5-HT2A Receptor and 5-HT Degradation Play a Crucial Role in Atherosclerosis by Modulating Macrophage Foam Cell Formation, Vascular Endothelial Cell Inflammation, and Hepatic Steatosis

Spatial Transcriptomics and Proteomics Profiling After Ischemic Stroke Reperfusion: Insights Into Vascular Alterations

BACKGROUND

More than half of patients with ischemic stroke experience futile reperfusion, increasing the risk of death and disabilities despite a successful recanalization. The reason behind this is debated, and we aim to investigate cerebrovascular changes toward a broader understanding of these conditions. We hypothesize that ischemic stroke reperfusion modifies the expression profile in the microvasculature in a spatial manner toward peri-infarct brain edema and circulatory failure.

METHODS

We investigated the early (24-hour) changes in spatial gene expression in the brain parenchymal endothelial cells and mural cells following ischemia stroke reperfusion in 13- to 14-week-old C57BL/6JRj male mice (n=5). Ischemia was induced by occlusion of the middle cerebral artery for 60 minutes, and Nissl staining was used to validate infarct size. Spatial transcriptomics complemented by bulk proteomics was conducted in the peri-infarct cortex region and validated with immunohistochemical semiquantification of proteins of interest. To avoid individual biological variations, changes in the peri-infarct cortex region were expressed relatively to the matching contralateral hemisphere region.

RESULTS

Ischemic stroke reperfusion impaired the blood-brain barrier integrity through junctional Cldn5 (claudin-5) downregulation, changes of the actin cytoskeleton adhesion, and high expression of the proinflammatory Il-6 (interleukin-6). Molecules important for extracellular Ca2+ influx and intracellular Ca2+ release, Cacna1e (R-type Ca2+ channels), Orai2, Ryr3, Itpr1, and Itpka (inositol-trisphosphate 3-kinase A), were markedly reduced. Furthermore, reduced Grm5 (glutamate receptor 5) associated with upregulated Nfatc3 and Stat3 implicates suppression of the contractile phenotype, suggesting reduced poststroke vascular resistance due to loss of mural cell tone. The complete spatial transcriptomics map over the ipsilateral and contralateral hemispheres is available online as a Web tool.

CONCLUSIONS

Emphasizing the spatial molecular pattern behind blood-brain barrier disruption and loss of the vascular tone in the acute phase following ischemic stroke reperfusion suggests the gene expression contribution for a therapeutic target in ischemia-reperfusion abnormalities.

Serotonin 3 receptor antagonism reduces angiotensin II-induced abdominal aortic aneurysms: Contribution of periaortic fat-derived serotonin

Serotonin (5-HT) has been implicated in cerebral aneurysm rupture, but it is unclear whether 5-HT plays a role in aortic aneurysm development and rupture, despite well known contractile effects of 5-HT through aortic 5-HT receptors. Abdominal aortic aneurysms (AAAs) induced by angiotensin II (AngII) infusion to mice exhibit periaortic inflammation and are prone to rupture. Periaortic fat (PAF), a potential source of 5-HT through tryptophan hydroxylase 1 (Tph1), has been implicated in AAA development. We quantified mRNA abundance of 5-HT receptors (Htr1b, Htr2a, Htr2b, Htr3a, and Htr7) and Tph1 in thoracic and abdominal aortas and surrounding PAF. Compared with other 5-HT receptors, we detected high levels of serotonin 3 receptor type a (Htr3a) mRNA in the abdominal aortas and abdominal PAF. Tph1 mRNA and 5-HT immunostaining were detected in aortas and PAF, with 5-HT levels higher in abdominal than thoracic PAF, and higher in epididymal white than interscapular brown fat. AngII infusion facilitated evoked [3H]5-HT release from thoracic PAF and modestly reduced 5-HT levels in thoracic PAF and brown fat. Based on a high level of Htr3a mRNA in abdominal aortas and PAF, we investigated the development of AngII-induced AAAs when serotonin 3 receptors were pharmacologically antagonized with tropisetron. Tropisetron abrogated abdominal aortic lumen diameters, aneurysm (distal thoracic aneurysm and AAA) incidence, maximal AAA diameters, and aortic weights of AngII-infused male mice. These findings indicate a novel role for serotonin 3 receptor in AAA development, with a potential clinically relevant contribution for PAF as a local source of 5-HT. SIGNIFICANCE STATEMENT: Aortic aneurysms are life-threatening vascular disorders with no effective therapeutics. This study identified antagonism of the serotonin 3 receptor as a potential therapeutic target to reduce the formation and severity of experimentally-induced aneurysms in the thoracic and abdominal aorta. Additionally, periaortic fat was identified as a potential site for serotonin production in the development of aortic aneurysms.

