Positive and Negative Selective Allosteric Modulators of α5 GABAA Receptors: Effects on Emotionality, Motivation, and Motor Function in the 5xFAD Model of Alzheimer's Disease

BACKGROUND

Positive and negative allosteric modulators of α5 GABAA receptors (PAM and NAM, respectively) are worthy of investigation as putative treatments of Alzheimer's disease (AD). However, their potential to modify a dynamic range of behaviors in AD models needs to be systematically examined.

OBJECTIVE

The study aimed to assess effects of MP-III-022 as PAM and PWZ-029 as NAM on emotional reactivity, motivation, and motor function, as well as on gene expression of GABRA2, GABRA3 and GABRA5 subunit of GABAA receptors in prefrontal cortex (PFC) and hippocampus (HC) in 5xFAD mice, as an early-onset transgenic AD model.

METHODS

The 6-month-old 5xFAD transgenic and non-transgenic mice of both genders underwent a battery of reflexes and behavioral tests (sensorimotor tests, elevated plus maze, and open field) after 10-day intraperitoneal treatment with MP-III-022, PWZ-029, or solvent. The behavioral battery was followed by qPCR analysis of gene expression.

RESULTS

MP-III-022 induced a decline in motor function, while PWZ-029 further decreased emotionality of transgenic males, as compared to the transgenic control. No interfering effects on non-cognitive behavior were observed in female mice. In HC, both treatments reversed reciprocal GABRA2 and GABRA3 changes in transgenic females. In PFC, MP-III-022 decreased GABRA5 in both genders, while PWZ-029 increased GABRA2 in male transgenic animals.

CONCLUSION

Gender-dependent protracted effects of PAMs and NAMs in AD model, with detrimental impact on motor capabilities of PAM, and attenuation of emotionality elicited by NAM in transgenic males, were revealed. This favors future research of α5 GABAA receptor modulation in females as more promising.

Trigeminal neuropathic pain development and maintenance in rats are suppressed by a positive modulator of α6 GABAA receptors

γ-Aminobutyric acid type A (GABAA ) receptors containing the α6 subunit are located in trigeminal ganglia, and their reduction by small interfering RNA increases inflammatory temporomandibular and myofascial pain in rats. We thus hypothesized that enhancing their activity may help in neuropathic syndromes originating from the trigeminal system. Here, we performed a detailed electrophysiological and pharmacokinetic analysis of two recently developed deuterated structurally similar pyrazoloquinolinone compounds. DK-I-56-1 at concentrations below 1 µM enhanced γ-aminobutyric acid (GABA) currents at recombinant rat α6β3γ2, α6β3δ and α6β3 receptors, whereas it was inactive at most GABAA receptor subtypes containing other α subunits. DK-I-87-1 at concentrations below 1 µM was inactive at α6-containing receptors and only weakly modulated other GABAA receptors investigated. Both plasma and brain tissue kinetics of DK-I-56-1 were relatively slow, with half-lives of 6 and 13 hr, respectively, enabling the persistence of estimated free brain concentrations in the range 10-300 nM throughout a 24-hr period. Results obtained in two protocols of chronic constriction injury of the infraorbital nerve in rats dosed intraperitoneally with DK-I-56-1 during 14 days after surgery or with DK-I-56-1 or DK-I-87-1 during 14 days after trigeminal neuropathy were already established, demonstrated that DK-I-56-1 but not DK-I-87-1 significantly reduced the hypersensitivity response to von Frey filaments. SIGNIFICANCE: Neuropathic pain induced by trigeminal nerve damage is poorly controlled by current treatments. DK-I-56-1 that positively modulates α6 GABAA receptors is appropriate for repeated administration and thus may represent a novel treatment option against the development and maintenance of trigeminal neuropathic pain.

Genetic relatedness and recombination analysis of Allorhizobium vitis strains associated with grapevine crown gall outbreaks in Europe

AIMS

To analyse genetic diversity and epidemiological relationships among 54 strains of Allorhizobium vitis isolated in Europe during an 8-year period and to assess the relative contribution of mutation and recombination in shaping their diversity.

METHODS AND RESULTS

By using random amplified polymorphic DNA (RAPD) PCR, strains studied were distributed into 12 genetic groups. Sequence analysis of dnaK, gyrB and recA housekeeping genes was employed to characterize a representative subcollection of 28 strains. A total of 15 different haplotypes were found. Nucleotide sequence analysis suggested the presence of recombination events in A. vitis, particularly affecting dnaK locus. Although prevalence of mutation over recombination was found, impact of recombination was about two times greater than mutation in the evolution of the housekeeping genes analysed.

