scholarly journals Inhibition of Toll-like Receptor and Cytokine Signaling—A Unifying Theme in Ischemic Tolerance

2004 ◽  
Vol 24 (11) ◽  
pp. 1288-1304 ◽  
Author(s):  
Katalin Karikó ◽  
Drew Weissman ◽  
Frank A. Welsh
Keyword(s):  
Immune System ◽  
Inflammatory Response ◽  
Lipid Rafts ◽  
Inflammatory Cytokines ◽  
Innate Immune System ◽  
Endotoxin Tolerance ◽  
Ischemic Tolerance ◽  
Innate Immune ◽  
Cytokine Signaling ◽  
The Brain

Cerebral ischemia triggers acute inflammation, which exacerbates primary brain damage. Activation of the innate immune system is an important component of this inflammatory response. Inflammation occurs through the action of proinflammatory cytokines, such as TNF, IL-1β and IL-6, that alter blood flow and increase vascular permeability, thus leading to secondary ischemia and accumulation of immune cells in the brain. Production of these cytokines is initiated by signaling through Toll-like receptors (TLRs) that recognize host-derived molecules released from injured tissues and cells. Recently, great strides have been made in understanding the regulation of the innate immune system, particularly the signaling mechanisms of TLRs. Negative feedback inhibitors of TLRs and inflammatory cytokines have now been identified and characterized. It is also evident that lipid rafts exist in membranes and play a role in receptor-mediated inflammatory signaling events. In the present review, using this newly available large body of knowledge, we take a fresh look at studies of ischemic tolerance. Based on this analysis, we recognize a striking similarity between ischemic tolerance and endotoxin tolerance, an immune suppressive state characterized by hyporesponsiveness to lipopolysaccharide (LPS). In view of this analogy, and considering recent discoveries related to molecular mechanisms of endotoxin tolerance, we postulate that inhibition of TLR and proinflammatory cytokine signaling contributes critically to ischemic tolerance in the brain and other organs. Ischemic tolerance is a protective mechanism induced by a variety of preconditioning stimuli. Tolerance can be established with two temporal profiles: (i) a rapid form in which the trigger induces tolerance to ischemia within minutes and (ii) a delayed form in which development of protection takes several hours or days and requires de-novo protein synthesis. The rapid form of tolerance is achieved by direct interference with membrane fluidity, causing disruption of lipid rafts leading to inhibition of TLR/cytokine signaling pathways. In the delayed form of tolerance, the preconditioning stimulus first triggers the TLR/cytokine inflammatory pathways, leading not only to inflammation but also to simultaneous upregulation of feedback inhibitors of inflammation. These inhibitors, which include signaling inhibitors, decoy receptors, and anti-inflammatory cytokines, reduce the inflammatory response to a subsequent episode of ischemia. This novel interpretation of the molecular mechanism of ischemic tolerance highlights new avenues for future investigation into the prevention and treatment of stroke and related diseases.

scholarly journals Lithium: Immunomodulatory and Anti-Infectious Activities

2019 ◽  
Vol 4 (1) ◽  
Keyword(s):  
Immune System ◽  
Inflammatory Cytokines ◽  
Human Body ◽  
Innate Immune System ◽  
Cell Types ◽  
Innate Immune ◽  
Signalling Pathways ◽  
Disease Models ◽  
Absolute Requirement ◽  
Different Cell Types

Lithium (Li), a well-known immunomodulatory agent, has been in use for the treatment of several infectious diseases. Li mainly acts through GSK3β inactivation and several other signalling pathways, which are directly involved in the activation of innate immune system. Li therapy has been shown to cause effective modulation of various inflammatory cytokines, and has also been shown to boost immunity in several disease models. Apart from treatment for mania, Li has also been proved to be effective against infections caused by viruses, bacteria, parasites, and certain life-style disorders. Its effects, ranging from common defensive capabilities to complex pathways for protection of human body, make Li extraordinary. Thus, Li is an absolute requirement that can be a solution for some of the immune related disorders. This review mainly focuses on pharmacology, immune reactions of different cell types, and anti-infectious activities of Li.

