nNOS-mediated protein-protein interactions:promising targets for treating neurological and neuropsychiatric disorders

Neurological and neuropsychiatric disorders are one of the leading causes of disability worldwide and affect the health of billions of people.Nitric oxide(NO),a free gas with multitudinous bioactivities,is mainly produced from the oxidation of L-arginine by neuronal nitric oxide synthase(nNOS)in the brain.Inhibiting nNOS benefits a variety of neurological and neuropsychiatric disorders,including stroke,depression and anxiety disorders,posttraumatic stress disorder,Parkinson’s disease,Alzheimer’s disease,chronic pain,and drug addiction.Due to critical roles of nNOS in learning and memory and synaptic plasticity,direct inhibition of nNOS may cause severe side effects.Importantly,interactions of several proteins,including post-synaptic density 95(PSD-95),carboxyterminal PDZ ligand of nNOS(CAPON)and serotonin transporter(SERT),with the PSD/Disc-large/ZO-1 homologous(PDZ)domain of nNOS have been demonstrated to influence the subcellular distribution and activity of the enzyme in the brain.Therefore,it will be a preferable means to interfere with nNOS-mediated proteinprotein interactions(PPIs),which do not lead to undesirable effects.Herein,we summarize the current literatures on nNOS-mediated PPIs involved in neurological and neuropsychiatric disorders,and the discovery of drugs targeting the PPIs,which is expected to provide potential targets for developing novel drugs and new strategy for the treatment of neurological and neuropsychiatric disorders.

(＋)-Borneol is neuroprotective against permanent cerebral ischemia in rats by suppressing production of proinflammatory cytokines

Stroke is one of the leading causes of disability and death globally.It occurs when a major artery is occluded in the brain and leads to death of cells within the injured tissue.（＋）-Borneol,a simple bicyclic monoterpene extracted from traditional Chinese medicine,is widely used in various types of diseases.However,no study has proved the effects of（＋）-borneol on functional recovery from permanent ischemic stroke and the mechanism is still unknown.Here,we report that in the rat model of permanent cerebral ischemia,we found that（＋）-borneol（1.0 mg/kg） significantly ameliorated infarct size and neurological scores via reducing the expression of inducible nitric oxide synthase（iNOS）and tumor necrosis factor-alpha（TNF-α） in a dose dependent manner.Notably,（＋）-borneol showed long-term effects on the improvement of sensorimotor functions in the photothrombotic model of stroke,which decreased the number of foot faults in the grid-walking task and forelimb asymmetry scores in the cylinder task,at least in part through reducing loss of dendritic spines in the length,brunch number and density.These findings suggest that（＋）-borneol could serve as a therapeutic target for ischemic stroke.

Phosphofructokinase-1 Negatively Regulates Neurogenesis from Neural Stem Cells

Phosphofructokinase-1（PFK-1）,a major regulatory glycolytic enzyme,has been implicated in the functions of astrocytes and neurons.Here,we report that PFK-1 negatively regulates neurogenesis from neural stem cells（NSCs）by targeting pro-neural transcriptional factors.Using in vitro assays,we found that PFK-1 knockdown enhanced,and PFK-1 overexpression inhibited the neuronal differentiation of NSCs,which was consistent with the findings from NSCs subjected to 5 h of hypoxia.Meanwhile,the neurogenesis induced by PFK-1 knockdown was attributed to the increased proliferation of neural progenitors and the commitment of NSCs to the neuronal lineage.Similarly,in vivo knockdown of PFK-1 also increased neurogenesis in the dentate gyrus of the hippocampus.Finally,we demonstrated that the neurogenesis mediated by PFK-1 was likely achieved by targeting mammalian achaete-scute homologue-1（Mash 1）,neuronal differentiation factor（NeuroD）,and sex-determining region Y（SRY）-related HMG box 2（Sox2）.All together,our results reveal PFK-1 as an important regulator of neurogenesis.

2-Methyl-5H-benzo[d]pyrazolo[5,1-b][1,3]oxazin-5-imine, an edaravone analog, exerts neuroprotective effects against acute ischemic injury via inhibiting oxidative stress

Oxidative stress plays an indispensable role in the pathogenesis of cerebral ischemia.Inhibiting oxidative stress has been considered as an effective approach for stroke treatment.Edaravone,a free radical scavenger,has been shown to prevent cerebral ischemic injury.However,the clinical efficacy of edaravone is limited because it has a low scavenging activity for superoxide anions（O_2-（·-））.Here,we report that 2-methyl-5 H-benzo[d]pyrazolo[5,1-b][1,3]oxazin-5-imine,a novel small-molecule compound structurally related to edaravone,showed a stronger inhibitory effect on oxidative stress in vitro.In vivo,2-methyl-5 H-benzo[d]pyrazolo[5,1-b][1,3]oxazin-5-imine reversed transient middle cerebral artery occlusion-induced dysfunctions of superoxide dismutases and malondialdehyde,two proteins crucial for oxidative stress,suggesting a strengthened antioxidant system.Moreover,2-methyl-5 H-benzo[d]pyrazolo[5,1-b][1,3]oxazin-5-imine decreased blood brain barrier permeability.Then,we found that 2-methyl-5 Hbenzo[d]pyrazolo[5,1-b][1,3]oxazin-5-imine had a stronger neuroprotective effect than edaravone.More importantly,2-methyl-5 H-benzo[d]pyrazolo[5,1-b][1,3]oxazin-5-imine decreased not only infarct size and neurological deficits in the acute phase but also modified neurological severity score and escape latency in Morris water maze task in the delayed period,indicating enhanced neuroprotection,sensorimotor function and spatial memory.Together,these findings suggest that 2-methyl-5 H-benzo[d]pyrazolo[5,1-b][1,3]oxazin-5-imine could be a preferable option for stroke treatment.

Projections from Infralimbic Cortex to Paraventricular Thalamus Mediate Fear Extinction Retrieval

The paraventricular nucleus of the thalamus(PVT),which serves as a hub,receives dense projections from the medial prefrontal cortex(mPFC)and projects to the lateral division of central amygdala(CeL).The infralimbic(IL)cortex plays a crucial role in encoding and recalling fear extinction memory.Here,we found that neurons in the PVT and IL were strongly activated during fear extinction retrieval.Silencing PVT neurons inhibited extinction retrieval at recent time point(24 h after extinction),while activating them promoted extinction retrieval at remote time point(7 d after extinction),suggesting a critical role of the PVT in extinction retrieval.In the mPFC-PVT circuit,projections from IL rather than prelimbic cortex to the PVT were dominant,and disrupting the IL-PVT projection suppressed extinction retrieval.Moreover,the axons of PVT neurons preferentially projected to the CeL.Silencing the PVT-CeL circuit also suppressed extinction retrieval.Together,our findings reveal a new neural circuit for fear extinction retrieval outside the classical IL-amygdala circuit.