Confirmation of the diagnosis of schizophrenia after death using DSM-IV: a Victorian experience

Activity-dependent neuroprotective protein (ADNP) expression level is correlated with the expression of the sister protein ADNP2: deregulation in schizophrenia

Activity-dependent neuroprotective protein (ADNP) and the homologous protein ADNP2 provide cell protection. ADNP is essential for brain formation, proper brain development and neuronal plasticity, all reported to be impaired in the schizophrenia patient brains. Furthermore, reduction in ADNP expression affects social interactions, a major hallmark of schizophrenia. To evaluate a possible involvement of ADNP and ADNP2 in the pathophysiology of schizophrenia in humans, we measured relative brain mRNA transcripts of both proteins compared with control subjects. Quantitative real time polymerase chain reaction in postmortem hippocampal specimens from normal control subjects exhibited a significant ADNP to ADNP2 transcript level correlation (r=0.931, p<0.001), also apparent in a neuroglial model system. In contrast, in the hippocampus of matched schizophrenia patients, this correlation (r=0.637, p=0.014) was drastically decreased in a statistically significant manner (p=0.03), mirroring disease-associated increased ADNP2 transcripts. In the prefrontal cortex of schizophrenia patients the correlation between ADNP and ADNP2 mRNA levels was apparently higher than in the hippocampus (r=0.854, p<0.001), but did not reach a significant difference (p=0.25). Thus, imbalance in ADNP/ADNP2 expression in the brain may impact disease progression in schizophrenia.

Effects of benzodiazepine treatment on cortical GABA(A) and muscarinic receptors: studies in schizophrenia and rats

Changes in cortical γ-aminobutyric acid A (GABA(A)) receptors and muscarinic receptors have been reported in schizophrenia, a disorder treated with antipsychotic drugs and benzodiazepines. As there is a reported functional relationship between the GABAergic and cholinergic systems in the human central nervous system we have investigated whether there are changes in the GABA(A) and muscarinic receptors in the cortex of subjects from APD-treated subjects with schizophrenia and whether changes were different in subjects who had also received benzodiazepine treatment. We failed to show any strong correlations between changes in GABA(A) and muscarinic receptors in the CNS of subjects with schizophrenia. We showed that subjects with schizophrenia treated with benzodiazepines had lower levels of muscarinic receptors; which was not the case in rats treated with APDs, benzodiazepines or a combination of both drugs. Further, the benzodiazepine binding site, but not the muscimol binding site, was decreased in the parietal cortex of subjects with schizophrenia independent of benzodiazepine status at death. These data would therefore support our previously stated hypotheses that changes in the cortical cholinergic and GABAergic systems are involved in the pathophysiology of schizophrenia.

Dopamine transporter polymorphism modulates oculomotor function and DAT1 mRNA expression in schizophrenia

Smooth pursuit eye movement (SPEM) deficit is an established schizophrenia endophenotype with a similar neurocognitive construct to working memory. Frontal eye field (FEF) neurons controlling SPEM maintain firing when visual sensory information is removed, and their firing rates directly correlate with SPEM velocity. We previously demonstrated a paradoxical association between a functional polymorphism of dopamine signaling (COMT gene) and SPEM. Recent evidence implicates the dopamine transporter gene (DAT1) in modulating cortical dopamine and associated neurocognitive functions. We hypothesized that DAT1 10/10 genotype, which reduces dopamine transporter expression and increases extracellular dopamine, would affect SPEM. We examined the effects of DAT1 genotype on: Clinical diagnosis in the study sample (n = 418; 190 with schizophrenia), SPEM measures in a subgroup with completed oculomotor measures (n = 200; 87 schizophrenia), and DAT1 gene expression in FEF tissue obtained from postmortem brain samples (n = 32; 16 schizophrenia). DAT1 genotype was not associated with schizophrenia. DAT1 10/10 genotype was associated with better SPEM in healthy controls, intermediate SPEM in unaffected first-degree relatives of schizophrenia subjects, and worse SPEM in schizophrenia subjects. In the gene expression study, DAT1 10/10 genotype was associated with significantly reduced DAT1 mRNA transcript in FEF tissue from healthy control donors (P < 0.05), but higher expression in schizophrenia donors. Findings suggest regulatory effects of another gene(s) or etiological factor in schizophrenia, which modulate DAT1 gene function.

