Szilvia Benkő

Aloe vera downregulates LPS-induced inflammatory cytokine production and expression of NLRP3 inflammasome in human macrophages

Aloe vera has been used in traditional herbal medicine as an immunomodulatory agent inducing anti-inflammatory effects. However, its role on the IL-1β inflammatory cytokine production has not been studied. IL-1β production is strictly regulated both at transcriptional and posttranslational levels through the activity of Nlrp3 inflammasome. In this study we aimed to determine the effect of Aloe vera on the molecular mechanisms of Nlrp3 inflammasome-mediated IL-1β production in LPS-activated human THP-1 cells and monocyte-derived macrophages. Our results show that Aloe vera significantly reduced IL-8, TNFα, IL-6 and IL-1β cytokine production in a dose dependent manner. The inhibitory effect was substantially more pronounced in the primary cells. We found that Aloe vera inhibited the expression of pro-IL-1β, Nlrp3, caspase-1 as well as that of the P2X7 receptor in the LPS-induced primary macrophages. Furthermore, LPS-induced activation of signaling pathways like NF-κB, p38, JNK and ERK were inhibited by Aloe vera in these cells. Altogether, we show for the first time that Aloe vera-mediated strong reduction of IL-1β appears to be the consequence of the reduced expression of both pro-IL-1β as well as Nlrp3 inflammasome components via suppressing specific signal transduction pathways. Furthermore, we show that the expression of the ATP sensor P2X7 receptor is also downregulated by Aloe vera that could also contribute to the attenuated IL-1β cytokine secretion. These results may provide a new therapeutic approach to regulate inflammasome-mediated responses.

Transient receptor potential vanilloid-1 signaling inhibits differentiation and activation of human dendritic cells

The goal of the current study was to investigate the expression of transient receptor potential vanilloid‐1 (TRPV1) on human in vitro differentiated monocyte‐derived dendritic cells (DCs) and to dissect the corresponding role of TRPV1‐signaling in DC‐specific functions. TRPV1 expression was identified both at the protein and gene levels in human DCs. Moreover, the prototypic TRPV1 agonist capsaicin specifically (i.e. via TRPV1) and dose‐dependently inhibited cytokine‐induced DC differentiation, phagocytosis of bacteria, activation of DCs, and pro‐inflammatory cytokine secretion. These data introduce TRPV1‐coupled signaling as a novel player in human monocyte‐derived DC biology with anti‐inflammatory actions.

Natural Compounds as Regulators of NLRP3 Inflammasome-Mediated IL-1β Production

IL-1β is one of the main proinflammatory cytokines that regulates a broad range of immune responses and also participates in several physiological processes. The canonical production of IL-1β requires multiprotein complexes called inflammasomes. One of the most intensively studied inflammasome complexes is the NLRP3 inflammasome. Its activation requires two signals: one signal “primes” the cells and induces the expression of NLRP3 and pro-IL-1β, while the other signal leads to the assembly and activation of the complex. Several stimuli were reported to function as the second signal including reactive oxygen species, lysosomal rupture, or cytosolic ion perturbation. Despite very intensive studies, the precise function and regulation of the NLRP3 inflammasome are still not clear. However, many chronic inflammatory diseases are related to the overproduction of IL-1β that is mediated via the NLRP3 inflammasome. In this review, we aimed to provide an overview of studies that demonstrated the effect of plant-derived natural compounds on NLRP3 inflammasome-mediated IL-1β production. Although many of these studies lack the mechanistic explanation of their action, these compounds may be considered as complementary supplements in the treatment of chronic inflammatory diseases, consumed as preventive agents, and may also be considered as molecular tools to study NLRP3 function.

Ragweed pollen extract intensifies lipopolysaccharide‐induced priming of NLRP3 inflammasome in human macrophages

Ragweed pollen extract (RWE) possesses intrinsic NADPH oxidase activity that induces oxidative stress by initiating the production of intracellular reactive oxygen species (ROS). The ROS are important contributors to the manifestation of allergic inflammation; furthermore, concomitant exposure to an allergen and an endotoxin trigger a stronger inflammatory response. One of the main pro‐inflammatory cytokines produced in inflammatory responses is interleukin‐1β (IL‐1β), and its production is associated with caspase‐1‐containing inflammasome complexes. Intracellular ROS have been implicated in NLRP3 inflammasome‐mediated IL‐1β production, therefore, we aimed to study whether RWE influences the function of NLRP3 inflammasome. Here we describe that, in the presence of NADPH, RWE significantly elevates lipopolysaccharide‐induced IL‐1β production of THP‐1 cells as well as human primary macrophages and dendritic cells. We also demonstrate that increased IL‐1β production is mediated through NLRP3 inflammasome in THP‐1 macrophages. We provide evidence that RWE elevates cytosolic ROS level in these cells, and ROS inhibitors abolish IL‐1β production. Furthermore, we show that RWE enhances lipopolysaccharide‐induced gene transcription/expression of pro‐IL‐1β and key components of the inflammasome via a ROS‐dependent mechanism.

