PPARgamma but not PPARalpha ligands are potent repressors of major histocompatibility complex class II induction in atheroma-associated cells

Multiscale 3D genome organization underlies duck fatty liver with no adipose inflammation or serious injury

Non-alcoholic fatty liver disease (NAFLD) is the most common form of chronic liver disease. Little is known about how gene expression and chromatin structure are regulated in NAFLD due to lack of suitable model. Ducks naturally develop fatty liver similar to serious human non-alcoholic fatty liver (NAFL) without adipose inflammation and liver fibrosis, thus serves as a good model for investigating molecular mechanisms of adipose metabolism and anti-inflammation. Here, we constructed a NAFLD model without adipose inflammation and liver fibrosis in ducks. By performing dynamic pathological and transcriptomic analyses, we identified critical genes involving in regulation of the NF-κB and MHCII signaling, which usually lead to adipose inflammation and liver fibrosis. We further generated dynamic three-dimensional chromatin maps during liver fatty formation and recovery. This showed that ducks enlarged hepatocyte cell nuclei to reduce inter-chromosomal interaction, decompress chromatin structure, and alter strength of intra-TAD and loop interactions during fatty liver formation. These changes partially contributed to the tight control the NF-κB and the MHCII signaling. Our analysis uncovers duck chromatin reorganization might be advantageous to maintain liver regenerative capacity and reduce adipose inflammation. These findings shed light on new strategies for NAFLD control.

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

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

Friend or foe? Telomerase as a pharmacological target in cancer and cardiovascular disease

Aging, cancer, and chronic disease have remained at the forefront of basic biological research for decades. Within this context, significant attention has been paid to the role of telomerase, the enzyme responsible for lengthening telomeres, the nucleotide sequences located at the end of chromosomes found in the nucleus. Alterations in telomere length and telomerase activity are a common denominator to the underlying pathology of these diseases. While nuclear-specific, telomere-lengthening effects of telomerase impact cellular/organismal aging and cancer development, non-canonical, extra-nuclear, and non-telomere-lengthening contributions of telomerase have only recently been described and their exact physiological implications are ill defined. Although the mechanism remains unclear, recent reports reveal that the catalytic subunit of telomerase, telomerase reverse transcriptase (TERT), regulates levels of mitochondrial-derived reactive oxygen species (mtROS), independent of its established role in the nucleus. Telomerase inhibition has been the target of chemotherapy (directed or indirectly) for over a decade now, yet no telomerase inhibitor is FDA approved and few are currently in late-stage clinical trials, possibly due to underappreciation of the distinct extra-nuclear functions of telomerase. Moreover, evaluation of telomerase-specific therapies is largely limited to the context of chemotherapy, despite reports of the beneficial effects of telomerase activation in the cardiovascular system in relation to such processes as endothelial dysfunction and myocardial infarction. Thus, there is a need for better understanding of telomerase-focused cell and organism physiology, as well as development of telomerase-specific therapies in relation to cancer and extension of these therapies to cardiovascular pathologies. This review will detail findings related to telomerase and evaluate its potential to serve as a therapeutic target.

CD4⁺CD28⁻ lymphocytes and cerebral ischaemic stroke. Part II: CD4⁺CD28⁻ lymphocytes and carotid artery atherosclerotic plaque characteristics

BACKGROUND AND PURPOSE

CD4⁺CD28⁻ lymphocytes can directly contribute to the instability of atherosclerotic plaque. This paper attempts to answer the question of the potential influence of the CD4⁺CD28⁻ lymphocyte population on the ultrasound image of atherosclerotic plaque in the common carotid artery (CCA) wall.

MATERIAL AND METHODS

The study involved a group of 109 patients, aged 45 to 65 years, including 42 patients with first ever ischaemic stroke, experiencing symptoms resulting from disturbances of the anterior area of cerebral circulation, arterial hypertension and/or type 2 diabetes mellitus (group 1). Group 2 consisted of 34 patients with mentioned risk factors, without ischaemic stroke. The control group comprised 33 heal-thy individuals. The percentage of CD4⁺CD28⁻ lymphocytes was assessed with flow cytometry.

RESULTS

A significant difference in the incidence of heterogeneous plaques was noted between groups 1 and 3 (p = 0.0023) as well as between group 2 and 3 (p = 0.0005), whereas groups 1 and 2 did not differ from each other. The proportion of CD4⁺CD28⁻ lymphocytes was similar in groups 1 and 2 (p = 0.97), but it differed between groups 1 and 3 (p < 0.0001) and between groups 2 and 3 (p < 0.001). A correlation was found between the proportion of CD4⁺CD28⁻ lymphocytes in the blood and the number of CCA atherosclerotic plaques (Rs = 0.191, p = 0.046). The proportion of CD4⁺CD28⁻ lymphocytes in peripheral blood did not correlate with the ultrasound types of atherosclerotic plaques. No correlation between the proportion of CD4⁺CD28 ⁻lymphocytes and the area of atherosclerotic plaques was found.