A Scoping Review of Eosinophilic Pneumonia and Antidepressants: An Association Not to Be Overlooked

Background: Eosinophilic pneumonias denote a rare condition, wherein infiltrating eosinophilic granulocytes accumulate within the lung parenchyma. Although eosinophilic pneumonias may be idiopathic, they are also associated with secondary causes. More than 110 medications have been linked to eosinophilic pneumonia, including several antidepressants. This review presents an analysis of case reports of eosinophilic pneumonia correlated to antidepressants. Objectives: The objectives of this study are to provide a contemporary overview of the literature delineating eosinophilic pneumonia as a potential sequela of antidepressant medication treatment, and to discuss possible pathogenetic mechanisms linking antidepressants to eosinophilic pneumonia. Methods and Data Selection: A literature search was performed in PubMed and Scopus databases from 1963 to October 2024. The search strategy used the terms "eosinophilic pneumonia AND antidepressants". Sources included in this review were screened for relevance, focusing on references discussing eosinophilic pneumonia associated with any class of antidepressants. Case reports meeting the diagnostic criteria for acute eosinophilic pneumonia (AEP) or chronic eosinophilic pneumonia (CEP) were included in the review. Clinical, epidemiological, laboratory, radiology and bronchoscopy data, implicated antidepressant and dosage, and therapeutic interventions were reported. Results: This study found that various types of antidepressants are associated with AEP and CEP. The clinical presentation ranges from mild symptoms to respiratory failure and intubation. Outcomes were favorable in most cases, with complete remission achieved after discontinuation of the causative drug and, in severe cases, a short course of corticosteroids. Conclusions: Although a rare cause, antidepressants may lead to eosinophilic pneumonia, and should be considered in the differential diagnosis of unexplained pulmonary infiltrates. Clinical suspicion must be aroused, as early recognition would prevent unnecessary work-up and navigation of the diagnosis.

Dysregulated tryptophan metabolism contributes to metabolic syndrome in Chinese community-dwelling older adults

BACKGROUND

As the prevalence of metabolic syndrome (MetS) rises among older adults, the associated risks of cardiovascular diseases and diabetes significantly increase, and it is closely linked to various metabolic processes in the body. Dysregulation of tryptophan (TRP) metabolism, particularly alterations in the kynurenine (KYN) and serotonin pathways, has been linked to the onset of chronic inflammation, oxidative stress, and insulin resistance, key contributors to the development of MetS. We aim to investigate the relationship between the TRP metabolites and the risk of MetS in older adults.

METHODS

Ultra-performance liquid chromatography tandem mass spectrometry was used to detect TRP and its seven metabolites in a study involving 986 participants. Physical examination included the following indicators: blood pressure, body mass index, triglyceride levels, and high-density lipoprotein cholesterol (HDL-C) levels. Multiple linear regression, restricted cubic spline curve, binary logistic analysis, and sex-stratified analysis were used to explore the relationship between the metabolites and the risk of MetS in older adults.

RESULTS

The results indicated that, after adjusting for covariates, higher levels of TRP, KYN, kynurenic acid (KA), and xanthurenic acid (XA) were risk factors for MetS (P for trend < 0.05). By contrast, higher ratios of 5-hydroxytryptamine to TRP and indole-3-propionic acid to TRP were protective factors against MetS (P for trend < 0.05).

CONCLUSIONS

TRP and its metabolites may serve as potential indicators for assessing and managing MetS in older adults, complementing existing biomarkers.

CLINICAL TRIAL NUMBER

Not applicable.

Monoamine oxidases: A missing link between mitochondria and inflammation in chronic diseases ?

