Cloning and characterization of the DNA region responsible for Megacin A-216 production in Bacillus megaterium 216

Upon induction, Bacillus megaterium 216 produces the bacteriocin megacin A-216, which leads to lysis of the producer cell and kills B. megaterium and a few other bacterial species. The DNA region responsible for megacinogeny was cloned in B. megaterium. The nucleotide sequence of a 5,494-bp-long subfragment was determined, and the function of the genes on this fragment was studied by generating deletions and analyzing their effects on MegA phenotypes. An open reading frame (ORF) encoding a 293-amino-acid protein was identified as the gene (megA) coding for megacin A-216. BLAST searches detected sequence similarity between megacin A-216 and proteins with phospholipase A2 activity. Purified biologically active megacin A-216 preparations contained three proteins. Mass spectrometry analysis showed that the largest protein is the full-length translation product of the megA gene, whereas the two shorter proteins are fragments of the long protein created by cleavage between Gln-185 and Val-186. The molecular masses of the three polypeptides are 32,855, 21,018, and 11,855 Da, respectively. Comparison of different megacin preparations suggests that the intact chain as well as the two combined fragments can form biologically active megacin. An ORF located next to the megA gene and encoding a 91-amino-acid protein was shown to be responsible for the relative immunity displayed by the producer strain against megacin A-216. Besides the megA gene, at least two other genes, including a gene encoding a 188-amino-acid protein sharing high sequence similarity with RNA polymerase sigma factors, were shown to be required for induction of megacin A-216 expression.     

Effect of prenatal treatment with methylazoxymethanol on carbachol-, norepinephrine- and glutamate-stimulated phosphoinositide metabolism in the neonatal,young, and adult offspring

Carbachol-, norepinephrine- and glutamate-stimulated phosphoinositide metabolism was investigated in the neonatal, young and adult cerebral cortex slices of rats prenatally treated with methylazoxymethanol (MAM) on gestational day 15 (GD15) or GD19. In rat offspring treated on GD15 there was a significant reduction in the accumulation of [³H]inositol phosphates induced by carbachol and a significant increase in the accumulation of [³H]inositol phosphates induced by norepinephrine on day 7, whereas no changes were observed at the other ages. No significant changes, on the other hand, were observed for glutamate-stimulated phosphoinositide metabolism in GD15 treated rats and for carbachol-, norepinephrine- and glutamate-stimulated phosphoinositide metabolism in animals treated on GD19 at any of the different ages evaluated. These results indicate that treatment with MAM on GD15, which results in a marked microencephaly, causes a marked alteration of muscarinic and ₁-adrenergic receptor-stimulated phosphoinositide metabolism during brain development and that these alterations undergo adaptive changes in the adult brain.     

Myrtucommulone production by a strain of Neofusicoccum australe endophytic in myrtle (Myrtus communis)

Myrtucommulones are acylphloroglucinol compounds reported from myrtle (Myrtus communis) and a few more plant species belonging in the Myrtaceae that have recently attracted the attention of pharmacologists for their anti-oxidant, anti-inflammatory and anti-tumor properties. An endophytic strain of Neofusicoccum australe recovered from a myrtle branch was selected based on the bioactivity of its culture extracts, and found to produce myrtucommulones A and D. A mixture of these compounds induced anti-proliferative effects on the human prostatic cancer cell lines DU145 and PC3, with a IC₅₀ of respectively 4.64 and 3.11 mg/l. Along the lines of recent evidences of the ability by endophytic fungi to produce bioactive compounds originally extracted from their host plants, this is the first report of myrtucommulones as secondary metabolites of an endophytic fungal strain. The availability of a microbial strain to be cultured in vitro may provide access to more substantial amounts of these products for further investigations in view of their possible pharmaceutical use.     

