Inhibition of miR-96-5p in the mouse brain increases glutathione levels by altering NOVA1 expression

Glutathione (GSH) is an important antioxidant that plays a critical role in neuroprotection. GSH depletion in neurons induces oxidative stress and thereby promotes neuronal damage, which in turn is regarded as a hallmark of the early stage of neurodegenerative diseases. The neuronal GSH level is mainly regulated by cysteine transporter EAAC1 and its inhibitor, GTRAP3-18. In this study, we found that the GTRAP3-18 level was increased by up-regulation of the microRNA miR-96-5p, which was found to decrease EAAC1 levels in our previous study. Since the 3'-UTR region of GTRAP3-18 lacks the consensus sequence for miR-96-5p, an unidentified protein should be responsible for the intermediate regulation of GTRAP3-18 expression by miR-96-5p. Here, we discovered that RNA-binding protein NOVA1 functions as an intermediate protein for GTRAP3-18 expression via miR-96-5p. Moreover, we show that intra-arterial injection of a miR-96-5p-inhibiting nucleic acid to living mice by a drug delivery system using microbubbles and ultrasound decreased the level of GTRAP3-18 via NOVA1 and increased the levels of EAAC1 and GSH in the dentate gyrus of the hippocampus. These findings suggest that the delivery of a miR-96-5p inhibitor to the brain would efficiently increase the neuroprotective activity by increasing GSH levels via EAAC1, GTRAP3-18 and NOVA1.

MicroRNA: A Key Player for the Interplay of Circadian Rhythm Abnormalities, Sleep Disorders and Neurodegenerative Diseases

Circadian rhythms are endogenous 24-h oscillators that regulate the sleep/wake cycles and the timing of biological systems to optimize physiology and behavior for the environmental day/night cycles. The systems are basically generated by transcription-translation feedback loops combined with post-transcriptional and post-translational modification. Recently, evidence is emerging that additional non-coding RNA-based mechanisms are also required to maintain proper clock function. MicroRNA is an especially important factor that plays critical roles in regulating circadian rhythm as well as many other physiological functions. Circadian misalignment not only disturbs the sleep/wake cycle and rhythmic physiological activity but also contributes to the development of various diseases, such as sleep disorders and neurodegenerative diseases. The patient with neurodegenerative diseases often experiences profound disruptions in their circadian rhythms and/or sleep/wake cycles. In addition, a growing body of recent evidence implicates sleep disorders as an early symptom of neurodegenerative diseases, and also suggests that abnormalities in the circadian system lead to the onset and expression of neurodegenerative diseases. The genetic mutations which cause the pathogenesis of familial neurodegenerative diseases have been well studied; however, with the exception of Huntington's disease, the majority of neurodegenerative diseases are sporadic. Interestingly, the dysfunction of microRNA is increasingly recognized as a cause of sporadic neurodegenerative diseases through the deregulated genes related to the pathogenesis of neurodegenerative disease, some of which are the causative genes of familial neurodegenerative diseases. Here we review the interplay of circadian rhythm disruption, sleep disorders and neurodegenerative disease, and its relation to microRNA, a key regulator of cellular processes.

Rab1a rescues the toxicity of PRAF3

The PRA1-superfamily member PRAF3 plays pivotal roles in membrane traffic as a GDI displacement factor via physical interaction with a variety of Rab proteins, as well as in the modulation of antioxidant glutathione through its interaction with EAAC1 (SLC1A1). Overproduction of PRAF3 is known to be toxic to the host cells, although the factors capable of cancelling the toxicity remained unknown. We here show that Rab1a can rescue the cytotoxicity caused by PRAF3 possibly by “positively” regulating ER-Golgi trafficking, cancelling the “negative” modulation by PRAF3. Our results illuminate the close physiological relationship between PRAF3 and Rab proteins.

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PRAF3 exhibits cytotoxicity both in yeast and human cells.

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Among Rabs, only Rab1a can rescue the toxicity of PRAF3.

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PRAF3 expression may be strictly regulated in accordance with Rab1a expression.

Neuroprotection afforded by circadian regulation of intracellular glutathione levels: A key role for miRNAs

Circadian rhythms are approximately 24-h oscillations of physiological and behavioral processes that allow us to adapt to daily environmental cycles. Like many other biological functions, cellular redox status and antioxidative defense systems display circadian rhythmicity. In the central nervous system (CNS), glutathione (GSH) is a critical antioxidant because the CNS is extremely vulnerable to oxidative stress; oxidative stress, in turn, causes several fatal diseases, including neurodegenerative diseases. It has long been known that GSH level shows circadian rhythm, although the mechanism underlying GSH rhythm production has not been well-studied. Several lines of recent evidence indicate that the expression of antioxidant genes involved in GSH homeostasis as well as circadian clock genes are regulated by post-transcriptional regulator microRNA (miRNA), indicating that miRNA plays a key role in generating GSH rhythm. Interestingly, several reports have shown that alterations of miRNA expression as well as circadian rhythm have been known to link with various diseases related to oxidative stress. A growing body of evidence implicates a strong correlation between antioxidative defense, circadian rhythm and miRNA function, therefore, their dysfunctions could cause numerous diseases. It is hoped that continued elucidation of the antioxidative defense systems controlled by novel miRNA regulation under circadian control will advance the development of therapeutics for the diseases caused by oxidative stress.

GTRAP3-18 regulates food intake and body weight by interacting with pro-opiomelanocortin

Pro-opiomelanocortin (POMC)-expressing neurons provide α-melanocyte-stimulating hormone (α-MSH), which stimulates melanocortin 4 receptor to induce hypophagia by AMPK inhibition in the hypothalamus. α-MSH is produced by POMC cleavage in secretory granules and released. However, it is not known yet whether any posttranscriptional regulatory mechanism of POMC signaling exists upstream of the secretory granules in neurons. Here we show that glutamate transporter-associated protein 3-18 (GTRAP3-18), an anchor protein that retains interacting proteins in the endoplasmic reticulum, is a critical regulator of food intake and body weight by interacting with POMC. GTRAP3-18-deficient mice showed hypophagia, lean bodies, and lower blood glucose, insulin, and leptin levels with increased serum and brain α-MSH levels, leading to AMPK inhibition. Intraperitoneal glucose tolerance tests revealed significantly decreased blood glucose levels and areas under the curve in GTRAP3-18-deficient mice compared to wild-type mice. An intracerebroventricular infusion of a selective melanocortin 4 receptor antagonist to GTRAP3-18-deficient mice significantly increased their food intake and body weight. A fluorescence resonance energy transfer study showed an interaction between GTRAP3-18 and POMC in vitro These findings suggest that activation of the melanocortin pathway by modulating GTRAP3-18/POMC interaction could be an alternative strategy for obesity and/or type 2 diabetes.-Aoyama, K., Bhadhprasit, W., Watabe, M., Wang, F., Matsumura, N., Nakaki, T. GTRAP3-18 regulates food intake and body weight by interacting with pro-opiomelanocortin.