CONCLUSIONS

The correlation between the proportion of CD4⁺CD28⁻ lymphocytes and the number of atherosclerotic plaques within the CCA suggests that the cells are involved in the mechanism of carotid plaque formation. There is no proof of the involvement of the above-mentioned cells in the mechanism of plaque destabilization in those arteries.

CD4⁺CD28⁻ lymphocytes and ischaemic stroke. Part I: CD4⁺CD28⁻ lymphocytes and common carotid artery intima-media thickness

BACKGROUND AND PURPOSE

More and more data point to the involvement of the CD4⁺CD28⁻ lymphocyte subpopulation in the pathogenesis of ischaemic stroke. This paper attempts to answer the question of whether an increase in the percentage of CD4⁺CD28⁻ lymphocytes in the blood may be associated with carotid artery intima-media thickness (IMT).

MATERIAL AND METHODS

The study involved a group of 109 patients, aged 45 to 65 years, including 42 patients with first-ever ischaemic stroke, experiencing symptoms resulting from disturbances of the anterior area of cerebral circulation, arterial hypertension and/or type 2 diabetes mellitus (group 1). Group 2 consisted of 34 patients with above-mentioned risk factors but without ischaemic stroke. The control group comprised 33 healthy individuals. Distribution of sex and mean age was comparable. The IMT of carotid arteries was measured by ultrasonography. Flow cytometry was applied to determine the percentage of CD4⁺CD28⁻ lymphocytes in the peripheral blood.

RESULTS

The IMT was significantly greater in patients with stroke than in patients without stroke. No significant correlation was found between the proportion of CD4⁺CD28⁻ lymphocytes in the blood and the IMT of carotid arteries.

CONCLUSIONS

The significant proportion of CD4⁺CD28⁻ lymphocytes in patients with ischaemic stroke points to the involvement of the cells in the pathogenesis of stroke. The CD4⁺CD28⁻ lymphocytes are not involved in the pathomechanism of common carotid arteries IMT thickening in this group of patients.

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.

Peroxisome proliferator-activated receptors in the modulation of the immune/inflammatory response in atherosclerosis

Inflammation has been recognized as an important hallmark of atherosclerosis. The pharmacological activation of PPAR-γ by the thiazolidinediones in diabetes, and of PPAR-α by the fibrates in hyperlipidemia has been shown to help to reduce inflammatory markers in preclinical and clinical studies. PPARs are known to modulate immune pathways through at least three different mechanisms: by direct binding to PPRE of anti-inflammatory cytokines genes; by transrepression of transcription factors like NF-κB and AP-1; or by corepression. The regulation of the inflammatory pathways by PPARs can be achieved on each one of the cells involved in the atherosclerotic process, that is, monocytes, macrophages, T cells, endothelial cells, and smooth muscle cells. Moreover, as each of these cellular components is interconnected with each other, PPAR activation in one cell type could affect the other ones. As activation of PPARs has clear ant-inflammatory benefits, PPARs ligands should be considered as a new therapeutical approach to ameliorate the exacerbated immune response in atherosclerotic diseases.

Peroxisome proliferator-activated receptor (PPAR)gamma can inhibit chronic renal allograft damage

Chronic inflammation and fibrosis are the leading causes of chronic allograft failure. The nuclear receptor peroxisome proliferator-activated receptor (PPAR)gamma is a transcription factor known to have antidiabetogenic and immune effects, and PPARgamma forms obligate heterodimers with the retinoid X receptor (RXR). We have reported that a retinoic acid (RAR)/RXR-agonist can potently influence the course of renal chronic allograft dysfunction. In this study, in a Fischer to Lewis rat renal transplantation model, administration of the PPARgamma-agonist, rosiglitazone, independent of dose (3 or 30 mg/kgBW/day), lowered serum creatinine, albuminuria, and chronic allograft damage with a chronic vascular damage score as follows: 35.0 +/- 5.8 (controls) vs. 8.1 +/- 2.4 (low dose-Rosi; P < 0.05); chronic tubulointerstitial damage score: 13.6 +/- 1.8 (controls) vs. 2.6 +/- 0.4 (low dose-Rosi; P < 0.01). The deposition of extracellular matrix proteins (collagen, fibronectin, decorin) was strikingly lower. The expression of transforming growth factor-beta1 was inhibited, whereas that of bone morphogenic protein-7 (BMP-7) was increased. Intragraft mononuclear cells and activated fibroblast numbers were reduced by 50%. In addition, the migratory and proliferative activity of these cells was significantly inhibited in vitro. PPARgamma activation diminished the number of cells expressing the proinflammatory and fibrogenic proteoglycan biglycan. In macrophages its secretion was blocked by rosiglitazone in a predominantly PPARgamma-dependent manner. The combination of PPARgamma- and RAR/RXR-agonists resulted in additive effects in the inhibition of fibrosis. In summary, PPARgamma activation was potently immunosuppressive and antifibrotic in kidney allografts, and these effects were enhanced by a RAR/RXR-agonist.

