Curcumin retunes cholesterol transport homeostasis and inflammation response in M1 macrophage to prevent atherosclerosis

PPARs in atherosclerosis: The spatial and temporal features from mechanism to druggable targets

BACKGROUND

Atherosclerosis is a chronic and complex disease caused by lipid disorder, inflammation, and other factors. It is closely related to cardiovascular diseases, the chief cause of death globally. Peroxisome proliferator-activated receptors (PPARs) are valuable anti-atherosclerosis targets that showcase multiple roles at different pathological stages of atherosclerosis and for cell types at different tissue sites.

AIM OF REVIEW

Considering the spatial and temporal characteristics of the pathological evolution of atherosclerosis, the roles and pharmacological and clinical studies of PPARs were summarized systematically and updated under different pathological stages and in different vascular cells of atherosclerosis. Moreover, selective PPAR modulators and PPAR-pan agonists can exert their synergistic effects meanwhile reducing the side effects, thereby providing novel insight into future drug development for precise spatial-temporal therapeutic strategy of anti-atherosclerosis targeting PPARs.

KEY SCIENTIFIC

Concepts of Review: Based on the spatial and temporal characteristics of atherosclerosis, we have proposed the importance of stage- and cell type-dependent precision therapy. Initially, PPARs improve endothelial cells' dysfunction by inhibiting inflammation and oxidative stress and then regulate macrophages' lipid metabolism and polarization to improve fatty streak. Finally, PPARs reduce fibrous cap formation by suppressing the proliferation and migration of vascular smooth muscle cells (VSMCs). Therefore, research on the cell type-specific mechanisms of PPARs can provide the foundation for space-time drug treatment. Moreover, pharmacological studies have demonstrated that several drugs or compounds can exert their effects by the activation of PPARs. Selective PPAR modulators (that specifically activate gene subsets of PPARs) can exert tissue and cell-specific effects. Furthermore, the dual- or pan-PPAR agonist could perform a better role in balancing efficacy and side effects. Therefore, research on cells/tissue-specific activation of PPARs and PPAR-pan agonists can provide the basis for precision therapy and drug development of PPARs.

Curcumin-Based Fixed Dose Combination Products for Cholesterol Management: A Narrative Review

Curcumin, a polyphenol compound that belongs to a class of molecules known as curcuminoids, may interact with various biological macromolecules in the body, including proteins, nucleic acids, and lipids. Curcumin-based fixed-dose combination (FDC) products enhance curcumin stability and bioavailability for better clinical use in cholesterol management. Preclinical studies on curcumin and cholesterol are mostly positive. Obstacles are the variable composition of the many different curcumin-based FDC products, the lack of standards, and the limitation of the randomized controlled trials (RCTs) conducted for specific products. Once these downfalls have been addressed, curcumin-based FDC products have great potential for cholesterol management. They can supplement the uptake of statins, reducing their dosage for the same controlling effects or even replacing them.

Review of the Protective Mechanism of Curcumin on Cardiovascular Disease

Cardiovascular diseases (CVDs) are the most common cause of death worldwide and has been the focus of research in the medical community. Curcumin is a polyphenolic compound extracted from the root of turmeric. Curcumin has been shown to have a variety of pharmacological properties over the past decades. Curcumin can significantly protect cardiomyocyte injury after ischemia and hypoxia, inhibit myocardial hypertrophy and fibrosis, improve ventricular remodeling, reduce drug-induced myocardial injury, improve diabetic cardiomyopathy(DCM), alleviate vascular endothelial dysfunction, inhibit foam cell formation, and reduce vascular smooth muscle cells(VSMCs) proliferation. Clinical studies have shown that curcumin has a protective effect on blood vessels. Toxicological studies have shown that curcumin is safe. But high doses of curcumin also have some side effects, such as liver damage and defects in embryonic heart development. This article reviews the mechanism of curcumin intervention on CVDs in recent years, in order to provide reference for the development of new drugs in the future.

Analysis of subsets and localization of macrophages in skin lesions and peripheral blood of patients with keloids

Keloids are a type of abnormal fibrous proliferation disease of the skin, characterized by local inflammation that lacks clear pathogenesis and satisfactory treatment. The phenomenon of distinct phenotypes, including M1 and M2 macrophages, is called macrophage polarization. Recently, macrophage polarization has been suggested to play a role in keloid formation. This study aimed to evaluate the relation between macrophage polarization and keloids and identify novel effective treatments for keloids. Differentially expressed genes were identified via RNA sequencing of the skin tissue of healthy controls and patients with keloids and validated using quantitative PCR. Multiplex immunofluorescence microscopy was used to detect different phenotypes of macrophages in keloid tissues. Finally, quantitative PCR validation of differentially expressed genes and flow cytometry were used to analyze macrophages in the peripheral blood of healthy controls and patients with keloids. Total and M2 macrophages were significantly increased in the local skin tissue and peripheral blood of patients with keloids compared with healthy controls. In addition, inflammation- and macrophage polarization-related differentially expressed genes in keloid tissue showed similar expression patterns in the peripheral blood. This study highlighted an increased frequency of total macrophages and M2 polarization in the local skin tissue and peripheral blood of patients with keloids. This systematic macrophage polarization tendency also indicates a potential genetic predisposition to keloids. These findings suggest the possibility of developing new diagnostic and therapeutic indicators for keloids focusing on macrophages.

Is the suppression of CD36 a promising way for atherosclerosis therapy?

Atherosclerosis is the main underlying pathology of many cardiovascular diseases and is marked by plaque formation in the artery wall. It has posed a serious threat to the health of people all over the world. CD36 acts as a significant regulator of lipid homeostasis, which is closely associated with the onset and progression of atherosclerosis and may be a new therapeutic target. The abnormal overexpression of CD36 facilitates lipid accumulation, foam cell formation, inflammation, endothelial apoptosis, and thrombosis. Numerous natural products and lipid-lowering agents are found to target the suppression of CD36 or inhibit the upregulation of CD36 to prevent and treat atherosclerosis. Here, the structure, expression regulation and function of CD36 in atherosclerosis and its related pharmacological therapies are reviewed. This review highlights the importance of drugs targeting CD36 suppression in the treatment and prevention of atherosclerosis, in order to develop new therapeutic strategies and potential anti-atherosclerotic drugs both preclinically and clinically.

