Emodin, an anthraquinone derivative, protects against gamma radiation-induced toxicity by inhibiting DNA damage and oxidative stress

High serum superoxide dismutase activity improves radiation-related quality of life in patients with esophageal squamous cell carcinoma

OBJECTIVES

Esophageal squamous cell carcinoma (ESCC) is one of the most common malignant tumors in China. Intensity-modulated radiation therapy and volume-modulated arc therapy have become the main treatments for esophageal carcinoma; however, side effects caused by radiotherapy greatly impact the quality of life in these patients. This study aimed to explore the impact of serum superoxide dismutase (SOD) levels on the prognosis of patients with ESCC undergoing radiotherapy.

METHODS

Patients aged between 18 and 80 years with lower-middle ESCC who underwent radiotherapy were eligible for this assessment. Adverse events, responses, treatment outcomes, and overall survival (OS) were assessed. Between 2012 and 2014, 195 patients were enrolled, of which 65 were assigned to the low- and high-SOD groups based on their serum SOD values.

RESULTS

The baseline characteristics were similar between the two groups, except for the T staging. Adverse events in the low-SOD group were significantly higher than those in the high-SOD group (radiation esophagitis, p=0.007; radiation pneumonitis, p=0.032; leukopenia, p=0.023; thrombocytopenia, p=0.037; anemia, p=0.041). There were no significant differences in response, treatment outcomes, or OS.

CONCLUSION

In conclusion, high serum SOD activity improved post-radiotherapy quality of life but did not impact the prognosis of patients with ESCC. To the best of our knowledge, this study is the first to report that serum SOD activity is associated with radiation-induced toxicity and moderately increased radiotherapeutic response in patients with ESCC undergoing radiotherapy.

Emodin protected against synaptic impairment and oxidative stress induced by fluoride in SH-SY5Y cells by modulating ERK1/2/Nrf2/HO-1 pathway

Excessive fluoride exposure contributes to neurotoxic effects. Emodin exhibits antioxidative functions in the central nervous system (CNS); however, its neuroprotective mechanism against fluoride remains to be elucidated. Our aim was to explore the neuroprotective efficacy and the possible mechanisms of emodin. In our study, synaptic proteins and oxidative stress damage were examined after human neuroblastoma SH-SY5Y cells were treated with high doses of NaF for 24 hours. Moreover, pretreatment with emodin was used to shed light on the neuroprotective effects in NaF-induced toxicity in SH-SY5Y cells. We found that NaF significantly lowered the protein expressions of SNAP 25, synaptophysin and PSD 95 in SH-SY5Y cells. In addition, NaF exposure increased the protein expression of p-ERK1/2 and decreased the protein expressions of Nrf2 and HO-1, as well as facilitated increasing ROS, 4-hydroxynonenal (4-HNE), and 8-Hydroxy-2'-deoxyguanosine (8-OHdG). Pretreatment with emodin significantly recovered these alterations caused by NaF. These data implied that the neuroprotective effects of emodin and pointed to the promising utilization for protecting against neurotoxicity induced by fluoride.

Naturally occurring anti-cancer compounds: shining from Chinese herbal medicine

Numerous natural products originated from Chinese herbal medicine exhibit anti-cancer activities, including anti-proliferative, pro-apoptotic, anti-metastatic, anti-angiogenic effects, as well as regulate autophagy, reverse multidrug resistance, balance immunity, and enhance chemotherapy in vitro and in vivo. To provide new insights into the critical path ahead, we systemically reviewed the most recent advances (reported since 2011) on the key compounds with anti-cancer effects derived from Chinese herbal medicine (curcumin, epigallocatechin gallate, berberine, artemisinin, ginsenoside Rg3, ursolic acid, silibinin, emodin, triptolide, cucurbitacin B, tanshinone I, oridonin, shikonin, gambogic acid, artesunate, wogonin, β-elemene, and cepharanthine) in scientific databases (PubMed, Web of Science, Medline, Scopus, and Clinical Trials). With a broader perspective, we focused on their recently discovered and/or investigated pharmacological effects, novel mechanism of action, relevant clinical studies, and their innovative applications in combined therapy and immunomodulation. In addition, the present review has extended to describe other promising compounds including dihydroartemisinin, ginsenoside Rh2, compound K, cucurbitacins D, E, I, tanshinone IIA and cryptotanshinone in view of their potentials in cancer therapy. Up to now, the evidence about the immunomodulatory effects and clinical trials of natural anti-cancer compounds from Chinese herbal medicine is very limited, and further research is needed to monitor their immunoregulatory effects and explore their mechanisms of action as modulators of immune checkpoints.

