Scabronine G-methylester enhances secretion of neurotrophic factors mediated by an activation of protein kinase C-zeta

Empagliflozin-activated AMPK elicits neuroprotective properties in reserpine-induced depression via regulating dynamics of hippocampal autophagy/inflammation and PKCζ-mediated neurogenesis

RATIONALE

Major depression has been an area of extensive research during the last decades, for it represents a leading cause of disability and suicide. The stark rise of depression rates influenced by life stressors, economic threats, pandemic era, and resistance to classical treatments, has made the disorder rather challenging. Adult hippocampal neurogenesis and plasticity are particularly sensitive to the dynamic interplay between autophagy and inflammation. In fact, the intricate balance between the two processes contributes to neuronal homeostasis and survival.

OBJECTIVES

Having demonstrated promising potentials in AMPK activation, a major metabolic sensor and autophagy regulator, empagliflozin (Empa) was investigated for possible antidepressant properties in the reserpine rat model of depression.

RESULTS

While the reserpine protocol elicited behavioral, biochemical, and histopathological changes relevant to depression, Empa outstandingly hindered these pathological perturbations. Importantly, hippocampal autophagic response markedly declined with reserpine which disrupted the AMPK/mTOR/Beclin1/LC3B machinery and, conversely, neuro-inflammation prevailed under the influence of the NLRP3 inflammasome together with oxidative/nitrative stress. Consequently, AMPK-mediated neurotrophins secretion obviously deteriorated through PKCζ/NF-κB/BDNF/CREB signal restriction. Empa restored hippocampal monoamines and autophagy/inflammation balance, driven by AMPK activation. By promoting the atypical PKCζ phosphorylation (Thr403) which subsequently phosphorylates NF-κB at Ser311, AMPK successfully reinforced BDNF/CREB signal and hippocampal neuroplasticity. The latter finding was supported by hippocampal CA3 toluidine blue staining to reveal intact neurons.

CONCLUSION

The current study highlights an interesting role for Empa as a regulator of autophagic and inflammatory responses in the pathology of depression. The study also pinpoints an unusual contribution for NF-κB in neurotrophins secretion via AMPK/PKCζ/NF-κB/BDNF/CREB signal transduction. Accordingly, Empa can have special benefits in diabetic patients with depressive symptoms.

LIMITATIONS

The influence of p-NF-κB (Ser311) on NLRP3 inflammasome assembly and activation has not been investigated, which can represent an interesting point for further research.

Scabronine G Methyl Ester Improves Memory-Related Behavior and Enhances Hippocampal Cell Proliferation and Long-Term Potentiation via the BDNF-CREB Pathway in Olfactory Bulbectomized Mice

A previous study reported that scabronine G methyl ester (SG-ME) potentially enhances the in vitro secretion of neurotrophic factors such as nerve growth factor via the protein kinase C (PKC)-ζ pathway. However, it remains unknown whether SG-ME can improve cognitive dysfunctions in olfactory bulbectomized (OBX) mice. To address this question, we evaluated SG-ME-treated and untreated OBX mice in a passive avoidance test. We also investigated potential effects of SG-ME on several parameters: cell proliferation and cAMP response element-binding protein (CREB) phosphorylation in the hippocampal dentate gyrus by immunohistochemistry, brain-derived neurotrophic factor (BDNF) levels in the hippocampus by Western blotting, p-CREB levels in the hippocampus by MapAnalyzer, and long-term potentiation (LTP) by electrophysiology. On the 14th day after surgery OBX mice showed altered passive avoidance and decreases in both cell proliferation and long-term potentiation in the hippocampus, while these changes were reversed by SG-ME (20 μg/mouse) 24 h after the treatment. The improvement in memory deficits was prevented when SG-ME was co-administeredwith either zeta inhibitory peptide (PKC-ζ inhibitor), anti-BDNF antibody, ANA-12 (TrkB antagonist), U0126 (MEK inhibitor), H-89 (PKA inhibitor), LY294002 (PI3K inhibitor) or KN-93 (CaMKII inhibitor). We found that SG-ME enhanced brain-derived neurotrophic factor and p-CREB levels in the hippocampus while p-CREB was localized in neurons, but not in astrocytes nor microglial cells. These findings revealed the potential of SG-ME in improving memory impairments by enhancing cell proliferation and LTP via activation of the BDNF/CREB signaling pathway in neurons.

