Activation of proliferator-activated receptors alpha and gamma induces apoptosis of human monocyte-derived macrophages

Sorbicillinoid HSL-2 inhibits the infection of influenza A virus via interaction with the PPAR-γ/NF-κB pathway

BACKGROUND

Drug resistance is an important factor in the fight against influenza A virus (IAV). Natural products offer a rich source of lead compounds for the discovery of novel antiviral drugs. In a previous study, we isolated the sorbicillinoid polyketide HSL-2 from the mycelium of fungus Trichoderma sp. T-4-1. Here, we show that this compound exerts strong antiviral activity against a panel of IAVs.

METHODS

The immunofluorescence and qRT-PCR assays were used to detect the inhibitory effect of HSL-2 toward the replication of influenza virus and IAV-induced expression of the pro-inflammatory cytokines such as TNF-α, IL-6, and IL-1β.

RESULTS

The results indicated that HSL-2 inhibited influenza virus replication, and it significantly inhibited IAV-induced overexpression of the pro-inflammatory cytokines TNF-α, IL-6, and IL-1β through modulating the PPAR-γ/NF-κB pathway. Notably, this effect was decreased when cells were transfected with PPAR-γ siRNA or treated with the PPAR-γ inhibitor T0070907. In addition, HSL-2 was able to attenuate lung inflammatory responses and to improve lung lesions in a mouse model of IAV infection.

CONCLUSIONS

In this paper, we identified a microbial secondary metabolite, HSL-2, with anti-influenza virus activity. This report is the first to describe the antiviral activity and mechanism of action of HSL-2, and it provides a new strategy for the development of novel anti-influenza virus drugs from natural sources.

An insight to treat cardiovascular diseases through phytochemicals targeting PPAR-α

Peroxisome proliferator-activated receptor-α (PPAR-α) belonging to the nuclear hormone receptor superfamily is a promising target for CVDs which mechanistically improves the production of high-density lipid as well as inhibit vascular smooth muscle cell proliferation. PPAR-α mainly interferes with adenosine monophosphate-activated protein kinase, transforming growth factor-β-activated kinase, and nuclear factor-κB pathways to protect against cardiac complications. Natural products/extracts could serve as a potential therapeutic strategy in CVDs for targeting PPAR-α with broad safety margins. In recent years, the understanding of naturally derived PPAR-α agonists has considerably improved; however, the information is scattered. In vitro and in vivo studies on acacetin, apigenin, arjunolic acid, astaxanthin, berberine, resveratrol, vaticanol C, hispidulin, ginsenoside Rb3, and genistein showed significant effects in CVDs complications by targeting PPAR-α. With the aim of demonstrating the tremendous chemical variety of natural products targeting PPAR-α in CVDs, this review provides insight into various natural products that can work to prevent CVDs by targeting the PPAR-α receptor along with their detailed mechanism.

Arachidonic acid-derived lipid mediators in multiple sclerosis pathogenesis: fueling or dampening disease progression?

BACKGROUND

Multiple sclerosis (MS) is a chronic autoimmune disease of the central nervous system (CNS), characterized by neuroinflammation, demyelination, and neurodegeneration. Considering the increasing prevalence among young adults worldwide and the disabling phenotype of the disease, a deeper understanding of the complexity of the disease pathogenesis is needed to ultimately improve diagnosis and personalize treatment opportunities. Recent findings suggest that bioactive lipid mediators (LM) derived from ω-3/-6 polyunsaturated fatty acids (PUFA), also termed eicosanoids, may contribute to MS pathogenesis. For example, disturbances in LM profiles and especially those derived from the ω-6 PUFA arachidonic acid (AA) have been reported in people with MS (PwMS), where they may contribute to the chronicity of neuroinflammatory processes. Moreover, we have previously shown that certain AA-derived LMs also associated with neurodegenerative processes in PwMS, suggesting that AA-derived LMs are involved in more pathological events than solely neuroinflammation. Yet, to date, a comprehensive overview of the contribution of these LMs to MS-associated pathological processes remains elusive.

MAIN BODY

This review summarizes and critically evaluates the current body of literature on the eicosanoid biosynthetic pathway and its contribution to key pathological hallmarks of MS during different disease stages. Various parts of the eicosanoid pathway are highlighted, namely, the prostanoid, leukotriene, and hydroxyeicosatetraenoic acids (HETEs) biochemical routes that include specific enzymes of the cyclooxygenases (COXs) and lipoxygenases (LOX) families. In addition, cellular sources of LMs and their potential target cells based on receptor expression profiles will be discussed in the context of MS. Finally, we propose novel therapeutic approaches based on eicosanoid pathway and/or receptor modulation to ultimately target chronic neuroinflammation, demyelination and neurodegeneration in MS.

SHORT CONCLUSION

The eicosanoid pathway is intrinsically linked to specific aspects of MS pathogenesis. Therefore, we propose that novel intervention strategies, with the aim of accurately modulating the eicosanoid pathway towards the biosynthesis of beneficial LMs, can potentially contribute to more patient- and MS subtype-specific treatment opportunities to combat MS.

Glomerular lipidosis as a feature of renal-limited macrophage activation syndrome in a transplanted kidney: a case report

BACKGROUND

Glomerular lipidosis is a rare histological feature presenting the extensive glomerular accumulation of lipids with or without histiocytic infiltration, which develops under various conditions. Among its various etiologies, macrophage activation syndrome (MAS) is a condition reported to be associated with histiocytic glomerular lipidosis. Here we describe the first case of glomerular lipidosis observed in a renal allograft that histologically mimicked histiocytic glomerulopathy owing to MAS.

CASE PRESENTATION

A 42-year-old man underwent successful living-donor kidney transplantation. However, middle-grade proteinuria and increased serum triglyceride levels indicative of type V hyperlipidemia developed rapidly thereafter. An allograft biopsy performed 6 months after the transplantation showed extensive glomerular infiltration of CD68+ foam cells (histiocytes) intermingled with many CD3+ T-cells (predominantly CD8+ cells). Furthermore, frequent contact between glomerular T-cells and histiocytes, and the existence of activated CD8+ cells (CD8+, HLA-DR+ cells) were observed by double immunostaining. There was no clinicopathological data suggesting lipoprotein glomerulopathy or lecithin cholesterol acyltransferase deficiency, both of which are well-known causes of glomerular lipidosis. The histological findings were relatively similar to those of histiocytic glomerulopathy caused by MAS. As systemic manifestations of MAS, such as fever, pancytopenia, coagulation abnormalities, hyperferritinemia, increased liver enzyme levels, hepatosplenomegaly, and lymphadenopathy were minimal, this patient was clinicopathologically diagnosed as having renal-limited MAS. Although optimal treatment strategies for MAS in kidney transplant patients remains unclear, we strengthened lipid-lowering therapy using pemafibrate, without modifying the amount of immunosuppressants. Serum triglyceride levels were normalized with this treatment; however, the patient's extensive proteinuria and renal dysfunction did not improve. Biopsy analysis at 1 year after the transplantation demonstrated the disappearance of glomerular foamy changes, but the number of glomerular infiltrating cells remained similar.

CONCLUSION

To our knowledge, this is the first reported case of glomerular lipidosis in a transplanted kidney. Increased interaction-activation of histiocytes (macrophages) and CD8+ T-cells, the key pathogenic feature of MAS, was observed in the glomeruli of this patient, who did not demonstrate overt systemic manifestations, suggesting a pathological condition of renal-limited MAS. The clinical effects of triglyceride-lowering therapy were limited, suggesting that hypertriglyceridemia was not the cause of but rather may be a consequence of renal-limited MAS.

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.

