NLRP3 inflammasome negatively regulates podocyte autophagy in diabetic nephropathy

Inflammasome mechanisms are recognized as a key pathophysiology of diabetic nephropathy (DN). The nucleotide-oligomerization domain-like receptor 3 (NLRP3) inflammasome has attracted the most attention. Autophagy as a conserved intracellular catabolic pathway plays essential roles in the maintenance of podocytes. Although autophagy was involved in preventing excessive inflammatory responses in kidney diseases, a clear understanding of the regulation of NLRP3 inflammasome on autophagy in glomerular damage in DN is still lacking. In this study, we focused on the effect of the activation of NLRP3 inflammasome on the suppression of podocyte autophagy and aimed to investigate the role of autophagy in podocyte injury in DN. Podocyte autophagy has been confirmed to be inhibited in high-fat diet/streptozotocin (HFD/STZ)-induced DN mice, and NLRP3 has been found to be upregulated in both mice and human DN biopsies and in vitro. Activation of NLRP3 inflammasome exacerbated podocyte autophagy and reduced podocyte nephrin expression, while silencing of NLRP3 efficiently restored podocyte autophagy and ameliorated podocyte injury induced by high glucose. The results showed that NLRP3 was a negative regulator of autophagy and suggested that restoration of podocyte autophagy by inactivation of NLRP3 under high glucose could reduce podocyte injury. Proper modification of autophagy and inflammasome has the potential to benefit the kidney in DN.     

Naoxintong attenuates Ischaemia/reperfusion Injury through inhibiting NLRP3 inflammasome activation

Naoxintong (NXT) is a Chinese Materia Medica standardized product extracted from 16 various kinds of Chinese traditional herbal medicines including Salvia miltiorrhiza, Angelica sinensis, Astragali Radix. Naoxintong is clinically effective in treating ischaemia heart disease. Nucleotide‐binding oligomerization domain‐Like Receptor with a Pyrin domain 3 (NLRP3) inflammasome has been critically involved in myocardial ischaemia/reperfusion (I/R) injury. Here, we have been suggested that NXT might attenuate myocardial I/R injury via suppression of NLRP3 inflammasome activation. Male C57BL6 mice were subjected to myocardial I/R injury via 45 min. coronary ligation and release for the indicated times. Naoxintong (0.7 g/kg/day) and PBS were orally administrated for 2 weeks before surgery. Cardiac function assessed by echocardiography was significantly improved in the NXT group compared to PBS group at day 2 after myocardial I/R. NLRP3 inflammasome activation is crucially involved in the initial inflammatory response after myocardial I/R injury, leading to cleaved caspase‐1, mature interleukin (IL)‐1β production, accompanying by macrophage and neutrophil infiltration. The cardioprotective effect of NXT was associated with a diminished NLRP3 inflammasome activation, decreased pro‐inflammatory macrophage (M1 macrophages) and neutrophil infiltration after myocardial I/R injury. In addition, serum levels of IL‐1β, indicators of NLRP3 inflammasome activation, were also significantly suppressed in the NXT treated group after I/R injury. Naoxintong exerts cardioprotive effects at least partly by suppression of NLRP3 inflammasome activation in this I/R injury model.     

Tojapride prevents CaSR‐mediated NLRP3 inflammasome activation in oesophageal epithelium irritated by acidic bile salts

