IU Indianapolis ScholarWorks :: Browsing by Author "Chen, Jinhui"

Browsing by Author "Chen, Jinhui"

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Aberrant Adult Neurogenesis in the Subventricular Zone-Rostral Migratory Stream-Olfactory Bulb System Following Subchronic Manganese Exposure
(Oxford University Press, 2016-04) Fu, Sherleen; Jiang, Wendy; Gao, Xiang; Zeng, Andrew; Cholger, Daniel; Cannon, Jason; Chen, Jinhui; Zheng, Wei; Department of Neurological Surgery, School of Medicine
Adult neurogenesis occurs in brain subventricular zone (SVZ). Our recent data reveal an elevated proliferation of BrdU(+) cells in SVZ following subchronic manganese (Mn) exposure in rats. This study was designed to distinguish Mn effect on the critical stage of adult neurogenesis, ie, proliferation, migration, survival and differentiation from the SVZ via the rostral migratory stream to the olfactory bulb (OB). Adult rats received a single ip-dose of BrdU at the end of 4-week Mn exposure to label proliferating cells. Immunostaining and cell-counting showed a 48% increase of BrdU(+) cells in Mn-exposed SVZ than in controls (P< .05). These BrdU(+) cells were identified as a mixed population of mainly GFAP(+) type-B neural stem cells, Nestin(+) type-C transit progenitor cells, DCX(+) migratory neuroblasts and Iba1(+) microglial cells. Another group of adult rats received 3 daily ip-injections of BrdU followed by subchronic Mn exposure. By 4-week post BrdU labeling, most of the surviving BrdU(+) cells in the OB were differentiated into NeuN(+) matured neurons. However, survival rates of BrdU/NeuN/DAPI triple-labeled cells in OB were 33% and 64% in Mn-exposed and control animals, respectively (P< .01). Infusion of Cu directly into the lateral ventricle significantly decreased the cell proliferation in the SVZ. Taken together, these results suggest that Mn exposure initially enhances the cell proliferation in adult SVZ. In the OB, however, Mn exposure significantly reduces the surviving adult-born cells and markedly inhibits their differentiation into mature neurons, resulting in an overall decreased adult neurogenesis in the OB.
Aging impairs dendrite morphogenesis of newborn neurons and is rescued by 7, 8-dihydroxyflavone
(Wiley Blackwell (Blackwell Publishing), 2017-04) Wang, Xiaoting; Romine, Jennifer Lynn; Gao, Xiang; Chen, Jinhui; Neurological Surgery, School of Medicine
All aging individuals will develop some degree of decline in cognitive capacity as time progresses. The molecular and cellular mechanisms leading to age-related cognitive decline are still not fully understood. Through our previous research, we discovered that active neural progenitor cells selectively become more quiescent in response to aging, thus leading to the decline of neurogenesis in the aged hippocampus. Here, we further find that aging impaired dendrite development of newborn neurons. Currently, no effective approach is available to increase neurogenesis or promote dendrite development of newborn neurons in the aging brain. We found that systemically administration of 7, 8-dihydroxyflavone (DHF), a small molecule imitating brain-derived neurotrophic factor (BDNF), significantly enhanced dendrite length in the newborn neurons, while it did not promote survival of immature neurons, in the hippocampus of 12-month-old mice. DHF-promoted dendrite development of newborn neurons in the hippocampus may enhance their function in the aging animal leading to a possible improvement in cognition.