Glutathione in Cellular Redox Homeostasis: Association with the Excitatory Amino Acid Carrier 1 (EAAC1)

Reactive oxygen species (ROS) are by-products of the cellular metabolism of oxygen consumption, produced mainly in the mitochondria. ROS are known to be highly reactive ions or free radicals containing oxygen that impair redox homeostasis and cellular functions, leading to cell death. Under physiological conditions, a variety of antioxidant systems scavenge ROS to maintain the intracellular redox homeostasis and normal cellular functions. This review focuses on the antioxidant system’s roles in maintaining redox homeostasis. Especially, glutathione (GSH) is the most important thiol-containing molecule, as it functions as a redox buffer, antioxidant, and enzyme cofactor against oxidative stress. In the brain, dysfunction of GSH synthesis leading to GSH depletion exacerbates oxidative stress, which is linked to a pathogenesis of aging-related neurodegenerative diseases. Excitatory amino acid carrier 1 (EAAC1) plays a pivotal role in neuronal GSH synthesis. The regulatory mechanism of EAAC1 is also discussed.

Contribution of Donor and Host Mesenchyme to the Transplanted Tooth Germs

Autologous tooth germ transplantation of immature teeth is an alternative method of tooth replacement that could be used instead of dental implants in younger patients. However, it is paramount that the dental pulp remain vital and that root formation continue in the transplanted location. The goal of this study is to characterize the healing of allogenic tooth grafts in an animal model using GFP-labeled donor or host postnatal mice. In addition, the putative stem cells were labeled before transplantation with a pulse-chase paradigm. Transplanted molars formed cusps and roots and erupted into occlusion by 2 wk postoperatively. Host label-retaining cells (LRCs) were maintained in the center of pulp tissue associating with blood vessels. Dual labeling showed that a proportion of LRCs were incorporated into the odontoblast layer. Host cells, including putative dendritic cells and the endothelium, also immigrated into the pulp tissue but did not contribute to the odontoblast layer. Therefore, LRCs or putative mesenchymal stem cells are retained in the transplanted pulps. Hertwig’s epithelial root sheath remains vital, and epithelial LRCs are present in the donor cervical loops. Thus, the dynamic donor-host interaction occurred in the developing transplant, suggesting that these changes affect the characteristics of the dental pulp.

Isobolographic analysis of the mechanisms of action of anticonvulsants from a combination effect

The nature of the pharmacodynamic interactions of drugs is influenced by the drugs׳ mechanisms of action. It has been hypothesized that drugs with different mechanisms are likely to interact synergistically, whereas those with similar mechanisms seem to produce additive interactions. In this review, we describe an extensive investigation of the published literature on drug combinations of anticonvulsants, the nature of the interaction of which has been evaluated by type I and II isobolographic analyses and the subthreshold method. The molecular targets of antiepileptic drugs (AEDs) include Na(+) and Ca(2+) channels, GABA type-A receptor, and glutamate receptors such as NMDA and AMPA/kainate receptors. The results of this review indicate that the nature of interactions evaluated by type I isobolographic analyses but not by the two other methods seems to be consistent with the above hypothesis. Type I isobolographic analyses may be used not only for evaluating drug combinations but also for predicting the targets of new drugs.

Rhythmic oscillations of the microRNA miR-96-5p play a neuroprotective role by indirectly regulating glutathione levels

Glutathione (GSH) is a key antioxidant that plays an important neuroprotective role in the brain. Decreased GSH levels are associated with neurodegenerative diseases such as Parkinson’s disease and Alzheimer’s disease. Here we show that a diurnal fluctuation of GSH levels is correlated with neuroprotective activity against oxidative stress in dopaminergic cells. In addition, we found that the cysteine transporter excitatory amino acid carrier 1 (EAAC1), which is involved in neuronal GSH synthesis, is negatively regulated by the microRNA miR-96-5p, which exhibits a diurnal rhythm. Blocking miR-96-5p by intracerebroventricular administration of an inhibitor increased the level of EAAC1 as well as that of GSH and had a neuroprotective effect against oxidative stress in the mouse substantia nigra. Our results suggest that the diurnal rhythm of miR-96-5p may play a role in neuroprotection by regulating neuronal GSH levels via EAAC1.

Glutathione is a key antioxidant that plays an important neuroprotective role in the brain. Here, Kinoshita et al. show that levels of glutathione exhibit diurnal fluctuations that are indirectly regulated by the microRNA miR-96-5p, and that this microRNA plays a neuroprotective role against oxidative stress.

Impaired glutathione synthesis in neurodegeneration

Glutathione (GSH) was discovered in yeast cells in 1888. Studies of GSH in mammalian cells before the 1980s focused exclusively on its function for the detoxication of xenobiotics or for drug metabolism in the liver, in which GSH is present at its highest concentration in the body. Increasing evidence has demonstrated other important roles of GSH in the brain, not only for the detoxication of xenobiotics but also for antioxidant defense and the regulation of intracellular redox homeostasis. GSH also regulates cell signaling, protein function, gene expression, and cell differentiation/proliferation in the brain. Clinically, inborn errors in GSH-related enzymes are very rare, but disorders of GSH metabolism are common in major neurodegenerative diseases showing GSH depletion and increased levels of oxidative stress in the brain. GSH depletion would precipitate oxidative damage in the brain, leading to neurodegenerative diseases. This review focuses on the significance of GSH function, the synthesis of GSH and its metabolism, and clinical disorders of GSH metabolism. A potential approach to increase brain GSH levels against neurodegeneration is also discussed.

