TNFα Triggers an Augmented Inflammatory Response in Brain Neurons from Dahl Salt-Sensitive Rats Compared with Normal Sprague Dawley Rats

The Impact of Hydrogen Sulfide in the Paraventricular Nucleus on the MAPK Pathway in High Salt-Induced Hypertension

ABSTRACT

The hypothalamic paraventricular nucleus (PVN) plays a central role in regulating cardiovascular activity and blood pressure. We administered hydroxylamine hydrochloride (HA), a cystathionine-β-synthase inhibitor, into the PVN to suppress endogenous hydrogen sulfide and investigate its effects on the mitogen-activated protein kinase (MAPK) pathway in high salt (HS)-induced hypertension. We randomly divided 40 male Dahl salt-sensitive rats into 4 groups: the normal salt (NS) + PVN vehicle group, the NS + PVN HA group, the HS + PVN vehicle group, and the HS + PVN HA group, with 10 rats in each group. The rats in the NS groups were fed a NS diet containing 0.3% NaCl, while the HS groups were fed a HS diet containing 8% NaCl. The mean arterial pressure was calculated after noninvasive measurement using an automatic sphygmomanometer to occlude the tail cuff once a week. HA or vehicle was infused into the bilateral PVN using Alzet osmotic mini pumps for 6 weeks after the hypertension model was successfully established. We measured the levels of H 2 S in the PVN and plasma norepinephrine using enzyme linked immunosorbent assay. In addition, we assessed the parameters of the MAPK pathway, inflammation, and oxidative stress through western blotting, immunohistochemical analysis, or real-time polymerase chain reaction. In this study, we discovered that decreased levels of endogenous hydrogen sulfide in the PVN contributed to the onset of HS-induced hypertension. This was linked to the activation of the MAPK signaling pathway, proinflammatory cytokines, and oxidative stress in the PVN, as well as the activation of the sympathetic nervous system.

Induction of Neuroinflammation and Brain Oxidative Stress by Brain-Derived Extracellular Vesicles from Hypertensive Rats

Neuroinflammation and brain oxidative stress are recognized as significant contributors to hypertension including salt sensitive hypertension. Extracellular vesicles (EVs) play an essential role in intercellular communication in various situations, including physiological and pathological ones. Based on this evidence, we hypothesized that EVs derived from the brains of hypertensive rats with salt sensitivity could trigger neuroinflammation and oxidative stress during hypertension development. To test this hypothesis, we compared the impact of EVs isolated from the brains of hypertensive Dahl Salt-Sensitive rats (DSS) and normotensive Sprague Dawley (SD) rats on inflammatory factors and mitochondrial reactive oxygen species (mtROS) production in primary neuronal cultures and brain cardiovascular relevant regions, including the hypothalamic paraventricular nucleus (PVN) and lamina terminalis (LT). We found that brain-derived DSS-EVs significantly increased the mRNA levels of proinflammatory cytokines (PICs) and chemokines, including TNFα, IL1β, CCL2, CCL5, and CCL12, as well as the transcriptional factor NF-κB in neuronal cultures. DSS-EVs also induced oxidative stress in neuronal cultures, as evidenced by elevated NADPH oxidase subunit CYBA coding gene mRNA levels and persistent mtROS elevation. When DSS-EVs were injected into the brains of normal SD rats, the mRNA levels of PICs, chemokines, and the chronic neuronal activity marker FOSL1 were significantly increased in the PVN and LT. Furthermore, DSS-EVs caused mtROS elevation in brain PVN and LT, particularly in neurons. Our study reveals a novel role for brain-derived EVs from hypertensive rats in triggering neuroinflammation, upregulating chemokine expression, and inducing excessive ROS production. These findings provide insight into the complex interactions between EVs and hypertension-associated processes, offering potential therapeutic targets for hypertension-linked neurological complications.

