Ramipril mitigates radiation-induced impairment of neurogenesis in the rat dentate gyrus. 2010

Kenneth A Jenrow, and Stephen L Brown, and Jianguo Liu, and Andrew Kolozsvary, and Karen Lapanowski, and Jae Ho Kim
Department of Neurosurgery, Henry Ford Hospital, Detroit, Michigan 48202, USA. nskje@neuro.hfh.edu

BACKGROUND Sublethal doses of whole brain irradiation (WBI) are commonly administered therapeutically and frequently result in late delayed radiation injuries, manifesting as severe and irreversible cognitive impairment. Neural progenitors within the subgranular zone (SGZ) of the dentate gyrus are among the most radiosensitive cell types in the adult brain and are known to participate in hippocampal plasticity and normal cognitive function. These progenitors and the specialized SZG microenvironment required for neuronal differentiation are the source of neurogenic potential in the adult dentate gyrus, and provide a continuous supply of immature neurons which may then migrate into the adjacent granule cell layer to become mature granule cell neurons. The extreme radiosensitivity of these progenitors and the SGZ microenvironment suggests the hippocampus as a prime target for radiation-induced cognitive impairment. The brain renin-angiotensin system (RAS) has previously been implicated as a potent modulator of neurogenesis within the SGZ and selective RAS inhibitors have been implicated as mitigators of radiation brain injury. Here we investigate the angiotensin converting enzyme (ACE) inhibitor, ramipril, as a mitigator of radiation injury in this context. METHODS Adult male Fisher 344 rats received WBI at doses of 10 Gy and 15 Gy. Ramipril was administered beginning 24 hours post-WBI and maintained continuously for 12 weeks. RESULTS Ramipril produced small but significant reductions in the deleterious effects of radiation on progenitor proliferation and neuronal differentiation in the rat dentate gyrus following 10 Gy-WBI, but was not effective following 15 Gy-WBI. Ramipril also reduced the basal rate of neurogenesis within the SGZ in unirradiated control rats. CONCLUSIONS Our results indicate that chronic ACE inhibition with ramipril, initiated 24 hours post-irradiation, may reduce apoptosis among SGZ progenitors and/or inflammatory disruption of neurogenic signaling within SGZ microenvironment, and suggest that angiotensin II may participate in maintaining the basal rate of granule cell neurogenesis.

UI MeSH Term Description Entries
D007150 Immunohistochemistry Histochemical localization of immunoreactive substances using labeled antibodies as reagents. Immunocytochemistry,Immunogold Techniques,Immunogold-Silver Techniques,Immunohistocytochemistry,Immunolabeling Techniques,Immunogold Technics,Immunogold-Silver Technics,Immunolabeling Technics,Immunogold Silver Technics,Immunogold Silver Techniques,Immunogold Technic,Immunogold Technique,Immunogold-Silver Technic,Immunogold-Silver Technique,Immunolabeling Technic,Immunolabeling Technique,Technic, Immunogold,Technic, Immunogold-Silver,Technic, Immunolabeling,Technics, Immunogold,Technics, Immunogold-Silver,Technics, Immunolabeling,Technique, Immunogold,Technique, Immunogold-Silver,Technique, Immunolabeling,Techniques, Immunogold,Techniques, Immunogold-Silver,Techniques, Immunolabeling
D008297 Male Males
D009474 Neurons The basic cellular units of nervous tissue. Each neuron consists of a body, an axon, and dendrites. Their purpose is to receive, conduct, and transmit impulses in the NERVOUS SYSTEM. Nerve Cells,Cell, Nerve,Cells, Nerve,Nerve Cell,Neuron
D011833 Radiation Injuries, Experimental Experimentally produced harmful effects of ionizing or non-ionizing RADIATION in CHORDATA animals. Experimental Radiation Injuries,Injuries, Experimental Radiation,Experimental Radiation Injury,Radiation Injury, Experimental
D011916 Rats, Inbred F344 An inbred strain of rat that is used for general BIOMEDICAL RESEARCH purposes. Fischer Rats,Rats, Inbred CDF,Rats, Inbred Fischer 344,Rats, F344,Rats, Inbred Fisher 344,CDF Rat, Inbred,CDF Rats, Inbred,F344 Rat,F344 Rat, Inbred,F344 Rats,F344 Rats, Inbred,Inbred CDF Rat,Inbred CDF Rats,Inbred F344 Rat,Inbred F344 Rats,Rat, F344,Rat, Inbred CDF,Rat, Inbred F344,Rats, Fischer
D002454 Cell Differentiation Progressive restriction of the developmental potential and increasing specialization of function that leads to the formation of specialized cells, tissues, and organs. Differentiation, Cell,Cell Differentiations,Differentiations, Cell
D000806 Angiotensin-Converting Enzyme Inhibitors A class of drugs whose main indications are the treatment of hypertension and heart failure. They exert their hemodynamic effect mainly by inhibiting the renin-angiotensin system. They also modulate sympathetic nervous system activity and increase prostaglandin synthesis. They cause mainly vasodilation and mild natriuresis without affecting heart rate and contractility. ACE Inhibitor,ACE Inhibitors,Angiotensin Converting Enzyme Inhibitor,Angiotensin I-Converting Enzyme Inhibitor,Angiotensin-Converting Enzyme Inhibitor,Kininase II Inhibitor,Kininase II Inhibitors,Angiotensin I-Converting Enzyme Inhibitors,Angiotensin-Converting Enzyme Antagonists,Antagonists, Angiotensin-Converting Enzyme,Antagonists, Kininase II,Inhibitors, ACE,Inhibitors, Angiotensin-Converting Enzyme,Inhibitors, Kininase II,Kininase II Antagonists,Angiotensin Converting Enzyme Antagonists,Angiotensin Converting Enzyme Inhibitors,Angiotensin I Converting Enzyme Inhibitor,Angiotensin I Converting Enzyme Inhibitors,Antagonists, Angiotensin Converting Enzyme,Enzyme Antagonists, Angiotensin-Converting,Enzyme Inhibitor, Angiotensin-Converting,Enzyme Inhibitors, Angiotensin-Converting,II Inhibitor, Kininase,Inhibitor, ACE,Inhibitor, Angiotensin-Converting Enzyme,Inhibitor, Kininase II,Inhibitors, Angiotensin Converting Enzyme
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D013234 Stem Cells Relatively undifferentiated cells that retain the ability to divide and proliferate throughout postnatal life to provide progenitor cells that can differentiate into specialized cells. Colony-Forming Units,Mother Cells,Progenitor Cells,Colony-Forming Unit,Cell, Mother,Cell, Progenitor,Cell, Stem,Cells, Mother,Cells, Progenitor,Cells, Stem,Colony Forming Unit,Colony Forming Units,Mother Cell,Progenitor Cell,Stem Cell
D016371 Cranial Irradiation The exposure of the head to roentgen rays or other forms of radioactivity for therapeutic or preventive purposes. Cranial Irradiations,Irradiation, Cranial,Irradiations, Cranial

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