Alpha(1A)-adrenergic control of piloerection and palpebral fissure width in rats

We determined the receptor subtypes of α1-adrenoceptor, which is involved in autonomic functions induced by methamphetamine (METH) in rats. An intraperitoneal injection of METH provoked the autonomic responses piloerection, eyelid retraction, and ejaculation. Pretreatment with prazosin, a nonselective α1-adrenoceptor antagonist, completely abolished the above METH-induced responses. Prazosin also provoked eyelid ptosis in saline controls. The effects of prazosin were mimicked only by a selective α1A-adrenoceptor antagonist, silodosin, not by selective α1B or α1D antagonists. These results suggest that α1A-adrenoceptor participates in the regulation of piloerection, palpebral fissure width, and ejaculation in rats.

Anticonvulsant action of indazole

Here we report that indazole is characterized as a potential anticonvulsant, inhibiting pentylenetetrazole-, electroshock- and strychnine-induced convulsions in mice (ED50's: 39.9, 43.2 and 82.4 mg/kg, respectively) but not bicuculline- and picrotoxin-induced convulsions. The median toxic dose (TD(50)) of indazole was 52.3 mg/kg by the minimal motor impairment test. Therefore, nontoxic doses produced anticonvulsant activity against pentylenetetrazole- and electroshock-induced seizures. Indazole (50 mg/kg) had no effect on spontaneous activity but induced hypothermia. It also inhibited the metabolism of dopamine and 5-hydroxytryptamine in the brain in vivo and the activities of monoamine oxidase A and B in vitro, with IC(50) values of 20.6 μM and 16.3 μM, respectively. However, these inhibitory effects do not account for the anticonvulsant activity because treatment with typical monoamine oxidase inhibitors such as pargyline or tranylcypromine did not completely reproduce the anticonvulsant activity of indazole. In the animal seizure models tested, the anticonvulsant profile of indazole most resembled that of gabapentin and somewhat resembled those of the AMPA/kainate antagonist NBQX and the sodium channel inhibitor phenytoin, but differed from that of benzodiazepine. The isobolographic analyses showed that the interactive mode of indazole with gabapentin, NBQX or phenytoin is additive. These results suggest that indazole has anticonvulsant activity and multiple mechanisms.

CK2 as anti-stress factor

Misfolded proteins are prone to form aggregates, which interfere with normal cellular functions. In general, the ubiquitin-proteasome system degrades such misfolded proteins to avoid aggregation. If this system becomes impaired or overloaded, an inclusion-body-like organelle, aggresome will operate. Misfolded protein aggregates are transported to aggresome with a deacetylase HDAC6 and dynein motors along the microtubule network, and are then removed by autophagic degradation. Although it is well known that the aggresome has evolved to cope with an excess of protein aggregates, the mechanisms underlying its formation remain unclear. It is now established that the protein kinase CK2 is a crucial factor in aggresome assembly and clearance. In particular, this kinase phosphorylates HDAC6 on serine 458 in response to cellular stress which is caused by misfolded proteins. The resultant increase in HDAC6 deacetylase activity is crucial for both the recruitment of misfolded proteins to the aggresome and its clearance. Interestingly, serine 458 is conserved only in higher primates such as the humans and chimpanzee, but not in the mouse, rat, dog, bovine or rhesus macaque. This regulatory mechanism by phosphorylation of the serine residue may have evolutional significance.

Inhibition of GTRAP3-18 may increase neuroprotective glutathione (GSH) synthesis

Glutathione (GSH) is a tripeptide consisting of glutamate, cysteine, and glycine; it has a variety of functions in the central nervous system. Brain GSH depletion is considered a preclinical sign in age-related neurodegenerative diseases, and it promotes the subsequent processes toward neurotoxicity. A neuroprotective mechanism accomplished by increasing GSH synthesis could be a promising approach in the treatment of neurodegenerative diseases. In neurons, cysteine is the rate-limiting substrate for GSH synthesis. Excitatory amino acid carrier 1 (EAAC1) is a neuronal cysteine/glutamate transporter in the brain. EAAC1 translocation to the plasma membrane promotes cysteine uptake, leading to GSH synthesis, while being negatively regulated by glutamate transport associated protein 3-18 (GTRAP3-18). Our recent studies have suggested GTRAP3-18 as an inhibitory factor for neuronal GSH synthesis. Inhibiting GTRAP3-18 function is an endogenous mechanism to increase neuron-specific GSH synthesis in the brain. This review gives an overview of EAAC1-mediated GSH synthesis, and its regulatory mechanisms by GTRAP3-18 in the brain, and a potential approach against neurodegeneration.

Protein kinase CK2 regulates the formation and clearance of aggresomes in response to stress

Misfolded protein aggregates elicit a stress response, and their clearance is crucial for cell survival. These aggregates are transported by cytoplasmic deacetylase HDAC6 and dynein motors to the aggresome via the microtubule network, and are removed by autophagic degradation. HDAC6 activity is necessary for both the transport and clearance of protein aggregates. However, the cellular factors that regulate HDAC6 activity remain unknown. Here we show that protein kinase CK2 is a crucial modulator of HDAC6 activity because CK2 directly phosphorylates HDAC6 and increases cytoplasmic deacetylase activity. Indeed, cells that expressed HDAC6 mutated at Ser458, a CK2-mediated phosphorylation site, failed to both form and clear aggresomes, and increased cytotoxicity. Interestingly, Ser458 is conserved only in higher primates, such as human and chimpanzee, but not in the rhesus macaque. These findings identify CK2 as a crucial protein involved in the formation and clearance of aggresomes, and hence in cell viability in response to misfolded protein stress.

