Neonatal bilateral whisker trimming in male mice age-dependently alters brain neurotransmitter levels and causes adolescent onsets of social behavior abnormalities

Tactile perception via whiskers is important in rodent behavior. Whisker trimming during the neonatal period affects mouse behaviors related to both whisker-based tactile cognition and social performance. However, the molecular basis of these phenomena is not completely understood. To solve this issue, we investigated developmental changes in transmitters and metabolites in various brain regions of male mice subjected to bilateral whisker trimming during the neonatal period (10 days after birth [BWT10 mice]). We discovered significantly lower levels of 3-methoxy-4-hydroxyphenyl glycol (MHPG), the major noradrenaline metabolite, in various brain regions of male BWT10 mice at both early/late adolescent stages (at P4W and P8W). However, reduced levels of dopamine (DA) and their metabolites were more significantly identified at P8W in the nuclear origins of monoamine (midbrain and medulla oblongata) and the limbic system (frontal cortex, amygdala, and hippocampus) than at P4W. Furthermore, the onset of social behavior deficits (P6W) was observed later to the impairment of whisker-based tactile cognitive behaviors (P4W). Taken together, these findings suggest that whisker-mediated tactile cognition may contribute toprogressive abnormalities in social behaviors in BWT10 mice accompanied by impaired development of dopaminergic systems.

Substantial acetylcholine reduction in multiple brain regions of Mecp2-deficient female rats and associated behavioral abnormalities

Rett syndrome (RTT) is a neurodevelopmental disorder with X-linked dominant inheritance caused mainly by mutations in the methyl-CpG-binding protein 2 (MECP2) gene. The effects of various Mecp2 mutations have been extensively assessed in mouse models, but none adequately mimic the symptoms and pathological changes of RTT. In this study, we assessed the effects of Mecp2 gene deletion on female rats (Mecp2^+/−) and found severe impairments in social behavior [at 8 weeks (w), 12 w, and 23 w of age], motor function [at 16 w and 26 w], and spatial cognition [at 29 w] as well as lower plasma insulin-like growth factor (but not brain-derived neurotrophic factor) and markedly reduced acetylcholine (30%–50%) in multiple brain regions compared to female Mecp2^+/+ rats [at 29 w]. Alternatively, changes in brain monoamine levels were relatively small, in contrast to reports on mouse Mecp2 mutants. Female Mecp2-deficient rats express phenotypes resembling RTT and so may provide a robust model for future research on RTT pathobiology and treatment.

FGF2-responsive genes in human dental pulp cells assessed using a rat spinal cord injury model

The central nervous system in adult mammals does not heal spontaneously after spinal cord injury (SCI). However, SCI treatment has been improved recently following the development of cell transplantation therapy. We recently reported that fibroblast growth factor (FGF) 2-pretreated human dental pulp cells (hDPCs) can improve recovery in a rat model of SCI. This study aimed to investigate mechanisms underlying the curative effect of SCI enhanced via FGF2 pretreatment; we selected three hDPC lines upon screening for the presence of mesenchymal stem cell markers and of their functionality in a rat model of SCI, as assessed using the Basso, Beattie, and Bresnahan score of locomotor functional scale, electrophysiological tests, and morphological analyses. We identified FGF2-responsive genes via gene expression analyses in these lines. FGF2 treatment upregulated GABRB1, MMP1, and DRD2, which suggested to contribute to SCI or central the nervous system. In an expanded screening of additional lines, GABRB1 displayed rather unique and interesting behavior; two lines with the lowest sensitivity of GABRB1 to FGF2 treatment displayed an extremely minor effect in the SCI model. These findings provide insights into the role of FGF2-responsive genes, especially GABRB1, in recovery from SCI, using hDPCs treated with FGF2.

Priming with FGF2 stimulates human dental pulp cells to promote axonal regeneration and locomotor function recovery after spinal cord injury

Human dental pulp cells (DPCs), adherent cells derived from dental pulp tissues, are potential tools for cell transplantation therapy. However, little work has been done to optimize such transplantation. In this study, DPCs were treated with fibroblast growth factor-2 (FGF2) for 5-6 consecutive serial passages and were transplanted into the injury site immediately after complete transection of the rat spinal cord. FGF2 priming facilitated the DPCs to promote axonal regeneration and to improve locomotor function in the rat with spinal cord injury (SCI). Additional analyses revealed that FGF2 priming protected cultured DPCs from hydrogen-peroxide-induced cell death and increased the number of DPCs in the SCI rat spinal cord even 7 weeks after transplantation. The production of major neurotrophic factors was equivalent in FGF2-treated and untreated DPCs. These observations suggest that FGF2 priming might protect DPCs from the post-trauma microenvironment in which DPCs infiltrate and resident immune cells generate cytotoxic reactive oxygen species. Surviving DPCs could increase the availability of neurotrophic factors in the lesion site, thereby promoting axonal regeneration and locomotor function recovery.

Cell Transplantation to the Brain with Microglia Labeled by Neuropathogenic Retroviral Vector System

A8 virus (A8-V) is a molecular clone of the neuropathogenic FrC6 virus derived from the Friend murine leukemia virus (F-MuLV). The A8-V infects endothelia and microglia in the brain. We constructed a gene transfer system with the A8-V gene. Pseudotyped virus carrying the surface protein of A8-V (A8-SU) transduced the β-glactosidase gene incorporated in the retroviral vector efficiently to cultured microglial cells derived from newborn rats. Ex vivo gene transferred microglial cells were then injected into the right hemi-sphere of 3-day-old and 3-week-old rat brains. All of the rats examined at 4 weeks after the injection contained the labeled microglial cells in the brain (7/7 and 5/5 of the rats injected at 3 days and 3 weeks, respectively). None of the rats showed pathological changes in the whole body investigated, including the central nervous system, 4 weeks after transplantation of the labeled microglial cells.

