TLR4 Pathway Research Articles

Toll-like receptor-mediated innate immune responses by recognition of the recombinant dormancy-associated Mycobacterium tuberculosis proteins Rv2659c and Rv1738.

Tuberculosis (TB) caused by Mycobacterium tuberculosis (Mtb) poses a major threat to the global public health. Importantly, latent tuberculosis infection (LTBI) still impedes the elimination of TB incidence since it has a substantial risk to develop active disease. A multi-stage subunit vaccine comprising active and latency antigens of Mtb has been raised as the promising vaccine to trigger immune protection against all stages of TB. Therefore, the discovery of new antigens that could trigger broad immune response is essential. While current development of TB vaccine mainly focuses on protective immunity mediated by adaptive immune response, the knowledge on triggering the innate immune response by antigens is still limited. We showed that recombinant dormancy-associated Mtb proteins Rv2659c and Rv1738 were recognized by human innate immune recognition molecules, Toll-like receptors (TLRs) 2 and 4 by using HEK-Blue™ hTLR2/hTLR4 systems. We further demonstrated that these two proteins activated phosphorylated NF-κB p65 (Ser536) in the human CD14+ blood cells. We also investigated that these two proteins significantly induced level of pro- and anti-inflammatory cytokines (IL-1β, IL-6, IL-8, IL-10 and TNF-α) which were mediated through TLR2 and TLR4 pathways in human peripheral blood mononuclear cells (hPBMCs). These findings suggest that proteins Rv2659c and Rv1738 stimulated innate immune response targeting TLR2 and TLR4 to produce inflammatory cytokines, and their benefits would be valuable for the development of an effective prophylactic tuberculosis vaccine.

Bacteroides thetaiotaomicron rough-type lipopolysaccharide: The chemical structure and the immunological activity

Bacteroides thetaiotaomicron is one of the most extensively studied symbionts of the human gut. Despite its widespread distribution among human populations, still very little is known about the role of its cell envelope in the crosstalk with the immune system. Due to the extraordinary characteristic of B. thetaiotaomicron to express multiple capsular polysaccharides on its surface, research activities focused on defining how these polymers affect immune responses. This resulted in the drawback of neglecting another immunostimulatory cell surface glycoconjugate, the lipopolysaccharide (LPS). By taking advantage of an acapsular mutant of B. thetaiotaomicron, here we describe the characterization of the structure of the rough-type LPS produced by this gut mutualist. This was made up of a mono-phosphorylated and hypoacylated lipid A and of a highly charged core oligosaccharide. In vitro studies revealed a weak ability to engage the MD-2/TLR4 pathway, while it was able to promote TLR2-mediated response.

Therapeutic effect of modified zengye decoction on primary Sjogren's syndrome and its effect on plasma exosomal proteins.

Background: Modified Zengye Decoction (MZD), a traditional Chinese medicine, is an effective treatment for patients with primary Sjögren’s syndrome (pSS). Purpose: To evaluate the efficacy of MZD and investigate its effect on plasma exosomal proteins. Methods: Eighteen pSS patients were treated with MZD for 2 weeks. The therapeutic effect was evaluated by observing the changes in clinical symptoms, laboratory parameters, and plasma cytokines before and after treatment. Then, the differentially expressed proteins (DEPs) in the plasma exosomes before and after treatment were identified via label-free proteomics, while Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment were used to analyze the possible biological functions and signaling pathways involved in the exosomal DEPs. Results: MZD can effectively relieve the clinical symptoms of pSS patients, downregulate the plasma IgG and IgM levels, and inhibit plasma cytokine production. Thirteen DEPs were identified via label-free proteomics in the plasma exosomes before and after MZD treatment, of which 12 were downregulated proteins. GO analysis showed that these downregulated proteins were mainly related to the insulin response involved in dryness symptoms and the Gram-negative bacterial defense response and proteoglycan binding involved in infection. KEGG enrichment analysis showed that these downregulated proteins were primarily associated with the porphyrin metabolism involved in oteoarthrosis and the NF-κB and TLR4 pathways involved in infection. Conclusion: MZD can effectively alleviate SS symptoms, while its mechanism may be associated with the reduced protein expression in insulin response, porphyrin metabolism, and the TLR4/NF-κB pathway.

