Increased longevity of hematopoiesis in continuous bone marrow cultures derived from NOS1 (nNOS, mtNOS) homozygous recombinant negative mice correlates with radioresistance of hematopoietic and marrow stromal cells

Targeting of cellular redox metabolism for mitigation of radiation injury

Accidental exposure to ionizing radiation is a serious concern to human life. Studies on the mitigation of side effects following exposure to accidental radiation events are ongoing. Recent studies have shown that radiation can activate several signaling pathways, leading to changes in the metabolism of free radicals including reactive oxygen species (ROS) and nitric oxide (NO). Cellular and molecular mechanisms show that radiation can cause disruption of normal reduction/oxidation (redox) system. Mitochondria malfunction following exposure to radiation and mutations in mitochondria DNA (mtDNA) have a key role in chronic oxidative stress. Furthermore, exposure to radiation leads to infiltration of inflammatory cells such as macrophages, lymphocytes and mast cells, which are important sources of ROS and NO. These cells generate free radicals via upregulation of some pro-oxidant enzymes such as NADPH oxidases, inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). Epigenetic changes also have a key role in a similar way. Other mediators such as mammalian target of rapamycin (mTOR) and peroxisome proliferator-activated receptor (PPAR), which are involved in the normal metabolism of cells have also been shown to regulate cell death following exposure to radiation. These mechanisms are tissue specific. Inhibition or activation of each of these targets can be suggested for mitigation of radiation injury in a specific tissue. In the current paper, we review the cellular and molecular changes in the metabolism of cells and ROS/NO following exposure to radiation. Furthermore, the possible strategies for mitigation of radiation injury through modulation of cellular metabolism in irradiated organs will be discussed.

Colorectal cancer susceptibility loci as predictive markers of rectal cancer prognosis after surgery

To understand the molecular mechanism of rectal cancer and develop markers for disease prognostication, we generated and explored a dataset from 243 rectal cancer patients by gene expression microarray analysis of cancer samples and matched controls, and SNP-arrays of germline DNA. We found that two of the loci most strongly linked with colorectal cancer (CRC) risk, 8q24 (upstream of MYC) and 18q21 (in the intron of SMAD7), as well as 20q13 (in the intron of LAMA5), are tightly associated with the prognosis of rectal cancer patients. For SNPs on 18q21 (rs12953717 and rs4464148) and 20q13 (rs4925386), alleles that correlate with higher risk for the development of CRC are associated with shorter disease free survival (DFS). However, for rs6983267 on 8q24, the low risk allele is associated with a higher risk for recurrence and metastasis after surgery, and importantly, is strongly correlated with the resistance of CRC cell lines to chemoradiotherapy (CRT). We also found that although MYC expression is dramatically increased in cancer, patients with higher levels of MYC have a better prognosis. The expression of SMAD7 is weakly correlated with DFS. Notably, the presence of the 8q24 and 18q21 SNP alleles is not correlated with expression levels of MYC and SMAD7. rs4464148, and probably rs6983267 and rs4925386, are linked with overall survival time of patients. In conclusion, we show that several CRC risk SNPs detect subpopulations of rectal cancer patients with poor prognosis, and that rs6983267 probably affects prognosis through interfering with the resistance of cancer cells to CRT.

Reliability of ROS and RNS detection in hematopoietic stem cells − potential issues with probes and target cell population

Many studies have provided evidence for the crucial role of the reactive oxygen species (ROS) and reactive nitrogen species (RNS) in the regulation of differentiation and/or self-renewal, and the balance between quiescence and proliferation of hematopoietic stem cells (HSCs). Several metabolic regulators have been implicated in the maintenance of HSC redox homeostasis; however, the mechanisms that are regulated by ROS and RNS, as well as their downstream signaling are still elusive. This is partially owing to a lack of suitable methods that allow unequivocal and specific detection of ROS and RNS. In this Opinion, we first discuss the limitations of the commonly used techniques for detection of ROS and RNS, and the problem of heterogeneity of the cell population used in redox studies, which, together, can result in inaccurate conclusions regarding the redox biology of HSCs. We then propose approaches that are based on single-cell analysis followed by a functional test to examine ROS and RNS levels specifically in HSCs, as well as methods that might be used in vivo to overcome these drawbacks, and provide a better understanding of ROS and RNS function in stem cells.

