NOD受体-细胞内的模式识别受体家族

真核生物通过先天免疫和获得性免疫识别和清除入侵的病原微生物。同获得性免疫相比,先天免疫在病原体入侵后能迅速被激活,形成了防御病原体入侵的第一道防线。先天免疫系统是通过特殊的模式识别受体(pattern-recognition receptors,PRRs)感知病原体关联的分子模式(pathogen-ass     

The role of neutrophils during intestinal inflammation

Polymorphonuclear leukocytes or neutrophils play a critical role in the maintenance of intestinal homeostasis. They have elegant defense mechanisms to eliminate microbes that have translocated across a single layer of mucosal epithelial cells that form a critical barrier between the gut lumen and the underlying tissue. During the inflammatory response, neutrophils also contribute to the recruitment of other immune cells and facilitate mucosal healing by releasing mediators necessary for the resolution of inflammation. Although the above responses are clearly beneficial, excessive recruitment and accumulation of activated neutrophils in the intestine under pathological conditions such as inflammatory bowel disease is associated with mucosal injury and debilitating disease symptoms. Thus, depending on the circumstances, neutrophils can be viewed as either good or bad. In this article, we summarize the beneficial and deleterious roles of neutrophils in the intestine during health and disease and provide an overview of what is known about neutrophil function in the gut.     

Nod-like receptors in the control of intestinal inflammation

The Nod-like receptor (NLR) family of intracellular pattern recognition molecules plays critical roles in the control of inflammation through the modulation of different signalling pathways, including those dependent on NF-κB and caspase-1-mediated cleavage of interleukin (IL)-1β and IL-18. A number of NLRs or NLR-associated proteins have been genetically associated with susceptibility to inflammatory bowel disease (IBD), either Crohn's disease or ulcerative colitis. Accordingly, recent studies have examined the role of NLR proteins in chemical-induced or bacteria-induced murine models of colitis. In this review, we will discuss the genetic associations of NLRs with IBD and the research using NLR-deficient mice in different colitis models.     

The role of mucosal T lymphocytes in regulating intestinal inflammation

Suppression of chronic intestinal inflammation by different subtypes of T cells has been described in recent years. In particular, naturally arising CD4⁺CD25⁺ regulatory T cells and IL-10-producing regulatory T cell type 1 CD4⁺ T lymphocytes have been implicated in the regulation of intestinal inflammation. Here we focus on the ability of CD4⁺CD25⁺ regulatory T cells to suppress innate and T-cell responses and discuss implications for immunoregulation in human inflammatory bowel disease. Besides the modulation of lymphoproliferation, a role for CD4⁺CD25⁺ T cells in down-modulation of innate immune responses is emerging and the immunoregulatory activities of regulatory T cells in vivo may be mediated via effects on dendritic cells. Considering the extraordinary regenerative potential of the intestinal mucosa, the ability to impede pathogenic T-cell responses by active regulation might be of particular therapeutic benefit for the treatment of chronic intestinal inflammatory diseases such as Crohns disease and ulcerative colitis.     

巨噬细胞LPS相关模式识别受体的研究进展

脓毒症(sepsis)是由各种致病微生物或其毒素引起的全身炎症反应综合征(systemic inflammatory response syndrome, SIRS),是严重感染、重度创伤、大手术后和休克常见的并发症,进一步发展可导致脓毒性休克、急性呼吸窘迫综合征(acute respiratory distress syndrome, ARDS)和多器官功能障碍综合征(multi-organ dysfunction syndrome,MODS)等致命性并发症.     

Autophagy and pattern recognition receptors in innate immunity

Summary:  Autophagy is a physiologically and immunologically controlled intracellular homeostatic pathway that sequesters and degrades cytoplasmic targets including macromolecular aggregates, cellular organelles such as mitochondria, and whole microbes or their products. Recent advances show that autophagy plays a role in innate immunity in several ways: (i) direct elimination of intracellular microbes by digestion in autolysosomes, (ii) delivery of cytosolic microbial products to pattern recognition receptors (PRRs) in a process referred to as topological inversion, and (iii) as an anti-microbial effector of Toll-like receptors and other PRR signaling. Autophagy eliminates pathogens in vitro and in vivo but, when aberrant due to mutations, contributes to human inflammatory disorders such as Crohn's disease. In this review, we examine these relationships and propose that autophagy is one of the most ancient innate immune defenses that has possibly evolved at the time of α-protobacteria–pre-eukaryote relationships, leading up to modern eukaryotic cell–mitochondrial symbiosis, and that during the metazoan evolution, additional layers of immunological regulation have been superimposed and integrated with this primordial innate immunity mechanism.     

