TLR2 Ligand Pam3CSK4 Regulates MMP-2/9 Expression by MAPK/NF-κB Signaling Pathways in Primary Brain Microvascular Endothelial Cells

Toll-Like Receptor 1/2 Postconditioning by the Ligand Pam3cys Tempers Posttraumatic Hyperexcitability, Neuroinflammation, and Microglial Response: A Potential Candidate for Posttraumatic Epilepsy

Toll-like receptors (TLRs) are activated by endogenous molecules released from damaged cells and contribute to neuroinflammation following traumatic brain injury (TBI) and epilepsy. TLR1/2 agonist tri-palmitoyl-S-glyceryl-cysteine (Pam3cys) is a vaccine adjuvant with confirmed safety in humans. We assessed impact of TLR1/2 postconditioning by Pam3cys on epileptogenesis and neuroinflammation in male rats, 6, 24, and 48 h after mild-to-moderate TBI. Pam3cys was injected into cerebral ventricles 30 min after controlled cortical impact (CCI) injury. After 24 h, rats underwent chemical kindling by once every other day injections of pentylenetetrazole (PTZ) 35 mg/kg until development of generalized seizures. Number of intact neurons, brain expression of proinflammatory cytokine TNF-α, anti-inflammatory cytokine IL-10, and marker of anti-inflammatory microglia arginase1 (Arg1) were determined by immunoblotting. Astrocytes and macrophage/microglia activation/polarization at the contused area was assessed by double immunostaining with Iba1/Arg1, Iba1/iNOS and GFAP/iNOS, specific antibodies. The CCI-injured rats became kindled by less number of PTZ injections than sham-operated rats (9 versus 14 injections, p < 0.0001). Pam3cys treatment returned the accelerated rate of epileptogenesis in TBI state to the sham level. Pam3cys decreased neural death 48 h after TBI. It decreased TNF-α (6 h post-TBI, p < 0.01), and up-regulated IL-10 (p < 0.01) and Arg1 (p < 0.05) 48 h after TBI. The iNOS-positive cells decreased (p < 0.001) whereas Iba1/Arg1-positive cells enhanced (p < 0.01) after Pam3cys treatment. Pam3cys inhibits TBI-accelerated acquisition of seizures. Pam3cys reprograms microglia and up-regulates anti-inflammatory cytokines during the first few days after TBI. This capacity along with the clinical safety, makes Pam3cys a potential candidate for development of effective medications against posttraumatic epilepsy.

Protective effects of butyrate on cerebral ischaemic injury in animal models: a systematic review and meta-analysis

Introduction

Cerebral ischaemic stroke is a common disease that poses a serious threat to human health. Butyrate is an important metabolite of intestinal microorganisms. Recent studies have shown that butyrate has a significant protective effect in animal models of cerebral ischaemic injury.

Objective

The aim of this study was to evaluate the protective effect of butyrate on cerebral ischaemic stroke by meta-analysis, aiming to provide a scientific basis for the clinical application of butyrate in patients with cerebral ischaemia.

Materials and methods

A systematic search was conducted for all relevant studies published before 23 January 2024, in PubMed, Web of Science, Cochrane Library, and Embase. Methodological quality was assessed using Syrcle's risk of bias tool for animal studies. Data were analysed using Rev Man 5.3 software.

Results

A total of nine studies were included, and compared with controls, butyrate significantly increased BDNF levels in the brain (SMD = 2.33, 95%CI = [1.20, 3.47], p < 0.005) and P-Akt expression (SMD = 3.53, 95% CI = [0.97, 6.10], p < 0.05). Butyrate also decreased IL-β levels in the brain (SMD = -2.02, 95% CI = [-3.22, -0.81], p < 0.005), TNF-α levels (SMD = -0.86, 95% CI = [-1.60, -0.12], p < 0.05), and peripheral vascular IL-1β levels (SMD = -2.10, 95%CI = [-3.59, -0.61], p < 0.05). In addition, butyrate reduced cerebral infarct volume (MD = -11.29, 95%CI = [-17.03, -5.54], p < 0.05), mNSS score (MD = -2.86, 95%CI = [-4.12, -1.60], p < 0.005), foot fault score (MD = -7.59, 95%CI = [-9.83, -5, 35], p < 0.005), and Morris water maze time (SMD = -2.49, 95%CI = [-4.42, -0.55], p < 0.05).

