Tonic NMDA Receptor Currents in the Brain: Regulation and Cognitive Functions

Synaptically localized NMDA receptors (NMDARs) play a crucial role in important cognitive functions by mediating synaptic transmission and plasticity. In contrast, a tonic NMDAR current, thought to be mediated by extrasynaptic NMDARs, has a less clear function. This review provides a comprehensive overview of tonic NMDAR currents, focusing on their roles in synaptic transmission/plasticity and their impact on cognitive functions and psychiatric disorders. We discuss the roles of 3 endogenous ligands (i.e., glutamate, glycine, and D-serine) and receptors in mediating tonic NMDAR currents and explore the diverse mechanisms that regulate tonic NMDAR currents. In light of recent controversies surrounding the source of D-serine, we highlight the recent findings suggesting that astrocytes release D-serine to modulate tonic NMDAR currents and control cognitive flexibility. Furthermore, we propose distinct roles of neuronal and astrocytic D-serine in different locations and their implications for synaptic regulation and cognitive functions. The potential roles of tonic NMDAR currents in various psychiatric disorders, such as schizophrenia and autism spectrum disorder, are discussed in the context of the NMDAR hypofunction hypothesis. By presenting the mechanisms by which various cells, particularly astrocytes, regulate tonic NMDAR currents, we aim to stimulate future research in NMDAR hypofunction- or hyperfunction-related psychiatric disorders. This review not only provides a better understanding of the complex interplay between tonic NMDAR currents and cognitive functions but also sheds light on its potential therapeutic target for the treatment of various psychiatric disorders.

Hypothalamic astrocyte NAD+ salvage pathway mediates the coupling of dietary fat overconsumption in a mouse model of obesity

Nicotinamide adenine dinucleotide (NAD)+ serves as a crucial coenzyme in numerous essential biological reactions, and its cellular availability relies on the activity of the nicotinamide phosphoribosyltransferase (NAMPT)-catalyzed salvage pathway. Here we show that treatment with saturated fatty acids activates the NAD+ salvage pathway in hypothalamic astrocytes. Furthermore, inhibition of this pathway mitigates hypothalamic inflammation and attenuates the development of obesity in male mice fed a high-fat diet (HFD). Mechanistically, CD38 functions downstream of the NAD+ salvage pathway in hypothalamic astrocytes burdened with excess fat. The activation of the astrocytic NAMPT-NAD+-CD38 axis in response to fat overload induces proinflammatory responses in the hypothalamus. It also leads to aberrantly activated basal Ca2+ signals and compromised Ca2+ responses to metabolic hormones such as insulin, leptin, and glucagon-like peptide 1, ultimately resulting in dysfunctional hypothalamic astrocytes. Our findings highlight the significant contribution of the hypothalamic astrocytic NAD+ salvage pathway, along with its downstream CD38, to HFD-induced obesity.

GABA tone regulation and its cognitive functions in the brain

γ-Aminobutyric acid (GABA) is the major inhibitory neurotransmitter released at GABAergic synapses, mediating fast-acting phasic inhibition. Emerging lines of evidence unequivocally indicate that a small amount of extracellular GABA - GABA tone - exists in the brain and induces a tonic GABA current that controls neuronal activity on a slow timescale relative to that of phasic inhibition. Surprisingly, studies indicate that glial cells that synthesize GABA, such as astrocytes, release GABA through non-vesicular mechanisms, such as channel-mediated release, and thereby act as the source of GABA tone in the brain. In this Review, we first provide an overview of major advances in our understanding of the cell-specific molecular and cellular mechanisms of GABA synthesis, release and clearance that regulate GABA tone in various brain regions. We next examine the diverse ways in which the tonic GABA current regulates synaptic transmission and synaptic plasticity through extrasynaptic GABAA-receptor-mediated mechanisms. Last, we discuss the physiological mechanisms through which tonic inhibition modulates cognitive function on a slow timescale. In this Review, we emphasize that the cognitive functions of tonic GABA current extend beyond mere inhibition, laying a foundation for future research on the physiological and pathophysiological roles of GABA tone regulation in normal and abnormal psychiatric conditions.

Hypothalamic GABRA5-positive neurons control obesity via astrocytic GABA

The lateral hypothalamic area (LHA) regulates food intake and energy balance. Although LHA neurons innervate adipose tissues, the identity of neurons that regulate fat is undefined. Here we show that GABRA5-positive neurons in LHA (GABRA5LHA) polysynaptically project to brown and white adipose tissues in the periphery. GABRA5LHA are a distinct subpopulation of GABAergic neurons and show decreased pacemaker firing in diet-induced obesity mouse models in males. Chemogenetic inhibition of GABRA5LHA suppresses fat thermogenesis and increases weight gain, whereas gene silencing of GABRA5 in LHA decreases weight gain. In the diet-induced obesity mouse model, GABRA5LHA are tonically inhibited by nearby reactive astrocytes releasing GABA, which is synthesized by monoamine oxidase B (Maob). Gene silencing of astrocytic Maob in LHA facilitates fat thermogenesis and reduces weight gain significantly without affecting food intake, which is recapitulated by administration of a Maob inhibitor, KDS2010. We propose that firing of GABRA5LHA suppresses fat accumulation and selective inhibition of astrocytic GABA is a molecular target for treating obesity.