Anti-atherosclerosis mechanisms associated with regulation of non-coding RNAs by active monomers of traditional Chinese medicine

Atherosclerosis is the leading cause of numerous cardiovascular diseases with a high mortality rate. Non-coding RNAs (ncRNAs), RNA molecules that do not encode proteins in human genome transcripts, are known to play crucial roles in various physiological and pathological processes. Recently, researches on the regulation of atherosclerosis by ncRNAs, mainly including microRNAs, long non-coding RNAs, and circular RNAs, have gradually become a hot topic. Traditional Chinese medicine has been proved to be effective in treating cardiovascular diseases in China for a long time, and its active monomers have been found to target a variety of atherosclerosis-related ncRNAs. These active monomers of traditional Chinese medicine hold great potential as drugs for the treatment of atherosclerosis. Here, we summarized current advancement of the molecular pathways by which ncRNAs regulate atherosclerosis and mainly highlighted the mechanisms of traditional Chinese medicine monomers in regulating atherosclerosis through targeting ncRNAs.

Regulation of Acetylation States by Nutrients in the Inhibition of Vascular Inflammation and Atherosclerosis

Atherosclerosis (AS) is a chronic metabolic disorder and primary cause of cardiovascular diseases, resulting in substantial morbidity and mortality worldwide. Initiated by endothelial cell stimulation, AS is characterized by arterial inflammation, lipid deposition, foam cell formation, and plaque development. Nutrients such as carotenoids, polyphenols, and vitamins can prevent the atherosclerotic process by modulating inflammation and metabolic disorders through the regulation of gene acetylation states mediated with histone deacetylases (HDACs). Nutrients can regulate AS-related epigenetic states via sirtuins (SIRTs) activation, specifically SIRT1 and SIRT3. Nutrient-driven alterations in the redox state and gene modulation in AS progression are linked to their protein deacetylating, anti-inflammatory, and antioxidant properties. Nutrients can also inhibit advanced oxidation protein product formation, reducing arterial intima-media thickness epigenetically. Nonetheless, knowledge gaps remain when it comes to understanding effective AS prevention through epigenetic regulation by nutrients. This work reviews and confirms the underlying mechanisms by which nutrients prevent arterial inflammation and AS, focusing on the epigenetic pathways that modify histones and non-histone proteins by regulating redox and acetylation states through HDACs such as SIRTs. These findings may serve as a foundation for developing potential therapeutic agents to prevent AS and cardiovascular diseases by employing nutrients based on epigenetic regulation.

Oxidized low-density lipoprotein regulates macrophage polarization in atherosclerosis

Atherosclerosis is the pathological basis of acute cardiovascular and cerebrovascular diseases. Oxidized LDL has been recognized as a major atherogenic factor in the vessel wall for decades. A growing body of evidence suggests that oxidized LDL modulates macrophage phenotypes in atherosclerosis. This article reviews the research progress on the regulation of macrophage polarization by oxidized LDL. Mechanistically, oxidized LDL induces macrophage polarization via cell signaling, metabolic reprogramming, epigenetic regulation, and intercellular regulation. This review is expected to provide new targets for the treatment of atherosclerosis.

Research progress on the active ingredients of traditional Chinese medicine in the intervention of atherosclerosis: A promising natural immunotherapeutic adjuvant

Atherosclerosis (AS) is a chronic inflammatory disease caused by disorders of lipid metabolism. Abnormal deposition of low-density lipoproteins in the arterial wall stimulates the activation of immune cells, including the adhesion and infiltration of monocytes, the proliferation and differentiation of macrophages and lymphocytes, and the activation of their functions. The complex interplay between immune cells coordinates the balance between pro- and anti-inflammation and plays a key role in the progression of AS. Therefore, targeting immune cell activity may lead to the development of more selective drugs with fewer side effects to treat AS without compromising host defense mechanisms. At present, an increasing number of studies have found that the active ingredients of traditional Chinese medicine (TCM) can regulate the function of immune cells in multiple ways to against AS, showing great potential for the treatment of AS and promising clinical applications. In this paper, we review the mechanisms of immune cell action in AS lesions and the potential targets and/or pathways for immune cell regulation by the active ingredients of TCM to promote the understanding of the immune system interactions of AS and provide a relevant basis for the use of active ingredients of TCM as natural adjuvants for AS immunotherapy.

Lipid Droplet Protein PLIN1 Regulates Inflammatory Polarity in Human Macrophages and is Involved in Atherosclerotic Plaque Development by Promoting Stable Lipid Storage

AIM

Perilipins (PLINs), peripheral lipid droplet (LD) proteins, play important roles in lipid accumulation and maturation in adipocytes. The relationship between PLIN family proteins and macrophage polarization in atherosclerosis has not been elucidated.

METHODS

The experiments used tissues from human arteries of 65 patients who had undergone a carotid endarterectomy, and cultured macrophages generated from healthy human peripheral blood mononuclear cells.

RESULTS

Plaque immunohistochemistry demonstrated co-expression of PLIN1 and PLIN2 in both symptomatic (n=31) and asymptomatic patients (n=34). PLIN2 mRNA expression increased 3.38-fold in the symptomatic group compared with those from asymptomatic. PLIN1 was not expressed on small LDs at a shorter incubation but was on large LDs at longer incubation with oxidized LDL and VLDL, while PLIN2 was observed after 24 h and increased with a longer incubation in cultured M1 macrophage. In M2 macrophages, PLIN1 was seen as early as 24 h following incubation with VLDL, and LD size increased with longer incubation. PLIN1 overexpression increased the size of LDs in M1 macrophages, even after a short incubation, and reduced the RNA expression of TNFA, MMP2, ABCA1, and ABCG1 versus the M1 control. Conversely, silencing of PLIN1 in M2 macrophages had the opposite effects on LD size and RNA expression.

CONCLUSION

There was a relationship between macrophage polarity, cytosolic LD size, and PLIN1/PLIN2 expression levels. PLIN2 was mainly expressed in arterial plaques in symptomatic stroke patients, and associated with the inflammatory phenotype of human macrophages, while PLIN1 expression is closely associated with plaque stability and the anti-inflammatory phenotype.

Epigenetic regulation of macrophage polarization in wound healing

The immune microenvironment plays a critical role in regulating skin wound healing. Macrophages, the main component of infiltrating inflammatory cells, play a pivotal role in shaping the immune microenvironment in the process of skin wound healing. Macrophages comprise the classic proinflammatory M1 subtype and anti-inflammatory M2 population. In the early inflammatory phase of skin wound closure, M1-like macrophages initiate and amplify the local inflammatory response to disinfect the injured tissue. In the late tissue-repairing phase, M2 macrophages are predominant in wound tissue and limit local inflammation to promote tissue repair. The biological function of macrophages is tightly linked with epigenomic organization. Transcription factors are essential for macrophage polarization. Epigenetic modification of transcription factors determines the heterogeneity of macrophages. In contrast, transcription factors also regulate the expression of epigenetic enzymes. Both transcription factors and epigenetic enzymes form a complex network that regulates the plasticity of macrophages. Here, we describe the latest knowledge concerning the potential epigenetic mechanisms that precisely regulate the biological function of macrophages and their effects on skin wound healing.

