Perinatal stress modulates glutamatergic functional connectivity: A post-synaptic density immediate early gene-based network analysis

Early life stress may induce synaptic changes within brain regions associated with behavioral disorders. Here, we investigated glutamatergic functional connectivity by a postsynaptic density immediate-early gene-based network analysis. Pregnant female Sprague-Dawley rats were randomly divided into two experimental groups: one exposed to stress sessions and the other serving as a stress-free control group. Homer1 expression was evaluated by in situ hybridization technique in eighty-eight brain regions of interest of male rat offspring. Differences between the perinatal stress exposed group (PRS) (n = 5) and the control group (CTR) (n = 5) were assessed by performing the Student's t-test via SPSS 28.0.1.0 with Bonferroni correction. Additionally, all possible pairwise Spearman's correlations were computed as well as correlation matrices and networks for each experimental group were generated via RStudio and Cytoscape. Perinatal stress exposure was associated with Homer1a reduction in several cortical, thalamic, and striatal regions. Furthermore, it was found to affect functional connectivity between: the lateral septal nucleus, the central medial thalamic nucleus, the anterior part of the paraventricular thalamic nucleus, and both retrosplenial granular b cortex and hippocampal regions; the orbitofrontal cortex, amygdaloid nuclei, and hippocampal regions; and lastly, among regions involved in limbic system. Finally, the PRS networks showed a significant reduction in multiple connections for the ventrolateral part of the anteroventral thalamic nucleus after perinatal stress exposure, as well as a decrease in the centrality of ventral anterior thalamic and amygdaloid nuclei suggestive of putative reduced cortical control over these regions. Within the present preclinical setting, perinatal stress exposure is a modifier of glutamatergic early gene-based functional connectivity in neuronal circuits involved in behaviors relevant to model neurodevelopmental disorders.

Relationships between early age at onset of psychotic symptoms and treatment resistant schizophrenia

AIM

Early age at schizophrenia onset (EOS) has been associated with a worse clinical course, although previous studies reported substantial heterogeneity. Despite the relevance of the subject, the relationship between the age of onset and treatment resistant schizophrenia (TRS) is less clear.

METHODS

We screened 197 non-affective psychotic patients. Of these, 99 suffered from schizophrenia and were putative TRS and were included in a prospective 4-to-8-week trial to assess their response to antipsychotics. According to status (TRS/nonTRS) and age-at-onset (early: ≤18 years, EOS; adult: >18 years, adult onset schizophrenia [AOS]) patients were subdivided in EOS-TRS, EOS-nonTRS, AOS-TRS, AOS-nonTRS. Multiple clinical variables were measured and compared by analysis of covariance (ANCOVA), using age as a covariate. Two-way analysis of variance (ANOVA) was used to assess whether significant differences were attributable to TRS status or age-at-onset.

RESULTS

The rate of TRS patients was significantly higher in EOS compared to AOS. At the ANCOVA, EOS-TRS had significantly worse clinical, cognitive, and psychosocial outcomes compared to the other groups. Overall, EOS-TRS were more impaired than EOS-nonTRS, while significant differences with AOS-TRS were less consistent, albeit appreciable. Two-way ANOVA demonstrated that, in the majority of the investigated variables, the significant differences among groups were attributable to the TRS status effect rather than to age-at-onset or combined effects.

CONCLUSIONS

These results suggest that refractoriness to antipsychotics may be strongly linked to the early onset of psychotic symptoms, possibly as a result of common neurobiology.

Modulation of glutamatergic functional connectivity by a prototypical antipsychotic: Translational inference from a postsynaptic density immediate-early gene-based network analysis

BACKGROUND

Although extensively studied, the effect of antipsychotics is not completely understood at a network level. We tested the hypothesis that acute administration of haloperidol would modulate functional connectivity of brain regions relevant to schizophrenia pathophysiology. To assess putative changes in brain network properties and regional interactivity, we studied the expression of Homer1a, an Immediate Early Gene (IEG) demonstrated to be induced by antipsychotic administration and coding for a protein involved in glutamatergic synapses remodeling.

METHODS

Sprague-Dawley rats (n = 26) assigned to vehicle (VEH; NaCl 0.9%) or haloperidol (HAL; 0.8 mg/kg) were included in the network analysis. Homer1a mRNA induction was evaluated by in situ hybridization. Signal intensity analysis was performed in 33 Regions of Interest (ROIs) in the cortex, the caudate putamen, and the nucleus accumbens. A signal correlation analysis was performed, computing all possible pairwise Pearson correlations among ROIs in the two groups. Two networks were generated for HAL and VEH groups, and their properties and topography were explored.

