Toll-like receptor signaling in cell proliferation and survival

Lactate: a rising star in tumors and inflammation

Lactate has been traditionally regarded as a mere byproduct of glycolysis or metabolic waste. However, an increasing body of literature suggests its critical role in regulating various physiological and pathological processes. Lactate is generally associated with hypoxia, inflammation, viral infections, and tumors. It performs complex physiological roles by activating monocarboxylate transporter (MCT) or the G protein-coupled receptor GPR81 across the cell membrane. Lactate exerts immunosuppressive effects by regulating the functions of various immune cells (such as natural killer cells, T cells, dendritic cells, and monocytes) and its role in macrophage polarization and myeloid-derived suppressor cell (MDSC) differentiation in the tumor microenvironment. Lactic acid has also recently been found to increase the density of CD8+ T cells, thereby enhancing the antitumor immune response. Acute or chronic inflammatory diseases have opposite immune states in the inflammatory disease microenvironment. Factors such as cell types, transcriptional regulators, ionic mediators, and the microenvironment all contribute to the diverse functions lactate exhibits. Herein, we reviewed the pleiotropic effects of lactate on the regulation of various functions of immune cells in the tumor microenvironment and under inflammatory conditions, which may help to provide new insights and potential targets for the diagnosis and treatment of inflammatory diseases and malignancies.

Programmed death of cardiomyocytes in cardiovascular disease and new therapeutic approaches

Cardiovascular diseases (CVDs) have a complex pathogenesis and pose a major threat to human health. Cardiomyocytes have a low regenerative capacity, and their death is a key factor in the morbidity and mortality of many CVDs. Cardiomyocyte death can be regulated by specific signaling pathways known as programmed cell death (PCD), including apoptosis, necroptosis, autophagy, pyroptosis, and ferroptosis, etc. Abnormalities in PCD can lead to the development of a variety of cardiovascular diseases, and there are also molecular-level interconnections between different PCD pathways under the same cardiovascular disease model. Currently, the link between programmed cell death in cardiomyocytes and cardiovascular disease is not fully understood. This review describes the molecular mechanisms of programmed death and the impact of cardiomyocyte death on cardiovascular disease development. Emphasis is placed on a summary of drugs and potential therapeutic approaches that can be used to treat cardiovascular disease by targeting and blocking programmed cell death in cardiomyocytes.

TIR domains of TLR family-from the cell culture to the protein sample for structural studies

Toll-like receptors (TLRs) are key players in the innate immune system. Despite the great efforts in TLR structural biology, today we know the spatial structures of only four human TLR intracellular TIR domains. All of them belong to one of five subfamilies of receptors. One of the main bottlenecks is the high-level production of correctly folded proteins in soluble form. Here we used a rational approach to find the optimal parameters to produce TIR domains of all ten human TLR family members in soluble form in E. coli cells. We showed that dozens of milligrams of soluble His-tagged TLR2/3/6/7TIR and MBP-tagged TLR3/5/7/8TIR can be produced. We also developed the purification protocols and demonstrated by CD and NMR spectroscopy that purified TLR2/3/7TIR demonstrate a structural organization inherent to TIR domains. This illustrates the correct folding of produced proteins and their suitability for further structural and functional investigations.

Prediction of the survival status and tumor microenvironment in colorectal cancer through genotyping analysis based on toll-like receptors

BACKGROUND

Colorectal cancer (CRC) ranks third in both the incidence and mortality rates among male and female cancers, and it is the leading digestive system cancer. Due to the inter- and intratumor heterogeneity of cancer, the TNM system is insufficient for predicting prognosis, necessitating the use of molecular biomarkers for prognostic prediction. Toll-like receptors (TLRs) have been associated with CRC survival rates. This study focused on the investigation of the role and potential value of TLRs in CRC genotyping to aid in immunotherapy for CRC patients.

METHODS

Differential gene expression analysis was performed on CRC transcriptomic data from The Cancer Genome Atlas database. TLRs were referred from the literature, and their intersection with differentially expressed genes (DEGs) in CRC yielded TLR-DEGs. The expression patterns of TLR-DEGs were predicted using the STRING website, and copy number variations of TLR-DEGs were analyzed. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were conducted on TLR-DEGs. ConsensusClusterPlus R package was used for clustering CRC patients, and ESTIMATE and GSEAbase were employed to analyze immune characteristics of different subtypes. Immune phenotyping scores and tumor immune dysfunction and exclusion scores were evaluated. DEGs of different subtypes were analyzed, followed by GO and KEGG enrichment analyses, the protein-protein interaction (PPI) network analysis, and further selection of hub genes. The sensitivity of drugs was assessed using the identified hub genes.

RESULTS

We identified 37 TLR-DEGs, and the PPI analysis revealed their coexpression, although they were distributed on different chromosomes. Enrichment analyses indicated that the 37 TLR-DEGs were linked to cancer cell immune response. Based on these TLR-DEGs, CRC patients were classified into three subtypes. Cluster2 exhibited lower survival rates and higher immune infiltration levels and predicted poorer response to immune checkpoint inhibitor therapy. The intersection of DEGs from cluster2 and cluster1 with DEGs from cluster2 and cluster3 yielded a set of 426 commonly shared DEGs. Enrichment analyses revealed that these shared DEGs might regulate immune cell viability. Eight common hub genes for different subtypes were further identified to predict drug-related correlations.

CONCLUSION

The developed TLR genotyping was used to predict the survival status and tumor microenvironment of CRC, providing a foundation for understanding the molecular mechanisms of TLR signaling and deepening its clinical significance.

From Immunity to Neurogenesis: Toll-like Receptors as Versatile Regulators in the Nervous System

Toll-like receptors (TLRs) are among the main components of the innate immune system. They can detect conserved structures in microorganisms and molecules associated with stress and cellular damage. TLRs are expressed in resident immune cells and both neurons and glial cells of the nervous system. Increasing evidence is emerging on the participation of TLRs not only in the immune response but also in processes of the nervous system, such as neurogenesis and cognition. Below, we present a review of the literature that evaluates the expression and role of TLRs in processes such as neurodevelopment, behavior, cognition, infection, neuroinflammation, and neurodegeneration.

Maintenance of homeostasis by TLR4 ligands

Immunotherapy is renowned for its capacity to elicit anti-infective and anti-cancer effects by harnessing immune responses to microbial components and bolstering innate healing mechanisms through a cascade of immunological reactions. Specifically, mammalian Toll-like receptors (TLRs) have been identified as key receptors responsible for detecting microbial components. The discovery of these mammalian Toll-like receptors has clarified antigen recognition by the innate immune system. It has furnished a molecular foundation for comprehending the interplay between innate immunity and its anti-tumor or anti-infective capabilities. Moreover, accumulating evidence highlights the crucial role of TLRs in maintaining tissue homeostasis. It has also become evident that TLR-expressing macrophages play a central role in immunity by participating in the clearance of foreign substances, tissue repair, and the establishment of new tissue. This macrophage network, centered on macrophages, significantly contributes to innate healing. This review will primarily delve into innate immunity, specifically focusing on substances targeting TLR4.

Expression of mRNA-TLR-5 Gene in Patients with Endometriosis using Real-time PCR in Tehran, Iran

BACKGROUND

Endometriosis is one of the common diseases of women, especially in reproductive age, and it is one of the most important causes of infertility in women. The aim of this study was to investigate the level of mRNA-TLR-5 expression in women with endometriosis.

METHODS

The present study was performed in Nikan Hospital, Tehran, Iran, in 2021. The samples of endometrial mucosa for the eutopic group and an ovarian endometriotic cyst for the ectopic group were obtained from the patients who underwent laparoscopic surgery at the Fetal Infertility Center and were diagnosed with endometriosis. Normal endometrial samples were also obtained from patients who had no history of infertility and underwent laparoscopic TL surgery for reasons other than endometriosis such as ovarian cysts (control group). After RNA extraction and cDNA synthesis, TLR-5 gene expression was evaluated by the Real-Time PCR method.

RESULTS

Based on the results of the comparison of TLR-5 gene expression in all three ectopic, eutopic endometrium, and control groups by Real-Time PCR, it was found that the TLR-5 gene expression is significantly higher in ectopic samples than in the other two groups, but there is a significant difference between two utopic and control groups.

CONCLUSION

The increase in TLR-5 expression in the ectopic group can probably be a reason for reducing the apoptosis of cells entered into the peritoneal cavity and creating an environment for the survival and proliferation of these cells.

