Peroxisome proliferator activated receptor γ agonists suppress TNFα-induced ICAM-1 expression by endothelial cells in a manner potentially dependent on inhibition of reactive oxygen species

PPARβ mediates mangiferin-induced neuronal differentiation of neural stem cells through DNA demethylation

Adult hippocampal neurogenesis (AHN) is heavily implicated in the pathogenesis of various neuropsychiatric disorders. The mangiferin (MGF), a bioactive compound of the mango, reportedly produces biological effects on a variety of neuropsychiatric disorders. However, the function and underlying mechanisms of MGF in regulating hippocampal neurogenesis remain unknown. Here we discovered that the transcriptome and methylome of MGF-induced neural stem cells (NSCs) are distinct from the control. RNA-seq analysis revealed that the diferentially expressed genes (DEGs) were signifcantly enriched in the PPARs. Furthermore, we found that MGF enhanced neuronal differentiation and proliferation of neural stem cells (NSCs) via PPARβ but not PPARα and PPARγ. The combination of WGBS and RNA-seq analysis showed that the expression of some neurogenesis genes was negatively correlated with the DNA methylation level generally. We further found that PPARβ increased demethylation of Mash1 promoter by modulating the expressions of active and passive DNA demethylation enzymes in MGF-treated NSCs. Importantly, genetic deficiency of PPARβ decreased hippocampal neurogenesis in the adult mice, whereas the defective neurogenesis was notably rescued by Mash1 overexpression. Our findings uncover a model that PPARβ-mediated DNA demethylation of Mash1 contributes to MGF-induced neuronal genesis, and advance the concept that targeting PPARβ-TET1/DNMT3a-Mash1 axis regulation of neurogenesis might serve as a novel neurotherapeutic strategy.

miR-573 rescues endothelial dysfunction during dengue infection under PPARγ regulation

Early prognosis of abnormal vasculopathy is essential for effective clinical management of severe dengue patients. An exaggerated interferon (IFN) response and release of vasoactive factors from endothelial cells cause vasculopathy. This study shows that dengue 2 (DENV2) infection of human umbilical vein endothelial cells (HUVEC) results in differentially regulated miRNAs important for endothelial function. miR-573 was significantly down-regulated in DENV2-infected HUVEC due to decreased Peroxisome Proliferator Activator Receptor Gamma (PPARγ) activity. Restoring miR-573 expression decreased endothelial permeability by suppressing the expression of vasoactive angiopoietin 2 (ANGPT2). We also found that miR-573 suppressed the proinflammatory IFN response through direct downregulation of toll like receptor 2 (TLR2) expression. Our study provides a novel insight into miR-573 mediated regulation of endothelial function during DENV2 infection which can be further translated into a potential therapeutic and prognostic agent for severe dengue patients. IMPORTANCE: We need to identify molecular factors which can predict the onset of endothelial dysfunction in dengue patients. Increase in endothelial permeability during severe dengue infections is poorly understood. In this study we focus on factors which regulate endothelial function and are dysregulated during DENV2 infection. We show that miR-573 rescues endothelial permeability and is downregulated during DENV2 infection in endothelial cells. This finding can have diagnostic as well as therapeutic applications.

Chronic Low-Dose Alcohol Consumption Attenuates Post-Ischemic Inflammation via PPARγ in Mice

Ischemic stroke is one of the leading causes of death and permanent disability in adults. Recently, we found that light alcohol consumption (LAC) suppresses post-ischemic inflammatory response, which plays an important role in ischemic brain damage. Our goal was to determine the role of peroxisome proliferator-activated receptor-gamma (PPARγ) in the anti-inflammatory effect of LAC against transient focal cerebral ischemia. In in vivo study, male C57BL/6J wild type (WT) and endothelial-specific conditional PPARγ knockout mice were gavage fed with 0.7 g/kg/day ethanol or volume-matched water daily for 8 weeks. From the 7th week, 3 mg/kg/day GW9662 (a selective PPARγ antagonist) was intraperitoneally given for two weeks. Cerebral ischemia/reperfusion (I/R) injury and expression of manganese superoxide dismutase (MnSOD) and adhesion molecules, neutrophil infiltration, and microglial activation in the cerebral cortex before and following a 90 min unilateral middle cerebral artery occlusion (MCAO)/24 h reperfusion were evaluated. In in vitro study, the impact of chronic alcohol exposure on expression of PPARγ and MnSOD in C57BL/6J mouse brain microvascular endothelial cells (MBMVECs) was measured. PPARγ and MnSOD were significantly upregulated in the cerebral cortex of ethanol-fed WT mice and low-concentration ethanol-exposed C57BL/6J MBMVECs. GW9662 significantly inhibited alcohol-induced upregulation of MnSOD. Eight-week ethanol feeding significantly reduced cerebral I/R injury and alleviated the post-ischemic inflammatory response (upregulation of intercellular adhesion molecule-1 (ICAM-1) and E-selectin, microglial activation, and neutrophil infiltration). Treatment with GW9662 and endothelial-specific conditional knockout of PPARγ did not alter cerebral I/R injury and the inflammatory response in the control mice but abolish the neuroprotective effect in ethanol-fed mice. In addition, GW9662 and endothelial-specific conditional knockout of PPARγ diminished the inhibitory effect of LAC on the post-ischemic expression of adhesion molecules and neutrophil infiltration. Our findings suggest that LAC may protect against cerebral I/R injury by suppressing the post-ischemic inflammation via activation of PPARγ.

Prediction of neonatal acne based on maternal lipidomic profiling

BACKGROUND

Neonatal acne occurs in the first few weeks after birth. Some lesions are more serious and leave scars. Maternal surface skin lipids (SSL) have a strong correlation with SSL of infants. The establishment of prediction rank model based on maternal SSL is essential to the prevention and treatment of neonatal acne.

