Expression of bone morphogenetic proteins in the brain during normal aging and in 6-hydroxydopamine-lesioned animals

BMP7 alleviates trigeminal neuralgia by reducing oligodendrocyte apoptosis and demyelination

BACKGROUND

BMP7 has been shown to have neuroprotective effects and to alleviate demyelination. However, its role in trigeminal neuralgia (TN) has not been well investigated. The current study aims to determine whether BMP7 plays a role in demyelination, its effects on pain behaviors and mechanism of action in rats with TN.

METHODS

We used an infraorbital-nerve chronic-constriction injury (ION-CCI) to establish a rat model of TN. Adeno-associated viruses (AAVs) were injected into the rats to upregulate or downregulate BMP7. The mechanical withdrawal thresholds (MWT) of the injured rats were detected using Von Frey filaments. The changes in expression levels of BMP7 and oligodendrocyte (OL) markers were examined by western blotting, quantitative real-time PCR, immunofluorescence, and transmission electron microscopy.

RESULTS

The ION-CCI induced mechanical allodynia, demyelination, and loss of OLs with a reduction of BMP7. Short-hairpin RNA (shRNA)-BMP7 that inhibited BMP7 expression also caused mechanical allodynia, demyelination, and loss of OLs, and its mechanism may be OL apoptosis. Overexpressing BMP7 in the trigeminal spinal subnucleus caudalis(VC) with AAV-BMP7 relieved all three phenotypes induced by the CCI, and its mechanism may be alleviating OLs apoptosis. Two signal pathways associated with apoptosis, STAT3 and p65, were significantly downregulated in the VC after CCI and rescued by BMP7 overexpression.

CONCLUSION

BMP7 can alleviate TN by reducing OLs apoptosis and subsequent demyelination. The mechanism behind this protection could be BMP7-mediated activation of the STAT3 and NF-κB/p65 signaling pathway and subsequent decrease in OL apoptosis. Importantly, our study presents clear evidence in support of BMP7 as a possible therapeutic target for the treatment of TN.

Bone morphogenetic protein inhibitors and mitochondria targeting agents synergistically induce apoptosis-inducing factor (AIF) caspase-independent cell death in lung cancer cells

BACKGROUND

Bone morphogenetic proteins (BMP) are evolutionarily conserved morphogens that are reactivated in lung carcinomas. In lung cancer cells, BMP signaling suppresses AMP activated kinase (AMPK) by inhibiting LKB1. AMPK is activated by mitochondrial stress that inhibits ATP production, which is enhanced 100-fold when phosphorylated by LKB1. Activated AMPK can promote survival of cancer cells but its "hyperactivation" induces cell death. The studies here reveal novel cell death mechanisms induced by BMP inhibitors, together with agents targeting the mitochondria, which involves the "hyperactivation" of AMPK.

METHODS

This study examines the synergistic effects of two BMP inhibitors together with mitochondrial targeting agents phenformin and Ym155, on cell death of lung cancer cells expressing LKB1 (H1299), LKB1 null (A549), and A549 cells transfected with LKB1 (A549-LKB1). Cell death mechanisms evaluated were the activation of caspases and the nuclear localization of apoptosis inducing factor (AIF). A769662 was used to allosterically activate AMPK. Knockdown of BMPR2 and LKB1 using siRNA was used to examine their effects on nuclear localization of AMPK. Validation studies were performed on five passage zero primary NSCLC.

RESULTS

Both BMP inhibitors synergistically suppressed growth when combined with Ym155 or phenformin in cells expressing LKB1. The combination of BMP inhibitors with mitochondrial targeting agents enhanced the activation of AMPK in lung cancer cells expressing LKB1. Allosteric activation of AMPK with A769662 induced cell death in both H1299 and A549 cells. Cell death induced by the combination of BMP inhibitors and mitochondrial-targeting agents did not activate caspases. The combination of drugs induced nuclear localization of AIF in cells expressing LKB1, which was attenuated by knockdown of LKB1. Knockdown of BMPR2 together with Ym155 increased nuclear localization of AIF. Combination therapy also enhanced cell death and AIF nuclear localization in primary NSCLC.

CONCLUSIONS

These studies demonstrate that inhibition of BMP signaling together with mitochondrial targeting agents induce AIF caspase-independent cell death, which involves the "hyperactivation" of AMPK. AIF caspase-independent cell death is an evolutionarily conserved cell death pathway that is infrequently studied in cancer. These studies provide novel insight into mechanisms inducing AIF caspase-independent cell death in cancer cells using BMP inhibitors. Video Abstract.

Bone morphogenetic protein signaling regulation of AMPK and PI3K in lung cancer cells and C. elegans

BACKGROUND

Bone morphogenetic protein (BMP) is a phylogenetically conserved signaling pathway required for development that is aberrantly expressed in several age-related diseases including cancer, Alzheimer's disease, obesity, and cardiovascular disease. Aberrant BMP signaling in mice leads to obesity, suggesting it may alter normal metabolism. The role of BMP signaling regulating cancer metabolism is not known.

METHODS

To examine BMP regulation of metabolism, C. elegans harboring BMP gain-of-function (gof) and loss-of-function (lof) mutations were examined for changes in activity of catabolic and anabolic metabolism utilizing Western blot analysis and fluorescent reporters. AMP activated kinase (AMPK) gof and lof mutants were used to examine AMPK regulation of BMP signaling. H1299 (LKB1 wild-type), A549 (LKB1 lof), and A549-LKB1 (LKB1 restored) lung cancer cell lines were used to study BMP regulation of catabolic and anabolic metabolism. Studies were done using recombinant BMP ligands to activate BMP signaling, and BMP receptor specific inhibitors and siRNA to inhibit signaling.

RESULTS

BMP signaling in both C. elegans and cancer cells is responsive to nutrient conditions. In both C. elegans and lung cancer cell lines BMP suppressed AMPK, the master regulator of catabolism, while activating PI3K, a regulator of anabolism. In lung cancer cells, inhibition of BMP signaling by siRNA or small molecules increased AMPK activity, and this increase was mediated by activation of LKB1. BMP2 ligand suppressed AMPK activation during starvation. BMP2 ligand decreased expression of TCA cycle intermediates and non-essential amino acids in H1299 cells. Furthermore, we show that BMP activation of PI3K is mediated through BMP type II receptor. We also observed feedback signaling, as AMPK suppressed BMP signaling, whereas PI3K increased BMP signaling.

