Treatment in vitro with PPARα and PPARγ ligands drives M1-to-M2 polarization of macrophages from T. cruzi-infected mice

Xiezhuo Tiaozhi formula inhibits macrophage pyroptosis in the non-alcoholic fatty liver disease by targeting the SIRT1 pathway

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is a challenging disease to interfere with and represents a potential long-term risk factor for hepatic fibrosis and liver cancer. The Xiezhuo Tiaozhi (XZTZ) formula, a water extract from crude herbs, has been widely used as an anti-NAFLD agent through clinical observation. However, the underlying pharmacological mechanisms of the XZTZ formula and its impact on the potential pathways against NAFLD have not been elucidated.

PURPOSE

Our study aims to investigate the pharmacological effects and underlying regulatory mechanisms of the XZTZ formula to treat NAFLD.

METHODS

The possible active components and pharmacological mechanisms of the XZTZ formula against NAFLD were identified using ultra-performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF/MS) and molecular docking. To further explore the potential mechanisms, forty-eight 6-week-old male C57BL/6 J mice were given individual attention with high-fat and high-sugar diet (HFHSD) or relevant control (Ctrl) diets for 16 weeks to successfully construct a NAFLD mouse model. Subsequently, the levels of serum biochemicals, pathological changes in the liver, and pyroptosis levels were assessed in mice to investigate the therapeutic effects of the XZTZ formula. Further, LPS-induced RAW264.7 cells and Immortalized Mouse Kupffer cells (ImKC) were used to verify the potential mechanisms of the XZTZ formula against NAFLD in vitro.

RESULTS

We identified 7 chemical compounds and 2 potential therapeutic targets as plausible therapeutic points for the treatment of NAFLD using the XZTZ formula. Subsequent histopathological analysis revealed marked hepatic steatosis and lipid accumulation in the HFHSD mice liver, while conditions were effectively ameliorated by administration of the XZTZ formula. Additionally, our work demonstrated that the XZTZ formula could attenuate M1 polarization, promote M2 polarization, and suppress pyroptosis via the SIRT1 pathway in tissue samples. Moreover, validation performed through LPS-induced RAW264.7 and ImKC cells by showing that silencing SIRT1 weaken the effects of the XZTZ formula on relative pyroptosis affirmed that its role was associated with the SIRT1 pathway in macrophage.

CONCLUSION

These findings suggest that the XZTZ formula alleviated hepatic steatosis and lipid accumulation in NAFLD mice. These ameliorations are associated with mechanisms involving the attenuation of M1 polarization, promotion of M2 polarization, and anti-pyroptosis effects through the SIRT1 pathway.

Fenofibrate Induces a Resolving Profile in Heart Macrophage Subsets and Attenuates Acute Chagas Myocarditis

Chagas disease, caused by Trypanosoma cruzi, stands as the primary cause of dilated cardiomyopathy in the Americas. Macrophages play a crucial role in the heart's response to infection. Given their functional and phenotypic adaptability, manipulating specific macrophage subsets could be vital in aiding essential cardiovascular functions including tissue repair and defense against infection. PPARα are ligand-dependent transcription factors involved in lipid metabolism and inflammation regulation. However, the role of fenofibrate, a PPARα ligand, in the activation profile of cardiac macrophages as well as its effect on the early inflammatory and fibrotic response in the heart remains unexplored. The present study demonstrates that fenofibrate significantly reduces not only the serum activity of tissue damage biomarker enzymes (LDH and GOT) but also the circulating proportions of pro-inflammatory monocytes (CD11b+ LY6Chigh). Furthermore, both CD11b+ Ly6Clow F4/80high macrophages (MΦ) and recently differentiated CD11b+ Ly6Chigh F4/80high monocyte-derived macrophages (MdMΦ) shift toward a resolving phenotype (CD206high) in the hearts of fenofibrate-treated mice. This shift correlates with a reduction in fibrosis, inflammation, and restoration of ventricular function in the early stages of Chagas disease. These findings encourage the repositioning of fenofibrate as a potential ancillary immunotherapy adjunct to antiparasitic drugs, addressing inflammation to mitigate Chagas disease symptoms.

Murine skeletal muscle satellite cells isolation and preliminary study on regulation in immune microenvironment during nurse cells formation of Trichinella spiralis infection

As an intracellular parasitic nematode, Trichinella spiralis (T. spiralis) can induce the formation of nurse cells (NC) in host muscles and keep it to survive within the NC for an extended period. The formation of NC is similar to muscle cell injury and repair which lead to the arrest of satellite cells in the G2/M phase and build a suitable parasitic environment for the muscle larvae of T. spiralis. However, the molecular mechanisms involved in skeletal muscle repair through skeletal muscle satellite cells (SMSC) and the host immune response during T. spiralis infection have not been fully elucidated. In this study, histopathological examination revealed that the severity of damage increased as the infection progressed in the soleus muscle. SMSCs were isolated from BALB/c mice infected with T. spiralis at 4, 21 and 35 days post-infection (dpi). The immunological characteristics of these cells were analyzed by real-time PCR and flow cytometry (FCM). FCM analysis revealed a notable increase in the expression of B7 homolog 1 (B7-H1) in SMSCs following T. spiralis infection, while conversely, the expression of inducible costimulatory ligand (ICOSL) significantly decreased. Furthermore, real-time PCR results showed that toll like receptor 3 (TLR3) expression in SMSCs of the infected mice was upregulated at 21 dpi. The expression levels of three subtypes (PPARα, PPARβ and PPARγ) of peroxisome proliferator-activated receptors (PPARs) also increased in the cells. This study highlights the immunological regulation significance of SMSCs host during T. spiralis infection and suggests that SMSCs actively participant in the local immune response to T. spiralis by regulating the interaction between the parasite and the host.

Gabapentin attenuates cardiac remodeling after myocardial infarction by inhibiting M1 macrophage polarization through the peroxisome proliferator-activated receptor-γ pathway

OBJECTIVES

Inflammation regulates ventricular remodeling after myocardial infarction (MI), and gabapentin exerts anti-inflammatory effects. We investigated the anti-inflammatory role and mechanism of gabapentin after MI.

METHODS

Rats were divided into the sham group (n = 12), MI group (n = 20), and MI + gabapentin group (n = 16). MI was induced by left coronary artery ligation. The effects of gabapentin on THP-1-derived macrophages were examined in vitro.

RESULTS

In vivo, 1 week after MI, gabapentin significantly reduced inducible nitric oxide synthase (iNOS; M1 macrophage marker) expression and decreased pro-inflammatory factors (tumor necrosis factor [TNF]-α and interleukin [IL]-1β). Gabapentin upregulated the M2 macrophage marker arginase-1, as well as CD163 expression, and increased the expression of anti-inflammatory factors, including chitinase-like 3, IL-10, and transforming growth factor-β. Four weeks after MI, cardiac function, infarct size, and cardiac fibrosis improved after gabapentin treatment. Gabapentin inhibited sympathetic nerve activity and decreased ventricular electrical instability in rats after MI. Tyrosine hydroxylase and growth-associated protein 43 were suppressed after gabapentin treatment. Gabapentin downregulated nerve growth factor (NGF) and reduced pro-inflammatory factors (iNOS, TNF-α, and IL-1β). In vitro, gabapentin reduced NGF, iNOS, TNF-α, and IL-1β expression in lipopolysaccharide-stimulated macrophages. Mechanistic studies revealed that the peroxisome proliferator-activated receptor-γ antagonist GW9662 attenuated the effects of gabapentin. Moreover, gabapentin reduced α2δ1 expression in the macrophage plasma membrane and reduced the calcium content of macrophages.

CONCLUSION

Gabapentin attenuates cardiac remodeling by inhibiting inflammation via peroxisome proliferator-activated receptor-γ activation and preventing calcium overload.

Peroxiredoxin 3 has a crucial role in the macrophage polarization by regulating mitochondrial homeostasis

Acute lung injury (ALI) is one of the life-threatening complications of sepsis, and macrophage polarization plays a crucial role in the sepsis-associated ALI. However, the regulatory mechanisms of macrophage polarization in ALI and in the development of inflammation are largely unknown. In this study, we demonstrated that macrophage polarization occurs in sepsis-associated ALI and is accompanied by mitochondrial dysfunction and inflammation, and a decrease of PRDX3 promotes the initiation of macrophage polarization and mitochondrial dysfunction. Mechanistically, PRDX3 overexpression promotes M1 macrophages to differentiate into M2 macrophages, and enhances mitochondrial functional recovery after injury by reducing the level of glycolysis and increasing TCA cycle activity. In conclusion, we identified PRDX3 as a critical hub integrating oxidative stress, inflammation, and metabolic reprogramming in macrophage polarization. The findings illustrate an adaptive mechanism underlying the link between macrophage polarization and sepsis-associated ALI.

