Neurogenesis in primates versus rodents and the value of non-human primate models.

Neurogenesis, the process of generating neurons from neural stem cells, occurs during both embryonic and adult stages, with each stage possessing distinct characteristics. Dysfunction in either stage can disrupt normal neural development, impair cognitive functions, and lead to various neurological disorders. Recent technological advancements in single-cell multiomics and gene-editing have facilitated investigations into primate neurogenesis. Here, we provide a comprehensive overview of neurogenesis across rodents, non-human primates, and humans, covering embryonic development to adulthood and focusing on the conservation and diversity among species. While non-human primates, especially monkeys, serve as valuable models with closer neural resemblance to humans, we highlight the potential impacts and limitations of non-human primate models on both physiological and pathological neurogenesis research.

C9orf72 poly(PR) aggregation in nucleus induces ALS/FTD-related neurodegeneration in cynomolgus monkeys.

Poly(PR) is a dipeptide repeat protein comprising proline and arginine residues. It is one of the translational product of expanded G4C2 repeats in the C9orf72 gene, and its accumulation is contributing to the neuropathogenesis of C9orf72-associated amyotrophic lateral sclerosis and/or frontotemporal dementia (C9-ALS/FTD). In this study, we demonstrate that poly(PR) protein alone is sufficient to induce neurodegeneration related to ALS/FTD in cynomolgus monkeys. By delivering poly(PR) via AAV, we observed that the PR proteins were located within the nucleus of infected cells. The expression of (PR)50 protein, consisting of 50 PR repeats, led to increased loss of cortical neurons, cytoplasmic lipofuscin, and gliosis in the brain, as well as demyelination and loss of ChAT positive neurons in the spinal cord of monkeys. While, these pathologies were not observed in monkeys expressing (PR)5, a protein comprising only 5 PR repeats. Furthermore, the (PR)50-expressing monkeys exhibited progressive motor deficits, cognitive impairment, muscle atrophy, and abnormal electromyography (EMG) potentials, which closely resemble clinical symptoms seen in C9-ALS/FTD patients. By longitudinally tracking these monkeys, we found that changes in cystatin C and chitinase-1 (CHIT1) levels in the cerebrospinal fluid (CSF) corresponded to the phenotypic progression of (PR)50-induced disease. Proteomic analysis revealed that the major clusters of dysregulated proteins were nuclear-localized, and downregulation of the MECP2 protein was implicated in the toxic process of poly(PR). This research indicates that poly(PR) expression alone induces neurodegeneration and core phenotypes associated with C9-ALS/FTD in monkeys, which may provide insights into the mechanisms of disease pathogenesis.

Application of single-cell RNA sequencing in probing oligodendroglia heterogeneity and neurological disorders.

In the central nervous system, oligodendrocytes are highly specialized myelinating glial cells that originate from oligodendrocyte precursor cells. In the past, research centered on the oligodendrocyte development, myelination, and the role of oligodendrocyte lineage in neurological disorders. The emerging single-cell RNA sequencing technology is a new tool to specifically identify cell-types at the transcriptome level, and recently have also been used to investigate oligodendrocyte lineage-related issues. In this review, we summarize the recent developments of single-cell RNA sequencing technologies and their application in the oligodendroglia heterogeneity and neurological disorders, thereby providing new ideas and references for the utilization of single-cell RNA sequencing technology in the research field of oligodendrocyte lineage and neurological disorders.

[Role of N6-methyladenosine RNA methylation in central nervous system: a review].

There are a variety of post-transcriptional modifications in mRNA, which regulate the stability, splicing, translation, transport and other processes of mRNA, followed by affecting cell development, body immunity, learning and cognition and other important physiological functions. m6A modification is one of the most abundant post-transcriptional modifications widely existing in mRNA, regulating the metabolic activities of RNA and affecting gene expression. m6A modified homeostasis is critical for the development and maintenance of the nervous system. In recent years, m6A modification has been found in neurodegenerative diseases, mental diseases and brain tumors. This review summarizes the role of m6A methylation modification in the development, function and related diseases of the central nervous system in recent years, providing potential clinical therapeutic targets for neurological diseases.