METHOD

Surface skin lipids samples were collected from the mothers (M) of 56 neonatal acne patients and the mothers (HM) of 19 healthy infants. Surface skin lipids from the right forehead were collected using a noninvasive method. UPLC-QTOF-MS was applied to detect SSL. Partial least squares discriminant analysis and receiver operating characteristic (ROC) analysis were performed to screen and validate potential lipids. Random forest (RF) and ROC analysis were used to establish a prediction model and evaluate its accuracy.

RESULTS

Sixteen altered potential lipids belonging to fatty acids, sphingomyelins, and glycerides were associated with M. M had less lipids than HM. Spearman's correlation of 16 lipids revealed 9 with high correlation. They were chosen as characteristic values of the RF prediction model. And the model showed an average accuracy of 98% in the validation set.

CONCLUSION

We have established an RF model for predicting neonatal acne and have shown that high skin barrier-related lipids were markers for predicting neonatal acne.

PPARs and Energy Metabolism Adaptation during Neurogenesis and Neuronal Maturation

Peroxisome proliferator activated receptors (PPARs) are a class of ligand-activated transcription factors, belonging to the superfamily of receptors for steroid and thyroid hormones, retinoids, and vitamin D. PPARs control the expression of several genes connected with carbohydrate and lipid metabolism, and it has been demonstrated that PPARs play important roles in determining neural stem cell (NSC) fate. Lipogenesis and aerobic glycolysis support the rapid proliferation during neurogenesis, and specific roles for PPARs in the control of different phases of neurogenesis have been demonstrated. Understanding the changes in metabolism during neuronal differentiation is important in the context of stem cell research, neurodegenerative diseases, and regenerative medicine. In this review, we will discuss pivotal evidence that supports the role of PPARs in energy metabolism alterations during neuronal maturation and neurodegenerative disorders.

Danshenol A inhibits TNF-α-induced expression of intercellular adhesion molecule-1 (ICAM-1) mediated by NOX4 in endothelial cells

ICAM-1 overexpression and subsequent adhesion of leukocytes to endothelial cells play critical roles in the early stage of atherosclerosis. Danshenol A (DA) is an abietane-type diterpenoid isolated from traditional Chinese herb Salvia miltiorrhiza Bunge. The mechanisms under its regulation of adhesion of molecular expression are explored. Here, the effect of DA on TNF-α-induced ICAM-1 expression was investigated in endothelial cells. TNF-α-induced ICAM-1 expression and subsequent adhesion of monocytes, as well as elevated reactive oxygen species (ROS) generation and NOX4 expression were all significantly reversed by DA, siNOX4 and NOX4 inhibitor GKT137831. Furthermore, TNF-α-induced ICAM-1 expression, which was increased via IKKβ/IκBα-mediated activation of NF-κB p65, was also inhibited by DA. Interestingly, NOX4 overexpression suppressed the ICAM-1 expression, and this finding may be ascribed to the activation of Nrf-2. Additionally, NF-κB inhibitor PDTC, siNOX4, or DA can decrease the TNF-α-induced ICAM-1 expression and suppress the adhesion of monocytes. In all, DA inhibited TNF-α-induced ICAM-1 expression and subsequent monocyte adhesion to endothelial cells through the NOX4-dependent IKKβ/NF-κB pathway. Besides, NOX4 played dual role in regulating ICAM-1 expression via diverse signal pathway. This novel bioactivity will make DA a good candidate to be further explored for therapeutic or preventive application for atherosclerosis.

Roles of PPAR transcription factors in the energetic metabolic switch occurring during adult neurogenesis

PPARs are a class of ligand-activated transcription factors belonging to the superfamily of receptors for steroid and thyroid hormones, retinoids and vitamin D that control the expression of a large number of genes involved in lipid and carbohydrate metabolism and in the regulation of cell proliferation, differentiation and death. The role of PPARs in the CNS has been primarily associated with lipid and glucose metabolism; however, these receptors are also implicated in neural cell differentiation and death, as well as neuronal maturation. Although it has been demonstrated that PPARs play important roles in determining NSCs fate, less is known about their function in regulating NSCs metabolism during differentiation. In order to identify the metabolic events, controlled by PPARs, occurring during neuronal precursor differentiation, the glucose and lipid metabolism was followed in a recognized model of neuronal differentiation in vitro, the SH-SY5Y neuroblastoma cell line. Moreover, PPARs distribution were also followed in situ in adult mouse brains. The concept of adult neurogenesis becomes relevant especially in view of those disorders in which a loss of neurons is described, such as Alzheimer disease, Parkinson disease, brain injuries and other neurological disorders. Elucidating the crucial steps in energetic metabolism and the involvement of PPARγ in NSC neuronal fate (lineage) may be useful for the future design of preventive and/or therapeutic interventions.

Maraviroc-Mediated Lung Protection following Trauma-Hemorrhagic Shock

Objectives. The peroxisome proliferator-activated receptor gamma (PPARγ) pathway exerts anti-inflammatory effects in response to injury. Maraviroc has been shown to have potent anti-inflammatory effects. The aim of this study was to investigate whether PPARγ plays an important role in maraviroc-mediated lung protection following trauma-hemorrhage. Methods. Male Sprague-Dawley rats underwent trauma-hemorrhage (mean blood pressure maintained at approximately 35-40 mmHg for 90 minutes), followed by fluid resuscitation. During resuscitation, a single dose of maraviroc (3 mg/kg, intravenously) with and without a PPARγ inhibitor GW9662 (1 mg/kg, intravenously), GW9662, or vehicle was administered. Lung water content, tissue histology, and other various parameters were measured (n = 8 rats/group) 24 hours after resuscitation. One-way ANOVA and Tukey's testing were used for statistical analysis. Results. Trauma-hemorrhage significantly increased lung water content, myeloperoxidase activity, intercellular adhesion molecule-1, interleukin-6, and interleukin-1β levels. These parameters significantly improved in the maraviroc-treated rats subjected to trauma-hemorrhage. Maraviroc treatment also decreased lung tissue damage as compared to the vehicle-treated trauma-hemorrhaged rats. Coadministration of GW9662 with maraviroc abolished the maraviroc-induced beneficial effects on these parameters and lung injury. Conclusion. These results suggest that PPARγ might play a key role in maraviroc-mediated lung protection following trauma-hemorrhage.