Revolutionizing medicine with toll-like receptors: A path to strengthening cellular immunity

Toll-like receptors play a vital role in cell-mediated immunity, which is crucial for the immune system's defense against pathogens and maintenance of homeostasis. The interaction between toll-like-receptor response and cell-mediated immunity is complex and essential for effectively eliminating pathogens and maintaining immune surveillance. In addition to pathogen recognition, toll-like receptors serve as adjuvants in vaccines, as molecular sensors, and recognize specific patterns associated with pathogens and danger signals. Incorporating toll-like receptor ligands into vaccines can enhance the immune response to antigens, making them potent adjuvants. Furthermore, they bridge the innate and adaptive immune systems and improve antigen-presenting cells' capacity to process and present antigens to T cells. The intricate signaling pathways and cross-talk between toll-like-receptor and T cell receptor (TCR) signaling emphasize their pivotal role in orchestrating effective immune responses against pathogens, thus facilitating the development of innovative vaccine strategies. This article provides an overview of the current understanding of toll-like receptor response and explores their potential clinical applications. By unraveling the complex mechanisms of toll-like-receptor signaling, we can gain novel insights into immune responses and potentially develop innovative therapeutic approaches. Ongoing investigations into the toll-like-receptor response hold promise in the future in enhancing our ability to combat infections, design effective vaccines, and improve clinical outcomes.

Paracrine Responses of Cardiosphere-Derived Cells to Cytokines and TLR Ligands: A Comparative Analysis

Cardiosphere-derived cells (CDCs) are currently being evaluated in clinical trials as a potential therapeutic tool for regenerative medicine. The effectiveness of transplanted CDCs is largely attributed to their ability to release beneficial soluble factors to enhance therapeutic effects. An emerging area of research is the pretreatment of stem cells, including CDCs, with various cytokines to improve their therapeutic properties. This strategy aims to enhance their survival, proliferation, differentiation, and paracrine activities after transplantation. In our study, we investigated the differential effects of various cytokines and TLR ligands on the secretory phenotype of human CDCs. Using a magnetic bead-based immunoassay, we analyzed the CDCs-conditioned media for 41 cytokines and growth factors and detected the presence of 21 cytokines. We found that CDC incubation with lipopolysaccharide, a TLR4 ligand, and the cytokine combination of TNF/IFN significantly increased the secretion of most of the cytokines detected. Specifically, we observed an increased secretion and gene expression of IP10, MCP3, IL8, and VEGFA. In contrast, the TLR3 ligand polyinosinic-polycytidylic acid and TGF-beta had minimal effects on CDC cytokine secretion. Additionally, TNF/IFN, but not LPS, enhanced ICAM1 expression. Our findings offer new insights into the role of cytokines in potentially modulating the biology and regenerative potential of CDCs.

Gut dysbacteriosis induces expression differences in the adult head transcriptome of Spodoptera frugiperda in a sex-specific manner

Mounting evidence indicates that the gut microbiota influences the neurodevelopment and behavior of insects through the gut-brain axis. However, it is currently unclear whether the gut microbiota affect the head profiles and immune pathway in pests. Here, we find that gut bacteria is essential for the immune and neural development of adult Spodoptera frugiperda, which is an extremely destructive agricultural pest worldwide. 16 S rRNA sequencing analysis showed that antibiotics exposure significantly disturbed the composition and diversity of gut bacteria. Further transcriptomic analysis revealed that the adult head transcripts were greatly affected by gut dysbacteriosis, and differently expression genes critical for brain and neural development including A4galt, Tret1, nsun4, Galt, Mitofilin, SLC2A3, snk, GABRB3, Oamb and SLC6A1 were substantially repressed. Interestingly, the dysbacteriosis caused sex-specific differences in immune response. The mRNA levels of pll (serine/threonine protein kinase Pelle), PGRP (peptidoglycan-sensing receptor), CECA (cecropin A) and CECB (cecropin B) involved in Toll and Imd signaling pathway were drastically decreased in treated male adults' heads but not in female adults; however, genes of HIVEP2, ZNF131, inducible zinc finger protein 1-like and zinc finger protein 99-like encoding zinc-finger antiviral protein (ZAP) involved in the interferon (IFNα/β) pathway were significantly inhibited in treated female adults' heads. Collectively, these results demonstrate that gut microbiota may regulate head transcription and impact the S. frugiperda adults' heads through the immune pathway in a sex-specific manner. Our finding highlights the relationship between the gut microbiota and head immune systems of S. frugiperda adults, which is an astonishing similarity with the discoveries of other animals. Therefore, this is the basis for further research to understand the interactions between hosts and microorganisms via the gut-brain axis in S. frugiperda and other insects.

The citrus flavonoid, nobiletin inhibits neuronal inflammation by preventing the activation of NF-κB

Nobiletin (5,6,7,8,3',4'-hexamethoxyflavone) is one of the flavonoids found in shikuwasa, a popular citrus fruit in Okinawa, Japan. It exerts various pharmacological effects, such as anti-tumor, antioxidant, and anti-inflammatory activities. We herein investigated whether nobiletin attenuated lipopolysaccharide (LPS)-induced inflammatory responses in the murine microglial cell line BV-2 and neuroinflammation in mice induced by an intracerebral injection of LPS. In BV-2 cells, nobiletin significantly inhibited the LPS-induced production of nitric oxide (NO) and prostaglandin E2 (PGE2) by preventing the mRNA expression of inducible NO synthase (iNOS) and cyclooxygenase-2 (COX-2), respectively. Nobiletin also inhibited the LPS-induced mRNA expression of CCL2, CXCL1, IL-6, and TNFα. Nobiletin markedly attenuated the transcriptional activity of the NF-κB p65 subunit without affecting the degradation of IκBα or the nuclear localization of the NF-κB p65 subunit. Nobiletin also inhibited the LPS-induced activation of JNK, but not ERK or p38, in BV-2 cells. Furthermore, the administration of nobiletin significantly suppressed the accumulation of microglia and induction of the mRNA expression of CCL2, CXCL1, IL-6, and TNFα in the murine brain induced by injecting LPS into the striatum. Collectively, these results suggest the potential of nobiletin as a candidate anti-inflammatory drug for the prevention of neuroinflammation.

Outer membrane protein 25 of Brucella suppresses TLR-mediated expression of proinflammatory cytokines through degradation of TLRs and adaptor proteins

Toll-like receptors (TLRs) are essential components of innate immunity that serves as the first line of defense against the invaded microorganisms. However, successful infectious pathogens subvert TLR signaling to suppress the activation of innate and adaptive responses. Brucella species are infectious intracellular bacterial pathogens causing the worldwide zoonotic disease, brucellosis, that impacts economic growth of many countries. Brucella species are considered as stealthy bacterial pathogens as they efficiently evade or suppress host innate and adaptive immune responses for their chronic persistence. However, the bacterial effectors and their host targets for modulating the immune responses remain obscure. Brucella encodes various outer membrane proteins (Omps) that facilitate their invasion, intracellular replication, and immunomodulation. Outer membrane protein 25 (Omp25) of Brucella plays an important role in the immune modulation through suppression of proinflammatory cytokines. However, the mechanism and the signaling pathways that are targeted by Omp25 to attenuate the production of proinflammatory cytokines remain obscure. Here, we report that Omp25 and its variants, viz. Omp25b, Omp25c, and Omp25d, suppress production of proinflammatory cytokines that are mediated by various TLRs. Furthermore, we demonstrate that Omp25 and its variants promote enhanced ubiquitination and degradation of TLRs and their adaptor proteins to attenuate the expression of proinflammatory cytokines. Targeting multiple TLRs and adaptor proteins enables Omp25 to effectively suppress the expression of proinflammatory cytokines that are induced by diverse pathogen-associated molecular patterns. This can contribute to the defective adaptive immune response and the chronic persistence of Brucella in the host.

Treponema pallidum recombinant protein Tp47 enhanced interleukin-6 secretion in human dermal fibroblasts through the toll-like receptor 2 via the p38, PI3K/Akt, and NF-κB signalling pathways

Interleukin-6 (IL-6) is a multi-effective cytokine involved in multiple immune responses. Whether fibroblasts also turn out to be a cytokine IL-6 factory during interaction with Treponema pallidum is not yet understood. To explore whether fibroblasts participate in inflammation due to syphilis, a series of experiments were performed to explore the role of T. pallidum lipoprotein Tp47 in IL-6 production in human dermal fibroblasts. The Toll-like receptor 2 (TLR2) and participating signalling pathways in this process were also evaluated. The results showed that the expressions of IL-6 and the protein levels of TLR2 in fibroblasts were upregulated after stimulation with Tp47, and this effect was impeded by the TLR2 inhibitor C29. In addition, Tp47 promoted the phosphorylation of p38, PI3K/Akt, and nuclear factor-kappaB (NF-κB), and the translocation of NF-κB in fibroblasts. Moreover, p38, PI3K, and NF-κB inhibitors significantly reduced IL-6 production in fibroblasts stimulated with Tp47. Furthermore, the TLR2 inhibitor C29 inhibited the phosphorylation of p38, Akt, and NF-κB, and the translocation of NF-κB in fibroblasts. In conclusion, our results showed that Tp47 enhanced IL-6 secretion in human dermal fibroblasts through TLR2 via p38, PI3K/Akt, and NF-κB signalling pathways. These findings contribute to our understanding of syphilis inflammation.

