Biological clocks, some clock-related diseases, and medicinal plants

Effects of circadian clock and light on melatonin concentration in Hypericum perforatum L. (St. John's Wort)

BACKGROUND

Melatonin acts as a signaling hormone and entraining agent in many organisms. We studied the spatiotemporal regulation and influence of light (photoperiods, intensities, and spectral qualities) on melatonin concentration in the medicinal herb Hypericum perforatum L. Furthermore, melatonin concentrations in the leaves of eight species of the Hypericum genus were compared and analyzed using high-performance liquid chromatography.

RESULTS

Melatonin concentration was found to be the highest in its flowers and leaves. The leaves exhibited a rhythmic variation in melatonin concentration of approximately 24 h under both light-dark entrained (Zeitgeber time) and constant light [circadian time (CT)] conditions, with melatonin concentration peaking at approximately CT6 in the middle of the subjective day. Melatonin concentration was influenced significantly by not only photoperiods but also applied light's wavelength and intensity. It was approximately six times higher under long-day conditions (18-h light:6-h dark) than under short-day photoperiods (10-h light:14-h dark) and was the highest (131 μg/g fresh weight [FW]) under treatment with blue light at an intensity of 45 µmol·m2/s of photons. The melatonin concentration of the two examined Hypericum spp., namely H. kouytchense Lev. and H. coris L., were approximately twice that of H. perforatum L.

CONCLUSION

Our findings provide first insights on melatonin-related functions and mechanisms in the circadian system of H. perforatum and useful resources for further melatonin-oriented research and possible applications in agriculture and pharmaceutical industries.

Circadian protein BMAL1 promotes breast cancer cell invasion and metastasis by up-regulating matrix metalloproteinase9 expression

Background

Metastasis is an important factor in the poor prognosis of breast cancer. As an important core clock protein, brain and muscle arnt-like 1 (BMAL1) is closely related to tumorigenesis. However, the molecular mechanisms that mediate the role of BMAL1 in invasion and metastasis remain largely unknown. In this study, we investigated the BMAL1 may take a crucial effect in the progression of breast cancer cells.

Methods

BMAL1 and MMP9 expression was measured in breast cell lines. Transwell and scratch wound-healing assays were used to detect the movement of cells and MTT assays and clonal formation assays were used to assess cells’ proliferation. The effects of BMAL1 on the MMP9/NF-κB pathway were examined by western blotting, co-immunoprecipitation and mammalian two-hybrid.

Results

In our study, it showed that cell migration and invasion were significantly enhanced when overexpressed BMAL1. Functionally, overexpression BMAL1 significantly increased the mRNA and protein level of matrix metalloproteinase9 (MMP9) and improved the activity of MMP9. Moreover, BMAL1 activated the NF-κB signaling pathway by increasing the phosphorylation of IκB and promoted human MMP9 promoter activity by interacting with NF-kB p65, leading to increased expression of MMP9. When overexpressed BMAL1, CBP (CREB binding protein) was recruited to enhance the activity of p65 and further activate the NF-κB signaling pathway to regulate the expression of its downstream target genes, including MMP9, TNFα, uPA and IL8, and then promote the invasion and metastasis of breast cancer cells.

Conclusions

This study confirmed a new mechanism by which BMAL1 up-regulated MMP9 expression to increase breast cancer metastasis, to provide research support for the prevention and treatment of breast cancer.