CaMKII regulation of astrocytic glutamate uptake
(2016-05-19) Chawla, Aarti R.; Hudmon, Andy; Cummins, Theodore; Oxford, Gerry S.; Chen, Jinhui; Hoang, Quyen
Glutamate clearance by astrocytes is an essential part of physiological excitatory neurotransmission. Failure to adapt or maintain low levels of glutamate in the central nervous system is associated with multiple acute and chronic neurodegenerative diseases. The primary excitatory amino acid transporters (EAATs) in human astrocytes are EAAT1 and EAAT2 (GLAST and GLT-1 respectively in rodents). While the inhibition of a ubiquitously-expressed serine/threonine protein kinase, the calcium/calmodulindependent kinase (CaMKII) results in diminished glutamate uptake in cultured primary rodent astrocytes, the molecular mechanism underlying this regulation is unknown. In order to delineate this mechanism, we use a heterologous expression model to explore CaMKII regulation of EAAT1 and EAAT2. In transiently transfected HEK293T cells, pharmacological inhibition of CaMKII and overexpression of a dominant-negative version of CaMKII (Asp136Asn) reduces [3H]-glutamate uptake by EAAT1, without altering EAAT2 mediated glutamate uptake. Surprisingly, overexpression of a constitutively active autophosphorylation mutant (Thr287Asp) to increase autonomous CaMKII activity and a mutant incapable of autophosphorylation (Thr287Val) had no effect on either EAAT1 or EAAT2 mediated glutamate uptake. Pulldown of FLAGtagged glutamate transporters suggests CaMKII does not interact with EAAT1 or EAAT2. SPOTS peptide arrays and recombinant GST-fusion proteins of the intracellular N- and C-termini of EAAT1 identified two potential phosphorylation sites at residues Thr26 and Thr37 in the N-terminus. Introducing an Ala (a non-phospho mimetic) but not an Asp (phosphomimetic) at Thr37 diminished EAAT1-mediated glutamate uptake, suggesting that the phosphorylation state of this residue is important for constitutive EAAT1 function. In sum, this is the first report of a glutamate transporter being identified as a direct CaMKII substrate. These findings indicate that CaMKII signaling is a critical driver of homeostatic glutamate uptake by EAAT1. Aberrations in basal CaMKII activity disrupt glutamate uptake, which can perpetuate glutamate-mediated excitotoxicity and result in cellular death.
Controlled cortical impact model for traumatic brain injury
(JoVE, 2014-08-05) Romine, Jennifer; Gao, Xiang; Chen, Jinhui; Department of Neurological Surgery, IU School of Medicine
Every year over a million Americans suffer a traumatic brain injury (TBI). Combined with the incidence of TBIs worldwide, the physical, emotional, social, and economical effects are staggering. Therefore, further research into the effects of TBI and effective treatments is necessary. The controlled cortical impact (CCI) model induces traumatic brain injuries ranging from mild to severe. This method uses a rigid impactor to deliver mechanical energy to an intact dura exposed following a craniectomy. Impact is made under precise parameters at a set velocity to achieve a pre-determined deformation depth. Although other TBI models, such as weight drop and fluid percussion, exist, CCI is more accurate, easier to control, and most importantly, produces traumatic brain injuries similar to those seen in humans. However, no TBI model is currently able to reproduce pathological changes identical to those seen in human patients. The CCI model allows investigation into the short-term and long-term effects of TBI, such as neuronal death, memory deficits, and cerebral edema, as well as potential therapeutic treatments for TBI.
Cytosolic phospholipase A2 expression patterns in brain following the traumatic brain injury
(2010-06-01T16:58:17Z) Yang, Shuangni; Cummins, Theodore R.; Chen, Jinhui; Xu, Xiaoming
Delayed and progressive damages to juvenile mice after moderate traumatic brain injury
(Nature Publishing Group, 2018-05-09) Zhao, Shu; Wang, Xiaoting; Gao, Xiang; Chen, Jinhui; Neurological Surgery, School of Medicine
Symptoms are commonly more severe in pediatric traumatic brain injury (TBI) patients than in young adult TBI patients. To understand the mechanism, juvenile mice received a controlled cortical impact (CCI) injury at moderate level. Tissue lesion and cell death were measured and compared to our previous reports on brain injury in the young adult mice that received same level of impact using same injury device. Tissue lesion and cell death in the cortex was much less in the juvenile mouse brain in the first few hours after injury. However, once the injury occurred, it developed more rapidly, lasted much longer, and eventually led to exaggerated cell death and a 32.7% larger tissue lesion cavity in the cortex of juvenile mouse brain than of young adult mouse brain. Moreover, we found significant cell death in the thalamus of juvenile brains at 72 h, which was not commonly seen in the young adult mice. In summary, cell death in juvenile mice was delayed, lasted longer, and finally resulted in more severe brain injury than in the young adult mice. The results suggest that pediatric TBI patients may have a longer therapeutic window, but they also need longer intensive clinical care after injury.
