Linghai Kong - Academia.edu (original) (raw)
Papers by Linghai Kong
Journal of Clinical and Translational Science
OBJECTIVES/GOALS: We aim to discover safer and more effective therapeutics for CNS disorders. Cur... more OBJECTIVES/GOALS: We aim to discover safer and more effective therapeutics for CNS disorders. Current therapeutic development is hindered by dosing out drugs for safe consumption. By identifying proteins with narrow functional roles in the brain (i.e., behavioral control), we can develop drugs targeting these proteins for improved treatment safety and efficacy. METHODS/STUDY POPULATION: We focused on an evolutionarily new, non-neuronal, non-synaptic glutamate signaling mechanism, system xc- (Sxc). Sxc activity was eliminated by mutating the gene Slc7a11 through pronuclear injection of zinc-finger nucleases into Sprague Dawley rat embryos to create a line of rats lacking Sxc (MSxc). To confirm Sxc mutation, we verified that tissue from MSxc rats had a complete lack of xCT, which is the regulatory subunit of Sxc that is encoded by Slc7a11. We also verified that astrocyte cultures generated from MSxc tissue lacked cystine-evoked glutamate release. Next, we measured development (body we...
Drug addiction involves heightened relapse vulnerability arising from persistent drug-induced neu... more Drug addiction involves heightened relapse vulnerability arising from persistent drug-induced neuro-adaptations, including a) hypofrontality which is thought to reflect reduced firing of cortical afferents to the nucleus accumbens (NAcc) and b) altered glutamate homeostasis in NAcc that likely involves reduced glutamate release and uptake by astrocytes. An important question is whether these forms of pathological plasticity are functionally linked such that reduced corticostriatal firing may result in aberrant regulation of astrocytes in the NAcc. To begin to evaluate this possibility, we first determined whether neurons regulate system xc(Sxc) activity, a mechanism of non-vesicular glutamate release by astrocytes. We found that the rate of Sxc activity in astrocyte cultures was significantly increased in cells exposed to neuronal conditioned media achieved using neuronal inserts. These experiments demonstrate that releasable neuronal factors significantly upregulate Sxc activity. W...
Psychopharmacology, 2014
Rationale-Gaps in our understanding of glutamatergic signaling may be key obstacles in accurately... more Rationale-Gaps in our understanding of glutamatergic signaling may be key obstacles in accurately modeling complex CNS diseases. System x c − is an example of a poorly understood component of glutamate homeostasis that has the potential to contribute to CNS diseases. Objectives-To determine whether system x c − contributes to behaviors used to model features of CNS disease states. Methods-In situ hybridization was used to map mRNA expression of xCT throughout the brain. Microdialysis in the prefrontal cortex was used to sample extracellular glutamate levels; HPLC was used to measure extracellular glutamate and tissue glutathione concentrations. Acute administration of sulfasalazine (8-16 mg/kg, IP) was used to decrease system x c − activity. Behavior was measured using attentional set shifting, elevated plus maze, open-field maze, Porsolt swim test, and social interaction paradigm. Results-The expression of xCT mRNA was detected throughout the brain, with high expression in several structures including the basolateral amygdala and prefrontal cortex. Doses of sulfasalazine that produced a reduction in extracellular glutamate levels were identified and subsequently used in the behavioral experiments. Sulfasalazine impaired performance in attentional set shifting, reduced the amount of time spent in an open arm of an elevated plus maze and the center of an open-field maze without altering behavior in a Porsolt swim test, total distance moved in an open-field maze, or social interaction. Conclusions-The widespread distribution of system x c − and involvement in a growing list of behaviors suggests that this form of nonvesicular glutamate release is a key component of excitatory signaling.