Kv7/KCNQ potassium channels in cortical hyperexcitability and juvenile seizure-related death in Ank2-mutant mice

Autism spectrum disorders (ASD) represent neurodevelopmental disorders characterized by social deficits, repetitive behaviors, and various comorbidities, including epilepsy. ANK2, which encodes a neuronal scaffolding protein, is frequently mutated in ASD, but its in vivo functions and disease-related mechanisms are largely unknown. Here, we report that mice with Ank2 knockout restricted to cortical and hippocampal excitatory neurons (Ank2-cKO mice) show ASD-related behavioral abnormalities and juvenile seizure-related death. Ank2-cKO cortical neurons show abnormally increased excitability and firing rate. These changes accompanied decreases in the total level and function of the Kv7.2/KCNQ2 and Kv7.3/KCNQ3 potassium channels and the density of these channels in the enlengthened axon initial segment. Importantly, the Kv7 agonist, retigabine, rescued neuronal excitability, juvenile seizure-related death, and hyperactivity in Ank2-cKO mice. These results suggest that Ank2 regulates neuronal excitability by regulating the length of and Kv7 density in the AIS and that Kv7 channelopathy is involved in Ank2-related brain dysfunctions.

Astrocytic urea cycle detoxifies Aβ-derived ammonia while impairing memory in Alzheimer's disease

Alzheimer's disease (AD) is one of the foremost neurodegenerative diseases, characterized by beta-amyloid (Aβ) plaques and significant progressive memory loss. In AD, astrocytes are proposed to take up and clear Aβ plaques. However, how Aβ induces pathogenesis and memory impairment in AD remains elusive. We report that normal astrocytes show non-cyclic urea metabolism, whereas Aβ-treated astrocytes show switched-on urea cycle with upregulated enzymes and accumulated entering-metabolite aspartate, starting-substrate ammonia, end-product urea, and side-product putrescine. Gene silencing of astrocytic ornithine decarboxylase-1 (ODC1), facilitating ornithine-to-putrescine conversion, boosts urea cycle and eliminates aberrant putrescine and its toxic byproducts ammonia and H₂O₂ and its end product GABA to recover from reactive astrogliosis and memory impairment in AD. Our findings implicate that astrocytic urea cycle exerts opposing roles of beneficial Aβ detoxification and detrimental memory impairment in AD. We propose ODC1 inhibition as a promising therapeutic strategy for AD to facilitate removal of toxic molecules and prevent memory loss.

Unaltered Tonic Inhibition in the Arcuate Nucleus of Diet-induced Obese Mice

The principal inhibitory transmitter, γ-aminobutyric acid (GABA), is critical for maintaining hypothalamic homeostasis and released from neurons phasically, as well as from astrocytes tonically. Although astrocytes in the arcuate nucleus (ARC) of the hypothalamus are shown to transform into reactive astrocytes, the tonic inhibition by astrocytic GABA has not been adequately investigated in diet-induced obesity (DIO). Here, we investigated the expression of monoamine oxidase-B (MAOB), a GABA-synthesizing enzyme, in reactive astrocytes in obese mice. We observed that a chronic high-fat diet (HFD) significantly increased astrocytic MAOB and cellular GABA content, along with enhanced hypertrophy of astrocytes in the ARC. Unexpectedly, we found that the level of tonic GABA was unaltered in chronic HFD mice using whole-cell patch-clamp recordings in the ARC. Furthermore, the GABA-induced current was increased with elevated GABAA receptor α5 (GABRA5) expression. Surprisingly, we found that a nonselective GABA transporter (GAT) inhibitor, nipecotic acid (NPA)-induced current was significantly increased in chronic HFD mice. We observed that GAT1 inhibitor, NO711-induced current was significantly increased, whereas GAT3 inhibitor, SNAP5114-induced current was not altered. The unexpected unaltered tonic inhibition was due to an increase of GABA clearance in the ARC by neuronal GAT1 rather than astrocytic GAT3. These results imply that increased astrocytic GABA synthesis and neuronal GABAA receptor were compensated by GABA clearance, resulting in unaltered tonic GABA inhibition in the ARC of the hypothalamus in obese mice. Taken together, GABA-related molecular pathways in the ARC dynamically regulate the tonic inhibition to maintain hypothalamic homeostasis against the HFD challenge.

Astrocytes Render Memory Flexible by Releasing D-Serine and Regulating NMDA Receptor Tone in the Hippocampus

BACKGROUND

NMDA receptor (NMDAR) hypofunction has been implicated in several psychiatric disorders with impairment of cognitive flexibility. However, the molecular mechanism of how NMDAR hypofunction with decreased NMDAR tone causes the impairment of cognitive flexibility has been minimally understood. Furthermore, it has been unclear whether hippocampal astrocytes regulate NMDAR tone and cognitive flexibility.

