Increased expression of peroxisome proliferator-activated receptor (PPAR)-α and PPAR-γ in human atherosclerosis

To clarify the mechanism of atherosclerosis development in humans, we studied the mRNA and protein expression of PPAR subtypes in various types of atherosclerotic lesions and their correlation with cell proliferation and macrophage invasion. Human aortas were obtained from 35 autopsied cases, and each sample was divided into halves. One half was used for the analysis of mRNA or protein expression with RT-PCR or Western blotting, respectively. The other was microscopically classified into atheromatous plaque (AP), fatty streak (FS), and diffuse intimal thickening (DIT), and was analyzed immunohistochemically. The mRNA levels of both PPARs increased significantly in atherosclerosis and tended to increase in proportion to the severity of the lesion, and the expression of PPAR-α correlated with that of PPAR-γ in FS and AP. The PPAR-γ protein increased in AP. Monocytes/macrophages, as well as endothelial and smooth muscle cells, expressed the PPAR-γ protein in plaques. This expression in the DIT was noted mainly in macrophages but was not correlated with the density of macrophages, suggesting that only certain macrophages express the PPARs in DIT. Cell proliferation did not correlate with PPARs expression in any lesion type. These findings suggest that PPARs may be associated with atheromatous plaque formation, and that PPAR-γ may be involved in the early stages of human atherosclerosis.     

Activation of peroxisome proliferators-activated receptor δ (PPARδ) promotes blastocyst hatching in mice

Prostaglandins participate in a variety of female reproductive processes, including ovulation, fertilization, embryo implantation and parturition. In particular, maternal prostacyclin (PGI(2)) is critical for embryo implantation and the action of PGI(2) is not mediated via its G-protein-coupled membrane receptor, IP, but its nuclear receptor, peroxisome-proliferator-activated receptor δ (PPARδ). Recently, several studies have shown that PGI(2) enhances blastocyst development and/or hatching rate in vitro, and subsequently implantation and live birth rates in mice. However, the mechanism by which PGI(2) improves preimplantation embryo development in vitro remains unclear. Using molecular, pharmacologic and genetic approaches, we show that PGI(2)-induced PPARδ activation accelerates blastocyst hatching in mice. mRNAs for PPARδ, retinoid X receptor (heterodimeric partners of PPARδ) and PGI(2) synthase (PGIS) are temporally induced after zygotic gene activation, and their expression reaches maximum levels at the blastocyst stage, suggesting that functional complex of PPARδ can be formed in the blastocyst. Carbaprostacyclin (a stable analogue of PGI(2)) and GW501516 (a PPARδ selective agonist) significantly accelerated blastocyst hatching but did not increase total cell number of cultured blastocysts. Whereas U51605 (a PGIS inhibitor) interfered with blastocyst hatching, GW501516 restored U51605-induced retarded hatching. In contrast to the improvement of blastocyst hatching by PPARδ agonists, PPAR antagonists significantly inhibited blastocyst hatching. Furthermore, deletion of PPARδ at early stages of preimplantation mouse embryos caused delay of blastocyst hatching, but did not impair blastocyst development. Taken together, PGI(2)-induced PPARδ activation accelerates blastocyst hatching in mice.     

Protective effect of Ulinastatin against murine models of sepsis: Inhibition of TNF-α and IL-6 and augmentation of IL-10 and IL-13

AimExcessive production of inflammatory mediators during invasive infection plays a key role in the pathogenesis of sepsis. In an attempt to improve survival of patients with this lethal syndrome, agents were developed to selectively inhibit mediators in this inflammatory response. Ulinastatin (UTI), a human protease inhibitor, inhibits the enhanced production of pro-inflammatory molecules. However, it is unknown if Ulinastatin treatment could result in protective effects for sepsis. The aim of this study was to investigate the role of Ulinastatin on septic rats.MethodsSixty male Wistar rats were divided into six groups, 10 of each: sham-operation plus PBS (5 ml), cecal ligation and puncture (CLP) plus PBS (5 ml), CLP plus UTI (5000 U/kg), CLP plus UTI (10,000 U/kg), CLP plus UTI (20,000 U/kg) and sham-operation plus UTI (10,000 U/kg). Rats in the UTI groups after CLP operation were treated with Ulinastatin by intraperitoneal injection at different doses and then compared with untreated sepsis control animals.ResultsThe intestinal concentrations of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), interleukin-10 (IL-10), and interleukin-13 (IL-13) were significantly higher in septic rats than those in normal rats. Ulinastatin administration effectively suppressed the levels of TNF-α and IL-6, whereas it markedly enhanced the levels of IL-10 and IL-13.ConclusionUlinastatin may possess a protective role in the septic process by inhibiting TNF-α and IL-6, and augmenting IL-10 and IL-13 concentrations in intestine of septic rats.     