Predictive value of C-reactive protein after drug-eluting stent implantation

During the last few decades, with the evolution of techniques and materials and the increasing experience of operators, percutaneous coronary interventions (PCI) have become an equally efficient alternative to coronary artery bypass grafts for the treatment of most coronary stenoses. Bare-metal stent implantation represented a major step forward, compared with plain old balloon angioplasty (POBA), by improving the immediate angiographic success. However, the incidence of in-stent restenosis (ISR) remained unacceptably high. Development of the drug-eluting stent (DES) significantly improved the outcome of PCI by dramatically abating the rate of ISR and reducing the incidence of target lesion revascularization. However, ISR has not been eliminated and the persistence of metal vessel scaffolding also raises concern regarding the occurrence of late or very late stent thrombosis. POBA and stent implantation have been shown to induce a local and systemic inflammatory response, whose magnitude is associated with worse clinical outcome, and they increase the risk of ISR. C-reactive protein, a marker of systemic inflammation, has been demonstrated to predict clinical and angiographic outcome after POBA or bare-metal stent implantation. However, conflicting data regarding the prognostic value of C-reactive protein following DES implantation are available. In this paper, we review the literature regarding the clinical and pathophysiological association between inflammation and prognosis after DES implantation and suggest some possible therapeutic approaches to reduce inflammatory burden with the aim to improve clinical and angiographic outcome after PCI.

PPARgamma enhances IFNgamma-mediated transcription and rescues the TGFbeta antagonism by stimulating CIITA in vascular smooth muscle cells

Chronic inflammatory response and active vascular remodeling are two featured pathophysiological events during atherogenesis. Gamma interferon (IFN-gamma) modulates these two processes through transcriptional control of major histocompatibility complex II (MHC II) and collagen type I (COL1A2) genes, mediated by class II transactivator (CIITA). Transforming growth factor (TGF-beta) antagonizes the effect of IFN-gamma in part by dampening the expression of CIITA. Here we report that peroxisome proliferator activated receptor gamma (PPARgamma) enhanced MHC II activation and COL1A2 repression by IFN-gamma while rescuing the antagonism by TGF-beta in a CIITA-dependent manner in human aortic smooth muscle cells judged by quantitative PCR and luciferase reporter assays. PPARgamma exerted its effect by augmenting the levels of CIITA and stimulating CIITA recruitment to target promoters as evidenced by chromatin immunoprecipitation assays. The up-regulation of CIITA levels was the result of PPARgamma-mediated transcriptional activation of CIITA through promoter IV, and increased CIITA protein stability. Thus, our data suggest that PPARgamma could be a key factor in fine-tuning inflammation as well as restructuring of vessel walls during atherogenesis by acting as a "balance tipper" of the differential effects exerted by cytokines.

PPARs and the cardiovascular system

Peroxisome proliferator-activated receptors (PPARs) belong to the nuclear hormone-receptor superfamily. Originally cloned in 1990, PPARs were found to be mediators of pharmacologic agents that induce hepatocyte peroxisome proliferation. PPARs also are expressed in cells of the cardiovascular system. PPAR gamma appears to be highly expressed during atherosclerotic lesion formation, suggesting that increased PPAR gamma expression may be a vascular compensatory response. Also, ligand-activated PPAR gamma decreases the inflammatory response in cardiovascular cells, particularly in endothelial cells. PPAR alpha, similar to PPAR gamma, also has pleiotropic effects in the cardiovascular system, including antiinflammatory and antiatherosclerotic properties. PPAR alpha activation inhibits vascular smooth muscle proinflammatory responses, attenuating the development of atherosclerosis. However, PPAR delta overexpression may lead to elevated macrophage inflammation and atherosclerosis. Conversely, PPAR delta ligands are shown to attenuate the pathogenesis of atherosclerosis by improving endothelial cell proliferation and survival while decreasing endothelial cell inflammation and vascular smooth muscle cell proliferation. Furthermore, the administration of PPAR ligands in the form of TZDs and fibrates has been disappointing in terms of markedly reducing cardiovascular events in the clinical setting. Therefore, a better understanding of PPAR-dependent and -independent signaling will provide the foundation for future research on the role of PPARs in human cardiovascular biology.

