Figure 4. The effect of hydroquinone (HQ) on retinal pigment epithelium (RPE) cytokine and growth factor secretion. A: Secreted cytokine/growth factor levels in the culture supernatant of RPE exposed to 75 μM HQ for 24 h were expressed as fold changes over unexposed controls (mean±SEM). When compared to control samples, three cytokines/growth factors were overexpressed by more than 1.5 times and reached a significance level of p<0.05: VEGF, IL-12, and IL-10. B: The changes in cytokines/growth factor secretion were compared between from RPE cells exposed to 75 μM HQ for 24 hours and controls.