Lumateperone Normalizes Pathological Levels of Acute Inflammation through Important Pathways Known to Be Involved in Mood Regulation.

Lumateperone is indicated for the treatment of schizophrenia in adults and for depressive episodes associated with bipolar I or II disorder (bipolar depression) in adults, as monotherapy and as adjunctive therapy with lithium or valproate (Calabrese et al., 2021). It is currently under evaluation for the treatment of major depressive disorder (www.ClinicalTrials.gov). Lumateperone acts by selectively modulating serotonin, dopamine, and glutamate neurotransmission in the brain. However, other mechanisms could be involved in the actions of lumateperone, and because of the connection between the immune system and psychiatric health, we hypothesized that lumateperone might improve symptoms of depression, at least in part, by normalizing pathologic inflammation. Here, we show that in male and female C57BL/6 mice subjected to an acute immune challenge, lumateperone reduced aberrantly elevated levels of key proinflammatory cytokines (e.g., IL-1ß, IL-6, and TNF-α) in both brain and serum; lumateperone also reduced proinflammatory cytokines in male mice under acute behavioral stress. Further, we demonstrate that lumateperone altered key genes/pathways involved in maintaining tissue integrity and supporting blood-brain barrier function, such as claudin-5 and intercellular adhesion molecule 1. In addition, in acutely stressed male Sprague Dawley rats, lumateperone conferred anxiolytic- and antianhedonic-like properties while enhancing activity in the mammalian target of rapamycin complex 1 pathway in the PFC. Together, our preclinical findings indicate that lumateperone, in addition to its ability to modulate multiple neurotransmitter systems, could also act by reducing the impact of acute inflammatory challenges.SIGNIFICANCE STATEMENT Lumateperone is indicated in adults to treat schizophrenia and depressive episodes associated with bipolar I or II disorder, as monotherapy and adjunctive therapy with lithium or valproate. Because aberrant immune system activity is associated with increased depressive symptoms, the relationship between lumateperone and immune function was studied. Here, lumateperone reduced the levels of proinflammatory cytokines that were increased following an immune challenge or stress in mice. Additionally, lumateperone altered genes and pathways that maintain blood-brain barrier integrity, restored an index of blood-brain barrier function, reduced anxiety-like behavior in rodents, and enhanced mammalian target of rapamycin complex 1 pathway signaling in the PFC. These results highlight the anti-inflammatory actions of lumateperone and describe how lumateperone may reduce immune pathophysiology, which is associated with depressive symptoms.

Hyperinsulinemia alters insulin receptor presentation and internalization in brain microvascular endothelial cells.

Insulin receptors are internalized by endothelial cells to facilitate their physiological processes; however, the impact of hyperinsulinemia in brain endothelial cells is not known. Thus, the aim of this study was to elucidate the impact hyperinsulinemia plays on insulin receptor internalization through changes in phosphorylation, as well as the potential impact of protein tyrosine phosphatase 1B (PTP1B). Hippocampal microvessels were isolated from high-fat diet fed mice and assessed for insulin signaling activation, a process known to be involved with receptor internalization. Surface insulin receptors in brain microvascular endothelial cells were labelled to assess the role hyperinsulinemia plays on receptor internalization in response to stimulation, with and without the PTP1B antagonist, Claramine. Our results indicated that insulin receptor levels increased in tandem with decreased receptor signaling in the high-fat diet mouse microvessels. Insulin receptors of cells subjected to hyperinsulinemic treatment demonstrate splice variation towards decreased IR-A mRNA expression and demonstrate a higher membrane-localized proportion. This corresponded with decreased autophosphorylation at sites critical for receptor internalization and signaling. Claramine restored signaling and receptor internalization in cells treated with hyperinsulinemia. In conclusion, hyperinsulinemia impacts brain microvascular endothelial cell insulin receptor signaling and internalization, likely via alternative splicing and increased negative feedback from PTP1B.

Quantification by Luminescence Tracking of Red Emissive Gold Nanoparticles in Cells.

