Lycium barbarum Ameliorates Neural Damage Induced by Experimental Ischemic Stroke and Radiation Exposure

Ischemic stroke and cranial radiotherapy may induce brain inflammatory response, oxidative stress, apoptosis and neuronal loss, and impairment of neurogenesis. Lycium barbarum has anti-oxidation, anti-inflammatory, anti-tumor and anti-aging properties, may produce both neuroprotective and radioprotective effects. In this narrative review paper, we described the neuroprotective effect of Lycium barbarum in different animal models of experimental ischemic stroke and limited studies in irradiated animal models. Relevant molecular mechanisms are also summarized. It has been shown that in experimental ischemic stroke models, Lycium barbarum produces neuroprotective effects by modulating neuroinflammatory factors such as cytokines and chemokines, reactive oxygen species, and neurotransmitter and receptor systems. In irradiation animal models, Lycium barbarum prevents radiation-induced loss of hippocampal interneurons. Given its minimal side-effects, these preclinical studies suggest that Lycium barbarum may be a promising radio-neuro-protective drug that can be used as an adjunct treatment to radiotherapy for brain tumor and in the treatment of ischemic stroke. At molecular levels, Lycium barbarum may regulate PI3K/Akt/GSK-3β, PI3K/Akt/mTOR, PKCε/Nrf2/HO-1, keap1-Nrf2/HO-1, and NR2A and NR2B receptor- related signal transduction pathways to produce neuroprotective effects.

Dual Effects of miR-181b-2-3p/SOX21 Interaction on Microglia and Neural Stem Cells after Gamma Irradiation

Ionizing radiation induces brain inflammation and the impairment of neurogenesis by activating microglia and inducing apoptosis in neurogenic zones. However, the causal relationship between microglial activation and the impairment of neurogenesis as well as the relevant molecular mechanisms involved in microRNA (miR) remain unknown. In the present study, we employed immunohistochemistry and real-time RT-PCR to study the microglial activation and miRNA expression in mouse brains. Real-time RT-PCR, western blot, ELISA, cell proliferation and cytotoxicity assay were used in BV2 and mouse neural stem cells (NSCs). In the mouse model, we found the acute activation of microglia at 1 day and an increased number of microglial cells at 1, 7 and 120 days after irradiation at postnatal day 3 (P3), day 10 (P10) and day 21 (P21), respectively. In cell models, the activation of BV2, a type of microglial cell line, was observed after gamma irradiation. Real-time RT-PCR analysis revealed a deceased expression of miR-181b-2-3p and an increased expression of its target SRY-related high-mobility group box transcription factor 21 (SOX21) in a dose- and time-dependent fashion. The results of the luciferase reporter assay confirmed that SOX21 was the target of miR-181b-2-3p. Furthermore, SOX21 knockdown by siRNA inhibited the activation of microglia, thereby suggesting that the direct interaction of 181b-2-3p with SOX21 might be involved in radiation-induced microglial activation and proliferation. Interestingly, the gamma irradiation of NSCs increased miR-181b-2-3p expression but decreased SOX21 mRNA, which was the opposite of irradiation-induced expression in BV2 cells. As irradiation reduced the viability and proliferation of NSCs, whereas the overexpression of SOX21 restored the impaired cell viability and promoted the proliferation of NSCs, the findings suggest that the radiation-induced interaction of miR-181b-2-3p with SOX21 may play dual roles in microglia and NSCs, respectively, leading to the impairment of brain neurogenesis.

Radiation-induced neuropathological changes in the oligodendrocyte lineage with relevant clinical manifestations and therapeutic strategies

PURPOSE

With technological advancements in radiation therapy for tumors of the central nervous system (CNS), high doses of ionizing radiation can be delivered to the tumors with improved accuracy. Despite the reduction of ionizing radiation-induced toxicity to surrounding tissues of the CNS, a wide array of side effects still occurs, particularly late-delayed changes. These alterations, such as white matter damages and neurocognitive impairments, are often debilitative and untreatable, significantly affecting the quality of life of these patients, especially children. Oligodendrocytes, a major class of glial cells, have been identified to be one of the targets of radiation toxicity and are recognized be involved in late-delayed radiation-induced neuropathological changes. These cells are responsible for forming the myelin sheaths that surround and insulate axons within the CNS. Here, the effects of ionizing radiation on the oligodendrocyte lineage as well as the common clinical manifestations resulting from radiation-induced damage to oligodendrocytes will be discussed. Potential prophylactic and therapeutic strategies against radiation-induced oligodendrocyte damage will also be considered.

CONCLUSION

Oligodendrocytes and oligodendrocyte progenitor cells (OPCs) are radiosensitive cells of the CNS. Here, general responses of these cells to radiation exposure have been outlined. However, several findings have not been consistent across various studies. For instance, cognitive decline in irradiated animals was observed to be accompanied by obvious demyelination or white matter changes in several studies but not in others. Hence, further studies have to be conducted to elucidate the level of contribution of the oligodendrocyte lineage to the development of late-delayed effects of radiation exposure, as well as to classify the dose and brain region-specific responses of the oligodendrocyte lineage to radiation. Several potential therapeutic approaches against late-delayed changes have been discussed, such as the transplantation of OPCs into irradiated regions and implementation of exercise. Many of these approaches show promising results. Further elucidation of the mechanisms involved in radiation-induced death of oligodendrocytes and OPCs would certainly aid in the development of novel protective and therapeutic strategies against the late-delayed effects of radiation.

The neuroprotective effects of icariin on ageing, various neurological, neuropsychiatric disorders, and brain injury induced by radiation exposure

Epimedium brevicornum Maxim, a Traditional Chinese Medicine, has been used for the treatment of impotence, sinew and bone disorders, “painful impediment caused by wind-dampness,” numbness, spasms, hypertension, coronary heart disease, menopausal syndrome, bronchitis, and neurasthenia for many years in China. Recent animal experimental studies indicate that icariin, a major bioactive component of epimedium may effectively treat Alzheimer’s disease, cerebral ischemia, depression, Parkinson’s disease, multiple sclerosis, as well as delay ageing. Our recent study also suggested that epimedium extract could exhibit radio-neuro-protective effects and prevent ionizing radiation-induced impairment of neurogenesis. This paper reviewed the pharmacodynamics of icariin in treating different neurodegenerative and neuropsychiatric diseases, ageing, and radiation-induced brain damage. The relevant molecular mechanisms and its anti-neuroinflammatory, anti-apoptotic, anti-oxidant, as well as pro-neurogenesis roles were also discussed.

Spatiotemporal dynamics of γH2AX in the mouse brain after acute irradiation at different postnatal days with special reference to the dentate gyrus of the hippocampus

Gamma H2A histone family member X (γH2AX) is a molecular marker of aging and disease. However, radiosensitivity of the different brain cells, including neurons, glial cells, cells in cerebrovascular system, epithelial cells in pia mater, ependymal cells lining the ventricles of the brain in immature animals at different postnatal days remains unknown. Whether radiation-induced γH2AX foci in immature brain persist in adult animals still needs to be investigated. Hence, using a mouse model, we showed an extensive postnatal age-dependent induction of γH2AX foci in different brain regions at 1 day after whole body gamma irradiation with 5Gy at postnatal day 3 (P3), P10 and P21. P3 mouse brain epithelial cells in pia mater, glial cells in white matter and cells in cerebrovascular system were more radiosensitive at one day after radiation exposure than those from P10 and P21 mice. Persistent DNA damage foci (PDDF) were consistently demonstrated in the brain at 120 days and 15 months after irradiation at P3, P10 and P21, and these mice had shortened lifespan compared to the age-matched control. Our results suggest that early life irradiation-induced PDDF at later stages of animal life may be related to the brain aging and shortened life expectancy of irradiated animals.

