Expression of neuronal nitric oxide synthase in the hippocampal formation in affective disorders

Hippocampal output is increased in affective disorders and is mediated by increased glutamatergic input via N-methyl-D-aspartate (NMDA) receptor and moderated by antidepressant treatment. Activation of NMDA receptors by glutamate evokes the release of nitric oxide (NO) by the activation of neuronal nitric oxide synthase (nNOS). The human hippocampus contains a high density of NMDA receptors and nNOS-expressing neurons suggesting the existence of an NMDA-NO transduction pathway which can be involved in the pathogenesis of affective disorders. We tested the hypothesis that nNOS expression is increased in the human hippocampus from affectively ill patients. Immunocytochemistry was used to demonstrate nNOS-expressing neurons in sections obtained from the Stanley Consortium postmortem brain collection from patients with major depression (MD, N = 15), bipolar disorder (BD, N = 15), and schizophrenia (N = 15) and from controls (N = 15). nNOS-immunoreactive (nNOS-IR) and Nissl-stained neurons were counted in entorhinal cortex, hippocampal CA1, CA2, CA3, and CA4 subfields, and subiculum. The numbers of Nissl-stained neurons were very similar in different diagnostic groups and correlated significantly with the number of nNOS-IR neurons. Both the MD and the BD groups had greater number of nNOS-IR neurons/400 µm² in CA1 (mean ± SEM: MD = 9.2 ± 0.6 and BD = 8.4 ± 0.6) and subiculum (BD = 6.7 ± 0.4) when compared to control group (6.6 ± 0.5) and this was significantly more marked in samples from the right hemisphere. These changes were specific to affective disorders since no changes were seen in the schizophrenic group (6.7 ± 0.8). The results support the current view of the NMDA-NO pathway as a target for the pathophysiology of affective disorders and antidepressant drug development.Stanley FoundationCoordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES

5-HT1A autoreceptor modulation of locomotor activity induced by nitric oxide in the rat dorsal raphe nucleus

The dorsal raphe nucleus (DRN) is the origin of ascending serotonergic projections and is considered to be an important component of the brain circuit that mediates anxiety- and depression-related behaviors. A large fraction of DRN serotonin-positive neurons contain nitric oxide (NO). Disruption of NO-mediated neurotransmission in the DRN by NO synthase inhibitors produces anxiolytic- and antidepressant-like effects in rats and also induces nonspecific interference with locomotor activity. We investigated the involvement of the 5-HT1A autoreceptor in the locomotor effects induced by NO in the DRN of male Wistar rats (280-310 g, N = 9-10 per group). The NO donor 3-morpholinosylnomine hydrochloride (SIN-1, 150, and 300 nmol) and the NO scavenger S-3-carboxy-4-hydroxyphenylglycine (carboxy-PTIO, 0.1-3.0 nmol) were injected into the DRN of rats immediately before they were exposed to the open field for 10 min. To evaluate the involvement of the 5-HT1A receptor and the N-methyl-D-aspartate (NMDA) glutamate receptor in the locomotor effects of NO, animals were pretreated with the 5-HT1A receptor agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT, 8 nmol), the 5-HT1A receptor antagonist N-(2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl)-N-2-pyridinyl-cyclohexanecarboxamide maleate (WAY-100635, 0.37 nmol), and the NMDA receptor antagonist DL-2-amino-7-phosphonoheptanoic acid (AP7, 1 nmol), followed by microinjection of SIN-1 into the DRN. SIN-1 increased the distance traveled (mean ± SEM) in the open-field test (4431 ± 306.1 cm; F7,63 = 2.44, P = 0.028) and this effect was blocked by previous 8-OH-DPAT (2885 ± 490.4 cm) or AP7 (3335 ± 283.5 cm) administration (P < 0.05, Duncan test). These results indicate that 5-HT1A receptor activation and/or facilitation of glutamate neurotransmission can modulate the locomotor effects induced by NO in the DRN

Blood-Brain Barrier Rescue by Roflumilast After Transient Global Cerebral Ischemia in Rats

Phosphodiesterase 4 inhibitors (PDE4-I), which selectively increase cyclic adenosine monophosphate (cAMP) levels, have shown neuroprotective effects after several neurological injuries inducing blood-brain barrier (BBB) damage including local/focal cerebral ischemia. The present investigated whether roflumilast confers BBB neuroprotection in the hippocampus after transient global cerebral ischemia (TGCI) in rats. TGCI resulted in whole BBB disruption as measured by the increase of Evans blue (EB) and IgG extravasation, neurodegeneration, and downregulation of claudin-5 and endothelial nitric oxide synthase (eNOS) levels in the CA1 hippocampal subfield of ischemic rats. Roflumilast attenuated BBB disruption and restored the levels of eNOS in the CA1 hippocampal area. Moreover, roflumilast increased the levels of B2 cell lymphoma (BcL-2) and neuron-glial antigen-2 (NG2) in the CA1 subfield after global ischemia in rats. The protective effects of roflumilast against TGCI-induced BBB breakdown might involve preservation of BBB integrity, vascularization and angiogenesis, and myelin repair

