Inhibition of Proteasome Activity Upregulates IL-6 Expression in RPE Cells through the Activation of P38 MAPKs

Figure 6

Inhibition of JNK cannot block proteasome inhibition-induced upregulation of IL-6. (a) ARPE-19 cells were cultured in the presence or absence of MG132 (10 μM), Sp600125 (40 μM), or MG132 plus Sp600125 for 2, 4, 6, 8, 10, and 12 h. Levels of IL-6 in the media were determined by ELISA. The results are the mean ± SD. and as compared with the control; ^# as compared with the control or Sp600125 alone; ^## as compared with the control or Sp600125 alone. (b) Levels of IL-6 in the medium were detected by ELISA at 0 h–6 h and 6 h–12 h in the presence or absence of MG132 (10 μM), SP600125 (40 μM), or MG132 plus SP600125. The results are the mean ± SD. and as compared with the control; ^# as compared with the control or Sp600125 alone. (c) To study whether JNK inhibition can block the activation of AP-1 induced by proteasome inhibition, the RPE cells were cultured in the presence or absence of MG132 (10 μM), SP600125 (40 μM), or MG132 plus SP600125 for 4 h; nuclear extracts were prepared; and electrophoretic mobility gel shift assays were performed for AP-1 binding. Coomassie staining gel was the internal standard.

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