Receptor basis of biological activity of polysaccharides

Polysaccharides, the most diverse forms of organic molecules in nature, exhibit a large number of different biological activities, such as immunomodulatory, radioprotective, antioxidant, regenerative, metabolic, signaling, antitumor, and anticoagulant. The reaction of cells to a polysaccharide is determined by its specific interaction with receptors present on the cell surface, the type of cells, and their condition. The effect of many polysaccharides depends non-linearly on their concentration. The same polysaccharide in different conditions can have very different effects on cells and organisms, up to the opposite; therefore, when conducting studies of the biological activity of polysaccharides, both for the purpose of developing new drugs or approaches to the treatment of patients, and in order to clarify the features of intracellular processes, information about already known research results is needed. There is a lot of scattered data on the biological activities of polysaccharides, but there are few reviews that would consider natural polysaccharides from various sources and possible molecular mechanisms of their action. The purpose of this review is to present the main results published at different times in order to facilitate the search for information necessary for conducting relevant studies.

A pattern recognition receptor CgTLR3 involves in regulating the proliferation of haemocytes in oyster Crassostrea gigas

Toll-like receptors (TLRs) are expressed on various immune cells as key elements of innate and adaptive immunity, and they also play significant roles in regulating cell proliferation and differentiation. In the present study, the binding activity of CgTLR3 to PAMPs and CgMyD88-2, and its role in mediating the proliferation of haemocytes was investigated. The recombinant proteins of the extracellular six LRR domains (rCgTLR3-LRR) and intracellular TIR domain (rCgTLR3-TIR) of CgTLR3 were obtained respectively. rCgTLR3-LRR exhibited binding activity to lipopolysaccharide (LPS), peptidoglycan (PGN), mannan (MAN) and Poly (I:C), with the highest affinity for LPS. While rCgTLR3-TIR displayed binding activity to the recombinant protein of rCgMyD88-2, with KD value of 7.22 × 10-7 M. The CgTLR3 mRNA and protein were detected in three subpopulations of oyster haemocytes, and they were mainly concentrated in granulocytes, which was 7.27-fold (p < 0.05) of that in semi-granulocytes and 8.51-fold (p < 0.01) of that in agranulocytes. The percentage of CgTLR3 positive cells (FITC+ haemocytes) in granulocytes was 4.45-fold (p < 0.01) and 2.57-fold (p < 0.05) of that in agranulocytes and semi-granulocytes, respectively. After Vibrio splendidus stimulation, the mRNA expression level of CgTLR3 in haemocytes significantly upregulated at 6 h and 12 h, which was 2.93-fold (p < 0.05) and 4.15-fold (p < 0.05) of that in the control group. After the expression of CgTLR3 was inhibited by the injection of si-CgTLR3, the expression levels of transcription factors associated with hematopoiesis (CgGATA, CgRunx), cell cycle-related genes (CgPCNA, CgCDC-45, CgCDK-2), the agranulocyte marker CgCD-9, the granulocyte marker CgAATase, and the inflammatory factor CgIL17-1 significantly decreased (p < 0.05) after the V. splendidus stimulation, which were 0.43-fold, 0.83-fold, 0.48-fold, 0.44-fold, 0.53-fold, 0.7-fold, 0.62-fold, and 0.47-fold of that in NC + V. s group in vivo, respectively. Meanwhile, the percentage of EdU+ haemocytes in si-CgTLR3+V. s group was significantly reduced by 0.54-fold (p < 0.05) compared to the control group (2.7%). These results collectively indicated that CgTLR3 was involved in modulating the proliferation of haemocytes by regulating the expression of proliferation-related genes and inflammatory factor in oyster C. gigas.

The Role of TLR4 in the Immunotherapy of Hepatocellular Carcinoma: Can We Teach an Old Dog New Tricks?

Hepatocellular carcinoma (HCC) is the most common type of primary liver cancer and is a leading cause of cancer-related death worldwide. Immunotherapy has emerged as the mainstay treatment option for unresectable HCC. Toll-like receptor 4 (TLR4) plays a crucial role in the innate immune response by recognizing and responding primarily to bacterial lipopolysaccharides. In addition to its role in the innate immune system, TLR4 has also been implicated in adaptive immunity, including specific anti-tumor immune responses. In particular, the TLR4 signaling pathway seems to be involved in the regulation of several cancer hallmarks, such as the continuous activation of cellular pathways that promote cell division and growth, the inhibition of programmed cell death, the promotion of several invasion and metastatic mechanisms, epithelial-to-mesenchymal transition, angiogenesis, drug resistance, and epigenetic modifications. Emerging evidence further suggests that TLR4 signaling holds promise as a potential immunotherapeutic target in HCC. The aim of this review was to explore the multilayer aspects of the TLR4 signaling pathway, regarding its role in liver diseases and HCC, as well as its potential utilization as an immunotherapy target for HCC.

Small-Molecule Modulators Targeting Toll-like Receptors for Potential Anticancer Therapeutics

Toll-like receptors (TLRs) are key components of the innate immune system and serve as a crucial link between innate and acquired immunity. In addition to immune function, TLRs are involved in other important pathological processes, including tumorigenesis. TLRs have dual regulatory effects on tumor immunity by activating nuclear factor κ-B signaling pathways, which induce tumor immune evasion or enhance the antitumor immune response. Therefore, TLRs have become a popular target for cancer prevention and treatment, and TLR agonists and antagonists offer considerable potential for drug development. The TLR7 agonist imiquimod (1) has been approved by the U.S. Food and Drug Administration as a treatment for malignant skin cancer. Herein, the structure, signaling pathways, and function of the TLR family are summarized, and the structure-activity relationships associated with TLR selective and multitarget modulators and their potential application in tumor therapy are systematically discussed.

Toll-like receptor-7 signaling in Kupffer cells exacerbates concanavalin A-induced liver injury in mice

Concanavalin A (ConA) is a plant lectin that can induce immune-mediated liver damage. ConA induced liver damage animal model is a widely accepted model that can mimic clinical acute hepatitis and immune-mediated liver injury in humans. Toll-like receptor-7 (TLR7), a member of the TLR family, plays a key role in pathogen recognition and innate immune activation. The aim of this study was to examine the role of TLR7 in the pathogenesis of ConA-induced liver injury. Acute liver injury was induced by intravenous injection with ConA in WT (wild-type) and TLR7 knockout (KO) mice. Results showed that attenuated liver injury in TLR7-deficient mice, as indicated by increased survival rate, decreased aminotransferase levels, and reduced pathological lesions, was associated with decreased release of pro-inflammatory cytokines in livers. Consistently, significantly decreased proliferation of CD4⁺ T cell was detected in ConA-stimulated TLR7-deficient splenocytes, but not in CD3/CD28 stimulated TLR7-deficient CD4⁺ T cells. Moreover, TLR7 deficiency in KCs specifically suppressed the expression of TNF-α (tumor necrosis factor-α). Depletion of KCs abolished the detrimental role of TLR7 in ConA-induced liver injury. Taken together, these results demonstrate that TLR7 can regulate the expression of TNF-α in KCs, which is necessary for the full progression of ConA-induced liver injury.

Gut Dysbiosis and Blood-Brain Barrier Alteration in Hepatic Encephalopathy: From Gut to Brain

A common neuropsychiatric complication of advanced liver disease, hepatic encephalopathy (HE), impacts the quality of life and length of hospital stays. There is new evidence that gut microbiota plays a significant role in brain development and cerebral homeostasis. Microbiota metabolites are providing a new avenue of therapeutic options for several neurological-related disorders. For instance, the gut microbiota composition and blood-brain barrier (BBB) integrity are altered in HE in a variety of clinical and experimental studies. Furthermore, probiotics, prebiotics, antibiotics, and fecal microbiota transplantation have been shown to positively affect BBB integrity in disease models that are potentially extendable to HE by targeting gut microbiota. However, the mechanisms that underlie microbiota dysbiosis and its effects on the BBB are still unclear in HE. To this end, the aim of this review was to summarize the clinical and experimental evidence of gut dysbiosis and BBB disruption in HE and a possible mechanism.

