Effect of TLR4/MyD88 signaling pathway on expression of IL-1β and TNF-α in synovial fibroblasts from temporomandibular joint exposed to lipopolysaccharide

A Potential Role of the Spike Protein in Neurodegenerative Diseases: A Narrative Review

Human prion protein and prion-like protein misfolding are widely recognized as playing a causal role in many neurodegenerative diseases. Based on in vitro and in vivo experimental evidence relating to prion and prion-like disease, we extrapolate from the compelling evidence that the spike glycoprotein of SARS-CoV-2 contains extended amino acid sequences characteristic of a prion-like protein to infer its potential to cause neurodegenerative disease. We propose that vaccine-induced spike protein synthesis can facilitate the accumulation of toxic prion-like fibrils in neurons. We outline various pathways through which these proteins could be expected to distribute throughout the body. We review both cellular pathologies and the expression of disease that could become more frequent in those who have undergone mRNA vaccination. Specifically, we describe the spike protein's contributions, via its prion-like properties, to neuroinflammation and neurodegenerative diseases; to clotting disorders within the vasculature; to further disease risk due to suppressed prion protein regulation in the context of widely prevalent insulin resistance; and to other health complications. We explain why these prion-like characteristics are more relevant to vaccine-related mRNA-induced spike proteins than natural infection with SARS-CoV-2. We note with an optimism an apparent loss of prion-like properties among the current Omicron variants. We acknowledge that the chain of pathological events described throughout this paper is only hypothetical and not yet verified. We also acknowledge that the evidence we usher in, while grounded in the research literature, is currently largely circumstantial, not direct. Finally, we describe the implications of our findings for the general public, and we briefly discuss public health recommendations we feel need urgent consideration. An earlier version of this article was previously posted to the Authorea preprint server on August 16, 2022.

Sophorolipids produced by Yarrowia lipolytica grown on Moringa oleifera oil cake protect against acetic acid-induced colitis in rats: impact on TLR-4/p-JNK/NFκB-p65 pathway

OBJECTIVES

Toll-like receptor-4 (TLR-4) activation plays a major role in triggering oxidative stress (OS) and inflammation implicated in the pathogenesis of ulcerative colitis (UC). Due to sophorolipids (SLs) antioxidant and anti-inflammatory properties, they are interestingly becoming more valued for their potential effectiveness in treating a variety of diseases. This study was designed to explore the effect of SLs produced by microbial conversion of Moringa oleifera oil cake using isolated yeast Yarrowia lipolytica against UC induced by acetic acid (AA) in rats.

METHODS

The produced SLs were identified by FTIR, 1H NMR and LC-MS/MS spectra, and administered orally for 7 days (200 mg/kg/day) before AA (2 ml, 4% v/v) to induce UC intrarectally on day eight. Biochemically, the levels of TLR-4, c-Jun N-terminal kinase (JNK), nuclear factor kappa B-p65 (NFκB-p65), interleukin-1beta (IL-1β), malondialdehyd, glutathione, Bax/Bcl2 ratio and the immunohistochemical evaluation of inducible nitric oxide synthase and caspase-3 were assayed.

KEY FINDINGS

SLs significantly reduced OS, inflammatory and apoptotic markers in AA-treated rats, almost like the reference sulfasalazine.

CONCLUSIONS

This study provided a novel impact for SLs produced by microbial conversion of M. oleifera oil cake against AA-induced UC in rats through hampering the TLR-4/p-JNK/NFκB-p65 signalling pathway.

The soluble CD83 protein prevents bone destruction by inhibiting the formation of osteoclasts and inducing resolution of inflammation in arthritis

Here we show that soluble CD83 induces the resolution of inflammation in an antigen-induced arthritis (AIA) model. Joint swelling and the arthritis-related expression levels of IL-1β, IL-6, RANKL, MMP9, and OC-Stamp were strongly reduced, while Foxp3 was induced. In addition, we observed a significant inhibition of TRAP⁺ osteoclast formation, correlating with the reduced arthritic disease score. In contrast, cell-specific deletion of CD83 in human and murine precursor cells resulted in an enhanced formation of mature osteoclasts. RNA sequencing analyses, comparing sCD83- with mock treated cells, revealed a strong downregulation of osteoclastogenic factors, such as Oc-Stamp, Mmp9 and Nfatc1, Ctsk, and Trap. Concomitantly, transcripts typical for pro-resolving macrophages, e.g., Mrc1/2, Marco, Klf4, and Mertk, were upregulated. Interestingly, members of the metallothionein (MT) family, which have been associated with a reduced arthritic disease severity, were also highly induced by sCD83 in samples derived from RA patients. Finally, we elucidated the sCD83-induced signaling cascade downstream to its binding to the Toll-like receptor 4/(TLR4/MD2) receptor complex using CRISPR/Cas9-induced knockdowns of TLR4/MyD88/TRIF and MTs, revealing that sCD83 acts via the TRIF-signaling cascade. In conclusion, sCD83 represents a promising therapeutic approach to induce the resolution of inflammation and to prevent bone erosion in autoimmune arthritis.

The Role of TNF-α in the Pathogenesis of Temporomandibular Disorders

Temporomandibular disorder (TMD) is an oral dentofacial disease that is related to multiple factors such as disordered dental occlusion, emotional stress, and immune responses. In the past decades, tumor necrosis factor-alpha (TNF-α), a pleiotropic cytokine, has provided valuable insight into the pathogenesis of TMD, particularly in settings associated with inflammation. It is thought that TNF-α participates in the pathogenesis of TMD by triggering immune responses, deteriorating bone and cartilage, and mediating pain in the temporomandibular joint (TMJ). Initially, TNF-α plays the role of "master regulator" in the complex immune network by increasing or decreasing the production of other inflammatory cytokines. Then, the effects of TNF-α on cells, particularly on chondrocytes and synovial fibroblasts, result in pathologic cartilage degradation in TMD. Additionally, multiple downstream cytokines induced by TNF-α and neuropeptides can regulate central sensitization and inflammatory pain in TMD. Previous studies have also found some therapies target TMD by reducing the production of TNF-α or blocking TNF-α-induced pathways. All this evidence highlights the numerous associations between TNF-α and TMD; however, they are currently not fully understood and further investigations are still required for specific mechanisms and treatments targeting specific pathways. Therefore, in this review, we explored general mechanisms of TNF-α, with a focus on molecules in TNF-α-mediated pathways and their potential roles in TMD treatment. In view of the high clinical prevalence rate of TMD and damage to patients' QOL, this review provides adequate evidence for studying links between inflammation and TMD in further research and investigation.