CONCLUSION

These studies show that BMP signaling suppresses catabolic metabolism and stimulates anabolic metabolism. We identified feedback mechanisms where catabolic induced signaling mediated by AMPK negatively regulates BMP signaling, whereas anabolic signaling produces a positive feedback regulation of BMP signing through Akt. These mechanisms were conserved in both lung cancer cells and C. elegans. These studies suggest that aberrant BMP signaling causes dysregulation of metabolism that is a potential mechanism by which BMP promotes survival of cancer cells.

BMP4 Exerts Anti-Neurogenic Effect via Inducing Id3 during Aging

Bone morphogenetic protein (BMP) signaling has been shown to be intimately associated with adult neurogenesis in the subventricular zone (SVZ) and subgranular zone (SGZ). Adult neurogenesis declines in aging rodents and primates. However, the role of BMP signaling in the age-related neurogenesis decline remains elusive and the effect of BMP4 on adult SVZ neurogenesis remains controversial. Here, the expression of BMP4 and its canonical effector phosphorylated-Smad1/5/8 (p-Smad1/5/8) in the murine SVZ and SGZ were found to be increased markedly with age. We identified Id3 as a major target of BMP4 in neuronal stem cells (NSCs) of both neurogenic regions, which exhibited a similar increase during aging. Intracerebroventricular infusion of BMP4 activated Smad1/5/8 phosphorylation and upregulated Id3 expression, which further restrained NeuroD1, leading to attenuated neurogenesis in both neurogenic regions and defective differentiation in the SGZ. Conversely, noggin, a potent inhibitor of BMP4, demonstrated opposing effects. In support of this, BMP4 treatment or lentiviral overexpression of Id3 resulted in decreased NeuroD1 protein levels in NSCs of both neurogenic regions and significantly inhibited neurogenesis. Thus, our findings revealed that the increased BMP4 signaling with age inhibited adult neurogenesis in both SVZ and SGZ, which may be attributed at least in part, to the changes in the Id3-NeuroD1 axis.

Bone morphogenetic proteins (BMPs) in the central regulation of energy balance and adult neural plasticity

The current worldwide obesity pandemic highlights a need to better understand the regulation of energy balance and metabolism, including the role of the nervous system in controlling energy intake and energy expenditure. Neural plasticity in the hypothalamus of the adult brain has been implicated in full-body metabolic health, however, the mechanisms surrounding hypothalamic plasticity are incompletely understood. Bone morphogenetic proteins (BMPs) control metabolic health through actions in the brain as well as in peripheral tissues such as adipose, together regulating both energy intake and energy expenditure. BMP ligands, receptors, and inhibitors are found throughout plastic adult brain regions and have been demonstrated to modulate neurogenesis and gliogenesis, as well as synaptic and dendritic plasticity. This role for BMPs in adult neural plasticity is distinct from their roles in brain development. Existing evidence suggests that BMPs induce weight loss through hypothalamic pathways, and part of the mechanism of action may be through inducing neural plasticity. In this review, we summarize the data regarding how BMPs affect neural plasticity in the adult mammalian brain, as well as the relationship between central BMP signaling and metabolic health.

Peptides Derived from Growth Factors to Treat Alzheimer's Disease

Alzheimer's disease (AD) is a devastating neurodegenerative disease characterized by progressive neuron losses in memory-related brain structures. The classical features of AD are a dysregulation of the cholinergic system, the accumulation of amyloid plaques, and neurofibrillary tangles. Unfortunately, current treatments are unable to cure or even delay the progression of the disease. Therefore, new therapeutic strategies have emerged, such as the exogenous administration of neurotrophic factors (e.g., NGF and BDNF) that are deficient or dysregulated in AD. However, their low capacity to cross the blood-brain barrier and their exorbitant cost currently limit their use. To overcome these limitations, short peptides mimicking the binding receptor sites of these growth factors have been developed. Such peptides can target selective signaling pathways involved in neuron survival, differentiation, and/or maintenance. This review focuses on growth factors and their derived peptides as potential treatment for AD. It describes (1) the physiological functions of growth factors in the brain, their neuronal signaling pathways, and alteration in AD; (2) the strategies to develop peptides derived from growth factor and their capacity to mimic the role of native proteins; and (3) new advancements and potential in using these molecules as therapeutic treatments for AD, as well as their limitations.

Crosstalk of Brain and Bone-Clinical Observations and Their Molecular Bases

As brain and bone disorders represent major health issues worldwide, substantial clinical investigations demonstrated a bidirectional crosstalk on several levels, mechanistically linking both apparently unrelated organs. While multiple stress, mood and neurodegenerative brain disorders are associated with osteoporosis, rare genetic skeletal diseases display impaired brain development and function. Along with brain and bone pathologies, particularly trauma events highlight the strong interaction of both organs. This review summarizes clinical and experimental observations reported for the crosstalk of brain and bone, followed by a detailed overview of their molecular bases. While brain-derived molecules affecting bone include central regulators, transmitters of the sympathetic, parasympathetic and sensory nervous system, bone-derived mediators altering brain function are released from bone cells and the bone marrow. Although the main pathways of the brain-bone crosstalk remain ‘efferent’, signaling from brain to bone, this review emphasizes the emergence of bone as a crucial ‘afferent’ regulator of cerebral development, function and pathophysiology. Therefore, unraveling the physiological and pathological bases of brain-bone interactions revealed promising pharmacologic targets and novel treatment strategies promoting concurrent brain and bone recovery.

