CNS & Neurological Disorders - Drug Targets (Formerly Current Drug Targets - CNS & Neurological Disorders) - Volume 20, Issue 3, 2021

Delirium is a clinical syndrome characterized by a temporary organic mental disorder, as well as abnormal attention and cognition. It is a very common, serious, and costly disease with high misdiagnosis and death/disability rates, especially for older patients after surgery. Several factors, such as systemic neuroinflammation, neurotransmitters, cerebral hypoperfusion and microthrombosis, contribute to the progress of delirium; however, the exact pathophysiologic mechanisms are not well known. Therefore, there are no specific therapeutic approaches that can treat delirium effectively. Statins, as inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, have been identified as potential medications for the treatment of delirium because they can significantly reduce the incidence of delirium. The major objective of the current review is to summarize recent advances in the understanding of the effects and mechanisms of statins on delirium. In basic research, statins can alleviate delirium via attenuation of neuroinflammation, neurotransmitters, cerebral hypoperfusion, and microthrombosis, which may highlight their potential clinical application for the treatment of delirium. Despite this, the clinical effects of statins still provoke debate.

Traumatic Brain Injury (TBI) is still the worldwide leading cause of mortality and morbidity in young adults. Improved safety measures and advances in critical care have increased chances of surviving a TBI, however, numerous secondary mechanisms contribute to the injury in the weeks and months that follow TBI. The past 4 decades of research have addressed many of the metabolic impairments sufficient to mitigate mortality, however, an enduring secondary mechanism, i.e. neuroinflammation, has been intractable to current therapy. Neuroinflammation is particularly difficult to target with pharmacological agents due to lack of specificity, the blood brain barrier, and an incomplete understanding of the protective and pathologic influences of inflammation in TBI. Recent insights into TBI pathophysiology have established microglial activation as a hallmark of all types of TBI. The inflammatory response to injury is necessary and beneficial while the death of activated microglial is not. This review presents new insights on the therapeutic and maladaptive features of the immune response after TBI with an emphasis on microglial polarization, followed by a discussion of potential targets for pharmacologic and non-pharmacologic treatments. In aggregate, this review presents a rationale for guiding TBI inflammation towards neural repair and regeneration rather than secondary injury and degeneration, which we posit could improve outcomes and reduce lifelong disease burden in TBI survivors.

Ischemic neuronal injury results from a complex series of pathophysiological events, including oxidative, excitotoxicity, inflammation and nitrative stress. Consequently, many of these events can induce cell death, including necrosis (unregulated cell death) and apoptosis (a type of regulated cell death). These are long-established paradigms to which newly discovered regulated cell death processes have been added, such as necroptosis (a regulated form of necrosis) and autophagydependent cell death. Moreover, many researchers have targeted products associated with Chinese herbal medicine at regulated pathways for the treatment of ischemic neuronal injury. In East Asia, these drugs have been known for centuries to protect and improve the nervous system. Herbal extracts, especially those used in Chinese herbal medicine, have emerged as new pharmaceuticals for the treatment of ischemic neuronal injury. Here, we review the evidence from preclinical studies investigating the neuroprotective properties and therapeutic application of Chinese herbal medicines (Chinese herbal monomer, extract, and medicinal compounds) and highlight the potential mechanisms underlying their therapeutic effects via targeting differently regulated cell death pathways. Notably, many herbs have been shown to target multiple mechanisms of regulated cell death and, in combination, may exert synergistic effects on signaling pathways, thereby attenuating multiple aspects of ischemic pathology. In this review, we summarize a generally regulated pathway of cell death as a target for novel natural herbal regimens against ischemic neuronal injury.