CONCLUSIONS

The RAPD analysis indicated high degree of genetic diversity among the strains. However, the most abundant RAPD group was composed of 35 strains, which could lead to the conclusion that they share a common origin and were distributed by the movement of infected grapevine planting material as a most common way of crossing long distances. Furthermore, it seems that recombination is acting as an important driving force in the evolution of A. vitis. As no substantial evidence of recombination was detected within recA gene fragment, this phylogenetic marker could be reliable to characterize phylogenetic relationships among A. vitis strains.

SIGNIFICANCE AND IMPACT OF THE STUDY

We demonstrated clear epidemiological relationship between majority of strains studied, suggesting a need for more stringent phytosanitary measures in international trade. Moreover, this is the first study to report recombination in A. vitis.

First Report of Broccoli Soft Rot Caused by Pectobacterium carotovorum subsp. carotovorum in Serbia

In September 2012, soft rot symptoms on broccoli (Brassica oleracea L. var. italica Plenck) were observed in several commercial fields in the western part of Serbia. Following the first harvest, water-soaked areas developed on broccoli stem tissue and progressed into soft rot decay of entire plants. The incidence of disease was approximately 30%. In Serbia, broccoli is grown on smaller fields compared to other vegetables, but its production and consumption increased significantly in recent years. From the diseased tissue, shiny, grayish white, round colonies were isolated on nutrient agar. Six non-fluorescent, gram-negative, facultative anaerobic, oxidase-negative, and catalase-positive bacterial strains were chosen for further identification. All strains caused soft rot on potato and carrot slices and did not induce hypersensitive reaction on tobacco leaves. They grew at 37°C and in yeast salts broth medium containing 5% NaCl (2), did not produce acid from α-methyl glucoside, but utilized lactose and trehalose, and did not produce indole or lecitinase. Investigated strains formed light red, 1.5-mm-diameter colonies on Logan's medium (2), and did not produce blue pigmented indigoidine on glucose yeast calcium carbonate agar (2) nor "fried egg" colonies on potato dextrose agar. Based on biochemical and physiological characteristics (1) and ITS-PCR and ITS-RFLP analysis (4), the strains were identified as Pectobacterium carotovorum subsp. carotovorum. The 16S rRNA gene sequence from two strains (GenBank KC527051 and KC527052) showed 100% identity with sequences of P. carotovorum subsp. carotovorum previously deposited in GenBank (3). Pathogenicity of the strains was confirmed by inoculation of broccoli head tissue fragments. Three florets per strain were inoculated by pricking the petals with a syringe and hypodermic needle and depositing a droplet of bacterial suspension (approx. 1 × 10⁸ CFU/ml) at the point of inoculation. Sterile distilled water was used as a negative control. Inoculated florets were placed in a sealed plastic container and incubated in high humidity conditions at 28°C. Tissue discoloration and soft rot developed around the inoculation point within 48 to 72 h. No symptoms developed on control florets. Identity of bacterial strains reisolated from inoculated plant tissues was confirmed by ITS-PCR using G1/L1 primers followed by digestion of PCR products with Rsa I restriction enzyme (4). In Serbia, P. carotovorum subsp. carotovorum has been isolated from potato, some vegetable crops, and ornamentals, but not from broccoli until now. References: (1) S. H. De Boer and A. Kelman. Page 56 in: Laboratory Guide for Identification of Plant Pathogenic Bacteria, 3rd ed. N. W. Schaad et al., eds. The American Phytopathological Society, St. Paul, MN, 2001. (2) P. C. Fahy and A. C. Hayward. Page 337 in: Plant Bacterial Diseases: A Diagnostic Guide. P. C. Fahy and G. J. Persley eds. Academic Press, New York, 1983. (3) S. Nabhan et al. J. Appl. Microbiol. 113: 904, 2012. (4) I. K. Toth et. al. Appl. Environ. Microbiol. 67:4070, 2001.

First Report of Brown Rot Caused by Monilinia fructicola on Stored Apple in Serbia

