NLRP3 Inflammasome: A Potential Alternative Therapy Target for Atherosclerosis

Lycopene inhibits pyroptosis of endothelial progenitor cells induced by ox-LDL through the AMPK/mTOR/NLRP3 pathway

The malfunction of endothelial progenitor cells (EPCs) due to ox-LDL is a risk contributor for arteriosclerotic disease. Meanwhile, lycopene possesses anti-inflammatory and antioxidative qualities. This investigation aimed to determine if lycopene can protect EPCs from ox-LDL-induced damage and to elucidate the underlying mechanism. The effects of lycopene on the survival, migration, and tube-forming capacity of EPCs were determined via in vitro assays. Expression of proteins related to pyroptosis and cellular proteins related to AMPK/mTOR/NLRP3 signaling was determined by western blot/flow cytometry. Our results demonstrated that lycopene treatment significantly enhanced proliferation, tube formation, and migration of EPCs stimulated by ox-LDL. Additionally, lycopene was found to suppress pyroptosis in ox-LDL-induced EPCs through the activation of AMPK, which led to the inhibition of mTOR phosphorylation and subsequent downregulation of the downstream NLRP3 inflammasome. In summary, our study suggests that lycopene mitigates ox-LDL-induced dysfunction in EPCs and inhibits pyroptosis via AMPK/mTOR/NLRP3 signaling. Our study suggests that lycopene may act as promising therapies for preventing atherosclerosis.

Melatonin alleviates pyroptosis by regulating the SIRT3/FOXO3α/ROS axis and interacting with apoptosis in Atherosclerosis progression

BACKGROUND

Atherosclerosis (AS), a significant contributor to cardiovascular disease (CVD), is steadily rising with the aging of the global population. Pyroptosis and apoptosis, both caspase-mediated cell death mechanisms, play an essential role in the occurrence and progression of AS. The human pineal gland primarily produces melatonin (MT), an indoleamine hormone with powerful anti-oxidative, anti-pyroptotic, and anti-apoptotic properties. This study examined MT's anti-oxidative stress and anti-pyroptotic effects on human THP-1 macrophages treated with nicotine.

METHODS

In vitro, THP-1 macrophages were induced by 1 µM nicotine to form a pyroptosis model and performed 30 mM MT for treatment. In vivo, ApoE-/- mice were administered 0.1 mg/mL nicotine solution as drinking water, and 1 mg/mL MT solution was intragastric administrated at 10 mg/kg/day. The changes in pyroptosis, apoptosis, and oxidative stress were detected.

RESULTS

MT downregulated pyroptosis, whose changes were paralleled by a reduction in reactive oxygen species (ROS) production, reversal of sirtuin3 (SIRT3), and Forkhead box O3 (FOXO3α) upregulation. MT also inhibited apoptosis, mainly caused by the interaction of caspase-1 and caspase-3 proteins. Vivo studies confirmed that nicotine could accelerate plaque formation. Moreover, mice treated with MT showed a reduction in AS lesion area.

CONCLUSIONS

MT alleviates pyroptosis by regulating the SIRT3/FOXO3α/ROS axis and interacting with apoptosis. Importantly, our understanding of the inhibitory pathways for macrophage pyroptosis will allow us to identify other novel therapeutic targets that will help treat, prevent, and reduce AS-associated mortality.

Anti-inflammation-based treatment of atherosclerosis using Gliclazide-loaded biomimetic nanoghosts