Antioxidant Approaches to Management of Ionizing Irradiation Injury

Ionizing irradiation induces acute and chronic injury to tissues and organs. Applications of antioxidant therapies for the management of ionizing irradiation injury fall into three categories: (1) radiation counter measures against total or partial body irradiation; (2) normal tissue protection against acute organ specific ionizing irradiation injury; and (3) prevention of chronic/late radiation tissue and organ injury. The development of antioxidant therapies to ameliorate ionizing irradiation injury began with initial studies on gene therapy using Manganese Superoxide Dismutase (MnSOD) transgene approaches and evolved into applications of small molecule radiation protectors and mitigators. The understanding of the multiple steps in ionizing radiation-induced cellular, tissue, and organ injury, as well as total body effects is required to optimize the use of antioxidant therapies, and to sequence such approaches with targeted therapies for the multiple steps in the irradiation damage response.

Hematopoietic stem cell injury induced by ionizing radiation

SIGNIFICANCE

Exposure to ionizing radiation (IR) as the result of nuclear accidents or terrorist attacks is a significant threat and a major medical concern. Hematopoietic stem cell (HSC) injury is the primary cause of death after accidental or intentional exposure to a moderate or high dose of IR. Protecting HSCs from IR should be a primary goal in the development of novel medical countermeasures against radiation.

RECENT ADVANCES

Significant progress has been made in our understanding of the mechanisms by which IR causes HSC damage. The mechanisms include (i) induction of HSC apoptosis via the p53-Puma pathway; (ii) promotion of HSC differentiation via the activation of the G-CSF/Stat3/BATF-dependent differentiation checkpoint; (iii) induction of HSC senescence via the ROS-p38 pathway; and (iv) damage to the HSC niche.

CRITICAL ISSUES

Induction of apoptosis in HSCs and hematopoietic progenitor cells is primarily responsible for IR-induced acute bone marrow (BM) injury. Long-term BM suppression caused by IR is mainly attributable to the induction of HSC senescence. However, the promotion of HSC differentiation and damage to the HSC niche can contribute to both the acute and long-term effects of IR on the hematopoietic system.

FUTURE DIRECTIONS

In this review, we have summarized a number of recent findings that provide new insights into the mechanisms whereby IR damages HSCs. These findings will provide new opportunities for developing a mechanism-based strategy to prevent and/or mitigate IR-induced BM suppression. Antioxid.

In vivo study of radioprotective effect of NO-synthase inhibitors and acetyl-L-carnitine

This study investigated the protective effect of two nitric oxide synthase inhibitors N(omega)-nitro-L-arginine methyl ester (L-NAME, 100 mg/kg i.p.) and aminoguanidine (AG, 400 mg/kg i.p.), and an antioxidant acetyl-L-carnitine (ALC, 250 mg/kg i.p., once daily for five days) against radiation-induced damage in Wistar rats. Blood samples were collected 6 h after whole-body irradiation with 8 Gy. Plasma concentrations of nitrite+nitrate (NO(x)) and malondialdehyde (MDA) were measured by high-performance liquid chromatography. A single injection of L-NAME one hour before exposure effectively prevented the radiation-induced elevation of plasma NO(x) and it reduced 2.6-fold the risk for death during the subsequent 30-day period. Pretreatment with ALC prevented the radiation-induced increase in plasma MDA and it had similar effect on mortality as L-NAME did. Presumably due to its short half-life, the partially iNOS-selective inhibitor and antioxidant AG given in a single dose before exposure did not attenuate MDA and NO(x) and it failed to significantly improve the 30-day survival. In conclusion, pretreatment with both the nonspecific NOS inhibitor L-NAME and the antioxidant ALC markedly reduce mortality to radiation sickness in rats. The radioprotective effect may be directly related to effective attenuation of the radiation-induced elevation of NO production by L-NAME and of oxidative stress by ALC.

Low molecular weight heparin inhibits circulating fibrocytes differentiation by modulating neuronal nitric oxide synthase and TGF-β1/Smad pathway

BACKGROUND/AIMS

Circulating fibrocytes (CFs) have been placed at the center of a number of fibrosing conditions. Recently, attention has been drawn to the non-anticoagulant activities of low molecular weight heparin (LH), especially its anti-fibrotic effects. The purpose of this study was to investigate the effects of LH on CFs differentiation and possible underlying mechanisms.

