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Figure 6 | Arthritis Research & Therapy

Figure 6

From: All-trans retinoic acid suppresses interleukin-6 expression in interleukin-1-stimulated synovial fibroblasts by inhibition of ERK1/2pathway independently of RAR activation

Figure 6

Contribution of ERK 1/2 pathway to the inhibitory effect of all- trans retinoic acid (ATRA). Rat synovial fibroblasts were stimulated with 10 ng/mL of interleukin-1-beta (IL-1β) in the presence or absence of the ERK1/2 inhibitor PD-98059 or ATRA. (a) Western blotting of phosphorylated ERK1/2 (P-ERK1/2) after 15 minutes of stimulation in the presence or absence of 10 μM PD-98059. (b) Production of IL-6 (nanograms per milliliter by enzyme-linked immunosorbent assay [ELISA]) in culture supernatant after 24 hours of stimulation in the presence or absence of 10 μM PD-98059 or 1 μM ATRA. (c) Nuclear content of nuclear factor-kappa-B (NF-κB) by ELISA-based TransAm™ kit after 30 minutes of stimulation in the presence or absence of 10 μM PD-98059 or 1 μM ATRA. Nuclear content of nuclear factor of interleukin-6 (NF-IL-6) (d) or activator protein-1 (AP-1) (c-Jun) (e) by ELISA-based TransAm™ kit after 4 hours of stimulation in the presence or absence of 10 μM PD-98059 or 1 μM ATRA. Data are expressed as mean ± standard deviation of IL-6 levels or absorbance value at 450 nm values from at least three independent experiments. Statistically significant differences from the control are indicated as *P < 0.05 and from IL-1β-stimulated cells as #P < 0.05. ERK1/2, extracellularly regulated kinase 1/2.

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