Astroglial Connexins in Neurological and Neuropsychological Disorders and Radiation Exposure

Radiotherapy is a common treatment for brain and spinal cord tumors and also a risk factor for neuropathological changes in the brain leading to different neurological and neuropsychological disorders. Astroglial connexins are involved in brain inflammation, development of Alzheimer's Disease (AD), depressive, epilepsy, and amyotrophic lateral sclerosis, and are affected by radiation exposure. Therefore, it is speculated that radiation-induced changes of astroglial connexins may be related to the brain neuropathology and development of neurological and neuropsychological disorders. In this paper, we review the functional expression and regulation of astroglial connexins expressed between astrocytes and different types of brain cells (including oligodendrocytes, microglia, neurons and endothelial cells). The roles of these connexins in the development of AD, depressive, epilepsy, amyotrophic lateral sclerosis and brain inflammation have also been summarized. The radiation-induced astroglial connexins changes and development of different neurological and neuropsychological disorders are then discussed. Based on currently available data, we propose that radiation-induced astroglial connexins changes may be involved in the genesis of different neurological and neuropsychological disorders which depends on the age, brain regions, and radiation doses/dose rates. The abnormal astroglial connexins may be novel therapeutic targets for the prevention of radiation-induced cognitive impairment, neurological and neuropsychological disorders.

Early postnatal irradiation-induced age-dependent changes in adult mouse brain: MRI based characterization

Background

Brain radiation exposure, in particular, radiotherapy, can induce cognitive impairment in patients, with significant effects persisting for the rest of their life. However, the main mechanisms leading to this adverse event remain largely unknown. A study of radiation-induced injury to multiple brain regions, focused on the hippocampus, may shed light on neuroanatomic bases of neurocognitive impairments in patients. Hence, we irradiated BALB/c mice (male and female) at postnatal day 3 (P3), day 10 (P10), and day 21 (P21) and investigated the long-term radiation effect on brain MRI changes and hippocampal neurogenesis.

Results

We found characteristic brain volume reductions in the hippocampus, olfactory bulbs, the cerebellar hemisphere, cerebellar white matter (WM) and cerebellar vermis WM, cingulate, occipital and frontal cortices, cerebellar flocculonodular WM, parietal region, endopiriform claustrum, and entorhinal cortex after irradiation with 5 Gy at P3. Irradiation at P10 induced significant volume reduction in the cerebellum, parietal region, cingulate region, and olfactory bulbs, whereas the reduction of the volume in the entorhinal, parietal, insular, and frontal cortices was demonstrated after irradiation at P21. Immunohistochemical study with cell division marker Ki67 and immature marker doublecortin (DCX) indicated the reduced cell division and genesis of new neurons in the subgranular zone of the dentate gyrus in the hippocampus after irradiation at all three postnatal days, but the reduction of total granule cells in the stratum granulosun was found after irradiation at P3 and P10.

Conclusions

The early life radiation exposure during different developmental stages induces varied brain pathophysiological changes which may be related to the development of neurological and neuropsychological disorders later in life.

Neuronal Development-Related miRNAs as Biomarkers for Alzheimer's Disease, Depression, Schizophrenia and Ionizing Radiation Exposure

Radiation exposure may induce Alzheimer's disease (AD), depression or schizophrenia. A number of experimental and clinical studies suggest the involvement of miRNA in the development of these diseases, and also in the neuropathological changes after brain radiation exposure. The current literature review indicated the involvement of 65 miRNAs in neuronal development in the brain. In the brain tissue, blood, or cerebral spinal fluid (CSF), 11, 55, or 28 miRNAs are involved in the development of AD respectively, 89, 50, 19 miRNAs in depression, and 102, 35, 8 miRNAs in schizophrenia. We compared miRNAs regulating neuronal development to those involved in the genesis of AD, depression and schizophrenia and also those driving radiation-induced brain neuropathological changes by reviewing the available data. We found that 3, 11, or 8 neuronal developmentrelated miRNAs from the brain tissue, 13, 16 or 14 miRNAs from the blood of patient with AD, depression and schizophrenia respectively were also involved in radiation-induced brain pathological changes, suggesting a possibly specific involvement of these miRNAs in radiation-induced development of AD, depression and schizophrenia respectively. On the other hand, we noted that radiationinduced changes of two miRNAs, i.e., miR-132, miR-29 in the brain tissue, three miRNAs, i.e., miR- 29c-5p, miR-106b-5p, miR-34a-5p in the blood were also involved in the development of AD, depression and schizophrenia, thereby suggesting that these miRNAs may be involved in the common brain neuropathological changes, such as impairment of neurogenesis and reduced learning memory ability observed in these three diseases and also after radiation exposure.

Epigenetic Regulation of the Hippocampus, with Special Reference to Radiation Exposure

The hippocampus is crucial in learning, memory and emotion processing, and is involved in the development of different neurological and neuropsychological disorders. Several epigenetic factors, including DNA methylation, histone modifications and non-coding RNAs, have been shown to regulate the development and function of the hippocampus, and the alteration of epigenetic regulation may play important roles in the development of neurocognitive and neurodegenerative diseases. This review summarizes the epigenetic modifications of various cell types and processes within the hippocampus and their resulting effects on cognition, memory and overall hippocampal function. In addition, the effects of exposure to radiation that may induce a myriad of epigenetic changes in the hippocampus are reviewed. By assessing and evaluating the current literature, we hope to prompt a more thorough understanding of the molecular mechanisms that underlie radiation-induced epigenetic changes, an area which can be further explored.

The Neuroprotective Effect of Amitriptyline on Radiation-Induced Impairment of Hippocampal Neurogenesis

The radioprotective effect of amitriptyline, an inhibitor of acid sphingomyelinase (ASMase), on radiation-induced impairment of hippocampal neurogenesis, loss of interneuron, and animal weight changes was investigated in BALB/c mice by immunostaining of biomarkers for cell division (Ki67), immature neurons (doublecortin or DCX), and interneurons (parvalbumin or PV) in the dentate gyrus (DG) of hippocampus. The results indicated that preirradiation (with 10 mg/kg, 2 times per day, for 7 consecutive days) or postirradiation (with 10 mg/kg, 2 times per day, for 14 consecutive days) treatment (pretreatment or posttreatment) with intraperitoneal injection of amitriptyline prevented the loss of newly generated neurons, proliferating cells, and interneurons in the subgranular zone of the DG. At the molecular level, pretreatment or posttreatment inhibited the expression of sphingomyelin phosphodiesterase 1 (SMPD1) gene which codes for ASMase. The pretreatment for 7 days also prevented radiation-induced weight loss from 2 to 3 weeks, but not within 1 week after irradiation. On the other hand, the posttreatment with amitriptyline for 14 days could improve animal weight gain from 4 to 6 weeks after irradiation. The present study suggests that amitriptyline may be a promising candidate radio-neuroprotective drug to improve radiation-induced impairment of hippocampal neurogenesis and relevant neurological and neuropsychological disorders.