RAE1 promotes nitrosamine-induced malignant transformation of human esophageal epithelial cells through PPARα-mediated lipid metabolism

Esophageal cancer (EC) is the sixth cause of cancer-related deaths and still is a significant public health problem globally. Nitrosamines exposure represents a major health concern increasing EC risks. Exploring the mechanisms induced by nitrosamines may contribute to the prevention and early detection of EC. However, the mechanism of nitrosamine carcinogenesis remains unclear. Ribonucleic acid export 1 (RAE1), has an important role in mediating diverse cancer types, but, to date, there has been no study for any functional role of RAE1 in esophageal carcinogenesis. Here, we successfully verified the nitrosamine-induced malignant transformation cell (MNNG-M) by xenograft tumor model, based on which it was found that RAE1 was upregulation in the early stage of nitrosamine-induced esophageal carcinogenesis and EC tissues. RAE1 knockdown led to severe blockade in G2/M phase and significant inhibition of proliferation of MNNG-M cells, whereas RAE1 overexpression had the opposite effect. In addition, peroxisome proliferator-activated receptor-alpha (PPARα), was demonstrated as a downstream target gene of RAE1, and its down-regulation reduced lipid accumulation, resulting in causing cells accumulation in the G2/M phase. Mechanistically, we found that RAE1 regulates the lipid metabolism by maintaining the stability of PPARα mRNA. Taken together, our study reveals that RAE1 promotes malignant transformation of human esophageal epithelial cells (Het-1A) by regulating PPARα-mediated lipid metabolism to affect cell cycle progression, and offers a new explanation of the mechanisms underlying esophageal carcinogenesis.

Chrysin inhibits adipogenesis by modulating PPARγ: in silico and in vitro studies

Adipose tissue is the major storage site of lipids and plays a vital role in energy homeostasis. Adipogenesis is a well-regulated process wherein preadipocytes differentiate into adipocytes. It requires the sequential activation of numerous transcription factors, including peroxisome proliferator activated receptor-γ (PPAR-γ). Phytochemicals have been reported to regulate adipogenesis and flavonoids represent the most researched groups of phytochemicals with regard to their effect on adipogenesis. Chrysin is a naturally occurring flavone and is reported to have anti-inflammatory effects in obese conditions. The present study was aimed to examine the effect of chrysin on adipogenesis. In silico Molecular docking, dynamic simulation studies and in vitro cell-based assays showed that chrysin inhibited adipogenesis by modulating key adipogenic transcription factor PPARγ. Enhanced adipogenesis leads to obesity and targeting adipogenesis is potential in regulating adipose tissue development. So, these investigations may provide important information for designing therapeutic interventions to control adiposity.Communicated by Ramaswamy H. Sarma.

Impaired autophagy contributes to the aggravated deterioration of osteoarthritis articular cartilage by peroxisome proliferator-activated receptor α deficiency, associated with decreased ERK and Akt activation

BACKGROUND

Although the chondroprotection of peroxisome proliferator-activated receptor α (PPARα) activation against osteoarthritis (OA) has been revealed, the regulatory mechanism of PPARα deficiency to aggravate osteoarthritic cartilage deterioration remains unclear. Here, we aimed to investigate whether and how autophagy is involved in OA pathological progression.

METHODS

Model of experimental OA was established using destabilization of the medial meniscus in PPARα-KO 129S4/SvJae male mice, followed by histopathological detection of articular cartilage and immunohistochemistry detection of extracellular matrix (ECM) or autophagy-related signal molecules. Meanwhile, human OA chondrocytes obtained from total knee replacement surgery patients with OA were cultured with the pretreatment of IL-1β, followed with the treatment of PPARα agonist WY14643 and the detection of related signal molecules.

RESULTS

PPARα deficiency aggravated cartilage damage with decreased LC3B level in combination with an increase in P62 level, accompanied with reduced p-Akt and p-ERK levels in PPARα-KO mouse model of experimental OA. On the contrary, PPARα activation by WY14643 promoted ECM synthesis in IL-1β-treated human OA chondrocytes, accompanied with increased LC3B-II/I ratio and Beclin 1 level and decreased P62 and Bcl2 levels. Meanwhile, it was observed that activated ERK and Akt by PPARα activation contributed to the enhancement of autophagy and ECM synthesis in human OA chondrocytes.

CONCLUSIONS

Impaired autophagy contributed to the aggravated deterioration of osteoarthritis articular cartilage by PPARα deficiency associated with the suppression of ERK and Akt, with an implication that triggering PPARα activation ought to be a potential promising therapeutic target for OA therapy.

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.

Pharmacological Utility of PPAR Modulation for Angiogenesis in Cardiovascular Disease

Peroxisome proliferator activated receptors, including PPARα, PPARβ/δ, and PPARγ, are ligand-activated transcription factors belonging to the nuclear receptor superfamily. They play important roles in glucose and lipid metabolism and are also supposed to reduce inflammation and atherosclerosis. All PPARs are involved in angiogenesis, a process critically involved in cardiovascular pathology. Synthetic specific agonists exist for all PPARs. PPARα agonists (fibrates) are used to treat dyslipidemia by decreasing triglyceride and increasing high-density lipoprotein (HDL) levels. PPARγ agonists (thiazolidinediones) are used to treat Type 2 diabetes mellitus by improving insulin sensitivity. PPARα/γ (dual) agonists are supposed to treat both pathological conditions at once. In contrast, PPARβ/δ agonists are not in clinical use. Although activators of PPARs were initially considered to have favorable effects on the risk factors for cardiovascular disease, their cardiovascular safety is controversial. Here, we discuss the implications of PPARs in vascular biology regarding cardiac pathology and focus on the outcomes of clinical studies evaluating their benefits in cardiovascular diseases.

Systemic and Airway Epigenetic Disruptions Are Associated with Health Status in COPD

Epigenetic modifications are common in chronic obstructive pulmonary disease (COPD); however, their clinical relevance is largely unknown. We hypothesized that epigenetic disruptions are associated with symptoms and health status in COPD. We profiled the blood (n = 57) and airways (n = 62) of COPD patients for DNA methylation (n = 55 paired). The patients' health status was assessed using the St. George's Respiratory Questionnaire (SGRQ). We conducted differential methylation analyses and identified pathways characterized by epigenetic disruptions associated with SGRQ scores and its individual domains. 29,211 and 5044 differentially methylated positions (DMPs) were associated with total SGRQ scores in blood and airway samples, respectively. The activity, impact, and symptom domains were associated with 9161, 25,689 and 17,293 DMPs in blood, respectively; and 4674, 3730 and 5063 DMPs in airways, respectively. There was a substantial overlap of DMPs between airway and blood. DMPs were enriched for pathways related to common co-morbidities of COPD (e.g., ageing, cancer and neurological) in both tissues. Health status in COPD is associated with airway and systemic epigenetic changes especially in pathways related to co-morbidities of COPD. There are more blood DMPs than in the airways suggesting that blood epigenome is a promising source to discover biomarkers for clinical outcomes in COPD.

Studies on the contribution of PPAR Gamma to tuberculosis physiopathology

Introduction

Tuberculosis (TB) is a major health problem characterized by an immuno-endocrine imbalance: elevated plasma levels of cortisol and pro- and anti-inflammatory mediators, as well as reduced levels of dehydroepiandrosterone. The etiological agent, Mycobacterium tuberculosis (Mtb), is captured by pulmonary macrophages (Mf), whose activation is necessary to cope with the control of Mtb, however, excessive activation of the inflammatory response also leads to tissue damage. Glucocorticoids (GC) are critical elements to counteract the immunoinflammatory reaction, and peroxisome proliferator-activated receptors (PPARs) are also involved in this regard. The primary forms of these receptors are PPARϒ, PPARα, and PPARβ/δ, the former being the most involved in anti-inflammatory responses. In this work, we seek to gain some insight into the contribution of PPARϒ in immuno-endocrine-metabolic interactions by focusing on clinical studies in pulmonary TB patients and in vitro experiments on a Mf cell line.

Methods and results

We found that TB patients, at the time of diagnosis, showed increased expression of the PPARϒ transcript in their peripheral blood mononuclear cells, positively associated with circulating cortisol and related to disease severity. Given this background, we investigated the expression of PPARϒ (RT-qPCR) in radiation-killed Mtb-stimulated human Mf. The Mtb stimulation of Mf derived from the human line THP1 significantly increased the expression of PPARϒ, while the activation of this receptor by a specific agonist decreased the expression of pro- and anti-inflammatory cytokines (IL-1β and IL-10). As expected, the addition of GC to stimulated cultures reduced IL-1β production, while cortisol treatment together with the PPARϒ agonist lowered the levels of this proinflammatory cytokine in stimulated cultures. The addition of RU486, a glucocorticoid receptor antagonist, only reversed the inhibition produced by the addition of GC.