The potential of bone morphogenetic protein 2 as a neurotrophic factor for Parkinson's disease

Parkinson's disease is the second most common neurodegenerative disorder; it affects 1% of the population over the age of 65. The number of people with Parkinson's disease is set to rapidly increase due to changing demographics and there is an unmet clinical need for disease-modifying therapies. The pathological hallmarks of Parkinson's disease are the progressive degeneration of dopaminergic neurons in the substantia nigra and their axons which project to the striatum, and the aggregation of α-synuclein; these result in a range of debilitating motor and non-motor symptoms. The application of neurotrophic factors to protect and potentially regenerate the remaining dopaminergic neurons is a major area of research interest. However, this strategy has had limited success to date. Clinical trials of two well-known neurotrophic factors, glial cell line-derived neurotrophic factor and neurturin, have reported limited efficacy in Parkinson's disease patients, despite these factors showing potent neurotrophic actions in animal studies. There is therefore a need to identify other neurotrophic factors that can protect against α-synuclein-induced degeneration of dopaminergic neurons. The bone morphogenetic protein (BMP) family is the largest subgroup of the transforming growth factor-β superfamily of proteins. BMPs are naturally secreted proteins that play crucial roles throughout the developing nervous system. Importantly, many BMPs have been shown to be potent neurotrophic factors for dopaminergic neurons. Here we discuss recent work showing that transcripts for the BMP receptors and BMP2 are co-expressed with several key markers of dopaminergic neurons in the human substantia nigra, and evidence for downregulation of BMP2 expression at distinct stages of Parkinson's disease. We also discuss studies that explored the effects of BMP2 treatment, in in vitro and in vivo models of Parkinson's disease. These studies found potent effects of BMP2 on dopaminergic neurites, which is important given that axon degeneration is increasingly recognized as a key early event in Parkinson's disease. Thus, the aim of this mini-review is to give an overview of the BMP family and the BMP-Smad signalling pathway, in addition to reviewing the available evidence demonstrating the potential of BMP2 for Parkinson's disease therapy.

9-cis retinoic acid induces neurorepair in stroke brain

The purpose of this study was to examine the neurorestorative effect of delayed 9 cis retinoic acid (9cRA) treatment for stroke. Adult male rats received a 90-min right distal middle cerebral artery occlusion (dMCAo). Animals were separated into two groups with similar infarction sizes, based on magnetic resonance imaging on day 2 after dMCAo. 9cRA or vehicle was given via an intranasal route daily starting from day 3. Stroke rats receiving 9cRA post-treatment showed an increase in brain 9cRA levels and greater recovery in motor function. 9cRA enhanced the proliferation of bromodeoxyuridine (+) cells in the subventricular zone (SVZ) and lesioned cortex in the stroke brain. Using subventricular neurosphere and matrigel cultures, we demonstrated that proliferation and migration of SVZ neuroprogenitor cells were enhanced by 9cRA. Our data support a delayed and non-invasive drug therapy for stroke. Intranasal 9cRA can facilitate the functional recovery and endogenous repair in the ischemic brain.

Increased bone morphogenetic protein signaling contributes to age-related declines in neurogenesis and cognition

Aging is associated with decreased neurogenesis in the hippocampus and diminished hippocampus-dependent cognitive functions. Expression of bone morphogenetic protein 4 (BMP4) increases with age by more than 10-fold in the mouse dentate gyrus while levels of the BMP inhibitor, noggin, decrease. This results in a profound 30-fold increase in phosphorylated-SMAD1/5/8, the effector of canonical BMP signaling. Just as observed in mice, a profound increase in expression of BMP4 is observed in the dentate gyrus of humans with no known cognitive abnormalities. Inhibition of BMP signaling either by overexpression of noggin or transgenic manipulation not only increases neurogenesis in aging mice, but remarkably, is associated with a rescue of cognitive deficits to levels comparable to young mice. Additive benefits are observed when combining inhibition of BMP signaling and environmental enrichment. These findings indicate that increased BMP signaling contributes significantly to impairments in neurogenesis and to cognitive decline associated with aging, and identify this pathway as a potential druggable target for reversing age-related changes in cognition.

BMP2-SMAD signaling represses the proliferation of embryonic neural stem cells through YAP

Previous studies have shown that the Hippo pathway effector yes-associated protein (YAP) plays an important role in maintaining stem cell proliferation. However, the precise molecular mechanism of YAP in regulating murine embryonic neural stem cells (NSCs) remains largely unknown. Here, we show that bone morphogenetic protein-2 (BMP2) treatment inhibited the proliferation of mouse embryonic NSCs, that YAP was critical for mouse NSC proliferation, and that BMP2 treatment-induced inhibition of mouse NSC proliferation was abrogated by YAP knockdown, indicating that the YAP protein mediates the inhibitory effect of BMP2 signaling. Additionally, we found that BMP2 treatment reduced YAP nuclear translocation, YAP-TEAD interaction, and YAP-mediated transactivation. BMP2 treatment inhibited YAP/TEAD-mediated Cyclin D1 (ccnd1) expression, and knockdown of ccnd1 abrogated the BMP2-mediated inhibition of mouse NSC proliferation. Mechanistically, we found that Smad1/4, effectors of BMP2 signaling, competed with YAP for the interaction with TAED1 and inhibited YAP's cotranscriptional activity. Our data reveal mechanistic cross talk between BMP2 signaling and the Hippo-YAP pathway in murine NSC proliferation, which may be exploited as a therapeutic target in neurodegenerative diseases and aging.

Anterograde Activin signaling regulates postsynaptic membrane potential and GluRIIA/B abundance at the Drosophila neuromuscular junction

Members of the TGF-β superfamily play numerous roles in nervous system development and function. In Drosophila, retrograde BMP signaling at the neuromuscular junction (NMJ) is required presynaptically for proper synapse growth and neurotransmitter release. In this study, we analyzed whether the Activin branch of the TGF-β superfamily also contributes to NMJ development and function. We find that elimination of the Activin/TGF-β type I receptor babo, or its downstream signal transducer smox, does not affect presynaptic NMJ growth or evoked excitatory junctional potentials (EJPs), but instead results in a number of postsynaptic defects including depolarized membrane potential, small size and frequency of miniature excitatory junction potentials (mEJPs), and decreased synaptic densities of the glutamate receptors GluRIIA and B. The majority of the defective smox synaptic phenotypes were rescued by muscle-specific expression of a smox transgene. Furthermore, a mutation in actβ, an Activin-like ligand that is strongly expressed in motor neurons, phenocopies babo and smox loss-of-function alleles. Our results demonstrate that anterograde Activin/TGF-β signaling at the Drosophila NMJ is crucial for achieving normal abundance and localization of several important postsynaptic signaling molecules and for regulating postsynaptic membrane physiology. Together with the well-established presynaptic role of the retrograde BMP signaling, our findings indicate that the two branches of the TGF-β superfamily are differentially deployed on each side of the Drosophila NMJ synapse to regulate distinct aspects of its development and function.

