A new mechanism involving ERK contributes to rosiglitazone inhibition of tumor necrosis factor-alpha and interferon-gamma inflammatory effects in human endothelial cells

Drug repositioning in thyroid cancer treatment: the intriguing case of anti-diabetic drugs

Cancer represents the main cause of death worldwide. Thyroid cancer (TC) shows an overall good rate of survival, however there is a percentage of patients that do not respond or are refractory to common therapies. Thus new therapeutics strategies are required. In the past decade, drug repositioning become very important in the field of cancer therapy. This approach shows several advantages including the saving of: i) time, ii) costs, iii) de novo studies regarding the safety (just characterized) of a drug. Regarding TC, few studies considered the potential repositioning of drugs. On the other hand, certain anti-diabetic drugs, were the focus of interesting studies on TC therapy, in view of the fact that they exhibited potential anti-tumor effects. Among these anti-diabetic compounds, not all were judjed as appropriate for repositioning, in view of well documented side effects. However, just to give few examples biguanides, DPP-4-inhibitors and Thiazolidinediones were found to exert strong anti-cancer effects in TC. Indeed, their effects spaced from induction of citotoxicity and inhibition of metastatic spread, to induction of de-differentiation of TC cells and modulation of TC microenvironment. Thus, the multifacial anti-cancer effect of these compounds would make the basis also for combinatory strategies. The present review is aimed at discuss data from studies regarding the anti-cancer effects of several anti-diabetic drugs recently showed in TC in view of their potential repositioning. Specific examples of anti-diabetic repositionable drugs for TC treatment will also be provided.

PPARγ in Atherosclerotic Endothelial Dysfunction: Regulatory Compounds and PTMs

The formation of atherosclerotic plaques is one of the main sources of cardiovascular disease. In addition to known risk factors such as dyslipidemia, diabetes, obesity, and hypertension, endothelial dysfunction has been shown to play a key role in the formation and progression of atherosclerosis. Peroxisome proliferator-activated receptor-gamma (PPARγ), a transcription factor belonging to the steroid superfamily, is expressed in the aorta and plays a critical role in protecting endothelial function. It thereby serves as a target for treating both diabetes and atherosclerosis. Although many studies have examined endothelial cell disorders in atherosclerosis, the role of PPARγ in endothelial dysfunction is still not well understood. In this review, we summarize the possible mechanisms of action behind PPARγ regulatory compounds and post-translational modifications (PTMs) of PPARγ in the control of endothelial function. We also explore the potential use of endothelial PPARγ-targeted agents in the prevention and treatment of atherosclerosis.

EGFR Activation Impairs Antiviral Activity of Interferon Signaling in Brain Microvascular Endothelial Cells During Japanese Encephalitis Virus Infection

The establishment of Japanese encephalitis virus (JEV) infection in brain microvascular endothelial cells (BMECs) is thought to be a critical step to induce viral encephalitis with compromised blood–brain barrier (BBB), and the mechanisms involved in this process are not completely understood. In this study, we found that epidermal growth factor receptor (EGFR) is related to JEV escape from interferon-related host innate immunity based on a STRING analysis of JEV-infected primary human brain microvascular endothelial cells (hBMECs) and mouse brain. At the early phase of the infection processes, JEV induced the phosphorylation of EGFR. In JEV-infected hBMECs, a rapid internalization of EGFR that co-localizes with the endosomal marker EEA1 occurred. Using specific inhibitors to block EGFR, reduced production of viral particles was observed. Similar results were also found in an EGFR-KO hBMEC cell line. Even though the process of viral infection in attachment and entry was not noticeably influenced, the induction of IFNs in EGFR-KO hBMECs was significantly increased, which may account for the decreased viral production. Further investigation demonstrated that EGFR downstream cascade ERK, but not STAT3, was involved in the antiviral effect of IFNs, and a lowered viral yield was observed by utilizing the specific inhibitor of ERK. Taken together, the results revealed that JEV induces EGFR activation, leading to a suppression of interferon signaling and promotion of viral replication, which could provide a potential target for future therapies for the JEV infection.

Human cell-based anti-inflammatory effects of rosiglitazone

PURPOSE

The C-X-C motif chemokine ligand 10 (CXCL10) participates in diabetes and diabetic cardiomyopathy development from the early stages. Rosiglitazone (RGZ) exhibits anti-inflammatory properties and can target cardiomyocytes secreting CXCL10, under interferon (IFN)γ and tumor necrosis factor (TNF)α challenge. Cardiomyocyte remodeling, CD4 + T cells and dendritic cells (DCs) significantly contribute to the inflammatory milieu underlying and promoting disease development. We aimed to study the effect of RGZ onto inflammation-induced secretion of CXCL10, IFNγ, TNFα, interleukin (IL)-6 and IL-8 by human CD4 + T and DCs, and onto IFNγ/TNFα-dependent signaling in human cardiomyocytes associated with chemokine release.

METHODS

Cells maintained within an inflammatory-like microenvironment were exposed to RGZ at near therapy dose (5 µM). ELISA quantified cytokine secretion; qPCR measured mRNA expression; Western blot analyzed protein expression and activation; immunofluorescent analysis detected intracellular IFNγ/TNFα-dependent trafficking.

RESULTS

In human CD4 + T cells and DCs, RGZ inhibited CXCL10 release likely with a transcriptional mechanism, and reduced TNFα only in CD4 + T cells. In human cardiomyocytes, RGZ impaired IFNγ/TNFα signal transduction, blocking the phosphorylation/nuclear translocation of signal transducer and activator of transcription 1 (Stat1) and nuclear factor-kB (NF-kB), in association with a significant decrease in CXCL10 expression, IL-6 and IL-8 release.

CONCLUSION

As the combination of Th1 biomarkers like CXCL10, IL-8, IL-6 with classical cardiovascular risk factors seems to improve the accuracy in predicting T2D and coronary events, future studies might be desirable to further investigate the anti-Th1 effect of RGZ.

Peroxisome Proliferator-Activated Receptor γ Agonist Rosiglitazone Protects Blood-Brain Barrier Integrity Following Diffuse Axonal Injury by Decreasing the Levels of Inflammatory Mediators Through a Caveolin-1-Dependent Pathway

Our early experiments confirmed that rosiglitazone (RSG), a peroxisome proliferator-activated receptor γ (PPARγ) agonist, had therapeutic potential for the treatment of diffuse axonal injury (DAI) by inhibiting the expression of amyloid-beta precursor protein and reducing the loss and abnormal phosphorylation of tau, but the underlying mechanisms were not fully defined. In this study, we aimed to investigate a possible role for PPARγ in the protection of blood-brain barrier (BBB) integrity in a rat model of DAI, and the underlying mechanisms. PPAR agonists and antagonists were intraperitoneally injected after DAI. Treatment with RSG ameliorated axonal injury, cell apoptosis, glia activation, and the release of inflammatory factors such as TNF-α, IL-1β, and IL-6. It also increased the expression of tight junction-associated proteins like ZO-1, claudin-5, and occludin-1, whereas the PPARγ antagonist GW9662 had the opposite effects. These effects were also studied in a BBB in vitro model, consisting of a monolayer of human microvascular endothelial cells (HBMECs) subjected to oxygen and glucose deprivation (OGD). Treatment with RSG ameliorated the loss of BBB integrity and the increased permeability induced by OGD by reducing the release of inflammatory factors and maintaining the expression of tight junction-associated proteins. Interestingly, caveolin-1 was found located mainly in endothelial cells, and RSG increased the expression of caveolin-1, which decreased following OGD. In contrast, caveolin-1 siRNA abrogated the protective effects of RSG in the in vitro BBB model. In conclusion, we provide evidence that PPARγ plays an important role in a series of processes associated with DAI, and that the PPARγ agonist RSG can protect BBB integrity by decreasing the levels of inflammatory mediators through a caveolin-1-dependent pathway.