Conclusion

The current results provide a stimulating background for further analysis of the interconnection between PPARs and steroid hormones in the context of Mtb infection.

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.

Alternatively Spliced Landscape of PPARγ mRNA in Podocytes Is Distinct from Adipose Tissue

Podocytes are highly differentiated epithelial cells, and their structural and functional integrity is compromised in a majority of glomerular and renal diseases, leading to proteinuria, chronic kidney disease, and kidney failure. Traditional agonists (e.g., pioglitazone) and selective modulators (e.g., GQ-16) of peroxisome-proliferator-activated-receptor-γ (PPARγ) reduce proteinuria in animal models of glomerular disease and protect podocytes from injury via PPARγ activation. This indicates a pivotal role for PPARγ in maintaining glomerular function through preservation of podocytes distinct from its well-understood role in driving insulin sensitivity and adipogenesis. While its transcriptional role in activating adipokines and adipogenic genes is well-established in adipose tissue, liver and muscle, understanding of podocyte PPARγ signaling remains limited. We performed a comprehensive analysis of PPARγ mRNA variants due to alternative splicing, in human podocytes and compared with adipose tissue. We found that podocytes express the ubiquitous PPARγ Var 1 (encoding γ1) and not Var2 (encoding γ2), which is mostly restricted to adipose tissue and liver. Additionally, we detected expression at very low level of Var4, and barely detectable levels of other variants, Var3, Var11, VartORF4 and Var9, in podocytes. Furthermore, a distinct podocyte vs. adipocyte PPAR-promoter-response-element containing gene expression, enrichment and pathway signature was observed, suggesting differential regulation by podocyte specific PPARγ1 variant, distinct from the adipocyte-specific γ2 variant. In summary, podocytes and glomeruli express several PPARγ variants, including Var1 (γ1) and excluding adipocyte-specific Var2 (γ2), which may have implications in podocyte specific signaling and pathophysiology. This suggests that that new selective PPARγ modulators can be potentially developed that will be able to distinguish between the two forms, γ1 and γ2, thus forming a basis of novel targeted therapeutic avenues.

Activation of PPARγ Protects Obese Mice from Acute Lung Injury by Inhibiting Endoplasmic Reticulum Stress and Promoting Mitochondrial Biogenesis

Objective

Obesity-induced endoplasmic reticulum (ER) stress plays a role in increased susceptibility to acute lung injury (ALI)/acute respiratory distress syndrome (ARDS). The activation of peroxisome proliferator-activated receptor-γ (PPARγ) is associated with lung protection and is effective in ameliorating ER stress and mitochondrial dysfunction. The aim of this study was to investigate the expression of PPARγ in the lung tissues of obese mice and explore whether the PPARγ-dependent pathway could mediate decreased ALI/ARDS by regulating ER stress and mitochondrial biogenesis.

Methods

We determined PPARγ expression in the lung tissues of normal and obese mice. ALI models of alveolar epithelial cells and of obese mice were used and treated with either PPARγ activator rosiglitazone (RSG) or PPARγ inhibitor GW9662. Lung tissue and cell samples were collected to assess lung inflammation and apoptosis, and ER stress and mitochondrial biogenesis were detected.

Results

PPARγ expression was significantly decreased in the lung tissue of obese mice compared with that in normal mice. Both in vivo and in vitro studies have shown that activation of PPARγ leads to reduced expression of the ER stress marker proteins 78-kDa glucose-regulated protein (GRP78), C/EBP homologous protein (CHOP), and Caspase12. Conversely, expression of the mitochondrial biogenesis-related proteins peroxisome proliferator-activated receptor γ coactivator 1 (PGC-1α), nuclear respiratory factor-1 (NRF-1), and mitochondrial transcription factor A (TFAM) increased. Furthermore, activation of PPARγ is associated with decreased levels of lung inflammation and epithelial apoptosis and increased expression of adiponectin (APN) and mitofusin2 (MFN2). GW9662 bound to PPARγ and blocked its transcriptional activity and then diminished the protective effect of PPARγ on lung tissues.

Conclusions

PPARγ activation exerts anti-inflammation effects in alveolar epithelia by alleviating ER stress and promoting mitochondrial biogenesis. Therefore, lower levels of PPARγ in the lung tissues of obese mice may lead to an increased susceptibility to ALI.

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.

Pemafibrate Prevents Rupture of Angiotensin II-Induced Abdominal Aortic Aneurysms

Background

Abdominal aortic aneurysm (AAA) is a life-threatening disease that lacks effective preventive therapies. This study aimed to evaluate the effect of pemafibrate, a selective peroxisome proliferator-activated receptor alpha (PPARα) agonist, on AAA formation and rupture.

Methods

Experimental AAA was induced by subcutaneous angiotensin II (AngII) infusion in ApoE ^{- / -} mice for 4 weeks. Pemafibrate (0.1 mg/kg/day) was administered orally. Dihydroethidium staining was used to evaluate the reactive oxygen species (ROS).

Results

The size of the AngII-induced AAA did not differ between pemafibrate- and vehicle-treated groups. However, a decreased mortality rate due to AAA rupture was observed in pemafibrate-treated mice. Pemafibrate ameliorated AngII-induced ROS and reduced the mRNA expression of interleukin-6 and tumor necrosis factor-α in the aortic wall. Gelatin zymography analysis demonstrated significant inhibition of matrix metalloproteinase-2 activity by pemafibrate. AngII-induced ROS production in human vascular smooth muscle cells was inhibited by pre-treatment with pemafibrate and was accompanied by an increase in catalase activity. Small interfering RNA-mediated knockdown of catalase or PPARα significantly attenuated the anti-oxidative effect of pemafibrate.

Conclusion

Pemafibrate prevented AAA rupture in a murine model, concomitant with reduced ROS, inflammation, and extracellular matrix degradation in the aortic wall. The protective effect against AAA rupture was partly mediated by the anti-oxidative effect of catalase induced by pemafibrate in the smooth muscle cells.

Fibrates: A Possible Treatment Option for Patients with Abdominal Aortic Aneurysm?

Abdominal aortic aneurysm (AAA) is a life-threatening disease; however, there is no established treatment for patients with AAA. Fibrates are agonists of peroxisome proliferator-activated receptor alpha (PPARα) that are widely used as therapeutic agents to treat patients with hypertriglyceridemia. They can regulate the pathogenesis of AAA in multiple ways, for example, by exerting anti-inflammatory and anti-oxidative effects and suppressing the expression of matrix metalloproteinases. Previously, basic and clinical studies have evaluated the effects of fenofibrate on AAA. In this paper, we summarize the results of these studies and discuss the problems associated with using fenofibrate as a therapeutic agent for patients with AAA. In addition, we discuss a new perspective on the regulation of AAA by PPARα agonists.

Mechanistic insights into the peroxisome proliferator-activated receptor alpha as a transcriptional suppressor

Non-alcoholic fatty liver disease (NAFLD) is one of the most prevalent hepatic disorders that 20-30% of the world population suffers from. The feature of NAFLD is excess lipid accumulation in the liver, exacerbating multiple metabolic syndromes such as hyperlipidemia, hypercholesterolemia, hypertension, and type 2 diabetes. Approximately 20-30% of NAFLD cases progress to more severe chronic hepatitis, known as non-alcoholic steatohepatitis (NASH), showing deterioration of hepatic functions and liver fibrosis followed by cirrhosis and cancer. Previous studies uncovered that several metabolic regulators had roles in disease progression as key factors. Peroxisome proliferator-activated receptor alpha (PPARα) has been identified as one of the main players in hepatic lipid homeostasis. PPARα is abundantly expressed in hepatocytes, and is a ligand-dependent nuclear receptor belonging to the NR1C nuclear receptor subfamily, orchestrating lipid/glucose metabolism, inflammation, cell proliferation, and carcinogenesis. PPARα agonists are expected to be novel prescription drugs for NASH treatment, and some of them (e.g., Lanifibranor) are currently under clinical trials. These potential novel drugs are developed based on the knowledge of PPARα-activating target genes related to NAFLD and NASH. Intriguingly, PPARα is known to suppress the expression of subsets of target genes under agonist treatment; however, the mechanisms of PPARα-mediated gene suppression and functions of these genes are not well understood. In this review, we summarize and discuss the mechanisms of target gene repression by PPARα and the roles of repressed target genes on hepatic lipid metabolism, fibrosis and carcinogenesis related to NALFD and NASH, and provide future perspectives for PPARα pharmaceutical potentials.

