Synthesis of new camptothecin analogs with improved antitumor activities

Novel hexacyclic camptothecin analogs containing cyclic amidine, urea, or thiourea moiety were designed and synthesized based on the proposed 3D-structure of the topoisomerase I (Topo I)/DNA/camptothecin ternary complex. The analogs were prepared from 9-nitrocamptothecin via 7,9-diaminocamptothecin derivatives as a key intermediate. Among them, 7c exhibited in vivo antitumor activities superior to CPT-11 in human cancer xenograft models in mice at their maximum tolerated doses though its in vitro antiproliferative activity was comparable to SN-38 against corresponding cell lines.     

Aldo-keto Reductase Family 1 Member B10 Promotes Cell Survival by Regulating Lipid Synthesis and Eliminating Carbonyls

Aldo-keto reductase family 1 member B10 (AKR1B10) is primarily expressed in the normal human colon and small intestine but overexpressed in liver and lung cancer. Our previous studies have shown that AKR1B10 mediates the ubiquitin-dependent degradation of acetyl-CoA carboxylase-α. In this study, we demonstrate that AKR1B10 is critical to cell survival. In human colon carcinoma cells (HCT-8) and lung carcinoma cells (NCI-H460), small-interfering RNA-induced AKR1B10 silencing resulted in caspase-3-mediated apoptosis. In these cells, the total and subspecies of cellular lipids, particularly of phospholipids, were decreased by more than 50%, concomitant with 2–3-fold increase in reactive oxygen species, mitochondrial cytochrome c efflux, and caspase-3 cleavage. AKR1B10 silencing also increased the levels of α,β-unsaturated carbonyls, leading to the 2–3-fold increase of cellular lipid peroxides. Supplementing the HCT-8 cells with palmitic acid (80 μm), the end product of fatty acid synthesis, partially rescued the apoptosis induced by AKR1B10 silencing, whereas exposing the HCT-8 cells to epalrestat, an AKR1B10 inhibitor, led to more than 2-fold elevation of the intracellular lipid peroxides, resulting in apoptosis. These data suggest that AKR1B10 affects cell survival through modulating lipid synthesis, mitochondrial function, and oxidative status, as well as carbonyl levels, being an important cell survival protein.Aldo-keto reductase family 1 member B10 (AKR1B10,² also designated aldose reductase-like-1, ARL-1) is primarily expressed in the human colon, small intestine, and adrenal gland, with a low level in the liver (1–3). However, this protein is overexpressed in hepatocellular carcinoma, cervical cancer, lung squamous cell carcinoma, and lung adenocarcinoma in smokers, being a potential diagnostic and/or prognostic marker (1, 2, 4–6).The biological function of AKR1B10 in the intestine and adrenal gland, as well as its role in tumor development and progression, remains unclear. AKR1B10 is a monomeric enzyme that efficiently catalyzes the reduction to corresponding alcohols of a range of aromatic and aliphatic aldehydes and ketones, including highly electrophilic α,β-unsaturated carbonyls and antitumor drugs containing carbonyl groups, with NADPH as a co-enzyme (1, 7–12). The electrophilic carbonyls are constantly produced by lipid peroxidation, particularly in oxidative conditions, and are highly cytotoxic; through interaction with proteins, peptides, and DNA, the carbonyls cause protein dysfunction and DNA damage (breaks and mutations), resulting in mutagenesis, carcinogenesis, or apoptosis (10, 13–19). AKR1B10 also shows strong enzymatic activity toward all-trans-retinal, 9-cis-retinal, and 13-cis-retinal, reducing them to the corresponding retinols, which may regulate the intracellular retinoic acid, a signaling molecule modulating cell proliferation and differentiation (6, 20–23). In lung cancer, AKR1B10 expression is correlated with the patient smoking history and activates procarcinogens in cigarette smoke, such as polycyclic aromatic hydrocarbons, thus involved in lung tumorigenesis (24–26).Recent studies have shown that in breast cancer cells, AKR1B10 associates with acetyl-CoA carboxylase-α (ACCA) and blocks its ubiquitination and proteasome degradation (27). ACCA is a rate-limiting enzyme of de novo synthesis of long chain fatty acids, catalyzing the ATP-dependent carboxylation of acetyl-CoA to form malonyl-CoA (28). Long chain fatty acids are the building blocks of biomembranes and the precursor of lipid second messengers, playing a critical role in cell growth and proliferation (29, 30). Therefore, ACCA activity is tightly regulated by both metabolite-mediated allosteric mechanisms and phosphorylation-dependent mechanisms; the latter are controlled by multiple hormones, such as insulin, glucagon, and growth factors (31–33). ACCA activity is also regulated through physical protein-protein interaction. For instance, breast cancer 1 (BRCA1) protein associates with the ACCA and blocks its Ser⁷⁹ residue from dephosphorylation (34, 35). The AKR1B10-mediated regulation on ACCA stability represents a novel regulatory mechanism, and this current study elucidated the biological significance of this regulation. The results show that AKR1B10 promotes cell survival via modulating lipid synthesis, mitochondrial function and oxidative stress, and carbonyl levels.     