Epigenetic signature in neural plasticity: the journey so far and journey ahead

Neural plasticity is a remarkable characteristic of the brain which allows neurons to rewire their structure in response to internal and external stimuli. Many external stimuli collectively referred to as 'epigenetic factors' strongly influence structural and functional reorganization of the brain, thereby acting as a potential driver of neural plasticity. DNA methylation and demethylation, histone acetylation, and deacetylation are some of the frontline epigenetic mechanisms behind neural plasticity. Epigenetic signature molecules (mostly proteins) play a pivotal role in epigenetic reprogramming. Though neuro-epigenetics is an incredibly important field of emerging research, the critical role of signature proteins associated with epigenetic alteration and their involvement in neural plasticity needs further attention. This study gives an integrated and systematic overview of the current state of knowledge with a clear idea of types of neural plasticity and the context-dependent role of epigenetic signature molecules and their modulation by some natural bioactive compounds.

Salvianolic acid B inhibits RAW264.7 cell polarization towards the M1 phenotype by inhibiting NF-κB and Akt/mTOR pathway activation

M1 macrophages secrete a large number of proinflammatory factors and promote the expansion of atherosclerotic plaques and processes. Salvianolic acid B (Sal B) exerts anti-inflammatory, antitumor and other effects, but no study has addressed whether Sal B can regulate the polarization of macrophages to exert these anti-atherosclerotic effects. Therefore, we investigated the inhibition of Sal B in M1 macrophage polarization and the underlying mechanism. The effects of different treatments on cell viability, gene expression and secretion of related proteins, phenotypic markers and cytokines were detected by MTT and western blot assays, RT‒qPCR and ELISAs. Cell viability was not significantly changed when the concentration of Sal B was less than 200 μM, and Lipopolysaccharide (LPS) (100 ng/mL) + interferon-γ (IFN-γ) (2.5 ng/mL) successfully induced M1 polarization. RT‒qPCR and ELISAs indicated that Sal B can downregulate M1 marker (Inducible Nitric Oxide Synthase (iNOS), Tumor Necrosis Factor-α (TNF-α), and Interleukin-6 (IL-6)) and upregulate M2 marker (Arginase-1 (Arg-1) and Interleukin-10 (IL-10)) expression. Western blotting was performed to measure the expression of Nuclear Factor-κB (NF-κB), p-Akt, p-mTOR, LC3-II, Beclin-1, and p62, and the results suggested that Sal B inhibits the M1 polarization of RAW264.7 macrophages by promoting autophagy via the NF-κB signalling pathway. The study indicated that Sal B inhibits M1 macrophage polarization by inhibiting NF-κB signalling pathway activation and downregulating Akt/mTOR activation to promote autophagy.

Potential Therapeutic Agents That Target ATP Binding Cassette A1 (ABCA1) Gene Expression

The cholesterol efflux protein ATP binding cassette protein A1 (ABCA) and apolipoprotein A1 (apo A1) are key constituents in the process of reverse-cholesterol transport (RCT), whereby excess cholesterol in the periphery is transported to the liver where it can be converted primarily to bile acids for either use in digestion or excreted. Due to their essential roles in RCT, numerous studies have been conducted in cells, mice, and humans to more thoroughly understand the pathways that regulate their expression and activity with the goal of developing therapeutics that enhance RCT to reduce the risk of cardiovascular disease. Many of the drugs and natural compounds examined target several transcription factors critical for ABCA1 expression in both macrophages and the liver. Likewise, several miRNAs target not only ABCA1 but also the same transcription factors that are critical for its high expression. However, after years of research and many preclinical and clinical trials, only a few leads have proven beneficial in this regard. In this review we discuss the various transcription factors that serve as drug targets for ABCA1 and provide an update on some important leads.

Effects of curcumin on low-density lipoprotein oxidation: From experimental studies to clinical practice

Atherosclerosis is the most frequent cause of death globally. Oxidized low-density lipoprotein (ox-LDL) has an essential role in the formation of atherosclerotic plaques and foamy macrophages. Ox-LDL increases the uptake of cholesterol by macrophages and is the major cause of blood flow disruption. Ox-LDL is produced during oxidative stress and treatment with antioxidants could inhibit the production and function of ox-LDL. Curcumin is a potent antioxidant and has a strong track record in the treatment of numerous diseases. Recent studies indicate that Curcumin exerts a lipid-lowering effect, and can modulate the formation of atherosclerotic plaque. The current review focuses upon the role of Curcumin in oxidation of LDL and foam cell formation in atherosclerotic lesions.

Macrophage polarization by potential nutraceutical compounds: A strategic approach to counteract inflammation in atherosclerosis

Chronic inflammation represents a main event in the onset and progression of atherosclerosis and is closely associated with oxidative stress in a sort of vicious circle that amplifies and sustains all stages of the disease. Key players of atherosclerosis are monocytes/macrophages. According to their pro- or anti-inflammatory phenotype and biological functions, lesional macrophages can release various mediators and enzymes, which in turn contribute to plaque progression and destabilization or, alternatively, lead to its resolution. Among the factors connected to atherosclerotic disease, lipid species carried by low density lipoproteins and pro-oxidant stimuli strongly promote inflammatory events in the vasculature, also by modulating the macrophage phenotyping. Therapies specifically aimed to balance macrophage inflammatory state are increasingly considered as powerful tools to counteract plaque formation and destabilization. In this connection, several molecules of natural origin have been recognized to be active mediators of diverse metabolic and signaling pathways regulating lipid homeostasis, redox state, and inflammation; they are, thus, considered as promising candidates to modulate macrophage responsiveness to pro-atherogenic stimuli. The current knowledge of the capability of nutraceuticals to target macrophage polarization and to counteract atherosclerotic lesion progression, based mainly on in vitro investigation, is summarized in the present review.

Self-oxygenation mesoporous MnO2 nanoparticles with ultra-high drug loading capacity for targeted arteriosclerosis therapy

Atherosclerosis (AS) is a leading cause of vascular diseases that severely threats the human health due to the lack of efficient therapeutic methods. During the development and progress of AS, macrophages play critical roles, which are polarized into pro-inflammatory M1 phenotype to excrete abundant cytokines and overproduce reactive oxygen species (ROS), and take up excess amount of lipid to form foam cells. In this work, we developed a MnO₂-based nanomedicine to re-educate macrophages for targeting AS therapy. The MnO₂ was one-pot synthesized under mild condition, showing intrinsic catalase-mimic activity for self-oxygenation by using endogenous H₂O₂ as substrate. Moreover, the mesoporous structure as well as the abundant metal coordination sites in MnO₂ structure facilitated the loading of an anti-AS drug of curcumin (Cur), achieving extraordinarily high drug loading capacity of 54%. Cur displayed a broad spectrum of anti-oxidant and anti-inflammatory capabilities to repolarize M1 macrophages into M2 phenotype, and the catalytic MnO₂ recovered the function of lipid efflux transporter to remove lipid from cells by suppressing HIF-1α. Collectively, the nanocarrier and the payload drug functioned as an all-active nanoplatform to synergistically alleviate the syndromes of AS. In ApoE−/− mice model, the nanosystem could significantly prolong the circulation half-life of Cur by sixfold, and enhance drug accumulation in atherosclerotic lesion by 3.5-fold after intravenous injection by virtue of surface hyaluronic acid (HA) modification. As a result, a robust anti-AS efficacy was achieved as evidenced by the decrease of atherosclerotic lesion, plaque area, lipid level.