Canonical BMP-Smad signalling promotes neurite growth in rat midbrain dopaminergic neurons

Ventral midbrain (VM) dopaminergic (DA) neurons project to the dorsal striatum via the nigrostriatal pathway to regulate voluntary movements, and their loss leads to the motor dysfunction seen in Parkinson's disease (PD). Despite recent progress in the understanding of VM DA neurogenesis, the factors regulating nigrostriatal pathway development remain largely unknown. The bone morphogenetic protein (BMP) family regulates neurite growth in the developing nervous system and may contribute to nigrostriatal pathway development. Two related members of this family, BMP2 and growth differentiation factor (GDF)5, have neurotrophic effects, including promotion of neurite growth, on cultured VM DA neurons. However, the molecular mechanisms regulating their effects on DA neurons are unknown. By characterising the temporal expression profiles of endogenous BMP receptors (BMPRs) in the developing and adult rat VM and striatum, this study identified BMP2 and GDF5 as potential regulators of nigrostriatal pathway development. Furthermore, through the use of noggin, dorsomorphin and BMPR/Smad plasmids, this study demonstrated that GDF5- and BMP2-induced neurite outgrowth from cultured VM DA neurons is dependent on BMP type I receptor activation of the Smad 1/5/8 signalling pathway.

Roles for the TGFβ superfamily in the development and survival of midbrain dopaminergic neurons

The adult midbrain contains 75% of all dopaminergic neurons in the CNS. Within the midbrain, these neurons are divided into three anatomically and functionally distinct clusters termed A8, A9 and A10. The A9 group plays a functionally non-redundant role in the control of voluntary movement, which is highlighted by the motor syndrome that results from their progressive degeneration in the neurodegenerative disorder, Parkinson's disease. Despite 50 years of investigation, treatment for Parkinson's disease remains symptomatic, but an intensive research effort has proposed delivering neurotrophic factors to the brain to protect the remaining dopaminergic neurons, or using these neurotrophic factors to differentiate dopaminergic neurons from stem cell sources for cell transplantation. Most neurotrophic factors studied in this context have been members of the transforming growth factor β (TGFβ) superfamily. In recent years, an intensive research effort has focused on understanding the function of these proteins in midbrain dopaminergic neuron development and their role in the molecular architecture that regulates the development of this brain region, with the goal of applying this knowledge to develop novel therapies for Parkinson's disease. In this review, the current evidence showing that TGFβ superfamily members play critical roles in the regulation of midbrain dopaminergic neuron induction, differentiation, target innervation and survival during embryonic and postnatal development is analysed, and the implications of these findings are discussed.

Bone morphogenetic protein-7 ameliorates cerebral ischemia and reperfusion injury via inhibiting oxidative stress and neuronal apoptosis

Previous studies have indicated that bone morphogenetic protein-7 (BMP-7) is neuroprotective against cerebral ischemia/reperfusion (IR) injury. The present study was undertaken to determine the molecular mechanisms involved in this effect. Adult male Wistar rats were subjected to 2 h of transient middle cerebral artery occlusion (MCAO), followed by 24 h of reperfusion. BMP-7 (10⁻⁴ g/kg) or vehicle was infused into rats at the onset of reperfusion via the tail vein. Neurological deficits, infarct volume, histopathological changes, oxidative stress-related biochemical parameters, neuronal apoptosis, and apoptosis-related proteins were assessed. BMP-7 significantly improved neurological and histological deficits, reduced the infarct volume, and decreased apoptotic cells after cerebral ischemia. BMP-7 also markedly enhanced the activities of antioxidant enzymes superoxide dismutase (SOD) and glutathione peroxidase (GSH-PX), and reduced the level of malondialdehyde (MDA) in IR rats. In addition, Western blot analysis indicated that BMP-7 prevented cytochrome c release, inhibited activation of caspase-3, caspase-9 and caspase-8. Our data suggested that BMP-7 has protective effects against cerebral IR injury in rats, and the neuroprotective effects may be attributed to attenuating oxidative stress and inhibiting neuronal apoptosis.

Bone morphogenetic protein 7 upregulates the expression of nestin and glial fibrillary acidic protein in rats with cerebral ischemia-reperfusion injury

Bone morphogenetic protein 7 (BMP7) is a member of the transforming growth factor-β (TGF-β) superfamily and was initially identified as a protein that may induce bone and cartilage growth in the bone matrix. The present study was conducted in order to investigate the effect of BMP7 on the expression of nestin and glial fibrillary acidic protein (GFAP) in the brain tissue of rats after cerebral ischemia-reperfusion injury. A total of 40 adult healthy male Sprague-Dawley rats were used in this study, of which 10 randomly received a sham operation and the remaining 30 were subjected to a 2-h ischemia and 24-h reperfusion by ligation of the left external and internal carotid arteries. Twenty successfully modeled rats were equally randomized into the treatment and control groups. The rats in the treatment group were intervened with 250 μl BMP7 (0.1 mg/kg) via tail vein injection, whereas the rats in the control and sham operation groups were injected with an equal volume of sterile water for injection. Neurological deficits were evaluated by the Bederson's method at 24 h after ischemia-reperfusion and the brain infarct volume was assessed by 2,3,5-triphenyl tetrazolium chloride coloring. The neuronal apoptosis was assessed by terminal deoxynucleotidyl transferase-mediated biotinylated deoxyuridine triphosphate nick end-labelling (TUNEL) staining and the expression of nestin and GFAP in the three groups was analyzed by immunohistochemistry. Bederson's score (t=4.66, P<0.01) and focus infarction (t=6.98, P<0.01) were lower in the BMP7 treatment group compared to those in the control group. In addition, the number of TUNEL-positive cells in the treatment group was lower compared to that in the control group (P<0.01). Compared to the control group, the expression of nestin and GFAP was enhanced in the BMP7 treatment group (P<0.01). Therefore, BMP7 may upregulate the expression of nestin and GFAP and promote neural regeneration to protect animals against ischemia-reperfusion injury.

Age-mediated transcriptomic changes in adult mouse substantia nigra

Substantia nigra pars compacta (SNpc) is highly sensitive to normal aging and selectively degenerates in Parkinson's disease (PD). Until now, molecular mechanisms behind SNpc aging have not been fully investigated using high throughput techniques. Here, we show early signs of aging in SNpc, which are more evident than in ventral tegmental area (VTA), a region adjacent to SNpc but less affected in PD. Aging-associated early changes in transcriptome were investigated comparing late middle-aged (18 months old) to young (2 months old) mice in both SNpc and VTA. A meta-analysis of published microarray studies allowed us to generate a common “transcriptional signature” of the aged (≥ 24 months old) mouse brain. SNpc of late-middle aged mice shared characteristics with the transcriptional signature, suggesting an accelerated aging in SNpc. Age-dependent changes in gene expression specific to SNpc were also observed, which were related to neuronal functions and inflammation. Future studies could greatly help determine the contribution of these changes to SNpc aging. These data help understand the processes underlying SNpc aging and their potential contribution to age-related disorders like PD.

