Intracellular recognition of lipopolysaccharide by toll-like receptor 4 in intestinal epithelial cells

Heat-Induced Secretion of Heat Shock Proteins 70 and 90 Does not Affect the Expression of the Glucocorticoid Receptor in Primary Airway Cells in COPD

PURPOSE

The response to glucocorticoids is hampered in many COPD patients by a yet unknown mechanism. Earlier we reported that short-term heat exposure of primary human bronchial epithelial cells (BEC) and airway smooth muscle cells (ASMC) of asthma patients increased the expression and secretion of extracellular heat shock proteins (eHSPs) resulting in increased expression of glucocorticoid receptor (GR) in BEC and inhibition of ASMC remodeling. The aim of the present study was to assess if the same mechanism is also present in primary airway wall cells of COPD patients.

METHODS

Primary BEC and ASMC were established from endobronchial biopsies obtained from COPD patients (n = 73), who participated in the HISTORIC study, an investigator-initiated and driven clinical trial. Secretion and protein expression of HSPs was assessed by ELISA and Western blotting. Expression of total GR, its isoforms GRα and GRβ and toll-like receptor 4 (TLR4) was determined by Western-blotting.

RESULTS

Short heat exposure (65 °C, 10 s) of BEC resulted in a significant increase of the secretion of eHSP70 and eHSP90, while the intracellular protein was not altered. Heat treatment or exposure to eHSP70 or eHSP90 had no effect on the expression of GR and GR-isoforms. However, eHSP70 and eHSP90 significantly reduced the expression of TLR4.

CONCLUSIONS

The results of this study indicate that primary airway cells from COPD patients respond differently to heat exposure and extracellular HSP70 or HSP90 than cells from asthma patients regarding the expression of GR and this may explain the reduced response to glucocorticoids in patients with COPD.

TRIAL REGISTRATION

ISRCTN11017699.

Manganese@Albumin Nanocomplex and Its Assembled Nanowire Activate TLR4-Dependent Signaling Cascades of Macrophages

The immunomodulatory effect of divalent manganese cations (Mn2+ ), such as activation of the cGAS-STING pathway or NLRP3 inflammasomes, positions them as adjuvants for cancer immunotherapy. In this study, it is found that trace Mn2+ ions, bound to bovine serum albumin (BSA) to form Mn@BSA nanocomplexes, stimulate pro-inflammatory responses in human- or murine-derived macrophages through TLR4-mediated signaling cascades. Building on this, the assembly of Mn@BSA nanocomplexes to obtain nanowire structures enables stronger and longer-lasting immunostimulation of macrophages by regulating phagocytosis. Furthermore, Mn@BSA nanocomplexes and their nanowires efficiently activate peritoneal macrophages, reprogramme tumor-associated macrophages, and inhibit the growth of melanoma tumors in vivo. They also show better biosafety for potential clinical applications compared to typical TLR4 agonists such as lipopolysaccharides. Accordingly, the findings provide insights into the mechanism of metalloalbumin complexes as potential TLR agonists that activate macrophage polarization and highlight the importance of their nanostructures in regulating macrophage-mediated innate immunity.

Losartan as a Reproposing Therapeutic Agent in Acute Respiratory Distress Syndrome: Modulating Inflammatory Responses and Cytokine Production

Seeking a new drug has become a significant milestone in drug discovery. However, it might not be immediately used in urgent situations or during a pandemic. Acute Respiratory Distress Syndrome (ARDS) contributes to mild-to-severe symptoms in patients due to cytokine storms, leading to morbidity and mortality. Hypertension is recognized as an independent risk factor for the severity of ARDS regarding to both ACE Inhibitors (ACEIs) and Angiotensin Receptor Blockers (ARBs) treatment, although the precise mechanism remains unclear. In this study, murine macrophage cell lines (RAW264.7) and alveolar epithelial type II-like cell lines (A549) were utilized to investigate the effect of Losartan (LOS). LOS attenuated nitric oxide production in a dose-dependent manner and collectively reduced intracellular reactive oxygen species (ROS) compared to Diclofenac under LPS-stimulation conditions. For ADRS-mimicking conditions, LPS-induced inflammatory A549 cells were performed to monitor the effect of LOS. The results showed that LOS exhibited a protective effect by increasing cell viability and decreasing intracellular ROS levels. Notably, a high dose of LOS increased intracellular ROS levels. Moreover, LOS treatment downregulated NF-kappaB activation and AT1R at the protein level. Correspondingly, proinflammatory mediator cytokines (TNF-alpha and IL-8) were downregulated, but not IL-6, during LOS treatment. Hence, LOS may provide substantial benefits to ARDS patients by modulating proinflammatory cytokine production through AT1R downregulation and NF-kappaB inactivation. The mechanistic insight into LOS's anti-inflammatory effect holds promise for reducing mortality rates among ARDS patients.

Lipopolysaccharide Stimulates A549 Cell Migration through p-Tyr 42 RhoA and Phospholipase D1 Activity

Cell migration is a crucial contributor to metastasis, a critical process associated with the mortality of cancer patients. The initiation of metastasis is triggered by epithelial-mesenchymal transition (EMT), along with the changes in the expression of EMT marker proteins. Inflammation plays a significant role in carcinogenesis and metastasis. Lipopolysaccharide (LPS), a typical inflammatory agent, promoted the generation of superoxide through the activation of p-Tyr42 RhoA, Rho-dependent kinase 2 (ROCK2), and the phosphorylation of p47phox. In addition, p-Tyr42 RhoA activated phospholipase D1 (PLD1), with PLD1 and phosphatidic acid (PA) being involved in superoxide production. PA also regulated the expression of EMT proteins. Consequently, we have identified MHY9 (Myosin IIA, NMIIA) as a PA-binding protein in response to LPS. MYH9 also contributed to cell migration and the alteration in the expression of EMT marker proteins. Co-immunoprecipitation revealed the formation of a complex involving p-Tyr42 RhoA, PLD1, and MYH9. These proteins were found to be distributed in both the cytosol and nucleus. In addition, we have found that p-Tyr42 RhoA PLD1 and MYH9 associate with the ZEB1 promoter. The suppression of ZEB1 mRNA levels was achieved through the knockdown of RhoA, PLD1, and MYH9 using si-RNAs. Taken together, we propose that p-Tyr42 RhoA and PLD1, responsible for producing PA, and PA-bound MYH9 are involved in the regulation of ZEB1 expression, thereby promoting cell migration.

Know your neighbors: microbial recognition at the intestinal barrier and its implications for gut homeostasis and inflammatory bowel disease

Intestinal epithelial cells (IECs) perform several physiological and metabolic functions at the epithelial barrier. IECs also play an important role in defining the overall immune functions at the mucosal region. Pattern recognition receptors (PRRs) on the cell surface and in other cellular compartments enable them to sense the presence of microbes and microbial products in the intestinal lumen. IECs are thus at the crossroads of mediating a bidirectional interaction between the microbial population and the immune cells present at the intestinal mucosa. This communication between the microbial population, the IECs and the underlying immune cells has a profound impact on the overall health of the host. In this review, we focus on the various PRRs present in different cellular compartments of IECs and discuss the recent developments in the understanding of their role in microbial recognition. Microbial recognition and signaling at the epithelial barrier have implications in the maintenance of intestinal homeostasis, epithelial barrier function, maintenance of commensals, and the overall tolerogenic function of PRRs in the gut mucosa. We also highlight the role of an aberrant microbial sensing at the epithelial barrier in the pathogenesis of inflammatory bowel disease (IBD) and the development of colorectal cancer.