A Mechanistic Review on Medicinal Mushrooms-Derived Bioactive Compounds: Potential Mycotherapy Candidates for Alleviating Neurological Disorders

According to the World Health Organization, neurological and neurodegenerative diseases are highly debilitating and pose the greatest threats to public health. Diseases of the nervous system are caused by a particular pathological process that negatively affects the central and peripheral nervous systems. These diseases also lead to the loss of neuronal cell function, which causes alterations in the nervous system structure, resulting in the degeneration or death of nerve cells throughout the body. This causes problems with movement (ataxia) and mental dysfunction (dementia), both of which are commonly observed symptoms in Alzheimer's disease, Parkinson's disease, Huntington's disease, and multiple sclerosis. Medicinal mushrooms are higher fungi with nutraceutical properties and are low in calories and fat. They are also a rich source of nutrients and bioactive compounds such as carbohydrates, proteins, fibers, and vitamins that have been used in the treatment of many ailments. Medicinal mushrooms such as Pleurotus giganteus, Ganoderma lucidium, and Hericium erinaceus are commonly produced worldwide for use as health supplements and medicine. Medicinal mushrooms and their extracts have a large number of bioactive compounds, such as polysaccharide β-glucan, or polysaccharide-protein complexes, like lectins, lactones, terpenoids, alkaloids, antibiotics, and metal-chelating agents. This review will focus on the role of the medicinal properties of different medicinal mushrooms that contain bioactive compounds with a protective effect against neuronal dysfunction. This information will facilitate the development of drugs against neurodegenerative diseases.

Erinacine A and related cyathane diterpenoids: Molecular diversity and mechanisms underlying their neuroprotection and anticancer activities

The presence of a fused 5/6/7 tricyclic core characterizes the group of cyathane diterpene natural products, that include more than 170 compounds, isolated from fungi such as Cyathus africanus and Hericium erinaceus. These compounds have a common biosynthetic precursor (cyatha-3,12-diene) and can be produced bio- or hemi-synthetically, or via total syntheses. Cyathane diterpenes display a range of pharmacological properties, including anti-inflammatory (possibly through binding to the iNOS protein) and neuroprotective effects. Many cyathanes like cyahookerin C, cyathin Q and cyafranines B and G can stimulate neurite outgrowth in cells, whereas conversely a few molecules (such as scabronine M) inhibit NGF-stimulated neurite outgrowth. The main anticancer cyathanes are erinacine A and cyathins Q and R, with a capacity to trigger cancer cell death dependent on the production of reactive oxygen species (ROS). These compounds, active both in vitro and in vivo, activate different signaling pathways in tumor cells to induce apoptosis (and autophagy) and to upregulate the expression of several proteins implicated in the organization and functioning of the actin cytoskeleton. An analysis of the functional analogy between erinacine A and other natural products known to interfere with the actin network in a ROS-dependent manner (notably cucurbitacin B) further supports the idea that erinacine A functions as a perturbator of the cytoskeleton organization. Collectively, we provide an overview of the molecular diversity of cyathane diterpenes and the main mechanisms of action of the lead compounds, with the objective to encourage further research with these fungal products. The anticancer potential of erinacine A deserves further attention but it will be necessary to better characterize the implicated targets and signaling pathways.

