Repression of NHE1 Expression by PPAR gamma Activation Is a Potential New Approach for Specific Inhibition of the Growth of Tumor Cells In vitro and In vivo

Ligand-induced activation of peroxisome proliferator-activated receptor gamma (PPAIR gamma) inhibits proliferation in cancer cells in vitro and in vivo; however, the downstream targets remain undefined. We report the identification of a peroxisome proliferator response element in the promoter region of the Na+/ H transporter gene NHE1, the overexpression of which has been associated with carcinogenesis. Exposure of breast cancer cells expressing high levels of PPAR gamma to its natural and synthetic agonists resulted in downregulation of NHE1 transcription as well as protein expression. Furthermore, the inhibitory effect of activated PPAR gamma on tumor colony-forming ability was abrogated on overexpression of NHE1, whereas small interfering RNA-mediated gene silencing of NHE1 significantly increased the sensitivity of cancer cells to growth-inhibitory stimuli. Finally, histopathologic analysis of breast cancer biopsies obtained from patients with type II diabetes treated with the synthetic agonist rosiglitazone showed significant repression of NHE1 in the tumor tissue. These data provide evidence for tumor-selective downregulation of NHE1 by activated PPAR gamma in vitro and in pathologic specimens from breast cancer patients and could have potential implications for the judicious use of low doses of PPAR gamma ligands in combination chemotherapy regimens for an effective therapeutic response. [Cancer Res 2009;69(22):8636-44]

Fenofibrate and pioglitazone improve endothelial function and reduce arterial stiffness in obese glucose tolerant men

Obesity is a low grade inflammatory state associated with premature cardiovascular morbidity and mortality. Along with traditional risk factors the measurement of endothelial function, insulin resistance, inflammation and arterial stiffness may contribute to the assessment of cardiovascular risk. We conducted a randomised placebo controlled trial to assess the effects of 12 weeks treatment with a PPAR-alpha agonist (fenofibrate) and a PPAR-gamma agonist (pioglitazone) on these parameters in obese glucose tolerant men. Arterial stiffness was measured using augmentation index and pulse wave velocity (PWV). E-selectin, VCAM-1 and ICAM-1 were used as markers of endothelial function. Insulin sensitivity improved with pioglitazone treatment (p=0.001) and, in keeping with this, adiponectin increased by 85.2% (p

Thiazolidinediones: effects on insulin resistance and the cardiovascular system.

Abstract
Thiazolidinediones (TZDs) have been used for the treatment of hyperglycaemia in type 2 diabetes for the past 10 years. They may delay the development of type 2 diabetes in individuals at high risk of developing the condition, and have been shown to have potentially beneficial effects on cardiovascular risk factors. TZDs act as agonists of peroxisome proliferator-activated receptor-gamma (PPAR-gamma) primarily in adipose tissue. PPAR-gamma receptor activation by TZDs improves insulin sensitivity by promoting fatty acid uptake into adipose tissue, increasing production of adiponectin and reducing levels of inflammatory mediators such as tumour necrosis factor-alpha (TNF-alpha), plasminogen activator inhibitor-1(PAI-1) and interleukin-6 (IL-6). Clinically, TZDs have been shown to reduce measures of atherosclerosis such as carotid intima-media thickness (CIMT). However, in spite of beneficial effects on markers of cardiovascular risk, TZDs have not been definitively shown to reduce cardiovascular events in patients, and the safety of rosiglitazone in this respect has recently been called into question. Dual PPAR-alpha/gamma agonists may offer superior treatment of insulin resistance and cardioprotection, but their safety has not yet been assured

Non-thiazolidinedione antihyperglycaemic agents. Part 3: The effects of stereochemistry on the potency of alpha-methoxy-beta-phenylpropanoic acids.

Rhizopus delemar lipase catalyzed ester hydrolysis of the alpha-methoxy-beta-phenylpropanoate (I) affords the (R)-(+) and (S)-(-) isomers in > 84% enantiomeric excess. Abs. stereochem. was detd. by a single crystal X-ray anal. of a related synthetic analog. The activity of these two enantiomers on glucose transport in vitro and as anti-diabetic agents in vivo is reported and their unexpected equivalence attributed to an enzyme-mediated stereospecific isomerization of the (R)-(+) isomer. Binding studies using recombinant human PPAR-gamma (peroxisomal proliferator activated receptor gamma), now established as a mol. target for this compd. class, indicate a 20-fold higher binding affinity for the (S) antipode relative to the (R) antipode.

