Therapeutic Targeting of Inflammatory Pathways with Emphasis on NLRP3 Inflammasomes by Natural Products: A Novel Approach for the Treatment of Inflammatory Eye Diseases

2021 ◽  
Vol 28 ◽  
Author(s):  
Amro M. Soliman ◽  
Ru Hui Sim ◽  
Srijit Das ◽  
Pasuk Mahakkannurauh

: There is an increase in the incidence of inflammatory eye diseases worldwide. Several dysregulated inflammatory pathways, including the NOD-like receptor protein 3 (NLRP3) inflammasome, have been reported to contribute significantly to the pathogenesis and progression of ophthalmic diseases. Although the available allopathic/conventional medicine has demonstrated effectiveness in managing eye diseases, there is an ongoing global demand for alternative therapeutics with minimal adverse drug reactions, easy availability, increase in patient-compliance, and better disease outcome. Therefore, several studies are investigating the utilization of natural products and herbal formulations in impeding inflammatory pathways, including the NLRP3 inflammasome, in order to prevent or manage eye diseases. In the present review, we highlight the recently reported inflammatory pathways with special emphasis on NLRP3 Inflammasomes involved in the development of eye diseases. Furthermore, we present a variety of natural products and phytochemicals that were reported to interfere with these pathways and their underlying mechanisms of action. These natural products represent potential therapeutic applications for the treatment of several inflammatory eye diseases.

2021 ◽  
Vol 12 ◽  
Author(s):  
Panpan Chang ◽  
Hao Li ◽  
Hui Hu ◽  
Yongqing Li ◽  
Tianbing Wang

Autophagy fights against harmful stimuli and degrades cytosolic macromolecules, organelles, and intracellular pathogens. Autophagy dysfunction is associated with many diseases, including infectious and inflammatory diseases. Recent studies have identified the critical role of the NACHT, LRR, and PYD domain-containing protein 3 (NLRP3) inflammasomes activation in the innate immune system, which mediates the secretion of proinflammatory cytokines IL-1β/IL-18 and cleaves Gasdermin D to induce pyroptosis in response to pathogenic and sterile stimuli. Accumulating evidence has highlighted the crosstalk between autophagy and NLRP3 inflammasome in multifaceted ways to influence host defense and inflammation. However, the underlying mechanisms require further clarification. Histone deacetylase 6 (HDAC6) is a class IIb deacetylase among the 18 mammalian HDACs, which mainly localizes in the cytoplasm. It is involved in two functional deacetylase domains and a ubiquitin-binding zinc finger domain (ZnF-BUZ). Due to its unique structure, HDAC6 regulates various physiological processes, including autophagy and NLRP3 inflammasome, and may play a role in the crosstalk between them. In this review, we provide insight into the mechanisms by which HDAC6 regulates autophagy and NLRP3 inflammasome and we explored the possibility and challenges of HDAC6 in the crosstalk between autophagy and NLRP3 inflammasome. Finally, we discuss HDAC6 inhibitors as a potential therapeutic approach targeting either autophagy or NLRP3 inflammasome as an anti-inflammatory strategy, although further clarification is required regarding their crosstalk.


2021 ◽  
Vol 11 ◽  
Author(s):  
Yufei Luo ◽  
Bojun Xiong ◽  
Haiping Liu ◽  
Zehong Chen ◽  
Huihui Huang ◽  
...  

Koumine (KM), one of the primary constituents of Gelsemium elegans, has been used for the treatment of inflammatory diseases such as rheumatoid arthritis, but whether KM impacts the activation of the NOD-like receptor protein 3 (NLRP3) inflammasome remains unknown. This study aimed to explore the inhibitory effect of KM on NLRP3 inflammasome activation and the underlying mechanisms both in vitro using macrophages stimulated with LPS plus ATP, nigericin or monosodium urate (MSU) crystals and in vivo using an MSU-induced peritonitis model. We found that KM dose-dependently inhibited IL-1β secretion in macrophages after NLRP3 inflammasome activators stimulation. Furthermore, KM treatment efficiently attenuated the infiltration of neutrophils and suppressed IL-1β production in mice with MSU-induced peritonitis. These results indicated that KM inhibited NLRP3 inflammasome activation, and consistent with this finding, KM effectively inhibited caspase-1 activation, mature IL-1β secretion, NLRP3 formation and pro-IL-1β expression in LPS-primed macrophages treated with ATP, nigericin or MSU. The mechanistic study showed that, KM exerted a potent inhibitory effect on the NLRP3 priming step, which decreased the phosphorylation of IκBα and p65, the nuclear localization of p65, and the secretion of TNF-α and IL-6. Moreover, the assembly of NLRP3 was also interrupted by KM. KM blocked apoptosis-associated speck-like protein containing a CARD (ASC) speck formation and its oligomerization and hampered the NLRP3-ASC interaction. This suppression was attributed to the ability of KM to inhibit the production of reactive oxygen species (ROS). In support of this finding, the inhibitory effect of KM on ROS production was completely counteracted by H2O2, an ROS promoter. Our results provide the first indication that KM exerts an inhibitory effect on NLRP3 inflammasome activation associated with blocking the ROS/NF-κB/NLRP3 signal axis. KM might have potential clinical application in the treatment of NLRP3 inflammasome-related diseases.


