Acinetobacter baumannii outer membrane protein 34 elicits NLRP3 inflammasome activation via mitochondria-derived reactive oxygen species in RAW264.7 macrophages

Acinetobacter baumannii (A. baumannii) is a Gram-negative bacterium, which acts as an opportunistic pathogen and causes hospital-acquired pneumonia and bacteremia by infecting the alveoli of epithelial cells and macrophages. Evidence reveals that A. baumannii outer membrane protein 34 (Omp34) elicits cellular immune responses and inflammation. The innate immunity NOD-like receptor 3 (NLRP3) inflammasome exerts critical function against pneumonia caused by A. baumannii infection, however, the role of Omp34 in the activation of the NLRP3 inflammasome and its corresponding regulatory mechanism are not clearly elucidated. The present study aimed to investigate whether Omp34 elicited NLRP3 inflammasome activation through the mitochondria-derived reactive oxygen species (ROS). Our results showed that Omp34 triggered cell pyroptosis by up-regulating the expression of NLRP3 inflammasome-associated proteins and IL-1β release in a time- and dose-dependent manner. Omp34 induced the expression of caspase-1-p10 and IL-1β, which was significantly attenuated by NLRP3 gene silencing in RAW264.7 mouse macrophage cells. Additionally, Omp34 stimulated RAW264.7 mitochondria to generate ROS, while the ROS scavenger Mito-TEMPO inhibited the Omp34-triggered expression of NLRP3 inflammasome-associated proteins and IL-1β synthesis. The above findings indicate that mitochondria-derived ROS play an important role in the process of NLRP3 inflammasome activation. In summary, our study demonstrates that the A. baumannii pathogen pattern recognition receptor Omp34 activates NLRP3 inflammasome via mitochondria-derived ROS in RAW264.7 cells. Accordingly, down-regulating the mitochondria-derived ROS prevents the severe infection consequences caused by A. baumannii-induced NLRP3 inflammasome hyper-activation.     

NLRP3 Inflammasome Activation by Paracoccidioides brasiliensis

Paracoccidioides brasiliensis is the etiologic agent of paracoccidioidomycosis (PCM), the most prevalent systemic mycosis that is geographically confined to Latin America. The pro-inflammatory cytokine IL-1β that is mainly derived from the activation of the cytoplasmic multiprotein complex inflammasome is an essential host factor against opportunistic fungal infections; however, its role in infection with a primary fungal pathogen, such as P. brasiliensis, is not well understood. In this study, we found that murine bone marrow-derived dendritic cells responded to P. brasiliensis yeast cells infection by releasing IL-1β in a spleen tyrosine kinase (Syk), caspase-1 and NOD-like receptor (NLR) family member NLRP3 dependent manner. In addition, P. brasiliensis-induced NLRP3 inflammasome activation was dependent on potassium (K+) efflux, reactive oxygen species production, phagolysosomal acidification and cathepsin B release. Finally, using mice lacking the IL-1 receptor, we demonstrated that IL-1β signaling has an important role in killing P. brasiliensis by murine macrophages. Altogether, our results demonstrate that the NLRP3 inflammasome senses and responds to P. brasiliensis yeast cells infection and plays an important role in host defense against this fungus.     

Chlamydia pneumoniae harness host NLRP3 inflammasome-mediated caspase-1 activation for optimal intracellular growth in murine macrophages

Chlamydia pneumoniae is an obligate intracellular pathogen that replicates within a vacuole and acquires host cell nutrients. We show that C. pneumoniae utilizes host innate immune signaling NLRP3/ASC/caspase-1 inflammasome for intracellular growth. Bone marrow-derived macrophages (BMMs) secreted mature interleukin-1β upon infection with C. pneumoniae depending on the NLRP3 inflammasome activation. Intracellular growth of C. pneumoniae was severely impaired in BMMs from Nlrp3^−/−, Asc^−/−, and Casp1^−/− mice but not wild type or Nlrc4^−/− mice. Furthermore defective NLRP3 inflammasome components led to accumulation of lipid droplets inside the infected BMMs, suggesting that uptake and/or utilization of lipids is disturbed in the absence of NLRP3 inflammasome activation. These results suggest C. pneumoniae has evolved to harness both host innate immune response and NLRP3 inflammasome activation, for the acquisition of essential nutrients necessary for intracellular growth. This unique property of C. pneumoniae may shed a new light on how C. pneumoniae increase the risk of atherosclerosis and metabolic syndrome.     