LPS-mediated activation of TLR4 controls Toxoplasma gondii growth in human trophoblast cell (BeWo) and human villous explants in a dependent-manner of TRIF, MyD88, NF-κB and cytokines

We evaluated the influence of the Toll-like receptor (TLR)-4 pathways on BeWo, JEG-3 and HTR-8/SVneo cells, as well as in human villous explants infected with Toxoplasma gondii. Cells and explants were stimulated with LPS for 24 or 48 h and processed for the MTT assay, and expression of TLR4 was evaluated by confocal microscopy. In addition, we used peptides that inhibit MyD88 or TRIF, and inhibitor to NF-κB. Finally, the parasite proliferation was verified, and ELISA was performed to verify the cytokine production. As results, LPS did not induce toxicity in cells and explants. However, LPS triggered a reduction in T. gondii proliferation only in BeWo cells and explants. Additionally, LPS downmodulated IL-10, TGF-β1 and TNF, but upregulated IFN-γ in BeWo cells. For explants, LPS induced high levels of IL-10, TGF-β1 and IFN-γ. Finally, it was observed that the inhibition of TRIF and NF-κB increased parasitism and modulated TGF-β1 in BeWo cells, while the inhibition of MyD88 and NF-κB increased T. gondii infection and modulated IFN-γ in explants. It can be concluded that the TLR4 pathway is important for the control of T. gondii replication in BeWo cells and villous explants, in a dependent-manner of TRIF, MyD88, NF-κB and cytokines.

Metal Ion Periplasmic-Binding Protein YfeA of Glaesserella parasuis Induces the Secretion of Pro-Inflammatory Cytokines of Macrophages via MAPK and NF-κB Signaling through TLR2 and TLR4

The YfeA gene, belonging to the well-conserved ABC (ATP-binding cassette) transport system Yfe, encodes the substrate-binding subunit of the iron, zinc, and manganese transport system in bacteria. As a potential vaccine candidate in Glaesserella parasuis, the functional mechanisms of YfeA in the infection process remain obscure. In this study, vaccination with YfeA effectively protected the C56BL6 mouse against the G. parasuis SC1401 challenge. Bioinformatics analysis suggests that YfeA is highly conserved in G. parasuis, and its metal-binding sites have been strictly conserved throughout evolution. Stimulation of RAW 264.7 macrophages with YfeA verified that toll-like receptors (TLR) 2 and 4 participated in the positive transcription and expression of pro-inflammatory cytokines IL-1β, IL-6, and TNF-α. The activation of TLR2 and TLR4 utilized the MyD88/MAL and TRIF/TRAM pairs to initiate TLRs signaling. Furthermore, YfeA was shown to stimulate nuclear translocation of NF-κB and activated diverse mitogen-activated protein (MAP) kinase signaling cascades, which are specific to the secretion of particular cytokine(s) in murine macrophages. Separate blocking TLR2, TLR4, MAPK, and RelA (p65) pathways significantly decreased YfeA-induced pro-inflammatory cytokine production. In addition, YfeA-stimulated RAW 264.7 produces the pro-inflammatory hallmark, reactive oxygen species (ROS). In conclusion, our findings indicate that YfeA is a novel pro-inflammatory mediator in G. parasuis and induces TLR2 and TLR4-dependent pro-inflammatory activity in RAW 264.7 macrophages through P38, JNK-MAPK, and NF-κB signaling pathways.

Pentoxifylline/Valsartan co-delivery in liposomal gel alters the inflammatory HMGB-1/ TLR pathway and promotes faster healing in burn wounds: A promising repurposed approach

Burn wounds are one of the most severe complex forms of trauma. Hence, new treatment strategies that facilitate the healing process; reduce the severity and the healing time is the main concern of the health care systems. In this work, pentoxifylline-valsartan, (PTX- VAL), loaded liposomes integrated into gel were designed for the first time as a novel co-delivery carrier for the treatment of burn wounds. The objective of this work was to investigate the ability of the nano-based liposomal system to co-entrap two repurposed drugs; hydrophilic pentoxifylline and lipophilic valsartan for topical treatment of burn wounds. The impact of increasing the phospholipid amount to enhance the co-entrapment of PTX and VAL was investigated and in-vitro evaluation of the prepared formulations was conducted to choose the optimum composition with the highest entrapment of both drugs adopting a simple, reliable derivative spectrophotometric method. Structure elucidation was also performed using a transmission electron microscope. In addition, A simple selected derivative spectrophotometric method was developed for the assay of PTX-VAL novel combination. The proven selectivity, precision and accuracy assured the reliability of this analytical method. Being economic and fast makes routine application of the developed analytical method is recommended in pharmaceutical industry. The selected liposomal formulation integrated into gel matrix (PTX-VAL-LG) showed; nanometric size, acceptable entrapment efficiency of both PTX and VAL as well as sustained release profiles and thus, enhanced action.