The interplay of DAMPs, TLR4, and proinflammatory cytokines in pulmonary fibrosis

Pulmonary fibrosis is a chronic debilitating condition characterized by progressive deposition of connective tissue, leading to a steady restriction of lung elasticity, a decline in lung function, and a median survival of 4.5 years. The leading causes of pulmonary fibrosis are inhalation of foreign particles (such as silicosis and pneumoconiosis), infections (such as post COVID-19), autoimmune diseases (such as systemic autoimmune diseases of the connective tissue), and idiopathic pulmonary fibrosis. The therapeutics currently available for pulmonary fibrosis only modestly slow the progression of the disease. This review is centered on the interplay of damage-associated molecular pattern (DAMP) molecules, Toll-like receptor 4 (TLR4), and inflammatory cytokines (such as TNF-α, IL-1β, and IL-17) as they contribute to the pathogenesis of pulmonary fibrosis, and the possible avenues to develop effective therapeutics that disrupt this interplay.

Modulatory Potential of Cannabidiol on the Opioid-Induced Inflammatory Response

Opioids are effective analgesics; however, there are many negative consequences of chronic use. One important side effect of chronic opioid use is the continuous engagement of the immune response that can exacerbate chronic pain. The opioid, morphine, initiates a Toll-like receptor 4 (TLR4) signaling cascade that drives the activation of NOD-, LRR-, and pyrin domain-containing protein 3 (NLRP3) inflammasome proteins, resulting in cytokine production and effectively creating a positive feedback loop for continuous TLR4 activation. In addition to driving cytokine production, morphine drives changes in proinflammatory lipid signaling. The alteration of both cytokine and lipid signaling systems by morphine suggests that its chronic use leads to a pathological immune response that would benefit from targeted therapy. Engaging the endogenous cannabinoid system has shown therapeutic benefit, particularly regarding its anti-inflammatory and immunosuppressive effects. Promising preclinical and clinical investigations suggest that cannabidiol (CBD) is an effective adjuvant for treatment of symptoms of opioid use disorders; however, the mechanism through which CBD drives this outcome is unclear. One potential source of insight into this mechanism is in how CBD regulates immune regulators such as cytokines and lipid signaling systems, including endocannabinoids and related immune-responsive lipids. In this review, we outline the immune response to chronic opioid use as well as CBD in the context of a lipopolysaccharide-induced immune response and speculate on the mechanism of CBD as a modulator of chronic opioid-induced immune system dysregulation.

Increased TLR/MyD88 signaling in patients with obesity: is there a link to COVID-19 disease severity?

COVID-19 is a pandemic disease caused by a coronavirus, designed as SARS CoV-2, whose clinical presentation is widely variable, with most patients having mild or no symptoms, but others developing a malign disease with multi-organ failure and even death. Accumulating data from different populations have shown that obesity is a risk factor for a severe evolution of the disease, however, the mechanisms that explain this association are not clearly understood. An ominous evolution of COVID-19 has been attributed to an exacerbated inflammatory response, designed as "cytokine storm" with augmented production of cytokines/chemokines through the activation of toll-like receptors (TLR) by pathogen-associated molecular patterns, that triggers an inflammatory downstream response, mediated in part by the adaptor molecule, myeloid differentiation factor 88 (MyD88). Previous studies have reported an increased expression of MyD88 and TLRs in people with obesity, mainly in those with metabolic complications. Therefore, we hypothesize, that an underlying increased Myd88/TLR signaling may predispose to patients with obesity to develop an exaggerated and dangerous inflammatory reaction against SARS CoV-2 infection, explaining at least in part, the higher severity of COVID-19. In addition, MyD88/TLR signaling in people with obesity could have a role in the development of several chronic diseases.

Toll-like receptor 4 activation modulates pericardium-myocardium interactions in lipopolysaccharide-induced atrial arrhythmogenesis

AIMS

Inflammation plays a role in the pathogenesis of atrial fibrillation (AF). Pericarditis enhanced atrial arrhythmogenesis, but the role of the pericardium remains unclear in AF. Activation of the toll-like receptor 4 (TLR4) by binding to lipopolysaccharide (LPS) promotes cardiac electrical remodelling. In this study, we hypothesized that pericarditis may induce atrial arrhythmogenesis via pericardium-myocardium interactions by TLR4 signalling.

METHODS AND RESULTS

Pericarditis was induced in rabbits by injecting LPS (1-2 mg/kg) into the pericardium. Conventional microelectrodes were used to record the action potentials of left atrial (LA) posterior walls (LAPWs) and LA appendages (LAAs) with and without attached pericardium in the control or pericarditis-induced rabbits. Cytokine array was used to measure the expression levels of proinflammatory cytokines in control and LPS-treated pericardium. Compared with the controls, the LPS-treated pericardium had higher expressions of IL-1α, IL-8, and MIP-1β. Rapid atrial pacing-induced burst firing in LPS-treated LAPWs and LAAs, and in control LAPWs (but not in LAAs). The incidence of pacing-induced spontaneous activity and burst firing was increased by LPS-treated pericardium but was attenuated by the control pericardium. Moreover, burst firing induced by LPS-treated pericardium was blocked upon administration of the TLR4 inhibitor, TAK-242 (100 ng/mL), ryanodine receptor inhibitor (ryanodine, 3 μM), or calmodulin kinase II inhibitor (KN-93, 1 μM).

CONCLUSIONS

Healthy and inflamed pericardium differently modulate LPS-induced atrial arrhythmogenesis. Targeting pericardium via TLR4 signalling may be a novel therapeutic strategy for AF.

