Radioprotective effects of roxadustat (FG-4592) in haematopoietic system

Modulation of radiation-induced intestinal injury by radioprotective agents: a cellular and molecular perspectives

The gastrointestinal (GI) system has rapidly proliferating and differentiating cells, which make it one of the most radiosensitive organs in the body. Exposure to high dose of ionising radiation (IR) during radiotherapy may generate a variety of reactive oxygen species (ROS) and reactive nitrogen species (RNS) including radicals, cause some side effects such as nausea, vomiting, diarrhoea, pain, ulceration, mal-absorption etc. Irradiation disrupts GI system by damaging proliferating stem cells of the crypts that alters the histology and physiology of intestine. Radiation damage reflects the qualitative and quantitative changes in intestinal epithelial stem cells like enterocytes, enteroendocrine cells, goblet cells and Paneth cells. The damaging effects of radiation to bio-molecules and cellular structures can alter gene signalling cascades and grounds genomic instability, protein modifications, cell senescence and cell death. The signalling pathways of GI tract includes Wnt, BMP, Hedgehog, PTEN/PI3K and Notch plays an important role in self-renewal of intestinal stem cells (ISCs) and maintaining the balance between self-renewal and differentiation of ISCs. Various radiation countermeasures including radioprotectors and mitigators are under development phase globally but still not approved for clinical applications during any radiation emergencies. In view of above, present review highlights cellular and molecular interruptions of GI system due to acute and chronic GI radiation injury, role of radioprotectors in signalling cascade modulations in GI epithelium and involvement of ISC markers in radioprotection.

HIF-α activation by the prolyl hydroxylase inhibitor roxadustat suppresses chemoresistant glioblastoma growth by inducing ferroptosis

Patients with glioblastoma (GBM) have poor prognosis and limited treatment options, largely due to therapy resistance upon the induction of apoptosis. Ferroptosis emerges as a potential antineoplastic strategy to bypass apoptosis resistance in traditional therapeutics. Hypoxia is a fundamental hallmark of GBM and hypoxia-inducible factor (HIF) is the main regulator of hypoxia response, however, the role of HIF has not been sufficiently explored in GBM. Herein, we first discovered that amplifying HIF signals by the prolyl hydroxylase (PHD) inhibitor roxadustat significantly suppressed GBM cell growth in vitro and in vivo, especially when the cells were resistant to temozolomide (TMZ). The accumulation of lipid peroxidation and cellular iron in GBM cells following roxadustat treatment indicated that the cells underwent ferroptosis, which was also supported by morphological changes in mitochondrial ultrastructure and immunogenic signals release. Moreover, in vivo studies further confirmed the ferroptosis induction and verified that roxadustat significantly prolonged survival of the mice harboring chemoresistant GBM without visible organ toxicity. Finally, we proved that the ferroptosis induction by roxadustat is HIF-α independent, especially activation of HIF-2α upregulating lipid regulatory genes was revealed to be mainly responsible for the enhanced lipid peroxidation. Altogether, our study provided novel evidence that amplifying HIF signals induced ferroptosis in chemoresistant GBM cells and suppressed the tumor growth in vivo, highlighting that ferroptosis induction by targeting HIF-α might provide new approaches to improve GBM treatment.

CRX-527 induced differentiation of HSCs protecting the intestinal epithelium from radiation damage

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.

Protection of the hematopoietic system against radiation-induced damage: drugs, mechanisms, and developments

Sometimes, people can be exposed to moderate or high doses of radiation accidentally or through the environment. Radiation can cause great harm to several systems within organisms, especially the hematopoietic system. Several types of drugs protect the hematopoietic system against radiation damage in different ways. They can be classified as "synthetic drugs" and "natural compounds." Their cellular mechanisms to protect organisms from radiation damage include free radical-scavenging, anti-oxidation, reducing genotoxicity and apoptosis, and alleviating suppression of the bone marrow. These topics have been reviewed to provide new ideas for the development and research of drugs alleviating radiation-induced damage to the hematopoietic system.

FG-4592 protects the intestine from irradiation-induced injury by targeting the TLR4 signaling pathway

Background

Severe ionizing radiation (IR)-induced intestinal injury associates with high mortality, which is a worldwide problem requiring urgent attention. In recent years, studies have found that the PHD-HIF signaling pathway may play key roles in IR-induced intestinal injury, and we found that FG-4592, the PHD inhibitor, has significant radioprotective effects on IR-induced intestinal injury.