Manganese Superoxide Dismutase Is a Promising Target for Enhancing Chemosensitivity of Basal-Like Breast Carcinoma

AIMS: Although earlier reports highlighted a tumor suppressor role for manganese superoxide dismutase (MnSOD), recent evidence indicates increased expression in a variety of human cancers including aggressive breast carcinoma. In the present article, we hypothesized that MnSOD expression is significantly amplified in the aggressive breast carcinoma basal subtype, and targeting MnSOD could be an attractive strategy for enhancing chemosensitivity of this highly aggressive breast cancer subtype.

RESULTS: Using MDA-MB-231 and BT549 as a model of basal breast cancer cell lines, we show that knockdown of MnSOD decreased the colony-forming ability and sensitized the cells to drug-induced cell death, while drug resistance was associated with increased MnSOD expression. In an attempt to develop a clinically relevant approach to down-regulate MnSOD expression in patients with basal breast carcinoma, we employed activation of the peroxisome proliferator-activated receptor gamma (PPARγ) to repress MnSOD expression; PPARγ activation significantly reduced MnSOD expression, increased chemosensitivity, and inhibited tumor growth. Moreover, as a proof of concept for the clinical use of PPARγ agonists to decrease MnSOD expression, biopsies derived from breast cancer patients who had received synthetic PPARγ ligands as anti-diabetic therapy had significantly reduced MnSOD expression. Finally, we provide evidence to implicate peroxynitrite as the mechanism involved in the increased sensitivity to chemotherapy induced by MnSOD repression.

INNOVATION AND CONCLUSION: These data provide evidence to link increased MnSOD expression with the aggressive basal breast cancer, and underscore the judicious use of PPARγ ligands for specifically down-regulating MnSOD to increase the chemosensitivity of this subtype of breast carcinoma.

Elevated NCOR1 disrupts a network of dietary-sensing nuclear receptors in bladder cancer cells

Increasingly invasive bladder cancer cells lines displayed insensitivity toward a panel of dietary-derived ligands for members of the nuclear receptor superfamily. Insensitivity was defined through altered gene regulatory actions and cell proliferation and reflected both reduced receptor expression and elevated nuclear receptor corepressor 1 (NCOR1) expression. Stable overexpression of NCOR1 in sensitive cells (RT4) resulted in a panel of clones that recapitulated the resistant phenotype in terms of gene regulatory actions and proliferative responses toward ligand. Similarly, silencing RNA approaches to NCOR1 in resistant cells (EJ28) enhanced ligand gene regulatory and proliferation responses, including those mediated by peroxisome proliferator-activated receptor (PPAR) gamma and vitamin D receptor (VDR) receptors. Elevated NCOR1 levels generate an epigenetic lesion to target in resistant cells using the histone deacetylase inhibitor vorinostat, in combination with nuclear receptor ligands. Such treatments revealed strong-additive interactions toward the PPARgamma, VDR and Farnesoid X-activated receptors. Genome-wide microarray and microfluidic quantitative real-time, reverse transcription-polymerase chain reaction approaches, following the targeting of NCOR1 activity and expression, revealed the selective capacity of this corepressor to govern common transcriptional events of underlying networks. Combined these findings suggest that NCOR1 is a selective regulator of nuclear receptors, notably PPARgamma and VDR, and contributes to their loss of sensitivity. Combinations of epigenetic therapies that target NCOR1 may prove effective, even when receptor expression is reduced.

Identification of high-affinity binding sites for the insulin sensitizer rosiglitazone (BRL-49653) in rodent and human adipocytes using a radioiodinated ligand for peroxisomal proliferator-activated receptor gamma.