Tollip suppresses MyD88-mediated NF-κB activation by enhancing MyD88 ubiquitination levels in large yellow croaker (Larimichthys crocea)

Toll-interacting protein (Tollip) plays an important role in the innate immune response by negative regulation of the TLR-IL-1R signaling pathway. MyD88 serves as a universal adaptor in TLR-mediated NF-κB activation. However, the regulation mechanisms of Tollip in piscine MyD88-mediated NF-κB activation is largely unknown. In the present study, the cDNA sequence of LcTollip was identified from the large yellow croaker (Larimichthys crocea). The putative LcTollip protein encoded 275 amino acid residues, containing a N-terminal TBD domain, a central C2 domain, and a C-terminal CUE domain. Quantitative PCR showed that the most predominant constitutive expression of LcTollip was detected in spleen. In addition, LcTollip transcripts enhanced significantly after LPS and poly I:C challenge (P < 0.05). Cellular localization revealed that LcTollip existed in the cytoplasm and nucleus. Furthermore, the overexpression plasmids of wild type LcTollip as well as its six domain truncated mutants of LcTollip were constructed by overlap PCR. Dual luciferase analysis showed that NF-κB activation could not be induced by overexpression of LcTollip or its domain truncated mutants alone. However, the LcMyD88-induced–NF–κB activation was significantly suppressed by overexpression with LcTollip, and the truncated mutants LcTollip-ΔTBD, LcTollip-ΔC2, LcTollip-ΔCUE and LcTollip-ΔTBDΔCUE while not by LcTollip-ΔLR and LcTollip-ΔTBDΔC2. Moreover, co-immunoprecipitation (Co-IP) assay revealed that the interaction between LcTollip and LcMyD88 was through CUE domain. More interesting, IP and immunoblotting examination of HEK293T cells co-transfected with LcMyD88, LcTollip and HA-ubiquitin showed that LcMyD88 induced a dose-dependent de-ubiquitination of LcTollip while LcTollip enhanced a dose-dependent ubiquitination of LcMyD88. However, protein degradation investigation displayed that the proteolysis and ubiquitination of LcMyD88 were not connected. Our findings suggested that the LcTollip might involve in negative regulation TLR pathway by suppressing LcMyD88-mediated immune activation and improving the ubiquitination level of LcMyD88.

Fra-1 induces apoptosis and neuroinflammation by targeting S100A8 to modulate TLR4 pathways in spinal cord ischemia/reperfusion injury.

Spinal cord ischemia/reperfusion injury (SCII) is a severe complication driven by apoptosis and neuroinflammation. An increase in the expression of c-Fos, a member of the AP-1 family, is known as a neuronal activation marker in SCII. The AP-1 family is composed of Jun, Fos, and is associated with the regulation of cytokines expression and apoptosis. Fra-1 is a member of the Fos family, however, the contribution of Fra-1 to SCII is still unclear. In our study, Fra-1 was highly upregulated especially in neurons and microglia and promoted apoptosis by changing the expression of Bax/Bcl-2 after SCII. Furthermore, we found that Fra-1 directly regulated the transcription expression of S100A8. We demonstrated that knockdown of Fra-1 alleviated S100A8 mediated neuronal apoptosis and inflammatory factor release, thus improved motor function after SCII. Interestingly, we showed that administration of TAK-242, the TLR4 inhibitor, to the ischemia/reperfusion (I/R) injury induced rats suppressed the activation of the ERK and NF-κB pathways, and further reduced Fra-1 expression. In conclusion, we found that Fra-1-targeted S100A8 was expressed the upstream of Fra-1, and the Fra-1/S100A8 interaction formed a feedback loop in the signaling pathways activated by SCII.