Conclusion

The results of this study indicate that butyrate has a protective effect on cerebral ischaemic stroke in animal models, and the mechanism is related to reducing inflammation and inhibiting apoptosis. It provides an evidence-based basis for the future clinical development of butyrate in the treatment of ischaemic stroke.

Systematic Review Registration

https://www.crd.york.ac.uk/PROSPERO/, CRD42023482844.

Targeting the blood-brain barrier to delay aging-accompanied neurological diseases by modulating gut microbiota, circadian rhythms, and their interplays

The blood-brain barrier (BBB) impairment plays a crucial role in the pathological processes of aging-accompanied neurological diseases (AAND). Meanwhile, circadian rhythms disruption and gut microbiota dysbiosis are associated with increased morbidity of neurological diseases in the accelerated aging population. Importantly, circadian rhythms disruption and gut microbiota dysbiosis are also known to induce the generation of toxic metabolites and pro-inflammatory cytokines, resulting in disruption of BBB integrity. Collectively, this provides a new perspective for exploring the relationship among circadian rhythms, gut microbes, and the BBB in aging-accompanied neurological diseases. In this review, we focus on recent advances in the interplay between circadian rhythm disturbances and gut microbiota dysbiosis, and their potential roles in the BBB disruption that occurs in AAND. Based on existing literature, we discuss and propose potential mechanisms underlying BBB damage induced by dysregulated circadian rhythms and gut microbiota, which would serve as the basis for developing potential interventions to protect the BBB in the aging population through targeting the BBB by exploiting its links with gut microbiota and circadian rhythms for treating AAND.

Mechanisms of Blood-Brain Barrier Protection by Microbiota-Derived Short-Chain Fatty Acids

Impairment of the blood-brain barrier (BBB) integrity is implicated in the numerous neurological disorders associated with neuroinflammation, neurodegeneration and aging. It is now evident that short-chain fatty acids (SCFAs), mainly acetate, butyrate and propionate, produced by anaerobic bacterial fermentation of the dietary fiber in the intestine, have a key role in the communication between the gastrointestinal tract and nervous system and are critically important for the preservation of the BBB integrity under different pathological conditions. The effect of SCFAs on the improvement of the compromised BBB is mainly based on the decrease in paracellular permeability via restoration of junctional complex proteins affecting their transcription, intercellular localization or proteolytic degradation. This review is focused on the revealed and putative underlying mechanisms of the direct and indirect effects of SCFAs on the improvement of the barrier function of brain endothelial cells. We consider G-protein-coupled receptor-mediated effects of SCFAs, SCFAs-stimulated acetylation of histone and non-histone proteins via inhibition of histone deacetylases, and crosstalk of these signaling pathways with transcriptional factors NF-κB and Nrf2 as mainstream mechanisms of SCFA's effect on the preservation of the BBB integrity.

Protocadherin gamma C3: a new player in regulating vascular barrier function

Defects in the endothelial cell barrier accompany diverse malfunctions of the central nervous system such as neurodegenerative diseases, stroke, traumatic brain injury, and systemic diseases such as sepsis, viral and bacterial infections, and cancer. Compromised endothelial sealing leads to leaking blood vessels, followed by vasogenic edema. Brain edema as the most common complication caused by stroke and traumatic brain injury is the leading cause of death. Brain microvascular endothelial cells, together with astrocytes, pericytes, microglia, and neurons form a selective barrier, the so-called blood-brain barrier, which regulates the movement of molecules inside and outside of the brain. Mechanisms that regulate blood-brain barrier permeability in health and disease are complex and not fully understood. Several newly discovered molecules that are involved in the regulation of cellular processes in brain microvascular endothelial cells have been described in the literature in recent years. One of these molecules that are highly expressed in brain microvascular endothelial cells is protocadherin gamma C3. In this review, we discuss recent evidence that protocadherin gamma C3 is a newly identified key player involved in the regulation of vascular barrier function.

