Low-dose ionizing radiation: Effects on the proliferation and migration of lens epithelial cells via activation of the Wnt/β-catenin pathway

Study on the factors influencing lens opacity among medical radiation workers exposed to long-term low-dose ionizing radiation

Background

Lens damage induced by occupational exposure to ionizing radiation has been extensively studied by radiation workers. This study aimed to investigate the factors influencing lens opacity in radiologists exposed to low-dose ionizing radiation.

Methods

Medical examination data of 1,456 radiological workers who underwent occupational health checkups between January 2023 and December 2024 were collected, along with their total personal radiation dose over a 10-year period from 2015 to 2024. The relationship between lens opacity and influencing factors such as sex, age, radiation dose, occupational type, and duration of radiation work was analyzed using multivariate logistic regression.

Results

Among the 1,456 radiological workers, 105 cases of lens opacity were detected, with a prevalence rate of 7.21%. The majority of lens opacities were located in the posterior subcapsular region, accounting for 52 cases (49.52%, 52/105). The prevalence of lens opacity revealed a linear increasing trend with age and years of service. In addition, the proportion of lens opacity gradually increased with increasing total and annual radiation doses. Age, occupational type, and total radiation dose were associated with posterior subcapsular opacity. Age and total radiation dose were regarded as independent risk factors [age Odds Ratio (OR), 1.068; 95% confidence interval (CI), 1.035-1.103; total dose OR, 1.111; 95% CI, 1.033-1.194]. The three occupational types with the highest prevalence were nuclear medicine (6/51), radiation therapy (14/240), and interventional radiology (18/340).

Conclusion

The prevalence of lens opacity among radiological workers was associated with age, radiation dose, occupational type, and duration of radiation work. Nuclear medicine poses the highest risk for posterior subcapsular opacity.

Differential Signaling Pathways Identified in Aqueous Humor, Anterior Capsule, and Crystalline Lens of Age-Related, Diabetic, and Post-Vitrectomy Cataract

Background: The purpose of this study was to detect proteomic alterations and corresponding signaling pathways involved in the formation of age-related cataract (ARC), diabetic cataract (DC), and post-vitrectomy cataract (PVC). Methods: Three sample types, the aqueous humor (AH), the anterior capsule (AC), and the content of the phaco cassette, were collected during phacoemulsification surgery. The samples were obtained from 12 participants without diabetes mellitus (DM), 11 participants with DM, and 7 participants without DM, with a history of vitrectomy surgery in the past 12 months. The Sp3 protocol (Single-Pot, Solid-Phase, Sample-Preparation) was used for the sample preparation. The recognition and quantification of proteins were carried out with liquid chromatography online with tandem mass spectrometry. The DIA-NN software was applied for the identification and quantification of peptides/proteins. Statistical analysis and data visualization were conducted on Perseus software. Data are available via ProteomeXchange. Results: A very rich atlas of the lens and AH proteome has been generated. Glycosaminoglycan biosynthesis and the non-canonical Wnt receptor signaling pathway were differentially expressed in ARC compared to both the DC and PVC groups. In the PVC group, complement activation was differentially expressed in AH samples, while glutathione metabolism and oxidoreductase activity were differentially expressed in AC samples. Microfilament motor activity, microtubule cytoskeleton organization, and microtubule binding were differentially expressed in the DC and PVC groups in both AH and AC samples. Conclusions: The results of this study expand the existing knowledge on pathways involved in the pathophysiology of cataract, and suggest possible important druggable targets for slower progression or even prevention of cataract.

Phenotypic and transcriptional changes in lens epithelial cells following acute and fractionated ionizing radiation exposure

PURPOSE

Exposure to ionizing radiation is one of the known risk factors for the development of lens opacities. It is believed that radiation interactions with lens epithelial cells (LEC) are the underlying cause of cataract development, however, the exact mechanisms have yet to be identified. The aim of this study was to investigate how different radiation dose and fractionation impact normal LEC function.