Functional Crosstalk between PCSK9 Internalization and Pro-Inflammatory Activation in Human Macrophages: Role of Reactive Oxygen Species Release.

Atherosclerosis is a cardiovascular disease caused mainly by dyslipidemia and is characterized by the formation of an atheroma plaque and chronic inflammation. Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a protease that induces the degradation of the LDL receptor (LDLR), which contributes to increased levels of LDL cholesterol and the progress of atherosclerosis. Given that macrophages are relevant components of the lipidic and inflammatory environment of atherosclerosis, we studied the effects of PCSK9 treatment on human macrophages. Our data show that human macrophages do not express PCSK9 but rapidly incorporate the circulating protein through the LDLR and also activate the pro-inflammatory TLR4 pathway. Both LDLR and TLR4 are internalized after incubation of macrophages with exogenous PCSK9. PCSK9 uptake increases the production of reactive oxygen species and reduces the expression of genes involved in lipid metabolism and cholesterol efflux, while enhancing the production of pro-inflammatory cytokines through a TLR4-dependent mechanism. Under these conditions, the viability of macrophages is compromised, leading to increased cell death. These results provide novel insights into the role of PCSK9 in the crosstalk of lipids and cholesterol metabolism through the LDLR and on the pro-inflammatory activation of macrophages through TLR4 signaling. These pathways are relevant in the outcome of atherosclerosis and highlight the relevance of PCSK9 as a therapeutic target for the treatment of cardiovascular diseases.

Anti-herpes simplex virus type Ⅰ of tectorigenin derivative and effect on Toll-like receptors in vitro

The study investigated the inhibitory effect and mechanism of tectorigenin derivative(SGY) against herpes simplex virus type Ⅰ(HSV-1) by in vitro experiments. The cytotoxicity of SGY and positive drug acyclovir(ACV) on African green monkey kidney(Vero) cells and mouse microglia(BV-2) cells was detected by cell counting kit-8(CCK-8) method, and the maximum non-toxic concentration and median toxic concentration(TC_(50)) of the drugs were calculated. After Vero cells were infected with HSV-1, the virulence was determined by cytopathologic effects(CPE) to calculate viral titers. The inhibitory effect of the tested drugs on HSV-1-induced cytopathy in Vero cells was measured, and their modes of action were initially explored by virus adsorption, replication and inactivation. The effects of the drugs on viral load of BV-2 cells 24 h after HSV-1 infection and the Toll-like receptor(TLR) mRNA expression were detected by real-time fluorescence quantitative PCR(RT-qPCR). The maximum non-toxic concentrations of SGY against Vero and BV-2 cells were 382.804 μg·mL~(-1) and 251.78 μg·mL~(-1), respectively, and TC_(50) was 1 749.98 μg·mL~(-1) and 2 977.50 μg·mL~(-1), respectively. In Vero cell model, the half maximal inhibitory concentration(IC_(50)) of SGY against HSV-1 was 54.49 μg·mL~(-1), and the selection index(SI) was 32.12, with the mode of action of significantly inhibiting replication and directly inactivating HSV-1. RT-qPCR results showed that SGY markedly reduced the viral load in cells. The virus model group had significantly increased relative expression of TLR2, TLR3 and tumor necrosis factor receptor-associated factor 3(TRAF3) and reduced relative expression of TLR9 as compared with normal group, and after SGY intervention, the expression of TLR2, TLR3 and TRAF3 was decreased to different degrees and that of TLR9 was enhanced. The expression of inflammatory factors inducible nitric oxide synthase(iNOS), tumor necrosis factor-α(TNF-α), and interleukin-1β(IL-1β) was remarkably increased in virus model group as compared with that in normal group, and the levels of these inflammatory factors dropped after SGY intervention. In conclusion, SGY significantly inhibited and directly inactivated HSV-1 in vitro. In addition, it modulated the expression of TLR2, TLR3 and TLR9 related pathways, and suppressed the increase of inflammatory factor levels.