Implantation of BDNF-Producing Packaging Cells into Brain

In order to invent a screening system to check in vivo gene function and the efficiency of gene transfer mediated by a retroviral vector system, we established a novel packaging cell, PacC6/A8, that is transplantable to rat brains. The packaging cell is based on the gene of the neuropatogenic retrovirus, A8-V. For expression in the brain, a vector that expresses brain-derived neurotrophic factor (BDNF) tagged by c-Myc-His6 (LxA/bdmh) was constructed. After transfection of LxA/bdmh to PacC6/A8, a cloned cell line, PacC6/ A8/bmh, was established. PacC6/A8/bmh cells stably produced pseudotyped retroviruses carrying LxA/ bdmh. For a control, a retroviral vector that bears the gene that codes enhanced green fluorescent protein (EGFP) tagged by C-Mic-His6 was also created and used for the establishment of PacC6/A8/gfmh cells that produce pseudotyped retroviruses carrying LxA/gfmh. PacC6/A8/bmh and PacC6/A8/gfmh cells were injected to the brain of newborn rats. A tumor was formed in all the rats injected that did not exhibit any symptoms until 3–4 weeks after the injection. A histological study of the injected rats revealed that the transferred BDNF gene was expressed in the brain of rats injected with PacC6/A8/bmh cells, but not in rats with PacC6/A8/gfmh cells. Interestingly, many activated microglia had migrated into the tumor induced by PacC6/A8/bmh cells, and expressed a high amount of BDNF.

Neonatal Whisker Trimming Impairs Fear/Anxiety-Related Emotional Systems of the Amygdala and Social Behaviors in Adult Mice

Abnormalities in tactile perception, such as sensory defensiveness, are common features in autism spectrum disorder (ASD). While not a diagnostic criterion for ASD, deficits in tactile perception contribute to the observed lack of social communication skills. However, the influence of tactile perception deficits on the development of social behaviors remains uncertain, as do the effects on neuronal circuits related to the emotional regulation of social interactions. In neonatal rodents, whiskers are the most important tactile apparatus, so bilateral whisker trimming is used as a model of early tactile deprivation. To address the influence of tactile deprivation on adult behavior, we performed bilateral whisker trimming in mice for 10 days after birth (BWT10 mice) and examined social behaviors, tactile discrimination, and c-Fos expression, a marker of neural activation, in adults after full whisker regrowth. Adult BWT10 mice exhibited significantly shorter crossable distances in the gap-crossing test than age-matched controls, indicating persistent deficits in whisker-dependent tactile perception. In contrast to controls, BWT10 mice exhibited no preference for the social compartment containing a conspecific in the three-chamber test. Furthermore, the development of amygdala circuitry was severely affected in BWT10 mice. Based on the c-Fos expression pattern, hyperactivity was found in BWT10 amygdala circuits for processing fear/anxiety-related responses to height stress but not in circuits for processing reward stimuli during whisker-dependent cued learning. These results demonstrate that neonatal whisker trimming and concomitant whisker-dependent tactile discrimination impairment severely disturbs the development of amygdala-dependent emotional regulation.

A novel 2-decenoic acid thioester ameliorates corticosterone-induced depression- and anxiety-like behaviors and normalizes reduced hippocampal signal transduction in treated mice

We characterized mice administered corticosterone (CORT) at a dose of 20 mg/kg for 3 weeks to determine their suitability as a model of mood disorders and found that the time immobilized in the tail suspension test was longer and the time spent in the open arms of the elevated plus-maze test was shorter than those of the vehicle-treated group, findings demonstrating that chronic CORT induced both depression-like and anxiety-like behaviors. Furthermore, the levels of phosphorylated extracellular signal-regulated kinase (pERK) 1/2 in the hippocampus and cerebral cortex were reduced in the CORT-treated group. Using this model, we investigated the protective effect of the ester, thioester, and amide compounds of 2-decenoic acid derivatives (termed compounds A, B, and C, respectively). The potency of the protective activity against the CORT-induced depression-like or anxiety-like behaviors and the reduction in pERK1/2 level were found to be in the following order: compound B > compound C > compound A. Therefore, we further investigated the therapeutic activity of only compound B, and its effect on depression-like behavior was observed after oral administration for 1 or 2 weeks, and its effect on anxiety-like behavior was observed after oral administration for 3 weeks. The ratios of phosphorylated ERK1/2, Akt, and cAMP-response element-binding protein to their respective nonphosphorylated forms were smaller in the CORT-treated group than in the vehicle-treated group; however, subsequent treatment with compound B at either 0.3 or 1.5 mg/kg significantly ameliorated this reduction. Compound B appeared to elicit intracellular signaling, similar to that elicited by brain-derived neurotrophic factor, and its mode of action was shown to be novel and different from that of fluvoxamine, a currently prescribed drug for mood disorders.

Neurotrophin-3 influences the number and the laminar fate of cortical progenitors in the developing cerebral cortex of mice through the MEK/ERK1/2 signaling pathway

The laminar formation in the developing cerebral cortex requires precisely regulated generation of phenotype-specific neurons. To determine whether neurotrophin-3 (NT3) is involved in this formation, we investigated the effects of NT3 administration in the telencephalic ventricular space on 13.5-day-old mouse embryos. NT3 increased the number of newly generated neurons and altered the neuronal phenotypes in the position and the transcription factors-expression profiles; the neuronal phenotypes originally committed for layer IV neurons were altered toward for layers II/III neurons. The former effects were observed when the parent progenitor cells were exposed to NT3 in the G1- to S-phase, whereas the latter effects were observed with exposure in the G1-phase. In addition, in vitro experiments revealed that the laminar fate alteration by NT3 was observed in the dissociated primary culture of cortical progenitors and the NT3 actions were suppressed by cotreatment with the MEK/ERK inhibitor. These observations suggest that NT3 is involved in the laminar formation of the developing cerebral cortex through the intercellular MEK/ERK pathway.