Braun Lipoprotein Protects against Escherichia coli-Induced Inflammatory Responses and Lethality in Mice

Escherichia coli (E. coli), a Gram-negative bacterium, is an important pathogen that causes several mammalian diseases. The outer membrane components of E. coli, namely, lipopolysaccharide (LPS) and bacterial lipoprotein, can induce the host innate immune response through pattern recognition receptors (PRRs). However, the detailed roles of the E. coli Braun lipoprotein (BLP) in the regulation of host inflammatory response to E. coli infection remain unclear. In this study, we sought to determine the effects of BLP on E. coli-induced host inflammatory response and lethality using mouse models. Experiments using the E. coli DH5α strain (BLP-positive), E. coli JE5505 strain (BLP-negative), and E. coli JE5505 strain combined with BLP indicated that the presence of BLP could alleviate mortality and organ (liver and lung) damage and decrease proinflammatory cytokine (tumor necrosis factor alpha [TNF-α] and interleukin-1β [IL-1β]) and chemokine (regulated on activation normal T-cell expressed and secreted [RANTES]) production in mouse serum and organs. Conversely, E. coli JE5505, E. coli DH5α strain, and E. coli JE5505 combined with BLP treatment induce enhanced anti-inflammatory cytokine (interleukin 10 [IL-10]) production in mouse serum and organs. In addition, BLP could regulate the secretion of proinflammatory cytokines (TNF-α and IL-1β), chemokines (RANTES), and anti-inflammatory factors (IL-10) through mitogen-activated protein kinase (MAPK) and nuclear factor-kappaB (NF-κB) signaling pathways in macrophages. Altogether, our results demonstrate that the bacterial component BLP plays crucial and protective roles in E. coli-infected mice, which may influence the outcome of inflammation in host response to E. coli infection. IMPORTANCE In this study, we investigated the roles of bacterial outer membrane component BLP in regulating inflammatory responses and lethality in mice that were induced by a ubiquitous and serious pathogen, Escherichia coli. BLP could alleviate the mortality of mice and organ damage, as well as decrease proinflammatory cytokines and chemokine production and enhance anti-inflammatory cytokine production in mouse serum and organs. Overall, our results demonstrate that the bacterial component BLP plays crucial and protective roles in E. coli-infected mice through regulating the production of an inflammatory mediator, which may influence the outcome of inflammation in host response to E. coli infection. Our findings provide new information about the basic biology involved in immune responses to E. coli and host-bacterial interactions, which have the potential to translate into novel approaches for the diagnosis and treatment of E. coli-related medical conditions, such as bacteremia and sepsis.

Emerging strategies and challenges of molecular therapeutics in antileishmanial drug development

Molecular therapy refers to targeted therapies based on molecules which have been intelligently directed towards specific biomolecular structures and include small molecule drugs, monoclonal antibodies, proteins and peptides, DNA or RNA-based strategies, targeted chemotherapy and nanomedicines. Molecular therapy is emerging as the most effective strategy to combat the present challenges of life-threatening visceral leishmaniasis, where the successful human vaccine is currently unavailable. Moreover, current chemotherapy-based strategies are associated with the issues of ineffective targeting, unavoidable toxicities, invasive therapies, prolonged treatment, high treatment costs and the development of drug-resistant strains. Thus, the rational approach to antileishmanial drug development primarily demands critical exploration and exploitation of biochemical differences between host and parasite biology, immunocharacteristics of parasite homing, and host-parasite interactions at the molecular/cellular level. Following this, the novel technology-based designing and development of host and/or parasite-targeted therapeutics having leishmanicidal and immunomodulatory activity is utmost essential to improve treatment efficacy. Thus, the present review is focused on immunological and molecular checkpoint targets in host-pathogen interaction, and molecular therapeutic prospects for Leishmania intervention, and the challenges ahead.

Glutathione deficiency in the pathogenesis of SARS-CoV-2 infection and its effects upon the host immune response in severe COVID-19 disease

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that causes coronavirus disease 19 (COVID-19) has numerous risk factors leading to severe disease with high mortality rate. Oxidative stress with excessive production of reactive oxygen species (ROS) that lower glutathione (GSH) levels seems to be a common pathway associated with the high COVID-19 mortality. GSH is a unique small but powerful molecule paramount for life. It sustains adequate redox cell signaling since a physiologic level of oxidative stress is fundamental for controlling life processes via redox signaling, but excessive oxidation causes cell and tissue damage. The water-soluble GSH tripeptide (γ-L-glutamyl-L-cysteinyl-glycine) is present in the cytoplasm of all cells. GSH is at 1-10 mM concentrations in all mammalian tissues (highest concentration in liver) as the most abundant non-protein thiol that protects against excessive oxidative stress. Oxidative stress also activates the Kelch-like ECH-associated protein 1 (Keap1)-Nuclear factor erythroid 2-related factor 2 (Nrf2)-antioxidant response element (ARE) redox regulator pathway, releasing Nrf2 to regulate the expression of genes that control antioxidant, inflammatory and immune system responses, facilitating GSH activity. GSH exists in the thiol-reduced and disulfide-oxidized (GSSG) forms. Reduced GSH is the prevailing form accounting for >98% of total GSH. The concentrations of GSH and GSSG and their molar ratio are indicators of the functionality of the cell and its alteration is related to various human pathological processes including COVID-19. Oxidative stress plays a prominent role in SARS-CoV-2 infection following recognition of the viral S-protein by angiotensin converting enzyme-2 receptor and pattern recognition receptors like toll-like receptors 2 and 4, and activation of transcription factors like nuclear factor kappa B, that subsequently activate nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX) expression succeeded by ROS production. GSH depletion may have a fundamental role in COVID-19 pathophysiology, host immune response and disease severity and mortality. Therapies enhancing GSH could become a cornerstone to reduce severity and fatal outcomes of COVID-19 disease and increasing GSH levels may prevent and subdue the disease. The life value of GSH makes for a paramount research field in biology and medicine and may be key against SARS-CoV-2 infection and COVID-19 disease.

Prophylactic and Therapeutic HPV Vaccines: Current Scenario and Perspectives

Persistent human papillomavirus (HPV) infection is recognized as the main cause of cervical cancer and other malignant cancers. Although early detection and treatment can be achieved by effective HPV screening methods and surgical procedures, the disease load has not been adequately mitigated yet, especially in the underdeveloped areas. Vaccine, being regarded as a more effective solution, is expected to prevent virus infection and the consequent diseases in the phases of both prevention and treatment. Currently, there are three licensed prophylactic vaccines for L1-VLPs, namely bivalent, quadrivalent and nonavalent vaccine. About 90% of HPV infections have been effectively prevented with the implementation of vaccines worldwide. However, no significant therapeutic effect has been observed on the already existed infections and lesions. Therapeutic vaccine designed for oncoprotein E6/E7 activates cellular immunity rather than focuses on neutralizing antibodies, which is considered as an ideal immune method to eliminate infection. In this review, we elaborate on the classification, mechanism, and clinical effects of HPV vaccines for disease prevention and treatment, in order to make improvements to the current situation of HPV vaccines by provoking new ideas.

Targeting DAMPs with nucleic acid scavengers to treat lupus

Systemic lupus erythematosus (SLE) is a chronic and often progressive autoimmune disorder marked clinically by a variable constellation of symptoms including fatigue, rash, joint pains, and kidney damage. The lungs, heart, gastrointestinal system, and brain can also be impacted, and individuals with lupus are at higher risk for atherosclerosis, thrombosis, thyroid disease, and other disorders associated with chronic inflammation . Autoimmune diseases are marked by erroneous immune responses in which the target of the immune response is a "self"-antigen, or autoantigen, driven by the development of antigen-specific B or T cells that have overcome the normal systems of self-tolerance built into the development of B and T cells. SLE is specifically characterized by the production of autoantibodies against nucleic acids and their binding proteins, including anti-double stranded DNA, anti-Smith (an RNA binding protein), and many others . These antibodies bind their nuclear-derived antigens to form immune complexes that cause injury and scarring through direct deposition in tissues and activation of innate immune cells . In over 50% of SLE patients, immune complex aggregation in the kidneys drives intrarenal inflammation and injury and leads to lupus nephritis, a progressive destruction of the glomeruli that is one of the most common causes of lupus-related death . To counter this pathology increasing attention has turned to developing approaches to reduce the development and continued generation of such autoantibodies. In particular, the molecular and cellular events that lead to long term, continuous activation of such autoimmune responses have become the focus of new therapeutic strategies to limit renal and other pathologies in lupus patients. The focus of this review is to consider how the innate immune system is involved in the development and progression of lupus nephritis and how a novel approach to inhibit innate immune activation by neutralizing the activators of this response, called Damage Associated Molecular Patterns, may represent a promising approach to treat this and other autoimmune disorders.

Ligation of TLR Homologue CD180 of B Cells Activates the PI3K/Akt/mTOR Pathway in Systemic Sclerosis and Induces a Pathological Shift in the Expression of BAFF Receptors

The phosphatidylinositol-3-kinase (PI3K)/Akt and the mammalian target of rapamycin (mTOR) pathways are known to play a key role in B-cell activation and fibrosis in systemic sclerosis (SSc). Receptors of B-cell activator factor (BAFF) utilize these pathways, which can be influenced by Toll-like receptors (TLRs), as TLRs can alter the expression of BAFF-binding receptors. Our results show that B-cell stimulation via TLR homologue CD180 phosphorylates Akt in diffuse cutaneous SSc (dcSSc) to a lower extent than in healthy controls (HCs). We found basal downregulated BAFF receptor (BAFF-R) and enhanced transmembrane activator and calcium-modulator and cyclophilin ligand interactor (TACI) expression in dcSSc B cells, which might enhance the formation of autoantibody-secreting plasma cells. Moreover, this pathological shift was observed in naive B cells, emphasizing the importance of their increase in SSc. Additionally, we measured higher serum levels of autoantibodies to BAFF in dcSSc patients, suggesting that an imbalance in the complex system of BAFF/anti-BAFF autoantibodies/BAFF-binding receptors may contribute to the development of SSc. Anti-CD180 antibody treatment had opposite effects on the expression of BAFF-R and TACI in HC B cells, resulting in similar levels as observed in SSc B cells without stimulation, which argues against the usefulness of such therapy in SSc.

