Acid-sensing ion channel 1a mediates acid-induced pyroptosis through calpain-2/calcineurin pathway in rat articular chondrocytes.

The pyroptosis is a causative agent of rheumatoid arthritis, a systemic autoimmune disease merged with degenerative articular cartilage. Nevertheless, the precise mechanism of extracellular acidosis on chondrocyte pyroptosis is largely unclear. Acid-sensing ion channels (ASICs) belong to an extracellular H+ -activated cation channel family. Accumulating evidence has highlighted activation of ASICs induced by extracellular acidosis upregulate calpain and calcineurin expression in arthritis. In the present study, to investigate the expression and the role of acid-sensing ion channel 1a (ASIC1a), calpain, calcineurin, and NLRP3 inflammasome proteins in regulating acid-induced articular chondrocyte pyroptosis, primary rat articular chondrocytes were subjected to different pH, different time, and different treatments with or without ASIC1a, calpain-2, and calcineurin, respectively. Initially, the research results showed that extracellular acidosis-induced the protein expression of ASIC1a in a pH- and time-dependent manner, and the messenger RNA and protein expressions of calpain, calcineurin, NLRP3, apoptosis-associated speck-like protein, and caspase-1 were significantly increased in a time-dependent manner. Furthermore, the inhibition of ASIC1a, calpain-2, or calcineurin, respectively, could decrease the cell death accompanied with the decreased interleukin-1ß level, and the decreased expression of ASIC1a, calpain-2, calcineurin, and NLRP3 inflammasome proteins. Taken together, these results indicated the activation of ASIC1a induced by extracellular acidosis could trigger pyroptosis of rat articular chondrocytes, the mechanism of which might partly be involved with the activation of calpain-2/calcineurin pathway.

[Characteristics of Advanced Treatment of Treated Petrochemical Water by O3-BAC and Analysis of Consortium Structure].

The advanced treatment of treated petrochemical water by Ozone-Biological Activated Carbon (O3-BAC) was carried out in this study. The effect of O3 on the removal of Chemical Oxygen Demand (COD) and Spectral Absorption Coefficient (UV254) were investigated. The characteristics of organic matter and the microbial consortium structure of BAC were also investigated at 20 mg·L-1 of O3 dosage concentration, 40 min of O3 single stage contact time and 1.5 h of the empty bed residence time of BAC. Results showed that the effluent COD concentration of O3-BAC was 24 mg·L-1 with the removal efficiency of 40.4%. The COD removal efficiency of O3-BAC was higher than that for the BAC process. The UV254 removal efficiency of O3-BAC was 55.1%. Meanwhile, UV254 correlated with COD with a correlation coefficient of 0.89. The percentage of dissolved organic matters with relative molecular weight less than 1×103 increased from 69.0% to 87.0% after O3 oxidation. The NPOC removal efficiency of O3-BAC (45.8%) was higher than that of the BAC process (23.0%). The NPOC removal efficiency of the BAC unit was mainly achieved by reduction of dissolved organic matters with relative molecular weight less than 1×103. GC-MS analysis results showed that organic substances such as alkanes, unsaturated esters, and phenols had been removed by O3 oxidation. The micro ecological environment of the BAC unit had been significantly improved after O3 oxidation, and the genera with relative abundance over 1.0% increased from 6 to 11. The combined O3-BAC system can be applied to the advanced treatment of petrochemical treated water.

Necrostatin-1 ameliorates adjuvant arthritis rat articular chondrocyte injury via inhibiting ASIC1a-mediated necroptosis.

Necroptosis, a necrotic cell death pathway regulated by receptor interacting protein (RIP) 1 and 3, plays a key role in pathophysiological processes, including rheumatoid arthritis (RA). However, whether necroptosis is involved in RA articular cartilage damage processes remain unclear. The aim of present study was to investigate the dynamic changes in arthritic chondrocyte necroptosis and the effect of RIP1 inhibitor necrostatin-1 (Nec-1) and acid-sensing ion channels (ASICs) inhibitor amiloride on arthritic cartilage injury and acid-induced chondrocyte necroptosis. Our results demonstrated that the expression of RIP1, RIP3 and mixed lineage kinase domain-like protein phosphorylation (p-MLKL) were increased in adjuvant arthritis (AA) rat articular cartilage in vivo and acid-induced chondrocytes in vitro. High co-expression of ASIC1a and RIP1 showed in AA rat articular cartilage. Moreover, Nec-1 and amiloride could reduce articular cartilage damage and necroinflammation in AA rats. In addition, acid-induced increase in necroptosis markers RIP1/RIP3 were inhibited by Nec-1, ASIC1a-specific blocker psalmotoxin-1 (PcTx-1) or ASIC1a-short hairpin RNA respectively, which revealed that necroptosis is triggered in acid-induced chondrocytes and mediated by ASIC1a. These findings indicated that blocking ASIC1a-mediated chondrocyte necroptosis may provide potential therapeutic strategies for RA treatment.