The Adipose Stem Cell as a Novel Metabolic Actor in Adrenocortical Carcinoma Progression: Evidence from an In Vitro Tumor Microenvironment Crosstalk Model

Metabolic interplay between the tumor microenvironment and cancer cells is a potential target for novel anti-cancer approaches. Among stromal components, adipocytes and adipose precursors have been shown to actively participate in tumor progression in several solid malignancies. In adrenocortical carcinoma (ACC), a rare endocrine neoplasia with a poor prognosis, cancer cells often infiltrate the fat mass surrounding the adrenal organ, enabling possible crosstalk with the adipose cells. Here, by using an in vitro co-culture system, we show that the interaction between adipose-derived stem cells (ASCs) and the adrenocortical cancer cell line H295R leads to metabolic and functional reprogramming of both cell types: cancer cells limit differentiation and increase proliferation of ASCs, which in turn support tumor growth and invasion. This effect associates with a shift from the paracrine cancer-promoting IGF2 axis towards an ASC-associated leptin axis, along with a shift in the SDF-1 axis towards CXCR7 expression in H295R cells. In conclusion, our findings suggest that adipose precursors, as pivotal components of the ACC microenvironment, promote cancer cell reprogramming and invasion, opening new perspectives for the development of more effective therapeutic approaches.

Growth Hormone Aggregates Activation of Human Dendritic Cells Is Controlled by Rac1 and PI3 Kinase Signaling Pathways

The presence of protein aggregates in biological products is suggested to promote immunogenicity, leading to the production of anti-drug antibodies with neutralizing capacities. This suggests a CD4⁺ T-cell dependent adaptive immune response, thus a pivotal role for antigen-presenting cells, such as dendritic cells (DCs). We previously showed that human growth hormone aggregates induced DC maturation, with notably an increase in CXCL10 production. DC phenotypic modifications were sufficient to promote allogeneic CD4⁺ T-cell proliferation with Th1 polarization. In this work, we identified the main intracellular signaling pathways involved in DC activation by human growth hormone aggregates, showing that aggregates induced p38 mitogen-activated protein kinase, extracellular signal-regulated kinase, and c-Jun N-terminal kinase phosphorylation, as well as nuclear factor κB subunit p65 nuclear translocation. Next, investigating the implication of Rho GTPases and phosphoinositide 3-kinase (PI3K) in activated DC showed that Rac1 and Cdc42 regulated the phosphorylation of MAP kinases, whereas PI3K was only implicated in c-Jun N-terminal kinase phosphorylation. Furthermore, we showed that Rac1 and PI3K pathways, but not Cdc42, regulated the production of CXCL10 via the MAP kinases and nuclear factor κB. Taken together, our results bring new insight on how protein aggregates could induce DC activation, leading to a better understanding of aggregates role in therapeutic proteins immunogenicity.

The paramount role of cytokines and chemokines in papillary thyroid cancer: a review and experimental results

Our study demonstrates that (C-X-C motif) ligand 9 and 11 (CXCL9, CXCL11) chemokines were absent basally in non-neoplastic thyroid (TFC) and papillary thyroid carcinoma (PTC) cells. Interferon (IFN)γ induced the chemokine secretion in TFC and PTC, while tumor necrosis factor (TNF)α induced it only in PTC. IFNγ+TNFα induced a synergistic chemokines release in PTC, and at a lower level in TFC. Peroxisome proliferator-activated receptor (PPAR)γ agonists suppressed dose-dependently IFNγ+TNFα-induced chemokine release in TFC, while stimulated it in PTC. PPARγ knocking down, by RNA interference technique in PTC cells, abolished the effect of PPARγ agonists on chemokines release. In PTC cells, PPARγ agonists reduced proliferation, and CXCL9 or CXCL11 (100 and 500 pg/mL) reduced proliferation and migration (P < 0.01, for all). In conclusion, in PTC cells: (a) IFNγ+TNFα induced a marked release of CXCL9 and CXCL11; (b) PPARγ agonists stimulated CXCL9 and CXCL11 secretion, while inhibited proliferation; (c) CXCL9 and CXCL11 inhibited proliferation and migration. The use of CXCL9 or CXCL11 as antineoplastic agents in PTC remains to be explored. HIGHLIGHTS: • IFNγ and IFNγ+TNFα induce dose-dependently CXCL9 (and less CXCL11) in PTC cells. • Rosi and Pio dose-dependently inhibit the PTC cells proliferation. • Rosi and Pio (at variance of normal TFC) stimulate CXCL9 or CXCL11 secretion. • CXCL9 or CXCL11 induce a significant antiproliferative effect in PTC cells. • Chemokines induced by IFNγ (CXCL9 or CXCL11) inhibit migration in PTC cells.

Schistosome infection and its effect on pulmonary circulation

Schistosomiasis is the most common parasitic disease associated with pulmonary hypertension. It induces remodelling via complex inflammatory processes, which eventually produce the clinical manifestation of pulmonary hypertension. The pulmonary hypertension shows clinical signs and symptoms that are not distinguishable from other forms of pulmonary arterial hypertension.

Chiglitazar Preferentially Regulates Gene Expression via Configuration-Restricted Binding and Phosphorylation Inhibition of PPARγ

Type 2 diabetes mellitus is often treated with insulin-sensitizing drugs called thiazolidinediones (TZD), which improve insulin resistance and glycemic control. Despite their effectiveness in treating diabetes, these drugs provide little protection from eminent cardiovascular disease associated with diabetes. Here we demonstrate how chiglitazar, a configuration-restricted non-TZD peroxisome proliferator-activated receptor (PPAR) pan agonist with moderate transcription activity, preferentially regulates ANGPTL4 and PDK4, which are involved in glucose and lipid metabolism. CDK5-mediated phosphorylation at serine 273 (S273) is a unique regulatory mechanism reserved for PPARγ, and this event is linked to insulin resistance in type 2 diabetes mellitus. Our data demonstrates that chiglitazar modulates gene expression differently from two TZDs, rosiglitazone and pioglitazone, via its configuration-restricted binding and phosphorylation inhibition of PPARγ. Chiglitazar induced significantly greater expression of ANGPTL4 and PDK4 than rosiglitazone and pioglitazone in different cell models. These increased expressions were dependent on the phosphorylation status of PPARγ at S273. Furthermore, ChIP and AlphaScreen assays showed that phosphorylation at S273 inhibited promoter binding and cofactor recruitment by PPARγ. Based on these results, activities from pan agonist chiglitazar can be an effective part of a long-term therapeutic strategy for treating type 2 diabetes in a more balanced action among its targeted organs.

Rosiglitazone increases endothelial cell migration and vascular permeability through Akt phosphorylation

Background

Thiazolidinediones (TZDs), peroxisome proliferator-activated receptor-γ (PPAR-γ) agonists, exhibit anti-inflammatory and antioxidant properties and inhibit endothelial inflammation and dysfunction, which is anti-atherogenic. However, fluid retention, which may lead to congestive heart failure and peripheral edema, is also a concern, which may result from endothelial cell leakage. In the current study, we examined the effects of PPAR-γ agonists on vascular endothelial cell migration and permeability in order to determine its underlying mechanisms.

Methods

We used rosiglitazone and conducted cell migration assay and permeability assay using HUVEC cells and measured vascular permeability and leakage in male C57BL/6 mice.

Results

Rosiglitazone significantly promoted endothelial cell migration and induced permeability via activation of phosphatidylinositol-3-kinase (PI3K) – Akt or protein kinase C (PKC)β. In addition, rosiglitazone increased vascular endothelial growth factor (VEGF) expression and suppressed expression of tight junction proteins (JAM-A and ZO-1), which might promote neovascularization and vascular leakage. These phenomena were reduced by Akt inhibition.

Conclusions

Vascular endothelial cell migration and permeability change through Akt phosphorylation might be a mechanism of induced fluid retention and peripheral tissue edema by TZD.

