Abstract 157: Toll like Receptor 4 Activation Promotes Cardiac Arrhythmias By Decreasing The Transient Outward Potassium Current (ito) Through An Irf3 dependent And Myd88 independent Pathway

2014 ◽  
Vol 115 (suppl_1) ◽  
Author(s):  
Emiliano Medei ◽  
Gustavo Monnerat-Cahli ◽  
Hiart Alonso ◽  
Monica Gallego ◽  
Micaela Lopez Alarcon ◽  
...  
Keyword(s):  
Cardiac Arrhythmias ◽  
Ventricular Myocytes ◽  
Cardiac Complications ◽  
Electrical Remodeling ◽  
Toll Like Receptor 4 ◽  
Triggered Activity ◽  
Tlr4 Agonist ◽  
Action Potential Prolongation ◽  
Tlr4 Activation

Cardiac arrhythmias are one of the main causes of death worldwide. Several studies have shown that inflammation plays a key role in different cardiac diseases and Toll like receptors (TLR’s) play an important role in cardiac complications. In the present study, we investigated whether the activation of TLR4 induces cardiac electrical remodeling and arrhythmias. Also the signaling pathway involved in these phenomena was studied. Action potentials, the presence of cardiac arrhythmias and transient outward K + current (I to ) were recorded in Wistar rat’s hearts after 24 h exposure to the TLR4 agonist ultrapure Lipopolysaccharide (LPS - 1μg/ml). TLR4 stimulation in vitro promotes a cardiac electrical remodeling that leads to cardiac action potential prolongation which evokes arrhythmic events such as delayed after depolarization (DAD's) and triggered activity. The perfusion of LPS (1μg/ml) during 30 minutes did not modify I to . Conversely, after 24 h of LPS incubation I to was reduced, with no changes in the biophysical properties of the current. Major changes in Ca 2+ cycling were not observed in ventricular myocytes after 24 h exposure to LPS; however, extrasystolic activity was present in a considerable number of cells (25%). Neither the blockade of Interleulink-1 receptor-associated kinase 4 nor nuclear factor kappa B (NF-kB) prevented the LPS effect on I to . However, interferon regulatory factor 3 (IRF3) inhibition prevented the effect of TLR4 activation on I to . Activation of TLR4 induced extrasystolic activity, longer AP duration and evoked DAD's and triggered activity because of a reduction in I to . The mechanism involved is MyD88-independent and IRF3-dependent.

scholarly journals Leishmania pifanoi Proteoglycolipid Complex P8 Induces Macrophage Cytokine Production through Toll-Like Receptor 4

2008 ◽  
Vol 76 (5) ◽  
pp. 2149-2156 ◽  
Author(s):  
Shanta M. Whitaker ◽  
Maria Colmenares ◽  
Karen Goldsmith Pestana ◽  
Diane McMahon-Pratt
Keyword(s):  
Toll Like Receptor ◽  
Toll Like Receptor 4 ◽  
Necrosis Factor Alpha ◽  
Cytokines And Chemokines ◽  
Inflammatory Protein ◽  
Tlr4 Ligand ◽  
Factor Alpha ◽  
Tlr4 Activation

ABSTRACT The P8 proteoglycolipid complex (P8 PGLC) is a glyconjugate expressed by Leishmania mexicana complex parasites. We previously have shown that vaccination with P8 PGLC provides protection against cutaneous leishmaniasis in susceptible BALB/c mice. However, the biological importance of this complex remains unknown. Here we show that P8 PGLC localizes to the surface of Leishmania pifanoi amastigotes and that upon exposure to macrophages, P8 PGLC binds and induces inflammatory cytokine and chemokine mRNAs such as tumor necrosis factor alpha and RANTES early after stimulation. Our studies indicate that cytokine and chemokine induction is dependent upon Toll-like receptor 4 (TLR4). Interestingly, key inflammatory cytokines and chemokines (such as interleukin-6 [IL-6], macrophage inflammatory protein 1β, and beta interferon [IFN-β]) that can be induced through TLR4 activation were not induced or only slightly upregulated by P8 PGLC. Activation by P8 PGLC does not occur in the presence of TLR4 alone and requires both CD14 and myeloid differentiation protein 2 for signaling; this requirement may be responsible for the limited TLR4 response. This is the first characterization of a TLR4 ligand for Leishmania. In vitro experiments indicate that L. pifanoi amastigotes induce lower levels of cytokines in macrophages in the absence of TLR4; however, notably higher IL-10/IFN-γ ratios were found for TLR4-deficient mice than for BALB/c mice. Further, increased levels of parasites persist in BALB/c mice deficient in TLR4. Taken together, these results suggest that TLR4 recognition of Leishmania pifanoi amastigotes is important for the control of infection and that this is mediated, in part, through the P8 PGLC.