The Lung Microbiome in Carcinogenesis and Immunotherapy Treatment

ABSTRACT

Lung cancer is the leading cause of cancer-related deaths. Over the past 10 years, significant advances in treatment modalities, including immune checkpoint inhibitor (ICI) blockade, have led to improved outcomes. Elucidating predicative biomarkers in responders and nonresponders to ICI will lead to development of therapeutic targets that could enhance ICI efficacy. Recently, the gut microbiome was identified as a predictive biomarker for ICI in patients with multiple cancer types. However, it is unclear how other host microbiomes influence tumorigenesis and response to ICI. Other groups have explored the lung microbiome as it relates to carcinogenesis and immunotherapy efficacy. In this review, we explore the role of the lung microbiome in health and disease. We also review the current state of lung microbiome research as it relates to tumorigenesis and treatments and provide potential insights into how the lung microbiome could improve outcomes in patients with cancer.

Antimicrobial peptides could antagonize uncontrolled inflammation via Toll-like 4 receptor

Antimicrobial peptides are part of the organism's defense system. They are multifunctional molecules capable of modulating the host's immune system and recognizing molecules present in pathogens such as lipopolysaccharides (LPSs). LPSs are recognized by molecular patterns associated with pathogens known as Toll-like receptors (TLRs) that protect the organism from pathological microorganisms. TLR4 is responsible for LPS recognition, thus inducing an innate immune response. TLR4 hyperstimulation induces the uncontrolled inflammatory process that is observed in many illnesses, including neurodegenerative, autoimmune and psoriasis). Molecules that act on TLR4 can antagonize the exacerbated inflammatory process. In this context, antimicrobial peptides (AMPs) are promising molecules capable of mediating toll-like receptor signaling. Therefore, here we address the AMPs studied so far with the aim of inhibiting the intense inflammatory process. In addition, we aim to explore some of the interactions between exogenous AMPs and TLR4.

The subversion of toll-like receptor signaling by bacterial and viral proteases during the development of infectious diseases

Toll-like receptors (TLRs) are pattern recognition receptors (PRRs) that respond to pathogen-associated molecular patterns (PAMPs). The recognition of specific microbial ligands by TLRs triggers an innate immune response and also promotes adaptive immunity, which is necessary for the efficient elimination of invading pathogens. Successful pathogens have therefore evolved strategies to subvert and/or manipulate TLR signaling. Both the impairment and uncontrolled activation of TLR signaling can harm the host, causing tissue destruction and allowing pathogens to proliferate, thus favoring disease progression. In this context, microbial proteases are key virulence factors that modify components of the TLR signaling pathway. In this review, we discuss the role of bacterial and viral proteases in the manipulation of TLR signaling, highlighting the importance of these enzymes during the development of infectious diseases.

Vitamin D and COVID-19: Narrative Review after 3 Years of Pandemic

Active vitamin D [1,25(OH)₂D₃-calcitriol] is a secosteroid hormone whose receptor is expressed on all cells of the immune system. Vitamin D has a global anti-inflammatory effect and its role in the management of a SARS-CoV-2 infection has been investigated since the beginning of the COVID-19 pandemic. In this narrative review, the laboratory and clinical results of a vitamin D supplementation have been collected from both open-label and blinded randomized clinical trials. The results are generally in favor of the utility of maintaining the serum concentrations of calcifediol [25(OH)D₃] at around 40 ng/mL and of the absolute usefulness of its supplementation in subjects with deficient serum levels. However, two very recent large-scale studies (one open-label, one placebo-controlled) have called into question the contribution of vitamin D to clinical practice in the era of COVID-19 vaccinations. The precise role of a vitamin D supplementation in the anti-COVID-19 armamentarium requires further investigations in light of the breakthrough which has been achieved with mass vaccinations.

Carbon monoxide mechanism of protection against renal ischemia and reperfusion injury

Carbon monoxide is quickly moving past its historic label as a molecule once feared, to a therapeutic drug that modulates inflammation. The development of carbon monoxide releasing molecules and utilization of heme oxygenase-1 inducers have shown carbon monoxide to be a promising therapy in reducing renal ischemia and reperfusion injury and other inflammatory diseases. In this review, we will discuss the developments and application of carbon monoxide releasing molecules in renal ischemia and reperfusion injury, and transplantation. We will review the anti-inflammatory mechanisms of carbon monoxide in respect to mitigating apoptosis, suppressing dendritic cell maturation and signalling, inhibiting toll-like receptor activation, promoting anti-inflammatory responses, and the effects on renal vasculature.

Fish-specific TLR18 in Nile tilapia (Oreochromis niloticus) recruits MyD88 and TRIF to induce expression of effectors in NF-κB and IFN pathways in melanomacrophages

Toll-like receptors (TLRs) are evolutionarily conserved proteins of pattern recognition receptors (PRRs) and play a crucial role in innate immune systems recognition of conserved pathogen-related molecular samples (PAMPs). We identified and characterized TLR18 from Nile tilapia (Oreochromis niloticus), OnTLR18, to elucidate its role in tissue expression patterns, modulation of gene expression after microbial challenge and TLR ligands, subcellular localization in fish and human cells, and the possible effectors TLR18 induces in a melanomacrophage-like cell line (tilapia head kidney (THK) cells). OnTLR18 expression was detected in all tissues examined, with the highest levels in the intestine and the lowest in the liver. OnTLR18 transcript was up-regulated in immune-related organs after bacterial and polyinosinic-polycytidylic acid (poly I:C) challenges and in the THK cells after lipopolysaccharide (LPS) stimulation. In transfected THK and human embryonic kidney (HEK) 293 cells, OnTLR18 localizes in the intracellular compartment. OnMyD88 and OnTRIF, but not OnTIRAP, were co-immunoprecipitated with OnTLR18, suggesting that the former two molecules are recruited by OnTLR18 as adaptors. The constitutively active form of OnTLR18 induced the production of pro-inflammatory cytokines, type I interferon (IFN), and antimicrobial peptides such as tumor necrosis factor α, interferon (IFN) d2.13, tilapia piscidin (TP)2, TP3, TP4, and hepcidin in THK cells. Our results suggest that OnTLR18 plays an important role in innate immunity through initiating nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and IFN signaling pathways via OnMyD88 and OnTRIF and induces the production of various effectors in melanomacrophages.

Intercrypt sentinel macrophages tune antibacterial NF-κB responses in gut epithelial cells via TNF

Intestinal epithelial cell (IEC) NF-κB signaling regulates the balance between mucosal homeostasis and inflammation. It is not fully understood which signals tune this balance and how bacterial exposure elicits the process. Pure LPS induces epithelial NF-κB activation in vivo. However, we found that in mice, IECs do not respond directly to LPS. Instead, tissue-resident lamina propria intercrypt macrophages sense LPS via TLR4 and rapidly secrete TNF to elicit epithelial NF-κB signaling in their immediate neighborhood. This response pattern is relevant also during oral enteropathogen infection. The macrophage-TNF-IEC axis avoids responses to luminal microbiota LPS but enables crypt- or tissue-scale epithelial NF-κB responses in proportion to the microbial threat. Thereby, intercrypt macrophages fulfill important sentinel functions as first responders to Gram-negative microbes breaching the epithelial barrier. The tunability of this crypt response allows the induction of defense mechanisms at an appropriate scale according to the localization and intensity of microbial triggers.

