JP2015205835A - Protector against disorder caused by neutron radiation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide means that protects against a disorder caused by neutron radiation, which is particularly high in penetrability among various radiation sources and causes severe damage.SOLUTION: This invention provides a protector against a disorder caused by neutron radiation, comprising nitroprusside or pharmacologically acceptable salt thereof.

Description

  The present invention relates to a medicine useful for protection against neutron radiation damage.

  Workers at nuclear power plants, non-destructive inspectors, clinical technologists handling radiopharmaceuticals, doctors engaged in radiotherapy such as X-ray examinations and cancer, and radiological technologists are always exposed to radiation during work. There is a possibility. In addition, when a nuclear power plant accident occurs, workers and nearby residents may be exposed to a large amount of radiation at once. Among radiations, neutrons have particularly strong penetrating power and there are concerns about adverse effects on the human body, but development of pharmaceuticals that protect the human body from damage caused by neutrons has not been promoted. Therefore, there is a demand for the development of pharmaceuticals useful for protecting neutron radiation damage.

  Exposure to radiation such as neutrons induces elastic scattering, inelastic scattering, capture, and nuclear reactions due to the interaction of the atoms that make up the body with the nuclei, causing damage such as cell death and mutation. Depending on the absorbed dose of neutrons, the hematopoietic / immune system, digestive system, respiratory system, central nervous system, etc. may be damaged, and the exposed person may die due to this.

  In addition, cancer patients undergoing treatment using neutron radiation, such as neutron capture therapy, suffer from significant damage to cancer cells that have taken up boron, but normal tissues that have taken up boron may also be damaged at the same time.

  The present inventors have previously found that nitroprusside is effective in preventing or treating radiation damage and has an effect of increasing the survival rate of an individual after irradiation (Patent Document 1), and the effect is induced by radiation. It has been found that it is exhibited by suppressing apoptosis that occurs (Patent Document 2).

JP 2011-207841 A Japanese Patent Application No. 2013-060747

  The problem to be solved by the present invention is to provide a pharmaceutical or the like that prevents or treats damage caused by neutron radiation that is very permeable and difficult to protect, and that increases the survival rate after exposure to neutron radiation.

  As a result of intensive studies to solve the above problems, the present inventors have found that nitroprusside, which is widely used as a therapeutic agent for hypertension and angina pectoris, is useful for protecting neutron radiation damage, It has been found that the survival rate of the woken individual is increased. It has also been found that nitroprusside has the effect of promoting recovery from the reduction of hematopoietic stem cells and peripheral blood cells caused by neutron radiation exposure.

The present invention has been completed based on the above findings. That is, the present invention is as follows.
[1] A neutron radiation protective agent containing nitroprusside or a pharmacologically acceptable salt thereof.
[2] The agent according to [1], wherein the neutron radiation disorder is one or more disorders selected from the group consisting of hematopoietic stem cell disorder, hematopoietic progenitor cell disorder, and peripheral blood cell production disorder.
[3] An agent for promoting recovery from hemocyte damage caused by neutrons, comprising nitroprusside or a pharmacologically acceptable salt thereof.
[4] The agent according to [3], wherein the hematopoietic cell disorder is one or more disorders selected from the group consisting of hematopoietic stem cell disorder, hematopoietic progenitor cell disorder and peripheral blood blood cell production disorder.

  According to the present invention, after exposure to neutrons, hematopoietic stem cells and peripheral blood cells have the effects of promoting recovery such as hematopoiesis and immune functions, effects of prolonging life, improving survival, etc. A neutron radiation protective agent useful for treatment can be provided.

FIG. 1 is a graph showing that the survival rate of mice after neutron exposure is increased by administration of nitroprusside. FIG. 2 is a graph showing that the number of bone marrow hematopoietic stem cells and hematopoietic progenitor cells after exposure to neutron radiation is recovered by administration of nitroprusside. FIG. 3 is a graph showing that administration of nitroprusside promotes recovery of the white blood cell count after neutron exposure. FIG. 4 is a graph showing that administration of nitroprusside promotes recovery of the platelet count after exposure to neutron radiation. FIG. 5 is a graph showing that administration of nitroprusside promotes recovery of sternum bone marrow cell damage after neutron exposure, recovery of thymic cortical cell damage, and recovery of white pulpal cell damage.

  The present invention provides a neutron radiation protective agent containing nitroprusside or a pharmacologically acceptable salt thereof.