NAAA-regulated lipid signaling in monocytes controls the induction of hyperalgesic priming in mice

Circulating monocytes participate in pain chronification but the molecular events that cause their deployment are unclear. Using a mouse model of hyperalgesic priming (HP), we show that monocytes enable progression to pain chronicity through a mechanism that requires transient activation of the hydrolase, N-acylethanolamine acid amidase (NAAA), and the consequent suppression of NAAA-regulated lipid signaling at peroxisome proliferator-activated receptor-α (PPAR-α). Inhibiting NAAA in the 72 hours following administration of a priming stimulus prevented HP. This effect was phenocopied by NAAA deletion and depended on PPAR-α recruitment. Mice lacking NAAA in CD11b+ cells - monocytes, macrophages, and neutrophils - were resistant to HP induction. Conversely, mice overexpressing NAAA or lacking PPAR-α in the same cells were constitutively primed. Depletion of monocytes, but not resident macrophages, generated mice that were refractory to HP. The results identify NAAA-regulated signaling in monocytes as a control node in the induction of HP and, potentially, the transition to pain chronicity.

Macrophage fatty acid oxidation in atherosclerosis

Atherosclerosis significantly contributes to the development of cardiovascular diseases (CVD) and is characterized by lipid retention and inflammation within the artery wall. Multiple immune cell types are implicated in the pathogenesis of atherosclerosis, macrophages play a central role as the primary source of inflammatory effectors in this pathogenic process. The metabolic influences of lipids on macrophage function and fatty acid β-oxidation (FAO) have similarly drawn attention due to its relevance as an immunometabolic hub. This review discusses recent findings regarding the impact of mitochondrial-dependent FAO in the phenotype and function of macrophages, as well as transcriptional regulation of FAO within macrophages. Finally, the therapeutic strategy of macrophage FAO in atherosclerosis is highlighted.

Molecular mechanisms and therapeutic perspectives of peroxisome proliferator-activated receptor α agonists in cardiovascular health and disease

The prevalence of cardiovascular disease (CVD) has been rising due to sedentary lifestyles and unhealthy dietary patterns. Peroxisome proliferator-activated receptor α (PPARα) is a nuclear receptor regulating multiple biological processes, such as lipid metabolism and inflammatory response critical to cardiovascular homeostasis. Healthy endothelial cells (ECs) lining the lumen of blood vessels maintains vascular homeostasis, where endothelial dysfunction associated with increased oxidative stress and inflammation triggers the pathogenesis of CVD. PPARα activation decreases endothelial inflammation and senescence, contributing to improved vascular function and reduced risk of atherosclerosis. Phenotypic switch and inflammation of vascular smooth muscle cells (VSMCs) exacerbate vascular dysfunction and atherogenesis, in which PPARα activation improves VSMC homeostasis. Different immune cells participate in the progression of vascular inflammation and atherosclerosis. PPARα in immune cells plays a critical role in immunological events, such as monocyte/macrophage adhesion and infiltration, macrophage polarization, dendritic cell (DC) embedment, T cell activation, and B cell differentiation. Cardiomyocyte dysfunction, a major risk factor for heart failure, can also be alleviated by PPARα activation through maintaining cardiac mitochondrial stability and inhibiting cardiac lipid accumulation, oxidative stress, inflammation, and fibrosis. This review discusses the current understanding and future perspectives on the role of PPARα in the regulation of the cardiovascular system as well as the clinical application of PPARα ligands.

The impact of vaccine-linked chemotherapy on liver health in a mouse model of chronic Trypanosoma cruzi infection

BACKGROUND

Chagas disease, chronic infection with Trypanosoma cruzi, mainly manifests as cardiac disease. However, the liver is important for both controlling parasite burdens and metabolizing drugs. Notably, high doses of anti-parasitic drug benznidazole (BNZ) causes liver damage. We previously showed that combining low dose BNZ with a prototype therapeutic vaccine is a dose sparing strategy that effectively reduced T. cruzi induced cardiac damage. However, the impact of this treatment on liver health is unknown. Therefore, we evaluated several markers of liver health after treatment with low dose BNZ plus the vaccine therapy in comparison to a curative dose of BNZ.

METHODOLOGY

Female BALB/c mice were infected with a bioluminescent T. cruzi H1 clone for approximately 70 days, then randomly divided into groups of 15 mice each. Mice were treated with a 25mg/kg BNZ, 25μg Tc24-C4 protein/ 5μg E6020-SE (Vaccine), 25mg/kg BNZ followed by vaccine, or 100mg/kg BNZ (curative dose). At study endpoints we evaluated hepatomegaly, parasite burden by quantitative PCR, cellular infiltration by histology, and expression of B-cell translocation gene 2(BTG2) and Peroxisome proliferator-activated receptor alpha (PPARα) by RT-PCR. Levels of alanine transaminase (ALT), aspartate transaminase (AST), alkaline phosphatase (ALP) and lactate dehydrogenase (LDH) were quantified from serum.

RESULTS

Curative BNZ treatment significantly reduced hepatomegaly, liver parasite burdens, and the quantity of cellular infiltrate, but significantly elevated serum levels of ALT, AST, and LDH. Low BNZ plus vaccine did not significantly affect hepatomegaly, parasite burdens or the quantity of cellular infiltrate, but only elevated ALT and AST. Low dose BNZ significantly decreased expression of both BTG2 and PPARα, and curative BNZ reduced expression of BTG2 while low BNZ plus vaccine had no impact.

CONCLUSIONS

These data confirm toxicity associated with curative doses of BNZ and suggest that while dose sparing low BNZ plus vaccine treatment does not reduce parasite burdens, it better preserves liver health.

Peroxisome proliferator-activated receptors as therapeutic target for cancer

Peroxisome proliferator-activated receptors (PPARs) are transcription factors belonging to the nuclear receptor family. There are three subtypes of PPARs, including PPAR-α, PPAR-β/δ and PPAR-γ. They are expressed in different tissues and act by regulating the expression of target genes in the form of binding to ligands. Various subtypes of PPAR have been shown to have significant roles in a wide range of biological processes including lipid metabolism, body energy homeostasis, cell proliferation and differentiation, bone formation, tissue repair and remodelling. Recent studies have found that PPARs are closely related to tumours. They are involved in cancer cell growth, angiogenesis and tumour immune response, and are essential components in tumour progression and metastasis. As such, they have become a target for cancer therapy research. In this review, we discussed the current state of knowledge on the involvement of PPARs in cancer, including their role in tumourigenesis, the impact of PPARs in tumour microenvironment and the potential of using PPARs combinational therapy to treat cancer by targeting essential signal pathways, or as adjuvants to boost the effects of current chemo and immunotherapies. Our review highlights the complexity of PPARs in cancer and the need for a better understanding of the mechanism in order to design effective cancer therapies.

Huangqin Decoction ameliorates ulcerative colitis by regulating fatty acid metabolism to mediate macrophage polarization via activating FFAR4-AMPK-PPARα pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Huangqin Decoction (HQD), a traditional Chinese medicine (TCM) formula chronicled in Shang Han Lun, is safe and effective for treatment of ulcerative colitis (UC).

AIM OF THE STUDY

To investigate the effect of HQD against dextran sulfate sodium (DSS)-induced UC mice by regulating gut microbiota and metabolites, and further explore the mechanism of fatty acid metabolism on macrophage polarization.

MATERIALS AND METHODS

Based on 3% dextran sulfate sodium (DSS)-induced UC mice model, clinical symptoms observation (body weight, DAI, and colon length) and histological inspection were used to evaluate the efficacy of HQD and fecal microbiota transplantation (FMT) from HQD-treated mice. The gut microbiota and metabolites were detected by 16S rRNA sequencing and metabolomics analysis. The parameters of fatty acid metabolism, macrophage polarization, and FFAR1/FFAR4-AMPK-PPARα pathway were analyzed by immunofluorescence analysis, western blotting, and real-time PCR. Then, the effects of FFAR1 and FFAR4 on macrophage polarization were examined by agonists based on LPS-induced RAW264.7 cell model.

RESULTS

The results showed that FMT, like HQD, ameliorated UC by improving weight loss, restoring colon length, and reducing DAI scores and histopathological scores. Besides, HQD and FMT both enhanced the richness of gut microbiota, and modulated intestinal bacteria and metabolites to achieve a new balance. Untargeted metabolomics analysis revealed that fatty acids, especially long-chain fatty acids (LCFAs), dominated in HQD against DSS-induced UC by regulating the gut microenvironment. Further, FMT and HQD recovered the expression of fatty acid metabolism-related enzymes, and simultaneously activated FFAR1/FFAR4-AMPK-PPARα pathway but suppressed NF-κB pathway. Combined with cell experiment, HQD and FMT promoted macrophage polarization from M1 toward M2, which were well associated with anti-inflammatory cytokines and combined with the activated FFAR4.

