Rapid isolation of extracellular vesicles from cell culture and biological fluids using a synthetic peptide with specific affinity for heat shock proteins.

Recent studies indicate that extracellular vesicles are an important source material for many clinical applications, including minimally-invasive disease diagnosis. However, challenges for rapid and simple extracellular vesicle collection have hindered their application. We have developed and validated a novel class of peptides (which we named venceremin, or Vn) that exhibit nucleotide-independent specific affinity for canonical heat shock proteins. The Vn peptides were validated to specifically and efficiently capture HSP-containing extracellular vesicles from cell culture growth media, plasma, and urine by electron microscopy, atomic force microscopy, sequencing of nucleic acid cargo, proteomic profiling, immunoblotting, and nanoparticle tracking analysis. All of these analyses confirmed the material captured by the Vn peptides was comparable to those purified by the standard ultracentrifugation method. We show that the Vn peptides are a useful tool for the rapid isolation of extracellular vesicles using standard laboratory equipment. Moreover, the Vn peptides are adaptable to diverse platforms and therefore represent an excellent solution to the challenge of extracellular vesicle isolation for research and clinical applications.

Hippocampal sulcal cavities in depression and healthy individuals.

BACKGROUND: A literature review suggested age and cognitive problems to be related to an increased prevalence of small areas of signal variation within the hippocampus observed on MRI, described as hippocampal sulcal cavities (HSCs; (Maller et al., 2011)). The current study aimed to describe the prevalence of HSCs in patients with treatment-resistant depression (TRD) and healthy controls over a large age-range. METHODS: 115 TRD patients and 86 controls underwent MRI brain scanning. Right and left HSCs were rated separately for prevalence and length. RESULTS: HSCs were observed in 73.04% of those with TRD, statistically more prevalent (p=0.001) than amongst controls (51.16%). These findings are consistent with our review (66% prevalence in memory disorders and 47% in healthy controls). Furthermore, HSC presence and length was associated with aging. LIMITATIONS: The study was cross-sectional so its implications for aging are tentative. A larger sample scanned longitudinally will allow for more sophisticated statistical methods by which to investigate the relationship between HSCs, aging, and TRD. CONCLUSIONS: Although their clinical significance remains uncertain, the results of the current study suggest that HSCs are related with age and those with TRD have more aged brains than their peers.

Hippocampal volumetrics in treatment-resistant depression and schizophrenia: the devil's in de-tail.

Studies of patients with major depressive disorder (MDD) and schizophrenia (SCH) have revealed reduced hippocampal volumes, but findings have been inconsistent due to sample and measurement differences. The current study sought to measure this structure in a large sample of MDD, SCH, and healthy subjects, using a strict measurement protocol, to elucidate morphological-specific volumetric differences. Patients with treatment-resistant MDD (N = 182) and treatment-resistant SCH with auditory-verbal hallucinations (N = 52), and healthy controls (N = 76) underwent psychiatric assessments and brain MRI. The findings indicate that (1) MDD and SCH patients have reduced total hippocampal volume which was marked in the tails (more so in patients with MDD), (2) region of interest estimation protocols and sample characteristics may help explain volumetric differences between previous SCH studies.

Evidence for cortical inhibitory and excitatory dysfunction in obsessive compulsive disorder.

Several lines of evidence suggest that obsessive-compulsive disorder (OCD) is associated with an inability to inhibit unwanted intrusive thoughts. The neurophysiological mechanisms mediating such inhibitory deficits include abnormalities in cortical γ-aminobutyric acid (GABA) inhibitory as well as N-methyl-D-aspartate (NMDA) receptor-mediated mechanisms. Molecular evidence suggests that both these neurotransmitter systems are involved in OCD. Transcranial magnetic stimulation (TMS) represents a noninvasive technique to ascertain neurophysiological indices of inhibitory GABA and facilitatory NMDA receptor-mediated mechanisms. In this study, both mechanisms were indexed in 34 patients with OCD (23 unmedicated and 11 medicated) and compared with 34 healthy subjects. Cortical inhibitory and facilitatory neurotransmission was measured using TMS paradigms known as short-interval cortical inhibition (SICI), cortical silent period (CSP), and intracortical facilitation (ICF). Patients with OCD demonstrated significantly shortened CSP (p<0.001, Cohen's d=0.91) and increased ICF (p<0.009, Cohen's d=0.71) compared with healthy subjects. By contrast, there were no significant deficits in SICI. After excluding patients with OCD and comorbid major depressive disorder (MDD) from the analysis, these differences remained significant. Our findings suggest that OCD is associated with dysregulation in cortical inhibitory and facilitatory neurotransmission. Specifically, these findings suggest impairments in GABA(B) receptor-mediated and NMDA receptor-mediated neurotransmission. These findings are consistent with previously published genetic studies implicating GABA(B), and NMDA transporter and receptor genes in OCD. It is posited that dysregulation of such mechanisms may lead to the generation and persistence of intrusive thoughts that form the basis for this disorder.