Effect of chiglitazar and sitagliptin on glucose variations, insulin resistance and inflammatory-related biomarkers in untreated patients with type 2 diabetes

AIMS

To evaluate glycemic variations, changes in insulin resistance and oxidative stress after chiglitazar or sitagliptin treatment in untreated patients with type 2 diabetes mellitus (T2DM).

METHODS

Based on the study inclusion and exclusion criteria, 81 patients with T2DM were randomly divided to receive chiglitazar or sitagliptin treatment for 24 weeks. Continuous glucose monitoring (CGM) systems were conducted for 72 h in eligible patients. We analyzed the following glycemic variation parameters derived from the CGM data and measured the serum levels of hemoglobin A1c (HbA1c), fasting blood glucose (FBG), 2-h postprandial blood glucose (2-h PBG), fasting insulin (Fins) and inflammatory-related indicators at baseline and the end of the study.

RESULTS

After treatment for 24 weeks, our data showed a similar reduction in HbA1c between chiglitazar and sitagliptin. The 24-h mean blood glucose (MBG), standard deviation (SD) and mean amplitude of glycemic excursion (MAGE) were significantly decreased, and the time in range (TIR) was increased after chiglitazar and sitagliptin therapy. Chiglitazar administration led to significant improvement in insulin resistance/insulin secretion (HOMA-IR, HOMA-IS), interleukin-6 (IL-6), prostaglandin F2α (PGF-2α), 17-hydroxyprogesterone (17-OHP) and adiponectin (ADP) score values compared with sitagliptin administration.

CONCLUSIONS

Chiglitazar therapy effectively reduced glucose variation and showed a larger improvement in insulin resistance and inflammatory parameters than sitagliptin.

STAT3 as a Potential Target for Tumor Suppressive Effects of 15-Deoxy-Δ12,14-prostaglandin J2 in Triple Negative Breast Cancer

STAT3 plays a prominent role in proliferation and survival of tumor cells. Thus, STAT3 has been considered to be a prime target for development of anti-cancer therapeutics. The electrophilic cyclopentenone prostaglandin,15-deoxy-Δ^12,14-prostaglandin J₂ (15d-PGJ₂) has been well recognized for its capability to modulate intracellular signaling pathways involved in cancer cell growth and progression. We previously reported that 15d-PGJ₂ had potent cytotoxicity against harvey-ras transformed human mammary epithelial cells through direct interaction with STAT3. In this study, we have attempted to verify the inhibitory effects of 15d-PGJ₂ on STAT3 signaling in human breast tumor cells. The triple negative breast cancer cell lines, MDA-MB-231 and MDA-MB-468 displaying constitutive phosphorylation of STAT3 on the tyrosine 705 (Tyr705) residue, underwent apoptosis upon inhibition of STAT3 by 15d-PGJ₂. In contrast, estrogen receptor positive MCF-7 breast cancer cells that do not exhibit elevated STAT3 phosphorylation were much less susceptible to 15d-PGJ₂-induced apoptosis as assessed by PARP cleavage. Furthermore, 15d-PGJ₂ inhibited interleukin-6-induced tyrosine phosphorylation of STAT3 in LNCaP cells. According to molecular docking studies, 15d-PGJ₂ may preferentially bind to the cysteine 259 residue (Cys259) present in the coiled-coil domain of STAT3. Site-directed mutagenesis of STAT3 identified Cys259 to be the critical amino acid for the 15d-PGJ₂-induced apoptosis as well as epithelial-to-mesenchymal transition. Taken together, these findings suggest STAT3 inactivation through direct chemical modification of its Cys259 as a potential therapeutic approach for treatment of triple negative breast cancer treatment.

Deficiency of peroxisome proliferator-activated receptor α attenuates apoptosis and promotes migration of vascular smooth muscle cells

Peroxisome proliferator-activated receptor (PPAR) α is widely expressed in the vasculature and has pleiotropic and lipid-lowering independent effects, but its role in the growth and function of vascular smooth muscle cells (VSMCs) during vascular pathophysiology is still unclear. Herein, VSMC-specific PPARα-deficient mice (Ppara ^ΔSMC) were generated by Cre-LoxP site-specific recombinase technology and VSMCs were isolated from mice aorta. PPARα deficiency attenuated VSMC apoptosis induced by angiotensin (Ang) II and hydrogen peroxide, and increased the migration of Ang II-challenged cells.

PRISMA and BioID disclose a motifs-based interactome of the intrinsically disordered transcription factor C/EBPα

C/EBPα represents a paradigm intrinsically disordered transcription factor containing short linear motifs and post-translational modifications (PTM). Unraveling C/EBPα protein interaction networks is a prerequisite for understanding the multi-modal functions of C/EBPα in hematopoiesis and leukemia. Here, we combined arrayed peptide matrix screening (PRISMA) with BioID to generate an in vivo validated and isoform specific interaction map of C/EBPα. The myeloid C/EBPα interactome comprises promiscuous and PTM-regulated interactions with protein machineries involved in gene expression, epigenetics, genome organization, DNA replication, RNA processing, and nuclear transport. C/EBPα interaction hotspots coincide with homologous conserved regions of the C/EBP family that also score as molecular recognition features. PTMs alter the interaction spectrum of C/EBP-motifs to configure a multi-valent transcription factor hub that interacts with multiple co-regulatory components, including BAF/SWI-SNF or Mediator complexes. Combining PRISMA and BioID is a powerful strategy to systematically explore the PTM-regulated interactomes of intrinsically disordered transcription factors.

The Emerging Role of COX-2, 15-LOX and PPARγ in Metabolic Diseases and Cancer: An Introduction to Novel Multi-target Directed Ligands (MTDLs)

Emerging evidence supports an intertwining framework for the involvement of different inflammatory pathways in a common pathological background for a number of disorders. Of importance are pathways involving arachidonic acid metabolism by cyclooxygenase-2 (COX-2) and 15-lipoxygenase (15-LOX). Both enzyme activities and their products are implicated in a range of pathophysiological processes encompassing metabolic impairment leading to adipose inflammation and the subsequent vascular and neurological disorders, in addition to various pro- and antitumorigenic effects. A further layer of complexity is encountered by the disparate, and often reciprocal, modulatory effect COX-2 and 15-LOX activities and metabolites exert on each other or on other cellular targets, the most prominent of which is peroxisome proliferator-activated receptor gamma (PPARγ). Thus, effective therapeutic intervention with such multifaceted disorders requires the simultaneous modulation of more than one target. Here, we describe the role of COX-2, 15-LOX, and PPARγ in cancer and complications of metabolic disorders, highlight the value of designing multi-target directed ligands (MTDLs) modifying their activity, and summarizing the available literature regarding the rationale and feasibility of design and synthesis of these ligands together with their known biological effects. We speculate on the potential impact of MTDLs in these disorders as well as emphasize the need for structured future effort to translate these early results facilitating the adoption of these, and similar, molecules in clinical research.

Morphine enhances LPS-induced macrophage apoptosis through a PPARγ-dependent mechanism

Morphine has been widely used for the treatment of pain and extensive studies have revealed a regulatory role for morphine in cell apoptosis. However, the molecular mechanisms underlying morphine-mediated apoptosis remain to be fully elucidated. The present study aimed to investigate the effects of morphine on lipopolysaccharide (LPS)-induced bone marrow-derived macrophage (BMDM) apoptosis and to determine the role of the peroxisome proliferator-activated receptor (PPAR)γ signaling pathway in this process. BMDMs were isolated from BALB/c mice and stimulated with LPS. Hoechst 33342 staining and flow cytometric analysis were performed to evaluate the effects of morphine on LPS-induced apoptosis of BMDMs. Caspase activity assays were used to determine the involvement of the apoptosis pathway. The expression levels of caspase-3, caspase-8, caspase-9 and PPARγ were analyzed using western blotting. Finally, GW9662, a specific PPARγ antagonist, was used to determine whether the regulatory effects of morphine on LPS-induced BMDM apoptosis were PPARγ-dependent. The results of the present study revealed that morphine increased the apoptosis of LPS-stimulated BMDMs. Morphine upregulated the expression levels and activity of caspase-3 in LPS-stimulated BMDMs, but downregulated the expression levels and activity of caspase-8. Morphine treatment also upregulated LPS-induced PPARγ expression levels in BMDMs. Finally, the stimulatory effects of morphine on LPS-induced apoptosis and caspase-3/9 activation were markedly reduced by GW9662. In conclusion, the findings of the present study indicated that morphine significantly promoted LPS-induced BMDM apoptosis and caspase-3/9 activation. These results suggested that the intrinsic pathway of apoptosis may be involved in the proapoptotic effects of morphine on LPS-stimulated BMDMs, which may be dependent, at least partially, on PPARγ activation.