Mechanisms underpinning AMP-activated protein kinase-related effects on behavior and hippocampal neurogenesis in an animal model of depression

Adenosine monophosphate-activated protein kinase (AMPK) is critical for whole-body energy metabolism regulation. Recent studies have suggested that physical exercise ameliorates depressive-like behaviors via AMPK activation; however, the underlying mechanism is unclear. Here, we examined the effects and underlying mechanisms of AMPK activation on depressive-like behavior in olfactory bulbectomized (OBX) mice. We treated OBX mice with the AMPK activator, 5-aminoimidazole-4-carboxamide-1-β-d-ribonucleotide (AICAR) on the 7th or 14th day after bilateral bulbectomy and evaluated depressive-like behavior using the tail-suspension test (TST) and forced swimming test (FST) on the 21st day. The expression of phosphorylated AMPK, protein kinase C ζ (PKCζ), nuclear factor-kappa B (NF-κB), brain-derived neurotrophic factor (BDNF), and cAMP response element-binding protein (CREB) in the hippocampus was assessed by western blotting. Hippocampal neurogenesis and localization of AMPK and phosphorylated NF-κB were examined by immunohistochemistry. Chronic AICAR treatment suppressed the prolonged immobility of OBX mice in the TST and FST, and increased the levels of phosphorylated AMPK, PKCζ, NF-κB, CREB, and BDNF. Hippocampal neurogenesis in OBX mice was promoted by chronic AICAR treatment. Co-administration of AICAR with the PKCζ inhibitor or the neurotrophic tyrosine kinase receptor type 2 (TrkB) antagonist, ANA-12, inhibited these effects. Phosphorylated AMPK was detected in mature and immature hippocampal neurons and microglia, while phosphorylated NF-κB was detected only in neurons in AICAR-treated OBX mice. These data indicate that AMPK activation produces anti-depressant effects, which are mediated by elevated hippocampal neurogenesis potentially via PKCζ/NF-κB/BDNF/TrkB/CREB signaling in neurons.

Sarcodonin G Derivatives Exhibit Distinctive Effects on Neurite Outgrowth by Modulating NGF Signaling in PC12 Cells

Sarcodonin G, one of the cyathane diterpenoids isolated from the mushroom Sarcodon scabrosus, possesses pronounced neurotrophic activity but ambiguous mechanical understanding. In this work, sarcodonin G was chosen as a lead compound to prepare a series of 19- O-benzoyl derivatives by semisynthesis and their neuritogenic activities were evaluated. 6 and 15 (10 μM) were investigated with opposite effects in PC12 cells. 6 exhibited a superior activity to sarcodonin G by promoting NGF-induced neurite outgrowth, while 15 showed an inhibitory effect. Supportingly, 6 and 15 (20 μM) significantly induced and suppressed neurite extension in primary cultured rat cortical neurons, respectively. In mechanism, the two derivatives were revealed to influence NGF-induced neurite outgrowth in PC12 cells through the regulation of PKC-dependent and -independent ERK/CREB signaling as well as the upstream TrkA receptor phosphorylation. Furthermore, a possible pattern of interaction among NGF, 6/15 and TrkA was presented using molecular simulations. It revealed that 6/15 may contribute to the stabilization of the NGF-TrkAd5 complex by establishing several hydrophobic and hydrogen-bond interactions with NGF and TrkA, respectively. Taken together, 6 and 15 modulate PKC-dependent and -independent ERK/CREB signaling pathways possibly by influencing the binding affinity of NGF to the receptor TrkA, and finally regulate neurite outgrowth in PC12 cells.

[A new strategy for preventive and functional therapeutic methods for dementia--approach using natural products]

Alzheimer's disease (AD) has become a serious social problem in Japan. However, effective preventive and fundamental therapeutic methods for AD have not yet been developed. Using a new strategy in the course of our survey of numerous natural resouces having neurotrophic activity, we isolated a variety of active constituents and proved their pharmacological properties. As a result, we successfully found nobiletin, a compound with anti-dementia activity that comes from citrus peels. Also, we have demonstrated that nobiletin ameliorates cognitive impairment in several dementia model animals such as chronically amyloid β(Aβ) infused rats, amyloid precursor protein transgenic (APPTg) mice, olfactory-bulbectomized (OBX) mice, N-methyl-D-aspartate (NMDA) receptor antagonist (MK-801)-treated mice, senescence-accelated mice and bilaterial common carotid arteries occlusion mice. In a APPTg mouse of AD, nobiletin greatly improved memory impairment, and this was accompanied by a marked decrease in Aβ deposition. Also, in OBX mice memory impairment was markedly recoverd by nobiletin, accompanied by improvement of a decrease indensity of cholinergic neurons. Interestingly, nobiletin improves age-related congnitive impairment and decreased hyperphosphorylation of tau as well as oxidative stress in senescence-accelerated mice. In cultured cells, nobiletin reversed the Aβ-induced inhibition of glutamate-induced increases in cAMP response element binding protein (CREB) phosphorylation and modulated gen expression of thioredoxin-interacting protein and NMDA resceptor subunits. These results suggest that nobiletin prevents memory impairment and exhibits a protecting action against neurodgeneration in AD model animals. Nobiletin and citrus peels thus have potential as functional foods for prevention of dementia.

