Synthesis and antibacterial activities of new quinolone derivatives utilizing 1-azabicyclo[1.1.0]butane

The ring-opening reactions of 1-azabicyclo[1.1.0]butane 3 with thiols 6a-f gave 3-sulfenylazetidine derivatives 7a-f in 50-92% yields. Treatment of 3 with aromatic amines 11a-e and dibenzylamine 11f in the presence of Mg(ClO(4))(2) afforded the corresponding 3-aminoazetidine derivatives 12a-f in 24-53% yields. These azetidine derivatives were introduced into the C7 position of a quinolone nucleus 8 to afford the corresponding fluoroquinolones 9a-f and 13a-f in 21-83% yields. Some of them exhibited superior antibacterial activity against quinolone-susceptible MRSA in comparison with clinically used fluoroquinolones, such as levofloxacin, ciprofloxacin, and gatifloxacin.     

Involvement of p38alpha in kainate-induced seizure and neuronal cell damage

We investigated how p38alpha mitogen-activated protein kinase (p38) is related to kainate-induced epilepsy and neuronal damages, by using the mice with a single copy disruption of the p38 alpha gene (p38alpha(+/-)). Mortality rate and seizure score of p38alpha(+/-) mice administered with kainate were significantly reduced compared with the case of wild-type (WT) mice. This was clearly supported by the electroencephalography data in which kainate-induced seizure duration and frequency in the brain of p38alpha(+/-) mice were significantly suppressed compared to those of WT mice. As a consequence of seizure, kainate induced delayed neuronal damages in parallel with astrocytic growth in the hippocampus and ectopic innervation of the mossy fibers into the stratum oriens in the CA3 region of hippocampus in WT mice, whose changes were moderate in p38alpha(+/-) mice. Likewise, kainate-induced phosphorylation of calcium/calmodulin-dependent kinase II in the hippocampus of p38alpha (+/-) mice was significantly decreased compared to that of WT mice. These results suggest that p38alpha signaling pathway plays an important role in epileptic seizure and excitotoxicity.     

Optimisation of a novel series of selective CNS penetrant CB(2) agonists

A series of benzimidazole CB₂ receptor agonists were prepared and their properties investigated. Optimisation of the three benzimidazole substituents led to the identification of compound 23, a potent CB₂ full agonist (EC₅₀ 2.7 nM) with excellent selectivity over the CB₁ receptor (>3000-fold). Compound 23 demonstrated good CNS penetration in rat. Further optimisation led to the identification of compound 34 with improved selectivity over hERG and excellent CNS penetration in rat.     

Multiple translocation of the AVR-Pita effector gene among chromosomes of the rice blast fungus Magnaporthe oryzae and related species

Magnaporthe oryzae is the causal agent of rice blast disease, a devastating problem worldwide. This fungus has caused breakdown of resistance conferred by newly developed commercial cultivars. To address how the rice blast fungus adapts itself to new resistance genes so quickly, we examined chromosomal locations of AVR-Pita, a subtelomeric gene family corresponding to the Pita resistance gene, in various isolates of M. oryzae (including wheat and millet pathogens) and its related species. We found that AVR-Pita (AVR-Pita1 and AVR-Pita2) is highly variable in its genome location, occurring in chromosomes 1, 3, 4, 5, 6, 7, and supernumerary chromosomes, particularly in rice-infecting isolates. When expressed in M. oryzae, most of the AVR-Pita homologs could elicit Pita-mediated resistance, even those from non-rice isolates. AVR-Pita was flanked by a retrotransposon, which presumably contributed to its multiple translocation across the genome. On the other hand, family member AVR-Pita3, which lacks avirulence activity, was stably located on chromosome 7 in a vast majority of isolates. These results suggest that the diversification in genome location of AVR-Pita in the rice isolates is a consequence of recognition by Pita in rice. We propose a model that the multiple translocation of AVR-Pita may be associated with its frequent loss and recovery mediated by its transfer among individuals in asexual populations. This model implies that the high mobility of AVR-Pita is a key mechanism accounting for the rapid adaptation toward Pita. Dynamic adaptation of some fungal plant pathogens may be achieved by deletion and recovery of avirulence genes using a population as a unit of adaptation.