A systems pharmacology approach to investigate the mechanisms of action of Semen Strychni and Tripterygium wilfordii Hook F for treatment of rheumatoid arthritis

ETHNOPHARMACOLOGY RELEVANCE

The angiogenesis control at the initiation of rheumatoid arthritis (RA) that mainly blocks the inflammatory cascades expects to attenuate the action of angiogenic mediators, synovial angiogenesis, and to partially reverse the erosive bone damage. Two typical Chinese herbs, Semen Strychni and Tripterygium wilfordii Hook F (TwHF) have been used as a remedy to treat RA since ancient time. However, their functioning mechanisms are still unknown. Thus it is necessary to exploit their underlying mechanism for the treatment of RA.

METHODS

This study was undertaken to analyze their underlying mechanism based on a systems biology platform. Firstly, active components of the two herbs were screened out from TcmSP database based on their OB and DL values. Then their potential targets were predicted by using Random Forest, Support Vector Machine, and validated via docking process. Finally, a network of compound-target was constructed.

RESULTS

In this work, 27 and 33 active compounds were screened out from Semen Strychni and TwHF, targeting 28 and 32 potential proteins, respectively. The results show that the two herbs modulate the angiogenesis mediators through both direct and indirect pathways, and 21 common targets shared by Semen Strychni and TwHF bear major responsibility for treating RA.

CONCLUSIONS

The underlying mechanism of Semen Strychni and TwHF in treatment of RA is through multiple targets interaction by their blocking of the angiogenesis mediator cascades. This may provide us a better understanding of the function of the two herbs for the treatment of RA, as well as a clue to unveil their possible treatment effects of other systemic diseases, and in this way, hopefully the screening models may facilitate the discovery of novel combined drugs.

Sphingosine 1-phosphate is a ligand for peroxisome proliferator-activated receptor-γ that regulates neoangiogenesis

Sphingosine 1-phosphate (S1P) is a bioactive lipid that can function both extracellularly and intracellularly to mediate a variety of cellular processes. Using lipid affinity matrices and a radiolabeled lipid binding assay, we reveal that S1P directly interacts with the transcription factor peroxisome proliferator-activated receptor (PPAR)γ. Herein, we show that S1P treatment of human endothelial cells (ECs) activated a luciferase-tagged PPARγ-specific gene reporter by ∼12-fold, independent of the S1P receptors. More specifically, in silico docking, gene reporter, and binding assays revealed that His323 of the PPARγ ligand binding domain is important for binding to S1P. PPARγ functions when associated with coregulatory proteins, and herein we identify that peroxisome proliferator-activated receptor-γ coactivator 1 (PGC1)β binds to PPARγ in ECs and their progenitors (nonadherent endothelial forming cells) and that the formation of this PPARγ:PGC1β complex is increased in response to S1P. ECs treated with S1P selectively regulated known PPARγ target genes with PGC1β and plasminogen-activated inhibitor-1 being increased, no change to adipocyte fatty acid binding protein 2 and suppression of CD36. S1P-induced in vitro tube formation was significantly attenuated in the presence of the PPARγ antagonist GW9662, and in vivo application of GW9662 also reduced vascular development in Matrigel plugs. Interestingly, activation of PPARγ by the synthetic ligand troglitazone also reduced tube formation in vitro and in vivo. To support this, Sphk1(-/-)Sphk2(+/-) mice, with low circulating S1P levels, demonstrated a similar reduction in vascular development. Taken together, our data reveal that the transcription factor, PPARγ, is a bona fide intracellular target for S1P and thus suggest that the S1P:PPARγ:PGC1β complex may be a useful target to manipulate neovascularization.

Troglitazone and Δ2Troglitazone enhance adiponectin expression in monocytes/macrophages through the AMP-activated protein kinase pathway

Accumulating evidence indicates that the regimen to increase adiponectin will provide a novel therapeutic strategy for inflammation and cardiovascular disorders. Here, we tested the effect of troglitazone (TG) and its newly synthesized derivative, 5-[4-(6-hydroxy-2,5,7,8-tetramethyl-chroman-2-yl-methoxy)-benzylidene]-2,4-thiazolidinedione (Δ2troglitazone, (Δ2TG)), on the adiponectin expression in monocytes/macrophages and the relative mechanisms. The expression of adiponectin was located in macrophages of atherosclerotic lesions from patients and cholesterol-fed rabbits. TG and Δ2TG enhanced adiponectin mRNA and protein expression in THP-1 cells by quantitative real-time PCR, Western blot, and immunocytochemistry. TG induced adiponectin mRNA expression through a PPARγ-dependent pathway whereas Δ2TG enhanced adiponectin mRNA expression through a PPARγ-independent pathway in THP-1 cells. Both TG and Δ2TG enhanced adiponectin mRNA expression through AMP-activated protein kinase (AMPK) activation. TG and Δ2TG decreased the adhesion of THP-1 cells to TNF-α-treated HUVECs and the inhibitory effect was abolished by specific antiadiponectin antibodies. TG- and Δ2TG-induced suppression on monocyte adhesion were inhibited by a selective AMPK inhibitor compound C. Our data suggest that the inhibitory effect of TG and Δ2TG on monocyte adhesion might be at least in part through de novo adiponectin expression and activation of an AMPK-dependent pathway, which might play an important role in anti-inflammation and antiatherosclerosis.