Contribution of PPARγ in modulation of acrolein-induced inflammatory signaling in gp91phox knock-out mice

Oxidative stress and inflammation are major contributors to acrolein toxicity. Peroxisome proliferator activated receptor gamma (PPARγ) has antioxidant and anti-inflammatory effects. We investigated the contribution of PPARγ ligand GW1929 to the attenuation of oxidative stress in acrolein-induced insult. Male gp91^phox knock-out (KO) mice were treated with acrolein (0.5 mg·(kg body mass)^-1 by intraperitoneal injection for 7 days) with or without GW1929 (GW; 0.5 mg·(kg body mass)^-1·day^-1, orally, for 10 days). The livers were processed for further analyses. Acrolein significantly increased 8-isoprostane and reduced PPARγ activity (P < 0.05) in the wild type (WT) and KO mice. GW1929 reduced 8-isoprostane (by 32% and 40% in WT and KO mice, respectively) and increased PPARγ activity (by 81% and 92% in WT and KO, respectively). Chemokine activity was increased (by 63%) in acrolein-treated WT mice, and was reduced by GW1929 (by 65%). KO mice exhibited higher xanthine oxidase (XO). Acrolein increased XO and COX in WT mice and XO in KO mice. GW1929 significantly reduced COX in WT and KO mice and reduced XO in KO mice. Acrolein significantly reduced the total antioxidant status in WT and KO mice (P < 0.05), which was improved by GW1929 (by 75% and 74%). The levels of NF-κB were higher in acrolein-treated WT mice. GW1929 reduced NF-κB levels (by 51%) in KO mice. Acrolein increased CD36 in KO mice (by 43%), which was blunted with GW1929. Data confirms that the generation of free radicals by acrolein is mainly through NAD(P)H, but other oxygenates play a role too. GW1929 may alleviate the toxicity of acrolein by attenuating NF-κB, COX, and CD36.

Rosiglitazone attenuates indoxyl sulphate-induced endothelial dysfunction

Indoxyl sulphate is a protein-bound uraemic toxin that has deleterious effects on the cardiovascular system. Rosiglitazone (RGZ) is an insulin sensitizer used for glycaemic control in type 2 diabetes. Rosiglitazone has been shown to be beneficial for cardiovascular disease because of its pleiotropic effects. Whether RGZ can improve indoxyl sulphate-induced endothelial damage has not been investigated. In the present in vitro study, we examined the effects of RGZ on indoxyl sulphate-induced endothelial injury. Endothelial cells were exposed to RGZ (5 and 10 μmol/L) and then treated with indoxyl sulphate (100 and 1000 μmol/L) for 48 h. Indoxyl sulphate upregulated intracellular cell adhesion molecule-1, vascular cell adhesion molecule-1 and monocyte chemotactic protein-1 expression. Indoxyl sulphate also increased the abundance of NADPH oxidase 4 (NOX4) and nuclear factor (NF)-κB. Both extracellular signal-regulated kinase (ERK) 1/2 and p38 mitogen-activated protein kinase (MAPK) signalling pathways were activated after 48 h treatment with indoxyl sulphate. Pretreatment of cells with both concentrations of RGZ improved indices of endothelial injury. In addition, RGZ attenuated the increase in NOX4 and NF-κB and prevented the activation of the ERK1/2 and p38 MAPK signalling pathways. We conclude that RGZ ameliorates indoxyl sulphate-induced endothelial injury.

Agent based modeling of the effects of potential treatments over the blood-brain barrier in multiple sclerosis

Multiple sclerosis is a disease of the central nervous system that involves the destruction of the insulating sheath of axons, causing severe disabilities. Since the etiology of the disease is not yet fully understood, the use of novel techniques that may help to understand the disease, to suggest potential therapies and to test the effects of candidate treatments is highly advisable. To this end we developed an agent based model that demonstrated its ability to reproduce the typical oscillatory behavior observed in the most common form of multiple sclerosis, relapsing-remitting multiple sclerosis. The model has then been used to test the potential beneficial effects of vitamin D over the disease. Many scientific studies underlined the importance of the blood-brain barrier and of the mechanisms that influence its permeability on the development of the disease. In the present paper we further extend our previously developed model with a mechanism that mimics the blood-brain barrier behavior. The goal of our work is to suggest the best strategies to follow for developing new potential treatments that intervene in the blood-brain barrier. Results suggest that the best treatments should potentially prevent the opening of the blood-brain barrier, as treatments that help in recovering the blood-brain barrier functionality could be less effective.

Rosiglitzone suppresses angiotensin II-induced production of KLF5 and cell proliferation in rat vascular smooth muscle cells

Krüppel-like factor (KLF) 5, which initiates vascular smooth muscle cell (VSMC) proliferation, also participates in Angiotensin (Ang) II-induced vascular remodeling. The protective effect of rosiglitazone on vascular remodeling may be due to their impact on VSMC proliferation. However, the underlying mechanisms involved remain unclear. This study was designed to investigate whether the antiproliferation effects of rosiglitazone are mediated by regulating Ang II/KLF5 response. We found that, in aortas of Ang II-infused rats, vascular remodeling and KLF5 expression were markedly increased, and its target gene cyclin D1 was overexpressed. Co-treatment with rosiglitazone diminished these changes. In growth-arrested VSMCs, PPAR-γ agonists (rosiglitazone and 15d-PGJ2) dose-dependently inhibited Ang II-induced cell proliferation and expression of KLF5 and cyclin D1. Moreover, these effects were attenuated by the PPAR-γ antagonists GW9662, bisphenol A diglycidyl ether and PPAR-γ specific siRNA. Furthermore, rosiglitazone inhibited Ang II-induced phosphorylation of protein kinase C (PKC) ζ and extracellular signal-regulated kinase (ERK) 1/2 and activation of early growth response protein (Egr). In conclusion, in Ang II-stimulated VSMCs, rosiglitazone might have an antiproliferative effect through mechanisms that include reducing KLF5 expression, and a crosstalk between PPAR-γ and PKCζ/ERK_1/2/Egr may be involved in. These findings not only provide a previously unrecognized mechanism by which PPAR-γ agonists inhibit VSMC proliferation, but also document a novel evidence for the beneficial vascular effect of PPAR-γ activation.

Rosiglitazone attenuates the metalloprotease/anti-metalloprotease imbalance in emphysema induced by cigarette smoke: involvement of extracellular signal-regulated kinase and NFκB signaling

Objective

We investigated how rosiglitazone attenuated cigarette smoke (CS)-induced emphysema in a rat model. In particular, we focused on its possible effects on the imbalance between metalloprotease (MMP) and anti-MMP activity, mitogen-activated protein kinase (MAPK) phosphorylation, and nuclear factor kappa-light-chain-enhancer of activated B cell (NFκB) signaling pathway over-activation.

Methods

A total of 36 Wistar rats were divided into three groups (n=12 each): animals were exposed to CS for 12 weeks in the absence (the CS group) or presence of 30 mg/kg rosiglitazone (the rosiglitazone-CS [RCS] group); a control group was treated with the rosiglitazone vehicle only, without any CS exposure. Histopathology of lung tissue in all groups was evaluated to grade severity of the disease. Expression levels of peroxisome proliferator-activated receptor γ (PPARγ), MMP2, and MMP9 in lung tissue were determined and compared using Western blotting and immunohistochemistry. Activation of MAPKs, NFκB, and the nuclear factor of kappa light polypeptide gene enhancer in B-cell inhibitor, alpha (IκBα) phosphorylation in lung tissue was examined by Western blotting.

Results

Emphysema-related pathology, based on inter-alveolar wall distance and alveolar density, was less severe in the RCS group than in the CS group. Compared with the CS group, levels of PPARγ were higher in the RCS group, and levels of MMP2 and MMP9 proteins were lower in the RCS rats. Levels of activated MAPKs and NFκB were also lower, while the IκBαphosphorylation was increased in the lung tissue of RCS rats.

Conclusion

Our findings suggest that oral administration of rosiglitazone attenuates the metalloprotease activity induced by CS, and the underlying mechanism might involve the activation of signaling pathways dependent on MAPKs or NFκB. Our results further suggest that PPARγ contributes to the pathogenesis of emphysema as well as airway inflammation induced by CS.