METHODS

We employed cell type-specific genetic manipulations, ex vivo electrophysiological recordings, sniffer patch recordings, cutting-edge biosensor for norepinephrine, and behavioral assays to investigate whether astrocytes can regulate NMDAR tone by releasing D-serine and glutamate. Subsequently, we further investigated the role of NMDAR tone in heterosynaptic long-term depression, metaplasticity, and cognitive flexibility.

RESULTS

We found that hippocampal astrocytes regulate NMDAR tone via BEST1-mediated corelease of D-serine and glutamate. Best1 knockout mice exhibited reduced NMDAR tone and impairments of homosynaptic and α₁ adrenergic receptor-dependent heterosynaptic long-term depression, which leads to defects in metaplasticity and cognitive flexibility. These impairments in Best1 knockout mice can be rescued by hippocampal astrocyte-specific BEST1 expression or enhanced NMDAR tone through D-serine supplement. D-serine injection in Best1 knockout mice during initial learning rescues subsequent reversal learning.

CONCLUSIONS

These findings indicate that NMDAR tone during initial learning is important for subsequent learning, and hippocampal NMDAR tone regulated by astrocytic BEST1 is critical for heterosynaptic long-term depression, metaplasticity, and cognitive flexibility.

The tripartite glutamatergic synapse

Astroglial cells were long considered as structural and metabolic supporting cells are which do not directly participate in information processing in the brain. Discoveries of responsiveness of astrocytes to synaptically-released glutamate and their capability to release agonists of glutamate receptors awakened extensive studies of glia-neuron communications and led to the revolutionary changes in our understanding of brain cellular networks. Nowadays, astrocytes are widely acknowledged as inseparable element of glutamatergic synapses and role for glutamatergic astrocyte-neuron interactions in the brain computation is emerging. Astroglial glutamate receptors, in particular of NMDA, mGluR3 and mGluR5 types, can activate a variety of molecular cascades leading astroglial-driven modulation of extracellular levels of glutamate and activity of neuronal glutamate receptors. Their preferential location to the astroglial perisynaptic processes facilitates interaction of astrocytes with individual excitatory synapses. Bi-directional glutamatergic communication between astrocytes and neurons underpins a complex, spatially-distributed modulation of synaptic signalling thus contributing to the enrichment of information processing by the neuronal networks. Still, further research is needed to bridge the substantial gaps in our understanding of mechanisms and physiological relevance of astrocyte-neuron glutamatergic interactions, in particular ability of astrocytes directly activate neuronal glutamate receptors by releasing glutamate and, arguably, d-Serine. An emerging roles for aberrant changes in glutamatergic astroglial signalling, both neuroprotective and pathogenic, in neurological and neurodegenerative diseases also require further investigation. This article is part of the special Issue on 'Glutamate Receptors - The Glutamatergic Synapse'.

Differential Proximity of Perisynaptic Astrocytic Best1 at the Excitatory and Inhibitory Tripartite Synapses in APP/PS1 and MAOB-KO Mice Revealed by Lattice Structured Illumination Microscopy

Bestrophin-1 (Best1) is a GABA- and glutamate-permeable, Ca2+-activated Cl- channel, which is mainly expressed in astrocytes and localized at the microdomain or perisynaptic junction of the tripartite synapse. Distribution of Best1 is dramatically changed in pathological conditions such as Alzheimer's disease. However, it is still unknown whether Best1 is located at the glutamatergic or GABAergic tripartite synapses. Here, we utilized the Lattice structured illumination microscopy (Lattice SIM) to visualize Best1 expression at the perisynaptic junctions of the tripartite synapses in CA1 of mouse hippocampus. We performed co-labeling with antibodies against 1) Best1 and vesicular glutamate transporter-2 (vGLUT2) or 2) Best1 and vesicular GABA transporter (vGAT) to measure the proximity of Best1-containing perisynapse to glutamatergic or GABAergic presynapse, respectively. In addition, we examined two transgenic mouse lines of 1) APP/PS1 mouse showing high astrocytic MAOB activity and cytosolic GABA and 2) MAOB-KO mouse showing low astrocytic GABA. Lattice SIM images were further processed by Imaris, which allowed 3D-rendering and spot identification. We found that astrocytic Best1 was distributed closer to the glutamatergic synapses than GABAergic synapses in the wild-type mice. In APP/PS1 mice, Best1 distribution was significantly changed by moving away from the glutamatergic synapses while moving closer to the GABAergic synapses. On the contrary, in MAOB-KO mice, the Best1 distribution was dramatically changed by moving closer to the glutamatergic synapses and moving far away from the GABAergic synapses. Our findings propose that the proximity of Best1-containing perisynapses to presynapses dynamically changes according to the level of astrocytic cytosolic GABA.

Adverse cardiovascular ageing among older women and cardiometabolic ageing

Funding Acknowledgements

Type of funding sources: Public hospital(s). Main funding source(s): National Medical Research Council (NMRC)

Background

Despite longer life expectancies, women may experience reduced ‘health-span’ (period of life spent in good health) due to accumulation of risks over their longer life spans. Metabolic factors present in diet and lifestyle may provide modifiable solutions to tackle burdens of cardiovascular (CV) ageing in women.

Objective

We aim to study gender differences in CV structure and function among community older adults without clinical CV disease, as well as metabolic perturbations in their study samples.

