Figure 2. Clustergram or heatmap analysis: Curcumin alters microRNAs (miRNAs) expression profiling in ARPE-19 cells. This clustergram or heatmap represents the expression levels of 81 microRNAs (miRNAs) in four conditions (control, curcumin, hydrogen peroxide [H₂O₂], and curc+H₂O₂) relative to an average of four housekeeping genes. ARPE-19 cells were treated with 20 μM curcumin and 200 μM H₂O₂ for 6 and 18 h, respectively. In the curc+H₂O₂ group, the cells were treated with curcumin for 6 h before H₂O₂ insult for 18 h. Cells with vehicle DMSO were used as control. Each vertical line in the heatmap represents a single miRNA, and the rows represent groups. Samples clustered according to the condition. Red represents high expression, while green represents low expression. The average C_t values for miRNAs with minimum (Min) and Maximum (Max) expression are given in parentheses. Based on clustering, curcumin and H₂O₂ alone changed the expression of several miRNAs compared with the control. In addition, curcumin pretreatment altered H₂O₂-induced miRNA expression. There were three samples (n=3) in each condition.