Statins and stroke

Statins play an important role in brain ischemia. These drugs reduce cholesterol levels, which have been related to a reduction in vascular event risk, but they also have other functions besides cholesterol metabolism, called pleiotropic effects. Statins play an important role during the acute phase of ischemia, and might have neuroprotective effects, as they act in several mechanisms during the acute phase of stroke, such as in nitric oxide (NO) and glutamate metabolism, inflammation, platelet aggregation, immune responses and apoptosis. They also have other functions that can be related, with better long-term outcome, to neurorepair mechanisms. Statins promote angiogenesis, endogenous cell proliferation, neurogenesis and new synapse formation.

Direct antiatherosclerotic effects of PPAR agonists

PURPOSE OF REVIEW

Peroxisome proliferator activated receptors (PPARs) are ligand-dependent transcription factors that mediate a range of important metabolic functions by transactivation, transrepression or corepression of various gene targets. PPAR agonists also have direct antiatherosclerotic effects, independent of their metabolic effects on glucose and lipid homeostasis. The purpose of this review is to evaluate the currently available evidence for a direct vasculoprotective effect of PPAR agonists.

RECENT FINDINGS

Current studies have emphasized PPAR-mediated effects on inflammatory and immune responses, oxidative stress, the renin-angiotensin system and modulation of plaque composition. Furthermore, it has become evident that the relative activation of the different PPAR isoforms and the contribution of transactivation of target genes against transrepression of transcription factors need to be considered when assessing the vasculoprotective effects of PPAR agonists.

SUMMARY

It is anticipated that the antiatherosclerotic effects of PPAR agonists observed in experimental studies will translate into reduced cardiovascular events. This promise is yet to be realized in short-to-medium term studies. Given the central role of the PPAR in gene regulation, particularly in metabolic states, it is possible that more targeted modulation of PPAR signalling may hold many rewards for the prevention of atherosclerosis.

Therapeutical effects of PPAR agonists assessed by biomarker modulation

The metabolic syndrome is defined as the clustering of cardiovascular risk factors, such as glucose intolerance, hyperinsulinemia, dyslipidemia, coagulation disturbances and hypertension. Activators of the nuclear receptors peroxisome proliferator-activated receptors (PPARs) modulate several of the metabolic risk factors pre-disposing to atherosclerosis. Fibrates are hypolipidemic drugs operating through activation of PPARalpha, whereas glitazones are insulin sensitizers activating PPARgamma. In addition, these drugs exert pleiotropic and anti-inflammatory actions. This review will focus on the different effects of fibrates and glitazones, as measured by biomarker modulation, on the development of atherosclerosis and cardiovascular disease.

Measuring biomarkers to assess the therapeutic effects of PPAR agonists?

The metabolic syndrome is defined as a clustering of cardiovascular risk factors with insulin resistance, including dyslipidemia, coagulation disturbances and hypertension. Activators of the peroxisome proliferator-activated receptors (PPARs) modulate several of the metabolic risk factors predisposing to atherosclerosis. Fibrates are hypolipidemic drugs acting through activation of PPARα, whereas glitazones are insulin sensitizers activating PPARγ. In addition, these drugs exert pleiotropic anti-inflammatory actions. In this review, we will focus on the effects of fibrates and glitazones on biomarker modulation and their usefulness in the treatment of cardiovascular disease.

Peroxisome proliferator-activated receptor gamma interacts with CIITA x RFX5 complex to repress type I collagen gene expression

Recent reports demonstrate that peroxisome proliferator-activated receptor gamma (PPARgamma), a member of the nuclear receptor superfamily, acts as a repressor of type I collagen synthesis. Our data demonstrate that exogenously expressed PPARgamma down-regulates collagen expression in a dose-responsive manner in human lung fibroblast cells. Silencing PPARgamma using lentiviruses expressing short hairpin RNAs partially reverses interferon-gamma (IFN-gamma)-induced repression and activates collagen mRNA levels. Previous studies indicate that IFN-gamma represses collagen gene expression and induces major histocompatibility complex II (MHC II) expression by activating the formation of a regulatory factor for X-box 5 (RFX5) complex with class II transactivator (CIITA). This report demonstrates that PPARgamma is within the RFX5.CIITA complex as judged by co-immunoprecipitation and DNA affinity precipitation studies. Most importantly, occupancy of PPARgamma on the collagen transcription start site and MHC II promoter increases with IFN-gamma treatment. The PPARgamma agonist, troglitazone, sensitizes the cells to IFN-gamma treatment by increasing recruitment of PPARgamma to collagen gene while repressing collagen expression, and these effects are blocked by the PPARgamma antagonist T0070907. PPARgamma may mediate IFN-gamma-stimulated collagen transcription down-regulation and MHC II up-regulation by interacting with CIITA as well as regulating CIITA expression. Therefore, PPARgamma is a critical target for investigations into therapeutics of diseases involving extracellular matrix remodeling and the immune response.