Modulation of neuronal glutathione synthesis by EAAC1 and its interacting protein GTRAP3-18

Glutathione (GSH) plays essential roles in different processes such as antioxidant defenses, cell signaling, cell proliferation, and apoptosis in the central nervous system. GSH is a tripeptide composed of glutamate, cysteine, and glycine. The concentration of cysteine in neurons is much lower than that of glutamate or glycine, so that cysteine is the rate-limiting substrate for neuronal GSH synthesis. Most neuronal cysteine uptake is mediated through the neuronal sodium-dependent glutamate transporter, known as excitatory amino acid carrier 1 (EAAC1). Glutamate transporters are vulnerable to oxidative stress and EAAC1 dysfunction impairs neuronal GSH synthesis by reducing cysteine uptake. This may start a vicious circle leading to neurodegeneration. Intracellular signaling molecules functionally regulate EAAC1. Glutamate transporter-associated protein 3-18 (GTRAP3-18) activation down-regulates EAAC1 function. Here, we focused on the interaction between EAAC1 and GTRAP3-18 at the plasma membrane to investigate their effects on neuronal GSH synthesis. Increased level of GTRAP3-18 protein induced a decrease in GSH level and, thereby, increased the vulnerability to oxidative stress, while decreased level of GTRAP3-18 protein induced an increase in GSH level in vitro. We also confirmed these results in vivo. Our studies demonstrate that GTRAP3-18 regulates neuronal GSH level by controlling the EAAC1-mediated uptake of cysteine.

Regulation of neuronal glutathione synthesis

The brain is among the major organs generating large amounts of reactive oxygen species and is especially susceptible to oxidative stress. Glutathione (GSH) plays critical roles as an antioxidant, enzyme cofactor, cysteine storage form, the major redox buffer, and a neuromodulator in the central nervous system. GSH deficiency has been implicated in neurodegenerative diseases. GSH is a tripeptide comprised of glutamate, cysteine, and glycine. Cysteine is the rate-limiting substrate for GSH synthesis within neurons. Most neuronal cysteine uptake is mediated by sodium-dependent excitatory amino acid transporter (EAAT) systems, known as excitatory amino acid carrier 1 (EAAC1). Previous studies demonstrated EAAT is vulnerable to oxidative stress, leading to impaired function. A recent study found EAAC1-deficient mice to have decreased brain GSH levels and increased susceptibility to oxidative stress. The function of EAAC1 is also regulated by glutamate transporter associated protein 3-18. This review focuses on the mechanisms underlying GSH synthesis, especially those related to neuronal cysteine transport via EAAC1, as well as on the importance of GSH functions against oxidative stress.

Mitochondrial complex I inhibitor rotenone inhibits and redistributes vesicular monoamine transporter 2 via nitration in human dopaminergic SH-SY5Y cells

Parkinson's disease is a progressive neurodegenerative disorder characterized by selective degeneration of nigrostriatal dopaminergic neurons. Long-term systemic mitochondrial complex I inhibition by rotenone induces selective degeneration of dopaminergic neurons in rats. We have reported dopamine redistribution from vesicles to the cytosol to play a crucial role in selective dopaminergic cell apoptosis. In the present study, we investigated how rotenone causes dopamine redistribution to the cytosol using an in vitro model of human dopaminergic SH-SY5Y cells. Rotenone stimulated nitration of the tyrosine residues of intracellular proteins. The inhibition of nitric-oxide synthase or reactive oxygen species decreased the amount of nitrotyrosine and attenuated rotenone-induced apoptosis. When we examined the intracellular localization of dopamine immunocytochemically using anti-dopamine/vesicular monoamine transporter 2 (VMAT2) antibodies and quantitatively using high-performance liquid chromatography, inhibiting nitration was found to suppress rotenone-induced dopamine redistribution from vesicles to the cytosol. We demonstrated rotenone to nitrate tyrosine residues of VMAT2 using an immunocytochemical method with anti-nitrotyrosine antibodies and biochemically with immunoprecipitation experiments. Rotenone inhibited the VMAT2 activity responsible for the uptake of dopamine into vesicles, and this inhibition was reversed by inhibiting nitration. Moreover, rotenone induced the accumulation of aggregate-like formations in the stained image of VMAT2, which was reversed by inhibiting nitration. Our findings demonstrate that nitration of the tyrosine residues of VMAT2 by rotenone leads to both functional inhibition and accumulation of aggregate-like formations of VMAT2 and consequently to the redistribution of dopamine to the cytosol and apoptosis of dopaminergic SH-SY5Y cells.

Activities of 7-nitroindazole and 1-(2-(trifluoromethylphenyl)-imidazole independent of neuronal nitric-oxide synthase inhibition

7-Nitroindazole (NI) is a widely used inhibitor of neuronal nitricoxide synthase (nNOS) used to study the role of the neuronal NO pathway in the nervous system. 7-NI prevents convulsions, including 2-amino-4-methylphosphinobutyric acid (glufosinate)-induced convulsions, in experimental models. Herein, we examined nNOS involvement in glufosinate-induced convulsions and the specificity of 7-NI for nNOS. Another nNOS inhibitor, 1-[2-(trifluoromethyl)phenyl]imidazole (TRIM), inhibited NOS activity in vivo, and it prevented glufosinate-induced convulsions. In contrast, an endothelial NOS inhibitor, N(5)-(1-iminoethyl)-l-ornithine, inhibited NOS activity in vivo, but it did not prevent the convulsions. These results suggest the involvement of nNOS in glufosinate-induced convulsions. However, a nonspecific NOS inhibitor, N(omega)-nitro-l-arginine methyl ester, inhibited NOS activity in vivo, but it failed to prevent glufosinate-induced convulsions. 6-NI and indazole, which did not inhibit NOS activity in vivo, suppressed glufosinate-induced convulsions. Moreover, glufosinate elicited convulsions in nNOS-deficient mice. These results suggest the anticonvulsant effects of 7-NI and TRIM on glufosinate-induced convulsions do not involve nNOS inhibition, instead possibly being related to an undefined property of nitrogen-containing chemical structures.