Methods

We examined a prospective cohort study of older adults, obtaining their medical history, serum sampling, echocardiography and cardiac magnetic resonance (CMR) imaging on a single day visit. Echo E/A ratio was computed as a ratio of peak velocity flow in early diastole E (m/s) to peak velocity flow in late diastole by atrial contraction A (m/s) mitral inflow velocities. Longitudinal strain (ε) at any time point (t) in the cardiac cycle from end-diastole (time 0) was calculated as: ε(t)=(L(t)-L0)/L0, obtaining left atrial (LA) reservoir strain (εs), conduit strain (εe) and booster strain (εa) by CMR. Metabolomics profiling was performed by standard mass spectrometry techniques.

Results

Among n = 492 (49.6%, n = 244 women, mean age 73 ± 4 years) participants, women had lower prevalence of hypertension (52% vs 58%, p < 0.0001), smoking (4% vs 35%, p < 0.0001), but higher prevalence of dyslipidemia (52% vs 50%, p = 0.001) compared to men. Women had lower left ventricular mass index (69 vs 71 g/m2, p < 0.0001) compared to men. However, women had more adverse CV function, such as lower E/A ratio (0.78 vs 0.85, p < 0.0001), lower LA booster (εa) (16.5 vs 17.8, p = 0.027) and lower LA reservoir (εs) strain rate (1.5 vs 1.6, p = 0.012), compared to men. Amino acids such as alanine, arginine, aspartate, citrulline, glycine, phenylalanine and valine were similar between gender. However, women had higher levels of tyrosine (76 vs 68 μM, p = 0.015). On multivariate adjustment, apart from age, tyrosine was independently associated with E/A ratio (β=0.002, 95%CI 0.00-0.004, p = 0.044) and εs (β=0.004, 95%CI 0.00-0.009, p = 0.048) among women. 

Conclusion

Utilizing conventional and sensitive CV imaging, women appeared to have more adverse CV functions with ageing. As a branched chain amino acid linked to future risk of CV disease, tyrosine may be linked to adverse CV function. Factors that contribute to these cardiometabolic profiles, such as menopause, diet or lifestyle warrant further research.

Astrocytes Control Sensory Acuity via Tonic Inhibition in the Thalamus

Sensory discrimination is essential for survival. However, how sensory information is finely controlled in the brain is not well defined. Here, we show that astrocytes control tactile acuity via tonic inhibition in the thalamus. Mechanistically, diamine oxidase (DAO) and the subsequent aldehyde dehydrogenase 1a1 (Aldh1a1) convert putrescine into GABA, which is released via Best1. The GABA from astrocytes inhibits synaptically evoked firing at the lemniscal synapses to fine-tune the dynamic range of the stimulation-response relationship, the precision of spike timing, and tactile discrimination. Our findings reveal a novel role of astrocytes in the control of sensory acuity through tonic GABA release.

Activation of Astrocytic μ-Opioid Receptor Causes Conditioned Place Preference

The underlying mechanisms of how positive emotional valence (e.g., pleasure) causes preference of an associated context is poorly understood. Here, we show that activation of astrocytic μ-opioid receptor (MOR) drives conditioned place preference (CPP) by means of specific modulation of astrocytic MOR, an exemplar endogenous Gi protein-coupled receptor (Gi-GPCR), in the CA1 hippocampus. Long-term potentiation (LTP) induced by a subthreshold stimulation with the activation of astrocytic MOR at the Schaffer collateral pathway accounts for the memory acquisition to induce CPP. This astrocytic MOR-mediated LTP induction is dependent on astrocytic glutamate released upon activation of the astrocytic MOR and the consequent activation of the presynaptic mGluR1. The astrocytic MOR-dependent LTP and CPP were recapitulated by a chemogenetic activation of astrocyte-specifically expressed Gi-DREADD hM4Di. Our study reveals that the transduction of inhibitory Gi-signaling into augmented excitatory synaptic transmission through astrocytic glutamate is critical for the acquisition of contextual memory for CPP.

The molecular mechanism of synaptic activity-induced astrocytic volume transient

KEY POINTS

Neuronal activity causes astrocytic volume change via K⁺ uptake through TREK-1 containing two-pore domain potassium channels. The volume transient is terminated by Cl^- efflux through the Ca²⁺ -activated anion channel BEST1. The source of the Ca²⁺ required to open BEST1 appears to be the stretch-activated TRPA1 channel. Intense neuronal activity is synaptically coupled with a physical change in astrocytes via volume transients.