CONCLUSIONS

The mechanism of HQD against UC was related to regulating fatty acid metabolism to mediate M2 macrophage polarization by activating the FFAR4-AMPK-PPARα pathway.

Macrophages in immunoregulation and therapeutics

Macrophages exist in various tissues, several body cavities, and around mucosal surfaces and are a vital part of the innate immune system for host defense against many pathogens and cancers. Macrophages possess binary M1/M2 macrophage polarization settings, which perform a central role in an array of immune tasks via intrinsic signal cascades and, therefore, must be precisely regulated. Many crucial questions about macrophage signaling and immune modulation are yet to be uncovered. In addition, the clinical importance of tumor-associated macrophages is becoming more widely recognized as significant progress has been made in understanding their biology. Moreover, they are an integral part of the tumor microenvironment, playing a part in the regulation of a wide variety of processes including angiogenesis, extracellular matrix transformation, cancer cell proliferation, metastasis, immunosuppression, and resistance to chemotherapeutic and checkpoint blockade immunotherapies. Herein, we discuss immune regulation in macrophage polarization and signaling, mechanical stresses and modulation, metabolic signaling pathways, mitochondrial and transcriptional, and epigenetic regulation. Furthermore, we have broadly extended the understanding of macrophages in extracellular traps and the essential roles of autophagy and aging in regulating macrophage functions. Moreover, we discussed recent advances in macrophages-mediated immune regulation of autoimmune diseases and tumorigenesis. Lastly, we discussed targeted macrophage therapy to portray prospective targets for therapeutic strategies in health and diseases.

The role of peroxisome proliferator-activated receptors in the tumor microenvironment, tumor cell metabolism, and anticancer therapy

Peroxisome proliferator-activated receptors (PPARs) have been extensively studied for over 3 decades and consist of three isotypes, including PPARα, γ, and β/δ, that were originally considered key metabolic regulators controlling energy homeostasis in the body. Cancer has become a leading cause of human mortality worldwide, and the role of peroxisome proliferator-activated receptors in cancer is increasingly being investigated, especially the deep molecular mechanisms and effective cancer therapies. Peroxisome proliferator-activated receptors are an important class of lipid sensors and are involved in the regulation of multiple metabolic pathways and cell fate. They can regulate cancer progression in different tissues by activating endogenous or synthetic compounds. This review emphasizes the significance and knowledge of peroxisome proliferator-activated receptors in the tumor microenvironment, tumor cell metabolism, and anti-cancer treatment by summarizing recent research on peroxisome proliferator-activated receptors. In general, peroxisome proliferator-activated receptors either promote or suppress cancer in different types of tumor microenvironments. The emergence of this difference depends on various factors, including peroxisome proliferator-activated receptor type, cancer type, and tumor stage. Simultaneously, the effect of anti-cancer therapy based on drug-targeted PPARs differs or even opposes among the three peroxisome proliferator-activated receptor homotypes and different cancer types. Therefore, the current status and challenges of the use of peroxisome proliferator-activated receptors agonists and antagonists in cancer treatment are further explored in this review.

Chitinases and chitinase-like proteins in asthma

Despite the lack of endogenous chitin synthesis, mammalian genomes encode two enzymatically active true chitinases (chitotriosidase and acidic mammalian chitinase) and a variable number of chitinase-like proteins (CLPs) that have no enzyme activity but bind chitin. Chitinases and CLPs are prominent components of type-2 immune response-mediated respiratory diseases. However, despite extensive research into their role in allergic airway disease, there is still no agreement on whether they are mere biomarkers of disease or actual disease drivers. Functions ascribed to chitinases and CLPs include, but are not limited to host defense against chitin-containing pathogens, directly promoting inflammation, and modulating tissue remodeling and fibrosis. Here, we discuss in detail the chitin-dependent and -independent roles of chitinases and CLPs in the context of allergic airway disease, and recent advances and emerging concepts in the field that might identify opportunities for new therapies.

PPARα alleviates inflammation via inhibiting NF-κB/Rel pathway in Vibrio splendidus challenged Apostichopus japonicus

Organisms trigger pro-inflammatory responses to resist the invasion of foreign pathogens in the early infection stage. However, excessive or chronic inflammation can also cause several diseases. We previously validated IL-17 from sea cucumbers mediated inflammatory response by the IL-17R-TRAF6 axis. But the anti-inflammatory effect was largely unknown in the species. In this study, the conserved PPARα gene was obtained from Apostichopus japonicus by RNA-seq and RACE approaches. The expression of AjPPARα was found to be significantly induced at the late stage of infection not only in Vibrio splendidus-challenged sea cucumbers, but also in LPS-exposed coelomocytes, which was negative correlation to that of AjIL-17 and AjNLRP3. Both silencing AjPPARα by specific siRNA and treatment with AjPAPRα inhibitor MK-886 could significantly upregulate the transcriptional levels of pro-inflammatory factors the AjIL-17 and AjNLRP3. The infiltration of inflammatory cells and tissues damage were also detected in the body walls in the same condition. In contrast, AjPAPRα agonist of WY14643 treatment could alleviate the V. splendidus-induced tissue injury. To further explore the molecular mechanism of AjPPARα-mediated anti-inflammatory in A. japonicus, the expression of the transcriptional factors of AjStat5 and AjRel (subunit of NF-κB) were investigated under AjPPARα aberrant expression conditions and found that AjRel exhibited a negative regulatory relationship to AjPPARα. Furthermore, silencing AjRel was led to down-regulation of AjIL-17 and AjNLRP3. Taken together, our results supported that AjPPARα exerted anti-inflammatory effects through inhibiting AjRel in response to V. splendidus infection.

Peroxisome Proliferator-Activated Receptor-Targeted Therapies: Challenges upon Infectious Diseases

Peroxisome proliferator-activated receptors (PPARs) α, β, and γ are nuclear receptors that orchestrate the transcriptional regulation of genes involved in a variety of biological responses, such as energy metabolism and homeostasis, regulation of inflammation, cellular development, and differentiation. The many roles played by the PPAR signaling pathways indicate that PPARs may be useful targets for various human diseases, including metabolic and inflammatory conditions and tumors. Accumulating evidence suggests that each PPAR plays prominent but different roles in viral, bacterial, and parasitic infectious disease development. In this review, we discuss recent PPAR research works that are focused on how PPARs control various infections and immune responses. In addition, we describe the current and potential therapeutic uses of PPAR agonists/antagonists in the context of infectious diseases. A more comprehensive understanding of the roles played by PPARs in terms of host-pathogen interactions will yield potential adjunctive personalized therapies employing PPAR-modulating agents.

Melatonin alleviates diet-induced steatohepatitis by targeting multiple cell types in the liver to suppress inflammation and fibrosis

The pathogenesis of nonalcoholic steatohepatitis (NASH), a severe stage of nonalcoholic fatty liver disease, is complex and implicates multiple cell interactions. However, therapies for NASH that target multiple cell interactions are still lacking. Melatonin (MEL) alleviates NASH with mechanisms not yet fully understood. Thus, we herein investigate the effects of MEL on key cell types involved in NASH, including hepatocytes, macrophages, and stellate cells. In a mouse NASH model with feeding of a methionine and choline-deficient (MCD) diet, MEL administration suppressed lipid accumulation and peroxidation, improved insulin sensitivity, and attenuated inflammation and fibrogenesis in the liver. Specifically, MEL reduced proinflammatory cytokine expression and inflammatory signal activation and attenuated CD11C+CD206- M1-like macrophage polarization in the liver of NASH mice. The reduction of proinflammatory response by MEL was also observed in the lipopolysaccharide-stimulated Raw264.7 cells. Additionally, MEL increased liver fatty acid β-oxidation, leading to reduced lipid accumulation, and restored the oleate-loaded primary hepatocytes. Finally, MEL attenuated hepatic stellate cell (HSC) activation and fibrogenesis in the liver of MCD-fed mice and in LX-2 human HSCs. In conclusion, MEL acts on multiple cell types in the liver to mitigate NASH-associated phenotypes, supporting MEL or its analog as potential treatment for NASH.

