intrarenal-injection-escherichia-coli-rat-model

Intrarenal Injection of <em>Escherichia coli</em> in a Rat Model of Pyelonephritis

Pyelonephritis is a bacterial infection of the kidney and is most commonly caused by Escherichia coli. Recurrent infections can cause significant renal ...

Case Western Reserve University

Tea is the second most consumed beverage in the world reported to have multiple health benefits. Preventive and therapeutic benefits of tea polyphenols include enhanced general well being and anti-neoplastic effects. The pharmacologic action of tea is often attributed to various catechins present therein. Experiments conducted in cancer cell lines and animal models demonstrate that tea polyphenols protect against cellular damage caused by oxidative stress and altered immunity. Tea polyphenols modify various metabolic and signaling pathways in the regulation of proliferation, apoptosis, angiogenesis, and metastasis and therefore restrict clonal expansion of cancer cells. Tea polyphenols have been shown to reactivate tumor suppressors, block the unlimited replicative potential of cancer cells, and physically bind to nucleic acids involved in epigenetic alterations of gene regulation. Remarkable interest in green tea as a potential chemopreventive agent has been generated since recent epigenetic data showed that tea polyphenols have the potential to reverse epigenetic modifications which might otherwise be carcinogenic. Like green tea, black tea may also possess chemopreventive and chemotherapeutic potential; however, there is still not enough evidence available to make any conclusive statements. Here we present a brief description of tea polyphenols and discuss the findings of various in vitro and in vivo studies of the anticancer effects of tea polyphenols. Detailed discussion of various studies related to epigenetic changes caused by tea polyphenols leading to prevention of oncogenesis or cancer progression is included. Finally, we discuss on the scope and development of tea polyphenols in cancer prevention and therapy.

The chemopreventive and chemotherapeutic potentials of tea polyphenols.

Green tea polyphenols (GTPs) reactivate epigenetically silenced genes in cancer cells and trigger cell cycle arrest and apoptosis; however, the mechanisms whereby these effects occur are not well understood. We investigated the molecular mechanisms underlying the antiproliferative effects of GTP, which may be similar to those of histone deacetylase (HDAC) inhibitors. Exposure of human prostate cancer LNCaP cells (harboring wild-type p53) and PC-3 cells (lacking p53) with 10-80 μg/ml of GTP for 24 h resulted in dose-dependent inhibition of class I HDAC enzyme activity and its protein expression. GTP treatment causes an accumulation of acetylated histone H3 in total cellular chromatin, resulting in increased accessibility to bind with the promoter sequences of p21/waf1 and Bax, consistent with the effects elicited by an HDAC inhibitor, trichostatin A. GTP treatment also resulted in increased expression of p21/waf1 and Bax at the protein and message levels in these cells. Furthermore, treatment of cells with proteasome inhibitor, MG132 together with GTP prevented degradation of class I HDACs, compared with cells treated with GTP alone, indicating increased proteasomal degradation of class I HDACs by GTP. These alterations were consistent with G(0)-G(1) phase cell cycle arrest and induction of apoptosis in both cell lines. Our findings provide new insight into the mechanisms of GTP action in human prostate cancer cells irrespective of their p53 status and suggest a novel approach to prevention and/or therapy of prostate cancer achieved via HDAC inhibition.

Green tea polyphenols causes cell cycle arrest and apoptosis in prostate cancer cells by suppressing class I histone deacetylases.

Acetylation of the tumor suppressor gene p53 at the carboxy-terminal lysine (Lys) residues enhances its transcriptional activity associated with cell cycle arrest and apoptosis. Histone deacetylases (HDACs), a family of evolutionarily conserved enzymes, counterbalance the acetylation of lysine residues on histone and non-histone proteins. In this study, we demonstrate that green tea polyphenols (GTPs) and their major constituent, (-) epigallocatechin-3-gallate (EGCG), activate p53 through acetylation at the Lys373 and Lys382 residues by inhibiting class I HDACs in LNCaP human prostate cancer cells. Treatment of cells with GTPs (2.5-10 µg/ml) and EGCG (5-20 µM) resulted in dose- and time-dependent inhibition of class I HDACs (HDAC1, 2, 3 and 8), albeit at varying levels. Discontinuation of treatment with GTP/EGCG resulted in the loss of p53 acetylation at both the sites in these cells. GTP/EGCG treatment also resulted in increased expression of p21/waf1 and Bax at the protein and message levels in these cells. The increased GTP/EGCG-mediated p53 acetylation enhanced its binding on the promoters of p21/waf1 and Bax, which was associated with increased accumulation of cells in the G0/G1 phase of the cell cycle and induction of apoptosis. Our findings indicate that GTP/EGCG causes acetylation of p53 by inhibiting class I HDACs, a function that is likely to be part of the mechanisms that control the physiological activity of p53.

Green tea polyphenols increase p53 transcriptional activity and acetylation by suppressing class I histone deacetylases.