Telmisartan attenuated LPS-induced neuroinflammation in human IMR-32 neuronal cell line via SARM in AT1R independent mechanism

AIM

The aim of this study was to find the protective role of Telmisartan (TS) in LPS intoxicated neuronal cells and elucidate the possible neuroprotective mechanism of action.

MAIN METHODS

TLR4 and AT1R specific primers were designed and used in rtPCR to confirm the receptor expression in IMR-32 and Neuro2A cell lines. The protective effect of TS was assayed by MTT assay. The mechanism of action of TS was elucidated by assessing the expression and activation of TLR4 specific adaptor proteins SARM and MyD88, phosphorylated NFκB, PPARγ, MAPK p38, c-JNK, ERK by Western blotting. Selective PPARγ antagonist GW9662 was used to confirm the link between PPARγ activation and TLR4 mediated NFκB inflammatory mechanisms. The pro-inflammatory cytokines TNFα, IL1β, and IL-6 and anti-inflammatory cytokine IL10 release were measured by ELISA.

KEY FINDINGS

IMR-32 cells expressed TLR4 receptor and Neuro2A cells expressed both AT1R and TLR4 receptors. TS significantly protected both the cell lines from LPS intoxication. TS significantly suppressed the TLR4 mediated inflammatory response by PPARγ and SARM protein activation and the effect was reversed significantly by selective PPARγ antagonist GW9662, confirming the existence of link between PPARγ activation and TLR4 mediated inflammation via SARM.

SIGNIFICANCE

LPS intoxicated human neuronal IMR-32 cells can be a good in vitro model to study inflammatory mediated neurodegeneration due to TLR4 receptor expression. Our study strongly recommends that the PPARγ activating pleiotropic effect of TS is responsible for the protective effect in LPS induced TLR4 mediated inflammation via SARM adaptor protein in the IMR-32 cell line.

Etanercept blocks inflammatory responses orchestrated by TNF-α to promote transplanted cell engraftment and proliferation in rat liver

Engraftment of transplanted cells is critical for liver-directed cell therapy, but most transplanted cells are rapidly cleared from liver sinusoids by proinflammatory cytokines/chemokines/receptors after activation of neutrophils or Kupffer cells (KCs). To define whether tumor necrosis factor alpha (TNF-α) served roles in cell-transplantation-induced hepatic inflammation, we used the TNF-α antagonist, etanercept (ETN), for studies in syngeneic rat hepatocyte transplantation systems. After cell transplantation, multiple cytokines/chemokines/receptors were overexpressed, whereas ETN before cell transplantation essentially normalized these responses. Moreover, ETN down-regulated cell-transplantation-induced intrahepatic release of secretory cytokines, such as high-mobility group box 1. These effects of ETN decreased cell-transplantation-induced activation of neutrophils, but not of KCs. Transplanted cell engraftment improved by several-fold in ETN-treated animals. These gains in cell engraftment were repeatedly realized after pretreatment of animals with ETN before multiple cell transplantation sessions. Transplanted cell numbers did not change over time, indicating absence of cell proliferation after ETN alone. By contrast, in animals preconditioned with retrorsine and partial hepatectomy, cell transplantation after ETN pretreatment significantly accelerated liver repopulation, compared to control rats.

CONCLUSION

TNF-α plays a major role in orchestrating cell-transplantation-induced inflammation through regulation of multiple cytokines/chemokines/receptor expression. Because TNF-α antagonism by ETN decreased transplanted cell clearance, improved cell engraftment, and accelerated liver repopulation, this pharmacological approach to control hepatic inflammation will help optimize clinical strategies for liver cell therapy.

Inhibition of tumor growth by U0126 is associated with induction of interferon-γ production

Several MEK1/2 inhibitors have been in clinical trial evaluation for cancer treatment. Interferon-γ (IFN-γ) is a cytokine with multiple biological functions including antitumor activity. Expression of IFN-γ can be induced by liver X receptor (LXR), a ligand-activated transcription factor. However, it remains unknown if the anti-cancer action of MEK1/2 inhibitors is completed, at least in part, by activating IFN-γ expression. In this study, we determined that U0126, a MEK1/2 inhibitor, increased tumor-free and survival rates and decreased growth of inoculated Lewis lung carcinomas in wild type mice. However, the protective effects were substantially attenuated in IFN-γ deficient (IFN-γ-/-) mice. At cellular and molecular levels, MEK1/2 inhibitors increased IFN-γ protein and mRNA expression and activated natural IFN-γ promoter but not the IFN-γ promoters with mutations of the LXR responsive elements (LXREs). MEK1/2 inhibitors also enhanced formation of the LXRE-nuclear protein complexes by inducing LXR expression and nuclear translocation. Similarly, MEK1/2 siRNA inhibited phosphorylation of ERK1/2 by MEK1/2 while activated IFN-γ expression. In contrast, inhibition of LXR expression by siRNA blocked MEK1/2 inhibitors-induced IFN-γ expression. U0126 also inhibited chemicals-induced pulmonary carcinomas, which was associated with increased IFN-γ expression in the lung. Taken together, our study suggests that MEK1/2 inhibitors induce IFN-γ production in an LXR-dependent manner and the induction of IFN-γ expression can partially contribute to the anti-tumorigenic properties of U0126.

MD-2 is involved in the stimulation of matrix metalloproteinase-1 expression by interferon-γ and high glucose in mononuclear cells - a potential role of MD-2 in Toll-like receptor 4-independent signalling

We reported recently that treatment of diabetic apolipoprotein E-deficient mice with the Toll-like receptor 4 (TLR4) antagonist Rs-LPS, a lipopolysaccharide isolated from Rhodobacter sphaeroides, inhibited atherosclerosis. Since it is known that Rs-LPS antagonizes TLR4 by targeting TLR4 co-receptor MD-2, this finding indicates that MD-2 is a potential target for the treatment of atherosclerosis. In this study, we determined if MD-2 is involved in the gene expression regulated by signalling pathways independent of TLR4. Given that interferon-γ (IFNγ) and hyperglycaemia play key roles in atherosclerosis, we determined if MD-2 is involved in IFN-γ and high-glucose-regulated gene expression in mononuclear cells. Results showed that IFN-γ and high glucose synergistically stimulated matrix metalloproteinase 1 (MMP-1), a proteinase essential for vascular tissue remodelling and atherosclerosis, in U937 mononuclear cells, but Rs-LPS inhibited the MMP-1 stimulation. To provide more evidence for a role of MD-2 in IFN-γ-stimulated MMP-1, studies using antibodies and small interfering RNA demonstrated that MD-2 blockade or knockdown attenuated the effect of IFN-γ on MMP-1. Furthermore, studies using PCR arrays showed that MD-2 blockade had a similar effect as IFN-γ receptor blockade on the inhibition of IFN-γ-stimulated pro-inflammatory molecules. Although these findings indicate the involvement of MD-2 in IFN-γ signalling, we also observed that MD-2 was up-regulated by IFN-γ and high glucose. We found that MD-2 up-regulation by IFN-γ played an essential role in the synergistic effect of IFN-γ and LPS on MMP-1 expression. Taken together, these findings indicate that MD-2 is involved in IFN-γ signalling and IFN-γ-augmented MMP-1 up-regulation by LPS.

Type I and type II interferons inhibit both basal and tumor necrosis factor-α-induced CXCL8 secretion in primary cultures of human thyrocytes

Interferons (IFNs) and tumor necrosis factor-α (TNF-α) cooperate in activating several inflammation-related genes, which sustain chronic inflammation in autoimmune thyroid disease (AITD). Much is known about the positive signaling of IFNs to activate gene expression in AITD, while the mechanisms by which IFNs negatively regulate genes remain less studied. While IFNs inhibit CXCL8 secretion in several human cell types, their effects on thyroid cells were not evaluated. Our aim was to study the interplay between TNF-α and type I or type II IFNs on CXCL8 secretion by human thyroid cells. CXCL8 was measured in supernatants of primary cultures of thyroid cells basally and after a 24-h incubation with TNF-α. CXCL8 was detected in thyroid cell supernatants in basal conditions (96.2±23.5 pg/mL) being significantly increased (784.7±217.3 pg/mL; P<0.0001 vs. basal) by TNF-α. Twenty-four hour incubation with IFN-γ or IFN-β or IFN-α dose dependently and significantly inhibited both basal and TNF-α-induced CXCL8 secretion. The degree of the inhibitory effect was IFN-γ>IFN-β>IFN-α. This study demonstrates that type I and type II IFNs downregulate both basal and TNF-α-induced CXCL8 secretion by human thyrocytes, IFN-γ being the most powerful inhibitor. Future studies aimed at a better comprehension of the interplay between CXCL8 and thyroid diseases appear worthwhile.