Nitroprusside in the present invention is a compound represented by the formula (Fe (CN) ₅ NO) ²⁻ .

  Nitroprusside has the action of releasing nitric oxide. Exposure to neutrons induces various obstacles by inducing elastic scattering, inelastic scattering, trapping, and nuclear reactions due to the interaction of atoms constituting the living body with the nucleus. Without being bound by theory, nitric oxide promotes the process of recovering tissue damage caused by neutron radiation exposure, and therefore nitroprusside is considered to have a neutron radiation protection capability.

  Therefore, any substance having an action of releasing nitric oxide may have a protective action against neutron radiation damage, and examples of such substances include isosorbide nitrate, nitroglycerin, nicorandil, nipradilol and the like. It is done.

  Examples of pharmacologically acceptable salts of nitroprusside include salts with inorganic bases and salts with organic bases.

  Preferable examples of the salt with an inorganic base include alkali metal salts such as sodium salt and potassium salt; alkaline earth metal salts such as calcium salt and magnesium salt; and aluminum salt and ammonium salt.

  Preferable examples of the salt with an organic base include salts with trimethylamine, triethylamine, pyridine, picoline, ethanolamine, diethanolamine, triethanolamine, dicyclohexylamine, N, N-dibenzylethylenediamine and the like.

Preferable examples of the pharmacologically acceptable salt of nitroprusside include sodium salt (Na ₂ Fe (CN) ₅ NO) and potassium salt (K ₂ Fe (CN) ₅ NO) of nitroprusside.

  Nitroprusside or a pharmacologically acceptable salt thereof may be crystalline or non-crystalline and may exist in the form of hydrates and / or solvates. And / or solvates are also encompassed by “nitroprusside or a pharmaceutically acceptable salt thereof”. Compounds containing various amounts of water obtained by methods such as stoichiometric amounts of hydrates and lyophilization are also within the scope of the present invention. The sodium salt or potassium salt of nitroprusside is usually used in the form of a dihydrate.

Radiation includes α rays, β rays, γ rays emitted from radioactive materials, artificially created neutron rays, X rays, proton rays, carbon rays, and electron rays, and neutron rays are extremely transparent. It is difficult to protect because of high price. Charged particle beams such as α rays and β rays are direct ionizing radiations that cause ionization by directly applying electric force to orbital electrons of atoms or bound electrons of molecules. On the other hand, electromagnetic waves such as γ-rays and X-rays, or neutron rays without charge generate charged particle beams through the interaction with atoms or nuclei, and secondary generated charged particle beams cause ionization. Indirect ionizing radiation. γ-rays and X-rays mainly generate electron beams through interactions with the atom's bound electrons (photoelectric effect and Compton effect), whereas neutron rays have a small interaction with bound electrons, Interaction with the nucleus causes elastic scattering, inelastic scattering, capture and nuclear reactions. Since the human body is composed of a large amount of water, when exposed to gamma rays or X-rays, electrons generated by the reaction with atoms react with water molecules to generate oxygen radicals. Various damages are caused to the constituent molecules. On the other hand, when exposed to neutron radiation, it directly collides with hydrogen atoms contained in water, and the bounced hydrogen nuclei (protons) ionize surrounding atoms and molecules, causing damage to cellular constituent molecules such as DNA. This ionization by neutron rays occurs more closely along the track than by γ rays and X rays, so that the effect of neutron radiation exposure is greater than that by γ rays and X rays.
The present inventors have found that nitroprusside has a neutron radiation damage at a dose lower than the dose used for protection from X-ray damage against damage caused by neutron radiation, which is said to cause more damage than γ-rays and X-rays. Has been found to provide a protective effect against Thus, the present invention also provides protection from neutron radiation damage by low dose nitroprusside administration. If the dose can be reduced while maintaining the effect of nitroprusside, the risk of undesirable side effects of nitroprusside such as lowering blood pressure can be suppressed.