Insulin Signaling in Arthritis

Inflammatory arthritis is burdened by an increased risk of metabolic disorders. Cytokines and other mediators in inflammatory diseases lead to insulin resistance, diabetes and hyperlipidemia. Accumulating evidence in the field of immunometabolism suggests that the cause-effect relationship between arthritis and metabolic abnormalities might be bidirectional. Indeed, the immune response can be modulated by various factors such as environmental agents, bacterial products and hormones. Insulin is produced by pancreatic cells and regulates glucose, fat metabolism and cell growth. The action of insulin is mediated through the insulin receptor (IR), localized on the cellular membrane of hepatocytes, myocytes and adipocytes but also on the surface of T cells, macrophages, and dendritic cells. In murine models, the absence of IR in T-cells coincided with reduced cytokine production, proliferation, and migration. In macrophages, defective insulin signaling resulted in enhanced glycolysis affecting the responses to pathogens. In this review, we focalize on the bidirectional cause-effect relationship between impaired insulin signaling and arthritis analyzing how insulin signaling may be involved in the aberrant immune response implicated in arthritis and how inflammatory mediators affect insulin signaling. Finally, the effect of glucose-lowering agents on arthritis was summarized.

Adiponectin Deregulation in Systemic Autoimmune Rheumatic Diseases

Deregulation of adiponectin is found in systemic autoimmune rheumatic diseases (SARDs). Its expression is downregulated by various inflammatory mediators, but paradoxically, elevated serum levels are present in SARDs with high inflammatory components, such as rheumatoid arthritis and systemic lupus erythematosus. Circulating adiponectin is positively associated with radiographic progression in rheumatoid arthritis as well as with cardiovascular risks and lupus nephritis in systemic lupus erythematosus. However, in SARDs with less prominent inflammation, such as systemic sclerosis, adiponectin levels are low and correlate negatively with disease activity. Regulators of adiponectin gene expression (PPAR-γ, Id3, ATF3, and SIRT1) and inflammatory cytokines (interleukin 6 and tumor necrosis factor α) are differentially expressed in SARDs and could therefore influence total adiponectin levels. In addition, anti-inflammatory therapy could also have an impact, as tocilizumab treatment is associated with increased serum adiponectin. However, anti-tumor necrosis factor α treatment does not seem to affect its levels. Our review provides an overview of studies on adiponectin levels in the bloodstream and other biological samples from SARD patients and presents some possible explanations why adiponectin is deregulated in the context of therapy and gene regulation.

Nuclear Receptors as Multiple Regulators of NLRP3 Inflammasome Function

Nuclear receptors are important bridges between lipid signaling molecules and transcription responses. Beside their role in several developmental and physiological processes, many of these receptors have been shown to regulate and determine the fate of immune cells, and the outcome of immune responses under physiological and pathological conditions. While NLRP3 inflammasome is assumed as key regulator for innate and adaptive immune responses, and has been associated with various pathological events, the precise impact of the nuclear receptors on the function of inflammasome is hardly investigated. A wide variety of factors and conditions have been identified as modulators of NLRP3 inflammasome activation, and at the same time, many of the nuclear receptors are known to regulate, and interact with these factors, including cellular metabolism and various signaling pathways. Nuclear receptors are in the focus of many researches, as these receptors are easy to manipulate by lipid soluble molecules. Importantly, nuclear receptors mediate regulatory mechanisms at multiple levels: not only at transcription level, but also in the cytosol via non-genomic effects. Their importance is also reflected by the numerous approved drugs that have been developed in the past decade to specifically target nuclear receptors subtypes. Researches aiming to delineate mechanisms that regulate NLRP3 inflammasome activation draw a wide range of attention due to their unquestionable importance in infectious and sterile inflammatory conditions. In this review, we provide an overview of current reports and knowledge about NLRP3 inflammasome regulation from the perspective of nuclear receptors, in order to bring new insight to the potentially therapeutic aspect in targeting NLRP3 inflammasome and NLRP3 inflammasome-associated diseases.

Adventitial delivery of nanoparticles encapsulated with 1α, 25-dihydroxyvitamin D3 attenuates restenosis in a murine angioplasty model

Percutaneous transluminal angioplasty (PTA) of stenotic arteriovenous fistulas (AVFs) is performed to maintain optimal function and patency. The one-year patency rate is 60% because of venous neointimal hyperplasia (VNH) and venous stenosis (VS) formation. Immediate early response gene X-1 (Iex-1) also known as Ier3 increases in response to wall shear stress (WSS), and can cause VNH/VS formation in murine AVF. In human stenotic samples from AVFs, we demonstrated increased gene expression of Ier3. We hypothesized that 1α, 25-dihydroxyvitamin D₃, an inhibitor of IER3 delivered as 1α, 25-dihydroxyvitamin D₃ encapsulated in poly lactic-co-glycolic acid (PLGA) nanoparticles loaded in Pluronic F127 hydrogel (1,25 NP) to the adventitia of the stenotic outflow vein after PTA would decrease VNH/VS formation by reducing Ier3 and chemokine (C–C motif) ligand 2 (Ccl2) expression. In our murine model of AVF stenosis treated with PTA, increased expression of Ier3 and Ccl2 was observed. Using this model, PTA was performed and 10-μL of 1,25 NP or control vehicle (PLGA in hydrogel) was administered by adventitial delivery. Animals were sacrificed at day 3 for unbiased whole genome transcriptomic analysis and at day 21 for immunohistochemical analysis. Doppler US was performed weekly after AVF creation. At day 3, significantly lower gene expression of Ier3 and Ccl2 was noted in 1,25 NP treated vessels. Twenty-one days after PTA, 1,25 NP treated vessels had increased lumen vessel area, with decreased neointima area/media area ratio and cell density compared to vehicle controls. There was a significant increase in apoptosis, with a reduction in CD68, F4/80, CD45, pro-inflammatory macrophages, fibroblasts, Picrosirius red, Masson’s trichrome, collagen IV, and proliferation accompanied with higher wall shear stress (WSS) and average peak velocity. IER3 staining was localized to CD68 and FSP-1 (+) cells. After 1,25 NP delivery, there was a decrease in the proliferation of α-SMA (+) and CD68 (+) cells with increase in the apoptosis of FSP-1 (+) and CD68 (+) cells compared to vehicle controls. RNA sequencing revealed a decrease in inflammatory and apoptosis pathways following 1,25 NP delivery. These data suggest that adventitial delivery of 1,25 NP reduces VNH and venous stenosis formation after PTA.

Serum metabonomics coupled with HPLC-LTQ/orbitrap MS and multivariate data analysis on the ameliorative effects of Bidens bipinnata L. in hyperlipidemic rats

ETHNOPHARMACOLOGICAL RELEVANCE

Hyperlipidemia (HLP) is a prevalence chronic cardiovascular disease, which is treated by traditional Chinese medicine (TCM) in China. More and more attention has been paid to the application of metabolomics in the study of TCM. Bidens bipinnata L. (BBL), a folk medicine in contemporary China, has the efficacy in the treatment of hyperlipidemia (HLP) in China. However, little is known of the underlying mechanism of BBL. This research aimed to investigate ameliorative effects of BBL on hyperlipidemic rats and explore the mechanism by metabolomics method.