The expanding roles of long non-coding RNAs in the regulation of cancer stem cells

Long non-coding RNAs (lncRNAs) are a novel class of gene regulators playing multifaceted roles in physiological processes as well as pathological conditions such as cancer. Cancer stem cells (CSCs) are a small subset of tumor cells that constitute the origin and development of various malignant tumors. CSCs have been identified in a wide spectrum of human tumors and could act as a critical link underlying the processes of tumor metastasis and recurrence. Mounting evidence indicates that lncRNAs are aberrantly expressed in diverse CSCs and regulate CSC properties at different molecular levels. Here, we very briefly summarize the recent findings on the potential roles of lncRNAs in regulating various functions of CSCs, and elaborate on how can lncRNAs impact CSC properties via interacting with other macromolecules at the epigenetic, transcriptional, and post-transcriptional levels. This mini-review also highlights the understanding of the modular regulatory principles of lncRNA interactions in CSCs.

The Disparity of Impairment of Neurogenesis and Cognition After Acute or Fractionated Radiation Exposure in Adolescent BALB/c Mice

The effect of acute X-ray irradiation with 2 Gy or fractionated exposure with 0.2 Gy continuously for 10 days (0.2 Gy × 10 = 2 Gy) was evaluated in the postnatal day 21 (P21) BALB/c mouse model. Both acute and fractionated irradiation induced impairment of cell proliferation and neurogenesis in the subgranular zone of the dentate gyrus labeled by Ki67 and doublecortin, respectively. Parvalbumin immunopositive interneurons in the subgranular zone were also reduced significantly. However, the 2 patterns of irradiation did not affect animal weight gain when measured at ages of P90 and P180 or 69 and 159 days after irradiation. Behavioral tests indicated that neither acute nor fractionated irradiation with a total dose of 2 Gy induced deficits in the contextual fear or spatial memory and memory for novel object recognition. Animal motor activity was also not affected in the open-field test. The disparity of the impairment of neurogenesis and unaffected cognition suggests that the severity of impairment of neurogenesis induced by acute or fractionated irradiation with a total dose of 2 Gy at P21 may not be worse enough to induce the deficit of cognition.

Low dose or low dose rate ionizing radiation-induced health effect in the human

The extensive literature review on human epidemiological studies suggests that low dose ionizing radiation (LDIR) (≤100 mSv) or low dose rate ionizing radiation (LDRIR) (<6mSv/H) exposure could induce either negative or positive health effects. These changes may depend on genetic background, age (prenatal day for embryo), sex, nature of radiation exposure, i.e., acute or chronic irradiation, radiation sources (such as atomic bomb attack, fallout from nuclear weapon test, nuclear power plant accidents, ⁶⁰Co-contaminated building, space radiation, high background radiation, medical examinations or procedures) and radionuclide components and human epidemiological experimental designs. Epidemiological and clinical studies show that LDIR or LDRIR exposure may induce cancer, congenital abnormalities, cardiovascular and cerebrovascular diseases, cognitive and other neuropsychiatric disorders, cataracts and other eye and somatic pathology (endocrine, bronchopulmonary, digestive, etc). LDIR or LDRIR exposure may also reduce mutation and cancer mortality rates. So far, the mechanisms of LDIR- or LDRIR -induced health effect are poorly understood. Further extensive studies are still needed to clarify under what circumstances, LDIR or LDRIR exposure may induce positive or negative effects, which may facilitate development of new therapeutic approaches to prevent or treat the radiation-induced human diseases or enhance radiation-induced positive health effect.

Potential role of genipin in cancer therapy

Genipin, an aglycone derived from the iridoid glycoside, geniposide, is isolated and characterized from the extract of Gardenia jasminoides Ellis fruit (family Rubiaceae). It has long been used in traditional oriental medicine for the prevention and treatment of several inflammation driven diseases, including cancer. Genipin has been shown to have hepatoprotective activity acting as a potent antioxidant and inhibitor of mitochondrial uncoupling protein 2 (UCP2), and also reported to exert significant anticancer effects. It is an excellent crosslinking agent that helps to make novel sustained or delayed release nanoparticle formulations. In this review, we present the latest developments of genipin as an anticancer agent and briefly describe its diverse mechanism(s) of action. Several lines of evidence suggest that genipin is a potent inhibitor of UCP2, which functions as a tumor promoter in a variety of cancers, attenuates generation of reactive oxygen species and the expression of matrix metalloproteinase 2, as well as induces caspase-dependent apoptosis in vitro and in in vivo models. These finding suggests that genipin can serve as both a prominent anticancer agent as well as a potent crosslinking drug that may find useful application in several novel pharmaceutical formulations.

Cx36 in the mouse hippocampus during and after pilocarpine-induced status epilepticus

Gap junctions play an important role in the synchronization activity of coupled cells. Hippocampal inhibitory interneurons are involved in epileptogenesis and seizure activity, and express gap junction protein connexin (Cx) 36. Cx36 is also localized in the axons (mossy fibers) of granule cells in the dentate gyrus. While it has been documented that Cx36 is involved in epileptogenesis, there are still controversies regarding the expression levels of Cx36 at different developmental stages of human and animal models of epileptogenesis. In this study, the expression of Cx36 was investigated in the mouse hippocampus at 1 h, 4 h during pilocarpine-induced status epilepticus (PISE) and 1 week, 2 months after PISE. We found that Cx36 was down-regulated in neurons at different time points during and after PISE, whereas it was increased significantly in the stratum lucidum of CA3 area at 2 months after PISE. Double immunofluorescence indicated that Cx36 was localized in parvalbumin (PV) immunopositive interneuron in CA1 area and in mossy fibers and their terminals in the stratum lucidum of CA3 area. It suggests that decreased expression of Cx36 in interneurons may be related to less effective inhibitory control of excitatory activity of hippocampal principal neurons. However, the increased Cx36 immunopositive product in mossy fibers at the chronic stage after PISE may enhance the contacts between granule cells in the dentate gyrus and pyramidal neurons in CA3 area. The two different changes of Cx36 may be implicated in the epileptogenesis.

Route towards the optimization at given power of thermoelectric heat engines with broken time-reversal symmetry

We investigate the performance at a given power of a thermoelectric heat engine with broken time-reversal symmetry, and derive analytically the efficiency at a given power of a thermoelectric generator within linear irreversible thermodynamics. A universal bound on the efficiency of the thermoelectric heat engine is achieved under a strong constraint on the Onsager coefficients, and some interesting features are further revealed. Our results demonstrate that there exists a trade-off between efficiency and power output, and the efficiency at a given power may surpass the Curzon-Ahlborn limit due to broken time-reversal symmetry. Moreover, optimal efficiency at a given power can be achieved, which indicates that broken time-reversal symmetry offers physically allowed ways to optimize the performance of heat engines. Our study may contribute to the interesting guidelines for optimizing actual engines.