MyD88 and NOS2 are essential for Toll-like receptor 4-mediated survival effect in cardiomyocytes

2006 ◽  
Vol 291 (4) ◽  
pp. H1900-H1909 ◽  
Author(s):  
Xinsheng Zhu ◽  
Huailong Zhao ◽  
Amanda R. Graveline ◽  
Emmanuel S. Buys ◽  
Ulrich Schmidt ◽  
...  
Keyword(s):  
Adaptor Protein ◽  
Toll Like Receptor ◽  
Toll Like Receptor 4 ◽  
Tlr4 Signaling ◽  
Beneficial Effects ◽  
Tlr4 Agonist ◽  
Vitro Model ◽  
And Function ◽  
Survival Effect

Innate immune system such as Toll-like receptor 4 (TLR4) represents the first line of defense against infection. In addition to its pivotal role in host immunity, recent studies have suggested that TLR4 may play a broader role in mediating tissue inflammation and cell survival in response to noninfectious injury. We and other investigators have reported that cardiac TLR4 signaling is dynamically modulated in ischemic myocardium and that activation of TLR4 confers a survival benefit in the heart and in isolated cardiomyocytes. However, the signaling pathways leading to these effects are not completely understood. Here, we investigate the role of MyD88, an adaptor protein of TLR4 signaling, and inducible nitric oxide synthase (NOS2) in mediating TLR4-induced cardiomyocyte survival in an in vitro model of apoptosis. Serum deprivation induced a significant increase in the number of apoptotic cardiomyocytes as demonstrated by transferase-mediated dUTP nick-end labeling (TUNEL) assay, nuclear morphology, DNA laddering, and DNA-histone ELISA. Lipopolysaccharide (LPS), a TLR4 agonist, activated TLR4 signaling and led to significant reduction in apoptotic cardiomyocytes and improved cellular function of surviving cardiomyocytes with enhanced Ca2+ transients and cell shortening. We found that both TLR4 and MyD88 are required for the LPS-induced beneficial effects as demonstrated by improved survival and function in wild-type but not in TLR4−/− or MyD88−/− cardiomyocytes. Moreover, genetic deletion or pharmacological inhibition of NOS2 abolished survival and functional rescue of cardiomyocytes treated with LPS. Taken together, these data suggest that TLR4 protects cardiomyocytes from stress-induced injury through MyD88- and NOS2-dependent mechanisms.

scholarly journals SARS-CoV-2 Spike S1 glycoprotein is a TLR4 agonist, upregulates ACE2 expression and induces pro-inflammatory M1 macrophage polarisation.

2021 ◽  
Author(s):  
Mohamed M Aboudounya ◽  
Mark R Holt ◽  
Richard J Heads
Keyword(s):  
Viral Entry ◽  
Human Cells ◽  
Cardiac Complications ◽  
Macrophage Phenotype ◽  
Macrophage Polarisation ◽  
Proximity Ligation ◽  
M1 Macrophage ◽  
Tlr4 Agonist ◽  
Ifn Γ ◽  
Tlr4 Activation