In the study, a biomimetic platform for anti-inflammatory-based treatment of atherosclerotic plaque was developed. Gliclazide (GL) as an anti-inflammasome agent was encapsulated in PLGA nanoparticles (NP), which were coated by monocyte membrane using an extrusion procedure. The size and zeta potential of the nanoghost (NG) changed to 292 and - 10 nm from 189.5 to -34.1 in the core NP. In addition, the actual size of 62.5 nm with a coating layer of 5 nm was measured using TEM. The NG was also showed a sustained release profile with the drug loading content of about 4.7%. Beside to attenuated TNFα, decrease in gene expression levels of NLRP3, MyD88, NOS, IL-1β, IL-18 and caspases 1/3/8/9 in LPS-primed monocytes exposed to NG strongly indicated remarkable inflammation control. After systemic toxicity evaluation and pharmacokinetic analysis of NP and NG, intravenous NG treatment of rabbits with experimentally induced atherosclerosis revealed remarkably less plaque lesions, foam cells, lipid-laden macrophages, and pathological issues in tunica media of aorta sections. Higher expression of CD163 than CD68 in aorta of NG-treated rabbits strongly reveals higher M2/M1 macrophage polarization. The bio/hemocompatible, biomimetic and anti-inflammatory NG can be considered as a potential platform for immunotherapy of particularly atherosclerosis in the field of personalized medicine.

Synthesis and Evaluation of [11C]MCC950 for Imaging NLRP3-Mediated Inflammation in Atherosclerosis

Overexpression of the NLRP3 inflammasome has been attributed to the progressive worsening of a multitude of cardiovascular inflammatory diseases such as myocardial infarction, pulmonary arterial hypertension, and atherosclerosis. The recently discovered potent and selective NLRP3 inhibitor MCC950 has shown promise in hindering disease progression, but NLRP3-selective cardiovascular positron emission tomography (PET) imaging has not yet been demonstrated. We synthesized [¹¹C]MCC950 with no-carrier-added [¹¹C]CO₂ fixation chemistry using an iminophosphorane precursor (RCY 45 ± 4%, >99% RCP, 27 ± 2 GBq/μmol, 23 ± 3 min, n = 6) and determined its distribution both in vivo and ex vivo in C57BL/6 and atherogenic ApoE^-/- mice. Small animal PET imaging was performed in both strains following intravenous administration via the lateral tail vein and revealed considerable uptake in the liver that stabilized by 20 min (7-8.5 SUV), coincident with secondary renal excretion. Plasma metabolite analysis uncovered excellent in vivo stability of [¹¹C]MCC950 (94% intact). Ex vivo autoradiography performed on excised aortas revealed heterogeneous uptake in atherosclerotic plaques of ApoE^-/- mice in comparison to C57BL/6 controls (48 ± 17 %ID/m² vs 18 ± 8 %ID/m², p = 0.002, n = 4-5). Treatment of ApoE^-/- mice with nonradioactive MCC950 (5 mg/kg, iv) 10 min prior to radiotracer administration increased uptake in the intestine (5.3 ± 1.8 %ID/g vs 11.0 ± 3.7 %ID/g, p = 0.04, n = 4-6) and in aortic lesions (48 ± 17 %ID/m² vs 104 ± 15 %ID/m², p = 0.0002, n = 5) by 108% and 117%, respectively, without significantly increasing plasma free fraction (f_p, 1.3 ± 0.4% vs 1.7 ± 0.8%, n = 2). These results suggest that [¹¹C]MCC950 uptake demonstrates specific binding and may prove useful for in vivo NLRP3 imaging in atherosclerosis.

Aldehyde dehydrogenase 2 and NOD-like receptor thermal protein domain associated protein 3 inflammasome in atherosclerotic cardiovascular diseases: A systematic review of the current evidence

Inflammation and dyslipidemia underlie the pathological basis of atherosclerosis (AS). Clinical studies have confirmed that there is still residual risk of atherosclerotic cardiovascular diseases (ASCVD) even after intense reduction of LDL. Some of this residual risk can be explained by inflammation as anti-inflammatory therapy is effective in improving outcomes in subjects treated with LDL-lowering agents. NOD-like receptor thermal protein domain associated protein 3 (NLRP3) inflammasome activation is closely related to early-stage inflammation in AS. Aldehyde dehydrogenase 2 (ALDH2) is an important enzyme of toxic aldehyde metabolism located in mitochondria and works in the metabolism of toxic aldehydes such as 4-HNE and MDA. Despite studies confirming that ALDH2 can negatively regulate NLRP3 inflammasome and delay the development of atherosclerosis, the mechanisms involved are still poorly understood. Reactive Oxygen Species (ROS) is a common downstream pathway activated for NLRP3 inflammasome. ALDH2 can reduce the multiple sources of ROS, such as oxidative stress, inflammation, and mitochondrial damage, thereby reducing the activation of NLRP3 inflammasome. Further, according to the downstream of ALDH2 and the upstream of NLRP3, the molecules and related mechanisms of ALDH2 on NLRP3 inflammasome are comprehensively expounded as possible. The potential mechanism may provide potential inroads for treating ASCVD.