Muscone Exerts Neuroprotection in an Experimental Model of Stroke via Inhibition of the Fas Pathway

Identifying small molecules that are neuroprotective against stroke injury will be highly beneficial for treatment therapies. A cell viability assay and gas chromatography-mass spectrometry were used to identify active small molecules in XingNaoJing, which is a well known Chinese Medicine prescribed for the effective treatment of stroke. Studies have found that muscone is the active compound that prevents PC12 cell and cortical neuron damage following various injuries. Analysis of apoptosis indicated that muscone inhibited glutamate-induced apoptotic cell death of PC12 cells and cortical neurons. Fas and caspase-8 expression were upregulated following glutamate treatment in cortical neurons, and was markedly attenuated in the presence of muscone. Furthermore, muscone significantly reduced cerebral infarct volume, neurological dysfunction and inhibited cortical neuron apoptosis in middle cerebral artery occluded (MCAO) rats in a dose-dependent manner. Moreover, a significant decrease in Fas and caspase-8 expression in the rat cortex was observed in MCAO rats treated with muscone. Our results demonstrate that muscone may be a small active molecule with neuroprotective properties, and that inhibition of apoptosis and Fas is an important mechanism of neuroprotection by muscone. These findings suggest a potential therapeutic role for muscone in the treatment of stroke.

Low gene expression of bone morphogenetic protein 7 in brainstem astrocytes in major depression

The noradrenergic locus coeruleus (LC) is the principal source of brain norepinephrine, a neurotransmitter thought to play a major role in the pathology of major depressive disorder (MDD) and in the therapeutic action of many antidepressant drugs. The goal of this study was to identify potential mediators of brain noradrenergic dysfunction in MDD. Bone morphogenetic protein 7 (BMP7), a member of the transforming growth factor-β superfamily, is a critical mediator of noradrenergic neuron differentiation during development and has neurotrophic and neuroprotective effects on mature catecholaminergic neurons. Real-time PCR of reversed transcribed RNA isolated from homogenates of LC tissue from 12 matched pairs of MDD subjects and psychiatrically normal control subjects revealed low levels of BMP7 gene expression in MDD. No differences in gene expression levels of other members of the BMP family were observed in the LC, and BMP7 gene expression was normal in the prefrontal cortex and amygdala in MDD subjects. Laser capture microdissection of noradrenergic neurons, astrocytes, and oligodendrocytes from the LC revealed that BMP7 gene expression was highest in LC astrocytes relative to the other cell types, and that the MDD-associated reduction in BMP7 gene expression was limited to astrocytes. Rats exposed to chronic social defeat exhibited a similar reduction in BMP7 gene expression in the LC. BMP7 has unique developmental and trophic actions on catecholamine neurons and these findings suggest that reduced astrocyte support for pontine LC neurons may contribute to pathology of brain noradrenergic neurons in MDD.

BMP2 expression in the adult rat brain

Bone morphogenetic protein-2 (BMP2) is a member of the transforming growth factor-β (TGF-β) superfamily and plays important roles in multiple biological events. Although BMP2 expression has been well described in the early development of the central nervous system (CNS), little information is available on its expression in the adult CNS. We thus investigated BMP2 expression in the adult rat CNS by using immunohistochemistry. Here we show that BMP2 is widely expressed throughout the adult CNS. In addition, besides intense BMP2 expression in almost all neurons, we found BMP2 expression in astrocytes and ependymal cells. Interestingly, we found that the axons of olfactory sensory neurons express BMP2. In addition, in the glomerular layer, BMP2 was very strongly expressed in some glomeruli, whereas the other glomeruli were weakly stained, suggesting that the variations in BMP2 expression level in each glomerus might be cues for each axon to find its adequate target and to keep its identity. Furthermore, we compared the expression patterns of BMP2 and BMP4. Interestingly, BMP4 was preferentially expressed in the dendrites of several neurons, whereas BMP2 was basically not expressed in the dendrites; however, it was detected in the axons. This means that in a single neuron the localizations of BMP2 and BMP4 are differentially regulated. These data indicate that BMP2 is more widely expressed throughout the adult CNS than previously reported, and its continued abundant expression in the adult brain strongly supports the idea that BMP2 also plays pivotal roles in the adult brain.

(+)-Cholesten-3-one induces differentiation of neural stem cells into dopaminergic neurons through BMP signaling

To identify small molecules that induce dopaminergic neurons from neural stem cells (NSCs) is promising for therapy of Parkinson's disease. Here we report the results of analyzing structurally related steroids in traditional Chinese medicine to identify agents that enhance dopaminergic differentiation of NSCs. Using P19 cells transfected by tyrosine hydroxylase (TH) promoter reporter construct, (+)-Cholesten-3-one with carbonyl, but not cholesterol and cholesterol myristate can effectively promote the activity of TH promoter. This effect depends on bone morphogenetic protein (BMP) signaling. Phenotypic cellular analysis indicated that (+)-Cholesten-3-one induces differentiation of NSCs to dopaminergic neurons with increased expression of specific dopaminergic markers including TH, dopamine transporter, dopa decarboxylase and higher level of dopamine secretion. (+)-Cholesten-3-one significantly increases the expression of BMPR IB, but not BMPR IA or BMPR II; p-Smad1/5/8 positive nuclei and expression of p-Smad1/5/8 were detected in NSCs treated with (+)-Cholesten-3-one, indicating that (+)-Cholesten-3-one may activate the BMP signaling. Moreover, overexpression of BMP4 or inhibition of BMP affects the effect of (+)-Cholesten-3-one on the dopaminergic phenotype. These findings may contribute to efficient production of dopaminergic neurons from NSCs culture for many applications and raise interesting questions about the role of (+)-Cholesten-3-one in neurogenesis.