Saving normal tissues - a goal for the ages

Almost since the earliest utilization of ionizing radiation, many within the radiation community have worked toward either preventing (i.e. protecting) normal tissues from unwanted radiation injury or rescuing them from the downstream consequences of exposure. However, despite over a century of such investigations, only incremental gains have been made toward this goal and, with certainty, no outright panacea having been found. In celebration of the 60th anniversary of the International Journal of Radiation Biology and to chronicle the efforts that have been made to date, we undertook a non-rigorous survey of the articles published by normal tissue researchers in this area, using those that have appeared in the aforementioned journal as a road map. Three 'snapshots' of publications on normal tissue countermeasures were taken: the earliest (1959-1963) and most recent (2013-2018) 5-year of issues, as well as a 5-year intermediate span (1987-1991). Limiting the survey solely to articles appearing within International Journal of Radiation Biology likely reduced the number of translational studies interrogated given the basic science tenor of this particular publication. In addition, by taking 'snapshots' rather than considering the entire breadth of the journal's history in this field, important papers that were published during the interim periods were omitted, for which we apologize. Nonetheless, since the journal's inception, we observed that, during the chosen periods, the majority of studies undertaken in the field of normal tissue countermeasures, whether investigating radiation protectants, mitigators or treatments, have focused on agents that interfere with the physical, chemical and/or biological effects known to occur during the acute period following whole body/high single dose exposures. This relatively narrow approach to the reduction of normal tissue effects, especially those that can take months, if not years, to develop, seems to contradict our growing understanding of the progressive complexities of the microenvironmental disruption that follows the initial radiation injury. Given the analytical tools now at our disposal and the enormous benefits that may be reaped in terms of improving patient outcomes, as well as the potential for offering countermeasures to those affected by accidental or mass casualty exposures, it appears time to broaden our approaches to developing normal tissue countermeasures. We have no doubt that the contributors and readership of the International Journal of Radiation Biology will continue to contribute to this effort for the foreseeable future.

A Novel Mechanism of High Dose Radiation Sensitization by Metformin

Introduction: Metformin, the most widely used treatment for diabetes, is lethal to cancer cells and increases in toxicity when used in combination with radiation. In addition to various molecular and metabolic mechanisms that have been previously proposed, the studies presented provide evidence of an additional, novel mechanism of sensitization following high dose radiotherapy; the magnitude of sensitization depends on the microenvironmental levels of glucose and oxygen which are in turn affected by high dose radiation.

Methods: Cancer cells (A549 and MCF7) were studied in vitro under various controlled conditions. Endpoints included clonogenic cell survival and ROS expression measured by DHE and DCFDA. CD1 nu/nu athymic mice implanted with A549 cells received metformin alone (200 mg/kg, i.p.), radiation alone (15 Gy) or a combination of metformin and radiation; the effect of treatment sequence on efficacy was assessed by tumor growth delay and histology. In a separate set of experiments, tumor blood flow was measured using a tracer clearance technique using SPECT after the administration of metformin alone, radiation alone and the combined treatment.

Results:In vivo, metformin provided equally effective tumor growth delay when given 24 h after radiation as when given 1 h or 4 h before radiation, an observation not previously reported and, in fact, unexpected based on published scientific literature. When drug followed radiation, the tumors were histologically characterized by massive cellular necrosis. In vitro, cancer cells when glucose depleted and/or hypoxic were preferentially killed by metformin, in a drug dose dependent manner. A549 cells exposed to 5.0 mM of metformin was reduced seven fold in survival when in a glucose deprived as compared to a low-glucose medium (0 vs. 1.0 g/L). Finally, using a SPECT detector to follow the washout of a radioactive tracer, it was shown that a high single dose of radiosurgery (15 Gy) could dramatically inhibit blood flow and presumably diminish glucose and oxygen.