Research progress of mechanisms for tight junction damage on blood-brain barrier inflammation

Inflammation in the central nervous system (CNS) contributes to disease pathologies by disrupting the integrity of the blood-brain barrier (BBB). Tight junctions (TJ) are a key component of the BBB. Following hypoxic-ischaemic or mechanical injury to the brain, inflammatory mediators are released such as cytokines, chemokines, and growth factors. Simultaneously, matrix metalloproteinases (MMPs) are released which can degrade TJ proteins. Subsequently, the function and morphology of the BBB are disrupted, which allows immune cells an opportunity to enter into the brain parenchyma. This review summarises the information on the role of TJ protein families in the BBB and provides a comprehensive summary of the mechanisms whereby inflammation breaks down the BBB by increasing degradation of TJ proteins.

The circRERE/miR-144-3p/TLR2/MMP9 signaling axis in COPD pulmonary monocytes promotes the EMT of pulmonary epithelial cells

Chronic obstructive pulmonary disease (COPD) is a serious threat to human health, but an effective targeted therapy for COPD is still lacking at present. During the progression of COPD, the epithelial mesenchymal transition (EMT) ensures the remodeling of pulmonary epithelial cells, and it could not be precisely targeted due to its complex and elusive mechanism. In this study, we determined that the TLR2/MMP9 axis is upregulated in the pulmonary monocytes in cigarette smoke (CS)-induced COPD mice. Using a co-culture system, we identified that the TLR2/MMP9 axis in pulmonary monocytes promotes the EMT of pulmonary epithelial cells. Further, our results confirmed that miR-144-3p inhibits TLR2 expression in monocytes by directly binding to the 3'UTR of TLR2. Finally, we proved that circRERE works as a sponge to antagonize miR-144-3p and promote TLR2 expression in monocytes. Thus, our results conclude that the circRERE/miR-144-3p/TLR2/MMP9 axis in COPD pulmonary monocytes is critical for CS-induced COPD and circRERE may serve as a potential target for COPD.

Leaf Extract and Active Fractions of Dillenia pentagyna Roxb. Reduce In Vitro Human Cancer Cell Migration Via NF-κB Pathway

Background:

Different parts of Dillenia pentagyna have long been used in traditional medicines to cure several diseases including cancer. However, the mechanism(s) of anti-cancer effects are still unknown. We aimed to elucidate the anti-metastatic potential of ethanolic extracts of leaves of D. pentagyna (EELDP) and active fractions of it in highly metastatic human cancer cells.

Methods:

We screened different HPLC fractions of EELDP based on their anti-metastatic effect. We used TLC and ESI-MS for determining the presence of various phytochemicals in EELDP and fractions. We monitored in vitro anti-metastasis effect of EELDP (0-0.6 mg/ml) and active fractions (0-0.050 mg/ml) on various human cancer cells like A549, HeLa, and U2OS.

Results:

EELDP significantly reduced cell viability and cell migration in A549, HeLa, and U2OS cells. However, higher sensitivity was observed in A549 cells. We screened 2 active HPLC fractions F6 and F8 having anti-MMPs activity. EELDP and active fractions reduced metastasis via the NF-κB pathway, decreased the expression of Vimentin, N-cadherin, and increased the expression of Claudin-1.

Conclusion:

Significant reduction of metastasis by EELDP at a dose of 0.1 mg/ml or by active fractions at 0.050 mg/ml implicates that the active compound(s) present in crude or fractions are extremely potent to control highly metastatic cancer.

Metabolomics assessment of vitamin D impact in Pam3CSK4 stimulation

Mycobacterium tuberculosis, a causative agent of tuberculosis, is amongst the leading causes of mycobacterial mortality worldwide. Although several studies have proposed the possible therapeutic role of vitamin D in antimycobacterial...