Potential Protective Effects of Ursolic Acid against Gamma Irradiation-Induced Damage Are Mediated through the Modulation of Diverse Inflammatory Mediators

This study was aimed to evaluate the possible protective effects of ursolic acid (UA) against gamma radiation induced damage both in vitro as well as in vivo. It was observed that the exposure to gamma radiation dose- and time-dependently caused a significant decrease in the cell viability, while the treatment of UA attenuated this cytotoxicity. The production of free radicals including reactive oxygen species (ROS) and NO increased significantly post-irradiation and further induced lipid peroxidation and oxidative DNA damage in cells. These deleterious effects could also be effectively blocked by UA treatment. In addition, UA also reversed gamma irradiation induced inflammatory responses, as indicated by the decreased production of TNF-α, IL-6, and IL-1β. NF-κB signaling pathway has been reported to be a key mediator involved in gamma radiation-induced cellular damage. Our results further demonstrated that gamma radiation dose- and time-dependently enhanced NF-κB DNA binding activity, which was significantly attenuated upon UA treatment. The post-irradiation increase in the expression of both phospho-p65, and phospho-IκBα was also blocked by UA. Moreover, the treatment of UA was found to significantly prolong overall survival in mice exposed to whole body gamma irradiation, and reduce the excessive inflammatory responses. Given its radioprotective efficacy as described here, UA as an antioxidant and NF-κB pathway blocker, may function as an important pharmacological agent in protecting against gamma irradiation-induced injury.

Radioprotective effect of ursolic acid in radiation-induced impairment of neurogenesis, learning and memory in adolescent BALB/c mouse

The effect of acute irradiation with 5Gy or fractionated exposure with 0.5Gy continuously for 10days (a total dose of 5Gy) was evaluated in an immature BALB/c mouse model. Radioprotective effect of ursolic acid (at 25mg/kg/daily administered 1h after acute or each of fractionated irradiations, and continuously for 30days) was also investigated. We found that both acute and fractionated irradiation at a total dose of 5Gy did not induce any mortality within 30days after exposure to postnatal day 26 (P26) BALB/c mice, but reduced animal weigh gain in the first few weeks. At 90days after irradiation, the weight of animals with acute irradiation was still significantly lower than the control group; no significant difference though was observed for those fractionatedly exposed mice compared to the control group. Behavioral tests indicated that acute irradiation at 5Gy induced deficits in learning and memory in the contextual fear conditioning test. The memory for novel object recognition was also impaired. Similar changes were not observed in mice with fractionated irradiation. Immunohistochemical study demonstrated clearly that acute and fractionated irradiations induced impairment of neurogenesis in the subgranular zone (SGZ) of the dentate gyrus although fractionated exposure induced much lesser loss of newly generated neurons. Ursolic acid administered at 25mg/kg/daily for 30days after irradiation greatly improved acute irradiation-induced deficits in contextual learning and memory and in novel object recognition memory although it exacerbated radiation-induced reduction of neurogenesis in SGZ.

Postnatal irradiation-induced hippocampal neuropathology, cognitive impairment and aging

Irradiation of the brain in early human life may set abnormal developmental events into motion that last a lifetime, leading to a poor quality of life for affected individuals. While the effect of irradiation at different early developmental stages on the late human life has not been investigated systematically, animal experimental studies suggest that acute postnatal irradiation with ⩾0.1Gy may significantly reduce neurogenesis in the dentate gyrus and endotheliogenesis in cerebral vessels and induce cognitive impairment and aging. Fractionated irradiation also reduces neurogenesis. Furthermore, irradiation induces hippocampal neuronal loss in CA1 and CA3 areas, neuroinflammation and reduces gliogenesis. The hippocampal neurovascular niche and the total number of microvessels are also changed after radiation exposures. Each or combination of these pathological changes may cause cognitive impairment and aging. Interestingly, acute irradiation of aged brain with a certain amount of radiation has also been reported to induce brain hormesis or neurogenesis. At molecular levels, inflammatory cytokines, chemokines, neural growth factors, neurotransmitters, their receptors and signal transduction systems, reactive oxygen species are involved in radiation-induced adverse effect on brain development and functions. Further study at different omics levels after low dose/dose rate irradiation may not only unravel the mechanisms of radiation-induced adverse brain effect or hormesis, but also provide clues for detection or diagnosis of radiation exposure and for therapeutic approaches to effectively prevent radiation-induced cognitive impairment and aging. Investigation focusing on radiation-induced changes of critical brain development events may reveal many previously unknown adverse effects.

Low-dose or low-dose-rate ionizing radiation-induced bioeffects in animal models

Animal experimental studies indicate that acute or chronic low-dose ionizing radiation (LDIR) (≤100 mSv) or low-dose-rate ionizing radiation (LDRIR) (<6 mSv/h) exposures may be harmful. It induces genetic and epigenetic changes and is associated with a range of physiological disturbances that includes altered immune system, abnormal brain development with resultant cognitive impairment, cataractogenesis, abnormal embryonic development, circulatory diseases, weight gain, premature menopause in female animals, tumorigenesis and shortened lifespan. Paternal or prenatal LDIR/LDRIR exposure is associated with reduced fertility and number of live fetuses, and transgenerational genomic aberrations. On the other hand, in some experimental studies, LDIR/LDRIR exposure has also been reported to bring about beneficial effects such as reduction in tumorigenesis, prolonged lifespan and enhanced fertility. The differences in reported effects of LDIR/LDRIR exposure are dependent on animal genetic background (susceptibility), age (prenatal or postnatal days), sex, nature of radiation exposure (i.e. acute, fractionated or chronic radiation exposure), type of radiation, combination of radiation with other toxic agents (such as smoking, pesticides or other chemical toxins) or animal experimental designs. In this review paper, we aimed to update radiation researchers and radiologists on the current progress achieved in understanding the LDIR/LDRIR-induced bionegative and biopositive effects reported in the various animal models. The roles played by a variety of molecules that are implicated in LDIR/LDRIR-induced health effects will be elaborated. The review will help in future investigations of LDIR/LDRIR-induced health effects by providing clues for designing improved animal research models in order to clarify the current controversial/contradictory findings from existing studies.

Prenatal irradiation-induced brain neuropathology and cognitive impairment

Embryo/fetus is much more radiosensitive than neonatal and adult human being. The main potential effects of pre-natal radiation exposure on the human brain include growth retardation, small head/brain size, mental retardation, neocortical ectopias, callosal agenesis and brain tumor which may result in a lifetime poor quality of life. The patterns of prenatal radiation-induced effects are dependent not only on the stages of fetal development, the sensitivity of tissues and organs, but also on radiation sources, doses, dose rates. With the increased use of low dose radiation for diagnostic or radiotherapeutic purposes in recent years, combined with postnatal negative health effect after prenatal radiation exposure to fallout of Chernobyl nuclear power plant accident, the great anxiety and unnecessary termination of pregnancies after the nuclear disaster, there is a growing concern about the health effect of radiological examinations or therapies in pregnant women. In this paper, we reviewed current research progresses on pre-natal ionizing irradiation-induced abnormal brain structure changes. Subsequent postnatal neuropsychological and neurological diseases were provided. Relationship between irradiation and brain aging was briefly mentioned. The relevant molecular mechanisms were also discussed. Future research directions were proposed at the end of this paper. With limited human data available, we hoped that systematical review of animal data could relight research interests on prenatal low dose/dose rate irradiation-induced brain microanatomical changes and subsequent neurological and neuropsychological disorders.