Morphological Evaluation of Nonlabeled Cells to Detect Stimulation of Nerve Growth Factor Expression by Lyconadin B

The success of drug development is greatly influenced by the efficiency of drug screening methods. Recently, phenotype-based screens have raised expectations, based on their proven record of identifying first-in-class drugs at a higher rate. Although fluorescence images are the data most commonly used in phenotype-based cell-based assays, nonstained cellular images have the potential to provide new descriptive information about cellular responses. In this study, we applied morphology-based evaluation of nonlabeled microscopic images to a phenotype-based assay. As a study case, we attempted to increase the efficiency of a cell-based assay for chemical compounds that induce production of nerve growth factor (NGF), using lyconadin B as a model compound. Because the total synthesis of lyconadin B was accomplished very recently, there is no well-established cell-based assay scheme for further drug screening. The conventional cell-based assay for evaluating NGF induction requires two types of cells and a total of 5 days of cell culture. The complexity and length of this assay increase both the risk of screening errors and the cost of screening. Our findings show that analysis of cellular morphology enables evaluation of NGF induction by lyconadin B within only 9 h.

Therapeutic potential of culinary-medicinal mushrooms for the management of neurodegenerative diseases: diversity, metabolite, and mechanism

Mushrooms have long been used not only as food but also for the treatment of various ailments. Although at its infancy, accumulated evidence suggested that culinary-medicinal mushrooms may play an important role in the prevention of many age-associated neurological dysfunctions, including Alzheimer's and Parkinson's diseases. Therefore, efforts have been devoted to a search for more mushroom species that may improve memory and cognition functions. Such mushrooms include Hericium erinaceus, Ganoderma lucidum, Sarcodon spp., Antrodia camphorata, Pleurotus giganteus, Lignosus rhinocerotis, Grifola frondosa, and many more. Here, we review over 20 different brain-improving culinary-medicinal mushrooms and at least 80 different bioactive secondary metabolites isolated from them. The mushrooms (either extracts from basidiocarps/mycelia or isolated compounds) reduced beta amyloid-induced neurotoxicity and had anti-acetylcholinesterase, neurite outgrowth stimulation, nerve growth factor (NGF) synthesis, neuroprotective, antioxidant, and anti-(neuro)inflammatory effects. The in vitro and in vivo studies on the molecular mechanisms responsible for the bioactive effects of mushrooms are also discussed. Mushrooms can be considered as useful therapeutic agents in the management and/or treatment of neurodegeneration diseases. However, this review focuses on in vitro evidence and clinical trials with humans are needed.

Recent applications of intramolecular Diels–Alder reaction in total synthesis of natural products

Diels–Alder (D–A) reaction is undoubtedly the most powerful [4 + 2] cycloaddition reaction in organic synthesis.

Neurotrophic natural products: chemistry and biology

Neurodegenerative diseases and spinal cord injury affect approximately 50 million people worldwide, bringing the total healthcare cost to over 600 billion dollars per year. Nervous system growth factors, that is, neurotrophins, are a potential solution to these disorders, since they could promote nerve regeneration. An average of 500 publications per year attests to the significance of neurotrophins in biomedical sciences and underlines their potential for therapeutic applications. Nonetheless, the poor pharmacokinetic profile of neurotrophins severely restricts their clinical use. On the other hand, small molecules that modulate neurotrophic activity offer a promising therapeutic approach against neurological disorders. Nature has provided an impressive array of natural products that have potent neurotrophic activities. This Review highlights the current synthetic strategies toward these compounds and summarizes their ability to induce neuronal growth and rehabilitation. It is anticipated that neurotrophic natural products could be used not only as starting points in drug design but also as tools to study the next frontier in biomedical sciences: the brain activity map project.