Effects of electrical stimulation and testosterone on regeneration-associated gene expression and functional recovery in a rat model of sciatic nerve crush injury
(2014) Meadows, Rena Marie; Xu, Xiao-Ming; Chen, Jinhui; Jones, Kathryn J.; White, Fletcher A.
Although peripheral motoneurons are phenotypically endowed with robust regenerative capacity, functional recovery is often suboptimal following peripheral nerve injury (PNI). Research to date indicates that the greatest success in achieving full functional recovery will require the use of a combinatorial approach that can simultaneously target different aspects of the post-injury response. In general, the concept of a combinatorial approach to neural repair has been established in the scientific literature but has yet to be successfully applied in the clinical situation. Emerging evidence from animal studies supports the use of electrical stimulation (ES) and testosterone as one type of combinatorial treatment after crush injury to the facial nerve (CN VII). With the facial nerve injury model, we have previously demonstrated that ES and testosterone target different stages of the regeneration process and enhance functional recovery after facial nerve crush injury. What is currently unknown, but critical to determine, is the impact of a combinatorial treatment strategy of ES and testosterone on functional recovery after crush injury to the sciatic nerve, a mixed sensory and motor spinal nerve which is one of the most serious PNI clinical problems. The results of the present study indicate that either treatment alone or in combination positively impact motor recovery. With regard to molecular effects,single and combinatorial treatments differentially alter the expression of regeneration-associated genes following sciatic nerve crush injury relative to facial nerve injury. Thus, our data indicate that not all injuries equally respond to treatment. Furthermore, the results support the importance of treatment strategy development in an injury-dependent manner and based upon the functional characteristics of spinal vs. cranial nerves.
HIV Tat Impairs Neurogenesis through Functioning As a Notch Ligand and Activation of Notch Signaling Pathway
(Society for Neuroscience., 2016-11-02) Fan, Yan; Gao, Xiang; Chen, Jinhui; Liu, Ying; He, Johnny J.; Neurological Surgery, School of Medicine
Alterations in adult neurogenesis have been noted in the brain of HIV-infected individuals and are likely linked to HIV-associated neurocognitive deficits, including those in learning and memory. But the underlying molecular mechanisms are not fully understood. In the study, we took advantage of doxycycline-inducible and astrocyte-specific HIV-1 Tat transgenic mice (iTat) and determined the relationship between Tat expression and neurogenesis. Tat expression in astrocytes was associated with fewer neuron progenitor cells (NPCs), fewer immature neurons, and fewer mature neurons in the dentate gyrus of the hippocampus of the mouse brain. In vitro NPC-derived neurosphere assays showed that Tat-containing conditioned media from astrocytes or recombinant Tat protein inhibited NPC proliferation and migration and altered NPC differentiation, while immunodepletion of Tat from Tat-containing conditioned media or heat inactivation of recombinant Tat abrogated those effects. Notch signaling downstream gene Hes1 promoter-driven luciferase reporter gene assay and Western blotting showed that recombinant Tat or Tat-containing conditioned media activated Hes1 transcription and protein expression, which were abrogated by Tat heat inactivation, immunodepletion, and cysteine mutation at position 30. Last, Notch signaling inhibitor N-[N-(3,5-difluorophenacetyl)-l-alanyl]-S-phenylglycine t-butyl ester (DAPT) significantly rescued Tat-impaired NPC differentiation in vitro and neurogenesis in vivo Together, these results show that Tat adversely affects NPCs and neurogenesis through Notch signaling and point to the potential of developing Notch signaling inhibitors as HIV/neuroAIDS therapeutics. SIGNIFICANCE STATEMENT: HIV infection of the CNS causes cognitive and memory deficits, which have become more prevalent in the era of combination antiretroviral therapy (cART). Neurogenesis is impaired in HIV-infected individuals. But the underlying molecular mechanisms remain largely unknown. In this study, we have discovered that HIV Tat impairs neurogenesis through the Notch signaling pathway. These findings are particularly important because Tat protein has recently been detected in the brain of HIV-infected individuals with HIV replication in the periphery being effectively controlled by cART. The current study not only further highlights the importance of HIV Tat protein in HIV/neuroAIDS, but also presents a new strategy to develop novel HIV/neuroAIDS therapeutics, particularly in the era of cART.