An index of 5-HT synthesis changes during early antidepressant treatment: alpha-[11C]methyl-L-tryptophan PET study

The antidepressant selective serotonin transporter inhibitors (SSRIs) are clinically active after a delay of several weeks. Indeed, the rapid increase of serotonin (5-HT) caused by SSRIs, stimulates the 5-HT(1A) autoreceptors, which exert a negative feedback on the 5-HT neurotransmission. Only when autoreceptors are desensitized, can SSRIs exert their therapeutic activity. The 5-HT(1A) receptor antagonist pindolol has been used to accelerate the clinical effects of antidepressant by preventing the negative feedback. Using the alpha-[(11)C]methyl-L-tryptophan/positron emission tomography (PET), the goal of the present double-blind, randomized study was to compare the changes in alpha-[(11)C]methyl-L-tryptophan trapping, an index of serotonin synthesis, in patients suffering from unipolar depression treated with the SSRI citalopram (20 mg/day) plus placebo versus patients treated with citalopram plus pindol (7.5 mg/day). PET and Hamilton depression rating scale (HDRS-17) were performed at baseline, and after 10 and 24 days of antidepressant treatment. Results show that the combination citalopram plus pindol, compared to citalopram alone shows a more rapid and greater increase of an index of 5-HT synthesis in prefrontal cortex (BA 9). This research is the first human PET study demonstrating that, after 24 days, the combination SSRIs plus pindolol produces a greater increase of the metabolism of serotonin in the prefrontal cortex, an area associated to depressive symptoms.     

Oxidative and nitrative modifications of enkephalins by reactive nitrogen species

The interaction of Leucine-enkephalin (Leu-enkephalin) with reactive nitrogen species has been investigated. Reactive nitrogen species are capable of nitrating and oxidizing Leu-enkephalin. HPLC analysis shows the formation of two major enkephalin derivatives by peroxynitrite. The tyrosine amino-terminal residue of Leu-enkephalin is converted either to 3-nitrotyrosine thus producing nitroenkephalin and to dityrosine by dimerization with the production of an enkephalin dimer. The evidence of the formation of the nitroenkephalin and of the enkephalin dimer—dienkephalin—was achieved by electrospray ionisation mass spectrometry. In addition to peroxynitrite, the methylene blue photosensitized oxidation of enkephalin in the presence of nitrite leads to the formation of the nitrated peptide. Moreover, the nitropeptide can be also obtained by peroxidase-generated nitrogen reactive species.     

Development of a receptor-based 3D-QSAR study for the analysis of MMP2, MMP3, and MMP9 inhibitors

The ability of Gold software to predict the binding disposition of matrix metalloproteinase (MMP) inhibitors was evaluated using MMP3 and MMP8. The best procedure was subsequently employed to dock into MMP2, MMP3 and MMP9 nearly 70 compounds that were tested for their inhibitory activity against the three MMP subtypes. The best binding poses were used as an alignment tool for the development of 3D-QSAR studies. Evaluation of the three resulting 3D-QSAR models allowed us to indicate the ligand properties and residues important for activity and selectivity. MMP2 is an important anticancer drug target, while MMP3 and MMP9 are considered to be anti-targets for tumor pathologies. As such, our results could predict the binding affinities of new MMP2 inhibitors, providing additional information regarding the selectivity against MMP3 and MMP9. Furthermore, this strategy may be used also for the investigation of other MMPs.     

Carbocysteine lysine salt monohydrate (SCMC-LYS) is a selective scavenger of reactive oxygen intermediates (ROIs)

Carbocysteine lysine salt monohydrate (SCMC-Lys) is a well-known mucoactive drug whose therapeutic efficacy is commonly related to the ability of SCMC-Lys to replace fucomucins by sialomucins. The aim of this study was to determine if SCMC-Lys could exert an anti-oxidant action by scavenging reactive oxygen intermediates (ROIs). Our results show that SCMC-Lys proved effective as a selective scavenger of hypochlorous acid (HOCl) and hydroxyl radical (OH.), this effect being related to the reactivity of the SCMC tioether group. The scavenger activity of SCMC-Lys was observed in free cellular system as well as in activated human polymorphonuclear neutrophils (PMNs). SCMC-Lys scavenger activity on HOCl was paralleled by a powerful protection from HOCl-mediated inactivation of alpha1-antitripsin (alpha1-AT) inhibitor, the main serum protease inhibitor. Production of interleukin-(IL-)8, a major mediator of PMN recruitment in inflammatory diseases, is known to be mediated by intracellular OH. SCMC-Lys significantly reduced IL-8 production on stimulated human peripheral blood mononuclear cells (PBMCs) in the same range of concentrations affecting OH. activity. It is concluded that SCMC-Lys could exert, in addition to its mucoactive capacity, an anti-oxidant action, thus contributing to the therapeutic efficacy of SCMC-Lys.     