FGF-2-responsive and spinal cord-resident cells improve locomotor function after spinal cord injury

The adult central nervous system has only a limited capacity for axonal regeneration. In this study, fibroblast growth factor-2 (FGF-2) was injected once into the spinal cord tissue around the injury site immediately after complete spinal cord transection in rats. This treatment markedly improved the locomotor function of the animals. Histological analysis demonstrated that tissue composed of FGF-2-induced fibronectin-positive cells (FIFs) had infiltrated the injury site and filled large cystic cavities, into which numerous axons with growth-associated protein-43 immunoreactivity penetrated. The FIFs could also be cultured from the intact spinal cord tissue, demonstrating that they were resident in the non-injured spinal cord. They had a spindle-shaped morphology and enhanced expression of mRNAs of N-cadherin and neurotrophic factors, suggesting the beneficial properties of the FIFs for axonal regeneration. Thus, these results argue for the continual use of autologous transplantation as a novel and promising cell therapy for the treatment of spinal cord injury.

Oral Administration of Royal Jelly Facilitates mRNA Expression of Glial Cell Line-Derived Neurotrophic Factor and Neurofilament H in the Hippocampus of the Adult Mouse Brain

Royal jelly (RJ) is known to have a variety of biological activities toward various types of cells and tissues of animal models, but nothing is known about its effect on brain functions. Hence, we examined the effect of oral administration of RJ on the mRNA expression of various neurotrophic factors, their receptors, and neural cell markers in the mouse brain. Our results revealed that RJ selectively facilitates the mRNA expression of glial cell line-derived neurotrophic factor (GDNF), a potent neurotrophic factor acting in the brain, and neurofilament H, a specific marker predominantly found in neuronal axons, in the adult mouse hippocampus. These observations suggest that RJ shows neurotrophic effects on the mature brain via stimulation of GDNF production, and that enhanced expression of neurofilament H mRNA is involved in events subsequently caused by GDNF. RJ may play neurotrophic and/or neuroprotective roles in the adult brain through GDNF.

Knockdown of pre-mRNA cleavage factor Im 25 kDa promotes neurite outgrowth

Mammalian precursor mRNA (pre-mRNA) cleavage factor I (CFIm) plays important roles in the selection of poly(A) sites in a 3'-untranslated region (3'-UTR), producing mRNAs with variable 3' ends. Because 3'-UTRs often contain cis elements that impact stability or localization of mRNA or translation, alternative polyadenylation diversifies utilization of primary transcripts in mammalian cells. However, the physiological role of CFIm remains unclear. CFIm acts as a heterodimer comprising a 25kDa subunit (CFIm25) and one of the three large subunits-CFIm59, CFIm68, or CFIm72. CFIm25 binds directly to RNA and introduces and anchors the larger subunit. To examine the physiological roles of CFIm, we knocked down the CFIm25 gene in neuronal cells using RNA interference. Knockdown of CFIm25 increased the number of primary dendrites of developing hippocampal neurons and promoted nerve growth factor (NGF)-induced neurite extension from rat pheochromocytoma PC12 cells without affecting the morphology of proliferating PC12 cells. On the other hand, CFIm25 knockdown did not influence constitutively active or dominantly negative RhoA suppression or promotion of NGF-induced neurite extension from PC12 cells, respectively. Taken together, our results indicate that endogenous CFIm may promote neuritogenesis in developing neurons by coordinating events upstream of NGF-induced RhoA inactivation.

2-decenoic acid ethyl ester, a compound that elicits neurotrophin-like intracellular signals, facilitating functional recovery from cerebral infarction in mice

In our previous study, we found that trans-2-decenoic acid ethyl ester (DAEE), a derivative of a medium-chain fatty acid, elicits neurotrophin-like signals including the activation of extracellular signal-regulated kinases 1 and 2 (ERK1/2) in cultured mouse cortical neurons. Here, we examined the efficacy of intraperitoneal administration of DAEE on the treatment of a mouse model of the cerebral infarction caused by unilateral permanent middle cerebral artery occlusion (PMCAO). DAEE-treatment (100 μg/kg body weight injected at 0.5, 24, 48, 72 h after PMCAO) significantly restored the mice from PMCAO-induced neurological deficits including motor paralysis when evaluated 48, 72, and 96 h after the PMCAO. Furthermore, DAEE facilitated the phosphorylation of ERK1/2 on the infarction side of the brain when analyzed by Western immunoblot analysis, and it enhanced the number of phosphorylated ERK1/2-positive cells in the border areas between the infarction and non-infarction regions of the cerebral cortex, as estimated immunohistochemically. As the infarct volume remained unchanged after DAEE-treatment, it is more likely that DAEE improved the neurological condition through enhanced neuronal functions of the remaining neurons in the damaged areas rather than by maintaining neuronal survival. These results suggest that DAEE has a neuro-protective effect on cerebral infarction.

Effect of environmental factor influencing the development of mouse cerebral cortex

The cerebral cortex is organized into six cell layers, each of which contains neurons with similar morphology, functions, gene-expression profiles, and projection patterns. These layer-specific neuronal phenotypes are sequentially generated from common cortical progenitor cells in the ventricular zone of dorsal telencephalon. Although recent investigations have clarified important roles of intrinsic factors such as transcription factors and regulators of the cell cycle for the maturation of cortical progenitors, growth factors and neurotrophic factors environmentally supplied by the cerebral cortex are thought to regulate proliferation and neural development and determine neuronal differentiation in the cerebral cortex. In this review, I focus on the function of neurotrophin-family neurotrophic factor, including nerve growth factor, brain-derived neurotrophic factor (BDNF), neurotropin-3 (NT-3) and neurotrophin-4 in the formation of the neuronal layer of the cerebral cortex. Especially, BDNF and NT-3 are expressed in the proliferating cortical progenitors and influence the biological properties of cortical progenitors prior to neurogenesis and play distinct roles in generation of cortical neuronal subtypes.

