Role of endoplasmic reticulum stress in disuse osteoporosis

Osteoporosis is a major skeletal disease with low bone mineral density, which leads to an increased risk of bone fracture. Salubrinal is a synthetic chemical that inhibits dephosphorylation of eukaryotic translation initiation factor 2 alpha (eIF2α) in response to endoplasmic reticulum (ER) stress. To understand possible linkage of osteoporosis to ER stress, we employed an unloading mouse model and examined the effects of salubrinal in the pathogenesis of disuse osteoporosis. The results presented several lines of evidence that osteoclastogenesis in the development of osteoporosis was associated with ER stress, and salubrinal suppressed unloading-induced bone loss. Compared to the age-matched control, unloaded mice reduced the trabecular bone area/total area (B.Ar/T.Ar) as well as the number of osteoblasts, and they increased the osteoclasts number on the trabecular bone surface in a time-dependent way. Unloading-induced disuse osteoporosis significantly increased the expression of Bip, p-eIF2α and ATF4 in short-term within 6 h of tail suspension, but time-dependent decreased in HU2d to HU14d. Furthermore, a significant correlation of ER stress with the differentiation of osteoblasts and osteoclasts was observed. Administration of salubrinal suppressed the unloading-induced decrease in bone mineral density, B.Ar/T.Ar and mature osteoclast formation. Salubrinal also increased the colony-forming unit-fibroblasts and colony-forming unit-osteoblasts. It reduced the formation of mature osteoclasts, suppressed their migration and adhesion, and increased the expression of Bip, p-eIF2α and ATF4. Electron microscopy showed that rough endoplasmic reticulum expansion and a decreased number of ribosomes on ER membrane were observed in osteoblast of unloading mice, and the abnormal ER expansion was significantly improved by salubrinal treatment. A TUNEL assay together with CCAAT/enhancer binding protein homologous protein (CHOP) expression indicated that ER stress-induced osteoblast apoptosis was rescued by salubrinal. Collectively, the results support the notion that ER stress plays a key role in the pathogenesis of disuse osteoporosis, and salubrinal attenuates unloading-induced bone loss by altering proliferation and differentiation of osteoblasts and osteoclasts via eIF2α signaling

Effect of Au-ions irradiation on microstructure and mechanical properties of FeCrAl coating

Six kinds of FeCrAl coatings with different Cr and Al contents were irradiated by 6 MeV Au-ions with a damage level of 20 dpa. The results showed that the surface roughness and grain size of the coatings increased significantly after irradiation. Nanoscale precipitation and irradiation-induced twins appeared in the coating with relatively lower Cr content. The increase of Cr content promotes the transformation from irradiation-induced softening to hardening. Changed Al content can cause the change in hardness, but cannot cause the transition of softening and hardening. The underlying evolution mechanism of microstructure and mechanical properties induced by Au-ions irradiation is discussed

Corrosion behavior of ZrN coated ferritic/martensitic steel in liquid lead-bismuth eutectic

The corrosion resistance of the ZrN coating deposited on ferritic/martensitic (F/M) steel by the magnetron sputtering method was investigated in static liquid lead–bismuth eutectic (LBE) at 450 ∼ 650 °C. After LBE corrosion test, although ZrN was oxidized to form ZrO2, no spallation, dissolution attack and liquid Pb/Bi penetration occurred in the coating. The results indicate that oxidized coatings still have good adhesion and could protect the F/M steels substrates from LBE corrosion. However, several microscopic cracks and voids inside the coating were observed, which was related to the volume expansion induced by Pilling-Bedworth ratio (PBR) effect and phase transformation. Further, the microscopic corrosion mechanism of the coating was discussed

Irradiation effects on microstructure, mechanical properties, and lead-bismuth eutectic corrosion resistance of alumina coating

A comprehensive evaluation including microstructure, mechanical properties, and lead-bismuth eutectic corrosion resistance of amorphous alumina coatings after different doses of Au2+ irradiation was done using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, nanoindentation, SRIM software, and eRDF Analyzer. The results showed that irradiation decreased the surface roughness and induced crystallization in the middle of the coating and at the interface. The middle crystallization might be dominated by electron energy loss, while the interface had to consider the influence of defects and doping. The regions that remain amorphous after irradiation also showed differences in topological bonding and nanovoid. The changes in topological bonding hardened the coating, while the nanovoids generated by atomic rearrangement weakened the mechanical properties. The irradiation deteriorated the lead-bismuth corrosion resistance of the coating due to the void formation and alumina phase transformation. In addition, enhanced temperature sensitivity at the interface was observed after irradiation