Telmisartan Mitigates TNF-α-Induced Type II Collagen Reduction by Upregulating SOX-9

Abstract

The proinflammatory cytokine tumor necrosis factor-α (TNF-α)-induced degradation of extracellular matrix (ECM), such as type II collagen in chondrocytes, plays an important role in the development of osteoarthritis (OA). Telmisartan, an angiotensin II (Ang-II) receptor blocker, is a licensed drug used for the treatment of hypertension. However, the effects of Telmisartan in tumor necrosis factor-α (TNF-α)-induced damage to chondrocytes and the progression of OA are unknown. In this study, we found that treatment with Telmisartan attenuated TNF-α-induced oxidative stress by reducing the levels of mitochondrial reactive oxygen species (ROS) and the production of protein carbonyl in human C28/I2 chondrocytes. Interestingly, Telmisartan inhibited TNF-α-induced expression and secretions of proinflammatory mediators such as interleukin-1β (IL-1β), interleukin-6 (IL-6), and monocyte chemotactic protein 1 (MCP-1). Notably, stimulation with TNF-α reduced the levels of type II collagen at both the mRNA and the protein levels, which was rescued by the treatment with Telmisartan. Mechanistically, we found that Telmisartan restored TNF-α-induced reduction of SOX-9. Silencing of SOX-9 blocked the inhibitory effects of Telmisartan against TNF-α-induced degradation of type II collagen. These findings suggest that Telmisartan might be a potential and promising agent for the treatment of OA.

Figure 1

Effects of Telmisartan in cell viability of human C28/I2 chondrocytes. (A) Molecular structure of Telmisartan. (B) Cells stimulated with Telmisartan at concentrations of 0.5, 1, 5, 10, 50, and 100 μM. Cell viability was measured using a cell counting kit-8 (CCK-8) assay (#, ##, P < 0.05, 0.01 vs vehicle group).

Figure 2

Telmisartan alleviated TNF-α-induced oxidative stress in human C28/I2 chondrocytes. The cells were incubated with TNF-α (10 ng/mL) in the presence or absence of Telmisartan (5 and 10 μM) for 24 h. (A) Production of mitochondrial ROS. (B) Production of protein carbonyl (####, P < 0.0001 vs vehicle group; &&, &&&, P < 0.01, 0.001 vs TNF-α group).

Figure 3

Telmisartan alleviated TNF-α-induced expression of inflammatory factors human C28/I2 chondrocytes. The cells were incubated with TNF-α (10 ng/mL) in the presence or absence of Telmisartan (5 and 10 μM) for 24 h. (A) mRNA of IL-1β, IL-6, and MCP-1. (B) Secretions of IL-1β, IL-6, and MCP-1 (####, P < 0.0001 vs vehicle group; &&, &&&, P < 0.01, 0.001 vs TNF-α group).

Figure 4

Telmisartan restored TNF-α-induced reduction of Col2a1 gene and type II collagen in human C28/I2 chondrocytes. The cells were incubated with TNF-α (10 ng/mL) in the presence or absence of Telmisartan (5 and 10 μM) for 24 h. (A) mRNA of Col2a1. (B) Protein of type II collagen (####, P < 0.0001 vs vehicle group; &&, &&&, P < 0.01, 0.001 vs TNF-α group).

Figure 5

Telmisartan restored TNF-α-induced reduction of SOX-9 in human C28/I2 chondrocytes. The cells were incubated with TNF-α (10 ng/mL) in the presence or absence of Telmisartan (5 and 10 μM) for 24 h. (A) mRNA of SOX-9. (B) Protein of SOX-9 (####, P < 0.0001 vs vehicle group; &&, &&&, P < 0.01, 0.001 vs TNF-α group).

Figure 6

Silencing of SOX-9 abolished the protective effects of Telmisartan against TNF-α-induced reduction of Col2a1 gene and type II collagen in human C28/I2 chondrocytes. The cells were transfected with SOX-9 siRNA, followed by stimulation with TNF-α (10 ng/mL) or Telmisartan (10 μM) for 24 h. (A) mRNA of Col2a1. (B) Protein of type II collagen (####, P < 0.0001 vs vehicle group; &&&, P < 0.001 vs TNF-α treatment group; $$$, P < 0.001 vs TNF-α+Telmisartan group).