TLR/WNT: A Novel Relationship in Immunomodulation of Lung Cancer

The most frequent cause of death by cancer worldwide is lung cancer, and the 5-year survival rate is still very poor for patients with advanced stage. Understanding the crosstalk between the signaling pathways that are involved in disease, especially in metastasis, is crucial to developing new targeted therapies. Toll-like receptors (TLRs) are master regulators of the immune responses, and their dysregulation in lung cancer is linked to immune escape and promotes tumor malignancy by facilitating angiogenesis and proliferation. On the other hand, over-activation of the WNT signaling pathway has been reported in lung cancer and is also associated with tumor metastasis via induction of Epithelial-to-mesenchymal-transition (EMT)-like processes. An interaction between both TLRs and the WNT pathway was discovered recently as it was found that the TLR pathway can be activated by WNT ligands in the tumor microenvironment; however, the implications of such interactions in the context of lung cancer have not been discussed yet. Here, we offer an overview of the interaction of TLR-WNT in the lung and its potential implications and role in the oncogenic process.

β-elemene regulates M1-M2 macrophage balance through the ERK/JNK/P38 MAPK signaling pathway

Macrophages are classified into classically activated M1 macrophages and alternatively activated M2 macrophages, and the two phenotypes of macrophages are present during the development of various chronic diseases, including obesity-induced inflammation. In the present study, β-elemene, which is contained in various plant substances, is predicted to treat high-fat diet (HFD)-induced macrophage dysfunction based on the Gene Expression Omnibus (GEO) database and experimental validation. β-elemene impacts the imbalance of M1-M2 macrophages by regulating pro-inflammatory cytokines in mouse white adipose tissue both in vitro and in vivo. In addition, the RAW 264 cell line, which are macrophages from mouse ascites, is used to identify the effects of β-elemene on inhibiting bacterial endotoxin lipopolysaccharide (LPS)-induced phosphorylation of mitogen-activated protein kinase (MAPK) pathways. These pathways both induce and are activated by pro-inflammatory cytokines, and they also participate in the process of obesity-induced inflammation. The results highlight that β-elemene may represent a possible macrophage-mediated therapeutic medicine.

Potential therapeutic strategies for myocardial infarction: the role of Toll-like receptors

Myocardial infarction (MI) is a life-threatening condition among patients with cardiovascular diseases. MI increases the risk of stroke and heart failure and is a leading cause of morbidity and mortality worldwide. Several genetic and epigenetic factors contribute to the development of MI, suggesting that further understanding of the pathomechanism of MI might help in the early management and treatment of this disease. Toll-like receptors (TLRs) are well-known members of the pattern recognition receptor (PRR) family and contribute to both adaptive and innate immunity. Collectively, studies suggest that TLRs have a cardioprotective effect. However, prolonged TLR activation in the response to signals generated by damage-associated molecular patterns (DAMPs) results in the release of inflammatory cytokines and contributes to the development and exacerbation of myocardial inflammation, MI, ischemia-reperfusion injury, myocarditis, and heart failure. The objective of this review is to discuss and summarize the association of TLRs with MI, highlighting their therapeutic potential for the development of advanced TLR-targeted therapies for MI.

TLR9 in the Human Papilloma Virus Infections: Friend or Foe?

Immune system plays dual roles during human papilloma virus (HPV) infections, from defense against the virus to induction or stimulation of the HPV-related cancers. It appears that various differences within the immune-related genes and the functions of the immunological parameters of the patients are the main factors responsible for the roles played by immune system during HPV infections. Toll-like receptors (TLRs) play key roles in the recognition of viruses and activation of immune responses. The molecules also can alter the target cell intracellular signaling and may participate in the transformation of the infected cells. TLR9 is the unique intracellular member of TLRs that recognize foreign DNA, including viral DNA. Thus, TLR9 may play significant roles in the defense against HPV and its related cancers. This review article discusses TLR9 antiviral and pathological roles during HPV infection.

Biological Activities, Pharmacokinetics and Toxicity of Nootkatone: A Review

Abstract:

Plant-based drugs have a significant impact on modern therapeutics due to their vast array of pharmacological activities. The integration of herbal plants in the current healthcare system has emerged as a new field of research. It can be used for the identification of novel lead compound candidates for future drug development. Nootkatone is a sesquiterpene derivative and an isolate of grapefruit. Shreds of evidence illustrate that nootkatone targets few molecular mechanisms to exhibit its pharmacological activity and yet needs more exploration to be established. The current review is related to nootkatone, drafted through a literature search using research articles and books from different sources, including Science Direct, Google Scholar, Elsevier, PubMed, and Scopus. It has been reported to possess a wide range of pharmacological activities such as anti-inflammatory, anticancer, antibacterial, hepatoprotective, neuroprotective, and cardioprotective. Although preclinical studies in experimental animal models suggest that nootkatone has therapeutic potential, it is further warranted to evaluate its toxicity and pharmacokinetic parameters before being applied to humans. Hence in the present review, we have summarized the scientific knowledge on nootkatone with a particular emphasis on its pharmacological properties to encourage researchers for further exploration in preclinical and clinical settings.

Salmonid MyD88 is a key adapter protein that activates innate effector mechanisms through the TLR5M/TLR5S signaling pathway and protects against Piscirickettsia salmonis infection

The membrane-anchored and soluble Toll-like Receptor 5 -TLR5M and TLR5S, respectively-from teleost recognize bacterial flagellin and induce the pro-inflammatory cytokines expression in a MyD88-dependent manner such as the TLR5 mammalian orthologous receptor. However, it has not been demonstrated whether the induced signaling pathway by these receptors activate innate effector mechanisms MyD88-dependent in salmonids. Therefore, in this work we study the MyD88 dependence on the induction of TLR5M/TLR5S signaling pathway mediated by flagellin as ligand on the activation of some innate effector mechanisms. The intracellular and extracellular Reactive Oxygen Species (ROS) production and conditioned supernatants production were evaluated in RTS11 cells, while the challenge with Piscirickettsia salmonis was evaluated in SHK-1 cells. Our results demonstrate that flagellin directly stimulates ROS production and indirectly stimulates it through the production of conditioned supernatants, both in a MyD88-dependent manner. Additionally, flagellin stimulation prevents the cytotoxicity induced by infection with P. salmonis in a MyD88-dependent manner. In conclusion we demonstrate that MyD88 is an essential adapter protein in the activation of the TLR5M/TLR5S signaling pathway mediated by flagellin in salmonids, which leads downstream to the induction of innate effector mechanisms, promoting immuno-protection against a bacterial challenge with P. salmonis.

Survival of HT29 Cancer Cells Is Affected by IGF1R Inhibition via Modulation of Self-DNA-Triggered TLR9 Signaling and the Autophagy Response

Purpose: In HT29 colon cancer cells, a close interplay between self-DNA-induced TLR9 signaling and autophagy response was found, with remarkable effects on cell survival and differentiation. IGF1R activation drives the development and malignant progression of colorectal cancer. IGF1R inhibition displays a controversial effect on autophagy. The interrelated roles of IGF1R inhibition and TLR9/autophagy signaling in HT29 cancer cells have not yet been clarified. In our study, we aimed to investigate the complex interplay of IGF1R inhibition and TLR9/autophagy signaling in HT29 cells. Methods: HT29 cells were incubated with tumor-originated self-DNA with or without inhibitors of IGF1R (picropodophyllin), autophagy (chloroquine), and TLR9 (ODN2088), respectively. Cell proliferation and metabolic activity measurements, direct cell counting, NanoString and Taqman gene expression analyses, immunocytochemistry, WES Simple Western blot, and transmission electron microscopy investigations were performed. Results: The concomitant use of tumor-derived self-DNA and IGF1R inhibitors displays anti-proliferative potential, which can be reversed by parallel TLR9 signaling inhibition. The distinct effects of picropodophyllin, ODN2088, and chloroquine per se or in combination on HT29 cell proliferation and autophagy suggest that either the IGF1R-associated or non-associated autophagy machinery is "Janus-faced" regarding its actions on cell proliferation. Autophagy, induced by different combinations of self-DNA and inhibitors is not sufficient to rescue HT29 cells from death but results in the survival of some CD133-positive stem-like HT29 cells. Conclusion: The creation of new types of combined IGF1R, autophagy, and/or TLR9 signaling inhibitors would play a significant role in the development of more personalized anti-tumor therapies for colorectal cancer.