Prenatal immune challenge compromises the normal course of neurogenesis during development of the mouse cerebral cortex

Maternal infection during pregnancy is an environmental risk factor for the development of severe brain disorders in offspring, including schizophrenia and autism. However, little is known about the neurodevelopmental mechanisms underlying the association between prenatal exposure to infection and the emergence of cognitive and behavioral dysfunctions in later life. By injecting viral mimetic polyriboinosinic-polyribocytidylic acid (Poly I:C) into mice, we investigated the influence of maternal immune challenge during pregnancy on the development of the cerebral cortex of offspring. Our previous study showed that stimulation of the maternal immune system compromised the expression properties of transcription factors and the synaptogenesis of cortical neurons in upper layers but not those in deeper layers. The objective of the current study was to examine further whether maternal immune challenge has an influence on the cellular-biological features of the cortical progenitors that generate distinct cortical neuronal subtypes. We found the following abnormalities in the cortex of mice given the prenatal Poly I:C injection during later stages of cortical neurogenesis. First, proliferative activity and the expression of Pax6, which is a master regulator of the gene expression of transcription factors, were significantly decreased in the cortical progenitors. Second, the laminar allocation and gene expression were significantly altered in the daughter neurons generated at the same birth dates. These results demonstrate that specific abnormalities in the cortical progenitors preceded deficits in neuronal phenotypes. These changes may underlie the emergence of psychiatric brain and behavioral dysfunctions after in utero exposure to an infection.

Caffeic acid phenethyl ester reduces spinal cord injury-evoked locomotor dysfunction

Caffeic acid phenethyl ester (CAPE) is a component of propolis, which is a substance taken from the hives of honeybees, and is known to exhibit an anti-inflammatory activity. Such activity has been thought to be partly based on its potential and specific inhibitory activities toward nuclear factor-κB, a transcription factor. Therefore, in the present study, we evaluated the effect of CAPE on functional locomotor recovery after spinal cord injury (SCI) caused by hemi-transection, because inflammatory responses are a major cause of the secondary injury observed following SCI and play a pivotal role in regulating the pathogenesis of acute and chronic SCI. When CAPE was i.p.-administered at a dosage of 10 µmol/kg, it enhanced the recovery of locomotor function and reduced the lesion size while suppressing the expression of the mRNAs for a pro-inflammatory cytokine interleukin-1β and the inflammatory enzymes, inducible nitric oxide synthase and cyclooxygenase-2. These results suggest CAPE to be a promising therapeutic tool for reducing the secondary neuronal damage following primary physical injury to the spinal cord.

Differentiation of embryonic stem cells

Mouse embryonic stem (ES) cells are derived from mouse blastocyst and are able to generate all embryonic tissues in vitro. This propensity of ES cells has acquired considerable attention in recent years due to the promising potential for future cell replacement-based therapies. Therefore, it is of fundamental interest to establish protocols that allow the differentiation of ES cells into specific cell types. In recent years, several such differentiation procedures have been described for mouse and human embryonic stem cells. This unit describes a simple procedure that promotes the neuronal differentiation of mouse embryonic stem cells and yields a high proportion of midbrain dopaminergic neurons. Furthermore, this procedure permits the isolation of neural stem cell lines from mouse ES cells.

AMP N1-oxide potentiates astrogenesis by cultured neural stem/progenitor cells through STAT3 activation

We earlier identified adenosine monophosphate (AMP) N1-oxide as a unique compound of royal jelly (RJ) that induces neurite outgrowth from cultured rat pheochromocytoma PC12 cells. In the present study, the effects of AMP N1-oxide on the proliferation and/or differentiation of cultured neural stem/progenitor cells (NSCs) were examined. As for cell proliferation, low micromolar concentrations of AMP N1-oxide or its parent compound, AMP, similarly enhanced the NSC proliferation-inducing activity of basic fibroblast growth factor (FGF-2), although neither compound tested alone affected cell proliferation. Conversely, high concentrations of AMP N1-oxide (over 20 microM) markedly suppressed cell growth even in the presence of FGF-2. However, this suppression was not observed with AMP. As for cell differentiation, AMP N1-oxide, but not AMP, increased the generation of astrocytes in a dose-dependent manner when the cells were cultured in medium lacking FGF-2. The generation of neurons or oligodendrocytes was not influenced by AMP N1-oxide. Furthermore, AMP N1-oxide increased the phosphorylation of STAT3 (signal transducer and activator of transcription 3), a transcription factor that mediates the expression of astrocytespecific genes. These results suggest that AMP N1-oxide is one of the components that facilitates astrogenesis by NSCs through activation of STAT3.

Royal jelly and its unique fatty acid, 10-hydroxy-trans-2-decenoic acid, promote neurogenesis by neural stem/progenitor cells in vitro

Neural stem/progenitor cells (NSCs) proliferate vigorously as neurospheres in medium containing basic fibroblast growth factor (FGF-2), but start differentiating into neurons, astrocytes or oligodendrocytes in FGF-2-free medium. An extract of royal jelly (RJ) significantly increased the percentage in the total cell population of not only neurons immunoreactive for class III beta-tubulin (Tuj1) but also astrocytes immunoreactive for glial fibrillary acidic protein (GFAP), and oligodendrocytes immunoreactive for 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNPase) generated from NSCs, but decreased that of nestin-positive NSCs. These results highlight a novel and outstanding property of the RJ, i.e., that it facilitates the differentiation of all types of brain cells (neurons, astrocytes, and oligodendrocytes). On the other hand, 10-hydroxy-trans-2-decenoic acid (HDEA), an unsaturated fatty acid characteristic of RJ, increased the generation of neurons and decreased that of astrocytes from NSCs. These observations suggest that RJ contains plural components that differently influence neuronal and/or glial lineages and that HDEA is one of such components of RJ that facilitates neurogenesis by NSCs.

AMP N(1)-oxide, a unique compound of royal jelly, induces neurite outgrowth from PC12 cells via signaling by protein kinase A independent of that by mitogen-activated protein kinase

Earlier we identified adenosine monophosphate (AMP) N₁-oxide as a unique compound of royal jelly (RJ) that induces neurite outgrowth (neuritegenesis) from cultured rat pheochromocytoma PC12 cells via the adenosine A_2A receptor. Now, we found that AMP N₁-oxide stimulated the phosphorylation of not only mitogen-activated protein kinase (MAPK) but also that of cAMP/calcium-response element-binding protein (CREB) in a dose-dependent manner. Inhibition of MAPK activation by a MEK inhibitor, PD98059, did not influence the AMP N₁-oxide-induced neuritegenesis, whereas that of protein kinase A (PKA) by a selective inhibitor, KT5720, significantly reduced neurite outgrowth. AMP N₁-oxide also had the activity of suppressing the growth of PC12 cells, which correlated well with the neurite outgrowth-promoting activity. KT5720 restored the growth of AMP N₁-oxide-treated PC12 cells. It is well known that nerve growth factor suppresses proliferation of PC12 cells before causing stimulation of neuronal differentiation. Thus, AMP N₁-oxide elicited neuronal differentiation of PC12 cells, as evidenced by generation of neurites, and inhibited cell growth through adenosine A_2A receptor-mediated PKA signaling, which may be responsible for characteristic actions of RJ.

