Bitao Bu

Neural cell cycle dysregulation and central nervous system diseases

The cell cycle is a delicately manipulated process essential for the development, differentiation, proliferation and death of cells. Inappropriate activation of cell cycle regulators is implicated in the pathophysiology of a wide range of central nervous system (CNS) diseases, including both acute damage and chronic neurodegenerative disorders. Cell cycle activation induces the dividing astrocytes and microglia to activate and proliferate in association with glial scar formation and inflammatory factor production, which play crucial roles in the development of pathology in CNS diseases. On the other hand, in terminally differentiated neurons, aberrant re-entry into the cell cycle triggers neuronal death instead of proliferation, which may be a common pathway shared by some acquired and neurodegenerative disorders, even though multiple pathways of the cell cycle machinery are involved in distinct neuronal demise in specific pathological circumstances. In this paper, we first provide a concise description of the roles of cell cycle in neural development. We then focus on how neural cell cycle dysregulation is related to CNS diseases. Neuronal apoptosis is often detected in acute injury to the CNS such as stroke and trauma, which are usually related to the blockade of the cell cycle at the G1-S phase. In neurodegenerative diseases such as Alzheimers disease, Parkinsons disease, amyotrophic lateral sclerosis and Niemann-Pick disease type C, however, some populations of neurons complete DNA synthesis but the cell cycle is arrested at the G2/M transition. This review summarizes advances in findings implicating cell cycle machinery in neuronal death in CNS diseases.

Cyclin-Dependent Kinase Inhibitors Attenuate Protein Hyperphosphorylation, Cytoskeletal Lesion Formation, and Motor Defects in Niemann-Pick Type C Mice

Dysregulation of cyclin-dependent kinases (cdks) and cytoskeletal protein hyperphosphorylation characterizes a subset of human neurodegenerative diseases, including Alzheimers disease, amyotrophic lateral sclerosis, and Niemann-Pick Type C (NPC). It is thought that these cytoskeletal changes lead eventually to development of hallmark cytoskeletal lesions such as neurofibrillary tangles and axonal spheroids. Although many studies support an involvement of cdks in these neurodegenerative cascades, it is not known whether cdk activity is essential. The naturally occurring npc-1 mutant mouse mimics human NPC, in displaying activation of cdk5, mitotic cdc2, and cdk4, with concomitant cytoskeletal pathology and neurodegeneration. We availed of this model and specific pharmacological inhibitors of cdk activity, to determine whether cdks are necessary for NPC neuropathology. The inhibitors were infused intracerebroventricularly for a 2-week period, initiated at a pathologically incipient stage. While an inactive stereoisomer, iso-olomoucine, was ineffective, two potent inhibitors, roscovitine and olomoucine, attenuated significantly the hyperphosphorylation of neurofilament, tau, and mitotic proteins, reduced the number of spheroids, modulated Purkinje neuron death, and ameliorated motor defects in npc mice. These results suggest that cdk activity is required for neuropathology and subsequent motor impairment in NPC. Studies aimed at knocking down individual cdks in these mice will help identify the specific cdk(s) that are essential, and delineate their precise roles in the neurodegenerative process.

Niemann-Pick Disease Type C Yields Possible Clue for Why Cerebellar Neurons Do Not Form Neurofibrillary Tangles ☆

It is unknown why cerebellar neurons resist neurofibrillary tangle (NFT) formation. In Niemann-Pick disease Type C (NPC), NFT-mediated neurodegeneration occurs throughout brain, but the cerebellum degenerates conspicuously without NFT. To understand why, we have studied markers of NFT pathogenesis in cerebellum from 17 NPC cases, all having abundant NFT in forebrain. Remarkably, we found that NPC cerebella display several early markers of NFT formation, i.e., hyperphosphorylated tau and an array of cell cycle regulators, suggesting that cerebellar neurons in NPC undergo similar modifications as other neurons that develop NFT. However, cerebellar neurons are deficient in tau, the building block of NFT, and this may be one reason for their inability to form NFT. Even without NFT, cerebellar neurodegeneration may be triggered by the inappropriate activation of the cell cycle cdc2 kinase, and the npc-1 murine model provides an opportunity to test this hypothesis.

Glial gap junctional communication involvement in hippocampal damage after middle cerebral artery occlusion

Most patients with stroke casued by middle cerebral artery occlusion (MCAO) show cognitive deficit that is generally regarded as resulting from damage to the cerebral cortex rather than the hippocampus. Whether MCAO induces hippocampal damage and whether this contributes to the cognitive defects remains unclear. Here we investigate the hippocampal damage and its correlation to cognitive defects after exclusively unilateral MCAO and the underlying mechanism for that damage.

