Hematopoietic Acute Radiation Syndrome (Bone marrow syndrome, Aplastic Anemia): Molecular Mechanisms of Radiation Toxicity.
Abstract
Key Words: Aplastic Anemia (AA), Pluripotential Stem Cells (PSC) Introduction: Aplastic Anemia (AA) is a disorder of the pluripotential stem cells involve a decrease in the number of cells of myeloid, erythroid and megakaryotic lineage [Segel et al. 2000 ]. The etiology of AA include idiopathic cases and secondary aplastic anemia after exposure to drugs, toxins, chemicals, viral infections, lympho-proliferative diseases, radiation, genetic causes, myelodisplastic syndromes and hypoplastic anemias, thymomas, lymphomas. [Brodskyet al. 2005.,Modan et al. 1975., Szklo et al. 1975]. Hematopoietic Acute Radiation Syndrome (or Bone marrow syndrome, or Radiation-Acquired Aplastic Anemia) is the acute toxic syndrome which usually occurs with a dose of irradiation between 0.7 and 10 Gy (70- 1000 rads), depending on the species irradiated. [Waselenko et al., 2004]. The etiology of bone morrow damage from high-level radiation exposure results depends on the radiosensitivity of certain bone marrow cell lines. [Waselenko et al. 2004] Aplastic anemia after radiation exposure is a clinical syndrome that results from a marked disorder of bone marrow blood cell production. [Waselenko et al. 2004] Radiation hematotoxicity is mediated via genotoxic and other specific toxic mechanisms, leading to aplasia, cell apoptosis or necrosis, initiation via genetic mechanisms of clonal disorders, in cases such as the acute radiation-acquired form of AA. AA results from radiation injury to pluripotential and multipotential stem cells in the bone marrow. The clinical signs displayed in reticulocytopenia, anemia, granulocytopenia, monocytopenia, and thrombocytopenia. The number of marrow CD34+ cells (multipotential hematopoietic progenitors) and their derivative colony-forming unit{granulocyte-macrophage (CFU-GM) and burst forming unit {erythroid (BFU{E) are reduced markedly in patients with AA. [Guinan 2011, Brodski et al. 2005, Beutler et al.,2000] Cells expressing CD34 (CD34+ cell) are normally found in the umbilical cord and bone marrow as hematopoietic cells, a subset of mesenchymal stem cells, endothelial progenitor cells, endothelial cells of blood vessels, etc. [Beutler et al. 2000 ] Potential mechanisms responsible for radiation-acquired marrow cell failure include direct toxicity , direct damage of hematopoietic multipotential cells or cellular or humoral immune suppression of the marrow multipotential cells. [ Beutler et al. 2000] Methods: These studies were conducted at several different research institutions and laboratories listed as follows: Kazan All-Union Scientific Research Veterinary, Biotechnology Centre of Russian Academy of Science (North Osetia), Institute Belarussian Scientific and Research Institute for Radiobiology in Gomel, the St. Petersburg Veterinary Institute, the Advanced Medical Technology and Systems Inc., Ontario, Canada. The studies were approved by the Animal Care and Use Committee for ethical animal research equivalent, at each institution. A critically important volume of purified Radiation Toxins (RT) was isolated from larger mammalian irradiated animals. Subsequently the RT were characterized chemically and biologically. The experimental design of later studies compared relative toxicity, potential for development of acute radiation hematopoietic syndrome, and potential cloning disorder of multipotential hematopoietic progenitors and their derivative and lethality after intravenous or intramuscular injections of SRD containing Hematopoietic Radiation Toxins. These experiments have employed a wide variety of experimental animals. The animals were irradiated in RUM-17, Puma, and Panorama devices. The dose varied from 0.7Gy to 100Gy. The methods of immune depletion, immuno-lympho plasmasabsorption, as well as direct extraction, were used to refine and purify the specific Radiation Toxins from the central lymph of animals with Hematopoietic forms of Radiation Toxins. Experiments include administration of Hematopoietic Radiation Toxins (SRD-4) to radiation naive animals in doses 0.1 mg/kg; 0,5 mg/kg; 1 mg/kg; 2 mg/kg; 3 mg/kg up to 30 mg/kg. Results: After I/V or I/M administration of Hematotoxic Radiation Toxins to radiation -naive animals the induction of specific clinical signs was observed- including thrombocytopenia, lymphocytosis followed by lymphocytopenia, granulocytopenia , aplastic anemia, and the clinical manifestations- ecchymosis, hemorrhage and coagulopathy. These observed clinical signs mimic the acute/hematopoietic acute radiation syndrome. Conclusions: Administration of Hematopoietic Radiation Toxins (SRD-4) to radiation naive animals in doses 0.1 mg/kg;0,5 mg/kg; 1 mg/kg; 2 mg/kg; 3 mg/kg up to 30 mg/kg produced specific toxic reactions with the development of signs and symptoms consistent with the hematological form of Acute Radiation Syndromes. Administration of high doses of Hematopoietic Radiation Toxins developed a clinical picture identical to severe Acute Radiation Exposure Syndrome and induces Toxic Multiple Organ Failure (TMOF) and Toxic Multiple Organ Involvement (TMOI) {i.e. pneumonitis, renal failure, renal hypo-perfusion, acute tubular necrosis, hepatic failure, etc.} essentially as which occurs as an acute consequence of radiation toxemia. Aplastic anemia is an important clinical and pathological process which develops after animals receive high doses of both radiation and administered radiation toxins.
- Publication:
-
40th COSPAR Scientific Assembly
- Pub Date:
- 2014
- Bibcode:
- 2014cosp...40E2593P