Total syntheses of cyanthiwigins B, F, and G

A concise and versatile approach toward the preparation of the cyanthiwigin family of cyathane natural products is described. By leveraging a unique double asymmetric catalytic alkylation procedure it is possible to quickly establish two of the most critical stereocenters of the cyanthiwigin framework with high levels of selectivity and expediency. The synthetic route additionally employs both a tandem ring-closing cross-metathesis reaction, and an aldehyde-olefin radical cyclization process, in order to rapidly arrive at the tricyclic cyathane core of the cyanthiwigin molecules. From this unifying intermediate, the preparations of cyanthiwigins B, F, and G are attained swiftly and without the need for protecting groups.

Bacteria-induced static batch fungal fermentation of the diterpenoid cyathin A(3), a small-molecule inducer of nerve growth factor

Cyathin A(3), produced by the fungus Cyathus helenae, is a member of the cyathane family of diterpene natural products. While many of the cyathanes display antibacterial/antimicrobial activity or have cytotoxic activity against human cancer cell lines, their most exciting therapeutic potential is derived from their ability to induce nerve growth factor (NGF) release from glial cells, making the cyathanes attractive lead molecules for the development of neuroprotective therapeutics to prevent/treat Alzheimer's disease. To investigate if cyathin A(3) has NGF-inducing activity, we set out to obtain it using published C. helenae bench-scale fungal fermentations. However, to overcome nonproducing fermentations, we developed an alternative, bacteria-induced static batch fermentation approach to the production of cyathin A(3), as described in this report. HPLC, UV absorption spectra, and mass spectrometry identify cyathin A(3) in fungal fermentations induced by the timely addition of Escherichia coli K12 or Bacillus megabacterium. Pre-filtration of the bacterial culture abolishes cyathin A(3) induction, suggesting that bacteria-associated media changes or physical interaction between the fungus and bacteria underlie the induction mechanism. Through alteration of incubation conditions, including agitation, the timing of induction, and media composition, we optimized the fermentation to yield nearly 1 mg cyathin A(3)/ml media, a sixfold increase over previously described yields. Additionally, by comparison of fermentation profiles, we reveal that cyathin A(3) biosynthesis is regulated by carbon catabolite repression. We have used an enzyme-linked immunosorbent assay to illustrate that cyathin A(3) induces NGF release from cultured glial cells, and therefore cyathin A(3) warrants further examination in the development of neuroprotective therapeutics.

Parallel kinetic resolution approach to the cyathane and cyanthiwigin diterpenes using a cyclopropanation/Cope rearrangement

Parallel effort: Stereodivergent parallel kinetic resolution of a racemic mixture of dienes using Davies' [Rh(2){(S)-dosp}(4)] or [Rh(2){(R)-dosp}(4)] catalysts promotes a tandem vinyl diazoacetate cyclopropanation/Cope rearrangement sequence to afford two diastereomeric, enantioenriched cycloheptadienes, which correspond to the natural antipodes of the title diterpenoids (see scheme).

Strategic use of nickel(0)-catalyzed enyne-epoxide reductive coupling towards the synthesis of (-)-cyatha-3,12-diene

Various situations are explored in which the nickel(0)-catalyzed enyne-epoxide reductive coupling was utilized to access key intermediates towards the total synthesis of (-)-cyatha-3,12-diene (1). Enantioenriched 3,5-dien-1-ols with a variety of functionality were obtained in a straightforward manner from easily accessible 1,3-enynes and terminal epoxides.

