Bone marrow mononuclear cell transplant prevents rat depression and modulates inflammatory and neurogenic molecules.

INTRODUCTION: Major depressive disorder is associated with chronic inflammation and deficient production of brain-derived neurotrophic factor (BDNF). Bone marrow mononuclear cell (BMMC) transplantation has an anti-inflammatory effect and has been proven effective in restoring non-depressive behavior. This study investigated whether BMMC transplantation can prevent the development of depression or anxiety in chronic mild stress (CMS), as well as its effect on inflammatory and neurogenic molecules. METHOD: Three groups of animals were compared: BMMC-transplanted animals subjected to CMS for 45 days, CMS non-transplanted rats, and control animals. After the CMS period, the three groups underwent the following behavioral tests: sucrose preference test (SPT), eating-related depression test (ERDT), social avoidance test (SAT), social interaction test (SIT), and elevated plus maze test (EPMT). Transplanted cell tracking and measurement of the expression of high-mobility group box 1 (HMGB1), interleukin-1ß (IL-1ß), tumor necrosis factor (TNFα), and BDNF were performed on brain and spleen tissues. RESULTS: BMMC transplantation prevented the effects of CMS in the SPT, ERDT, SAT, and SIT, while prevention was less pronounced in the EPMT. It was found to prevent increased HMGB-1 expression induced by CMS in the hippocampus and spleen, increase BDNF expression in both tissues, and prevent increased IL-1ß expression in the hippocampus alone, while no effect of the transplant was observed in the TNFα expression. In addition, no transplanted cells were found in either the brain or spleen. CONCLUSIONS: BMMC transplantation prevents the development of depression and anxiety-like behavior triggered by CMS. It could prevent increased HMGB-1 and IL-1ß expression in the hippocampus and increased BDNF expression in the same tissue. Cell treatment represents a further perspective in the research and treatment of depression and possible mood disorders.

Neurotoxic and convulsant effects induced by jack bean ureases on the mammalian nervous system.

Ureases are microbial virulence factors either because of the enzymatic release of ammonia or due to many other non-enzymatic effects. Here we studied two neurotoxic urease isoforms, Canatoxin (CNTX) and Jack Bean Urease (JBU), produced by the plant Canavalia ensiformis, whose mechanisms of action remain elusive. The neurotoxins provoke convulsions in rodents (LD50 ∼2 mg/kg) and stimulate exocytosis in cell models, affecting intracellular calcium levels. Here, electrophysiological and brain imaging techniques were applied to elucidate their mode of action. While systemic administration of the toxins causes tonic-clonic seizures in rodents, JBU injected into rat hippocampus induced spike-wave discharges similar to absence-like seizures. JBU reduced the amplitude of compound action potential from mouse sciatic nerve in a tetrodotoxin-insensitive manner. Hippocampal slices from CNTX-injected animals or slices treated in vitro with JBU failed to induce long term potentiation upon tetanic stimulation. Rat cortical synaptosomes treated with JBU released L-glutamate. JBU increased the intracellular calcium levels and spontaneous firing rate in rat hippocampus neurons. MicroPET scans of CNTX-injected rats revealed increased [18]Fluoro-deoxyglucose uptake in epileptogenesis-related areas like hippocampus and thalamus. Curiously, CNTX did not affect voltage-gated sodium, calcium or potassium channels currents, neither did it interfere on cholinergic receptors, suggesting an indirect mode of action that could be related to the ureases' membrane-disturbing properties. Understanding the neurotoxic mode of action of C. ensiformis ureases could help to unveil the so far underappreciated relevance of these toxins in diseases caused by urease-producing microorganisms, in which the human central nervous system is affected.

The antidepressant effect of bone marrow mononuclear cell transplantation in chronic stress.