Spleen-Targeted Glabridin-Loaded Nanoparticles Regulate Polarization of Monocyte/Macrophage (Mo /Mφ ) for the Treatment of Cerebral Ischemia-Reperfusion Injury

During cerebral ischemia-reperfusion (I-R) injury, the infiltration of monocyte/macrophages (Mo /Mφ ) into the ischemic penumbra causes inflammatory damage but also regulates tissue repair in the penumbra. The regulation and balance of Mo /Mφ polarization is considered as a potential therapeutic target for treating cerebral I-R injury. Herein, these findings demonstrate that glabridin (Gla)-loaded nanoparticles (i.e., NPGla -5k) can effectively inhibit M1-polarization and enhance M2-polarization of Mo /Mφ . Positron emission tomography (PET) imaging shows that NPGla -5k can selectively accumulate in the spleen following intravenous injection. Spleen-targeted Cy5-NPGla -5k can co-localize with peripheral macrophages in the penumbra at 24 h after tail-vein injection. Interestingly, NPGla -5k treatment can reduce inflammatory damage, protect dying neurons, and improve nervous system function. The protective effect of spleen-targeted NPGla -5k against cerebral I-R injury in mice encourages an exploration of their use for clinical treatment of patients with cerebral I-R injury.

Peroxisome Proliferator-Activated Receptors and the Hallmarks of Cancer

Peroxisome proliferator-activated receptors (PPARs) function as nuclear transcription factors upon the binding of physiological or pharmacological ligands and heterodimerization with retinoic X receptors. Physiological ligands include fatty acids and fatty-acid-derived compounds with low specificity for the different PPAR subtypes (alpha, beta/delta, and gamma). For each of the PPAR subtypes, specific pharmacological agonists and antagonists, as well as pan-agonists, are available. In agreement with their natural ligands, PPARs are mainly focused on as targets for the treatment of metabolic syndrome and its associated complications. Nevertheless, many publications are available that implicate PPARs in malignancies. In several instances, they are controversial for very similar models. Thus, to better predict the potential use of PPAR modulators for personalized medicine in therapies against malignancies, it seems necessary and timely to review the three PPARs in relation to the didactic concept of cancer hallmark capabilities. We previously described the functions of PPAR beta/delta with respect to the cancer hallmarks and reviewed the implications of all PPARs in angiogenesis. Thus, the current review updates our knowledge on PPAR beta and the hallmarks of cancer and extends the concept to PPAR alpha and PPAR gamma.

Bidirectional cytokine-microRNA control: A novel immunoregulatory framework in leishmaniasis

As effector innate immune cells and as a host to the protozoan parasite Leishmania, macrophages play a dual role in antileishmanial immunoregulation. The 2 key players in this immunoregulation are the macrophage-expressed microRNAs (miRNAs) and the macrophage-secreted cytokines. miRNAs, as small noncoding RNAs, play vital roles in macrophage functions including cytokines and chemokines production. In the reverse direction, Leishmania-regulated cytokines alter miRNAs expression to regulate the antileishmanial functions of macrophages. The miRNA patterns vary with the time and stage of infection. The cytokine-regulated macrophage miRNAs not only help parasite elimination or persistence but also regulate cytokine production from macrophages. Based on these observations, we propose a novel immunoregulatory framework as a scientific rationale for antileishmanial therapy.

An update on Ym1 and its immunoregulatory role in diseases

Ym1 is a rodent-specific chitinase-like protein (CLP) lacking catalytic activity, whose cellular origins are mainly macrophages, neutrophils and other cells. Although the detailed function of Ym1 remains poorly understood, Ym1 has been generally recognized as a fundamental feature of alternative activation of macrophages in mice and hence one of the prevalent detecting targets in macrophage phenotype distinguishment. Studies have pointed out that Ym1 may have regulatory effects, which are multifaceted and even contradictory, far more than just a mere marker. Allergic lung inflammation, parasite infection, autoimmune diseases, and central nervous system diseases have been found associations with Ym1 to varying degrees. Thus, insights into Ym1’s role in diseases would help us understand the pathogenesis of different diseases and clarify the genuine roles of CLPs in mammals. This review summarizes the information on Ym1 from the gene to its expression and regulation and focuses on the association between Ym1 and diseases.

Sinapic Acid Attenuated Cardiac Remodeling After Myocardial Infarction by Promoting Macrophage M2 Polarization Through the PPARγ Pathway

Background

Macrophage polarization is an important regulatory mechanism of ventricular remodeling. Studies have shown that sinapic acid (SA) exerts an anti-inflammatory effect. However, the effect of SA on macrophages is still unclear.

Objectives

The purpose of the study was to investigate the role of SA in macrophage polarization and ventricular remodeling after myocardial infarction (MI).

Methods

An MI model was established by ligating the left coronary artery. The rats with MI were treated with SA for 1 or 4 weeks after MI. The effect of SA on bone marrow-derived macrophages (BMDMs) was also observed in vitro.

Results

Cardiac systolic dysfunction was significantly improved after SA treatment. SA reduced MCP-1 and CCR2 expression and macrophage infiltration. SA decreased the levels of the inflammatory factors TNF-α, IL-1α, IL-1β, and iNOS and increased the levels of the M2 macrophage markers CD206, Arg-1, IL-10, Ym-1, Fizz-1, and TGF-β at 1 week after MI. SA significantly increased CD68⁺/CD206⁺ macrophage infiltration. Myocardial interstitial fibrosis and MMP-2 and MMP-9 levels were decreased, and the sympathetic nerve marker TH and nerve sprouting marker GAP43 were suppressed after SA treatment at 4 weeks after MI. The PPARγ level was notably upregulated after SA treatment. In vitro, SA also increased the expression of PPARγ mRNA in BMDMs and IL-4-treated BMDMs in a concentration-dependent manner. SA enhanced Arg1 and IL-10 expression in BMDMs, and the PPARγ antagonist GW9662 attenuated M2 macrophage marker expression.

Conclusions

Our results demonstrated that SA attenuated structural and neural remodeling by promoting macrophage M2 polarization via PPARγ activation after MI.

Peroxisome Proliferator-Activated Receptors Regulate Hepatic Immunity and Assist in the Treatment of Primary Biliary Cholangitis

Fibrates, which are agonists of peroxisome proliferator-activated receptor alpha, have received increasing attention in the treatment of primary biliary cholangitis. Reduced alkaline phosphatase levels and improved clinical outcomes were observed in patients with primary biliary cholangitis with an inadequate response to ursodeoxycholic acid (UDCA) monotherapy4 when treated with bezafibrate or fenofibrate combined with UDCA. In contrast to obeticholic acid, which exacerbates pruritus in patients, fibrates have been shown to relieve pruritus. Clinical trial outcomes show potential for the treatment of primary biliary cholangitis by targeting peroxisome proliferator-activated receptors. It is currently agreed that primary biliary cholangitis is an autoimmune-mediated cholestatic liver disease, and peroxisome proliferator-activated receptor is a nuclear receptor that regulates the functions of multiple immune cells, thus playing an important role in regulating innate and adaptive immunity. Therefore, this review focuses on the immune disorder of primary biliary cholangitis and summarizes the regulation of hepatic immunity when peroxisome proliferator-activated receptors are targeted for treating primary biliary cholangitis.

Eicosanoid-Activated PPARα Inhibits NFκB-Dependent Bacterial Clearance During Post-Influenza Superinfection

Secondary bacterial infection (superinfection) post influenza is a serious clinical complication often leading to pneumonia and death. Eicosanoids are bioactive lipid mediators that play critical roles in the induction and resolution of inflammation. CYP450 lipid metabolites are anti-inflammatory lipid mediators that are produced at an excessive level during superinfection potentiating the vulnerability to secondary bacterial infection. Using Nanostring nCounter technology, we have defined the targeted transcriptional response where CYP450 metabolites dampen the Toll-like receptor signaling in macrophages. CYP450 metabolites are endogenous ligands for the nuclear receptor and transcription factor, PPARα. Activation of PPARα hinders NFκB p65 activities by altering its phosphorylation and nuclear translocation during TLR stimulation. Additionally, activation of PPARα inhibited anti-bacterial activities and enhanced macrophage polarization to an anti-inflammatory subtype (M2b). Lastly, Ppara^–/– mice, which are partially protected in superinfection compared to C57BL/6 mice, have increased lipidomic responses and decreased M2-like macrophages during superinfection.