Negative Correlation between Serum NLRP3 and the Ratio of Treg/Th17 in Patients with Obstructive Coronary Artery Disease

Background

Regulatory T (Treg) cells are a class of anti-inflammatory lymphocyte subpopulations with a potential protective effect against atherosclerosis, whereas T helper 17 (Th17) cells have been reported to possess proatherogenic activity. It was believed that disturbed circulating Treg/Th17 balance was associated with the onset and progression of atherosclerosis. This study is designed to probe the regulative action of serum Nod-like receptor protein 3 (NLRP3) on the Treg/Th17 balance in patients with atherosclerosis.

Methods

Fifty-two patients with coronary atherosclerosis and stenosis degrees of more than 50% were assigned to the coronary artery disease (CAD) group, and an equal number of people without coronary atherosclerosis were assigned to the control group (assessed by coronary angiography). Peripheral blood mononuclear cells (PBMCs) from two group patients were extracted and cultivated. The calculation of the Treg/Th17 ratio and quantitative analysis of the Treg and Th17 cell frequencies were performed through flow cytometry. Real-time fluorescence quantitative polymerase chain reaction (RT-PCR) was executed for the quantitative mRNA detection of the fork head-winged helix transcription factor (Foxp3) and the retinoic acid-related orphan nuclear receptor C (RORC) in PBMCs. Enzyme-linked immunosorbent assays were applied to measure the serum level of NLRP3, interleukin (IL)-10, IL-1 β , IL-17A, IL-23, and transforming growth factor (TGF)- β 1. Additionally, the connection between serum Treg/Th17 ratio and NLRP3 levels was analyzed using the Pearson correlation coefficient.

Results

The baseline parameters, including sex, age, or blood biochemical indices had no difference in both groups (p > 0.05). The CAD group showed higher Th17 cell frequency, lower Treg cell frequency, and a lower Treg/Th17 ratio when compared to the control (p < 0.05). Consistent with the variation in the T-cell subset ratio, in patients with atherosclerosis, the Th17-cell-related transcription factor RORC showed a markedly higher mRNA level (p < 0.05), conversely, the mRNA expression of the Treg cell-related transcription factor Foxp3 was notably reduced (p < 0.05). Similarly, the serum levels of NLRP3, IL-17A, IL-1, and IL-23 were significantly enhanced in CAD group but IL-10 and TGF- β 1 were reduced (p < 0.05). Additionally, a negative correlation was found between NLRP3 and the Treg/Th17 ratio (r = -0.69, p < 0.001).

Conclusions

Due to the potential impact on the serum Treg/Th17 ratio, NLRP3 may act as an aggravator in the onset and progression of atherosclerotic disease.

Melatonin Suppresses NLRP3 Inflammasome Activation via TLR4/NF-κB and P2X7R Signaling in High-Fat Diet-Induced Murine NASH Model

Background

NLRP3 inflammasome activation plays a critical role in mediating inflammation and NASH (non-alcoholic steatohepatitis) progression that ultimately leads to cirrhosis and hepatocellular carcinoma. Melatonin (MLT) controls high-fat diet-induced NASH in the murine model by modulating NLRP3 mediated inflammation. P2X7R-mediated inflammasome activation is reported in several inflammatory models including NASH.

Objective

The role of MLT in P2X7R-mediated inflammation in the NASH model has not yet been explored. The present study investigated the role of MLT in amending high-fat diet-induced nonalcoholic steatohepatitis in the murine liver.

Methods

To evaluate the hepatological changes, mice were divided into four groups to investigate the improvement potential of this MLT (10 and 20 mg/kg) and to assess the experimental findings. Histology, biochemical assays, ELISA, FACS analysis, Western blotting, and IF were performed to assess the physical and molecular changes upon melatonin treatment.