Tumor Necrosis Factor-stimulated Gene-6 (TSG-6) Secreted by BMSCs Regulates Activated Astrocytes by Inhibiting NF-κB Signaling Pathway to Ameliorate Blood Brain Barrier Damage After Intracerebral Hemorrhage

To investigate the influence of tumor necrosis factor-stimulated gene-6 (TSG-6) secreted by bone mesenchymal stem cells (BMSCs) on blood brain barrier (BBB) after intracerebral hemorrhage (ICH) and its related mechanisms. BMSCs and astrocytes were isolated and induced by TNF-α and LPS respectively. The effect of TSG-6 secreted by BMSCs on the proliferation and apoptosis of astrocytes and inflammatory response were assessed by CCK8, flow cytometry, and ELISA respectively. Then we studied the effects of TSG-6 secreted by BMSCs through the paracrine mechanism on the integrity of BBB after ICH via NF-κB signaling pathway in vitro and in vivo. We successfully isolated BMSCs and astrocytes. After LPS treatment of astrocytes, IL-1β, IL-6, and TNF-α showed an upward trend. TSG-6 secreted by TNF-α-activated BMSCs could antagonize the inflammatory response in activated astrocytes. Through the co-culture of astrocytes and BMSCs and the ICH animal model, we found that TSG-6 regulates activated astrocytes by inhibiting the NF-κB signaling pathway and ameliorates BBB damage. Furthermore, we found that TNF-α-activated BMSCs secreted exosomes containing TSG-6 and played an anti-inflammatory effect. TSG-6 secreted by BMSCs regulates activated astrocytes by inhibiting the NF-κB signaling pathway, thereby ameliorating BBB damage.

Elucidation of the Molecular Pathways Involved in the Protective Effects of AUY-922 in LPS-Induced Inflammation in Mouse Lungs

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) cause thousands of deaths every year and are associated with high mortality rates (~40%) due to the lack of efficient therapies. Understanding the molecular mechanisms associated with those diseases will most probably lead to novel therapeutics. In the present study, we investigated the effects of the Hsp90 inhibitor AUY-922 in the major inflammatory pathways of mouse lungs. Mice were treated with LPS (1.6 mg/kg) via intratracheal instillation for 24 h and were then post-treated intraperitoneally with AUY-922 (10 mg/kg). The animals were examined 48 h after AUY-922 injection. LPS activated the TLR4-mediated signaling pathways, which in turn induced the release of different inflammatory cytokines and chemokines. AUY-922 suppressed the LPS-induced inflammation by inhibiting major pro-inflammatory pathways (e.g., JAK2/STAT3, MAPKs), and downregulated the IL-1β, IL-6, MCP-1 and TNFα. The expression levels of the redox regulator APE1/Ref1, as well as the DNA-damage inducible kinases ATM and ATR, were also increased after LPS treatment. Those effects were counteracted by AUY-922. Interestingly, this Hsp90 inhibitor abolished the LPS-induced pIRE1α suppression, a major component of the unfolded protein response. Our study elucidates the molecular pathways involved in the progression of murine inflammation and supports our efforts on the development of new therapeutics against lung inflammatory diseases and sepsis.

Curcumin ameliorates ischemic stroke injury in rats by protecting the integrity of the blood-brain barrier

The blood-brain barrier (BBB) is critical for proper cerebral homeostasis and its dysfunction during ischemic stroke can result in significant neurological injury. The major goal of the present study was to identify whether curcumin pretreatment possessed protective effects on BBB integrity during the 24 h of acute ischemic brain injury. To investigate the protective effects of curcumin, male Sprague-Dawley rats were divided into multiple groups, including sham, middle cerebral artery occlusion/reperfusion (MCAO/R) vehicle and curcumin pretreated MCAO/R groups. The effects of curcumin were measured by analyzing neurological deficits, infarct size, BBB permeability and expression levels of permeability-related proteins in the brain. It was found that curcumin pretreatment significantly improved neurological scores, decreased infarct size, and protected synaptic remodeling of hippocampal neurons and upregulated the protein expression level of tight junction proteins, ZO-1, occludin and claudin-5 in ischemic rat brains. Furthermore, curcumin pretreatment before stroke was shown to downregulate the phosphorylation of NF-κB and MMP-9, which are central mediators of inflammation. The results from the present study indicated that curcumin pretreatment ameliorated ischemic stroke injury by protecting BBB integrity and synaptic remodeling, as well as inhibiting inflammatory responses.