High temperature effects on photosynthate partitioning and sugar metabolism during ear expansion in maize (Zea mays L.) genotypes

Short hot and dry spells before, or during, silking have an inordinately large effect on maize (Zea mays L.; corn) grain yield. New high yielding genotypes could be developed if the mechanism of yield loss were more fully understood and new assays developed. The aim here was to determine the effects of high temperature (35/27 °C) compared to cooler (25/18 °C) temperatures (day/night). Stress was applied for a 14 d-period during reproductive stages prior to silking. Effects on whole plant biomass, ear development, photosynthesis and carbohydrate metabolism were measured in both dent and sweet corn genotypes. Results showed that the whole plant biomass was increased by the high temperature. However, the response varied among plant parts; in leaves and culms weights were slightly increased or stable; cob weights decreased; and other ear parts of dent corn also decreased by high temperature. Photosynthetic activity was not affected by the treatments. The ¹³C export rate from an ear leaf was decreased by the high temperature treatment. The amount of ¹³C partitioning to the ears decreased more than to other plant parts by the high temperature. Within the ear decreases were greatest in the cob than the shank within an ear. Sugar concentrations in both hemicellulose and cellulose fractions of cobs in sweet corn were decreased by high temperature, and the hemicellulose fraction in the shank also decreased. In dent corn there was no reduction of sugar concentration except in the in cellulose fraction, suggesting that synthesis of cell-wall components is impaired by high temperatures. The high temperature treatment promoted the growth of vegetative plant parts but reduced ear expansion, particularly suppression of cob extensibility by impairing hemicellulose and cellulose synthesis through reduction of photosynthate supply. Therefore, plant biomass production was enhanced and grain yield reduced by the high temperature treatment due to effects on sink activity rather than source activity. Heat resistant ear development can be targeted for genetic improvement     

The effect of willow leaf extracts on human leukemic cells in vitro

The young developing leaves of willow (Salix safsaf, Salicaceae) trees have antileukemic activity. After a 24-h incubation in vitro, the crude water extracts of the leaves killed a majority of the blasts of acute myeloid leukemia (AML, 73.8%).     

Essential contribution of monocyte chemoattractant protein-1/C-C chemokine ligand-2 to resolution and repair processes in acute bacterial pneumonia

Neutrophil infiltration is the first step in eradication of bacterial infection, but neutrophils rapidly die after killing bacteria. Subsequent accumulation of macrophage lineage cells, such as alveolar macrophages (AMs), is essential to remove dying neutrophils, which are a source of injurious substances. Macrophage lineage cells can promote tissue repair, by producing potential growth factors including hepatocyte growth factor (HGF). However, it remains elusive which factor activates macrophage in these processes. Intratracheal instillation of Pseudomonas aeruginosa caused neutrophil infiltration in the airspace; subsequently, the numbers of total AMs and neutrophil ingested AMs were increased. Bronchoalveolar lavage (BAL) fluid levels of monocyte chemoattractant protein (MCP)-1/CC chemokine ligand-2 (CCL2), a potent macrophage-activating factor, were increased before the increases in the number of AM ingesting neutrophils and HGF levels in BAL fluid. Immunoreactive MCP-1 proteins were detected in alveolar type II epithelial cells and AMs only after P. aeruginosa infection. The administration of anti-MCP-1/CCL2 Abs reduced the increases in the number of AM-ingesting neutrophils and HGF levels in BAL fluid, and eventually aggravated lung tissue injury. In contrast, the administration of MCP-1/CCL2 enhanced the increases in the number of AM ingesting neutrophils and HGF levels in BAL fluid, and eventually attenuated lung tissue injury. Furthermore, MCP-1/CCL2 enhanced the ingestion of apoptotic neutrophils and HGF production by a mouse macrophage cell line, RAW 267.4, in a dose-dependent manner. Collectively, MCP-1/CCL2 has a crucial role in the resolution and repair processes of acute bacterial pneumonia by enhancing the removal of dying neutrophils and HGF production by AMs.     

