Ascorbic acid-2 glucoside mitigates intestinal damage during pelvic radiotherapy in a rat bladder tumor model

Abstract

Purpose

Ascorbic acid is a strong antioxidant and has potent radioprotective effects on radiation injuries. Ascorbic acid 2-glucoside (AA2G) is a stabilized derivative of ascorbic acid and rapidly hydrolyzed into ascorbic acid and glucose. Since there is the possibility that AA2G treatment interferes with the antitumor activity of radiotherapy, we investigated the effect of AA2G treatment during radiotherapy on acute radiation enteritis and antitumor activity of radiotherapy in rats.

Materials and methods

AY-27 rat bladder tumor cells were used to induce bladder tumors in rats. Two weeks after inoculation rats received fractionated pelvic radiotherapy in eight fractions for 4 weeks totaling 40 Gy. During radiotherapy, one group of rats received per os AA2G (ascorbic acid: 250 mg/kg/day) and its bolus engulfment (ascorbic acid: 250 mg/kg) 8 h before each X-irradiation fraction. Seven days after the last X-irradiation, we studied histology, DNA double strand break (DSB) damage (by 53BP1 foci staining), and the M1/M2 macrophage response by immunohistochemistry of paraffin-fixed bladder and intestinal tissues.

Results

AA2G treatment reduced the intestinal damage (shortening of villi) but did not reduce antitumor effectiveness of radiotherapy against bladder tumors. Like the controls, AA2G-treated rats showed no residual tumor lesions in the bladder after X-irradiation. Both AA2G-treated and control groups showed similar persistent DSB damage (53BP1 foci) both in bladders and ilea seven days after radiotherapy. Radiotherapy tended to reduce CD163⁺ M2 macrophages, which are considered as an anti-inflammatory subtype favoring tissue repair, in the bladders. X-irradiation also reduced the occurrence of M2 macrophages in the ilea. AA2G treatment significantly increased CD163⁺/CD68⁺ macrophage ratio in the ilea of rats after pelvic irradiation in comparison to the sham irradiated control rats. AA2G treatment increased, albeit not significantly, the CD163⁺/CD68⁺ macrophage ratio in the irradiated bladders relative to the control irradiated rats. On the other hand, bladders and ilea of the irradiated rats with and without AA2G treatment showed similar frequencies of CD68⁺ macrophages.

Conclusions

AA2G treatment mitigated radiation-induced intestinal damage without reducing antitumor activity after fractionated pelvic radiotherapy against bladder tumors in rats. The beneficial effect of AA2G treatment seems to promote a restoration of the M2 answer as well as tissue remodeling and wound healing. Similar residual DNA damage in bladders and ilea seven days post-irradiation is consistent with tumor control in both groups.

Keywords:

• AY-27 cells
• DNA damage
• 53BP1
• CD163
• M1/M2 macrophages

Disclosure statement

All authors have no conflict of interest.

Additional information

Funding

This work is supported by the Advanced Defense Medical Research from Ministry of Defense Japan.

Notes on contributors

Yasutoshi Ito

Yasutoshi Ito, RT, is a radiological technologist and a research fellow of the Military Medicine Research Unit of the Japan Ground Self-Defense Force, Tokyo, Japan.

Tetsuo Yamamoto

Tetsuo Yamamoto, MD, PhD, is a specialist in radiology and a commander of the NBC Counter Medical Unit of the Japan Ground Self-Defense Force, Tokyo, Japan.

Kosuke Miyai

Kosuke Miyai, MD, PhD, is a pathologist of the Self-Defense Forces Central Hospital, Tokyo, Japan.

Junya Take

Junya Take, MD, is a specialist in pediatrics and emergency medicine of the National Defense Medical College, Tokorozawa, Japan.

Harry Scherthan

Harry Scherthan, PhD, is a professor and specialist for molecular cytology at the Bundeswehr Institute of Radiobiology, Munich, Germany.

Anna Rommel

Anna Rommel, MD, is a pathologist and a scientist of the Bundeswehr Institute of Radiobiology, Munich, Germany.

Stefan Eder

Stefan Eder, MD, is a specialist in occupation medicine and a scientist of the Bundeswehr Institute of Radiobiology, Munich, Germany.

Konrad Steinestel

Konrad Steinestel, MD, PhD, is a professor and the Head of Pathology and Molecular Pathology in the Bundeswehrkrankenhaus Ulm, Germany.

Alexis Rump

Alexis Rump, MD, PhD, MHBA, is a specialist in anesthesiology, emergency medicine, and clinical pharmacology, and a senior scientist of Bundeswehr Institute of Radiobiology, Munich, Germany.

Matthias Port

Matthias Port, MD, PhD, is a professor of internal medicine (hematology/oncology) and radiology and the director of the Bundeswehr Institute of Radiobiology, Munich, Germany.

Nariyoshi Shinomiya

Nariyoshi Shinomiya, MD, PhD, is the president of the National Defense Medical College, Tokorozawa, Japan.

Manabu Kinoshita

Manabu Kinoshita, MD, PhD, is a professor of immunology and microbiology, National Defense Medical College, Tokorozawa, Japan.