Human NAIP/NLRC4 and NLRP3 inflammasomes detect Salmonella type III secretion system activities to restrict intracellular bacterial replication

Salmonella enterica serovar Typhimurium is a Gram-negative pathogen that uses two distinct type III secretion systems (T3SSs), termed Salmonella pathogenicity island (SPI)-1 and SPI-2, to deliver virulence factors into the host cell. The SPI-1 T3SS enables Salmonella to invade host cells, while the SPI-2 T3SS facilitates Salmonella’s intracellular survival. In mice, a family of cytosolic immune sensors, including NAIP1, NAIP2, and NAIP5/6, recognizes the SPI-1 T3SS needle, inner rod, and flagellin proteins, respectively. Ligand recognition triggers assembly of the NAIP/NLRC4 inflammasome, which mediates caspase-1 activation, IL-1 family cytokine secretion, and pyroptosis of infected cells. In contrast to mice, humans encode a single NAIP that broadly recognizes all three ligands. The role of NAIP/NLRC4 or other inflammasomes during Salmonella infection of human macrophages is unclear. We find that although the NAIP/NLRC4 inflammasome is essential for detecting T3SS ligands in human macrophages, it is partially required for responses to infection, as Salmonella also activated the NLRP3 and CASP4/5 inflammasomes. Importantly, we demonstrate that combinatorial NAIP/NLRC4 and NLRP3 inflammasome activation restricts Salmonella replication in human macrophages. In contrast to SPI-1, the SPI-2 T3SS inner rod is not sensed by human or murine NAIPs, which is thought to allow Salmonella to evade host recognition and replicate intracellularly. Intriguingly, we find that human NAIP detects the SPI-2 T3SS needle protein. Critically, in the absence of both flagellin and the SPI-1 T3SS, the NAIP/NLRC4 inflammasome still controlled intracellular Salmonella burden. These findings reveal that recognition of Salmonella SPI-1 and SPI-2 T3SSs and engagement of both the NAIP/NLRC4 and NLRP3 inflammasomes control Salmonella infection in human macrophages.     

Going green in Cryptococcus neoformans: The recycling of a selectable drug marker

Cryptococcus neoformans is an opportunistic fungal pathogen that primarily affects immunocompromised individuals. Reverse genetics is commonly used to identify and characterize genes involved in a variety of cellular processes. In C. neoformans there is a limited set of positive selectable markers available to make gene deletions or other genetic manipulations. This has hampered the application of reverse genetics in this organism. We have adapted the Bacteriophage P1 Cre-loxP system for use in C. neoformans and successfully excised and reused the same drug marker, G418, to make two sequential gene deletions, lac1Δ and cap59Δ, in the same strain. This tool will allow investigators to make multiple sequential gene deletions in the same strain, which should facilitate the analysis of multigene families.     

NLRP3 inflammasome activation in COVID-19: an interlink between risk factors and disease severity

NLRP3 inflammasome is a critical immune component that plays a crucial role in mounting innate immune responses. The deleterious effects of inflammasome activation have been correlated with the COVID-19 disease severity. In the presence of several underlying disorders, the immune components of our bodies are dysregulated, creating conditions that could adversely affect us other than providing a required level of protection. In this review, we focused on the occurrence of NLRP3 inflammasome activation in response to SARS-COV-2 infection, dysregulation of NLRP3 activation events in the presence of several comorbidities, the contribution of activated NLRP3 inflammasome to the severity of COVID-19, and available therapeutics for the treatment of such NLRP3 inflammasome related diseases based on current knowledge. The primed state of immunity in individuals with comorbidities (risk factors) could accelerate many deaths and severe COVID-19 cases via activation of NLRP3 inflammasome and the release of downstream inflammatory molecules. Therefore, a detailed understanding of the host–pathogen interaction is needed to clarify the pathophysiology and select a potential therapeutic approach.     