Docosahexaenoic acid reverts resistance to UV-induced apoptosis in human keratinocytes: involvement of COX-2 and HuR

The dramatic increase in the incidence of nonmelanoma skin cancer over the last decades has been related to the augmented exposure to ultraviolet (UV) radiation (UVR). It is known that apoptosis is induced as a protective mechanism after the acute irradiation of keratinocytes, whereas apoptotic resistance and carcinogenesis may follow the chronic exposure to UVR. We found that not all the human keratinocytes lines studied underwent apoptosis following acute exposure to UVR (10-60 mJ/cm²). Whereas UVR induced apoptosis in the HaCaT cells, NCTC 2544 and nr-HaCaT cells showed apoptosis resistance. The cytokeratin pattern of the apoptosis-resistant cells indicated that they possessed a degree of differentiation lower than that of HaCaT cells. They also showed an enhanced expression of cyclooxygenase-2 (COX-2), an early marker of carcinogenesis in various tissues, including skin. n-3 polyunsaturated fatty acids have drawn increasing interest as nutritional factors with the potential to reduce UVR carcinogenesis, and since they are apoptosis inducers and COX-2 inhibitors in cancer cells, we investigated the ability of n-3 polyunsaturated fatty acids to influence the resistance to UVR-induced apoptosis in keratinocytes. We observed that docosahexaenoic acid (DHA) reverted the resistance of nr-HaCaT cells to UVR-induced apoptosis, increasing the Bax/Bcl-2 ratio and caspase-3 activity, and reduced COX-2 levels by inhibiting the expression of the human antigen R (HuR), a known COX-2 mRNA stabilizer in keratinocytes. The transfection of nr-HaCaT cells with HuR siRNA mimicked the proapoptotic effect of DHA. Overall, our findings further support the role of DHA as a suitable anticarcinogenic factor against nonmelanoma skin cancers.     

Atnoa1 mutant Arabidopsis plants induce compensation mechanisms to reduce the negative effects of the mutation

Alterations in temperature adaptation processes and changes in the content of stress-related compounds, polyamines and salicylic acid were evaluated in Atnoa1 (NO-associated 1) Arabidopsis mutant. The F_v/F_m chlorophyll-a fluorescence induction parameter and the actual quantum yield were significantly lower in the Atnoa1 mutant than in the wild-type. In the wild-type Col-0, the fastest increase in the non-photochemical quenching (NPQ) occurred in plants pre-treated at low temperature (4 °C), while the slowest was in those adapted to 30 °C. The NPQ showed not only a substantially increased level in the light-adapted state, but also more rapid light induction after the dark-adapted state in the Atnoa1 mutant than in the wild-type. The results of freezing tests indicated that both the wild-type and the mutant had better freezing tolerance after cold hardening, since no significant differences were found between the genotypes. The level of putrescine increased substantially, while that of spermine decreased by the end of the cold-hardening (4 °C, 4 d) period. The quantity of spermidine in Atnoa1 was significantly higher than in Col-0, at both control and cold-hardening temperatures. A similar trend was observed for spermine, but only under control conditions. The mutant plants showed substantially higher salicylic acid (SA) contents for both the free and bound forms. This difference was significant not only in the control, but also in the cold-hardened plants. These results suggest that there is a compensation mechanism in Atnoa1 mutant Arabidopsis plants to reduce the negative effects of the mutation. These adaptation processes include the stimulation of photoprotection and alterations in the SA and polyamine compositions.