Dexamethasone promotes osteoblast apoptosis through the Chk2/p53 signaling pathway

Abstract

Background. Glucocorticoids (GCs) are widely used to treat inflammatory or autoimmune diseases. However, several studies have reported that the use of GCs can lead to numerous complications, the most serious of which are osteoporosis and osteonecrosis of the femoral head (ONFH). Osteoblast apoptosis has been identified as an important event in the development of GC-induced osteoporosis and ONFH. However, the mechanisms underlying the regulation of these processes have not yet been explored. Objectives.To observe the effect of dexamethasone (Dex) on the apoptosis of osteoblasts and explore its mechanism, as well as provide a new therapeutic idea for GC-induced osteoporosis and ONFH. Materials and methods.Cell proliferation and apoptosis of MC3T3-E1 cells after Dex treatment were determined using the CellTiter-Glo® Luminescent Cell Viability Assay kit and Annexin V-FITC/PI Double Staining Apoptosis Detection Kit, respectively. The expression of caspase-3/cleaved caspase-3 and poly(ADPribose) polymerase (PARP)/cleaved PARP in MC3T3-E1 cells after Dex treatment was determined with western blotting. The expression of p53 and checkpoint kinase 2 (Chk2) in MC3T3-E1 cells after Dex treatment was analyzed using western blotting and polymerase chain reaction (PCR). The effects of p53 knockdown and Chk2 knockdown on Dex-induced apoptosis of MC3T3-E1 cells were also characterized.Results. Dexamethasone remarkably inhibited cell growth and induced the apoptosis of MC3T3-E1 cells. We also observed that Dex induced osteoblast apoptosis by promoting p53 expression. The regulatory effect of Dex on p53 expression is mediated by the upregulation of Chk2, which interacted with p53 and inhibited p53 degradation. The knockdown of p53 alleviated Dex-induced MC3T3-E1 cell apoptosis by decreasing the expression of cleaved caspase-3 and cleaved PARP.Conclusions. We demonstrated that Dex increased Chk2 protein expression, which stabilized the protein expression of p53, and in turn promoted osteoblast apoptosis.

TRAIL pathway suppression of cancer cell growth and immune cell-mediated tumor cell-killing in a senescent fibroblast-constructed tumor microenvironment

“…Indeed, we noted that immune cell-mediated tumor cell-killing was dampened by senescent fibroblasts in co-culture models using both NK- and T-cells. Moreover, ONC201 has been found to increase NK-mediated tumor cell-killing [42]. Our studies show that ONC201 treatment of tri-cultures enhanced immune-mediated tumor cell death in a senescent fibroblast-constructed microenvironment.…”

“…Indeed, we noted that immune cell-mediated tumor cell-killing was dampened by senescent fibroblasts in co-culture models using both NKand T-cells. Moreover, ONC201 has been found to increase NK-mediated tumor cell-killing [42]. In summary, we characterized cytokine landscapes to explore modulation of SASP within senescent fibroblasts and sought to promote anti-tumor immunity by inducing TRAIL or by reversing a p21-driven SASP in the senescent TME.…”