Endoplasmic reticulum stress mediates nitric oxide-induced chondrocyte apoptosis

Abstract

Nitric oxide (NO) is one of the most important mediators of chondrocyte apoptosis, which is a notable feature of cartilage degeneration. While apoptosis of chondrocytes is induced by p53, NO can also induce endoplasmic reticulum (ER) stress, which may be involved in the process of NO-induced chondrocyte apoptosis. The aims of this study were to determine whether NO-induced ER stress (ERS) leads to apoptosis of chondrocytes and to investigate the temporal relationship between the expression of C/EBP-homologous protein (CHOP), an ERS-associated apoptotic molecule, and the expression of p53 during apoptosis in NO-stimulated chondrocytes. Rat chondrocytes were stimulated by sodium nitroprusside (SNP), a NO donor. Real-time polymerase chain reaction (PCR) was performed to analyze the mRNA expression of CHOP, glucose-regulated protein (GRP78) and p53. Apoptosis of chondrocytes was quantified using an enzyme-linked immunosorbent assay (ELISA). SNP-treated chondrocytes showed an increase in CHOP and GRP78 mRNA expression and underwent apoptosis. Sodium 4-phenylbutyrate (PBA), an ERS inhibitor, reduced CHOP and GRP78, as well as SNP-stimulated apoptosis of chondrocytes, without affecting the SNP-dependent generation of NO. In addition, the blockade of CHOP following siRNA transfection reduced SNP-induced apoptosis of chondrocytes. The CHOP expression increased after apoptosis was detected in the SNP-treated chondrocytes, whereas the p53 expression increased prior to apoptosis. These data demonstrated that NO-induced ERS leads chondrocytes to apoptosis, although this effect appears to be limited to persistent impairment of NO stimulation. These findings may provide insight into the pathology of cartilage degeneration.

β-Arrestin-1 protects against endoplasmic reticulum stress/p53-upregulated modulator of apoptosis-mediated apoptosis via repressing p-p65/inducible nitric oxide synthase in portal hypertensive gastropathy

“…Therefore, excess NO could directly disturb ER function and activate ER stress, which could mediate PUMA-induced apoptosis in PHG as described in our previous and current studies [11]. Several reports have also revealed that the ER stress pathway involving C/EBP homologous protein (CHOP) was important in NO-induced apoptosis of some cell types, and that blockage of NO production could alleviate apoptosis [16][17][18]. While, the role played by TNF-α in PHG was via regulation of NO production, which has been also shown to activate ER stress.…”

“…The ER stress/PUMA pro-apoptotic signaling network plays a pivotal role in cell death in a variety of tissues in response to hypoxia, ischemia and noxious drugs [12][13][14], of which nitric oxide (NO), an important mediator of physiological and pathological processes, contributes to the ER stress reaction and apoptosis of cells in various diseases [15][16][17][18]. NO is produced by NO synthase (NOS), with three main isoforms of NOS having been identified: neuronal NOS (nNOS), endothelial NOS (eNOS), and inducible NOS (iNOS) [19].…”

Antimicrobial Peptide CMA3 Derived from the CA-MA Hybrid Peptide: Antibacterial and Anti-inflammatory Activities with Low Cytotoxicity and Mechanism of Action in Escherichia coli

“…The NO produced was measured on a microplate reader at 540 nm. The changes evoked in NO levels were determined by comparison with data points obtained in the absence of CMA3 (25).…”

Nitric oxide has contrasting age-dependent effects on the functionality of murine hematopoietic stem cells

“…Yet another TF that was strongly upregulated by NO in juvenile HSCs was Chop1 . It is a basic leucine-zipper protein induced by a variety of stimuli, including NO [52], that evokes cellular stress responses. On the other hand, deletion of its homologous TF, C/EBP, has been shown to affect self-renewal of HSCs [31].…”