Nutrients ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 611 ◽  
Author(s):  
Yunchang Zhang ◽  
Xiaoshi Ma ◽  
Da Jiang ◽  
Jingqing Chen ◽  
Hai Jia ◽  
...  

Glycine supplementation has been reported to alleviate lipopolysaccharide (LPS)-induced lung injury in mice. However, the underlying mechanisms responsible for this beneficial effect remain unknown. In the present study, male C57BL/6 mice were treated with aerosolized glycine (1000 mg in 5 mL of 0.9% saline) or vehicle (0.9% saline) once daily for 7 continuous days, and then were exposed to aerosolized LPS (5 mg in 5 mL of 0.9% saline) for 30 min to induce lung injury. Sera and lung tissues were collected 24 h post LPS challenge. Results showed that glycine pretreatment attenuated LPS-induced decreases of mucin at both protein and mRNA levels, reduced LPS-triggered upregulation of pro-inflammatory cytokines, such as tumor necrosis factor-α (TNF-α), interferons, granulocyte-macrophage colony-stimulating factor (GM-CSF), and interleukins. Further study showed that glycine-reduced LPS challenge resulted in the upregulation of nuclear factor κB (NF-κB), nucleotide binding domain (NOD)-like receptor protein 3 (NLRP3) inflammasome. In addition, LPS exposure led to the downregulation of NRF2 and downstream targets, which were significantly improved by glycine administration in the lung tissues. Our findings indicated that glycine pretreatment prevented LPS-induced lung injury by regulating both NLRP3 inflammasome and NRF2 signaling.


2017 ◽  
Vol 2017 ◽  
pp. 1-8 ◽  
Author(s):  
Qingfei Xiao ◽  
Zhihui Qu ◽  
Ying Zhao ◽  
Liming Yang ◽  
Pujun Gao

Inflammation is a complex response to diverse pathological conditions, resulting in negative rather than protective effects when uncontrolled. Orientin (Ori), a flavonoid component isolated from natural plants, possesses abundant properties. Thus, we aimed to discover the potential therapeutic effects of orientin on lipopolysaccharide- (LPS-) induced inflammation in RAW 264.7 cells and the underlying mechanisms. In our studies, we evaluated the effects of Ori on proinflammatory mediator production stimulated by LPS, including tumor necrosis factor- (TNF-) α, interleukin- (IL-) 6, IL-18, and IL-1β, along with prostaglandin E2 (PGE2) and NO. Our data indicated that orientin dramatically inhibited the levels of these mediators. Consistent with these results, the expression levels of cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) were also reduced. Further study demonstrated that such inhibitory effects of Ori were due to suppression of the nuclear factor-kappa B (NF-κB) pathway and nucleotide-binding domain- (NOD-) like receptor protein 3 (NLRP3) inflammasome activation, which may contribute to its anti-inflammatory effects. Together, these findings show that Ori may be an effective candidate for ameliorating LPS-induced inflammatory responses.


2018 ◽  
Vol 2018 ◽  
pp. 1-13 ◽  
Author(s):  
Yu Chen ◽  
Xingxiang He ◽  
Xinxu Yuan ◽  
Jinni Hong ◽  
Owais Bhat ◽  
...  