Impairment of the oesophageal epithelium in patients with reflux oesophagitis (RE) is a cytokine‐mediated injury rather than a chemical burn. The present study was conducted to explore CaSR/NLRP3 inflammasome pathway activation and cytokines IL‐1β and IL‐18 release in oesophageal epithelia injured by refluxates and the effects of Tojapride on that signal regulation. Using a modified RE rat model with Tojapride administration and Tojapride‐pretreated SV40‐immortalized human oesophageal epithelial cells (HET‐1A) exposed to acidic bile salts pretreated with Tojapride, we evaluated the therapeutic effects of Tojapride on oesophageal epithelial barrier function, the expression of CaSR/NLRP3 inflammasome pathway‐related proteins and the release of downstream cytokines in response to acidic bile salt irritation. In vivo, Tojapride treatment ameliorated the general condition and pathological lesions of the oesophageal epithelium in modified RE rats. In addition, Tojapride effectively blocked the CaSR‐mediated NLRP3 inflammasome activation in modified RE rats. In vitro, Tojapride treatment can reverse the harmful effect of acidic bile salts, which reduced transepithelial electrical resistance (TEER), up‐regulated the CaSR‐mediated NLRP3 inflammasome pathway and increased caspase‐1 activity, LDH release and cytokines secretion. Taken together, these data show that Tojapride can prevent CaSR‐mediated NLRP3 inflammasome activation and alleviate oesophageal epithelial injury induced by acidic bile salt exposure.     

CD36 aggravates podocyte injury by activating NLRP3 inflammasome and inhibiting autophagy in lupus nephritis

A major cause of proteinuria in lupus nephritis (LN) is podocyte injury, and determining potential therapeutic targets to prevent podocyte injury is important from a clinical perspective in the treatment of LN. CD36 is involved in podocyte injury in several glomerulopathies and was reported to be a vital candidate gene in LN. Here, we determined the role of CD36 in the podocyte injury of LN and the underlying mechanisms. We observed that CD36 and NLRP3 (NLR family pyrin domain containing 3) were upregulated in the podocytes of lupus nephritis patients and MRL/lpr mice with renal impairment. In vitro, CD36, NLRP3 inflammasome, and autophagy were elevated accompanied with increased podocyte injury stimulated by IgG extracted from lupus nephritis patients compared that from healthy donors. Knocking out CD36 with the CRISPR/cas9 system decreased the NLRP3 inflammasome levels, increased the autophagy levels and alleviated podocyte injury. By enhancing autophagy, NLRP3 inflammasome was decreased and podocyte injury was alleviated. These results demonstrated that, in lupus nephritis, CD36 promoted podocyte injury by activating NLRP3 inflammasome and inhibiting autophagy by enhancing which could decrease NLRP3 inflammasome and alleviate podocyte injury.Subject terms: Mechanisms of disease, Inflammasome, Lupus nephritis, Autophagy     

TAK1 mediates excessive autophagy via p38 and ERK in cisplatin‐induced acute kidney injury

The ability of cisplatin (cis‐diamminedichloroplatinum II) toxicity to induce acute kidney injury (AKI) has attracted people's attention and concern for a long time, but its molecular mechanisms are still widely unknown. We found that the expression of transforming growth factor‐β (TGF‐β)‐activated kinase 1 (TAK1) could be increased in kidneys of mice administrated with cisplatin. Autophagy is an evolutionarily conserved catabolic pathway and is involved in various acute and chronic injuries. Moreover, p38 MAPK (mitogen‐activated protein kinase) and ERK regulate autophagy in response to various stimuli. Therefore, our hypothesis is that cisplatin activates TAK1, which phosphorylates p38 and ERK, leading to excessive autophagy of tubular epithelial cells and thus exacerbating kidney damage. Here, BALB/c mice were intraperitoneally injected with a TAK1 inhibitor and were then administrated with sham or cisplatin at 20 mg/kg by intraperitoneal injection. Compared with mice in the vehicle cisplatin group, mice intraperitoneally injected with a TAK1 inhibitor were found to have lower serum creatinine and less tubular damage following cisplatin‐induced AKI. Furthermore, inhibition of TAK1 reduced p38 and Erk phosphorylation, decreased expression of LC3II and reversed the down‐regulation of P62 expression induced by cisplatin. The hypothesis was verified with tubular epithelial cells administrated with cisplatin in vitro. Finally, p38 inhibitor or ERK inhibitor abated autophagy activation and cell viability reduction in tubular epithelial cells treated with cisplatin plus TAK1 overexpression vector. Taken together, our results show that cisplatin activates TAK1, which phosphorylates p38 and ERK, leading to excessive autophagy of tubular epithelial cells that exacerbates kidney damage.     