Methylation and Expression of the Exercise-Related TLR1 Gene Is Associated With Low Grade Glioma Prognosis and Outcome

Background: Exercise improves function, reduces disability, maintains independence, and improves quality of life for low-grade glioma (LGG) patients. Exercise can also improve the effectiveness of cancer treatment. The goal of this research was to find potential exercise related genes that may be used to predict exercise levels and may be used as a biomarker for cancer outcomes.

Methods: The GSE111551 database was thoroughly examined in this research, and the resulting conclusion of exercise-related genes was reached. The protein interaction network (PPI) was used to examine the differentially expressed genes (DEGs). Then the exercise-related gene TLR1 was chosen. The expression, methylation degree, prognosis, and immune relevance of TLR1 were investigated using bioinformatics. In addition, we verified the role of TLR1 in Glioma cell lines.

Results: LGG patients with reduced TLR1 expression and hypermethylation had a better overall survival (OS) and progression free survival (PFS), using the TCGA database. Low TLR1 expression and hypermethylation of TLR1 were found to be independent biomarkers for OS using Cox regression. Furthermore, the CGGA database was used to confirm the prognostic function of TLR1 in this cancer. Finally, most methylation sites of TLR1 were strongly correlated with immune infiltration and immune checkpoint. Then, reducing TLR1 expression substantially slowed the cell cycle and decreased LGG cell proliferation, emigration, and infiltration in vitro.

Conclusions: Exercise-related gene TLR1 has the potential to be a useful prognostic biomarker, and it is thought to be involved in immune cell infiltration and immunotherapy in LGG.

High expression of Toll-like receptor 7 is a survival factor in pediatric medulloblastoma

PURPOSE

Medulloblastoma is an embryonal brain tumor that predominantly occurs in childhood with a wide histological and molecular variability. Our aim was to investigate the expression of Toll-like receptors (TLRs), their association with the infiltration of immune cells and with the histological subgroups, and, also, with the overall survival of patients.

METHODS

Fifty-six paraffin-preserved biopsies from children with medulloblastoma of the classic, desmoplastic, and anaplastic subtypes were included. Microarrays of tissues were performed, and the infiltration of T and NK cells was quantified, as well as the expression of TLR7, TLR8, and TLR9. For all statistical analyses, significance was p < 0.05.

RESULTS

CD4 + and CD8 + T lymphocytes and NK cells were found infiltrating the tumor. The infiltration of NK and CD4 + cells was greater in the classic and desmoplastic subtypes than in anaplastic. We found an important expression of TLRs in all medulloblastomas, but TLR7 and TLR8 were considerably higher in classic and desmoplastic subtypes than in anaplastic. Importantly, we observed that TLR7 was a prognostic factor for survival.

CONCLUSIONS

Medulloblastomas present cellular infiltration and a differential expression of TLRs depending on the histological subtype. TLR7 is a prognostic factor of survival that is dependent on treatment and age.

Role of Toll-Like Receptors in Neuroimmune Diseases: Therapeutic Targets and Problems

Toll-like receptors (TLRs) are a class of proteins playing a key role in innate and adaptive immune responses. TLRs are involved in the development and progression of neuroimmune diseases via initiating inflammatory responses. Thus, targeting TLRs signaling pathway may be considered as a potential therapy for neuroimmune diseases. However, the role of TLRs is elusive and complex in neuroimmune diseases. In addition to the inadequate immune response of TLRs inhibitors in the experiments, the recent studies also demonstrated that partial activation of TLRs is conducive to the production of anti-inflammatory factors and nervous system repair. Exploring the mechanism of TLRs in neuroimmune diseases and combining with developing the emerging drug may conquer neuroimmune diseases in the future. Herein, we provide an overview of the role of TLRs in several neuroimmune diseases, including multiple sclerosis, neuromyelitis optica spectrum disorder, Guillain-Barré syndrome and myasthenia gravis. Emerging difficulties and potential solutions in clinical application of TLRs inhibitors will also be discussed.

Tlr2/4 Double Knockout Attenuates the Degeneration of Primary Auditory Neurons: Potential Mechanisms From Transcriptomic Perspectives

The transcriptomic landscape of mice with primary auditory neurons degeneration (PAND) indicates key pathways in its pathogenesis, including complement cascades, immune responses, tumor necrosis factor (TNF) signaling pathway, and cytokine-cytokine receptor interaction. Toll-like receptors (TLRs) are important immune and inflammatory molecules that have been shown to disrupt the disease network of PAND. In a PAND model involving administration of kanamycin combined with furosemide to destroy cochlear hair cells, Tlr 2/4 double knockout (DKO) mice had auditory preservation advantages, which were mainly manifested at 4–16 kHz. DKO mice and wild type (WT) mice had completely damaged cochlear hair cells on the 30th day, but the density of spiral ganglion neurons (SGN) in the Rosenthal canal was significantly higher in the DKO group than in the WT group. The results of immunohistochemistry for p38 and p65 showed that the attenuation of SGN degeneration in DKO mice may not be mediated by canonical Tlr signaling pathways. The SGN transcriptome of DKO and WT mice indicated that there was an inverted gene set enrichment relationship between their different transcriptomes and the SGN degeneration transcriptome, which is consistent with the morphology results. Core module analysis suggested that DKO mice may modulate SGN degeneration by activating two clusters, and the involved molecules include EGF, STAT3, CALB2, LOX, SNAP25, CAV2, SDC4, MYL1, NCS1, PVALB, TPM4, and TMOD4.

Toll-like receptor 2 signaling in liver pathophysiology

Chronic liver diseases (CLD) are among the major cause of mortality and morbidity worldwide. Despite current achievements in the area of hepatitis virus, chronic alcohol abuse and high-fat diet are still fueling an epidemic of severe liver disease, for which, an effective therapy has yet not been discovered. In particular, the therapeutic regimens that could prevent the progression of fibrosis and, in turn, aid cirrhotic liver to develop a robust regenerative capability are intensively needed. To this context, a better understanding of the signaling pathways regulating hepatic disease development may be of critical value. In general, the liver responds to various insults with an orchestrated healing process involving variety of signaling pathways. One such pathway is the TLR2 signaling pathway, which essentially regulates adult liver pathogenesis and thus has emerged as an attractive target to treat liver disease. TLR2 is expressed by different liver cells, including Kupffer cells (KCs), hepatocytes, and hepatic stellate cells (HSCs). From a pathologic perspective, the crosstalk between antigens and TLR2 may preferentially trigger a distinctive set of signaling mechanisms in these liver cells and, thereby, induce the production of inflammatory and fibrogenic cytokines that can initiate and prolong liver inflammation, ultimately leading to fibrosis. In this review, we summarize the currently available evidence regarding the role of TLR2 signaling in hepatic disease progression. We first elaborate its pathological involvement in liver-disease states, such as inflammation, fibrosis, and cirrhosis. We then discuss how therapeutic targeting of this pathway may help to alleviate its disease-related functioning.

Design and optimisation of a small-molecule TLR2/4 antagonist for anti-tumour therapy

In anti-tumour therapy, the toll-like receptor 2/4 (TLR2/4) signalling pathway has been a double-edged sword. TLR2/4 agonists are commonly considered adjuvants for immune stimulation, whereas TLR2/4 antagonists demonstrate more feasibility for anti-tumour therapy under specific chronic inflammatory situations. In individuals with cancer retaliatory proliferation and metastasis after surgery, blocking the TLR2/4 signalling pathway may produce favourable prognosis for patients. Therefore, here, we developed a small-molecule co-inhibitor that targets the TLR2/4 signalling pathway. After high-throughput screening of a compound library containing 14 400 small molecules, followed by hit-to-lead structural optimisation, we finally obtained the compound TX-33, which has effective inhibitory properties against the TLR2/4 signalling pathways. This compound was found to significantly inhibit multiple pro-inflammatory cytokines released by RAW264.7 cells. This was followed by TX-33 demonstrating promising efficacy in subsequent anti-tumour experiments. The current results provide a novel understanding of the role of TLR2/4 in cancer and a novel strategy for anti-tumour therapy.

A 192 bp ERV fragment insertion in the first intron of porcine TLR6 may act as an enhancer associated with the increased expressions of TLR6 and TLR1

Background

Toll-like receptors (TLRs) play important roles in building innate immune and inducing adaptive immune responses. Associations of the TLR genes polymorphisms with disease susceptibility, which are the basis of molecular breeding for disease resistant animals, have been reported extensively. Retrotransposon insertion polymorphisms (RIPs), as a new type of molecular markers developed recently, have great potential in population genetics and quantitative trait locus mapping. In this study, bioinformatic prediction combined with PCR-based amplification was employed to screen for RIPs in porcine TLR genes. Their population distribution was examined, and for one RIP the impact on gene activity and phenotype was further evaluated.