Postmortem diagnosis and toxicological validation of illicit substance use

The present study examines the diagnostic challenges of identifying ante-mortem illicit substance use in human postmortem cases. Substance use, assessed by clinical case history reviews, structured next-of-kin interviews, by general toxicology of blood, urine and/or brain, and by scalp hair testing, identified 33 cocaine, 29 cannabis, 10 phencyclidine and nine opioid cases. Case history identified 42% cocaine, 76% cannabis, 10% phencyclidine and 33% opioid cases. Next-of-kin interviews identified almost twice as many cocaine and cannabis cases as Medical Examiner (ME) case histories, and were crucial in establishing a detailed lifetime substance use history. Toxicology identified 91% cocaine, 68% cannabis, 80% phencyclidine and 100% opioid cases, with hair testing increasing detection for all drug classes. A cocaine or cannabis use history was corroborated by general toxicology with 50% and 32% sensitivity, respectively, and with 82% and 64% sensitivity by hair testing. Hair testing corroborated a positive general toxicology for cocaine and cannabis with 91% and 100% sensitivity, respectively. Case history corroborated hair toxicology with 38% sensitivity for cocaine and 79% sensitivity for cannabis, suggesting that both case history and general toxicology underestimated cocaine use. Identifying ante-mortem substance use in human postmortem cases are key considerations in case diagnosis and for characterization of disorder-specific changes in neurobiology. The sensitivity and specificity of substance use assessments increased when ME case history was supplemented with structured next-of-kin interviews to establish a detailed lifetime substance use history, while comprehensive toxicology, and hair testing in particular, increased detection of recent illicit substance use.

Competing definitions of schizophrenia: what can be learned from polydiagnostic studies?

The contemporary diagnoses of schizophrenia (sz)-Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition(DSM-IV) and International Classification of Diseases, 10th Revision(ICD-10)-are widely considered as important scientific achievements. However, these algorithms were not a product of explicit conceptual analyses and empirical studies but defined through consensus with the purpose of improving reliability. The validity status of current definitions and of their predecessors remains unclear. The so-called "polydiagnostic approach" applies different definitions of a disorder to the same patient sample in order to compare these definitions on potential validity indicators. We reviewed 92 polydiagnostic sz studies published since the early 1970s. Different sz definitions show a considerable variation concerning frequency, concordance, reliability, outcome, and other validity measures. The DSM-IV and the ICD-10 show moderate reliability but both definitions appear weak in terms of concurrent validity, eg, with respect to an aggregation of a priori important features. The first-rank symptoms of Schneider are not associated with family history of sz or with prediction of poor outcome. The introduction of long duration criteria and exclusion of affective syndromes tend to restrict the diagnosis to chronic stable patients. Patients fulfilling the majority of definitions (core sz patients) do not seem to constitute a strongly valid subgroup but rather a severely ill subgroup. Paradoxically, it seems that a century after the introduction of the sz concept, research is still badly needed, concerning conceptual and construct validity of sz, its essential psychopathological features, and phenotypic boundaries.