Reorganization of Basolateral Amygdala-Subiculum Circuitry in Mouse Epilepsy Model

In this study, we investigated the reorganized basolateral amygdala (BLA)-subiculum pathway in a status epilepticus (SE) mouse model with epileptic episodes induced by pilocarpine. We have previously observed a dramatic loss of neurons in the CA1-3 fields of the hippocampus in epileptic mice. Herein, we observed a 43-57% reduction in the number of neurons in the BLA of epileptic mice. However, injection of an anterograde tracer, Phaseolus vulgaris leucoagglutinin (PHA-L) into the BLA indicated 25.63% increase in the number of PHA-L-immunopositive terminal-like structures in the ventral subiculum (v-Sub) of epileptic mice as compared to control mice. These data suggest that the projections from the basal nucleus at BLA to the vSub in epileptic mice are resistant to epilepsy-induced damage. Consequently, these epileptic mice exhibit partially impairment but not total loss of context-dependent fear memory. Epileptic mice also show increased c-Fos expression in the BLA and vSub when subjected to contextual memory test, suggesting the participation of these two brain areas in foot shock-dependent fear conditioning. These results indicate the presence of functional neural connections between the BLA-vSub regions that participate in learning and memory in epileptic mice.

Astrocytic Cx 43 and Cx 40 in the mouse hippocampus during and after pilocarpine-induced status epilepticus

Astrocytes have now been well accepted to play important roles in epileptogenesis by controlling gliotransmitter release and neuronal excitability, contributing to blood-brain barrier dysfunction and involving in brain inflammation. Recent studies indicate that abnormal expression of gap junction protein connexin (Cx) may also be a contributing factor for seizure generation. To further address this issue, we investigated the progressive changes of Cx 43 and Cx 40 in the mouse hippocampus at 4 h, 1 day, 1 week and 2 months during and after pilocarpine-induced status epilepticus (PISE). The co-localization of Cx 43 and Cx 40 with glial fibrillary acidic protein (GFAP) was also examined. We observed that Cx 43 and Cx 40 protein expression remained unaltered at 4 h during and at 1 day (acute stage) after PISE. However, their expression was significantly increased in CA1 and CA3 areas and in the dentate gyrus at 1 week (latent stage) and 2 months (chronic stage) after PISE. Double immunofluorescence labeling indicated the localization of Cx 43 and Cx 40 in astrocytes. Combined with progressive neuronal loss in the mouse hippocampus, our results suggest that the increase in gap junctions in the neuronoglial syncytium of reactive astrocytes may be implicated in synchronization of hippocampal hyperactivity leading to neuronal loss and epileptogenesis.

CCL28 in the mouse hippocampal CA1 area and the dentate gyrus during and after pilocarpine-induced status epilepticus

The present study showed a wide presence of CCL28 in mouse CNS, including cerebral, cerebellum, brain stem and spinal cord. In hippocampus, the expression of CCL28 at both mRNA and protein level was clarified. The CCL28 expression was mainly localized in pyramidal cells of CA area, granular cells of dentate gyrus and some interneurons in CA area and hilus. Double-labelling immunocytochemistry revealed that most of calbindin, calretinin and parvalbumin immunopositive neurons expressed CCL28. During and after pilocarpine induced status epilepticus (SE), a down-regulated expression of CCL28 in hippocampal interneurons in the CA1 area and in the hilus of the dentate gyrus was demonstrated. The present study may, therefore provide evidence that CCL28 may have a novel role in CNS and may be involved in the loss of hippocampal interneurons, and subsequent disinhibition of pyramidal neurons.

Corticotropin releasing factor (CRF) in the hippocampus of the mouse pilocarpine model of status epilepticus

We investigated the cellular localization and progressive changes of corticotropin releasing factor (CRF) in the mouse hippocampus, during and after pilocarpine induced status epilepticus (PISE) and subsequent epileptogenesis. We found that CRF gene expression was up-regulated significantly at 2h during and 1d after PISE in comparison to control mice. Immunohistochemical analysis showed that the number of CRF and Fos immunoreactive cells was increased significantly in the strata oriens and pyramidale of CA1 area and in the stratum pyramidale of CA3 area at 2h during and 1d after PISE. CRF was induced in calbindin (CB) or calretinin (CR) immunoreactive interneurons in stratum oriens at 2h during PISE. It suggests that induced CRF may be related to the over excitation of hippocampal neurons and occurrence of status epilepticus. It may also cause excitoneurotoxicity and delayed loss of CA3 and CA1 pyramidal neurons, leading to the onset of epilepsy.

Comparison of status epilepticus models induced by pilocarpine and nerve agents - a systematic review of the underlying aetiology and adopted therapeutic approaches

Among potential radiological, nuclear, biological and chemical weapons, cholinergic nerve agents from chemical weapons remain a realistic terrorist threat due to its combination of high lethality, demonstrated use and relative abundance of un-destroyed stockpiles in various militaries around the world. While current fielded antidotes are able to mitigate acute poisoning, effective neuroprotection in the field remains a challenge amongst subjects with established status epilepticus following nerve agent intoxication. Due to ethical, safety and surety issues, extensive preclinical and clinical research on cholinergic nerve agents is not possible. This may have been a contributory factor for the slow progress in uncovering new neuroprotectants for nerve agent casualties with established status epilepticus. To overcome this challenge, comparative research with surrogate chemicals that produce similar hypercholinergic toxicity but with less security concerns would be a useful approach forward. In this paper, we will systemically compare the mechanism of seizure generation, propagation and the subsequent clinical, hematologic, and metabolic, biochemical, neuroinflammatory changes and current therapeutic approaches reported in pilocarpine, soman, and sarin models of seizures. This review will be an important first step in closing this knowledge gap among different closely related models of seizures and neurotoxicity. Hopefully, it will spur further efforts in using surrogate cholinergic models by the wider scientific community to expedite the development of a new generation of antidotes that are better able to protect against delayed neurological effects inflicted by nerve agents.

Pilocarpine-induced status epilepticus alters hippocampal PKC expression in mice

We investigated the protein expression of different protein kinase C (PKC) isoforms (PKC-alpha, PKC-beta1, PKC-beta2, PKC-gamma, PKC-delta, PKC-epsilon, PKC-eta and PKC-zeta) in the hippocampus of normal control mice and progressive changes in PKC isoforms expression during and after pilocarpine induced status epilepticus (PISE). We showed the reduced expression of PKC-delta, PKC-eta and PKC-zeta in interneurons in the CA1 area and in the hilus of the dentate gyrus during or after PISE. Increased expression of PKC-alpha and PKC-beta1 was demonstrated in the stratum pyramidale of CA3 area, and PKC-epsilon was up-regulated in the stratum lucidum of the CA3 area during or after PISE. Our results suggest that hippocampal PKC isoforms may play different roles in seizure generation, and be targets for development of anti-convulsive drugs.

Status epilepticus alters hippocampal PKAbeta and PKAgamma expression in mice

OBJECTIVES

To investigate the localization and progressive changes of cyclic-AMP dependent protein kinase (cPKA) in the mouse hippocampus at acute stages during and after pilocarpine induced status epilepticus.

METHODS

Pilocarpine induced status epilepticus mice were sacrificed 30 min, 2 h or 1 day after the start of a approximately 7 h lasting status as assessed by video-electroencephalography. Brains were processed for quantitative immunohistochemistry of hippocampal cPKAbeta and cPKAgamma, and immunohistochemical co-localization of cPKAbeta and cPKAgamma with calbindin (CB), calretinin (CR), and parvalbumin (PV).