Isolates of Salmonella typhimurium circumvent NLRP3 inflammasome recognition in macrophages during the chronic phase of infection

Inflammasome signaling results in cell death and release of cytokines from the IL-1 family, which facilitates control over an infection. However, some pathogens such as Salmonella typhimurium (ST) activate various innate immune signaling pathways, including inflammasomes, yet evade these cell death mechanisms, resulting in a chronic infection. Here we investigated inflammasome signaling induced by acute and chronic isolates of ST obtained from different organs. We show that ST isolated from infected mice during the acute phase displays an increased potential to activate inflammasome signaling, which then undergoes a protracted decline during the chronic phase of infection. This decline in inflammasome signaling was associated with reduced expression of virulence factors, including flagella and the Salmonella pathogenicity island I genes. This reduction in cell death of macrophages induced by chronic isolates had the greatest impact on the NLRP3 inflammasome, which correlated with a reduction in caspase-1 activation. Furthermore, rapid cell death induced by Casp-1/11 by ST in macrophages limited the subsequent activation of cell death cascade proteins Casp-8, RipK1, RipK3, and MLKL to prevent the activation of alternative forms of cell death. We observed that the lack of the ability to induce cell death conferred a competitive fitness advantage to ST only during the acute phase of infection. Finally, we show that the chronic isolates displayed a significant attenuation in their ability to infect mice through the oral route. These results reveal that ST adapts during chronic infection by circumventing inflammasome recognition to promote the survival of both the host and the pathogen.     

NLRP3 polymorphism is associated with protection against human T-lymphotropic virus 1 infection

Inter-individual heterogeneity in the response to human T-lymphotropic virus 1 (HTLV-1) infection has been partially attributed to host genetic background. The antiviral activity of the inflammasome cytoplasmic complex recognises viral molecular patterns and regulates immune responses via the activation of interleukin (IL)-1 family (IL-1, IL-18 and IL-33) members. The association between polymorphisms in the inflammasome receptors NLRP1 and NLRP3 and HTLV-1 infection was evaluated in a northeastern Brazilian population (84 HTLV-1 carriers and 155 healthy controls). NLRP3 rs10754558 G/G was associated with protection against HTLV-1 infection (p = 0.012; odds ratio = 0.37). rs10754558 affects NLRP3 mRNA stability; therefore, our results suggest that higher NLRP3 expression may augment first-line defences, leading to the effective protection against HTLV-1 infection.     

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.     

Malarial Hemozoin Activates the NLRP3 Inflammasome through Lyn and Syk Kinases

The intraerythrocytic parasite Plasmodium—the causative agent of malaria—produces an inorganic crystal called hemozoin (Hz) during the heme detoxification process, which is released into the circulation during erythrocyte lysis. Hz is rapidly ingested by phagocytes and induces the production of several pro-inflammatory mediators such as interleukin-1β (IL-1β). However, the mechanism regulating Hz recognition and IL-1β maturation has not been identified. Here, we show that Hz induces IL-1β production. Using knockout mice, we showed that Hz-induced IL-1β and inflammation are dependent on NOD-like receptor containing pyrin domain 3 (NLRP3), ASC and caspase-1, but not NLRC4 (NLR containing CARD domain). Furthermore, the absence of NLRP3 or IL-1β augmented survival to malaria caused by P. chabaudi adami DS. Although much has been discovered regarding the NLRP3 inflammasome induction, the mechanism whereby this intracellular multimolecular complex is activated remains unclear. We further demonstrate, using pharmacological and genetic intervention, that the tyrosine kinases Syk and Lyn play a critical role in activation of this inflammasome. These findings not only identify one way by which the immune system is alerted to malarial infection but also are one of the first to suggest a role for tyrosine kinase signaling pathways in regulation of the NLRP3 inflammasome.     

Virulent Mycobacterium bovis Beijing Strain Activates the NLRP7 Inflammasome in THP-1 Macrophages

Mycobacterium bovis is the causative agent of tuberculosis in a wide range of mammals, including humans. Macrophages are the first line of host defense. They secrete proinflammatory cytokines, such as interleukin-1 beta (IL-1β), in response to mycobacterial infection, but the underlying mechanisms by which human macrophages are activated and release IL-1β following M. bovis infection are poorly understood. Here we show that the ‘nucleotide binding and oligomerization of domain-like receptor (NLR) family pyrin domain containing 7 protein’ (NLRP7) inflammasome is involved in IL-1β secretion and caspase-1 activation induced by M. bovis infection in THP-1 macrophages. NLRP7 inflammasome activation promotes the induction of pyroptosis as well as the expression of tumor necrosis factor alpha (TNF-α), Chemokine (C-C motif) ligand 3 (CCL3) and IL-1β mRNAs. Thus, the NLRP7 inflammasome contributes to IL-1β secretion and induction of pyroptosis in response to M. bovis infection in THP-1 macrophages.     