Curcumin improves atherosclerosis by inhibiting the epigenetic repression of lncRNA MIAT to miR-124

Objectives: Atherosclerosis is a dominant cardiovascular disease. Curcumin has protective effect on atherosclerosis. However, the mechanisms remain to be explored. Methods: Atherosclerosis was induced by feeding mice with high-fat diet (HFD) and ox-low-density lipoprotein (LDL)-induced human umbilical vein endothelial cells (HUVECs) were structured. Oil Red O staining was used to evaluate the plaques in the artery. Quantitative real-time PCR (qRT-PCR) was conducted to detect the level of myocardial infarction associated transcript (MIAT), miR-124, and enhancer of zeste homolog 2 (EZH2). We performed western blotting and enzyme linked immunosorbent assay to examine the expression of EZH2 and cytokines including IL-1β, TNFα, IL-6, and IL-8, respectively. RNA immunoprecipitation and chromatin immunoprecipitation (ChIP) were used to validate the interaction between myocardial infarction associated transcript and EZH2. Flow cytometry and CCK-8 assay were used to examine cell apoptosis and proliferation, respectively. Results: Curcumin suppressed inflammation in atherosclerosis mouse model and ox-LDL-induced cell model. MIAT overexpression and miR-124 inhibition relieved the anti-inflammation effect of curcumin in ox-LDL-induced cell. MIAT regulated miR-124 by interacting with EZH2. Curcumin relieved ox-LDL-induced cell inflammation via regulating MIAT/miR-124 pathway. Conclusion: MIAT/miR-124 axis mediated the effect of curcumin on atherosclerosis and altered cell apoptosis and proliferation, both in vivo and in vitro. These data further support the application of curcumin in control of atherosclerosis advancement.

Curcumin promotes cholesterol efflux by regulating ABCA1 expression through miR-125a-5p/SIRT6 axis in THP-1 macrophage to prevent atherosclerosis

OBJECTIVE

To seek out the effect of curcumin on cholesterol efflux in THP-1 macrophages and clarify its specific mechanism.

METHODS

THP-1 macrophages were cultured with curcumin at different concentrations, followed by detection of the toxicity of curcumin to cells utilizing CCK-8 assay. Following culturing with serum-free ox-LDL, THP-1 macrophages were transfected with mi-miR-125a-5p, or in-miR-125a-5p, or pcDNA3.1-SIRT6, or si-SIRT6 for 24 hr, prior to treatment with curcumin at different concentrations. Oil red O staining was applied to examine the formation rate of foam cells, the kits were used for measuring intracellular lipid content of THP-1 macrophages, and the fluorescence detection kit for observing the cholesterol efflux rate. The expressions of miR-125a-5p, SIRT6, and ABCA1 were assayed by qRT-PCR and Western blot. ELISA was adopted to assess the contents of TNF-α, IL-6, and MCP-1. The interaction between miR-125a-5p and SIRT6 was evaluated by dual-luciferase reporter gene assay.

RESULTS

The optimal dosage of curcumin could reduce foam cell formation and intracellular lipid content, and promote cholesterol efflux in THP-1 macrophages. Meanwhile, curcumin markedly suppressed the expression of miR-125a-5p and upregulated the expression of SIRT6. MiR-125a-5p negatively targeted SIRT6. Overexpression of SIRT6 partially reversed the inhibition role of miR-125a-5p mimic in the biological function of curcumin. Silencing of SIRT6 could partially reverse the effect of the miR-125a-5p inhibitor on the biological function of curcumin.

CONCLUSION

urcumin could promote cholesterol efflux of THP-1 macrophages through miR-125a-5p/SIRT6 axis and regulate the expression of ABCA1.

Targeting interleukin-β by plant-derived natural products: Implications for the treatment of atherosclerotic cardiovascular disease

Inflammation is the main contributing factor to atheroma formation in atherosclerosis. Interleukin-1 beta (IL-1β) is an inflammatory mediator found in endothelial cells and resident leukocytes. Canakinumab is a selective monoclonal antibody against IL-1β which attenuates inflammation and concurrently precipitates fatal infections and sepsis. Natural products derived from medicinal plants, herbal remedy and functional foods are widely used nowadays. Experimental and clinical trial evidence supports that some natural products such as curcumin, resveratrol, and quercetin have potential effects on IL-1β suppression. In this review, we tried to document findings that used medicinal plants and plant-based natural products for treating atherosclerosis and its related diseases through the suppression of IL-1β.

Curcumin as a Natural Remedy for Atherosclerosis: A Pharmacological Review

Curcumin, a natural polyphenolic compound present in Curcuma longa L. rhizomes, shows potent antioxidant, anti-inflammatory, anti-cancer, and anti-atherosclerotic properties. Atherosclerosis is a comprehensive term for a series of degenerative and hyperplasic lesions such as thickening or sclerosis in large- and medium-sized arteries, causing decreased vascular-wall elasticity and lumen diameter. Atherosclerotic cerebro-cardiovascular disease has become a major concern for human health in recent years due to its clinical sequalae of strokes and heart attacks. Curcumin concoction treatment modulates several important signaling pathways related to cellular migration, proliferation, cholesterol homeostasis, inflammation, and gene transcription, among other relevant actions. Here, we provide an overview of curcumin in atherosclerosis prevention and disclose the underlying mechanisms of action of its anti-atherosclerotic effects.