Hepatoprotective effect of allicin against acetaminophen‐induced liver injury: Role of inflammasome pathway,apoptosis, and liver regeneration

Acetaminophen (APAP) overdose leads to liver injury. NLRP3 inflammasome is a key player in APAP‐induced inflammation. Also, apoptosis and liver regeneration play an important role in liver injury. Therefore, we assessed allicin's protective effect on APAP‐induced hepatotoxicity and studied its effect on NLRP3 inflammasome and apoptosis. Mice in the APAP group were injected by APAP (250 mg/kg, intraperitoneal). The allicin‐treated group received allicin orally (10 mg/kg/d) during 7 days before APAP injection. Serum and hepatic tissues were separated 24 hours after APAP injection. Serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), albumin, alkaline phosphatase (ALP), and hepatic malondialdehyde (MDA) were assessed using the colorimetric method. Hepatic NLRP3 inflammasome, caspase‐1, and interleukin‐1β (IL‐1β) were estimated using enzyme‐linked immunosorbent assay. Hepatic Bcl‐2 and Ki‐67 were investigated by immunohistochemistry. APAP significantly increased AST, ALT, and ALP, whereas allicin significantly decreased their levels. Also, APAP significantly decreased albumin and allicin significantly improved it. APAP produced changes in liver morphology, including inflammation and massive coagulative necrosis. Allicin protected the liver from APAP‐induced necrosis, apoptosis, and hepatocellular degeneration via increasing Bcl‐2 and Ki‐67 levels. APAP significantly increased the hepatic MDA, whereas allicin significantly prevented this increase. APAP markedly activated the NLRP3 inflammasome pathway and consequently increased the production of caspase‐1 and IL‐1β. Interestingly, we found that allicin significantly inhibited NLRP3 inflammasome activation, which resulted in decreased caspase‐1 and IL‐1β levels. Allicin has a hepatoprotective effect against APAP‐induced liver injury via the decline of oxidative stress and inhibition of the inflammasome pathway and apoptosis. Therefore, allicin might be a novel tool to halt the progression of APAP‐stimulated hepatotoxicity.     

γ‐secretase inhibitor DAPT mitigates cisplatin‐induced acute kidney injury by suppressing Notch1 signaling

Organ toxicity, including kidney injury, limits the use of cisplatin for the treatment of multiple human cancers. Hence, interventions to alleviate cisplatin‐induced nephropathy are of benefit to cancer patients. Recent studies have demonstrated that pharmacological inhibition of the Notch signaling pathway enhances cisplatin efficacy against several cancer cells. However, whether augmentation of the anti‐cancer effect of cisplatin by Notch inhibition comes at the cost of increased kidney injury is unclear. We show here that treatment of mice with cisplatin resulted in a significant increase in Notch ligand Delta‐like 1 (Dll1) and Notch1 intracellular domain (N1ICD) protein expression levels in the kidneys. N‐[N‐(3,5‐difluorophenacetyl)‐L‐alanyl]‐S‐phenylglycine t‐butyl ester (DAPT), a γ‐secretase inhibitor reversed cisplatin‐induced increase in renal N1ICD expression and plasma or urinary levels of predictive biomarkers of acute kidney injury (AKI). DAPT also mitigated cisplatin‐induced tubular injury and reduction in glomerular filtration rate. Real‐time multiphoton microscopy revealed marked necrosis and peritubular vascular dysfunction in the kidneys of cisplatin‐treated mice which were abrogated by DAPT. Cisplatin‐induced Dll1/Notch1 signaling was recapitulated in a human proximal tubule epithelial cell line (HK‐2). siRNA‐mediated Dll1 knockdown and DAPT attenuated cisplatin‐induced Notch1 cleavage and cytotoxicity in HK‐2 cells. These data suggest that Dll1‐mediated Notch1 signaling contributes to cisplatin‐induced AKI. Hence, the Notch signaling pathway could be a potential therapeutic target to alleviate renal complications associated with cisplatin chemotherapy.     