METHODS/RESULTS

CFs were cultured from human peripheral blood mononuclear cells and identified by dual-immunofluorescence staining. Incubation with LH inhibited CFs trans-differentiation by upregulating CD34 and downregulating pro-Collagen I and a-SMA in a concentration- and time-dependent manner, all of which were detected by flow cytometry. Similar effects were observed after incubation with L-NAME, an inhibitor of NOS. NO production was measured by Griess methods and markedly decreased in CFs treated with LH. Three NOS isoforms were assessed by western blot and nNOS was the predominant isoform involved in this process. Additionally, LH and L-NAME had similar down-regulating effects on the expression of TGF-β1 and pSmad2/3, which indicated that TGF-β/Smad pathway might be a downstream signaling of nNOS/NO during LH treatment.

CONCLUSION

These results suggested that LH could exhibit anti-fibrotic effects by inhibiting CFs transdifferentiation, in which the involvement of nNOS/NO and TGF-β/Smad pathway were identified.

Strategies for discovery of small molecule radiation protectors and radiation mitigators

Mitochondrial targeted radiation damage protectors (delivered prior to irradiation) and mitigators (delivered after irradiation, but before the appearance of symptoms associated with radiation syndrome) have been a recent focus in drug discovery for (1) normal tissue radiation protection during fractionated radiotherapy, and (2) radiation terrorism counter measures. Several categories of such molecules have been discovered: nitroxide-linked hybrid molecules, including GS-nitroxide, GS-nitric oxide synthase inhibitors, p53/mdm2/mdm4 inhibitors, and pharmaceutical agents including inhibitors of the phosphoinositide-3-kinase pathway and the anti-seizure medicine, carbamazepine. Evaluation of potential new radiation dose modifying molecules to protect normal tissue includes: clonogenic radiation survival curves, assays for apoptosis and DNA repair, and irradiation-induced depletion of antioxidant stores. Studies of organ specific radioprotection and in total body irradiation-induced hematopoietic syndrome in the mouse model for protection/mitigation facilitate rational means by which to move candidate small molecule drugs along the drug discovery pipeline into clinical development.

Effects of bone marrow stromal cells and umbilical cord blood-derived stromal cells on daunorubicin-resistant residual Jurkat cells

OBJECTIVE

To observe the effects of the hematopoietic inductive microenvironment (HIM) simulated by stromal cells of different origins on daunorubicin-resistant residual Jurkat cells (Jurkat/DNR cells).

METHODS

Jurkat/DNR cells were cultured and identified. Human umbilical cord blood-derived stromal cells (UCBDSCs) and normal human bone marrow stromal cells (BMSCs) were isolated and cocultured with Jurkat/DNR cells. Jurkat/DNR cells were collected after 14 days of coculture and analyzed with regard to cell proliferation and differentiation abilities, apoptosis, drug sensitivity, and MRD1 multidrug resistance gene mRNA expression.

RESULTS

UCBDSC-simulated HIM suppressed proliferation and promoted apoptosis, differentiation, and drug sensitivity of Jurkat/DNR cells more significantly than BMSC-simulated HIM.

CONCLUSIONS

Both BMSCs and UCBDSCs reconstruct the leukemic HIM and reverse drug resistance in Jurkat/DNR cells. UCBDSCs reconstruct the leukemic HIM and reverse drug resistance more significantly than BMSCs.

Intraesophageal manganese superoxide dismutase-plasmid liposomes ameliorates novel total-body and thoracic radiation sensitivity of NOS1-/- mice

