Reactive astrocytes contribute to increased epileptic susceptibility induced by subthreshold dose of pilocarpine.

Seizures may influence epileptogenesis, but it is not yet clearly established whether subthreshold stimulations that are not sufficient to induce visible behavioral seizures change epileptic susceptibility, and the possible underlying mechanisms have not been completely understood. We assessed the susceptibility to epilepsy after subthreshold dose of pilocarpine, as well as glial fibrillary acidic protein (GFAP) expression using immunohistochemistry. An increase in the susceptibility to pentylenetetrazole (PTZ)-induced seizures was observed in rats previously subjected to subthreshold dose of pilocarpine. The immunoreactivity of GFAP was also increased, indicating that astrocytes became reactive in some brain subfields. The increased epileptic susceptibility was significantly reduced by L-alpha-aminoadipic acid (L-AAA), an inhibitor of astrocytic function. Our results suggest that subthreshold stimulation may increase the susceptibility to subsequent development of epilepsy, and reactive astrocytes might be an important contributor to this process. Adequate inhibition of astrocytic function may be a potential preventive approach against epileptogenesis.

Inhibition of reactive gliosis attenuates excitotoxicity-mediated death of retinal ganglion cells.

Reactive gliosis is a hallmark of many retinal neurodegenerative conditions, including glaucoma. Although a majority of studies to date have concentrated on reactive gliosis in the optic nerve head, very few studies have been initiated to investigate the role of reactive gliosis in the retina. We have previously shown that reactive glial cells synthesize elevated levels of proteases, and these proteases, in turn, promote the death of retinal ganglion cells (RGCs). In this investigation, we have used two glial toxins to inhibit reactive gliosis and have evaluated their effect on protease-mediated death of RGCs. Kainic acid was injected into the vitreous humor of C57BL/6 mice to induce reactive gliosis and death of RGCs. C57BL/6 mice were also treated with glial toxins, alpha-aminoadipic acid (AAA) or Neurostatin, along with KA. Reactive gliosis was assessed by immunostaining of retinal cross sections and retinal flat-mounts with glial fibrillary acidic protein (GFAP) and vimentin antibodies. Apoptotic cell death was assessed by TUNEL assays. Loss of RGCs was determined by immunostaining of flat-mounted retinas with Brn3a antibodies. Proteolytic activities of matrix metalloproteinase-9 (MMP-9), tissue plasminogen activator (tPA), and urokinase plasminogen activator (uPA) were assessed by zymography assays. GFAP-immunoreactivity indicated that KA induced reactive gliosis in both retinal astrocytes and in Muller cells. AAA alone or in combination with KA decreased GFAP and vimentin-immunoreactivity in Mϋller cells, but not in astrocytes. In addition AAA failed to decrease KA-mediated protease levels and apoptotic death of RGCs. In contrast, Neurostatin either alone or in combination with KA, decreased reactive gliosis in both astrocytes and Mϋller cells. Furthermore, Neurostatin decreased protease levels and prevented apoptotic death of RGCs. Our findings, for the first time, indicate that inhibition of reactive gliosis decreases protease levels in the retina, prevents apoptotic death of retinal neurons, and provides substantial neuroprotection.

Combining ketamine with astrocytic inhibitor as a potential analgesic strategy for neuropathic pain ketamine, astrocytic inhibitor and pain.

BACKGROUND: Neuropathic pain is an intractable clinical problem. Intrathecal ketamine, a noncompetitive N-methyl-D-aspartate receptor (NMDAR) antagonist, is reported to be useful for treating neuropathic pain in clinic by inhibiting the activity of spinal neurons. Nevertheless, emerging studies have disclosed that spinal astrocytes played a critical role in the initiation and maintenance of neuropathic pain. However, the present clinical therapeutics is still just concerning about neuronal participation. Therefore, the present study is to validate the coadministration effects of a neuronal noncompetitive N-methyl-D-aspartate receptor (NMDAR) antagonist ketamine and astrocytic cytotoxin L-α-aminoadipate (LAA) on spinal nerve ligation (SNL)-induced neuropathic pain. RESULTS: Intrathecal ketamine (10, 100, 1000 µg/kg) or LAA (10, 50, 100 nmol) alleviated SNL-induced mechanical allodynia in a dose-dependent manner respectively. Phosphorylated NR1 (pNR1) or glial fibrillary acidic protein (GFAP) expression was down-regulated by intrathecal ketamine (100, 1000 µg/kg) or LAA (50, 100 nmol) respectively. The combination of ketamine (100 µg/kg) with LAA (50 nmol) showed superadditive effects on neuropathic pain compared with that of intrathecal administration of either ketamine or LAA alone. Combined administration obviously relieved mechanical allodynia in a quick and stable manner. Moreover, down-regulation of pNR1 and GFAP expression were also enhanced by drugs coadministration. CONCLUSIONS: These results suggest that combining NMDAR antagonist ketamine with an astrocytic inhibitor or cytotoxin, which is suitable for clinical use once synthesized, might be a potential strategy for clinical management of neuropathic pain.