Effects of autophagy on acid-sensing ion channel 1a-mediated apoptosis in rat articular chondrocytes.

Rheumatoid arthritis (RA) is a degenerative joint disease that is caused by multiple pathogenic factors. However, the precise etiology of RA is still unknown. Our previous studies demonstrated that acid-sensing ion channel 1a (ASIC1a)-mediated articular chondrocyte apoptosis played a key role in the progression of RA. In this study, we aim to explore whether ASIC1a mediates autophagy or not and the effect of autophagy on ASIC1a-mediated apoptosis. Primary articular chondrocytes, extracted from rat knee joints, were exposed to different concentrations of concentrated hydrochloric acid for different time intervals in vitro. The results indicated that extracellular acid treatment induced autophagy of rat articular chondrocytes. Moreover, inhibition of ASIC1a with either psalmotoxin 1 or ASIC1a short hairpin RNA reduced the autophagy flux. The results suggested that ASIC1a mediated acid-induced autophagy. Pretreatment with autophagy antagonist 3-methyladenine decreased the autophagy, but increased the apoptosis mediated by ASIC1a. Furthermore, knockdown of Beclin 1 by small interfering RNA attenuated autophagy but potentiated ASIC1a-mediated apoptosis of rat articular chondrocytes. Taken together, these findings suggested that both inhibition and silencing of autophagy could enhance ASIC1a-mediated apoptosis in rat articular chondrocytes, and therefore, autophagy is likely to be a new mechanism involved in ASIC1a-mediated apoptosis of articular chondrocytes during the pathogenesis of RA.

Interleukin-1ß and tumor necrosis factor-α augment acidosis-induced rat articular chondrocyte apoptosis via nuclear factor-kappaB-dependent upregulation of ASIC1a channel.

The acute-phase proinflammatory cytokines interleukin-1ß (IL-1ß) and tumor necrosis factor-α (TNF-α) demonstrate high-level expression and pleiotropic biological effects, and contribute to the progression and persistence of rheumatoid arthritis (RA). Acid hydrarthrosis is also an important pathological characteristic of RA, and the acid-sensing ion channel 1a (ASIC1a) plays a critical role in acidosis-induced chondrocyte cytotoxicity. However, the roles of IL-1ß and TNF-α in acid-induced apoptosis of chondrocytes remain unclear. Rat adjuvant arthritis and primary articular chondrocytes were used as in vivo and in vitro model systems, respectively. ASIC1a expression in articular cartilage was increased and highly colocalized with nuclear factor (NF)-κB expression in vivo. IL-1ß and TNF-α could upregulate ASIC1a expression. These cytokines activated mitogen-activated protein kinase and NF-κB pathways in chondrocytes, while the respective inhibitors of these signaling pathways could partially reverse the ASIC1a upregulation induced by IL-1ß and TNF-α. Dual luciferase and gel-shift assays and chromatin immunoprecipitation-polymerase chain reaction demonstrated that IL-1ß and TNF-α enhanced ASIC1a promoter activity in chondrocytes by increasing NF-κB DNA-binding activities, which was in turn prevented by the NF-κB inhibitor ammonium pyrrolidinedithiocarbamate. IL-1ß and TNF-α also decreased cell viability but enhanced LDH release, intracellular Ca2+ concentration elevation, loss of mitochondrial membrane potential, cleaved PARP and cleaved caspase-3/9 expression, and apoptosis in acid-stimulated chondrocytes, which effects could be abrogated by the specific ASIC1a inhibitor psalmotoxin-1 (PcTX-1), ASIC1a-short hairpin RNA or calcium chelating agent BAPTA-AM. These results indicate that IL-1ß and TNF-α can augment acidosis-induced cytotoxicity through NF-κB-dependent up-regulation of ASIC1a channel expression in primary articular chondrocytes.

ASIC2a overexpression enhances the protective effect of PcTx1 and APETx2 against acidosis-induced articular chondrocyte apoptosis and cytotoxicity.