The Nod-like receptor protein 3 (NLRP3) inflammasome activation not only serves as an intracellular machinery triggering inflammation but also produces uncanonical effects beyond inflammation such as changing cell metabolism and increasing cell membrane permeability. The present study was designed to test whether this NLRP3 inflammasome activation contributes to the “two-hit” injury during nonalcoholic steatohepatitis (NASH) and whether it can be a therapeutic target for the action of Fufang Zhenzhu Tiaozhi (FTZ), a widely used herbal remedy for hyperlipidemia and metabolic syndrome in China. We first demonstrated that NLRP3 inflammasome formation and activation as well as lipid deposition occurred in the liver of mice on the high-fat diet (HFD), as shown by increased NLRP3 aggregation, enhanced production of IL-1β and high mobility group box 1 (HMGB1), and remarkable lipid deposition in liver cells. FTZ extracts not only significantly reduced the NLRP3 inflammasome formation and activation but also attenuated the liver steatosis and fibrogenic phenotype changed. In in vitro studies, palmitic acid (PA) was found to increase colocalization of NLRP3 components and enhanced caspase-1 activity in hepatic stellate cells (HSCs), indicating enhanced formation and activation of NLRP3 inflammasomes by PA. PA also increased lipid deposition. Nlrp3 siRNA can reverse this effect by silencing the NLRP3 inflammasome and both with FTZ. In FTZ-treated cells, not only inflammasome formation and activation was substantially attenuated but also lipid deposition in HSCs was blocked. This inhibition of FTZ on lipid deposition was similar to the effects of glycyrrhizin, an HMGB1 inhibitor. Mechanistically, stimulated membrane raft redox signaling platform formation and increased O2•− production by PA to activate NLRP3 inflammasomes in HSCs was blocked by FTZ treatment. It is concluded that FTZ extracts inhibit NASH by its action on both inflammatory response and liver lipid metabolism associated with NLRP3 inflammasome formation and activation.


2020 ◽  
Vol 11 ◽  
Author(s):  
Kelaier Yang ◽  
Jiannan Liu ◽  
Xiaohui Zhang ◽  
Ziqi Ren ◽  
Lei Gao ◽  
...  

Introduction: P2X7R excitation-interrelated NLRP3 inflammasome activation induced by high glucose contributes to the pathogenesis of diabetic retinopathy (DR). Relaxin-3 is a bioactive peptide with a structure similar to insulin, which has been reported to be effective in diabetic cardiomyopathy models in vivo and in vitro. However, it is not known whether relaxin-3 has a beneficial impact on DR, and the underlying mechanisms of the effect are also remain unknown.Methods and Results: The retinas of male streptozotocin (STZ)-induced diabetic Sprague-Dawley (SD) rats were characterized. Human retinal microvascular endothelial cells (HRMECs) were used to evaluate the anti-inflammatory, antiapoptotic, antipyroptotic and anti-migration effects of H3 relaxin by transmission electron microscopy, wound-healing assay, transwell assay, flow cytometry, cytokine assays and western-blot analysis. After H3 relaxin treatment, changes of the ultrastructure and expression of NLRP3 inflammasome related proteins in the retinas of rats were compared with those in the diabetic group. In vitro, H3 relaxin played a beneficial role that decreased cell inflammation, apoptosis, pyroptosis and migration stimulated by advanced glycation end products (AGEs). Moreover, inhibition of P2X7R and NLRP3 inflammasome activation decreased NLRP3 inflammasome-mediated injury that similar to the effects of H3 relaxin. H3 relaxin suppressed the stimulation of apoptosis, pyroptosis and migration of HRMECs in response to AGEs mediated by P2X7R activation of the NLRP3 inflammasome.Conclusion: Our findings provide new insights into the mechanisms of the inhibitory effect of H3 relaxin on AGE-induced retinal injury, including migration, apoptosis and pyroptosis, mediated by P2X7R-dependent activation of the NLRP3 inflammasome in HRMECs.


2020 ◽  
Vol 11 ◽  
Author(s):  
Nan Ding ◽  
Bo Wei ◽  
Xiaohui Fu ◽  
Chuan Wang ◽  
Yimou Wu

Fibrosis is a common pathway followed by different organs after injury, and it can lead to parenchymal scarring, cellular dysfunction, and even organ failure. The NLRP3 inflammasome is a multiprotein complex composed of the sensor molecule NLRP3, the adaptor apoptosis-associated speck-like protein containing a CARD (ASC), and the effector protease caspase-1. Overactivation of the NLRP3 inflammasome triggers the abundant secretion of IL-1β and IL-18, induces pyroptosis, and promotes the release of a swathe of proinflammatory proteins, all of which contribute to fibrogenic processes in multiple organs. In recent years, screening bioactive natural compounds for NLRP3 inhibitors to alleviate fibrosis has gained broad interest from the scientific community because of the associated cost-effectiveness and easy access. In this review, we systematically and comprehensively summarize the natural products, including terpenoids, phenols, and alkaloids, among others, and the plant-derived crude extracts, that have been reported to ameliorate fibrosis via inhibiting NLRP3 inflammasome activation and highlight the underlying mechanisms. Among all the compounds, diterpenoids is the most promising candidates for inhibiting NLRP3 inflammasome activation and improving fibrosis, as they possess combined inhibitory effect on NLRP3 inflammasome assembly and NF-κB signaling pathway. All the information may aid in the development of therapeutic strategies for the treatment of fibrotic diseases.