Cloning, Expression, and Purification of a Pathogenesis-Related Protein from Oenanthe javanica and Its Biological Properties

Pathogenesis-related (PR) proteins are inducible and accumulated in plants upon pathogen challenge for survival. Interest in these proteins has arisen in many fields of research, including areas of protein defense mechanisms and plant-derived allergens. In this study, we cloned a PR protein gene (OJPR) from Oenanthe javanica, which consisted of 465 bp with an approximate molecular mass of 16 kDa. The DNA and deduced amino acid sequences of OJPR were 87% similar to Pimpinella brachycarpa PR-1 together with a glycine-rich loop which is a signature motif of PR-10. In microarray analysis, OJPR-transfected Raw264.7 (OJPR⁺) upregulated high mobility group box 1 and protein kinase Cα, and downregulated chemokine ligand 3 and interleukin 1β which are all related to toll-like receptor 4 (TLR4) and inflammation. TAK-242 and PD98059 inhibited the activation by OJPR, suggesting that OJPR transduce TLR4-mediated signaling. Interestingly, OJPR increased anti-viral repertoires, including interferon (IFN)α, IFNγ, OAS1, and Mx1 in CD4⁺ primary T cells. Taken together, we concluded that OJPR may play a role in modulating host defense responses via TLR signal transduction and provide new insights into the therapeutic and diagnostic advantages as a potential bioactive protein.

TLR4 contributes to the damage of cartilage and subchondral bone in discectomy-induced TMJOA mice

The abundance of inflammatory mediators in injured joint indicates innate immune reactions activated during temporomandibular joint osteoarthritis (TMJOA) progression. Toll‐like receptor 4 (TLR4) can mediate innate immune reaction. Herein, we aimed to investigate the expression profile and effect of TLR4 in the cartilage and subchondral bone of the discectomy‐induced TMJOA mice. The expression of TLR4 and NFκB p65 in the synovium of TMJOA patients was measured by immunohistochemistry, Western blotting and RT‐PCR. H&E and Masson staining were utilized to assess the damage of cartilage and subchondral bone of the discectomy‐induced TMJOA mice. A TLR4 inhibitor, TAK‐242, was used to assess the effect of TLR4 in the cartilage and subchondral bone of the discectomy‐induced TMJOA mice by Safranin O, micro‐CT, immunofluorescence and immunohistochemistry. Western blotting was used to quantify the expression and effect of TLR4 in IL‐1β–induced chondrocytes. The expression of TLR4 and NFκB p65 was elevated in the synovium of TMJOA patients, compared with the normal synovium. TLR4 elevated in the damaged cartilage and subchondral bone of discectomy‐induced TMJOA mice, and the rate of TLR4 expressing chondrocytes positively correlated with OA score. Intraperitoneal injections of TAK‐242 ameliorate the extent of TMJOA. Furthermore, TLR4 promotes the expression of MyD88/NFκB, pro‐inflammatory and catabolic mediators in cartilage of discectomy‐induced TMJOA. Besides, TLR4 participates in the production of MyD88/NFκB, pro‐inflammatory and catabolic mediators in IL‐1β–induced chondrocytes. TLR4 contributes to the damage of cartilage and subchondral bone in discectomy‐induced TMJOA mice through activation of MyD88/NFκB and release of pro‐inflammatory and catabolic mediators.

Synthetic immunomodulation with a CRISPR super-repressor in vivo

Transient modulation of the genes involved in immunity, without exerting a permanent change in the DNA code, can be an effective strategy to modulate the course of many inflammatory conditions. CRISPR-Cas9 technology represents a promising platform for achieving this goal. Truncation of guide RNA (gRNA) from the 5' end enables the application of a nuclease competent Cas9 protein for transcriptional modulation of genes, allowing multifunctionality of CRISPR. Here, we introduce an enhanced CRISPR-based transcriptional repressor to reprogram immune homeostasis in vivo. In this repressor system, two transcriptional repressors-heterochromatin protein 1 (HP1a) and Krüppel-associated box (KRAB)-are fused to the MS2 coat protein and subsequently recruited by gRNA aptamer binding to a nuclease competent CRISPR complex containing truncated gRNAs. With the enhanced repressor, we demonstrate transcriptional repression of the Myeloid differentiation primary response 88 (Myd88) gene in vitro and in vivo. We demonstrate that this strategy can efficiently downregulate Myd88 expression in lung, blood and bone marrow of Cas9 transgenic mice that receive systemic injection of adeno-associated virus (AAV)2/1-carrying truncated gRNAs targeting Myd88 and the MS2-HP1a-KRAB cassette. This downregulation is accompanied by changes in downstream signalling elements such as TNF-α and ICAM-1. Myd88 repression leads to a decrease in immunoglobulin G (IgG) production against AAV2/1 and AAV2/9 and this strategy modulates the IgG response against AAV cargos. It improves the efficiency of a subsequent AAV9/CRISPR treatment for repression of proprotein convertase subtilisin/kexin type 9 (PCSK9), a gene that, when repressed, can lower blood cholesterol levels. We also demonstrate that CRISPR-mediated Myd88 repression can act as a prophylactic measure against septicaemia in both Cas9 transgenic and C57BL/6J mice. When delivered by nanoparticles, this repressor can serve as a therapeutic modality to influence the course of septicaemia. Collectively, we report that CRISPR-mediated repression of endogenous Myd88 can effectively modulate the host immune response against AAV-mediated gene therapy and influence the course of septicaemia. The ability to control Myd88 transcript levels using a CRISPR-based synthetic repressor can be an effective strategy for AAV-based CRISPR therapies, as this pathway serves as a key node in the induction of humoral immunity against AAV serotypes.

Uric Acid Has Direct Proinflammatory Effects on Human Macrophages by Increasing Proinflammatory Mediators and Bacterial Phagocytosis Probably via URAT1

The relationship of uric acid with macrophages has not been fully elucidated. We investigated the effect of uric acid on the proinflammatory ability of human macrophages and then examined the possible molecular mechanism involved. Primary human monocytes were differentiated into macrophages for subsequent exposure to 0, 0.23, 0.45, or 0.9 mmol/L uric acid for 12 h, in the presence or absence of 1 mmol/L probenecid. Flow cytometry was used to measure proinflammatory marker production and phagocytic activity that was quantified as a percentage of GFP-labeled Escherichia coli positive macrophages. qPCR was used to measure the macrophage expression of the urate anion transporter 1 (URAT1). As compared to control cells, the production of tumor necrosis factor-alpha (TNF-alpha), toll-like receptor 4 (TLR4), and cluster of differentiation (CD) 11c was significantly increased by uric acid. In contrast, macrophages expressing CD206, CX3C-motif chemokine receptor 1 (CX3CR1), and C-C chemokine receptor type 2 (CCR2) were significantly reduced. Uric acid progressively increased macrophage phagocytic activity and downregulated URAT1 expression. Probenecid-a non-specific blocker of URAT1-dependent uric acid transport-inhibited both proinflammatory cytokine production and phagocytic activity in macrophages that were exposed to uric acid. These results suggest that uric acid has direct proinflammatory effects on macrophages possibly via URAT1.

