Trans-Cinnamaldehyde Inhibits IL-1 β-Stimulated Inflammation in Chondrocytes by Suppressing NF- κ B and p38-JNK Pathways and Exerts Chondrocyte Protective Effects in a Rat Model of Osteoarthritis

Abstract

Objective: Trans-cinnamaldehyde (TCA), a compound from Cinnamomum cassia Presl, has been reported to have anti-inflammatory effect. However, its effect on cartilage degradation in osteoarthritis is unclear. This study is designed to examine the effects of TCA on cartilage in vitro and in vivo.

Material and methods: SW1353 cells and human primary chondrocytes were treated with varying concentrations of TCA (2-20 μg/ml) for 2 h followed by IL-1β stimulation. Cell viability was examined by the MTT assay. Expression of MMP-1, MMP-3, MMP-13, ADAMTS-4, and ADAMTS-5 was examined by Western blot and RT-qPCR. Monosodium iodoacetate (MIA)-induced OA was established in rats to assess the chondrocyte protective effects of intraperitoneal injection of TCA (50 mg/kg).

Results: TCA at a concentration of 10 μg/ml had no significant effect on cell viability. MMP-1, MMP-3, MMP-13, ADAMTS-4, and ADAMTS-5 were decreased by TCA 2-10 μg/ml in a dose-dependent manner (all P<0.05). Pretreatment with TCA decreased the degradation of IκBα and increased the expression of p-IκBα, indicating that NF-κB inactivation was induced by TCA in IL-1β-stimulated SW1353 cells. Pretreatment with TCA decreased the levels of p-p38 and p-JNK, while the levels of p-ERK were not significantly affected. TCA 10 μg/ml significantly decreased expression levels of MMP-1, MMP-3, MMP-13, ADAMTS-4, and ADAMTS-5. In vivo results showed that TCA alleviated cartilage destruction and the OARSI scores.

Conclusion: TCA possesses anti-inflammatory effect in vitro and exerts chondrocyte protective effects in vivo, in which NF-κB and p38-JNK were involved.

Figure 1

Chemical structure of trans-cinnamaldehyde (TCA).

Figure 2

High concentration of TCA decreases cell viability. We initially examined the cytotoxicity of TCA to primary SW1353 cells and varying concentrations of TCA (2-20 μg/ml) for 24 h. Each value indicates the mean ± SEM from three independent experiments. ∗P<0.05.

Figure 3

TCA reduces the mRNA expression of MMP-1, MMP-3, MMP-13, ADAMTS-4, and ADAMTS-5 in IL-1β-stimulated SW1353 cells. The SW1353 cells were pretreated with varying concentrations of TCA (2-20 μg/ml) for 2 h followed by IL-1β (10ng/ml) stimulation for 6 h. The mRNA was assessed by RT-qPCR. (a) MMP-1. (b) MMP-3. (c) MMP-13. (d) ADAMTS-4. (e) ADAMTS-5. ∗P<0.05; ∗∗P<0.01.

Figure 4

TCA suppresses NF-κB activation and IκB degradation in IL-1β-stimulated SW1353 cells. The SW1353 cells were preprocessed with varying concentrations of TCA (2-20 μg/ml) for 2 h, then stimulated with IL-1β (10 ng/ml) for 6 h. The proteins were detected by Western blot. The protein expression of IκBα (b) and p-IκBα (c) was standardized according to the respective level of GAPDH protein. Value was used to express relative changes compared with control, which was set to 1. ∗ P <0.05.

Figure 5

TCA suppresses p38-JNK activation in IL-1β-stimulated SW1353 cells. The SW1353 cells were preprocessed with varying concentrations of TCA (2-20 μg/ml) for 2 h and then stimulated with IL-1β (10 ng/ml) for 6 h. The proteins were detected by Western blot. The protein expression of p-ERK (a), p-p38 (b), and p-JNK1/2 (c) was standardized based on the respective level of GAPDH protein. Value was expressed as relative changes in comparison to control, which was set to 1. ∗ P < 0.05.

Figure 6

TCA reduced the mRNA expression of MMP-1, MMP-3, MMP-13, ADAMTS-4, and ADAMTS-5 in IL-1β-stimulated chondrocytes. The mRNAs were assessed by RT-qPCR. (a) MMP-1. (b) MMP-2. (c) MMP-3. (d) MMP-9. (e) MMP-13. (f) ADAMTS-4. (g) ADAMTS-5. ∗P<0.05.

Figure 7

TCA exerts cartilage protective effects in MIA-induced rats after 4 weeks of intraperitoneal injection. (a) Knee joint sections were stained with Safranin O/fast green. The sections were from rats after 4 weeks administration of TCA or vehicle. Representative sections are shown. Formation of osteophytes (yellow arrow), severe disruption of meniscal tissue (yellow box), and hyperplasia of synoviocyte (red arrow) were observed in vehicle-treated MIA-induced rats. There was mild fibroid-like change in TCA-treated MIA-induced group (red box). (b) OARSI scores of articular cartilage at 4 weeks after surgery. ∗P<0.05, NS: not statistically significant.