Fenofibrate Increases the Population of Non-Classical Monocytes in Asymptomatic Chagas Disease Patients and Modulates Inflammatory Cytokines in PBMC

Chronic Chagas disease cardiomyopathy (CCC) is the most important clinical manifestation of infection with Trypanosma cruzi (T. cruzi) due to its frequency and effects on morbidity and mortality. Peripheral blood mononuclear cells (PBMC) infiltrate the tissue and differentiate into inflammatory macrophages. Advances in pathophysiology show that myeloid cell subpopulations contribute to cardiac homeostasis, emerging as possible therapeutic targets. We previously demonstrated that fenofibrate, PPARα agonist, controls inflammation, prevents fibrosis and improves cardiac function in a murine infection model. In this work we investigated the spontaneous release of inflammatory cytokines and chemokines, changes in the frequencies of monocyte subsets, and fenofibrate effects on PBMC of seropositive patients with different clinical stages of Chagas disease. The results show that PBMC from Chagas disease patients display higher levels of IL-12, TGF-β, IL-6, MCP1, and CCR2 than cells from uninfected individuals (HI), irrespectively of the clinical stage, asymptomatic (Asy) or with Chagas heart disease (CHD). Fenofibrate reduces the levels of pro-inflammatory mediators and CCR2 in both Asy and CHD patients. We found that CHD patients display a significantly higher percentage of classical monocytes in comparison with Asy patients and HI. Besides, Asy patients have a significantly higher percentage of non-classical monocytes than CHD patients or HI. However, no difference in the intermediate monocyte subpopulation was found between groups. Moreover, monocytes from Asy or CHD patients exhibit different responses upon stimulation in vitro with T. cruzi lysates and fenofibrate treatment. Stimulation with T. cruzi significantly increases the percentage of classical monocytes in the Asy group whereas the percentage of intermediate monocytes decreases. Besides, there are no changes in their frequencies in CHD or HI. Notably, stimulation with T. cruzi did not modify the frequency of the non-classical monocytes subpopulation in any of the groups studied. Moreover, fenofibrate treatment of T. cruzi-stimulated cells, increased the frequency of the non-classical subpopulation in Asy patients. Interestingly, fenofibrate restores CCR2 levels but does not modify HLA-DR expression in any groups. In conclusion, our results emphasize a potential role for fenofibrate as a modulator of monocyte subpopulations towards an anti-inflammatory and healing profile in different stages of chronic Chagas disease.

PPARγ Targets-Derived Diagnostic and Prognostic Index for Papillary Thyroid Cancer

Simple Summary

Through targeted next-generation sequencing of thyroid cancer-related genes in monozygotic twins with papillary thyroid cancer (PTC), we identified common variants of the gene encoding peroxisome proliferator activated receptor gamma (PPARG). Notably, the expression levels of PPARγ target genes were frequently deregulated in PTC compared to benign tissues and were closely associated with disease-specific survival (DSS) outcomes in a TCGA-PTC cohort. Machine learning-powered personalized scoring index comprising 10 PPARγ targets, termed as PPARGi, achieved a near-perfect accuracy in distinguishing cancers from benign tissues, and further identified a small subpopulation of patients at high-risk across different profiling platforms.

Abstract

In most cases, papillary thyroid cancer (PTC) is highly curable and associated with an excellent prognosis. Yet, there are several clinicopathological features that lead to a poor prognosis, underscoring the need for a better genomic strategy to refine prognostication and patient management. We hypothesized that PPARγ targets could be potential markers for better diagnosis and prognosis due to the variants found in PPARG in three pairs of monozygotic twins with PTC. Here, we developed a 10-gene personalized prognostic index, designated PPARGi, based on gene expression of 10 PPARγ targets. Through scRNA-seq data analysis of PTC tissues derived from patients, we found that PPARGi genes were predominantly expressed in macrophages and epithelial cells. Machine learning algorithms showed a near-perfect performance of PPARGi in deciding the presence of the disease and in selecting a small subset of patients with poor disease-specific survival in TCGA-THCA and newly developed merged microarray data (MMD) consisting exclusively of thyroid cancers and normal tissues.

The Role of PPAR Alpha in the Modulation of Innate Immunity

Peroxisome proliferator-activated receptor α is a potent regulator of systemic and cellular metabolism and energy homeostasis, but it also suppresses various inflammatory reactions. In this review, we focus on its role in the regulation of innate immunity; in particular, we discuss the PPARα interplay with inflammatory transcription factor signaling, pattern-recognition receptor signaling, and the endocannabinoid system. We also present examples of the PPARα-specific immunomodulatory functions during parasitic, bacterial, and viral infections, as well as approach several issues associated with innate immunity processes, such as the production of reactive nitrogen and oxygen species, phagocytosis, and the effector functions of macrophages, innate lymphoid cells, and mast cells. The described phenomena encourage the application of endogenous and pharmacological PPARα agonists to alleviate the disorders of immunological background and the development of new solutions that engage PPARα activation or suppression.

On Deep Landscape Exploration of COVID-19 Patients Cells and Severity Markers

COVID-19 is a disease with a spectrum of clinical responses ranging from moderate to critical. To study and control its effects, a large number of researchers are focused on two substantial aims. On the one hand, the discovery of diverse biomarkers to classify and potentially anticipate the disease severity of patients. These biomarkers could serve as a medical criterion to prioritize attention to those patients with higher prone to severe responses. On the other hand, understanding how the immune system orchestrates its responses in this spectrum of disease severities is a fundamental issue required to design new and optimized therapeutic strategies. In this work, using single-cell RNAseq of bronchoalveolar lavage fluid of nine patients with COVID-19 and three healthy controls, we contribute to both aspects. First, we presented computational supervised machine-learning models with high accuracy in classifying the disease severity (moderate and severe) in patients with COVID-19 starting from single-cell data from bronchoalveolar lavage fluid. Second, we identified regulatory mechanisms from the heterogeneous cell populations in the lungs microenvironment that correlated with different clinical responses. Given the results, patients with moderate COVID-19 symptoms showed an activation/inactivation profile for their analyzed cells leading to a sequential and innocuous immune response. In comparison, severe patients might be promoting cytotoxic and pro-inflammatory responses in a systemic fashion involving epithelial and immune cells without the possibility to develop viral clearance and immune memory. Consequently, we present an in-depth landscape analysis of how transcriptional factors and pathways from these heterogeneous populations can regulate their expression to promote or restrain an effective immune response directly linked to the patients prognosis.

Xenoextracellular matrix-rosiglitazone complex-mediated immune evasion promotes xenogenic bioengineered root regeneration by altering M1/M2 macrophage polarization

Xenogenic extracellular matrix (xECM)-based organ transplantation will be a promising approach to address the problem of donor shortage for allotransplantation, which has achieved great success in organ regeneration. However, current approaches to utilize xECM-based organ have limited capacity to yield the host a biofriendly microenvironment for long-term immunity homeostasis, compromising the application of these xenografts for repairing and replacing damaged tissues. As the key innate immune cells, macrophages directly determine the prognosis of xenografts in long term. However, it has not been fully elucidated that how to modulate their biological behavior for microenvironment homeostasis in tissue reconstruction. In this study, we report a robust strategy to impart an immunosuppressive surface to naturally sponge-like porous xECM scaffolds by loading rosiglitazone (RSG) to activate peroxisome proliferators receptors-γ (PPAR-γ). The resultant xECM-RSG complex, enabling RSG to be delivered sequentially and continuously to cells without obvious systemic side effects, is recognized as "self" to escape immune monitoring in local immunoregulation by downregulating the expression of proinflammatory NOS2+ M1 macrophages and oxygen species (ROS) through suppressing NF-κB expression, greatly facilitating the regeneration of enthesis anchoring between the transplanted xenograft and host in both heterotopic and orthotopic models. The newly formed bio-root is morphologically and biomechanically equivalent to native tooth root with a significant expression of odontogenic differentiation-related critical proteins. Therefore, the PPAR-γ-NF-κB axis activated by the xECM-RSG complex enables the xenografts to converse towards M2 macrophages with a modest immunosuppressive capacity for facilitating in xECM-based tissue or organ regeneration.

Regular swimming exercise prevented the acute and persistent mechanical muscle hyperalgesia by modulation of macrophages phenotypes and inflammatory cytokines via PPARγ receptors

Physically active individuals are less likely to develop chronic pain, and physical exercise is an established strategy to control inflammatory diseases. Here, we hypothesized that 1) peripheral pro-inflammatory macrophages phenotype contribute to predisposition of the musculoskeletal to chronic pain, and that 2) activation of PPARγ receptors, modulation of macrophage phenotypes and cytokines through physical exercise would prevent persistent muscle pain. We tested these hypotheses using swimming exercise, pharmacological and immunochemical techniques in a rodent model of persistent muscle hyperalgesia. Swimming prevented the persistent mechanical muscle hyperalgesia most likely through activation of PPARγ receptors, as well as activation of PPARγ receptors by 15d-PGJ₂ and depletion of muscle macrophages in sedentary animals. Acute and persistent muscle hyperalgesia were characterized by an increase in pro-inflammatory macrophages phenotype, and swimming and the 15d-PGJ₂ prevented this increase and increased anti-inflammatory macrophages phenotype. Finally, IL-1β concentration in muscle increased in the acute phase, which was also prevented by PPARγ receptors activation through swimming. Besides, swimming increased muscle concentration of IL-10 in both acute and chronic phases, but only in the persistent phase through PPARγ receptors. Our findings suggest physical exercise activates PPARγ receptors and increases anti-inflammatory responses in the muscle tissue by modulating macrophages phenotypes and cytokines, thereby preventing the establishment of persistent muscle hyperalgesia. These results further highlight the potential of physical exercise to prevent chronic muscle pain.

