TLR4-Dependent Immune Response Promotes Radiation-Induced Liver Disease by Changing the Liver Tissue Interstitial Microenvironment during Liver Cancer Radiotherapy

Abstract

Liver tissue interstitial fluid (TIF) a special microenvironment around liver cells, which may play a vital role in cell communication during liver injury. Moreover, toll-like receptor 4 (TLR4) is an important trigger of the immune response that may also play a role in liver injuries, including radiation-induced liver disease (RILD). Therefore, the purpose of this study was to identify the roles of the TLR4-dependent immune response and TIFs in RILD after radiation therapy (RT) for liver cancer. This study consisted of two phases, and in the primary phase, the livers of TLR4 mutant (TLR4(-)) and normal (TLR4(+)) mice were irradiated with 30 Gy. TIF was then obtained from mouse livers and assessed by cytokine array analysis 20 days after irradiation, and cytokines in the TIFs, TLR4 and RILD were analyzed. In the second or validation phase, hepatocytes were isolated from TLR4(+) or TLR4(-) mice irradiated with 8 Gy and were co-cultured with TIFs from mouse livers, apoptosis of the hepatocytes was then measured using flow cytometry. We found that severe RILD was accompanied by higher expression of granulocyte macrophage colony-stimulating factor (GM-CSF), tumor necrosis factor-related apoptosis inducing ligand (TRAIL) and vascular endothelial growth factor receptor 2(VEGFR-2) in liver TIFs, from in TLR4(+) mice compared with TLR4(-) mice (P < 0.05). In both TLR4(+) and TLR4(-) hepatocytes, apoptosis after irradiaton was increased significantly after co-culture in TIFs from TLR4(+) mice that had their livers irradiated, compared with TIFs from TLR4(-) mice that had their livers irradiated or TIFs from unirradiated mice (P < 0.05). In summary, these findings indicate that the TLR4-dependent immune response may promote RILD by enhancing the expression of GM-CSF, VEGFR-2 and TRAIL in liver TIFs.

Toll‑like receptor 4 and its associated proteins as prognostic factors for HCC treated by post‑radiotherapy surgery

“…Although the expression levels of TLR4, VEGFR2 and TRAIL in liver tissue were not identified as predictors for survival outcomes in patients with HCC treated by post-RT surgery, the results of the present study indicated that they were associated with the severity of RILDs, potentially fatal complications that restrict radiotherapeutic efficacy against HCC, including liver piecemeal necrosis, inflammation, hepatic veno-occlusive disease and sinusoidal obstruction syndrome ( 30 , 31 ). In the present study, patients with low TLR4 expression presented with milder RILDs than those with high TLR4 expression in the peritumoral liver tissue subsequent to liver RT, which was consistent with the preliminary data of another study of ours, in mice ( 10 ). TRAIL not only promotes the malignant behavior of cancer cells, but is also associated with hepatocyte toxicity when combined with RT ( 26 , 32 ).…”

“…The excessive activation of TLR4 signaling may induce liver damage ( 8 – 10 ). Although the expression levels of TLR4, VEGFR2 and TRAIL in liver tissue were not identified as predictors for survival outcomes in patients with HCC treated by post-RT surgery, the results of the present study indicated that they were associated with the severity of RILDs, potentially fatal complications that restrict radiotherapeutic efficacy against HCC, including liver piecemeal necrosis, inflammation, hepatic veno-occlusive disease and sinusoidal obstruction syndrome ( 30 , 31 ).…”

“…The excessive activation of TLR4 signaling, as may be stimulated by DAMPs derived from distress or injury in tissues following RT, may induce liver damage ( 6 ), and further influence the apoptosis, proliferation, invasion and metastasis of HCC ( 7 , 8 ). Our previous studies identified that the TLR4-dependant immune response may promote radiation-induced liver diseases (RILDs) via enhancing the expression of certain proteins in mice, including tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and vascular endothelial growth factor receptor 2 (VEGFR2) ( 9 , 10 ). However, the clinical value of these potentially influencing factors in estimating the prognosis for patients with HCC treated by surgical resection post-RT remains unclear.…”

MicroRNA-146a-5p attenuates irradiation-induced and LPS-induced hepatic stellate cell activation and hepatocyte apoptosis through inhibition of TLR4 pathway

“…Radiotherapy is one of the most effective treatment modalities for liver cancer 1 . However, the occurrence of radiation-induced liver disease (RILD) limits the delivery of curative doses of radiation therapy for liver cancer, which is attributed to low tolerance of the liver to radiation 2 . 6.5–17.6% of patients treated with stereotactic body radiotherapy develop RILD, depending on the irradiated liver volume and hepatic functional reserve 3 .…”

Downregulation of high mobility group box 1 enhances the radiosensitivity of non‑small cell lung cancer by acting as a crucial target of microRNA‑107

“…For instance, HMGB1 and the TLR4 signaling pathway were found to be overactive in malignant epithelial ovarian cancer, and to be associated with tumor cell proliferation and invasiveness that may be mediated via NF-κB signaling ( 41 ). Moreover, TLR4 and NF-κB are closely associated with the radiosensitivity of several cancers, such as esophageal and liver cancer ( 42 , 43 ). In the present study, HMGB1-knockdown and irradiation downregulated the expression of TLR4/NF-κB signaling pathway related-proteins.…”