Stearic acid protects primary cultured cortical neurons against oxidative stress

AIM

To observe the effects of stearic acid against oxidative stress in primary cultured cortical neurons.

METHODS

Cortical neurons were exposed to glutamate, hydrogen peroxide (H2O2), or NaN3 insult in the presence or absence of stearic acid. Cell viability of cortical neurons was determined by MTT assay and LDH release. Endogenous antioxidant enzymes activity[superoxide dismutases (SOD), glutathione peroxidase (GSH-Px), and catalase (CAT)] and lipid peroxidation in cultured cortical neurons were evaluated using commercial kits. {3-[1(p-chlorobenzyl)- 5-(isopropyl)-3-t-butylthiondol-2-yl]-2,2-dimethylpropanoic acid, Na} [MK886; 5 micromol/L; a noncompetitive inhibitor of proliferator-activated receptor (PPAR) alpha], bisphenol A diglycidyl ether (BADGE; 100 micromol/L; an antagonist of PPAR gamma), and cycloheximide (CHX; 30 micromol/L, an inhibitor of protein synthesis) were tested for their effects on the neuroprotection afforded by stearic acid. Western blotting was used to determine the PPAR gamma protein level in cortical neurons.

RESULTS

Stearic acid dose-dependently protected cortical neurons against glutamate or H2O2 injury and increased glutamate uptake in cultured neurons. This protection was concomitant to the inhibition of lipid peroxidation and to the promotion activity of Cu/Zn SOD and CAT in cultured cortical neurons. Its neuroprotective effects were completely blocked by BADGE and CHX. After incubation with H2O2 for 24 h, the expression of the PPAR gamma protein decreased significantly (P<0.05), and the inhibitory effect of H2O2 on the expression of PPAR gamma can be attenuated by stearic acid.

CONCLUSION

Stearic acid can protect cortical neurons against oxidative stress by boosting the internal antioxidant enzymes. Its neuroprotective effect may be mainly mediated by the activation of PPAR gamma and new protein synthesis in cortical neurons.

Neuroprotective effects of arachidonic acid against oxidative stress on rat hippocampal slices

Arachidonic acid (AA), 5,8,11,14-eicosateraenoic acid is abundant, active and necessary in the human body. In the present study, we reported the neuroprotective effects and mechanism of arachidonic acid on hippocampal slices insulted by glutamate, NaN(3) or H(2)O(2)in vitro. Different types of models of brain injury in vitro were developed by 1mM glutamate, 10mM NaN(3) or 2mM H(2)O(2). After 30 min of preincubation with arachidonic acid or linoleic acid, hippocampal slices were subjected to glutamate, NaN(3) or H(2)O(2), then the tissue activities were evaluated by using the 2,3,5-triphenyltetrazolium chloride method. Endogenous antioxidant enzymes activities (SOD, GSH-PX and catalase) in hippocampal slices were evaluated during the course of incubation. MK886 (5 microM; a noncompetitive inhibitor of proliferator-activated receptor [PPAR]alpha), BADGE (bisphenol A diglycidyl ether; 100 microM; an antagonist of PPARgamma) and cycloheximide (CHX; 30 microM; an inhibitor of protein synthesis) were tested for their effects on the neuroprotection afforded by arachidonic acid. Population spikes were recorded in randomly selected hippocapal slices. Arachidonic acid (1-10 microM) dose dependently protected hippocampal slices from glutamate and H(2)O(2) injury (P<0.01), and arachidonic acid (10 microM) can significantly improve the activities of Cu/Zn-SOD in hippocampal slices after 1h incubation. In addition, 10 microM arachidonic acid significantly increased the activity of Mn-SOD and catalase, and decreased the activities of Cu/Zn-SOD to control value after 3h incubation. These secondary changes of SOD during incubation can be reversed by indomethacine (10 microM; a nonspecific cyclooxygenase inhibitor) or AA 861 (20 microM; a 5-lipoxygenase inhibitor). Its neuroprotective effect was completely abolished by BADGE and CHX. These observations reveal that arachidonic acid can defense against oxidative stress by boosting the internal antioxidant system of hippocampal slices. Its neuroprotective effect may be mainly mediated by the activation of PPARgamma and synthesis of new protein in tissue.

