Glycyrrhizin Ameliorates Radiation Enteritis in Mice Accompanied by the Regulation of the HMGB1/TLR4 Pathway

Abstract

Radiation enteritis is a common side effect of radiotherapy for abdominal and pelvic malignancies, which can lead to a decrease in patients’ tolerance to radiotherapy and the quality of life. It has been demonstrated that glycyrrhizin (GL) possesses significant anti-inflammatory activity. However, little is known about its anti-inflammatory effect in radiation enteritis. In the present study, we aimed to investigate the potential anti-inflammatory effects of GL on radiation enteritis and elucidate the possible underlying molecular mechanisms involved. The C57BL/6 mice were subjected to 6.5 Gy abdominal X-ray irradiation to establish a model of radiation enteritis. Hematoxylin and eosin staining was performed to analyze the pathological changes in the jejunum. The expression of TNF-α in the jejunum was analyzed by immunochemistry. The levels of inflammatory cytokines, such as TNF-α, IL-6, IL-1β, and HMGB1 in the serum were determined by enzyme-linked immunosorbent assay. The intestinal absorption capacity was tested using the D-xylose absorption assay. The levels of HMGB1 and TLR4 were analyzed by western blotting and immunofluorescence staining. We found that GL significantly alleviated the intestinal damage and reduced the levels of inflammatory cytokines, such as TNF-α, IL-6, IL-1β, and HMGB1 levels. Furthermore, the HMGB1/TLR4 signaling pathway was significantly downregulated by GL treatment. In conclusion, these findings indicate that GL has a protective effect against radiation enteritis through the inhibition of the intestinal damage and the inflammatory responses, as well as the HMGB1/TLR4 signaling pathway. Thereby, GL might be a potential therapeutic agent for the treatment of radiation enteritis.

Glycyrrhizin ameliorating sterile inflammation induced by low-dose radiation exposure

“…In contrast to PAMPs, endogeneous molecules which incur immune response are defined as alarmin (or damage associated molecular patterns, DAMPs) and HMGB1 is an example of this category 24 , 25 . Radiation is one stimuli that cause tissue damage without pathogens 24 , and extracellular HMGB1 has been found to increase after irradiation 22 , 23 . In this study, we demonstrated that both mRNA expression and serum levels of HMGB1 and pro-inflammatory cytokines such as TNF-α, IL-6, IL-1α and IL-1β increase dose dependently after 0.1 Gy and 1 Gy radiation exposure.…”

“…According to previous studies, GL can ameliorate ischemic-reperfusion injury, hepatotoxicity, and acute kidney injury by inhibiting the HMGB1 pathway 20 , 21 . It can also mitigate radiation-induced tissue injuries such as radiation-induced acute lung injury 22 or radiation enteritis 23 . However, past studies have only looked into HMGB1 and the abovementioned protective effects of GL after relatively high doses of radiation (20 Gy and 6.5 Gy, respectively) 22 , 23 .…”

“…It can also mitigate radiation-induced tissue injuries such as radiation-induced acute lung injury 22 or radiation enteritis 23 . However, past studies have only looked into HMGB1 and the abovementioned protective effects of GL after relatively high doses of radiation (20 Gy and 6.5 Gy, respectively) 22 , 23 . Hence, the purpose of this study was to assess changes in HMGB1 and pro-inflammatory cytokines and to investigate the protective effect of GL after low-dose radiation exposure.…”

Glycyrrhizin Attenuates Carcinogenesis by Inhibiting the Inflammatory Response in a Murine Model of Colorectal Cancer

“…For IHC analysis, paraffin-embedded mouse colon sections were deparaffinized in xylene and hydrated in a series of alcohols. After heat-induced antigen retrieval and blocking with 1% skim milk, the sections were incubated overnight with primary antibodies (8-NitroG (Pinlaor et al, 2004 [ 31 ], 1:400)); 8-OxodG (JaICA, MOG-100p, 1:400); HMGB1 (Abcam, 18256, 1:400); COX2 (Santa Cruz Biotechnology, Inc., SC-1745, 1:400); YAP1 (Abcam, ab 39361, 1:400); SOX9 (Abcam, ab 185230, 1:400)), and then incubated with an avidin–biotin complex (Vectastain ABC kit, Vector Laboratories Burlingame, CA, USA). The immunoreaction was visualized using a peroxidase DAB kit (Nacalai Tesque Inc., Kyoto, Japan).…”

“…Although some researchers have studied the effect of GL on colitis [ 30 , 31 , 32 ], the effect of GL on ulcerative colitis colorectal cancer caused by an azoxymethane (AOM)/dextran sodium sulfate (DSS) model is not known. Therefore, we investigated whether GL can suppress inflammation and carcinogenesis, using a carcinogen (AOM)/colorectal inflammatory agent (DSS)-induced murine model of colorectal cancer, and assessed the molecular mechanisms involved.…”