The effect of combining rosuvastatin with sartans of different peroxisome proliferator receptor-γ activating capacity on plasma 8-isoprostane prostaglandin F2a levels

Introduction

Oxidative stress is associated with the development and progression of cardiovascular disease. Plasma 8-isoprostane prostaglandin F_2a (8-iso-PGF_2a) levels are a reliable marker of oxidative stress.

Material and methods

Patients (n = 151) with hypertension, dyslipidemia and impaired fasting glucose were randomly allocated to rosuvastatin (10 mg/day) plus telmisartan 80 mg/day (RT group, n = 52) or irbesartan 300 mg/day (RI group, n = 48) or olmesartan 20 mg/day (RO group, n = 51). After 6 months of treatment, changes in plasma 8-iso-PGF_2a levels were blindly evaluated.

Results

A decrease of 8-iso-PGF_2a levels vs baseline was observed only in the RT group (–8.6%; p = 0.02). A trend for decrease vs. baseline was observed in the RI (–5.7%; p = 0.40) and RO (–3.7%; p = 0.60) groups. Changes of 8-iso-PGF_2a levels between groups were not significantly different (p = 0.70).

Conclusions

The combination of rosuvastatin with sartans of different peroxisome proliferator receptor-γ activating capacity was associated with a decrease in levels of plasma 8-iso-PGF_2a. This decrease reached significance only in the telmisartan group.     

Peroxisome proliferator activated receptor gamma (PPARγ) as a therapeutic target for improvement of cognitive performance in Fragile-X

Rare disorders leading to intellectual disability, such as Fragile X syndrome (FXS) alter synaptic plasticity. Ligand identification of orphan nuclear receptors has led to the discovery of many signaling pathways and has revealed a direct link of nuclear receptors with human conditions such as mental retardation and neurodegenerative diseases. PPARγ agonists can act as neuroprotective agents, promoting synaptic plasticity and neurite outgrowth. Therefore, selective PPARγ agonists are good candidates for therapeutic evaluation in intellectual disabilities. Preliminary results suggest that PPARγ agonists such as Pioglitazone, Rosiglitazone and synthetic agonist, GW1929, are used as the therapeutic agent in neurological disorders. These components interact with intracellular transduction signals (e.g. GSK3β, PI3K/Akt, Wnt/β-Catenin, Rac1 and MMP-9). It seems that interaction with these pathways can improve memory recognition in FXS animal models. The present hypothesis consists of enhancing synaptic plasticity that may then rescue the learning and memory in FXS. This will open many new therapeutic avenues for a variety of human diseases.     

Protective effect of (−)clausenamide against Aβ-induced neurotoxicity in differentiated PC12 cells

The neurotoxicity of aggregated β-amyloid (Aβ) has been implicated as a critical cause in the pathogenesis of Alzheimer's disease (AD). In the present study, we investigated the effect of (−)clausenamide ((−)Clau), an aqueous extract of leaves of Clausena lassium (lour) skeel, on the neurotoxicity of Aβ_25–35. The viability of differentiated PC12 cells was determined by MTT assay. Apoptosis was detected by flow cytometry. DCFH-DA was used for assessment of intracellular ROS generation, JC-1 and Rhodamine 123 for measurement of mitochondrial transmembrane potential (MMP). The intracellular calcium was determined with Fluo-3. The phosphorylation of p38 MAPK and the expression of Bcl-2, Bax, P53, Caspase 3 were examined by Western blot. The results showed that (−)Clau significantly elevated cell viability. Furthermore, (−)Clau arrested the apoptotic cascade by reversing overload of calcium, preventing ROS generation, moderated the dissipation of MMP and the misbalance of Bcl-2 and Bax, inhibiting the activation of p38 MAPK and the expression of P53 and cleaved Caspase 3. Our results suggested that (−)Clau may be a therapeutic agent for AD.     