LncRNA PVT1 induces chondrocyte apoptosis through upregulation of TNF-α in synoviocytes by sponging miR-211-3p

Temporomandibular joint osteoarthritis (TMJ OA) is an important subtype of temporomandibular disorders (TMD). Articular cartilage destruction is considered a common pathological feature of TMJ OA, which is reported to be mainly induced by chondrocyte apoptosis. Synovial sterile inflammation is an initial factor of TMJ OA-associated articular cartilage destruction. Therefore, determining the mechanism of synovial membrane inflammation-induced articular cartilage destruction in TMJ OA is important for the TMJ OA therapy. In this study, we detected the function of synoviocytes in chondrocyte apoptosis under lipopolysaccharide (LPS)-induced inflammatory conditions and explored the underlying mechanism. We found that synoviocytes in inflammatory conditions facilitated LPS-induced chondrocytes apoptosis by secreting increased Tumor Necrosis Factor α (TNF-α), which was induced by long non-coding RNA plasmacytoma variant translocation 1 (PVT1) upregulation. PVT1 served as a competing endogenous RNA that sponged the microRNA miR-211-3p and prevented the inhibition of TNF-α expression. In conclusion, our in vitro study revealed that PVT1 has a previously unknown role in chondrocyte apoptosis, which may also be a mechanism underlying synoviocyte involvement in TMJ OA.

Transcriptional profiling indicates cAMP-driven reversal of HIV latency in monocytes occurs via transcription factor SP-1

Latent HIV reservoir is a major barrier to absolute HIV cure. Studies on latency reversal agents (LRA) have by far focused mainly on CD4+ T-lymphocytes, while myeloid reservoirs remain under-represented despite their persistence and key contribution to HIV pathogenesis. cAMP has been shown to increase HIV-1 transcription in latently-infected monocytes/macrophages. In this communication, we explored the potential of commercially available pharmacological drugs and phosphodiesterase inhibitors to reactivate HIV in latently-infected monocytic cell-line, U1. We showed that increased levels of intracellular cAMP reverse HIV latency in vitro, which is specific to cells of the myeloid lineage. High throughput RNA-seq analysis revealed that cAMP modulates transcriptional profile of latently HIV-infected cells and provides favourable cellular environment for HIV to produce viral proteins. This reactivation of latent HIV was inhibited by Mithramycin A, a selective Sp1 inhibitor, indicating that the reversal of HIV latency in monocytes is driven by transcription factor Sp1.

MicroRNA exporter HuR clears the internalized pathogens by promoting pro-inflammatory response in infected macrophages

HuR is a miRNA derepressor protein that can act as miRNA sponge for specific miRNAs to negate their action on target mRNAs. Here we have identified how HuR, by inducing extracellular vesicles‐mediated export of miRNAs, ensures robust derepression of miRNA‐repressed cytokines essential for strong pro‐inflammatory response in activated mammalian macrophages. Leishmania donovani, the causative agent of visceral leishmaniasis, on the contrary alters immune response of the host macrophage by a variety of complex mechanisms to promote anti‐inflammatory response essential for the survival of the parasite. We have found that during Leishmania infection, the pathogen targets HuR to promote onset of anti‐inflammatory response in mammalian macrophages. In infected macrophages, Leishmania also upregulate protein phosphatase 2A that acts on Ago2 protein to keep it in dephosphorylated and miRNA‐associated form. This causes robust repression of the miRNA‐targeted pro‐inflammatory cytokines to establish an anti‐inflammatory response in infected macrophages. HuR has an inhibitory effect on protein phosphatase 2A expression, and mathematical modelling of macrophage activation process supports antagonistic miRNA‐modulatory roles of HuR and protein phosphatase 2A which mutually balances immune response in macrophage by targeting miRNA function. Supporting this model, ectopic expression of the protein HuR and simultaneous inhibition of protein phosphatase 2A induce strong pro‐inflammatory response in the host macrophage to prevent the virulent antimonial drug‐sensitive or drug‐resistant form of L. donovani infection. Thus, HuR can act as a balancing factor of immune responses to curtail the macrophage infection process by the protozoan parasite.

miR-382-3p suppressed IL-1β induced inflammatory response of chondrocytes via the TLR4/MyD88/NF-κB signaling pathway by directly targeting CX43

miR-382-3p has been reported to be upregulated in synovial membrane in knee osteoarthritis (OA). Nevertheless, its role in OA remains largely unknown. The aim of this study was to investigate the specific function and mechanisms of miR-382-3p in the course of OA. In this study, human OA chondrocytes were pretreated with interleukin-1β (IL-1β) at 5 ng/ml for 12 hr to stimulate inflammatory response and matrix metalloproteinases (MMPs) expression in chondrocytes. Meanwhile, miR-382-3p was downregulated in IL-1β-stimulated chondrocytes. In addition, we found that miR-382-3p directly interacts with connexin 43 (CX43) and attenuates the increase of cytochrome c oxidase polypeptide II, inducible nitric oxide synthase, and MMP-1/13 that is induced by IL-1β. Furthermore, our observations indicated that miR-382-3p inhibited the expression of Toll-like receptor 4 (TLR4), Myeloid differentiation primary response 88 (MyD88) and nuclear factor κB (NF-κB) in IL-1β-stimulated chondrocytes, while CX43 overexpression could partly reverse these decreases. In conclusion, miR-382-3p participated in OA may through the TLR4/MyD88/NF-κB signaling pathway by directly targeting CX43.

MyD88 overexpression deteriorates Ang-II-induced ED via upregulating MPO and COX2 and downregulating eNOS in the corpus cavernosum of rats

INTRODUCTION

Erectile dysfunction (ED) is a common sexual problem for men and the exploration of its treatment is still in mire demand. We aim to investigate the role of the Toll-like receptor 4 (TLR4)/myeloid differentiation primary response gene 88 (MyD88) signaling pathway in the pathogenesis of angiotensin II (Ang-II) induced ED.