Aims: Our work aims to revealing the underlying microtubule mechanism of neurites outgrowth during neuronal development and also proposes a feasible intervention pathway for reconstructing neural network connections after nerve injury. Background: Microtubule polymerization and severing form the basis for neurite outgrowth and branch formation. However, the mechanisms that underlie the dynamic instability of microtubules are unclear. Here, we showed that neurite outgrowth mediated by collapsing response mediator protein 2 (CRMP2) can be enhanced by spastin, which had an effect on the severing of microtubule cytoskeleton. Objective: To explore whether neurite outgrowth was mediated by coordination of CRMP2 and spastin. Methods: Hippocampal neurons were cultured in vitro in 24-well culture plates for 4 days before being used to perform the transfection. Calcium phosphate was used to transfect the CRMP2 and spastin constructs and their control into the neurons. An interaction between CRMP2 and spastin was examined by using pull down, CoIP and immunofluorescence colocalization assays. And immunostaining was also performed to determine the morphology of neurites. Results: We first demonstrated that CRMP2 interacted with spastin to promote neurite outgrowth and branch formation. Then our results identified that CRMP2 interacted with the microtubule- binding domain of spastin via its C-terminus, and deleting these binding sites inhibited neurite outgrowth and branch formation. In addition, we confirmed one phosphorylation site at S210 of spastin in hippocampal neurons. Spastin phosphorylation at S210 failed to alter the binding affinity of CRMP2 but inhibited its binding to microtubules. Further study showed that phosphorylation spastin at S210 inhibited the neurite outgrowth induced by CRMP2 and spastin interaction through downregulation of microtubule-severing activity. Conclusion: Taken together, our data demonstrated that both CRMP2 and spastin interaction and the microtubule-severing activity of spastin were required for neurite outgrowth and branch formation.

Background: Perampanel is a highly selective and non-competitive α-amino-3-hydroxy- 5 -methyl-4-isoxazole propionate (AMPA) receptor (AMPAR) antagonist, which has been licensed as an orally administered antiepileptic drug in more than 55 countries. Recently, perampanel was found to exert neuroprotective effects in hemorrhagic and ischemic stroke models. Objective: In this study, the protective effect of perampanel was investigated. Methods: The protective effect of perampanel was investigated in an in vitro Traumatic Neuronal Injury (TNI) model in primary cultured cortical neurons. Results: We found that perampanel significantly preserved morphological changes, attenuated lactate dehydrogenase (LDH) release and inhibited caspase-3 activation after TNI. The TNI-induced necroptosis, as evidenced by flow cytometry, was markedly reduced by perampanel treatment. The results of western blot showed that perampanel decreased the expression and phosphorylation of the necroptotic factors, receptor protein interacting kinase 1 (RIPK1) and RIPK3. In addition, treatment with perampanel increased the phosphorylation of Akt and GSK3β in a time-dependent manner up to 24 h after TNI. Treatment with the Akt inhibitor LY294002 partially reversed the protective effects of perampanel. Conclusion: Our present data suggest that necroptosis plays a key role in the pathogenesis of neuronal death after TNI, and that perampanel might have therapeutic potential for patients with Traumatic Brain Injury (TBI).

Background: The long interspersed element-1 (L1) participates in memory formation, and DNA methylation patterns of L1 may suggest resilience or vulnerability factors for Post-Traumatic Stress Disorder (PTSD), of which the principal manifestation is a pathological exacerbation of fear memory. However, the unique roles of L1 in the reconsolidation of fear memory remain poorly understood. Objective: The study aimed to investigate the role of L1 in the reconsolidation of context-dependent fear memory. Methods: Mice underwent fear conditioning and fear recall in the observation chambers. Fear memory was assessed by calculating the percentage of time spent freezing in 5 min. The medial prefrontal cortex (mPFC) and hippocampus were removed for further analysis. Open Reading Frame 1 (ORF1) mRNA and ORF2 mRNA of L1 were analyzed by real-time quantitative polymerase chain reaction. After reactivation of fear memory, lamivudine was administered and its effects on fear memory reconsolidation were observed. Results: ORF1 and ORF2 mRNA expressions in the mPFC and hippocampus after recent (24 h) and remote (14 days) fear memory recall exhibited augmentation via different temporal and spatial patterns. Reconsolidation of fear memory was markedly inhibited in mice treated with lamivudine, which could block L1. DNA methyltransferase mRNA expression declined following lamivudine treatment in remote fear memory recall. Conclusion: The retrotransposition of L1 participated in the reconsolidation of fear memory after reactivation of fear memory, and with lamivudine treatment, spontaneous recovery decreased with time after recent and remote fear memory recall, providing clues for understanding the roles of L1 in fear memory.