Total synthesis of cyathin A(3) and cyathin B(2)

A stereoselective synthesis of cyathin A(3) and cyathin B(2) has been achieved by a Prins-type reaction of a cycloalkenyl cyclopropanol. Particularly noteworthy is the use of a spirocyclobutanone moiety as a convenient scaffold for an efficient ring-closing metathesis to stereoselectively construct a suitably functionalized seven-membered ring (see scheme).

Imaging induction of cytoprotective enzymes in intact human cells: coumberone, a metabolic reporter for human AKR1C enzymes reveals activation by panaxytriol, an active component of red ginseng

We here present an optical method for monitoring the activity of the inducible aldo-keto reductases AKR1C2 and AKR1C3 in living human cells. The induction of these enzymes is regulated by the antioxidant response element (ARE), as demonstrated in recent literature, which in turn is dependent on the transcription factor Nrf2. The activation of ARE leads to the transcription of a coalition of cytoprotective enzymes and thus represents an important target for the development of new therapies in the area of neurodegenerative diseases and cancer. Through the use of Coumberone, a metabolic fluorogenic probe, and isoform-selective inhibitors, the upregulation of cellular stress markers AKR1C2 and AKR1C3 can be quantitatively measured in the presence of ARE activator compounds, via either a fluorimetric assay or fluorescence microscopy imaging of intact cells. The method has both high sensitivity and broad dynamic range, as demonstrated by induction studies in three cell lines with dramatically different metabolic capabilities (transfected monkey kidney COS-1 cells, human neuroblastoma IMR-32 cells, and human liver HepG2 cells). We applied the new method to examine a number of neurotrophic natural products (spirotenuipesine A, spirotenuipesine B, scabronine G-methylester, and panaxytriol), and discovered that panaxytriol, an active component of red ginseng extracts, is a potent ARE inducer. The upregulation of AKR1C enzymes, induced by chemically homogeneous panaxytriol, was partially dependent on PKC and PI3K kinases as demonstrated by the application of selective inhibitors. This cellular mechanism may account for panaxytriol's neurotrophic, neuroprotective, and anticancer properties. The protective effects of ARE inducers against tumorgenesis and neurodegeneration fuel the growing interest in this area of research and the method described here will greatly enable these endeavors.

5,19-cyclo-9beta,10xi-androstane-3,17-dione promotes neurotrophic factor biosynthesis in 1321N1 human astrocytoma cells and improves passive avoidance learning impairment

Since neurotrophic factors are essential for neurons to form neuronal networks and maintain neuronal functions, neurotrophic factor-like substances or inducers of neurotrophic factors can be useful for the treatment of serious neuronal diseases such as Alzheimer's and Parkinson's diseases. In the present study, we examined an effect of 5,19-cyclo-9beta,10xi-androstane-3,17-dione (CAD) on neurotrophic factor synthesis in glial cells and scopolamine-induced impairment of learning in mice. 1321N1 human astrocytoma cells promoted secretion of certain neurotrophic factors in response to CAD with no cytotoxicity, which caused dramatic neurite outgrowth in rat pheochromocytoma (PC12) cells. In fact, CAD significantly enhanced nerve growth factor (NGF) secretion and its gene expression in 1321N1 cells, in a time and concentration-dependent manner. Because second messengers such as cAMP, inositol 1,4,5-trisphosphates and Ca(2+) induce NGF gene expression, we measured activities of adenylyl cyclase and phospholipase C and intracellular Ca(2+) concentration in 1321N1 cells. However, CAD changed neither second messenger levels. CAD enhanced the gene expression of proto-oncogene, c-fos that is one of the components of transcription factor (AP-1). In addition to those above, the in vivo effects of CAD were also examined. Although injection of muscarinic receptor antagonist scopolamine impaired passive avoidance learning in mice, pretreatment with CAD significantly reversed the adverse effect in a dose-dependent manner. Taking these results together, CAD has enormous therapeutic potential for serious neuronal diseases.