New insights into the role and mechanisms of ginsenoside Rg1 in the management of Alzheimer’s disease

Alzheimer's disease (AD) is a common neurodegenerative disorder in the elderly characterized by memory loss and cognitive dysfunction. The pathogenesis of AD is complex. One-targeted anti-AD drugs usually fail to delay AD progression. Traditional Chinese medicine records have documented the use of the roots of Panax ginseng (ginseng roots) and its prescriptions to treat dementia. Ginsenoside Rg1, the main ginsenoside component of ginseng roots, exhibits a certain therapeutic effect in the abovementioned diseases, suggesting its potential in the management of AD. Therefore, we combed the pathogenesis of AD and currently used anti-AD drugs, and reviewed the availability, pharmacokinetics, and pharmaceutic studies of ginsenoside Rg1. This review summarizes the therapeutic effects and mechanisms of ginsenoside Rg1 and its deglycosylated derivatives in AD in vivo and in vitro. The main mechanisms include improvement in Aβ and Tau pathologies, regulation of synaptic function and intestinal microflora, and reduction of inflammation, oxidative stress, and apoptosis. The underlying mechanisms mainly involve the regulation of PKC, MAPK, PI3K/Akt, CDK5, GSK-3β, BDNF/TrkB, PKA/CREB, FGF2/Akt, p21WAF1/CIP1, NF-κB, NLRP1, TLR3, and TLR4 signaling pathways. As the effects and underlying mechanisms of ginsenoside Rg1 on AD have not been systematically reviewed, we have provided a comprehensive review and shed light on the future directions in the utilization of ginsenoside Rg1 and ginseng roots as well as the development of anti-AD drugs.

Distinct activities of Vδ1+ T-cells upon different cytomegalovirus reactivation status after haematopoietic transplantation.

Cytomegalovirus (CMV) reactivation is the most frequent viral infectious complication correlating to non-relapse mortality after allogeneic haematopoietic cell transplantation (alloHCT). The intrinsic anti-CMV immunity has not been completely elucidated. γδ T-cells have drawn increasing attentions due to their distinct biological features and potential ability against viral infections. Previous studies reported a general association of γδ T-cells or Vδ2-negative γδ T-cells with CMV reactivation. Whereas researches for the direct responses and specific functions of γδ T subsets remain limited, especially in the scenario of alloHCT. Herein, we initially demonstrated that Vδ1+ T-cells directly and independently recognized cell-free CMV and CMV-infected target cells, and inhibited CMV replication in vitro. The anti-CMV effect of Vδ1+ T-cells was partially through TCRγδ, TLR2 and NKG2D receptor pathways. Further investigation about the anti-CMV characteristics of Vδ1+ T-cells was performed in a clinical cohort with different CMV reactivation status after alloHCT. We found that occasional CMV reactivation remarkably increased the recovery levels and stimulated the functional activity of Vδ1+ T-cells. Whereas disability of Vδ1+ T-cells was observed upon refractory CMV reactivation indicating the differential responses of Vδ1+ T-cells under different CMV reactivation status. CXCL10 and IFN-β that were dramatically induced by occasional CMV reactivation could re-activate the deficient Vδ1+ T-cells from recipients with refractory CMV reactivation. These findings unveiled the distinct activities of Vδ1+ T-cells in anti-CMV immunity after alloHCT and may help develop novel strategies for the treatment of CMV infectious diseases.

Inhibition of human macrophage activation via pregnane neurosteroid interactions with toll-like receptors: Sex differences and structural requirements.

We recently discovered that (3α,5α)3-hydroxypregnan-20-one (allopregnanolone) inhibits pro-inflammatory toll-like receptor (TLR) activation and cytokine/chemokine production in mouse macrophage RAW264.7 cells. The present studies evaluate neurosteroid actions upon TLR activation in human macrophages from male and female healthy donors. Buffy coat leukocytes were obtained from donors at the New York Blood Center (http://nybloodcenter.org/), and peripheral blood mononuclear cells were isolated and cultured to achieve macrophage differentiation. TLR4 and TLR7 were activated by lipopolysaccharide (LPS) or imiquimod in the presence/absence of allopregnanolone or related neurosteroids and pro-inflammatory markers were detected by ELISA or western blotting. Cultured human monocyte-derived-macrophages exhibited typical morphology, a mixed immune profile of both inflammatory and anti-inflammatory markers, with no sex difference at baseline. Allopregnanolone inhibited TLR4 activation in male and female donors, preventing LPS-induced elevations of TNF-α, MCP-1, pCREB and pSTAT1. In contrast, 3α,5α-THDOC and SGE-516 inhibited the TLR4 pathway activation in female, but not male donors. Allopregnanolone completely inhibited TLR7 activation by imiquimod, blocking IL-1-β, IL-6, pSTAT1 and pIRF7 elevations in females only. 3α,5α-THDOC and SGE-516 partially inhibited TLR7 activation, only in female donors. The results indicate that allopregnanolone inhibits TLR4 and TLR7 activation in cultured human macrophages resulting in diminished cytokine/chemokine production. Allopregnanolone inhibition of TLR4 activation was found in males and females, but inhibition of TLR7 signals exhibited specificity for female donors. 3α,5α-THDOC and SGE-516 inhibited TLR4 and TLR7 pathways only in females. These studies demonstrate anti-inflammatory effects of allopregnanolone in human macrophages for the first time and suggest that inhibition of pro-inflammatory cytokines/chemokines may contribute to its therapeutic actions.