scholarly journals The Autumn Low Milk Yield Syndrome in High Genetic Merit Dairy Cattle: The Possible Role of a Dysregulated Innate Immune Response

Animals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 388
Author(s):  
Massimo Amadori ◽  
Chiara Spelta
Keyword(s):  
Immune System ◽  
Inflammatory Response ◽  
Dairy Cattle ◽  
Memory Effect ◽  
Milk Yield ◽  
Innate Immune System ◽  
Innate Immune ◽  
Effective Control ◽  
Dry Period ◽  
Genetic Merit

The analysis of milk yield data shows that high genetic merit dairy cows do not express their full production potential in autumn. Therefore, we focused on metabolic stress and inflammatory response in the dry and peripartum periods as possible causes thereof. It was our understanding that some cows could not cope with the stress imposed by their physiological and productive status by means of adequate adaptation strategies. Accordingly, this study highlights the noxious factors with a potential to affect cows in the above transition period: hot summer climate, adverse genetic traits, poor coping with unfavorable environmental conditions, outright production diseases and consequences thereof. In particular, the detrimental effects in the dry period of overcrowding, photoperiod change and heat stress on mammary gland development and milk production are highlighted in the context of the autumn low milk yield syndrome. The latter could be largely accounted for by a “memory” effect on the innate immune system induced in summer by diverse stressors after dry-off, according to strong circumstantial and indirect experimental evidence. The “memory” effect is based on distinct epigenetic changes of innate immunity genes, as already shown in cases of bovine mastitis. Following a primary stimulation, the innate immune system would be able to achieve a state known as “trained immunity”, a sort of “education” which modifies the response to the same or similar stressors upon a subsequent exposure. In our scenario, the “education” of the innate immune system would induce a major shift in the metabolism of inflammatory cells following their reprogramming. This would entail a higher basal consumption of glucose, in competition with the need for the synthesis of milk. Also, there is strong evidence that the inflammatory response generated in the dry period leads to a notable reduction of dry matter intake after calving, and to a reduced efficiency of oxidative phosphorylation in mitochondria. On the whole, an effective control of the stressors in the dry period is badly needed for better disease control and optimal production levels in dairy cattle.

scholarly journals MiR-146b Mediates Endotoxin Tolerance in Human Phagocytes

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Tiziana Ada Renzi ◽  
Marcello Rubino ◽  
Laura Gornati ◽  
Cecilia Garlanda ◽  
Massimo Locati ◽  
...  
Keyword(s):  
Immune Response ◽  
Immune System ◽  
Inflammatory Response ◽  
Innate Immune Response ◽  
Endotoxin Tolerance ◽  
Innate Immune ◽  
Human Monocytes ◽  
Key Factors ◽  
Tlr Signaling ◽  
Tolerant State

A proper regulation of the innate immune response is fundamental to keep the immune system in check and avoid a chronic status of inflammation. As they act as negative modulators of TLR signaling pathways, miRNAs have been recently involved in the control of the inflammatory response. However, their role in the context of endotoxin tolerance is just beginning to be explored. We here show that miR-146b is upregulated in human monocytes tolerized by LPS, IL-10, or TGFβpriming and demonstrate that its transcription is driven by STAT3 and RUNX3, key factors downstream of IL-10 and TGFβsignaling. Our study also found that IFNγ, known to revert LPS tolerant state, inhibits miR-146b expression. Finally, we provide evidence that miR-146b levels have a profound effect on the tolerant state, thus candidating miR-146b as a molecular mediator of endotoxin tolerance.

scholarly journals Location, Location, Location: Is Membrane Partitioning Everything When It Comes to Innate Immune Activation?