Monilinia fructicola (G. Winter) Honey is a causal agent of brown rot of stone fruits, occasionally affecting pome fruits as well. The pathogen is commonly present in North and South America, Oceania, and Asia, but listed as a quarantine organism in Europe (4). After its first discovery in France in 2001, its occurrence has been reported in Germany, Hungary, Italy, Poland, Romania, Slovenia, Spain, Switzerland, Austria, and the Slovak Republic (1). In February 2011, during a survey for fungal postharvest pathogens in cold storage conditions, apple fruits (Malus domestica Borkh.) grown and stored in the Grocka Region, Serbia, were collected. All pathogens from symptomatic fruits were isolated on potato dextrose agar (PDA). One isolate from apple fruit cv. Golden Delicious with brown rot symptoms was identified as M. fructicola based on morphological and molecular characters. Colonies cultivated on PDA at 22°C in darkness were colorless, but later became grayish, developing mass of spores in concentric rings. Colony margins were even. Conidia were one-celled, limoniform, hyaline, measured 12.19 to 17.37 (mean 13.8) × 8.62 to 11.43 μm (mean 9.9), and were produced in branched monilioid chains (3). Morphological identification was confirmed by PCR (2) using genomic DNA extracted from the mycelium of pure culture, and an amplified product of 535 bp, specific for the species M. fructicola, was obtained. Sequence of the ribosomal (internal transcribed spacer) ITS1-5.8S-ITS2 region was obtained using primers ITS1 and ITS4 and deposited in GenBank (Accession No. JN176564). Control fruits were inoculated with sterile PDA plugs. After 3 days of incubation in plastic containers with high humidity at room temperature, typical symptoms of brown rot developed on inoculated fruits, while control fruits remained symptomless. The isolate recovered from symptomatic fruits showed the same morphological and molecular features of the original isolate. To our knowledge, this is the first report of M. fructicola in Serbia. Further studies are necessary for estimation of economic importance and geographic distribution of this quarantine organism in Serbia. References: (1) R. Baker et al. European Food Safety Authority. Online publication. www.efsa.europa.eu/efsajournal . EFSA J. 9(4):2119, 2011. (2) M.-J. Côté et al. Plant Dis. 88:1219, 2004. (3) J. E. M. Mordue. CMI Descriptions of Pathogenic Fungi and Bacteria. No. 616, 1979. (4) OEPP/EPPO. EPPO A2 List of Pests Recommended for Regulation as Quarantine Pests. Online publication. Version 2010-09. Retrieved from http://www.eppo.org/QUARANTINE/listA2.htm , June 27, 2011.

First Report of Agrobacterium vitis as the Causal Agent of Grapevine Crown Gall in Serbia

In November 2010, a serious outbreak of crown gall disease was observed on 3-year-old grapevine (Vitis vinifera L.) cv. Cabernet Sauvignon grafted onto Kober 5BB rootstock in two commercial vineyards located in the South Banat District in Serbia. Large, aerial tumors were visible above the grafting point on grapevine trunks, and in most cases, the tumors completely girdled the trunk. From the gall tissues, white, circular, and glistening bacterial colonies were isolated on yeast mannitol agar medium. Eight, nonfluorescent, gram-negative, and oxidase-positive strains were isolated from seven tumor samples and selected for further identification. PCR assays with A/C' (1) and VCF3/VCR3 (4) primers corresponding to the virD2 and virC genes yielded 224- and 414-bp fragments, respectively, confirming that the strains harbored the plasmid responsible for pathogenicity. The strains were differentiated to the species/biovar level with a multiplex PCR assay targeting 23S rRNA gene sequences (3) and were identified as Agrobacterium vitis. The 16S rDNA gene sequence from one isolate (GenBank Accession No. JN185718) showed 99% identity to the sequences of A. vitis previously deposited in NCBI GenBank database. The physiological and biochemical test results corresponded to the results of genetic analysis (2). The strains grew at 35°C and in nutrient broth supplemented with 2% NaCl. They were negative in 3-ketolactose, acid clearing on PDA supplemented with CaCO₃, and ferric ammonium citrate tests; nonmotile at pH 7.0; pectolytic at pH 4.5; utilized citrate; produced acid from sucrose and alkali from tartarate. Pathogenicity was confirmed by inoculation of three plants per bacterial strain on grapevine cv. Cabernet Franc and on a local cultivar of tomato (Lycopersicon esculentum L.). The plants were inoculated on the stem by pricking one to three times through a drop of inoculum (10⁸ CFU/ml) at three inoculation sites. Sterile distilled water was used as a negative control. Inoculated plants were maintained in a greenhouse at 24 ± 3°C. Typical tumors developed at the inoculation sites on tomatoes 3 weeks after inoculation and on grapevine 6 weeks after inoculation. No symptoms were observed on the control plants. Bacteria were reisolated from tumorigenic tissues and identified as pathogenic A. vitis by PCR. Crown gall disease was sporadically observed in vineyards in Serbia in previous years, but did not cause significant damage. Therefore, the causal agent was not studied in detail. To our knowledge, this is the first report of A. vitis determined as the causal agent of grapevine crown gall in Serbia. References: (1) J. H. Haas et al. Appl. Environ. Microbiol. 61:2879, 1995. (2) L. W. Moore et al. Page 17 in: Laboratory Guide for Identification of Plant Pathogenic Bacteria. 3rd ed. N. W. Schaad et al., eds. The American Phytopathological Society, St. Paul, MN, 2001. (3) J. Pulawska et al. Syst. Appl. Microbiol. 29:470, 2006. (4) K. Suzaki et al. J. Gen. Plant Pathol. 70:342, 2004.

