Role of autophagy in temozolomide-induced cytotoxicity for malignant glioma cells

Autophagy is originally named as a process of protein recycling. It begins with sequestering cytoplasmic organelles in a membrane vacuole called autophagosome. Autophagosomes then fuse with lysosomes, where the materials inside are degraded and recycled. To date, however, little is known about the role of autophagy in cancer therapy. In this study, we present that temozolomide (TMZ), a new alkylating agent, inhibited the viability of malignant glioma cells in a dose-dependent manner and induced G2/M arrest. At a clinically achievable dose (100 microM), TMZ induced autophagy, but not apoptosis in malignant glioma cells. After the treatment with TMZ, microtubule-associated protein light-chain 3 (LC3), a mammalian homologue of Apg8p/Aut7p essential for amino-acid starvation-induced autophagy in yeast, was recruited on autophagosome membranes. When autophagy was prevented at an early stage by 3-methyladenine, a phosphatidylinositol 3-phosphate kinase inhibitor, not only the characteristic pattern of LC3 localization, but also the antitumor effect of TMZ was suppressed. On the other hand, bafilomycin A1, a specific inhibitor of vacuolar type H(+)-ATPase, that prevents autophagy at a late stage by inhibiting fusion between autophagosomes and lysosomes, sensitized tumor cells to TMZ by inducing apoptosis through activation of caspase-3 with mitochondrial and lysosomal membrane permeabilization, while LC3 localization pattern stayed the same. These results indicate that TMZ induces autophagy in malignant glioma cells. Application of an autophagy inhibitor that works after the association of LC3 with autophagosome membrane, such as bafilomycin A1, is expected to enhance the cytotoxicity of TMZ for malignant gliomas.     

Morphological characteristics of the Pterodoras granulosus digestive tube (Valenciennes, 1821) (Osteichthyes,Doradidae)

Little is known about the digestive tube (DT) morphology of the fish Pterodoras granulosus. Therefore, macro‐, meso‐ and microscopic aspects of 15 P. granulosus DTs were analysed. The muscular layer was composed of striated skeletal muscle in the oesophagus and smooth muscle in the other segments. The epithelium progressed from a stratified pavement in the oesophagus to a simple column in the other segments, with a flat striated border in the intestine. A large number of mucus‐secreting periodic acid‐Schiff (PAS)‐positive cells were observed in the oesophagus. In the stomach, the number of glands in the region decreased towards the cardiac–fundic region, and none were found in the pylorus. The intestine showed an epithelium with absorption cells and an increasing number of PAS‐positive caliciform cells towards the distal region. Tests showed that the oesophagus is adapted for passing and preparing food for the chemical digestion that occurs in the stomach, which also has storage functions without grinding action. The proximal intestinal region was consistent with fat absorption, and the medium region, with the absorption of other nutrients. The distal region was short and consistent with a role in absorption for osmoregulation as well as in the formation, storage and disposal of faeces.     

Downregulation of melanocortin-4 receptor during refeeding and its modulation by adrenalectomy in rats

Melanocortin system and corticotropin releasing hormone (CRH) are implicated in the control of feeding behavior. Besides its anorexigenic effect on food intake, CRH is one of the most important regulators of hypothalamic-pituitary-adrenal (HPA) axis activity. Therefore, there could be an interplay between HPA axis activity and melanocortin system. We investigated the expression of melanocortin-4 receptor (MC4-R) mRNA in the hypothalamus of rats after 14 days of food restriction or after a fasting-refeeding regimen, in sham or adrenalectomized rats. Male Wistar rats were subjected to free access to food or food ingestion restricted for 2 h a day (8-10 AM) during 14 d, when plasma corticosterone, ACTH, insulin, leptin concentrations, and MC4-R mRNA expression were determined before and after refeeding. Another set of rats was fasted for 48 h, followed by refeeding during 2 or 4 h on the seventh day after adrenalectomy (ADX) or sham surgery. On the day of the experiment, rats were anesthetized and perfused and the brain processed for MC4-R mRNA by in situ hybridization. Long-term reduction of food intake, either secondary to food restriction or adrenalectomy, reduced body weight gain and also leptin and insulin plasma concentrations. Food ingestion reduced MC4-R expression in the paraventricular nucleus in naive rats subjected to food restriction and also in sham rats fasted for 48 h. However, after ADX, MC4-R expression was not changed by refeeding. In conclusion, the present data indicate that MC4-R expression is downregulated by food ingestion and this response could be modulated by glucocorticoid withdrawal.     

Improved nutrient medium for biomass and valepotriate production in extended period stock cultures of Valeriana glechomifolia

Valeriana glechomifolia, a southern Brazilian endemic species commonly known as Valerian, accumulates the bioactive terpene derivatives valepotriates in all of its organs. In vitro growth of V. glechomifolia on solid Murashige and Skoog (MS) without phytohormones at full, 75% (MS 75), or on a modified formulation (M Δ) was compared in stock cultures kept for up to 9 mo. without subculture. Changes in biomass accumulation, development of roots and shoots, and the production of the valepotriates acevaltrate, didrovaltrate, and valtrate were monthly evaluated. The highest biomass accumulation and root development was observed in plants grown on M Δ, whereas better leaf development was detected in M-Δ- and MS-medium-grown plants after 8 and 9 mo. of culture, respectively. Maximal didrovaltrate and valtrate yields were observed in M-Δ-grown plants harvested after 5 and 6 mo. of culture, respectively, whereas acevaltrate concentration was highest on M-Δ- and MS-75-grown plants after 7 mo. of culture. Plants grown for 6 mo. without subculture in M Δ were successfully propagated, showing stable growth and valepotriate yields three- to sixfold higher that those observed in field-grown plants. The results showed a positive effect of combined moderate reduction in salt concentration and increases in selected micronutrients and myo-inositol amounts on both growth and valepotriate yields of extended period stock cultures of V. glechomifolia.     