MATERIALS AND METHODS

Hyperlipidemic rats were established by high fat diet (HFD). Biochemical assay was used to evaluate the efficacy of BBL. A metabolomics approach based on high performance liquid chromatography-linear ion trap/orbitrap high-resolution mass spectrometry (HPLC-LTQ/orbitrap MS) was performed to analyze the serum biomarkers from model group, control group and BBL group. Principle component analysis (PCA) and partial least-squares discriminate analysis (PLS-DA) were utilized to identify differences of metabolic profiles in rats among the three groups. In order to identify possible pathways that were affected by HLP, the identified endogenous metabolites were analyzed by using MetaboAnalyst. In the network pharmacology study, our research group found that PPAR signaling pathway was the most important pathway of BBL in the treatment of HLP. Then, it was found that changes in the major metabolic pathways would affect the PPAR signaling pathway through comprehensive analysis based on KEGG database. Therefore, the expression of key genes in the PPAR signaling pathway was detected by real-time quantitative fluorescence PCR (RT-qPCR).

RESULTS

Six metabolites, which showed a significantly restoring trend from HLP to normal condition, were regarded as potential biomarkers of BBL treatment. The levels of phosphorylcholine, mevalonic acid and leukotriene B₄ (LTB₄) increased significantly (P < 0.01) in hyperlipidemic rats, while the levels of linoleic acid, arachidonic acid (AA) and lysophosphatidylcholine (18:0) (Lyso PC (18:0)) decreased significantly (P < 0.01) in comparison with control rats. Those endogenous metabolites were chiefly involved in linoleic acid metabolism, AA metabolism and terpenoid backbone biosynthesis. According to the results of RT-qPCR analysis, the mRNA expressions of PPAR α, PPAR β and PPARγ in model group were difference compared with control group. And the expression difference could be regulated closer to normal level after BBL intervention.

CONCLUSIONS

The results of biochemical assay, serum metabolic pattern and RT-qPCR analysis showed that BBL could exert a significant improvement on lipid levels, liver function, renal function, as well as the mRNA expression level of PPAR signaling pathway.

Nuclear receptors in podocyte biology and glomerular disease

Nuclear receptors have a broad spectrum of biological functions in normal physiology and in the pathology of various diseases, including glomerular disease. The primary therapies for many glomerular diseases are glucocorticoids, which exert their immunosuppressive and direct podocyte protective effects via the glucocorticoid receptor (GR). As glucocorticoids are associated with important adverse effects and a substantial proportion of patients show resistance to these therapies, the beneficial effects of selective GR modulators are now being explored. Peroxisome proliferator-activated receptor-γ (PPARγ) agonism using thiazolidinediones has potent podocyte cytoprotective and nephroprotective effects. Repurposing of thiazolidinediones or identification of novel PPARγ modulators are potential strategies to treat non-diabetic glomerular disease. Retinoic acid receptor-α is the key mediator of the renal protective effects of retinoic acid, and repair of the endogenous retinoic acid pathway offers another potential therapeutic strategy for glomerular disease. Vitamin D receptor, oestrogen receptor and mineralocorticoid receptor modulators regulate podocyte injury in experimental models. Further studies are needed to better understand the mechanisms of these nuclear receptors, evaluate their synergistic pathways and identify their novel modulators. Here, we focus on the role of nuclear receptors in podocyte biology and non-diabetic glomerular disease.

PPARα exacerbates necroptosis, leading to increased mortality in postinfluenza bacterial superinfection

Patients infected with influenza are at high risk of secondary bacterial infection, which is a major proximate cause of morbidity and mortality. We have shown that in mice, prior infection with influenza results in increased inflammation and mortality upon Staphylococcus aureus infection, recapitulating the human disease. Lipidomic profiling of the lungs of superinfected mice revealed an increase in CYP450 metabolites during lethal superinfection. These lipids are endogenous ligands for the nuclear receptor PPARα, and we demonstrate that Ppara ^-/- mice are less susceptible to superinfection than wild-type mice. PPARα is an inhibitor of NFκB activation, and transcriptional profiling of cells isolated by bronchoalveolar lavage confirmed that influenza infection inhibits NFκB, thereby dampening proinflammatory and prosurvival signals. Furthermore, network analysis indicated an increase in necrotic cell death in the lungs of superinfected mice compared to mice infected with S. aureus alone. Consistent with this, we observed reduced NFκB-mediated inflammation and cell survival signaling in cells isolated from the lungs of superinfected mice. The kinase RIPK3 is required to induce necrotic cell death and is strongly induced in cells isolated from the lungs of superinfected mice compared to mice infected with S. aureus alone. Genetic and pharmacological perturbations demonstrated that PPARα mediates RIPK3-dependent necroptosis and that this pathway plays a central role in mortality following superinfection. Thus, we have identified a molecular circuit in which infection with influenza induces CYP450 metabolites that activate PPARα, leading to increased necrotic cell death in the lung which correlates with the excess mortality observed in superinfection.

In vitro and in vivo Antiallergic Effects of Taurine on Allergic Rhinitis

BACKGROUND

The current treatment for allergic rhinitis (AR) is inadequate.

OBJECTIVE

The present study aimed to investigate the therapeutic effect of taurine on AR and to identify the underlying molecular mechanisms.

METHODS

The serum level of the antioxidant enzyme extracellular superoxide dismutase (SOD3) was determined in AR patients and in healthy controls. The antiallergic inflammatory effects of taurine were evaluated in a dinitrophenyl-human serum albumin (DNP-HSA)-stimulated human mast cell line (HMC-1) and in an ovalbumin (OVA)-induced AR mouse model.

RESULTS

Clinically, a reduction in serum level of SOD3 was observed in AR patients. Taurine treatment led to dose-dependent increases in SOD3 at both protein and mRNA levels in HMC-1 cells. SOD3 production was regulated by peroxisome proliferator-activated receptor-γ (PPAR-γ) in response to taurine. SOD3 overexpression inhibited the release of proinflammatory cytokines including tumor necrosis factor-α (, interleukin (IL)-4, and IL-6. Its overexpression also ameliorated the loss of interferon-γ. SOD3 and PPAR-γ influenced inflammatory cytokine production via regulation of the phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2). An OVA-induced AR animal model study showed that taurine was efficacious in alleviating allergic inflammatory reactions by relieving behavior symptoms of AR mice and reducing eosinophilic and mast cell infiltration into the nasal cavity. In addition, taurine treatment increased the production of SOD3 and PPAR-γ, which, in turn, suppressed expression of proinflammatory cytokines through phosphorylation of ERK1/2.

CONCLUSION

Taurine could potentially serve as a therapeutic treatment for allergic disorders.

Neurovascular protection by peroxisome proliferator-activated receptor α in ischemic stroke

Ischemic stroke is a leading cause of death and disability worldwide. Currently, the only pharmacological therapy for ischemic stroke is thrombolysis with tissue plasminogen activator that has a narrow therapeutic window and increases the risk of intracerebral hemorrhage. New pharmacological treatments for ischemic stroke are desperately needed, but no neuroprotective drugs have successfully made it through clinical trials. Beneficial effects of peroxisome proliferator-activated receptor alpha (PPARα) activation on vascular integrity and function have been reported, and PPARα agonists have clinically been used for many years to manage cardiovascular disease. Thus, PPARα has gained interest in recent years as a target for neurovascular disease such as ischemic stroke. Accumulating preclinical evidence suggests that PPARα activation modulates several pathophysiological hallmarks of stroke such as oxidative stress, blood-brain barrier (BBB) dysfunction, and neuroinflammation to improve functional recovery. Therefore, this review summarizes the various actions PPARα exerts in neurovascular health and disease and the potential of employing exogenous PPARα agonists for future pharmacological treatment of ischemic stroke.

Reinterpreting Cardiorenal Protection of Renal Sodium-Glucose Cotransporter 2 Inhibitors via Cellular Life History Programming

Cardiovascular outcome trials have provided evidence that sodium-glucose cotransporter 2 inhibitor (SGLT2i) treatment is associated with remarkably favorable cardiovascular outcomes. Here, we offer a novel hypothesis that may encompass many of these hypothetical mechanisms, i.e., the ability of SGLT2i to modify the trajectory of cell response to a toxic environment through modifications of cellular life history programs, either the defense program or the dormancy program. The choice between these programs is mainly determined by the environment. Hyperglycemia can be considered a toxic determinant able to interfere with the basic programs of cell evolution. While the defense program is characterized by activation of the immune response and anabolic metabolism, the dormancy program is an energy-preserving state with high resistance to environmental stressors, and it has strong analogy with animal hibernation where fuel is stored, metabolic rate is suppressed, and insulin secretion is reduced. The metabolic changes that follow treatment with SGLT2i are reminiscent of the metabolic picture characteristic of the dormancy program. Therefore, we hypothesize that the beneficial cardioprotective effects of SGLT2i may be related to their ability to switch cell life programming from a defense to a dormancy state, thus lending additional benefit.