Targeting protein homodimerization: a novel drug discovery system

To identify a novel class of antibiotics, we have developed a high-throughput genetic system for targeting the homodimerization (HD system) of histidine kinase (HK), which is essential for a bacterial signal transduction system (two-component system, TCS). By using the HD system, we screened a chemical library and identified a compound, I-8-15 (1-dodecyl-2-isopropylimidazole), that specifically inhibited the dimerization of HK encoded by the YycG gene of Staphylococcus aureus and induced concomitant bacterial cell death. I-8-15 also showed antibacterial activity against MRSA (methicillin-resistant S. aureus) and VRE (vancomycin-resistant Enterococcus faecalis) with MICs at 25 and 50 microg/ml, respectively.     

The effect of phosphorus deficiency on nutrient uptake,nitrogen fixation and photosynthetic rate in mashbean,mungbean and soybean

Phosphorous (P) fertilization is the major mineral nutrient yield determinant among legume crops. However, legume crops vary widely in the ability to take up and use P during deficiency. The aim here was to compare P uptake and translocation, biological nitrogen fixing ability and photosynthetic rate among mashbean (Vigna aconitifolia cv. ‘Mash-88’), mungbean (Vigna radiata cv. ‘Moong-6601’) and soybean (Glycine max L. cv. ‘Tamahomare’) during deficiency in hydroponics. Two treatments, the withdrawal of P from the solution (P-deprivation) and continued P at 160 μM (P sufficient) were effected at the pod initiation stage. Plants were grown for 20 days. Short-term labeling with ³²P showed the uptake and distribution of P into plant parts. Withdrawal of P from the solution reduced biomass, photosynthetic activity, and nitrogen fixing ability in mungbean, and mashbean more than in soybean. P deprivation decreased P accumulation more than N accumulation. The decrease was more severe in mungbean and mashbean than soybean. More P was translocated and distributed into leaves in soybean than in mungbean and mashbean. Leaf P amount was more correlated to leaf area than to photosynthetic rate per unit leaf area among all three legume species. The results indicate that selection for increased efficiency of P utilization and leaf area may be used to improve leguminous crops.     

Competition for phosphorus among plant parts in early and medium-duration cultivars of pigeon pea (Cajanus cajan L.)

Differences in absorption and distribution of phosphorus (P) between early and medium-duration cultivars of pigeon pea grown on nutrient solution at two P concentrations were investigated. Low-P treatment (0.03 ppm) significantly reduced shoot weight, root length and root surface area in both cultivars compared to the control (1.0 ppm), but the reduction was more pronounced in the early than the medium-duration cultivar. Dry-matter accumulation in shoots was slightly higher in the medium-duration than in the early cultivar.³²P-labelled P in the whole plant, P uptake rate and P-absorption ability were higher in the medium than in the early cultivar. At the low-P, however, no differences in these parameters were observed for control plants. In shoots,³²P-labelled P tended to accumulate in the stem of the early cultivar whereas more P was distributed to the leaves and petioles in the medium cultivar. The results suggest that when P supply is limited, medium-duration cultivars accumulate more dry matter through high efficiency of P absorption and distribution P to leaves and petioles.     

In vitro complex formation between bacteriophage φ29 terminal protein and deoxynucleotide

It has previously been shown that the 5′-terminal deoxyadenosine residue of each φ29 DNA strand is linked covalently to the 30,000 dalton terminal protein. When extracts prepared from φ29-infected$\text{Bacillus}\text{subtilis}$ cells are incubated with [α-³²p]dATP, complexes consisting of the nucleotide covalently linked to a 30,000 dalton protein can be detected. The formation of this complex requires the presence of φ29 DNA containing the bound 30,000 dalton terminal protein and Mg⁺⁺. When uninfected cell extracts were used, there was no complex formation. When [α-³²p]dCTP was used in place of [α-³²p]dATP, no complex was formed. DNA-protein templates prepared from φ29 related phages, φ15, Nf, M2Y and GA-1, also supported the complex formation in various degrees. These results support the hypothesis that the terminal protein serves as a primer for the initiation of φ29 DNA replication.