细胞内模式识别受体研究进展

天然免疫系统要依赖模式识别受体识别人侵的外源病原微生物,然后将其清除.哺乳动物主要具有两类微生物识别系统,一类是膜结合受体,如Toll样受体,可识别胞外微生物,然后活化细胞内信号来激发机体的免疫反应;另一类是细胞内的模式识别受体,包括NOD样受体和具有螺旋酶结构域的抗病毒蛋白RIG-1和MDA5.这些胞浆分子可识别病原微生物、非微生物以及一些危险信号,在机体的健康与疾病中发挥着十分重要的作用.本文就细胞内天然免疫受体的种类和功能作一综述.     

Intracellular pattern recognition receptors and renal ischemia

Renal ischemia is a common cause of acute kidney injury in hospitalized patients. In certain settings renal ischemia is unavoidable, such as in kidneys harvested for transplantation. The molecular and cellular mechanisms that lead to the syndrome of ischemic renal injury are complicated and involve multiple cell types within the kidney, including renal epithelium and vasculature. Although it has been difficult to define pharmacologic targets for AKI, emerging information about a newly discovered host defense system is providing hope for novel pharmacologic targets to prevent and treat AKI. Molecular initiators of damage associated with hypoxia involve a phylogenically conserved host defense system called the innate immune system. Data point to an essential role for receptors of the innate immune system, particularly the membrane-bound Toll-like receptors and the intracellular nucleotide-binding oligomerization domain-like receptors. These receptors have been identified in human and rodent kidneys, and many investigators have shown that their deletion protects from experimental ischemia/reperfusion injury (a model for ischemic acute kidney injury). This review details current information about the innate immune system and the ischemic kidney with a focus on the emerging role of intracellular innate immune receptors.     

An overview of mast cell pattern recognition receptors

Background

Mast cells (MCs) are long-lived immune cells of the connective tissue which play a key role in development and amplification of inflammatory process initiated inter alia by allergic reactions or microbial infections. They reside in strategic locations in the body that are notably exposed to deleterious factors disturbing homeostasis, which enables them to become one of the first-line defense strategy. MCs have developed a wide range of various mechanisms to deal with invading intruders and harmful endogenic factors. Those include storage and synthesis with a subsequent release of inflammatory mediators, forming of MC-extracellular traps, and phagocytosis.

Findings

Particularly, important role in microbial sensing is achieved due to the presence of different pattern recognition receptors (PRRs). The best-described receptors are Toll-like receptors activated by different pathogen- and damage-associated molecular patterns. However, MCs express also C-type lectin receptors specialized in antifungal defense, NOD-like receptors detecting bacterial peptidoglycans, and RIG-like receptors relevant in viral sensing.

Conclusion

This review will focus on the current knowledge of PRRs expressed within different types of MCs.

     

The role of scavenger receptors in pathogen recognition and innate immunity

Scavenger receptors represent a large family of structurally unrelated distinct gene products, expressed by myeloid and selected endothelial cells and able to recognise modified low-density lipoproteins. They also bind and internalise a variety of microbial pathogens, as well as modified or endogenous molecules derived from the host, and contribute to a range of physiological or pathological processes.     

脂多糖模式识别受体的研究进展

G-细菌的脂多糖（LPS）是重要的病原体相关模式分子。PAMPsd均可被动物作为低外来分子进行识别,LPS能激发机体细胞因子IL-1、TNF-α等活性分子的合成,对感染具有十分重要的作用。LPS是通过什么受体怎样将信号传玫免疫细胞并启动免疫反应的,人们一直都不十分清楚,近年来,一种名为Toll蛋白的发现,使人们对机体识别LPS机制的认识向前跨进了一大步,本文试对该模式识别受体的研究进展做一综述。     

Nod-like receptors in intestinal homeostasis, inflammation, and cancer

NLRs have been shown in a number of models to protect against microbial infection through their ability to participate in "pattern recognition" and their triggering of inflammatory pathways to control infection. Over the past few years, however, the role of NLRs, especially Nod1, Nod2, and NLRP3, in intestinal homeostasis has been highlighted. Indeed, these specific NLRs have been implicated in IBD, in particular, the association of Nod2 with CD, yet a clear understanding of how dysfunctional NLR activation leads to aberrant inflammation is still the focus of much investigation. In this review, we will examine how NLRs participate in the maintenance of gut homeostasis and how upset of this regulation can tip the balance toward chronic inflammation and intestinal cancer.     