  The neutron radiation damage in the present invention refers to, for example, acute and / or late neutron radiation damage caused by systemic neutron radiation exposure caused by a nuclear accident or nuclear explosion, or neutron irradiation for medical purposes such as cancer treatment or Examples include, but are not limited to, acute and / or late neutron radiation damage due to local neutron radiation exposure due to a neutron radiation accident or the like. Specific examples of the disorder include DNA damage, hematopoietic / immune system tissue disorder, digestive system tissue disorder, respiratory system tissue disorder, central nervous system tissue disorder, gonad disorder and skin disorder. Examples include, but are not limited to, cluster DNA damage, hematopoietic stem cell disorder, hematopoietic progenitor cell disorder, peripheral blood cell production disorder, small intestinal stem cell disorder, intestinal cell production disorder and the like. Peripheral blood cell production disorder means a disorder in which the supply is reduced to the extent that peripheral blood cells are not supplied due to damage to hematopoietic stem cells and hematopoietic progenitor cells, or the body cannot maintain homeostasis, Intestinal cell production disorder means a disorder in which the supply of intestinal cells is reduced to such an extent that the intestinal cells are not supplied due to damage to the small intestinal stem cells or the homeostasis cannot maintain homeostasis.

  In the present specification, the term “hematopoietic stem cell” means an undifferentiated cell that has been directed to differentiation into a hematopoietic cell and is capable of differentiating into all hematopoietic cell types. Since differentiation is more advanced than hematopoietic stem cells, it cannot be differentiated into all blood cell types, but it has not yet reached terminal differentiation and can be differentiated into a plurality of types of blood cells. Further, “peripheral blood cells” include terminally differentiated blood cells, and in the present specification, peripheral blood cells are not terminally differentiated but are differentiated into one type of blood cell. Also means a cell. Specific examples of peripheral blood cells include lymphocytes, monocytes, neutrophils, eosinophils, basophils, erythrocytes and platelets. Unless otherwise specified, in the present specification, “blood cell” means all blood cell types including hematopoietic / immune cells.

  In the present specification, “cytotoxicity” refers to inducing cell death such as apoptosis and necrosis, inducing or losing or reducing the original function of cells by inducing DNA mutation, and causing tumor development by DNA mutation. Includes triggering.

  As used herein, the term “protection” includes prevention and treatment of neutron damage. For the prevention, the symptoms of acute and / or late neutron radiation damage are not manifested by administration of the protective agent of the present invention before or after exposure to neutron radiation and when no damage has occurred. Or even when manifested, the symptoms are alleviated compared to when the protective agent of the present invention is not administered. The treatment also includes completely curing the symptoms of acute and / or late neutron damage, alleviating the symptoms, and not exacerbating the symptoms.

  If the desired effect is obtained, the dosage form of the protective agent of the present invention is not particularly limited, and various dosage forms suitable for parenteral administration or oral administration can be appropriately selected.

  Examples of preparations for parenteral administration include injections, ointments, lotions, creams, suppositories, eye drops, and the like, with injections being preferred. For example, in the case of an injection, a solution for injection is prepared using a carrier comprising a salt solution, a glucose solution, or a mixture of salt water and a glucose solution. In addition, the preparation suitable for parenteral administration may be in the form of dissolving the nitroprusside or pharmacologically acceptable salt powder or lyophilized product of the present invention at the time of use. An agent or the like can be added and used.

In addition to nitroprusside, which is an active ingredient, the protective agent of the present invention includes pharmaceutically acceptable additives such as buffers, isotonic agents, solubilizers, preservatives, viscous bases, chelating agents, cooling agents An agent, pH adjuster, antioxidant and the like can be appropriately selected and added.
Examples of the buffer include a phosphate buffer, a borate buffer, a citrate buffer, a tartrate buffer, an acetate buffer, and an amino acid.
Examples of the isotonic agent include saccharides such as sorbitol, glucose and mannitol, polyhydric alcohols such as glycerin and propylene glycol, salts such as sodium chloride, boric acid and the like.
Examples of solubilizers include polyoxyethylene sorbitan monooleate (for example, polysorbate 80), polyoxyethylene hydrogenated castor oil, nonionic surfactants such as tyloxapol and pluronic, and polyhydric alcohols such as glycerin and macrogol. It is done.
Examples of the preservative include quaternary ammonium salts such as benzalkonium chloride, benzethonium chloride, and cetylpyridinium chloride, paraoxybenzoic acid such as methyl paraoxybenzoate, ethyl paraoxybenzoate, propyl paraoxybenzoate, and butyl paraoxybenzoate. Examples include esters, benzyl alcohol, sorbic acid and salts thereof (sodium salt, potassium salt, etc.), thimerosal (trade name), chlorobutanol, sodium dehydroacetate and the like.
Examples of the viscous base include water-soluble polymers such as polyvinyl pyrrolidone, polyethylene glycol, and polyvinyl alcohol, and celluloses such as hydroxyethyl cellulose, methyl cellulose, hydroxypropyl methyl cellulose, and sodium carboxymethyl cellulose.
Examples of chelating agents include sodium edetate and citric acid.
Examples of the refreshing agent include l-menthol, borneol, camphor, and eucalyptus oil.
Examples of the pH adjuster include sodium hydroxide, potassium hydroxide, sodium carbonate, sodium hydrogen carbonate, boric acid or a salt thereof (borax), hydrochloric acid, citric acid or a salt thereof (sodium citrate, sodium dihydrogen citrate). Etc.), phosphoric acid or a salt thereof (disodium hydrogen phosphate, potassium dihydrogen phosphate, etc.), acetic acid or a salt thereof (sodium acetate, ammonium acetate, etc.), tartaric acid or a salt thereof (sodium tartrate, etc.), and the like.
Examples of the antioxidant include sodium bisulfite, dry sodium sulfite, sodium pyrosulfite, and concentrated mixed tocopherol.