METHODS

Male Sprague-Dawlay rats were treated with Ang-II and intracavernous pressure (ICP) was measured to confirm the occurrence of ED. The corpus cavernosum penises of rats were transfected with plasmids to overexpressed MyD88. Inflammatory and vascular parameters including myeloperoxidase (MPO), cyclooxygenase2 (COX2), endothelial nitric oxide synthase (eNOS), malondialdehyde (MDA), superoxide dismutase (SOD), reactive oxygen species (ROS), and cytokines in treated and untreated ED rats were measured. Flow cytometry was used to determine the apoptosis of endothelial cells of corpus cavernosum penises of rats.

RESULTS

Ang-II-induced ED rats were found to contain upregulated TLR4, MyD88, MPO, and COX2, and downregulated eNOS. MyD88 overexpression deteriorates cavernous structural damage, reduces ICP and ICP/MAP values and reverses the therapeutic effect of anti-TLR4 antibodies in rats with Ang-II-induced ED. Moreover, overexpression of MyD88 further upregulated MPO and COX2, downregulated eNOS, promoted oxidative stress, inflammation, and cell apoptosis rate via positively regulating the TLR4/MyD88 signaling pathway, while anti-TLR4 antibodies downregulated MPO and COX2, upregulated eNOS, suppressed oxidative stress, inflammation, and cell apoptosis rate via inactivating the TLR4/MyD88 signaling pathway in the rat corpus cavernosum penises. Furthermore, MyD88 overexpression promotes oxidative stress and inflammation and reverses the effect of anti-TLR4 antibodies in the penis of ED rats.

CONCLUSION

MyD88 overexpression deteriorates Ang-II-induced ED via upregulating MPO and COX2 and downregulating eNOS in the corpus cavernosum rats.

Understanding the hidden relations between pro- and anti-inflammatory cytokine genes in bovine oviduct epithelium using a multilayer response surface method

An understanding gene-gene interaction helps users to design the next experiments efficiently and (if applicable) to make a better decision of drugs application based on the different biological conditions of the patients. This study aimed to identify changes in the hidden relationships between pro- and anti-inflammatory cytokine genes in the bovine oviduct epithelial cells (BOECs) under various experimental conditions using a multilayer response surface method. It was noted that under physiological conditions (BOECs with sperm or sex hormones, such as ovarian sex steroids and LH), the mRNA expressions of IL10, IL1B, TNFA, TLR4, and TNFA were associated with IL1B, TNFA, TLR4, IL4, and IL10, respectively. Under pathophysiological + physiological conditions (BOECs with lipopolysaccharide + hormones, alpha-1-acid glycoprotein + hormones, zearalenone + hormones, or urea + hormones), the relationship among genes was changed. For example, the expression of IL10 and TNFA was associated with (IL1B, TNFA, or IL4) and TLR4 expression, respectively. Furthermore, under physiological conditions, the co-expression of IL10 + TNFA, TLR4 + IL4, TNFA + IL4, TNFA + IL4, or IL10 + IL1B and under pathophysiological + physiological conditions, the co-expression of IL10 + IL4, IL4 + IL10, TNFA + IL10, TNFA + TLR4, or IL10 + IL1B were associated with IL1B, TNFA, TLR4, IL10, or IL4 expression, respectively. Collectively, the relationships between pro- and anti-inflammatory cytokine genes can be changed with respect to the presence/absence of toxins, sex hormones, sperm, and co-expression of other gene pairs in BOECs, suggesting that considerable cautions are needed in interpreting the results obtained from such narrowly focused in vitro studies.

Protective Effect of Hesperidin Against Sepsis-Induced Lung Injury by Inducing the Heat-Stable Protein 70 (Hsp70)/Toll-Like Receptor 4 (TLR4)/ Myeloid Differentiation Primary Response 88 (MyD88) Pathway

Background

Sepsis-induced lung injury is associated with high mortality. The present investigation evaluated the protective effect of hesperidin against sepsis-induced lung injury and also postulates the possible mechanism of its action.

Material/Methods

Lung injury was induced by sepsis in all animals, in which sepsis was produced by cecal ligation and puncture (CLP). Animals were treated with hesperidin 10 and 20 mg/kg i.v. 30 min after the surgery. Oxygenation index and lung injury score were determined and levels of pro-inflammatory mediators and markers of oxidative stress were also estimated in the lung tissues. Moreover, expression of caspase-3, B-cell lymphoma (Bcl-2), Toll-like receptor 4 (TLR4), heat-stable protein 70 (Hsp70) and myeloid differentiation primary response 88 (MyD88) protein was estimated by Western blot assay and immunofluorescence assay.

Results

Hesperidin attenuated the partial pressure of arterial oxygen/fraction of inspired oxygen (PaO2/FiO2) ratio and lung injury score in CLP-induced lung injury mice. There was a significant (p<0.01) decrease in the level of pro-inflammatory mediators in the lung tissue of CLP-induced lung injury mice. Moreover, markers of oxidative stress were attenuated in the hesperidin-treated group. Treatment with hesperidin attenuated the expression of caspase-3, Bcl-2, TLR4, Hsp70, and MyD88 protein in the lung tissue of CLP-induced lung injury mice.

Conclusions

Hesperidin protects against lung injury by attenuating the Hsp70/TLR4/MyD88 pathway in CLP-induced lung injury mice.

Innate immune adaptor MyD88 deficiency prevents skin inflammation in SHARPIN-deficient mice

Mice deficient in SHANK-associated RH domain-interacting protein (SHARPIN), a component of the linear ubiquitin chain assembly complex (LUBAC), develop a spontaneous inflammatory disorder with pathologic hallmarks similar to atopic dermatitis and psoriasis in humans. Previous studies identified the crucial role of components of the TNF and IL-1 signaling pathways in the progression of disease in SHARPIN-deficient mice. However, an innate immune adaptor or sensor that relates to the disease progression has remained unknown. In this study, we found that the genetic ablation of myeloid differentiation primary response 88 (MyD88) completely rescued skin inflammation in SHARPIN-deficient (Sharpin^cpdm) mice. Systemic inflammation and immune cell dysregulation were partially rescued. Fibroblasts derived from Sharpin^cpdmMyd88^-⁄- mice failed to provide protection against TNF-induced cell death. Sharpin^cpdmMyd88^-⁄- mice had reduced TNF production in their skin. Furthermore, depletion of the microbiota through the oral administration of antibiotics (ABX) partially rescued both the skin inflammation and systemic inflammation, demonstrating a role for the gut microbiota in SHARPIN-deficient mice. Our findings suggest a detrimental role for the innate immune adaptor MyD88 in instigating skin inflammation in Sharpin^cpdm mice.