Inhibition of CSPG receptor PTPσ promotes migration of newly born neuroblasts, axonal sprouting, and recovery from stroke.

In addition to neuroprotective strategies, neuroregenerative processes could provide targets for stroke recovery. However, the upregulation of inhibitory chondroitin sulfate proteoglycans (CSPGs) impedes innate regenerative efforts. Here, we examine the regulatory role of PTPσ (a major proteoglycan receptor) in dampening post-stroke recovery. Use of a receptor modulatory peptide (ISP) or Ptprs gene deletion leads to increased neurite outgrowth and enhanced NSCs migration upon inhibitory CSPG substrates. Post-stroke ISP treatment results in increased axonal sprouting as well as neuroblast migration deeply into the lesion scar with a transcriptional signature reflective of repair. Lastly, peptide treatment post-stroke (initiated acutely or more chronically at 7 days) results in improved behavioral recovery in both motor and cognitive functions. Therefore, we propose that CSPGs induced by stroke play a predominant role in the regulation of neural repair and that blocking CSPG signaling pathways will lead to enhanced neurorepair and functional recovery in stroke.

Diphtheria toxin induced but not CSF1R inhibitor mediated microglia ablation model leads to the loss of CSF/ventricular spaces in vivo that is independent of cytokine upregulation.

BACKGROUND: Two recently developed novel rodent models have been reported to ablate microglia, either by genetically targeting microglia (via Cx3cr1-creER: iDTR + Dtx) or through pharmacologically targeting the CSF1R receptor with its inhibitor (PLX5622). Both models have been widely used in recent years to define essential functions of microglia and have led to high impact studies that have moved the field forward. METHODS: Using either Cx3cr1-iDTR mice in combination with Dtx or via the PLX5622 diet to pharmacologically ablate microglia, we compared the two models via MRI and histology to study the general anatomy of the brain and the CSF/ventricular systems. Additionally, we analyzed the cytokine profile in both microglia ablation models. RESULTS: We discovered that the genetic ablation (Cx3cr1-iDTR + Dtx), but not the pharmacological microglia ablation (PLX5622), displays a surprisingly rapid pathological condition in the brain represented by loss of CSF/ventricles without brain parenchymal swelling. This phenotype was observed both in MRI and histological analysis. To our surprise, we discovered that the iDTR allele alone leads to the loss of CSF/ventricles phenotype following diphtheria toxin (Dtx) treatment independent of cre expression. To examine the underlying mechanism for the loss of CSF in the Cx3cr1-iDTR ablation and iDTR models, we additionally investigated the cytokine profile in the Cx3cr1-iDTR + Dtx, iDTR + Dtx and the PLX models. We found increases of multiple cytokines in the Cx3cr1-iDTR + Dtx but not in the pharmacological ablation model nor the iDTR + Dtx mouse brains at the time of CSF loss (3 days after the first Dtx injection). This result suggests that the upregulation of cytokines is not the cause of the loss of CSF, which is supported by our data indicating that brain parenchyma swelling, or edema are not observed in the Cx3cr1-iDTR + Dtx microglia ablation model. Additionally, pharmacological inhibition of the KC/CXCR2 pathway (the most upregulated cytokine in the Cx3cr1-iDTR + Dtx model) did not resolve the CSF/ventricular loss phenotype in the genetic microglia ablation model. Instead, both the Cx3cr1-iDTR + Dtx ablation and iDTR + Dtx models showed increased activated IBA1 + cells in the choroid plexus (CP), suggesting that CP-related pathology might be the contributing factor for the observed CSF/ventricular shrinkage phenotype. CONCLUSIONS: Our data, for the first time, reveal a robust and global CSF/ventricular space shrinkage pathology in the Cx3cr1-iDTR genetic ablation model caused by iDTR allele, but not in the PLX5622 ablation model, and suggest that this pathology is not due to brain edema formation but to CP related pathology. Given the wide utilization of the iDTR allele and the Cx3cr1-iDTR model, it is crucial to fully characterize this pathology to understand the underlying causal mechanisms. Specifically, caution is needed when utilizing this model to interpret subtle neurologic functional changes that are thought to be mediated by microglia but could, instead, be due to CSF/ventricular loss in the genetic ablation model.