Amyloid β induces NLRP3 inflammasome activation in retinal pigment epithelial cells via NADPH oxidase‐ and mitochondria‐dependent ROS production

Amyloid β (Aβ)‐induced chronic inflammation is believed to be a key pathogenic process in early‐stage age‐related macular degeneration (AMD). Nucleotide oligomerization domain (NOD)‐like receptor family, pyrin domain containing 3 (NLRP3) inflammasome activation triggered by Aβ is responsible for retinal pigment epithelium (RPE) dysfunction in the onset of AMD; however, the detailed molecular mechanism remains unclear. In this study, we investigated the involvement of NADPH oxidase‐ and mitochondria‐derived reactive oxygen species (ROS) in the process of Aβ_1–40‐induced NLRP3 inflammasome activation in LPS‐primed ARPE‐19 cells. The results showed that Aβ_1–40 could induce excessive ROS generation, MAPK/NF‐κB signaling activation and subsequently NLRP3 inflammasome activation in LPS‐primed ARPE‐19 cells. Furthermore, the inductive effect of Aβ_1–40 on NLRP3 inflammasome activation was mediated in a manner dependent on NADPH oxidase‐ and mitochondria‐derived ROS. Our findings may provide a novel insight into the molecular mechanism by which Aβ contributes to the early‐stage AMD.     

Cyclic‐di‐GMP and cyclic‐di‐AMP activate the NLRP3 inflammasome

The cyclic dinucleotides 3'‐5'diadenylate (c‐diAMP) and 3'‐5' diguanylate (c‐diGMP) are important bacterial second messengers that have recently been shown to stimulate the secretion of type I Interferons (IFN‐Is) through the c‐diGMP‐binding protein MPYS/STING. Here, we show that physiologically relevant levels of cyclic dinucleotides also stimulate a robust secretion of IL‐1β through the NLRP3 inflammasome. Intriguingly, this response is independent of MPYS/STING. Consistent with most NLRP3 inflammasome activators, the response to c‐diGMP is dependent on the mobilization of potassium and calcium ions. However, in contrast to other NLRP3 inflammasome activators, this response is not associated with significant changes in mitochondrial potential or the generation of mitochondrial reactive oxygen species. Thus, cyclic dinucleotides activate the NLRP3 inflammasome through a unique pathway that could have evolved to detect pervasive bacterial pathogen‐associated molecular patterns associated with intracellular infections.     

Effect of low-dose ethanol on NLRP3 inflammasome in diabetes-induced lung injury

To observe the changes in NLR family pyrin domain containing 3 (NLRP3) inflammasome in a rat model of diabetes-induced lung injury, and investigate the effect of low-dose ethanol on the production of NLRP3 inflammasome. The type I diabetic mellitus (DM) rat model was established, and the rats were divided into four groups: normal control group (CON group), low-dose ethanol group (EtOH group), diabetes group (DM group) and DM+EtOH group. The rats were fed for 6 and 12 weeks, respectively. The ratio of lung wet weight/body weight (lung/body coefficient) was calculated, and the changes of pulmonary morphology and fibrosis were observed by HE and Masson staining. The changes in pulmonary ultra-structure were examined by electron microscopy. The expressions of mitochondrial acetaldehyde dehydrogenase 2 (ALDH2) and NLRP3 inflammasome key factors, NLRP3, ASC and caspase-1 proteins were detected by western blot. Compared with the CON group, the lung/body coefficient was increased (P<0.05), lung fibrosis occurred, ALDH2 protein expression was decreased, and NLRP3, ASC and caspase-1 protein expressions were increased in the DM rats (P<0.05). Compared with the DM group, the lung/body coefficient and fibrosis degree were decreased, ALDH2 protein expression was increased (P<0.05), and NLRP3, ASC and caspase-1 protein expressions were decreased in the DM+EtOH group (P<0.05). Hence, low-dose ethanol increased ALDH2 protein expression and alleviated diabetes-induced lung injury by inhibiting the production of NLRP3 inflammasome.     