Results

Five RIPs, located at the 3' flank of TLR3, 5' flank of TLR5, intron 1 of TLR6, intron 1 of TLR7, and 3' flank of TLR8 respectively, were identified. These RIPs were detected in different breeds with an uneven distribution among them. By using the dual luciferase activity assay a 192 bp endogenous retrovirus (ERV) in the intron 1 of TLR6 was shown to act as an enhancer increasing the activities of TLR6 putative promoter and two mini-promoters. Furthermore, real-time quantitative polymerase chain reaction (qPCR) analysis revealed significant association (p < 0.05) of the ERV insertion with increased mRNA expression of TLR6, the neighboring gene TLR1, and genes downstream in the TLR signaling pathway such as MyD88 (Myeloid differentiation factor 88), Rac1 (Rac family small GTPase 1), TIRAP (TIR domain containing adaptor protein), Tollip (Toll interacting protein) as well as the inflammatory factors IL6 (Interleukin 6), IL8 (Interleukin 8), and TNFα (Tumor necrosis factor alpha) in tissues of 30 day-old piglet. In addition, serum IL6 and TNFα concentrations were also significantly upregulated by the ERV insertion (p < 0.05).

Conclusions

A total of five RIPs were identified in five different TLR loci. The 192 bp ERV insertion in the first intron of TLR6 was associated with higher expression of TLR6, TLR1, and several genes downstream in the signaling cascade. Thus, the ERV insertion may act as an enhancer affecting regulation of the TLR signaling pathways, and can be potentially applied in breeding of disease resistant animals.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13100-021-00248-w.

Microbiota and cancer: current understanding and mechanistic implications

During last few decades, role of microbiota and its importance in several diseases has been a hot topic for research. The microbiota is considered as an accessory organ for maintaining normal physiology of an individual. These microbiota organisms which normally colonize several epithelial surfaces are known to secrete several small molecules leading to local and systemic effects on normal biological processes. The role of microbiota is also established in carcinogenesis as per several recent findings. The effects of microbiota on cancer is not only limited to their contribution in oncogenesis, but the overall susceptibility for oncogenesis and its subsequent progression, development of coinfections, and response to anticancer therapy is also found to be affected by microbiota. The information about microbiota and subsequent contributions of microbes in anticancer response motivated researchers in development of microbes-based anticancer therapeutics. We provided current status of microbiota contribution in oncogenesis with special reference to their mechanistic implications in different aspects of oncogenesis. In addition, the mechanistic implications of bacteria in anticancer therapy are also discussed. We conclude that several mechanisms of microbiota-mediated regulation of oncogenesis is known, but approaches must be focused on understanding contribution of microbiota as a community rather than single organisms-mediated effects.

Identification of covalent modifications regulating immune signaling complex composition and phenotype

Cells signal through rearrangements of protein communities governed by covalent modifications and reversible interactions of distinct sets of proteins. A method that identifies those post‐transcriptional modifications regulating signaling complex composition and functional phenotypes in one experimental setup would facilitate an efficient identification of novel molecular signaling checkpoints. Here, we devised modifications, interactions and phenotypes by affinity purification mass spectrometry (MIP‐APMS), comprising the streamlined cloning and transduction of tagged proteins into functionalized reporter cells as well as affinity chromatography, followed by MS‐based quantification. We report the time‐resolved interplay of more than 50 previously undescribed modification and hundreds of protein–protein interactions of 19 immune protein complexes in monocytes. Validation of interdependencies between covalent, reversible, and functional protein complex regulations by knockout or site‐specific mutation revealed ISGylation and phosphorylation of TRAF2 as well as ARHGEF18 interaction in Toll‐like receptor 2 signaling. Moreover, we identify distinct mechanisms of action for small molecule inhibitors of p38 (MAPK14). Our method provides a fast and cost‐effective pipeline for the molecular interrogation of protein communities in diverse biological systems and primary cells.

Inhibition of TLR9 signaling stimulates apoptosis and cell cycle arrest and alleviates angiogenic property in human cervical cancer cells

AIMS

The aim of the study was to assess the effect of blocking TLR9 signaling on the proliferation of cervical cancer cells and its angiogenic property.

BACKGROUND

Toll-like receptors (TLRs) have been implicated for their crucial role in not only cervical cancer but also in other malignancies. TLR9 is expressed on an array of cells such as macrophages, dendritic cells, melanocytes, and keratinocytes. It is reported to modulate oncogenesis along with tumorigenesis by augmenting NF-κB mediated inflammation within the tumor environment. TLR9 has also been reported to positively regulate oncogenesis within the cervix and as a marker to evaluate malignant remodeling of cervical squamous cells. Therefore, this study was designed to explore the functional relevance of blocking the TLR9 signaling pathway in cervical cancer cells.

OBJECTIVE

The objective of the current study was to investigate the effect of human TLR9 antagonist, ODN INH-18, on apoptosis and cell cycle regulation and angiogenic property of human cervical cancer Caski cells.

METHOD

MTT assay was performed to measure cell viability, and flow cytometry analysis was performed to assess cell cycle arrest. Quantitative real-time PCR (qRT-PCR) analysis was performed to measure fold change in the gene expression of various markers of apoptosis, cell cycle regulation, and angiogenesis.

RESULT

The qRT-PCR results showed a higher expression level of TLR9 mRNA in Caski cervical cancer cells as compared to normal cervical keratinocytes. The apoptotic, angiogenic, and cell cycle regulatory factors were also deregulated in Caski cells in comparison to normal keratinocytes. The MTT assay demonstrated that treatment of TLR9 antagonist, ODN INH18, significantly reduced the proliferation of Caski cells in a dose-dependent manner. Treatment of ODN INH18 led to substantial cell cycle arrest in Caski cells at G0/G1 phase. Moreover, the qRT-PCR results demonstrated that ODN INH18 treatment led to suppressed mRNA expression of Bcl-2 and enhanced expression of Bax, signifying induction of apoptosis in Caski cells. Moreover, the expression of cyclin D1, Cdk4, and Cdc25A was found to be reduced, whereas expression of p27 was increased in ODN INH18-treated Caski cells, indicating G0/G1 phase arrest. Interestingly, expression of VEGF and VCAM-1 were found to be significantly inhibited in ODN INH18-treated Caski cells, substantiating alleviation of angiogenic property of cervical cancer cells.

CONCLUSION

The results of our study suggest that inhibiting TLR9 signaling might be an interesting therapeutic intervention for the treatment of cervical cancer.

Effect of probiotic Lactobacillus rhamnosus by-products on gingival epithelial cells challenged with Porphyromonas gingivalis

OBJECTIVE

Probiotics are usually given as living cells, but their effects may be also achieved by postbiotics. We hypothesized that probiotics products (spent media and lysate) altered the response induced by P. gingivalis in gingival epithelial cells (GECS).

METHODS

Immortalized human OBA-9 GECs (∼2,5 × 10⁵cells/well) were challenged with P. gingivalis ATCC33277, and co-infected with L. rhamnosus Lr-32 for 4 h. L. rhamnosus Lr-32 spent medium or cells lysate was added to GECs co-infected with P. gingivalis. Another set of OBA-9 GECs were first exposed to P. gingivalis ATCC 33277 and then to the living probiotic or probiotic products. Transcription of genes encoding inflammatory mediators (IL-1β, TNF-α, IL-6, and CXCL-8) and receptors (TLR2 and TLR4) were evaluated by RT-qPCR. P. gingivalis growth under L. rhamnosus Lr-32 postbiotics was also evaluated.

RESULTS

L. rhamnosus Lr-32 spent media decreased cell viability, while living cells and cell lysates did not. L. rhamnosus Lr-32 lysate, but not spent media, upregulated transcription of inflammatory mediators (IL-1β, TNF-α, IL-6, and CXCL-8) in GECs infected with P. gingivalis. Transcription of TRL2 was upregulated in all experimental groups compared to control, whereas TLR4 was upregulated by the probiotic or its postbiotics in P. gingivalis infected cells. Spent media and lysates reduced the growth of P. gingivalis.

CONCLUSION

L. rhamnosus Lr-32 cell components rather than live probiotic enhanced the expression of inflammatory mediators in P. gingivalis infected gingival epithelial cells. The increased potential of Lr-32 cell lysates to promote immune response to the periodontopathogen may favor pathogen elimination but may also lead to additional deleterious effects of the exacerbated inflammation.

The Akt pathway mediates the protective effects of myeloid differentiation protein 1 in pathological cardiac remodelling

Aims

Myeloid differentiation protein 1 (MD1) was shown to ameliorate pressure overload‐induced cardiac hypertrophy and fibrosis by negatively regulating the MEK–ERK1/2 and NF‐κB pathways. However, whether MD1 modulates cardiac function and whether the Akt pathway mediates the benefits of MD1 in pressure overload‐induced cardiac remodelling remain unclear.