In vivo and in vitro evidence that PPARγ ligands are antagonists of leptin signaling in breast cancer

Obesity is a major risk factor for the development and progression of breast cancer. Leptin, a cytokine mainly produced by adipocytes, plays a crucial role in mammary carcinogenesis and is elevated in hyperinsulinemia and insulin resistance. The antidiabetic thiazolidinediones inhibit leptin gene expression through ligand activation of the peroxisome proliferator-activated receptor-γ (PPARγ) and exert antiproliferative and apoptotic effects on breast carcinoma. In this study, we investigated the ability of PPARγ ligands to counteract leptin stimulatory effects on breast cancer growth in either in vivo or in vitro models. The results show that activation of PPARγ prevented the development of leptin-induced MCF-7 tumor xenografts and inhibited the increased cell-cell aggregation and proliferation observed on leptin exposure. PPARγ ligands abrogated the leptin-induced up-regulation of leptin gene expression and its receptors in breast cancer. PPARγ-mediated repression of leptin gene involved the recruitment of nuclear receptor corepressor protein and silencing mediator of retinoid and thyroid hormone receptors corepressors on the glucocorticoid responsive element site in the leptin gene expression regulatory region in the presence of glucocorticoid receptor and PPARγ. In addition, PPARγ ligands inhibited leptin signaling mediated by MAPK/STAT3/Akt phosphorylation and counteracted leptin stimulatory effect on estrogen signaling. These findings suggest that PPARγ ligands may have potential therapeutic benefits in the treatment of breast cancer.     

Anti-inflammatory effect of peroxisome proliferator-activated receptor-γ (PPAR-γ) on non-obese diabetic mice with Sjogren’s syndrome

Objective: To investigate the anti-inflammatory effect of peroxisome proliferator-activated receptor-γ (PPAR-γ) on non-obese diabetic mice (NOD mice) with Sjogren’s syndrome. Methods: 22 eight-week-old female NOD mice were randomly divided into 2 groups. Rosiglitazone and normal saline were administered in the PPAR-γ group and the control group respectively. At the age of 9, 12 and 15 weeks, one mouse in each group was sacrificed respectively, and the remaining mice were sacrificed at the age of 18 weeks. Blood were obtained by cardiac puncture, and salivary glands were resected. The degree of salivary gland damage and infiltration of lymphocytes were examined by H&E staining. The level of IL-1β, IL-4, IL-6 and TNF-α in serum were measured by ELISA. The mRNA expression level of IL-1β, IL-4, IL-6 and TNF-α in MSG were detected by Real-time PCR. Expression of PPAR-γ in the salivary glands was detected by Immunohistochemistry. Results: Compared with the control group, mice in the PPAR-γ group showed that (1) histopathologic changes in the salivary glands were significantly ameliorated; (2) at the age of 18 weeks, IL-6 [(25.86 ± 7.32) vs (37.41 ± 11.34)] and TNF-α [(56.88 ± 22.19) vs (78.61 ± 20.76)] were expressed significantly lower and IL-4 [(25.76 ± 12.65) vs (12.11 ± 3.70)] was expressed significantly higher in serum (P < 0.05); (3) the expression of TNF-α was significantly decreased and the expression of IL-4 was significantly increased in MSG (P < 0.05). Conclusion: PPAR-γ ameliorates Sjogren’s syndrome on NOD mice effectively. The mechanism may be related to the reduction of Th1 cytokines and change of T helper cell balance from Th1 to Th2.     

Overexpression of dominant negative peroxisome proliferator-activated receptor-γ (PPARγ) in alveolar type II epithelial cells causes inflammation and T-cell suppression in the lung

Peroxisome proliferator-activated receptor-γ (PPARγ) is an anti-inflammatory molecule. To assess its biological function in lung alveolar epithelial cells, a CCSP-rtTA/(tetO)(7)-dnPPARγ bitransgenic mouse model was generated. In this model, a dominant negative (dn) PPARγ-Flag fusion protein was overexpressed in lung alveolar type II (AT II) epithelial cells in an inducible manner to suppress the endogenous PPARγ function. Overexpression of dnPPARγ induces up-regulation of proinflammatory cytokines and chemokines at both mRNA and protein levels in AT II epithelial cells. This up-regulation was due to dnPPARγ directly DNA binding on the promoter regions. Up-regulation of proinflammatory molecules activated multiple intracellular signaling pathways in AT II epithelial cells. In addition, inflammatory CD11b(+)Gr-1(+) myeloid-derived suppressor cells were significantly accumulated but T cells were decreased in the lung and circulation system of doxycycline-treated mice. In vitro, myeloid-derived suppressor cells from the lung suppressed T-cell proliferation and function. As a pathogenic consequence, emphysema was observed in the doxycycline-treated lung in association with up-regulation of matrix metalloproteases. Chronic inflammation and lung injury also induced conversion of bone marrow mesenchymal stem cells into AT II epithelial cells in bitransgenic mice. These findings support that PPARγ and its negatively regulated downstream genes in AT II epithelial cells possess multiple functions to control alveolar homeostasis through inflammatory and noninflammatory mechanisms.