Arterial and venous endothelia display differential functional fractalkine (CX3CL1) expression by angiotensin-II

OBJECTIVE

Angiotensin-II (Ang-II) promotes the interaction of mononuclear cells with arterioles and neutrophils with postcapillary venules. To investigate the mechanisms underlying this dissimilar response, the involvement of fractalkine (CX(3)CL1) was explored.

METHODS AND RESULTS

Enhanced CX(3)CL1 expression was detected in both cremasteric arterioles and postcapillary venules 24 hours after Ang-II intrascrotal injection. Arteriolar leukocyte adhesion was the unique parameter significantly reduced (83%) in animals lacking CX(3)CL1 receptor (CX(3)CR1). Human umbilical arterial and venous endothelial cell stimulation with 1 μmol/L Ang-II increased CX(3)CL1 expression, yet neutralization of CX(3)CL1 activity only significantly inhibited Ang-II-induced mononuclear cell-human umbilical arterial endothelial cell interactions (73%) but not with human umbilical venous endothelial cells. The use of small interfering RNA revealed the involvement of tumor necrosis factor-α in Ang-II-induced CX(3)CL1 upregulation and mononuclear cell arrest. Nox5 knockdown with small interfering RNA or pharmacological inhibition of extracellular signal-regulated kinases1/2, p38 mitogen-activated protein kinase, and nuclear factor-κB also abolished these responses. Finally, when human umbilical arterial endothelial cells were costimulated with Ang-II, tumor necrosis factor-α, and interferon-γ, CX(3)CL1 expression and mononuclear cell adhesiveness were more pronounced than when each stimulus was provided alone.

CONCLUSIONS

These results suggest that Ang-II induces functional CX(3)CL1 expression in arterial but not in venous endothelia. Thus, targeting endothelial CX(3)CL1-mononuclear leukocyte CX(3)CR1 interactions may constitute a new therapeutic strategy in the treatment of Ang-II-associated cardiovascular diseases.

15-deoxy-Δ¹²,¹⁴ -prostaglandin J₂ inhibits human immunodeficiency virus-1 tat-induced monocyte chemoattractant protein-1/CCL2 production by blocking the extracellular signal-regulated kinase-1/2 signaling pathway independently of peroxisome proliferator-activated receptor-γ and heme oxygenase-1 in rat hippocampal slices

Human immunodeficiency virus (HIV)-induced inflammation, and its consequences within the central nervous system (CNS), must be countered by multiple pharmacologic agents, and 15-deoxy-Δ(12,14) -prostaglandin J(2) (15d-PGJ2) may hold promise in the treatment of pathologies associated with this inflammatory response. 15d-PGJ2 can repress the inflammatory response by means of peroxisome proliferator-activated receptor-γ (PPARγ)-dependent and -independent mechanisms. However, its precise role and antiinflammatory mechanism in the hippocampus remain poorly understood. In the present study, rat hippocampal slices were stimulated with full-length HIV-1 Tat protein to investigate the role of 15d-PGJ2 8in the hippocampal inflammatory response. Pretreatment of slices with 15d-PGJ2 markedly reduced Tat-induced monocyte chemoattractant protein-1 (MCP-1/CCL2) production. Interestingly, the PPARγ antagonist GW9662 did not inhibit action of 15d-PGJ2, confirming the latter's PPARγ-independent mechanism of mediating antiinflammatory effects. Despite 15d-PGJ2's increasing the expression of heme oxygenase-1 (HO-1), its action was not abrogated by the HO-1 inhibitor zinc protoporphyrin IX (ZnPPIX), nor was it recapitulated by HO-1 inducers such as cobalt protoporphyrin (CoPP). Moreover, short interfering RNA (siRNA)-directed knockdown of HO-1 did not abolish the antiinflammatory action of 15d-PGJ2 against Tat-induced MCP-1 production in human microglia-like THP-1 cells. Conversely, 15d-PGJ2 suppressed Tat-induced ERK1/2 activation, decreasing MCP-1 production upon Tat stimulation. The NADPH oxidase inhibitors DPI and apocynin also abrogated Tat-stimulated ERK1/2 activation, reducing MCP-1 production. Collectively, these data demonstrate that the antiinflammatory effects of 15d-PGJ2 on the hippocampus are exerted through inhibition of Tat-mediated ERK1/2 activation, coupled with that of a redox-sensitive pathway, independent of PPARγ and HO-1.

Interferon-α, -β and -γ induce CXCL11 secretion in human thyrocytes: modulation by peroxisome proliferator-activated receptor γ agonists

It has been previously shown IFN-α, -β, -γ and TNF-α (synergically with IFNs) dose-dependently induce the release of CXCL9 and CXCL10 chemokines by thyroid follicular cells, suggesting that this process may be related, at least in part, to the appearance of thyroid dysfunction during IFNs therapy. No study has evaluated the effect of IFN-α and -β on CXCL11 chemokine production in thyrocytes. The aims of this study were: (a) to test the effect of IFN-α, -β and -γ on the secretion of the Th1 chemokine CXCL11, in primary cultures of human thyroid follicular cells; (b) to assess the effect of PPAR-γ activation on CXCL11 secretion. In primary cultures of human thyroid follicular cells, CXCL11 was undetectable in the supernatant. IFN-γ, -α and -β dose dependently induced CXCL11 release. TNF-α alone had no effect. The combination of each of the IFNs with TNF-α had a significant synergistic effect on CXCL11 secretion. Treatment of primary cultures of human thyroid follicular cells with rosiglitazone dose dependently inhibited the IFNs stimulated CXCL11 release. Compared with IFN-α and -β, IFN-γ was the most potent stimulus of CXCL11 secretion. In conclusion, we first show that IFN-α, -β and -γ and TNF-α (synergically with IFNs) dose-dependently induce the release of CXCL11 by primary cultures of human thyroid follicular cells, suggesting that this process may be related to the appearance of thyroid dysfunction during IFNs therapy. Furthermore, PPAR-γ activation partially inhibits this process.

Mitochondrial function and content in pheochromocytoma/paraganglioma of succinate dehydrogenase mutation carriers

To date, the consequences of succinate dehydrogenase (SDH) impairment on overall mitochondrial functions are still obscure. In this study, we evaluated SDH activity and expression and mitochondrial homeostasis in 57 tissue samples of pheochromocytoma (PHEO)/paraganglioma (PGL) obtained from patients genotyped for PHEO/PGL susceptibility genes. The resulted SDH activity and content always decreased in SDH-mutated tumors, in one out of two MAX-mutated patients and in four patients resulted wild type (wt) at genetic screening. All these four wt patients were further screened for large deletions in SDH genes, TMEM127 and MAX and resulted wt but two had somatic SDHD mutations. The RT-PCR in the MAX-mutated sample suggests that the decrease in SDH depends on complex instability and not on a reduced SDHB expression. SDH mutations neither alter citrate synthase (CS) activity nor the content of voltage-dependent anion channel (VDAC) while the expression of the mitochondrial complex IV (cytochrome c oxidase (COX)) was found extremely variable in all (mutated and wt) samples suggesting an impairment of mitochondrial cristae in these tumors. In conclusion, tumors from patients with germ line SDH mutations invariably show decreased enzymatic activity and content, but an SDH impairment may also depend on SDH somatic mutations or, seemingly, on MAX mutations. The impaired SDH activity in the two wt tissues suggests mutations in other still unknown susceptibility genes. Finally, the extreme variability in COX expression levels is yet to be explained and this strongly suggests to evaluate other mitochondrial features to better understand the mitochondrial role in the pathogenesis of these tumors.