Spectroscopic properties of PSI-IsiA supercomplexes from the cyanobacterium Synechococcus PCC 7942

The cyanobacterium Synechococcus PCC 7942 grown under iron starvation assembles a supercomplex consisting of a trimeric Photosystem I (PSI) complex encircled by a ring of 18 CP43' or IsiA light-harvesting complexes [Nature 412 (2001) 745]. Here we present a spectroscopic characterization by temperature-dependent absorption and fluorescence spectroscopy, site-selective fluorescence spectroscopy at 5 K, and circular dichroism of isolated PSI-IsiA, PSI and IsiA complexes from this cyanobacterium grown under iron starvation. The results suggest that the IsiA ring increases the absorption cross-section of PSI by about 100%. Each IsiA subunit binds about 16-17 chlorophyll a (Chl a) molecules and serves as an efficient antenna for PSI. Each of the monomers of the trimeric PSI complex contains two red chlorophylls, which presumably give rise to one exciton-coupled dimer and at 5 K absorb and fluoresce at 703 and 713 nm, respectively. The spectral properties of these C-703 chlorophylls are not affected by the presence of the IsiA antenna ring. The spectroscopic properties of the purified IsiA complexes are similar to those of the related CP43 complex from plants, except that the characteristic narrow absorption band of CP43 at 682.5 nm is missing in IsiA.     

A Pyrosequencing assay for rapid recognition of SNPs in Mycobacterium tuberculosis embB306 region

Ethambutol (EMB) is in use worldwide as a first-line anti-tuberculosis drug and substitutions in codon 306 of the embB gene are the most common mutations found in EMB resistant Mycobacterium tuberculosis (MTB) strains. Pyrosequencing is a real time sequencing method able to rapidly detect mutations in a large number of samples. Using this technique we analyzed, in parallel with conventional sequencing, a 24 bp region of the embB gene of 28 MTB clinical isolates. Pyrosequencing efficiently identified all embB306 mutations, detecting three different single-base substitutions leading to 2 amino acid changes (Met to Val or Ile). Mutated embB alleles were detected in 2 multidrug-resistant (MDR) EMB-susceptible strains. Overall, our results demonstrated that the Pyrosequencing method efficiently recognizes mutations in embB in a very short time and represents a valid molecular method to detect mutations in the MTB embB306 region.     

Structure-affinity relationship studies on arylpiperazine derivatives related to quipazine as serotonin transporter ligands. Molecular basis of the selectivity SERT/5HT3 receptor

A series of quipazine derivatives, previously synthesized to probe the 5-HT(3) receptor, was evaluated for its potential interaction with serotonin transporter (SERT). Some of them show nanomolar affinity for the rodent SERT comparable to or slightly higher than quipazine or N-methylquipazine. Subsequently a candidate was selected on the basis of its SERT affinity and submitted to a molecular manipulation of the basic moiety. The structure-affinity relationships obtained provided information on the role of the fused benzene ring of quipazine in the interaction with the SERT binding site and on the stereoelectronic requirements for the interaction of both the heteroaromatic component and the basic moiety. Moreover, the comparison of the structure-affinity relationships obtained in the present work with those concerning the interaction of these heteroarylpiperazine derivatives with 5-HT3 receptor suggested some molecular determinants of the selectivity SERT/5HT3 receptor.     

Characterization of S3Pvac Anti-Cysticercosis Vaccine Components: Implications for the Development of an Anti-Cestodiasis Vaccine

Background

Cysticercosis and hydatidosis seriously affect human health and are responsible for considerable economic loss in animal husbandry in non-developed and developed countries. S3Pvac and EG95 are the only field trial-tested vaccine candidates against cysticercosis and hydatidosis, respectively. S3Pvac is composed of three peptides (KETc1, GK1 and KETc12), originally identified in a Taenia crassiceps cDNA library. S3Pvac synthetically and recombinantly expressed is effective against experimentally and naturally acquired cysticercosis.

Methodology/Principal Findings

In this study, the homologous sequences of two of the S3Pvac peptides, GK1 and KETc1, were identified and further characterized in Taenia crassiceps WFU, Taenia solium, Taenia saginata, Echinococcus granulosus and Echinococcus multilocularis. Comparisons of the nucleotide and amino acid sequences coding for KETc1 and GK1 revealed significant homologies in these species. The predicted secondary structure of GK1 is almost identical between the species, while some differences were observed in the C terminal region of KETc1 according to 3D modeling. A KETc1 variant with a deletion of three C-terminal amino acids protected to the same extent against experimental murine cysticercosis as the entire peptide. On the contrary, immunization with the truncated GK1 failed to induce protection. Immunolocalization studies revealed the non stage-specificity of the two S3Pvac epitopes and their persistence in the larval tegument of all species and in Taenia adult tapeworms.

Conclusions/Significance

These results indicate that GK1 and KETc1 may be considered candidates to be included in the formulation of a multivalent and multistage vaccine against these cestodiases because of their enhancing effects on other available vaccine candidates.