A molecular model of the full-length human NOD-like receptor family CARD domain containing 5 (NLRC5) protein

BackgroundPattern recognition receptors of the immune system have key roles in the regulation of pathways after the recognition of microbial- and danger-associated molecular patterns in vertebrates. Members of NOD-like receptor (NLR) family typically function intracellularly. The NOD-like receptor family CARD domain containing 5 (NLRC5) is the largest member of this family that also contains the largest number of leucine-rich repeats (LRRs).Due to the lack of crystal structures of full-length NLRs, projects have been initiated with the aim to model certain or all members of the family, but systematic studies did not model the full-length NLRC5 due to its unique domain architecture.Our aim was to analyze the LRR sequences of NLRC5 and some NLRC5-related proteins and to build a model for the full-length human NLRC5 by homology modeling.ResultsLRR sequences of NLRC5 were aligned and were compared with the consensus pattern of ribonuclease inhibitor protein (RI)-like LRR subfamily. Two types of alternating consensus patterns previously identified for RI repeats were also found in NLRC5. A homology model for full-length human NLRC5 was prepared and, besides the closed conformation of monomeric NLRC5, a heptameric platform was also modeled for the opened conformational NLRC5 monomers.ConclusionsIdentification of consensus patterns of leucine-rich repeat sequences helped to identify LRRs in NLRC5 and to predict their number and position within the protein. In spite of the lack of fully adequate template structures, the presence of an untypical CARD domain and unusually high number of LRRs in NLRC5, we were able to construct a homology model for both the monomeric and homo-heptameric full-length human NLRC5 protein.

NLRC5 Functions beyond MHC I Regulation—What Do We Know So Far?

NLRC5 is a member of the NLR family that acts as a transcriptional activator of MHC class I genes. In line with the function of several related NLR proteins in innate immune responses, there is, however, also ample evidence that NLRC5 contributes to innate and adaptive immune responses beyond the regulation of MHC class I genes. In human and murine cells, for example, NLRC5 was proposed to contribute to inflammatory and type I interferon responses. The role of NLRC5 in these and other cellular processes is hitherto still not well understood and blurred by discrepancies in the reported data. Here, we provide a detailed and critical discussion of the available experimental data on the emerging biological functions of NLRC5 in innate immune responses in men and mice. Better awareness of the multiple roles of NLRC5 will help to define its overall contribution to immune responses and cancer.

Different dynamics of NLRP3 inflammasome‐mediated IL‐1β production in GM‐CSF– and M‐CSF–differentiated human macrophages

IL‐1β is a “master” cytokine regulating a wide variety of physiologic and immunologic processes. The most frequently studied models for NLRP3 inflammasome‐mediated IL‐1β production are the macrophages; however, depending on their microenvironment, they can develop into functionally different cells. Several protocols have been developed to model the diversity of these cells in vitro. Here, we report for the first time, to our knowledge, a comparative study about the dynamics and molecular mechanisms of NLRP3 inflammasome priming and activation in LPS‐stimulated, human, monocyte‐derived GM‐ or M‐macrophages, differentiated in the presence of GM‐CSF or M‐CSF, respectively. Our results show that IL‐1β production by LPS‐stimulated M‐macrophages is a rapid and short event that requires ATP supplementation and is attenuated, in part, by the presence of IL‐10, which reduces Akt signaling. However, IL‐1β production by GM‐macrophages develops gradually, and these cells produce IL‐1β, even in the absence of ATP supplementation, because of the constitutively active caspase‐1 enzyme. We show that the membrane‐bound ectonucleotidases have an important regulatory role on the IL‐1β secretion in GM‐macrophages. Furthermore, we provide evidence that adenosine treatment enhances LPS‐primed IL‐1β secretion by GM‐macrophages, but not by M‐macrophages. These results show that, because of the different activation status and expression levels of the NLRP3 inflammasome components, as well as the signaling activity of the pathways, the two subtypes of macrophages respond very differently to the same stimuli. For this reason, the molecular composition of the microenvironment that shapes macrophage development should be considered when research or therapeutic methods are planned to control IL‐1β production.

Újdonságok köszvényben: patogenezis, társbetegségek, diagnosztika és terápia

Absztrakt: Tobb evtizedes „szunetet” kovetően az utobbi evekben szamos uj adat jelent meg a koszveny patogenezise, diagnosztikaja es terapiaja vonatkozasaban. Megismertuk a hugysavanyagcsere ujabb ...