Light touch induces ERK activation in superficial dorsal horn neurons after inflammation: involvement of spinal astrocytes and JNK signaling in touch-evoked central sensitization and mechanical allodynia.

Activation of extracellular signal-regulated kinase (ERK) in spinal cord neurons could serve as a marker for sensitization of dorsal horn neurons in persistent pain. ERK is normally activated by high-threshold noxious stimuli. We investigated how low-threshold mechanical stimuli could activate ERK after complete Freund's adjuvant (CFA)-induced inflammation. Unilateral injection of CFA induced ipsilateral heat hyperalgesia and bilateral mechanical allodynia. CFA-induced ERK activation in ipsilateral dorsal horn neurons declined after 2 days. Interestingly, low-threshold mechanical stimulation given by light touch either on the inflamed paw or the contralateral non-inflamed paw dramatically increased ERK phosphorylation in the dorsal horn ipsilateral to touch stimulation. Notably, light touch induced ERK phosphorylation mainly in superficial neurons in laminae I-IIo. Intrathecal administration of the astroglial toxin L-α-aminoadipate on post-CFA day 2 reversed CFA-induced bilateral mechanical allodynia but not heat hyperalgesia. Furthermore, L-α-aminoadipate, the glial inhibitor fluorocitrate, and a peptide inhibitor of c-Jun N-terminal Kinase all reduced light touch-evoked ERK activation ipsilateral to touch. Collectively, these data suggest that (i) ERK can be activated in superficial dorsal horn neurons by low-threshold mechanical stimulation under pathological condition and (ii) ERK activation by light touch is associated with mechanical allodynia and requires an astrocyte network.

Methotrexate and MX-68, a new derivative of methotrexate, limit infarct size via adenosine-dependent mechanisms in canine hearts.

Methotrexate, an anti-rheumatic agent, has recently been reported to show an anti-inflammatory action via ecto-5'-nucleotidase- and adenosine-dependent mechanisms. Because ecto-5'-nucleotidase contributes to the production of adenosine and adenosine has a potent cardioprotective effect against ischemia/reperfusion injury, we investigated whether methotrexate or MX-68 [N-1-((2,4-diamino-6-pteridinyl) methyl)-3,4-dihydro-2H-1,4-benzothiazine-7- carbonyl]-N-2- aminoadipic acid] could reduce infarct size via adenosine-dependent mechanisms. In beagle dogs, the left anterior descending coronary artery was perfused through a bypass tube, which was occluded for 90 minutes followed by 6 hours of reperfusion. The size of infarcts was assessed by TTC staining. MX-68 reduced infarct size compared with that in untreated dogs (13.7 +/- 1.9 versus 38.6 +/- 5.3%, P < 0.01). This effect was completely blunted by either the adenosine receptor antagonist 8-sulfophenyltheophylline (8-SPT) (45.0 +/- 4.6% and 46.8 +/- 5.8% in the 8-SPT and MX-68 + 8-SPT groups, respectively) or by the ecto-5'-nucleotidase inhibitoralpha,beta-methylenadenosine 5'-diphosphate (AMP-CP) (44.0 +/- 4.5% and 46.7 +/- 5.8% in the AMP-CP and MX-68 + AMP-CP groups, respectively). Methotrexate also reduced infarct size to a level comparable with that in the MX-68 group, and its effect was also blunted by 8-SPT. There were no significant differences of collateral blood flow or risk area between the groups. We conclude that methotrexate and its derivative (MX-68) both limit infarct size via adenosine-dependent mechanisms.

Effect of MX-68 on airway inflammation and hyperresponsiveness in mice and guinea-pigs.