Differential Role of p53 in Oligodendrocyte Survival in Response to Various Stresses: Experimental Autoimmune Encephalomyelitis, Cuprizone Intoxication or White Matter Stroke.

Promoting oligodendrocyte viability has been proposed as a therapeutic strategy for alleviating many neuronal diseases, such as multiple sclerosis and stroke. However, molecular pathways critical for oligodendrocyte survival under various stresses are still not well known. p53 is a strong tumor suppressor and regulates cell cycle, DNA repair and cell death. Our previous studies have shown that p53 plays an important role in promoting neuronal survival after insults, but its specific role in oligodendrocyte survival is not known. Here, we constructed the mice with oligodendrocyte-specific p53 loss by crossing TRP53flox/flox mice and CNP-cre mice, and found that p53 was dispensable for oligodendrocyte differentiation and myelin formation under physiological condition. In the experimental autoimmune encephalomyelitis (EAE) model, p53 loss of function, specifically in oligodendrocytes, did not affect the EAE disease severity and had no effect on demyelination in the spinal cord of the mice. Interestingly, p53 deficiency in oligodendrocytes significantly attenuated the demyelination of corpus callosum and alleviated the functional impairment of motor coordination and spatial memory in the cuprizone demyelination model. Moreover, the oligodendrocyte-specific loss of p53 provided protection against subcortical white matter damage and mitigated recognition memory impairment in mice in the white matter stroke model. These results suggest that p53 plays different roles in the brain and spinal cord or in response to various stresses. Thus, p53 may be a therapeutic target for oligodendrocyte prevention in specific brain injuries, such as white matter stroke and multiple sclerosis.

Cuprizone-induced demyelination under physiological and post-stroke condition leads to decreased neurogenesis response in adult mouse brain.

Due to the limitation in treatment window of the rtPA (recombinant tissue plasminogen activator), the development of delayed treatment for stroke is needed. We previously reported that there is a difference in neurogenesis and neuroblast migration patterns in different mouse stroke models (proximal and distal middle cerebral artery occlusion models, pMCAo or dMCAo). Specifically, compared to robust neurogenesis and substantial migration of newly born neuroblasts in pMCAo model, dMCAo only illicit limited neurogenesis and migration of neuroblasts towards ischemic area. One potential reason for this difference is the relative location of ischemic area to white matter and the neurogenic niche (subventricular zone, SVZ). Specifically, white matter could serve as a physical barrier or inhibitory factor to neurogenesis and migration in the dMCAo model. Given that a major difference in human and rodent brains is the content of white matter in the brain, in this study, we further characterize these two models and test the important hypothesis that white matter is an important contributing inhibitory factor for the limited neurogenesis in the dMCAo model. We utilized a genetically inducible NSC-specific reporter mouse line (nestin-CreERT2-R26R-YFP) to label and track NSC proliferation, survival and differentiation in ischemic brain. To test whether myelin is inhibitory to neurogenesis in dMCAo model, we demyelinated mouse brains using cuprizone treatment after stroke and examined whether there is enhanced neurogenesis or migration of neuroblasts cells in stroke mice treated with cuprizone. Our data suggests that demyelination of the brain does not result in enhanced neurogenesis or migration of neuroblasts, supporting that myelin is not a major inhibitory factor for stroke-induced neurogenesis. In addition, our results suggest that in non-stroke mice, demyelination causes decreased neurogenesis in adult brain, indicating a potential positive role of myelin in maintenance of adult neural stem cell niche.

Modulation of proteoglycan receptor PTPσ enhances MMP-2 activity to promote recovery from multiple sclerosis.