Optical microscopy techniques are ideal for live cell imaging for real-time nanoparticle tracking of nanoparticle localization. However, the quantification of nanoparticle uptake is usually evaluated by analytical methods that require cell isolation. Luminescent labeling of gold nanoparticles with transition metal probes yields particles with attractive photophysical properties, enabling cellular tracking using confocal and time-resolved microscopies. In the current study, gold nanoparticles coated with a red-luminescent ruthenium transition metal complex are used to quantify and track particle uptake and localization. Analysis of the red-luminescence signal from particles is used as a metric of cellular uptake, which correlates to total cellular gold and ruthenium content, independently measured and correlated by inductively coupled plasma mass spectrometry. Tracking of the luminescence signal provides evidence of direct diffusion of the nanoparticles across the cytoplasmic membrane with particles observed in the cytoplasm and mitochondria as nonclustered "free" nanoparticles. Electron microscopy and inhibition studies identified macropinocytosis of clusters of particles into endosomes as the major mechanism of uptake. Nanoparticles were tracked inside GFP-tagged cells by following the red-luminescence signal of the ruthenium complex. Tracking of the particles demonstrates their initial location in early endosomes and, later, in lysosomes and autophagosomes. Colocalization was quantified by calculating the Pearson's correlation coefficient between red and green luminescence signals and confirmed by electron microscopy. Accumulation of particles in autophagosomes correlated with biochemical evidence of active autophagy, but there was no evidence of detachment of the luminescent label or breakup of the gold core. Instead, accumulation of particles in autophagosomes caused organelle swelling, breakdown of the surrounding membranes, and endosomal release of the nanoparticles into the cytoplasm. The phenomenon of endosomal release has important consequences for the toxicity, cellular targeting, and therapeutic future applications of gold nanoparticles.

High-Fat Diet Impairs Tactile Discrimination Memory in the Mouse.

Research on the impact of diet and memory has garnered considerable attention while exploring the link between obesity and cognitive impairment. High-fat diet (HFD) rodent models recapitulate the obesity phenotype and subsequent cognitive impairments. While it is known that HFD is associated with sensory impairment, little attention has been given to the potential role these sensory deficits may play in recognition memory testing, one of the most commonly used cognitive tests. Because mice utilize their facial whiskers as their primary sensory apparatus, we modified a common recognition test, the novel object recognition task, by replacing objects with sandpaper grits at ground level, herein referred to as the novel tactile recognition task (NTR). First, we tested whisker-manipulated mice in this task to determine its reliance on intact whiskers. Then, we tested the HFD mouse in the NTR. Finally, to ensure that deficits in the NTR are due to cognitive impairment and not HFD-induced sensory deficiencies, we tested the whisker sensitivity of HFD mice via the corner test. Our results indicate that the NTR is a whisker dependent task, and that HFD mice exhibit tactile recognition memory impairment, not accompanied by whisker sensory deficits.

Obesity-related cognitive impairment: The role of endothelial dysfunction.

Obesity is a global pandemic associated with macro- and microvascular endothelial dysfunction. Microvascular endothelial dysfunction has recently emerged as a significant risk factor for the development of cognitive impairment. In this review, we present evidence from clinical and preclinical studies supporting a role for obesity in cognitive impairment. Next, we discuss how obesity-related hyperinsulinemia/insulin resistance, systemic inflammation, and gut dysbiosis lead to cognitive impairment through induction of endothelial dysfunction and disruption of the blood brain barrier. Finally, we outline the potential clinical utility of dietary interventions, exercise, and bariatric surgery in circumventing the impacts of obesity on cognitive function.

Neuronally derived extracellular vesicles: an emerging tool for understanding Alzheimer's disease.

In order for Alzheimer's disease (AD) to manifest, cells must communicate "pathogenic material" such as proteins, signaling molecules, or genetic material to ensue disease propagation. Small extracellular vesicles are produced via the endocytic pathways and released by nearly all cell types, including neurons. Due to their intrinsic interrelationship with endocytic processes and autophagy, there has been increased interest in studying the role of these neuronally-derived extracellular vesicles (NDEVs) in the propagation of AD. Pathologic cargo associated with AD have been found in a number of studies, and NDEVs have been shown to induce pathogenesis in vivo and in vitro. Exogenous NDEVs are also shown to reduce plaque burden in AD models. Thus, the NDEV has the potential to become a useful biomarker, a pathologic potentiator, and a therapeutic opportunity. While the field of NDEV research in AD is still in its infancy, we review the current literature supporting these three claims.