Background and aims: TLR4 is an important innate immune receptor that recognizes bacterial LPS, viral proteins and other pathogen associated molecular patterns (PAMPs). It is expressed on tissue-resident and immune cells. We previously proposed a model whereby SARS-CoV-2 activation of TLR4 via its spike glycoprotein S1 domain increases ACE2 expression, viral loads and hyperinflammation with COVID-19 disease [1]. Here we test this hypothesis in vitro and demonstrate that the SARS-CoV-2 spike S1 domain is a TLR4 agonist in rat and human cells and induces a pro-inflammatory M1 macrophage phenotype in human THP-1 monocyte-derived macrophages. Methods: Adult rat cardiac tissue resident macrophage-derived fibrocytes (rcTMFs) were treated with either bacterial LPS or recombinant SARS-CoV-2 spike S1 glycoprotein. The expression of ACE2 and other inflammatory and fibrosis markers were assessed by immunoblotting. S1/TLR4 co-localisation/binding was assessed by immunocytochemistry and proximity ligation assays on rcTMFs and human HEK-293 HA-TLR4-expressing cells. THP-1 monocytes were differentiated into M1 or M2 macrophages with LPS/IFN-γ, S1/IFN-γ or IL-4 and RNA was extracted for RT-qPCR of M1/M2 markers and ACE2. Results: TLR4 activation by spike S1 or LPS resulted in the upregulation of ACE2 in rcTMFs as shown by immunoblotting. Likewise, spike S1 caused TLR4-mediated induction of the inflammatory/wound healing marker COX-2 and concomitant downregulation of the fibrosis markers CTGF and Col3a1, similar to LPS. The specific TLR4 TIR domain signalling inhibitor CLI-095 (Resatorvid), blocked the effects of spike S1 and LPS, confirming that spike S1 is a TLR4 agonist and viral PAMP (VAMP). ACE2 expression was also inhibited by the dynamin inhibitor Dynasore, suggesting ACE2 expression is mediated by the alternative endosomal/β-interferon pathway. Confocal immunofluorescence microscopy confirmed 1:1 stoichiometric spike S1 co-localisation with TLR4 in rat and human cells. Furthermore, proximity ligation assays confirmed spike S1 and TLR4 binding in human and rat cells. Spike S1/IFN-γ treatment of THP-1-derived macrophages induced pro-inflammatory M1 polarisation as shown by an increase in IL-1-β and IL-6 mRNA. Conclusions: These results confirm that TLR4 is activated by the SARS-CoV-2 spike protein S1 domain and therefore TLR4 may be a receptor/accessory factor for the virus. By binding to and activating TLR4, spike S1 caused upregulation of ACE2, which may facilitate viral entry into cells. In addition, pro-inflammatory M1 macrophage polarisation via TLR4 activation, links TLR4 activation by spike S1 to inflammation. The clinical trial testing of CLI-095 (Resatorvid) and other TLR4 antagonists in severe COVID-19, to reduce both viral entry into cells and hyperinflammation, is warranted. Our findings likely represent an important development in COVID-19 pathophysiology and treatment, particularly regarding cardiac complications and the role of macrophages.

scholarly journals Evidence for the Involvement of Toll-Like Receptor 4 (TLR4)-Mediated Apoptosis in Gynecological Cancers

2016 ◽  
Author(s):  
Jinyoung Won ◽  
Youngjeon Lee ◽  
Kyu-Tae Chang ◽  
Yonggeun Hong
Keyword(s):  
Cancer Cells ◽  
Apoptotic Cell ◽  
Gynecological Cancer ◽  
Mechanism Analysis ◽  
Toll Like Receptor ◽  
Gynecological Cancers ◽  
Toll Like Receptor 4 ◽  
Tlr4 Agonist ◽  
Apoptotic Activity ◽  
Tlr4 Activation

Toll-like receptor 4 (TLR4) is a member of the TLR family. Members of the TLR family play an important role in innate immune responses and are induced by recognition of pathogen-associated molecular patterns. They are also involved in cell proliferation and apoptosis in cancer. We investigated the role of TLR4 in apoptotic cell death in gynecological cancer cells; gynecological cancer is associated with infertility and spontaneous abortion. To examine the effect of TLR4 activation on apoptotic signaling in cancer cells, cultured primary cancer cells were treated with the TLR4 agonist lipopolysaccharide (LPS). The morphology of cancer cells was compared with normal myometrial cells. Enhanced growth rate and loss of contact inhibition with cellular overlap was observed in the cancer cells. The molecular mechanism analysis revealed differential expression of tumor suppressor genes in LPS-treated cancer cells. The expression of apoptosis-related caspase-3 was increased significantly in cancer cells with TLR4 activation after exposure to LPS. Taken together, these results suggest the pro-apoptotic activity of TLR4 as a potential therapeutic target for the treatment of gynecological cancers.

Elevated Cytoplasmic Sodium and Chloride Is Associated With Purinergic Receptor Stimulation of Rat Ventricular Myocytes: Implications For Myocardial Ischemia

1997 ◽  
Vol 3 (S2) ◽  
pp. 917-918
Author(s):  
Meredith Bond ◽  
Bin-Xian Zhang ◽  
Russell W. Desnoyer
Keyword(s):  
Myocardial Ischemia ◽  
Intracellular Ph ◽  
Cardiac Arrhythmias ◽  
Ventricular Arrhythmias ◽  
Purinergic Receptors ◽  
Ventricular Myocytes ◽  
Purinergic Receptor ◽  
Membrane Depolarization ◽  
Perfusion Medium

