Effects of osteoblast autophagy on glucocorticoid-induced femoral head necrosis

Amentoflavone Induces Ferroptosis to Alleviate Proliferation, Migration, Invasion and Inflammation in Rheumatoid Arthritis Fibroblast-like Synoviocytes by Inhibiting PIN1

Rheumatoid arthritis (RA) is a systemic autoimmune disease that is prevalent worldwide and seriously threatens human health. RA-fibroblast-like synoviocytes (FLS) play important roles in almost all aspects of RA progression. This study aimed to study the effect of Amentoflavone (AMF), a polyphenol compound derived from extracts of Selaginella tamariscina, on the abnormal biological behaviors of RA-FLS. The immortalized human RA-FLS cell line (MH7A) was treated with AMF or transfected with small interfering RNAs (siRNAs) targeting peptidyl-prolyl cis-trans isomerase NIMA-interacting 1 (PIN1). Then, cell viability was detected by CCK-8 assay. EDU staining, wound healing and transwell assays were employed to measure the capacities of MH7A cell proliferation, migration and invasion. The levels of inflammatory factors were assessed using ELISA kits. Additionally, ferroptosis was analyzed by detecting Fe2+ content, lipid reactive oxygen species (ROS) level and expression of ferroptosis-related proteins. Pull-down assay was employed to verify the targeted binding of AMF to PIN1. Further, PIN1 overexpression or ferroptosis inhibitor Ferrostatin-1 (Fer-1) addition was conducted to elucidate the regulatory mechanism of AMF on PIN1 and ferroptosis. Results revealed that AMF intervention or PIN1 knockdown inhibited the proliferation, migration, invasion and inflammation in MH7A cells. AMF facilitated lipid peroxidation and ferroptosis in MH7A cells. Moreover, AMF targeted inhibition of PIN1 expression, and PIN1 overexpression restored the promoting effect of AMF on lipid peroxidation and ferroptosis in MH7A cells. Besides, Fer-1 reversed the impacts of AMF on the abnormal biological behaviors of MH7A cells. In summary, AMF induced ferroptosis to inhibit the proliferation, migration, invasion and inflammation in RA-FLS by inhibiting PIN1, providing a promising candidate for RA treatment.

TRIM21 silencing inhibits the apoptosis and expedites the osteogenic differentiation of dexamethasone‑induced MC3T3‑E1 cells by activating the Keap1/Nrf2 pathway

Steroid-induced osteonecrosis of the femoral head (ONFH) is a serious complication caused by long-term or excessive use of glucocorticoids. The present study aimed to ascertain the effects of tripartite motif-containing protein 21 (TRIM21) on the process of steroid-induced ONFH and its hidden action mechanism. TRIM21 expression in dexamethasone (Dex)-treated mouse MC3T3-E1 preosteoblast cells was examined using reverse transcription-quantitative PCR and western blotting. The Cell Counting Kit-8 (CCK-8) method and lactate dehydrogenase release assay were used to respectively measure cell viability and injury. Flow cytometry analysis was used to assay cell apoptosis. Caspase 3 activity was evaluated using a specific assay, while alkaline phosphatase and Alizarin red S staining were used to evaluate osteogenesis. 2,7-dichloro-dihydrofluorescein diacetate fluorescence probe was used to estimate reactive oxygen species generation. Specific assay kits were used to appraise oxidative stress levels. In addition, the expression of apoptosis-, osteogenic differentiation- and Kelch-like ECH-associated protein 1 (Keap1)/nuclear factor erythroid 2-related factor 2 (Nrf2) signaling-associated proteins was assessed using western blotting. In Nrf2 inhibitor (ML385)-pretreated MC3T3-E1 cells exposed to Dex, cell apoptosis, osteogenesis and oxidative stress were detected again as aforementioned. Results revealed that TRIM21 expression was raised in Dex-induced MC3T3-E1 cells and TRIM21 deletion improved the viability and osteogenic differentiation, whereas it hampered the oxidative stress and apoptosis in MC3T3-E1 cells with Dex induction. In addition, silencing of TRIM21 activated Keap1/Nrf2 signaling. Moreover, ML385 partially abrogated the effects of TRIM21 depletion on the oxidative stress, apoptosis and osteogenic differentiation in MC3T3-E1 cells exposed to Dex. In conclusion, TRIM21 silencing might activate Keap1/Nrf2 signaling to protect against steroid-induced ONFH.

Comparison of the prophylactic use of ibandronate and its use in early-stage osteonecrosis in rats with steroid-induced osteonecrosis of the femoral head

OBJECTIVES

The aim of this study was to investigate the effects of ibandronate before and after the onset of osteonecrosis in rats with steroid-induced osteonecrosis of the femoral head.