Evidence of cortical inhibitory deficits in major depressive disorder.

BACKGROUND: Several lines of evidence suggest that major depressive disorder is associated with deficits in gamma-aminobutyric acid (GABA) inhibitory neurotransmission. Transcranial magnetic stimulation represents a noninvasive technique to measure cortical inhibition. In this study, we endeavored to measure cortical inhibition in medicated patients with treatment resistant major depressive disorder (TRD), unmedicated patients with major depressive disorder, and medicated euthymic patients with a history of major depressive disorder and compare them with healthy subjects. METHODS: Twenty-five patients with TRD, 16 unmedicated patients with major depressive disorder, 19 medicated euthymic patients with previous major depressive disorder (i.e., 17-item Hamilton Rating Scale for Depression < 8), and 25 healthy subjects were enrolled. Cortical inhibition was measured with transcranial magnetic stimulation paradigms known as short-interval cortical inhibition and the cortical silent period, which index GABA(A) and GABA(B) receptor-mediated inhibitory neurotransmission, respectively. RESULTS: All major depressive disorder patient groups demonstrated significant cortical silent period deficits compared with healthy subjects. By contrast, only TRD patients demonstrated significant deficits in short-interval cortical inhibition compared with healthy subjects, medicated euthymic major depressive disorder patients, and unmedicated major depressive disorder patients. The TRD patients also demonstrated a significantly greater resting motor threshold compared with all other clinical subgroups and healthy subjects, suggesting that TRD was also associated with hypoexcitability of the frontal cortex. CONCLUSIONS: Our findings suggest that GABA(B) neurophysiological deficits are closely related to pathophysiology of major depressive disorder. Our findings also suggest that more severe illness is selectively associated with GABA(A) receptor-mediated inhibitory deficits.

The relationship between cortical inhibition, antipsychotic treatment, and the symptoms of schizophrenia.

BACKGROUND: Cortical inhibition (CI) deficits assessed by transcranial magnetic stimulation paradigms, short-interval cortical inhibition (SICI), and cortical silent period (CSP) have been demonstrated in schizophrenia (SCZ) patients. Antipsychotic treatments can modify CI and improve clinical symptoms, suggesting a neurophysiological link between the two. Previous studies have demonstrated that clozapine is associated with prolongation in CSP, a gamma-hydroxybutyric acid (GABA)(B)-mediated phenomenon. Furthermore, SICI deficits were associated with psychotic symptom severity, suggesting alternation in GABA(A)-mediated neurotransmission. Such differential association patterns between clinical symptoms and CI deficits and their relationship to antipsychotic treatment thus might provide insights to the pathophysiology of schizophrenia. METHODS: CI was assessed in 78 SCZ patients and 38 healthy subjects. Clinical symptoms were evaluated using the Positive and Negative Syndrome Scale (PANSS). Subjects were grouped according to antipsychotic medication status: unmedicated (n = 7), clozapine (n = 19), olanzapine/quetiapine (n = 32), and risperidone/typical antipsychotics (n = 20). RESULTS: Relative to control subjects, patients receiving clozapine had longer CSP and reduced SICI, whereas patients receiving other antipsychotics and unmedicated patients had shorter CSP. Across all subjects with SCZ, CSP was inversely associated with negative symptoms, and SICI was inversely associated with positive symptoms. CONCLUSIONS: These results confirm that unmedicated SCZ patients have CI deficits and that clozapine treatment is associated with potentiation of GABA(B)-inhibitory neurotransmission and reduced GABA(A) inhibitory neurotransmission. Also, the differential associations among SICI, CSP, and clinical symptom dimensions suggest that GABA(A)- and GABA(B)-mediated CI might have different roles in the pathophysiology of symptoms of schizophrenia.

Evidence for impaired long-term potentiation in schizophrenia and its relationship to motor skill learning.

Several lines of evidence suggest that schizophrenia (SCZ) is associated with disrupted plasticity in the cortex. However, there is little direct neurophysiological evidence of aberrant long-term potentiation (LTP)-like plasticity in SCZ and little human evidence to establish a link between LTP to learning and memory. LTP was evaluated using a neurophysiological paradigm referred to as paired associative stimulation (PAS). PAS involves pairing of median nerve electric stimulation with transcranial magnetic stimulation (TMS) over the contralateral motor cortex (for abductor pollicis brevis muscle activation) delivered at 25-ms interstimulus interval. This pairing was delivered at a frequency of 0.1 Hz for 30 min. LTP was reflected by the change in motor evoked potentials (MEPs) before and after PAS. In addition, motor skill learning was assessed using the rotary pursuit task. Compared with healthy subjects, patients with SCZ demonstrated significant MEP facilitation deficits following PAS and impaired rotary-pursuit motor learning. Across all subjects there was a significant association between LTP and motor skill learning. These data provide evidence for disrupted LTP in SCZ, whereas the association between LTP with motor skill learning suggests that the deficits in learning and memory in SCZ may be mediated through disordered LTP.