RESULTS

VEH and HAL networks showed qualitative differences in global efficiency and clustering coefficient. The HAL network showed enhanced interactivity between cortical and striatal regions, and within caudate putamen subdivisions. On the other hand, it exhibited reduced inter-correlations between cingulate cortex and anterior insula and caudate putamen and nucleus accumbens. Moreover, haloperidol was able to modulate centrality of crucial functional hubs. These preclinical results corroborate and expand the clinical evidence that antipsychotics may modulate specific brain network properties and disease-related circuits' interactivity.

Synthesis and Preclinical Evaluation of 6-[18F]Fluorine-α-methyl-l-tryptophan, a Novel PET Tracer for Measuring Tryptophan Uptake

The positron emission tomography (PET) radioligand α-[¹¹C]methyl-l-tryptophan ([¹¹C]AMT) has been used to assess tryptophan metabolism in cancer, epilepsy, migraine, and autism. Despite its extensive application, the utility of this tracer is currently hampered by the short half-life of the radionuclide used for its labeling (¹¹C, t_1/2 = 20.4 min). We herein report the design, synthesis, radiolabeling, and initial in vivo evaluation of a fluorine-18 (¹⁸F, t_1/2 = 109.7 min) labeled analogue that is fluorinated in the 6-position of the aromatic ring ([¹⁸F]6-F-AMTr). In a head-to-head comparison between [¹⁸F]6-F-AMTr and [¹¹C]AMT in mice using PET, peak brain radioactivity, regional brain distribution, and kinetic profiles were similar between the two tracers. [¹⁸F]6-F-AMTr was however not a substrate for IDO1 or TPH as determined in in vitro enzymatic assays. The brain uptake of the tracer is thus more likely related to LAT1 transport over the blood-brain barrier than metabolism along the serotonin or kynurenine pathways.

Treatment resistant schizophrenia and neurological soft signs may converge on the same pathology: Evidence from explanatory analysis on clinical, psychopathological, and cognitive variables

Here, we investigated neurological soft signs (NSSs) in treatment resistant schizophrenia (TRS) vs treatment responder schizophrenia (SZ) patients. TRS is a severe condition, affecting approximately one-third of schizophrenia patients and representing a relevant clinical challenge. NSSs are neurological abnormalities reportedly described in schizophrenia patients and linked to dysregulated network connections. We explored the possibility that NSSs may be: i) more severe in TRS patients; ii) differentially associated to clinical/cognitive variables in TRS vs SZ; iii) predictive of having TRS. In addition, we evaluated whether diagnosis may mediate NSSs associations with the above-mentioned variables. Consecutive patients with schizophrenia diagnosis underwent stringent assessment for TRS diagnosis. Demographics and clinical variables were recorded. Psychopathology (by Positive and Negative Syndrome Scale, PANSS), cognitive performances, and NSSs (by Neurological Evaluation Scale, NES) were tested. TRS had higher scores than SZ patients in total NES score and in almost all NES subscales, even after correction for duration of illness and antipsychotic dose (ANCOVA, p<0.05). NSSs significantly correlated with multiple clinical, psychopathological, and cognitive variables (above all: duration of disease and negative symptoms) in TRS but not in SZ patients. Two-way ANOVA showed NSS-x-diagnosis interaction in determining outcomes on multiple cognitive performances, but not in other clinical variables. However, simple main effect analysis detected a significant relationship between high severity NSSs and TRS diagnosis on multiple clinical and cognitive outcomes. Hierarchical regression analysis showed that diagnosis was among a discrete number of predictors yielding significant increases in variance explained on NES total, Sensory Integration and Other Signs subscales' scores. NSSs, together with antipsychotic dose and disease severity, were found to be significantly predictive of TRS diagnosis in a binary logistic regression model. These results suggest a stringent association between NSSs and TRS diagnosis, and may imply that NSSs association with clinical, psychopathological, and cognitive variables may be in part mediated by TRS diagnosis.

Disease Severity in Treatment Resistant Schizophrenia Patients Is Mainly Affected by Negative Symptoms, Which Mediate the Effects of Cognitive Dysfunctions and Neurological Soft Signs

This post-hoc study was aimed at assessing whether disease severity was higher in a sample of Treatment Resistant Schizophrenia patients (TRS) compared to schizophrenia patients responsive to antipsychotics (non-TRS). Determinants of disease severity were also investigated in these groups. Eligible patients were screened by standardized diagnostic algorithm to categorize them as TRS or non-TRS. All patients underwent the following assessments: CGI-S; PANSS; DAI; NES; a battery of cognitive tests. Socio-demographic and clinical variables were also recorded. TRS patients exhibited significantly higher disease severity and psychotic symptoms, either as PANSS total score or subscales' scores. A preliminary correlation analysis ruled out clinical and cognitive variables not associated with disease severity in the two groups. Hierarchical linear regression showed that negative symptoms were the clinical variable explaining the highest part of variation in disease severity in TRS, while in non-TRS patients PANSS-General Psychopathology was the variable explaining the highest variation. Mediation analysis showed that negative symptoms mediate the effects of verbal fluency dysfunctions and high-level neurological soft signs (NSS) on TRS' disease severity. These results show that determinants of disease severity sharply differ in TRS and non-TRS patients, and let hypothesize that TRS may stem from cognitive disfunctions and putatively neurodevelopmental aberrations.

