Impaired Cholesterol Metabolism, Neurons, and Neuropsychiatric Disorders

Cholesterol metabolism plays an essential role in cellular functions (including as a component of the plasma membrane, as an energy source, and in hormone production) under normal conditions. Dysregulated cholesterol metabolism causes a wide spectrum of pathological conditions, leading to neuropsychiatric disorders, such as anxiety and depression. In addition, patients with neuropsychiatric disorders also have impaired cholesterol metabolism. Therefore, metabolic disturbances are closely associated with the neuropsychiatric disorders. Although immune disturbance, neuroinflammation, a dysregulated neurotransmitter system, and oxidative stress have been suggested as pathophysiology of neuropsychiatric disorders, dysregulation of cholesterol metabolism is also found in patients with psychiatric diseases. As expected, patients with mental illness appear to be at risk of metabolic disorders, including metabolic syndrome, in which cholesterol influences altered neuronal homeostasis, such as neuronal cell toxicity, neuronal cell death, and neuronal structures and functions, including synaptogenesis, neurogenesis, axonogenesis, and action potential. Therefore, reversing impaired or abnormal cholesterol metabolism may help restore neuronal injury found in mental illness. This review is aimed to discuss the links between cholesterol metabolism impairment and neuropsychiatric disorders and provides insights into neuronal dysfunction due to abnormal cholesterol metabolism in neuropsychiatric disorders.

Autophagy Enhancers Regulate Cholesterol-Induced Cytokine Secretion and Cytotoxicity in Macrophages

Objective@#Hypercholesterolaemia transforms macrophages into lipid-laden foam cells in circulation, which can activate the immune response. Compromised autophagy and inflammatory cytokines are involved in the pathogenesis and progression of metabolic diseases.The aim of this study was to identify the role of autophagy as a modulator of the inflammatory response and cytotoxicity in macrophages under hypercholesterolaemic conditions. @*Methods@#High cholesterol-induced cytokine secretion and alteration of autophagyassociated molecules were confirmed by cytokine array and western blot analysis, respectively. To confirm whether autophagic regulation affects high cholesterol-induced cytokine release and cytotoxicity, protein levels of autophagic molecules, cell viability, and cytotoxicity were measured in cultured macrophages treated autophagy enhancers. @*Results@#Cholesterol treatment increased cytokine secretion, cellular toxicity, and lactate dehydrogenase release in lipopolysaccharide (LPS)-primed macrophages. Concomitantly, altered levels of autophagy-related molecules were detected in LPS-primed macrophages under hypercholesterolaemic conditions. Treatment with autophagy enhancers reversed the secretion of cytokines, abnormally expressed autophagy-associated molecules, and cytotoxicity of LPS-primed macrophages. @*Conclusion@#Autophagy enhancers inhibit inflammatory cytokine secretion and reduce cytotoxicity under metabolic disturbances, such as hypercholesterolaemia. Modulation of autophagy may be a novel approach to control the inflammatory response observed in metabolic diseases.

Extracellular Vesicles and Immune System in Ageing and Immune Diseases

Immune system is essential for host homeostasis. Immune cells communicate with each other by binding to receptors or by releasing vesicles including chemokines and cytokines. Under healthy circumstances, immune cell-derived factors are critical for cellular growth, division and function, whereas under conditions such as ageing and inflammatory states, they can aggravate pathologies and cause disease. Cell-derived membranous extracellular vesicles mediate cell-to-cell communication and are implicated in various physiological and pathological processes involving ageing and age-related diseases. Extracellular vesicles are responsible for spreading detrimental factors to the surroundings and the propagation phase of inflammatory diseases. The regulation of extracellular vesicles is a putative target for treatment of inflammatory diseases. Moreover, their features are ideal for developing biomarkers and drug delivery systems modulated by bioengineering in inflammatory diseases. The present review summarizes the current understanding of extracellular vesicles in ageing and inflammatory diseases.

Autophagy, Cellular Aging and Age-related Human Diseases

Macroautophagy/autophagy is a conserved degradation system that engulfs intracytoplasmic contents, including aggregated proteins and organelles, which is crucial for cellular homeostasis. During aging, cellular factors suggested as the cause of aging have been reported to be associated with progressively compromised autophagy. Dysfunctional autophagy may contribute to age-related diseases, such as neurodegenerative disease, cancer, and metabolic syndrome, in the elderly. Therefore, restoration of impaired autophagy to normal may help to prevent age-related disease and extend lifespan and longevity. Therefore, this review aims to provide an overview of the mechanisms of autophagy underlying cellular aging and the consequent disease. Understanding the mechanisms of autophagy may provide potential information to aid therapeutic interventions in age-related diseases.