Royal jelly-induced neurite outgrowth from rat pheochromocytoma PC12 cells requires integrin signal independent of activation of extracellular signal-regulated kinases

We showed earlier that neurite outgrowth of rat pheochromocytoma PC12 cells was stimulated by royal jelly extract (PERJ) or its unique component, AMP N(1)-oxide, via adenosine A2a receptors. In this study, we found that stimulated neurite outgrowth occurred in medium supplemented with serum, but not in serum-free medium. The pentapeptide GRGDS, which includes the RGD sequence commonly shared by extracellular matrix (ECM) components, could attenuate the effect of serum, suggesting that integrin receptor signaling was essential for the neurite outgrowth induced by PERJ or AMP N(1)-oxide. PERJ or AMP N(1)-oxide also activated extracellular signal-regulated kinases 1 or 2 (ERK1/2); however, this activation was not associated with the neurite outgrowth. As it is known that Mn(2+) induces neurite outgrowth from PC12 cells and activates ERK1/2 through integrin signals and that activation of ERK1/2 is essential for Mn2+-induced neurite outgrowth, a difference in the mechanism between Mn(2+)-induced and PERJ- or AMP N(1)-oxide-induced neurite outgrowth is suggested. Furthermore, we demonstrated that PERJ contained no ECM component-like substances. These results demonstrate that AMP N(1)-oxide and its analogues were the only entities in PERJ with neurite outgrowth-inducing activity and that they required integrin signaling in addition to activation of A2a receptors to induce neurite outgrowth.

Brain-derived neurotrophic factor participates in determination of neuronal laminar fate in the developing mouse cerebral cortex

Lamina formation in the developing cerebral cortex requires precisely regulated generation and migration of the cortical progenitor cells. To test the possible involvement of brain-derived neurotrophic factor (BDNF) in the formation of the cortical lamina, we investigated the effects of BDNF protein and anti-BDNF antibody separately administered into the telencephalic ventricular space of 13.5-d-old mouse embryos. BDNF altered the position, gene-expression properties, and projections of neurons otherwise destined for layer IV to those of neurons for the deeper layers, V and VI, of the cerebral cortex, whereas anti-BDNF antibody changed some of those of neurons of upper layers II/III. Additional analysis revealed that BDNF altered the laminar fate of neurons only if their parent progenitor cells were exposed to it at approximately S-phase and that it hastened the timing of the withdrawal of their daughter neurons from the ventricular proliferating pool by accelerating the completion of S-phase, downregulation of the Pax6 (paired box gene 6) expression, an essential transcription factor for generation of the upper layer neurons, and interkinetic nuclear migration of cortical progenitors in the ventricular zone. These observations suggest that BDNF participates in the processes forming the neuronal laminas in the developing cerebral cortex. BDNF can therefore be counted as one of the key extrinsic factors that regulate the laminar fate of cortical neurons.

Autocrine activation of cultured macrophages by brain-derived neurotrophic factor

To elucidate a significance of the expression of brain-derived neurotrophic factor (BDNF) in the activated microglia/macrophages of the injured central nervous system, we examined BDNF actions on or BDNF synthesis by macrophages cultured from the mouse peritoneal cavity. They synthesized BDNF and neurotrophin-3 (NT-3) in addition to expressing high-affinity neurotrophin receptors, full-length TrkB (FL), truncated TrkB (TK(-)), and TrkC, thus suggesting an autocrine influence of BDNF and NT-3. BDNF, but not NT-3, enhanced phagocytic activity and stimulated synthesis/secretion of interleukin-1beta in the same manner as lipopolysaccharide (LPS). Furthermore, there was a significant correlation of the phagocytic activity with the expression of BDNF or TrkB (FL). These results imply that the phagocytic activity of macrophages depends on BDNF synthesis and/or TrkB (FL) expression, suggesting that BDNF participates in the activation processes of macrophages by acting in an autocrine manner.

Inflammation-induced GDNF improves locomotor function after spinal cord injury

Activation of microglia/macrophages after injury occurs limitedly in the CNS, which finding may explain unsuccessful axonal regeneration. Therefore, the relationship between lipopolysaccharide (LPS)-induced inflammation and recovery of locomotor function of rats after spinal cord injury was examined. High-dose LPS improved locomotor function greater than low-dose LPS, being consistent with the expression of neurotrophic factor (GDNF) in microglia/macrophages. Experiments using GDNF gene mutant mice confirmed that the increase in the GDNF mRNA level, rather than the reduction in the mRNA level of inducible NO synthase, could be correlated with the restoration activity of locomotor function. These results suggest that a higher degree of inflammation leads to a higher degree of repair of CNS injuries through GDNF produced by activated microglia/macrophages.

In Vivo and In Vitro Tissue-Specific Expression of Green Fluorescent Protein Using the Cre-Lox System in Mouse Embryonic Stem Cells

Embryonic stem cells (ES) are pluripotent and may therefore serve as a source for the generation of specific cell types required for future therapies based on cell replacement. The isolation of defined cell populations from a certain lineage or tissue is a prerequisite for the analysis of the potential of such ES-derived cells in animal transplantation studies. Here, using the Cre/loxP system, we report the generation of murine ES cells conditionally expressing the hrGFP gene at the cell surface. Such ES cells can be differentiated in vitro into neurons displaying GFP activity in neurites. Transgenic mice derived from these ES cells permit the targeting of GFP-expression to specific tissues and provide material from the three germ layers suitable for molecular and biochemical analysis.