2011 ◽  
Vol 2011 ◽  
pp. 1-10 ◽  
Author(s):  
Martha Triantafilou ◽  
Philipp M. Lepper ◽  
Robin Olden ◽  
Ivo de Seabra Rodrigues Dias ◽  
Kathy Triantafilou
Keyword(s):  
Plasma Membrane ◽  
Immune System ◽  
Lipid Rafts ◽  
Immune Activation ◽  
Innate Immune System ◽  
Innate Immune ◽  
Membrane Microdomains ◽  
General View ◽  
Immune Recognition ◽  
Innate Immune Activation

In the last twenty years, the general view of the plasma membrane has changed from a homogeneous arrangement of lipids to a mosaic of microdomains. It is currently thought that islands of highly ordered saturated lipids and cholesterol, which are laterally mobile, exist in the plane of the plasma membrane. Lipid rafts are thought to provide a means to explain the spatial segregation of certain signalling pathways emanating from the cell surface. They seem to provide the necessary microenvironment in order for certain specialised signalling events to take place, such as the innate immune recognition. The innate immune system seems to employ germ-lined encoded receptors, called pattern recognition receptors (PRRs), in order to detect pathogens. One family of such receptors are the Toll-like receptors (TLRs), which are the central “sensing” apparatus of the innate immune system. In recent years, it has become apparent that TLRs are recruited into membrane microdomains in response to ligands. These nanoscale assemblies of sphingolipid, cholesterol, and TLRs stabilize and coalesce, forming signalling platforms, which transduce signals that lead to innate immune activation. In the current paper, we will investigate all past and current literature concerning recruitment of extracellular and intracellular TLRs into lipid rafts and how this membrane organization modulates innate immune responses.

scholarly journals Role of pattern recognition receptors of the neurovascular unit in inflamm-aging

2017 ◽  
Vol 313 (5) ◽  
pp. H1000-H1012 ◽  
Author(s):  
Imola Wilhelm ◽  
Ádám Nyúl-Tóth ◽  
Mihály Kozma ◽  
Attila E. Farkas ◽  
István A. Krizbai
Keyword(s):  
Pattern Recognition ◽  
Immune System ◽  
Chronic Inflammation ◽  
Blood Brain Barrier ◽  
Innate Immune System ◽  
Neurovascular Unit ◽  
Innate Immune ◽  
Brain Barrier ◽  
Pyrin Domain ◽  
The Brain

Aging is associated with chronic inflammation partly mediated by increased levels of damage-associated molecular patterns, which activate pattern recognition receptors (PRRs) of the innate immune system. Furthermore, many aging-related disorders are associated with inflammation. PRRs, such as Toll-like receptors (TLRs) and nucleotide-binding oligomerization domain-like receptors (NLRs), are expressed not only in cells of the innate immune system but also in other cells, including cells of the neurovascular unit and cerebral vasculature forming the blood-brain barrier. In this review, we summarize our present knowledge about the relationship between activation of PRRs expressed by cells of the neurovascular unit-blood-brain barrier, chronic inflammation, and aging-related pathologies of the brain. The most important damage-associated molecular pattern-sensing PRRs in the brain are TLR2, TLR4, and NLR family pyrin domain-containing protein-1 and pyrin domain-containing protein-3, which are activated during physiological and pathological aging in microglia, neurons, astrocytes, and possibly endothelial cells and pericytes.

scholarly journals Receptor Mincle promotes skin allergies and is capable of recognizing cholesterol sulfate

2017 ◽  
Vol 114 (13) ◽  
pp. E2758-E2765 ◽  
Author(s):  
Alexey V. Kostarnoy ◽  
Petya G. Gancheva ◽  
Bernd Lepenies ◽  
Amir I. Tukhvatulin ◽  
Alina S. Dzharullaeva ◽  
...  
Keyword(s):  
Immune System ◽  
Inflammatory Response ◽  
Innate Immune System ◽  
Molecular Mechanisms ◽  
Tissue Injury ◽  
Innate Immune ◽  
Sterile Inflammation ◽  
Skin Damage ◽  
Cholesterol Sulfate ◽  
Local Inflammatory Response

Sterile (noninfected) inflammation underlies the pathogenesis of many widespread diseases, such as allergies and autoimmune diseases. The evolutionarily conserved innate immune system is considered to play a key role in tissue injury recognition and the subsequent development of sterile inflammation; however, the underlying molecular mechanisms are not yet completely understood. Here, we show that cholesterol sulfate, a molecule present in relatively high concentrations in the epithelial layer of barrier tissues, is selectively recognized by Mincle (Clec4e), a C-type lectin receptor of the innate immune system that is strongly up-regulated in response to skin damage. Mincle activation by cholesterol sulfate causes the secretion of a range of proinflammatory mediators, and s.c. injection of cholesterol sulfate results in a Mincle-mediated induction of a severe local inflammatory response. In addition, our study reveals a role of Mincle as a driving component in the pathogenesis of allergic skin inflammation. In a well-established model of allergic contact dermatitis, the absence of Mincle leads to a significant suppression of the magnitude of the skin inflammatory response as assessed by changes in ear thickness, myeloid cell infiltration, and cytokine and chemokine secretion. Taken together, our results provide a deeper understanding of the fundamental mechanisms underlying sterile inflammation.