Psychopharmacology, 2012
Rationale-Aspects of schizophrenia, including deficits in sensorimotor gating, have been linked t... more Rationale-Aspects of schizophrenia, including deficits in sensorimotor gating, have been linked to glutamate dysfunction and/or oxidative stress in the prefrontal cortex. System x c − , a cystineglutamate antiporter, is a poorly understood mechanism that contributes to both cellular antioxidant capacity and glutamate homeostasis. Objectives-Our goal was to determine whether increased system x c − activity within the prefrontal cortex would normalize a rodent measure of sensorimotor gating. Methods-In situ hybridization was used to map mRNA expression of xCT, the active subunit of system x c − , in the prefrontal cortex. Prepulse inhibition was used to measure sensorimotor gating; deficits in prepulse inhibition were produced using phencyclidine (0.3-3 mg/kg, sc). Nacetylcysteine (10-100 μM) and the system x c − inhibitor (S)-4-carboxyphenylglycine (CPG, 0.5 μM) were used to increase and decrease system x c − activity, respectively. The uptake of 14 Ccystine into tissue punches obtained from the prefrontal cortex was used to assay system x c − activity. Results-The expression of xCT mRNA in the prefrontal cortex was most prominent in a lateral band spanning primarily the prelimbic cortex. Although phencyclidine did not alter the uptake of 14 C-cystine in prefrontal cortical tissue punches, intra-prefrontal cortical infusion of Nacetylcysteine (10-100 μM) significantly reduced phencyclidine-(1.5 mg/kg, sc) induced deficits in prepulse inhibition. N-acetylcysteine was without effect when co-infused with CPG (0.5 μM), indicating an involvement of system x c −. Conclusions-These results indicate that phencyclidine disrupts sensorimotor gating through system x c − independent mechanisms, but that increasing cystine-glutamate exchange in the prefrontal cortex is sufficient to reduce behavioral deficits produced by phencyclidine.
Addiction Biology, 2012
Factors that result in augmented reinstatement, including increased withdrawal period duration an... more Factors that result in augmented reinstatement, including increased withdrawal period duration and high levels of cocaine consumption, may provide insight into relapse vulnerability. The neural basis of augmented reinstatement may arise from more pronounced changes in plasticity required for reinstatement and/or the emergence of plasticity expressed only during a specific withdrawal period or under specific intake conditions. In this study, we examined the impact of withdrawal period duration and cocaine intake on the magnitude of cocaine-primed reinstatement and extracellular glutamate in the nucleus accumbens, which has been shown to be required for cocaine-primed reinstatement. Rats were assigned to self-administer under conditions resulting in low (2 hr/day; 0.5 mg/kg/infusion, IV) or high (6 hr/day; 1.0 mg/kg/infusion, IV) levels of cocaine intake. After 1, 21, or 60 days of withdrawal, drug seeking and extracellular glutamate levels in the nucleus accumbens were measured before and after a cocaine injection. Cocaine reinstated lever pressing and elevated extracellular glutamate at every withdrawal time point tested, which is consistent with the conclusion that increased glutamatergic signaling in the nucleus accumbens is required for cocaine-induced reinstatement. Interestingly, high-intake rats exhibited augmented reinstatement at every time point tested, yet failed to exhibit higher levels of cocaine-induced increases in extracellular glutamate relative to low-intake rats. Our current data indicate that augmented reinstatement in high-intake rats is not due to relative differences in extracellular levels of glutamate in the nucleus accumbens, but rather may stem from intake-dependent plasticity.
REGULATION OF SYSTEM XCBY THE NEUROPEPTIDE PACAP: IMPLICATIONS FOR GLUTAMATE TRANSMISSION IN DRUG... more REGULATION OF SYSTEM XCBY THE NEUROPEPTIDE PACAP: IMPLICATIONS FOR GLUTAMATE TRANSMISSION IN DRUG ADDICTION Linghai Kong, B.S. Marquette University, 2017 Drug addiction is a chronic brain disorder characterized by heightened relapse susceptibility. Drug-induced aberrant glutamate signaling in corticostriatal circuitry contributes to behaviors in virtually every preclinical model of drug seeking and correlates with drug craving in human. Here, we propose that glutamate signaling is a product of integrated activity between neurons and astrocytes, such that disruptions within astrocytes can stem from abnormal neuronal signaling (e.g., altered corticostriatal firing) and be the source of additional disruptions in other neuronal circuits. The astrocytic mechanism studied in these experiments is system xc(Sxc) since drug-induced changes to this non-vesicular glutamate release mechanism contribute to heightened relapse vulnerability in preclinical models of addiction. My first objective wa...