Toll-Like Receptors in Adaptive Immunity

The immune (innate and adaptive) system has evolved to protect the host from any danger present in the surrounding outer environment (microbes and associated MAMPs or PAMPs, xenobiotics, and allergens) and dangers originated within the host called danger or damage-associated molecular patterns (DAMPs) and recognizing and clearing the cells dying due to apoptosis. It also helps to lower the tissue damage during trauma and initiates the healing process. The pattern recognition receptors (PRRs) play a crucial role in recognizing different PAMPs or MAMPs and DAMPs to initiate the pro-inflammatory immune response to clear them. Toll-like receptors (TLRs) are first recognized PRRs and their discovery proved milestone in the field of immunology as it filled the gap between the first recognition of the pathogen by the immune system and the initiation of the appropriate immune response required to clear the infection by innate immune cells (macrophages, neutrophils, dendritic cells or DCs, and mast cells). However, in addition to their expression by innate immune cells and controlling their function, TLRs are also expressed by adaptive immune cells. We have identified 10 TLRs (TLR1-TLR10) in humans and 12 TLRs (TLR1-TLR13) in laboratory mice till date as TLR10 in mice is present only as a defective pseudogene. The present chapter starts with the introduction of innate immunity, timing of TLR evolution, and the evolution of adaptive immune system and its receptors (T cell receptors or TCRs and B cell receptors or BCRs). The next section describes the role of TLRs in the innate immune function and signaling involved in the generation of inflammation. The subsequent sections describe the expression and function of different TLRs in murine and human adaptive immune cells (B cells and different types of T cells, including CD4⁺T cells, CD8⁺T cells, CD4⁺CD25⁺T_regs, and CD8⁺CD25⁺T_regs, etc.). The modulation of TLRs expressed on T and B cells has a great potential to develop different vaccine candidates, adjuvants, immunotherapies to target various microbial infections, including current COVID-19 pandemic, cancers, and autoimmune and autoinflammatory diseases.

Polymorphisms in genes related to oxidative stress and inflammation: Emerging links with the pathogenesis and severity of Cerebral Cavernous Malformation disease

Cerebral Cavernous Malformation (CCM) is a cerebrovascular disease of genetic origin affecting 0.5% of the population and characterized by abnormally enlarged and leaky capillaries that predispose to seizures, neurological deficits, and intracerebral hemorrhage (ICH). CCM occurs sporadically or is inherited as dominant condition with incomplete penetrance and highly variable expressivity. Three disease genes have been identified: KRIT1 (CCM1), CCM2 and CCM3. Previous results demonstrated that loss-of-function mutations of CCM genes cause pleiotropic effects, including defective autophagy, altered reactive oxygen species (ROS) homeostasis, and enhanced sensitivity to oxidative stress and inflammatory events, suggesting a novel unifying pathogenetic mechanism, and raising the possibility that CCM disease onset and severity are influenced by the presence of susceptibility and modifier genes. Consistently, genome-wide association studies (GWAS) in large and homogeneous cohorts of patients sharing the familial form of CCM disease and identical mutations in CCM genes have led to the discovery of distinct genetic modifiers of major disease severity phenotypes, such as development of numerous and large CCM lesions, and susceptibility to ICH. This review deals with the identification of genetic modifiers with a significant impact on inter-individual variability in CCM disease onset and severity, including highly polymorphic genes involved in oxidative stress, inflammatory and immune responses, such as cytochrome P450 monooxygenases (CYP), matrix metalloproteinases (MMP), and Toll-like receptors (TLR), pointing to their emerging prognostic value, and opening up new perspectives for risk stratification and personalized medicine strategies.

Lipopolysaccharide promotes metastasis via acceleration of glycolysis by the nuclear factor-κB/snail/hexokinase3 signaling axis in colorectal cancer

BACKGROUND

Cancer cell is generally characterized by enhanced glycolysis. Inflammasome activation is interaction with glycolysis. The concentration of lipopolysaccharide (LPS), a classic inflammasome activator, is significantly higher in colorectal cancer tissue than in normal intestinal mucosa. However, the mechanism of LPS on glycolysis and metastasis has not been fully elucidated. This study aimed to investigate the roles of LPS on inflammasome activation, glycolysis, and metastasis, and unravel metformin's potential in treatment of CRC.

METHODS

We detected inflammasome activation and cell motility following LPS exposure in CRC cell lines. Glycolysis analysis was performed, and the key glycolytic rate-limiting enzymes were detected. Dual-luciferase reporter gene assay, co-immunoprecipitation, chromatin immunoprecipitation (ChIP) analysis, and ChIP-reChIP assay were performed to identify the specific mechanisms of LPS on glycolysis. Mouse metastasis models were used to determine the effects of LPS and metformin on metastasis. Correlation analysis of the expression of various molecules was performed in 635 CRC samples from The Cancer Genome Atlas and 83 CRC samples from our lab.

RESULTS

LPS activates caspase-1 through NF-κB and upregulates the expression of Snail and HK3 depending on caspase-1 activation. LPS potentiates migration and invasion depending on accelerated glycolysis, which could be reversed by knockdown of glycolytic rate-limiting enzyme HK3. Nuclear Snail is upregulated by NF-κB under LPS treatment and then forms a complex with NF-κB, then directly binds to the HK3 promoter region to upregulate the expression of HK3. Metformin suppresses the NF-κB/Snail/HK3 signaling axis that is activated by LPS and then inhibits LPS-induced metastasis. In vivo, LPS-treated cells form more metastasis in the lungs of mice, and metformin completely reverses this effect of LPS.

CONCLUSION

LPS activates inflammasomes in cancer cells through NF-κB and promotes metastasis through glycolysis enhanced by the NF-κB/Snail/HK3 signaling pathway in CRC. Metformin could prevent this effect of LPS.

Location-specific cell identity rather than exposure to GI microbiota defines many innate immune signalling cascades in the gut epithelium

OBJECTIVE

The epithelial layer of the GI tract is equipped with innate immune receptors to sense invading pathogens. Dysregulation in innate immune signalling pathways is associated with severe inflammatory diseases, but the responsiveness of GI epithelial cells to bacterial stimulation remains unclear.

DESIGN

We generated 42 lines of human and murine organoids from gastric and intestinal segments of both adult and fetal tissues. Genome-wide RNA-seq of the organoids provides an expression atlas of the GI epithelium. The innate immune response in epithelial cells was assessed using several functional assays in organoids and two-dimensional monolayers of cells from organoids.

RESULTS

Results demonstrate extensive spatial organisation of innate immune signalling components along the cephalocaudal axis. A large part of this organisation is determined before birth and independent of exposure to commensal gut microbiota. Spatially restricted expression of Toll-like receptor 4 (Tlr4) in stomach and colon, but not in small intestine, is matched by nuclear factor kappa B (NF-κB) responses to lipopolysaccharide (LPS) exposure. Gastric epithelial organoids can sense LPS from the basal as well as from the apical side.

CONCLUSION

We conclude that the epithelial innate immune barrier follows a specific pattern per GI segment. The majority of the expression patterns and the function of TLR4 is encoded in the tissue-resident stem cells and determined primarily during development.

Plasma Lipopolysaccharide-Binding Protein Reflects Risk and Progression of Parkinson's Disease

BACKGROUND

Lipopolysaccharide-binding protein (LBP) presents bacterial endotoxin, lipopolysaccharides, to cellular surface pattern receptors for immune responses in the gut-brain axis of Parkinson's disease (PD).

OBJECTIVE

We investigated whether plasma LBP levels were associated with PD severity and progression.

METHODS

This study included 397 participants (248 PD patients and 149 controls). We measured participants' plasma levels of LBP and pro-inflammatory cytokines, including TNF-α, IL-6, andIL-17A. PD patients underwent motor and cognition evaluations at baseline and at a mean follow-up interval of 4.7±2.3 years. We assessed the progression of motor and cognition symptoms based on changes in the Movement Disorder Society-Unified Parkinson's Disease Rating Scale (MDS-UPDRS) part III motor score and Mini-Mental State Examination (MMSE) score, respectively.

RESULTS

Plasma LBP levels were lower in PD patients than controls (9.08±2.91 vs. 10.10±3.00μg/ml, p < 0.01). A multiple logistic regression model with adjustment for age, sex, and plasma cytokine levels revealed that reduced plasma LBP levels were associated with increased PD risk (odds ratio 0.816, [95% CI 0.717-0.929], p = 0.002). Among PD patients, LBP levels were correlated with MDS-UPDRS part III motor score after adjustment for confounders (coefficient = 0.636, p = 0.017), but not with MMSE score. Adjusted Cox regression analysis showed that higher plasma LBP levels associated with faster motor progression (adjusted hazard ratio 1.084 [95% CI 1.011-1.163], p = 0.024) during follow-up.