During myocardial ischemia, several factors have been identified which contribute to the development of cardiac arrhythmias. These include membrane depolarization, increased cytosolic Na+ and decreased intracellular pH. This increase in intracellular Na+ has been shown to be associated with the development of ventricular arrhythmias. Changes in intracellular Cl- may also be involved in development of cardiac arrhythmias since decreasing extracellular Cl- concentration in the perfusion medium can prevent development of arrhythmias during myocardial ischemia in vitro. Extracellular ATP is known to increase in the heart during myocardial ischemia. ATP activation of p2 purinergic receptors on cardiac myocytes has been proposed to contribute to the initiation of the arrhythmias and ventricular fibrillations which characterize myocardial ischemia. Activation of p2 purinergic receptors results in membrane depolarization and decreased intracellular pH, thus reproducing some of the changes that occur during ischemia. We recently showed that activation of p2 purinergic receptors in both quiescent and electrically stimulated ventricular myocytes triggers spontaneous oscillatory contractions and Ca2+ transients.

scholarly journals Immunomodulatory Drugs Alter the Metabolism and the Extracellular Release of Soluble Mediators by Normal Monocytes

Molecules ◽  
2020 ◽  
Vol 25 (2) ◽  
pp. 367 ◽  
Author(s):  
Ida Marie Rundgren ◽  
Anita Ryningen ◽  
Tor Henrik Anderson Tvedt ◽  
Øystein Bruserud ◽  
Elisabeth Ersvær
Keyword(s):  
Cell Communication ◽  
Cell Subset ◽  
Mediator Release ◽  
Immunomodulatory Drugs ◽  
Toll Like Receptor 4 ◽  
Anticancer Effects ◽  
Extracellular Release ◽  
Soluble Mediator ◽  
Tlr4 Agonist

Immunomodulatory drugs (IMiDs) are used in the treatment of hematological malignancies, especially multiple myeloma. IMiDs have direct anticancer effects but also indirect effects via cancer-supporting stromal cells. Monocytes are a stromal cell subset whose metabolism is modulated by the microenvironment, and they communicate with neighboring cells through extracellular release of soluble mediators. Toll-like receptor 4 (TLR4) is then a common regulator of monocyte metabolism and mediator release. Our aim was to investigate IMiD effects on these two monocyte functions. We compared effects of thalidomide, lenalidomide, and pomalidomide on in vitro cultured normal monocytes. Cells were cultured in medium alone or activated by lipopolysaccharide (LPS), a TLR4 agonist. Metabolism was analyzed by the Seahorse XF 96 cell analyzer. Mediator release was measured as culture supernatant levels. TLR4 was a regulator of both monocyte metabolism and mediator release. All three IMiDs altered monocyte metabolism especially when cells were cultured with LPS; this effect was strongest for lenalidomide that increased glycolysis. Monocytes showed a broad soluble mediator release profile. IMiDs decreased TLR4-induced mediator release; this effect was stronger for pomalidomide than for lenalidomide and especially thalidomide. To conclude, IMiDs can alter the metabolism and cell–cell communication of normal monocytes, and despite their common molecular target these effects differ among various IMiDs.

scholarly journals Toll-Like Receptor 4 Activation Prevents Rat Cardiac Fibroblast Death Induced by Simulated Ischemia/Reperfusion

2021 ◽  
Vol 8 ◽  
Author(s):  
Pablo Parra-Flores ◽  
Jenaro Espitia-Corredor ◽  
Claudio Espinoza-Pérez ◽  
Cristian Queirolo ◽  
Pedro Ayala ◽  
...  
Keyword(s):  
Cell Viability ◽  
Apoptotic Cell ◽  
Ischemia Reperfusion ◽  
Protective Effects ◽  
Toll Like Receptor ◽  
Toll Like Receptor 4 ◽  
Trypan Blue Exclusion ◽  
Simulated Ischemia ◽  
Tlr4 Activation

Death of cardiac fibroblasts (CFs) by ischemia/reperfusion (I/R) has major implications for cardiac wound healing. In in vivo models of myocardial infarction, toll-like receptor 4 (TLR4) activation has been reported as a cardioprotector; however, it remains unknown whether TLR4 activation can prevent CF death triggered by simulated I/R (sI/R). In this study, we analyzed TLR4 activation in neonate CFs exposed to an in vitro model of sI/R and explored the participation of the pro-survival kinases Akt and ERK1/2. Simulated ischemia was performed in a free oxygen chamber in an ischemic medium, whereas reperfusion was carried out in normal culture conditions. Cell viability was analyzed by trypan blue exclusion and the MTT assay. Necrotic and apoptotic cell populations were evaluated by flow cytometry. Protein levels of phosphorylated forms of Akt and ERK1/2 were analyzed by Western blot. We showed that sI/R triggers CF death by necrosis and apoptosis. In CFs exposed only to simulated ischemia or only to sI/R, blockade of the TLR4 with TAK-242 further reduced cell viability and the activation of Akt and ERK1/2. Preconditioning with lipopolysaccharide (LPS) or treatment with LPS in ischemia or reperfusion was not protective. However, LPS incubation during both ischemia and reperfusion periods prevented CF viability loss induced by sI/R. Furthermore, LPS treatment reduced the sub-G1 population, but not necrosis of CFs exposed to sI/R. On the other hand, the protective effects exhibited by LPS were abolished when TLR4 was blocked and Akt and ERK1/2 were inhibited. In conclusion, our results suggest that TLR4 activation protects CFs from apoptosis induced by sI/R through the activation of Akt and ERK1/2 signaling pathways.