Aging Cell, 2021
This is an open access article under the terms of the Creat ive Commo ns Attri bution License, wh... more This is an open access article under the terms of the Creat ive Commo ns Attri bution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Journal of Clinical and Translational Science
OBJECTIVES/GOALS: We aim to discover safer and more effective therapeutics for CNS disorders. Cur... more OBJECTIVES/GOALS: We aim to discover safer and more effective therapeutics for CNS disorders. Current therapeutic development is hindered by dosing out drugs for safe consumption. By identifying proteins with narrow functional roles in the brain (i.e., behavioral control), we can develop drugs targeting these proteins for improved treatment safety and efficacy. METHODS/STUDY POPULATION: We focused on an evolutionarily new, non-neuronal, non-synaptic glutamate signaling mechanism, system xc- (Sxc). Sxc activity was eliminated by mutating the gene Slc7a11 through pronuclear injection of zinc-finger nucleases into Sprague Dawley rat embryos to create a line of rats lacking Sxc (MSxc). To confirm Sxc mutation, we verified that tissue from MSxc rats had a complete lack of xCT, which is the regulatory subunit of Sxc that is encoded by Slc7a11. We also verified that astrocyte cultures generated from MSxc tissue lacked cystine-evoked glutamate release. Next, we measured development (body we...
Drug addiction involves heightened relapse vulnerability arising from persistent drug-induced neu... more Drug addiction involves heightened relapse vulnerability arising from persistent drug-induced neuro-adaptations, including a) hypofrontality which is thought to reflect reduced firing of cortical afferents to the nucleus accumbens (NAcc) and b) altered glutamate homeostasis in NAcc that likely involves reduced glutamate release and uptake by astrocytes. An important question is whether these forms of pathological plasticity are functionally linked such that reduced corticostriatal firing may result in aberrant regulation of astrocytes in the NAcc. To begin to evaluate this possibility, we first determined whether neurons regulate system xc(Sxc) activity, a mechanism of non-vesicular glutamate release by astrocytes. We found that the rate of Sxc activity in astrocyte cultures was significantly increased in cells exposed to neuronal conditioned media achieved using neuronal inserts. These experiments demonstrate that releasable neuronal factors significantly upregulate Sxc activity. W...
Psychopharmacology, 2014
Rationale-Gaps in our understanding of glutamatergic signaling may be key obstacles in accurately... more Rationale-Gaps in our understanding of glutamatergic signaling may be key obstacles in accurately modeling complex CNS diseases. System x c − is an example of a poorly understood component of glutamate homeostasis that has the potential to contribute to CNS diseases. Objectives-To determine whether system x c − contributes to behaviors used to model features of CNS disease states. Methods-In situ hybridization was used to map mRNA expression of xCT throughout the brain. Microdialysis in the prefrontal cortex was used to sample extracellular glutamate levels; HPLC was used to measure extracellular glutamate and tissue glutathione concentrations. Acute administration of sulfasalazine (8-16 mg/kg, IP) was used to decrease system x c − activity. Behavior was measured using attentional set shifting, elevated plus maze, open-field maze, Porsolt swim test, and social interaction paradigm. Results-The expression of xCT mRNA was detected throughout the brain, with high expression in several structures including the basolateral amygdala and prefrontal cortex. Doses of sulfasalazine that produced a reduction in extracellular glutamate levels were identified and subsequently used in the behavioral experiments. Sulfasalazine impaired performance in attentional set shifting, reduced the amount of time spent in an open arm of an elevated plus maze and the center of an open-field maze without altering behavior in a Porsolt swim test, total distance moved in an open-field maze, or social interaction. Conclusions-The widespread distribution of system x c − and involvement in a growing list of behaviors suggests that this form of nonvesicular glutamate release is a key component of excitatory signaling.
