In order to test the hypothesis that SA is protective against the development of osteoarthritis (OA), primary mouse chondrocytes were treated <i>in vitro</i> with SA and the promoter transactivation activity of heme oxygenase 1 (HO-1), nuclear translocation of Nrf2, and protein expression of HO-1 were assayed.
The finding in mice that deletion of SOD2 or the anti-oxidant gene transcriptional regulator nuclear factor-erythroid 2- related factor (Nrf2) result in more severe OA, while overexpression or treatment with mitochondrial targeted anti-oxidants reduces OA, further support a role for excessive ROS in the pathogenesis of OA.
In conclusion, this study has demonstrated that SIN inhibits the IL-1β-induced inflammatory response and cartilage destruction by activating the Nrf2/HO-1 signaling pathway and inhibiting the NF-κB signaling pathway in mouse chondrocytes, suggesting a new use for SIN in the treatment of OA.
DC32 remarkably inhibited the activation of ERK and NF-κB pathway, increased the expression of Nrf2 and HO-1 in cultured OA-FLSs detected by western blot.
Visfatin significantly induced apoptosis and superoxide anion production, increased miR-34a, miR-181a, superoxide dismutase (SOD)-2, catalase (CAT), NRF2 and decreased BCL2 gene and protein expression in OA chondrocytes.
Inducible nitric oxide synthase, nuclear factor (NF)‑κB, phosphorylated‑(p)‑AMP‑activated protein kinase and sirtuin 1 protein expression were significantly suppressed and heme oxygenase 1 (HO‑1) and nuclear factor erythroid 2‑related factor 2 (Nrf‑2) protein expression was stimulated in rats with OA treated with resveratrol.
Importantly, Nrf2 over-expression activated ERK1/2 and its downstream targets-ELK1, P70S6K and P90RSK and suppressed the IL-1β-induced apoptosis whereas inhibition of ERK1/2 activation abrogated the protective effects of Nrf2 in OA chondrocytes.
Reducing ROS production in the mitochondria, stimulating antioxidant gene expression through Nrf2 activation, or inhibiting specific redox-sensitive signaling proteins represent additional approaches to disease modification in osteoarthritis that require further investigation.
Compared to the control, OA-treatment led to a result as follows: (1) increased the intracellular levels of TG and NO; (2) up-regulated the protein expression of SREBP-1C, PNPLA3, pJNK, CYP 2E1 and CYP 4A; (3) decreased the uptake of 2-NBDG; (4) down-regulated the protein expression of CFLAR, PPARα, PI3K, pAKT and NRF2.
<i>Ex vivo</i> experiments indicated that Nrf-2 and HO-1 expression is reduced in T2DM <i>versus</i> non-T2DM OA cartilage (0.57-fold Nrf-2 and 0.34-fold HO-1), and prostaglandin E<sub>2</sub> (PGE<sub>2</sub>) release was increased in samples with low HO-1 expression.
Genetic ablation of Nrf2 using specific siRNA, significantly abrogated the anti-inflammatory and chondroprotective potential of Wogonin in IL-1β-stimulated OA chondrocytes.
Piceatannol inhibits the IL-1β-induced inflammatory response in human osteoarthritic chondrocytes and ameliorates osteoarthritis in mice by activating Nrf2.