ABSTRACT

The brain volume changes dynamically and transiently upon intense neuronal activity through a tight regulation of ion concentrations and water movement across the plasma membrane of astrocytes. We have recently demonstrated that an intense neuronal activity and subsequent astrocytic AQP4-dependent volume transient are critical for synaptic plasticity and memory. We have also pharmacologically demonstrated a functional coupling between synaptic activity and the astrocytic volume transient. However, the precise molecular mechanisms of how intense neuronal activity and the astrocytic volume transient are coupled remain unclear. Here we utilized an intrinsic optical signal imaging technique combined with fluorescence imaging using ion sensitive dyes and molecular probes and electrophysiology to investigate the detailed molecular mechanisms in genetically modified mice. We report that a brief synaptic activity induced by a train stimulation (20 Hz, 1 s) causes a prolonged astrocytic volume transient (80 s) via K⁺ uptake through TREK-1 containing two-pore domain potassium (K2P) channels, but not Kir4.1 or NKCC1. This volume change is terminated by Cl^- efflux through the Ca²⁺ -activated anion channel BEST1, but not the volume-regulated anion channel TTYH. The source of the Ca²⁺ required to open BEST1 appears to be the stretch-activated TRPA1 channel in astrocytes, but not IP₃ R2. In summary, our study identifies several important astrocytic ion channels (AQP4, TREK-1, BEST1, TRPA1) as the key molecules leading to the neuronal activity-dependent volume transient in astrocytes. Our findings reveal new molecular and cellular mechanisms for the synaptic coupling of intense neuronal activity with a physical change in astrocytes via volume transients.

Vitamin B6 catabolism and lung cancer risk: results from the Lung Cancer Cohort Consortium (LC3)

BACKGROUND

Increased vitamin B6 catabolism related to inflammation, as measured by the PAr index (the ratio of 4-pyridoxic acid over the sum of pyridoxal and pyridoxal-5'-phosphate), has been positively associated with lung cancer risk in two prospective European studies. However, the extent to which this association translates to more diverse populations is not known.

MATERIALS AND METHODS

For this study, we included 5323 incident lung cancer cases and 5323 controls individually matched by age, sex, and smoking status within each of 20 prospective cohorts from the Lung Cancer Cohort Consortium. Cohort-specific odds ratios (ORs) and 95% confidence intervals (CIs) for the association between PAr and lung cancer risk were calculated using conditional logistic regression and pooled using random-effects models.

RESULTS

PAr was positively associated with lung cancer risk in a dose-response fashion. Comparing the fourth versus first quartiles of PAr resulted in an OR of 1.38 (95% CI: 1.19-1.59) for overall lung cancer risk. The association between PAr and lung cancer risk was most prominent in former smokers (OR: 1.69, 95% CI: 1.36-2.10), men (OR: 1.60, 95% CI: 1.28-2.00), and for cancers diagnosed within 3 years of blood draw (OR: 1.73, 95% CI: 1.34-2.23).

CONCLUSION

Based on pre-diagnostic data from 20 cohorts across 4 continents, this study confirms that increased vitamin B6 catabolism related to inflammation and immune activation is associated with a higher risk of developing lung cancer. Moreover, PAr may be a pre-diagnostic marker of lung cancer rather than a causal factor.

Pharmacological Dissection of Intrinsic Optical Signal Reveals a Functional Coupling between Synaptic Activity and Astrocytic Volume Transient

The neuronal activity-dependent change in the manner in which light is absorbed or scattered in brain tissue is called the intrinsic optical signal (IOS), and provides label-free, minimally invasive, and high spatial (~100 µm) resolution imaging for visualizing neuronal activity patterns. IOS imaging in isolated brain slices measured at an infrared wavelength (>700 nm) has recently been attributed to the changes in light scattering and transmittance due to aquaporin-4 (AQP4)-dependent astrocytic swelling. The complexity of functional interactions between neurons and astrocytes, however, has prevented the elucidation of the series of molecular mechanisms leading to the generation of IOS. Here, we pharmacologically dissected the IOS in the acutely prepared brain slices of the stratum radiatum of the hippocampus, induced by 1 s/20 Hz electrical stimulation of Schaffer-collateral pathway with simultaneous measurement of the activity of the neuronal population by field potential recordings. We found that 55% of IOSs peak upon stimulation and originate from postsynaptic AMPA and NMDA receptors. The remaining originated from presynaptic action potentials and vesicle fusion. Mechanistically, the elevated extracellular glutamate and K⁺ during synaptic transmission were taken up by astrocytes via a glutamate transporter and quinine-sensitive K2P channel, followed by an influx of water via AQP-4. We also found that the decay of IOS is mediated by the DCPIB- and NPPB-sensitive anion channels in astrocytes. Altogether, our results demonstrate that the functional coupling between synaptic activity and astrocytic transient volume change during excitatory synaptic transmission is the major source of IOS.

AAV-Mediated Astrocyte-Specific Gene Expression under Human ALDH1L1 Promoter in Mouse Thalamus