The role of mitochondria spans from the regulation of the oxidative phosphorylation, cell metabolism and survival/death pathways to a more recently identified function in chronic inflammation. In stress situations, mitochondria release some pro-inflammatory mediators such as ATP, cardiolipin, reactive oxygen species (ROS) or mitochondrial DNA, that are believed to participate in chronic diseases and aging. These mitochondrial Damage-Associated Molecular Patterns (mito-DAMPs) can modulate specific receptors among which TLR9, NLRP3 and cGAS-STING, triggering immune cells activation and sterile inflammation. In order to counter the development of chronic diseases, a better understanding of the underlying mechanisms of low grade inflammation induced by mito-DAMPs is needed. In this context, monoamine oxidases (MAO), the mitochondrial enzymes that degrade catecholamines and serotonin, have recently emerged as potent regulators of chronic inflammation in obesity-related disorders, cardiac diseases, cancer, rheumatoid arthritis and pulmonary diseases. The role of these enzymes in inflammation embraces their action in both immune and non-immune cells, where they regulate monoamines levels and generate toxic ROS and aldehydes, as by-products of enzymatic reaction. Here, we discuss the more recent advances on the role and mechanisms of action of MAOs in chronic inflammatory diseases.

Human and gut microbiota synergy in a metabolically active superorganism: a cardiovascular perspective

Despite significant advances in diagnosis and treatment over recent decades, cardiovascular disease (CVD) remains one of the leading causes of morbidity and mortality in Western countries. This persistent burden is partly due to the incomplete understanding of fundamental pathogenic mechanisms, which limits the effectiveness of current therapeutic interventions. In this context, recent evidence highlights the pivotal role of immuno-inflammatory activation by the gut microbiome in influencing cardiovascular disorders, potentially opening new therapeutic avenues. Indeed, while atherosclerosis has been established as a chronic inflammatory disease of the arterial wall, accumulating data suggest that immune system regulation and anti-inflammatory pathways mediated by gut microbiota metabolites play a crucial role in a range of CVDs, including heart failure, pericardial disease, arrhythmias, and cardiomyopathies. Of particular interest is the emerging understanding of how tryptophan metabolism-by both host and microbiota-converges on the Aryl hydrocarbon Receptor (AhR), a key regulator of immune homeostasis. This review seeks to enhance our understanding of the role of the immune system and inflammation in CVD, with a focus on how gut microbiome-derived tryptophan metabolites, such as indoles and their derivatives, contribute to cardioimmunopathology. By exploring these mechanisms, we aim to facilitate the development of novel, microbiome-centered strategies for combating CVD.

Membrane Transporter of Serotonin and Hypercholesterolemia in Children

The serotonin membrane transporter is one of the main mechanisms of plasma serotonin concentration regulation. Serotonin plays an important role in the pathogenesis of various cardiovascular diseases, stimulating the proliferation of smooth muscle cells, key cells in the process of hypertrophic vascular remodeling. Vascular remodeling is one of the leading prognostically unfavorable factors of atherosclerosis, the main manifestation of familial hypercholesterolemia. Familial hypercholesterolemia is one of the most common genetically determined lipid metabolism disorders and occurs in 1 in 313 people. The aim of our study was to investigate the levels of plasma and platelet serotonin, 5-hydroxyindoleacetic acid, and membrane transporter in a cross-sectional study of two pediatric groups, including patients with familial hypercholesterolemia and the control group, which consisted of apparently healthy children without cardiovascular diseases. The study involved 116 children aged 5 to 17 years old. The proportion of boys was 50% (58/116) and the average age of the children was 10.5 years (CI 2.8-18.1). The concentrations of serotonin in blood plasma and platelets and 5-hydroxyindoleacetic acid were higher in children with familial hypercholesterolemia than in the controls. The concentration of the serotonin transporter in platelets in healthy children, compared with the main group, was 1.3 times higher. A positive correlation was revealed between the level of serotonin (5-HT and PWV: ρ = 0.6, p < 0.001), its transporter (SERT and PWV: ρ = 0.5, p < 0.001), and the main indicators of arterial vascular stiffness. Our study revealed the relationship between high serotonin and SERT concentrations and markers of arterial stiffness. The results we obtained suggest the involvement of serotonin and SERT in the process of vascular remodeling in familial hypercholesterolemia in children.