BACKGROUND: Inflammation could be a risk factor for the development of depression and change the outcome of this common chronic-recurrent mental disorder. AIMS: This study aimed to investigate if bone marrow mononuclear cell (BMMC) transplantation is effective in restoring sucrose preference in rats subjected to chronic stress (CS), if it has an anti-inflammatory effect and is able to restore damaged DNA. METHODS: The effect of BMMC transplantation was studied in a controlled protocol (compared with a control group and a selective serotonin reuptake inhibitor escitalopram group) involving sucrose preference in CS in rats. Measurements were taken of the amygdala, hippocampus, frontal cortex, and other brain areas, the spleen and blood pro-inflammatory cytokines, namely interleukin-1ß, interleukin-6, tumor necrosis factor-alpha, and interferon-gamma, as well as anti-inflammatory cytokine interleukin-10. Finally, 8-hydroxy-2'-deoxyguanosine (a DNA damage marker) was determined. RESULTS: BMMC transplantation was as effective as escitalopram in restoring sucrose preference. It also had an anti-inflammatory effect and slightly improved damaged DNA after one week. CONCLUSIONS: These findings suggest administration of BMMC in rats subjected to CS restores sucrose preference, resolves inflammation in both the peripheral and central nervous system, as well as diminishes DNA damage. This effect was similar to that of escitalopram, which is effective in the treatment of depressive patients.

Methylprednisolone as a memory enhancer in rats: Effects on aversive memory, long-term potentiation and calcium influx.

It is well recognized that stress or glucocorticoids hormones treatment can modulate memory performance in both directions, either impairing or enhancing it. Despite the high number of studies aiming at explaining the effects of glucocorticoids on memory, this has not yet been completely elucidated. Here, we demonstrate that a low daily dose of methylprednisolone (MP, 5mg/kg, i.p.) administered for 10-days favors aversive memory persistence in adult rats, without any effect on the exploring behavior, locomotor activity, anxiety levels and pain perception. Enhanced performance on the inhibitory avoidance task was correlated with long-term potentiation (LTP), a phenomenon that was strengthen in hippocampal slices of rats injected with MP (5mg/kg) during 10days. Additionally, in vitro incubation with MP (30-300µM) concentration-dependently increased intracellular [Ca2+]i in cultured hippocampal neurons depolarized by KCl (35mM). In conclusion, a low daily dose of MP for 10days may promote aversive memory persistence in rats.

Bothriurus bonariensis scorpion venom activates voltage-dependent sodium channels in insect and mammalian nervous systems.

Animal venoms have been widely recognized as a major source of biologically active molecules. Bothriurus bonariensis, popularly known as black scorpion, is the arthropod responsible for the highest number of accidents involving scorpion sting in Southern Brazil. Here we reported the first attempt to investigate the neurobiology of B. bonariensis venom (BBV) in the insect and mammalian nervous system. BBV (32 µg/g) induced a slow neuromuscular blockade in the in vivo cockroach nerve-muscle preparations (70 ± 4%, n = 6, p < 0.001), provoking repetitive twitches and significantly decreasing the frequency of spontaneous leg action potentials (SNCAPs) from 82 ± 3 min(-1) to 36 ± 1.3 min(-1) (n = 6, p < 0.05), without affecting the amplitude. When tested in primary cultures of rat hippocampal cells, BBV induced a massive increase of Ca(2+) influx (250 ± 1% peak increase, n = 3, p < 0.0001). The disturbance of calcium homeostasis induced by BBV on the mammalian central nervous system was not accompanied by cellular death and was prevented by the co-treatment of the hippocampal cells with tetrodotoxin, a selective sodium channel blocker. The results suggest that the biological activity of BBV is mostly related to a modulation of sodium channels function. Our biological activity survey suggests that BBV may have a promising insecticidal and therapeutic potential.

The antiepileptic activity of JSTX-3 is mediated by N-methyl-D-aspartate receptors in human hippocampal neurons.