scholarly journals Genetic variability associated with OAS1 expression in myeloid cells increases the risk of Alzheimer's disease and severe COVID-19 outcomes

2021 ◽  
Author(s):  
Naciye Magusali ◽  
Andrew C Graham ◽  
Thomas M Piers ◽  
Pantila Panichnantakul ◽  
Umran Yaman ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Immune System ◽  
Critical Illness ◽  
Inflammatory Response ◽  
Innate Immune System ◽  
Transcriptional Network ◽  
Innate Immune ◽  
Genome Wide Association Studies ◽  
Oligoadenylate Synthetase

Genome-wide association studies of late-onset Alzheimer's disease (AD) have highlighted the importance of variants associated with genes expressed by the innate immune system in determining risk for AD. Recently, we and others have shown that genes associated with variants that confer risk for AD are significantly enriched in transcriptional networks expressed by amyloid-responsive microglia. This allowed us to predict new risk genes for AD, including the interferon-responsive oligoadenylate synthetase 1 (OAS1). However, the function of OAS1 within microglia and its genetic pathway are not known. Using genotyping from 1,313 individuals with sporadic AD and 1,234 control individuals, we confirm that the OAS1 variant, rs1131454, is associated with increased risk for AD and decreased OAS1 expression. Moreover, we note that the same locus was recently associated with critical illness in response to COVID-19, linking variants that are associated with AD and a severe response to COVID-19. By analysing single-cell RNA-sequencing (scRNA-seq) data of isolated microglia from APPNL-G-F knock-in and wild-type C57BL/6J mice, we identify a transcriptional network that is significantly upregulated with age and amyloid deposition, and contains the mouse orthologue Oas1a, providing evidence that Oas1a plays an age-dependent function in the innate immune system. We identify a similar interferon-related transcriptional network containing OAS1 by analysing scRNA-seq data from human microglia isolated from individuals with AD. Finally, using human iPSC-derived microglial cells (h-iPSC-Mg), we see that OAS1 is required to limit the pro-inflammatory response of microglia. When stimulated with interferon-gamma (IFN-γ), we note that cells with lower OAS1 expression show an exaggerated pro-inflammatory response, with increased expression and secretion of TNF-α. Collectively, our data support a link between genetic risk for AD and susceptibility to critical illness with COVID-19 centred on OAS1 and interferon signalling, a finding with potential implications for future treatments of both AD and COVID-19, and the development of biomarkers to track disease progression.

scholarly journals Vaccination against the Protozoan Parasite Histomonas meleagridis Primes the Activation of Toll-like Receptors in Turkeys and Chickens Determined by a Set of Newly Developed Multiplex RT-qPCRs

Vaccines ◽  
2021 ◽  
Vol 9 (9) ◽  
pp. 960
Author(s):  
Taniya Mitra ◽  
Beatrice Bramberger ◽  
Ivana Bilic ◽  
Michael Hess ◽  
Dieter Liebhart
Keyword(s):  
Immune System ◽  
Inflammatory Cytokines ◽  
Host Species ◽  
Innate Immune System ◽  
Innate Immune ◽  
Post Inoculation ◽  
Avian Host ◽  
Toll Like Receptors ◽  
Immune System Activation ◽  
Pro Inflammatory Cytokines

