□National Institute of Biological Resources (NIBR) under Ministry of Environment announced Friday that its recent study on health effects of particulate matter (PM) using embryos of Korean indigenous frog, Bombina orientalis has indicated how PM reduces secretion of gel forming mucin in respiratory epithelial cells.

※ Mucin is a slippery aqueous secretion produced by, and covering, mucous membrane. Mucin serves to protect epithelial cells in the linings of the respiratory, digestive, and urogenital systems, controlling mineralization.

◦ For air breathing species such as mammals and amphibians, mucus secretion is important. When the secretion is reduced, airways become dry.

□ Since 2017, NIBR researchers and Dr. Tae Ju Park team of Ulsan National Institute of Science and Technology (UNIST) has investigated a major cause of dry airways when exposed by PM, using embryos of Bombina orientalis.

◦ In the study, the researchers had injected 50-100 µg/ml of each PM 2.5 and PM 10 derived from a heavy diesel engine into the frog’s embryonic mucociliary epithelium. They have investigated acute responses of mucus-secreting goblet cells upon exposure to different PM levels.

※ Goblet cells are goblet shaped like epithelial cells that secrete gel-forming mucins to protect the mucous membranes.

◦ The research results have indicated that PM decreases 20-40% of mucus secretion from goblet cells in the mucociliary epithelium of Bombina orientalis compared to the control embroyos. The research also has shown that PM exposure significantly accumulates mucus vesicles in the cytoplasm causing hyposecrtion of mucus.

□ The reason why they use embryos of Bombina orientalis is that the frog’s mucociliary epithelium is structurally and physiologically similar to human airway epithelium.

◦ In addition, Bombina orientalis has similar mucus-secreting goblet and multi-ciliated cells to the African clawed frog, Xenopus laevis, which has been widely used in previous research on the pathophysiology of mucociliary epithelium.

※ Xenopus laevis is a species of African aquatic frog and a popular experimental animal for many biological studies. The species has been classified as harmful invasive species under the Public Notice No. 2015-228 by Ministry of Environment, enforced in December 2015.

□ The researchers also have measured the mucus secretion of the frog’s embryos that had been pretreated with well-known antioxidants: α-tocopherol, trolox, and NAC (N-acetyl cysteine) on exposure to PM.

◦ In consequence, the pretreated embryos had displayed few hyposecretion of mucus upon exposure to PM. Researchers have concluded that antioxidants treatment may recover the reduced mucus secretion from PM. Based on the findings, NIBR is planning to explore effective Korean indigenous species that have potentials to treat respiratory disorders caused by PM.

◦ The study results will be published in Scientific Reports, which is online open access scientific journal published by Nature, in the middle of April.

□ Bae, Yeon Jae, President of NIBR said: “The research has significant meaning in that the mystery of dry airways caused by PM has been first unraveled by using the Korean red bellied frog”. “NIBR will conduct the subsequent study using the embryos to develop asthma treatments”, he said.

Appendixes

A. The accepted manuscript.