Variable modulation by cytokines and thiazolidinediones of the prototype Th1 chemokine CXCL10 in anaplastic thyroid cancer

Until now, no data are present in literature about the prototype Th1 chemokine (C-X-C motif) ligand 10 (CXCL10) in anaplastic thyroid cancer (ATC). This study aimed to test in "primary human ATC cells" (ANA) vs "normal thyroid follicular cells" (TFC): (a) CXCL10 secretion basally and after interferon (IFN)-γ and/or tumor necrosis factor (TNF)-α stimulation; (b) peroxisome proliferator-activated receptor (PPAR)-γ activation by thiazolidinediones, rosiglitazone or pioglitazone, on CXCL10 secretion, on proliferation and apoptosis in ANA. We demonstrate that: (a) ANA, but not TFC, produced basally CXCL10, and did so in half of cases; (b) IFN-γ stimulated dose-dependently CXCL10, in ANA and TFC; (c) TNF-α did not induce CXCL10 secretion, in ANA and TFC; (d) IFN-γ+TNF-α induced a synergistic but variable release of CXCL10 in the different ANA preparations, while it was more reproducible in TFC; (e) rosiglitazone action on CXCL10 in ANA was inhibitory in 2/6, stimulatory in 1/6 and nil in 3/6, whereas it was inhibitory in TFC; (f) rosiglitazone inhibition of proliferation in ANA was not associated with the effect on CXCL10; (g) nuclear factor-κB and ERK1/2 were basally activated in ANA, increased by IFN-γ+TNF-α, and rosiglitazone inhibited that activation. On the whole, the present data first show that ANA cells are able to produce CXCL10, basally and under the influence of cytokines. However, the pattern of modulation by IFN-γ, TNF-α or thiazolidinediones is extremely variable, suggesting that the intracellular pathways involved in the chemokine modulation in ATC have different types of deregulation.

β (CCL2) and α (CXCL10) chemokine modulations by cytokines and peroxisome proliferator-activated receptor-α agonists in Graves' ophthalmopathy

No data are present in the literature about the effect of cytokines on the prototype β chemokine (C-C motif) ligand 2 (CCL2) or of peroxisome proliferator-activated receptor α (PPARα (PPARA)) activation on CCL2 and CXCL10 chemokines secretion in fibroblasts or preadipocytes in Graves' ophthalmopathy (GO). We have tested the effect of interferon γ (IFNγ (IFNG)) and tumor necrosis factor α (TNFα) on CCL2, and for comparison on the prototype α chemokine (C-X-C motif) ligand 10 (CXCL10), and the possible modulatory role of PPARα activation on secretion of these chemokines in normal and GO fibroblasts or preadipocytes in primary cell cultures. This study shows that IFNγ alone, or in combination with TNFα, stimulates the secretion of CCL2 in primary orbital fibroblasts or preadipocytes from patients with GO at levels similar to those observed in controls. IFNγ and TNFα also stimulated CXCL10 chemokine secretion as expected. The presence of PPARα and PPARγ (PPARG) in primary fibroblasts or preadipocytes of patients with GO has been confirmed. PPARα activators were able to inhibit the secretion of CXCL10 and CCL2, while PPARγ activators were confirmed to be able to inhibit CXCL10 but had no effect on CCL2. PPARα activators were stronger inhibitors of chemokine secretions than PPARγ agonists. In conclusion, CCL2 and CXCL10 are modulated by IFNγ and TNFα in GO. PPARα activators inhibit the secretion of the main prototype α (CXCL10) and β (CCL2) chemokines in GO fibroblasts or preadipocytes, suggesting that PPARα may be involved in the modulation of the immune response in GO.

Telmisartan ameliorates lipopolysaccharide-induced innate immune response through peroxisome proliferator-activated receptor-γ activation in human monocytes

OBJECTIVE

Angiotensin II type 1 receptor (AT1) blockers (ARBs) reduce the bacterial endotoxin lipopolysaccharide (LPS)-induced innate immune response in human circulating monocytes expressing few AT1. To clarify the mechanisms of anti-inflammatory effects of ARBs with different peroxisome proliferator-activated receptor-γ (PPARγ)-activating potencies, we focused our study on telmisartan, an ARB with the highest PPARγ-stimulating activity.

METHODS

Human circulating monocytes and monocytic THP-1 (human acute monocytic leukemia cell line) cells were exposed to 50 ng/ml LPS with or without pre-incubation with telmisartan. AT1 mRNA and protein expressions were determined by real-time PCR and membrane receptor binding assay, respectively. The expression of pro-inflammatory factors was determined by real-time PCR, western blot analysis and ELISA. PPARγ activation was measured by electrophoretic mobility shift assay and its role was determined by pharmacological inhibition and PPARγ gene silencing.

RESULTS

In human monocytes, telmisartan significantly attenuated the LPS-induced expression of pro-inflammatory factors, the release of pro-inflammatory cytokines and prostaglandin E2, nuclear factor-κB activation and reactive oxygen species formation. In THP-1 cells, telmisartan significantly reduced LPS-induced tumor necrosis factor-α, inhibitor of κB-α, monocyte chemotactic protein-1 (MCP-1) and lectin-like oxidized low-density lipoprotein receptor-1 gene expression and MCP-1-directed migration. Telmisartan also stimulated the expression of the PPARγ target genes cluster of differentiation 36 and ATP-binding cassette subfamily G member 1 in monocytes. The anti-inflammatory effects of telmisartan were prevented by both PPARγ antagonism and PPARγ gene silencing. Anti-inflammatory effects of ARBs correlated with their PPARγ agonist potency.

CONCLUSION

Our observations demonstrate that in human monocytes, ARBs inhibit the LPS-induced pro-inflammatory response to a major extent through the PPARγ activation pathway and may be beneficial for the treatment of cardiovascular and metabolic disorders in which inflammation plays a major role.

Peroxisome proliferator-activated receptor-α agonists modulate CXCL9 and CXCL11 chemokines in Graves' ophthalmopathy fibroblasts and preadipocytes

Peroxisome proliferator-activated receptors (PPAR)α have been shown to exert immunomodulatory effects in autoimmune disorders; no study evaluated the effect of PPARα activation in Graves' ophthalmopathy (GO). We show the presence of PPARα, δ and γ in GO fibroblasts and preadipocytes. PPARα activators have a potent inhibitory action on the secretion of CXCL9 and CXCL11 chemokines (induced by IFNγ and TNFα) in fibroblasts and preadipocytes. The potency of the used PPARα agonists was maximum on the secretion of CXCL11 (67% inhibition by fenofibrate) in fibroblasts. The relative potency of the compounds in GO fibroblasts was different with each chemokine. PPARα agonists were stronger inhibitors of CXCL9 and CXCL11 (in GO fibroblasts and preadipocytes) than PPARγ activators. This study first shows that PPARα activators inhibit CXCL9 and CXCL11 chemokines in normal and GO fibroblasts and preadipocytes, suggesting that PPARα may be involved in the modulation of the immune response in GO.

General molecular biology and architecture of nuclear receptors

Nuclear receptors (NRs) regulate and coordinate multiple processes by integrating internal and external signals, thereby maintaining homeostasis in front of nutritional, behavioral and environmental challenges. NRs exhibit strong similarities in their structure and mode of action: by selective transcriptional activation or repression of cognate target genes, which can either be controlled through a direct, DNA binding-dependent mechanism or through crosstalk with other transcriptional regulators, NRs modulate the expression of gene clusters thus achieving coordinated tissue responses. Additionally, non genomic effects of NR ligands appear mediated by ill-defined mechanisms at the plasma membrane. These effects mediate potential therapeutic effects as small lipophilic molecule targets, and many efforts have been put in elucidating their precise mechanism of action and pathophysiological roles. Currently, numerous nuclear receptor ligand analogs are used in therapy or are tested in clinical trials against various diseases such as hypertriglyceridemia, atherosclerosis, diabetes, allergies and cancer and others.