Adeno-associated virus (AAV)-mediated gene delivery has been proposed to be an essential tool of gene therapy for various brain diseases. Among several cell types in the brain, astrocyte has become a promising therapeutic target for brain diseases, as more and more contribution of astrocytes in pathophysiology has been revealed. Until now, genetically targeting astrocytes has been possible by utilizing the glial fibrillary acidic protein (GFAP) promoter. In some brain areas including thalamus, however, the GFAP expression in astrocytes is reported to be low, making it difficult to genetically target astrocytes using GFAP promoter. To study the function of astrocytes in thalamus, which serves as a relay station, there is a great need for identifying an alternative astrocyte-specific promoter in thalamus. Recently, a new astrocyte-specific promoter of ALDH1L1 has been identified. However, it has not been examined in thalamus. Here we developed and characterized an AAV vector expressing Cre recombinase under the human ALDH1L1 promoter, AAV-hALDH1L1-Cre. To test the cell-type specific expression of AAV-hALDH1L1-Cre, AAV virus was injected into several brain regions of Ai14 (RCL-tdTomato) mouse, which reports Cre activity by tdTomato expression. In thalamus, we observed that tdTomato was found mostly in astrocytes (91.71%), with minimal occurrence in neurons (2.67%). In contrast, tdTomato signal was observed in both neurons and astrocytes of the amygdala (neuron: 68.13%, astrocyte: 28.35%) and hippocampus (neuron: 76.25%, astrocyte: 18.00%), which is consistent with the previous report showing neuronal gene expression under rat ALDH1L1 promoter. Unexpectedly, tdTomato was found mostly in neurons (91.98%) with minimal occurrence in astrocytes (6.66%) of the medial prefrontal cortex. In conclusion, hALDH1L1 promoter shows astrocyte-specificity in thalamus and may prove to be useful for targeting thalamic astrocytes in mouse.

Development and clinical validation of a novel photography-based skin pigmentation evaluation system: a comparison with the calculated consensus of dermatologists

OBJECTIVE

Various cosmetics, medicines, and light and laser treatments have been increasingly developed to improve pigmentary skin alterations such as melasma, actinic lentigo and dyschromia. To determine the efficacy of these modalities in view of the changes in pigmentation, an objective and reliable device that has a comparable performance to that of physicians is required. We developed a novel photography-based skin pigmentation evaluation system and validated its accuracy and reliability with a newly proposed method.

METHODS

A novel photography-based system was developed that integrates a consistent photography setting and image processing diagnostic algorithms. To automatically detect areas of pigmentation, the diagnostic algorithms were applied to photographs, which were obtained from 31 female patients. To validate its performance in comparison with the physicians' evaluation, five dermatologists independently evaluated the area of pigmentation. The clinical consensus area of pigmentation (CCAP) was calculated based on the consensus of five dermatologists' to exclude subjectivity or bias, and it was compared with the pigmentation area determined by the system.

RESULTS

Forty-four photographs with pigmented areas were evaluated by the system and the physicians. In contrast to the individual physician assessments, CCAP reduced the error that occurred due to subjectivity and bias, particularly for areas with indistinct pigmentation, and it was set as the gold standard. The results from the system showed a mean accuracy of 92.1% and a standard deviation of 4.6% in comparison with CCAP.

CONCLUSION

This pigmentation evaluation system can reproduce the physicians' consensus, suggesting that this system can support the dermatologists' objective evaluation of pigmentation.

Novel fast semi-automated software to segment cartilage for knee MR acquisitions

OBJECTIVE

Validation of a new fast software technique to segment the cartilage on knee magnetic resonance (MR) acquisitions. Large studies of knee osteoarthritis (OA) will require fast and reproducible methods to quantify cartilage changes for knee MR data. In this report we document and measure the reproducibility and reader time of a software-based technique to quantify the volume and thickness of articular cartilage on knee MR images.

METHODS

The software was tested on a set of duplicate sagittal three-dimensional (3D) dual echo steady state (DESS) acquisitions from 15 (8 OA, 7 normal) subjects. The repositioning, inter-reader, and intra-reader reproducibility of the cartilage volume (VC) and thickness (ThC) were measured independently as well as the reader time for each cartilage plate. The root-mean square coefficient of variation (RMSCoV) was used as metric to quantify the reproducibility of VC and mean ThC.

RESULTS

The repositioning RMSCoV was as follows: VC=2.0% and ThC=1.2% (femur), VC=2.9% and ThC=1.6% (medial tibial plateau), VC=5.5% and ThC=2.4% (lateral tibial plateau), and VC=4.6% and ThC=2.3% (patella). RMSCoV values were higher for the inter-reader reproducibility (VC: 2.5-8.6%) (ThC: 1.9-5.2%) and lower for the intra-reader reproducibility (VC: 1.6-2.5%) (ThC: 1.2-1.9%). The method required an average of 75.4min per knee.

CONCLUSIONS

We have documented a fast reproducible semi-automated software method to segment articular cartilage on knee MR acquisitions.

The efficacy of radiotherapy as postoperative treatment for desmoid tumors

PURPOSE

The purpose of this study was to determine if radiotherapy is a beneficial adjuvant treatment after desmoid tumor resection.

METHODS AND MATERIALS

A retrospective analysis was performed on 54 patients who underwent surgery without prior radiation at our institution between 1982 and 1998 to remove a desmoid tumor. Thirty-five patients had adjuvant radiation therapy after surgery, and 19 patients had surgery alone without immediate postoperative radiation. Sixteen of the 35 patients who underwent immediate postoperative radiation treatment had at least one prior resection before reoperation at our institution. Recurrence was defined as radiographic increase in tumor size after treatment. Follow-up interval (mean 39 months) and duration of local control were measured from the date of surgery at our institution. Potential prognostic factors for time to tumor progression were analyzed.