Chemical and biological characterization of the DPP-IV inhibitory activity exerted by lupin (Lupinus angustifolius) peptides: From the bench to the bedside investigation

Dipeptidyl peptidase IV (DPP-IV) is considered a key target for the diabetes treatment, since it is involved in glucose metabolism. Although lupin protein consumption shown hypoglycemic activity, there is no evidence of its effect on DPP-IV activity. This study demonstrates that a lupin protein hydrolysate (LPH), obtained by hydrolysis with Alcalase, exerts anti-diabetic activity by modulating DPP-IV activity. In fact, LPH decreased DPP-IV activity in a cell-free and cell-based system. Contextually, Caco-2 cells were employed to identify LPH peptides that can be intestinally trans-epithelial transported. Notably, 141 different intestinally transported LPH sequences were identified using nano- and ultra-chromatography coupled to mass spectrometry. Hence, it was demonstrated that LPH modulated the glycemic response and the glucose concentration in mice, by inhibiting the DPP-IV. Finally, a beverage containing 1 g of LPH decreased DPP-IV activity and glucose levels in humans.

Profile of 5-HT2A receptor involved in signaling cascades associated to intracellular inflammation and apoptosis in hepatocytes and its role in carbon tetrachloride-induced hepatotoxicity

Previously, we found that the 5-HT_2A receptor plays a key role in cell injury. However, the mechanism by which the 5-HT_2A receptor mediates intracellular processes remains unclear. In this study, we aimed to clarify this intracellular process in hepatocyte LO2 cells and evaluate its role in CCl₄-induced hepatotoxicity in mice. In vitro, both the agonist and overexpression of 5-HT_2A receptor could promote 5-HT degradation by upregulating the expression of 5-HT synthases and monoamine oxidase-A (MAO-A) to cause overproduction of ROS in mitochondria. We refer to this as the activation of the 5-HT degradation system (5DS) axis, which leads to the phosphorylation of JNK, p38 MAPK, STAT3, and NF-κB; upregulation of Bax, cleaved-caspase3, and cleaved-caspase9; and downregulation of Bcl-2, followed by apoptosis and oversecretion of TNF-α and IL-1β in cells. This phenomenon could be markedly blocked by the 5-HT_2A receptor antagonist, MAO-A inhibitor, or gene-silencing MAO-A. Through protein kinases C epsilon (PKCε) agonist treatment and gene silencing of the PKCε and 5-HT_2A receptor, we demonstrated that the 5-HT_2A receptor controls 5-HT synthases and MAO-A expression via the PKCε pathway in cells. Unexpectedly, we discovered that PKCε-mediated phosphorylation of the AKT/mTOR pathway is also a consequence of the activation of the 5DS axis. Furthermore, we confirmed that the inhibition of the 5DS axis using the 5-HT_2A receptor antagonist could prevent hepatotoxicity induced by CCl₄ both in vitro and in vivo, inhibiting the aforementioned signaling cascades, inflammation, and apoptosis, and that the 5DS activation area overlapped the necrotic area of mouse liver. Taken together, we revealed a 5DS axis in hepatocytes that controls the signaling cascades associated with inflammation and apoptosis and confirmed its role in CCl₄-induced hepatotoxicity.

Western Diet-Fed ApoE Knockout Male Mice as an Experimental Model of Non-Alcoholic Steatohepatitis

One of the consequences of the Western lifestyle and high-fat diet is non-alcoholic fatty liver disease (NAFLD) and its aggressive form, non-alcoholic steatohepatitis (NASH), which can progress to cirrhosis and hepatocellular carcinoma (HCC) and is rapidly becoming the leading cause of end-stage liver disease or liver transplantation. Currently, rodent NASH models lack significant aspects of the full NASH spectrum, representing a major problem for NASH research. Therefore, this work aimed to characterize a fast rodent model with all characteristic features of NASH. Eight-week-old male ApoE KO mice were fed with Western diet (WD), high fatty diet (HFD) or normal chow (Chow) for 7 weeks. Whole-body fat was increased by ~2 times in WD mice and HFD mice and was associated with increased glucose intolerance, hepatic triglycerides, and plasma ALT and plasma AST compared with Chow mice. WD mice also showed increased galectin-3 expression compared with Chow or HFD mice and increased plasma cholesterol compared with Chow mice. WD and HFD displayed increased hepatic fibrosis and increased F4/80 expression. WD mice also displayed increased levels of plasma MCP-1. Hepatic inflammatory markers were evaluated, and WD mice showed increased levels of TNF-α, MCP-1, IL-6 and IFN-γ. Taken together, these data demonstrated that the ApoE KO mouse fed with WD is a great model for NASH research, once it presents the fundamental parameters of the disease, including hepatic steatosis, fibrosis, inflammation, and metabolic syndrome.