15-Deoxy-12,14-prostaglandin J2 inhibits interferon gamma induced MHC class II but not class I expression on ARPE cells through a PPAR gamma independent mechanism

Retinal pigment epithelial (RPE) cells constitute the external part of the blood-retinal-barrier and play a pivotal role in the regulation of retinal immunity. In the present work, we investigated the effects of 15-deoxy-12,14-prostaglandin J2 (15 PGJ2), an endogenous ligand of PPARgamma, on the IFNgamma-induced expression of MHC class II on RPE cells. Indeed, pathological expression of MHC class II molecules at the surface of RPE cells is a common feature of many blinding conditions. We demonstrated that 15 PGJ2 inhibited the IFNgamma-mediated induction of MHC class II on RPE cells without affecting the level of MHC class I and CD54 expression. The other PPARgamma agonist rosiglitazone or troglitazone had no similar effects. Moreover, the inhibitory effect of 15 PGJ2 was not abrogated by co-incubation with PPARgamma antagonists and did not involve the modulation of STAT-1, AKT or ERK1/2 phosphorylation, nor CIITA, IRF1 or IRF2 transcription. In conclusion, 15 PGJ2 inhibits strongly and specifically the IFNgamma-induced MHC class II expression on RPE cells by a PPARgamma independent mechanism. Given the differential role of MHC classes I and II in the development of autoimmune uveitis and the potential toxicity of 15 PGJ2, our data's suggest that the development of novel small molecules targeting similar PPARgamma independent pathways would be useful for the future management of uveitis.

Peroxisome proliferator-activated receptor-γ agonists inhibit the replication of respiratory syncytial virus (RSV) in human lung epithelial cells

We have previously shown that peroxisome proliferator-activated receptor-gamma (PPARgamma) agonists inhibited the inflammatory response of RSV-infected human lung epithelial cells. In this study, we supply evidence that specific PPARgamma agonists (15d-PGJ2, ciglitazone, troglitazone, Fmoc-Leu) efficiently blocked the RSV-induced cytotoxicity and development of syncytia in tissue culture (A549, HEp-2). All PPARgamma agonists under study markedly inhibited the cell surface expression of the viral G and F protein on RSV-infected A549 cells. This was paralleled by a reduced cellular amount of N protein-encoding mRNA determined by real-time RT-PCR. Concomitantly, a reduced release of infectious progeny virus into the cell supernatants of human lung epithelial cells (A549, normal human bronchial epithelial cells (NHBE)) was observed. Similar results were obtained regardless whether PPARgamma agonists were added prior to RSV infection or thereafter, suggesting that the agonists inhibited viral gene expression and not the primary adhesion or fusion process.

Cardiovascular effects of the thiazolidinediones

Thiazolidinediones, used for the treatment of diabetes mellitus type 2, modulate gene expression by binding to nuclear transcription factor, peroxisome proliferator-activated receptor-gamma. Peroxisome proliferator-activated receptor-gamma is expressed in several tissues, therefore, thiazolidinediones have biological effects on multiple organ systems. Here, we describe evidence that thiazolidinediones have beneficial effects on the cardiovascular system independent of their antidiabetic effect. Studies in animals have clearly shown that thiazolidinediones decrease blood pressure, left ventricular hypertrophy, development of atherosclerotic lesions, and protect myocardium from ischemia/reperfusion injury. Although relatively few studies in humans have been reported, the preponderance of available evidence suggests a beneficial effect of thiazolidinediones. Thus, by modulating gene expression, thiazolidinediones may provide a novel method for the prevention and treatment of cardiovascular diseases.

Neuroprotective effects of stearic acid against toxicity of oxygen/glucose deprivation or glutamate on rat cortical or hippocampal slices

AIM

To observe the effects of stearic acid, a long-chain saturated fatty acid consisting of 18 carbon atoms, on brain (cortical or hippocampal) slices insulted by oxygen-glucose deprivation (OGD), glutamate or sodium azide (NaN3) in vitro.

METHODS

The activities of hippocampal slices were monitored by population spikes recorded in the CA1 region. In vitro injury models of brain slice were induced by 10 min of OGD, 1 mmol/L glutamate or 10 mmol/L NaN3. After 30 min of pre-incubation with stearic acid (3-30 micromol/L), brain slices (cortical or hippocampal) were subjected to OGD, glutamate or NaN3, and the tissue activities were evaluated by using the 2,3,5-triphenyltetrazolium chloride method. MK886 [5 mmol/L; a noncompetitive inhibitor of proliferator-activated receptor (PPAR-alpha)] or BADGE (bisphenol A diglycidyl ether; 100 micromol/L; an antagonist of PPAR-gamma) were tested for their effects on the neuroprotection afforded by stearic acid.

RESULTS

Viability of brain slices was not changed significantly after direct incubation with stearic acid. OGD, glutamate and NaN3 injury significantly decreased the viability of brain slices. Stearic acid (3-30 micromol/L) dose-dependently protected brain slices from OGD and glutamate injury but not from NaN3 injury, and its neuroprotective effect was completely abolished by BADGE.

