Inhibition of acid‐sensing ion channels by amiloride protects rat articular chondrocytes from acid‐induced apoptosis via a mitochondrial‐mediated pathway

Abstract

A significant decrease in tissue pH or acidosis is a common feature of numerous diseases, including RA (rheumatoid arthritis). Cartilage homoeostasis is profoundly affected by local acidosis in the joints. The diuretic, amiloride, is neuroprotective in models of cerebral ischaemia, a property attributable to the inhibition of ASICs (acid-sensing ion channels) by the drug. However, little is known about the effect of amiloride on apoptosis induced by extracellular acid in articular chondrocytes. We have found that amiloride could restrain the acid-induced apoptosis of rat articular chondrocytes in vitro. Primary rat articular chondrocytes were isolated, cultured and induced to apoptose by exposure to extracellular solution (pH 6.0), while simultaneously treated with 50-200 μM amiloride. Apoptotic rate, mitochondrial function, levels of apoptosis-related gene Bcl-2 family mRNA and activity of caspase 3/9 in chondrocytes were examined. Amiloride inhibited chondrocyte apoptosis in a dose-dependent manner. Furthermore, amiloride partly restored the levels of mitochondrial membrane potential by regulation of Bcl-2 family gene mRNA expression, and activity of caspase 3/9 in chondrocytes induced by extracellular acid. Our results indicated that amiloride protected against acid-induced apoptosis in rat articular chondrocytes by increasing anti-apoptotic ability and down-regulation of pro-apoptotic factors, thus protecting mitochondrial function.

Novel Insights into Acid-Sensing Ion Channels: Implications for Degenerative Diseases

“…Similarly, the ASIC1a-specific blocker PcTX venom attenuated acid-induced articular chondrocyte damage [25]. Furthermore, blocking ASICs markedly decreased calpain and calcineurin expression levels as well as caspase-3/9 activity, and led to recovery of mitochondrial membrane potential via regulation of B-cell lymphoma-2 family gene expression in acid-induced chondrocytes [9,73]. A more recent study reported that interleukin-6 promotes acid-induced articular chondrocyte apoptosis to a significant extent by activating the JAK2/STAT3 and MAPK/NF-κB signaling pathways, resulting in upregulation of ASIC1a expression and function [4].…”

“…Ca 2+ influx into cells is commonly mediated through activating channels or receptors, such as voltage-gated Ca 2+ channels, α-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate receptors, transient receptor potential channels, and N-methyl-Daspartate receptors [8]. Interestingly, ASICs have been shown to play crucial roles in modulating cell behavior via regulation of intracellular Ca 2+ accumulation, including apoptosis [4,9], differentiation [10], and autophagy [11]. Multiple lines of evidence suggest that aberrant expression and activation of ASICs contribute to the progression of various degenerative diseases, including multiple sclerosis, Parkinson's disease, Huntington's disease, intervertebral disc degeneration and arthritis.…”

Saponin-rich fraction from Clematis chinensis Osbeck roots protects rabbit chondrocytes against nitric oxide-induced apoptosis via preventing mitochondria impairment and caspase-3 activation

“…Therefore, prevention of excessive apoptosis of chondrocytes is believed to be beneficial for OA management. Drugs that can ameliorate OA have been reported to show anti-apoptotic effects on chondrocytes, such as sinomenine (Ju et al 2010), ADAM15 (Böhm et al 2010) and amiloride (Rong et al 2011). Many triterpenoid saponin ingredients in traditional Chinese medicine have anti-apoptotic effects, such as astragaloside (Shang et al 2011), Panax notoginseng saponins , Ginsenoside-Rg2 (Zhang et al 2008).…”

Synergy between Piezo1 and Piezo2 channels confers high-strain mechanosensitivity to articular cartilage

“…This signal transduction chain is in keeping with a recent publication (48) that reports a key role for L-type voltage-gated channels in osteoarthritis, evoked and aggravated by mechanical trauma. We consider it an appealing possibility that the chondrocytic Ca 2+ signal of cartilage traumatic injury impacts chondrocytes' cytoskeleton, energy homeostasis, apoptotic equilibrium, and inflammatory phenotype (15,(62)(63)(64)(65).…”