CONCLUSION

Our results demonstrated that plasma LBP levels reflect risk, motor symptom severity and progression in patients with PD.

Molecular characterization and functional analysis of duck IKKα

IκB kinase α (IKKα) is a vital component of the IKK complex, which is involved in innate immune response, inflammation, cell death and proliferation. Although the functional characteristics of IKKα have been extensively studied in mammals and fish, the roles of IKKα in avian remain largely unknown. In this study, we cloned and characterized the duck IKKα (duIKKα) gene for the first time. DuIKKα encoded a protein of 757 amino acid residues and showed high sequence identities with the goose IKKα. The duIKKα was expressed in all tested tissues, and a relatively high expression of duIKKα mRNA was detected in liver and heart. Overexpression of duIKKα dramatically increased NF-κB activity and induced the expression of duck cytokines IFN-β, IL-1β, IL-6, IL-8 and RANTES in DEFs. Knockdown of duIKKα by small interfering RNA significantly decreased LPS-, poly(I:C)-, poly(dA:dT)-, duck enteritis virus (DEV)-, or duck Tembusu virus (DTMUV)-induced NF-κB activation. Moreover, duIKKα exhibited antiviral activity against DTMUV infection. These findings provide important insights into the roles of duIKKα in avian innate immunity.

The Lung Microbiome: A Central Mediator of Host Inflammation and Metabolism in Lung Cancer Patients?

Simple Summary

Lung cancer is the major cause of cancer related deaths in the world. New therapies have improved outcomes. Unfortunately, overall 5 year survival is ~20%. Therefore, better understanding of tumor biology and the microenvironment may lead to new therapeutic targets. The lung microbiome has recently emerged as a major mediator of host inflammation and pathogenesis. Understanding how the lung microbiota exerts its effects on lung cancer and the tumor microenvironment will allow for novel development of therapies.

Abstract

Lung cancer is the leading cause of cancer-related death. Over the past 5–10 years lung cancer outcomes have significantly improved in part due to better treatment options including immunotherapy and molecularly targeted agents. Unfortunately, the majority of lung cancer patients do not enjoy durable responses to these new treatments. Seminal research demonstrated the importance of the gut microbiome in dictating responses to immunotherapy in melanoma patients. However, little is known regarding how other sites of microbiota in the human body affect tumorigenesis and treatment responses. The lungs were traditionally thought to be a sterile environment; however, recent research demonstrated that the lung contains its own dynamic microbiota that can influence disease and pathophysiology. Few studies have explored the role of the lung microbiome in lung cancer biology. In this review article, we discuss the links between the lung microbiota and cancer, with particular focus on immune responses, metabolism and strategies to target the lung microbiome for cancer prevention.

Cathelicidin-mediated lipopolysaccharide signaling via intracellular TLR4 in colonic epithelial cells evokes CXCL8 production

We hypothesized that the antimicrobial peptide cathelicidin has a physiological role in regulating gut inflammatory homeostasis. We determined that cathelicidin synergizes with LPS to facilitate its internalization and signaling via endosomic TLR4 in colonic epithelium, evoking synthesis of the human neutrophil chemoattractant, CXCL8 (or murine homolog, CXCL1). Interaction of cathelicidin with LPS in the control of CXCL8/CXCL1 synthesis was assessed in human colon epithelial cells, murine colonoids and cathelicidin-null mice (Camp^-/- ). Mechanistically, human cathelicidin (LL-37), as an extracellular complex with LPS, interacted with lipid raft-associated GM1 gangliosides to internalize and activate intracellular TLR4. Two signaling pathways converged on CXCL8/CXCL1 production: (1) a p38MAPK-dependent pathway regulated by Src-EGFR kinases; and, (2) a p38MAPK-independent, NF-κB-dependent pathway, regulated by MEK1/2-MAPK. Increased cathelicidin-dependent CXCL8 secretion in the colonic mucosa activated human blood-derived neutrophils. These cathelicidin effects occurred in vitro at concentrations well below those needed for microbicidal function. The important immunomodulatory role of cathelicidins was evident in cathelicidin-null/Camp^-/- mice, which had diminished colonic CXCL1 secretion, decreased neutrophil recruitment-activation and reduced bacterial clearance when challenged with the colitis-inducing murine pathogen, Citrobacter rodentium. We conclude that in addition to its known microbicidal action, cathelicidin has a unique pathogen-sensing role, facilitating LPS-mediated intestinal responses, including the production of CXCL8/CXCL1 that would contribute to an integrated tissue response to recruit neutrophils during colitis.

TAK1: a potent tumour necrosis factor inhibitor for the treatment of inflammatory diseases

Aberrant tumour necrosis factor (TNF) signalling is a hallmark of many inflammatory diseases including rheumatoid arthritis (RA), irritable bowel disease and lupus. Maladaptive TNF signalling can lead to hyper active downstream nuclear factor (NF)-κβ signalling in turn amplifying a cell's inflammatory response and exacerbating disease. Within the TNF intracellular inflammatory signalling cascade, transforming growth factor-β-activated kinase 1 (TAK1) has been shown to play a critical role in mediating signal transduction and downstream NF-κβ activation. Owing to its role in TNF inflammatory signalling, TAK1 has become a potential therapeutic target for the treatment of inflammatory diseases such as RA. This review highlights the current development of targeting the TNF-TAK1 signalling axis as a novel therapeutic strategy for the treatment of inflammatory diseases.

Caspase-11 Non-canonical Inflammasomes in the Lung

The airway epithelium and underlying innate immune cells comprise the first line of host defense in the lung. They recognize pathogen-associated molecular patterns (PAMPs) using membrane-bound receptors, as well as cytosolic receptors such as inflammasomes. Inflammasomes activate inflammatory caspases, which in turn process and release the inflammatory cytokines IL-1β and IL-18. Additionally, inflammasomes trigger a form of lytic cell death termed pyroptosis. One of the most important inflammasomes at the host-pathogen interface is the non-canonical caspase-11 inflammasome that responds to LPS in the cytosol. Caspase-11 is important in defense against Gram-negative pathogens, and can drive inflammatory diseases such as LPS-induced sepsis. However, pathogens can employ evasive strategies to minimize or evade host caspase-11 detection. In this review, we present a comprehensive overview of the function of the non-canonical caspase-11 inflammasome in sensing of cytosolic LPS, and its mechanism of action with particular emphasis in the role of caspase-11 in the lung. We also explore some of the strategies pathogens use to evade caspase-11.

The lung microbiota: role in maintaining pulmonary immune homeostasis and its implications in cancer development and therapy

Like other body districts, lungs present a complex bacteria community. An emerging function of lung microbiota is to promote and maintain a state of immune tolerance, to prevent uncontrolled and not desirable inflammatory response caused by inhalation of harmless environmental stimuli. This effect is mediated by a continuous dialog between commensal bacteria and immune cells resident in lungs, which express a repertoire of sensors able to detect microorganisms. The same receptors are also involved in the recognition of pathogens and in mounting a proper immune response. Due to its important role in preserving lung homeostasis, the lung microbiota can be also considered a mirror of lung health status. Indeed, several studies indicate that lung bacterial composition drastically changes during the occurrence of pulmonary pathologies, such as lung cancer, and the available data suggest that the modifications of lung microbiota can be part of the etiology of tumors in lungs and can influence their progression and response to therapy. These results provide the scientific rationale to analyze lung microbiota composition as biomarker for lung cancer and to consider lung microbiota a new potential target for therapeutic intervention to reprogram the antitumor immune microenvironment. In the present review, we discussed about the role of lung microbiota in lung physiology and summarized the most relevant data about the relationship between lung microbiota and cancer.