Mitochondrial complex I inhibitor rotenone-elicited dopamine redistribution from vesicles to cytosol in human dopaminergic SH-SY5Y cells

Parkinson's disease is a chronic neurodegenerative disorder characterized by loss of dopaminergic neurons in the substantia nigra. Rotenone, a pesticide, produces selective degeneration of dopaminergic neurons and motor dysfunction in rats. To determine the mechanisms underlying rotenone-induced neuronal death, we investigated whether intracellular dopamine plays a role in rotenone (0.1-0.4 microM)-induced apoptosis, using an in vitro model of human dopaminergic SH-SY5Y cells. The 40% decrease of dopamine content by inhibition of dopamine synthesis suppressed rotenone-induced apoptosis. On the other hand, the 30% increase of dopamine content by inhibition of dopamine metabolism enhanced rotenone-induced apoptosis. Depletion of intracellular dopamine using reserpine (0.1-10 microM) also prevented rotenone-induced apoptosis, and this effect was counteracted by dopamine (10-100 microM) replenishment. Inhibition of dopamine reverse transport increased cytosolic dopamine and enhanced rotenone-induced apoptosis. We examined the intracellular localization of dopamine in rotenone-treated cells immunocytochemically and quantitatively. Rotenone induced dopamine redistribution from vesicles to the cytosol. In this process, rotenone stimulated reactive oxygen species and protein carbonylation and decreased an antioxidant, glutathione. Addition of an antioxidant, N-acetylcysteine (3 mM), prevented dopamine being expelled from vesicles and inhibited rotenone-induced apoptosis. Our findings demonstrate that rotenone-generated reactive oxygen species are involved in dopamine redistribution to the cytosol, which in turn may play a role in rotenone-induced apoptosis of dopaminergic cells.

Regulation of glutathione synthesis via interaction between glutamate transport-associated protein 3-18 (GTRAP3-18) and excitatory amino acid carrier-1 (EAAC1) at plasma membrane

Regulation of the cysteine transporter known as excitatory amino acid carrier-1 (EAAC1) for intracellular glutathione (GSH) content was investigated using human embryonic kidney (HEK) 293 cells as a model system. GSH content was significantly reduced by l-aspartate-beta-hydroxamate (50-250 microM), an inhibitor of both EAAC1 and GLT1, both of which are transporters to take up cysteine, whereas dihydrokainate (1-100 microM), a specific inhibitor of GLT1, failed to do so. This indicates that EAAC1 is involved in GSH content in HEK293 cells. We examined the effect of glutamate transport-associated protein 3-18 (GTRAP3-18), which is capable of interacting with EAAC1. The GSH content decreased when the GTRAP3-18 protein level at the plasma membrane was increased by methyl-beta-cyclodextrin (250 microM), rendering the cells more vulnerable to oxidative stress. Intracellular GSH increased when the GTRAP3-18 protein level at the plasma membrane was decreased by antisense oligonucleotides, rendering the cells more resistant to oxidative stress. Furthermore, we found that the increase in GSH content produced by stimulating protein kinase C, a translocator and activator of EAAC1, was inhibited by an increase in cell surface GTRAP3-18 protein. These results show GTRAP3-18 to negatively and dominantly regulate cellular GSH content via interaction with EAAC1 at the plasma membrane.

ATP depletion does not account for apoptosis induced by inhibition of mitochondrial electron transport chain in human dopaminergic cells

As the mitochondrial electron transport chain (ETC) is necessary for life, its inhibition results in cell death. To date, ETC complex (I-IV) inhibitors (ETCIs) have been thought to induce ATP depletion, triggering cellular apoptosis. To clarify whether the depletion of intracellular ATP is relevant to apoptosis induced by ETCIs, we conducted comparative studies using oxidative phosphorylation inhibitors (OPIs), including a specific F(0)F(1)ATP synthase inhibitor oligomycin, an ionophore valinomycin and an uncoupler 2,4-dinitrophenol, as tools to deplete only ATP without influencing the ETC. In human dopaminergic SH-SY5Y cells, ETCIs (rotenone, thenoyltrifluoroacetone, antimycin A and potassium cyanide) depleted ATP and induced apoptosis. However, OPIs failed to induce apoptosis despite ATP being decreased to an extent comparable to that observed with ETCIs. Reactive oxygen species (ROS) production was augmented by ETCIs, but not by OPIs. Furthermore, ETCI-induced apoptosis was inhibited by the addition of an antioxidant N-acetylcysteine. Apoptosis was induced without ATP depletion by H(2)O(2) at a concentration that generated ROS at an amount comparable to that induced by ETCIs. Our findings demonstrate that ROS production is more relevant than ATP depletion to apoptosis induced by ETCIs.

Interstitial cells of Cajal in dysmotility in intestinal ischemia and reperfusion injury in rats

BACKGROUND

Intestinal ischemia and reperfusion (I/R) injury is an obligatory occurrence in small bowel transplantation. I/R may impair the normal gastrointestinal motility. Interstitial cells of Cajal (ICC) are known as pacemaker cells in the gastrointestinal tract. The aim of this study was to assess the role of ICC in the gastrointestinal motility in a rat model of I/R injury.

MATERIALS AND METHODS

Wistar rats were subjected to 30- or 80-min intestinal ischemia by occluding the mesenteric vessels followed by reperfusion. Small intestinal segments were resected at 12 h or 4 days. The spontaneous mechanical activity was evaluated by organ bath technique. Immunopositivity of c-Kit and PGP9.5 at the level of the myenteric plexus was evaluated as markers of ICC and enteric nerves, respectively.

RESULTS

In the bowel segment with 80-min ischemia followed by 12-h reperfusion, muscles showed a 25% reduction (P < 0.05) in the frequency of contractions compared to that with 30-min ischemia followed by 12-h reperfusion, whereas amplitude of contractions was not significantly different. This change was associated with a 70% decrease (P < 0.01) of c-Kit immunopositivity. These changes of intestinal motility pattern and distribution of c-Kit-positive cells were both recovered from 80-min ischemia followed by 4 days reperfusion. In contrast, the immunopositivity of PGP9.5 was not affected in any I/R injury group.

CONCLUSIONS

Transient functional changes in ICC were induced by prolonged I/R injury but they recovered after 4 days, suggesting a central role of ICC in both disrupting and restoring the normal gastrointestinal motility in I/R injury.