MX-68 is a newly synthesized antifolate, which is a derivative of methotrexate (MTX). In this paper, the effect of MX-68 on allergic airway responses in mice and guinea-pigs was studied. In the first experiment, antigen-induced airway inflammation and airway hyperresponsiveness (AHR) to acetylcholine in mice were examined and compared with the effects of classical antifolate methotrexate and prednisolone. Mice were sensitized with ovalbumin as an antigen and challenged with ovalbumin inhalation three times. After the last inhalation, AHR and airway inflammation were observed. An increase in Th2 cytokines (IL-4 and IL-5) and a decrease in a Th1 cytokine (IFN-gamma) in the bronchoalveolar lavage fluid (BALF), as well as an elevation of the immunoglobulin level in serum, were observed in sensitized mice. Oral administration of MX-68 had no effect on changes of body weight, but prednisolone reduced body weight during the experiment. The antigen-induced AHR and increases in the number of eosinophils and lymphocytes in BALF were significantly inhibited by MX-68. MX-68 interfered with the elevation of IL-4 and IL-5 levels in BALF, but had no effect on the decrease in IFN-gamma. Moreover, MX-68 significantly inhibited the elevation of serum IgE and IgG levels. In the guinea-pig model for bronchial asthma, biphasic increases in airway resistance (immediate asthmatic response, IAR, and late asthmatic response, LAR), as well as accumulated inflammatory cells in BALF, were observed after repeated antigen challenge. These asthmatic responses and inflammatory signs were significantly decreased by administration of MX-68. These results suggest that MX-68 obviously has an anti-inflammatory effect in an animal model of asthma and would be useful clinically for the treatment of bronchial asthma.

Polyglutamation of a novel antifolate, MX-68, is not necessary for its anti-arthritic effect.

N-[[4-[(2,4-diaminopteridin-6-yl)methyl]-3,4-dihydro-2H-1,4-benzothiazin-7-yl]-carbonyl]-L-homoglutamic acid (MX-68), a derivative of methotrexate, was chemically designed to resist polyglutamation and to have a high affinity for dihydrofolate reductase, in an attempt to reduce the side effects of methotrexate. We confirmed that MX-68 did not undergo polyglutamation and investigated the pharmacological activities of MX-68 compared with methotrexate. (1) In vitro: MX-68 inhibited the activity of dihydrofolate reductase to the same degree as methotrexate-tetraglutamate. MX-68 treatment produced a similar anti-proliferative effect to that of methotrexate. However, the intracellular concentration of MX-68 was much lower than the sum of the levels of methotrexate and its polyglutamate, and the effects of MX-68 disappeared when it was removed from the culture medium. (2) In vivo: Oral administration of MX-68 suppressed the development of collagen-induced arthritis in mice and adjuvant-induced arthritis in rats, in a similar fashion to that of methotrexate. These results indicate that polyglutamation is not essential for the anti-arthritic effect of antifolates.

A novel non-polyglutamable anti-folate, MX-68, inhibits the induction of experimental autoimmune uveitis in rats.

MX-68 is a novel antifolate which is chemically designed not to undergo intracellular polyglutamation thus preventing the development of adverse effects. The present study was carried out to examine both the in vitro and in vivo effects of MX-68 on experimental autoimmune uveitis (EAU) and to compare its effect on collagen-induced arthritis (CIA) in rats. EAU was induced by injecting Lewis rats with retinal S-antigen in complete Freund's adjuvant. Either MX-68 or methotrexate (MTX), which forms several polyglutamates intracellularly, was orally administered five days a week for three weeks beginning on the day of immunization. In vivo, both MX-68 and MTX significantly delayed the onset of EAU and inhibited the antibody response to S-antigen in a dose-dependent manner. High dose MX-68 (2.5 mg kg-1 day-1) completely abrogated the induction of EAU. No adverse effects were observed in either MX-68- or MTX-treated rats. However, the cessation of MX-68 administration after a period of three weeks resulted in the induction of EAU. In contrast, both MX-68 and MTX suppressed the severity of CIA without affecting the onset of the disease and inhibited anti-collagen antibody production in a dose-dependent fashion. Discontinuation of the drugs did not result in the recurrence of CIA. In vitro, both MX-68 and MTX significantly suppressed the proliferation of S-antigen- and Con A-stimulated lymph node cells obtained from immunized rats in a dose-dependent fashion. These data suggest that MX-68 may be useful for the treatment of autoimmune diseases including EAU and that the pathophysiology of EAU could be different from that of CIA.

