*2.9. Immunofluorescence Assay*

HaCaT cells were cultured at a density of 1 × 10<sup>4</sup> cells/well in DMEM supplement with 10% FBS in an 8-well Lab Tek chamber (Thermo Fisher Scientific, Waltham, MA, USA). We pretreated the cells with 1.5 μM Ectoine for the indicated time followed by irradiation in the absence or presence of UVA. The cells were subjected to an immunofluorescence assay, which uses a method previously described [21].