Plasticizer DBP Activates NLRP3 Inflammasome through the P2X7 Receptor in HepG2 and L02 Cells

Ditubyl phthalate (DBP), one of the most widely used plasticizers, can migrate out to contaminate our bodies and environment. A number of studies have showed that DBP is closely related to liver pathological changes and diseases. Inflammasomes are multiprotein complexes composed of procaspase and pattern recognition receptors such as Nucleotide oligomerization domain (NOD) like receptor family, pyrin domain containing 3 (NLRP3). Activation of NLRP3 inflammasome is implicated in the pathogeneses of liver damage. The aim of this study was to determine the effects of DBP on NLRP3 inflammasome. We found that DBP triggered the activation of NLRP3 inflammasome in hepatocyte cell lines. By using Ca‐074‐Me, N‐acetylcysteine and KN‐62, we observed that the P2X₇ receptor participated in the DBP‐induced activation of NLRP3 inflammasome. DBP could also trigger the ATP release. In conclusion, we demonstrated that DBP is one of the activator of NLRP3 inflammasome and may play an important role in liver damage.     

Expression of the NLRP3 Inflammasome in Cerebral Cortex After Traumatic Brain Injury in a Rat Model

Inflammatory response plays an important role in the pathogenesis of secondary damage after traumatic brain injury (TBI). The inflammasome is a multiprotein complex involved in innate immunity and a number of studies have suggested that the inflammasome plays a critical role in a host inflammatory signaling. Nucleotide-binding domain, leucine-rich repeat, pyrin domain containing 3 (NLRP3) is a key component of the NLRP3-inflammasome, which also includes apoptotic speck-containing protein (ASC) with a cysteine protease (caspase) -activating recruitment domain and pro-caspase1. Activation of the NLRP3-inflammasome causes the processing and release of the interleukin 1 beta (IL-1β) and interleukin 18 (IL-18). Based on this, we hypothesized that the NLRP3-inflammasome could participate in the inflammatory response following TBI. However, the expression of NLRP3-inflammasome in cerebral cortex after TBI is not well known. Rats were randomly divided into control, sham and TBI groups (including 6 h, 1 day, 3 day and 7 day sub-group). TBI model was induced, and animals were sacrificed at each time point respectively. The expression of NLRP3-inflammasome was measured by quantitative real-time polymerase chain reaction, western blot and immunohistochemistry respectively. Immunofluorescent double labeling was performed to identify the cell types of NLRP3-inflammasome’s expression. Moreover, enzyme linked immunosorbent assay was used to detect the alterations of IL-1β and IL-18 at each time point post-injury. The results showed that, TBI could induce assembly of NLRP3-inflammasome complex, increased expression of ASC, activation of caspase1, and processing of IL-1β and IL-18. These results suggested that NLRP3-inflammasome might play an important role in the inflammation induced by TBI and could be a target for TBI therapy.     

The Microbiota‐Inflammasome Hypothesis of Major Depression

We propose the “microbiota‐inflammasome” hypothesis of major depressive disorder (MDD, a mental illness affecting the way a person feels and thinks, characterized by long‐lasting feelings of sadness). We hypothesize that pathological shifts in gut microbiota composition (dysbiosis) caused by stress and gut conditions result in the upregulation of pro‐inflammatory pathways mediated by the Nod‐like receptors family pyrin domain containing 3 (NLRP3) inflammasome (an intracellular platform involved in the activation of inflammatory processes). This upregulation exacerbates depressive symptomatology and further compounds gut dysbiosis. In this review we describe MDD/chronic stress‐induced changes in: 1) NLRP3 inflammasome; 2) gut microbiota; and 3) metabolic pathways; and how inflammasome signaling may affect depressive‐like behavior and gut microbiota composition. The implication is that novel therapeutic strategies could emerge for MDD and co‐morbid conditions. A number of testable predictions surface from this microbiota‐gut‐inflammasome‐brain hypothesis of MDD, using approaches that modulate gut microbiota composition via inflammasome modulation, fecal microbiota transplantation, psychobiotics supplementation, or dietary change.     