Involvement of glial cell line-derived neurotrophic factor in activation processes of rodent macrophages

The physiological roles of glial cell line-derived neurotrophic factor (GDNF) expressed in the microglia/macrophages of the injured spinal cord have not yet been clarified. mRNA expression of chemokines, including monocyte chemoattractant protein (MCP)-1, was evoked within 1 hr after transection of the spinal cord, and GDNF mRNA expression was similarly up-regulated. Immunohistochemical analysis showed that GDNF was coexpressed with MCP-1 in the CD11b-positive cells. Therefore, we examined further the effects of GDNF on cultured rat peritoneal macrophages. GDNF enhanced the phagocytic activity of the macrophages via GFRalpha-1, glycosylphosphatidylinositol-anchored specific binding site of GDNF, in a c-Ret-independent manner. The influence of autocrine and/or paracrine GDNF synthesis was evaluated by performing activation experiments using macrophages cultured from heterozygous (+/-) GDNF gene-deficient mice or wild-type (+/+) mice. There were no morphological differences dependent on genetic types or stimulators. However, the GDNF mRNA level, but not the MCP-1 or GFRalpha-1 mRNA level, was substantially lower in the mutant macrophages than in the +/+ cells irrespective of stimulation with MCP-1 or lipopolysaccharide (LPS). The phagocytic activity enhanced by MCP-1 or LPS was significantly lower in the mutant cells (+/-) than in the +/+ ones, demonstrating the involvement of endogenous GDNF in the activation processes of macrophages in vitro and suggesting that not only neuroprotective function but also activation of macrophages is effected by the GDNF produced after a spinal cord injury.

Stimulation of production of glial cell line-derived neurotrophic factor and nitric oxide by lipopolysaccharide with different dose-responsiveness in cultured rat macrophages

To understand the molecular basis of inflammation-induced neurotrophic influences, we investigated the effects of lipopolysaccharide (LPS) on production of glial cell line-derived neurotrophic factor (GDNF) in the injured rat spinal cord or in cultured rat macrophages in comparison with the effects on synthesis/secretion of inducible nitric oxide synthase (iNOS) and nitric oxide (NO). We found that GDNF mRNA expression lasted longer than that of iNOS mRNA in the injured spinal cord after injection of the high-dose LPS that had improved locomotor function, suggesting that the GDNF expression and its balance with NO generation were critical for injury regeneration. Therefore, we next investigated the effects of LPS on cultured macrophages. Levels of iNOS mRNA and secreted NO were enhanced by LPS at lower concentrations (10 ng/mL and above), whereas mRNA expression and secretion of GDNF were elevated only at higher concentrations (100 ng/mL and above). The culture medium of macrophages treated with 10 ng/mL of LPS was actually neurotoxic against cultured cortical neurons, whereas that conditioned at 1000 ng/mL was not. These observations suggest that neurotoxicity partly based on NO is induced by a lower degree of inflammation, whereas neurotrophic effects based on GDNF are manifested at a higher degree of inflammatory activity.

Hydrophobic dipeptide Leu-Ile protects against neuronal death by inducing brain-derived neurotrophic factor and glial cell line-derived neurotrophic factor synthesis

We investigated whether certain hydrophobic dipeptides, Leu-Ile, Leu-Pro, and Pro-Ile, which partially resemble the site on FK506 that binds to immunophilin, could stimulate glial cell line-derived neurotrophic factor (GDNF) and brain-derived neurotrophic factor (BDNF) synthesis in cultured neurons and found only Leu-Ile to be an active dipeptide. Leu-Ile protected against the death of mesencephalic neurons from wild-type mice but not from mice lacking the BDNF or GDNF gene. Next, we examined the effects of i.p. or i.c.v. administration of Leu-Ile on BDNF and GDNF contents. Both types of administration increased the contents of BDNF and GDNF in the striatum of mice. Also, peripheral administration of Leu-Ile inhibited dopaminergic (DA) denervation caused by unilateral injection of 6-hydroxydopamine (6-OHDA) into the striatum of mice. The number of rotations following a methamphetamine challenge was lower in the Leu-Ile-treated group than in the nontreated group. Next, we compared the calcineurin activity and immunosuppressant activity of Leu-Ile with those of FK506. Leu-Ile was not inhibitory toward calcineurin cellular activity in cultured neuronal cells. Furthermore, Leu-Ile did not suppress concanavalin A (ConA)-induced synthesis/secretion of interleukin-2 by cultured spleen cells, suggesting that the immunosuppressant activity of Leu-Ile may be negligible when used as a therapeutic tool for neurodegenerative diseases.

Axonal regrowth downregulates the synthesis of glial cell line-derived neurotrophic factor in the lesioned rat sciatic nerve

The effect of axonal regeneration on de novo synthesis of glial cell line-derived neurotrophic factor (GDNF) in rat sciatic nerves was examined. Transection of the sciatic nerve caused a prominent increase in the GDNF content in the distal segments within 1 week. The high level was sustained until 4 weeks in the animal model in which the nerve ends were ligated with thread (non-regeneration group); however, it was reduced to the original level within 2 or 4 weeks after the transection only in the segments invaded by regenerating axons in the models in which the nerve ends were coaptated (regeneration group). Expression of both GDNF protein and mRNA was decreased with a reciprocal increase in the density of neurofilaments, used as a marker of axonal ingrowth in distal segments of the regeneration group, suggesting that axonal contact turned off the GDNF-mediated nerve regeneration activity.