Peroxisome proliferating activating receptor gamma-independent attenuation of interleukin 6 and interleukin 8 secretion from primary endometrial stromal cells by thiazolidinediones

OBJECTIVE

To assess the effect of thiazolidinediones on the regulation of inflammatory cytokines related to endometriosis in endometrial tissue and determine whether these effects occur via activation of the peroxisome proliferating activating receptor gamma (PPAR)-γ.

DESIGN

In vitro study using eutopic endometrial tissue.

SETTING

University hospital.

PATIENT(S)

Premenopausal women undergoing laparoscopy for infertility or abdominal pain.

INTERVENTION(S)

Isolation of endometrial stromal cells and the culture of these cells in the presence of thiazolidinediones, ciglitazone and pioglitazone, both with and without a pretreatment of the specific, irreversible PPAR-γ antagonist GW9662.

MAIN OUTCOME MEASURE(S)

Quantitation of interleukin (IL)-6 and IL-8 released into the cell culture medium by ELISA. Real-time polymerase chain reaction to quantitate PPAR-γ gene expression in the primary cell preparations and the expression of IL-6 and IL-8 after thiazolidinedione treatment.

RESULT(S)

Treatment of stromal cells with thiazolidinediones attenuated IL-6 and IL-8 release in a dose-dependent manner. This effect was not inhibited by GW9662 pretreatment. Ciglitazone induced IL-6 messenger RNA expression, an effect that was suppressed by GW9662 pretreatment.

CONCLUSION(S)

Thiazolidinediones decrease the proinflammatory cytokines IL-6 and IL-8 in endometrial stromal cells via a PPAR-γ-independent mechanism. A better understanding of the anti-inflammatory action of this class of drugs may improve their safety and efficacy for endometriosis treatment.

PPARα and PPARγ protect against HIV-1-induced MMP-9 overexpression via caveolae-associated ERK and Akt signaling

Activation of matrix metalloproteinase-9 (MMP-9) is involved in HIV-1-induced disruption of the blood-brain barrier (BBB). In the present study, we hypothesize that peroxisome proliferator-activated receptor (PPAR)-α or PPARγ can protect against HIV-1-induced MMP-9 overexpression in brain endothelial cells (hCMEC cell line) by attenuating cellular oxidative stress and down-regulation of caveolae-associated redox signaling. Exposure to HIV-1-infected monocytes induced phosphorylation of ERK1/2 and Akt in hCMEC by 2.5- and 3.6-fold, respectively; however, these effects were attenuated by overexpression of PPARα or PPARγ and by silencing of caveolin-1 (cav-1). Coculture of hCMEC with HIV-1-infected monocytes significantly induced MMP-9 promoter and enzyme activity by 3- to 3.5-fold. Promoter mutation studies indicated that SP-1 (g1940t_g1941t) is an essential transcription factor involved in induction of MMP-9 promoter by HIV-1. In addition, HIV-1-stimulated activity of MMP-9 promoter was inhibited by mutation of AP-1 site 2 (c1918t_a1919g) and both (but not individual) NF-κB binding sites (g1389c and g1664c). PPAR overexpression, ERK1/2 or Akt inhibition, and silencing of cav-1 all effectively protected against HIV-1-induced MMP-9 promoter activity, indicating a close relationship among HIV-1-induced cerebrovascular toxicity, redox-regulated mechanisms, and functional caveolae. Such a link was further confirmed in MMP-9-deficient mice exposed to PPARα or PPARγ agonist and injected with the HIV-1-specific protein Tat into cerebral vasculature. Overall, our results indicate that ERK1/2, Akt, and cav-1 are involved in the regulatory mechanisms of PPAR-mediated protection against HIV-1-induced MMP-9 expression in brain endothelial cells.

Adiponectin is required for PPARγ-mediated improvement of endothelial function in diabetic mice

Rosiglitazone is a PPARγ agonist commonly used to treat diabetes. In addition to improving insulin sensitivity, rosiglitazone restores normal vascular function by a mechanism that remains poorly understood. Here we show that adiponectin is required to mediate the PPARγ effect on vascular endothelium of diabetic mice. In db/db and diet-induced obese mice, PPARγ activation by rosiglitazone restores endothelium-dependent relaxation of aortae, whereas diabetic mice lacking adiponectin or treated with an anti-adiponectin antibody do not respond. Rosiglitazone stimulates adiponectin release from fat explants, and subcutaneous fat transplantation from rosiglitazone-treated mice recapitulates vasodilatation in untreated db/db recipients. Mechanistically, adiponectin activates AMPK/eNOS and cAMP/PKA signaling pathways in aortae, which increase NO bioavailability and reduce oxidative stress. Taken together, these results demonstrate that adipocyte-derived adiponectin is required for PPARγ-mediated improvement of endothelial function in diabetes. Thus, the adipose tissue represents a promising target for treating diabetic vasculopathy.

The Case for the Use of PPARγ Agonists as an Adjunctive Therapy for Cerebral Malaria

Cerebral malaria is a severe complication of Plasmodium falciparum infection associated with high mortality even when highly effective antiparasitic therapy is used. Adjunctive therapies that modify the pathophysiological processes caused by malaria are a possible way to improve outcome. This review focuses on the utility of PPARγ agonists as an adjunctive therapy for the treatment of cerebral malaria. The current knowledge of PPARγ agonist use in malaria is summarized. Findings from experimental CNS injury and disease models that demonstrate the potential for PPARγ agonists as an adjunctive therapy for cerebral malaria are also discussed.

How do immune cells overcome the blood-brain barrier in multiple sclerosis?

The presence of the blood-brain barrier (BBB) restricts the movement of soluble mediators and leukocytes from the periphery to the central nervous system (CNS). Leukocyte entry into the CNS is nonetheless an early event in multiple sclerosis (MS), an inflammatory disorder of the CNS. Whether BBB dysfunction precedes immune cell infiltration or is the consequence of perivascular leukocyte accumulation remains enigmatic, but leukocyte migration modifies BBB permeability. Immune cells of MS subjects express inflammatory cytokines, reactive oxygen species (ROS) and enzymes that can facilitate their migration to the CNS by influencing BBB function, either directly or indirectly. In this review, we describe how immune cells from the peripheral blood overcome the BBB and promote CNS inflammation in MS through BBB disruption.

Pulmonary vascular disease associated with parasitic infection--the role of schistosomiasis

Parasitic diseases have been known to cause pulmonary vascular lesions. Schistosomiasis is the most common parasitic disease associated with pulmonary arterial hypertension, although other trematodes have been implicated. Systematic evaluation of and interest in this problem have been rekindled because of the current availability of pulmonary arterial hypertension treatment.

Pioglitazone suppresses advanced glycation end product-induced expression of plasminogen activator inhibitor-1 in vascular smooth muscle cells

Advanced glycation end products (AGEs) play an important role in vascular complications of diabetes, including fibrinolytic abnormalities. Pioglitazone, a peroxisome proliferator-activated receptor gamma (PPARγ) agonist, has recently been shown to reduce circulating plasminogen activator inhibitor-1 (PAI-1) levels in diabetes mellitus. In the present study, we investigated the effects of pioglitazone on the expression of local PAI-1 in rat vascular smooth muscle cells (VSMCs) induced by AGEs and the underlying mechanism. The result showed that AGEs could enhance the PAI-1 expression by 5.1-fold in mRNA and 2.7-fold in protein level, as evaluated by real-time RT-PCR and Western blotting, respectively. Pioglitazone was found to down-regulate the AGE-stimulated PAI-1 expression in VSMCs. However, these inhibitory effects were partially attenuated by the PPARγ antagonist, GW9662. Furthermore, we found that AGEs induced a rapid increase in phosphorylation and activation of extracellular signal-regulated protein kinase 1/2 (ERK1/2). The ERK kinase inhibitor, U0126, partially prevented the induction of PAI-1 by AGEs. Moreover, pioglitazone was also found to inhibit the phosphorylation of ERK1/2. Taken together, it was concluded that pioglitazone could inhibit AGE-induced PAI-1 expression, which was mediated by the ERK1/2 and PPARγ pathways. Our findings suggested pioglitazone had a therapeutic potential in improving fibrinolytic activity, and consequently preventing thromboembolic complications of diabetes and cardiovascular disease.