Acid hydrarthrosis is another important pathological character in rheumatoid arthritis (RA), and acid-sensing ion channel 1a (ASIC1a) plays a destructive role in acidosis-induced articular chondrocyte cytotoxicity. Recently, ASIC2a has been reported to possess neuroprotective effect on acidosis-induced injury of neuronal cells. However, whether ASIC2a has an enhanced effect on the protective effect of blocking ASIC1a and ASIC3 against acid-induced chondrocyte apoptosis is still unclear. The aim of present study was to investigate the chondroprotective effect of ASIC2a with PcTx1 (ASIC1a specific blocker) and APETx2 (ASIC3 specific blocker) on acidosis-induced chondrocyte apoptosis. Our results revealed that acid (pH 6.0) decreased the cell viability and induced apoptosis of articular chondrocytes. PcTx1 and APETx2 combination significantly attenuated acidosis-induced chondrocyte cytotoxicity due to inhibit apoptosis, and this role could be enhanced by ASIC2a overexpression compared with the PcTx1 and APETx2 combination alone group. Moreover, both the [Ca2+]i levels and the levels of phosphorylated ERK1/2 as well as p38 were further reduced in acidosis-induced chondrocytes after ASIC2a overexpression in the presence of PcTx1 and APETx2. Furthermore, ASIC2a overexpression also reduced acid-induced the expression of ASIC1a. In addition, ASIC2a overexpression further promoted the PcTx1 and APETx2-increased levels of type II collagen in acidosis-induced chondrocytes. Taken together, the current data suggested that ASIC2a overexpression might enhance the anti-apoptotic and protective role of PcTx1 and APETx2 against acid-induced rat articular chondrocyte apoptosis by regulating ASIC1a expression and the [Ca2+]i levels and at least in part, suppressing p38 and ERK1/2 MAPK signaling pathways.

Association of Inflammatory Cytokines With the Symptom Cluster of Pain, Fatigue, Depression, and Sleep Disturbance in Chinese Patients With Cancer.

CONTEXT: Pain, fatigue, depression, and sleep disturbance are common in patients with cancer and usually co-occur as a symptom cluster. However, the mechanism underlying this symptom cluster is unclear. OBJECTIVES: This study aimed to identify subgroups of cluster symptoms, compare demographic and clinical characteristics between subgroups, and examine the associations between inflammatory cytokines and cluster symptoms. METHODS: Participants were 170 Chinese inpatients with cancer from two tertiary hospitals. Inflammatory markers including interleukin-6 (IL-6), interleukin-1 receptor antagonist, and tumor necrosis factor alpha were measured. Intergroup differences and associations of inflammatory cytokines with the cluster symptoms were examined with one-way analyses of variance and logistic regression. RESULTS: Based on cluster analysis, participants were categorized into Subgroup 1 (all low symptoms), Subgroup 2 (low pain and moderate fatigue), or Subgroup 3 (moderate-to-high on all symptoms). The three subgroups differed significantly in Eastern Cooperative Oncology Group (ECOG) performance status, sex, residence, current treatment, education, economic status, and inflammatory cytokines levels (all P < 0.05). Compared with Subgroup 1, Subgroup 3 had a significantly poorer ECOG physical performance status and higher IL-6 levels, were more often treated with combined chemoradiotherapy, and were more likely to be rural residents. IL-6 and ECOG physical performance status were significantly associated with 1.246-fold (95% CI 1.114-1.396) and 31.831-fold (95% CI 6.017-168.385) increased risk of Subgroup 3. CONCLUSION: Our findings suggest that IL-6 levels are associated with cluster symptoms in cancer patients. Clinicians should identify patients at risk for more severe symptoms and formulate novel target interventions to improve symptom management.

Functions of interleukin-34 and its emerging association with rheumatoid arthritis.

Rheumatoid arthritis (RA) is a systemic autoimmune disease characterized by chronic, synovial inflammation affecting multiple joints, finally leading to extra-articular lesions for which limited effective treatment options are currently available. Interleukin-34 (IL-34), recently discovered as the second colony-stimulating factor-1 receptor (CSF-1R) ligand, is a newly discovered cytokine. Accumulating evidence has disclosed crucial roles of IL-34 in the proliferation and differentiation of mononuclear phagocyte lineage cells, osteoclastogenesis and inflammation. Recently, IL-34 was detected at high levels in patients with active RA and in experimental models of inflammatory arthritis. Blockade of functional IL-34 with a specific monoclonal antibody can reduce the severity of inflammatory arthritis, suggesting that targeting IL-34 or its receptors may constitute a novel therapeutic strategy for autoimmune diseases such as RA. Here, we have comprehensively discussed the structure and biological functions of IL-34, and reviewed recent advances in our understanding of the emerging role of IL-34 in the development of RA as well as its potential utility as a therapeutic target.