5-HT1A autoreceptor modulation of locomotor activity induced by nitric oxide in the rat dorsal raphe nucleus

The dorsal raphe nucleus (DRN) is the origin of ascending serotonergic projections and is considered to be an important component of the brain circuit that mediates anxiety- and depression-related behaviors. A large fraction of DRN serotonin-positive neurons contain nitric oxide (NO). Disruption of NO-mediated neurotransmission in the DRN by NO synthase inhibitors produces anxiolytic- and antidepressant-like effects in rats and also induces nonspecific interference with locomotor activity. We investigated the involvement of the 5-HT1A autoreceptor in the locomotor effects induced by NO in the DRN of male Wistar rats (280-310 g, N = 9-10 per group). The NO donor 3-morpholinosylnomine hydrochloride (SIN-1, 150, and 300 nmol) and the NO scavenger S-3-carboxy-4-hydroxyphenylglycine (carboxy-PTIO, 0.1-3.0 nmol) were injected into the DRN of rats immediately before they were exposed to the open field for 10 min. To evaluate the involvement of the 5-HT1A receptor and the N-methyl-D-aspartate (NMDA) glutamate receptor in the locomotor effects of NO, animals were pretreated with the 5-HT1A receptor agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT, 8 nmol), the 5-HT1A receptor antagonist N-(2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl)-N-2-pyridinyl-cyclohexanecarboxamide maleate (WAY-100635, 0.37 nmol), and the NMDA receptor antagonist DL-2-amino-7-phosphonoheptanoic acid (AP7, 1 nmol), followed by microinjection of SIN-1 into the DRN. SIN-1 increased the distance traveled (mean ± SEM) in the open-field test (4431 ± 306.1 cm; F7,63 = 2.44, P = 0.028) and this effect was blocked by previous 8-OH-DPAT (2885 ± 490.4 cm) or AP7 (3335 ± 283.5 cm) administration (P < 0.05, Duncan test). These results indicate that 5-HT1A receptor activation and/or facilitation of glutamate neurotransmission can modulate the locomotor effects induced by NO in the DRN

Roflumilast protects against spatial memory impairments and exerts anti-inflammatory effects after transient global cerebral ischemia

Phosphodiesterase 4 (PDE4) inhibitors have been shown to present beneficial effects in cerebral ischemic injury because of their ability to improve cognition and target different phases and mechanisms of cerebral ischemia, including apoptosis, neurogenesis, angiogenesis, and inflammation. The present study investigated whether repeated treatment with the PDE4 inhibitor roflumilast rescued memory loss and attenuated neuroinflammation in rats following transient global cerebral ischemia (TGCI). TGCI caused memory impairments, neuronal loss (reflected by Neuronal nuclei (NeuN) immunoreactivity), and compensatory neurogenesis (reflected by doublecortin (DCX) immunoreactivity) in the hippocampus. Also, increases in the protein expression of the phosphorylated response element-binding protein (pCREB) and inflammatory markers such as the glial fibrillary acidic protein (GFAP) and ionized calcium-binding adaptor molecule 1 (Iba-1), were detected in the hippocampus in TGCI rats. Repeated treatment with roflumilast (0.003 and 0.01 mg/kg) prevented spatial memory deficits without promoting hippocampal protection in ischemic animals. Roflumilast increased the levels of pCREB, arginase-1, interleukin (IL) 4, and IL-10 in the hippocampus 21 days after TGCI. These data suggest a protective effect of roflumilast against functional sequelae of cerebral ischemia, which might be related to its anti-inflammatory properties

Neuroinflammation in Ischemic Stroke: Inhibition of cAMP-Specific Phosphodiesterases (PDEs) to the Rescue

Ischemic stroke is caused by a thromboembolic occlusion of a major cerebral artery, with the impaired blood flow triggering neuroinflammation and subsequent neuronal damage. Both the innate immune system (e.g., neutrophils, monocytes/macrophages) in the acute ischemic stroke phase and the adaptive immune system (e.g., T cells, B cells) in the chronic phase contribute to this neuroinflammatory process. Considering that the available therapeutic strategies are insufficiently successful, there is an urgent need for novel treatment options. It has been shown that increasing cAMP levels lowers neuroinflammation. By inhibiting cAMP-specific phosphodiesterases (PDEs), i.e., PDE4, 7, and 8, neuroinflammation can be tempered through elevating cAMP levels and, thereby, this can induce an improved functional recovery. This review discusses recent preclinical findings, clinical implications, and future perspectives of cAMP-specific PDE inhibition as a novel research interest for the treatment of ischemic stroke. In particular, PDE4 inhibition has been extensively studied, and is promising for the treatment of acute neuroinflammation following a stroke, whereas PDE7 and 8 inhibition more target the T cell component. In addition, more targeted PDE4 gene inhibition, or combined PDE4 and PDE7 or 8 inhibition, requires more extensive research