Risk factors of myasthenic crisis after thymectomy in 178 generalized myasthenia gravis patients in a five-year follow-up study

Purpose: The aims of this study were to assess the clinical characteristics of patients with postoperative myasthenic crisis (PMC) and to identify the risk factors affecting the occurrence of PMC. Method: Extended thymectomy was performed on 178 patients with generalized MG with a mean onset age of 36.8 years. The potentially risk factors were analyzed by binary logistic regression analysis. Result: During the over five-year follow-up, 44 patients (24.7%) experienced 58 episodes of PMC. The mean interval between surgery and the first episodes of PMC was 13.8 months, and for 81.8% of the patients it occurred within the first 2 years after thymectomy. Nine of 16 patients (56.3%) with a history of preoperative MC had recurrent crises. Respiratory tract infection was the most common precipitant of PMC. Univariate analysis showed that age at onset, preoperative MGFA class, preoperative MC, presence of bulbar symptoms, operation duration, amount of intraoperative blood loss, and the presence of thymoma were significantly associated with the occurrence of PMC. However, multivariate logistic regression analysis revealed that a history of preoperative MC (OR = 2.845, p = 0.044), presence of bulbar symptoms (OR = 3.062, p = 0.027), and longer operation duration (OR = 1.026, p = 0.009) were the independent risk factors for PMC. Conclusion: The important risk factors for developing PMC in generalized MG patients include the presence of bulbar symptoms, history of preoperative MC, and longer operation duration. Optimization of the preoperative evaluation and proper perioperative care of MG patients may decrease the frequency of PMC.

Mitotic Epitopes are Incorporated into Age‐dependent Neurofibrillary Tangles in Niemann–Pick Disease Type C

The mechanism underlying neurofibrillary tangles (NFTs) in Alzheimers disease (AD) and other neurodegenerative disorders remains elusive. Niemann–Pick disease type C (NPC) is a kind of genetic neurovisceral disorder in which the intracellular sequestration of cholesterol and other lipids in neurons, NFT formation and neuronal degeneration in brain are the neuropathology hallmarks. The age of onset and progression of the disease vary dramatically. We have analyzed the hippocampus from 17 NPC cases, aged from 7 months to 55 years, to depict the temporal characteristics of NFT formation. Unexpectedly, classic NFT was observed in about 4‐year‐old NPC brain, suggesting that NFT is not aging dependent, and that juvenile brain neurons satisfy the requirements for NFT formation. NFT in the hippocampus of NPC was significantly increased in number with the advance of age. More importantly, multiple mitotic phase markers, which are not usually found in normal mature neurons, were abundant in the affected neurons and incorporated into NFT. The unusual activation of cdc2/cyclin B kinase and downstream mitotic indices are closely associated with the age‐dependent NFT formation, signifying the contribution of abortive cell cycle to neurodegeneration. The cdc2 inhibitors may be therapeutically used for early intervention of neurodegeneration and NFT formation in NPC.

Intracranial Hypertension Syndrome in Systemic Lupus Erythematosus： Clinical Analysis and Review of the Literature

In order to better understand the clinical manifestation of systemic lupus erythematosus (SLE) with intracranial hypertension syndrome (IHS), we analyzed the clinical features and treatment of a typical SLE patient with IHS. SLE is one of the most unpredictable autoimmune diseases involving multiple organ systems that is defined clinically and associated with antibodies directed against cell nuclei. IHS is an uncommon manifestation of neuropsychiatric SLE (NPSLE) and is characterized by an elevated intracranial pressure, papilledema, and headache with occasional abducens nerve paresis, absence of a space-occupying lesion or ventricular enlargement, and normal cerebrospinal fluid chemical and hematological constituents. IHS has been reported in a few sporadic cases in patients with SLE worldwide, but rarely has been reported in China. In this study, a 34-year-old female SLE patient with IHS was reported and pertinent literature reviewed. The clinical presentation, image logical features, and investigatory findings were discussed.SummaryIn order to better understand the clinical manifestation of systemic lupus erythematosus (SLE) with intracranial hypertension syndrome (IHS), we analyzed the clinical features and treatment of a typical SLE patient with IHS. SLE is one of the most unpredictable autoimmune diseases involving multiple organ systems that is defined clinically and associated with antibodies directed against cell nuclei. IHS is an uncommon manifestation of neuropsychiatric SLE (NPSLE) and is characterized by an elevated intracranial pressure, papilledema, and headache with occasional abducens nerve paresis, absence of a space-occupying lesion or ventricular enlargement, and normal cerebrospinal fluid chemical and hematological constituents. IHS has been reported in a few sporadic cases in patients with SLE worldwide, but rarely has been reported in China. In this study, a 34-year-old female SLE patient with IHS was reported and pertinent literature reviewed. The clinical presentation, image logical features, and investigatory findings were discussed.