Enteropathogenic Escherichia coli Uses NleA to Inhibit NLRP3 Inflammasome Activation

Enteropathogenic and enterohemorrhagic Escherichia coli (EPEC and EHEC) are related strains capable of inducing severe gastrointestinal disease. For optimal infection, these pathogens actively modulate cellular functions through the deployment of effector proteins in a type three secretion system (T3SS)-dependent manner. In response to enteric pathogen invasion, the Nod-like receptor pyrin domain containing (NLRP) inflammasome has been increasingly recognized as an important cytoplasmic sensor against microbial infection by activating caspase-1 and releasing IL-1β. EPEC and EHEC are known to elicit inflammasome activation in macrophages and epithelial cells; however, whether the pathogens actively counteract such innate immune responses is unknown. Using a series of compound effector-gene deletion strains of EPEC, we screened and identified NleA, which could subdue host IL-1β secretion. It was found that the reduction is not because of blocked NF-κB activity; instead, the reduction results from inhibited caspase-1 activation by NleA. Immunostaining of human macrophage-like cells following infection revealed limited formation of inflammasome foci with constituents of total caspase-1, ASC and NLRP3 in the presence of NleA. Pulldown of PMA-induced differentiated THP-1 lysate with purified MBP-NleA reveals that NLRP3 is a target of NleA. The interaction was verified by an immunoprecipitation assay and direct interaction assay in which purified MBP-NleA and GST-NLRP3 were used. We further showed that the effector interacts with regions of NLRP3 containing the PYD and LRR domains. Additionally, NleA was found to associate with non-ubiquitinated and ubiquitinated NLRP3 and to interrupt de-ubiquitination of NLRP3, which is a required process for inflammasome activation. Cumulatively, our findings provide the first example of EPEC-mediated suppression of inflammasome activity in which NieA plays a novel role in controlling the host immune response through targeting of NLRP3.     

NLRP3 Inflammasome Mediates Albumin-induced Renal Tubular Injury through Impaired Mitochondrial Function

Proteinuria serves as a direct causative factor of renal tubular cell injury and is highly associated with the progression of chronic kidney disease via uncertain mechanisms. Recently, evidence demonstrated that both NLRP3 inflammasome and mitochondria are involved in the chronic kidney disease progression. The present study was undertaken to examine the role of NLRP3 inflammasome/mitochondria axis in albumin-induced renal tubular injury. In patients with proteinuria, NLRP3 was significantly up-regulated in tubular epithelial cells and was positively correlated with the severity of proteinuria. In agreement with these results, albumin remarkably activated NLRP3 inflammasome in both in vitro renal tubular cells and in vivo kidneys in parallel with significant epithelial cell phenotypic alteration and cell apoptosis. Genetic disruption of NLRP3 inflammasome remarkably attenuated albumin-induced cell apoptosis and phenotypic changes under both in vitro and in vivo conditions. In addition, albumin treatment resulted in a significant mitochondrial abnormality as evidenced by the impaired function and morphology, which was markedly reversed by invalidation of NLRP3/caspase-1 signaling pathway. Interestingly, protection of mitochondria function by Mn(III)tetrakis (4-benzoic acid) porphyrin (MnTBAP) or cyclosporin A (CsA) robustly attenuated albumin-induced injury in mouse proximal tubular cells. Collectively, these findings demonstrated a pathogenic role of NLRP3 inflammasome/caspase-1/mitochondria axis in mediating albumin-induced renal tubular injury. The discovery of this novel axis provides some potential targets for the treatment of proteinuria-associated renal injury.     