Enantioselective total synthesis of cyathin A3

The total synthesis of (-)-cyathin A3 is described. The key step involves an unusual enantioselective Diels-Alder reaction of 2,5-dimethyl-1,4-benzoquinone with 2,4-bis(trimethylsilyloxy)-1,3-pentadiene, using Mikami's catalyst [(R)-BINOL + Cl2Ti(OiPr)2 + 4 A mol sieves] modified by addition of Mg and SiO2. Because cyathin A3 is easily transformed into allocyathin B3, cyathin B3, cyathin C3, and neoallocyathin A4, this route also constitutes formal syntheses of these natural products.

Pattern Recognition in Retrosynthetic Analysis: Snapshots in Total Synthesis

In this Perspective, the value of small molecule natural products (SMNPs) in the discovery of active biological agents is discussed. The usefulness of the natural products-based method of potential pharma discovery is much augmented by the capacities of chemical synthesis. The great advances in synthetic methodology allow for major editing of the natural product in the hopes of optimizing potency and therapeutic index. As a consequence of the enormous increase in the power of multistep chemical synthesis, one can now approach structures of previously impractical complexity. In constructing a plan for a multistep synthesis, two complementary thought styles are often encountered. One is the traditional and extremely powerful concept of prioritized strategic bond disconnections. The other, which we term "pattern recognition," involves the identification of moieties within the target, which are associated with reliable chemistry, and can serve to facilitate progress to the target. Recognition of such targets may require substantial recasting of the target structure to connect it to well-established types of transformations. Some of our older ventures, where ideas about pattern recognition were first being fashioned and used productively, are revisited. In addition, we provide snapshots of recently achieved total syntheses of SMNPs of novel biological potential. These vignettes serve to harmonize insights occasioned by pattern recognition, in concert with transformations enabled by the enormous growth in the power of synthesis.

A novel cyathane diterpene, cyrneine A, induces neurite outgrowth in a Rac1-dependent mechanism in PC12 cells

We examined the effects of cyrneine A, a novel diterpene isolated from the mushroom Sarcodon cyrneus, on morphology of rat pheochromocytoma cells (PC12). In response to cyrneine A, PC12 cells extended their neurites, an effect partially blocked by the extracellular signal-regulated kinase (ERK) kinase inhibitor PD98059, but not by the protein kinase C inhibitor GF109203X, nor the phosphatidylinositol-3-kinase inhibitor wortmannin. Cyrneine A did not activate ERK at any of the time points tested (5-120 min), indicating that only the basal activity of ERK is required for cyrneine A-induced neurite outgrowth. As transcriptional regulation is required for neurite extension, the activity of three major transcription factors was determined. Cyrneine A enhanced activation of the transcription factors activator protein-1 (AP-1) and nuclear factor-kappaB, but not CREB, and this was accompanied by enhanced c-fos expression. Moreover, we determined the role of Rac1, a small GTPase protein of the Rho family that regulates actin dynamics, in cyrneine A-induced neurite outgrowth. Treatment with cyrneine A led to actin translocation and subsequently, to accumulation of F-actin at the tip of neurites. Rac1 activity was increased by cyrneine A and expression of a dominant-negative Rac1 mutant significantly inhibited the cyrneine A-induced extension of neurites. These results suggest that cyrneine A induces neurite outgrowth in a Rac1-dependent mechanism.

Cyathane diterpenes from Sarcodon cyrneus and evaluation of their activities of neuritegenesis and nerve growth factor production

Two new cyathane diterpenes, cyrneine C (4) and D (5), were isolated from the mushroom Sarcodon cyrneus, along with previously isolated cyrneine A, B and glaucopine C. The structures of the novel diterpenoids were determined by the analysis of spectroscopic data. Effects of the cyrneines and glaucopine C on the NGF gene expression in 1321N1 cells and on neurite outgrowth on PC12 cells were evaluated.

Complanadines C and D, new dimeric alkaloids from Lycopodium complanatum

Two new dimeric Lycopodium alkaloids, complanadines C (1) and D (2), have been isolated from the club moss Lycopodium complanatum, and the structures and relative stereochemistry of 1 and 2 were elucidated on the basis of the spectral data. Complanadine D (2) enhanced mRNA expression for NGF.