Fenofibrate Facilitates Post-Active Tuberculosis Infection in Macrophages and is Associated with Higher Mortality in Patients under Long-Term Treatment

Background: Mycobacterium tuberculosis (Mtb) is an intracellular pathogen that infects and persists in macrophages. This study aimed to investigate the effects of long-term fenofibrate treatment in patients with tuberculosis (TB), and the intracellular viability of Mtb in human macrophages. Methods: Epidemiological data from the National Health Insurance Research Database of Taiwan were used to present outcomes of TB patients treated with fenofibrate. In the laboratory, we assessed Mtb infection in macrophages treated with or without fenofibrate. Mtb growth, lipid accumulation in macrophages, and expression of transcriptional genes were examined. Results: During 11 years of follow-up, TB patients treated with fenofibrate presented a higher risk of mortality. Longer duration of fenofibrate use was associated with a significantly higher risk of mortality. Treatment with fenofibrate significantly increased the number of bacilli in human macrophages in vitro. Fenofibrate did not reduce, but induced an increasing trend in the intracellular lipid content of macrophages. In addition, dormant genes of Mtb, icl1, tgs1, and devR, were markedly upregulated in response to fenofibrate treatment. Our results suggest that fenofibrate may facilitate intracellular Mtb persistence. Conclusions: Our data shows that long-term treatment with fenofibrate in TB patients is associated with a higher mortality. The underlying mechanisms may partly be explained by the upregulation of Mtb genes involved in lipid metabolism, enhanced intracellular growth of Mtb, and the ability of Mtb to sustain a nutrient-rich reservoir in human macrophages, observed during treatment with fenofibrate.

Meglumine acridone acetate, the ionic salt of CMA and N-methylglucamine, induces apoptosis in human PBMCs via the mitochondrial pathway

Meglumine acridone acetate (MA) is used in Russia for the treatment of influenza and other acute respiratory viral infections. It was assumed, until recently, that its antiviral effect was associated with its potential ability to induce type I interferon. Advanced studies, however, have shown the failure of 10-carboxymethyl-9-acridanone (CMA) to activate human STING. As such, MA's antiviral properties are still undergoing clarification. To gain insight into MA's mechanisms of action, we carried out RNA-sequencing analysis of global transcriptomes in MA-treated (MA+) human peripheral blood mononuclear cells (PBMCs). In response to treatment, approximately 1,223 genes were found to be differentially expressed, among which 464 and 759 were identified as either up- or down-regulated, respectively. To clarify the cellular and molecular processes taking place in MA+ cells, we performed a functional analysis of those genes. We have shown that evident MA subcellular localizations are: at the nuclear envelope; inside the nucleus; and diffusely in perinuclear cytoplasm. Postulating that MA may be a nuclear receptor agonist, we carried out docking simulations with PPARα and RORα ligand binding domains including prediction and molecular dynamics-based analysis of potential MA binding poses. Finally, we confirmed that MA treatment enhanced nuclear apoptosis in human PBMCs. The research presented here, in our view, indicates that: (i) MA activity is mediated by nuclear receptors; (ii) MA is a possible PPARα and/or RORα agonist; (iii) MA has an immunosuppressive effect; and (iv) MA induces apoptosis through the mitochondrial signaling pathway.

Molecular determinants for the polarization of macrophage and osteoclast

Emerging evidence suggest that macrophage and osteoclast are two competing differentiation outcomes from myeloid progenitors. In this review, we summarize recent advances in the understanding of the molecular mechanisms controlling the polarization of macrophage and osteoclast. These include nuclear receptors/transcription factors such as peroxisome proliferator-activated receptor γ (PPARγ) and estrogen-related receptor α (ERRα), their transcription cofactor PPARγ coactivator 1-β (PGC-1β), metabolic factors such as mitochondrial complex I (CI) component NADH:ubiquinone oxidoreductase iron-sulfur protein 4 (Ndufs4), as well as transmembrane receptors such as very-low-density-lipoprotein receptor (VLDLR). These molecular rheostats promote osteoclast differentiation but suppress proinflammatory macrophage activation and inflammation, by acting lineage-intrinsically, systemically or cross generation. These findings provide new insights to the understanding of the interactions between innate immunity and bone remodeling, advancing the field of osteoimmunology.

Different Approaches to Modulation of Microglia Phenotypes After Spinal Cord Injury

Microglial cells, which are highly plastic, immediately respond to any change in the microenvironment by becoming activated and shifting the phenotype toward neurotoxicity or neuroprotection. The polarization of microglia/macrophages after spinal cord injury (SCI) seems to be a dynamic process and can change depending on the microenvironment, stage, course, and severity of the posttraumatic process. Effective methods to modulate microglia toward a neuroprotective phenotype in order to stimulate neuroregeneration are actively sought for. In this context, available approaches that can selectively impact the polarization of microglia/macrophages regulate synthesis of trophic factors and cytokines/chemokines in them, and their phagocytic function and effects on the course and outcome of SCI are discussed in this review.

IL4Rα Signaling Abrogates Hypoxic Neutrophil Survival and Limits Acute Lung Injury Responses In Vivo

Rationale: Acute respiratory distress syndrome is defined by the presence of systemic hypoxia and consequent on disordered neutrophilic inflammation. Local mechanisms limiting the duration and magnitude of this neutrophilic response remain poorly understood. Objectives: To test the hypothesis that during acute lung inflammation tissue production of proresolution type 2 cytokines (IL-4 and IL-13) dampens the proinflammatory effects of hypoxia through suppression of HIF-1α (hypoxia-inducible factor-1α)-mediated neutrophil adaptation, resulting in resolution of lung injury. Methods: Neutrophil activation of IL4Ra (IL-4 receptor α) signaling pathways was explored ex vivo in human acute respiratory distress syndrome patient samples, in vitro after the culture of human peripheral blood neutrophils with recombinant IL-4 under conditions of hypoxia, and in vivo through the study of IL4Ra-deficient neutrophils in competitive chimera models and wild-type mice treated with IL-4. Measurements and Main Results: IL-4 was elevated in human BAL from patients with acute respiratory distress syndrome, and its receptor was identified on patient blood neutrophils. Treatment of human neutrophils with IL-4 suppressed HIF-1α-dependent hypoxic survival and limited proinflammatory transcriptional responses. Increased neutrophil apoptosis in hypoxia, also observed with IL-13, required active STAT signaling, and was dependent on expression of the oxygen-sensing prolyl hydroxylase PHD2. In vivo, IL-4Ra-deficient neutrophils had a survival advantage within a hypoxic inflamed niche; in contrast, inflamed lung treatment with IL-4 accelerated resolution through increased neutrophil apoptosis. Conclusions: We describe an important interaction whereby IL4Rα-dependent type 2 cytokine signaling can directly inhibit hypoxic neutrophil survival in tissues and promote resolution of neutrophil-mediated acute lung injury.

Bone Immune Response to Materials, Part II: Copper and Polyetheretherketone (PEEK) Compared to Titanium at 10 and 28 Days in Rabbit Tibia

Osseointegration is likely the result of an immunologically driven bone reaction to materials such as titanium. Osseointegration has resulted in the clinical possibility to anchor oral implants in jaw bone tissue. However, the mechanisms behind bony anchorage are not fully understood and complications over a longer period of time have been reported. The current study aims at exploring possible differences between copper (Cu) and polyetheretherketone (PEEK) materials that do not osseointegrate, with osseointegrating cp titanium as control. The implants were placed in rabbit tibia and selected immune markers were evaluated at 10 and 28 days of follow-up. Cu and PEEK demonstrated at both time points a higher immune activation than cp titanium. Cu demonstrated distance osteogenesis due to a maintained proinflammatory environment over time, and PEEK failed to osseointegrate due to an immunologically defined preferential adipose tissue formation on its surface. The here presented results suggest the description of two different mechanisms for failed osseointegration, both of which are correlated to the immune system.