Flos lonicerae extracts and chlorogenic acid protect human umbilical vein endothelial cells from the toxic damage of perfluorooctane sulphonate

Chlorogenic acid (CGA), one of the most common phenolic acids, is found in many food and traditional Chinese herbs. Various bioactivities of CGA are studied. However, little is known about these properties of Flos Lonicerae extracts, and the difference in the effect between Flos Lonicerae extracts and CGA has not been reported. CGA was identified in Flos Lonicerae extracts by HPLC and determined qualitatively by quadrupole ion trap mass spectrometry. In this study, we evaluated the effect of Flos Lonicerae extracts and CGA on inflammatory-related gene expression, adhesion molecule expression and reactive oxygen species (ROS) production in perfluorooctane sulphonate (PFOS)-treated human umbilical vein endothelial cells (HUVECs). The suppression of transcription of IL-1β, IL-6, COX-2, and P-Selectin genes with Flos Lonicerae extracts was greater than that of CGA in PFOS-treated HUVECs, while the degree of suppression on PFOS-induced expression of NOS3 and ICAM-1 was greater for CGA. Furthermore, the suppressive effect of Flos Lonicerae extracts on adhesion of monocytes onto PFOS-induced HUVECs was greater than that of CGA. In addition, Flos Lonicerae extracts and CGA were highly effective in reducing ROS although their effects were almost comparable. So, Flos Lonicerae extracts exhibited antioxidant activity and CGA was a major contributor to this activity. These results suggest that Flos Lonicerae extracts could be useful to prevent PFOS-mediated inflammatory diseases.

Maraviroc attenuates trauma-hemorrhage-induced hepatic injury through PPAR gamma-dependent pathway in rats

Maraviroc is a CC-chemokine receptor 5 (CCR5) antagonist with potent antiviral and cancer preventive effects. Recent evidence suggests that the co-existence of CCR5 in various cell types is involved in inflammation. However, the effects that CCR5 antagonists produce in trauma-hemorrhage remain unknown. The peroxisome proliferator-activated receptor gamma (PPAR_γ) pathway exerts anti-inflammatory effects in injury. In this study, we hypothesized that maraviroc administration in male rats, after trauma-hemorrhage, decreases cytokine production and protects against hepatic injury through a PPAR_γ-dependent pathway. Male Sprague-Dawley rats underwent trauma-hemorrhage (mean blood pressure maintained at approximately 35-40 mmHg for 90 minutes), followed by fluid resuscitation. During resuscitation, a single dose of maraviroc (3 mg/kg, intravenously) with and without a PPAR_γ antagonist GW9662 (1 mg/kg, intravenously), GW9662 or vehicle was administered. Plasma alanine aminotransferase (ALT) with aspartate aminotransferase (AST) concentrations and various hepatic parameters were measured (n=8 rats/group) at 24 hours after resuscitation. The results showed that trauma-hemorrhage increased hepatic myeloperoxidase activity, intercellular adhesion molecule-1 and interleukin-6 levels, and plasma ALT and AST concentrations. These parameters were significantly improved in the maraviroc-treated rats subjected to trauma-hemorrhage. Maraviroc treatment also increased hepatic PPAR_γ expression compared with vehicle-treated trauma-hemorrhaged rats. Co-administration of GW9662 with maraviroc abolished the maraviroc-induced beneficial effects on the above parameters and hepatic injury. These results suggest that the protective effect of maraviroc administration on alleviation of hepatic injury after trauma-hemorrhage, which is, at least in part, through PPAR_γ-dependent pathway.

Hypoxia modulation of peroxisome proliferator-activated receptors (PPARs) in human glioblastoma stem cells. Implications for therapy

Gliobastoma (GB), the most common adult brain tumor, infiltrates normal brain area rendering impossible the complete surgical resection, resulting in a poor median survival (14-15 months), despite the aggressive multimodality treatments post-surgery, such as radiation and chemo-therapy. GB is characterized by hypoxic and necrotic regions due to a poorly organized tumor vascularization, leading to inadequate blood supply and consequently to hypoxic and necrotic areas. We have previously shown that, under hypoxia GB primary cells increased the expression of stemness markers as well as the expression of the nuclear receptor peroxisome proliferator-activated receptor α (PPARα) and also the crucial role played by PPARs in mouse neural stem cells maintenance and differentiation. Due to the importance of lipid signaling in cell proliferation and differentiation, in this work, we analyzed the expression of PPARs in GB neurospheres both in normoxic and hypoxic conditions. The results obtained suggest a differential regulation of the three PPARs by hypoxia, thus indicating a possible therapeutic strategy to counteract GB recurrencies.

Endothelial cell peroxisome proliferator-activated receptor γ reduces endotoxemic pulmonary inflammation and injury

Bacterial endotoxin (LPS)-mediated sepsis involves severe, dysregulated inflammation that injures the lungs and other organs, often fatally. Vascular endothelial cells are both key mediators and targets of LPS-induced inflammatory responses. The nuclear hormone receptor peroxisome proliferator-activated receptor γ (PPARγ) exerts anti-inflammatory actions in various cells, but it is unknown whether it modulates inflammation through actions within endothelial cells. To determine whether PPARγ acts within endothelial cells to diminish endotoxemic lung inflammation and injury, we measured inflammatory responses and mediators in mice with endothelial-targeted deletion of PPARγ. Endothelial cell PPARγ (ePPARγ) knockout exacerbated LPS-induced pulmonary inflammation and injury as shown by several measures, including infiltration of inflammatory cells, edema, and production of reactive oxygen species and proinflammatory cytokines, along with upregulation of the LPS receptor TLR4 in lung tissue and increased activation of its downstream signaling pathways. In isolated LPS-stimulated endothelial cells in vitro, absence of PPARγ enhanced the production of numerous inflammatory markers. We hypothesized that the observed in vivo activity of the ligand-activated ePPARγ may arise, in part, from nitrated fatty acids (NFAs), a novel class of endogenous PPARγ ligands. Supporting this idea, we found that treating isolated endothelial cells with physiologically relevant concentrations of the endogenous NFA 10-nitro-oleate reduced LPS-induced expression of a wide range of inflammatory markers in the presence of PPARγ, but not in its absence, and also inhibited neutrophil mobility in a PPARγ-dependent manner. Our results demonstrate a key protective role of ePPARγ against endotoxemic injury and a potential ePPARγ-mediated anti-inflammatory role for NFAs.