The role of epithelial Toll-like receptor signaling in the pathogenesis of intestinal inflammation

Emerging evidence suggests that the innate immune system, comprised of Toll-like receptors (TLRs) and their associated molecules, plays a pivotal role in the regulation of intestinal inflammation and in the response to invading pathogens. Although TLRs are thought to have predominantly beneficial effects in pathogen recognition and bacterial clearance by leukocytes, their dysregulation and unique signaling effects within intestinal epithelia in the setting of inflammation may have devastating consequences. For instance, activation of TLR4 in enterocytes leads to an inhibition of enterocyte migration and proliferation as well as the induction of enterocyte apoptosis-factors that would be expected to promote intestinal injury while inhibiting intestinal repair. TLR signaling has been shown to be abnormal in several intestinal inflammatory diseases, including Crohn's disease, ulcerative colitis, and necrotizing enterocolitis. This review serves to examine the evidence regarding the patterns of expression and signaling of TLRs in the intestinal mucosa at basal levels and during physiologic stressors to gain insights into the pathogenesis of intestinal inflammation. We conclude that the data reviewed suggest that epithelial TLR signaling-acting in concert with TLR signaling by leukocytes-participates in the development of intestinal inflammation. We further conclude that the evidence reviewed provides a rationale for the development of novel, epithelial-specific, TLR-based agents in the management of diseases of intestinal inflammation.     

模式识别受体PRRs在急性肺损伤/急性呼吸窘迫综合征发病机制中的作用研究进展

急性肺损伤(ALI)/急性呼吸窘迫综合征(ARDS)是继发于肺内或全身的炎症反应过程,它由肺泡损伤导致并形成炎症性非心源性的肺水肿.模式识别受体(PRRs)参与先天免疫系统的激活,PRRs可以启动炎症信号级联反应,并释放促炎细胞因子.本综述对PRRs所包括的跨膜受体TLRs、胞质受体RLRs和NLRs以及下游炎症通路N...     

Reading the viral signature by Toll-like receptors and other pattern recognition receptors

Successful host defense against viral infections relies on early production of type I interferon (IFN) and subsequent activation of a cellular cytotoxic response. The acute IFN and inflammatory response against virus infections is mediated by cellular pattern-recognition receptors (PRRs) that recognize specific molecular structures on viral particles or products of viral replication. Toll-like receptors (TLRs) constitute a class of membrane-bound PRRs capable of detecting microbial infections. While TLR2 and TLR4, which were first identified to recognize Gram-positive and Gram-negative bacteria, respectively, sense specific viral proteins on the cell surface, TLRs 3, 7, 8, and 9 serve as receptors for viral nucleic acids in endosomic compartments. In addition to TLRs, cells express cytoplasmic PRRs such as the RNA helicase retinoic acid inducible gene I and the kinase double-stranded RNA-activated protein kinase R, both of which sense dsRNA, a characteristic signature of viral replication, and initiate a protective cellular response. Here we review the recent progress in our understanding of PRRs and viral infections and discuss the molecular and cellular responses evoked by virus-activated PRRs. Finally, we look into what is currently known about the role of PRRs in viral infections in vivo.     

The role of serotonin and its receptors in activation of immune responses and inflammation

Serotonin or 5‐hydroxytryptamine (5‐HT) is a neurotransmitter and hormone that contributes to the regulation of various physiological functions by its actions in the central nervous system (CNS) and in the respective organ systems. Peripheral 5‐HT is predominantly produced by enterochromaffin (EC) cells of the gastrointestinal (GI) tract. These gut‐resident cells produce much more 5‐HT than all neuronal and other sources combined, establishing EC cells as the main source of this biogenic amine in the human body. Peripheral 5‐HT is also a potent immune modulator and affects various immune cells through its receptors and via the recently identified process of serotonylation. Alterations in 5‐HT signalling have been described in inflammatory conditions of the gut, such as inflammatory bowel disease. The association between 5‐HT and inflammation, however, is not limited to the gut, as changes in 5‐HT levels have also been reported in patients with allergic airway inflammation and rheumatoid arthritis. Based on searches for terms such as ‘5‐HT’, ‘EC cell’, ‘immune cells’ and ‘inflammation’ in pubmed.gov as well as by utilizing pertinent reviews, the current review aims to provide an update on the role of 5‐HT in biological functions with a particular focus on immune activation and inflammation.     

C-reactive protein: ligands, receptors and role in inflammation

C-reactive protein (CRP) is the prototypical acute phase serum protein, rising rapidly in response to inflammation. CRP binds to phosphocholine (PC) and related molecules on microorganisms and plays an important role in host defense. However, a more important role may be the binding of CRP to PC in damaged membranes. CRP increases clearance of apoptotic cells, binds to nuclear antigens and by masking autoantigens from the immune system or enhancing their clearance, CRP may prevent autoimmunity. CRP binds to both the stimulatory receptors, FcgammaRI and FcgammaRIIa, increasing phagocytosis and the release of inflammatory cytokines; and to the inhibitory receptor, FcgammaRIIb, blocking activating signals. We have shown that, in two animal models of systemic lupus erythematosus (SLE), the (NZB x NZW)F1 mouse and the MRL/lpr mouse, a single injection of CRP before onset of proteinuria delayed disease development and late treatment reversed proteinuria. Thus, in these models, CRP plays an anti-inflammatory role.