Investigations on the potential radio-protective properties of edible Cyanobacterium during pelvic irradiation in a mouse model

Although the intestine is rarely the primary target, it is often damaged as collateral damage during exposure to pelvic irradiation. Exposure to ionizing radiation is known to increase oxidative stress which on its turn induced DNA damage by the high ROS levels. After pelvic irradiation, patients can develop radiation enteritis due to epithelial damage which results in a loss of barrier function. This loss can increase inflammation. Another aspect is a disruption of the bacterial community after exposure to irradiation called dysbiosis. Until now, different types of products such as probiotics have yet been tested whether they decrease these side effects, but they are not yet well substantiated with studies on modes of action and they are not yet applied to a large extent. In this study, we tested a promising cyanobacterium: Arthrospira sp. PCC8005 which is highly radio-resistant (up to 6400Gy) and has anti-oxidative properties which can help combat the increased oxidative stress during pelvic irradiation. The possible radio-protective properties of freeze-dried whole cell preparations of Arthrospira sp. were tested on different tissues: (1) effect on ileum morphology, (2) effect on radiation-induced inflammation in the ileum, (3) cholesterol-lowering effect in the blood plasma and (4) changes in bacterial community by next gen sequencing. Our results showed that exposure to ionizing radiation caused a decrease in villus length , which could not be significantly reversed by the freeze-dried whole cell preparations of Arthrospira sp.. In addition, the expression of selected pro-inflammatory and anti-inflammatory cytokines (TNF-α, TGFβ and IL6) was not significantly modulated. Nevertheless, a significant decrease in total cholesterol levels was observed. More specifically, we observed a decrease in HDL levels and no significant difference in LDL levels in the blood plasma. Characterization of the impact on the gut bacterial community in still ongoing. In this pilot study, different high end points were used to evaluate the potential radio-protective properties but to really understand the mechanism, more in depth techniques have to be used e.g. immunological staining for apoptosis. Another aspect of this study is that freeze-dried preparation of dead whole cell Arthrospira sp. were used, which might interfere/inactivate with the radio-protective properties of the molecules in the cytoplasm (e.g. phycocyanin, vitamins, unsaturated fatty acids). Therefore, the use of fresh preparation of Arthrospira sp. could be envisaged in the future.