Design and Characterization of Immune-Stimulating Imidazo[4,5-c]quinoline Antibody-Drug Conjugates.

Traditional antibody-drug conjugate (ADC) technology has employed tumor-targeting antibodies to selectively deliver ultrapotent cytotoxins to tumor tissue. While this technology has been highly successful, resulting in the FDA approval of over 10 ADCs, the field continues to struggle with modest efficacy and significant off-target toxicity. Concurrent with the struggles of the ADC field, a new generation of immune-activating therapeutics has arisen, most clearly exemplified by the PD-1/PD-L1 inhibitors that are now part of standard-of-care treatment regimens for a variety of cancers. The success of these immuno-oncology therapeutic agents has prompted the investigation of a variety of new immuno-stimulant approaches, including toll-like receptor (TLR) activators. Herein, we describe the optimization of ADC technology for the selective delivery of a potent series of TLR7 agonists. A series of imidazole[4,5-c]quinoline agonists (as exemplified by compound 1) were shown to selectively agonize the human and mouse TLR7 receptor at low nanomolar concentrations, resulting in the release of IFNα from human peripheral blood mononuclear cells (hPBMCs) and the upregulation of CD86 on antigen-presenting cells. Compound 1 was attached to a deglycosylated (Fc-γ null) HER2-targeting antibody via a cleavable linker, resulting in an ADC (anti-HER2_vc-1) that potently and selectively activated the TLR7 pathway in tumor-associated macrophages via a "bystander" mechanism. We demonstrated that this ADC rapidly released the TLR7 agonist into the media when incubated with HER2+ cells. This release was not observed upon incubation with an isotype control ADC and furthermore was suppressed by co-administration of the naked antibody. In co-culture experiments with HER2+ HCC1954 cells, this ADC induced the activation of the NFκB pathway in mouse macrophages and the release of IFNα from hPBMCs, while a corresponding isotype control ADC did not. Finally, we demonstrated that IP administration of anti-HER2_vc-1 induced complete tumor regression in an HCC1954 xenograft study in SCID beige mice. Unlike related ADC technology that has been reported recently, our technology relies on the passive diffusion of the TLR7 agonist into tumor-associated macrophages rather than Fc-γ-mediated uptake. Based on these observations, we believe that this ADC technology holds significant potential for both oncology and infectious disease applications.

Jujuboside B post-treatment attenuates PM2.5-induced lung injury in mice

ABSTRACT Fine particulate matter (PM2.5) is an air pollutant that causes severe lung injury. We investigated the effects of Jujuboside B (JB), a component of Zizyphi Spinosi Semen, on lung toxicity caused by PM2.5, and we identified the mechanism of its protective effect. Lung injury in an animal model was induced by intratracheal administration of a PM2.5 suspension. After 2 days of PM2.5 pretreatment, mice were administered JB via the tail vein three times over a 2-day period. JB significantly reduced the histological lung damage as well as the lung wet/dry weight ratio. JB also considerably reduced PM2.5-induced autophagy dysfunction, apoptosis, inflammatory cytokine levels, and the number of PM2.5-induced lymphocytes in the bronchial alveolar fluid. We conclude that by regulating TLR2, 4-MyD88, and mTOR-autophagy pathways, JB exerts a protective effect on lung injury. Thus, JB can be used as a potential therapeutic agent for PM2.5-induced lung damage.