Methods and Results

Male cardiac‐specific transgenic MD1 (MD1‐TG) mice, MD1‐knockout (KO) mice and wild‐type (WT) littermates aged 8–10 weeks were subjected to sham operation and aortic banding (AB) for 4 weeks. Then, left ventricular (LV) hypertrophy, fibrosis and function of the mice were assessed. When compared with WT‐AB mice, MD1‐TGs showed decreased cross‐sectional area (CSA) of cardiomyocytes (P < 0.001), mRNA expression of β‐myosin heavy chain (β‐MHC) (P < 0.02), ratios of heart weight/body weight and heart weight/tibia length (P < 0.04) and collagen volume fraction (P < 0.001). The LV end‐diastolic diameter was reduced, and LV ejection fraction and fractional shortening were improved in MD1‐TG‐AB mice than in WT‐AB mice (P < 0.05). In cultured H9C2 cells, adenovirus vector‐mediated MD1 overexpression decreased angiotensin II‐induced mRNA expression of brain natriuretic peptide (BNP) and β‐MHC and cell CSA (P < 0.002), whereas knockdown of MD1 by shRNA exhibited opposite effects (P < 0.04). Mechanistically, MD1 suppressed pathological cardiac remodelling at least partly by blocking Akt pathway. Akt inactivation by MK2206 largely offset the pro‐hypertrophic effects of MD1 deficiency in angiotensin II‐stimulated cardiomyocytes.

Conclusions

The Akt pathway mediates the protective effects of MD1 in pressure overload‐induced cardiac remodelling in mice. Targeting MD1 may provide therapeutic strategy for the treatment of pathological cardiac remodelling and heart failure.

Design, Synthesis, and Structure-Activity Relationship of N-Aryl-N'-(thiophen-2-yl)thiourea Derivatives as Novel and Specific Human TLR1/2 Agonists for Potential Cancer Immunotherapy

The previous virtual screening of ten million compounds yielded two novel nonlipopeptide-like chemotypes as TLR2 agonists. Herein, we present the chemical optimization of our initial hit, 1-phenyl-3-(thiophen-2-yl)urea, which resulted in the identification of SMU-C80 (EC₅₀ = 31.02 ± 1.01 nM) as a TLR2-specific agonist with a 370-fold improvement in bioactivity. Mechanistic studies revealed that SMU-C80, through TLR1/2, recruits the adaptor protein MyD88 and triggers the NF-κB pathway to release cytokines such as TNF-α and IL-1β from human, but not murine, cells. To the best of our knowledge, it is the first species-specific TLR1/2 agonist reported until now. Moreover, SMU-C80 increased the percentage of T, B, and NK cells ex vivo and activated the immune cells, which suppressed cancer cell growth in vitro. In summary, we obtained a highly efficient and specific human TLR1/2 agonist that acts through the MyD88 and NF-κB pathway, facilitating cytokine release and the simultaneous activation of immune cells that in turn affects the apoptosis of cancer cells.

Nootkatone attenuates myocardial oxidative damage, inflammation, and apoptosis in isoproterenol-induced myocardial infarction in rats

BACKGROUND

Myocardial infarction (MI) is a lethal manifestation of cardiovascular diseases. Oxidative stress, inflammation, and subsequent cell death are known to play crucial roles in the pathogenesis of MI. Despite tremendous developments in interventional cardiology, there is need for novel drugs for the prevention and treatment of MI. For the development of novel drugs, usage of natural products has gained attention as a therapeutic approach for ischemic myocardial injury. Among many popular plant-derived compounds, Nootkatone (NKT), a natural bioactive sesquiterpene, abundantly found in grapefruit, has attracted attention for its plausible health benefits and pharmacological properties.

PURPOSE

The present study investigated the cardioprotective effects of NKT in rats against MI induced by isoproterenol (ISO), a synthetic catecholamine and β-adrenergic agonist that produces MI in a physiologically relevant manner.

METHODS

MI was induced in male Wistar albino rats by subcutaneous injection of ISO (85 mg/kg body weight) on 9^th and 10^th day. Rats were pre- and co-treated with NKT (10 mg/kg) through daily oral administration for eleven days.

RESULTS

ISO-induced MI was characterized by a significant decline in cardiac function, increased serum levels of cardiomyocyte injury markers, enhanced oxidative stress, and altered PI3K/Akt and NrF2/Keap1/HO-1 signaling pathways. ISO also elevated the levels of myocardial pro-inflammatory cytokines, promoted lysosomal dysfunction, altered TLR4-NFκB/MAPK signaling, and triggered intrinsic apoptotic pathway in heart tissues. However, NKT administration significantly restored or modulated majority of the altered biochemical and molecular parameters in ISO-treated rats. Furthermore, histopathological observations confirmed the myocardial restoring effect of NKT.

CONCLUSION

The present study concludes the cardioprotective effects and underlying mechanisms of NKT against ISO-induced MI in rats, and suggests that NKT or plants containing NKT could be an alternative to cardioprotective agents in ischemic heart diseases.

m6A methylation potentiates cytosolic dsDNA recognition in a sequence-specific manner

Nucleic acid sensing through pattern recognition receptors is critical for immune recognition of microbial infections. Microbial DNA is frequently methylated at the N⁶ position of adenines (m6A), a modification that is rare in mammalian host DNA. We show here how that m6A methylation of 5′-GATC-3′ motifs augments the immunogenicity of synthetic double-stranded (ds)DNA in murine macrophages and dendritic cells. Transfection with m6A-methylated DNA increased the expression of the activation markers CD69 and CD86, and of Ifnβ, iNos and Cxcl10 mRNA. Similar to unmethylated cytosolic dsDNA, recognition of m6A DNA occurs independently of TLR and RIG-I signalling, but requires the two key mediators of cytosolic DNA sensing, STING and cGAS. Intriguingly, the response to m6A DNA is sequence-specific. m6A is immunostimulatory in some motifs, but immunosuppressive in others, a feature that is conserved between mouse and human macrophages. In conclusion, epigenetic alterations of DNA depend on the context of the sequence and are differentially perceived by innate cells, a feature that could potentially be used for the design of immune-modulating therapeutics.

S-deoxydihydroglyparvin from Glycosmis parva inhibits lipopolysaccharide induced murine macrophage activation through inactivating p38 mitogen activated protein kinase

Macrophages play major roles to produce several pro-inflammatory and inflammatory mediators in chronic inflammatory diseases. All current anti-inflammatory drugs target these mediators to alleviate inflammation. Searching for new anti-inflammatory agents is always needed due to problems from the clinical use of current anti-inflammatory drugs. We intended to evaluate the anti-inflammatory potential of three main compounds, arborinine, methylatalaphylline, and S-deoxydihydroglyparvin (DDGP), from Glycosmis parva leaves and branches on macrophage stimulated by lipopolysaccharide (LPS). Only DDGP demonstrated a potent inhibitor of LPS-activated macrophages. Results indicated that the mRNA level of inducible nitric oxide synthase (iNOS) was inhibited by the treatment in accompany with the decreased nitric oxide (IC50 at 3.47 ± 0.1 μM). DDGP was shown to suppress tumor necrosis factor-α, interleukin (IL)-1, and IL-6 at the mRNA expression and at the released protein levels. In addition, DDGP inhibited the several chemokines, monocyte chemoattractant protein-1 and macrophage inflammatory proteins-1α, and enzymes for prostaglandin (PG) synthesis. It also inhibited PGE2 production. On LPS signaling pathways, DDGP profoundly decreased phosphorylation of p38 mitogen-activated protein kinase (MAPK) in the LPS-treated cells. It had little or no effect on the activation of JNK, ERK and nuclear factor kappa B. In conclusion, results suggested that DDGP from G. parva inhibited expression and production of inflammatory molecules in LPS-activated macrophages through suppressing p38 MAPK activation. DDGP should be a good candidate anti-inflammatory agent in the future.

LPS Preconditioning Attenuates Apoptosis Mechanism by Inhibiting NF-κB and Caspase-3 Activity: TLR4 Pre-activation in the Signaling Pathway of LPS-Induced Neuroprotection

Neuroinflammation, an inflammatory response within the nervous system, has been shown to be implicated in the progression of various neurodegenerative diseases. Recent in vivo studies showed that lipopolysaccharide (LPS) preconditioning provides neuroprotection by activating Toll-like receptor 4 (TLR4), one of the members for pattern recognition receptor (PRR) family that play critical role in host response to tissue injury, infection, and inflammation. Pre-exposure to low dose of LPS could confer a protective state against cellular apoptosis following subsequent stimulation with LPS at higher concentration, suggesting a role for TLR4 pre-activation in the signaling pathway of LPS-induced neuroprotection. However, the precise molecular mechanism associated with this protective effect is not well understood. In this article, we provide an overall review of the current state of our knowledge about LPS preconditioning in attenuating apoptosis mechanism and conferring neuroprotection via TLR4 signaling pathway.