Effects of Doxycycline on gene expression in <it>Wolbachia </it>and <it>Brugia malayi </it>adult female worms in vivo

• Main Authors: Rao Ramakrishna U, Huang Yuefang, Abubucker Sahar, Heinz Michael, Crosby Seth D, Mitreva Makedonka, Weil Gary J
• Format: Article
• Language: English
• Published: BMC 2012-02-01
• Series: Journal of Biomedical Science
• Subjects: Doxycycline; <it>Brugia malayi</it>; <it>Wolbachia</it>; Filariasis; Gene expression; Microarray
• Online Access: http://www.jbiomedsci.com/content/19/1/21
• ISSN: 1021-7770; 1423-0127

<p>Abstract</p> <p>Background</p> <p>Most filarial nematodes contain <it>Wolbachia </it>symbionts. The purpose of this study was to examine the effects of doxycycline on gene expression in <it>Wolbachia </it>and adult female <it>Brugia malayi</it>.</p> <p>Methods</p> <p><it>Brugia malayi </it>infected gerbils were treated with doxycycline for 6-weeks. This treatment largely cleared <it>Wolbachia </it>and arrested worm reproduction. RNA recovered from treated and control female worms was labeled by random priming and hybridized to the Version 2- filarial microarray to obtain expression profiles.</p> <p>Results and discussion</p> <p>Results showed significant changes in expression for 200 <it>Wolbachia </it>(29% of <it>Wolbachia </it>genes with expression signals in untreated worms) and 546 <it>B. malayi </it>array elements after treatment. These elements correspond to known genes and also to novel genes with unknown biological functions. Most differentially expressed <it>Wolbachia </it>genes were down-regulated after treatment (98.5%). In contrast, doxycycline had a mixed effect on <it>B. malayi </it>gene expression with many more genes being significantly up-regulated after treatment (85% of differentially expressed genes). Genes and processes involved in reproduction (gender-regulated genes, collagen, amino acid metabolism, ribosomal processes, and cytoskeleton) were down-regulated after doxycycline while up-regulated genes and pathways suggest adaptations for survival in response to stress (energy metabolism, electron transport, anti-oxidants, nutrient transport, bacterial signaling pathways, and immune evasion).</p> <p>Conclusions</p> <p>Doxycycline reduced <it>Wolbachia </it>and significantly decreased bacterial gene expression. <it>Wolbachia </it>ribosomes are believed to be the primary biological target for doxycycline in filarial worms. <it>B. malayi </it>genes essential for reproduction, growth and development were also down-regulated; these changes are consistent with doxycycline effects on embryo development and reproduction. On the other hand, many <it>B. malayi </it>genes involved in energy production, electron-transport, metabolism, anti-oxidants, and others with unknown functions had increased expression signals after doxycycline treatment. These results suggest that female worms are able to compensate in part for the loss of <it>Wolbachia </it>so that they can survive, albeit without reproductive capacity. This study of doxycycline induced changes in gene expression has provided new clues regarding the symbiotic relationship between <it>Wolbachia </it>and <it>B. malayi</it>.</p>