Rosiglitazone attenuates NF-κB-mediated Nox4 upregulation in hyperglycemia-activated endothelial cells

Vascular complications, a major cause of morbidity and mortality in diabetic patients, are related to hyperglycemia-induced oxidative stress. Previously, we reported that rosiglitazone (RSG) attenuated vascular expression and activity of NADPH oxidases in diabetic mice. The mechanisms underlying these effects remain to be elucidated. We hypothesized that RSG acts directly on endothelial cells to modulate vascular responses in diabetes. To test this hypothesis, human aortic endothelial cells (HAECs) were exposed to normal glucose (NG; 5.6 mmol/l) or high glucose (HG; 30 mmol/l) concentrations. Select HAEC monolayers were treated with RSG, caffeic acid phenethyl ester (CAPE), diphenyleneiodonium (DPI), small interfering (si)RNA (to NF-κB/p65 or Nox4), or Tempol. HG increased the expression and activity of the NADPH oxidase catalytic subunit Nox4 but not Nox1 or Nox2. RSG attenuated HG-induced NF-κB/p65 phosphorylation, nuclear translocation, and binding to the Nox4 promoter. Inhibiting NF-κB with CAPE or siNF-κB/p65 also reduced HG-induced Nox4 expression and activity. HG-induced H(2)O(2) production was attenuated by siRNA-mediated knockdown of Nox4, and HG-induced HAEC monocyte adhesion was attenuated by treatment with RSG, DPI, CAPE, or Tempol. These results indicate that HG exposure stimulates HAEC NF-κB activation, Nox4 expression, and H(2)O(2) production and that RSG attenuates HG-induced oxidative stress and subsequent monocyte-endothelial interactions by attenuating NF-κB/p65 activation and Nox4 expression. This study provides novel insights into mechanisms by which the thiazolidinedione peroxisome proliferator-activated receptor-γ ligand RSG favorably modulates endothelial responses in the diabetic vasculature.

A six-month supplementation of mulberry, korean red ginseng, and banaba decreases biomarkers of systemic low-grade inflammation in subjects with impaired glucose tolerance and type 2 diabetes

We sought the long-term efficacy of traditionally used antidiabetic herbs in controlling blood glucose homeostasis and low-grade inflammation. Ninety-four subjects with either impaired glucose tolerance or mild T2D were randomized either to treatment arm or placebo arm and received 1 : 1 : 1 mixture of ginseng roots, mulberry leaf water extract, and banaba leaf water extract (6 g/d) for 24 weeks. Oral 75 g glucose tolerance test was performed to measure glucose and insulin responses. Blood biomarkers of low-grade inflammation were also determined. Results found no significant difference in glucose homeostasis control measure changes. However, plasma intracellular adhesion molecule-1 (ICAM-1) concentration was decreased showing a significant between-treatment changes (P = 0.037). The concentrations of vascular cell adhesion molecule-1 (VCAM-1) (P = 0.014) and ICAM-1 (P = 0.048) were decreased in the treatment group at week 24, and the oxidized low-density lipoprotein (ox-LDL) concentration was reduced at week 24 compared to the baseline value in the treatment group (P = 0.003). These results indicate a long-term supplementation of ginseng, mulberry leaf, and banaba leaf suppresses inflammatory responses in T2D.

Peroxisome proliferator-activated receptor-γ and the endothelium: implications in cardiovascular disease

Peroxisome proliferator-activated receptors-γ (PPARγs) are ligand-activated transcription factors that play a crucial regulatory role in the transcription of a large number of genes involved in lipid metabolism and inflammation. In addition to physiological ligands, synthetic ligands (the thiazoledinediones) have been developed. In spite of the much publicized adverse cardiovascular effects of one such thiazoledinedione (rosiglitazone), PPARγ activation may have beneficial cardiovascular effects. In this article we review the effects of PPARγ activation on the endothelium with special emphasis on the possible implications in cardiovascular disease. We discuss its possible role in inflammation, vasomotor function, thrombosis, angiogenesis, vascular aging and vascular rhythm. We also briefly review the clinical implications of these lines of research.

Atherogenic ω-6 Lipids Modulate PPAR- EGR-1 Crosstalk in Vascular Cells

Atherogenic ω-6 lipids are physiological ligands of peroxisome proliferator-activated receptors (PPARs) and elicit pro- and antiatherogenic responses in vascular cells. The objective of this study was to investigate if ω-6 lipids modulated the early growth response-1 (Egr-1)/PPAR crosstalk thereby altering vascular function. Rat aortic smooth muscle cells (RASMCs) were exposed to ω-6 lipids, linoleic acid (LA), or its oxidized form, 13-HPODE (OxLA) in the presence or absence of a PPARα antagonist (MK886) or PPARγ antagonist (GW9662) or PPAR-specific siRNA. Our results demonstrate that ω-6 lipids, induced Egr-1 and monocyte chemotactic protein-1 (MCP-1) mRNA and protein levels at the acute phase (1-4 hrs) when PPARα was downregulated and at subacute phase (4-12 hrs) by modulating PPARγ, thus resulting in altered monocyte adhesion to RASMCs. We provide novel insights into the mechanism of action of ω-6 lipids on Egr-1/PPAR interactions in vascular cells and their potential in altering vascular function.