Psychopharmacology, 2012
Rationale-Aspects of schizophrenia, including deficits in sensorimotor gating, have been linked t... more Rationale-Aspects of schizophrenia, including deficits in sensorimotor gating, have been linked to glutamate dysfunction and/or oxidative stress in the prefrontal cortex. System x c − , a cystineglutamate antiporter, is a poorly understood mechanism that contributes to both cellular antioxidant capacity and glutamate homeostasis. Objectives-Our goal was to determine whether increased system x c − activity within the prefrontal cortex would normalize a rodent measure of sensorimotor gating. Methods-In situ hybridization was used to map mRNA expression of xCT, the active subunit of system x c − , in the prefrontal cortex. Prepulse inhibition was used to measure sensorimotor gating; deficits in prepulse inhibition were produced using phencyclidine (0.3-3 mg/kg, sc). Nacetylcysteine (10-100 μM) and the system x c − inhibitor (S)-4-carboxyphenylglycine (CPG, 0.5 μM) were used to increase and decrease system x c − activity, respectively. The uptake of 14 Ccystine into tissue punches obtained from the prefrontal cortex was used to assay system x c − activity. Results-The expression of xCT mRNA in the prefrontal cortex was most prominent in a lateral band spanning primarily the prelimbic cortex. Although phencyclidine did not alter the uptake of 14 C-cystine in prefrontal cortical tissue punches, intra-prefrontal cortical infusion of Nacetylcysteine (10-100 μM) significantly reduced phencyclidine-(1.5 mg/kg, sc) induced deficits in prepulse inhibition. N-acetylcysteine was without effect when co-infused with CPG (0.5 μM), indicating an involvement of system x c −. Conclusions-These results indicate that phencyclidine disrupts sensorimotor gating through system x c − independent mechanisms, but that increasing cystine-glutamate exchange in the prefrontal cortex is sufficient to reduce behavioral deficits produced by phencyclidine.
Addiction Biology, 2012
Factors that result in augmented reinstatement, including increased withdrawal period duration an... more Factors that result in augmented reinstatement, including increased withdrawal period duration and high levels of cocaine consumption, may provide insight into relapse vulnerability. The neural basis of augmented reinstatement may arise from more pronounced changes in plasticity required for reinstatement and/or the emergence of plasticity expressed only during a specific withdrawal period or under specific intake conditions. In this study, we examined the impact of withdrawal period duration and cocaine intake on the magnitude of cocaine-primed reinstatement and extracellular glutamate in the nucleus accumbens, which has been shown to be required for cocaine-primed reinstatement. Rats were assigned to self-administer under conditions resulting in low (2 hr/day; 0.5 mg/kg/infusion, IV) or high (6 hr/day; 1.0 mg/kg/infusion, IV) levels of cocaine intake. After 1, 21, or 60 days of withdrawal, drug seeking and extracellular glutamate levels in the nucleus accumbens were measured before and after a cocaine injection. Cocaine reinstated lever pressing and elevated extracellular glutamate at every withdrawal time point tested, which is consistent with the conclusion that increased glutamatergic signaling in the nucleus accumbens is required for cocaine-induced reinstatement. Interestingly, high-intake rats exhibited augmented reinstatement at every time point tested, yet failed to exhibit higher levels of cocaine-induced increases in extracellular glutamate relative to low-intake rats. Our current data indicate that augmented reinstatement in high-intake rats is not due to relative differences in extracellular levels of glutamate in the nucleus accumbens, but rather may stem from intake-dependent plasticity.
REGULATION OF SYSTEM XCBY THE NEUROPEPTIDE PACAP: IMPLICATIONS FOR GLUTAMATE TRANSMISSION IN DRUG... more REGULATION OF SYSTEM XCBY THE NEUROPEPTIDE PACAP: IMPLICATIONS FOR GLUTAMATE TRANSMISSION IN DRUG ADDICTION Linghai Kong, B.S. Marquette University, 2017 Drug addiction is a chronic brain disorder characterized by heightened relapse susceptibility. Drug-induced aberrant glutamate signaling in corticostriatal circuitry contributes to behaviors in virtually every preclinical model of drug seeking and correlates with drug craving in human. Here, we propose that glutamate signaling is a product of integrated activity between neurons and astrocytes, such that disruptions within astrocytes can stem from abnormal neuronal signaling (e.g., altered corticostriatal firing) and be the source of additional disruptions in other neuronal circuits. The astrocytic mechanism studied in these experiments is system xc(Sxc) since drug-induced changes to this non-vesicular glutamate release mechanism contribute to heightened relapse vulnerability in preclinical models of addiction. My first objective wa...
Aging Cell, 2021
This is an open access article under the terms of the Creat ive Commo ns Attri bution License, wh... more This is an open access article under the terms of the Creat ive Commo ns Attri bution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.