The endocannabinoidome in neuropsychiatry: Opportunities and potential risks

The endocannabinoid system (ECS) comprises two cognate endocannabinoid receptors referred to as CB1R and CB2R_. ECS dysregulation is apparent in neurodegenerative/neuro-psychiatric disorders including but not limited to schizophrenia, major depressive disorder and potentially bipolar disorder. The aim of this paper is to review mechanisms whereby both receptors may interact with neuro-immune and neuro-oxidative pathways, which play a pathophysiological role in these disorders. CB1R is located in the presynaptic terminals of GABAergic, glutamatergic, cholinergic, noradrenergic and serotonergic neurons where it regulates the retrograde suppression of neurotransmission. CB1R plays a key role in long-term depression, and, to a lesser extent, long-term potentiation, thereby modulating synaptic transmission and mediating learning and memory. Optimal CB1R activity plays an essential neuroprotective role by providing a defense against the development of glutamate-mediated excitotoxicity, which is achieved, at least in part, by impeding AMPA-mediated increase in intracellular calcium overload and oxidative stress. Moreover, CB1R activity enables optimal neuron-glial communication and the function of the neurovascular unit. CB2R receptors are detected in peripheral immune cells and also in central nervous system regions including the striatum, basal ganglia, frontal cortex, hippocampus, amygdala as well as the ventral tegmental area. CB2R upregulation inhibits the presynaptic release of glutamate in several brain regions. CB2R activation also decreases neuroinflammation partly by mediating the transition from a predominantly neurotoxic "M1" microglial phenotype to a more neuroprotective "M2" phenotype. CB1R and CB2R are thus novel drug targets for the treatment of neuro-immune and neuro-oxidative disorders including schizophrenia and affective disorders.

PPARs and Tumor Microenvironment: The Emerging Roles of the Metabolic Master Regulators in Tumor Stromal-Epithelial Crosstalk and Carcinogenesis

Peroxisome proliferator-activated receptors (PPARs) have been extensively studied for more than three decades. Consisting of three isotypes, PPARα, γ, and β/δ, these nuclear receptors are regarded as the master metabolic regulators which govern many aspects of the body energy homeostasis and cell fate. Their roles in malignancy are also increasingly recognized. With the growing interest in crosstalk between tumor stroma and epithelium, this review aims to highlight the current knowledge on the implications of PPARs in the tumor microenvironment. PPARγ plays a crucial role in the metabolic reprogramming of cancer-associated fibroblasts and adipocytes, coercing the two stromal cells to become substrate donors for cancer growth. Fibroblast PPARβ/δ can modify the risk of tumor initiation and cancer susceptibility. In endothelial cells, PPARβ/δ and PPARα are pro- and anti-angiogenic, respectively. Although the angiogenic role of PPARγ remains ambiguous, it is a crucial regulator in autocrine and paracrine signaling of cancer-associated fibroblasts and tumor-associated macrophages/immune cells. Of note, angiopoietin-like 4 (ANGPTL4), a secretory protein encoded by a target gene of PPARs, triggers critical oncogenic processes such as inflammatory signaling, extracellular matrix derangement, anoikis resistance and metastasis, making it a potential drug target for cancer treatment. To conclude, PPARs in the tumor microenvironment exhibit oncogenic activities which are highly controversial and dependent on many factors such as stromal cell types, cancer types, and oncogenesis stages. Thus, the success of PPAR-based anticancer treatment potentially relies on innovative strategies to modulate PPAR activity in a cell type-specific manner.

Transcription Factors Interplay Orchestrates the Immune-Metabolic Response of Leishmania Infected Macrophages

Leishmaniasis is a group of heterogenous diseases considered as an important public health problem in several countries. This neglected disease is caused by over 20 parasite species of the protozoa belonging to the Leishmania genus and is spread by the bite of a female phlebotomine sandfly. Depending on the parasite specie and the immune status of the patient, leishmaniasis can present a wide spectrum of clinical manifestations. As an obligate intracellular parasite, Leishmania colonize phagocytic cells, mainly the macrophages that orchestrate the host immune response and determine the fate of the infection. Once inside macrophages, Leishmania triggers different signaling pathways that regulate the immune and metabolic response of the host cells. Various transcription factors regulate such immune-metabolic responses and the associated leishmanicidal and inflammatory reaction against the invading parasite. In this review, we will highlight the most important transcription factors involved in these responses, their interactions and their impact on the establishment and the progression of the immune response along with their effect on the physiopathology of the disease.

Pemafibrate Pretreatment Attenuates Apoptosis and Autophagy during Hepatic Ischemia-Reperfusion Injury by Modulating JAK2/STAT3β/PPARα Pathway

Hepatic ischemia-reperfusion injury (HIRI) is a common phenomenon in liver transplantation and liver surgery. This article is aimed at clarifying the role of pemafibrate in HIRI through JAK2/STAT3β/PPARα. In the experiment, we divided Balb/c into seven groups, namely, normal control (NC), Sham, PEM (1.0 mg/kg), IRI, IRI + PEM (0.1 mg/kg), IRI + PEM (0.5 mg/kg), and IRI + PEM (1.0 mg/kg). We used biochemical assay, histopathological evaluation, immunohistochemistry, RT-PCR and qRT-PCR, ELISA analysis, and other methods to determine the level of serum AST, ALT, IL-1β, and TNF-α in the liver at three time points (2 h, 8 h, and 24 h) after reperfusion of apoptosis factor, autophagy factor, and the JAK2/STAT3/PPARα content in tissues. Our experiment results showed that the pemafibrate can effectively reduce the level of hepatic IR injury. In addition, pemafibrate has anti-inflammatory, antiapoptotic, and antiautophagy effects, which are mediated by the JAK2/STAT3β/PPARα pathway.

Carcinogenesis: Failure of resolution of inflammation?

Inflammation in the tumor microenvironment is a hallmark of cancer and is recognized as a key characteristic of carcinogens. However, the failure of resolution of inflammation in cancer is only recently being understood. Products of arachidonic acid and related fatty acid metabolism called eicosanoids, including prostaglandins, leukotrienes, lipoxins, and epoxyeicosanoids, critically regulate inflammation, as well as its resolution. The resolution of inflammation is now appreciated to be an active biochemical process regulated by endogenous specialized pro-resolving lipid autacoid mediators which combat infections and stimulate tissue repair/regeneration. Environmental and chemical human carcinogens, including aflatoxins, asbestos, nitrosamines, alcohol, and tobacco, induce tumor-promoting inflammation and can disrupt the resolution of inflammation contributing to a devastating global cancer burden. While mechanisms of carcinogenesis have focused on genotoxic activity to induce mutations, nongenotoxic mechanisms such as inflammation and oxidative stress promote genotoxicity, proliferation, and mutations. Moreover, carcinogens initiate oxidative stress to synergize with inflammation and DNA damage to fuel a vicious feedback loop of cell death, tissue damage, and carcinogenesis. In contrast, stimulation of resolution of inflammation may prevent carcinogenesis by clearance of cellular debris via macrophage phagocytosis and inhibition of an eicosanoid/cytokine storm of pro-inflammatory mediators. Controlling the host inflammatory response and its resolution in carcinogen-induced cancers will be critical to reducing carcinogen-induced morbidity and mortality. Here we review the recent evidence that stimulation of resolution of inflammation, including pro-resolution lipid mediators and soluble epoxide hydrolase inhibitors, may be a new chemopreventive approach to prevent carcinogen-induced cancer that should be evaluated in humans.

Aerobic exercise attenuates ectopic renal sinus adipose tissue accumulation-related renal hypoxia injury in obese mice

AIMS

We explored the effect of aerobic exercise on renal sinus adipose (RSA) accumulation and RSA accumulation-related renal injury in obese mice.