Musculin/MyoR is expressed in kidney side population cells and can regulate their function

Musculin/MyoR is a new member of basic helix-loop-helix transcription factors, and its expression is limited to skeletal muscle precursors. Here, we report that musculin/MyoR is expressed in adult kidney side population (SP) cells and can regulate their function. SP phenotype can be used to purify stem cell–rich fractions. Microarray analysis clarified that musculin/MyoR was exclusively expressed in kidney SP cells, and the cells resided in the renal interstitial space. Musculin/MyoR-positive cells were decreased in acute renal failure, but infusion of kidney SP cells increased musculin/MyoR-positive cells and improved renal function. Kidney SP cells in reversible acute renal failure expressed a high level of renoprotective factors and leukemia inhibitory factor (LIF), but not in irreversible chronic renal failure. In cultured kidney SP cells, LIF stimulated gene expression of renoprotective factors, and down-regulation of musculin/MyoR augmented LIF-induced gene expression. Our results suggest that musculin/MyoR may play important roles not only in developmental processes but also in regenerative processes in adult tissue.

Leukemia inhibitory factor induces multi-lineage differentiation of adult stem-like cells in kidney via kidney-specific cadherin 16

Side population (SP) is reported to be a stem cell-rich population. In the presence of leukemia inhibitory factor (LIF), cultured kidney SP cells differentiated into multi-lineage in collagen gel but not in synthesized polymer that has no cell adhesion factor. In cultured kidney SP cells, gene expression of kidney-specific cadherin 16 was specifically upregulated in collagen gel but not in synthesized polymer. Moreover, decreasing cadherin 16 expression using siRNA abolished LIF-induced multi-lineage differentiation of kidney SP in collagen gel. These results indicated that LIF induced multi-lineage differentiation of adult stem-like cells in kidney via cadherin 16.

Imatinib blocks spontaneous mechanical activities in the adult mouse small intestine: possible inhibition of c-Kit signaling

Interstitial cells of Cajal (ICCs) are postulated to serve as pacemakers that physiologically generate electrical slow waves in the gastrointestinal tract. Imatinib is a novel and potent inhibitor of c-Kit tyrosine kinase and a new therapeutic agent for gastrointestinal stromal tumors (GIST) which presumably arise from ICCs. The effects of imatinib on the basal rhythmic mechanical activities of small intestinal circular muscles were investigated in ring preparations of the gut. The small intestinal rings of BALB/c mice exhibited spontaneous contractile activity at a rate of 40.8 +/- 4.9 contractions/min. Imatinib (1- 81 micromol/l) dose-dependently abolished spontaneous contractile activity in the 9- to 27-micromol/l concentration range. Contraction was restored by washing imatinib out with a fresh buffer. High K(+)-induced contraction was not affected by imatinib, suggesting that the drug does not have nonspecific inhibitory actions on the smooth muscles. The small intestinal rings of adult W/W(v)mice, which lack a functional c-Kit activity,exhibited only small and irregular spontaneous contractions. These results demonstrate that imatinib affects bowel contractions, and suggest that the c-Kit signaling of ICCs plays an essential role in the spontaneous movements in circular muscles of the mouse small intestine.

Aconiti tuber increases plasma nitrite and nitrate levels in humans

Some herbal medicines, including Aconiti tuber (Aconitum carmichaeli Debeaux, Ranunculaceae), have been recognized as being effective for the treatment of a "peripheral uncomfortable feeling of cold (hie)". We hypothesized that these compounds affect peripheral vascular function via the nitric oxide (NO) system, which leads to recovery from "hie". To answer this question, we investigated Aconiti tuber-induced changes in plasma levels of nitrite (p-NO2-) and nitrate (p-NO3-), final nitric oxide-oxidation products measurable in vivo. After written informed consent was obtained, patients suffering from "hie" were treated with several kinds of kampo (Japanese traditional herbal medicine), selected on the basis of traditional theory. Twenty-four patients took kampo formulas, some included Aconiti tuber (n=11; A-group) and others did not (n=13; C-group), for 4 weeks. p-NO2- and p-NO3- levels were measured before the start and after 4 weeks of treatment. In the A-group, the p-NO2- plus p-NO3- (p-NOx) level was significantly increased at 4 weeks (p=0.04), while that of the C-group was not. There was a statistically significant increase in the p-NOx level of the A-group as compared to the C-group (d.f.=1,22, F=9.38, p=0.006). The results suggest that Aconiti tuber may increase NO production in humans.

Reduced renal ClC-5 Cl− channel expression in spontaneously hypertensive rats with microalbuminuria

Mutations in a renal-specific Cl(-) channel, ClC-5, result in low-molecular-weight proteinuria. Herein we studied ClC-5 expression in the kidneys of spontaneously hypertensive rats (SHR) to identify possible causes of their increased urinary excretion of albumin. The amount of ClC-5 protein was significantly reduced in 3-month-old SHR as compared with normotensive Wistar/Kyoto (WKY) rats. The ClC-5 protein level was partially restored by short term administration of perindopril, an inhibitor of angiotensin-converting enzyme. Corresponding to the increase in ClC-5 expression, the albuminuria in SHR improved to the control level. These results implicate the ClC-5 Cl(-) channel reduction in the development of albuminuria in the early stage of essential hypertension.

Rotenone Induces Apoptosis via Activation of Bad in Human Dopaminergic SH-SY5Y Cells

Chronic complex I inhibition caused by rotenone induces features of Parkinson's disease in rats, including selective nigrostriatal dopaminergic degeneration and Lewy bodies with alpha-synuclein-positive inclusions. To determine the mechanisms underlying rotenone-induced neuronal death, we used an in vitro model of human dopaminergic SH-SY5Y cells. In rotenone-induced cell death, rotenone induced Bad dephosphorylation without changing the amount of Bad proteins. Rotenone also increased the amount of alpha-synuclein in cells showing morphological changes in response to rotenone. Because Bad and alpha-synuclein are known to bind to 14-3-3 proteins, we examined the effects of rotenone on these complexes. Whereas a decreased Bad amount bound to 14-3-3 proteins, rotenone increased alpha-synuclein binding to these proteins. Because dephosphorylation by calcineurin activates Bad, we examined the possible involvement of Bad activation in rotenone-induced apoptosis by using the calcineurin inhibitor tacrolimus (FK506). Tacrolimus suppressed two rotenone-induced actions: Bad dephosphorylation and apoptosis. Furthermore, the inhibition of caspase-9, which functions downstream from Bad, completely suppressed rotenone-induced apoptosis. Our findings demonstrate that Bad activation plays a role in rotenone-induced apoptosis of SH-SY5Y cells.