Palbinone alleviates diabetic retinopathy in STZ‐induced rats by inhibiting NLRP3 inflammatory activity

Diabetic retinopathy (DR) is the primary cause of blindness and visual impairment in diabetes patients worldwide. However, laser and surgical therapies at DR have short‐term effectiveness and cause side effects. Treatment with natural products is a reasonable alternative treatment for DR. The main objective of this investigation is to explore the efficacy of a bioactive compound such as palbinone (PB) in DR. Experimental rats were injected intraperitoneally with streptozotocin (STZ, 65 mg/kg), and these established experimental rats were treated with PB (20 mg/kg/bw) for 42 days. The observed results showed that PB considerably reduced the proinflammatory cytokine (interleukin‐18 [IL‐18] and IL‐1β) production as well as improved the activities of antioxidant enzymes (superoxide dismutase, catalase, and glutathione peroxidase) particularly in the retinal region of STZ‐induced DR rats. In addition, PB treatment improved nuclear factor erythroid 2‐related factor 2 (Nrf2) accumulation and enhanced the heme oxygenase‐1 expression, and major antioxidants downregulated Nrf2 in the damaged retina. Also, the expression levels of nod‐like receptor family pyrin domain containing 3 (NLRP3), cleaved‐caspase‐1, IL‐1β, and apoptosis‐associated speck‐like protein containing CARD in the retinal region were notably upregulated in STZ‐induced DR, which was eliminated by PB interference. PB administration exerted efficient antioxidant activities, Nrf2 pathway activation, and inhibition of NLRP3 inflammasome. This current investigation concluded that PB considerably reduced the retinal inflammation and oxidative stress stimulated via high glucose, and also activated the antioxidative Nrf2 pathway and inhibited the NLRP3 inflammasome formation in rats.     

POP1 might be recruiting its type‐Ia interface for NLRP3‐mediated PYD‐PYD interaction: Insights from MD simulation

Inflammasomes are multiprotein caspase‐activating complexes that enhance the maturation and release of proinflammatory cytokines (IL‐1β and IL‐18) in response to the invading pathogen and/or host‐derived cellular stress. These are assembled by the sensory proteins (viz NLRC4, NLRP1, NLRP3, and AIM‐2), adaptor protein (ASC), and effector molecule procaspase‐1. In NLRP3‐mediated inflammasome activation, ASC acts as a mediator between NLRP3 and procaspase‐1 for the transmission of signals. A series of homotypic protein‐protein interactions (NLRP3^PYD:ASC^PYD and ASC^CARD:CASP1^CARD) propagates the downstream signaling for the production of proinflammatory cytokines. Pyrin‐only protein 1 (POP1) is known to act as the regulator of inflammasome. It modulates the ASC‐mediated inflammasome assembly by interacting with pyrin domain (PYD) of ASC. However, despite similar electrostatic surface potential, the interaction of POP1 with NLRP3^PYD is obscured till date. Herein, to explore the possible PYD‐PYD interactions between NLRP3^PYD and POP1, a combined approach of protein‐protein docking and molecular dynamics simulation was adapted. The current study revealed that POP1's type‐Ia interface and type‐Ib interface of NLRP3^PYD might be crucial for 1:1 PYD‐PYD interaction. In addition to type‐I mode of interaction, we also observed type‐II and type‐III interaction modes in two different dynamically stable heterotrimeric complexes (POP1‐NLRP3‐NLRP3 and POP1‐NLRP3‐POP1). The inter‐residual/atomic distance calculation exposed several critical residues that possibly govern the said interaction, which need further investigation. Overall, the findings of this study will shed new light on hitherto concealed molecular mechanisms underlying NLRP3‐mediated inflammasome, which will have strong future therapeutic implications.     