[Development of anti-dementia drugs related to neurotrophic factors]

Neurotrophic factor-like substances and inducers of neurotrophic factor biosynthesis have enormous therapeutic potential for serious neuronal diseases such as Alzheimer's disease. Here, we discuss about the pharmacological effects of scabronines and beta-eudesmol as promising candidates of leading compounds against the dementia. In addition, we discuss about the signaling pathway of nerve growth factor and cyclic AMP in order to seek the signaling molecules as targets of drug development.

Lycopladines B–D and lyconadin B, new alkaloids from Lycopodium complanatum

Four new alkaloids, lycopladines B-D (1-3) and lyconadin B (4), have been isolated from the club moss Lycopodium complanatum and the structures including the stereochemistry were elucidated on the basis of spectral data and modified Mosher's method. Lyconadin B (4) elevated NGF mRNA expression in 1321N1 human astrocytoma cells.

Applications of total synthesis to problems in neurodegeneration: Fascinating chemistry along the way

The possibility for the application of organic synthesis to the discovery of new agents in combating neurodegenerative disorders is described. Our focus has been on agents derived from natural-product leads and natural products themselves prepared through total synthesis. Herein, we describe some of the chemistry as well as interesting observations made along the way.

Multiple role of histamine H1-receptor-PKC-MAPK signalling pathway in histamine-stimulated nerve growth factor synthesis and secretion

Histamine is a potent stimulator of nerve growth factor (NGF) production in the central nerve system and in the periphery as well. In this review, the biochemical mechanisms of histamine-stimulated NGF synthesis and secretion, and interactions between histamine, interleukin-1beta, and interleukin-6 are discussed. The main signalling pathway, involved in the stimulation of NGF production by histamine, includes activation of histamine H(1)-receptor, stimulation of Ca(2+)-dependent protein kinase C and mitogen-activated protein kinase. The same signalling pathway is involved in the interactions between histamine, interleukin-1beta, and interleukin-6, where NGF secretion is amplified. Whereas histamine and interleukin-1beta cause additive stimulatory effect on NGF secretion, interaction between histamine and interleukin-6 causes a long-term synergism. Thus, activation of histamine H(1)-receptor-protein kinase C-mitogen-activated protein kinase signalling pathway plays a crucial role not only in the direct stimulation of NGF secretion by histamine, but also in the indirect stimulation via different types of interactions between histamine, interleukin-1beta, and interleukin-6, which may have important therapeutic implications in modulation of NGF production.

Neurotrophic factor production in human astrocytoma cells by 2,5,6-tribromogramine via activation of epsilon isoform of protein kinase C

It is known that astrocytes secrete several neurotrophic factors to promote the survival of neurons. For the treatment of neuronal disorders, low molecular weight compounds inducing neurotrophic factor synthesis are useful, because neurotrophic factors are polypeptides which cannot cross the blood brain barrier. When rat pheochromocytoma (PC-12) cells were cultivated in the medium of human astrocytoma cells (1321N1) treated with 2,5,6-tribromogramine, they differentiated to neuron-like cells possessing neurites, indicating that 2,5,6-tribromogramine released neurotrophic factors from 1321N1 cells. In fact, 2,5,6-tribromogramine increased nerve growth factor (NGF) protein synthesis and secretion through mRNA expression. 2,5,6-Tribromogramine inhibited carbachol-induced phosphoinositide hydrolysis as well as phorbol 12,13-myristate acetate did. The inhibition was recovered by bisindolylmaleimide I (GF109203X), a specific protein kinase C (PKC) inhibitor, indicating that 2,5,6-tribromogramine may activate PKC. The morphological differentiation of PC-12 cells by the medium treated with 2,5,6-tribromogramine was also reduced by GF109203X. 2,5,6-Tribromogramine translocated PKC-epsilon but not PKC-alpha or PKC-zeta, to membrane fraction from cytosol fraction. These results indicate that 2,5,6-tribromogramine promotes the synthesis and secretion of neurotrophic factors including NGF in 1321N1 cells via an activation of PKC-epsilon.