Magnesium protects mouse hippocampal HT22 cells against hypoxia-induced injury by upregulation of miR-221.

Magnesium (Mg2+ ) has been shown to exert neuroprotective effects against hypoxia. However, it still remains elusive whether Mg2+ protected mouse hippocampal HT22 cells against hypoxia-evoked damages. Therefore, we aimed to investigate the function of Mg2+ and mechanisms associated with microRNA-221 (miR-221). HT22 cells were exposed to 3% O2 for 24 hours to induce hypoxic damages with 21% as a normoxic culture condition. The damages were monitored by viability, migration, and apoptosis of HT22 cells with or without Mg2+ pretreatment. Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) was applied to examine the alteration of miR-221, miR-210, and miR-17-5p. Transduction was carried out to artificially alter the expression of miR-221 and nerve growth factor (NGF), which was confirmed by qRT-PCR or Western blot assays. To blunt phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) and nuclear factor κB (NF-κB), LY294002 (10 µM) and BAY 11-7082 (10 µM) were used. We observed Mg2+ protected HT22 cells against hypoxia-induced damages by upregulating miR-221. Further, miR-221 positively regulated NGF expression. Overexpression of NGF alleviated cell injury, while suppression of NGF aggravated cell injury. Moreover, miR-221 elevated NGF by inducing phosphorylation of regulators in PI3K/AKT and NF-κB transduction cascades and then alleviated cell injury. In conclusion, Mg2+ protected HT22 cells against hypoxia-induced damages by upregulation of miR-221 and NGF. These findings provided insights into the development of improved strategies for clinical application.

Up-regulated CST5 inhibits bone resorption and activation of osteoclasts in rat models of osteoporosis via suppression of the NF-κB pathway.

Here, we aim at exploring the effect of CST5 on bone resorption and activation of osteoclasts in osteoporosis (OP) rats through the NF-κB pathway. Microarray analysis was used to screen the OP-related differentially expressed genes. Osteoporosis was induced in rats by intragastric retinoic acid administration. The serum levels of tartrate-resistant acid phosphatase (TRAP), bone alkaline phosphatase (BALP) and osteocalcin (OC) and the expression of CD61 on the surface of osteoclasts were examined. The number of osteoclasts and the number and area of resorption pits were detected. Besides, the pathological changes and bone mineral density in bone tissues of rats were assessed. Also, the relationship between CST5 and the NF-κB pathway was identified through determining the expression of CST5, RANKL, RANK, OPG, p65 and IKB. Poorly expressed CST5 was indicated to affect the OP. CST5 elevation and inhibition of the NF-κB pathway decreased serum levels of TRAP, BALP and OC and expression of CD61 in vivo and in vitro. In OP rats, CST5 overexpression increased trabecular bones and bone mineral density of bone tissues, but decreased trabecular separation, fat within the bone marrow cavities and the number of osteoclasts through inhibiting the NF-κB pathway. In vivo experiments showed that CST5 elevation inhibited growth in number and area of osteoclastic resorption pits and restrained osteoclastic bone absorption by inhibiting the NF-κB pathway. In summary, overexpression of CST5 suppresses the activation and bone resorption of osteoclasts by inhibiting the activation of the NF-κB pathway.