NHE-1 and β1 integrin dependent monocyte adhesion and migration after glucose, insulin or PPARγ stimulation

In the present study the effect of high glucose concentrations, insulin, PPARγ activators (rosiglitazone) and NHE-1 inhibitors (cariporide) in atherosclerosis-related functions of human monocytes was investigated. Monocyte adhesion to laminin-1, collagen type IV and endothelial cells, as well as monocyte migration through the same substrates were studied. Incubation of the monocyte suspension with high glucose concentrations, insulin and rosiglitazone induced all the studied atherosclerosis-related functions of the monocytes. In all these functions the addition of cariporide counteracted the activity of glucose, insulin and rosiglitazone. The use of antigen for β1 integrin also counteracted the activity of the above in monocyte adhesion in all three substrates. The data of the present study suggests that PPARγ activation in monocytes induces atherosclerosis, and that NHE-1 and β1 integrin play an important role in the beginning of atherosclerosis.

Induction of intercellular adhesion molecule-1 by water-soluble components of Hericium erinaceum in human monocytes

AIM OF THE STUDY

Hericium erinaceum is a medicinal mushroom that has been traditionally used in Asian countries for the treatment of cancers and infectious diseases. Although the immunomodulating activity of H. erinaceum is considered to be responsible for its medicinal activity, its action mechanisms are poorly understood. In the present study, we investigated the capability of water-extracted H. erinaceum (WEHE) to induce the expression of intercellular adhesion molecule-1 (ICAM-1), which regulates the migration of immune cells.

MATERIALS AND METHODS

THP-1, a human monocytic cell-line, or human peripheral blood mononuclear cells (PBMC) were stimulated with WEHE (0-30 μg/mL) and subsequently analyzed using flow cytometry to examine the surface expression of ICAM-1 protein. Steady-state levels of ICAM-1 mRNA were estimated using real-time reverse transcription-polymerase chain reaction analysis. Electrophoretic mobility shift assay was conducted to examine transcription factors involved in ICAM-1 transcription.

RESULTS

WEHE induced ICAM-1 expression at both protein and mRNA levels in THP-1 cells in a dose- and time-dependent fashion. A similar pattern of ICAM-1 induction was also observed in CD14(+) monocytes in human PBMC that were stimulated with WEHE. The ICAM-1 expression on THP-1 cells stimulated with WEHE was suppressed by specific inhibitors for extracellular signal-regulated kinases (ERK) and reactive oxygen species (ROS). Additionally, exposure of THP-1 cells to WEHE increased the DNA binding activities of NF-κB, AP-1, SP-1 and STAT-1 transcription factors, all of which are known to be required for ICAM-1 gene expression.

CONCLUSIONS

These results suggest that WEHE induces ICAM-1 expression in human monocytes through ERK- and ROS-dependent signaling pathways, resulting in the subsequent activations of NF-κB, AP-1, SP-1, and STAT-1 transcription factors.

Induction of ICAM-1 by Armillariella mellea is mediated through generation of reactive oxygen species and JNK activation

ETHNOPHARMACOLOGICAL RELEVANCE

Armillariella mellea is an edible mushroom that has been traditionally used as an alternative medicine in many countries because of its anti-microbial and anti-cancer effects.

AIM OF THE STUDY

In this study, we examined the ability of Armillariella mellea to induce the expression of intercellular adhesion molecule (ICAM)-1, an important cellular adhesion molecule for the recruitment of immune cells to regional inflammatory sites.

MATERIALS AND METHODS

A human monocytic cell line, THP-1 or human peripheral blood mononuclear cells (PBMC) were stimulated with Armillariella mellea extract (AME) and subjected to flow cytometry to examine the expression of ICAM-1 protein on the cell surface. Steady-state mRNA level of ICAM-1 was determined by real-time reverse transcription-polymerase chain reaction. The phosphorylation of JNK protein was examined by Western blot analysis using antibodies specific for non-phosphorylated and phosphorylated forms of JNK. For the analysis of transcription factors regulating ICAM-1 transcription, the nuclear fraction was extracted from AME-treated THP-1 cells and subjected to electrophoretic mobility shift assay.

RESULTS

AME induced expression of ICAM-1 and its mRNA in THP-1 cells in dose- and time-dependent manners. AME-induced ICAM-1 expression was also observed on CD14-positive monocytes in human PBMC. Interestingly, AME-induced ICAM-1 production was inhibited by the specific inhibitors of reactive oxygen species (ROS) and JNK, whereas no inhibitory effect was observed when inhibitors of ERK, p38 kinase, phosphatidylinositol 3-kinase, or protein kinase C were used. Concomitantly, AME increased phosphorylation of JNK in a time-dependent fashion. DNA binding activities of NF-kappaB, AP-1, SP-1, and STAT-1 were increased by AME treatment.

CONCLUSION

These results suggest that AME induces ICAM-1 expression in human monocytic cells through ROS/JNK-dependent signaling pathways leading to the activation of NF-kappaB, AP-1, SP-1, and STAT-1 transcription factors.

Propionyl- l -Carnitine Improves Postischemic Blood Flow Recovery and Arteriogenetic Revascularization and Reduces Endothelial NADPH-Oxidase 4–Mediated Superoxide Production

Objective— The beneficial effect of the natural compound propionyl- l -carnitine (PLC) on intermittent claudication in patients with peripheral arterial disease is attributed to its anaplerotic function in ischemic tissues, but inadequate information is available concerning action on the vasculature.

