Because of special water-rich circulation and relatively poor heat dissipation in eyes, it is a sensitive target organ under microwave action. Radiation could lead to increased apoptosis and decreased cell proliferation [10–11]. And injuries to the retina is the researching focus . Modern medical research has found the pathogenesis of microwave injury to the retinal is oxidative damage .
VU is mainly distributed in north China, Korea, Japan, northern Europe and North America. Its berry is nearly spherical or oval. It was named Wenpu (Shengjing Tongzhi) and xiongguo (Chinese Bencao) in ancient Chinese books. It’s commonly known as red beans, tooth pimples and Wenpu black rice tree. They are warm in nature and bitter in taste.
Light damage is called "light poison" in traditional medicine. Its nature is hot and dirty. Many ophthalmology monographs such as "the secret biography ophthalmology Longmu Lun · Volume 7" and "syndrome and treatment guidelines · qiqiaomen" called it "dark eyes". Just because of its diuretic and detoxifying characteristic, VU was used for curing "light poison" and "dark eyes" by detoxification and supplementing the deficiency of liver and kidney. The main active component of VU is anthocyanin, whose antioxidant effect has been widely proved in modern medicine [14–15].While, in modern medical research, the pathogenesis of light injury is oxidative damage . Based on the consistency of traditional and modern medicine in the treatment mechanism of antioxidantion, the anthocyanins extracted from VU could be used to study the prevention and treatment of microwave damage. The school of food science and nutrition engineering of China Agricultural University was responsible for purification of VU which was applied in this study. And the high performance liquid chromatography (HPLC) and total ion flow diagram of anthocyanins from VU extracts were provided, which can not only maximize the natural antioxidant capacity of plants, but also ensure the uniqueness and scientificity of the research object.
When assessing retinal function through ERG, no significant difference was found between group 1 and group 3 in a-wave ERG amplitude, but both of them were higher than group 2. Besides, the b-wave amplitude of group 3 was significantly higher than group 2 but lower than group 1 in photopic condition. Generally speaking, a-wave originates in rod and cone cells and represents the electrical activity of photoreceptor, and b-wave represents the electrical activity of bipolar cells and inner nuclear layers . So these results indicate the retina is injured by microwave from the inner layer to the outer layer, and the VU extracts could prevent and alleviate the injury.
Histopathologic findings of this experiment confirm such results. Retinal edema, IS/OS getting disordered, pyknosis and vacuolar degeneration in INL and GCL could be seen in group 2, which could be obtained the same findings in Wang’s study , but all of those presented minor changes in group 3. In quantitative terms, the thickness of ONL of group 2 was thicker than group 1 and group 3, and there was no significant difference between group 1 and 3. The cell density of INL and GCL showed that group 3 was more than group 2 but less than group 1.
To confirm such protective effect by VU extracts is for the reason of antioxidative function, classic oxidative stress markers were tested in this study. Similarly, the SOD activity of group 2 was found significantly lower than group 1 and group3, but there was no difference between group 1 and group 3. The GPx activity of group 3 was significantly lower than group 1 but higher than group 2.
SOD plays an important role in the main antioxidant defense system in the body . GPx widely exists in the body as a peroxidase which could clear the peroxides in living cells from free radical damage. When cells encounter harmful conditions caused by reactive oxygen species (ROS), as antioxidant enzymes, SOD and GPx could ensure the integrity of the cells as a compensation mechanism . While it has been demonstrated that ROS is an initiating factor in the injury induced by microwave irradiation .
Previous studies have found anthocyanins extracted from VU could reduce apoptosis and alleviate oxidant injury of mouse retina by activating Nrf2/HO-1 signal pathway and inducing HO-1 translation . Combined with the functional and tissue structure performance, the changes of these oxidative stress markers further showed that anthocyanins extracted by VU were protective to rat retina against microwave-induced damage through antioxidation.