Methods

In the presence or absence of FG-4592 treatment, the survival time, pathology, cell viability, cell apoptosis, and organoids of mice after irradiation were compared, and the mechanism was verified after transcriptome sequencing. The data were analyzed using SPSS ver. 19 software.

Results

Our results show that FG-4592 had significant radioprotective effects on the intestine. FG-4592 improved the survival of irradiated mice, inhibited the radiation damage of intestinal tissue, promoted the regeneration of intestinal crypts after IR and reduced the apoptosis of intestinal crypt cells. Through organoid experiments, it is found that FG-4592 promoted the proliferation and differentiation of intestinal stem cells (ISCs). Moreover, the results of RNA sequencing and Western blot showed that FG-4592 significantly upregulated the TLR4 signaling pathway, and FG-4592 had no radioprotection on TLR4 KO mice, suggesting that FG-4592 may play protective role against IR by targeting TLR4.

Conclusion

Our work proves that FG-4592 may promote the proliferation and regeneration of ISCs through the targeted regulation of the TLR4 signaling pathway and ultimately play radioprotective roles in IR-induced injury. These results enrich the molecular mechanism of FG-4592 in protecting cells from IR-induced injury and provide new methods for the radioprotection of intestine.

Histopathological Evaluation of Protective Effect of Telmisartan against Radiation-Induced Bone Marrow Injury

BACKGROUND

Radiation-induced hematopoietic suppression and myelotoxicity can occur due to the nuclear accidents, occupational irradiation and therapeutic interventions. Bone marrow dysfunction has always been one of the most important causes of morbidity and mortality after ionizing irradiation.

OBJECTIVE

This study aims to investigate the protective effect of telmisartan against radiation-induced bone marrow injuries in a Balb/c mouse model.

MATERIAL AND METHODS

In this experimental study, male Balb/c mice were divided into four groups as follow: group 1: mice received phosphate buffered saline (PBS) without irradiation, group 2: mice received a solution of telmisartan in PBS without irradiation, group 3: mice received PBS with irradiation, and group 4: mice received a solution of telmisartan in PBS with irradiation. A solution of telmisartan was prepared and administered orally at 12 mg/kg body weight for seven consecutive days prior to whole body exposing to a single sub-lethal dose of 5 Gy X-rays. Protection of bone marrow against radiation induced damage was investigated by Hematoxylin-Eosin (HE) staining assay at 3, 9, 15 and 30 days after irradiation.

RESULTS

Histopathological analysis indicated that administration of telmisartan reduced X-radiation-induced damage and improved bone marrow histology. The number of different cell types in bone marrow, including polymorphonuclear /mononuclear cells and megakaryocytes significantly increased in telmisartan treated group compared to the only irradiated group at all-time points.

CONCLUSION

The results of the present study demonstrated an efficient radioprotective effect of telmisartan in mouse bone marrow against sub-lethal X-irradiation.

ceRNA regulatory network of FIH inhibitor as a radioprotector for gastrointestinal toxicity by activating the HIF-1 pathway

Given the relentless renewal ability of intestinal crypt-base stem cells, small intestine in the gastrointestinal (GI) tract is more vulnerable to radiation-induced disruption. Through promoting epithelial integrity and reducing intracellular reactive oxygen species (ROS) levels, hypoxia-inducible factors (HIFs) have been proved to exhibit radioprotective effects in the GI tract. Therefore, enhancing stability or transcriptional activity of HIFs might be a therapeutic strategy for developing radioprotectors. Factor inhibiting HIF (FIH or HIF-1AN) can hamper transcriptional capacity of HIF-1α via interacting with Asn803 in its C-terminal domain. Previously, we discovered promoting HIF-1α transcriptional activity in vitro by FIH inhibitor-N-oxalyl-D-phenylalanine (NOFD) exerts radioprotection on cells. However, the radioprotective effect of FIH inhibitor on the GI tract and its competing endogenous RNA (ceRNA) regulatory network from the FIH/HIF axis has never been addressed. Here we verified radioprotection of NOFD for the GI tract by an animal model and performed whole-transcriptome analysis to fully elucidate the radioprotective mechanism from the FIH/HIF axis against GI syndrome. We identified two novel circular RNAs (circRNAs) (circRNA_2909 and circRNA_0323) and two long non-coding RNAs (lncRNAs) (NONMMUT140549.1 and NONMMUT148249.1) that promote expression of HIF1A and NOS2 in the HIF-1 pathway by sponging microRNAs (miRNAs), especially mmu-miR-92a-1-5p. The de-repression of HIF-1α transcriptional capacity by inhibiting FIH proteomic activity suggests a new therapeutic strategy in alleviating radiation-induced GI syndrome.