Discussion: Insight into the best timing of drug and radiation administration is gained through an understanding of the mechanisms of interaction. A new mechanism of metformin sensitization by high dose radiation is proposed based on the blood flow, glucose and oxygen.

Salvianolic acid B, an antioxidant derived from Salvia militarize, protects mice against γ‑radiation‑induced damage through Nrf2/Bach1

Salvianolic acid B (SB) is an antioxidant derived from Salvia militarize, and is one of the most widely used herbs in traditional Chinese medicine. SB is a potent antioxidant that has been well documented as a scavenger of oxygen free radicals, and has been used for the prevention and treatment of atherosclerosis-associated disorders. To explore its potential therapeutic effects in treating radiation damage, in this study, mice were treated with SB at different doses of 5, 12.5 and 20 mg/kg, subsequent to receiving γ-irradiation. The effects of SB on peripheral blood, bone marrow nucleated cells, spleen and thymus indices, and oxidation resistance were evaluated in both radiated mice and control groups. The results indicated that SB significantly increased the counts of peripheral white blood cells, red blood cells and platelets. The number of nucleated cells in the bone marrow and the level of protein increased as well. In addition, improved spleen and thymus indices in the bone marrow were observed. SB treatment additionally reversed the deterioration of both the thymus and spleen indices, which is associated with increased serum superoxide dismutase activity and decreasing malondialdehyde levels via nuclear factor (erythroid-derived 2)-like 2 protein/BTB and CNC homology 1 mediated antioxidant effect. Furthermore, ROS levels and Bax protein expression were also suppressed by SB. The data suggested that SB is effective in protecting mice from γ-radiation injury, and could potentially be applicable for clinical use. Notably, the present study identified a promising candidate drug for enhancing the hematopoietic and immune systems.

Transposable elements, placental development, and oocyte activation: Cellular stress and AMPK links jumping genes with the creation of human life

Transposable elements (TEs), also known as "jumping genes", are DNA sequences first described by Nobel laureate Barbara McClintock that comprise nearly half of the human genome and are able to transpose or move from one genomic location to another. As McClintock also noted that a genome "shock" or stress may induce TE activation and transposition, accumulating evidence suggests that cellular stress (e.g. mediated by increases in intracellular reactive oxygen species [ROS] and calcium [Ca2+], etc.) induces TE mobilization in several model organisms and L1s (a member of the retrotransposon class of TEs) are active and capable of retrotransposition in human oocytes, human sperm, and in human neural progenitor cells. Cellular stress also plays a critical role in human placental development, with cytotrophoblast (CTB) differentiation leading to the formation of the syncytiotrophoblast (STB), a cellular layer that facilitates nutrient and gas exchange between the mother and the fetus. Syncytin-1, a protein that promotes fusion of CTB cells and is necessary for STB formation, and its receptor is found in human sperm and human oocytes, respectively, and increases in ROS and Ca2+ promote trophoblast differentiation and syncytin-1 expression. Cellular stress is also essential in promoting human oocyte maturation and activation which, similar to TE mobilization, can be induced by compounds that increase intracellular Ca2+ and ROS levels. AMPK is a master metabolic regulator activated by increases in ROS, Ca2+, and/or an AMP(ADP)/ATP ratio increase, etc. as well as compounds that induce L1 mobilization in human cells. AMPK knockdown inhibits trophoblast differentiation and AMPK-activating compounds that promote L1 mobility also enhance trophoblast differentiation. Cellular stressors that induce TE mobilization (e.g. heat shock) also promote oocyte maturation in an AMPK-dependent manner and the antibiotic ionomycin activates AMPK, promotes TE activation, and induces human oocyte activation, producing normal, healthy children. Metformin promotes AMPK-dependent telomerase activation (critical for telomere maintenance) and induces activation of the endonuclease RAG1 (promotes DNA cleavage and transposition) via AMPK. Both RAG1 and telomerase are derived from TEs. It is our hypothesis that cellular stress and AMPK links TE activation and transposition with placental development and oocyte activation, facilitating both human genome evolution and the creation of all human life. We also propose the novel observation that various cellular stress-inducing compounds (e.g. metformin, resveratrol, etc.) may facilitate beneficial TE activation and transposition and enhance fertilization and embryological development through a common mechanism of AMPK activation.