Cyclic AMP/protein kinase a signal attenuates Ca2+-induced fibroblast growth factor-1 synthesis in rat cortical neurons

Fibroblast growth factor (FGF)-1 is increased in particular brain regions after birth, suggesting an involvement of some regulatory neuronal circuits. To address the neuronal activity responsible for FGF-1 synthesis, effects of various neurotransmitter receptor activation on cellular FGF-1 content were examined using cultured rat cortical neurons. Histamine, glutamate, carbachol, serotonin or gamma-aminobutyric acid (GABA) caused an increase of FGF-1 content. Because this effect was mimicked by (1) N-methyl-D-aspartate, a glutamatergic agonist; (2) Ca(2+) ionophore; (3) depolarization with high concentration of KCl, but was abolished in Ca(2+)-free medium, Ca(2+) influx was thought to trigger FGF-1 synthesis. Such Ca(2+)-mediated enhancement of FGF-1 synthesis, however, did not occur in the presence of norepinephrine (NE), but was restored by KT-5720, an inhibitor of protein kinase A (PKA), suggesting an interplay between Ca(2+)-activated and cAMP/PKA signals for neuronal FGF-1 synthesis. This mechanism was proved to function in vivo by stimulation of FGF-1 expression in neurons of the cerebral cortex after intracerebral administration of propranolol, an antagonist of adrenergic beta receptors. This demonstrates that FGF-1 synthesis is essentially upregulated by Ca(2+) influx through excitatory neuronal activities, but such an effect is abolished by neurotransmission that evokes cAMP/PKA signals. FGF-1 produced is thought to act on establishment and maintenance of particular neuronal circuits in the brain, which may be one of the ways neurotransmitters regulate brain function.

Cell transplantation to the brain with microglia labeled by neuropathogenic retroviral vector system

A8 virus (A8-V) is a molecular clone of the neuropathogenic FrC6 virus derived from the Friend murine leukemia virus (F-MuLV). The A8-V infects endothelia and microglia in the brain. We constructed a gene transfer system with the A8-V gene. Pseudotyped virus carrying the surface protein of A8-V (A8-SU) transduced the beta-glactosidase gene incorporated in the retroviral vector efficiently to cultured microglial cells derived from newborn rats. Ex vivo gene transferred microglial cells were then injected into the right hemisphere of 3-day-old and 3-week-old rat brains. All of the rats examined at 4 weeks after the injection contained the labeled microglial cells in the brain (7/7 and 5/5 of the rats injected at 3 days and 3 weeks, respectively). None of the rats showed pathological changes in the whole body investigated, including the central nervous system, 4 weeks after transplantation of the labeled microglial cells.

Implantation of BDNF-producing packaging cells into brain

In order to invent a screening system to check in vivo gene function and the efficiency of gene transfer mediated by a retroviral vector system, we established a novel packaging cell, PacC6/A8, that is transplantable to rat brains. The packaging cell is based on the gene of the neuropatogenic retrovirus, A8-V. For expression in the brain, a vector that expresses brain-derived neurotrophic factor (BDNF) tagged by c-Myc-His6 (LxA/bdmh) was constructed. After transfection of LxA/bdmh to PacC6/A8, a cloned cell line, PacC6/A8/bmh, was established. PacC6/A8/bmh cells stably produced pseudotyped retroviruses carrying LxA/bdmh. For a control, a retroviral vector that bears the gene that codes enhanced green fluorescent protein (EGFP) tagged by C-Mic-His6 was also created and used for the establishment of PacC6/A8/gfmh cells that produce pseudotyped retroviruses carrying LxA/gfmh. PacC6/A8/bmh and PacC6/A8/gfmh cells were injected to the brain of newborn rats. A tumor was formed in all the rats injected that did not exhibit any symptoms until 3-4 weeks after the injection. A histological study of the injected rats revealed that the transferred BDNF gene was expressed in the brain of rats injected with PacC6/A8/bmh cells, but not in rats with PacC6/A8/gfmh cells. Interestingly, many activated microglia had migrated into the tumor induced by PacC6/A8/bmh cells, and expressed a high amount of BDNF.

Neuropathology of experimental autoimmune encephalomyelitis modified by retroviral infection

The A8 virus is a molecular clone of the neuropathogenic FrC6 virus derived from the Friend murine leukemia virus (F-MuLV). To elucidate the effects of A8 virus-infection on immune-mediated diseases in the central nervous system, we investigated the development of acute and monophasic experimental autoimmune encephalomyelitis (EAE) in A8 virus-infected Lewis rats. In EAE rats after A8 virus infection (A8-EAE), many inflammatory cells were found in the gray matter including the frontal lobe, where almost no inflammatory cells were found in rats with EAE alone. The modified distribution of inflammatory cells was not dependent on the ages of A8 virus-infected rats, although the frequency of the modified distribution was reduced in older rats. The chimeric virus Rec2, which contains the pol and env genes of 57 virus on the background of A8 and does not induce spongiform degeneration in the CNS, caused the same distributional modification of inflammatory cells in the rats with EAE as in A8-EAE rats. Furthermore, the incidence and intensity of spongiform degeneration, thymoma and splenomegaly caused by A8 virus were reduced by the induction of EAE.

A case of duodenal involvement of multiple myeloma imaged by positron emission tomography with 18F-fluorodeoxyglucose

A 61-year-old woman had been treated for multiple myeloma for 4 years when she developed abdominal pain. Ultrasonography and computed tomography revealed a tumor in the abdomen. Positron emission tomography (PET) with 18F-fluorodeoxyglucose (FDG) showed increased FDG uptake in the tumor. In previous bone marrow lesions, which were in clinical remission after chemotherapy and radiotherapy, abnormal FDG uptake was not recognized. Pathological examination after surgery revealed the tumor to be a plasmacytoma of the duodenum. Plasmacytoma of the duodenum is rare but can be seen during the clinical course of multiple myeloma. A few reports have described FDG PET findings of plasmacytoma. Those previous reports and our present case suggest a potential value of FDG PET in the evaluation of multiple myeloma.