MAIN METHODS

C57BL/6J male mice (n = 30) were evenly divided into three groups: control group (CON, n = 10), obese group (OB, n = 10; given high-fat diet) and obese + aerobic exercise group (OB + E, n = 10; given HFD and 8 weeks of moderate-intensity exercise training). The body weight and kidney weight were measured after sacrificing. Morphological alterations of adipose and renal tissues were measured on hematoxylin-eosin (HE) stained slides. The macrophages surface markers (F4/80, CD68, CD206, CD163), monocyte chemotactic protein 1 (MCP-1) and hypoxia inducible factor-1α (HIF-1α) were examined by immunohistochemistry assay. Inflammation-related factors (FGF-21, KIM-1, IL-6) were analyzed via serum enzyme-linked immunosorbent assay.

KEY FINDINGS

We found that aerobic exercise significantly reduced body weight, kidney weight, serum FGF-21 and KIM-1 levels, and ameliorated glomerular hypertrophy and RSA size accumulation in OB + E group compared with OB group. Furthermore, HIF-1α in the RSA and renal tissues was significantly increased in the OB group (P < 0.05), but exercise effectively reduced the expression of HIF-1α and ameliorated renal inflammation by reducing MCP-1 and CD68 expression (both P < 0.05), improving the conversion from M1 (CD68) to M2 (CD206, CD163) macrophages (P < 0.05), and finally alleviating the level of IL-6 (P < 0.01).

SIGNIFICANCE

Aerobic exercise could reduce RSA accumulation-related adipose hypoxia and macrophage infiltration, and subsequently attenuate the progress of renal injury.

Nuclear receptors, the aryl hydrocarbon receptor, and macrophage function

Nuclear receptors (NRs) are key regulators of innate immune responses and tissue homeostasis. Evidence indicates that NRs significantly impact steady-state immune regulation, uptake and processing of apoptotic cells, tolerance induction, and control of inflammatory immunity. In this review, we describe our current understanding of the NR activity for balancing inflammation and tolerance, the signaling cascade inducing the NR activation and functional responses, and different mechanisms of the NR-driven immune effects in the context of autoimmune diseases. We further describe the ligand-activated transcription factor the aryl hydrocarbon receptor (AhR) that exhibits analogous functionality. Moreover, we will discuss the putative role of NRs and AhR in immune regulation and disease pathogenesis providing a rationale for therapeutic targeting as a unique opportunities in the clinical management of autoimmune diseases.

Repeated acute stress modulates hepatic inflammation and markers of macrophage polarisation in the rat

Bidirectional communication between the neuroendocrine stress and immune systems permits classically anti-inflammatory glucocorticoids to exert pro-inflammatory effects in specific cells and tissues. Liver macrophages/Kupffer cells play a crucial role in initiating inflammatory cascades mediated by the release of pro-inflammatory cytokines following tissue injury. However, the effects of repeated acute psychological stress on hepatic inflammatory phenotype and macrophage activation state remains poorly understood. We have utilised a model of repeated acute stress in rodents to observe the changes in hepatic inflammatory phenotype, including anti-inflammatory vitamin D status, in addition to examining markers of classically and alternatively-activated macrophages. Male Wistar rats were subjected to control conditions or 6 h of restraint stress applied for 1 or 3 days (n = 8 per group) after which plasma concentrations of stress hormone, enzymes associated with liver damage, and vitamin D status were examined, in addition to hepatic expression of pro- and anti-inflammatory markers. Stress increased glucocorticoids and active vitamin D levels in addition to expression of glucocorticoid alpha/beta receptor, whilst changes in circulating hepatic enzymes indicated sustained liver damage. A pro-inflammatory response was observed in liver tissues following stress, and inducible nitric oxide synthase being observed within hepatic macrophage/Kupffer cells. Together, this suggests that stress preferentially induces a pro-inflammatory response in the liver.

The role of peroxisome proliferator-activated receptors (PPAR) in immune responses

Peroxisome proliferator-activated receptors (PPARs) are fatty acid-activated transcription factors of nuclear hormone receptor superfamily that regulate energy metabolism. Currently, three PPAR subtypes have been identified: PPARα, PPARγ, and PPARβ/δ. PPARα and PPARδ are highly expressed in oxidative tissues and regulate genes involved in substrate delivery and oxidative phosphorylation (OXPHOS) and regulation of energy homeostasis. In contrast, PPARγ is more important in lipogenesis and lipid synthesis, with highest expression levels in white adipose tissue (WAT). In addition to tissues regulating whole body energy homeostasis, PPARs are expressed in immune cells and have an emerging critical role in immune cell differentiation and fate commitment. In this review, we discuss the actions of PPARs in the function of the innate and the adaptive immune system and their implications in immune-mediated inflammatory conditions.

Alzheimer's Disease: Protective Effects of Mycobacterium vaccae, a Soil-Derived Mycobacterium with Anti-Inflammatory and Anti-Tubercular Properties, on the Proteomic Profiles of Plasma and Cerebrospinal Fluid in Rats

BACKGROUND

Alzheimer's disease (AD) is an inflammatory neurodegenerative disease that may be associated with prior bacterial infections. Microbial "old friends" can suppress exaggerated inflammation in response to disease-causing infections or increase clearance of pathogens such as Mycobacterium tuberculosis, which causes tuberculosis (TB). One such "old friend" is Mycobacterium vaccae NCTC 11659, a soil-derived bacterium that has been proposed either as a vaccine for prevention of TB, or as immunotherapy for the treatment of TB when used alongside first line anti-TB drug treatment.

OBJECTIVE

The goal of this study was to use a hypothesis generating approach to explore the effects of M. vaccae on physiological changes in the plasma and cerebrospinal fluid (CSF).

METHODS

Liquid chromatography-tandem mass spectrometry-based proteomics were performed in plasma and CSF of adult male rats after immunization with a heat-killed preparation of M. vaccae NCTC 11659 or borate-buffered saline vehicle. Gene enrichment analysis and analysis of protein-protein interactions were performed to integrate physiological network changes in plasma and CSF. We used RT-qPCR to assess immune and metabolic gene expression changes in the hippocampus.

RESULTS

In both plasma and CSF, immunization with M. vaccae increased proteins associated with immune activation and downregulated proteins corresponding to lipid (including phospholipid and cholesterol) metabolism. Immunization with M. vaccae also increased hippocampal expression of interleukin-4 (IL-4) mRNA, implicating anti-inflammatory effects in the central nervous system.

CONCLUSION

M. vaccae alters host immune activity and lipid metabolism. These data are consistent with the hypothesis that microbe-host interactions may protect against possible infection-induced, inflammation-related cognitive impairments.

Bacterial chatter in chronic wound infections

One of the hallmark characteristics of chronic diabetic wounds is the presence of biofilm-forming bacteria. Bacteria encapsulated in a biofilm may coexist as a polymicrobial community and communicate with each other through a phenomenon termed quorum sensing (QS). Here, we describe the QS circuits of bacterial species commonly found in chronic diabetic wounds. QS relies on diffusion of signaling molecules and the local concentration changes of these molecules that bacteria experience in wounds. These biochemical signaling pathways play a role not only in biofilm formation and virulence but also in wound healing. They are, therefore, key to understanding the distinctive nature of these infections. While several in vivo and in vitro models exist to study QS in wounds, there has been limited progress in understanding the interplay between QS molecules and host factors that contribute to wound healing. Lastly, we examine the potential of targeting QS for both diagnosis and therapeutic intervention purposes.

Regulation of Proinflammatory Enzymes by Peroxisome Proliferator-Activated Receptor Gamma in Astroglia Infected with Toxoplasma gondii

Peroxisome proliferator-activated receptor gamma (PPARγ) regulates neuroinflammation, and its agonists act as neuroprotective agents. This study aims to investigate the correlation between PPARγ and proinflammatory enzyme expression in astroglia infected with Toxoplasma gondii tachyzoite in vitro. Our results showed that matrix metalloprotease (MMP)-2, MMP-9, cyclooxygenase-2 (COX-2), prostaglandin (PGE)-2, inducible nitric-oxide synthase (iNOS), and nitric oxide (NO) were significantly increased in T. gondii-infected astroglia. Furthermore, the expression levels of MMP-2, MMP-9, COX-2, PGE-2, iNOS, and NO were significantly decreased by rosiglitazone-a PPARγ agonist. By contrast, the treatment with GW9662, a PPARγ antagonist, efficiently increased the expression levels of MMP-2, MMP-9, COX-2, PGE-2, iNOS, and NO. These results suggested that the treatment with rosiglitazone offers a potential strategy for controlling the inflammatory factors in T. gondii infection.