scholarly journals Lycopene Inhibits Toll-Like Receptor 4-Mediated Expression of Inflammatory Cytokines in House Dust Mite-Stimulated Respiratory Epithelial Cells

Molecules ◽  
2021 ◽  
Vol 26 (11) ◽  
pp. 3127
Author(s):  
Jiyeon Choi ◽  
Joo Weon Lim ◽  
Hyeyoung Kim
Keyword(s):  
Epithelial Cells ◽  
A549 Cells ◽  
Cytokine Expression ◽  
Ros Production ◽  
Toll Like Receptor ◽  
Respiratory Epithelial Cells ◽  
Toll Like Receptor 4 ◽  
Mitochondrial Ros ◽  
Tlr4 Activation ◽  
Respiratory Epithelial

House dust mites (HDM) are critical factors in airway inflammation. They activate respiratory epithelial cells to produce reactive oxygen species (ROS) and activate Toll-like receptor 4 (TLR4). ROS induce the expression of inflammatory cytokines in respiratory epithelial cells. Lycopene is a potent antioxidant nutrient with anti-inflammatory activity. The present study aimed to investigate whether HDM induce intracellular and mitochondrial ROS production, TLR4 activation, and pro-inflammatory cytokine expression (IL-6 and IL-8) in respiratory epithelial A549 cells. Additionally, we examined whether lycopene inhibits HDM-induced alterations in A549 cells. The treatment of A549 cells with HDM activated TLR4, induced the expression of IL-6 and IL-8, and increased intracellular and mitochondrial ROS levels. TAK242, a TLR4 inhibitor, suppressed both HDM-induced ROS production and cytokine expression. Furthermore, lycopene inhibited the HDM-induced TLR4 activation and cytokine expression, along with reducing the intracellular and mitochondrial ROS levels in HDM-treated cells. These results collectively indicated that the HDM induced TLR4 activation and increased intracellular and mitochondrial ROS levels, thus resulting in the induction of cytokine expression in respiratory epithelial cells. The antioxidant lycopene could inhibit HDM-induced cytokine expression, possibly by suppressing TLR4 activation and reducing the intracellular and mitochondrial ROS levels in respiratory epithelial cells.

scholarly journals Antimalarial drugs—are they beneficial in rheumatic and viral diseases?—considerations in COVID-19 pandemic

2021 ◽  
Author(s):  
Bogna Grygiel-Górniak
Keyword(s):  
Connective Tissue ◽  
Viral Infections ◽  
Current Knowledge ◽  
Inflammatory Diseases ◽  
Antiviral Drugs ◽  
In Vivo Studies ◽  
Viral Diseases ◽  
Cardiac Complications

AbstractThe majority of the medical fraternity is continuously involved in finding new therapeutic schemes, including antimalarial medications (AMDs), which can be useful in combating the 2019-nCoV: coronavirus disease (COVID-19). For many decades, AMDs have been widely used in the treatment of malaria and various other anti-inflammatory diseases, particularly to treat autoimmune disorders of the connective tissue. The review comprises in vitro and in vivo studies, original studies, clinical trials, and consensus reports for the analysis, which were available in medical databases (e.g., PubMed). This manuscript summarizes the current knowledge about chloroquine (CQ)/hydroxychloroquine (HCQ) and shows the difference between their use, activity, recommendation, doses, and adverse effects on two groups of patients: those with rheumatic and viral diseases (including COVID-19). In the case of connective tissue disorders, AMDs are prescribed for a prolonged duration in small doses, and their effect is observed after few weeks, whereas in the case of viral infections, they are prescribed in larger doses for a short duration to achieve a quick saturation effect. In rheumatic diseases, AMDs are well tolerated, and their side effects are rare. However, in some viral diseases, the effect of AMDs is questionable or not so noticeable as suggested during the initial prognosis. They are mainly used as an additive therapy to antiviral drugs, but recent studies have shown that AMDs can diminish the efficacy of some antiviral drugs and may cause respiratory, kidney, liver, and cardiac complications.

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