CONCLUSION

Stearic acid can protect brain slices (cortical or hippocampal) against injury induced by OGD or glutamate. Its neuroprotective effect may be mainly mediated by the activation of PPAR-gamma.

Tendon xanthomas in familial hypercholesterolemia are associated with a differential inflammatory response of macrophages to oxidized LDL

Tendon xanthomas (TX) are pathognomonic lipid deposits commonly found in familial hypercholesterolemia (FH) patients. The aim of this study was to determine whether macrophages from FH patients with TX (TX+) have higher predisposition to foam cells formation after oxidized LDL (oxLDL) overload than those from FH patients without TX (TX-), and if their differential gene expression profile could explain these different phenotypes. Total RNA pools from macrophages from FH patients TX+ and TX- were analyzed using Affymetrix oligonucleotide arrays to evaluate the gene expression profile in presence and absence of oxLDL. Also, the intracellular lipid content was measured by fluorescence flow cytometry. Results of these studies suggest that macrophages from FH subjects TX+ compared to those TX- have a differential response to oxLDL, since they show higher intracellular cholesterol ester accumulation and a differential gene expression profile. The gene array data were validated by relative quantitative real-time RT-PCR and quantitative ELISA in culture media and plasma samples. FH subjects TX+ showed increased plasma tryptase, TNF-alpha, IL-8 and IL-6 concentrations. We propose that TX formation are associated with higher intracellular lipid content, and higher inflammatory response of macrophages in response to oxLDL.

A potent activator of PPARα and γ reduces the vascular cell recruitment and inhibits the intimal thickning in hypercholesterolemic rabbits

Peroxisome proliferator-activated receptors (PPARs) regulate the vascular cell functions as well as systemic lipid and glucose metabolism. Here, we studied the effect of TAK-559, a newly developed potent activator both for PPARalpha and gamma, on the vascular cell recruitment. TNF-alpha- or interleukin-1beta (IL-1beta)-induced THP-1 cell attachment to cultured endothelial cells was significantly reduced in the presence of 10 microM TAK-559 (P < 0.05). The secretion of monocyte chemoattractant protein-1 (MCP-1) from endothelial cells is reduced by 36% in the presence of 10 microM TAK-559, accompanied with the decreased mRNA expression in the cells. The proliferation and migration of cultured smooth muscle cells (SMCs) were significantly decreased in the presence of TAK-559 (P < 0.05). TAK-559-treated hypercholesterolemic rabbits showed the significant reduction of intimal thickning after balloon catheterization by 51% compared with control (P < 0.05), although the plasma lipid and glucose level was not changed between them. The numbers of macrophage and SMCs were decreased to 34% and 49% in the hyperplastic intima of arteries from TAK-559-treated rabbits compared to those from control, respectively. These results suggest that the PPARalpha and gamma activator inhibits the recruitment of macrophages and SMCs in intima, possibly leading to the reduction of intimal hyperplasia in hypercholesterolemia.

Experimental allergic encephalomyelitis is exacerbated in mice deficient for 12/15-lipoxygenase or 5-lipoxygenase

12/15-Lipoxygenase (12/15-LO) produces 15-hydroxyeicosatetraenoic acid (15-HETE) and 13-hydroxyoctadecadienoic acid (13-HODE) which are agonists for peroxisome proliferator-activated receptor-gamma (PPARgamma). PPARgamma agonists reduce clinical severity of experimental allergic encephalomyelitis (EAE), an animal model of multiple sclerosis. In contrast, 5-lipoxygenase (5-LO) produces the generally proinflammatory leukotrienes (LTs) which would be expected to worsen EAE. We tested the hypotheses that EAE severity would be exacerbated in 12/15-LO-deficient mice and attenuated in 5-LO-deficient mice. 12/15-LO deficiency conferred a significantly worse disease course, and surprisingly, 5-LO deficiency also caused significantly more severe EAE compared to control mice. These data suggest that PPARgamma-regulated gene expression and that 5-LO production of certain LTs have the ability to diminish EAE. Continued analysis will provide insight into the endogenous LO-generated effectors that assist in tempering EAE.

Peroxisome proliferator-activated receptor-gamma agonists in atherosclerosis: current evidence and future directions

PURPOSE OF REVIEW

The prevalence of type 2 diabetes globally is reaching epidemic proportions. Type 2 diabetes is strongly associated with increased risk of cardiovascular disease. Atherosclerosis is thought to arise as a result of a chronic inflammatory process within the arterial wall. Insulin resistance is central to the pathogenesis of type 2 diabetes and may contribute to atherogenesis, either directly or through associated risk factors. The peroxisome proliferator-activated receptor-gamma agonists, the thiazolidinediones, pioglitazone and rosiglitazone, are insulin sensitizing agents, that are licensed for the management of hyperglycaemia. Growing evidence supports an array of additional effects of thiazolidinedione therapy, both immunomodulatory and antiinflammatory, which may attenuate atherogenesis in type 2 diabetes.

