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Updated: Jul 19, 2026
Determining the Toxicity of UV Radiation and Chemicals on Primary and Immortalized Human Corneal Epithelial Cells
Published on: July 22, 2021
Transglutaminase participates in UVB-induced cell death pathways in human corneal epithelial cells
Louis Tong1, Zhuo Chen, Cintia S De Paiva
1Ocular Surface Center, Cullen Eye Institute, Baylor College of Medicine, Houston, Texas 77030, USA.
Purpose:
Ultraviolet light (UVB) is known to cause apoptosis in human corneal epithelial cells. This study evaluates the role of transglutaminase in regulating tumor necrosis factor (TNF) receptor clustering as well as caspase activation in UVB-induced apoptosis in human corneal epithelial cells.
Methods:
A human corneal epithelial cell line was used. A single dose of UVB (20 mJ/cm2) was used as a stimulus. Cell viability and cell death were investigated by MTT, terminal deoxynucleotidyl transferase-mediated dUTP-digoxigenin nick end labeling (TUNEL), and caspase-3 assays. Immunofluorescent staining was used to investigate TNF receptor-I clustering at various time intervals after UVB. Short interfering RNA was used to knock down transglutaminase-2 expression. Fluorescein-cadaverine uptake was used to assess transglutaminase activity. A noncovalent peptide delivery system was used to transfect guinea pig liver transglutaminase into corneal epithelial cells.
Results:
UVB increased transglutaminase activity, reduced cell viability, and increased TUNEL staining. UVB or TNF-alpha promoted TNF-receptor-I clustering, a process inhibited by the transglutaminase inhibitor, mono-dansyl cadaverine. UVB also increased activated caspase-3, in a manner suppressible by mono-dansyl cadaverine. Intracellular delivery of exogenous transglutaminase markedly increase caspase-3 activation compared with the vehicle control.
Conclusions:
Transglutaminase enzymatic activity is involved in corneal epithelial cell death after UVB and appears to participate in two steps regulating this process, clustering of TNF receptor-I and caspase-3 activation.
Insights
Transglutaminase activity regulates corneal cell death from UVB exposure by influencing tumor necrosis factor (TNF) receptor clustering and caspase activation, key steps in apoptosis.
Area of Science:
- Ophthalmology
- Cell Biology
- Biochemistry
Background:
- Ultraviolet B (UVB) radiation induces apoptosis in human corneal epithelial cells.
- Tumor necrosis factor (TNF) receptors play a role in cellular stress responses and apoptosis.
- Transglutaminases are enzymes involved in protein cross-linking and cellular processes.
Purpose of the Study:
- To investigate the role of transglutaminase in UVB-induced apoptosis of human corneal epithelial cells.
- To determine if transglutaminase regulates tumor necrosis factor receptor clustering and caspase activation following UVB exposure.
Main Methods:
- Utilized a human corneal epithelial cell line exposed to UVB radiation.
- Assessed cell viability and apoptosis using MTT, TUNEL, and caspase-3 assays.
- Examined TNF receptor-I clustering via immunofluorescent staining and transglutaminase activity using fluorescein-cadaverine uptake; transglutaminase expression was modulated using siRNA and exogenous enzyme delivery.
Main Results:
- UVB exposure increased transglutaminase activity, decreased cell viability, and elevated TUNEL staining.
- UVB and TNF-alpha induced TNF receptor-I clustering, which was inhibited by a transglutaminase inhibitor.
- UVB elevated activated caspase-3 levels, an effect suppressed by the transglutaminase inhibitor; exogenous transglutaminase enhanced caspase-3 activation.
Conclusions:
- Transglutaminase enzymatic activity is integral to corneal epithelial cell death induced by UVB.
- Transglutaminase appears to regulate UVB-induced apoptosis by modulating TNF receptor-I clustering and caspase-3 activation.