Multiple Sclerosis (MS) is characterized by focal CNS inflammation leading to the death of oligodendrocytes (OLs) with subsequent demyelination, neuronal degeneration, and severe functional deficits. Inhibitory chondroitin sulfate proteoglycans (CSPGs) are increased in the extracellular matrix in the vicinity of MS lesions and are thought to play a critical role in myelin regeneration failure. We here show that CSPGs curtail remyelination through binding with their cognate receptor, protein tyrosine phosphatase σ (PTPσ) on oligodendrocyte progenitor cells (OPCs). We report that inhibition of CSPG/PTPσ signaling by systemically deliverable Intracellular Sigma Peptide (ISP), promotes OPC migration, maturation, remyelination, and functional recovery in animal models of MS. Furthermore, we report a downstream molecular target of PTPσ modulation in OPCs involving upregulation of the protease MMP-2 that allows OPCs to enzymatically digest their way through CSPGs. In total, we demonstrate a critical role of PTPσ/CSPG interactions in OPC remyelination in MS.

Oligodendrocyte-specific loss of Cdk5 disrupts the architecture of nodes of Ranvier as well as learning and memory.

Myelination of the central nervous system is important for normal motor and sensory neuronal function and recent studies also link it to efficient learning and memory. Cyclin-dependent kinase 5 (Cdk5) is required for normal oligodendrocyte development, myelination and myelin repair. Here we show that conditional deletion of Cdk5 by targeting with CNP (CNP;Cdk5 CKO) results in hypomyelination and disruption of the structural integrity of Nodes of Ranvier. In addition, CNP;Cdk5 CKO mice exhibited a severe impairment of learning and memory compared to controls that may reflect perturbed neuron-glial interactions. Co-culture of cortical neurons with CNP;Cdk5 CKO oligodendrocyte lineage cells resulted in a significant reduction in the density of neuronal dendritic spines. In short term fear-conditioning studies, CNP;Cdk5 CKO mice had decreased hippocampal levels of immediate early genes such as Arc and Fos, and lower levels of p-CREB and p-cofilin suggested these pathways are affected by the levels of myelination. The novel roles of Cdk5 in oligodendrocyte lineage cells may provide insights for helping understand the cognitive changes sometimes seen in demyelinating diseases such as multiple sclerosis.

Inhibition of Drp1 hyper-activation is protective in animal models of experimental multiple sclerosis.

Multiple Sclerosis (MS), a leading neurological disorder of young adults, is characterized by the loss of oligodendrocytes (OLs), demyelination, inflammation and neuronal degeneration. Here we show that dynamin-related protein 1 (Drp1), a mitochondrial fission protein, is activated in primary OL cells exposed to TNF-α induced inflammation or oxidative stress, as well as in EAE-immunized and cuprizone toxicity-induced demyelinating mouse models. Inhibition of Drp1 hyper-activation by the selective inhibitor P110 abolishes Drp1 translocation to the mitochondria, reduces mitochondrial fragmentation and stems necrosis in primary OLs exposed to TNF-α and H2O2. Notably, in both types of mouse models, treatment with P110 significantly reduces the loss of mature OLs and demyelination, attenuates the number of active microglial cells and astrocytes, yet has no effect on the differentiation of oligodendrocyte precursor cells. Drp1 activation appears to be mediated through the RIPK1/RIPK3/MLKL/PGAM5 pathway during TNF-α-induced oligodendroglia necroptosis. Our results demonstrate a critical role of Drp1 hyper-activation in OL cell death and suggest that an inhibitor of Drp1 hyper-activation such as P110 is worth exploring for its ability to halt or slow the progression of MS.

The Activators of Cyclin-Dependent Kinase 5 p35 and p39 Are Essential for Oligodendrocyte Maturation, Process Formation, and Myelination.

The regulation of oligodendrocyte development and myelin formation in the CNS is poorly defined. Multiple signals influence the rate and extent of CNS myelination, including the noncanonical cyclin-dependent kinase 5 (Cdk5) whose functions are regulated by its activators p35 and p39. Here we show that selective loss of either p35 or p39 perturbed specific aspects of oligodendrocyte development, whereas loss of both p35 and p39 completely inhibited the development of mature oligodendrocytes and myelination. In the absence of p35, oligodendrocyte differentiation was delayed, process outgrowth was truncated in vitro, and the patterning and extent of myelination were perturbed in the CNS of p35(-/-) mice. In the absence of p39, oligodendrocyte maturation was transiently affected both in vitro and in vivo. However, loss of both p35 and p39 in oligodendrocyte lineage cells completely inhibited oligodendrocyte progenitor cell differentiation and myelination both in vitro and after transplantation into shiverer slice cultures. Loss of p35 and p39 had a more profound effect on oligodendrocyte development than simply the loss of Cdk5 and could not be rescued by Cdk5 overexpression. These data suggest p35 and p39 have specific and overlapping roles in oligodendrocyte development, some of which may be independent of Cdk5 activation.