Silencing TAK1 reduces MAPKs-MMP2/9 expression to reduce inflammation-driven neurohistological disruption post spinal cord injury

Microglia activation post traumatic spinal cord injury (SCI) provokes accumulation of inflammatory metabolites, leading to increasing neurological disruption. Our previous studies demonstrated that blocking MAPKs pathway mitigated microglia inflammatory activation and prevented cords from neuroinflammation-induced secondary injury. Transforming growth factor-β-activated kinase 1 (TAK1) is an upstream gate regulating activation of MAPKs signaling. To validate the therapeutic effect of TAK1 inhibition in neuroinflammation post SCI, in the current study, cultures of microglia BV2 line was undergone lipopolysaccharide (LPS) stimulation in the presence of TAK1 inhibitor 5Z-7-Oxozeaenol (ZO), LPS, or control. LPS triggered inflammatory level, cell migration, and matrix metalloproteinase (MMP) 2/9 production, which was reduced in ZO-treated cultures. TAK1 inhibition by ZO also decreased activation of MAPKs pathway, indicating that ZO-mediated alleviation of neuroinflammation is likely modulated via TAK1/MAPKs axis. In vivo, neuroinflammatory level and tissue destruction were assessed in adult male mice that were undergone SCI by mechanical trauma, and treated with ZO by intraperitoneal injection. Compared with SCI mice, ZO-treated mice exhibited less microglia pro-inflammatory activation and accumulation adjacent to injured core linked to reduced MMP2/9 expression, leading to minor tissue damage and better locomotor recovery. To sum up, the obtained data proved that in the early phase post SCI, TAK1 inhibition impedes microglia biological activities including activation, enzymatic synthesis, and migration via downregulation of MAPKs pathway, and the effects may be accurately characterized as potent anti-inflammation.

Increase in Blood-Brain Barrier (BBB) Permeability Is Regulated by MMP3 via the ERK Signaling Pathway

BACKGROUND

The blood-brain barrier (BBB) regulates the exchange of molecules between the brain and peripheral blood and is composed primarily of microvascular endothelial cells (BMVECs), which form the lining of cerebral blood vessels and are linked via tight junctions (TJs). The BBB is regulated by components of the extracellular matrix (ECM), and matrix metalloproteinase 3 (MMP3) remodels the ECM's basal lamina, which forms part of the BBB. Oxidative stress is implicated in activation of MMPs and impaired BBB. Thus, we investigated whether MMP3 modulates BBB permeability.

METHODS

Experiments included in vivo assessments of isoflurane anesthesia and dye extravasation from brain in wild-type (WT) and MMP3-deficient (MMP3-KO) mice, as well as in vitro assessments of the integrity of monolayers of WT and MMP3-KO BMVECs and the expression of junction proteins.

RESULTS

Compared to WT mice, measurements of isoflurane usage and anesthesia induction time were higher in MMP3-KO mice and lower in WT that had been treated with MMP3 (WT+MMP3), while anesthesia emergence times were shorter in MMP3-KO mice and longer in WT+MMP3 mice than in WT. Extravasation of systemically administered dyes was also lower in MMP3-KO mouse brains and higher in WT+MMP3 mouse brains, than in the brains of WT mice. The results from both TEER and Transwell assays indicated that MMP3 deficiency (or inhibition) increased, while MMP3 upregulation reduced barrier integrity in either BMVEC or the coculture. MMP3 deficiency also increased the abundance of TJs and VE-cadherin proteins in BMVECs, and the protein abundance declined when MMP3 activity was upregulated in BMVECs, but not when the cells were treated with an inhibitor of extracellular signal related-kinase (ERK).