Targeting drug delivery in the vascular system: Focus on endothelium

The bloodstream is the main transporting pathway for drug delivery systems (DDS) from the site of administration to the intended site of action. In many cases, components of the vascular system represent therapeutic targets. Endothelial cells, which line the luminal surface of the vasculature, play a tripartite role of the key target, barrier, or victim of nanomedicines in the bloodstream. Circulating DDS may accumulate in the vascular areas of interest and in off-target areas via mechanisms bypassing specific molecular recognition, but using ligands of specific vascular determinant molecules enables a degree of precision, efficacy, and specificity of delivery unattainable by non-affinity DDS. Three decades of research efforts have focused on specific vascular targeting, which have yielded a multitude of DDS, many of which are currently undergoing a translational phase of development for biomedical applications, including interventions in the cardiovascular, pulmonary, and central nervous systems, regulation of endothelial functions, host defense, and permeation of vascular barriers. We discuss the design of endothelial-targeted nanocarriers, factors underlying their interactions with cells and tissues, and describe examples of their investigational use in models of acute vascular inflammation with an eye on translational challenges.

The Role of Hyaluronan Treatment in Intestinal Innate Host Defense

Hyaluronan (HA) is best known as an abundantly present extracellular matrix component found throughout the body of all vertebrates, including humans. Recent evidence, however, has demonstrated benefits of providing HA exogenously as a therapeutic modality for several medical conditions. Here we discuss the effects of providing HA treatment to increase innate host defense of the intestine, elucidate the size specific effects of HA, and discuss the role of various HA receptors as potential mediators of the HA effects in the intestine. This review especially focuses on HA interaction with the epithelium because it is the primary cellular barrier of the intestine and these cells play a critical balancing role between allowing water and nutrient absorption while excluding microbes and harmful dietary metabolites that are constantly in that organ's environment.

Polymorphisms in the P2X7 receptor, and differential expression of Toll-like receptor-mediated cytokines and defensins, in a Canadian Indigenous group

Canadian Indigenous peoples (First Nations and Inuit) exhibit a high burden of infectious diseases including tuberculosis influenced by societal factors, and biological determinants. Toll-like receptor (TLR)-mediated innate immune responses are the first line of defence against infections. We examined the production of a panel of 30 cytokines in peripheral blood-derived mononuclear cells (PBMC) isolated from Indigenous and non-Indigenous participants, following stimulation with five different TLR ligands. The levels of TLR-induced pro-inflammatory cytokines such as IL-12/23p40, IL-16, and IFN-γ, and chemokines (MCP-4, MDC and eotaxin) were different between Indigenous compared to non-Indigenous participants. Antimicrobial cationic host defence peptides (CHDP) induced by TLR activation are critical for resolution of infections and modulate the TLR-to-NFκB pathway to alter downstream cytokine responses. Therefore, we examined the expression of human CHDP defensins and cathelicidin in PBMC. mRNA expression of genes encoding for def-A1 and def-B1 were significantly higher following stimulation with TLR ligands in Indigenous compared to non-Indigenous participants. The purinergic receptor P2X7 known to be activated by ATP released following TLR stimulation, is a receptor for CHDP. Therefore, we further examined single nucleotide polymorphisms (SNP) in P2X7. Indigenous participants had a significantly higher percentage of a P2X7 SNP which is associated with reduced function and lower ability to clear infections. These results suggest that a higher frequency of non-functional P2X7 receptors may influence the activity of downstream immune mediators required for resolution of infections such as pro-inflammatory cytokines and CHDP defensins, thus contributing to higher burden of infections in Indigenous population.

The effects of dihydroxyphenyl lactic acid on alleviating blood-brain barrier injury following subarachnoid hemorrhage in rats

BACKGROUND

In this study, the protective effects of 3,4-dihydroxyphenyl lactic acid (DLA) on blood-brain barrier (BBB) injury following subarachnoid hemorrhage (SAH) has been explored.

METHODS

Male Sprague-Dawley rats (weight 300-350 g) were used to establish the SAH model using the endovascular perforation method. The animals were randomly divided into four groups: sham (n = 40), SAH (n = 46), SAH + vehicle (n = 44), and SAH + DLA (n = 40) treatment groups. At 1 h after SAH, either DLA (10 mg/kg) or normal saline (vehicle) was administered by femoral vein injection. The effects of DLA on mortality, neurological function, brain water content, and BBB were observed. Additionally, immunohistochemistry and western blot techniques were applied to investigate the mechanism of action of DLA.

RESULTS

We found that the administration of DLA (10 mg/kg) following SAH could improve neurological functions, reduce brain water content, and maintain BBB integrity. The expression of pro-inflammatory and pro-apoptotic factors such as toll-like receptor 4 (TLR4), NF-κB (p-p65), tumor necrosis factor-α, p-p38 MAPK, p-p53, and caspase-3 were significantly increased after SAH. These same factors were markedly attenuated following treatment with DLA.

CONCLUSIONS

These findings showed that DLA can alleviate BBB injury following SAH through its anti-inflammatory and anti-apoptotic effects via suppression of TLR4 and its downstream NF-κB and p38 MAPK pathways.

Pro-Inflammatory Responses in Human Bronchial Epithelial Cells Induced by Spores and Hyphal Fragments of Common Damp Indoor Molds

Damp indoor environments contaminated with different mold species may contribute to the development and exacerbation of respiratory illnesses. Human bronchial epithelial BEAS-2B cells were exposed to X-ray treated spores and hyphal fragments from pure cultures of Aspergillus fumigatus, Penicillum chrysogenum, Aspergillus versicolor and Stachybotrys chartarum. Hyphal fragments of A. fumigatus and P. chrysogenum induced expression and release of the pro-inflammatory cytokine interleukin (IL)-6 and the chemokine IL-8, while none of the other hyphal preparations had effects. Hyphal fragments from A. fumigatus and P. chrysogenum also increased the expression of IL-1α, IL-1β and tumor necrosis factor (TNF)-α, but these cytokines were not released. X-ray treated spores had little or no inflammatory potential. Attenuating Toll-like receptor (TLR)-2 by blocking antibodies strongly reduced the A. fumigatus and P. chrysogenum hyphae-induced IL-6 and IL-8 release, whereas TLR4 antagonist treatment was without effects. Untreated A. fumigatus spores formed hyphae and triggered expression of pro-inflammatory genes with similarities to the effects of hyphal fragments. In conclusion, while X-ray treated spores induced no pro-inflammatory responses, hyphal fragments of A. fumigatus and P. chrysogenum enhanced a TLR2-dependent expression and release of IL-6 and IL-8.

Myristoylated rhinovirus VP4 protein activates TLR2-dependent proinflammatory gene expression

Asthma exacerbations are often caused by rhinovirus (RV). We and others have shown that Toll-like receptor 2 (TLR2), a membrane surface receptor that recognizes bacterial lipopeptides and lipoteichoic acid, is required and sufficient for RV-induced proinflammatory responses in vitro and in vivo. We hypothesized that viral protein-4 (VP4), an internal capsid protein that is myristoylated upon viral replication and externalized upon viral binding, is a ligand for TLR2. Recombinant VP4 and myristoylated VP4 (MyrVP4) were purified by Ni-affinity chromatography. MyrVP4 was also purified from RV-A1B-infected HeLa cells by urea solubilization and anti-VP4 affinity chromatography. Finally, synthetic MyrVP4 was produced by chemical peptide synthesis. MyrVP4-TLR2 interactions were assessed by confocal fluorescence microscopy, fluorescence resonance energy transfer (FRET), and monitoring VP4-induced cytokine mRNA expression in the presence of anti-TLR2 and anti-VP4. MyrVP4 and TLR2 colocalized in TLR2-expressing HEK-293 cells, mouse bone marrow-derived macrophages, human bronchoalveolar macrophages, and human airway epithelial cells. Colocalization was absent in TLR2-null HEK-293 cells and blocked by anti-TLR2 and anti-VP4. Cy3-labeled MyrVP4 and Cy5-labeled anti-TLR2 showed an average fractional FRET efficiency of 0.24 ± 0.05, and Cy5-labeled anti-TLR2 increased and unlabeled MyrVP4 decreased FRET efficiency. MyrVP4-induced chemokine mRNA expression was higher than that elicited by VP4 alone and was attenuated by anti-TLR2 and anti-VP4. Cytokine expression was similarly increased by MyrVP4 purified from RV-infected HeLa cells and synthetic MyrVP4. We conclude that, during RV infection, MyrVP4 and TLR2 interact to generate a proinflammatory response.