First Report of Pear Decline Phytoplasmas on Pear in Serbia

During August of 2004, pear (Pyrus communis L.) plants with typical symptoms of pear decline (PD) were observed in orchards in central Serbia. The affected plants showed premature reddening and upward rolling of leaves that often showed down-turned petioles. In some cases, premature defoliation was observed. Although a similar decline of pear was observed earlier, until now, the causal agent had not been identified. DNA was extracted with a chloroform/phenol procedure from fresh leaf midribs and branch phloem scrapes of four symptomatic and one asymptomatic pear plants separately. A nested polymerase chain reaction assay (PCR) was used for phytoplasma detection (first PCR round with P1/P7 (4) phytoplasma universal primer pair, followed by nested PCR with group 16SrX specific primers f01/r01) (3). With these primers, the expected products from phloem scrapes and midrib extracts of symptomatic plant samples were obtained. Restriction fragment length polymorphism (RFLP) analyses of the f01/r01 amplicon, with RsaI and SspI restriction enzymes, discriminating among 16SrX subgroup phytoplasmas, showed profiles corresponding to those of the apple proliferation phytoplasma group, 16SrX-C subgroup, "Candidatus Phytoplasma pyri" (2). A 1,155-bp sequence of 16S rDNA gene for one of the PA2f/r (1) amplicons obtained in nested PCR on P1/P7 products from one of the leaf midrib samples was deposited in GenBank (Accession No. AY949984); both strands of the fragment were sequenced with the Big Dye Terminator reaction kit (Applied Biosystems, Foster City, CA). The sequences were analyzed with the Chromas 1.55 DNA sequencing software (Technelysium, Queensland, Australia) and aligned with BLAST software ( http://www.ncbi.nlm.nih.gov ). The blast search showed 100% homology of this sequence with that of PD strain Y16392, confirming the identity with PD of the phytoplasma detected. To our knowledge, this is the first report of pear decline phytoplasmas in Serbia. References: (1) M. Heinrich et al. Plant Mol. Biol. Rep. 19:169, 2001. (2) IRPCM Phytoplasma/Spiroplasma Working Team-Phytoplasma Taxonomy Group. Int. J. Syst. Evol. Microbiol. 54:1243, 2004. (3) K.-H. Lorenz et al. Phytopathology 85:771, 1995. (4) Schneider et al. Pages 369-380 in: Molecular and Diagnostic Procedures in Mycoplasmology. Vol I. S. Razin and J. G. Tully, eds. The American Phytopathological Society, 1995.

First Report of Black Rot of Cauliflower and Kale Caused by Xanthomonas campestris pv. campestris in Yugoslavia

In Yugoslavia, Xanthomonas campestris pv. campestris was isolated from forage kale in 1964 and cabbage in 1997 (1). Recently, the incidence and severity of black rot symptoms on cabbage, cauliflower, and kale have increased. Gram-negative, rod-shaped, motile bacteria were isolated from the diseased leaf and vascular tissues of cauliflower and kale plants collected from 1995 to 1998. The isolates formed yellow, convex, mucoid colonies on yeast dextrose chalk medium, metabolized glucose oxidatively, grew at 37°C, hydrolyzed gelatin and esculin, produced acids from d-arabinose, glucose, sucrose, and trehalose, and did not reduce nitrates. They were nonfluorescent, amylolytic and pectolytic, oxidase negative and catalase positive, and tolerant to 5% NaCl but not to 0.1% triphenyl tetrazolium chloride. Koch's postulates were completed by injecting bacterial suspensions (10⁸ CFU/ml) into leaf petioles of cabbage, cauliflower, and kale seedlings (2- to 3-leaf stage). Dark green watersoaking of petioles and leaf veins followed by yellowing and collapse of inoculated plants was observed after 3 to 5 days. When compared with published information (2), the isolates were identified as X. campestris pv. campestris. This is the first occurrence of this bacterium in cauliflower and kale in Yugoslavia. References: (1) O. Jovanovic et al. Plant Prot. Belgrade 221:175, 1997. (2) N. W. Schaad. 1988. Laboratory Guide for Identification of Plant Pathogenic Bacteria. 2nd ed. The American Phytopathological Society, St. Paul, MN.