CONCLUSION

MMP3 increases BBB permeability following the administration of isoflurane by upregulating the ERK signaling pathway, which subsequently reduces TJ and VE-cadherin proteins in BMVECs.

Deletion of Protocadherin Gamma C3 Induces Phenotypic and Functional Changes in Brain Microvascular Endothelial Cells In Vitro

Inflammation of the central nervous system (CNS) is associated with diseases such as multiple sclerosis, stroke and neurodegenerative diseases. Compromised integrity of the blood-brain barrier (BBB) and increased migration of immune cells into the CNS are the main characteristics of brain inflammation. Clustered protocadherins (Pcdhs) belong to a large family of cadherin-related molecules. Pcdhs are highly expressed in the CNS in neurons, astrocytes, pericytes and epithelial cells of the choroid plexus and, as we have recently demonstrated, in brain microvascular endothelial cells (BMECs). Knockout of a member of the Pcdh subfamily, PcdhgC3, resulted in significant changes in the barrier integrity of BMECs. Here we characterized the endothelial PcdhgC3 knockout (KO) cells using paracellular permeability measurements, proliferation assay, wound healing assay, inhibition of signaling pathways, oxygen/glucose deprivation (OGD) and a pro-inflammatory cytokine tumor necrosis factor alpha (TNFα) treatment. PcdhgC3 KO showed an increased paracellular permeability, a faster proliferation rate, an altered expression of efflux pumps, transporters, cellular receptors, signaling and inflammatory molecules. Serum starvation led to significantly higher phosphorylation of extracellular signal-regulated kinases (Erk) in KO cells, while no changes in phosphorylated Akt kinase levels were found. PcdhgC3 KO cells migrated faster in the wound healing assay and this migration was significantly inhibited by respective inhibitors of the MAPK-, β-catenin/Wnt-, mTOR- signaling pathways (SL327, XAV939, or Torin 2). PcdhgC3 KO cells responded stronger to OGD and TNFα by significantly higher induction of interleukin 6 mRNA than wild type cells. These results suggest that PcdhgC3 is involved in the regulation of major signaling pathways and the inflammatory response of BMECs.

The Impact of Gut Microbiota Disorders on the Blood-Brain Barrier

The gut microbiota is symbiotic with the human host and has been extensively studied in recent years resulting in increasing awareness of the effects of the gut microbiota on human health. In this review, we summarize the current evidence for the effects of gut microbes on the integrity of the cerebral blood-brain barrier (BBB), focusing on the pathogenic impact of gut microbiota disorders. Based on our description and summarization of the effects of the gut microbiota and its metabolites on the nervous, endocrine, and immune systems and related signaling pathways and the resulting destruction of the BBB, we suggest that regulating and supplementing the intestinal microbiota as well as targeting immune cells and inflammatory mediators are required to protect the BBB.

When Innate Immunity Meets Angiogenesis-The Role of Toll-Like Receptors in Endothelial Cells and Pulmonary Hypertension

Toll-like receptors serve a central role in innate immunity, but they can also modulate cell function in various non-immune cell types including endothelial cells. Endothelial cells are necessary for the organized function of the vascular system, and part of their fundamental role is also the regulation of immune function and inflammation. In this review, we summarize the current knowledge of how Toll-like receptors contribute to the immune and non-immune functions of the endothelial cells.

Role of the neurovascular unit in the process of cerebral ischemic injury

Cerebral ischemic injury exhibits both high morbidity and mortality worldwide. Traditional research of the pathogenesis of cerebral ischemic injury has focused on separate analyses of the involved cell types. In recent years, the neurovascular unit (NVU) mechanism of cerebral ischemic injury has been proposed in modern medicine. Hence, more effective strategies for the treatment of cerebral ischemic injury may be provided through comprehensive analysis of brain cells and the extracellular matrix. However, recent studies that have investigated the function of the NVU in cerebral ischemic injury have been insufficient. In addition, the metabolism and energy conversion of the NVU depend on interactions among multiple cell types, which make it difficult to identify the unique contribution of each cell type. Therefore, in the present review, we comprehensively summarize the regulatory effects and recovery mechanisms of four major cell types (i.e., astrocytes, microglia, brain-microvascular endothelial cells, and neurons) in the NVU under cerebral ischemic injury, as well as discuss the interactions among these cell types in the NVU. Furthermore, we discuss the common signaling pathways and signaling factors that mediate cerebral ischemic injury in the NVU, which may help to provide a theoretical basis for the comprehensive elucidation of cerebral ischemic injury.

