Figure 4.

Presentation of UVR-induced release of LDH in human keratinocytes in dose- and time-dependent manner. Investigation was conducted using immortalized (HaCaT) (A) and normal (NHEK) (B) keratinocytes first pre-incubated with melatonin for 1 h (10⁻³ M) and irradiated with the UVB dose of 50 mJ/cm². Data were presented as the mean ± SEM of three independent experiments. Values were normalized and expressed as percentage of the control value, i.e., sham-irradiated sample (0 h 0 mJ/cm²) without melatonin (Mel). Statistically significant differences in melatonin versus non-melatonin treated samples at corresponding UVR doses and time points post-UVR were indicated as ** p < 0.01; *** p < 0.001; n.s., not significant, using the ANOVA with appropriate post-hoc testing (modified after Kleszczyński et al. [142] with permission from the publisher).