Postmortem brain calcineurin protein levels in schizophrenia patients are not different from controls

Calcineurin (CaN), also designated as protein phosphatase 2B, is a major Ca2+/calmodulin-binding protein in the brain and the only serine/threonine phosphatase under the control of Ca2+/calmodulin. CaN activity has been implicated in downstream regulation of dopaminergic signal transduction and in NMDA receptor-dependent synaptic plasticity. Thus, it serves as a point of convergence for the abnormalities of these two neurotransmitter systems in schizophrenia. The aim of the present study was to determine if levels of CaN were altered in two schizophrenia- and CaN-related brain regions--the dorsolateral prefrontal cortex and hippocampus from subjects with schizophrenia compared to that in tissue from age and sex matched controls. CaN protein levels were measured by Western-blot analysis in samples from 15 schizophrenia patients vs. 15 control subjects. No significant differences in CaN protein levels were found either in the prefrontal cortex or in the hippocampus of schizophrenia patients compared to matched control subjects. Our result of lack of difference does not support the concept that brain CaN levels are a pathophysiological factor in this disorder. Further studies with antibodies against specific CaN catalytic subunit isoforms (presently unavailable) are required to resolve this issue.

Reliability of psychiatric diagnosis in postmortem research

BACKGROUND

Postmortem human brain research is an important approach for identifying the cellular, molecular, and genetic pathways involved in the pathophysiology of psychiatric disorders. One critical component in postmortem research is the reliability of psychiatric diagnoses used to define study cohorts. Finding reliable methods for assessing lifetime psychiatric diagnoses in subjects after death is extremely challenging.

METHODS

Two commonly used approaches were compared: psychiatric record reviews and postmortem family interviews. We hypothesized that these two methods would lead to more diagnostic agreement for subjects with schizophrenia than those with mood disorders. For 37 cases, psychiatric records were reviewed retrospectively using the Diagnostic Evaluation After Death, and family members were interviewed using the Structured Clinical Interview for DSM-IV.

RESULTS

Comparison of diagnoses derived from these two approaches generated an overall kappa coefficient of .67. Kappa coefficients for the schizophrenia cohort were .94, .68 for the major depressive disorder cohort, and .58 for the bipolar disorder cohort.

CONCLUSIONS

Thus, although it may be sufficient to establish the postmortem diagnosis of schizophrenia using one of the two methods, the best method for reaching an accurate postmortem diagnosis for mood disorders is more difficult to determine and requires further study.

GSK-3 parameters in postmortem frontal cortex and hippocampus of schizophrenic patients

The protein kinase glycogen synthase kinase-3 (GSK-3) is highly abundant in brain and involved in signal transduction cascades, particularly during neurodevelopment. We have previously found reduced GSK-3beta mRNA levels, protein levels and GSK-3 total (alpha+beta isoforms) activity in postmortem frontal cortex of schizophrenic patients in the Stanley Medical Research Institute's Brain Collection. To verify and extend these findings, GSK-3 parameters were now measured in the frontal cortex (BA9) and hippocampus obtained from the Rebecca L. Cooper Research Laboratories postmortem brain collection. Fifteen pairs of schizophrenic patients and matched control subjects have been studied. No significant differences in GSK-3alpha and GSK-3beta mRNA levels, GSK-3beta protein levels or total GSK-3 (alpha+beta) activity were found in the frontal cortex of the two diagnostic groups. Hippocampal GSK-3alpha and GSK-3beta mRNA levels were significantly lower (22% and 28%, respectively) in the tissue from the schizophrenic patients compared with the normal controls. Hippocampal GSK-3beta protein levels in the schizophrenic patients were 24% significantly lower than control values only after omission of three outlier subjects. Hippocampal total GSK-3 (alpha+beta) activity in the patients was 31% lower in the schizophrenic patients vs. control subjects. This difference was marginally significant. While our previous data on GSK-3beta in postmortem brain and the recent report that there is impaired AKT1-GSK-3beta signaling in schizophrenia suggest that changes in pathways involving protein kinases such as AKT1 and GSK-3beta in schizophrenia are complex, our present data do not provide strong evidence in support of the involvement of GSK-3beta in schizophrenia. Therefore, further investigation in a greater number of brain samples is warranted to better clarify the possible role of this enzyme in the pathophysiology of schizophrenia.