Human microglia transplanted in rat focal ischemia brain induce neuroprotection and behavioral improvement

Background and Purpose

Microglia are resident immunocompenent and phagocytic cells of central nervous system (CNS), which produce various cytokines and growth factors in response to injury and thereby regulate disease pathology. The purpose of this study is to investigate the effects of microglial transplantation on focal cerebral ischemia model in rat.

Methods

Transient middle cerebral artery occlusion (MCAO) in rats was induced by the intraluminal filament technique. HMO6 cells, human microglial cell line, were transplanted intravenously at 48 hours after MCAO. Functional tests were performed and the infarct volume was measured at 7 and 14 days after MCAO. Migration and cell survival of transplanted microglial cells and host glial reaction in the brain were studied by immunohistochemistry. Gene expression of neurotrophic factors, cytokines and chemokines in transplanted cells and host rat glial cells was determined by laser capture microdissection (LCM) and quantitative real time-PCR.

Results

HMO6 human microglial cells transplantion group demonstrated significant functional recovery compared with control group. At 7 and 14 days after MCAO, infarct volume was significantly reduced in the HMO group. In the HMO6 group, number of apoptotic cells was time-dependently reduced in the infarct core and penumbra. In addition, number of host rat microglia/macrophages and reactive astrocytes was significantly decreased at 7 and 14 days after MCAO in the penumbra. Gene expression of various neurotrophic factors (GDNF, BDNF, VEGF and BMP7) and anti-inflammatory cytokines (IL4 and IL5) was up-regulated in transplanted HMO6 cells of brain tissue compared with those in culture. The expression of GDNF and VEGF in astrocytes in penumbra was significantly up-regulated in the HMO6 group.

Conclusions

Our results indicate that transplantation of HMO6 human microglial cells reduces ischemic deficits and apoptotic events in stroke animals. The results were mediated by modulation of gliosis and neuroinflammation, and neuroprotection provided by neurotrophic factors of endogenous and transplanted cells-origin.

BAMBI (bone morphogenetic protein and activin membrane-bound inhibitor) reveals the involvement of the transforming growth factor-beta family in pain modulation

Transforming growth factors-beta (TGF-betas) signal through type I and type II serine-threonine kinase receptor complexes. During ligand binding, type II receptors recruit and phosphorylate type I receptors, triggering downstream signaling. BAMBI [bone morphogenetic protein (BMP) and activin membrane-bound inhibitor] is a transmembrane pseudoreceptor structurally similar to type I receptors but lacks the intracellular kinase domain. BAMBI modulates negatively pan-TGF-beta family signaling; therefore, it can be used as an instrument for unraveling the roles of these cytokines in the adult CNS. BAMBI is expressed in regions of the CNS involved in pain transmission and modulation. The lack of BAMBI in mutant mice resulted in increased levels of TGF-beta signaling activity, which was associated with attenuation of acute pain behaviors, regardless of the modality of the stimuli (thermal, mechanical, chemical/inflammatory). The nociceptive hyposensitivity exhibited by BAMBI(-/-) mice was reversed by the opioid antagonist naloxone. Moreover, in a model of chronic neuropathic pain, the allodynic responses of BAMBI(-/-) mice also appeared attenuated through a mechanism involving delta-opioid receptor signaling. Basal mRNA and protein levels of precursor proteins of the endogenous opioid peptides proopiomelanocortin (POMC) and proenkephalin (PENK) appeared increased in the spinal cords of BAMBI(-/-). Transcript levels of TGF-betas and their intracellular effectors correlated directly with genes encoding opioid peptides, whereas BAMBI correlated inversely. Furthermore, incubation of spinal cord explants with activin A or BMP-7 increased POMC and/or PENK mRNA levels. Our findings identify TGF-beta family members as modulators of acute and chronic pain perception through the transcriptional regulation of genes encoding the endogenous opioids.

Neurotrophic factors for the treatment of Parkinson's disease

Parkinson's disease (PD) is a slowly progressive disorder with no known etiology. Pathologically, there is a loss of the dopaminergic neurons in the substantia nigra that project to the striatum. Current available therapies for PD are targeted to the restoration of striatal dopamine. These approaches may alleviate symptoms transiently, but fail to slow the progression of disease. One emergent therapeutic approach is the use of neurotrophic factors to halt or reverse the loss of dopaminergic neurons. There have been intensive research efforts both preclinically and clinically testing the efficacy and safety of neurotrophic factors for the treatment of PD. In this review, we discuss the neuroprotective and neuroregenerative properties of various trophic factors, both old and recent, and their status as therapeutic molecules for PD.

Nigrostriatal alterations in bone morphogenetic protein receptor II dominant negative mice

BACKGROUND

We previously demonstrated that exogenous application of bone morphogenetic protein 7 (BMP7) reduced 6-hydroxydopamine-mediated neurodegeneration in a rodent model of Parkinson's disease. The purpose of this study is to examine the endogenous neurotrophic properties of BMP Receptor II in dopaminergic neurons of the nigrostriatal pathway.

METHODS

Adult male BMPRII dominant negative (BMPRIIDN) mice and their wild type controls (WT) were placed in the activity chambers for 3 days to monitor locomotor activity. Animals were sacrificed for tyrosine hydroxylase (TH) immunostaining. A subgroup of BMPRIIDN and WT mice were injected with high doses of methamphetamine (MA) and were sacrificed for terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) histochemistry at 4 days after injection.

RESULTS

BMPRIIDN mice had lower locomotor activity than the WT. There is a significant decrease in TH neuronal number in substantia nigra compacta, TH fiber density in the substantia nigra reticulata, and TH immunoreactivity in striatum in the BMPRIIDN mice, suggesting that deficiency in endogenous BMP signaling reduces dopaminergic innervation and motor function in the nigrostriatal pathway. Administration of MA increased TUNEL labeling in the substantia nigra in the BMPRIIDN mice.

CONCLUSIONS

Endogenous BMPs have trophic effects on nigrostriatal dopaminergic neurons. Deficiency in BMP signaling increases vulnerability to insults induced by high doses of MA.