Enhanced Inflammatory Reaction and Thrombosis in High-Fat Diet-Fed ApoE-/- Mice are Attenuated by Celastrol

OBJECTIVE

High-fat diet (HFD) increases the risk of inflammatory reaction and acute arterial thrombosis. Celastrol has been confirmed to regulate inflammatory cytokine levels in atherosclerotic animal models. However, the anti-thrombotic effects of celastrol have remained to be fully demonstrated. The present study was performed to investigate the beneficial effect of celastrol in HFD-induced inflammatory reaction and thrombosis in apolipoprotein (apo)E^-/- mice.

MATERIALS AND METHODS

Thrombogenic mice model was established using HFD-fed apoE^-/- mice. The levels of mRNA and protein were assayed by RT-qPCR and western blotting, respectively. Immunohistochemistry (IHC) staining was performed to measure the protein expression of matrix metalloproteinase-2 and matrix metalloproteinase-9 in the aortic endothelium of HFD-fed apoE^-/- mice.

RESULTS

The results demonstrated that the effect of HFD on inflammatory cytokines in mice with apoE^-/- background was reversed by celastrol administration, and celastrol treatment inhibited the NOD-like receptor family, pyrin domain containing 3 (NLRP3)/caspase-1/interleukin-1β signaling cascades in peripheral blood mononuclear cells from HFD-fed apoE^-/- mice. In addition, HFD enhanced adenosine diphosphate-induced platelet aggregation in normal C57BL/6 and apoE^-/- mice, while celastrol administration reversed this. Furthermore, celastrol inhibited the pro-thrombotic effects of HFD in apoE^-/- mice, and the underlying mechanism was mediated, at least partially, through the suppression of matrix metalloproteinase-2 and -9 expression.

CONCLUSIONS

Celastrol administration significantly attenuated HFD-induced inflammatory reaction, platelet aggregation and thrombosis in apoE^-/- mice, and celastrol may be used as a drug for the prevention of HFD-induced inflammatory reaction and thrombus.

Endothelial tight junctions and their regulatory signaling pathways in vascular homeostasis and disease

Endothelial tight junctions (TJs) regulate the transport of water, ions, and molecules through the paracellular pathway, serving as an important barrier in blood vessels and maintaining vascular homeostasis. In endothelial cells (ECs), TJs are highly dynamic structures that respond to multiple external stimuli and pathological conditions. Alterations in the expression, distribution, and structure of endothelial TJs may lead to many related vascular diseases and pathologies. In this review, we provide an overview of the assessment methods used to evaluate endothelial TJ barrier function both in vitro and in vivo and describe the composition of endothelial TJs in diverse vascular systems and ECs. More importantly, the direct phosphorylation and dephosphorylation of TJ proteins by intracellular kinases and phosphatases, as well as the signaling pathways involved in the regulation of TJs, including and the protein kinase C (PKC), PKA, PKG, Ras homolog gene family member A (RhoA), mitogen-activated protein kinase (MAPK), phosphatidylinositol 3-kinase (PI3K)/Akt, and Wnt/β-catenin pathways, are discussed. With great advances in this area, targeting endothelial TJs may provide novel treatment for TJ-related vascular pathologies.

