Electrochemical adsorption studies of urea on copper surface in alkaline medium

The inhibitive action of urea on the corrosion behavior of copper was investigated in borate buffer pH (8.4) by means of cyclic voltammetry and electrochemical impedance spectroscopy (EIS). A consistent trend of increase in inhibition efficiency was observed as a function of concentration of urea. The adsorption of urea on copper surface was found to obey the Langmuir adsorption isotherm with ΔG = −35.2 kJ/mole and adsorption constant K = 2.7 × 10⁴ dm³/mole. Impedance spectroscopic measurements confirmed that charge transfer resistance increases in presence of urea upon increasing its concentration.     

Ferrochelatase, a novel target for photodynamic therapy of cancer.

This study was designed to investigate the hypothesis that the inhibition of ferrochelatase will cause in situ build up of high concentrations of protoporphyrin-IX which may act as a putative agent for photodestruction of cancer cells. The parenteral administration of lead acetate, a known inhibitor of ferrochelatase, to mice bearing cutaneous tumors (papillomas and carcinomas) caused a six-fold enhancement in the concentration of protoporphyrin-IX in tumors within a period of one month. Forty-eight hours after the second injection of lead, mice were exposed to visible light, at a light dose of about nine kilo lux for a period of one hour (in four sittings of fifteen minutes each keeping a gap of ten minutes between two exposures). A significant reduction in tumor size was observed starting as early as day one following the treatment. Continuous treatment for six consecutive days resulted in almost complete ablation of the tumor mass in most of the animals. Complete regression of the tumors was observed at two to three days following the first exposure. Our observations on in situ accumulation of protoporphyrin-IX by heme-biosynthesis inhibition represent a novel method for photodynamic therapy of cancer cells. It is important to emphasize that lead is a fairly toxic agent and developing a non-toxic agent is one of our future goals.     

D-Limonene modulates inflammation, oxidative stress and Ras-ERK pathway to inhibit murine skin tumorigenesis

D-Limonene, a common monoterepene has been shown to have antiproliferative, apoptosis-inducing and chemopreventive effects. In the present study, we have investigated the effects of D-limonene on the growth of 7,12-dimethylbenz[a]anthracene (DMBA)-initiated and 12-O-tetradecanoylphorbol-13-acetate (TPA)-promoted skin tumor development. We found that D-limonene (50 and 100 mg/kg body weight) treatments to the mouse skin significantly reduced the TPA-induced (a) edema and hyperplasia (p < 0.001); (b) expression of cyclooxygenase-2; (c) ornithine decarboxylase activity (p < 0.001); and (d) [(3)H] thymidine incorporation into DNA (p < 0.001). In addition, treatment of D-limonene effectively restored the level of reduced glutathione, glutathione peroxidase, glutathione reductase, glutathione S-transferase, catalase and malondialdehyde production in TPA-treated mouse skin. In a two-stage skin tumorigenesis study, D-limonene significantly reduced the tumor burden (p < 0.005) and tumor incidence as compared to DMBA/TPA-treated mice. D-Limonene treatment also extended the latency period of tumor development from 4 to 9 weeks. D-Limonene treatment decreased the expression level of Ras, Raf and phosphorylation of extracellular signal-regulated protein kinase 1/2 in DMBA/TPA-induced tumors. A decrease in the expression of Bcl-2 and an increase in Bax expression were also observed in tumor tissues of mice treated with D-limonene. Taken together, our findings suggest that D-limonene may exert its chemopreventive activity through the inhibition of inflammation, oxidative stress and Ras-signaling as well as the induction of pro-apoptotic state during TPA-mediated promotion of DMBA-induced skin cancer in mouse model.     

Phosphorylation-independent dual-site binding of the FHA domain of KIF13 mediates phosphoinositide transport via centaurin alpha1

Phosphatidylinositol 3,4,5-triphosphate (PIP3) plays a key role in neuronal polarization and axon formation. PIP3-containing vesicles are transported to axon tips by the kinesin KIF13B via an adaptor protein, centaurin α1 (CENTA1). KIF13B interacts with CENTA1 through its forkhead-associated (FHA) domain. We solved the crystal structures of CENTA1 in ligand-free, KIF13B-FHA domain-bound, and PIP3 head group (IP4)-bound conformations, and the CENTA1/KIF13B-FHA/IP4 ternary complex. The first pleckstrin homology (PH) domain of CENTA1 specifically binds to PIP3, while the second binds to both PIP3 and phosphatidylinositol 3,4-biphosphate (PI(3,4)P(2)). The FHA domain of KIF13B interacts with the PH1 domain of one CENTA1 molecule and the ArfGAP domain of a second CENTA1 molecule in a threonine phosphorylation-independent fashion. We propose that full-length KIF13B and CENTA1 form heterotetramers that can bind four phosphoinositide molecules in the vesicle and transport it along the microtubule.     