Fusobacterium nucleatum infection of gingival epithelial cells leads to NLRP3 inflammasome‐dependent secretion of IL‐1β and the danger signals ASC and HMGB1

Fusobacterium nucleatum is an invasive anaerobic bacterium that is associated with periodontal disease. Previous studies have focused on virulence factors produced by F. nucleatum, but early recognition of the pathogen by the immune system remains poorly understood. Although an inflammasome in gingival epithelial cells (GECs) can be stimulated by danger‐associated molecular patterns (DAMPs) (also known as danger signals) such as ATP, inflammasome activation by this periodontal pathogen has yet to be described in these cells. This study therefore examines the effects of F. nucleatum infection on pro‐inflammatory cytokine expression and inflammasome activation in GECs. Our results indicate that infection induces translocation of NF‐κB into the nucleus, resulting in cytokine gene expression. In addition, infection activates the NLRP3 inflammasome, which in turn activates caspase‐1 and stimulates secretion of mature IL‐1β. Unlike other pathogens studied until now, F. nucleatum activates the inflammasome in GECs in the absence of exogenous DAMPs such as ATP. Finally, infection promotes release of other DAMPs that mediate inflammation, such as high‐mobility group box 1 protein and apoptosis‐associated speck‐like protein, with a similar time‐course as caspase‐1 activation. Thus, F. nucleatum expresses the pathogen‐associated molecular patterns necessary to activate NF‐κB and also provides an endogenous DAMP to stimulate the inflammasome and further amplify inflammation through secretion of secondary DAMPs.     

Intravenous immunoglobulin suppresses NLRP1 and NLRP3 inflammasome-mediated neuronal death in ischemic stroke

Multi-protein complexes called inflammasomes have recently been identified and shown to contribute to cell death in tissue injury. Intravenous immunoglobulin (IVIg) is an FDA-approved therapeutic modality used for various inflammatory diseases. The objective of this study is to investigate dynamic responses of the NLRP1 and NLRP3 inflammasomes in stroke and to determine whether the NLRP1 and NLRP3 inflammasomes can be targeted with IVIg for therapeutic intervention. Primary cortical neurons were subjected to glucose deprivation (GD), oxygen–glucose deprivation (OGD) or simulated ischemia-reperfusion (I/R). Ischemic stroke was induced in C57BL/6J mice by middle cerebral artery occlusion, followed by reperfusion. Neurological assessment was performed, brain tissue damage was quantified, and NLRP1 and NLRP3 inflammasome protein levels were evaluated. NLRP1 and NLRP3 inflammasome components were also analyzed in postmortem brain tissue samples from stroke patients. Ischemia-like conditions increased the levels of NLRP1 and NLRP3 inflammasome proteins, and IL-1β and IL-18, in primary cortical neurons. Similarly, levels of NLRP1 and NLRP3 inflammasome proteins, IL-1β and IL-18 were elevated in ipsilateral brain tissues of cerebral I/R mice and stroke patients. Caspase-1 inhibitor treatment protected cultured cortical neurons and brain cells in vivo in experimental stroke models. IVIg treatment protected neurons in experimental stroke models by a mechanism involving suppression of NLRP1 and NLRP3 inflammasome activity. Our findings provide evidence that the NLRP1 and NLRP3 inflammasomes have a major role in neuronal cell death and behavioral deficits in stroke. We also identified NLRP1 and NLRP3 inflammasome inhibition as a novel mechanism by which IVIg can protect brain cells against ischemic damage, suggesting a potential clinical benefit of therapeutic interventions that target inflammasome assembly and activity.     

3,4-Methylenedioxy-β-nitrostyrene Inhibits NLRP3 Inflammasome Activation by Blocking Assembly of the Inflammasome