Fórmulas infantiles: aporte lipídico y perfil de ácidos grasos / Infant formulas: fat intake and fatty acid profile

Introducción y objetivos: La ingestión de grasas durante el primer año de vida es fundamental no sólo para cubrir las necesidades energéticas sino también como fuente de nutrientes esenciales. Los objetivos del presente trabajo son los de evaluar el aporte de calorías grasas, ácido linoleico, relación ácido linoleico/ácido a-linolénico y agregado de ácidos grasos poliinsaturados de cadena larga en fórmulas infantiles. Material y Métodos: Se realizó un relevamiento de las fórmulas infantiles existentes en el mercado y se trabajó con información provista por los fabricantes. De las 34 fórmulas del mercado se seleccionaron 21 en base a leche de vaca y 4 a base de soja. Resultados: En todas las fórmulas el aporte de grasas se encontraba dentro de las cifras recomendadas. La mayoría tenía una relación ácido linoleico/ácido a-linolénico entre 5 y 15, de acuerdo a las recomendaciones, mientras que 5 de ellas la superaban. Ocho fórmulas presentaban un contenido de ácido linoleico fuera del rango recomendado. Sólo tres tenían ácido grasos poliinsaturados de cadena larga adicionados. Conclusiones: Los altos niveles de ácido linoleico y de la relación ácido linoleico/ácido a-linolénico en algunas fórmulas así como la falta de ácidos grasos poliinsaturados de cadena larga en la mayoría, podrían influir sobre el metabolismo lipídico y las funciones del sistema nervioso. Sin embargo, antes de proponer su adición en forma generalizada, sería importante realizar estudios sobre la forma más adecuada de hacerlo, teniendo en cuenta su biodisponibilidad y eventuales efectos adversos (AU)

A novel antifolate, MX-68, inhibits the development of autoimmune disease in MRL/lpr mice.

We compared a novel unpolyglutamable antifolate, MX-68, with polyglutamable antifolate, methotrexate (MTX), for treatment of an autoimmune kidney disease which develops spontaneously in MRL/Mp-lpr/lpr (MRL/lpr) mice. Oral administration of either MX-68 or MTX was commenced in 8-week-old female mice and continued 3 times a week until they reached 30 weeks of age. MX-68 delayed the onset of proteinuria and prolonged life span dose-dependently. Furthermore, it suppressed the elevation of serum blood urea nitrogen and cholesterol levels. MX-68 was as effective as MTX at ameliorating events which accompany the development of lupus nephritis, despite that MX-68 did not undergo polyglutamation. These ameliorative effects of MX-68 and MTX did not occur via inhibition of either autoantibody production or cell proliferation. Neither compound suppressed age-dependent elevation of immune complexes or antibodies for single-stranded DNA and TNP in serum nor did they influence the associated enlargement of lymph nodes and spleen. We conclude that MX-68 is beneficial for the treatment of autoimmune kidney disease in mice and may be useful for other related diseases such as systemic lupus erythematosus.

Phosphonic analogues of excitatory amino acids raise the threshold for maximal electroconvulsions in mice.

2-Amino-5-phosphonopentanoic acid (100 and 200 mg/kg) and 2-amino-7-phosphonoheptanoic acid (50-200 mg/kg i.p.) significantly elevated the threshold for maximal electroconvulsions in mice, the latter being more effective in this respect. In contrast, neither alpha-aminoadipic acid nor L-glutamic acid diethyl ester (up to 200 and 400 mg/kg, respectively) offered any protection. The present results add further evidence to support the importance of the blockade of N-methyl-D-aspartic acid receptor-mediated events in the suppression of seizure activity.

Effects of L-lysine and its metabolites on pentylenetetrazol-induced seizures.

Lysine and its metabolic intermediates were studied for their effect on pentylenetetrazol (PTZ)-induced seizures in mice. L-Lysine at dosages above 2 mmol/kg given i.p. significantly increased seizure protection and seizure latency (the time required to develop seizures after PTZ injection) with a peak effect dose at 10 mmol/kg. A pretreatment time of 15 min was required to significantly prolong seizure latency with a peak effect time of 45 min. D-Lysine at 10 mmol/kg i.p. afforded some seizure protection and significantly prolonged seizure latency but has a peak effect time of 15 min. When administered intracerebroventricularly, both L-lysine and piperidine at 0.1 mmol/kg prolonged seizure latency significantly, and increased seizure protection slightly. L-Pipecolic acid at the same dose given through the same route, however, shortened seizure latency significantly. L-alpha-Aminoadipic acid, on the other hand, had no significant effect. Lysine metabolites that prolonged seizure latency also increased seizure protection and decreased seizure death, and one that shortened seizure latency had the opposite effect. The anticonvulsant activity of lysine and its metabolites was explained on the basis of their connection with the GABAergic transmission.