Catalpol Inhibits Macrophage Polarization and Prevents Postmenopausal Atherosclerosis Through Regulating Estrogen Receptor Alpha

Lacking estrogen increases the risk of atherosclerosis (AS) in postmenopausal women. Inflammation plays a vital role in the pathological process of AS, and macrophages are closely related to inflammation. Catalpol is an iridoid glucoside extracted from the fresh roots of the traditional Chinese herb Rehmanniae radix preparata. In this study, we aimed to evaluate the effects of catalpol on macrophage polarization and postmenopausal AS. In addition, we investigated whether the mechanism of catalpol was dependent on regulating the expression of estrogen receptors (ERs). In vitro, lipopolysaccharides (LPS) and interferon-γ (IFN-γ) were applied to induce M1 macrophage polarization. In vivo, the ApoE^−/− mice were fed with a high-fat diet to induce AS, and ovariectomy was operated to mimic the estrogen cessation. We demonstrated catalpol inhibited M1 macrophage polarization induced by LPS and INF-γ, and eliminated lipid accumulation in postmenopausal AS mice. Catalpol not only suppressed the inflammatory response but also reduced the level of oxidative stress. Then, ERs (ERα and ERβ) inhibitors and ERα siRNA were also applied in confirming that the protective effect of catalpol was mediated by ERα, rather than ERβ. In conclusion, catalpol significantly inhibited macrophage polarization and prevented postmenopausal AS by increasing ERα expression.

Anti-atherosclerotic Effects of Spice-Derived Phytochemicals

Cardiovascular diseases are the leading cause of death in the world. Atherosclerosis is characterized by oxidized lipid deposition and inflammation in the arterial wall and represents a significant problem in public health and medicine. Some dietary spices have been widely used in many countries; however, the mechanism of their action as it relates to the prevention and treatment of atherosclerosis is still poorly understood. In this review, we focus on the properties of various spice-derived active ingredients used in the prevention and treatment of atherosclerosis, as well as associated atherosclerotic risk factors. We provide a summary of the mechanisms of action, epidemiological analyses, and studies of various components of spice used in the clinic, animal models, and cell lines related to atherosclerosis. Most notably, we focused on mechanisms of action by which these spice-derived compounds elicit their lipid-lowering, anti-inflammatory, antioxidant, and immunomodulatory properties, as well as their involvement in selected biochemical and signal transduction pathways. It is suggested that future research should aim to design well-controlled clinical trials and more thoroughly investigate the role of spices and their active components in the prevention/treatment of atherosclerosis. Based on this literature review, it appears that spices and their active components are well tolerated and have few adverse side effects and, therefore, provide a promising adjunctive treatment strategy for patients with atherosclerosis.

Curcumin promotes AApoAII amyloidosis and peroxisome proliferation in mice by activating the PPARα signaling pathway

Curcumin is a polyphenol compound that exhibits multiple physiological activities. To elucidate the mechanisms by which curcumin affects systemic amyloidosis, we investigated amyloid deposition and molecular changes in a mouse model of amyloid apolipoprotein A-II (AApoAII) amyloidosis, in which mice were fed a curcumin-supplemented diet. Curcumin supplementation for 12 weeks significantly increased AApoAII amyloid deposition relative to controls, especially in the liver and spleen. Liver weights and plasma ApoA-II and high-density lipoprotein concentrations were significantly elevated in curcumin-supplemented groups. RNA-sequence analysis revealed that curcumin intake affected hepatic lipid metabolism via the peroxisome proliferator-activated receptor (PPAR) pathway, especially PPARα activation, resulting in increased Apoa2 mRNA expression. The increase in liver weights was due to activation of PPARα and peroxisome proliferation. Taken together, these results demonstrate that curcumin is a PPARα activator and may affect expression levels of proteins involved in amyloid deposition to influence amyloidosis and metabolism in a complex manner.

Effects of phytochemicals on macrophage cholesterol efflux capacity: Impact on atherosclerosis

High-density lipoprotein cholesterol (HDL) is the major promoter of reverse cholesterol transport and efflux of excess cellular cholesterol. The functions of HDL, such as cholesterol efflux, are associated with cardiovascular disease rather than HDL levels. We have reviewed the evidence base on the major classes of phytochemicals, including polyphenols, alkaloids, carotenoids, phytosterols, and fatty acids, and their effects on macrophage cholesterol efflux and its major pathways. Phytochemicals show the potential to improve the efficiency of each of these pathways. The findings are mainly in preclinical studies, and more clinical research is warranted in this area to develop novel clinical applications.

Potential roles of dietary flavonoids from Citrus aurantium L. var. amara Engl. in atherosclerosis development

Dietary consumption of flavonoids correlated positively with lower risk of cardiovascular disease. However, the precise roles of flavonoids from the blossoms of Citrus aurantium Linn variant amara Engl (CAVA) in atherosclerosis (AS) are still poorly understood. This study aimed to find novel flavonoid-type skeletons with protection against AS. Total flavonoids (CAVAF), homoeriodictyol (HE) and hesperetin-7-O-β-d-glucopyranoside (HG) were isolated from the blossoms of Citrus aurantium Linn variant amara Engl. by chromatography. Their suppressive effects on lipopolysaccharide (LPS)-induced inflammatory responses and ox-LDL-induced foam cell formation were systematically and comparatively investigated using macrophage RAW264.7 cells. HE was more powerful than HG in inhibiting LPS-induced production of nitric oxide (NO), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), interleukin-1 beta (IL-1β) and gene expression in RAW264.7 cells. HE and HG showed different responses to extracellular signal-regulated kinases (ERK), c-Jun N-terminal kinases (JNK), P38, P65, IκBα, IκKα/β phosphorylation, and nuclear factor-kappa B (NF-κB) nuclear translocation. HE and HG also differentially decreased oxidized low-density lipoprotein (ox-LDL)-induced foam cell formation by regulating peroxisome proliferator-activated receptor-gamma (PPARγ), phospholipid ATP-binding cassette transporter A1 (ABCA1), phospholipid ATP-binding cassette transporter G1 (ABCG1), scavenger receptor class B type I (SRB1), scavenger receptor class A type I (SRA1) and cluster of differentiation 36 (CD36) expression at gene and protein levels in RAW264.7 cells. HG showed weaker potential than HE in preventing AS development. Their chemical differences might partially explain the discrepancy in their bioactivity. In conclusion, HE and HG might be developed into novel therapeutic agents against inflammation and AS-associated diseases.

Shen-Hong-Tong-Luo Formula Attenuates Macrophage Inflammation and Lipid Accumulation through the Activation of the PPAR-γ/LXR-α/ABCA1 Pathway

Atherosclerosis (AS) is the killer of human health and longevity, which is majorly caused by oxidized lipoproteins that attack macrophages in the endarterium. The Shen-Hong-Tong-Luo (SHTL) formula has shown great clinical efficacy and vascular protective effect for over 30 years in China, to attenuate AS progression. However, its pharmacological mechanism needs more investigation. In this study, we first investigated the chemical composition of SHTL by fingerprint analysis using high-performance liquid chromatography. In primary mouse peritoneal macrophages induced by lipopolysaccharide (LPS), we found that SHTL pretreatment suppressed reactive oxygen species accumulation and reversed the increases of the inflammatory factors, TNF-α and IL-6. Moreover, lipid accumulation induced by oxidized low-density lipoprotein (Ox-LDL) in macrophages was inhibited by SHTL. Additionally, network pharmacology was used to predict the potential targets of SHTL as the PPAR-γ/LXR-α/ABCA1 signaling pathway, which was validated in macrophages and ApoE^-/- mice by histopathological staining, qPCR, and Western blot analysis. Importantly, the protective effect of SHTL in the LPS- and Ox-LDL-induced macrophages against inflammation and lipid accumulation was attenuated by GW9662, a PPAR-γ antagonist, which confirmed the prediction results of network pharmacology. In summary, these results indicated that SHTL pretreatment reduced inflammation and lipid accumulation of macrophages by activating the PPAR-γ/LXR-α/ABCA1 pathway, which may provide a new insight into the mechanism of SHTL in the suppression of AS progression.