Ultrasound guided double injection of blood into cisterna magna: a rabbit model for treatment of cerebral vasospasm.

BACKGROUND: Double injection of blood into cisterna magna using a rabbit model results in cerebral vasospasm. An unacceptably high mortality rate tends to limit the application of model. Ultrasound guided puncture can provide real-time imaging guidance for operation. The aim of this paper is to establish a safe and effective rabbit model of cerebral vasospasm after subarachnoid hemorrhage with the assistance of ultrasound medical imaging. METHODS: A total of 160 New Zealand white rabbits were randomly divided into four groups of 40 each: (1) manual control group, (2) manual model group, (3) ultrasound guided control group, and (4) ultrasound guided model group. The subarachnoid hemorrhage was intentionally caused by double injection of blood into their cisterna magna. Then, basilar artery diameters were measured using magnetic resonance angiography before modeling and 5 days after modeling. RESULTS: The depth of needle entering into cisterna magna was determined during the process of ultrasound guided puncture. The mortality rates in manual control group and model group were 15 and 23 %, respectively. No rabbits were sacrificed in those two ultrasound guided groups. We found that the mortality rate in ultrasound guided groups decreased significantly compared to manual groups. Compared with diameters before modeling, the basilar artery diameters after modeling were significantly lower in manual and ultrasound guided model groups. The vasospasm aggravated and the proportion of severe vasospasms was greater in ultrasound guided model group than that of manual group. In manual model group, no vasospasm was found in 8 % of rabbits. CONCLUSIONS: The ultrasound guided double injection of blood into cisterna magna is a safe and effective rabbit model for treatment of cerebral vasospasm.

Cyclin-dependent kinase 5 mediates adult OPC maturation and myelin repair through modulation of Akt and GsK-3ß signaling.

Failure of remyelination in diseases, such as multiple sclerosis (MS), leads to permanent axonal damage and irreversible functional loss. The mechanisms controlling remyelination are currently poorly understood. Recent studies implicate the cyclin-dependent kinase 5 (Cdk5) in regulating oligodendrocyte (OL) development and myelination in CNS. In this study, we show that Cdk5 is also an important regulator of remyelination. Pharmacological inhibition of Cdk5 inhibits repair of lysolecithin lesions. This inhibition is a consequence of Cdk5 disruption in neural cells because remyelination in slice cultures is blocked by Cdk5 inhibitors, whereas specific deletion of Cdk5 in OLs inhibits myelin repair. In CNP-Cre;Cdk5(fl/fl) conditional knock-out mouse (Cdk5 cKO), myelin repair was delayed significantly in response to focal demyelinating lesions compared with wild-type animals. The lack of myelin repair was reflected in decreased expression of MBP and proteolipid protein and a reduction in the total number of myelinated axons in the lesion. The number of CC1(+) cells in the lesion sites was significantly reduced in Cdk5 cKO compared with wild-type animals although the total number of oligodendrocyte lineage cells (Olig2(+) cells) was increased, suggesting that Cdk5 loss perturbs the transition of early OL lineage cell into mature OL and subsequent remyelination. The failure of remyelination in Cdk5 cKO animals was associated with a reduction in signaling through the Akt pathway and an enhancement of Gsk-3ß signaling pathways. Together, these data suggest that Cdk5 is critical in regulating the transition of adult oligodendrocyte precursor cells to mature OLs that is essential for myelin repair in adult CNS.

The decreased expression of thioredoxin-1 in brain of mice with experimental autoimmune myasthenia gravis.

