Current Enzyme Inhibition - Volume 5, Issue 4, 2009

Evidence is mounting that NO plays a role in the cardiovascular and renal adaptation to the hemorrhagic shock secondary to major blood loss. Recently, we reported cardiac and renal NO-dependent protective mechanisms activated by the hypovolemic state that include stimulation of NO synthase (NOS) expression and activity. In the heart, an increase in endothelial NOS is an early response to regulate cardiac function after blood loss. Meanwhile, inducible NOS increases heart dysfunction in later stages of sustained hemorrhagic shock. Additionally, the hypovolemic state induced changes in water homeostasis associated with alterations in inner medullary aquaporin water channel type 2 (AQP2) protein expressions and subcellular localization. NO production is one of the causes of the age-associated response that modulates AQP2 expression/trafficking in the inner collecting duct principal cells in response to hemorrhage. The complex regulation of NOS in cardiovascular and renal physiology depends on the magnitude of hemorrhage and age. The adaptive enhancement of NO synthesis and availability activates or increases expression of other protective factors, including heat shock proteins, antioxidants and prostaglandins, making the protection more robust and sustained. The work with laboratory animals and experimental hemorrhagic shock identified mitochondria as a sensitive subcellular compartment involved in the NO-mediated response to hypovolemic state. In a separate line of research, mtNOS was probed as a likely pacemaker of mammalian aging. Finally, further research based on the participation of mtNOS and the relationships between NO and other modulators of heart and kidney function, as well as the impact of aging in tissue adaptation to hypovolemia, are new research lines and hypothetical therapeutic strategies for the prevention and early treatment of tissue dysfunction.

Anthocyanins (Greek antos, flower and kyanos, blue) are part of a widespread group of plant constituents, collectively known as flavonoids, which occur in the western diet at relatively high concentrations and own a variety of pharmacological properties which make them potential anti-inflammatory and cancer agents. Besides their ability to scavenge reactive oxygen species, anthocyanins exhibit anticancer effects through impaired expression and function of enzymes, most of which are involved in abnormal activation of signaling pathways leading to cancer cell growth and progression. Antiproliferative and antiangiogenetic properties of anthocyanins encompass inhibition of phosphorylation of receptor tyrosine kinases (EGFR, VEGFR, Met receptor, PDGFR) and down-regulation of downstream signaling cascades, impaired activity of cAMP-specific phosphodiesterases, chymotrypsin-like proteasome activity, ornithine decarboxylase and cyclin-dependent kinases/cyclin complex. Transcription activity of NF-κB, involved in the carcinogenesis process, is affected by anthocyanins through inhibition of the IκB kinase complex phosphorylation. The antiproliferative activity is dependent on the presence of hydroxyl groups on ring B of the anthocyanin molecule. Anthocyanins influence cancer cell invasion as well, through the decrease of metalloproteinases and plasmin activity. Finally, inhibition of cyclooxygenase activity may counteract a number of characteristics of tumor progression and metastasis. Conversely, one potential drawback of the anthocyanin's effect is their inhibitory activity on topoisomerases I and II. This review will deal with the current knowledge on the anthocyanins ability to hamper the expression and function of signaling pathway enzymes involved in cancer development and discuss anthocyanins preventive/therapeutic potential against human cancers.

The increasing knowledge regarding breast cancer carcinogenesis has provided possible opportunities to prevent breast cancer. This paper reviews the issues related to breast cancer chemoprevention including the identification of high-risk groups, biomarkers and potential chemopreventive agents. Trials with tamoxifen have clearly shown that the risk of developing estrogen receptor (ER)-positive breast cancer can be reduced at the later stage of this malignancy. However, there was no beneficial effect on ER-negative cancers. The challenge is to find new agents, which achieve same or better efficacy but with fewer side effects. Raloxifene has similar efficacy to tamoxifen, but leads to more favorable histologic profiles of endometrial tumors and fewer gynecologic symptoms and thrombo-embolic events. Adjuvant trials for contralateral tumors suggest that aromatase inhibitors may be able to prevent up to 70-80% of ER-positive breast cancers. This is currently being investigated in two large prevention trials, the IBIS-II trial using anastrozole and the MAP.3 trial using exemestane. We therefore need to discover novel agents for ER-negative breast cancer.

Approximately up to 200 million new cases of infections caused by viruses of the Flaviviridae family, like hepatitis C virus (HCV), West-Nile virus (WNV), dengue virus (DENV) and Japanese encephalitis virus (JEV) are registered annually. Up to date, there is no effective antiviral therapy directed against Flaviviridae viruses. For the replication of all viruses the intact function of nonstructural proteins is necessary. The blockade of their activities leads to inhibition of the virus propagation. Thus, the nucleotide triphosphatase (NTPase) as well as helicase activities of NS3 and the RNA-dependent RNA polymerase (RdRp) activity of NS5 (or NS5B) appear to be exceptionally attractive targets for antiviral compounds. In this context, a systematic screening of chemical libraries and computational analysis are necessary which will lead to the development of effective inhibitors of the Flaviviridae replication complex. In this review the most promissing methods based on different techniques to quantify the enzymatic activities, like radioactivity, fluorescence, colorimetry as well as a coupled second enzymatic reaction are summarized and discussed. These methods serve as a starting point to establish a high throughput system (HTS) that permits more efficient screenings.

Creatine in its free and phosphorylated form plays an essential role for maintenance and distribution of ATP levels in tissues with high and fluctuating energy demands such as muscle, brain and heart. Alterations in the creatine concentration in these tissues produce marked functional changes. Creatine concentration is largely determined by a specific creatine transporter, a member of the Na+ dependent transporters family, that is localized on the cells' plasma membrane. This transporter is needed to carry creatine into the cells against a high concentration gradient. In recent years the mechanisms regulating the expression and the function of this transporter are being unraveled. Even if our knowledge of this matter is still limited, we have now tools for either stimulating or inhibiting this transporter, tools that may be relevant to several experimental and clinical conditions. This review will examine the data and the tools that are available in relation to the regulation and expression of the creatine transporter. Furthermore, we will briefly review the possible practical relevance of manipulating the creatine transporter activity.

Viral infection in animals and plants is a serious problem worldwide. It causes dramatic losses in health and economy. Many approaches to combat with viral infectious diseases have been intensively investigated. Measures taken against viral infections can either aim for protecting from viral infection or eliminating the viruses after infection. RNA dependent RNA polymerase (RdRp) is a key enzyme for viral replication and found in all positive strand RNA viruses. Disturbing the RdRp activity therefore results in reducing or inhibiting the virus infection. In this review we focus on reviewing different strategies and agents to inhibit the RdRps of different mammalian and plant positive-sense (ss) RNA viruses. The strategies described in this review are mainly focusing on interference of the nucleotides which are the substrates need for RdRp and blocking the RdRp itself by using chemical agents or antibodies specifically binding to the different domains of the RdRps. Moreover using small interfering (si) RNA technology platform to inhibit the RdRp activity is also discussed.