Bergaptol from blossoms of Citrus aurantium L. var. amara Engl inhibits LPS-induced inflammatory responses and ox-LDL-induced lipid deposition

Aberrant activation of inflammation and excess accumulation of lipids play pivotal roles in atherosclerosis (AS) progression. Constituents from Citrus aurantium Linn variant amara Engl (CAVA) were effectively investigated for their various bioactivities, especially anti-inflammation. Bergaptol (BER) is particularly abundant in Citrus products. Accumulating studies have confirmed its predominant anti-cancer and antioxidant functions, whereas few studies focused on its antiatherogenic functions. In the current study, BER was isolated from CAVA for the first time. Macrophages were stimulated with lipopolysaccharides (LPSs) or oxidized low-density lipoproteins (ox-LDL) to mimic inflammatory responses and AS development. BER treatment significantly inhibited LPS-induced production of nitric oxide (NO), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α), and gene expression of inducible nitric oxide synthase (iNOS), IL-6, TNF-α, interleukin-1 beta (IL-1β) and cyclooxygenase-2 (COX-2). BER also potently blocked LPS-induced mitogen-activated protein kinase (MAPK) phosphorylation and nuclear factor-kappa B (NF-κB) activation, as evidenced by the inhibitory effects on c-Jun N-terminal kinase (JNK), P38, P65, IκBα and IκKα/β phosphorylation, and NF-κB nuclear translocation. Furthermore, BER treatment markedly mitigated ox-LDL-induced foam cell formation by inhibiting scavenger receptor class A type I (SRA1) and cluster of differentiation 36 (CD36)-dependent cholesterol uptake. In conclusion, BER might be a novel therapeutic agent for AS prevention through inhibiting inflammatory responses and cholesterol uptake.

Phenolic Compounds Exerting Lipid-Regulatory, Anti-Inflammatory and Epigenetic Effects as Complementary Treatments in Cardiovascular Diseases

Atherosclerosis is the main process behind cardiovascular diseases (CVD), maladies which continue to be responsible for up to 70% of death worldwide. Despite the ongoing development of new and potent drugs, their incomplete efficacy, partial intolerance and numerous side effects make the search for new alternatives worthwhile. The focus of the scientific world turned to the potential of natural active compounds to prevent and treat CVD. Essential for effective prevention or treatment based on phytochemicals is to know their mechanisms of action according to their bioavailability and dosage. The present review is focused on the latest data about phenolic compounds and aims to collect and correlate the reliable existing knowledge concerning their molecular mechanisms of action to counteract important risk factors that contribute to the initiation and development of atherosclerosis: dyslipidemia, and oxidative and inflammatory-stress. The selection of phenolic compounds was made to prove their multiple benefic effects and endorse them as CVD remedies, complementary to allopathic drugs. The review also highlights some aspects that still need clear scientific explanations and draws up some new molecular approaches to validate phenolic compounds for CVD complementary therapy in the near future.

Impact of natural products on the cholesterol transporter ABCA1

ETHNOPHARMACOLOGICAL RELEVANCE

In different countries and areas of the world, traditional medicine has been and is still used for the treatment of various disorders, including chest pain or liver complaints, of which we now know that they can be linked with altered lipid and cholesterol homeostasis. As ATP-binding cassette transporter A1 (ABCA1) plays an essential role in cholesterol metabolism, its modulation may be one of the molecular mechanisms responsible for the experienced benefit of traditional recipes. Intense research activity has been dedicated to the identification of natural products from traditional medicine that regulate ABCA1 expression.

AIMS OF THE REVIEW

This review surveys natural products, originating from ethnopharmacologically used plants, fungi or marine sources, which influence ABCA1 expression, providing a reference for future study.

MATERIALS AND METHODS

Information on regulation of ABCA1 expression by natural compounds from traditional medicine was extracted from ancient and modern books, materia medica, and electronic databases (PubMed, Google Scholar, Science Direct, and ResearchGate).

RESULTS

More than 60 natural compounds from traditional medicine, especially traditional Chinese medicine (TCM), are reported to regulate ABCA1 expression in different in vitro and in vivo models (such as cholesterol efflux and atherosclerotic animal models). These active compounds belong to the classes of polyketides, terpenoids, phenylpropanoids, tannins, alkaloids, steroids, amino acids and others. Several compounds appear very promising in vivo, which need to be further investigated in animal models of diseases related to ABCA1 or in clinical studies.

CONCLUSION

Natural products from traditional medicine constitute a large promising pool for compounds that regulate ABCA1 expression, and thus may prevent/treat diseases related to cholesterol metabolism, like atherosclerosis or Alzheimer's disease. In many cases, the molecular mechanisms of these natural products remain to be investigated.

Macrophage iron retention aggravates atherosclerosis: Evidence for the role of autocrine formation of hepcidin in plaque macrophages

Iron accumulation has been frequently found in atherosclerotic lesions, especially in macrophages/foam cells, but the exact mechanisms by which hepcidin induces iron retention in plaque macrophages and its roles in atherogenesis remain unknown. Double immunofluorescence staining showed colocalization of hepcidin-positive macrophages with ox-LDL, TLR4, p-p65 and ferritin light chain (ferritin-L) both in human and murine atherosclerotic lesions. RAW264.7 macrophages incubated with ox-LDL showed elevated expression of TLR4, p-p65, hepcidin, ferritin-L/H, CYP27A1, CD36, PPARγ, liver X receptor α (LXRα), and ATP binding cassette transporter A1/G1 (ABCA1/G1), as well as increased intracellular labile iron pool level and lipid accumulation. Ox-LDL-induced iron retention and lipid accumulation were aggravated by lipopolysaccharide but blocked by TAK-242, an antagonist of TLR4. Moreover, macrophage TLR4/NF-κB pathway activation and foaming triggered by ox-LDL was enhanced by ferric ammonium citrate or exogenous hepcidin but attenuated by hepcidin silencing or the use of iron chelator. Meanwhile, the addition of hepcidin stimulated CD36-mediated Dil-labeled-ox-LDL uptake and inhibited the LXRα-ABCA1/G1 pathway-dependent cholesterol efflux in macrophages, which was significantly reversed by 27-hydroxycholesterol but further exacerbated by cyclosporin A, a selective inhibitor of CYP27A1. Our study provided the evidence that iron trapped in atherosclerosis plaque macrophages contributes to cholesterol disequilibrium-initiated foam cell formation, which is provoked by the unique but largely unknown autocrine formation of hepcidin in plaque macrophages via activating the TLR4/NF-κB pathway when exposed to ox-LDL. Such findings, considering the intricate vicious cycle between macrophage hepcidin autocrine-triggered iron retention and cholesterol disequilibrium, may shed new light on the "iron hypothesis" of atherosclerosis.