Noggin enhances dopamine neuron production from human embryonic stem cells and improves behavioral outcome after transplantation into Parkinsonian rats

Symptoms of Parkinson's disease have been improved by transplantation of fetal dopamine neurons recovered from aborted fetal tissue, but tissue recovery is difficult. Human embryonic stem cells may provide unlimited cells for transplantation if they can be converted to dopamine neurons and survive transplantation into brain. We have found that the bone morphogenic protein antagonist Noggin increased the number of dopamine neurons generated in vitro from human and mouse embryonic stem cells differentiated on mouse PA6 stromal cells. Noggin effects were seen with either early (for mouse, days 0-7, and for human, days 0-9) or continuous treatment. After transplant into cyclosporin-immunosuppressed rats, human dopamine neurons improved apomorphine circling in direct relation to the number of surviving dopamine neurons, which was fivefold greater after Noggin treatment than with control human embryonic stem cell transplants differentiated only on PA6 cells. We conclude that Noggin promotes dopamine neuron differentiation and survival from human and mouse embryonic stem cells. Disclosure of potential conflicts of interest is found at the end of this article.

Glial aromatization increases the expression of bone morphogenetic protein-2 in the injured zebra finch brain

In songbirds, brain injury upregulates glial aromatase. The resulting local estrogen synthesis mitigates apoptosis and enhances cytogenesis by poorly understood mechanisms. Bone morphogenetic proteins (BMPs), long studied for their role in neural development, are also neuroprotective and cytogenic in the adult brain. BMPs remain uncharacterized in songbirds, as do the mechanisms regulating their post-injury expression. We first established the expression of BMPs 2, 4, 6, and 7 in the adult zebra finch brain using RT-PCR. Next, we determined the effect of neural insult on BMP expression, by comparing BMP transcripts between injured and uninjured telencephalic hemispheres using semi-quantitative PCR. The expression of BMPs 2 and 4, but not 6 and 7, increased 24 h post-injury. To determine the influence of aromatase on BMP expression, we compared BMP expression following delivery of the aromatase inhibitor Fadrozole or vehicle into contralateral hemispheres. Fadrozole decreased BMP2, but not BMP4, expression, suggesting that aromatization may induce BMP2 expression following injury. Since BMPs are gliogenic and neurotrophic, future studies will test if the neuroprotective and cytogenic effects of aromatase upregulation are mediated by BMP2. Songbirds may be excellent models towards understanding the role of local estrogen synthesis and its downstream mechanisms on neuroprotection and repair.

Bone morphogenetic protein-7 reduces toxicity induced by high doses of methamphetamine in rodents

Methamphetamine (MA) is a drug of abuse as well as a dopaminergic neurotoxin. We have previously demonstrated that pretreatment with bone morphogenetic protein 7 (BMP7) reduced 6-hydroxydopamine-mediated neurodegeneration in a rodent model of Parkinson's disease. In this study, we examined the neuroprotective effects of BMP7 against MA-mediated toxicity in dopaminergic neurons. Primary dopaminergic neurons, prepared from rat embryonic ventral mesencephalic tissue, were treated with MA. High doses of MA decreased tyrosine hydroxylase immunoreactivity (THir) while increasing terminal deoxynucleotidyl transferase-mediated dNTP nick end labeling. These toxicities were significantly antagonized by BMP7. Interaction of BMP7 and MA in vivo was first examined in CD1 mice. High doses of MA (10 mg/kgx4 s.c.) significantly reduced locomotor activity and THir in striatum. I.c.v. administration of BMP7 antagonized these changes. In BMP7 +/- mice, MA suppressed locomotor activity and reduced TH immunoreactivity in nigra reticulata to a greater degree than in wild type BMP7 +/+ mice, suggesting that deficiency in BMP7 expression increases vulnerability to MA insults. Since BMP7 +/- mice also carry a LacZ-expressing reporter allele at the BMP7 locus, the expression of BMP7 was indirectly measured through the enzymatic activity of beta-galactosidase (beta-gal) in BMP7 +/- mice. High doses of MA significantly suppressed beta-gal activity in striatum, suggesting that MA may inhibit BMP7 expression at the terminals of the nigrostriatal pathway. A similar effect was also found in CD1 mice in that high doses of MA suppressed BMP7 mRNA expression in nigra. In conclusion, our data indicate that MA can cause lesioning in the nigrostriatal dopaminergic terminals and that BMP7 is protective against MA-mediated neurotoxicity in central dopaminergic neurons.

Brorin, a Novel Secreted Bone Morphogenetic Protein Antagonist, Promotes Neurogenesis in Mouse Neural Precursor Cells

We identified a gene encoding a novel secreted protein in mice and humans and named it Brorin. Mouse Brorin consists of 324 amino acids with a putative secreted signal sequence at its amino terminus and two cysteine-rich domains in its core region. Positions of 10 cysteine residues in the domains of Brorin are similar to those in the cysteine-rich domains of members of the Chordin family. However, the amino acid sequence of Brorin is not significantly similar to that of any other member of the Chordin family, indicating that Brorin is a unique member of the family. Mouse Brorin protein produced in cultured cells was efficiently secreted into the culture medium. The protein inhibited the activity of bone morphogenetic protein 2 (BMP2) and BMP6 in mouse preosteoblastic MC3T3-E1 cells. Mouse Brorin was predominantly expressed in neural tissues in embryos and also predominantly expressed in the adult brain. In the brain, the expression was detected in neurons, but not glial cells. The neural tissue-specific expression profile of Brorin is quite distinct from that of any other member of the Chordin family. Brorin protein promoted neurogenesis, but not astrogenesis, in mouse neural precursor cells. The present findings indicate that Brorin is a novel secreted BMP antagonist that potentially plays roles in neural development and functions.

Concise Review: Bone Morphogenetic Protein Pleiotropism in Neural Stem Cells and Their Derivatives-Alternative Pathways, Convergent Signals

Bone morphogenetic proteins (BMPs) are a class of morphogens that are critical regulators of the central nervous system (CNS), peripheral nervous system, and craniofacial development. Modulation of BMP signaling also appears to be an important component of the postnatal stem cell niche. However, describing a comprehensive model of BMP actions is complicated by their paradoxical effects in precursor cells, which include dorsal specification, promoting proliferation or mitotic arrest, cell survival or death, and neuronal or glial fate. In addition, in postmitotic neurons BMPs can promote dendritic growth, act as axonal chemorepellants, and stabilize synapses. Although many of these responses depend on interactions with other incoming signals, some reflect the recruitment of distinct BMP signal transduction pathways. In this review, we classify the diverse effects of BMPs on neural cells, focus on the known mechanisms that specify distinct responses, and discuss the remaining challenges in identifying the cellular basis of BMP pleiotropism. Addressing these issues may have importance for stem cell mobilization, differentiation, and cell integration/survival in reparative therapies.