Role of Oxidative Stress in the Pathogenesis of Atherothrombotic Diseases

Oxidative stress is generated by the imbalance between reactive oxygen species (ROS) formation and antioxidant scavenger system’s activity. Increased ROS, such as superoxide anion, hydrogen peroxide, hydroxyl radical and peroxynitrite, likely contribute to the development and complications of atherosclerotic cardiovascular diseases (ASCVD). In genetically modified mouse models of atherosclerosis, the overexpression of ROS-generating enzymes and uncontrolled ROS formation appear to be associated with accelerated atherosclerosis. Conversely, the overexpression of ROS scavenger systems reduces or stabilizes atherosclerotic lesions, depending on the genetic background of the mouse model. In humans, higher levels of circulating biomarkers derived from the oxidation of lipids (8-epi-prostaglandin F_2α, and malondialdehyde), as well as proteins (oxidized low-density lipoprotein, nitrotyrosine, protein carbonyls, advanced glycation end-products), are increased in conditions of high cardiovascular risk or overt ASCVD, and some oxidation biomarkers have been reported as independent predictors of ASCVD in large observational cohorts. In animal models, antioxidant supplementation with melatonin, resveratrol, Vitamin E, stevioside, acacetin and n-polyunsaturated fatty acids reduced ROS and attenuated atherosclerotic lesions. However, in humans, evidence from large, placebo-controlled, randomized trials or prospective studies failed to show any athero-protective effect of antioxidant supplementation with different compounds in different CV settings. However, the chronic consumption of diets known to be rich in antioxidant compounds (e.g., Mediterranean and high-fish diet), has shown to reduce ASCVD over decades. Future studies are needed to fill the gap between the data and targets derived from studies in animals and their pathogenetic and therapeutic significance in human ASCVD.

Psychedelics and Anti-inflammatory Activity in Animal Models

The serotonin (5-hydroxytryptamine, 5-HT) 2A receptor is most well known as the common target for classic psychedelic compounds. Interestingly, the 5-HT_2A receptor is the most widely expressed mammalian serotonin receptor and is found in nearly every examined tissue type including neural, endocrine, endothelial, immune, and muscle, suggesting it could be a novel and pharmacological target for several types of disorders. Despite this, the bulk of research on the 5-HT_2A receptor is focused on its role in the central nervous system (CNS). Recently, activation of 5-HT_2A receptors has emerged as a new anti-inflammatory strategy. This review will describe recent findings regarding psychedelics as anti-inflammatory compounds, as well as parse out differences in functional selectivity and immune regulation that exist between a number of well-known hallucinogenic compounds.

Renal ischemia/reperfusion injury in rats is probably due to the activation of the 5-HT degradation system in proximal renal tubular epithelial cells

AIMS

To explore the relationship between renal ischemia/reperfusion injury (RIRI) and the activation of the renal 5-HT degradation system, including 5-HT_2A receptor (5-HT_2AR), 5-HT synthases and monoamine oxidase-A (MAO-A).

MAIN METHODS

Rat RIRI was induced by removing the right kidney, causing ischemia of the left kidney for 45 min and reperfusion for different times. RIRI model (ischemia for 45 min and reperfusion for 24 h) was pretreated with 5-HT_2AR antagonist sarpogrelate hydrochloride (SH) and the 5-HT synthase inhibitor carbidopa. In HK-2 cells, cellular damage was induced by hypoxia (24 h)/reoxygenation (12 h) (H/R) and treated with SH, carbidopa or the MAO-A inhibitor clorgyline. Hematoxylin-eosin, immunohistochemistry, TUNEL and fluorescent probe staining, RT-qPCR, western blotting, ELISA, etc. were used in the tests.