We analyzed the effect of the acylpolyaminetoxin JSTX-3 on the epileptogenic discharges induced by perfusion of human hippocampal slices with artificial cerebrospinal fluid lacking Mg2+ or N-methyl-D-aspartate. Hippocampi were surgically removed from patients with refractory medial temporal lobe epilepsy, sliced in the surgical room and taken to the laboratory immersed in normal artificial cerebrospinal fluid. Epileptiform activity was induced by perfusion with Mg2+-free artificial cerebrospinal fluid or by iontophoretically applied N-methyl-D-aspartate and intracellular and field recordings of CA1 neurons were performed. The ictal-like discharges induced by Mg2+-free artificial cerebrospinal fluid and N-methyl-D-aspartate were blocked by incubation with JSTX-3. This effect was similar to that obtained with the N-methyl-D-aspartate receptor antagonist DL (-)2-amino-5 phosphonovaleric acid. Our findings suggest that in human hippocampal neurons, the antiepileptic effect of JSTX-3 is mediated by its action on N-methyl-D-aspartate receptor.

Antiepileptic effect of acylpolyaminetoxin JSTX-3 on rat hippocampal CA1 neurons in vitro.

The Joro spider toxin (JSTX-3), derived from Nephila clavata, has been found to block glutamate excitatory activity. Epilepsy has been studied in vitro, mostly on rat hippocampus, through brain slices techniques. The aim of this study is to verify the effect of the JSTX-3 on the epileptiform activity induced by magnesium-free medium in rat CA1 hippocampal neurons. Experiments were performed on hippocampus slices of control and pilocarpine-treated Wistar rats, prepared and maintained in vitro. Epileptiform activity was induced through omission of magnesium from the artificial cerebrospinal fluid (0-Mg2+ ACSF) superfusate and iontophoretic application of N-methyl-D-aspartate (NMDA). Intracellular recordings were obtained from CA1 pyramidal neurons both of control and epileptic rats. Passive membrane properties were analyzed before and after perfusion with the 0-Mg2+ ACSF and the application of toxin JSTX-3. During the ictal-like activity, the toxin JSTX-3 was applied by pressure ejection, abolishing this activity. This effect was completely reversed during the washout period when the slices were formerly perfused with artificial cerebrospinal fluid (ACSF) and again with 0-Mg2+ ACSF. Our results suggest that the toxin JSTX-3 is a potent blocker of induced epileptiform activity.

Estudo eletrofisiológico das propriedades neuronais intrínsicas passivas de CAI em fatias hipocampais de ratos e tecido humano / Electrophysiological study of the intrinsic passive properties neurons of the CAI in slices hippocampal rats and hippocampal human tissue

O presente estudo tem como objetivo verificar a utilização de ratos como controle experimentais para estudos In vitro com tecido hipocampal humano. As fatias obtidas de hipocampo de ratos Wistar machos (espessura de 400 um) e amostras de tecido hipocampal humano (espessura 500um) removidos durante o procedimento cirúrgico para o tratamento de epilepsia de lobo temporal refratária ao tratamento medicamentoso. As fatias mantidas imersas numa cuba com solução de Ringer em temperatura ambiente continuamente oxigenadas e posteriormente transferidas para uma cãmara de interface para registro eletrofisiológico. Registros intracelulares foram obtidos a partir dos neurônios piramidais de CA1 de ratos controles (CR), epilépticos no modelo da pilocarpina (ER) e tecido hipocampal humanos (HHT). Foram avaliadas as propriedades passivas (potencial de membrana, resistência de entrada, constante de tempo) antes e depois da perfusão com o Ringer O-Mg2+. A análise entre CR (n: 40) e ER (n:22) não demonstrou diferenças significativas nas propriedades estudadas. Entre CR e HHT (n:30) não foram observadas diferenças significativas nas propriedades intrínsecas passivas. A análise entre ET e HHT não revelou diferença no potencial de membrana e resistência de entrada, porém a constante de tempo antes da perfusão com o Ringer O-Mg2+ apresentou diferença. Nossos achados sugerem que neurônios hipocampais de CAI de ratos são válidos como grupo controle para estudos experimentais com tecido hipocampal humano