RESULTS

Based on anatomical and morphological assessment, cPKAbeta was primarily expressed by principal cells and cPKAgamma by interneurons. In CA1, cPKAbeta co-localized with 76% of CB, 41% of CR, and 95% of PV-immunopositive cells, while cPKAgamma co-localized with 50% of CB, 29% of CR, and 80% of PV-immunopositive cells. Upon induction of status epilepticus, cPKAbeta expression was transiently reduced in CA1, whereas cPKAgamma expression was sustainably reduced.

CONCLUSION

cPKA may play an important role in neuronal hyperexcitability, death and epileptogenesis during and after pilocarpine induced status epilepticus.

NCAM-mediated locomotor recovery from spinal cord contusion injury involves neuroprotection, axon regeneration, and synaptogenesis

The expression level of neural cell adhesion molecule (NCAM), which plays a critical role in pathways involving development and plasticity of the nervous system, changes markedly after spinal cord injury (SCI). However, the significance of NCAM-involved mechanisms in SCI remains elusive. The present study demonstrates that NCAM-deficient (ND) mice exhibited significantly poorer locomotor activity than wildtype (WT) littermates with the same injury intensity by the contusion model. To determine detailed contribution of NCAM, quantitative immunohistochemistry examination was performed on the injured spinal cord of 6mm along the rostrocaudal axis in the animals for up to 5 weeks after SCI. Overall level of NCAM decreased initially in the lesion site but increased around the center of the injury thereafter. At acute stage, more apoptotic cells were found in the gray and white matter in ND mice. Between the two animal groups, no obvious difference in expression levels of GFAP (astrocytosis marker) and MBP (remyelination marker) was detected. However, diverse expression trends of NF200 (axon marker), GAP-43 (synaptogenesis indicator) and phosphorylated ERK (active signal molecule) were observed in the area encompassing the lesion site, and remarkable differences were illustrated between WT mice and ND littermates. Detailed analysis indicates that NCAM-mediated pathways may be involved in the activation of ERK at acute stages and bi-phasic upregulation of GAP-43 expression at acute and sub-acute stages after SCI to promote cell survival, outgrowth of regenerated axons, synaptogenesis, and function recovery.

CCR3, CCR2A and macrophage inflammatory protein (MIP)-1a, monocyte chemotactic protein-1 (MCP-1) in the mouse hippocampus during and after pilocarpine-induced status epilepticus (PISE)

AIMS

To investigate protein and gene expressions of chemokine subtypes CCR3, CCR2A and their respective ligands macrophage inflammatory protein 1-alpha (MIP-1alpha), monocyte chemotactic protein-1 (MCP-1) in the normal mouse central nervous system (CNS) and in the hippocampus at different time points during and after pilocarpine-induced status epilepticus (PISE).

METHODS

CCR3 and MIP-1alpha protein expressions were mapped in the mouse CNS. The protein and gene expressions of CCR3 and CCR2A and their respective ligands MIP-1alpha, MCP-1 in the hippocampus were studies by immunocytochemical and quantitative real-time RT-PCR during and after PISE.

RESULTS

CCR3 and MIP-1alpha gene expression and immunopositive neurones were broadly distributed in the CNS. CCR3 and CCA2A gene and their protein expression were downregulated in the hippocampus at 1 h during PISE. The protein expression of MIP-1alpha, MCP-1 decreased but gene expression increased at 2 h during PISE. In the hilus of the dentate gyrus, significant reduction of the numbers of CCR3, CCR2A, MCP-1 immunopositive neurones occurred from 1 h during to 2 months after PISE, but the number of MIP-1alpha neurones reduced from 2 h during to 2 months after PISE. Induced expression of CCR3 at 1 week, CCR2A, MCP-1 or MIP-1alpha at 1 week and 2 months after PISE was found in reactive astrocytes. MCP-1 was also demonstrated in the blood vessels of the hippocampus at 2 months after PISE.

CONCLUSIONS

CCR3 and MIP-1alpha may play important functional roles in the mouse brain. The downregulation of CCR3, CCR2A, MIP-1alpha and MCP-1 in the hippocampal neurones at the acute stage during and after PISE may weaken the neuroprotective mechanisms. However, induced expression of MCP-1 in hippocampal blood vessel may be related to changes in permeability of the blood-brain barrier during epileptogenesis.

Metabotropic glutamate receptors in the control of neuronal activity and as targets for development of anti-epileptogenic drugs

The anticonvulsant and neuroprotective properties of agonist and antagonist of metabotropic glutamate receptors (mGluRs) have been known for 15 years or so. However, it is not yet clear whether these agents, and allied compounds, can be considered as candidate drugs for eventual use in the clinic to control the development of epilepsy, (i.e. as anti- epileptogenics), or for the control of seizures themselves (i.e. as anticonvulsants). In fact, few studies have been designed to test for these properties by, for instance, administering these agents during the chronic stages of experimental epilepsy to determine whether a tendency to generate spontaneously recurrent seizures, which often appear by epileptogenesis, could be prevented or stopped. Even in the acute stages, there are substantial differences in experimental design between the published studies. Thus, there are large variations in such factors as timing, and the route of administration of candidate drugs, the age, or species and strain of experimental animal used, and the experimental epilepsy model employed. Such variations often make it difficult to accurately assess the anticonvulsant, neuroprotective and anti-epileptogenic properties of each candidate drug across a wide range of studies. This paper, will review neuroanatomical, neurochemical, neuropharmacological studies of mGluRs in animal models and in patients with temporal lobe epilepsy, and summarize anticonvulsive and neuroprotective effects of their agonists and antagonists in different seizure and epilepsy models in order to give direction for the development of new generation anti-epileptogenic and anticonvulsive drugs.

Morpho-physiologic characteristics of dorsal subicular network in mice after pilocarpine-induced status epilepticus

The goal of this study was to examine the morpho-physiologic changes in the dorsal subiculum network in the mouse model of temporal lobe epilepsy using extracellular recording, juxtacellular and immunofluorescence double labeling, and anterograde tracing methods. A significant loss of total dorsal subicular neurons, particularly calbindin, parvalbumin (PV) and immunopositive interneurons, was found at 2 months after pilocarpine-induced status epilepticus (SE). However, the sprouting of axons from lateral entorhinal cortex (LEnt) was observed to contact with surviving subicular neurons. These neurons had two predominant discharge patterns: bursting and fast irregular discharges. The bursting neurons were mainly pyramidal cells, and their dendritic spine density and bursting discharge rates were increased significantly in SE mice compared with the control group. Fast irregular discharge neurons were PV-immunopositive interneurons and had less dendritic spines in SE mice when compared with the control mice. When LEnt was stimulated, bursting and fast irregular discharge neurons had much shorter latency and stronger excitatory response in SE mice compared with the control group. Our results illustrate that morpho-physiologic changes in the dorsal subiculum could be part of a multilevel pathologic network that occurs simultaneously in many brain areas to contribute to the generation of epileptiform activity.

mGluR5-PLCbeta4-PKCbeta2/PKCgamma pathways in hippocampal CA1 pyramidal neurons in pilocarpine model of status epilepticus in mGluR5+/+ mice