Emerging Approach for the Application of Hibiscus sabdariffa Extract Ointment in the Superficial Burn Care

Wound healing comprises organized events involving tissue repair and regeneration. The discovery of toll-like receptors (TLRs) sheds recent light on the mechanisms involved in initiating inflammatory responses throughout the healing cascades. Hibiscus sabdariffa (HS) components may exhibit a wound healing action, owing to their antioxidant and anti-inflammatory activities. This study was designed to investigate the early effects of HS loaded in an ointment base on wound healing, antioxidant, antimicrobial effects, burning intensity, and histopathological features on the rat burn model in comparison to the standard treatment, Iruxol® ointment. A burn injury model was used to evaluate the wound healing potency of the preparation. Rats were treated with ointments three times on the day of the induction of the burn. Findings revealed that the strong antioxidant properties of the HS-loaded ointment augmented the skin healing potential by stimulating biomarkers required for skin regeneration. HS repressed the burning-induced inflammation by the effective reduction in the levels of tumor necrosis factor α (TNF-α) and IL-6 through TLR4 protein inhibition. Topical HS downregulates transforming growth factor-beta (TGF-β) levels. HS extract possesses a potential bactericidal activity against highly resistant clinical isolates of Pseudomonas aeruginosa. Overall, this study proclaims that HS-loaded topical preparations could be a valuable product that serves as adjuvants to accelerate burn wound healing through inactivating the TLR4 pathway.

Pathogenic Leptospires Limit Dendritic Cell Activation Through Avoidance of TLR4 and TRIF Signaling.

Leptospira interrogans is a bacterial species responsible for leptospirosis, a neglected worldwide zoonosis. Mice and rats are resistant and can become asymptomatic carriers, whereas humans and some other mammals may develop severe forms of leptospirosis. Uncommon among spirochetes, leptospires contain lipopolysaccharide (LPS) in their outer membrane. LPS is highly immunogenic and forms the basis for a large number of serovars. Vaccination with inactivated leptospires elicits a protective immunity, restricted to serovars with related LPS. This protection that lasts in mice, is not long lasting in humans and requires annual boosts. Leptospires are stealth pathogens that evade the complement system and some pattern recognition receptors from the Toll-like (TLR) and Nod-Like families, therefore limiting antibacterial defense. In macrophages, leptospires totally escape recognition by human TLR4, and escape the TRIF arm of the mouse TLR4 pathway. However, very little is known about the recognition and processing of leptospires by dendritic cells (DCs), although they are crucial cells linking innate and adaptive immunity. Here we tested the activation of primary DCs derived from human monocytes (MO-DCs) and mouse bone marrow (BM-DCs) 24h after stimulation with saprophytic or different pathogenic virulent or avirulent L. interrogans. We measured by flow cytometry the expression of DC-SIGN, a lectin involved in T-cell activation, co-stimulation molecules and MHC-II markers, and pro- and anti-inflammatory cytokines by ELISA. We found that exposure to leptospires, live or heat-killed, activated dendritic cells. However, pathogenic L. interrogans, especially from the Icterohaemorraghiae Verdun strain, triggered less marker upregulation and less cytokine production than the saprophytic Leptospira biflexa. In addition, we showed a better activation with avirulent leptospires, when compared to the virulent parental strains in murine BM-DCs. We did not observe this difference in human MO-DCs, suggesting a role for TLR4 in DC stimulation. Accordingly, using BM-DCs from transgenic deficient mice, we showed that virulent Icterohaemorraghiae and Manilae serovars dampened DC activation, at least partly, through the TLR4 and TRIF pathways. This work shows a novel bacterial immune evasion mechanism to limit DC activation and further illustrates the role of the leptospiral LPS as a virulence factor.