MATERIALS AND METHODS

A total of 24 female Sprague-Dawley rats were used in this study. Three groups were formed with eight rats in each group. The first group was the prophylactic group that received ibandronate treatment before and after the onset of osteonecrosis (Group PT). The second group received ibandronate treatment three weeks after the development of osteonecrosis (Group TAO). The third group was the control group in which osteonecrosis was created, but only normal saline (NS) was given. At the end of the study, all rats were sacrificed, and their right femoral heads were removed, fixed with formalin, and sent for micro-computed tomography. Hematoxylin-eosin (H&E) and immunohistochemical examinations of the right femoral head sections were performed.

RESULTS

In the PT group, the trabecular thickness was significantly higher compared to those of the TAO and control groups (p<0.05). The trabecular thickness did not significantly differ between the TAO and control groups. The trabecular bone pattern factor was significantly higher in the PT group compared to the control and TAO groups (p<0.05); however, it showed no significant difference between the TAO and control groups. The incidence of type 2 osteonecrosis in the PT and TAO groups was significantly lower than that in the control group (p<0.05). The incidence of tissue-non-specific alkaline phosphatase (TNAPase) immunoreactivity of osteoblast positivity was significantly higher in the PT and TAO groups compared to the control group (p<0.05), whereas the incidence of TRAPase immunoreactivity of osteoclastic positivity was significantly lower in the PT and TAO groups compared to the control group (p<0.05).

CONCLUSION

Intravenous administration of ibandronate before the onset of the disease was more effective in the treatment of osteonecrosis in rats with steroid-induced osteonecrosis of the femoral head.

Aucubin prevents steroid-induced osteoblast apoptosis by enhancing autophagy via AMPK activation

Steroid‐induced osteoblast apoptosis is a crucial pathological process in steroid‐induced osteonecrosis of the femoral head (SONFH). Autophagy can resist apoptosis and AMPK plays an important role in autophagy regulation. Aucubin from the small tree Eucommia ulmoides Oliv., which has a long history of use in orthopaedics and traumatology in Asian medicine, can promote bone formation, but whether it can slow or prevent steroid‐osteoblast apoptosis is unclear. Therefore, we investigated the pathogenesis of SONFH and how the osteoblast responds to aucubin under the dexamethasone stimulation. In human femoral head osteonecrosis specimens, we found that the autophage and apoptosis level were increased, and the AMPK signalling was crucial to autophagy. We observed that aucubin could prevent dexamethasone‐induced apoptosis in osteoblasts by enhancing the level of autophagy. Further, we confirmed that the regulatory effect of aucubin on autophagy and apoptosis was achieved by activating AMPK signalling. We have demonstrated a mechanism of disease progression and shown that aucubin could enhance autophagy through AMPK signalling to prevent osteoblast apoptosis. These findings provide a basis for the further investigation of the potential therapeutic role of aucubin in the SONFH.

Endoplasmic reticulum stress, chondrocyte apoptosis and oxidative stress in cartilage of broilers affected by spontaneous femoral head necrosis

With the promotion of the intensive breeding model, the incidence of leg diseases has risen in fast-growing commercial broilers with higher body weight, seriously affecting their feed efficiency and causing animal welfare problems. Femoral head necrosis (FHN) is the most common leg disease in broilers. Previous studies reported that hormone-induced FHN is related to endoplasmic reticulum (ER) stress, apoptosis, and oxidative stress, but no detailed study has been conducted in broilers with spontaneous FHN. In the study, the articular cartilage of 5-wk-old Ross 308 broilers with spontaneous FHN was used to investigate the pathogenesis of the disease. According to the degree of femoral head injury, the birds participating in the experiment were divided into 3 groups, namely a control group, femoral head separation group and femoral head separation with growth plate lacerations group. The morphological changes in articular cartilage were observed by hematoxylin and eosin, toluidine blue, alcian blue and safranine O-solid green staining, and the expressions of genes related to cartilage homeostasis, ER stress, autophagy, apoptosis and oxidative stress was detected using Real-Time Quantitative PCR. In the results, the expression of aggrecan and collagen-2 mRNA levels decreased in the articular cartilage of spontaneous FHN broilers, and the same changes were observed in the tissue staining results, indicating the disordered nature of articular cartilage homeostasis. At the same time, FHN in broilers causes ER stress in articular chondrocytes and regulates oxidative stress by activating the nuclear factor erythroid 2-related factor 2/antioxidant response element pathway through protein kinase RNA-like ER kinase. Autophagy can be activated through the protein kinase RNA-like ER kinase-activating transcription factor-4 pathway, and apoptosis can even be activated through CCAAT-enhancer-binding protein homologous protein. Therefore, the secretory activity of articular chondrocytes in spontaneous FHN broilers is negatively affected, which leads to the disorder of cartilage homeostasis and results in FHN due to ER-stress-mediated chondrocyte apoptosis and oxidative stress.