Long-Term Imipramine Treatment Increases Nitrate Levels in the Rat Hypothalamus

1. Animal experiments have shown nitric oxide synthase inhibitors to have antidepressant-like properties. However, the effects of clinically available antidepressants on nitric oxide production in the brain remain unclear. In the present study, we examined whether imipramine, a conventional antidepressant, changes the levels of type-II nitric oxide synthase mRNA and nitrate, a final nitric-oxide-oxidation product measurable in vivo, in the rat brain. 2. Type-II nitric oxide synthase mRNA was detected using a reverse transcription-polymerase chain reaction method and nitrate was measured with a combination of high-performance liquid chromatography and the Griess reaction. 3. In untreated rats, type-II nitric oxide synthase mRNA was not detected in the hypothalamus, hippocampus, cerebral cortex, brain stem, or cerebellum. However, after 28-day oral administration of imipramine, it was detected in every brain region tested. Nitrate levels in the hypothalamus and cerebral cortex increased after 28-day treatment. In the hypothalamus, nitrate levels increased dose-dependently. These dose-dependent nitrate level changes were prevented by pretreatment with a nitric oxide synthase inhibitor. Moreover, the preventive effect of NG-nitro-L-arginine methyl ester was reversed by coadministration of L-arginine, a nitric oxide substrate. 4. These results suggest that chronic imipramine treatment induces nitric oxide synthase gene expression in the brain, followed by augmented NO production.

Nitric Oxide Induced Heat Shock Protein 70 mRNA in Rat Hypothalamus During Acute Restraint Stress Under Sucrose Diet

1. Sucrose feeding increases the level of stress-induced heat shock protein 70 mRNA in the rat hypothalamus. However, the mechanism by which a sucrose diet induces mRNA remains unclear. The issues investigated in this study were (1) whether a sucrose diet affects nitric oxide production in the hypothalamus, and (2) whether nitric oxide mediates the sucrose and stress-induced elevation of heat shock protein 70 mRNA. 2. To address the first question, we measured the level of nitrate, a final nitric-oxide-oxidation product measurable in vivo, using a microdialysis method. To address the second question, we administered a nitric oxide synthase inhibitor. NG-nitro-L-arginine methyl ester, prior to stress, then measured the mRNA level of heat shock protein 70 by the reverse transcription-competitive polymerase chain reaction method. 3. After the initiation of restraint stress, rats fed a sucrose-containing diet, unlike those fed standard chow, displayed a transient nitrate elevation. This nitrate elevation was attenuated by pretreatment with NG-nitro-L-arginine methyl ester. The mRNA level increases in rats fed a sucrose diet were dose-dependently attenuated by NG-nitro-L-arginine methyl ester. 4. These data suggest that a sucrose diet induces heat shock protein 70 under stress by enhancing nitric oxide production in the hypothalamus.

Caffeic acid phenethyl ester induces apoptosis by inhibition of NFkappaB and activation of Fas in human breast cancer MCF-7 cells

The transcription factor NFkappaB plays a role in cell survival. Apoptosis, programmed cell death, via numerous triggers including death receptor ligand binding is antagonized by NFkappaB activation and potentiated by its inhibition. In the present study, we found that caffeic acid phenethyl ester (CAPE), known to inhibit NFkappaB, induced apoptosis via Fas signal activation in human breast cancer MCF-7 cells. CAPE activated Fas by a Fas ligand (Fas-L)-independent mechanism, induced p53-regulated Bax protein, and activated caspases. CAPE also activated MAPK family proteins p38 and JNK. SB203580, a specific inhibitor of p38 MAPK, partially suppressed CAPE-induced p53 activation, Bax expression, and apoptosis, consistent with a mechanism by which CAPE leads to Bax activation, known to be regulated by p38 and p53. The expression of dominant negative c-Jun, which inhibits the JNK signal, also suppresses CAPE-induced apoptosis, suggesting MAPKs are involved in CAPE-induced apoptosis. The expression of Fas antisense oligomers significantly suppressed the CAPE-induced activations of JNK and p38 and apoptosis as compared with Fas sense oligomers. To ascertain whether these phenomena are attributable to the inhibition of NFkappaB by CAPE, we examined the effect of a truncated form of IkappaBalpha (IkappaBDeltaN) lacking the phosphorylation sites essential for NFkappaB activation. IkappaBDeltaN expression not only inhibited NFkappaB activity but also induced Fas activation, Bax expression, and apoptosis. Our findings demonstrate that NFkappaB inhibition is sufficient to induce apoptosis and that Fas activation plays a role in NFkappaB inhibition-induced apoptosis in MCF-7 cells.

Plasma nitrate levels in deficit versus non-deficit forms of schizophrenia

OBJECTIVE

To determine whether nitric oxide production levels differ in patients with deficit and non-deficit forms of schizophrenia.

METHODS

We investigated plasma nitrate levels, an index of in vivo nitric oxide production, in patients with deficit syndrome (n = 11) and non-deficit syndrome (n = 14) and healthy controls (n = 12) with a combination of high-performance liquid chromatography and the Griess reaction.

RESULTS

There was no difference found in mean plasma nitrite levels, but plasma nitrate levels of patients with deficit syndrome were significantly lower than those with non-deficit syndrome (28.0 [SEM 2.5] micromol/L v. 44.2 [SEM 5.5] micromol/L, p < 0.05).

CONCLUSIONS

A decline in nitric oxide production may be involved in primary negative symptoms in schizophrenia.

Identification of interleukin-8 converting enzyme as cathepsin L

IL-8 is produced by various cells, and the NH(2)-terminal amino acid sequence of IL-8 displays heterogeneity among cell types. The mature form of IL-8 has 72 amino acids (72IL-8), while a precursor form (77IL-8) of IL-8 has five additional amino acids to the 72IL-8 NH(2)-terminal. However, it has been unclear how IL-8 is processed to yield the mature form. In this study, converting enzyme was purified as a single 31-kDa band on silver-stained polyacrylamide gel from 160 l of cultured fibroblast supernatant by sequential chromatography. NH(2)-terminal amino acid sequence analysis revealed a sequence, EAPRSVDWRE, which was identified as a partial sequence of cathepsin L. Polyclonal antibodies raised against cathepsin L recognized the purified converting enzyme on Western blot. Moreover, human hepatic cathepsin L cleaved 77IL-8 between Arg(5) and Ser(6), which is the same cleavage site as the putative converting enzyme, resulting in 72IL-8 formation. These data indicate that the converting enzyme of the partially purified fraction of the human fibroblast culture supernatant was cathepsin L. Furthermore, 72IL-8 was sevenfold more potent than 77IL-8 in a neutrophil chemotaxis assay. These results show that cathepsin L is secreted from human fibroblasts in response to external stimuli and plays an important role in IL-8 processing in inflammatory sites.