  The pH of the protective agent of the present invention is usually adjusted to about 6 to about 8, and preferably sterilization such as filtration sterilization using a membrane filter or the like is performed.

  On the other hand, when the agent of the present invention is a preparation for oral administration, for example, tablets (including sugar-coated tablets and film-coated tablets), pills, granules, powders, capsules (including soft capsules), syrups, It can be formulated into an emulsion, suspension or the like. These preparations can be produced by a method known per se, for example, the method described in the 14th revised Japanese Pharmacopoeia, General Rules for Preparations, and can be used for the protective agent of the present invention. In addition to products, excipients, lubricants, binders, disintegrants, water-soluble polymers, basic inorganic salts and the like that are usually used in the pharmaceutical field may be contained.

Examples of the excipient include lactose, sucrose, D-mannitol, starch, corn starch, crystalline cellulose, light anhydrous silicic acid, titanium oxide and the like.
Examples of the lubricant include magnesium stearate, sucrose fatty acid ester, polyethylene glycol, talc, stearic acid and the like.
Examples of the binder include hydroxypropylcellulose, hydroxypropylmethylcellulose, crystalline cellulose, starch, polyvinylpyrrolidone, gum arabic powder, gelatin, pullulan, and low-substituted hydroxypropylcellulose.
Disintegrants include (1) crospovidone, (2) disintegrants called super disintegrants such as croscarmellose sodium (FMC-Asahi Kasei), carmellose calcium (Gotoku Pharmaceutical), (3) sodium carboxymethyl starch ( Examples include Matsutani Chemical Co., Ltd.), (4) Low-substituted hydroxypropyl cellulose (eg, Shin-Etsu Chemical Co., Ltd.), and (5) Corn starch. The “crospovidone” is crosslinked with a chemical name of 1-ethenyl-2-pyrrolidinone homopolymer, including polyvinyl polypyrrolidone (PVPP) and 1-vinyl-2-pyrrolidinone homopolymer. Specific examples include Kollidon CL (manufactured by BASF), Polyplaston XL (manufactured by ISP), Polyplaston XL-10 (manufactured by ISP), and Polyplastidone. INF-10 (manufactured by ISP) or the like.
Examples of the water-soluble polymer include ethanol-soluble water-soluble polymers [eg, cellulose derivatives such as hydroxypropyl cellulose (hereinafter sometimes referred to as HPC), polyvinylpyrrolidone, etc.], ethanol-insoluble water-soluble polymers [for example, , Hydroxypropylmethylcellulose (hereinafter sometimes referred to as HPMC), cellulose derivatives such as methylcellulose and sodium carboxymethylcellulose, sodium polyacrylate, polyvinyl alcohol, sodium alginate, guar gum and the like].
Examples of the basic inorganic salt include basic inorganic salts of sodium, potassium, magnesium and / or calcium. Preferred is a basic inorganic salt of magnesium and / or calcium. More preferred is a basic inorganic salt of magnesium. Examples of the basic inorganic salt of sodium include sodium carbonate, sodium hydrogen carbonate, disodium hydrogen phosphate and the like. Examples of the basic inorganic salt of potassium include potassium carbonate and potassium hydrogen carbonate. Examples of the basic inorganic salt of magnesium include heavy magnesium carbonate, magnesium carbonate, magnesium oxide, magnesium hydroxide, magnesium metasilicate aluminate, magnesium silicate, magnesium aluminate, synthetic hydrotalcite [Mg ₆ Al ₂ ( OH) ₁₆ · CO ₃ · 4H ₂ O] and alumina / magnesium hydroxide, preferably heavy magnesium carbonate, magnesium carbonate, magnesium oxide, magnesium hydroxide and the like. Examples of the basic inorganic salt of calcium include precipitated calcium carbonate and calcium hydroxide.