Immunohistochemical expression of TLR-4 in temporomandibular joint dysfunction

Objective Toll-like receptor 4 (TLR-4) is a transmembrane protein involved in the innate immune system and has been implicated in the pathogenesis of temporomandibular joint dysfunction (TMD). The purpose of this study was to histologically examine the level of expression of TLR-4 relative to severity of TMD. Methods Thirty-one human TMJ disc samples were immunostained for TLR-4 and evaluated for intensity of stain. Among the samples, 8 were control samples, 16 were from patients with anterior disc displacement with reduction (ADDwR), and 7 were from patients with anterior disc displacement without reduction (ADDwoR). Results There was no statistically significant difference in intensity of stain between groupings (p = 0.673). Conclusions The results indicate a negative correlation between TMD and the expression of TLR-4.

Effect of TLR4/MyD88 signaling pathway on sepsis-associated acute respiratory distress syndrome in rats, via regulation of macrophage activation and inflammatory response

The present study aimed to investigate the effects of the Toll-like receptor (TLR)4/myeloid differentiation primary response (MyD)88 signaling pathway on sepsis-associated acute respiratory distress syndrome (ARDS) in rats, and the involvement of macrophage activation and the inflammatory response. A total of 36 specific pathogen-free male Sprague-Dawley rats were selected to establish the rat model of sepsis-associated ARDS using cecal ligation and puncture (CLP). Rats were assigned into the Ab (anti-TLR4 monoclonal antibody)-CLP, CLP and Sham groups. Arterial partial pressure of oxygen (P_aO₂) was detected using blood gas analysis. Bronchoalveolar lavage fluid (BALF) and alveolar macrophages were collected. The pathological structure of lung tissue was observed following hematoxylin-eosin staining. The ultrastructural alterations of alveolar epithelial cells were observed under transmission electron microscope. The ratios of wet/dry weight of lung tissue and total protein content in BALF were measured. The concentration of tumor necrosis factor (TNF)-α and interleukin (IL)-1β in BALF and peripheral blood was determined by enzyme-linked immunosorbent assay. The TLR4, TLR9, MyD88 and nuclear factor (NF)-κΒ mRNA and protein expression levels in alveolar macrophages were measured by reverse transcription-quantitative polymerase chain reaction and western blotting. Compared with the Sham group, the rats in the CLP group demonstrated significantly increased respiratory frequency, lung permeability, lung edema, inflammatory infiltration, TNF-α and IL-1β expression levels in BALF and peripheral blood and TLR4, TLR9, MyD88 and NF-κΒ expression levels in macrophages, however decreased arterial P_aO₂. Following pretreatment with anti-TLR4 monoclonal antibody, rats exhibited decreased lung injury, inflammatory infiltration, lung edema, TNF-α and IL-1β expressions in BALF and peripheral blood, and TLR4, TLR9, MyD88 and NF-κΒ expression levels in macrophages, with increased arterial P_aO₂. These results suggested that the inhibition of TLR4/MyD88 signaling pathway may relieve sepsis-associated ARDS in rats through regulating macrophage activation and the inflammatory response.

Recognition of Candida albicans by gingival fibroblasts: The role of TLR2, TLR4/CD14, and MyD88

Recent evidence indicates that nonprofessional immune cells such as epithelial cells, endothelial cells, and fibroblasts also contribute to innate immunity via secretion of cytokines. Fibroblasts are the principal type of cell found in the periodontal connective tissues and they are involved in the immune response during periodontal disease. The role of fibroblasts in the recognition of pathogens via Toll-like receptors (TLRs) has been established; however, few studies have been conducted concerning the involvement of innate immune receptors in the recognition of Candida albicans by gingival fibroblast. In the current study, we investigate the functional activity of TLR2, cluster of differentiation 14 (CD14), and myeloid differentiation primary response gene 88 (MyD88) molecules in the recognition of C. albicans by gingival fibroblast. First, we identified that gingival fibroblasts expressed TLR2, TLR3, and TLR4. Our results showed that TLR agonists had no effect on these receptors' expression by TLR2, MyD88, and CD14-deficient cells. Notably, C. albicans and a synthetic triacylated lipoprotein (Pam3CSK4) induced a remarkable increase of TLR3 expression on MyD88-deficient gingival fibroblasts. TLR4 expression levels were lower than TLR2 and TLR3 levels and remained unchanged after TLR agonist stimulation. Gingival fibroblasts presented morphological similarities; however, TLR2 deficiency on these cells leads to a lower proliferative response, whereas the deficiency on CD14 expression resulted in lower levels of type I collagen by these cells. In addition, the recognition of C. albicans by gingival fibroblasts had an effect on the secretion of cytokines and it was dependent on a specific recognition molecule. Specifically, tumor necrosis factor-α (TNF-α) production after the recognition of C. albicans was dependent on MyD88, CD14, and TLR2 molecules, whereas the production of interleukin-1β (IL-1β) and IL-13 was dependent on TLR2. These findings are the first to describe a role of gingival fibroblast in the recognition of C. albicans and the pathways involved in this process. An understanding of these pathways may lead to alternative treatments for patients with periodontal disease.

RIG-I and IL-6 are negative-feedback regulators of STING induced by double-stranded DNA

The stimulator of interferon genes (STING) protein has emerged as a critical signal transduction molecule in the innate immune response. Sustained activation of the STING signaling induced by cytosolic DNA has been considered to be the cause of a variety of autoimmune diseases characterized by uncontrolled inflammation. Therefore, it is important to understand the molecular basis of the regulation of STING signaling pathway. Here we demonstrate that the STING protein undergoes a proteasome-mediated degradation in human diploid cell (HDC) lines including MRC-5 following the transfection of double-stranded DNA (dsDNA). The degradation of STING is accompanied by the increased expression of both RIG-I and IL-6. Employing the RIG-I siRNA knockdown and an IL-6 neutralizing antibody greatly inhibits the degradation of STING induced by dsDNA. We further demonstrate that both IL-6 and RIG-I are downstream molecules of STING along the DNA sensor pathway. Therefore, STING degradation mediated by RIG-I and IL-6 may serve as a negative feedback mechanism to limit the uncontrolled innate immune response induced by dsDNA. We have further shown that RIG-I and IL-6 promote STING degradation by activating/dephosphorylating UNC-51-like kinase (ULK1). Interestingly, the STING protein is not significantly affected by dsDNA in non-HDC HEK293 cells. Our study thus has identified a novel signaling pathway for regulating STING in HDCs.