Aging aggravated liver ischemia and reperfusion injury by promoting STING‐mediated NLRP3 activation in macrophages

Although aggravated liver injury has been reported in aged livers post‐ischemia and reperfusion (IR), the underlying mechanism of innate immune activation of aged macrophages is not well understood. Here, we investigated whether and how Stimulator of interferon genes (STING) signaling regulated macrophage proinflammatory activation and liver IR injury. Mice were subjected to hepatic IR in vivo. Macrophages isolated from IR‐stressed livers and bone marrow‐derived macrophages (BMDMs) from young and aged mice were used for in vitro studies. Enhanced nucleotide‐binding domain and leucine‐rich repeat containing protein 3 (NLRP3) activation was found in both livers and macrophages of aged mice post‐IR. NLRP3 knockdown in macrophages inhibited intrahepatic inflammation and liver injury in both young and aged mice. Interestingly, enhanced activation of the STING/ TANK‐binding kinase 1 (TBK1) signaling pathway was observed in aged macrophages post‐IR and mitochondria DNA (mtDNA) stimulation. STING suppression blocked over‐activation of NLRP3 signaling and excessive secretion of proinflammatory cytokines/chemokines in the mtDNA‐stimulated BMDMs from aged mice. More importantly, STING knockdown in macrophages abrogated the detrimental role of aging in aggravating liver IR injury and intrahepatic inflammation. Finally, peripheral blood from the recipients undergoing liver transplantation was collected and analyzed. The results showed that the elderly recipients had much higher levels of TNF‐α, IL‐6, IL‐1β, and IL‐18 post‐transplantation, indicating increased NLRP3 activation in lR‐stressed livers of elderly recipients. In summary, our study demonstrated that the STING‐NLRP3 axis was critical for the proinflammatory response of aged macrophages and would be a novel therapeutic target to reduce IR injury in elderly patients.     

Effects of NIX‐mediated mitophagy on ox‐LDL‐induced macrophage pyroptosis in atherosclerosis

Pyroptosis is a form of cell death that is uniquely dependent on caspase‐1. Pyroptosis involved in oxidized low‐density lipoprotein (ox‐LDL)‐induced human macrophage death through the promotion of caspase‐1 activation is important for the formation of unstable plaques in atherosclerosis. The mitochondrial outer membrane protein NIX directly interacts with microtubule‐associated protein 1 light chain 3 (LC3). Although we previously showed that NIX‐mediated mitochondrial autophagy is involved in the clearance of damaged mitochondria, how NIX contributes to ox‐LDL‐induced macrophage pyroptosis remains unknown. Here, immunoperoxidase staining Nix expression decreased in human atherosclerosis. When we silenced NIX expression in murine macrophage cell, active caspase‐1, and mature interleukin‐1β expression levels were increased and LC3 was reduced. In addition, LDH release and acridine orange and ethidium bromide staining indicated that damage to macrophage cell membranes induced by ox‐LDL was substantially worse. Moreover, intracellular reactive oxygen species and NLRP3 inflammasome levels increased. Taken together, these results demonstrated that NIX inhibits ox‐LDL‐induced macrophage pyroptosis via autophagy in atherosclerosis.     

Soluble uric acid induces myocardial damage through activating the NLRP3 inflammasome

Uric acid crystal is known to activate the NLRP3 inflammasome and to cause tissue damages, which can result in many diseases, such as gout, chronic renal injury and myocardial damage. Meanwhile, soluble uric acid (sUA), before forming crystals, is also related to these diseases. This study was carried out to investigate whether sUA could also activate NLRP3 inflammasome in cardiomyocytes and to analyse the mechanisms. The cardiomyocyte activity was monitored, along with the levels of mature IL‐1β and caspase‐1 from H9c2 cells following sUA stimulus. We found that sUA was able to activate NLRP3 inflammasome, which was responsible for H9c2 cell apoptosis induced by sUA. By elevating TLR6 levels and then activating NF‐κB/p65 signal pathway, sUA promoted NLRP3, pro‐caspase 1 and pro‐IL‐1β production and provided the first signal of NLRP3 inflammasome activation. Meanwhile, ROS production regulated by UCP2 levels also contributed to NLRP3 inflammasome assembly and subsequent caspase 1 activation and mature IL‐1β secretion. In addition, the tlr6 knockdown rats suffering from hyperuricemia showed the lower level of IL‐1β and an ameliorative cardiac function. These findings suggest that sUA activates NLRP3 inflammasome in cardiomyocytes and they may provide one therapeutic strategy for myocardial damage induced by sUA.     

