Related Experiment Video
Updated: Aug 30, 2026
Determining the Toxicity of UV Radiation and Chemicals on Primary and Immortalized Human Corneal Epithelial Cells
Published on: July 22, 2021
UV-induced corneal epithelial cell death by activation of potassium channels
1Division of Molecular Medicine, Harbor-UCLA Medical Center, UCLA School of Medicine, University of California-Los Angeles, 1124 W. Carson Street, Torrance, CA 90502, USA.
Purpose:
The purpose of the present study is to determine the role of K+ channel activity as an early event in UV-induced corneal epithelial cell apoptosis.
Method:
Both cell-attached and nystatin-perforated patch-clamping were performed to record K+ channel activity in rabbit corneal epithelial (RCE) and primary cultured rabbit corneal epithelial (PRCE) cells exposed to UV irradiation. On exposure of corneal epithelial cells or intact corneas to UV-C irradiation or treatment of corneal epithelial cells with etoposide, cell apoptosis was determined by DNA fragmentation, ethidium bromide-acridine orange nuclear stain and TdT-mediated dUTP nick-end labeling (TUNEL).
Results:
In the present study, UV-irradiation-induced corneal epithelial cell apoptosis through activation of a K+ channel in the cell membrane was an early event in response to UV irradiation. UV-C irradiation (42 microJ/cm(2)) activated robust K+ channel activity in RCE and PRCE cells at both the single-channel and whole-cell levels, when measured with the cell-attached and nystatin-perforated patch clamps, respectively. Suppression of UV-irradiation-induced K+ channel activity with the specific K+ channel blocker 4-aminopurydine (4-AP) prevented UV-irradiation-induced apoptosis in the RCE and PRCE cells, loss of the superficial layer of corneal epithelium, and apoptosis in the basal layer corneal epithelium. However, suppression of K+ channel activity did not protect RCE and PRCE cells from etoposide, a topoisomerase II inhibitor, which induced cell death by bypassing the membrane. Furthermore, application of valinomycin, a K+ ionophore, to mimic the effect of mass activation of the K+ channel in RCE and PRCE cells caused cell apoptosis.
Conclusions:
The results indicate that UV irradiation induces superactivity of K+ channels in the membrane is an early event mediating signaling transduction and resulting in corneal epithelial cell death in response to UV irradiation.
Insights
Ultraviolet (UV) irradiation activates potassium (K+) channels in corneal epithelial cells, triggering apoptosis. Blocking these K+ channels prevents UV-induced cell death, highlighting their role in UV damage.
Area of Science:
- Ophthalmology
- Cell Biology
- Biophysics
Background:
- Corneal epithelial cells are susceptible to UV-induced damage.
- Apoptosis is a key mechanism in cellular response to UV radiation.
- The specific molecular events leading to UV-induced corneal apoptosis are not fully understood.
Purpose of the Study:
- To investigate the role of potassium (K+) channel activity as an early event in UV-induced corneal epithelial cell apoptosis.
- To determine if K+ channel activation is a necessary step for UV-induced cell death in corneal epithelium.
Main Methods:
- Utilized cell-attached and nystatin-perforated patch-clamp techniques to record K+ channel activity in rabbit corneal epithelial (RCE) and primary cultured rabbit corneal epithelial (PRCE) cells.
- Exposed cells and intact corneas to UV-C irradiation.
- Assessed apoptosis using DNA fragmentation, ethidium bromide-acridine orange staining, and TUNEL assay.
- Investigated the effect of the K+ channel blocker 4-aminopyridine (4-AP) and the K+ ionophore valinomycin.
Main Results:
- UV-C irradiation (42 microJ/cm(2)) robustly activated K+ channel activity in RCE and PRCE cells.
- Blocking K+ channel activity with 4-AP prevented UV-induced apoptosis and corneal epithelial layer loss.
- Valinomycin, mimicking K+ channel activation, induced apoptosis in corneal epithelial cells.
- K+ channel blockers did not protect cells from etoposide-induced apoptosis, indicating a specific role in UV-induced pathways.
Conclusions:
- UV irradiation induces K+ channel superactivity in the corneal epithelial cell membrane.
- This K+ channel activation is an early signaling event that mediates corneal epithelial cell death following UV exposure.
- Targeting K+ channels may offer a protective strategy against UV-induced ocular damage.
