Anti-oxidative and DNA protecting effects of flavonoids-rich Scutellaria lateriflora.

Scutellaria lateriflora (American skullcap), a native plant of North America, has been used by Americans and Europeans as a nerve tonic for more than 200 years. In vivo studies have shown anxiolytic activity ofS. lateriflora in animals and humans. However, the neuroprotective mechanisms ofS. lateriflora are not fully understood. Oxidative stress plays a vital role in the neurodegenerative and neuropsychiatric diseases such as anxiety, Alzheimer's disease, depression, and Parkinson's disease. Bioactive compounds present in various medicinal plants neutralize or scavenge toxic free radicals and thus suppress oxidative stress. Therefore, the objective of this study was to investigate the antioxidant effects of S. lateriflora. The antioxidant potential of aqueous or ethanolic extracts of S. lateriflora was determined in mouse brain tissue using various biochemical assays. Protective effects of S. lateriflora against oxidative stress induced DNA fragmentation was determined using plasmid DNA. The ethanolic and aqueous extracts scavenged the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals. The ethanolic extract reduced tert-butyl peroxide-induced reactive oxygen species (ROS) and lipid peroxides in the mouse brain homogenates. Furthermore, the ethanolic extract of S. lateriflora protected hydrogen peroxide-UV induced cleavage of supercoiled plasmid DNA. In conclusion, S. lateriflora exhibited significant antioxidant effects. The current findings posit S. lateriflora as one of the potential experimental herbal drugs that should be screened for its therapeutic potential against various oxidative stress associated mental disorders.

C. elegans germ cells show temperature and age-dependent expression of Cer1, a Gypsy/Ty3-related retrotransposon.

Virus-like particles (VLPs) have not been observed in Caenorhabditis germ cells, although nematode genomes contain low numbers of retrotransposon and retroviral sequences. We used electron microscopy to search for VLPs in various wild strains of Caenorhabditis, and observed very rare candidate VLPs in some strains, including the standard laboratory strain of C. elegans, N2. We identified the N2 VLPs as capsids produced by Cer1, a retrotransposon in the Gypsy/Ty3 family of retroviruses/retrotransposons. Cer1 expression is age and temperature dependent, with abundant expression at 15°C and no detectable expression at 25°C, explaining how VLPs escaped detection in previous studies. Similar age and temperature-dependent expression of Cer1 retrotransposons was observed for several other wild strains, indicating that these properties are common, if not integral, features of this retroelement. Retrotransposons, in contrast to DNA transposons, have a cytoplasmic stage in replication, and those that infect non-dividing cells must pass their genomic material through nuclear pores. In most C. elegans germ cells, nuclear pores are largely covered by germline-specific organelles called P granules. Our results suggest that Cer1 capsids target meiotic germ cells exiting pachytene, when free nuclear pores are added to the nuclear envelope and existing P granules begin to be removed. In pachytene germ cells, Cer1 capsids concentrate away from nuclei on a subset of microtubules that are exceptionally resistant to microtubule inhibitors; the capsids can aggregate these stable microtubules in older adults, which exhibit a temperature-dependent decrease in egg viability. When germ cells exit pachytene, the stable microtubules disappear and capsids redistribute close to nuclei that have P granule-free nuclear pores. This redistribution is microtubule dependent, suggesting that capsids that are released from stable microtubules transfer onto new, dynamic microtubules to track toward nuclei. These studies introduce C. elegans as a model to study the interplay between retroelements and germ cell biology.

Perinuclear P granules are the principal sites of mRNA export in adult C. elegans germ cells.

Germline-specific granules of unknown function are found in a wide variety of organisms, including C. elegans, where they are called P granules. P granules are cytoplasmic bodies in oocytes and early embryos. Throughout most of the C. elegans life cycle, however, P granules are associated with clusters of nuclear pore complexes (NPCs) on germ cell nuclei. We show that perinuclear P granules differ from cytoplasmic P granules in many respects, including structure, stability and response to metabolic changes. Our results suggest that nuclear-associated P granules provide a perinuclear compartment where newly exported mRNAs are collected prior to their release to the general cytoplasm. First, we show that mRNA export factors are highly enriched at the NPCs associated with P granules. Second, we discovered that the expression of high-copy transgenes could be induced in a subset of germ cells, and used this system to demonstrate that nascent mRNA traffics directly to P granules. P granules appear to sequester large amounts of mRNA in quiescent germ cells, presumably preventing translation of that mRNA. However, we did not find evidence that P granules normally sequester aberrant mRNAs, or mRNAs targeted for destruction by the RNAi pathway.