Allergic asthma aggravated atherosclerosis increases cholesterol biosynthesis and foam cell formation in apolipoprotein E-deficient mice

Several studies have demonstrated that allergic asthma can induce atherosclerosis formation in mice. Moreover, allergic asthma and atherosclerosis have been shown to be strongly associated with dyslipidemia. In this study, we investigated the underlying mechanism of allergic asthma-aggravated atherosclerosis-induced cholesterol metabolism disorder in asthmatic apoE^-/- mice. We found that allergic asthma increased the expression of 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR) in the liver and CD36 in the aorta during the acute and advanced stages of atherosclerosis, respectively. These results indicate that cholesterol biosynthesis is increased during acute atherosclerosis and cholesterol uptake and foam cell formation is increased during advanced atherosclerosis. Simvastatin administration significantly ameliorated the aortic root lesion size of asthmatic mice and significantly decreased HMGCR and CD36 expression. However, the expression of the low-density lipoprotein receptor and ATP-binding cassette transporter A1 was markedly increased, indicating that the beneficial effect of statins in allergic asthma and coronary artery disease was mediated, at least in part, by decreasing cholesterol biosynthesis and foam cell formation. In conclusion, allergic asthma aggravates atherosclerosis by regulating cholesterol metabolism in apoE^-/- mice. Allergic asthma selectively promotes cholesterol biosynthesis in acute atherosclerosis and increases foam cell formation in advanced atherosclerosis.

Mechanics insights of curcumin in myocardial ischemia: Where are we standing?

Cardiovascular disorders are known as one of the main health problems which are associated with mortality worldwide. Myocardial ischemia (MI) is improper blood supply to myocardium which leads from serious complications to life-threatening problems like AMI, atherosclerosis, hypertension, cardiac-hypertrophy as well as diabetic associated complications as diabetic atherosclerosis/cardiomyopathy/hypertension. Despite several efforts, the current therapeutic platforms are not related with significant results. Hence, it seems, developing novel therapies are required. In this regard, increasing evidences indicated, curcumin (CRC) acts as cardioprotective agent. Given that CRC and its analogs exert their cardioprotective effects via affecting on a variety of cardiovascular diseases-related mechanisms (i.e., Inflammation, and oxidative stress). Herein, for first time, we have highlighted the protective impacts of CRC against MI. This review might be a steppingstone for further investigation into the clinical implications of the CRC against MI. Furthermore, it pulls in light of a legitimate concern for scientific community, seeking novel techniques and characteristic dynamic biopharmaceuticals for use against myocardial ischemia.

The role of traditional Chinese medicine in the treatment of atherosclerosis through the regulation of macrophage activity

Atherosclerosis (AS) is the main cause of ischemic cardiovascular, cerebrovascular and peripheral vascular diseases. Macrophage activity has been proven to play a critical role during the AS pathological process, which involves the adhesion, aggregation of mononuclear-macrophages, cell differentiation of M1/M2 macrophages as part of complex mechanisms occurring during lipid metabolism, apoptosis, autophagy, inflammation and immune reaction. Therefore, the development of effective AS treatments is likely to target macrophage activity. Certain herbal extracts (such as Salvia miltiorrhiza) have exhibited enormous potential for AS treatment in the past. Here, we aim to provide a summary on the current understanding of the type of action and the underlying target/pathway in macrophage regulation of certain herbal extracts used in Traditional Chinese Medicine for treatment of AS.

Biological properties of metal complexes of curcumin

Curcumin, a naturally occurring phenolic compound isolated from Curcuma longa, has different pharmacological effects, including antiinflammatory, antimicrobial, antioxidant, and anticancer properties. However, curcumin has been found to have a limited bioavailability because of its hydrophobic nature, low-intestinal absorption, and rapid metabolism. Therefore, there is a need for enhancing the bioavailability and its solubility in water in order to increase the pharmacological effects of this bioactive compound. One strategy is curcumin complexation with transition metals to circumvent the abovementioned problems. Curcumin can undergo chelation with various metal ions to form metallo-complexes of curcumin, which may show greater effects as compared with curcumin alone. Promising results with metal curcumin complexes have been observed with regard to antioxidant, anticancer, and antimicrobial activity, as well as in treatment of Alzheimer's disease. The present review provides a concise summary of the characterization and biological properties of curcumin-metal complexes. © 2019 BioFactors, 45(3):304-317, 2019.

Cellular and molecular mechanisms of curcumin in prevention and treatment of disease

Curcumin is a naturally occurring polyphenolic compound present in rhizome of Curcuma longa belonging to the family zingiberaceae. Growing experimental evidence revealed that curcumin exhibit multitarget biological implications signifying its crucial role in health and disease. The current review highlights the recent progress and mechanisms underlying the wide range of pharmacological effects of curcumin against numerous diseases like neuronal, cardiovascular, metabolic, kidney, endocrine, skin, respiratory, infectious, gastrointestinal diseases and cancer. The ability of curcumin to modulate the functions of multiple signal transductions are linked with attenuation of acute and chronic diseases. Numerous preclinical and clinical studies have revealed that curcumin modulates several molecules in cell signal transduction pathway including PI3K, Akt, mTOR, ERK5, AP-1, TGF-β, Wnt, β-catenin, Shh, PAK1, Rac1, STAT3, PPARγ, EBPα, NLRP3 inflammasome, p38MAPK, Nrf2, Notch-1, AMPK, TLR-4 and MyD-88. Curcumin has a potential to prevent and/or manage various diseases due to its anti-inflammatory, anti-oxidant and anti-apoptotic properties with an excellent safety profile. In contrast, the anti-cancer effects of curcumin are reflected due to induction of growth arrest and apoptosis in various premalignant and malignant cells. This review also carefully emphasized the pharmacokinetics of curcumin and its interaction with other drugs. Clinical studies have shown that curcumin is safe at the doses of 12 g/day but exhibits poor systemic bioavailability. The use of adjuvant like piperine, liposomal curcumin, curcumin nanoparticles and curcumin phospholipid complex has shown enhanced bioavailability and therapeutic potential. Further studies are warranted to prove the potential of curcumin against various ailments.

