Hypoxia-Induced Mesenchymal Stromal Cells Exhibit an Enhanced Therapeutic Effect on Radiation-Induced Lung Injury in Mice due to an Increased Proliferation Potential and Enhanced Antioxidant Ability

Background/Aims: Radiation therapy is an important treatment for thoracic cancer; however, side effects accompanied with radiotherapy lead to limited tumor control and a decline in patient quality of life. Among these side effects, radiation-induced lung injury (RILI) is the most serious and common. Hence, an effective remedy for RILI is needed. Mesenchymal stromal cells (MSCs) are multipotent adult stem cells that have been demonstrated to be an effective treatment in some disease caused by tissue damage. However, unlike other injuries, RILI received limited therapeutic effects from implanted MSCs due to local hypoxia and extensive reactive oxygen species (ROS) in irradiated lungs. Since the poor survival of MSCs is primarily due to hypoxia and ROS generation, we hypothesize that persistent and adaptive hypoxia treatment induces enhanced resistance to hypoxic stress in implanted MSC. The aim of this study is to investigate whether persistent and adaptive hypoxia treatment of bmMSCs prior to their transplantation in injured mice enhanced survival and improved curative effects in RILI. Methods: Primary bmMSCs were obtained from the marrow of six-week-old male C57BL6/J mice and were cultured either under normoxic conditions (21% O2) or hypoxic conditions (2.5% O2). Mice were injected with normoxia/hypoxia MSCs after thoracic irradiation (20 Gy). The therapeutic effects of MSCs on RILI were assessed by pathological examinations that included H&E staining, Masson staining and α-SMA staining; meanwhile, inflammatory factors were measured using an ELISA. The morphology of MSCs in vitro was recorded using a microscope and identified by flow cytometry, cell viability was measured using the CCK-8 assay, the potential for proliferation was detected by the EdU assay, and ROS levels were measured using a ROS fluorogenic probe. In addition, HIF-1α and several survival pathway proteins (Akt, p-Akt, Caspase-3) were also detected by western blotting. Results: Implanted MSCs alleviated both early radiation-induced pneumonia and late pulmonary fibrosis. However, hypoxia MSCs displayed a more pronounced therapeutic effect compared to normoxia MSCs. Compared to normoxia MSCs, the hypoxia MSCs demonstrated greater cell viability, an enhanced proliferation potential, decreased ROS levels and increased resistance to hypoxia and ROS stress. In addition, hypoxia MSCs achieved higher activation levels of HIF-1α and Akt, and HIF-1α played a critical role in the development of resistance. Conclusion: Hypoxia enhances the therapeutic effect of mesenchymal stromal cells on radiation-induced lung injury by promoting MSC proliferation and improving their antioxidant ability, mediated by HIF-1α

Zymosan-a Protects the Hematopoietic System from Radiation-Induced Damage by Targeting TLR2 Signaling Pathway

Background/Aims: The hematopoietic system is vulnerable to ionizing radiation and is often severely damaged by radiation. Molecules affecting radioresistance include Toll-like receptor 2. We investigated whether Zymosan-A, a novel TLR2 agonist, can protect the hematopoietic system from radiation-induced damage after total body irradiation. Methods: Mice were exposed to total body radiation after treatment with Zymosan-A or normal saline, and their survival was recorded. Tissue damage was evaluated by hematoxylin–eosin staining. The number of nucleated cells in bone marrow was determined by flow cytometry. Cell viability and apoptosis assay were determined by CCK-8 assay and flow cytometry assay. Enzyme-linked immunosorbent assay was used to detect the level of cytokines. Results: Zymosan-A protected mice from radiation-induced death and prevented radiation-induced hematopoietic system damage. Zymosan-A also promoted cell viability and inhibited cell apoptosis caused by radiation, induced radioprotective effects via TLR2, upregulated IL-6, IL-11, IL-12, and TNF-α in vivo. Conclusion: Zymosan-A can provide protection against radiation-induced hematopoietic system damage by targeting the TLR2 signaling pathway. Thus, Zymosan-A can be potentially effective radioprotectant

Radioprotective Effects of Heat-Killed Mycobacterium Tuberculosis in Cultured Cells and Radiosensitive Tissues