Engineering Exosomes to Specifically Target the Mitochondria of Brain Cells

Mitochondrial dysfunction is associated with various health conditions, including cardiovascular and neurodegenerative diseases. Mitochondrial-targeting therapy aims to restore or enhance mitochondrial function to treat or alleviate these conditions. Exosomes, small vesicles that cells secrete, containing a variety of biomolecules, are critical in cell-to-cell communication and have been studied as potential therapeutic agents. Exosome-based therapy has the potential to treat both cardiovascular and neurodegenerative diseases. Combining these two approaches involves using exosomes as carriers to transport mitochondrial-targeting agents to dysfunctional or damaged mitochondria within target cells. This article presents a new technique for engineering brain-derived exosomes that target mitochondria and has demonstrated promise in initial tests with primary neuron cells and healthy rats. This promising development represents a significant step forward in treating these debilitating conditions.

The Regulatory Effect of the Paraventricular Nucleus on Hypertension

Hypertension is among the most harmful factors of cardiovascular and cerebrovascular diseases and poses an urgent problem for the development of human society. In addition to previous studies on its pathogenesis focusing on the peripheral sympathetic nervous system, investigating the central causes of high blood pressure involving the neuroendocrine and neuroinflammatory mechanisms of the hypothalamic paraventricular nucleus (PVN) is paramount. This nucleus is considered to regulate the output of neurohormones and sympathetic nerve activity. In this article, we focussed on the neuroendocrine mechanism, primarily exploring the specific contributions and interactions of various neurons and neuroendocrine hormones, including GABAergic and glutamatergic neurons, nitric oxide, arginine vasopressin, oxytocin, and the renin-angiotensin system. Additionally, the neuroinflammatory mechanism in the PVN was discussed, encompassing microglia, reactive oxygen species, inflammatory factors, and pathways, as well as immune connections between the brain and extracerebral organs. Notably, the two central mechanisms involved in the PVN not only exist independently but also communicate with each other, jointly maintaining the hypertensive state of the body. Furthermore, we introduce well-known molecules and signal transduction pathways within the PVN that can play a regulatory role in the two mechanisms to provide a basis and inspire ideas for further research.

Design, Synthesis, and Biological Evaluation of Novel Mitochondria-targeting Exosomes

Mitochondrial dysfunction is implicated in both brain tumors and neurodegenerative diseases, leading to various cellular abnormalities that can promote tumor growth and resistance to thera-pies, as well as impaired energy production and compromised neuronal function. Developing targeted therapies aimed at restoring mitochondrial function and improving overall cellular health could potentially be a promising approach to treating these conditions. Brain-derived exosomes (BR-EVs) have emerged as potential drug delivery vessels for neurological conditions. Herein, we report a new method for creating mitochondria-targeting exosomes and test its application in vitro and in vivo.

Microglia-derived TNF-α contributes to RVLM neuronal mitochondrial dysfunction via blocking the AMPK-Sirt3 pathway in stress-induced hypertension

BACKGROUND

Neuroinflammation in the rostral ventrolateral medulla (RVLM) has been associated with the pathogenesis of stress-induced hypertension (SIH). Neuronal mitochondrial dysfunction is involved in many pathological and physiological processes. However, the impact of neuroinflammation on neuronal mitochondrial homeostasis and the involved signaling pathway in the RVLM during SIH are largely unknown.

METHODS

The morphology and phenotype of microglia and the neuronal mitochondrial injury in vivo were analyzed by immunofluorescence, Western blot, RT-qPCR, transmission electron microscopy, and kit detection. The underlying mechanisms of microglia-derived tumor necrosis factor-α (TNF-α) on neuronal mitochondrial function were investigated through in vitro and in vivo experiments such as immunofluorescence and Western blot. The effect of TNF-α on blood pressure (BP) regulation was determined in vivo via intra-RVLM microinjection of TNF-α receptor antagonist R7050.