Novel chimeric TLR2/NOD2 agonist CL429 exhibited significant radioprotective effects in mice

Severe ionizing radiation causes the acute lethal damage of haematopoietic system and gastrointestinal tract. Here, we found CL429, the novel chimeric TLR2/NOD2 agonist, exhibited significant radioprotective effects in mice. CL429 increased mice survival, protected mice against the lethal damage of haematopoietic system and gastrointestinal tract. CL429 was more effective than equivalent amounts of monospecific (TLR2 or NOD2) and combination (TLR2 + NOD2) of molecules in preventing radiation‐induced death. The radioprotection of CL429 was mainly mediated by activating TLR2 and partially activating NOD2. CL429‐induced radioprotection was largely dependent on the activation of TLR2‐MyD88‐NF‐κB signalling pathway. In conclusion, the data suggested that the co‐activation of TLR2 and NOD2 could induce significant synergistic radioprotective effects and CL429 might be a potential high‐efficiency selective agent.

The prolyl hydroxylase inhibitor roxadustat: Paradigm in drug discovery and prospects for clinical application beyond anemia

Prolyl hydroxylase (PHD) inhibitors, such as roxadustat, can stabilize hypoxia-inducible factor (HIF)-2α and induce erythropoietin (EPO) production under normal conditions. Roxadustat was recently approved as a first-in-class orally active drug for the treatment of renal anemia. In addition, it has garnered growing therapeutic interest for use against various diseases, such as carcinoma, neurological diseases, ocular diseases, and tissue and organ injuries. In this review, we systemically review target validation, hit identification, and further key clinical trials of roxadustat. The prospective clinical applications of PHD inhibitors are then discussed based on this marketed drug.

Protective Effect of Asiaticoside on Radiation-induced Proliferation Inhibition and DNA Damage of Fibroblasts and Mice Death

Background

Radiation-induced injuries (RII) mainly result from reactive oxygen species (ROS), which are harmful compounds that can damage DNA. Asiaticoside (AC), one of the main functional components extracted from Centella asiatica, has potent pharmacological effects such as anti-inflammatory and anti-oxidant activity. However, its role in RII remains unclear.

Purpose

The purpose of the current study is to investigate whether AC can mitigate RII in vitro and in vivo.

Material and Methods

Cell model of RII was successfully established by 5J/m₂ radiation in vitro. For the in vivo RII model, mice were irradiated with 5 Gy to the thorax. The degree of damage to cells or mouse tissue was determined by measuring the numbers of DNA double-strand breaks (DSBs), oxidative stress, and mouse survival rates.

Results

In the in vitro assay, AC administration significantly reduced radiation-induced growth inhibition of Escherichia coli and fibroblasts, DSBs and apoptosis of fibroblasts; in the in vivo study, AC could decrease antioxidant capacity (T-AOC) of plasma and protect mice from RII, thereby improving the survival rates of mice after radiation.

Conclusions

These novel data indicate that AC is able to prevent radiation-initiated genotoxicity by mitigating DNA damage, and might serve as a safe and effective radio-protective agent.

Radioprotective effects of roxadustat (FG-4592) in haematopoietic system

Background

Ionizing radiation often causes severe injuries to radiosensitive tissues, especially haematopoietic system. Novel radioprotective drugs with low toxicity and high effectiveness are required. Prolyl hydroxylases domain (PHD) inhibitors have been reported to protect against radiation‐induced gastrointestinal toxicity. In this study, we demonstrated the protective effects of a PHD inhibitor, roxadustat (FG‐4592), against radiation‐induced haematopoietic injuries in vitro and in vivo.

Methods

Tissue injuries were evaluated by Haematoxilin‐Eosin (HE) staining assay. HSCs were determined by flow cytometry with the Lin⁻Sca‐1⁺c‐Kit⁺ (LSK) phenotype. Cell apoptosis was determined by Annexin V/PI staining assay. Immunofluorescence was performed to measure radiation‐induced DNA damage. A western blot assay was used to detect the changes of proteins related to apoptosis.

Results

We found that FG‐4592 pretreatment increased survival rate of irradiated mice and protected bone marrow and spleen from damages. Number of bone marrow cells (BMCs) and LSK cells were also increased both in irradiated mice and recipients after bone marrow transplantation (BMT). FG‐4592 also protected cells against radiation‐induced apoptosis and double strand break of DNA.

Conclusions

Our data showed that FG‐4592 exhibited radioprotective properties in haematopoietic system both in vivo and in vitro through up‐regulating HIF‐1α, indicating a potential role of FG‐4592 as a novel radioprotector.