DNA vaccination for finfish aquaculture

In fish, DNA vaccines have been shown to give very high protection in experimental facilities against a number of viral diseases, particularly diseases caused by rhabdoviruses. However, their efficacy in generating protection against other families of fish viral pathogens is less clear. One DNA vaccine is currently in use commercially in fish farms in Canada and the commercialisation of another was authorised in Europe in 2017. The mechanism of action of DNA vaccines, including the role of the innate immune responses induced shortly after DNA vaccination in the activation of the adaptive immunity providing longer term specific protection, is still not fully understood. In Europe the procedure for the commercialisation of a veterinary DNA vaccine requires the resolution of certain concerns particularly about safety for the host vaccinated fish, the consumer and the environment. Relating to consumer acceptance and particularly environmental safety, a key question is whether a DNA vaccinated fish is considered a Genetically Modified Organism (GMO). In the present opinion paper these key aspects relating to the mechanisms of action, and to the development and the use of DNA vaccines in farmed fish are reviewed and discussed.

Spatially controlled assembly of affinity ligand and enzyme cargo enables targeting ferritin nanocarriers to caveolae

One of the goals of nanomedicine is targeted delivery of therapeutic enzymes to the sub-cellular compartments where their action is needed. Endothelial caveolae-derived endosomes represent an important yet challenging destination for targeting, in part due to smaller size of the entry aperture of caveolae (ca. 30-50 nm). Here, we designed modular, multi-molecular, ferritin-based nanocarriers with uniform size (20 nm diameter) for easy drug-loading and targeted delivery of enzymatic cargo to these specific vesicles. These nanocarriers targeted to caveolar Plasmalemmal Vesicle-Associated Protein (Plvap) deliver superoxide dismutase (SOD) into endosomes in endothelial cells, the specific site of influx of superoxide mediating by such pro-inflammatory signaling as some cytokines and lipopolysaccharide (LPS). Cell studies showed efficient internalization of Plvap-targeted SOD-loaded nanocarriers followed by dissociation from caveolin-containing vesicles and intracellular transport to endosomes. The nanocarriers had a profound protective anti-inflammatory effect in an animal model of LPS-induced inflammation, in agreement with the characteristics of their endothelial uptake and intracellular transport, indicating that these novel, targeted nanocarriers provide an advantageous platform for caveolae-dependent delivery of biotherapeutics.

Herpes simplex virus type 2 infection triggers AP-1 transcription activity through TLR4 signaling in genital epithelial cells

Background

The pattern recognition receptors (PPRs) are the earliest phase of the host defense against pathogens in genital epithelium, and toll-like receptors (TLRs) are best characterized PPRs mediating innate immune responses. Herpes simplex virus type 2 (HSV-2), a member of herpesviridae family, causes one of the most prevalent sexually transmitted infection in the world. In this paper, we described that HSV-2 infection would induce activator protein 1 (AP-1) via TLR4-MyD88/TRIF pathway in human genital epithelial cell.

Methods

TLRs expression profiles and changes was investigated in HSV-2-infected cells. The effect of TLR4-MyD88/TRIF on HSV-2-induced AP-1 activation and viral replication was also evaluated. The TLR4 translocation change was examined after viral infection. Finally, viral ICP0 effect on TLR4 signaling and TLR4-promoter regulation were primarily studied.

Results

HSV-2-induced AP-1 activation was dependent on TLR4 and downstream adaptor molecules MyD88 and TRIF. And also, TLR4, MyD88 and TRIF was proved to affect HSV-2 replication. AP-1 activation would also be enhanced via overexpression of myeloid differentiation protein 2 (MD2), implicating that it might be a necessary accessory for TLR4 to sense HSV-2 infection. Protein quantification of cytoplasmic and membrane-associated TLR4 revealed that HSV-2 infection increased membrane-anchoring TLR4 level, but not cytoplasmic ones. Viral ICP0 could augment cellular AP-1, TLR4 promoter activation and TLR4 expression level. The specific inhibitor treatment and transcription factor binding site scanning in TLR4 promoter region showed that AP-1 activity was essential for TLR4-promoter activation.

Conclusions

Taken together, HSV-2 infection could stimulate AP-1 activation via TLR4-MyD88/TRIF axis, and then feedback to up-regulate TLR4 expression in human genital epithelial cells.

Pulmonary immunity and extracellular matrix interactions

The lung harbors a complex immune system composed of both innate and adaptive immune cells. Recognition of infection and injury by receptors on lung innate immune cells is crucial for generation of antigen-specific responses by adaptive immune cells. The extracellular matrix of the lung, comprising the interstitium and basement membrane, plays a key role in the regulation of these immune systems. The matrix consists of several hundred assembled proteins that interact to form a bioactive scaffold. This template, modified by enzymes, acts to facilitate cell function and differentiation and changes dynamically with age and lung disease. Herein, we explore relationships between innate and adaptive immunity and the lung extracellular matrix. We discuss the interactions between extracellular matrix proteins, including glycosaminoglycans, with prominent effects on innate immune signaling effectors such as toll-like receptors. We describe the relationship of extracellular matrix proteins with adaptive immunity and leukocyte migration to sites of injury within the lung. Further study of these interactions will lead to greater knowledge of the role of matrix biology in lung immunity. The development of novel therapies for acute and chronic lung disease is dependent on a comprehensive understanding of these complex matrix-immunity interactions.

Preventive effects of bovine colostrum supplementation in TNBS-induced colitis in mice

Inflammatory bowel disease (IBD) is a chronic inflammatory disorder for which the current medical therapy is not completely effective. Bovine colostrum (BC) is a biological fluid rich in bioactive molecules that may have beneficial effects on several gastrointestinal disorders. The objectives of this study were to assess the preventive effects of BC supplementation in a mouse model of 2,4,6 trinitrobenzene sulfonic acid (TNBS)-induced colitis using a multidisciplinary approach. Specifically, the following parameters were evaluated: (i) disease activity index (DAI), (ii) histological score, (iii) expression levels of TLR4, anti- and pro-inflammatory cytokines, and (iv) count of some bacterial species of the intestinal microbiota. Mice received a daily suspension of BC (BC group, n = 12) or saline solution (control, CN group, n = 12) for 21 days before the intrarectal inoculation with 1% of TNBS solution. BC was well tolerated and did not induce any histological damage or clinical symptoms. After TNBS treatment, BC group showed a reduction of body weight (BW) loss (P<0.01) and histological score (P<0.05) compared to CN. Moreover, the expression levels of TLR4 (P<0.05), IL-1β (P<0.001), IL-8 (P<0.001), and IL-10 (P<0.001) were lower in mice administered with BC, while the concentrations of TNF-α did not show any differences between groups. Finally, the supplementation with BC resulted in a differential response to TNBS treatment in the bacterial count. In CN group, E. coli and Enterococci increased (P<0.001), while Anaerobes (P<0.01), Lactobacilli, and Bifidobacteria (P<0.001) reduced. Conversely, no significant changes in bacterial load were found after the inoculation of TNBS in BC pre-treated mice. This study confirms that TNBS-induced colitis model in mice is useful for studying the mechanisms involved in IBD pathogenesis and shows that pre-treatment with BC reduces the intestinal damages and clinical signs of the colitis. Molecular mechanisms and intestinal microflora could be involved in the protective effect of colostrum.