RESULTS

Adjuvant treatment with radiation was the only significant prognostic factor for local control. The five-year actuarial local control rate was 81% for the 35 patients who underwent radiation in addition to surgery, compared to 53% for the 19 patients who underwent surgery alone (p = 0.018). For the patients who did not receive adjuvant radiation, only younger age at the time of surgery was associated with increased risk of failure (p = 0.035). Gross or microscopic margin status and number of prior operations were not detected as prognostic for local failure. For patients who did receive postoperative radiation, only abdominal location was associated with increased risk of failure (p = 0.0097).

CONCLUSION

Radiation treatment as an adjuvant to surgery improved local control over surgery alone. Multiple operations before adjuvant radiation did not decrease the probability of subsequent tumor control. Radiation should be considered as adjuvant therapy to surgery if repeated surgery for a recurrent tumor would be complicated by a significant risk of morbidity.

Metastasis to a percutaneous gastrostomy site from head and neck cancer: radiobiologic considerations

BACKGROUND

The use of percutaneously placed feeding tubes has increased in recent years in an effort to maintain adequate caloric balance in patients receiving combined therapy for head and neck cancers, particularly concurrent radiotherapy and chemotherapy.

METHODS

We report a case of a metastasis to a percutaneous endoscopic gastrostomy site occurring in a patient with an advanced tonsillar squamous cell carcinoma and review the published literature regarding this subject. Radiobiologic principles were examined to explain the most likely cause of such metastases.

RESULTS

Six cases of percutaneous endoscopic site metastases occurring in patients with head and neck primary tumors have been reported in the literature. The interval from performance of the procedure to development of the metastases ranged from 3 to 16 months. Tumor kinetics suggest that a significant tumor burden (10(5)-10(6) cells) would need to be present at the site to manifest a metastatic lesion in such a short time interval.

CONCLUSIONS

The development of metastases at percutaneous endoscopic gastrostomy sites is a relatively uncommon occurrence. Direct tumor implantation by means of instrumentation at the time of the procedure is most likely explanation for such metastases, although hematogenous seeding cannot be completely discounted. Techniques should be used so as not to disrupt the tumor bed, particularly when gross residual disease is present.

Treatment of locally advanced adenoid cystic carcinoma of the head and neck with neutron radiotherapy

PURPOSE

To examine the efficacy of fast neutron radiotherapy for the treatment of locally advanced and/or recurrent adenoid cystic carcinoma of the head and neck and to identify prognostic variables associated with local-regional control and survival.

METHODS AND MATERIALS

One hundred fifty-nine patients with nonmetastatic, previously unirradiated, locally advanced, and/or recurrent adenoid cystic carcinoma (ACC) of the head and neck region were treated with fast neutron radiotherapy during the years 1985-1997. One hundred fifty-one patients had either unresectable disease, or gross residual disease (GRD) after an attempted surgical extirpation. Eight patients had microscopic residual disease and were analyzed separately. Sixty-two percent of patients had tumors arising in minor salivary glands, 29% in major salivary glands, and 9% in other sites such as the lacrimal glands, tracheal-bronchial tree, etc. Fifty-five percent of patients were treated for postsurgical recurrent disease and 13% of patients had lymph node involvement at the time of treatment. The median duration of follow-up was 32 months (range 3-142 months). Actuarial curves for survival, cause-specific survival, local-regional control, and the development of distant metastases are presented for times out to 11 years.

RESULTS

The 5-year actuarial local-regional tumor control rate for the 151 patients with GRD was 57%; the 5-year actuarial overall survival rate was 72%; and the 5-year actuarial cause-specific survival rate was 77%. Variables associated with decreased local-regional control in the patients with GRD as determined by multivariate analysis included base of skull involvement (p < 0.01) and biopsy only versus an attempted surgical resection prior to treatment (p = 0.03). Patients without these negative factors had an actuarial local-regional control rate of 80% at 5 years. Patients with microscopic residual disease (n = 8) had a 5-year actuarial local-regional control rate of 100%. Base of skull involvement (p < 0.001), lymph node metastases at the time of treatment (p < 0.01), biopsy only prior to neutron radiotherapy (p = 0.03), and recurrent tumors (p = 0.04) were found to be associated with a diminished cause-specific survival as ascertained by multivariate analysis. Patients with base of skull involvement and positive lymph nodes at presentation had an increased rate of the development of distant metastases at 5 years, (p < 0.01 and p < 0.001, respectively). No statistical difference in outcome was observed between major and minor salivary gland sites.

CONCLUSIONS

Fast neutron radiotherapy is an effective treatment for locally advanced ACC of the head and neck region with acceptable toxicity. Further improvements in local-regional control are not likely to impact survival until more effective systemic agents are developed to prevent and/or treat distant metastatic disease.

Neutron radiotherapy for the treatment of locally advanced major salivary gland tumors

BACKGROUND

Malignant salivary gland tumors are rare tumors of the head and neck region. The treatment of these tumors has generally consisted of surgical extirpation, with postoperative radiotherapy improving locoregional control and survival in patients with high risk tumors. Neutron radiotherapy has been found to be more efficacious than conventional radiotherapy in the setting of inoperable or subtotally resected salivary gland tumors.