Severe acute respiratory syndrome coronavirus papain-like protease suppressed alpha interferon-induced responses through downregulation of extracellular signal-regulated kinase 1-mediated signalling pathways

Severe acute respiratory syndrome coronavirus (SARS-CoV) papain-like protease (PLpro), a deubiquitinating enzyme, reportedly blocks poly I : C-induced activation of interferon regulatory factor 3 and nuclear factor kappa B, reducing interferon (IFN) induction. This study investigated type I IFN antagonist mechanism of PLpro in human promonocytes. PLpro antagonized IFN-α-induced responses such as interferon-stimulated response element- and AP-1-driven promoter activation, protein kinase R, 2'-5'-oligoadenylate synthetase (OAS), interleukin (IL)-6 and IL-8 expression, and signal transducers and activators of transcription (STAT) 1 (Tyr701), STAT1 (Ser727) and c-Jun phosphorylation. A proteomics approach demonstrated downregulation of extracellular signal-regulated kinase (ERK) 1 and upregulation of ubiquitin-conjugating enzyme (UBC) E2-25k as inhibitory mechanism of PLpro on IFN-α-induced responses. IFN-α treatment significantly induced mRNA expression of UBC E2-25k, but not ERK1, causing time-dependent decrease of ERK1, but not ERK2, in PLpro-expressing cells. Poly-ubiquitination of ERK1 showed a relationship between ERK1 and ubiquitin proteasome signalling pathways associated with IFN antagonism by PLpro. Combination treatment of IFN-α and the proteasome inhibitor MG-132 showed a time-dependent restoration of ERK1 protein levels and significant increase of ERK1, STAT1 and c-Jun phosphorylation in PLpro-expressing cells. Importantly, PD098059 (an ERK1/2 inhibitor) treatment significantly reduced IFN-α-induced ERK1 and STAT1 phosphorylation, inhibiting IFN-α-induced expression of 2'-5'-OAS in vector control cells and PLpro-expressing cells. Overall results proved downregulation of ERK1 by ubiquitin proteasomes and suppression of interaction between ERK1 and STAT1 as type I IFN antagonist function of SARS-CoV PLpro.

CXCL9 and CXCL11 chemokines modulation by peroxisome proliferator-activated receptor-alpha agonists secretion in Graves' and normal thyrocytes

CONTEXT

Peroxisome proliferator-activated receptor (PPAR)-α has been shown to exert immunomodulatory effects in autoimmune disorders. However, until now, no data were present in the literature about the effect of PPARα activation on CXCL9 and CXCL11 chemokines in general or on secretion of these chemokines in thyroid cells.

OBJECTIVE AND DESIGN

The presence of PPARα and PPARγ has been evaluated by real-time-PCR in Graves' disease (GD) and control cells in primary culture. Furthermore, we have tested the role of PPARα and PPARγ activation on CXCL9 and CXCL11 secretion in GD and control cells after stimulation of these chemokines secretion with IFNγ and TNFα.

RESULTS

This study shows the presence of PPARα and PPARγ in GD and control cells. A potent dose-dependent inhibition by PPARα-agonists was observed on the cytokines-stimulated secretion of CXCL9 and CXCL11 in GD and control cells. The potency of the PPARα agonists used was maximum on the secretion of CXCL9, reaching about 90% of inhibition by fenofibrate and 85% by ciprofibrate. The relative potency of the compounds was different with each chemokine; for example, gemfibrozil exerted a 55% inhibition on CXCL11, whereas it had a weaker activity on CXCL9 (40% inhibition). PPARα agonists were stronger (ANOVA, P<0.001) inhibitors of CXCL9 and CXCL11 secretion in thyrocytes than PPARγ agonists.

CONCLUSIONS

Our study shows the presence of PPARα in GD and control thyrocytes. PPARα activators are potent inhibitors of the secretion of CXCL9 and CXCL11, suggesting that PPARα may be involved in the modulation of the immune response in the thyroid.

Grape seed extract ameliorates tumor necrosis factor-α-induced inflammatory status of human umbilical vein endothelial cells

BACKGROUND

Inflammation has played a key role in the causation of atherosclerosis. However, the effects of grape seed extract (GSE) on the pro-inflammatory intracellular signaling, enzyme activity, and inflammatory mediators of endothelial cells have not been sufficiently studied, and less information exists on the comparison between GSE and vitamin C, a well-known antioxidant compound, on their anti-inflammatory properties.

PURPOSE

We investigated the effects of GSE and vitamin C on the cell viability, oxidative stress, monocyte adhesion, the expression of nuclear factor-κB inhibitor (IκB), intercellular adhesion molecule-1 (ICAM-1) and cyclooxygenase-2 (COX-2), and the production of prostaglandin E(2) (PG E(2)) in TNF-α-treated human umbilical vein endothelial cells (HUVECs).

METHODS

Cell viability was measured by MTT assay. The adhesion of THP-1 to HUVECs was evaluated by cell adhesion assay. The oxidized nucleoside 8-hydroxydeoxyguanosine (8-OHdG) (an indicator of oxidative damage to DNA), ICAM-1, and PG E(2) were measured by ELISA. IκB and COX-2 expression were evaluated by western blot analysis.

RESULTS

TNF-α (10, 20, and 50 ng/mL), GSE (50 and 200 μg/mL), or vitamin C (100 μM) did not affect cell viability. GSE (50-100 μg/mL) attenuated TNF-α (20 ng/mL)-induced 8-OHdG production, THP-1 adhesion, the expression of IκB degradation, ICAM-1 and COX-2, and the production of PGE(2) in a dose-dependent manner. Vitamin C (100 μM) also showed significant antioxidative and anti-inflammatory effects.

CONCLUSIONS

GSE effectively ameliorates TNF-α-induced inflammatory status of HUVECs. The findings of the present study suggest that consumption of GSE may be beneficial to inflammatory atherosclerosis.

Hypoxia abrogates antichlamydial properties of IFN-γ in human fallopian tube cells in vitro and ex vivo

IFN-γ has an important role in the adaptive immune response against intracellular pathogens. In urogenital tract (UGT) infections with the obligate intracellular pathogen Chlamydia trachomatis, IFN-γ-mediated control of chlamydial growth implies the JAK-STAT signaling cascades and subsequent induction of the indoleamine 2,3-dioxygenase (IDO). As oxygen concentrations in the UGT are low under physiological conditions (O(2) < 5%) and further decrease during an inflammatory process, we wondered whether antibacterial properties of IFN-γ are maintained under hypoxic conditions. Using primary cells that were isolated from human fallopian tubes and an ex vivo human fallopian tube model (HFTM), we found that even high IFN-γ concentrations (200 units/mL) were not sufficient to limit growth of C. trachomatis under hypoxia. Reduced antibacterial activity of IFN-γ under hypoxia was restricted to the urogenital serovars D and L(2), but was not observed with the ocular serovar A. Impaired effectiveness of IFN-γ on chlamydial growth under hypoxia was accompanied by reduced phosphorylation of Stat-1 on Tyr701 and diminished IDO activity. This study shows that IFN-γ effector functions on intracellular C. trachomatis depend on the environmental oxygen supply, which could explain inadequate bacterial clearance and subsequent chronic infections eventually occurring in the UGT of women.

PPAR modulation of kinase-linked receptor signaling in physiology and disease

Kinase-linked receptors and nuclear receptors connect external cues to gene transcription. Among nuclear receptors, peroxisome proliferator-activated receptors (PPARs) are of special interest in relation to widespread human diseases. Mapping out connections between PPARs and kinase-linked receptor signaling is central to better understand physiological and pathophysiological processes and to better define therapeutic strategies. This is the aim of the present review.