Flexible Nanoparticles Reach Sterically Obscured Endothelial Targets Inaccessible to Rigid Nanoparticles

Molecular targeting of nanoparticle drug carriers promises maximized therapeutic impact to sites of disease or injury with minimized systemic effects. Precise targeting demands addressing to subcellular features. Caveolae, invaginations in cell membranes implicated in transcytosis and inflammatory signaling, are appealing subcellular targets. Caveolar geometry has been reported to impose a ≈50 nm size cutoff on nanocarrier access to plasmalemma vesicle associated protein (PLVAP), a marker found in caveolae in the lungs. The use of deformable nanocarriers to overcome that size cutoff is explored in this study. Lysozyme-dextran nanogels (NGs) are synthesized with ≈150 or ≈300 nm mean diameter. Atomic force microscopy indicates the NGs deform on complementary surfaces. Quartz crystal microbalance data indicate that NGs form softer monolayers (≈60 kPa) than polystyrene particles (≈8 MPa). NGs deform during flow through microfluidic channels, and modeling of NG extrusion through porous filters yields sieving diameters less than 25 nm for NGs with 150 and 300 nm hydrodynamic diameters. NGs of 150 and 300 nm diameter target PLVAP in mouse lungs while counterpart rigid polystyrene particles do not. The data in this study indicate a role for mechanical deformability in targeting large high-payload drug-delivery vehicles to sterically obscured targets like PLVAP.

Toll-like receptors in immunity and inflammatory diseases: Past, present, and future

The immune system is a very diverse system of the host that evolved during evolution to cope with various pathogens present in the vicinity of environmental surroundings inhabited by multicellular organisms ranging from achordates to chordates (including humans). For example, cells of immune system express various pattern recognition receptors (PRRs) that detect danger via recognizing specific pathogen-associated molecular patterns (PAMPs) and mount a specific immune response. Toll-like receptors (TLRs) are one of these PRRs expressed by various immune cells. However, they were first discovered in the Drosophila melanogaster (common fruit fly) as genes/proteins important in embryonic development and dorso-ventral body patterning/polarity. Till date, 13 different types of TLRs (TLR1-TLR13) have been discovered and described in mammals since the first discovery of TLR4 in humans in late 1997. This discovery of TLR4 in humans revolutionized the field of innate immunity and thus the immunology and host-pathogen interaction. Since then TLRs are found to be expressed on various immune cells and have been targeted for therapeutic drug development for various infectious and inflammatory diseases including cancer. Even, Single nucleotide polymorphisms (SNPs) among various TLR genes have been identified among the different human population and their association with susceptibility/resistance to certain infections and other inflammatory diseases. Thus, in the present review the current and future importance of TLRs in immunity, their pattern of expression among various immune cells along with TLR based therapeutic approach is reviewed.

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TLRs are first described PRRs that revolutionized the biology of host-pathogen interaction and immune response

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The discovery of different TLRs in humans proved milestone in the field of innate immunity and inflammation

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The pattern of expression of all the TLRs expressed by human immune cells

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An association of various TLR SNPs with different inflammatory diseases

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Currently available drugs or vaccines based on TLRs and their future in drug targeting along with the role in reproduction, and regeneration

Toll-Like Receptors: Regulators of the Immune Response in the Human Gut

Toll-like receptors (TLRs) are powerful molecular regulators by which the immune system may "sense" the environment and protect the host from pathogens or endogenous threats. In mammalian cells, several TLRs were identified with a tissue and cell type-specific distribution. Understanding the functions of specific TLRs is crucial for the development and discovery of compounds useful to maintaining or re-establishing homeostasis in the gastrointestinal tract (GIT). Due to their relevance in regulating the inflammatory response in the GIT, we will focus here on TLR2, TLR4, and TLR5. In particular, we describe (a) the molecular pathways activated by the stimulation of these receptors with their known bacterial ligands; (b) the non-bacterial ligands known to interact directly with TLR2 and TLR4 and their soluble forms. The scope of this minireview is to highlight the importance of bacterial and non-bacterial compounds in affecting the gut immune functions via the activation of the TLRs.

Targeting superoxide dismutase to endothelial caveolae profoundly alleviates inflammation caused by endotoxin

Inflammatory mediators binding to Toll-Like receptors (TLR) induce an influx of superoxide anion in the ensuing endosomes. In endothelial cells, endosomal surplus of superoxide causes pro-inflammatory activation and TLR4 agonists act preferentially via caveolae-derived endosomes. To test the hypothesis that SOD delivery to caveolae may specifically inhibit this pathological pathway, we conjugated SOD with antibodies (Ab/SOD, size ~10nm) to plasmalemmal vesicle-associated protein (Plvap) that is specifically localized to endothelial caveolae in vivo and compared its effects to non-caveolar target CD31/PECAM-1. Plvap Ab/SOD bound to endothelial cells in culture with much lower efficacy than CD31 Ab/SOD, yet blocked the effects of LPS signaling with higher efficiency than CD31 Ab/SOD. Disruption of cholesterol-rich membrane domains by filipin inhibits Plvap Ab/SOD endocytosis and LPS signaling, implicating the caveolae-dependent pathway(s) in both processes. Both Ab/SOD conjugates targeted to Plvap and CD31 accumulated in the lungs after IV injection in mice, but the former more profoundly inhibited LPS-induced pulmonary inflammation and elevation of plasma level of interferon-beta and -gamma and interleukin-27. Taken together, these results indicate that targeted delivery of SOD to specific cellular compartments may offer effective, mechanistically precise interception of pro-inflammatory signaling mediated by reactive oxygen species.

Lipopolysaccharide potentiates platelet responses via toll-like receptor 4-stimulated Akt-Erk-PLA2 signalling

Lipopolysaccharide (LPS) from the cell envelope of Gram-negative bacteria is a principal cause of the symptoms of sepsis. LPS has been reported to modulate the function of platelets although the underlying mechanisms of LPS action in these cells remain unclear. Platelets express the Toll-like receptor 4 (TLR4) which serves as a receptor for LPS, although the potential role of TLR4 and associated cell signalling in controlling platelet responses to LPS has not been extensively explored. In this study, we therefore investigated the actions of LPS prepared from different strains of Escherichia coli on platelet function, the underlying signalling mechanisms, and the potential role of TLR4 in orchestrating these. We report that LPS increased the aggregation of washed platelets stimulated by thromboxane (U46619) or GPVI collagen receptor agonists, effects that were prevented by a TLR4 antagonist. Associated with this, LPS enhanced fibrinogen binding, P-selectin exposure and reactive oxygen species (ROS) release. Increase of ROS was found to be important for the actions of LPS on platelets, since these were inhibited in the presence of superoxide dismutase or catalase. The effects of LPS were associated with phosphorylation of Akt, ERK1/2 and PLA2 in stimulated platelets, and inhibitors of PI3-kinase, Akt and ERK1/2 reduced significantly LPS enhanced platelet function and associated ROS production. Furthermore, inhibition of platelet cyclooxygenase or the thromboxane receptor, revealed an important role for thromboxane A2. We therefore conclude that LPS increases human platelet activation through a TLR4-PI3K-Akt-ERK1/2-PLA2 -dependent pathway that is dependent on ROS and TXA2 formation.