A radioiodinated ligand, [125I]SB-236636 [(S)-(-)3-[4-[2-[N-(2-benzoxazolyl)-N-methylamino]ethoxy]3-[125I]iodophenyl]2-ethoxy propanoic acid], which is specific for the ? isoform of the peroxisomal proliferator activated receptor (PPAR?), was developed. [125I]SB-236636 binds with high affinity to full-length human recombinant PPAR?1 and to a GST (glutathione S-transferase) fusion protein contg. the ligand binding domain of human PPAR?1 (KD = 70 nM). Using this ligand, the authors characterized binding sites in adipose-derived cells from rat, mouse and humans. In competition expts., rosiglitazone (BRL-49653), a potent antihyperglycemic agent, binds with high affinity to sites in intact adipocytes (IC50 = 12, 4 and 9 nM for rat, 3T3-L1 and human adipocytes, resp.). Binding affinities (IC50) of other thiazolidinediones for the ligand binding domain of PPAR?1 were comparable with those detd. in adipocytes and reflected the rank order of potencies of these agents as stimulants of glucose transport in 3T3-L1 adipocytes and antihyperglycemic agents in vivo: rosiglitazone > pioglitazone > troglitazone. Competition of [125I]SB-236636 binding was stereoselective in that the IC50 value of SB-219994, the (S)-enantiomer of an ?-trifluoroethoxy propanoic acid insulin sensitizer, was 770-fold lower than that of SB-219993 [(R)-enantiomer] at recombinant human PPAR?1. The higher binding affinity of SB-219994 also was evident in intact adipocytes and reflected its 100-fold greater potency as an antidiabetic agent. The results strongly suggest that the high-affinity binding site for [125I]SB-236636 in intact adipocytes is PPAR? and that the pharmacol. of insulin-sensitizer binding in rodent and human adipocytes is very similar and, moreover, predictive of antihyperglycemic activity in vivo.

Experimental and Modelling Studies of the Thermodynamics and Kinetics of Phase and Structural Transformations in a Gamma TiAl-based Alloy

This work combines microscopy, synchrotron radiation X-ray diffraction, differential scanning calorimetry and thermodynamic calculations in the characterisation of phase transformation behaviour of a Ti–46Al–1.9Cr–3Nb alloy upon continuous heating at constant rates. It has been found that the Ti–46Al–1.9Cr–3Nb alloy after being forged at 1200 °C without further treatment has a duplex microstructure consisting of fine equiaxed and lamellar ? grains with a small amount of a2 plates and particles and about 1 wt.% B2 phase. Differential scanning calorimetry revealed reproducibly several thermal effects upon heating of the as-forged alloy. These thermal effects are related to the equilibration and homogenisation of the sample, change of phase ratios between a2, ? and B2 phases in particular the increase of B2 in respect to a2 and ?, and the following five phase transformations: a2 + ? + B2 a + ? + B2, a + ? + B2 a + ?, ? + a a, a a + ß, a + ß a + ß + L. The observation of these transformations by differential scanning calorimetry is largely in agreement with literature phase diagrams and thermodynamic calculations, though care is needed to consider the different alloy compositions. Kinetics of the ? + a a phase transformation in the Ti–46Al–1.9Cr–3Nb alloy has been quantitatively derived from the calorimetry data, giving phase compositions at any point during the transformation upon continuous heating.

The Influence of Inert Packaging on the shelf Ageing of Gamma-Irradiation Sterilised ultra-high molecular weight polyethylene

Ultra-high molecular weight polyethylene (UHMWPE) is used for wear applications in total hip prostheses and total knee prostheses. Sterilisation of these prostheses is commonly by gamma-irradiation. This process creates reactive free radicals in the UHMWPE, greatly increasing its susceptibility to oxidative degradation. This study has investigated the influence of air and vacuum packaging on the properties of gamma-irradiated UHMWPE (GUR1050) following 3 years of shelf ageing. The findings indicate that vacuum packaging minimises oxidative degradation reactions that occur for UHMWPE during shelf ageing. However, gamma-irradiation of vacuum-packaged UHMWPE promotes a degree of cross-linking. It is proposed that this may enhance the wear performance of UHMWPE. Accelerated ageing studies indicate that 3 years of shelf ageing would also seem to reduce the susceptibility of gamma-irradiated UHMWPE to oxidative degradation upon removal from its vacuum packaging.