Environmental contaminants modulate the transcriptional activity of polar bear (Ursus maritimus) and human peroxisome proliferator-activated receptor alpha (PPARA)

Peroxisome proliferator-activated receptor alfa (PPARA/NR1C1) is a ligand activated nuclear receptor that is a key regulator of lipid metabolism in tissues with high fatty acid catabolism such as the liver. Here, we cloned PPARA from polar bear liver tissue and studied in vitro transactivation of polar bear and human PPARA by environmental contaminants using a luciferase reporter assay. Six hinge and ligand-binding domain amino acids have been substituted in polar bear PPARA compared to human PPARA. Perfluorocarboxylic acids (PFCA) and perfluorosulfonic acids induced the transcriptional activity of both human and polar bear PPARA. The most abundant PFCA in polar bear tissue, perfluorononanoate, increased polar bear PPARA-mediated luciferase activity to a level comparable to that of the potent PPARA agonist WY-14643 (~8-fold, 25 μM). Several brominated flame retardants were weak agonists of human and polar bear PPARA. While single exposures to polychlorinated biphenyls did not, or only slightly, increase the transcriptional activity of PPARA, a technical mixture of PCBs (Aroclor 1254) strongly induced the transcriptional activity of human (~8-fold) and polar bear PPARA (~22-fold). Polar bear PPARA was both quantitatively and qualitatively more susceptible than human PPARA to transactivation by less lipophilic compounds.

Pioglitazone suppresses macrophage proliferation in apolipoprotein-E deficient mice by activating PPARγ

BACKGROUND AND AIMS

Local macrophage proliferation is linked to enhanced atherosclerosis progression. Our previous study found that troglitazone, a thiazolidinedione (TZD), suppressed oxidized low-density lipoprotein (Ox-LDL)-induced macrophage proliferation. However, its effects and mechanisms are unclear. Therefore, we investigated the effects of pioglitazone, another TZD, on macrophage proliferation.

METHODS

Normal chow (NC)- or high-fat diet (HFD)-fed apolipoprotein E-deficient (Apoe^-/-) mice were treated orally with pioglitazone (10 mg/kg/day) or vehicle (water) as a control. Mouse peritoneal macrophages were used in in vitro assays.

RESULTS

Atherosclerosis progression was suppressed in aortic sinuses of pioglitazone-treated Apoe^-/- mice, which showed fewer proliferating macrophages in plaques. Pioglitazone suppressed Ox-LDL-induced macrophage proliferation in a dose-dependent manner. However, treatment with peroxisome proliferator-activated receptor-γ (PPARγ) siRNA ameliorated pioglitazone-induced suppression of macrophage proliferation. Low concentrations (less than 100 μmol/L) of pioglitazone, which can suppress macrophage proliferation, activated PPARγ in macrophages, but did not induce macrophage apoptosis. Pioglitazone treatment did not induce TUNEL-positive cells in atherosclerotic plaques of aortic sinuses in Apoe^-/- mice.

CONCLUSIONS

Pioglitazone suppressed macrophage proliferation through PPARγ without inducing macrophage apoptosis. These findings imply that pioglitazone could prevent macrovascular complications in diabetic individuals.

Local miscommunications between glomerular cells as potential therapeutic targets for crescentic glomerulonephritides

Necrotizing and crescentic rapidly progressive glomerulonephritis or crescentic glomerulonephritis is one of the severest forms of acquired glomerular diseases with significant mortality. Risk of end-stage renal failure at 5 years is near 30%, with a number of patients developing chronic kidney disease. Currently, autoimmune crescentic glomerulonephritides are treated with broad-spectrum immunosuppression inducing remission of the injury in the majority of patients. However, treatment is associated with significant side effects and by the time remission is achieved the majority of patients have developed renal tissue damage and significant impairment of their kidney function with a steep slope of deterioration within the first weeks following initiation of immunosuppression. It is therefore important to develop complementary strategies that would be immediately active on the common process of destructive epithelial processes. We have worked to identify the major cellular pathways contributing to glomerular destruction in this context by a systematic comparison of patient tissues and experimental models. Our studies demonstrate the pivotal role of local intra- and intercellular communications in orchestrating the global glomerular tolerance to a severe rapidly progressive glomerulonephritis model with excellent anatomoclinical correlative expressions in kidney biopsies of individuals diagnosed with crescentic glomerulonephritis, irrespectively of the causal immune disorder. We hope that such approaches deciphering mechanisms of cellular adaptation that underlie kidney damage control in response to vasculitides, integrating both stress and damage responses, will delineate novel complementary therapies.

Exploiting the Therapeutic Potential of Endogenous Immunomodulatory Systems in Multiple Sclerosis-Special Focus on the Peroxisome Proliferator-Activated Receptors (PPARs) and the Kynurenines

Multiple sclerosis (MS) is a progressive neurodegenerative disease, characterized by autoimmune central nervous system (CNS) demyelination attributable to a disturbed balance between encephalitic T helper 1 (Th1) and T helper 17 (Th17) and immunomodulatory regulatory T cell (Treg) and T helper 2 (Th2) cells, and an alternatively activated macrophage (M2) excess. Endogenous molecular systems regulating these inflammatory processes have recently been investigated to identify molecules that can potentially influence the course of the disease. These include the peroxisome proliferator-activated receptors (PPARs), PPARγ coactivator-1alpha (PGC-1α), and kynurenine pathway metabolites. Although all PPARs ameliorate experimental autoimmune encephalomyelitis (EAE), recent evidence suggests that PPARα, PPARβ/δ agonists have less pronounced immunomodulatory effects and, along with PGC-1α, are not biomarkers of neuroinflammation in contrast to PPARγ. Small clinical trials with PPARγ agonists have been published with positive results. Proposed as immunomodulatory and neuroprotective, the therapeutic use of PGC-1α activation needs to be assessed in EAE/MS. The activation of indolamine 2,3-dioxygenase (IDO), the rate-limiting step of the kynurenine pathway of tryptophan (Trp) metabolism, plays crucial immunomodulatory roles. Indeed, Trp metabolites have therapeutic relevance in EAE and drugs with structural analogy to kynurenines, such as teriflunomide, are already approved for MS. Further studies are required to gain deeper knowledge of such endogenous immunomodulatory pathways with potential therapeutic implications in MS.

Radiation-induced lung injury: impact on macrophage dysregulation and lipid alteration - a review

Lung cancer continues to be the leading cause of cancer deaths and more than one million lung cancer patients will die every year worldwide. Radiotherapy (RT) plays an important role in lung cancer treatment, but the side effects of RT are pneumonitis and pulmonary fibrosis. RT-induced lung injury causes damage to alveolar-epithelial cells and vascular endothelial cells. Macrophages play an important role in the development of pulmonary fibrosis despite its role in immune response. These injury activated macrophages develop into classically activated M1 macrophage or alternative activated M2 macrophage. It secretes cytokines, interleukins, interferons, and nitric oxide. Several pro-inflammatory lipids and pro-apoptotic proteins cause lipotoxicity such as LDL, FC, DAG, and FFA. The overall findings in this review conclude the importance of macrophages in inducing toxic/inflammatory effects during RT of lung cancer, which is clinically vital to treat the radiation-induced fibrosis.

Molecular Actions of PPARα in Lipid Metabolism and Inflammation

Peroxisome proliferator-activated receptor α (PPARα) is a nuclear receptor of clinical interest as a drug target in various metabolic disorders. PPARα also exhibits marked anti-inflammatory capacities. The first-generation PPARα agonists, the fibrates, have however been hampered by drug-drug interaction issues, statin drop-in, and ill-designed cardiovascular intervention trials. Notwithstanding, understanding the molecular mechanisms by which PPARα works will enable control of its activities as a drug target for metabolic diseases with an underlying inflammatory component. Given its role in reshaping the immune system, the full potential of this nuclear receptor subtype as a versatile drug target with high plasticity becomes increasingly clear, and a novel generation of agonists may pave the way for novel fields of applications.