Myasthenia gravis (MG) is an autoimmune disease caused by circulating antibodies that block acetylcholine receptor (AchR) at the neuromuscular junction. There is the cognitive and memory impairment in patients with MG. However, the molecular mechanisms underlying the alteration of central nervous system in MG remain unknown. In the present study, we found that the level of malondialdehyde (MDA) was increased in the brain of experimental autoimmune myasthenia gravis (EAMG). Furthermore, the expression of thioredoxin-1 (Trx-1) and the activity of cAMP response element-binding protein (CREB) were significantly decreased in frontal lobe and hippocampus of mice with EAMG. We also found that the expression of pro-apoptotic C/EBP homologous protein (CHOP) was increased in the frontal lobe and hippocampus of mice. However, the expressions of glucose regulated protein 78 (GRP78/Bip) was not changed in same areas. Inversely, the expressions of pro-caspase-12, pro-caspase-3 and pro-caspase-9 were decreased. These data indicate that Trx-1 mediated endoplasmic reticulum and mitochondria pathways are involved in brain damage in MG. Trx-1 may be a pivotal target for brain protective treatment in MG.

Comparative analysis of the neuroprotective effects of ginsenosides Rg1 and Rb1 extracted from Panax notoginseng against cerebral ischemia.

Panax notoginseng, a traditional Chinese medicine, has been used for thousands of years to treat ischemic patients. More than 20 saponin components have been isolated from P. notoginseng root and identified chemically. However, these different chemical components have different roles. In this study we compared the neuroprotective mechanisms of ginsenosides Rg1, Rb1, Rg1/Rb1, and panax notoginsenoside (PNS) against injuries caused by cerebral ischemia-reperfusion (I/R). Our results show that all of these treatments significantly reduced infarction volume and alleviated neurological deficits caused by cerebral I/R. The increase in malondialdehyde (MDA) concentration was inhibited by these treatments in the hippocampus. The decreased expressions of thioredoxin-1 (Trx-1), copper-zinc superoxide dismutase (SOD-1), protein kinase B (PKB/Akt), and nuclear factor-kappa B (NF-κB) caused by cerebral I/R were restored by these treatments. The expression of heat shock protein 70 (HSP70) was enhanced in the middle cerebral artery occlusion (MCAO) group, as well as in all of the treatment groups. These results suggest that Rg1 and Rb1 have similar roles in protecting the brain from ischemic damage; however, neither Rg1/Rb1 nor PNS have synergistic effects, thus either Rg1 or the Rb1 monomer should be considered as a pharmacological neuroprotective strategy for use in the case of ischemic stroke.

Panaxatriol saponin ameliorated liver injury by acetaminophen via restoring thioredoxin-1 and pro-caspase-12.

BACKGROUND & AIMS: Acetaminophen (APAP) is widely used as an antipyretic agent which is safe at therapeutic doses. However, overdose of APAP induces fatal and non-fatal hepatic necroses. The chemical reactive metabolites of APAP initiate toxicity and inflammatory response within the liver and lead to acute liver failure. However, the mechanism underlying APAP-induced liver injury is unknown. Thioredoxin-1 (TRX-1) is an important redox regulator, which plays roles in resisting oxidative stress, regulating inflammation and inhibiting apoptosis. Panaxatriol saponin (PTS) is one of the biologically active fractions of Panax notoginseng which is a traditional Chinese medicine. The aim of this study was to investigate the mechanism on PTS protecting liver from APAP hepatotoxicity. METHODS: Mice were divided into three groups, control group, APAP group and APAP combined with PTS group. Alanine aminotransferase (ALT) and tumour necrosis factor-alpha (TNF-α) were detected by ELISA. TRX-1 and pro-caspase-12 were examined by Western blotting. RESULTS: Our results showed PTS inhibited the levels of ALT and TNF-α by APAP. Pretreatment with PTS ameliorated liver injury induced by APAP. The decrease in TRX-1 expression was restored by PTS, as well as decreased pro-caspase-12 expression was inhibited by PTS. These data suggest that PTS has roles in suppressing the hepatotoxicity by APAP. CONCLUSION: Panaxatriol saponin ameliorated liver injury by APAP through restoring the expression TRX-1 and inhibiting pro-caspase-12 decrease.

Comparative expression of thioredoxin-1 in uterine leiomyomas and myometrium.