Background: Exposure to ionizing radiation (IR) often causes severe damage to radiosensitive tissues, which limits the use of radiotherapy in cancer patients. Novel safe and effective radioprotectant is urgently required. It has been reported toll like receptor 2 (TLR2) plays a critical role in radioresistance. In this study, we demonstrated the protective effects of Heat-Killed Mycobacterium tuberculosis (HKMT), a potent TLR2 agonist, against IR. Methods: Cell survival and apoptosis were determined by CCK-8 assay and Annexin V assay, respectively. An immunofluorescence staining assay was used to detect the translocation of nuclear faktor-kappa beta (NF-kB) p65. Tissue damage was evaluated by Haematoxilin-Eosin (HE) staining assay. We also used a flow cytometry assay to measure the number of nucleated cells and CD34+ hemopoietic stem cells in bone marrow. A western blot assay was used to detect the changes of proteins involving TLR signaling pathway. Results: We found that HKMT increased cell viability and inhibited cell apoptosis after irradiation. HKMT induced NF-kB translocation and activated Erk1/2, p38 signaling pathway. HKMT also protected bone marrow and testis from destruction. Radiation-induced decreases of nucleated cells and CD34+ hemopoietic stem cells in bone marrow were also inhibited by HKMT treatment. We found that radiation caused increase of inflammatory cytokines was also suppressed by HKMT. Conclusion: Our data showed that HKMT exhibited radioprotective effects in vivo and in vitro through activating NF-kB and MAPK signaling pathway, suggesting a potential of HKMT as novel radioprotector

Polymyxin B Attenuates LPS-Induced Death but Aggravates Radiation-Induced Death via TLR4-Myd88-IL-6 Pathway

Background/Aims: Polymyxin B (PMB) is a cyclic cationic polypeptide antibiotic widely used to counteract the effects of endotoxin contamination, both in vitro and in vivo. Lipopolysaccharide (LPS) is an endotoxin that acts as a radiation protection factor. In this study, we focus on the role of PMB in LPS-induced and radiation-induced mortality in mice. Methods: Mice received total-body radiation or were pretreated by LPS or PMB, and the survival of mice was recorded. Elisa were used to detect the cytokines levels. Results: PMB decreased LPS-induced, but increased radiation-induced mortality in mice. Moreover, PMB could block the LPS-induced radioprotective effect. The ELISA and gene knock-out experiments indicated that PMB reduces TNF-α level to block LPS-induced mortality in mice, and inhibits IL-6, G-CSF and IL-10 to increase radiation-induced mortality via the TLR4-Myd88-IL-6 pathway. Conclusions: Our study revealed a role of PMB in LPS-induced endotoxemia and radiation exposure. We infer that the TLR4-Myd88-IL-6 pathway may play a crucial role in the process

Image_3_CRX-527 induced differentiation of HSCs protecting the intestinal epithelium from radiation damage.tif

Recently, Toll-like receptors (TLRs) have been extensively studied in radiation damage, but the inherent defects of high toxicity and low efficacy of most TLR ligands limit their further clinical transformation. CRX-527, as a TLR4 ligand, has rarely been reported to protect against radiation. We demonstrated that CRX-527 was safer than LPS at the same dose in vivo and had almost no toxic effect in vitro. Administration of CRX-527 improved the survival rate of total body irradiation (TBI) to 100% in wild-type mice but not in TLR4-/- mice. After TBI, hematopoietic system damage was significantly alleviated, and the recovery period was accelerated in CRX-527-treated mice. Moreover, CRX-527 induced differentiation of HSCs and the stimulation of CRX-527 significantly increased the proportion and number of LSK cells and promoted their differentiation into macrophages, activating immune defense. Furthermore, we proposed an immune defense role for hematopoietic differentiation in the protection against intestinal radiation damage, and confirmed that macrophages invaded the intestines through peripheral blood to protect them from radiation damage. Meanwhile, CRX-527 maintained intestinal function and homeostasis, promoted the regeneration of intestinal stem cells, and protected intestinal injury from lethal dose irradiation. Furthermore, After the use of mice, we found that CRX-527 had no significant protective effect on the hematopoietic and intestinal systems of irradiated TLR4-/- mice. in conclusion, CRX-527 induced differentiation of HSCs protecting the intestinal epithelium from radiation damage.</p