MATERIALS AND METHODS

A human derived LEC cell line (HLE-B3) was exposed to a single acute x-ray dose (0.25 Gy) and 6 fractionated doses (total dose of 0.05, 0.1, 0.25, 0.5, 1, and 2 Gy divided over 5 equal fractions). LEC were examined for proliferation using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and migration using a Boyden chamber assay at various time points (0.25, 0.5, 1, 2, 4, 7, 9, 11, and 14 d) post-irradiation. Transcriptomic analysis through RNA sequencing was also performed to identify differentially expressed genes and regulatory networks in cells following 4 different acute exposures and 1 fractionated exposure.

RESULTS

Exposure to an acute dose of 0.25 Gy significantly increased proliferation and migration rates, peaking at 7 d post irradiation (20% and 240% greater than controls, respectively), before returning to baseline levels by day 14. Fractionated exposures had minimal effects up to a dose of 0.5 Gy, but significantly reduced proliferation and migration after 1 and 2 Gy by up to 50%. The largest transcriptional response occurred 12 h after an acute 0.25 Gy dose, with 362 genes up-regulated and 288 genes down-regulated. A unique panel of differentially expressed genes was observed between moderate versus high dose exposures, suggesting a dose-dependent transcriptional response in LEC that is more pronounced at lower doses. Gene ontology and upstream regulator analysis identified multiple biological processes and molecular functions implicated in the radiation response, in particular differentiation, motility, receptor/ligand binding, cell signaling and epithelial-mesenchymal cell transition.

CONCLUSIONS

Overall, this research provides novel insights into the dose and fractionation effects on functional changes and transcriptional regulatory networks in LEC, furthering our understanding of the mechanisms behind radiation induced cataracts.

Noncancer Effects of Ionizing Radiation Exposure on the Eye, the Circulatory System and beyond: Developments made since the 2011 ICRP Statement on Tissue Reactions

For radiation protection purposes, noncancer effects with a threshold-type dose-response relationship have been classified as tissue reactions (formerly called nonstochastic or deterministic effects), and equivalent dose limits aim to prevent occurrence of such tissue reactions. Accumulating evidence demonstrates increased risks for several late occurring noncancer effects at doses and dose rates much lower than previously considered. In 2011, the International Commission on Radiological Protection (ICRP) issued a statement on tissue reactions to recommend a threshold of 0.5 Gy to the lens of the eye for cataracts and to the heart and brain for diseases of the circulatory system (DCS), independent of dose rate. Literature published thereafter continues to provide updated knowledge. Increased risks for cataracts below 0.5 Gy have been reported in several cohorts (e.g., including in those receiving protracted or chronic exposures). A dose threshold for cataracts is less evident with longer follow-up, with limited evidence available for risk of cataract removal surgery. There is emerging evidence for risk of normal-tension glaucoma and diabetic retinopathy, but the long-held tenet that the lens represents among the most radiosensitive tissues in the eye and in the body seems to remain unchanged. For DCS, increased risks have been reported in various cohorts, but the existence or otherwise of a dose threshold is unclear. The level of risk is less uncertain at lower dose and lower dose rate, with the possibility that risk per unit dose is greater at lower doses and dose rates. Target organs and tissues for DCS are also unknown, but may include heart, large blood vessels and kidneys. Identification of potential factors (e.g., sex, age, lifestyle factors, coexposures, comorbidities, genetics and epigenetics) that may modify radiation risk of cataracts and DCS would be important. Other noncancer effects on the radar include neurological effects (e.g., Parkinson's disease, Alzheimer's disease and dementia) of which elevated risk has increasingly been reported. These late occurring noncancer effects tend to deviate from the definition of tissue reactions, necessitating more scientific developments to reconsider the radiation effect classification system and risk management. This paper gives an overview of historical developments made in ICRP prior to the 2011 statement and an update on relevant developments made since the 2011 ICRP statement.