  The protective agent of the present invention has other active ingredients such as vitamin ingredients and amino acid ingredients other than effective amino acids (eg, valine, leucine, isoleucine, serine, threonine; Methionine, proline, phenylalanine, tyrosine, tryptophan, aspartic acid, glutamic acid, lysine, histidine, citrulline, ornithine, cystine, taurine, glycine) and the like. As such other active ingredients, various drugs known per se can be appropriately used.

  In addition, since the antihypertensive agent (injection) which uses sodium nitroprusside as an active ingredient is already used clinically as nitroprusside in this invention, or its pharmacologically acceptable salt, [Nitopro (Maruishi Pharmaceutical Co., Ltd. )), Nitropress (manufactured by Abbott Co., Ltd.), Nipride (manufactured by Roche Co., Ltd.)], and the neutron radiation protective agent of the present invention, the above-mentioned commercial preparation can be used as it is.

  The administration target of the neutron radiation protective agent of the present invention is a mammal, and examples thereof include humans, monkeys, mice, rats, rabbits, dogs, cats, cows, horses, goats, pigs, etc., preferably humans. is there.

  The protective agent of the present invention is preferably administered immediately before or immediately after neutron exposure, specifically within 60 minutes, preferably within 30 minutes, more preferably within 15 minutes before or after neutron exposure. More preferably, the administration is started within 10 minutes, particularly preferably within 5 minutes. In addition, it is preferable to perform additional administration one day after exposure to neutron radiation from the viewpoint of improving drug efficacy. Specifically, the additional administration is performed one or more times (for example, once, preferably 2 times) after 1 day from neutron irradiation and within 10 days (more preferably within 8 days, particularly preferably within 7 days). More preferably, it is preferably 3 times, more preferably 4 times, still more preferably 5 times, particularly preferably 6 times, and most preferably 7 times. The interval between doses is usually 0.5 days or longer (for example, 1 day), but as long as the protective effect against neutron radiation damage is enhanced as compared to single administration within 60 minutes before or after neutron exposure. It is not limited to.

  For example, the additional administration is preferably performed on the next day after the neutron exposure, and more preferably on the next day and 2 days after the neutron exposure. Further, in addition to the additional administration on the next day of neutron radiation exposure, or on the next day and 2 days later, it is preferable that additional administration is performed 6 to 10 days after neutron radiation exposure (preferably 7 days later) from the viewpoint of further improving the drug efficacy. . Specific examples of the administration schedule include a total of 4 administrations within 60 minutes before or after neutron exposure, 1 day, 2 days and 7 days after neutron exposure.

  In another preferred embodiment, the additional administration can be performed once a day from the next day to 7 days after the neutron irradiation. As an example of a specific administration schedule, there can be mentioned a total of 8 administrations within 60 minutes before or after neutron exposure and once a day from 1 day to 7 days after neutron exposure. In this administration schedule, it is possible to administer at a reduced dose without impairing the effect of nitroprusside, and it can be suitably employed when it is necessary to avoid undesirable symptoms such as a decrease in blood pressure due to nitroprusside administration. A single dose at a low dose is, for example, 5 to 15 μM, preferably 10 μM. The definition of “dosage” is in accordance with the definition described later.

  Note that the above description of additional administration does not exclude administration at other times.