The effect of deletion of the nitric oxide synthase 1 gene (NOS1(-/-)) on radiosensitivity was determined. In vitro, long-term cultures of bone marrow stromal cells derived from NOS1(-/-) were more radioresistant than cells from C57BL/6NHsd (wild-type), NOS2(-/-) or NOS3(-/-) mice. Mice from each strain received 20 Gy thoracic irradiation or 9.5 Gy total-body irradiation (TBI), and NOS1(-/-) mice were more sensitive to both. To determine the etiology of radiosensitivity, studies of histopathology, lower esophageal contractility, gastrointestinal transit, blood counts, electrolytes and inflammatory markers were performed; no significant differences between irradiated NOS1(-/-) and control mice were found. Video camera surveillance revealed the cause of death in NOS1(-/-) mice to be grand mal seizures; control mice died with fatigue and listlessness associated with low blood counts after TBI. NOS1(-/-) mice were not sensitive to brain-only irradiation. MnSOD-PL therapy delivered to the esophagus of wild-type and NOS1(-/-) mice resulted in equivalent biochemical levels in both; however, in NOS1(-/-) mice, MnSOD-PL significantly increased survival after both thoracic and total-body irradiation. The mechanism of radiosensitivity of NOS1(-/-) mice and its reversal by MnSOD-PL may be related to the developmental esophageal enteric neuronal innervation abnormalities described in these mice.

Combined effect of IL-17 and blockade of nitric oxide biosynthesis on haematopoiesis in mice

AIM

The study was undertaken to extend our investigation concerning both the in vivo activity of interleukin (IL)-17 and the specific role of nitric oxide (NO) in IL-17-induced effects in the process of haematopoiesis.

METHODS

CBA mice were simultaneously treated with IL-17 and/or nitric oxide synthase (NOS) inhibitor, l-NAME, for 5 days and changes within various haematopoietic cell lineages in bone marrow, spleen and peripheral blood were analysed.

RESULTS

Findings showed that administration of both IL-17 and l-NAME stimulated increase in net haematopoiesis in normal mice. IL-17-enhanced myelopoiesis was characterized by stimulation of both femoral and splenic haematopoietic progenitor cells and morphologically recognizable granulocytes. Additionally, IL-17 induced alterations in the frequency of erythroid progenitor cells in both bone marrow and spleen, accompanied with their mobilization to the peripheral blood. As a consequence of these changes in the erythroid cell compartments, significant reticulocytosis was observed, which evidenced that in IL-17-treated mice effective erythropoiesis occurred. Exposure of mice to NOS inhibitor also increased the number of both granulocyte-macrophage and erythroid progenitors in bone marrow and spleens, and these alterations were followed by the mobilization of erythroid progenitors and elevated content of reticulocytes in peripheral blood. The specific role of NO in IL-17-induced haematopoiesis was demonstrated only in the IL-17-reducing effect on bone marrow late stage erythroid progenitors, CFU-E.

CONCLUSION

The results demonstrated the involvement of both IL-17 and NO in the regulation of haematopoietic cell activity in various haematopoietic compartments. They further suggest that IL-17 effects are differentially mediated depending on the haematopoietic microenvironments.

Hematopoietic stem cell development is dependent on blood flow

During vertebrate embryogenesis, hematopoietic stem cells (HSCs) arise in the aorta-gonads-mesonephros (AGM) region. We report here that blood flow is a conserved regulator of HSC formation. In zebrafish, chemical blood flow modulators regulated HSC development, and silent heart (sih) embryos, lacking a heartbeat and blood circulation, exhibited severely reduced HSCs. Flow-modifying compounds primarily affected HSC induction after the onset of heartbeat; however, nitric oxide (NO) donors regulated HSC number even when treatment occurred before the initiation of circulation, and rescued HSCs in sih mutants. Morpholino knockdown of nos1 (nnos/enos) blocked HSC development, and its requirement was shown to be cell autonomous. In the mouse, Nos3 (eNos) was expressed in HSCs in the AGM. Intrauterine Nos inhibition or embryonic Nos3 deficiency resulted in a reduction of hematopoietic clusters and transplantable murine HSCs. This work links blood flow to AGM hematopoiesis and identifies NO as a conserved downstream regulator of HSC development.