Possible identity of IL-8 converting enzyme in human fibroblasts as a cysteine protease

A converting activity was characterized in human diploid fibroblasts, which secrete 72IL-8 and 77IL-8 in treatment with IFN-beta and poly I: poly C. 77IL-8 was significantly converted to 72IL-8 by a partially purified fraction of the culture supernatant of human diploid fibroblasts. The converting activity, which was temperature-dependent and optimal at pH 6, was completely inhibited by cysteine protease inhibitors, antipain dihydrochloride and E-64, but not by other types of protease inhibitors. These data clearly show that human diploid fibroblasts are capable of processing IL-8 to produce a mature IL-8 and that the putative converting enzyme appears to be a cysteine protease.

Antipsychotic, antidepressant, anxiolytic, and anticonvulsant drugs induce type II nitric oxide synthase mRNA in rat brain

Nitric oxide synthase inhibitors have been regarded as potentially beneficial for psychiatric disorders such as depression and schizophrenia, though little is known about how nitric oxide synthases are affected by psychotropic drugs in the brain. Using reverse transcription-polymerase chain reaction analysis, we investigated the effects of short- and long-term oral treatments with several psychotropics on type II nitric oxide synthase gene expression in the rat brain. With maprotiline and fluvoxamine, enzyme mRNA levels were higher after a 28 day treatment than after 1 and 4 day treatments. Zonisamide, carbamazepine and diazepam also increased mRNA, though differences in levels between 1, 4 and 28 day treatments were not significant. These results suggest that psychotropics modulate the gene expression of type-II nitric oxide synthase in the brain.

Learning adverse drug effects from judicial precedents

In order to help students to become familiar with the official web site on drug safety information in Japan, a short course, in which they actively learn the adverse effects of drugs, has been introduced in our pharmacology curriculum. Each student was allotted a personal computer that was connected to the internet, and was informed of the URL (www.pharmasys.gr.jp/homepage.html) where they were able to search for pertinent essential information on drugs and to report adverse events to the official concerned organization. There were three students to a group, each of which was provided with a judicial precedent. Each judicial case record was deliberately truncated after the section where the physician committed misuse of drugs, so that the students had freedom to imagine the rest of the story. Each group was asked to summarize the case, to speculate on the prognosis and to point out the inappropriate use of drugs. Most groups predicted the outcome optimistically at first, but as they scrutinized the cases, they became aware of serious mistakes that the physicians had committed in patient care. The results suggest that the internet is a powerful tool for gleaning drug information and reporting adverse effects. Judicial precedents provide an excellent teaching material for giving students an incentive to access web sites that are essential for healthcare professionals.

[The arginine paradox]

L-Arginine has attracted major interest because it has been identified as the natural substrate of nitric oxide synthase and is now recognized as a major player in the regulation of biological function. The arginine paradox refers to the phenomenon that exogenous L-arginine causes NO-mediated biological effects despite the fact that nitric oxide synthases (NOS) are theoretically saturated with the substrate L-arginine. There have been several explanations for this phenomenon, although none of them can explain the arginine paradox fully: (1) L-arginine-induced insulin, which has vasodilatory actions. (2) Neither extracellular nor intracellular concentration determines the NOS activity but rather the L-arginine amount transported across the plasma membrane may do so. (3) Endogenous NOS inhibitors reduce the enzyme sensitivity to L-arginine. These inhibitors include, NG, NG-dimethyl-L-arginine, L-citrulline, argininosuccinic acid and agmatine. (4) Intracellular L-citrulline, an NOS product, is a potent inhibitor of NOS so that the cells may need extra L-arginine to compete with L-citrulline inhibition.

[NF-kappa B as a therapeutic drug target]

The transcription factor NF-kappa B has attracted widespread interest based on its unusual regulation, the variety of stimuli that activate it, the diverse genes and biological responses that it controls, the striking evolutionary conservation of structure and function among family members, and its apparent involvement in a variety of human diseases. Recently NF-kappa B has been shown to be the target of new drug discovery. Here, we discuss the so-called NF-kappa B inhibitors and consider the development of new therapeutic agents.

Static pressure regulates connective tissue growth factor expression in human mesangial cells

Connective tissue growth factor (CTGF) is overexpressed in a variety of fibrotic disorders such as renal fibrosis and atherosclerosis. Fibrosis is a common final pathway of renal diseases of diverse etiology, including inflammation, hemodynamics, and metabolic injury. Mechanical strains such as stretch, shear stress, and static pressure are possible regulatory elements in CTGF expression. In this study, we examined the ability of static pressure to modulate CTGF gene expression in cultured human mesangial cells. Low static pressure (40-80 mm Hg) stimulated cell proliferation via a protein kinase C-dependent pathway. In contrast, high static pressure (100-180 mm Hg) induced apoptosis in human mesangial cells. This effect was reversed by treatment with CTGF antisense oligonucleotide but not with transforming growth factor beta1-neutralizing antibody or protein kinase C inhibitor. High static pressure not only up-regulated the expression of CTGF, but also the expression of extracellular matrix proteins (collagen I and IV, laminin). This up-regulation of extracellular matrix proteins was also reversed by treatment with CTGF antisense oligonucleotide. As judged by mRNA expression of a total of 1100 genes, including apoptosis-associated genes using DNA microarray techniques, recombinant CTGF protein induced apoptosis by down-regulation of a number of anti-apoptotic genes. Overexpression of CTGF in mesangial cells by transient transfection had similar effects. Taken together, these results suggest that high blood pressure up-regulates CTGF expression in mesangial cells. High levels of CTGF in turn enhance extracellular matrix production and induce apoptosis in mesangial cells, and may contribute to remodeling of mesangium and ultimately glomerulosclerosis.