Methods and Results— We investigated the effects of PLC in rabbit hind limb collateral vessels after femoral artery excision, mouse dorsal air pouch, chicken chorioallantoic membrane, and vascular cells by angiographic, Doppler flow, and histomorphometrical and biomolecular analyses. PLC injection accelerated hind limb blood flow recovery after 4 days ( P <0.05) and increased angiographic quadriceps collateral vascularization after 7 days ( P <0.001) Histomorphometry confirmed the increased vascular area ( P <0.05), with unchanged intramuscular capillary density. PLC-induced dilatative adaptation, and growth was found associated with increased inducible nitric oxide synthase and reduced arterial vascular endothelial growth factor and intracellular adhesion molecule-1 expression. PLC also increased vascularization in air pouch and chorioallantoic membrane ( P <0.05), particularly in large vessels. PLC increased endothelial and human umbilical vascular endothelial cell proliferation and rapidly reduced inducible nitric oxide synthase and NADPH-oxidase 4–mediated reactive oxygen species production in human umbilical vascular endothelial cells; NADPH-oxidase 4 also regulated NF-κB–independent intracellular adhesion molecule-1 expression.

Conclusion— Our results provided strong evidence that PLC improves postischemic flow recovery and revascularization and reduces endothelial NADPH-oxidase–related superoxide production. We recommend that PLC should be included among therapeutic interventions that target endothelial function.

Docosahexaenoic acid down-regulates endothelial Nox 4 through a sPLA2 signalling pathway

We investigated the anti-inflammatory and antioxidant activities of docosahexaenoic acid (DHA) by evaluating its modulation of the two enzymes most involved in vascular inflammation, i.e. endothelial secreted phospholipase A(2) (sPLA(2)) and NADPH oxidase 4 (Nox) 4. Exposure of human aortic endothelial cells (HAECs) to DHA led to its preferential incorporation into outer leaflet phospholipids. Pre-treatment with DHA abolished HAECs stimulation induced by A23187 and Ang II, whereas the effects on IL-1beta treatment were less pronounced. Group V sPLA(2) RNA was similarly modulated by DHA supplementation. In addition, DHA decreased Nox 4 expression and activity; this effect was associated with reduced production of reactive oxygen species. Further, the use of specific inhibitors allowed demonstrating that group V sPLA(2) is involved in the down-regulation of Nox 4 expression and activity by DHA. This interplay is mediated by ERK and PKC.

Increased sensitivity for troglitazone-induced cytotoxicity using a human in vitro co-culture model

Drug-induced hepatotoxicity is a major reason for withdrawal of drugs from development as well as from the market. A major problem predicting hepatotoxicity is the lack of suitable predictive in vitro system. Drug-induced hepatotoxicity is usually associated with the recruitment of immune cells to the liver accelerating an inflammatory response often initiated by activation of the Kupffer cells. In order to evaluate whether the introduction of inflammatory cells could increase the sensitivity for drug-induced cytotoxicity we developed an in vitro co-culture system based on two human cell lines; a hepatoma (Huh-7) and monocytic (THP-1) cell line. As model drugs we chose two peroxisome proliferator activated receptor gamma (PPAR gamma) agonists, the hepatotoxic troglitazone and the non-hepatotoxic rosiglitazone. In the co-cultures, troglitazone caused an enhanced cytotoxicity as compared to single cultures of either cell line, whereas little cytotoxicity was seen after treatment with rosiglitazone. Troglitazone treatment increased gene expression of pro-inflammatory mediators and stress-related genes in both cell types, which in general was more pronounced in co-cultures than in single cell cultures. Based on these results we suggest that co-cultures of human hepatoma cells and monocytes might provide an important in vitro system for better prediction of cytotoxicity mediated by potential hepatotoxins.

Protective effect of peroxisome proliferator-activated receptor-gamma agonists on activated renal proximal tubular epithelial cells in IgA nephropathy

BACKGROUND

We have previously demonstrated a glomerulo-tubular 'crosstalk' operating in the pathogenesis of tubulointerstitial injury in IgA nephropathy (IgAN). The present study aims to explore any possible beneficial effect of a peroxisome proliferator-activated receptor-gamma (PPAR-gamma) agonist in alleviating the tubulointerstitial inflammation in IgAN.

METHODS

Human proximal tubular epithelial cells (PTEC) were pre-treated with increasing concentration of a PPAR-gamma agonist rosiglitazone or troglitazone (0-5 microM) followed by further incubation with the conditioned medium (IgA-HMC) collected from human mesangial cells (HMC) incubated with polymeric IgA isolated from IgAN patients. Gene expression of interleukin-6 (IL-6) and angiotensin II type 1 receptor (ATR1) was detected by reverse transcription-polymerase chain reaction (RT-PCR); protein expression of IL-6 and ATR1 was determined by ELISA and western blot, respectively. The mitogen-activated protein kinase extracellular signal-related kinase 1/2 (ERK1/2) activation was examined by western blot.

RESULTS

An IgA-HMC conditioned medium prepared from IgAN patients increased gene expression and protein synthesis of IL-6 and ATR1 in PTEC when compared with a conditioned medium prepared from healthy controls. The upregulated gene expression and protein synthesis of IL-6 and ATR1 in PTEC induced by the IgA-HMC conditioned medium were readily attenuated following pre-treatment with a PPAR-gamma agonist, thiazolidinedione (TZD). The ATR1-downregulating effect exerted by the PPAR-gamma agonist occurred through the inhibition of ERK1/2 activation. The PPAR-gamma antagonist, GW9662, significantly attenuated the inhibitory action of rosiglitazone on the increased synthesis of IL-6 and ATR1 protein.