Postoperative cognitive dysfunction: advances based on pre-clinical studies

Postoperative cognitive dysfunction (POCD) occurs immediately after surgery and is characterized by impairment of memory and changes in cognition. POCD can last for several months or years and have adverse effects including delayed hospital stays, diminished function in daily life, and increased complications and mortality. Despite improvements in surgical technique, anesthesia management, and intensive care, many patients suffer from POCD. POCD is one of the important clinical issues in surgical management and understanding its pathophysiology is necessary. In this review, therefore, we have focused on animal models of POCD and measurements of cognitive ability in preclinical studies, and we have suggested novel approaches for prevention/treatment of POCD. In preclinical studies, major abdominal surgery (laparotomy, hepatectomy, and splenectomy), minor abdominal surgery (laparotomy, probe exploration), and tibial fracture surgery, are used as POCD models. In addition, cognitive function is assessed by Morris water maze, passive avoidance task, elevated plus maze, and T maze test. Neuroinflammation, blood-brain barrier dysfunction, beta amyloid deposition, and tau phosphorylation are suggested as pathological mechanisms of POCD in preclinical studies. Based on several studies of these, we suggest erythropoietin, nuclear factor kappa B, interleukin17A, tumor necrosis factor alpha, and nicotinamide adenine dinucleotide phosphate oxidase 2 as candidates for prevention/treatment of POCD. In the preclinical stage, drug development/exploration and research is being carried out to solve cognitive dysfunction after surgery. Ultimately, based on the results of preclinical studies, we expect to overcome POCD.

Intranasal Administration of Interleukin-1 Receptor Antagonist in a Transient Focal Cerebral Ischemia Rat Model

The interleukin-1 receptor antagonist (IL-1RA) is a potential stroke treatment candidate. Intranasal delivery is a novel method thereby a therapeutic protein can be penetrated into the brain parenchyma by bypassing the blood-brain barrier. Thus, this study tested whether intranasal IL-1RA can provide neuroprotection and brain penetration in transient cerebral ischemia. In male Sprague-Dawley rats, focal cerebral ischemia was induced by middle cerebral artery occlusion (MCAO) for 1 h. The rats simultaneously received 50 mg/kg human IL-1RA through the intranasal (IN group) or intraperitoneal route (IP group). The other rats were given 0.5 mL/kg normal saline (EC group). Neurobehavioral function, infarct size, and the concentration of the administered human IL-1RA in the brain tissue were assessed. In addition, the cellular distribution of intranasal IL-1RA in the brain and its effect on proinflammatory cytokines expression were evaluated. Intranasal IL-1RA improved neurological deficit and reduced infarct size until 7 days after MCAO (p<0.05). The concentrations of the human IL-1RA in the brain tissue 24 h after MCAO were significantly greater in the IN group than in the IP group (p<0.05). The human IL-1RA was confirmed to be co-localized with neuron and microglia. Furthermore, the IN group had lower expression of interleukin-1β and tumor necrosis factor-α at 6 h after MCAO than the EC group (p<0.05). These results suggest that intranasal IL-1RA can reach the brain parenchyma more efficiently and provide superior neuroprotection in the transient focal cerebral ischemia.

Apoptosis signal-regulating kinase 1 (ASK1) is linked to neural stem cell differentiation after ischemic brain injury

Neural stem cells (NSCs) have been suggested as a groundbreaking solution for stroke patients because they have the potential for self-renewal and differentiation into neurons. The differentiation of NSCs into neurons is integral for increasing the therapeutic efficiency of NSCs during inflammation. Apoptosis signal-regulating kinase 1 (ASK1) is preferentially activated by oxidative stress and inflammation, which is the fundamental pathology of brain damage in stroke. ASK1 may be involved in the early inflammation response after stroke and may be related to the differentiation of NSCs because of the relationship between ASK1 and the p38 mitogen-activated protein kinase pathway. Therefore, we investigated whether ASK1 is linked to the differentiation of NSCs under the context of inflammation. On the basis of the results of a microarray analysis, we performed the following experiments: western blot analysis to confirm ASK1, DCX, MAP2, phospho-p38 expression; fluorescence-activated cell sorting assay to estimate cell death; and immunocytochemistry to visualize and confirm the differentiation of cells in brain tissue. Neurosphere size and cell survival were highly maintained in ASK1-suppressed, lipopolysaccharide (LPS)-treated brains compared with only LPS-treated brains. The number of positive cells for MAP2, a neuronal marker, was lower in the ASK1-suppressed group than in the control group. According to our microarray data, phospho-p38 expression was inversely linked to ASK1 suppression, and our immunohistochemistry data showed that slight upregulation of ASK1 by LPS promoted the differentiation of endogenous, neuronal stem cells into neurons, but highly increased ASK1 levels after cerebral ischemic damage led to high levels of cell death. We conclude that ASK1 is regulated in response to the early inflammation phase and regulates the differentiation of NSCs after inflammatory-inducing events, such as ischemic stroke.