Melatonin inhibits UVB-induced melanin synthesis by regulating p53-mediated premature senescence in HaCaT cells / 中华放射医学与防护杂志

Objective:To explore the mechanism and regulatory effects of melatonin on UVB-induced melanin synthesis in human immortalized keratinocytes (HaCaT), so as to provide a theoretical basis for the skin protection of melatonin.Methods:HaCaT cells were pretreated with 10 -5 mol/L melatonin and then irradiated with 80 mJ/cm 2UVB. The melanin content was detected by NaOH assay, the proportion of premature senescence cells was detected by β-galactosidase staining kit, and the protein expression levels of both p53 and tyrosinase (TYR) were detected by Western blot at 72 h after UVB exposure. After 12 h pretreatment of ATM/ATR inhibitor, p53 inhibitor and melatonin, the proportion of premature senescence and the change of melanin content in HaCaT cells were detected at 72 h after 80 mJ/cm 2 UVB irradiation. Results:Melatonin inhibited UVB-induced increases of melanin content ( t=56.65, 13.39, P<0.05) and TYR expression ( t=16.46, P<0.05) in HaCaT cells. Melatonin alleviated UVB-induced premature senescence ( t=7.139, P<0.05) and inhibited UVB-induced increase of p53 expression ( t=19.08, P<0.05) in HaCaT cells. In addition, ATM/ATR inhibitor, p53 inhibitor and melatonin all inhibited UVB-induced increase of melanin content in HaCaT cells. Conclusions:Melatonin inhibits TYR-mediated melanin synthesis by regulating p53-related premature senescence in HaCaT cells after UVB irradiation.

Melatonin Rescues Human Dental Pulp Cells from Premature Senescence Induced by H₂O₂

Although anti-aging activities of melatonin, a hormone secreted by the pineal gland, have been reported in senescence-accelerated mouse models and several types of cells, its impact and mechanism on the senescence of human dental pulp cells (HDPCs) remains unknown. In this study, we examined the impact of melatonin on cellular premature senescence of HDPCs. Here, we found that melatonin markedly inhibited senescent characteristics of HDPCs after exposure to hydrogen peroxide (H₂O₂), including the increase in senescence-associated β-galactosidase (SA-β-gal)-positive HDPCs and the upregulation of p21 protein, an indicator for senescence. In addition, as melatonin attenuated H₂O₂-stimulated phosphorylation of c-Jun N-terminal kinase (JNK), while selective inhibition of JNK activity with SP600125 significantly attenuated H₂O₂-induced increase in SA-beta-gal activity. Results reveal that melatonin antagonizes premature senescence of HDPCs via JNK pathway. Thus, melatonin may have therapeutic potential to prevent stress-induced premature senescence, possibly correlated with development of dental pulp diseases, and to maintain oral health across the life span.

Pathogenesis of endothelial cell dysfunction in chronic kidney disease: a retrospective and what the future may hold

Cardiovascular complications dominate the landscape of chronic kidney diseases (CKD). Endothelial cell dysfunction (ECD) is a well-known culprit of cardiovascular morbidity and it develops in CKD with remarkable frequency. This brief overview of ECD in CKD scans two decades of studies performed in my laboratory, from genetic analyses to proteomic and metabolomics screens. I provide a detailed description of findings related to the premature senescence of endothelial cells, cell transition from the endothelial to mesenchymal phenotype, and stages of development of ECD. Clinical utility of some of these findings is illustrated with data on laser-Doppler flowmetry and imaging in patients with CKD. Some currently available and emerging therapeutic options for the management of ECD are briefly presented.

Stem Cell Factor Inhibits Premature Senescence of Megakaryocytes during ex vivo Expansion of Human Cord Blood CD34+ Cells Using Thrombopoietin / 대한소아혈액종양학회지

PURPOSE: Thrombopoietin (TPO) has been currently used for ex vivo expansion of hematopoietic stem cells. Previously, we have reported that TPO induces apoptosis during ex vivo expansion of cord blood CD34 cells. In this study, we have investigated the stem cell factor (SCF) to determine whether it affects the TPO-induced apoptosis. METHPDS: CD34+ cells, purified from four separate human cord bloods by magnetic bead selection, were expanded in Iscoves modified Dulbeccos medium with several cytokines. Apoptosis has been confirmed by several ways; 7-amino-actinomycin D (7-AAD) or annexin V staining, and morphologic analysis with light and electron microscopic examinations. And cell maturation was also analysed with DNA staining. RESULTS: Apoptosis was reached peak (67.8+/-5.24% of total cells) at day 9 in the cultures with TPO alone. Morphological examination of Giemsa-stained cytospin preparations revealed many immature cells with cytoplasmic blebbing and eccentric nuclei. However, multilobed nuclei were rarely observed while bilobed nuclei were frequently observed. These results suggest that premature senescence occurs in the megakaryocytic cells before full polyploidization. SCF was affective for the TPO-induced apoptosis; the peak apoptotic fraction was significantly decreased to 37.2+/-3.31% at day 9. In the cultures with SCF, the fractions of CD41+ cells were also decreased in parallel with decrease in apoptosis. Notwithstanding reduction of differentiation into megakaryocytic lineage, polyploidization(> 6N) in CD41 cell faction was significantly increased in the cultures with SCF at day 9 and day 11, respectively (P<0.05). CONCLUSION: These results suggest that SCF inhibits premature senescence of the differentiating cells of megakaryocytic lineage during ex vivo expansion using TPO.