Far-Ultraviolet Light at 222 nm Affects Membrane Integrity in Monolayered DLD1 Colon Cancer Cells

Area of Science:

• Cell Biology
• Photobiology
• Biophysics

Background:

• Far-ultraviolet (F-UV) light, specifically at 222 nm, exhibits bactericidal properties comparable to deep-ultraviolet (D-UV) light (~260 nm).
• The cytotoxic effects of 222 nm F-UV on mammalian cells, particularly in monolayer cultures, remain incompletely understood.
• Understanding wavelength-specific UV effects is crucial for applications in disinfection and sterilization.

Purpose of the Study:

• To compare the cytotoxicity of 222 nm F-UV and 254 nm D-UV on DLD-1 cells in a monolayer culture.
• To investigate the distinct cellular mechanisms underlying the cytotoxic effects of these two UV wavelengths.
• To assess DNA damage and cell membrane integrity following irradiation.

Main Methods:

• DLD-1 cells were cultured and exposed to varying doses of 222 nm F-UV and 254 nm D-UV.
• Cell morphology was monitored using time-lapse imaging after F-UV irradiation.
• DNA damage was quantified by measuring cyclobutane pyrimidine dimer (CPD) formation.
• Cell membrane integrity was assessed using Syto9 and propidium iodide (PI) staining.

Main Results:

• Both 222 nm F-UV and 254 nm D-UV demonstrated radiant energy-dependent cytotoxicity.
• Comparable cytotoxicity was observed at 30 mJ/cm² for both F-UV and D-UV.
• 222 nm F-UV irradiation led to immediate cell expansion and significant propidium iodide (PI) uptake, indicating compromised membrane integrity.
• 254 nm D-UV irradiation resulted in lower PI uptake but a higher amount of cyclobutane pyrimidine dimer (CPD), indicative of DNA damage.

Conclusions:

• 222 nm F-UV and 254 nm D-UV exhibit comparable cytotoxicity in DLD-1 monolayer cells at specific radiant energies.
• The primary mechanism of F-UV cytotoxicity involves disruption of cell membrane integrity.
• D-UV primarily induces apoptosis through DNA damage, whereas F-UV affects membrane integrity.