Methylglyoxal-induced mitochondrial dysfunction in vascular smooth muscle cells

The effects of methylglyoxal (MG) on mitochondria with specific foci on peroxynitrite (ONOO(-)) production, manganese superoxide dismutase (MnSOD) activity, and mitochondrial functions in vascular smooth muscle A-10 cells were investigated. Mitochondrial MG content was significantly increased after A-10 cells were treated with exogenous MG, and so did advanced glycated endproducts (AGEs) formation, indicated by the appearance of N(epsilon)-(carboxyethyl) lysine, in A-10 cells. The levels of mitochondrial reactive oxygen species (mtROS) and ONOO(-) were significantly increased by MG treatment. Application of ONOO(-) specific scavenger uric acid lowered the level of mtROS. MG significantly enhanced the production of mitochondrial superoxide (O(2)(-)) and nitric oxide (NO), which were inhibited by SOD mimic 4-hydroxy-tempo and mitochondrial nitric oxide synthase (mtNOS) specific inhibitor 7-nitroindazole, respectively. The activity of MnSOD was decreased by MG treatment. Furthermore, MG decreased respiratory complex III activity and ATP synthesis in mitochondria, indicating an impaired mitochondrial respiratory chain. AGEs cross-link breaker alagebrium reversed all aforementioned mitochondrial effects of MG. Our data demonstrated that mitochondrial function is under the control of MG. By inhibiting Complex III activity, MG induces mitochondrial oxidative stress and reduces ATP production. These discoveries will help unmask molecular mechanisms for various MG-induced mitochondrial dysfunction-related cellular disorders.

Thrombospondin-1 and CD47 limit cell and tissue survival of radiation injury

Radiation, a primary mode of cancer therapy, acutely damages cellular macromolecules and DNA and elicits stress responses that lead to cell death. The known cytoprotective activity of nitric oxide (NO) is blocked by thrombospondin-1, a potent antagonist of NO/cGMP signaling in ischemic soft tissues, suggesting that thrombospondin-1 signaling via its receptor CD47 could correspondingly increase radiosensitivity. We show here that soft tissues in thrombospondin-1-null mice are remarkably resistant to radiation injury. Twelve hours after 25-Gy hindlimb irradiation, thrombospondin-1-null mice showed significantly less cell death in both muscle and bone marrow. Two months after irradiation, skin and muscle units in null mice showed minimal histological evidence of radiation injury and near full retention of mitochondrial function. Additionally, both tissue perfusion and acute vascular responses to NO were preserved in irradiated thrombospondin-1-null hindlimbs. The role of thrombospondin-1 in radiosensitization is specific because thrombospondin-2-null mice were not protected. However, mice lacking CD47 showed radioresistance similar to thrombospondin-1-null mice. Both thrombospondin-1- and CD47-dependent radiosensitization is cell autonomous because vascular cells isolated from the respective null mice showed dramatically increased survival and improved proliferative capacity after irradiation in vitro. Therefore, thrombospondin-1/CD47 antagonists may have selective radioprotective activity for normal tissues.

Fullerenol C60(OH)24 effects on antioxidative enzymes activity in irradiated human erythroleukemia cell line

Radiotherapy-induced toxicity is a major dose-limiting factor in anti-cancer treatment. Ionizing radiation leads to the formation of reactive oxygen and nitrogen species (ROS/RNS) that are associated with radiation-induced cell death. Investigations of biological effects of fullerenol have provided evidence for its ROS/RNS scavenger properties in vitro and radioprotective efficiency in vivo. Therefore we were interested to evaluate its radioprotective properties in vitro in the human erythroleukemia cell line. Pre-treatment of irradiated cells by fullerenol exerted statistically significant effects on cell numbers and the response of antioxidative enzymes to X-ray irradiation-induced oxidative stress in cells. Our study provides evidence that the pre-treatment with fullerenol enhanced the enzymatic activity of superoxide dismutase and glutathione peroxidase in irradiated K562 cells.

Gene therapy approaches for stem cell protection

Cytotoxic exposure of bone marrow and other non-hematopoietic organs containing self-renewing stem cell populations is associated with damage to the supportive microenvironment. Recent evidence indicates that radical oxygen species resulting from the initial oxidative stress persist for months after ionizing irradiation exposure of tissues including oral cavity, esophagus, lung and bone marrow. Antioxidant gene therapy using manganese superoxide dismutase plasmid liposomes has provided organ-specific radiation protection associated with delay or prevention of acute and late toxicity. Recent evidence has suggested that manganese superoxide dismutase transgene expression in cells of the organ microenvironment contributes significantly to the mechanism of protection. Incorporating this knowledge into designs of novel approaches for stem cell protection is addressed in the present review.