Background: Glaucoma is a multifactorial optic neuropathy progressively characterized by structural loss of Retinal Ganglion Cells (RGCs) and irreversible loss of vision. High Intraocular Pressure (HIOP) is a high-risk factor for glaucoma. It has been reported that the mechanisms of the loss of RGCs are explored in-depth after acute HIOP injury, such as apoptosis, autophagy, and necrosis. However, pyroptosis, a novel type of pro-inflammatory cell programmed necrosis, is rarely reported after HIOP injury. Research studies also showed that melatonin (MT) possesses substantial anti-inflammatory properties. However, whether melatonin could alleviate retinal neuronal death, especially pyroptosis, by HIOP injury is still unclear. Objective: This study explored pyroptosis of retinal neurons and the effects of melatonin in preventing retinal neurons from pyroptosis after acute HIOP injury. Methods: An acute HIOP model of rats was established by increasing the IOP followed by reperfusion. Western Blot (WB) was adopted to detect molecules related to pyroptosis at the protein level, such as GSDMD, GASMDp32, Caspase-1, and caspase-1 p20, and the products of inflammatory reactions, such as IL -18 and IL-1β. At the same time, immunofluorescence (IF) was used to co-localize caspase-1 with retinal neurons to determine the position of caspase-1 expression. Morphologically, ethidium homodimer III staining, a method commonly used to evaluate cell death, was carried out to stain dead cells. Subsequently, Lactate Dehydrogenase (LDH) cytotoxicity assay kit was used to quantitatively analyze the LDH released after cell disruption. Results: The results suggested that pyroptosis played a vital role in retinal neuronal death, especially in the Ganglion Cell Layer, by acute HIOP injury and peaked at 6h after HIOP injury. Furthermore, it was found that melatonin (MT) might prevent retinal neurons of pyroptosis via NF-Κ B/NLRP3 axis after HIOP injury in rats. Conclusion: Melatonin treatment might be considered a new strategy for protecting retinal neurons against pyroptosis following acute HIOP injury.

Background: Traumatic Spinal Cord Injury (SCI) is a severe condition usually accompanied by an inflammatory process that gives rise to uncontrolled local apoptosis and a subsequent unfavorable prognosis. One reason for this unfavorable outcome could be the activation of the NLRP3 inflammasome. Objective: MCC950 is a specific inhibitor of NLRP3 that further inhibits the formation of the NLRP3 inflammasome. The purpose of this study was to determine whether the NLRP3 inflammasome was associated with the severity of local apoptosis and whether MCC950 could prevent neuronal apoptosis following SCI. Methods: In this study, primary cortical neurons were cultured in vitro. With or without pretreatment/ posttreatment with MCC950, neurons were subjected to Oxygen-Glucose Deprivation (OGD) for 2 h and then reperfusion for 20 h. Immunofluorescence was used to determine the expression of NLRP3, ASC, and cleaved caspase-1 in neurons. In vivo, SCI model mice were established with a 5 g weight-drop method. MCC950 was intraperitoneally injected at 0, 2, 4, 6, 8, 10, and 12 days after SCI. Basso Mouse Scale (BMS) scores and footprint assays were used to assess motor function. Paw withdrawal threshold and tail-flick latency were used to assess somatosensory function. H&E, Nissl, and TUNEL staining were used to measure histological changes and apoptosis at 3 days after SCI, and scar formation was observed by Masson staining and GFAP immunohistochemical analysis at 28 days after SCI. Results: Immunofluorescence analysis confirmed that MCC950 inhibited OGD-induced activation of the NLRP3 inflammasome in neurons. Behavioral tests, Masson staining, and GFAP immunohistochemical analysis showed that MCC950-treated mice had improved neuronal functional recovery and reduced scar formation at 28 days after SCI. H, Nissl, and TUNEL staining confirmed that there were more living neurons and fewer apoptotic neurons in MCC950-treated mice than control mice at 3 days after SCI. Conclusion: These results reveal that MCC950 exerts neuroprotective effects by reducing neuronal apoptosis, preserving the survival of the remaining neurons, attenuating the severity of the damage, and promoting the recovery of motor function after SCI.