While it is generally accepted that phospholipase C (PLC) and protein kinase C (PKC) are down-stream proteins involved in metabotropic glutamate receptor 5 (mGluR5)-related signal transduction, we still do not know which subtype of PLC or PKC is specifically regulated after mGluR5 activation. In the present study in mGluR5 wild-type (mGluR5+/+) mice, we showed induced PKCbeta2 or PKCgamma expression at the border between the stratum oriens and alveus (O/A border) at 2h during pilocarpine induced status epilepticus (SE), and in the stratum pyramidale in CA1 area at 1 day after pilocarpine induced SE; at 1 day, induced expression of PLCbeta4 in the stratum pyramidale of CA1 area was observed. Furthermore, double labeling revealed the co-localization of induced PKCbeta2 or PKCgamma with mGluR5 or with induced PLCbeta4 in the stratum pyramidale of CA1 area. These induced expression, however, were not found in mGluR5 mutant (mGluR5-/-) mice. It suggests that induced PLCbeta4-PKCbeta2/PKCgamma at 1 day after pilocarpine induced SE in pyramidal neurons or PKCbeta2 or PKCgamma in interneurons at O/A border at 2h during pilocarpine induced SE may be specifically linked to the activation of mGluR5. When compared to mGluR5+/+ mice, significant shorter latency (from pilocarpine injection to the occurrence of status epilepticus) and maintenance period (from beginning to the end of status epilepticus) for status epilepticus in mGluR5-/- mice were also demonstrated. It is possible that mGluR5 may play a negative role in initiation of status epilepticus by interacting with muscarinic acetylcholine receptor in mGluR5+/+ mice.

Melatonin attenuates hypoxia-induced ultrastructural changes and increased vascular permeability in the developing hippocampus

Hypoxic injury in the perinatal period may be involved in damaging the developing hippocampus. The damage may be mediated by excess production of vascular endothelial growth factor (VEGF) and nitric oxide (NO). We examined the hippocampus of neonatal Wistar rats subjected to hypoxia for VEGF and NO production. The mRNA and protein expression of hypoxia inducible factor-1alpha, endothelial, neuronal, inducible nitric oxide synthase and VEGF was found to be up-regulated significantly after the hypoxic exposure. Tissue VEGF concentration and NO production were also increased. By electron microscopy, swollen dendrites, vacuolated axons and hypertrophic astrocyte end feet associated with blood vessels were observed in hypoxic animals. In hypoxic rats, the passage of rhodamine isothiocyanate (RhIC) and horseradish peroxidase, administered intraperitoneally or intravenously, was observed through vascular walls. Furthermore, immunoglobulin G was localized in the neuropil and neurons. We suggest that increased VEGF and NO production in hypoxia had resulted in increased vascular permeability, leading to structural alteration of the dendrites and axons. Melatonin administration reduced VEGF and NO levels as well as leakage of RhIC, suggesting that it has a therapeutic potential in reducing hypoxia-associated damage in the developing hippocampus.

Two-methyl-6-phenylethynyl-pyridine (MPEP), a metabotropic glutamate receptor 5 antagonist, with low doses of MK801 and diazepam: A novel approach for controlling status epilepticus

By intravenous administration of group I metabotropic glutamate receptor antagonists at 1 or 2h during pilocarpine induced status epilepticus (PISE), we showed that mGluR1 antagonists AIDA or LY367385 (at dosages ranging from 25 to 200mg/kg), mGluR5 antagonists SIB1757 (at dosages ranging from 25 to 200mg/kg), SIB1893 (from 25 to 100mg/kg), MPEP (from 25 to 100mg/kg) injected at 1 or 2h during PISE were ineffective in controlling status epilepticus (SE). However, when administered at 1h during PISE, MPEP at 200mg/kg, combination of MPEP (200mg/kg) with MK801 (0.1mg/kg) or with MK801 (0.1mg/kg) and diazepam (0.5mg/kg), combination of SIB1893 (200mg/kg) with MK801 (0.1mg/kg) could effectively control behavioral SE, and were neuroprotective. In particular, the combination of MPEP with MK801 and diazepam could stop both behavioral SE and electrical SE (under EEG monitoring) within a few minutes after the administration. HPLC study showed that a high level of MPEP was maintained in the blood and its metabolism rate was slow in experimental mice with PISE. We therefore concluded that the combination of MPEP (200mg/kg) with MK801 (0.1mg/kg) and diazepam (0.5mg/kg) could effectively stop SE and its subsequent neuronal loss in the hippocampus when administered 1h during PISE. It may provide a new approach to effectively control intractable SE.

Anticonvulsive Effect of a Selective mGluR8 Agonist (S)-3,4-Dicarboxyphenylglycine (S-3,4-DCPG) in the Mouse Pilocarpine Model of Status Epilepticus

PURPOSE

We sought to investigate the anticonvulsive and neuroprotective effect of a selective metabotropic glutamate receptor 8 (mGluR8) agonist (S)-3,4-dicarboxyphenylglycines (S-3,4-DCPG) on pilocarpine-induced status epilepticus (PISE) and subsequent loss of hilar neurons in the dentate gyrus after systemic (intravenous) or local (intracerebroventricular) administration. We compared the difference in granular cell responses after paired-pulse stimulation of the perforant pathway and the sensitivity to local injection of S-3,4-DCPG into the stratum granulosum in the control and mice at 2 months after PISE.

METHODS

We used intravenous, intracerebroventricular, or intrahippocampal administration of S-3,4-DCPG to mice with status epilepticus or temporal lobe epilepsy and neurophysiologic recording of somatic field excitatory postsynaptic potential (sfEPSP) and population spike (PS) of granular cells in response to perforant-pathway stimulation or S-3,4-DCPG treatment.

RESULTS

Intracerebroventricular (1.91 micromol) but not systemic administration of S-3,4-DCPG (at doses of 12.5, 50, 100, 200, 400, 800, and 1,200 mg/kg) could control PISE with no neuroprotective effect. In epileptic mice, mGluR8-mediated inhibition of fEPSPs was reduced significantly in granular cell bodies.

CONCLUSIONS

At doses ranging from 12.5 to 1,200 mg/kg, intravenous administration of S-3,4-DCPG may not be effective in controlling status epilepticus. Down-regulation of mGluR8 may be related to reduced S-3,4-DCPG-mediated inhibition and the subsequent occurrence of spontaneously recurrent seizures.

CCR7, CCR8, CCR9 and CCR10 in the mouse hippocampal CA1 area and the dentate gyrus during and after pilocarpine-induced status epilepticus

The present study showed CCR7, CCR8, CCR9 and CCR10 in the normal Swiss mouse hippocampus at both protein and mRNA levels. CCR7, CCR9 and CCR10 were mainly localized in hippocampal principal cells and some interneurons. CCR9 was also found in the mossy fibres and/or terminals, suggesting an axonal or presynaptic localization, and CCR10 in apical dendrites of pyramidal neurons in the CA1 area. CCR8 was observed in interneurons. Double-labelling immunocytochemistry revealed that most of calbindin (CB)-, calretinin (CR)- and parvalbumin (PV)-immunopositive neurons expressed CCR7-10, except CR-immunopositive cells in which only 10 to 12% expressed CCR8. During and after pilocarpine-induced status epilepticus, progressive changes of each of CCR7, CCR8, CCR9 and CCR10 proteins occurred in different patterns at various time points. Sensitive real-time PCR showed similar change patterns at mRNA level. At the chronic stage, i.e. at 2 months after pilocarpine-induced status epilepticus, significant reduction of CCR7-10 expression in CB-, CR- and PV-immunpositive interneurons may suggest the phenotype change of surviving interneurons. Double labelling of CCR7, CCR8 and CCR9 with glial fibrillary acidic protein (GFAP) at the chronic stage may suggest an induced expression in reactive astrocytes. The present study may, therefore, for the first time, provide evidence that CCR7-10 may be involved in normal hippocampal activity. The demonstration of the progressive changes of CCR7-10 during and after status epilepticus may open a new area to reveal the mechanism of neuronal loss after status epilepticus and of epileptogenesis.