Symmetric dimethylarginine in dysfunctional high-density lipoprotein mediates endothelial glycocalyx breakdown in chronic kidney disease

Dysfunctional high-density lipoprotein (d-HDL) in chronic kidney disease is known to have a change in composition towards an endothelial-damaging phenotype, amongst others, via the accumulation of symmetric dimethylarginine. The endothelial glycocalyx, a carbohydrate-rich layer lining the endothelial luminal surface, is a first line defense against vascular diseases including atherosclerosis. Here we conducted a translational, cross-sectional study to determine the role of symmetric dimethylarginine in d-HDL as a mediator of glycocalyx damage. Using confocal and atomic force microscopy, intact HDL from healthy donors was found to maintain the glycocalyx while isolated HDL from hemodialysis patients and exogenous symmetric dimethylarginine caused significant damage to the glycocalyx in endothelial cells in vitro in a dose-dependent manner. Symmetric dimethylarginine triggered glycocalyx deterioration via molecular pathways mediated by toll-like-receptor 2 and matrix metalloprotease-9. Corresponding intravital microscopy revealed that exogenous symmetric dimethylarginine and d-HDL from hemodialysis patients caused glycocalyx breakdown, which subsequently contributed to alterations in leukocyte rolling. Biologically effective HDL, which estimates the functionality of HDL, was calculated from circulating HDL-cholesterol and symmetric dimethylarginine, as described in the literature. Biologically effective HDL was the only parameter that could independently predict glycocalyx damage in vivo. Thus, our data suggest that symmetric dimethylarginine in d-HDL mediates glycocalyx breakdown in chronic kidney disease.

Culture Model for Non-human Primate Choroid Plexus

While there are murine and rat choroid plexus epithelial cell cultures, a translationally relevant model for choroid plexus activation and function is still lacking. The rhesus macaque is the gold standard for modeling viral infection and activation of CNS, including HIV-associated neurocognitive disorders. We have developed a rhesus macaque choroid plexus epithelial cell culture model which we believe to be suitable for studies of inflammation associated with viral infection of the CNS. Epithelial morphology and function were assessed using vimentin, phalloidin, the tight junction protein zonula-occludens-1 (ZO-1), and focal adhesion kinase (FAK). Choroid plexus epithelial cell type was confirmed using immunofluorescence with two proteins highly expressed in the choroid plexus: transthyretin and α-klotho. Finally, barrier properties of the model were monitored using pro- and anti-inflammatory mediators (TNF-α, the TLR2 agonist PamCys3K, and dexamethasone). When pro-inflammatory TNF-α was added to the xCelligence wells, there was a decrease in barrier function, which decreased in a step-wise fashion with each additional administration. This barrier function was repaired upon addition of the steroid dexamethasone. The TLR2 agonist PAM3CysK increased barrier functions in TNF-α treated wells. We have presented a model of the blood-CSF barrier that will allow study into pro- and anti-inflammatory conditions in the brain, while simultaneously measuring real time changes to epithelial cells.

Cryptotanshinone Attenuates Oxygen-Glucose Deprivation/ Recovery-Induced Injury in an in vitro Model of Neurovascular Unit

Cryptotanshinone (CTs), an active component isolated from the root of Salvia miltiorrhiza (SM), has been shown to exert potent neuroprotective property. We here established an oxygen-glucose deprivation/recovery (OGD/R)-injured Neurovascular Unit (NVU) model in vitro to observe the neuroprotective effects of CTs on cerebral ischemia/reperfusion injury (CIRI), and explore the underlying mechanisms. CTs was observed to significantly inhibit the OGD/R-induced neuronal apoptosis, and decease the activation of Caspase-3 and the degradation of poly-ADP-ribose polymerase (PARP), as well as the increase of Bax/Bcl-2 ratio in neurons under OGD/R condition. The inhibitory effects of CTs on neuron apoptosis were associated with the blocking of mitogen-activated protein kinase (MAPK) signaling pathway. CTs also remarkably ameliorated OGD/R-induced reduction of transepithelial electrical resistance (TEER) values and the increase of transendothelial permeability coefficient (Pe) of sodium fluorescein (SF) by upregulating the expression of ZO-1, Claudin-5, and Occludin in brain microvascular endothelial cells (BMECs), which might be related to the down-regulation of matrix metalloproteinase (MMP)-9 expression. Based on these findings, CTs may play a neuroprotective role in OGD/R injure in NVU models in vitro by inhibiting cell apoptosis and alleviating the damage of blood-brain barrier (BBB).