The role of melatonin in bone regeneration: A review of involved signaling pathways.

Increasing bone resorption followed by decreasing bone mineralization are hallmarks of bone degeneration, which mostly occurs in the elderly population and post-menopausal women. The use of mesenchymal stem cells (MSCs) has raised many promises in the field of bone regeneration due to their high osteoblastic differentiation capacity and easy availability from abundant sources. A variety of compounds, including growth factors, cytokines, and other internal factors, have been combined with MSCs to increase their osteoblastic differentiation capacity. One of these factors is melatonin, whose possible regulatory role in bone metabolism and formation has recently been suggested by many studies. Melatonin also is a potential signaling molecule and can affect many of the signaling pathways involved in MSCs osteoblastic differentiation, such as activation of PI3K/AKT, BMP/Smad, MAPK, NFkB, Nrf2/HO-1, Wnt, SIRT/SOD, PERK/ATF4. Furthermore, melatonin in combination with other components such as strontium, vitamin D3, and vitamin K2 has a synergistic effect on bone microstructure and improves bone mineral density (BMD). In this review article, we aim to summarize the regulatory mechanisms of melatonin in osteoblastic differentiation of MSCs and underling involved signaling pathways as well as the clinical potential of using melatonin in bone degenerative disorders.

Molecular mechanisms involved in DNA repair in human cancers: An overview of PI3k/Akt signaling and PIKKs crosstalk.

The cellular genome is frequently subjected to abundant endogenous and exogenous factors that induce DNA damage. Most of the Phosphatidylinositol 3-kinase-related kinases (PIKKs) family members are activated in response to DNA damage and are the most important DNA damage response (DDR) proteins. The DDR system protects the cells against the wrecking effects of these genotoxicants and repairs the DNA damage caused by them. If the DNA damage is severe, such as when DNA is the goal of chemo-radiotherapy, the DDR drives cells toward cell cycle arrest and apoptosis. Some intracellular pathways, such as PI3K/Akt, which is overactivated in most cancers, could stimulate the DDR process and failure of chemo-radiotherapy with the increasing repair of damaged DNA. This signaling pathway induces DNA repair through the regulation of proteins that are involved in DDR like BRCA1, HMGB1, and P53. In this review, we will focus on the crosstalk of the PI3K/Akt and PIKKs involved in DDR and then discuss current achievements in the sensitization of cancer cells to chemo-radiotherapy by PI3K/Akt inhibitors.

Fractalkine and apoptotic/anti-apoptotic markers in granulosa cells of women with polycystic ovarian syndrome.

Owing to the role of fractalkine in regulating cellular apoptosis/proliferation, we investigated fractalkine effects on apoptosis/proliferation signaling of granulosa cells in polycystic ovarian syndrome (PCOS) patients through in vitro and in vivo experiments. In vivo, granulosa cells were collected from 40 women undergoing oocyte retrieval (20 controls and 20 PCOS). The expression levels of fractalkine, BAX, Bcl2, Bcl2-XL, Bad, and TNF-α were assessed using RT-PCR. In vitro, we determined the effect of different doses of fractalkine on the expression of the above mentioned genes in GCs of both groups. We found that the expression levels of fractalkine and Bcl-2 were significantly lower in the GCs of PCOS patients compared to the control group (p < 0.05). In contrast, the expression levels of TNF-α and BAX were higher in the patient's group than in the control group. The results suggested that expression levels of fractalkine were negatively and positively correlated with the number of oocytes and fertilized oocytes respectively. Moreover, fractalkine could dose-dependently increase fractalkine and decrease BAD, BAX, Bcl-xl, and TNF-α expressions in the control GCs. In contrast, GCs collected from PCOS patients revealed an increase in expression of BAD, BAX, and Bcl-xl following fractalkine treatment. Our findings indicated that insufficient expression of fractalkine in PCOS patients is related with elevated apoptotic and inflammatory markers and reduced anti-apoptotic genes in the GCs.