IL-10-Dependent and -Independent Mechanisms Are Involved in the Cardiac Pathology Modulation Mediated by Fenofibrate in an Experimental Model of Chagas Heart Disease

IL-10 is an anti-inflammatory cytokine that plays a significant role in the modulation of the immune response in many pathological conditions, including infectious diseases. Infection with Trypanosoma cruzi (T. cruzi), the etiological agent of Chagas disease, results in an ongoing inflammatory response that may cause heart dysfunction, ultimately leading to heart failure. Given its infectious and inflammatory nature, in this work we analyzed whether the lack of IL-10 hinders the anti-inflammatory effects of fenofibrate, a PPARα ligand, in a murine model of Chagas heart disease (CHD) using IL-10 knockout (IL-10 KO) mice. Our results show fenofibrate was able to restore the abnormal cardiac function displayed by T. cruzi-infected mice lacking IL-10. Treatment with fenofibrate reduced creatine kinase (CK) levels in sera of IL-10 KO mice infected with T. cruzi. Moreover, although fenofibrate could not modulate the inflammatory infiltrates developing in the heart, it was able to reduce the increased collagen deposition in infected IL-10 KO mice. Regarding pro-inflammatory mediators, the most significant finding was the increase in serum IL-17. These were reduced in IL-10 KO mice upon fenofibrate treatment. In agreement with this, the expression of RORγt was reduced. Infection of IL-10 KO mice increased the expression of YmI, FIZZ and Mannose Receptor (tissue healing markers) that remained unchanged upon treatment with fenofibrate. In conclusion, our work emphasizes the role of anti-inflammatory mechanisms to ameliorate heart function in CHD and shows, for the first time, that fenofibrate attains this through IL-10-dependent and -independent mechanisms.

Immunoregulation of microglial polarization: an unrecognized physiological function of α-synuclein

Background

Microglial function is vital for maintaining the health of the brain, and their activation is an essential component of neurodegeneration. There is significant research on factors that provoke “reactive” or “inflammatory” phenotypes in conditions of injury or disease. One such factor, exposure to the aggregated or oligomeric forms of α-synuclein, an abundant brain protein, plays an essential role in driving microglial activation; including chemotactic migration and production of inflammatory mediators in Lewy body (LB) diseases such as Parkinson’s disease. On the other hand, it is increasingly recognized that microglia also undergo changes, dependent on the cellular environment, that promote mainly reconstructive and anti-inflammatory functions, i.e., mostly desirable functions of microglia in a physiological state. What maintains microglia in this physiological state is essentially unknown.

Methods

In this study, using in vitro and in vivo models, we challenged primary microglia or BV2 microglia with LPS + IFN-γ, IL-4 + IL-13, α-synuclein monomer, and α-synuclein oligomer, and examined microglia phenotype and the underlying mechanism by RT-PCR, Western blot, ELISA, IF, IHC, Co-IP.

Results

We described a novel physiological function of α-synuclein, in which it modulates microglia toward an anti-inflammatory phenotype by interaction with extracellular signal-regulated kinase (ERK) and recruitment of the ERK, nuclear factor kappa B (NF-κB), and peroxisome proliferator-activated receptor γ (PPARγ) pathways.

Conclusions

These findings suggest a previously unrecognized function of monomeric α-synuclein that likely gives new insights into the pathogenesis and potential therapies for Lewy body-related diseases and beyond, given the abundance and multiple functions of α-synuclein in brain tissue.

Differential Modulation of the Phospholipidome of Proinflammatory Human Macrophages by the Flavonoids Quercetin, Naringin and Naringenin

The immunomodulatory activity of flavonoids is increasingly appreciated. Macrophage phospholipids (PLs) play crucial roles in cell-mediated inflammatory responses. However, little is known on how these PLs are affected upon flavonoid treatment. In this work, we have used mass-spectrometry-based lipidomics to characterize the changes in the phospholipidome of proinflammatory human-macrophage-like cells (THP-1-derived and LPS+IFN-γ-stimulated) incubated with non-cytotoxic concentrations of three flavonoids: quercetin, naringin and naringenin. One hundred forty-seven PL species belonging to various classes were identified, and their relative abundances were determined. Each flavonoid displayed its own unique signature of induced effects. Quercetin produced the strongest impact, acting both on constitutive PLs (phosphatidylcholines, phosphatidylethanolamines and sphingomyelins) and on minor signaling lipids, such as phosphatidylinositol (PI) and phosphatidylserine (PS) species. Conversely, naringin hardly affected structural PLs, producing changes in signaling molecules that were opposite to those seen in quercetin-treated macrophages. In turn, albeit sharing some effects with quercetin, naringenin did not change PI and PS levels and interfered with a set of phosphatidylcholines distinct from those modulated by quercetin. These results demonstrate that flavonoids bioactivity involves profound and specific remodeling of macrophage phospholipidome, paving the way to future studies on the role of cellular phospholipids in flavonoid-mediated immunomodulatory effects.

N-Propargyl caffeate amide (PACA) prevents cardiac fibrosis in experimental myocardial infarction by promoting pro-resolving macrophage polarization

Macrophages control the initiation and resolution of cardiac fibrosis in post-infarction cardiac remodeling. The aim of the present study was to investigate whether N-propargyl caffeate amide (PACA) could suppress myocardial fibrosis via regulating macrophage polarization. By using rat model of isoproterenol-induced myocardial fibrosis, we discovered that PACA could reduce cardiac fibrosis in a dose-dependent manner. To elucidate the anti-fibrotic mechanisms, we examined whether PACA affected pro-inflammatory M1 and pro-resolving macrophage biomarkers in macrophage polarization. As result, PACA reduced the expression of pro-inflammatory M1 biomarkers (e.g., iNOS, TNF-α, CXCL10, IL-6, CCL2 and CD80) while increased the expression of pro-resolving M2a biomarkers (e.g., IL-10, arginase-1, FZZ1, YM-1 and CD163) in LPS-stimulated RAW264.7 macrophages. PACA also suppressed the elevation of M1 biomarker ED1 in the early phase but up-regulated the expression of pro-resolving biomarker ED2 in the later phase. Moreover, PACA reduced the expression of pro-fibrotic TGF-β1 and PDGF-α while maintained or even increased the production of pro-apoptotic MMP-13, MMP-9 and TRAIL. Importantly, mechanistic studies revealed that PACA might promote the switch of macrophage polarization towards a pro-resolving macrophage phenotype via activating PPAR-γ pathway. Taken together, this study suggested that PACA might be a drug candidate for preventing cardiac fibrosis in myocardial infarction.

Pyridinecarboxylic Acid Derivative Stimulates Pro-Angiogenic Mediators by PI3K/AKT/mTOR and Inhibits Reactive Nitrogen and Oxygen Species and NF-κB Activation Through a PPARγ-Dependent Pathway in T. cruzi-Infected Macrophages

Chagas disease is caused by Trypanosoma cruzi infection and represents an important public health concern in Latin America. Macrophages are one of the main infiltrating leukocytes in response to infection. Parasite persistence could trigger a sustained activation of these cells, contributing to the damage observed in this pathology, particularly in the heart. HP₂₄, a pyridinecarboxylic acid derivative, is a new PPARγ ligand that exerts anti-inflammatory and pro-angiogenic effects. The aim of this work was to deepen the study of the mechanisms involved in the pro-angiogenic and anti-inflammatory effects of HP₂₄ in T. cruzi-infected macrophages, which have not yet been elucidated. We show for the first time that HP₂₄ increases expression of VEGF-A and eNOS through PI3K/AKT/mTOR and PPARγ pathways and that HP₂₄ inhibits iNOS expression and NO release, a pro-inflammatory mediator, through PPARγ-dependent mechanisms. Furthermore, this study shows that HP₂₄ modulates H₂O₂ production in a PPARγ-dependent manner. It is also demonstrated that this new PPARγ ligand inhibits the NF-κB pathway. HP₂₄ inhibits IKK phosphorylation and IκB-α degradation, as well as p65 translocation to the nucleus in a PPARγ-dependent manner. In Chagas disease, both the sustained increment in pro-inflammatory mediators and microvascular abnormalities are crucial aspects for the generation of cardiac damage. Elucidating the mechanism of action of new PPARγ ligands is highly attractive, given the fact that it can be used as an adjuvant therapy, particularly in the case of Chagas disease in which inflammation and tissue remodeling play an important role in the pathophysiology of this disease.

PPARs and the Development of Type 1 Diabetes

Peroxisome proliferator-activated receptors (PPARs) are a family of transcription factors with a key role in glucose and lipid metabolism. PPARs are expressed in many cell types including pancreatic beta cells and immune cells, where they regulate insulin secretion and T cell differentiation, respectively. Moreover, various PPAR agonists prevent diabetes in the non-obese diabetic (NOD) mouse model of type 1 diabetes. PPARs are thus of interest in type 1 diabetes (T1D) as they represent a novel approach targeting both the pancreas and the immune system. In this review, we examine the role of PPARs in immune responses and beta cell biology and their potential as targets for treatment of T1D.