Role of ESAT-6 in renal injury by regulating microRNA-155 expression via TLR4/MyD88 signaling pathway in mice with Mycobacterium tuberculosis infection

The study aims to investigate the underlying mechanism involved in the early secretory antigenic target-6 (ESAT-6) in renal injury through regulation of the expression of miR-155 through the oll-like receptor (TLR)-4 (TLR4)/myeloid differentiation factor 88 (MyD88) signaling pathway in Mycobacterium tuberculosis (MTB)-infected mice. Sixty C57BL/6 mice with MTB-induced renal injury were randomly assigned into control, MTB, mimic, inhibitor, inhibitor + ESAT6, and inhibitor + ESAT6 + TAK242 groups. Body weight, the ratio of kidney weight to body weight (Kw/Bw), blood urea nitrogen (BUN), and serum creatinine (Scr) of mice were measured. Flow cytometry was used to detect renal activation in mice. Expressions of miR-155 and ESAT6 were detected by quantitative real-time PCR (qRT-PCR), and Western blotting was used to examine the expressions of ESAT6, TLR4, and MyD88. Expressions of tumor necrosis factor-α (TNF-α), interleukin-17 (IL-17), and interferon-γ (IFN-γ) were measured by qRT-PCR and ELISA. Compared with the control group, the BUN and Scr levels as well as the expression levels of miR-155, TLR4, MyD88, TNF-α, IL-17, and IFN-γ increased, while Kw/Bw decreased in the MTB and mimic groups. In comparison with the MTB group, the above indexes except Kw/Bw were elevated in the mimic group, but were reduced in the inhibitor group, while the Kw/Bw dropped in the mimic group but increased in the inhibitor group. Compared with the inhibitor group, the Kw/Bw decreased while the rest of the indexes increased in the inhibitor + ESAT6 group. ESAT6 may induce renal injury by promoting miR-155 expression through the TLR-4/MyD88 signaling pathway in MTB-infected mice.

Suppression of MyD88-dependent signaling alleviates neuropathic pain induced by peripheral nerve injury in the rat

Background

MyD88 is the adaptor protein of MyD88-dependent signaling pathway of TLRs and IL-1 receptor and regulates innate immune response. However, it was not clear whether and how MyD88 and related signaling pathways in the dorsal root ganglion (DRG) and spinal dorsal horn (SDH) are involved in neuropathic pain.

Methods

Chronic constriction injury (CCI) was used to induce neuropathic pain in the rat. The expression of MyD88, TRIF, IBA1, and GFAP was detected with immunofluorescent staining and Western blot. The expression of interleukin-1 beta (IL-1β), high mobility group box 1 (HMGB1), NF-κB-p65, phosphorylated NF-κB-p65, ERK, phosphorylated ERK, and tumor necrosis factor-alpha (TNF-α) was detected with Western blot. Pain-related behavioral effects of MyD88 homodimerization inhibitory peptide (MIP) were accessed up to 3 weeks after intrathecal administration.

Results

Peripheral nerve injury significantly increased the protein level of MyD88 in the DRG and SDH, but had no effect on TRIF. MyD88 was found partly distributed in the nociceptive neurons in the DRGs and the astrocytes and microglia in the SDH. HMGB1 and IL-1β were also found upregulated in nociceptive pathways of CCI rats. Intrathecal application of MIP significantly alleviated mechanical and thermal hyperalgesia in the CCI rats and also reversed CCI-induced upregulation of MyD88 in both DRG and SDH. Further investigation revealed that suppression of MyD88 protein reduced the release of TNF-α and glial activation in the SDH in the CCI rats.

Conclusions

MyD88-dependent TIR pathway in the DRG and SDH may play a role in CCI-induced neuropathic pain. MyD88 might serve as a potential therapeutic target for neuropathic pain.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-017-0822-9) contains supplementary material, which is available to authorized users.

Effects of the TLR4 signaling pathway on apoptosis of neuronal cells in diabetes mellitus complicated with cerebral infarction in a rat model

This study aims to explore the effects of the TLR4 signaling pathway on the apoptosis of neuronal cells in rats with diabetes mellitus complicated with cerebral infarction (DMCI). A DMCI model was established with 40 Sprague Dawley rats, which were assigned into blank, sham, DM + middle cerebral artery occlusion (MCAO) and DM + MCAO + TAK242 groups. Superoxide dismutase (SOD) activity and malondialdehyde (MDA) content were measured. A TUNEL assay was applied for detecting cell apoptosis, and Western blotting was used for detecting the expression of TLR4, TNF-α, IL-1β and apoptosis-related proteins. Compared with the blank and sham groups, there was an increase in cell apoptosis, expression of Bcl-2, Bax, cleaved caspase-3, TNF-α, IL-1β and TLR4 proteins and MDA content and a decrease in SOD activity in the DM + MCAO and DM + MCAO + TAK242 groups. Compared with those in the DM + MCAO group, rats in the DM + MCAO + TAK242 group exhibited an increase in SOD activity and a decrease in cell apoptosis, expression of Bcl-2, Bax, cleaved caspase-3, TNF-α, IL-1β and TLR4 proteins and MDA content. Inhibition of the TLR4 signaling pathway reduces neuronal cell apoptosis and nerve injury to protect the brain.

Systemic TAK-242 prevents intrathecal LPS evoked hyperalgesia in male, but not female mice and prevents delayed allodynia following intraplantar formalin in both male and female mice: The role of TLR4 in the evolution of a persistent pain state

OBJECTIVE

Pain resulting from local tissue injury or inflammation typically resolves with time. Frequently, however, this pain may unexpectedly persist, becoming a pathological chronic state. Increasingly, the innate and adaptive immune systems are being implicated in the initiation and maintenance of these persistent conditions. In particular, Toll-like receptor 4 (TLR4) signaling has been shown to mediate the transition to a persistent pain state in a sex-dependent manner. In the present work, we explored this contribution using the TLR4 antagonist, TAK-242.