Behaviour and prefrontal protein differences in C57BL/6N and 129 X1/SvJ mice

Experimental animals provide valuable opportunities to establish aetiological mechanisms and test new treatments for neurodevelopmental psychiatric conditions. However, it is increasingly appreciated that inter-strain differences cannot be neglected in the experimental design. In addition, the importance of including females in preclinical - but also clinical - research is now recognised. Here, we compared behaviour and prefrontal protein differences in male and female C57BL/6N and 129X1/SvJ mice as both are commonly used experimental rodents. Relative to 129X1/SvJ mice, both sexes of C57BL/6N mice had weaker sensorimotor gating, measured in the prepulse inhibition (PPI) of startle paradigm, and were more sensitive to amphetamine challenge in the open field. The pattern of protein expression in the prefrontal cortex of C57BL6N mice was also clearly distinct from 129X1/SvJ mice. Proteins differentially expressed were those associated with oxidative metabolism, receptor protein signalling, cell communication and signal transduction and energy pathways. We suggest that the C57BL/6N mouse may usefully proxy features of the neurodevelopmental disorders and could have application in pre-translational screening of new therapeutic approaches. The 129X1/SvJ strain in contrast, might be better suited to experimental studies of causal risk factors expected to lower PPI and increase amphetamine sensitivity.

Eight‐year follow‐up of patients with myasthenia gravis after thymectomy

To depict the long‐term outcome of patients with myasthenia gravis after thymectomy in combination with immunotherapy, and the factors that may potentially affect the outcome.

Lentivector-mediated RNAi efficiently downregulates expression of murine TNF-α gene in vitro and in vivo

SummaryIn order to explore the role of TNF-α in Niemann-Pick type C (NPC) disease, lentiviral-delivered RNA interference (RNAi) was used to silence the expression of murine TNF-α gene in vitro and in npc mice. Interference efficiency of the lentivirus expressing TNF-α-siRNA, previously constructed with the concentration of 2×108 ifu/mL, was determined by RT-PCR and ELISA in BV-2 cells and astrocytes. At the same time, the constructed Lenti-TNF-α-siRNA was intracerebroven-tricularly infused into 4-week old npc mice for a 4-week period, and the mice were divided into 3 groups: Lenti-TNF-α-siRNA (n=6), control lentivirus (n=6), and NPC mice without any intervention (n=4). By using immunohistochemistry and real-time PCR, the down-regulation of the target genes was detected. The Lenti-TNF-α-siRNA downregulated the expression of murine TNF-α gene efficiently in vitro and the interference efficiency was 66.7%. Lentivirus could be expressed stably for long-term in the npc mice brain. Immunohistochemistry and real-time PCR revealed that, as compared with non-intervention group and Lenti-control group, Lenti-TNF-α-siRNA efficiently down-regulated the expression of murine TNF-α gene with the interference efficiency being 66.9%. TNF-α-siRNA down-regulated the expression of TNF-α gene in vitro and in vivo, which provided a potential tool for studying and treating neurodegenerative diseases and TNF-α-related diseases.In order to explore the role of TNF-α in Niemann-Pick type C (NPC) disease, lentiviral-delivered RNA interference (RNAi) was used to silence the expression of murine TNF-α gene in vitro and in npc mice. Interference efficiency of the lentivirus expressing TNF-α-siRNA, previously constructed with the concentration of 2×108 ifu/mL, was determined by RT-PCR and ELISA in BV-2 cells and astrocytes. At the same time, the constructed Lenti-TNF-α-siRNA was intracerebroven-tricularly infused into 4-week old npc mice for a 4-week period, and the mice were divided into 3 groups: Lenti-TNF-α-siRNA (n=6), control lentivirus (n=6), and NPC mice without any intervention (n=4). By using immunohistochemistry and real-time PCR, the down-regulation of the target genes was detected. The Lenti-TNF-α-siRNA downregulated the expression of murine TNF-α gene efficiently in vitro and the interference efficiency was 66.7%. Lentivirus could be expressed stably for long-term in the npc mice brain. Immunohistochemistry and real-time PCR revealed that, as compared with non-intervention group and Lenti-control group, Lenti-TNF-α-siRNA efficiently down-regulated the expression of murine TNF-α gene with the interference efficiency being 66.9%. TNF-α-siRNA down-regulated the expression of TNF-α gene in vitro and in vivo, which provided a potential tool for studying and treating neurodegenerative diseases and TNF-α-related diseases.