Growth-associated gene and protein expression in the region of axonal sprouting in the aged brain after stroke

Aged individuals exhibit reduced functional recovery after stroke. We examined the expression profile in aged animals of a recently identified group of growth-associated genes that underlies post-stroke axonal sprouting in the young adult. Basal levels of most growth-promoting genes are higher in aged cortex compared with young adult, and are further induced after stroke. Compared with the young adult, these genes are induced at later time points after stroke. For growth-inhibitory molecules, myelin-associated glycoprotein and ephrin A5 are uniquely induced in the aged brain; chondroitin sulfate proteoglycans and oligodendrocyte myelin glycoprotein are induced at earlier time points; and Nogo-A, semaphorin IIIa and NG2 decline in aged vs. young adult after stroke. The aged brain does not simply have a reduction in growth-associated molecules after stroke, but a completely unique molecular profile of post-stroke axonal sprouting.

Neuroregenerative effects of BMP7 after stroke in rats

Previous reports have indicated that the expression of bone morphogenetic protein-7 (BMP7) is enhanced after ischemic injury in brain. This upregulation may induce endogenous neurorepair in the ischemic brain. The purpose of this study was to examine neuroregenerative effects of BMP7 after ischemia-reperfusion injury. Adult Sprague-Dawley rats were anesthetized with chloral hydrate. Right middle cerebral artery (MCA) was transiently ligated with 10-O suture for 1 h. One day after MCA occlusion, vehicle or BMP7 was infused to the contralateral cerebral ventricle. To identify possible neurogenesis, bromodeoxyurindine (BrdU) was systemically injected on the fourth and fifth days after MCA occlusion. Animals treated with BMP7 showed a rapid correction of body asymmetry and neurological deficits, suggesting BMP7 facilitates recovery after stroke. Animals were sacrificed at 1 month after stroke and brains were analyzed using immunohistological techniques. BMP7 treatment enhanced immunoreactivity of BrdU in the subventricular zone, lesioned cortex, and corpus callosum. These BrdU-positive cells co-labeled with nestin and NeuN. Our behavioral and anatomical data suggest that BMP7 promotes neuroregeneration in stroke animals, possibly through the proliferation of new neuronal precursors after ischemia.

Intrastriatal transforming growth factor alpha delivery to a model of Parkinson's disease induces proliferation and migration of endogenous adult neural progenitor cells without differentiation into dopaminergic neurons

We examined the cell proliferative, neurogenic, and behavioral effects of transforming growth factor alpha (TGFalpha) in a 6-OHDA Parkinson's disease model when compared with naive rats. Intrastriatal TGFalpha infusion induced significant proliferation, hyperplastic nodules, and substantial migratory waves of nestin-positive progenitor cells from the adult subventricular zone (SVZ) of dopamine-denervated rats. Interestingly, SVZ cells in naive rats displayed proliferation but minimal migration in response to the TGFalpha infusion. The cells in the expanded SVZ accumulated cytoplasmic beta-catenin, indicating activation of classical Wnt signaling. However, no evidence of any neuronal differentiation was found of these recruited progenitor cells anywhere examined in the brain. Consequently, no evidence of dopaminergic (DA) neurogenesis was found in the striatum or substantia nigra in any experimental group, and amphetamine-induced behavioral rotations did not improve. In summary, the cells in the TGFalpha-induced migratory cellular wave remain undifferentiated and do not differentiate into midbrain-like DA neurons.

Neurotrophic effects of bone morphogenetic protein-7 in a rat model of Parkinson's disease

Previous studies have demonstrated that pretreatment with bone morphogenetic protein-7 (BMP7) reduces ischemic neuronal injury in vivo. Moreover, exogenous application of BMP7 increases both the number of tyrosine hydroxylase (+) cells and dopamine (DA) uptake in rat mesencephalic cell cultures. The purpose of this study was to investigate the in vivo effects of BMP7 on 6-hydroxydopamine (6-OHDA) induced lesioning of midbrain DA neurons. Adult Fischer 344 rats were anesthetized and injected with BMP7 or vehicle into the left substantia nigra, followed by local administration of 9 microg of 6-OHDA into the left medial forebrain bundle. The lesioned animals that received BMP7 pretreatment, as compared to vehicle/6-OHDA controls, had a significant reduction in methamphetamine-induced rotation 1 month after the surgery. BMP7-pretreatment partially preserved KCl-induced dopamine release in the lesioned striatum and significantly increased TH immunoreactivity in the lesioned nigra and striatum. In summary, our data suggest that BMP7 has neuroprotective and/or neuroreparative effects against 6-OHDA lesioning of the nigrostriatal DA pathway in an animal model of Parkinson's disease (PD).

Effects of growth/differentiation factor 5 on the survival and morphology of embryonic rat midbrain dopaminergic neurones in vitro

Growth/differentiation factor 5 (GDF5) is a member of the transforming growth factor-beta superfamily that is expressed in the developing CNS, including the ventral mesencephalon (VM). GDF5 has been shown to increase the survival of dopaminergic neurones in animal models of Parkinson's disease. This study was aimed at characterising the effects of GDF5 on dopaminergic neurones in vitro. Treatment with GDF5 induced a three-fold increase in the number of dopaminergic neurones in embryonic day 14 rat VM cultures after six days in vitro. A significant increase was also observed in the numbers of astrocytes in GDF5-treated cultures. GDF5 treatment also had significant effects on the morphology of dopaminergic neurones in these cultures; total neurite length, number of branch points and somal area were all significantly increased after six days in vitro. Analysis of neurite length and numbers of branch points at each level of the neuritic field revealed that the most pronounced effects of GDF5 were on the secondary and tertiary levels of the neuritic field. The specific type I receptor for GDF5, bone morphogenetic protein receptor (BMPR)-Ib, was found to be strongly expressed in freshly-dissected E14 VM tissue, but its expression was lost with increasing time in culture. Accordingly, treatment with GDF5 for 24 h from the time of plating induced increases in the numbers of dopaminergic neurones, while treatment with GDF5 for 24 h after six days in vitro did not. This study shows that GDF5 can promote both the survival and morphological differentiation of VM dopaminergic neurones in vitro, lending support to its potential as a candidate dopaminergic neurotrophin for use in the treatment of Parkinson's disease.