Protection Effect of Curcumin for Macrophage-Involved Polyethylene Wear Particle-Induced Inflammatory Osteolysis by Increasing the Cholesterol Efflux

BACKGROUND Periprosthetic osteolysis, induced by wear particles and inflammation, is a common reason for failure of primary arthroplasty. Curcumin, a nature phenol from plants, has been reported to reduce the inflammation in macrophages. This study aimed to investigate the potential effect of curcumin on macrophage involved, wear particle-induced osteolysis and its mechanism. MATERIAL AND METHODS RAW264.7 macrophages were used to test the effects of polyethylene (PE) particles and curcumin on macrophage cholesterol efflux and phenotypic changes. A mouse model of PE particle-induced calvarial osteolysis was established to test the effects of curcumin in vivo. After 14 days of treatment, the bone quality of the affected areas was analyzed by micro-computed tomography (micro-CT) and histology, and the bone surrounding soft tissues were analyzed at the cellular and molecular levels. RESULTS We found that PE particles can stimulate osteoclastogenesis and produce an M1-like phenotype in macrophages in vitro. Curcumin enhanced the cholesterol efflux in macrophages, and maintained the M0-like phenotype under the influence of PE particles in vitro. Additionally, the cholesterol transmembrane regulators ABCA1, ABCG1, and CAV1 were enhanced by curcumin in vivo. We also found enhanced bone density, reduced osteoclastogenesis, and fewer inflammatory responses in the curcumin treated groups in our mouse osteolysis model. CONCLUSIONS Our study findings indicated that curcumin can inhibit macrophage involved osteolysis and inflammation via promoting cholesterol efflux. Maintaining the cholesterol efflux might be a potential strategy to prevent periprosthetic osteolysis after total joint arthroplasty surgery.

Curcumin ameliorates atherosclerosis in apolipoprotein E deficient asthmatic mice by regulating the balance of Th2/Treg cells

BACKGROUND

Allergic asthma and atherosclerosis represent different directions of inflammatory responses of CD4⁺ T cells, and allergic asthma accelerates atherosclerosis formation. Curcumin could ameliorate the progression of both atherosclerosis and allergic asthma.

PURPOSE

We aimed to investigate the roles of curcumin in asthma-accelerated atherosclerosis plaque formation, and the change of CD4⁺ T-cell subsets in this process.

METHODS

Six to eight-week-old apolipoprotein E^-/- (apoE^-/-) mice were sensitized and challenged by ovalbumin (OVA) to establish an allergic asthma model, and then received curcumin or vehicle treatment for 8 weeks.

RESULTS

The accelerated atherosclerosis was induced by allergic asthma accompanied by increased T helper cell (Th)2 and Th17 cells and decreased regulatory T cells (Tregs) in the spleen. After the 8-week treatment with curcumin, the lesion areas in the aortic root in asthmatic mice significantly improved, and the elevated Th2 and Th17 cells significantly decreased, but Tregs markedly increased. Although curcumin treatment markedly reduced the interleukin (IL)-4 and IL-13 in serum and spleen, the elevated IL-17A did not decrease. Moreover, Th1 cells showed no significant change between different groups. The mRNA expression levels of M1 macrophage-related inflammatory factors IL-6, iNOS and IL-1β were markedly elevated in the spleens of asthmatic mice, but significantly decreased after the 8-week treatment with curcumin.

CONCLUSION

Curcumin ameliorated the aggravation of atherosclerotic lesions and stabilised plaque by modulating the balance of Th2/Tregs in asthmatic apoE^-/- mice.

Macrophage plasticity, polarization and function in response to curcumin, a diet-derived polyphenol, as an immunomodulatory agent

Monocytes and macrophages are important cells of the innate immune system that have diverse functions, including defense against invading pathogens, removal of dead cells by phagocytosis, antigen presentation in the context of MHC class I and class II molecules, and production of various pro-inflammatory cytokines and chemokines such as IL-1β, IL-6, TNF-α and MCP-1. In addition, pro-inflammatory (M1) and anti-inflammatory (M2) macrophages clearly play important roles in the progression of several inflammatory diseases. Therefore, therapies that target macrophage polarization and function by either blocking their trafficking to sites of inflammation, or skewing M1 to M2 phenotype polarization may hold clinical promise in several inflammatory diseases. Dietary-derived polyphenols have potent natural anti-oxidative properties. Within this group of polyphenols, curcumin has been shown to suppress macrophage inflammatory responses. Curcumin significantly reduces co-stimulatory molecules and also inhibits MAPK activation and the translocation of NF-κB p65. Curcumin can also polarize/repolarize macrophages toward the M2 phenotype. Curcumin-treated macrophages have been shown to be highly efficient at antigen capture and endocytosis via the mannose receptor. These novel findings provide new perspectives for the understanding of the immunopharmacological role of curcumin, as well as its therapeutic potential for impacting macrophage polarization and function in the context of inflammation-related disease. However, the precise effects of curcumin on the migration, differentiation, polarization and immunostimulatory functions of macrophages remain unknown. Therefore, in this review, we summarized whether curcumin can influence macrophage polarization, surface molecule expression, cytokine and chemokine production and their underlying pathways in the prevention of inflammatory diseases.

IRE1α aggravates ischemia reperfusion injury of fatty liver by regulating phenotypic transformation of kupffer cells

Fatty liver is one of the widely accepted marginal donor for liver transplantation, but is also more sensitive to ischemia and reperfusion injury (IRI) and produces more reactive oxygen species (ROS). Moreover, so far, no effective method has been developed to alleviate it. Endoplasmic reticulum stress (ER-stress) of hepatocyte is associated with the occurrence of fatty liver disease, but ER-stress of kupffer cells (KCs) in fatty liver is not clear at all. This study evaluates whether ER-stress of KCs is activated in fatty liver and accelerate IRI of fatty livers. ER-stress of KCs was activated in fatty liver, especially the IRE1α signal pathway. KCs with activated ER-stress secreted more proinflammatory cytokine to induce its M1-phenotypic shift in fatty liver, resulting in more severe IRI. Also, activated ER-stress of BMDMs in vitro by tunicamycin can induce its pro-inflammatory shift and can be reduced by 4-PBA, an ER-stress inhibitor. Knockdown of IRE1α could regulate the STAT1 and STAT6 pathway of macrophage to inhibit the M1-type polarization and promote M2-phenotypic shift. Furthermore, transfusion of IRE1α-knockdown KCs significantly reduced the liver IRI as well as the ROS of HFD feeding mice. Altogether, these data demonstrated that IRE1α of KCs may be a potential target to reduce the fatty liver associated IRI in liver transplantation.