CONCLUSION

Our current findings suggest that the PPAR-gamma agonist attenuates excessive inflammatory response in activated PTEC in IgAN through suppressing ATR1 expression. This ATR1-downregulating effect is likely through the inhibition of ERK1/2 activation and is found to be PPAR-gamma dependent. TZDs may possibly be new therapeutic additives to established treatment regime for renin-angiotensin system (RAS) blockade in IgAN.

Iron behaving badly: inappropriate iron chelation as a major contributor to the aetiology of vascular and other progressive inflammatory and degenerative diseases

BACKGROUND

The production of peroxide and superoxide is an inevitable consequence of aerobic metabolism, and while these particular 'reactive oxygen species' (ROSs) can exhibit a number of biological effects, they are not of themselves excessively reactive and thus they are not especially damaging at physiological concentrations. However, their reactions with poorly liganded iron species can lead to the catalytic production of the very reactive and dangerous hydroxyl radical, which is exceptionally damaging, and a major cause of chronic inflammation.

REVIEW

We review the considerable and wide-ranging evidence for the involvement of this combination of (su)peroxide and poorly liganded iron in a large number of physiological and indeed pathological processes and inflammatory disorders, especially those involving the progressive degradation of cellular and organismal performance. These diseases share a great many similarities and thus might be considered to have a common cause (i.e. iron-catalysed free radical and especially hydroxyl radical generation).The studies reviewed include those focused on a series of cardiovascular, metabolic and neurological diseases, where iron can be found at the sites of plaques and lesions, as well as studies showing the significance of iron to aging and longevity. The effective chelation of iron by natural or synthetic ligands is thus of major physiological (and potentially therapeutic) importance. As systems properties, we need to recognise that physiological observables have multiple molecular causes, and studying them in isolation leads to inconsistent patterns of apparent causality when it is the simultaneous combination of multiple factors that is responsible.This explains, for instance, the decidedly mixed effects of antioxidants that have been observed, since in some circumstances (especially the presence of poorly liganded iron) molecules that are nominally antioxidants can actually act as pro-oxidants. The reduction of redox stress thus requires suitable levels of both antioxidants and effective iron chelators. Some polyphenolic antioxidants may serve both roles.Understanding the exact speciation and liganding of iron in all its states is thus crucial to separating its various pro- and anti-inflammatory activities. Redox stress, innate immunity and pro- (and some anti-)inflammatory cytokines are linked in particular via signalling pathways involving NF-kappaB and p38, with the oxidative roles of iron here seemingly involved upstream of the IkappaB kinase (IKK) reaction. In a number of cases it is possible to identify mechanisms by which ROSs and poorly liganded iron act synergistically and autocatalytically, leading to 'runaway' reactions that are hard to control unless one tackles multiple sites of action simultaneously. Some molecules such as statins and erythropoietin, not traditionally associated with anti-inflammatory activity, do indeed have 'pleiotropic' anti-inflammatory effects that may be of benefit here.

CONCLUSION

Overall we argue, by synthesising a widely dispersed literature, that the role of poorly liganded iron has been rather underappreciated in the past, and that in combination with peroxide and superoxide its activity underpins the behaviour of a great many physiological processes that degrade over time. Understanding these requires an integrative, systems-level approach that may lead to novel therapeutic targets.

Emerging roles of peroxisome proliferator-activated receptors (PPARs) in the regulation of neural stem cells proliferation and differentiation

The molecular mechanisms controlling the specification of neural cell fates have been the focus of intense research in recent years. Neural precursor cells (NPCs) sequentially undergo expansion, neurogenic and gliogenic fates during development, but the underlying mechanisms are poorly understood. Recent studies have identified a number of extrinsic factors that regulate the fate of NPCs. Wnt signaling induces neuronal differentiation of NPCs in an instructive manner. Wnt plays this role in the neurogenic phase of NPCs but not in the early expansion phase, when this pathway promotes proliferation. Likewise, STAT3-activating ligands induce astrocytic differentiation in late gliogenic phase of NPCs but not in the early expansion and neurogenic phases. The mechanisms underlying these remarkable changes in progenitor behaviour and fate during development are not understood, but are thought to include changes in the intrinsic properties of neural progenitors, as well as changes in their signalling environment. PPARs are ligand-activated transcription factors belonging to the nuclear hormone receptor superfamily, which activate the transcription of their target genes as heterodimers with retinoid X receptors (RXR). PPARs have been recently involved in NSC acquisition of a specific fate. They have been described to be involved in pathways present also in the control of the proliferation, migration and differentiation of NSC, i.e. Wnt signalling pathway, STAT3 and NFkB pathways. In this review the findings related to PPARs and NSC are reported as well as their possible linkage to other signal transduction pathways involved in NSC specification.

Protective Actions of PPAR-gamma Activation in Renal Endothelium

Renal endothelial damage is pivotal in the initiation and progression of renal disease. Damaged renal endothelium may be regenerated through proliferation of local endothelium and circulation-derived endothelial progenitor cells. Activation of the PPAR-gamma-receptors present on endothelial cells affects their cellular behavior. Proliferation, apoptosis, migration, and angiogenesis by endothelial cells are modulated, but may involve both stimulation and inhibition depending on the specific circumstances. PPAR-gamma-receptor activation stimulates the production of nitric oxide, C-type natriuretic peptide, and superoxide dismutase, while endothelin-1 production is inhibited. Together, they augment endothelial function, resulting in blood pressure lowering and direct renoprotective effects. The presentation of adhesion molecules and release of cytokines recruiting inflammatory cells are inhibited by PPAR-gamma-agonism. Finally, PPAR-gamma-receptors are also found on endothelial progenitor cells and PPAR-gamma-agonists stimulate progenitor-mediated endothelial repair. Together, the stimulatory effects of PPAR-gamma-agonism on endothelium make an important contribution to the beneficial actions of PPAR-gamma-agonists on renal disease.