Transforming growth factor-beta1 enhances expression of brain-derived neurotrophic factor and its receptor, TrkB, in neurons cultured from rat cerebral cortex

The effects of transforming growth factor (TGF)-beta1 on expression of brain-derived neurotrophic factor (BDNF) and its high-affinity receptor, TrkB, in neurons cultured from the cerebral cortex of 18-day-old embryonic rats were examined. BDNF mRNA was significantly increased from 24-48 hr after the TGF-beta1 treatment over 20 ng/ml. Accumulation of BDNF protein in the culture medium was also potentiated by TGF-beta1, although the intracellular content of BDNF was nearly unchanged. The enhancement of BDNF mRNA expression was suppressed by the co-presence of decorin, a small TGF-beta-binding proteoglycan that inhibits the biological activities of TGF-betas. mRNA expression of full-length TrkB, the bioactive high-affinity receptor for BDNF, was also upregulated after treatment with TGF-beta1. These observations suggest that: 1) TGF-beta1 potentiates BDNF/TrkB autocrine or local paracrine system; and 2) the neurotrophic activity of TGF-beta1 is partly responsible for the BDNF induced by TGF-beta1 itself. To test this latter possibility, we examined the neuronal survival activity of TGF-beta1 with or without K252a, a selective inhibitor of Trk family tyrosine kinases. TGF-beta1 significantly enhanced neuronal survival, but the co-presence of K252a completely suppressed the activity, demonstrating the involvement of Trk receptor signaling in TGF-beta1-mediated neuronal survival in cultured rat cortical neurons. These results seem to be in line with recent findings by other investigators that some neurotrophic factors including BDNF require TGF-betas as a cofactor to exert their neurotrophic activities.

Administration of FGF-2 to embryonic mouse brain induces hydrocephalic brain morphology and aberrant differentiation of neurons in the postnatal cerebral cortex

Fibroblast growth factor-2 (FGF-2) was injected into mouse cerebral ventricles at embryonic day (E) 14 in utero and its effects on developing brain morphology and expression of various cell- or differentiation-associated protein markers in the cerebral cortex were examined. High doses of FGF-2 (200 or 300 ng) caused encephalic alternations such as deformation of the calvarium, enlargement of the ventricular spaces, and thinning of the cerebral cortex. There was no gross abnormality in the alignment of the cerebral neuronal layers, however, both cell number and cell density of the upper layers (II/III) and the lower layers (IV-VI) of the cerebral cortex were increased. Brain-derived neurotrophic factor (BDNF), tyrosine hydroxylase, nestin, and microtubule-associated protein 2 were aberrantly or ectopically expressed in the deep areas of the cerebral cortex. A substantial number of these cells coexpressed these antigens. These observations demonstrate that a subpopulation of neurons in the cortical deep layer abnormally differentiated or partly sustained their immature state following a single administration of FGF-2 at E14. Developmental analysis of localization of BDNF-positive cells suggested that the abnormality started around P5. Furthermore, cell migration was not affected by FGF-2 administration. FGF-2 seems to play predominant roles in the proliferation of neuronal precursors and in neuronal differentiation in the developing mouse cerebral cortex even at relatively late stages of brain neurogenesis.

Aberrant expression of neurotrophic factors in the ventricular progenitor cells of infant congenitally hydrocephalic rats

OBJECTS

This study was conducted to investigate the roles of neurotrophic factors in the development of hydrocephalus in HTX rats.

METHODS

Expressions of brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3), and fibroblast growth factor (FGF)-1 were examined immunohistochemically in the cerebral cortex and ventricular zone of 6-day-old rats with congenital hydrocephalus (HTX rats). In the ventricular zone of hydrocephalic rats, potent BDNF-like immunoreactivity (-LI) and weak but significant signals for NT-3- and FGF-1-LIs were observed. However, no significant signals were detected in non-HTX rats. A small subpopulation of ventricular cells was positive for microtubule-associated protein 2 in HTX and non-HTX rats. The positive cells in the HTX rats had neurites much longer than those in the non-HTX animals, suggesting that some ventricular cells of the hydrocephalics had ectopically differentiated into mature neurons.

CONCLUSIONS

This abnormal differentiation may have been responsible for the aberrant expressions of neurotrophic factors. In contrast, the cerebral neuronal layers did not show such prominent alterations in neurotrophic factor expression.

4-methylcatechol increases brain-derived neurotrophic factor content and mRNA expression in cultured brain cells and in rat brain in vivo

Practical use of brain-derived neurotrophic factor (BDNF) as therapy is limited by two serious problems, i.e., its inability to cross the blood-brain barrier and its instability in the bloodstream. In the present study, we investigated the effects of 4-methylcatechol (4-MC), which stimulates nerve growth factor synthesis and protects against peripheral neuropathies in rats, on BDNF content and mRNA expression in cultured brain cells and in vivo in the rat brain. 4-MC elevated BDNF content in culture media of both rat astrocytes and neurons with different dose-response relations. The increase in BDNF mRNA level was correlated with the increase in BDNF content, demonstrating that 4-MC can stimulate BDNF synthesis of both neurons and astrocytes. Then we examined the in vivo effects of 4-MC. First, we found that ventricularly administered 4-MC facilitated an increase in the BDNF content in the cerebral cortex and hippocampus in association with its diffusion into the brain parenchyma. Second, i.p. administration of 4-MC enhanced BDNF mRNA expression in the infant rat brain, in which the blood-brain has not yet fully been established. These results demonstrate that 4-MC, once delivered into the brain, can stimulate BDNF synthesis.

Induction of a physiologically active brain-derived neurotrophic factor in the infant rat brain by peripheral administration of 4-methylcatechol

Effects of 4-methylcatechol (4MC), a known potent stimulator of nerve growth factor (NGF) synthesis, on expression of brain-derived neurotrophic factor (BDNF) mRNA and BDNF-like immunoreactivity (BDNF-LI) was investigated in infant rat brains. A single intraperitoneal administration of 4MC caused transient increases in the levels of BDNF mRNA and BDNF-LI in neurons of the cerebral cortex from 1 to 3 h and 3 to 12 h, respectively, after the injection. Repetitive injections of 4MC to newborn rats (12-h intervals for 10 days) caused a marked and dose-dependent elevation of the level of BDNF mRNA in the whole brain besides elevating the number of cells containing calbindin D-28 and enhancing its immunoreactive intensity in the pyriform cortex and hippocampus. These findings demonstrate that 4MC stimulates de novo synthesis of BDNF in the infant rat brain, resulting in acceleration of the developmental expression of calbindin D-28.