Sulfavant A as the first synthetic TREM2 ligand discloses a homeostatic response of dendritic cells after receptor engagement

ObjectiveThe immune response arises from a fine balance of mechanisms that provide for surveillance, tolerance, and elimination of dangers. Sulfavant A (SULF A) is a sulfolipid with a promising adjuvant activity. Here we studied the mechanism of action of SULF A and addressed the identification of its molecular target in human dendritic cells (hDCs).MethodsAdjuvant effect and immunological response to SULF A were assessed on DCs derived from human donors. In addition to testing various reporter cells, target identification and downstream signalling was supported by a reverse pharmacology approach based on antibody blocking and gene silencing, crosstalk with TLR pathways, use of human allogeneic mixed lymphocyte reaction.ResultsSULF A binds to the Triggering Receptor Expressed on Myeloid cells-2 (TREM2) and initiates an unconventional maturation of hDCs leading to enhanced migration activity and up-regulation of MHC and co-stimulatory molecules without release of conventional cytokines. This response involves the SYK-NFAT axis and is compromised by blockade or gene silencing of TREM2. Activation by SULF A preserved the DC functions to excite the allogeneic T cell response, and increased interleukin-10 release after lipopolysaccharide stimulation.ConclusionSULF A is the first synthetic small molecule that binds to TREM2. The receptor engagement drives differentiation of an unprecedented DC phenotype (homeDCs) that contributes to immune homeostasis without compromising lymphocyte activation and immunogenic response. This mechanism fully supports the adjuvant and immunoregulatory activity of SULF A. We also propose that the biological properties of SULF A can be of interest in various physiopathological mechanisms and therapies involving TREM2.

Silencing the Tlr4 Gene Alleviates Methamphetamine-Induced Hepatotoxicity by Inhibiting Lipopolysaccharide-Mediated Inflammation in Mice.

Methamphetamine (METH) is a stimulant drug. METH abuse induces hepatotoxicity, although the mechanisms are not well understood. METH-induced hepatotoxicity was regulated by TLR4-mediated inflammation in BALB/c mice in our previous study. To further investigate the underlying mechanisms, the wild-type (C57BL/6) and Tlr4−/− mice were treated with METH. Transcriptomics of the mouse liver was performed via RNA-sequencing. Histopathological changes, serum levels of metabolic enzymes and lipopolysaccharide (LPS), and expression of TLR4-mediated proinflammatory cytokines were assessed. Compared to the control, METH treatment induced obvious histopathological changes and significantly increased the levels of metabolic enzymes in wild-type mice. Furthermore, inflammatory pathways were enriched in the liver of METH-treated mice, as demonstrated by expression analysis of RNA-sequencing data. Consistently, the expression of TLR4 pathway members was significantly increased by METH treatment. In addition, increased serum LPS levels in METH-treated mice indicated overproduction of LPS and gut microbiota dysbiosis. However, antibiotic pretreatment or silencing Tlr4 significantly decreased METH-induced hepatic injury, serum LPS levels, and inflammation. In addition, the dampening effects of silencing Tlr4 on inflammatory pathways were verified by the enrichment analysis of RNA-sequencing data in METH-treated Tlr4−/− mice compared to METH-treated wild-type mice. Taken together, these findings implied that Tlr4 silencing, comparable to antibiotic pretreatment, effectively alleviated METH-induced hepatotoxicity by inhibiting LPS-TLR4-mediated inflammation in the liver.

Activation of lnc-ALVE1-AS1 inhibited ALV-J replication through triggering the TLR3 pathway in chicken macrophage like cell line.

Endogenous retroviruses (ERVs) are remnants of the historical retroviral infections, and their derived transcripts with viral signatures are important sources of long noncoding RNAs (lncRNAs). We have previously shown that the chicken ERV-derived lncRNA lnc-ALVE1-AS1 exerts antiviral innate immunity in chicken embryo fibroblasts. However, it is not clear whether this endogenous retroviral RNA has a similar function in immune cells. Here, we found that lnc-ALVE1-AS1 was persistently inhibited in chicken macrophages after avian leukosis virus subgroup J (ALV-J) infection. Furthermore, overexpression of lnc-ALVE1-AS1 significantly inhibited the replication of exogenous ALV-J, whereas knockdown of lnc-ALVE1-AS1 promoted the replication of ALV-J in chicken macrophages. This phenomenon is attributed to the induction of antiviral innate immunity by lnc-ALVE1-AS1 in macrophages, whereas knockdown of lnc-ALVE1-AS1 had the opposite effect. Mechanistically, lnc-ALVE1-AS1 can be sensed by the cytosolic pattern recognition receptor TLR3 and trigger the type I interferons response. The present study provides novel insights into the antiviral defense of ERV-derived lncRNAs in macrophages and offers new strategies for future antiviral solutions.