardioprotective role. The present study examined the effect of API on ADR-induced cardiotoxicity in mice. Sixty male Kunming mice were randomly divided into 4 groups: a control group, ADR model group, low-dose API treatment group (125 mg·kg⁻¹), and high-dose API treatment group (250 mg·kg⁻¹). Blood samples were taken to evaluate a spectrum of myocardial enzymes. Cardiomyocyte apoptosis was measured using a TUNEL assay, and cardiomyocyte autophagy was observed using electron microscopy. Moreover, apoptosis-related proteins, such as Bax and Bcl-2, autophagy-related proteins, including Beclin1 and LC3B, and PI3K/AKT/mTOR pathway-related proteins were examined with western blot. Our results demonstrate that ADR caused an increase in the serum levels of cardiac injury markers and enhanced cardiomyocyte apoptosis and autophagy. API administration prevented the effects associated with ADR-induced cardiotoxicity in mice and inhibited ADR-induced apoptosis and autophagy. API also promoted PI3K/AKT/mTOR pathway activity in ADR-treated mice. In conclusion, API may have a protective effect against ADR-induced cardiotoxicity by inhibiting apoptosis and autophagy via activation of the PI3K/AKT/mTOR pathway.

NLRP3 signaling drives macrophage-induced adaptive immune suppression in pancreatic carcinoma

The tumor microenvironment (TME) in pancreatic ductal adenocarcinoma (PDA) is characterized by immune tolerance, which enables disease to progress unabated by adaptive immunity. However, the drivers of this tolerogenic program are incompletely defined. In this study, we found that NLRP3 promotes expansion of immune-suppressive macrophages in PDA. NLRP3 signaling in macrophages drives the differentiation of CD4+ T cells into tumor-promoting T helper type 2 cell (Th2 cell), Th17 cell, and regulatory T cell populations while suppressing Th1 cell polarization and cytotoxic CD8+ T cell activation. The suppressive effects of NLRP3 signaling were IL-10 dependent. Pharmacological inhibition or deletion of NLRP3, ASC (apoptosis-associated speck-like protein containing a CARD complex), or caspase-1 protected against PDA and was associated with immunogenic reprogramming of innate and adaptive immunity within the TME. Similarly, transfer of PDA-entrained macrophages or T cells from NLRP3-/- hosts was protective. These data suggest that targeting NLRP3 holds the promise for the immunotherapy of PDA.

The cardiac glycoside ouabain activates NLRP3 inflammasomes and promotes cardiac inflammation and dysfunction

Cardiac glycosides such as digoxin are Na⁺/K⁺-ATPase inhibitors that are widely used for the treatment of chronic heart failure and cardiac arrhythmias; however, recent epidemiological studies have suggested a relationship between digoxin treatment and increased mortality. We previously showed that nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing 3 (NLRP3) inflammasomes, which regulate caspase-1-dependent interleukin (IL)-1β release, mediate the sterile cardiovascular inflammation. Because the Na⁺/K⁺–ATPase is involved in inflammatory responses, we investigated the role of NLRP3 inflammasomes in the pathophysiology of cardiac glycoside-induced cardiac inflammation and dysfunction. The cardiac glycoside ouabain induced cardiac dysfunction and injury in wild-type mice primed with a low dose of lipopolysaccharide (LPS), although no cardiac dysfunction was observed in mice treated with either ouabain or LPS alone. Ouabain also induced cardiac inflammatory responses, such as macrophage infiltration and IL-1β release, when mice were primed with LPS. These cardiac manifestations were all significantly attenuated in mice deficient in IL-1β. Furthermore, deficiency of NLRP3 inflammasome components, NLRP3 and caspase-1, also attenuated ouabain-induced cardiac dysfunction and inflammation. In vitro experiments revealed that ouabain induced NLRP3 inflammasome activation as well as subsequent IL-1β release from macrophages, and this activation was mediated by K⁺ efflux. Our findings demonstrate that cardiac glycosides promote cardiac inflammation and dysfunction through NLRP3 inflammasomes and provide new insights into the mechanisms underlying the adverse effects of cardiac glycosides.

Mechanisms of Organ Injury and Repair by Macrophages

Macrophages regulate tissue regeneration following injury. They can worsen tissue injury by producing reactive oxygen species and other toxic mediators that disrupt cell metabolism, induce apoptosis, and exacerbate ischemic injury. However, they also produce a variety of growth factors, such as IGF-1, VEGF-α, TGF-β, and Wnt proteins that regulate epithelial and endothelial cell proliferation, myofibroblast activation, stem and tissue progenitor cell differentiation, and angiogenesis. Proresolving macrophages in turn restore tissue homeostasis by functioning as anti-inflammatory cells, and macrophage-derived matrix metalloproteinases regulate fibrin and collagen turnover. However, dysregulated macrophage function impairs wound healing and contributes to the development of fibrosis. Consequently, the mechanisms that regulate these different macrophage activation states have become active areas of research. In this review, we discuss the common and unique mechanisms by which macrophages instruct tissue repair in the liver, nervous system, heart, lung, skeletal muscle, and intestine and illustrate how macrophages might be exploited therapeutically.