  The dose of the protective agent of the present invention can be appropriately selected according to the use, conditions such as the age and condition of the patient, but the concentration of nitroprusside or a pharmacologically acceptable salt thereof in vivo is It is preferable to administer so that it may become 5-25 micromol immediately after administration, Preferably it will be 10-20 micromol. Specifically, the dose is set on the assumption that nitroprusside is equally distributed to the extracellular fluid, the average extracellular fluid volume, the molecular weight of nitroprusside (251.95, 297.95 when sodium nitroprusside is used) and the above. It can be calculated from the concentration immediately after administration of nitroprusside in vivo. The average amount of extracellular fluid is obtained from body weight (kg) × 0.2 for humans and body weight (kg) × 0.35 for mice, with the specific gravity of the extracellular fluid being 1.00. However, a low dose that does not cause blood pressure lowering action is preferable, and per administration, nitroprusside is 0.6 to 1.5 mg / kg, more preferably 0.8 to 1.5 mg / kg, particularly preferably 1 0.0 to 1.2 mg / kg. In addition, the dose limiting rate is 0.5 to 1.5 μg / kg / min.

  In one aspect, the present invention provides an agent for promoting recovery from hematopoietic cell damage caused by neutron radiation, comprising nitroprusside or a pharmacologically acceptable salt thereof. Hereinafter, the agent may be simply referred to as “the recovery accelerator of the present invention”.

  The definition of nitroprusside or a pharmacologically acceptable salt thereof, neutron beam, hematopoietic cell and cytotoxicity is as described above. In addition, the dosage form, additives, dose, administration subject, administration method and the like of the recovery accelerator of the present invention are also the same as described above.

  In the present invention, “acceleration of recovery from hemocyte damage caused by neutrons” means that when the recovery accelerator of the present invention is administered, the number of blood cells reduced by neutron exposure is reduced compared to the case of no administration. If the recovery accelerator of the present invention is not administered or the recovery accelerator of the present invention is not administered, the recovery accelerator of the present invention can be administered even if recovery of the number of blood cells after exposure to neutrons is not observed at all or hardly. This means that recovery of the number of blood cells is observed. The recovery is that the number of blood cells recovers to the same number as that before neutron exposure, and the number of blood cells is smaller than that before the exposure, but the blood cell system has reached a level where an individual can survive. It means that the cell number is restored.

  Hereinafter, the present invention will be described more specifically with reference to examples, but it goes without saying that the present invention is not limited thereto.

(Materials and methods)
Mice used in this example (8-week-old male jcl: ICR mice (CLEA Japan, Inc.)) were fed with a commercial solid feed and reared in an SPF environment.
1. Neutron irradiation Irradiation of 12 mice in an acrylic irradiation container without anesthesia, and using a neutron irradiation apparatus (NASBEE) installed at the National Institute of Radiological Sciences, a dose rate of 0.02 Gy The mice were irradiated with neutrons by irradiating 3.5 Gy at / min. Mice were fed with normal solid feed and distilled water even after irradiation in an SPF environment.
2. Administration of sodium nitroprusside Administration method 1: Immediately after neutron irradiation, sodium nitroprusside (Maruishi Pharmaceutical Co., Ltd.) was intraperitoneally administered so that the final concentration was 20 μM in terms of body fluid volume after 1, 2, and 7 days. Here, “the sodium nitroprusside was administered so that the final concentration was 20 μM in terms of the amount of body fluid” is assumed that sodium nitroprusside is equally distributed to the extracellular fluid, and the average extracellular fluid volume, sodium nitroprusside sodium The dose was calculated from the molecular weight (297.95) and the concentration (20 μM) immediately after administration of sodium nitroprusside in vivo, and administered. The average amount of extracellular fluid was determined from mouse body weight (kg) × 0.35, with the specific gravity of the mouse extracellular fluid being 1.00.
Administration method 2: From immediately after neutron irradiation to 7 days later, sodium nitroprusside was intraperitoneally administered once a day so that the final concentration was 10 μM in terms of body fluid volume. The definition of dosage is as described above.
The decrease in body temperature due to a drop in blood pressure after administration of sodium nitroprusside was dealt with by placing the mouse on a hot plate set at 42 ° C.
3. Analysis of mouse survival rate The day of neutron irradiation was defined as day 0, the number of surviving mice was recorded until 30 days after irradiation, and the survival rate of mice after neutron irradiation was determined.
4). Analysis of hematopoietic stem cells of bone marrow The mice were euthanized by cervical dislocation 3 to 24 days after neutron irradiation, the left and right femurs were removed and bone marrow cells were collected, and MethoCult (registered trademark) (StemCell Technologies) was used. The number of hematopoietic stem cells and hematopoietic progenitor cells having proliferation ability and differentiation ability was counted.
5. Analysis of peripheral blood blood cells Under anesthesia (using pentobarbital sodium) 3, 8, and 14 days after neutron irradiation, 200 μL of peripheral blood was collected from the axilla, diluted with physiological saline, and fully automated for animals. White blood cell count, red blood cell count, and platelet count were measured using a hemocytometer (MEK-6458 (Nihon Kohden Co., Ltd.)) (n = 4).
6). Analysis of sternum bone marrow, thymus and spleen 3 to 24 days after neutron irradiation, mice were euthanized by cervical dislocation, and the sternum, thymus and spleen were removed, fixed with neutral formalin and embedded in paraffin. Cut and fixed to a slide glass, deparaffinized, stained with hematoxylin and eosin, and observed under an optical microscope to obtain histopathological findings.
(result)

