An antioxidant screen identifies ascorbic acid for prevention of light-induced mitotic prolongation in live cell imaging.

Phototoxicity is an important issue in fluorescence live imaging of light-sensitive cellular processes such as mitosis. Among several approaches to reduce phototoxicity, the addition of antioxidants to the media has been used as a simple method. Here, we analyzed the impact of phototoxicity on the mitotic progression in fluorescence live imaging of human cells and performed a screen to identify the most efficient antioxidative agents that reduce it. Quantitative analysis shows that high amounts of light illumination cause various mitotic defects such as prolonged mitosis and delays of chromosome alignment and centrosome separation. Among several antioxidants, our screen reveals that ascorbic acid significantly alleviates these phototoxic effects in mitosis. Furthermore, we demonstrate that adding ascorbic acid to the media enables fluorescence imaging of mitotic events at very high temporal resolution without obvious photodamage. Thus, this study provides an optimal method to effectively reduce the phototoxic effects in fluorescence live cell imaging.

A CRISPR-del-based pipeline for complete gene knockout in human diploid cells.

The advance of CRISPR/Cas9 technology has enabled us easily to generate gene knockout cell lines by introducing insertion-deletion mutations (indels) at the target site via the error-prone non-homologous end joining repair system. Frameshift-promoting indels can disrupt gene functions by generation of a premature stop codon. However, there is growing evidence that targeted genes are not always knocked out by the indel-based gene disruption. Here, we established a pipeline of CRISPR-del, which induces a large chromosomal deletion by cutting two different target sites, to perform 'complete' gene knockout efficiently in human diploid cells. Quantitative analyses show that the frequency of gene deletion with this approach is much higher than that of conventional CRISPR-del methods. The lengths of the deleted genomic regions demonstrated in this study are longer than those of 95% of the human protein-coding genes. Furthermore, the pipeline enabled the generation of a model cell line having a bi-allelic cancer-associated chromosomal deletion. Overall, these data lead us to propose that the CRISPR-del pipeline is an efficient and practical approach for producing 'complete' gene knockout cell lines in human diploid cells.

Curcuma sp.-derived dehydrocurdione induces heme oxygenase-1 through a Michael reaction between its α, ß-unsaturated carbonyl and Keap1.

To elucidate the anti-inflammatory mechanism of Curcuma sp., we investigated whether dehydrocurdione, a sesquiterpene contained in Curcuma sp., induces heme oxygenase (HO)-1, an antioxidative enzyme, in RAW 264.7 macrophages. Dehydrocurdione was extracted from the rhizome of Curcuma sp., and its purity was verified by high performance liquid chromatography. Treatment with 10-100 µM dehydrocurdione transiently and concentration-dependently increased HO-1 mRNA and protein levels. Docking simulation suggested the presence of the Michael reaction between dehydrocurdione and Kelch-like ECH-associated protein (Keap)1 keeping nuclear factor-erythroid2-related-factor (Nrf)2, a transcription factor, in the cytoplasm. Nrf2 that was definitely free from Keap1 was detected in the nuclei after dehydrocurdione treatment. Subsequently, the HO-1 E2 enhancer, a target of Nrf2, was activated, resulting in HO-1 expression. Also, an investigation using 6-shogaol and 6-gingerol supported the concept that the α, ß-unsaturated carbonyl structure plays an important role in the interaction with Keap1. Dehydrocurdione suppressed lipopolysaccharide-induced NO release, a marker of inflammation. Clarification of the HO-1 synthesis increase mechanism revealed in this study will help contribute to the development of novel phytotherapeutic strategies against inflammation-associated diseases.

Selective enhancement of wnt4 expression by cyclic AMP-associated cooperation between rat central astrocytes and microglia.

The wnt protein family has important members involved in cell differentiation, proliferation and plasticity expression; however, little is known about its biosynthesis processes. On the other hand, an increase in the intracerebral cyclic adenosine 3', 5'-monophosphate (cAMP) level leads to synaptic plasticity via the de novo synthesis of any protein. Here, the effect of dibutyryl cAMP (dbcAMP), a membrane permeability cAMP analog, on the wnt family was investigated in rat primary-cultured glial cells containing astrocytes and microglia. Among wnt3a, 4, 5a, 7a and 11 mRNA, only wnt4 expression was increased by longer treatment (24 h), compared with short treatment (2 h), with dbcAMP in a concentration-dependent manner, and its effect reached statistical significance at 1 mM. In cultures of isolated astrocytes or microglia, wnt4 expression was not affected by 1 mM dbcAMP for 24 h, and microglial wnt4 protein was undetectable even when cells were treated with the drug. Mixed glial cells treated for 24 h with 1 mM dbcAMP showed significantly increased wnt4 protein, as well as mRNA. Immunofluorescence manifested that cells that expressed wnt4 protein were astrocytes, but not microglia. Intraperitoneal injection of 1.25 mg/kg rolipram, a phosphodiesterase (PDE) IV inhibitor that can pass through the blood brain barrier and inhibits cAMP degradation specifically, showed a tendency to increase wnt4 expression in the adult rat brain after 24 h, and the increases in wnt4 mRNA and protein levels reached statistical significance in the hippocampus and striatum, respectively. This is the first finding to help elucidate the selective biosynthesis of central wnt4 through cAMP-stimulated microglia and astrocytes interaction.