RESULTS

The results demonstrated that BP, heart rate (HR), renal sympathetic nerve activity (RSNA), plasma norepinephrine (NE), and electroencephalogram (EEG) power increased in SIH rats. Furthermore, the branching complexity of microglia in the RVLM of SIH rats decreased and polarized into M1 phenotype, accompanied by upregulation of TNF-α. Increased neuronal mitochondria injury was observed in the RVLM of SIH rats. Mechanistically, Sirtuin 3 (Sirt3) and p-AMPK expression were markedly downregulated in both SIH rats and TNF-α-treated N2a cells. AMPK activator A769662 upregulated AMPK-Sirt3 signaling pathway and consequently reversed TNF-α-induced mitochondrial dysfunction. Microinjection of TNF-α receptor antagonist R7050 into the RVLM of SIH rats significantly inhibited the biological activities of TNF-α, increased p-AMPK and Sirt3 levels, and alleviated neuronal mitochondrial injury, thereby reducing c-FOS expression, RSNA, plasma NE, and BP.

CONCLUSIONS

This study revealed that microglia-derived TNF-α in the RVLM impairs neuronal mitochondrial function in SIH possibly through inhibiting the AMPK-Sirt3 pathway. Therefore, microglia-derived TNF-α in the RVLM may be a possible therapeutic target for the intervention of SIH.

Resveratrol ameliorates the behavioural and molecular changes in rats exposed to uninephrectomy: role of hippocampal SIRT1, BDNF and AChE

Subtle memory and cognitive changes may occur in uninephrectomized (Unix) patients long before the development of chronic kidney disease, such changes may be unnoticed. The dietary polyphenol, Resveratrol, displayed various neuroprotective effects, its role in chronic kidney disease is an area of intense studies. This work was designed to investigate the behavioural and molecular changes that may occur following 7 months of Unix in rats, and to determine whether Resveratrol intake can improve such pathology. Male Wistar rats were divided into three groups: sham operated, Unix and Unix group treated with Resveratrol (20 mg/kg/day). Rats were subjected to series of behavioural testing, different biochemical parameters along with RT-PCR and immunohistochemistry of the hippocampal tissue to track the development of functional or structural brain changes. Anxiety behaviour and reduced spatial memory performance were observed in rats 7 months post-nephrectomy; these deficits were remarkably reversed with Resveratrol. Among the species typical behaviour, burrowing was assessed; it showed significant impairment post-nephrectomy. Resveratrol intake was almost able to increase the burrowing behaviour. Decreased SIRT1 in immune-stained sections, oxidative stress, inflammatory changes, and increased AChE activity in hippocampal homogenates were found in Unix rats, and Resveratrol once more was capable to reverse such pathological changes. This work has investigated the occurrence of behavioural and structural brain changes 7 months following Unix and underlined the importance of Resveratrol to counterbalance the behavioural impairment, biochemical and brain pathological changes after uninephrectomy. These findings may raise the possible protective effects of Resveratrol intake in decreased kidney function.

Acne Comorbidities

Acne vulgaris is a multifactorial chronic inflammatory disorder of the pilosebaceous unit, and it represents the most common skin disease affecting about 85% of adolescents in Western populations. The prevalence of acne vulgaris in developed countries is higher than that in developing countries.Emerging data has shown some systemic diseases closely associated with acne, including obesity, diabetes mellitus, cardiovascular diseases, metabolic syndrome (Mets), and so on.This review summarizes acne-associated diseases that have been reported in studies, and analyzes the possible co-pathogenesis of these diseases and acne.