Novel antimalarial drug targets: hope for new antimalarial drugs

Malaria is a major global threat, that results in more than 2 million deaths each year. The treatment of malaria is becoming extremely difficult due to the emergence of drug-resistant parasites, the absence of an effective vaccine, and the spread of insecticide-resistant vectors. Thus, malarial therapy needs new chemotherapeutic approaches leading to the search for new drug targets. Here, we discuss different approaches to identifying novel antimalarial drug targets. We have also given due attention to the existing validated targets with a view to develop novel, rationally designed lead molecules. Some of the important parasite proteins are claimed to be the targets; however, further in vitro or in vivo structure-function studies of such proteins are crucial to validate these proteins as suitable targets. The interactome analysis among apicoplast, mitochondrion and genomic DNA will also be useful in identifying vital pathways or proteins regulating critical pathways for parasite growth and survival, and could be attractive targets. Molecules responsible for parasite invasion to host erythrocytes and ion channels of infected erythrocytes, essential for intra-erythrocyte survival and stage progression of parasites are also becoming attractive targets. This review will discuss and highlight the current understanding regarding the potential antimalarial drug targets, which could be utilized to develop novel antimalarials.     

Inhibition of benzoyl peroxide-mediated tumor promotion in 7,12-dimethylbenz(a)anthracene-initiated skin of Sencar mice by antioxidants nordihydroguaiaretic acid and diallyl sulfide

Benzoyl peroxide (BPO), a free radical generating compound, is widely used in topical medications prescribed for acne vulgaris and in cosmetic products. It has been shown to possess tumor-promoting activity in murine skin initiated with chemical carcinogens such as 7,12-dimethylbenz(a)anthracene (DMBA). In the present study we assessed the effect of the antioxidants nordihydroguaiaretic acid (NDGA) and diallyl sulfide (DAS) against BPO-mediated tumor promotion in murine skin. Pretreatment of Sencar mice with NDGA and DAS prior to skin application of BPO resulted in a time- and dose-dependent inhibition of epidermal ODC induction caused by BPO. Tumor initiation was achieved by a single topical application of DMBA (10 micrograms/animal) to Sencar mice. Ten days later tumor promotion was begun by twice-weekly topical application of BPO (20 mg/animal). The anticarcinogenic effects of NDGA (25 mumol/mouse) and DAS (20 mumol/mouse) were evaluated by administering these agents topically 60 min prior to each BPO application. After 26 weeks on test, the number of benign papillomas/mouse were 0.10 +/- 0.07 and 2.15 +/- 0.30 in the NDGA and DAS pretreated group of animals as compared to 4.40 +/- 1.14 in animals receiving BPO alone. After 51 weeks on test, the number of squamous cell carcinomas/mouse were 0.00 +/- 0.00, 0.35 +/- 0.10 in the NDGA and DAS pretreated group of animals as compared to 0.65 +/- 0.12 in animals receiving BPO alone. From these data we suggest that the antioxidants NDGA and DAS can abrogate the tumor-promoting effects of BPO in murine skin and that NDGA is substantially more effective than DAS in this regard.     

Designing zonal organization into tissue-engineered cartilage

Cartilage tissue engineering strategies generally result in homogeneous tissue structures with little resemblance to the native zonal organization of articular cartilage. The objective of this study was to use bilayered photopolymerized hydrogels to organize zone-specific chondrocytes in a stratified framework and study the effects of this three-dimensional coculture system on the properties of the engineered tissue. Superficial and deep zone chondrocytes from bovine articular cartilage were photoencapsulated in separate hydrogels as well as in adjacent layers of a bilayered hydrogel. Histology, mechanical testing, and biochemical analysis was performed after culturing in vitro. To evaluate the influence of coculture on tissue properties, the layers were separated and compared to constructs containing only superficial or deep cells. In the bilayered constructs, deep cells produced more collagen and proteoglycan than superficial cells, resulting in cartilage tissue with stratified, heterogeneous properties. Deep cells cocultured with superficial cells in the bilayered system demonstrated reduced proliferation and increased matrix synthesis compared to deep cells cultured alone. The bilayered constructs demonstrated greater shear and compressive strength than homogenous cell constructs. This study demonstrated that interactions between zone-specific chondrocytes affect the biological and mechanical properties of engineered cartilage. Strategies aimed to structurally organize zone-specific cells and encourage heterotypic cell interactions may contribute to improved functional properties of engineered cartilage.     

Roles of catalase and hydrogen peroxide in green tea polyphenol-induced chemopreventive effects

The green tea polyphenol (-)-epigallocatechin-3-gallate (EGCG) possesses promising anticancer potential. Although in vivo studies unveiled the metabolic routes and pharmacokinetics of EGCG and showed no adverse effects, in vitro studies at high concentrations demonstrated oxidative stress. EGCG causes differential oxidative environments in tumor versus normal epithelial cells, but the roles that EGCG, hydrogen peroxide (H2O2), and intracellular catalase play in the epithelial system are largely unknown. The current study employed enzyme activity assays, reactive oxygen species quantification, and immunoblotting to investigate whether EGCG-induced differential effects correlate with levels of key antioxidant enzymes and H2O2. It was found that normal human keratinocytes with high catalase activity are least susceptible to H2O2, whereas H2O2 caused significant cytotoxicity in oral carcinoma cell lines. However, the EGCG-induced differential effects could not be duplicated by H2O2 alone. The addition of exogenous catalase failed to completely prevent the EGCG-induced cytotoxicity and rescue the EGCG-induced growth arrest in the tumor cells. The antioxidant N-acetyl-L-cysteine rescued the tumor cells from H2O2-induced damage only, but not from EGCG-induced mitochondrial damage. Finally, alterations in catalase or superoxide dismutase activities were not observed upon EGCG exposure. In conclusion, although endogenous catalase may play a role in response to H2O2-induced cytotoxicity, the EGCG-induced cytotoxic effects on tumor cells mainly result from sources other than H2O2.