Example 1: Improvement of survival rate by administration of sodium nitroprusside after neutron irradiation In a group of mice treated by the above administration method 1, sodium nitroprusside was administered, but a control group in which neutron irradiation was not performed (FIG. 1, non-irradiation) In the group / drug-administered group (n = 10)), no mice die in 30 days, and in the mouse group irradiated with neutrons without administering sodium nitroprusside (FIG. 1, irradiated group (n = 48)) The rate was 41.7%. On the other hand, in the group administered with sodium nitroprusside after neutron irradiation (FIG. 1, irradiation + drug administration group (n = 48)), the survival rate was 70%. Therefore, it was shown that sodium nitroprusside has the effect of improving the survival rate after neutron irradiation. In the figure, SNP means sodium nitroprusside.
Further, in the group of mice treated by the above administration method 2, the survival rate of the group of mice irradiated with neutron rays without administering nitroprusside was 40%, and the survival rate of the group administered with sodium nitroprusside after neutron irradiation was 70%. It was confirmed that.

Example 2: Promotion of recovery of the number of hematopoietic stem cells and hematopoietic progenitor cells (hereinafter sometimes abbreviated as "hematopoietic stem cells") by administration of sodium nitroprusside after neutron irradiation Irradiation with both neutron irradiation and nitroprusside No mouse group (FIG. 2, non-irradiated group (n = 4 for each quantification)) and mouse group (FIG. 2, drug-administered group (for each quantification) that were administered nitroprusside but not irradiated with neutron radiation In n = 4)), the number of hematopoietic stem cells and the like is substantially constant, and 2.6 × 0.3 × 10 ² hematopoietic stem cells, etc. in the non-irradiated group per 1 × 10 ⁵ bone marrow cells throughout the analysis period However, 2.6 ± 0.1 × 10 ² hematopoietic stem cells and the like were observed in the drug administration group. In the group of mice that were irradiated with neutron radiation and not administered nitroprusside (FIG. 2, irradiation group (n = 4 for each quantification)), hematopoietic stem cells and the like were below the detection limit until 14 days after irradiation. A slight recovery was observed from the 15th day, and the number of hematopoietic stem cells and the like was 2.0 ± 0.4 × 10 ¹ per 1 × 10 ⁵ bone marrow cells even on the 24th day after irradiation. On the other hand, in the group of mice administered with nitroprusside after neutron irradiation (FIG. 2, irradiation + drug administration group (n = 4 for each quantification)), hematopoietic stem cells and the like were 1 × 10 ^{5 on the} 8th day after irradiation. number of myeloid cells per 2.5 ± 2.3 × 10 ⁰ cells was observed, gradually increased, 1 × 10 ⁵ per bone marrow cells 2.5 ± 0.2 × 10 ² cells in 24 days after irradiation Admitted. That is, it was shown that administration of nitroprusside promotes the recovery of the number of hematopoietic stem cells and the like decreased by neutron radiation exposure.