Androgen regulation of host defenses and response to inflammatory stimuli in the prostate gland

The prostate gland is a strictly androgen-dependent organ which is also the main target of infectious and inflammatory diseases in the male reproductive tract. Host defenses and immunity of the gland have unique features to maintain a constant balance between response and tolerance to diverse antigens. In this context, the effects of reproductive hormones on the male tract are thus complex and have just started to be defined. From the classical description of "the prostatic antibacterial factor," many host defense proteins with potent microbicidal and anti-tumoral activities have been described in the organ. Indeed, it has been proposed a central role for resident cells, that is, epithelial and smooth muscle cells, in the prostatic response against injuries. However, these cells also represent the target of the inflammatory damage, leading to the development of a Proliferative Inflammatory Atrophy-like process in the epithelium and a myofibroblastic-like reactive stroma. Available data on androgen regulation of inflammation led to a model of the complex control, in which the final effect will depend on the tissue microenvironment, the cause of inflammation, and the levels of androgens among other factors. In this paper, we review the current scientific literature about the inflammatory process in the gland, the modulation of host defense proteins, and the influence of testosterone on the resolution of prostatitis.

Assessment of Pasteurella multocida A Lipopolysaccharide, as an Adhesin in an In Vitro Model of Rabbit Respiratory Epithelium

The role of the P. multocida lipopolysaccharide (LPS) as a putative adhesin during the early stages of infection with this bacterium in the respiratory epithelium of rabbits was investigated. By light microscopy and double enzyme labeling of nasal septa tissues, the amount of bacteria attached to the respiratory epithelium and the amount of LPS present in goblet cells at different experimental times were estimated. Transmission electron microscopy (TEM) and LPS labeling with colloidal gold particles were also used to determine the exact location of LPS in the cells. Septa that were challenged with LPS of P. multocida and 30 minutes later with P. multocida showed more adherent bacteria and more severe lesions than the other treatments. Free LPS was observed in the lumen of the nasal septum, forming bilamellar structures and adhering to the cilia, microvilli, cytoplasmic membrane, and cytoplasm of epithelial ciliated and goblet cells. The above findings suggest that P. multocida LPS plays an important role in the process of bacterial adhesion and that it has the ability of being internalized into host cells.

SNAP23-Dependent Surface Translocation of Leukotriene B4 (LTB4) Receptor 1 Is Essential for NOX2-Mediated Exocytotic Degranulation in Human Mast Cells Induced by Trichomonas vaginalis-Secreted LTB4

Trichomonas vaginalis is a sexually transmitted parasite that causes vaginitis in women and itself secretes lipid mediator leukotriene B₄ (LTB₄). Mast cells are important effector cells of tissue inflammation during infection with parasites. Membrane-bridging SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) complexes are critical for fusion during exocytosis. Although T. vaginalis-derived secretory products (TvSP) have been shown to induce exocytosis in mast cells, information regarding the signaling mechanisms between mast cell activation and TvSP is limited. In this study, we found that SNAP23-dependent surface trafficking of LTB₄ receptor 1 (BLT1) is required for nicotinamide adenine dinucleotide phosphate oxidase 2 (NOX2)-mediated exocytotic degranulation of mast cells induced by TvSP. First, stimulation with TvSP induced exocytotic degranulation and reactive oxygen species (ROS) generation in HMC-1 cells. Next, TvSP-induced ROS generation and exocytosis were strongly inhibited by transfection of BLT1 small interfering RNA (siRNA). TvSP induced trafficking of BLT1 from the cytosol to the plasma membrane. We also found that knockdown of SNAP23 abrogated TvSP-induced ROS generation, exocytosis, and surface trafficking of BLT1 in HMC-1 cells. By coimmunoprecipitation, there was a physical interaction between BLT1 and SNAP23 in TvSP-stimulated HMC-1 cells. Taken together, our results suggest that SNAP23-dependent surface trafficking of BLT1 is essential for exocytosis in human mast cells induced by T. vaginalis-secreted LTB₄ Our data collectively demonstrate a novel regulatory mechanism for SNAP23-dependent mast cell activation of T. vaginalis-secreted LTB₄ involving surface trafficking of BLT1. These results can help to explain how the cross talk mechanism between parasite and host can govern deliberately tissue inflammatory responses.

How Toll-like receptors and Nod-like receptors contribute to innate immunity in mammals

Innate immune detection of pathogens relies on specific classes of microbial sensors called pattern-recognition molecules (PRM). In mammals, such PRM include Toll-like receptors (TLRs) and the intracellular proteins NOD1 and NOD2, which belong to the family of Nod-like receptors (NLRs). Over the last decade as these molecules were discovered, a function in innate immunity has been assigned for the majority of them and, for most, the microbial motifs that these molecules detect were identified. One of the next challenges in innate immunity is to establish a better understanding of the complex interplay between signaling pathways induced simultaneously by distinct PRMs and how this affects tailoring first-line responses and the induction of adaptive immunity to a given pathogen.

Gastrointestinal and hepatic mechanisms limiting entry and dissemination of lipopolysaccharide into the systemic circulation

The human microbiota consists of 100 trillion microorganisms that provide important metabolic and biological functions benefiting the host. However, the presence in host plasma of a gut-derived bacteria component, the lipopolysaccharide (LPS), has been identified as a causal or complicating factor in multiple serious diseases such as sepsis and septic shock and, more recently, obesity-associated metabolic disorders. Understanding the precise mechanisms by which gut-derived LPS is transported from the gut lumen to the systemic circulation is crucial to advance our knowledge of LPS-associated diseases and elaborate targeted strategies for their prevention. The aim of this review is to synthetize current knowledge on the host mechanisms limiting the entry and dissemination of LPS into the systemic circulation. To prevent bacterial colonization and penetration, the intestinal epithelium harbors multiple defense mechanisms including the secretion of antimicrobial peptides and mucins as well as detoxification enzymes. Despite this first line of defense, LPS can reach the apical site of intestinal epithelial cells (IECs) and, because of its large size, likely crosses IECs via transcellular transport, either lipid raft- or clathrin-mediated endocytosis or goblet cell-associated passage. However, the precise pathway remains poorly described. Finally, if LPS crosses the gut mucosa, it is directed via the portal vein to the liver, where major detoxification processes occur by deacetylation and excretion through the bile. If this disposal process is not sufficient, LPS enters the systemic circulation, where it is handled by numerous transport proteins that clear it back to the liver for further excretion.

Toll-like receptor stimulation in cancer: A pro- and anti-tumor double-edged sword

Toll-like receptors (TLRs) are a family of transmembrane receptors that recognize various pathogen- and damage-associated molecular pattern molecules playing an important role in inflammation by activating NF-кB. TLRs, mainly expressed by innate immune cells, are involved in inducing and regulating adaptive immune responses. However, the expression of TLRs has also been observed in many tumors, and their stimulation results in tumor progression or regression, depending on the TLR and tumor type. Here we review the role of TLRs in conferring anti- or pro-tumoral effects. The anti-tumoral effects can result from direct induction of tumor cell death and/or activation of efficient anti-tumoral immune responses, and the pro-tumoral effects may be due to inducing tumor cell survival and proliferation or by acting on suppressive or inflammatory immune cells in the tumor microenvironment.

Toll-like receptors and chronic inflammation in rheumatic diseases: new developments

In the past few years, new developments have been reported on the role of Toll-like receptors (TLRs) in chronic inflammation in rheumatic diseases. The inhibitory function of TLR10 has been demonstrated. Receptors that enhance the function of TLRs, and several TLR inhibitors, have been identified. In addition, the role of the microbiome and TLRs in the onset of rheumatic diseases has been reported. We review novel insights on the role of TLRs in several inflammatory joint diseases, including rheumatoid arthritis, systemic lupus erythematosus, gout and Lyme arthritis, with a focus on the signalling mechanisms mediated by the Toll-IL-1 receptor (TIR) domain, the exogenous and endogenous ligands of TLRs, and the current and future therapeutic strategies to target TLR signalling in rheumatic diseases.