2021 ◽  
Vol 12 ◽  
Author(s):  
Hua Bai ◽  
Qifang Zhang

The nucleotide-binding domain leucine-rich repeat and pyrin domain containing receptor protein 3 (NLRP3) is an important pattern recognition receptor in human innate immunity. Activation of the NLRP3 inflammasome play a key role in the pathogenesis of Alzheimer’s disease (AD). Theories explaining activation of the NLRP3 inflammasome include the reactive oxygen species theory, the lysosomal damage theory and the mitochondrial DNA theory. The NLRP3 activation promotes occurrence of AD by producing IL-1β, IL-18 and other cytokines, and then by affecting the deposition of Aβ and tau proteins. Over-activated NLRP3 inflammasome often impair cell function and induces immune-related diseases. Some mechanisms have been found to negatively regulate activation of the NLRP3 inflammasome, which may be through receptor binding blocking mechanism, autophagy related mechanism, abnormal cytokine secretion mechanism, or interference related gene expression regulation mechanism. In this review, we summarize the possible mechanisms by which the activation of NLRP3 inflammasomes affects the pathogenesis of AD, and the recent advances in the prevention and treatment of AD by controlling the activation of NLRP3 inflammasomes. By researching the activation or inactivation of NLRP3 inflammasome, it is possible to reveal the pathogenesis of AD from a new perspective and provide a new idea for the prevention and treatment of AD.


2019 ◽  
Vol 26 (5) ◽  
pp. 837-854 ◽  
Author(s):  
Effimia Zacharia ◽  
Nikolaos Papageorgiou ◽  
Adam Ioannou ◽  
Gerasimos Siasos ◽  
Spyridon Papaioannou ◽  
...  

During the last few years, a significant number of studies have attempted to clarify the underlying mechanisms that lead to the presentation of atrial fibrillation (AF). Inflammation is a key component of the pathophysiological processes that lead to the development of AF; the amplification of inflammatory pathways triggers AF, and, in tandem, AF increases the inflammatory state. Indeed, the plasma levels of several inflammatory biomarkers are elevated in patients with AF. In addition, the levels of specific inflammatory biomarkers may provide information regarding to the AF duration. Several small studies have assessed the role of anti-inflammatory treatment in atrial fibrillation but the results have been contradictory. Large-scale studies are needed to evaluate the role of inflammation in AF and whether anti-inflammatory medications should be routinely administered to patients with AF.


2020 ◽  
Vol 25 (46) ◽  
pp. 4893-4913 ◽  
Author(s):  
Fan Cao ◽  
Jie Liu ◽  
Bing-Xian Sha ◽  
Hai-Feng Pan

: Inflammatory bowel disease (IBD) is a chronic, elusive disorder resulting in relapsing inflammation of intestine with incompletely elucidated etiology, whose two representative forms are ulcerative colitis (UC) and Crohn’s disease (CD). Accumulating researches have revealed that the individual genetic susceptibility, environmental risk elements, intestinal microbial flora, as well as innate and adaptive immune system are implicated in the pathogenesis and development of IBD. Despite remarkable progression of IBD therapy has been achieved by chemical drugs and biological therapies such as aminosalicylates, corticosteroids, antibiotics, anti-tumor necrosis factor (TNF)-α, anti-integrin agents, etc., healing outcome still cannot be obtained, along with inevitable side effects. Consequently, a variety of researches have focused on exploring new therapies, and found that natural products (NPs) isolated from herbs or plants may serve as promising therapeutic agents for IBD through antiinflammatory, anti-oxidant, anti-fibrotic and anti-apoptotic effects, which implicates the modulation on nucleotide- binding domain (NOD) like receptor protein (NLRP) 3 inflammasome, gut microbiota, intestinal microvascular endothelial cells, intestinal epithelia, immune system, etc. In the present review, we will summarize the research development of IBD pathogenesis and current mainstream therapy, as well as the therapeutic potential and intrinsic mechanisms of NPs in IBD.


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