Results

The result demonstrated that MLT administration reduced HFD (high-fat diet)-induced non-alcoholic steatohepatitic indices, which successively restored the hepatic morphological architecture and other pathophysiological features too. Moreover, the application of MLT suppressed HFD-induced activation of the inflammasome and through TLR4/NF-κB signaling. Herein, we report that MLT significantly suppresses P2X7R expression and calcium influx along with inflammasome in both in vitro and in vivo. The docking study revealed a strong binding affinity of MLT with P2X7R. Moreover, the results also showed that the Nrf2 level was boosted which may normalize the expression of antioxidant proteins that safeguard against oxidative damage triggered by inflammation. Furthermore, some matrix metalloproteinases like MMP 2 and MMP 9 were repressed and TIMP-1 level was increased, which also signifies that MLT could improve liver fibrosis in this model.

Conclusion

Based on our findings, this study may conclude that MLT could be used as a therapeutic agent in the high-fat diet-induced NASH model as it has persuasive anti-inflammatory potential.

Regulation of Inflammasomes by Application of Omega-3 Polyunsaturated Fatty Acids in a Spinal Cord Injury Model

Omega-3 polyunsaturated fatty acids (PUFA n3) ameliorate inflammation in different diseases and potentially improve neurological function after neuronal injury. Following spinal cord injury (SCI), inflammatory events result in caspase-1 mediated activation of interleukin-1 beta (IL-1b) and 18. We aim to evaluate the neuroprotective potency of PUFA n3 in suppressing the formation and activation of inflammasomes following SCI. Male Wistar rats were divided into four groups: control, SCI, SCI+PUFA n3, and SCI+Lipofundin MCT (medium-chain triglyceride; vehicle). PUFA n3 or vehicle was intravenously administered immediately after SCI and every 24 h for the next three days. We analyzed the expression of NLRP3, NLRP1, ASC, caspase-1, IL-1b, and 18 in the spinal cord. The distribution of microglia, oligodendrocytes, and astrocytes was assessed by immunohistochemistry analysis. Behavioral testing showed significantly improved locomotor recovery in PUFA n3-treated animals and the SCI-induced upregulation of inflammasome components was reduced. Histopathological evaluation confirmed the suppression of microgliosis, increased numbers of oligodendrocytes, and the prevention of demyelination by PUFA n3. Our data support the neuroprotective role of PUFA n3 by targeting the NLRP3 inflammasome. These findings provide evidence that PUFA n3 has therapeutic effects which potentially attenuate neuronal damage in SCI and possibly also in other neuronal injuries.

Atherosclerosis as Mitochondriopathy: Repositioning the Disease to Help Finding New Therapies

Atherosclerosis is a complex pathology that involves both metabolic dysfunction and chronic inflammatory process. During the last decade, a considerable progress was achieved in describing the pathophysiological features of atherosclerosis and developing approaches that target the abnormal lipid metabolism and chronic inflammation. However, early events in the arterial wall that initiate the disease development still remain obscure. Finding effective therapeutic targets in these early processes would allow developing methods for disease prevention and, possibly, atherosclerotic plaque regression. Currently, these early events are being actively studied by several research groups. One of the processes that are being investigated is the development of mitochondrial dysfunction, which was demonstrated to be present in the affected areas of the arterial wall. Detection and characterization of mitochondrial dysfunction associated with several chronic human disorders was made possible by the improved methods of studying mitochondrial biology and detecting mitochondrial DNA (mtDNA) mutations. It was found to be involved in several key atherogenic processes, such as oxidative stress, chronic inflammation, and intracellular lipid accumulation. Mitochondrial dysfunction can occur in all types of cells involved in the pathogenesis of atherosclerosis: monocytes and macrophages, smooth muscle cells, lymphocytes, and the endothelial cells. However, therapies that would specifically target the mitochondria to correct mitochondrial dysfunction and neutralize the defective organelles are still remain to be developed and characterized. The aim of this review is to outline the prospects for mitochondrial therapy for atherosclerosis. We discuss mechanisms of mitochondria-mediated atherogenic processes, known mitochondria-targeting therapy strategies, and novel mitochondria-targeting drugs in the context of atherosclerosis.