Uterine leiomyomas are benign tumors that develop from smooth muscle cells (SMCs). The reactive oxygen species (ROS) have been shown to be involved in the signaling pathways that stimulate proliferation of a variety of cell types. Thioredoxin-1 (TRX-1) is a redox-regulating protein, which is overexpressed in various tumors. In the present study, we investigated the expressions of TRX-1 and its related molecules in uterine leiomyomas and matched adjacent myometrium. Our results showed the expression of TRX-1 was increased in leiomyomas compared with the matched adjacent myometrium by quantitative RT-PCR and western blotting. FOXO3A expression was increased in leiomyomas compared with myometrium by western blotting. The mRNA levels of hypoxia-inducible factor-1α, cyclooxygenase-2 and cyclin D1 were increased in leiomyomas compared with the adjacent myometrium. The mRNA level of (thioredoxin-1-binding protein) TBP-2 in leiomyomas was not altered when compared with the matched adjacent myometrium. These results suggest that TRX-1 and some of its related molecules are associated with the pathogenesis of uterine leiomyomas. The identification of TRX-1 signaling pathways leading to cell proliferation points to another potential therapeutic target for treatment and/or prevention of uterine leiomyomas.

Cyclin dependent kinase 5 is required for the normal development of oligodendrocytes and myelin formation.

The development of oligodendrocytes, the myelinating cells of the vertebrate CNS, is regulated by a cohort of growth factors and transcription factors. Less is known about the signaling pathways that integrate extracellular signals with intracellular transcriptional regulators to control oligodendrocyte development. Cyclin dependent kinase 5 (Cdk5) and its co-activators play critical roles in the regulation of neuronal differentiation, cortical lamination, neuronal cell migration and axon outgrowth. Here we demonstrate a previously unrecognized function of Cdk5 in regulating oligodendrocyte maturation and myelination. During late embryonic development Cdk5 null animals displayed a reduction in the number of MBP+ cells in the spinal cord, but no difference in the number of OPCs. To determine whether the reduction of oligodendrocytes reflected a cell-intrinsic loss of Cdk5, it was selectively deleted from Olig1+ oligodendrocyte lineage cells. In Olig1(Cre/+); Cdk5(fl/fl) conditional mutants, reduced levels of expression of MBP and PLP mRNA were observed throughout the CNS and ultrastructural analyses demonstrated a significant reduction in the proportion of myelinated axons in the optic nerve and spinal cord. Pharmacological inhibition or RNAi knockdown of Cdk5 in vitro resulted in the reduction in oligodendrocyte maturation, but had no effect on OPC cell proliferation. Conversely, over-expression of Cdk5 promoted oligodendrocyte maturation and enhanced process outgrowth. Consistent with this data, Cdk5(-/-) oligodendrocytes developed significantly fewer primary processes and branches than control cells. Together, these findings suggest that Cdk5 function as a signaling integrator to regulate oligodendrocyte maturation and myelination.

Geranylgeranylacetone protects against morphine-induced hepatic and renal damage in mice.

The acute or chronic administration of opioid drugs may induce oxidative damage and cellular apoptosis in the liver and kidney, and hence result in hepatic and renal damage. Thioredoxin-1 (Trx-1) and heat shock protein 70 (Hsp70) are emerging as important modulators of cellular functions. They have been shown to be involved in cellular protective mechanisms against a variety of toxic stressors. The present study was designed to investigate the effects of geranylgeranylacetone (GGA), a pharmacological inducer of Trx-1 and Hsp70, on morphine-induced hepatic and renal damage. Morphine induced apoptosis in the liver and kidney through the mitochondria-mediated apoptosis pathway, but not the endoplasmic reticulum-mediated pathway. The activation of caspases-9 and -3 was attenuated by pre­treatment with GGA. In addition, the morphine-induced increase of malondialdehyde (MDA) levels was suppressed by GGA. Furthermore, GGA enhanced morphine-induced expression of Trx-1 and Hsp70 in the liver and kidney. The findings of this study suggest that GGA may be a safe and novel therapeutic agent for morphine­induced hepatic and renal damage.