RECENT FINDINGS

Studies have shown that thiazolidinedione therapy may lead to risk factor modulation in type 2 diabetes. Thiazolidinediones treatment has been shown to reduce blood pressure, modify the atherogenic lipid profile associated with type 2 diabetes, reduce microalbuminuria and ameliorate the prothrombotic diathesis. Further evidence suggests that thiazolidinediones therapy inhibits the inflammatory processes which may be involved in atherosclerotic plaque initiation, propagation and destabilization.

SUMMARY

Modification of insulin resistance by thiazolidinedione therapy in type 2 diabetes and the range of pleiotropic effects may not only impact on incident type 2 diabetes, but also on associated cardiovascular disease. Numerous large clinical endpoint studies are under way to investigate these issues.

Peroxisome proliferator-activated receptors and the cardiovascular system

Insulin resistance syndrome (also called syndrome X) includes obesity, diabetes, hypertension, and dyslipidemia and is a complex phenotype of metabolic abnormalities. The disorder poses a major public health problem by predisposing individuals to coronary heart disease and stroke, the leading causes of mortality in Western countries. Given that hypertension, diabetes, dyslipidemia, and obesity exhibit a substantial heritable component, it is postulated that certain genes may predispose some individuals to this cluster of cardiovascular risk factors. Emerging data suggest that peroxisome proliferator-activated receptors (PPARs), including alpha, gamma, and delta, are important determinants that may provide a functional link between obesity, hypertension, and diabetes. It has been well documented that hypolipidemic fibrates and antidiabetic thiazolidinediones are synthetic ligands for PPAR alpha and PPAR gamma, respectively. In addition, PPAR natural ligands, such as leukotriene B4 for PPAR alpha, 15-deoxy-delta 12,14-prostaglandin J2 for PPAR gamma, and prostacyclin for PPAR delta, are known to be eicosanoids and fatty acids. Studies have documented that PPARs are present in all critical vascular cells: endothelial cells, vascular smooth muscle cells, and monocyte-macrophages. These observations suggest that PPARs not only control lipid metabolism but also regulate vascular diseases such as atherosclerosis and hypertension. In this review, we present structure and tissue distribution of PPAR nuclear receptors, discuss the mechanisms of action and regulation, and summarize the rapid progress made in this area of study and its impact on the cardiovascular system.

Lipids and the immune response: from molecular mechanisms to clinical applications

PURPOSE OF REVIEW

This review critically evaluates recent studies investigating the effects of fatty acids on immune and inflammatory responses in both healthy individuals and in patients with inflammatory diseases, with some reference to animal studies where relevant. It examines recent findings describing the cellular and molecular basis for the modulation of immune function by fatty acids. The newly emerging area of diet-genotype interactions will also be discussed, with specific reference to the anti-inflammatory effects of fish oil.

RECENT FINDINGS

Fatty acids are participants in many intracellular signalling pathways. They act as ligands for nuclear receptors regulating a host of cell responses, they influence the stability of lipid rafts, and modulate eicosanoid metabolism in cells of the immune system. Recent findings suggest that some or all of these mechanisms may be involved in the modulation of immune function by fatty acids.

SUMMARY

Human studies investigating the relationship between dietary fatty acids and some aspects of the immune response have been disappointingly inconsistent. This review presents the argument that most studies have not been adequately powered to take into account the influence of variation (genotypic or otherwise) on parameters of immune function. There is well-documented evidence that fatty acids modulate T lymphocyte activation, and recent findings describe a range of potential cellular and molecular mechanisms. However, there are still many questions remaining, particularly with respect to the roles of nuclear receptors, for which fatty acids act as ligands, and the modulation of eicosanoid synthesis, for which fatty acids act as precursors.

Insulin resistance, diabetes, and atherosclerosis: thiazolidinediones as therapeutic interventions

The insulin resistance syndrome, a cluster of metabolic abnormalities involving dyslipidemia, hypertension, diabetes, impaired glucose tolerance, and hypercoagulability, carries an increased risk of atherosclerosis. Although interventions targeting elements of this syndrome have dramatically reduced cardiovascular risk, the impact of glucose-lowering has been more disappointing. Thiazolidinediones (TZDs) are a new class of insulin-sensitizing agents that activate the nuclear receptor peroxisome proliferator-activated receptor-g. TZDs may improve not only glucose levels but also other metabolic parameters associated with insulin resistance. The TZD data are reviewed, with a focus on their potential cardiovascular effects.