Histomonosis in turkeys and chickens is caused by the extracellular parasite Histomonas meleagridis, but the outcome of the disease varies depending on the host species. So far, studies on the immune response against histomonosis focus mainly on different traits of the adaptive immune system. Activation of toll like receptors (TLR) leads to the interplay between cells of innate and adaptive immunity with consequences on B and T cell clonal expansion. Therefore, the present investigation focused on the interaction of virulent and/or attenuated histomonads with the innate immune system of turkeys and chickens at 4, 10, 21 days post inoculation. The expression of TLRs (TLR1A, 1B, 2A, 2B, 3, 4, 5, 6(Tu), 7, 13(Tu) and 21(Ch)) and pro-inflammatory cytokines (IL1β and IL6) were analysed in caecum and spleen samples by RT-qPCR. Most frequent significant changes in expression levels of TLRs were observed in the caecum following infection with virulent parasites, an effect noticed to a lower degree in tissue samples from birds vaccinated with attenuated parasites. TLR1B, 2B and 4 showed a continuous up-regulation in the caecum of both species during infection or vaccination, followed by challenge with virulent parasites. Vaccinated birds of both species showed a significant earlier change in TLR expression following challenge than birds kept non-vaccinated but challenged. Expression of TLRs and pro-inflammatory cytokines were associated with severe inflammation of diseased birds in the local organ caecum. In the spleen, changes in TLRs and pro-inflammatory cytokines were less prominent and mainly observed in turkey samples. In conclusion, a detailed comparison of TLRs and pro-inflammatory cytokines of the innate immune system following inoculation with attenuated and/or virulent H. meleagridis of two avian host species provides an insight into regulative mechanisms of TLRs in the development of protection and limitation of the disease.

scholarly journals Effects of mannose-binding lectin on pulmonary gene expression and innate immune inflammatory response to ozone

2016 ◽  
Vol 311 (2) ◽  
pp. L280-L291 ◽  
Author(s):  
Jonathan M. Ciencewicki ◽  
Kirsten C. Verhein ◽  
Kevin Gerrish ◽  
Zachary R. McCaw ◽  
Jianying Li ◽  
...  
Keyword(s):  
Immune System ◽  
Inflammatory Response ◽  
Innate Immune System ◽  
Bronchoalveolar Lavage Fluid ◽  
Lavage Fluid ◽  
Innate Immune ◽  
Gene Sets ◽  
Mannose Binding ◽  
Gene Transcripts ◽  
Binding Lectin

Ozone is a common, potent oxidant pollutant in industrialized nations. Ozone exposure causes airway hyperreactivity, lung hyperpermeability, inflammation, and cell damage in humans and laboratory animals, and exposure to ozone has been associated with exacerbation of asthma, altered lung function, and mortality. The mechanisms of ozone-induced lung injury and differential susceptibility are not fully understood. Ozone-induced lung inflammation is mediated, in part, by the innate immune system. We hypothesized that mannose-binding lectin (MBL), an innate immunity serum protein, contributes to the proinflammatory events caused by ozone-mediated activation of the innate immune system. Wild-type ( Mbl+/+) and MBL-deficient ( Mbl−/−) mice were exposed to ozone (0.3 ppm) for up to 72 h, and bronchoalveolar lavage fluid was examined for inflammatory markers. Mean numbers of eosinophils and neutrophils and levels of the neutrophil attractants C-X-C motif chemokines 2 [ Cxcl2 (major intrinsic protein 2)] and 5 [ Cxcl5 (limb expression, LIX)] in the bronchoalveolar lavage fluid were significantly lower in Mbl−/− than Mbl+/+ mice exposed to ozone. Using genome-wide mRNA microarray analyses, we identified significant differences in transcript response profiles and networks at baseline [e.g., nuclear factor erythroid-related factor 2 (NRF2)-mediated oxidative stress response] and after exposure (e.g., humoral immune response) between Mbl+/+ and Mbl−/− mice. The microarray data were further analyzed to discover several informative differential response patterns and subsequent gene sets, including the antimicrobial response and the inflammatory response. We also used the lists of gene transcripts to search the LINCS L1000CDS2 data sets to identify agents that are predicted to perturb ozone-induced changes in gene transcripts and inflammation. These novel findings demonstrate that targeted deletion of Mbl caused differential levels of inflammation-related gene sets at baseline and after exposure to ozone and significantly reduced pulmonary inflammation, thus indicating an important innate immunomodulatory role of the gene in this model.

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