mTOR SIGNALING MEDIATES TBI-ENHANCED NEURAL STEM CELL PROLIFERAION
(Office of the Vice Chancellor for Research, 2012-04-13) Seekaew, Pich; Chen, Liang; Gao, Xiang; Chen, Jinhui
Traumatic Brain Injury (TBI) induced neuron death was once thought to be irreversible. However, the identification of neural stem cells (NSCs) in the adult brain holds the hope of repairing injured brain following TBI. Our pre-vious study showed that TBI promotes NSC proliferation in an attempt to ini-tial an innate repair and/or plasticity mechanisms. However, this induced proliferation is transient without significantly increasing neurogenesis. It suggests that additional intervention is required to further increase NSC pro-liferation to enhance neurogenesis for successfully repairing the damaged brain following TBI. In order to determine the molecular mechanism that mediates TBI-enhanced NSC proliferation, we assessed the activity of mam-malian target of rapamycin (mTOR) signaling by detecting the level of Phospho-S6 Ribosomal protein (pS6), an indicator of the activity of mTOR signaling. We found that the level of pS6 was transient but dramatically in-creased prior to TBI-enhanced NSC proliferation. In contrast inhibiting the activity of mTOR signaling with rapamycin attenuated this effect, indicating that mTOR signaling mediates TBI-enhanced NSC proliferation. Further stimulating mTOR signaling strengthened the effect of TBI-enhanced NSC proliferation. These results suggest that mTOR signaling mediates TBI-enhanced neural stem cell proliferation and stimulating mTOR signaling may be a potential therapeutic approach to enhance neurogenesis for post-traumatic functional recovery.
NEROPATHOLOGICAL APPROACH FOR BLAST-WAVE INDUCED MILD BRAIN INJURY
(Office of the Vice Chancellor for Research, 2012-04-13) Meece, Callie; Chen, Jinhui; Gao, Xiang
Veterans of Iraq and Afghanistan are extremely susceptible to complica-tions derived from blast-wave induced mild traumatic brain injury (mTBI) sustained from road-side bombs and IEDs. Furthermore, there are 1.5 mil-lion civilian incidences of TBIs annually in the United States, and as many as nearly 75% of them are mTBIs. An mTBI is an important medical concern because it can lead to long-term cognitive, emotional difficulties and behav-ioral disturbances. Neuroimaging with CT or MRI is usually negative. That is why mTBI has been called an “invisible wound.” There are no effective treatments for these disorders, partially due to the fact that the pathological basis leading to neurological disorders are poorly understood. Using a blast-wave injury model, several mice were given injuries similar to those from the front lines. The damaged brains were collected, mounted, stained, and imaged to track the dendrite and spine degeneration, both over all and by type of spine. After quantification, the results showed that the injured brain is intact without showing dramatic lesion or cell death, however, when we further assessed the morphologies of the spared neurons by using Golgi staining to visualize the individual neurons including their processes and spines in a very high resolution, we found that the dendrites of the spared neurons in the injured cortex demonstrated dramatic swelling with beading, a hallmark of dendritic injury, and there was a significant decrease in the number of mature (mushroom) spines, as well as a significant decrease in the overall number of spines. The function of the central nervous system critically relies on the synaptic connection from the different neurons be-tween the spines. The widespread synapse loss disrupts neural circuitry fol-lowing mTBI and will certainly contribute to neurological disorders. Our re-sults showed that mild blast-wave induced injury led to extensive dendrite degeneration and synapse reduction in the cortex in an animal model. This experimental study sheds light on the neuropathology of mild TBI in humans, and suggests that neurodegeneration may be a novel target for developing diagnostic methods and therapeutic approaches for mTBI in the future.

Browsing by Author "Chen, Jinhui"

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