Emodin protects mice against radiation-induced mortality and intestinal injury via inhibition of apoptosis and modulation of p53

The aim of this study was to explore the protective effect of emodin, a plant-derived anthraquinone, against gamma radiation-induced mortality and intestinal injury in mice, and to investigate the radioprotective molecular mechanism. C57BL/6 male mice were pre-treated with emodin for 7days via oral gavage before gamma radiation. We found that pretreatment with emodin prolonged mice survival time after 9Gy total body irradiation (TBI). Mice were sacrificed at 1 week after 7Gy TBI, we found that emodin attenuated intestinal morphological changes and increased villus height, crypt numbers, and reduced villus and crypt apoptosis as well as inhibited the expression of p53. MTT assay, flow cytometry, Hoechst 33258 staining, real-time PCR, and Western blotting indicated that emodin pretreatment can effectively increase human umbilical venous endothelial cells (HUVECs) viability and attenuate cell apoptosis; it also inhibited the expression of p53, Bax, and Caspase3 in HUVECs after irradiation. In summary, these results suggest the potential of emodin as an effective radioprotectant against radiation-induced intestinal injury.

A Small Molecule Screen Exposes mTOR Signaling Pathway Involvement in Radiation-Induced Apoptosis

Individuals are at risk of exposure to acute ionizing radiation (IR) from a nuclear accident or terrorism, but we lack effective therapies to mitigate the lethal IR effects. In the current study, we exploited an optimized, cell-based, high throughput screening assay to interrogate a small molecule library comprising 3437 known pharmacologically active compounds for mitigation against IR-induced apoptosis. Thirty-three library compounds significantly reduced apoptosis when administered 1 h after 4 Gy IR. Two- or three-dimensional computational structural analyses of the compounds indicated only one or two chemical clusters with most of the compounds being unique structures. The mechanistic target of rapamycin complex 1 (mTORC1) inhibitor, rapamycin, was the most potent compound, and it mitigated apoptosis by 50% at 200 ± 50 pM. Other mTOR inhibitors, namely everolimus, AZD8055, and torin 1, also suppressed apoptosis, providing additional pharmacological evidence for mTOR pathway involvement in regulating cell death after IR. Everolimus and torin 1 treatment after IR decreased the S phase population and enforced both G1 and G2 phase arrest. This prorogation of cell cycle progression was accompanied by decreased IR-induced DNA damage measured by γH2AX phosphorylation at Ser139. RNA interference-mediated knockdown of the respective mTORC1 and mTORC2 subunits, Raptor or Rictor, also mitigated IR-induced apoptosis. Collectively, this study suggests a central role for the mTOR signaling in the cytotoxic response to IR and offers a useful platform to probe for additional agents.

Emodin inhibits splenocyte proliferation and inflammation by modulating cytokine responses in a mouse model system

Emodin, an anthraquinone derivative, was investigated for potential anti-inflammatory and anti-proliferative effects in vitro. The potential to induce these outcomes was assessed using concanavalin A (ConA)-stimulated mouse splenocytes. Dose-response studies showed that emodin at 100 µM was not cytotoxic to naive cells, and that the same dose caused proliferation to be significantly reduced in ConA-stimulated cells. In addition, emodin significantly reduced ConA-induced nitric oxide (NO) production and the formation/release of TH1 (IL-2, IFNγ, TNFα) and TH17 (IL-6 and IL-17) cell cytokines, but induced those of TH2 (IL-4) and Treg (IL-10) cells. From the results, it is concluded that earlier-reported immunomodulatory effects imparted by emodin may have been attributable, in part, to anti-proliferative effects on lymphocytes, as well as a shift within the TH1/TH2 and TH17/Treg balance (towards TH2 and Treg). These findings, while providing evidence of mechanisms of emodin immunomodulation, are also potentially important for sparking studies that ultimately may result in the potential use of this agent in preventive and/or corrective strategies against autoimmune and other inflammatory diseases.