Re-arrangements of gene transcripts at glutamatergic synapses after prolonged treatments with antipsychotics: A putative link with synaptic remodeling

OBJECTIVES

The postsynaptic density (PSD) represents a site of dopamine-glutamate integration. Despite multiple evidence of PSD involvement in antipsychotic-induced synaptic changes, there are no direct head-to-head comparisons of the effects at the PSD of antipsychotics with different receptor profile and at different doses after chronic administration.

METHODS

Molecular imaging of gene expression was used to investigate whether chronic treatment with first and second generation antipsychotics (haloperidol, asenapine and olanzapine) may induce changes in the expression levels of PSD transcripts involved in schizophrenia pathophysiology, i.e. Homers, Shank1, PSD-95 and Arc.

RESULTS

Genes' expression patterns were differentially modulated after chronic administration of typical and atypical antipsychotics as well as by the same compound administered at different doses. Antipsychotic treatment reduced gene expression in cortical regions, while Homer1a was still induced in striatum by haloperidol even after prolonged treatment. Moreover, chronic treatments appeared to cause a "de-recruitment" of brain regions demonstrated to be activated in acute treatments, with a prominent effect in the cortex rather than in striatum.

CONCLUSIONS

These results let hypothesize that prolonged antipsychotic treatment may trigger a set of plastic changes involving scaffolding and effector molecules causing a possible re-arrangement of PSD transcripts in brain regions relevant to schizophrenia pathophysiology.

Alginate-hyaluronan composite hydrogels accelerate wound healing process

In this paper we propose polysaccharide hydrogels combining alginate (ALG) and hyaluronan (HA) as biofunctional platform for dermal wound repair. Hydrogels produced by internal gelation were homogeneous and easy to handle. Rheological evaluation of gelation kinetics of ALG/HA mixtures at different ratios allowed understanding the HA effect on ALG cross-linking process. Disk-shaped hydrogels, at different ALG/HA ratio, were characterized for morphology, homogeneity and mechanical properties. Results suggest that, although the presence of HA does significantly slow down gelation kinetics, the concentration of cross-links reached at the end of gelation is scarcely affected. The in vitro activity of ALG/HA dressings was tested on adipose derived multipotent adult stem cells (Ad-MSC) and an immortalized keratinocyte cell line (HaCaT). Hydrogels did not interfere with cell viability in both cells lines, but significantly promoted gap closure in a scratch assay at early (1 day) and late (5 days) stages as compared to hydrogels made of ALG alone (p<0.01 and 0.001 for Ad-MSC and HaCaT, respectively). In vivo wound healing studies, conducted on a rat model of excised wound indicated that after 5 days ALG/HA hydrogels significantly promoted wound closure as compared to ALG ones (p<0.001). Overall results demonstrate that the integration of HA in a physically cross-linked ALG hydrogel can be a versatile strategy to promote wound healing that can be easily translated in a clinical setting.

Central administration of oxytocin reduces hyperalgesia in mice: implication for cannabinoid and opioid systems

The neuropeptide oxytocin (OXT) contributes to the regulation of diverse cognitive and physiological functions including nociception. Indeed, OXT has been reported to be analgesic when administered directly into the brain, the spinal cord, or systemically. Although many authors have reported the analgesic effects of OXT, its mechanism has not been well elucidated. Recently, it has been also hypothesize that OXT, increasing intracellular concentration of calcium, could regulate the production of mediators, like endocannabinoids (eCB). It has been well documented that eCB are able to suppress pain pathways. The present study investigates the effect of OXT in paw carrageenan-induced pain. Intracerebroventricular (icv) administration of OXT, but neither intraperitoneal nor intraplantar route, induces an antihyperalgesic effect increasing paw withdrawal latency to mechanical or thermal stimuli. Our results clearly demonstrate that 3 and 6h following carrageenan challenge, central administration of OXT (30 ng/mouse) shows a significant antihyperalgesic activity. Moreover, for the first time, we demonstrate that CB1 receptor plays a key role in the antihyperalgesic effect of OXT. In fact our results show CB1 antagonist, but not the specific CB2 antagonist reduce OXT-induced antihyperalgesic effect. In addition, our data show that central OXT administration is able to reduce carrageenan-induced hyperalgesia but does not modify carrageenan-induced paw edema. Finally, using opioid antagonists we confirm an important role of opioid receptors. In conclusion, our experiments suggest that central administration of OXT reduces hyperalgesia induced by intraplantar injection of carrageenan, and this effect may work via cannabinoid and opioid systems.