From Mitochondria to Atherosclerosis: The Inflammation Path

Inflammation is a key process in metazoan organisms due to its relevance for innate defense against infections and tissue damage. However, inflammation is also implicated in pathological processes such as atherosclerosis. Atherosclerosis is a chronic inflammatory disease of the arterial wall where unstable atherosclerotic plaque rupture causing platelet aggregation and thrombosis may compromise the arterial lumen, leading to acute or chronic ischemic syndromes. In this review, we will focus on the role of mitochondria in atherosclerosis while keeping inflammation as a link. Mitochondria are the main source of cellular energy. Under stress, mitochondria are also capable of controlling inflammation through the production of reactive oxygen species (ROS) and the release of mitochondrial components, such as mitochondrial DNA (mtDNA), into the cytoplasm or into the extracellular matrix, where they act as danger signals when recognized by innate immune receptors. Primary or secondary mitochondrial dysfunctions are associated with the initiation and progression of atherosclerosis by elevating the production of ROS, altering mitochondrial dynamics and energy supply, as well as promoting inflammation. Knowing and understanding the pathways behind mitochondrial-based inflammation in atheroma progression is essential to discovering alternative or complementary treatments.

NLRP3 Inflammasome at the Interface of Inflammation, Endothelial Dysfunction, and Type 2 Diabetes

Type 2 diabetes mellitus (T2DM), accounting for 90–95% cases of diabetes, is characterized by chronic inflammation. The mechanisms that control inflammation activation in T2DM are largely unexplored. Inflammasomes represent significant sensors mediating innate immune responses. The aim of this work is to present a review of links between the NLRP3 inflammasome, endothelial dysfunction, and T2DM. The NLRP3 inflammasome activates caspase-1, which leads to the maturation of pro-inflammatory cytokines interleukin 1β and interleukin 18. In this review, we characterize the structure and functions of NLRP3 inflammasome as well as the most important mechanisms and molecules engaged in its activation. We present evidence of the importance of the endothelial dysfunction as the first key step to activating the inflammasome, which suggests that suppressing the NLRP3 inflammasome could be a new approach in depletion hyperglycemic toxicity and in averting the onset of vascular complications in T2DM. We also demonstrate reports showing that the expression of a few microRNAs that are also known to be involved in either NLRP3 inflammasome activation or endothelial dysfunction is deregulated in T2DM. Collectively, this evidence suggests that T2DM is an inflammatory disease stimulated by pro-inflammatory cytokines. Finally, studies revealing the role of glucose concentration in the activation of NLRP3 inflammasome are analyzed. The more that is known about inflammasomes, the higher the chances to create new, effective therapies for patients suffering from inflammatory diseases. This may offer potential novel therapeutic perspectives in T2DM prevention and treatment.

Endoplasmic Reticulum Stress in Macrophages: The Vicious Circle of Lipid Accumulation and Pro-Inflammatory Response

The endoplasmic reticulum (ER) stress is an important event in the pathogenesis of different human disorders, including atherosclerosis. ER stress leads to disturbance of cellular homeostasis, apoptosis, and in the case of macrophages, to foam cell formation and pro-inflammatory cytokines production. In atherosclerosis, several cell types can be affected by ER stress, including endothelial cells, vascular smooth muscular cells, and macrophages. Modified low-density lipoproteins (LDL) and cytokines, in turn, can provoke ER stress through different processes. The signaling cascades involved in ER stress initiation are complex and linked to other cellular processes, such as lysosomal biogenesis and functioning, autophagy, mitochondrial homeostasis, and energy production. In this review, we discuss the underlying mechanisms of ER stress formation and the interplay of lipid accumulation and pro-inflammatory response. We will specifically focus on macrophages, which are the key players in maintaining chronic inflammatory milieu in atherosclerotic lesions, and also a major source of lipid-accumulating foam cells.