The NLRP3 inflammasome is a critical component of the innate immune system. NLRP3 activation is induced by diverse stimuli associated with bacterial infection or tissue damage, but its inappropriate activation is involved in the pathogenesis of inherited and acquired inflammatory diseases. However, the mechanism by which NLRP3 is activated remains poorly understood. In this study, we explored the role of kinases in NLRP3 inflammasome activation by screening a kinase inhibitor library and identified 3,4-methylenedioxy-β-nitrostyrene (MNS) as an inhibitor for NLRP3 inflammasome activation. Notably, MNS did not affect the activation of the NLRC4 or AIM2 (absent in melanoma 2) inflammasome. Mechanistically, MNS specifically prevented NLRP3-mediated ASC speck formation and oligomerization without blocking potassium efflux induced by NLRP3 agonists. Surprisingly, Syk kinase, the reported target of MNS, did not mediate the inhibitory activity of MNS on NLRP3 inflammasome activation. We also found that the nitrovinyl group of MNS is essential for the inhibitory activity of MNS. Immunoprecipitation, mass spectrometry, and mutation studies suggest that both the nucleotide binding oligomerization domain and the leucine-rich repeat domain of NLRP3 were the intracellular targets of MNS. Administration of MNS also inhibited NLRP3 ATPase activity in vitro, suggesting that MNS blocks the NLRP3 inflammasome by directly targeting NLRP3 or NLRP3-associated complexes. These studies identified a novel chemical probe for studying the molecular mechanism of NLRP3 inflammasome activation which may advance the development of novel strategies to treat diseases associated with abnormal activation of NLRP3 inflammasome.     

Caspase-6 promotes activation of the caspase-11-NLRP3 inflammasome during gram-negative bacterial infections

The innate immune system acts as the first line of defense against infection. One key component of the innate immune response to gram-negative bacterial infections is inflammasome activation. The caspase-11 (CASP11)-nucleotide-binding oligomerization domain-like receptor pyrin domain-containing 3 (NLRP3) inflammasome is activated by cytosolic lipopolysaccharide, a gram-negative bacterial cell wall component, to trigger pyroptosis and host defense during infection. Although several cellular signaling pathways have been shown to regulate CASP11-NLRP3 inflammasome activation in response to lipopolysaccharide, the upstream molecules regulating CASP11 activation during infection with live pathogens remain unclear. Here, we report that the understudied caspase-6 (CASP6) contributes to the activation of the CASP11-NLRP3 inflammasome in response to infections with gram-negative bacteria. Using in vitro cellular systems with bone marrow-derived macrophages and 293T cells, we found that CASP6 can directly process CASP11 by cleaving at Asp59 and Asp285, the CASP11 auto-cleavage sites, which could contribute to the activation of CASP11 during gram-negative bacterial infection. Thus, the loss of CASP6 led to impaired CASP11-NLRP3 inflammasome activation in response to gram-negative bacteria. These results demonstrate that CASP6 potentiates activation of the CASP11-NLRP3 inflammasome to produce inflammatory cytokines during gram-negative bacterial infections.     

PGC-1α inhibits the NLRP3 inflammasome via preserving mitochondrial viability to protect kidney fibrosis

The NLRP3 inflammasome is activated by mitochondrial damage and contributes to kidney fibrosis. However, it is unknown whether PGC-1α, a key mitochondrial biogenesis regulator, modulates NLRP3 inflammasome in kidney injury. Primary renal tubular epithelial cells (RTECs) were isolated from C57BL/6 mice. The NLRP3 inflammasome, mitochondrial dynamics and morphology, oxidative stress, and cell injury markers were examined in RTECs treated by TGF-β1 with or without Ppargc1a plasmid, PGC-1α activator (metformin), and siPGC-1α. In vivo, adenine-fed and unilateral ureteral obstruction (UUO) mice were treated with metformin. In vitro, TGF-β1 treatment to RTECs suppressed the expressions of PGC-1α and mitochondrial dynamic-related genes. The NLRP3 inflammasome was also activated and the expression of fibrotic and cell injury markers was increased. PGC-1α induction with the plasmid and metformin improved mitochondrial dynamics and morphology and attenuated the NLRP3 inflammasome and cell injury. The opposite changes were observed by siPGC-1α. The oxidative stress levels, which are inducers of the NLRP3 inflammasome, were increased and the expression of TNFAIP3, a negative regulator of NLRP3 inflammasome regulated by PGC-1α, was decreased by TGF-β1 and siPGC-1α. However, PGC-1α restoration reversed these alterations. In vivo, adenine-fed and UUO mice models showed suppression of PGC-1α and TNFAIP3 and dysregulated mitochondrial dynamics. Moreover, the activation of oxidative stress and NLRP3 inflammasome, and kidney fibrosis were increased in these mice. However, these changes were significantly reversed by metformin. This study demonstrated that kidney injury was ameliorated by PGC-1α-induced inactivation of the NLRP3 inflammasome via modulation of mitochondrial viability and dynamics.Subject terms: Mechanisms of disease, Experimental models of disease