Inactivation of the tumor suppressor gene p53 is commonly observed in human prostate cancer and is associated with therapeutic resistance. We have previously demonstrated that green tea polyphenols (GTP) induce apoptosis in prostate cancer cells irrespective of p53 status. However, the molecular mechanisms underlying these observations remain elusive. Here we investigated the mechanisms of GTP-induced apoptosis in human prostate cancer LNCaP cells stably-transfected with short hairpin-RNA against p53 (LNCaPshp53) and control vector (LNCaPshV). GTP treatment induced p53 stabilization and activation of downstream targets p21/waf1 and Bax in a dose-dependent manner specifically in LNCaPshV cells. However, GTP-induced FAS upregulation through activation of c-jun-N-terminal kinase resulted in FADD phosphorylation, caspase-8 activation and truncation of BID, leading to apoptosis in both LNCaPshV and LNCaPshp53 cells. In parallel, treatment of cells with GTP resulted in inhibition of survival pathway, mediated by Akt deactivation and loss of BAD phosphorylation more prominently in LNCaPshp53 cells. These distinct routes of cell death converged to a common pathway, leading to loss of mitochondrial transmembrane potential, cytochrome c release and activation of terminal caspases, resulting in PARP-cleavage. GTP-induced apoptosis was attenuated with JNK inhibitor, SP600125 in both cell lines; whereas PI3K-Akt inhibitor, LY294002 resulted in increased cell death prominently in LNCaPshp53 cells, establishing the role of two distinct pathways of GTP-mediated apoptosis. Furthermore, GTP exposure resulted in inhibition of class I HDAC protein, accumulation of acetylated histone-H3 in total cellular chromatin, resulting in increased accessibility of transcription factors to bind with the promoter sequences of p21/waf1 and Bax, regardless of the p53 status of cells, consistent with effects elicited by an HDAC inhibitor, trichostatin A. These results demonstrate that GTP induces prostate cancer cell death by two distinct mechanisms regardless of p53 status, thus identifying specific well-defined molecular mechanisms that may be targeted by chemopreventive and/or therapeutic strategies.

Green tea polyphenols induce p53-dependent and p53-independent apoptosis in prostate cancer cells through two distinct mechanisms.

Epigenetic and genetic alterations contribute to cancer initiation and progression. Epigenetics refers to the study of heritable changes in gene expression without alterations in DNA sequences. Epigenetic changes are reversible and include key processes of DNA methylation, chromatin modifications, nucleosome positioning, and alterations in noncoding RNA profiles. Disruptions in epigenetic processes can lead to altered gene function and cellular neoplastic transformation. Epigenetic modifications precede genetic changes and usually occur at an early stage in neoplastic development. Recent technological advances offer a better understanding of the underlying epigenetic alterations during carcinogenesis and provide insight into the discovery of putative epigenetic biomarkers for detection, prognosis, risk assessment, and disease monitoring. In this chapter we provide information on various epigenetic mechanisms and their role in carcinogenesis, in particular, epigenetic modifications causing genetic changes and the potential clinical impact of epigenetic research in the future.

Cancer epigenetics: an introduction.

Catalase is a tetrameric heme-containing enzyme with essential antioxidant functions in biology. Multiple factors including nitric oxide (NO) have been shown to attenuate its activity. However, the possible impact of NO in relation to the maturation of active catalase, including its heme acquisition and tetramer formation, has not been investigated. We found that NO attenuates heme insertion into catalase in both short-term and long-term incubations. The NO inhibition in catalase heme incorporation was associated with defective oligomerization of catalase, such that inactive catalase monomers and dimers accumulated in place of the mature tetrameric enzyme. We also found that GAPDH plays a key role in mediating these NO effects on the structure and activity of catalase. Moreover, the NO sensitivity of catalase maturation could be altered up or down by manipulating the cellular expression level or activity of thioredoxin-1, a known protein-SNO denitrosylase enzyme. In a mouse model of allergic inflammatory asthma, we found that lungs from allergen-challenged mice contained a greater percentage of dimeric catalase relative to tetrameric catalase in the unchallenged control, suggesting that the mechanisms described here are in play in the allergic asthma model. Together, our study shows how maturation of active catalase can be influenced by NO, S-nitrosylated GAPDH, and thioredoxin-1, and how maturation may become compromised in inflammatory conditions such as asthma.

Novel insights in mammalian catalase heme maturation: effect of NO and thioredoxin-1.

Large vessel vasculitides (LVV) are a group of autoimmune diseases characterized by injury to and anatomic modifications of large vessels, including the aorta and its branch vessels. Disease etiology is unknown. This study was undertaken to identify antigen targets within affected vessel walls in aortic root, ascending aorta, and aortic arch surgical specimens from patients with LVV, including giant cell arteritis, Takayasu arteritis, and isolated focal aortitis.

14-3-3 in Thoracic Aortic Aneurysms: Identification of a Novel Autoantigen in Large Vessel Vasculitis.

Previous studies have shown that Magnetic Resonance Imaging (MRI) techniques can be used to non-invasively assess lung disease in CF patients. In this study, we compare the sensitivity of normalized T1 (nT1) and non-contrast perfusion MRI techniques to detect regional lung disease in CF patients.

Karishma Gupta

Department of Radiology

Case Western Reserve University

Intrarenal Injection of Escherichia coli in a Rat Model of Pyelonephritis

Karishma Gupta

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Department of Radiology

Case Western Reserve University

Intrarenal Injection of Escherichia coli in a Rat Model of Pyelonephritis

Department of Radiology