METHODS

One hundred forty-eight patients with malignant salivary tumors of major salivary gland origin were treated at the University of Washington Medical Center with fast neutron radiotherapy between the years 1984 and 1995. One hundred twenty-eight patients were treated with curative intent, and of these, 120 patients had evidence of gross residual disease at the time of treatment. These patients constitute the main analysis of this paper. Of these patients, 19% had recurrent disease, 39% were initially seen with positive lymph nodes, and 11% had previously received full dose conventional radiotherapy. At the time of analysis, the median period at risk of survivors was 26 months.

RESULTS

The 5-year actuarial locoregional control rate for all patients with gross tumor treated with curative intent was 59%. A tumor size < or =4 cm was associated with an excellent locoregional control rate (80%), and cause-specific survival (73%) at 5 years compared with patients with larger tumors (35% and 22%, respectively, p<.001 in both cases). On univariate analysis, there appeared to be an advantage in locoregional control for patients with smaller sized tumors (< or =4 cm) who underwent an attempted surgical extirpation. Locoregional control was excellent (100%) in patients having a complete surgical resection of their tumors and undergoing postoperative neutron radiotherapy because of the presence of other high risk factors. Lymph node status at the time of treatment, base of skull involvement, and male sex were associated with the development of distant metastasis, with 52% of node positive patients developing distant metastases by 5 years, compared with 32% of node negative patients (p = .04).

CONCLUSIONS

Neutron radiotherapy is an effective form of treatment for patients with high risk, locally advanced tumors of major salivary gland origin. An initial surgical resection appears beneficial in patients for whom such an approach is feasible.

Common emergencies in cancer medicine: infectious and treatment-related syndromes, Part I

This two-part article, the last in a series of articles on cancer emergencies, summarizes the common medical emergencies that can occur as a result of infectious processes (Part I) and antitumor treatment secondary to chemotherapy, biological response modifiers, or radiotherapy (Part II). The use of high-dose cytotoxic agents, coupled with the common instillation of indwelling central venous access devices, have altered the spectrum of infectious etiologies that are appreciated in clinical practice. In addition, a myriad of cytotoxic agents and radiotherapeutic treatment schemes are used widely in clinical oncologic practice. While most of their related side effects are not considered life-threatening emergencies, they can be fatal if not recognized early and treated promptly. Moreover, some of these infectious and treatment-related sequelae can be prevented.

Combined 5-fluorouracil and irradiation for transitional cell carcinoma of the urinary bladder

Thirty-four patients have completed treatment on a bladder-preservation protocol using primary irradiation combined with infusion 5-fluorouracil (5-FU). 4,000 cGy pelvic irradiation was delivered in 5 weeks, with 1,000 mg/m2/day of 5-FU administered as a 96 hr infusion on days 1-4 of week 1 and 4. After a 3-week rest period, patients eligible for cystectomy underwent cystoscopy and biopsy. Those with residual tumor underwent cystectomy, and those without tumor received an additional cycle of chemotherapy and irradiation. Patients ineligible for cystectomy for reasons medical, surgical, or refusal received a third cycle without the 4-week delay or re-evaluation. With a median follow-up of 18 months (range 2-45 months), and with 25/34 patients having T3 (16) or T4 (9) tumors, 17 patients are NED, 4 have died of intercurrent deaths, 7 have died with bladder cancer, and 6 are alive with tumor (2 confined to the bladder). The actuarial cancer-specific survival for the entire group of patients is 64% (+/- 12%) at 45 months, with a freedom from relapse of invasive cancer of 54% (+/- 10%). Twenty-four of the 34 patients retained intact bladders, with 20/24 reporting entirely normal voiding. Of 18 potential surgical candidates, 13/16 (81%) who underwent pathologic re-staging after 2 cycles of chemoradiotherapy had no histologic evidence of residual cancer. Of these 13 patients, 8 remain NED and 2/13 have locally recurrent non-invasive tumors only. Treatment was well-tolerated, with 28/34 patients having received 100% of the planned 5-FU and 34/34 having received greater than 80%. This regimen appears more successful than radiotherapy alone in achieving complete tumor responses, and is an attractive alternative for patients who are unable to receive more aggressive chemotherapy/radiation combinations.

Fast neutron radiotherapy for sarcomas of soft tissue, bone, and cartilage

The basic radiobiological rationale for the use of fast neutron radiotherapy in the treatment of classically radioresistant tumors such as soft tissue sarcomas, osteogenic sarcomas, and chondrosarcomas is reviewed. There are no definitive randomized studies comparing high and low linear energy transfer radiotherapy for these tumor systems, but a review of published series is highly suggestive of a therapeutic advantage for fast neutrons. For soft tissue sarcomas, the local control rate is 53% (158 of 297) with fast neutrons, compared with 38% (49 of 128) with photons/electrons; for osteogenic sarcomas, the local control rate is 55% (40 of 73) with fast neutrons, compared with 21% (15 of 73) with photons/electrons; and for chondrosarcomas, the local control rate is 49% (25 of 51) with fast neutrons, compared with 33% (10 of 30) with photons/electrons. An ongoing clinical trial for these tumors is also described.