METHODS

Male and female C57Bl/6 mice were given intravenous (IV), intrathecal (IT), or intraperitoneal (IP) TAK-242 prior to IT delivery of lipopolysaccharide (LPS), and tactile reactivity was assessed at regular intervals over 72-h. Additional groups of mice were treated with IP TAK-242 prior to intraplantar formalin, and flinching was monitored for 1-h. Tactile reactivity was assessed at 7-days after formalin delivery.

RESULTS

LPS evoked TNF release from male and female macrophages and RAW267.4 cells, which was blocked in a concentration dependent fashion by TAK-242. In vivo, IT LPS evoked tactile allodynia to a greater degree in male than female mice. TAK-242, given by all routes, prevented development of IT LPS-induced tactile allodynia in male animals, but did not reverse their established allodynia. TLR4 deficiency and TAK-242 treatment attenuated IT LPS-induced allodynia in male, but not female mice. In the formalin model, pre-treatment with TAK-242 did not affect Phase 1 or Phase 2 flinching, but prevented the delayed tactile allodynia in both male and unexpectedly in female mice (Phase 3).

CONCLUSIONS

Together, these results suggest that TAK-242 is a TLR4 antagonist that has efficacy after systemic and intrathecal delivery and confirms the role of endogenous TLR4 signaling in triggering the development of a delayed allodynia in both male and female mice.

Effect of Toll-Like Receptor 4 on Synovial Injury of Temporomandibular Joint in Rats Caused by Occlusal Interference

Synovitis is an important disease that causes intractable pain in TMJ. Some investigations suggested that the increasing expression of IL-1β secreted by synovial lining cells plays an important role in synovial inflammation and cartilage destruction in TMJ. In our previous research, the results demonstrated that TLR4 is involved in the expression of IL-1β in SFs from TMJ with lipopolysaccharide stimulation. However, the inflammatory response that occurred in synovial membrane is not caused by bacterial infection. In the current study, we investigated whether or not TLR4 participates in the inflammatory responses and the expression of IL-1β in synovial membrane of rats induced by occlusal interference. The results showed that obvious inflammation changes were observed in the synovial membranes and the expression of TLR4 and IL-1β was increased at both mRNA and protein levels in the occlusal interference rats. In addition, the inflammation reactions and the increased expression of IL-1β could be restrained by treatment with TAK-242, a blocker of TLR4 signaling. The results prompted us that the activation of TLR4 may be involved in the inflammatory reactions and increased expression of IL-1β in patients with synovitis and participate in the mechanisms of the initiation and development of synovial injury by regulating the expression of inflammatory mediators like IL-1β in synovial membranes.

Fibronectin EDA and CpG synergize to enhance antigen-specific Th1 and cytotoxic responses

•

FNIII 11-EDA and CpG synergize in vitro to enhance activation of dendritic cells.

•

Immunization with both adjuvants induces a potent antigen-specific Th1 response in vivo.

•

Co-adjuvanted OVA mediates regression of E.G7-OVA tumors through CTL response.

•

Co-adjuvanted HBsAg induces seroconversion and clearance of circulating virus in HBV-Tg mice.

Subunit vaccines, employing purified protein antigens rather than intact pathogens, require the addition of adjuvants for enhanced immunogenicity with a correct balance between strong activation of the immune system and low toxicity. Here we show that the endogenous (i.e., autologous) non-toxic TLR4 agonist extra domain A type III repeat of fibronectin (FNIII EDA) can synergize with the exogenous (i.e., bacterial), toxic-at-high-dose, TLR9 agonist CpG to induce efficient cellular immune responses while keeping the dose of CpG low. The efficacy of the combined TLR agonists, even at half-doses, led to stronger dendritic cell activation, enhanced cytotoxic T lymphocyte activation as well as stronger humoral response, compared to the individual agonists given at full doses. Immune cells induced after vaccination with the co-adjuvanted formulation could mediate tumor regression in an E.G7-OVA tumor model, and eradicate circulating hepatitis B virus (HBV) in a transgenic HBV model. Together, these results show that endogenous TLR agonists, such as variants of FNIII EDA, can synergize with exogenous TLR ligands, such as CpG, and strongly enhance cellular immune responses, while improving their safety profile.

Myelin-specific T cells induce interleukin-1beta expression in lesion-reactive microglial-like cells in zones of axonal degeneration

Infiltration of myelin-specific T cells into the central nervous system induces the expression of proinflammatory cytokines in patients with multiple sclerosis (MS). We have previously shown that myelin-specific T cells are recruited into zones of axonal degeneration, where they stimulate lesion-reactive microglia. To gain mechanistic insight, we used RNA microarray analysis to compare the transcript profile in hippocampi from perforant pathway axonal-lesioned mice with and without adoptively transferred myelin-specific T cells 2 days postlesion, when microglia are clearly lesion reactive. Pathway analysis revealed that, among the 1,447 differently expressed transcripts, the interleukin (IL)-1 pathway including all IL-1 receptor ligands was upregulated in the presence of myelin-specific T cells. Quantitative polymerase chain reaction showed increased mRNA levels of IL-1β, IL-1α, and IL-1 receptor antagonist in the T-cell-infiltrated hippocampi from axonal-lesioned mice. In situ hybridization and immunohistochemistry showed a T-cell-enhanced lesion-specific expression of IL-1β mRNA and protein, respectively, and induction of the apoptosis-associated speck-like protein, ASC, in CD11b(+) cells. Double in situ hybridization showed colocalization of IL-1β mRNA in a subset of CD11b mRNA(+) cells, of which many were part of cellular doublets or clusters, characteristic of proliferating, lesion-reactive microglia. Double-immunofluorescence showed a T-cell-enhanced colocalization of IL-1β to CD11b(+) cells, including lesion-reactive CD11b(+) ramified microglia. These results suggest that myelin-specific T cells stimulate lesion-reactive microglial-like cells to produce IL-1β. These findings are relevant to understand the consequences of T-cell infiltration in white and gray matter lesions in patients with MS.