In Silico Drug Repurposing for Anti-Inflammatory Therapy: Virtual Search for Dual Inhibitors of Caspase-1 and TNF-Alpha

Inflammation involves a complex biological response of the body tissues to damaging stimuli. When dysregulated, inflammation led by biomolecular mediators such as caspase-1 and tumor necrosis factor-alpha (TNF-alpha) can play a detrimental role in the progression of different medical conditions such as cancer, neurological disorders, autoimmune diseases, and cytokine storms caused by viral infections such as COVID-19. Computational approaches can accelerate the search for dual-target drugs able to simultaneously inhibit the aforementioned proteins, enabling the discovery of wide-spectrum anti-inflammatory agents. This work reports the first multicondition model based on quantitative structure–activity relationships and a multilayer perceptron neural network (mtc-QSAR-MLP) for the virtual screening of agency-regulated chemicals as versatile anti-inflammatory therapeutics. The mtc-QSAR-MLP model displayed accuracy higher than 88%, and was interpreted from a physicochemical and structural point of view. When using the mtc-QSAR-MLP model as a virtual screening tool, we could identify several agency-regulated chemicals as dual inhibitors of caspase-1 and TNF-alpha, and the experimental information later retrieved from the scientific literature converged with our computational results. This study supports the capabilities of our mtc-QSAR-MLP model in anti-inflammatory therapy with direct applications to current health issues such as the COVID-19 pandemic.

Local ionotropic glutamate receptors are required to trigger and sustain ramping of sympathetic nerve activity by hypothalamic paraventricular nucleus TNF

Tumor necrosis factor-α (TNFα) in the hypothalamic paraventricular nucleus (PVN) contributes to increased sympathetic nerve activity (SNA) in cardiovascular disease models, but mechanisms are incompletely understood. As previously reported, bilateral PVN TNFα (0.6 pmol, 50 nL) induced acute ramping of splanchnic SNA (SSNA) that averaged +64 ± 7% after 60 min and +109 ± 17% after 120 min (P < 0.0001, n = 10). Given that TNFα can rapidly strengthen glutamatergic transmission, we hypothesized that progressive activation of ionotropic glutamate receptors is critically involved. When compared with that of vehicle (n = 5), prior blockade of PVN AMPA or NMDA receptors in anesthetized (urethane/α-chloralose) adult male Sprague-Dawley rats dose-dependently (ED₅₀: 2,3-dioxo-6-nitro-1,2,3,4-tetrahydrobenzo[f]quinoxaline-7-sulfonamide (NBQX), 2.48 nmol; D-(-)-2-amino-5-phosphonopentanoic acid (APV), 12.33 nmol), but incompletely (E_max: NBQX, 64%; APV, 41%), attenuated TNFα-induced SSNA ramping (n = 5/dose). By contrast, combined receptor blockade prevented ramping (1.3 ± 2.1%, P < 0.0001, n = 5). Whereas separate blockade of PVN AMPA or NMDA receptors (n = 5/group) had little effect on continued SSNA ramping when performed 60 min after TNFα injection, combined blockade (n = 5) or PVN inhibition with the GABA-A receptor agonist muscimol (n = 5) effectively stalled, without reversing, the SSNA ramp. Notably, PVN TNFα increased local TNFα immunofluorescence after 120, but not 60 min. Findings indicate that AMPA and NMDA receptors each contribute to SSNA ramping to PVN TNFα, and that their collective availability and ongoing activity are required to initiate and sustain the ramping response. We conclude that acute sympathetic activation by PVN TNFα involves progressive local glutamatergic excitation that recruits downstream neurons capable of maintaining heightened SSNA, but incapable of sustaining SSNA ramping.NEW & NOTEWORTHY The proinflammatory cytokine TNFα contributes to heightened SNA in cardiovascular disease models, but mechanisms remain obscure. Here, we demonstrate that TNFα injection into the hypothalamic PVN triggers SNA ramping by mechanisms dependent on local ionotropic glutamate receptor availability, but largely independent of TNFα autoinduction. Continued SNA ramping depends on ionotropic glutamate receptor and neuronal activity in PVN, indicating that strengthening and/or increased efficacy of glutamatergic transmission is necessary for acute sympathoexcitation by PVN TNFα.