KEY FINDINGS

The development of RIRI and the emergence of the RIRI peak were consistent with renal 5-HT degradation system activation. The highest expression regions of the 5-HT degradation system overlapped with those of the most severe lesions in the kidney, which were in proximal renal tubules. Rat RIRI and HK-2 cell damage, including oxidative stress, inflammation and apoptosis, could be almost abolished by synergistic inhibition of SH and carbidopa. Clorgyline also abolished the cellular damage induced by H/R. H/R-induced production of mitochondrial ROS in HK-2 cells was due to MAO-A-catalyzed 5-HT degradation, and 5-HT_2AR was involved by mediating the expression of 5-HT synthases and MAO-A.

SIGNIFICANCE

These findings revealed a close association between RIRI and activation of the renal 5-HT degradation system.

Nephrotoxicity induced by cisplatin is primarily due to the activation of the 5-hydroxytryptamine degradation system in proximal renal tubules

As a widely used anticancer drug in the clinic, cisplatin has obvious side effects, especially nephrotoxicity. Previous studies have suggested that the accumulation of intracellular reactive oxygen species (ROS) is a hallmark of cisplatin-induced acute kidney injury. This study aimed to investigate the relationship between ROS accumulation induced by cisplatin and 5-HT degradation. In vivo, by HE and TUNEL staining, we found that cisplatin-induced renal lesions and apoptotic regions, which were located in proximal tubular epithelial cells, were also the regions in which tryptophan hydroxylase 1 (Tph1), aromatic l-amino acid decarboxylase (AADC), 5-HT_2A receptor (5-HT_2AR) and monoamine oxidase A (MAO-A) were overexpressed, as determined by immunohistochemistry. Notably, the 5-HT_2AR antagonist sarpogrelate hydrochloride (SH) and the AADC inhibitor carbidopa (CDP) significantly attenuated cisplatin-induced increases in serum creatinine and blood urea nitrogen levels, renal ROS levels, oxidative stress (SOD activity and MDA), proinflammatory cytokine levels (NF-κB, TNF-α and IL-1β), proapoptotic factor levels (Bax, Bcl-2, C-caspase 3 and C-caspase 9) and the phosphorylation of p38 and STAT3, as well as renal lesions and apoptosis. The combination of SH and CDP could almost abolish the effects of cisplatin challenge. In vitro, the effects of cisplatin challenge and the inhibitory effects of SH and CDP were also observed in HK-2 cells. Additionally, similar to the combination of SH and CDP, the MAO-A inhibitor clorgyline could also abolish the effects of cisplatin challenge. More importantly, by western blotting, we detected that the upregulation of Tph1, AADC and MAO-A expression induced by cisplatin both in vivo and in vitro could be obviously suppressed by SH to decrease 5-HT synthesis and mitochondrial 5-HT degradation. Altogether, these findings suggested that cisplatin-induced nephrotoxicity is due to the activation of the 5-HT degradation system in proximal tubular epithelial cells, including 5-HT_2AR and 5-HT synthesis and degradation. 5-HT_2AR plays a role by mediating the expression of MAO-A and the 5-HT synthases Tph1 and AADC.

The poorly conducted orchestra of steroid hormones, oxidative stress and inflammation in frailty needs a maestro: Regular physical exercise

This review outlines the various factors associated with unhealthy aging which includes becoming frail and dependent. With many people not engaging in recommended exercise, facilitators and barriers to engage with exercise must be investigated to promote exercise uptake and adherence over the lifespan for different demographics, including the old, less affluent, women, and those with different cultural-ethnic backgrounds. Governmental and locally funded public health messages and environmental facilitation (gyms, parks etc.) can play an important role. Studies have shown that exercise can act as a conductor to balance oxidative stress, immune and endocrine functions together to promote healthy aging and reduce the risk for age-related morbidities, such as cardiovascular disease and atherosclerosis, and promote cognition and mood over the lifespan. Like a classic symphony orchestra, consisting of four groups of related musical instruments - the woodwinds, brass, percussion, and strings - the aging process should also perform in harmony, with compassion, avoiding the aggrandizement of any of its individual parts during the presentation. This review discusses the wide variety of molecular, cellular and endocrine mechanisms (focusing on the steroid balance) underlying this process and their interrelationships.