Role of HSP90α in osteoclast formation and osteoporosis development

Possible mechanisms underlying the regulation of postmenopausal osteoporosis by follicle-stimulating hormone

Objective

To explore the possible mechanisms by which follicle-stimulating hormone (FSH) regulates postmenopausal osteoporosis through the FSH/FSH receptor (FSHr)/G protein/C/EBPβ/heat shock protein 90 alpha (HSP90α) signalling pathways.

Methods

We measured serum FSH, luteinising hormone (LH), and HSP90α levels in the serum and adipose tissue of women of childbearing age and menopausal status. In the in vivo studies, 12 B57CL female mice were divided equally into Sham, OVX, and OVX + FSHr Blocker groups. Serum levels of alkaline phosphatase, FSH, and HSP90α, along with StRACP vitality, were determined, and femur micro-computed tomography was performed. Additionally, FSH, FSHr, G protein, C/EBPβ, and HSP90α levels were assessed using quantitative polymerase chain reaction. Finally, we divided the human multiple myeloma cell line U266 into three groups. The activity of tartrate-resistant acid phosphatase (TRAP) in the supernatant at different stages was detected, and myeloma cells were stained with TRAP.

Results

HSP90α levels in adipose tissue supernatant and serum were lower in women of childbearing age than in menopausal women (P < 0.05). Serum FSH and HSP90α levels demonstrated a strong correlation. Treatment with FSHr blockers resulted in decreased FSH, FSHr, G protein, C/EBPβ, and HSP90α levels in mice. TRAP staining of osteoclast-like cells exhibited a significantly higher intensity in the M-CSF + RANKL + recombinant HSP90α group than in the M-CSF + RANKL and blank control groups (P < 0.05).

Conclusions

Our results indicate that FSH promotes HSP90α secretion by adipocytes via the FSHr/G protein/C/EBPβ pathway. This mechanism affects osteoclast activity and exacerbates osteoporosis.

Osteogenesis imperfecta type 10 and the cellular scaffolds underlying common immunological diseases

Osteogenesis imperfecta type 10 (OI10) is caused by loss of function codon variants in the gene SERPINH1 that encodes heat shock protein 47 (HSP47), rather than in a gene specifying bone formation. The HSP47 variants disrupt the folding of both collagen and the endonuclease IRE1α (inositol-requiring enzyme 1α) that splices X-Box Binding Protein 1 (XBP1) mRNA. Besides impairing bone development, variants likely affect osteoclast differentiation. Three distinct biochemical scaffold play key roles in the differentiation and regulated cell death of osteoclasts. These scaffolds consist of non-templated protein modifications, ordered lipid arrays, and protein filaments. The scaffold components are specified genetically, but assemble in response to extracellular perturbagens, pathogens, and left-handed Z-RNA helices encoded genomically by flipons. The outcomes depend on interactions between RIPK1, RIPK3, TRIF, and ZBP1 through short interaction motifs called RHIMs. The causal HSP47 nonsynonymous substitutions occur in a novel variant leucine repeat region (vLRR) that are distantly related to RHIMs. Other vLRR protein variants are causal for a variety of different mendelian diseases. The same scaffolds that drive mendelian pathology are associated with many other complex disease outcomes. Their assembly is triggered dynamically by flipons and other context-specific switches rather than by causal, mendelian, codon variants.

Predictive Value of Serum Heat Shock Protein 90α on the Prognosis of Patients with Lung Adenocarcinoma

Purpose

Heat shock protein 90α (HSP90α) is highly expressed in tumors, and predicts tumor progression. This study analyzed the correlation between the expression level of HSP90α in the serum and the prognosis of patients with lung adenocarcinoma.

Patients and methods

The medical records of patients with 228 lung adenocarcinoma from September 2015 to December 2021 were analyzed. HSP90α expression in the patients' serum was detected by ELISA and the cut-off value (93.76 ng/mL) was determined according to the ROC curve, then the patients were divided into high- and low-level groups. The differences in the medical records of the two groups were compared using the X² test, and Univariate and multivariate Cox regression analyses showed that serum HSP90α level were independent risk factors for both PFS and OS (P < 0.05).

Results

HSP90α was positively correlated with TNM staging (P < 0.01) by One-way analysis of variance. The results of the correlation analysis and the Kaplan-Meier survival curve showed that the expression levels of HSP90α and CEA of patients were positively correlated (R=0.54, P < 0.001), and patients with high HSP90α and CEA levels had the worst OS (P < 0.001).

Conclusion

HSP90α expression is negatively correlated with the prognosis of patients with lung adenocarcinoma and is a potential prognostic marker.

Proteomic Changes of Osteoclast Differentiation in Rheumatoid and Psoriatic Arthritis Reveal Functional Differences

Background

Osteoclasts play a crucial role in the maintenance, repair, and remodeling of bones of the adult vertebral skeleton due to their bone resorption capability. Rheumatoid arthritis (RA) and psoriatic arthritis (PsA) are associated with increased activity of osteoclasts.

Objectives

Our study aimed to investigate the dynamic proteomic changes during osteoclast differentiation in healthy donors, in RA, and PsA.

Methods

Blood samples of healthy donors, RA, and PsA patients were collected, and monocytes were isolated and differentiated into osteoclasts in vitro using macrophage colony-stimulating factor (M-CSF) and receptor activator of nuclear factor κB ligand (RANK-L). Mass spectrometry-based proteomics was used to analyze proteins from cell lysates. The expression changes were analyzed with Gene Set Enrichment Analysis (GSEA).

Results

The analysis of the proteomic changes revealed that during the differentiation of the human osteoclasts, expression of the proteins involved in metabolic activity, secretory function, and cell polarity is increased; by contrast, signaling pathways involved in the immune functions are downregulated. Interestingly, the differences between cells of healthy donors and RA/PsA patients are most pronounced after the final steps of differentiation to osteoclasts. In addition, both in RA and PsA the differentiation is characterized by decreased metabolic activity, associated with various immune pathway activities; furthermore by accelerated cytokine production in RA.

Conclusions

Our results shed light on the characteristic proteomic changes during human osteoclast differentiation and expression differences in RA and PsA, which reveal important pathophysiological insights in both diseases.