Purple sweet potato color attenuated NLRP3 inflammasome by inducing autophagy to delay endothelial senescence

Autophagy is a vital negative factor regulating cellular senescence. Purple sweet potato color (PSPC), one type of flavonoid, has been demonstrated to suppress endothelial senescence and restore endothelial function in diabetic mice by inhibiting the nucleotide-binding oligomerization domain, leucine rich repeat and pyrin domain containing protein 3 (NLRP3) inflammasome. However, the roles of autophagy in the inflammatory response during endothelial senescence are unknown. Here, we found that PSPC augmented autophagy to restrict high-glucose-induced premature endothelial senescence. In addition, PSPC administration impaired endothelium aging in diabetic mice by increasing autophagy. Inhibition of autophagy accelerated endothelial senescence, while enhancement of autophagy delayed senescence. Moreover, deactivation of the NLRP3 inflammasome triggered by PSPC was autophagy-dependent. Autophagy receptor microtubule-associated protein 1 light chain 3 and p62 interacted with the inflammasome component NLRP3, suggesting that autophagosomes target the NLRP3 inflammasome and deliver it to the lysosome for degradation. Altogether, PSPC amplified cellular autophagy, subsequently attenuated NLRP3 inflammasome activity and finally delayed endothelial senescence to ameliorate cardiovascular complication. These results suggest a potential therapeutic target in senescence-related cardiovascular diseases.     

Scutellarin protects against myocardial ischemia-reperfusion injury by suppressing NLRP3 inflammasome activation

BackgroundActivation of NLRP3 inflammasome plays a key role in cardiac dysfunction for acute myocardial ischemia-reperfusion injury. Scutellarin (Scu) is a flavonoid purified from Erigeron breviscapus. Whether Scu has any influence on the activation of NLRP3 inflammasome in cardiomyocytes remains unknown.PurposeWe aimed to examine the therapeutic effect of Scu on cardiomyocyte ischemia-reperfusion (I/R) injury and its effect on NLRP3 inflammasome in rats with acute myocardial I/R injury and anoxia/reoxygenation (A/R)-induced H9c2 injuries.MethodsHeart injuries were induced through 30 min of ischemia followed by 24 h of reperfusion. Scu was intraperitoneally administered 15 min before vascular ligation. Effects of Scu on cardiac injury were detected by echocardiograms, TTC staining, and histological and immunohistochemical analyses. The effects of Scu on biochemical parameters were analyzed. H9c2 cells were pretreated with different concentrations of Scu for 6 h before A/R exposure. Afterward, cell viability, LDH release, and Hoechst 33342 and peromide iodine double staining were determined. Western blot analyses of proteins, including those involved in autophagy, NLRP3, mTOR complex 1 (mTORC1), and Akt signaling, were conducted.ResultsIn vivo study revealed that Scu improved diastolic dysfunction, ameliorated myocardium structure abnormality, inhibited myocyte apoptosis and inflammatory response, and promoted autophagy. Scu reduced NLRP3 inflammasome activation, inhibited mTORC1 activity, and increased Akt phosphorylation. In vitro investigation showed the same results. The Scu-mediated NLRP3 inflammasome and mTORC1 inhibition and cardioprotection were abolished through the genetic silencing of Akt by siRNA.ConclusionsThe cardioprotective effect of Scu was achieved through its anti-inflammatory effect. It suppressed the activation of NLRP3 inflammasome. In addition, inflammasome restriction by Scu was dependent on Akt activation and mTORC1 inhibition.