Cav1.2, Cav1.3, and Cav2.1 in the mouse hippocampus during and after pilocarpine-induced status epilepticus

Calcium binding proteins are well known to be expressed by different groups of hippocampal interneurons; however, whether voltage-dependent calcium channels (Ca(v)) are also localized in these neurons, changed during and after status epilepticus (SE), and involved in epileptic activity have not been reported. In the present study, we showed the colocalization of three subtypes of voltage-gated calcium channels (Ca(v)1.2, Ca(v)1.3, or Ca(v)2.1) with different calcium binding proteins such as calbindin (CB), calretinin (CR), and parvalbumin (PV). At early stages during and after pilocarpine-induced status epilepticus (PISE), significant changes of expression of Ca(v)1.2, Ca(v)1.3 (L-type), and Ca(v)2.1 (P/Q-type) were found in different groups of hippocampal neurons. Induced expression of Ca(v)1.3 or Ca(v)2.1 in reactive astrocytes was shown at 1 week and 2 months after PISE. At the latter time point, higher percentages of colocalization of PV and Ca(v)1.2, CB, or PV and Ca(v)1.3 or Ca(v)2.1, lower percentages of CR and Ca(v)1.3 or Ca(v)2.1 immunoposivie neurons were observed in gliotic CA1 area. We therefore conclude that voltage-gated calcium channels are expressed by different groups of hippocampal interneurons in the mouse. At acute stages during and after PISE, up- or down-regulation of Ca(v)1.2, Ca(v)1.3, or Ca(v)2.1 in functionally different groups of interneurons in CA1 area may be related to the changes of their plasticity. Up-regulation of Ca(v)1.2, Ca(v)1.3, or Ca(v)2.1 in granule cells may be directly related to the occurrence of SE. The induced expression of Ca(v)1.3 or Ca(v)2.1 in reactive astrocytes at 1 week and 2 months after PISE suggests that Ca(v)1.3 or Ca(v)2.1-related calcium signaling in reactive astrocytes may be involved in initiation, maintenance or spread of seizure activity. In gliotic CA1 area at chronic stage (i.e., 2 months after PISE), the occurrence of higher percentages of colocalization of PV and Ca(v)1.2, CB, or PV and Ca(v)1.3 or Ca(v)2.1, lower percentages of CR and Ca(v)1.3 or Ca(v)2.1 immunopositive neurons may suggest that such colocalizations may be linked to the survival or loss of particular group of hippocampal neurons.

Spastin in the human and mouse central nervous system with special reference to its expression in the hippocampus of mouse pilocarpine model of status epilepticus and temporal lobe epilepsy

In the present in situ hybridization and immunocytochemical studies in the mouse central nervous system (CNS), a strong expression of spastin mRNA and protein was found in Purkinje cells and dentate nucleus in the cerebellum, in hippocampal principal cells and hilar neurons, in amygdala, substantia nigra, striatum, in the motor nuclei of the cranial nerves and in different layers of the cerebral cortex except piriform and entorhinal cortices where only neurons in layer II were strongly stained. Spastin protein and mRNA were weakly expressed in most of the thalamic nuclei. In selected human brain regions such as the cerebral cortex, cerebellum, hippocampus, amygdala, substania nigra and striatum, similar results were obtained. Electron microscopy showed spastin immunopositive staining in the cytoplasma, dendrites, axon terminals and nucleus. In the mouse pilocarpine model of status epilepticus and subsequent temporal lobe epilepsy, spastin expression disappeared in hilar neurons as early as at 2h during pilocarpine induced status epilepticus, and never recovered. At 7 days and 2 months after pilocarpine induced status epilepticus, spastin expression was down-regulated in granule cells in the dentate gyrus, but induced expression was found in reactive astrocytes. The demonstration of widespread distribution of spastin in functionally different brain regions in the present study may provide neuroanatomical basis to explain why different neurological, psychological disorders and cognitive impairment occur in patients with spastin mutation. Down-regulation or loss of spastin expression in hilar neurons may be related to their degeneration and may therefore initiate epileptogenetic events, leading to temporal lobe epilepsy.

Reorganization of CA3 area of the mouse hippocampus after pilocarpine induced temporal lobe epilepsy with special reference to the CA3-septum pathway

We showed that when CA3 pyramidal neurons in the caudal 80% of the dorsal hippocampus had almost disappeared completely, the efferent pathway of CA3 was rarely detectable. We used the mouse pilocarpine model of temporal lobe epilepsy (TLE), and injected iontophoretically the anterograde tracer phaseolus vulgaris leucoagglutinin (PHA-L) into gliotic CA3, medial septum and the nucleus of diagonal band of Broca, median raphe, and lateral supramammillary nuclei, or the retrograde tracer cholera toxin B subunit (CTB) into gliotic CA3 area of hippocampus. In the afferent pathway, the number of neurons projecting to CA3 from medial septum and the nucleus of diagonal band of Broca, median raphe, and lateral supramammillary nuclei increased significantly. In the hippocampus, where CA3 pyramidal neurons were partially lost, calbindin, calretinin, parvalbumin immunopositive back-projection neurons from CA1-CA3 area were observed. Sprouting of Schaffer collaterals with increased number of large boutons in both sides of CA1 area, particularly in the stratum pyramidale, was found. When CA3 pyramidal neurons in caudal 80% of the dorsal hippocampus have almost disappeared completely, surviving CA3 neurons in the rostral 20% of the dorsal hippocampus may play an important role in transmitting hyperactivity of granule cells to surviving CA1 neurons or to dorsal part of the lateral septum. We concluded that reorganization of CA3 area with its downstream or upstream nuclei may be involved in the occurrence of epilepsy.

Calcium binding protein containing neurons in the gliotic mouse hippocampus with special reference to their afferents from the medial septum and the entorhinal cortex

In CA1 area and the hilus of the dentate gyrus of the mouse hippocampus, drastic reduction of NeuN, calbindin, calretinin, or parvalbumin immunopositive neurons was shown at 3, 7 and 60 days after pilocarpine-induced status epilepticus. In gliotic CA1 area at 60 days, few dendritic branches of calcium binding protein immunopositive neurons could be found suggesting reorganization of the afferents of surviving calcium binding protein immunopositive neurons. Calbindin, calretinin, or parvalbumin and 5-bromo-2'-deoxyuridine (BrdU) double labeling showed that calcium binding protein immunopositive neurons in gliotic CA1 area at 60 days were surviving instead of newly generated neurons. Iontophoretic injection of Phaseolus vulgaris leucoagglutinin into the medial septum and the nucleus of the diagonal band of Broca or the lateral entorhinal cortex showed contacts between Phaseolus vulgaris leucoagglutinin immunopositive en passant and terminal boutons and surviving calcium binding protein immunopositive neurons in the hippocampus. The presence in the gliotic hippocampus of enlarged and/or aggregated bouton-like structures 60 days after pilocarpine-induced status epilepticus is indicative for the reorganization of connections between the hippocampal afferents and surviving hippocampal neurons. This reconstruction could be a factor in the ongoing epileptic activity in this model of mesial temporal lobe epilepsy.