Example 3: Promoting recovery of peripheral blood blood cell count by administration of sodium nitroprusside after neutron irradiation The number of white blood cells in the peripheral blood of mice not subjected to neutron irradiation was 32.0 ± 10.5 × 10 ² / μL.
In the peripheral blood of a group of mice that were irradiated with neutron radiation and not administered with sodium nitroprusside (FIG. 3, irradiation only group (n = 4 for each quantification)), the white blood cell count was 0. 9 ± 0.1 × 10 ² cells / μL, 0.8 ± 0.1 × 10 ² cells / μL on the 8th day after irradiation, 1.8 ± 0.2 × 10 ² cells / μL on the 14th day after irradiation μL. From these results, it was shown that peripheral blood leukocyte production disorder occurred by neutron irradiation.
On the other hand, in the peripheral blood of a group of mice administered with sodium nitroprusside after neutron irradiation (FIG. 3, irradiation + drug administration group (n = 4 for each quantification)), the white blood cell count was 1 on the third day after irradiation. .1 ± 0.1 × 10 ² cells / μL, 0.9 ± 0.1 × 10 ² cells / μL on the 8th day after irradiation, 3.3 ± 0.5 × 10 ² cells on the 14th day after irradiation / ΜL. From these results, it was shown that the leukocyte production disorder caused by neutron irradiation was significantly recovered by administration of sodium nitroprusside.
In addition, the platelets were analyzed. The number of platelets in the peripheral blood of mice not subjected to neutron irradiation was 14.4 ± 1.2 × 10 ⁵ cells / μL (FIG. 4, normal value).
In the peripheral blood of a group of mice that were irradiated with neutron radiation and not administered with sodium nitroprusside (FIG. 4, irradiation only group (n = 4 for each quantification)), the platelet count was 6. 8 ± 0.3 × 10 ⁵ cells / μL, 0.2 ± 0.01 × 10 ⁵ cells / μL on the 8th day after irradiation, 0.2 ± 0.02 × 10 ⁵ cells / μL on the 14th day after irradiation μL. From these results, it was shown that peripheral blood platelet production disorder occurred by neutron irradiation.
On the other hand, in the peripheral blood of a group of mice administered with sodium nitroprusside after neutron irradiation (FIG. 4, irradiation + drug administration group (n = 4 for each quantification)), the platelet count was 8 on the third day after irradiation. .3 ± 0.3 × 10 ⁵ cells / μL, 0.2 ± 0.04 × 10 ⁵ cells / μL on the 8th day after irradiation, 0.5 ± 0.06 × 10 ⁵ cells on the 14th day after irradiation / ΜL. From these results, it was shown that the platelet production disorder due to neutron irradiation was slightly recovered by administration of sodium nitroprusside on the 14th day after irradiation.

Example 4: Administration of sodium nitroprusside after neutron irradiation promotes recovery of sternum bone marrow cells, thymic cortex cells and white splenic cells against neutron radiation damage of sternum bone marrow cells, thymic cortex cells and white splenic cells The effect of sodium nitroprusside was investigated. Hematopoietic stem cells are present in the sternum bone marrow. Stem cells of the immune system are distributed in the thymic cortex, and these differentiate to become T cells and transfer to the medulla. In the white pulp, immune system cells such as B cells, T cells and plasma cells are activated.
As is clear from FIG. 5, the mouse 14 days after neutron irradiation compared to the sternum bone marrow cells, thymic cortex cells and white spleen cells in mice not subjected to neutron irradiation (FIG. 5, untreated). (FIG. 5, neutron beam (3.5 Gy) irradiation) showed that these cells were greatly damaged.
On the other hand, in mice treated with sodium nitroprusside after neutron irradiation (Fig. 5, neutron (3.5Gy) irradiation + SNP), sternal bone marrow cells, thymic cortex cells and white splenic spinal cord cells were the same as those untreated. It was confirmed that it recovered to the extent.
Therefore, it was also shown histopathologically that hematological cell damage caused by neutron irradiation was remarkably recovered by administration of sodium nitroprusside.

  According to the present invention, since the permeability is very high, it is difficult to protect, and it is possible to effectively protect the living body from damage caused by neutron radiation that is greatly affected by exposure. Specifically, effects such as promoting recovery of immune function and the like, and prolonging survival and improving survival rate of hematopoietic stem cells and peripheral blood cells can be obtained, and neutron damage can be effectively prevented and treated. .

Claims (4)

  A neutron radiation protective agent containing nitroprusside or a pharmacologically acceptable salt thereof.   The agent according to claim 1, wherein the neutron radiation disorder is one or more disorders selected from the group consisting of hematopoietic stem cell disorder, hematopoietic progenitor cell disorder, and peripheral blood cell production disorder.   An agent for promoting recovery from hematopoietic cell damage caused by neutrons, comprising nitroprusside or a pharmacologically acceptable salt thereof.   The agent according to claim 3, wherein the hematopoietic cell disorder is one or more disorders selected from the group consisting of hematopoietic stem cell disorder, hematopoietic progenitor cell disorder, and peripheral blood blood cell production disorder.