Disrupted-in-schizophrenia 1 protein aggregates in cerebrospinal fluid are elevated in patients with first-episode psychosis

Long-term treatment with haloperidol modulates angiotensin I-converting enzyme (ACE) activity in transgenic animal model with construct validity for schizophrenia studies

Elevated angiotensin I-converting enzyme (ACE) activity has been correlated with worse cognitive performance in patients with first-episode psychosis (FEP) and chronic schizophrenia (SZ). In this study, we investigated ACE activity in drug-naïve transgenic rats overexpressing the full-length non-mutated human Disrupted-in-Schizophrenia 1 (tgDISC1) compared to wild-type (WT) controls, while we also assessed the effects of long-term treatment with typical antipsychotic haloperidol. Our findings indicated that untreated tgDISC1 rats show elevated serum ACE activity compared to WT animals, which is consistent with clinical observations in drug-naïve FEP patients. In contrast, baseline ACE activity in the brain of tgDISC1 was generally lower than in WT rats, with the exception of no difference in ACE activity observed in brain regions associated with learning, memory, and reward, such as the hippocampus and nucleus accumbens. Consistent with clinical observations in FEP patients following treatment with antipsychotics, 30-days of daily haloperidol-treatment significantly increased serum ACE activity in blood serum of both tgDISC1 and WT rats. However, ACE responses in brain were markedly different, as haloperidol treatment reduced ACE activity in most brain regions of both rat strains. These results support the existence of a central renin-angiotensin system (RAS) distinct from the peripheral RAS, suggesting that the treatment with a dopamine blocker exerts brain-specific effects on ACE activity, which was essentially opposite to that observed in the periphery. This region-specific alterations observed in cognition-related brain areas (notably with a relative stronger effect size in hippocampus and nucleus accumbens of tgDISC1 compared to WT rats) also suggest a critical interplay among dopamine homeostasis, ACE activity, and cognitive deficits in SZ. Understanding this interplay could help identifying novel biomarkers and/or therapeutic strategies for improving cognitive outcomes in SZ patients.

Transgenic Drosophila melanogaster Carrying a Human Full-Length DISC1 Construct (UAS-hflDISC1) Showing Effects on Social Interaction Networks

Disrupted in Schizophrenia 1 (DISC1) is a scaffold protein implicated in major mental illnesses including schizophrenia, with a significant negative impact on social life. To investigate if DISC1 affects social interactions in Drosophila melanogaster, we created transgenic flies with second or third chromosome insertions of the human full-length DISC1 (hflDISC1) gene fused to a UAS promotor (UAS-hflDISC1). Initial characterization of the insertion lines showed unexpected endogenous expression of the DISC1 protein that led to various behavioral and neurochemical phenotypes. Social interaction network (SIN) analysis showed altered social dynamics and organizational structures. This was in agreement with the altered levels of the locomotor activity of individual flies monitored for 24 h. Together with a decreased ability to climb vertical surfaces, the observed phenotypes indicate altered motor functions that could be due to a change in the function of the motor neurons and/or central brain. The changes in social behavior and motor function suggest that the inserted hflDISC1 gene influences nervous system functioning that parallels symptoms of DISC1-related mental diseases in humans. Furthermore, neurochemical analyses of transgenic lines revealed increased levels of hydrogen peroxide and decreased levels of glutathione, indicating an impact of DISC1 on the dynamics of redox regulation, similar to that reported in transgenic mammals. Future studies are needed to address the localization of DISC1 expression and to address how the redox parameter changes correlate with the observed behavioral changes.

Clinical and CSF single-cell profiling of post-COVID-19 cognitive impairment

Natural history and mechanisms for persistent cognitive symptoms ("brain fog") following acute and often mild COVID-19 are unknown. In a large prospective cohort of people who underwent testing a median of 9 months after acute COVID-19 in the New York City/New Jersey area, we found that cognitive dysfunction is common; is not influenced by mood, fatigue, or sleepiness; and is correlated with MRI changes in very few people. In a subgroup that underwent cerebrospinal fluid analysis, there are no changes related to Alzheimer's disease or neurodegeneration. Single-cell gene expression analysis in the cerebrospinal fluid shows findings consistent with monocyte recruitment, chemokine signaling, cellular stress, and suppressed interferon response-especially in myeloid cells. Longitudinal analysis shows slow recovery accompanied by key alterations in inflammatory genes and increased protein levels of CXCL8, CCL3L1, and sTREM2. These findings suggest that the prognosis for brain fog following COVID-19 correlates with myeloid-related chemokine and interferon-responsive genes.

Aβ oligomers peak in early stages of Alzheimer's disease preceding tau pathology

INTRODUCTION

Soluble amyloid beta (Aβ) oligomers have been suggested as initiating Aβ related neuropathologic change in Alzheimer's disease (AD) but their quantitative distribution and chronological sequence within the AD continuum remain unclear.

METHODS

A total of 526 participants in early clinical stages of AD and controls from a longitudinal cohort were neurobiologically classified for amyloid and tau pathology applying the AT(N) system. Aβ and tau oligomers in the quantified cerebrospinal fluid (CSF) were measured using surface-based fluorescence intensity distribution analysis (sFIDA) technology.

RESULTS

Across groups, highest Aβ oligomer levels were found in A+ with subjective cognitive decline and mild cognitive impairment. Aβ oligomers were significantly higher in A+T- compared to A-T- and A+T+. APOE ε4 allele carriers showed significantly higher Aβ oligomer levels. No differences in tau oligomers were detected.

DISCUSSION

The accumulation of Aβ oligomers in the CSF peaks early within the AD continuum, preceding tau pathology. Disease-modifying treatments targeting Aβ oligomers might have the highest therapeutic effect in these disease stages.

Highlights

Using surface-based fluorescence intensity distribution analysis (sFIDA) technology, we quantified Aβ oligomers in cerebrospinal fluid (CSF) samples of the DZNE-Longitudinal Cognitive Impairment and Dementia (DELCODE) cohortAβ oligomers were significantly elevated in mild cognitive impairment (MCI)Amyloid-positive subjects in the subjective cognitive decline (SCD) group increased compared to the amyloid-negative control groupInterestingly, levels of Aβ oligomers decrease at advanced stages of the disease (A+T+), which might be explained by altered clearing mechanisms.