Core Hydrophobicity of Supramolecular Nanoparticles Induces NLRP3 Inflammasome Activation

Varying the hydrophobic core composition of polymeric nanoparticles affects NLRP3 inflammasome activation

Understanding the interactions of nanoparticle carriers with innate immune cells is crucial for informing the design and efficacy of future nano-immunotherapies. An intriguing aspect of their interaction with the immune system has recently emerged, i.e., their ability to activate the NLRP3 inflammasome, a key component of the innate immune response. While the effect of the surface properties of nanoparticles has been extensively investigated in the context of nanoparticle-immune cell interactions, the influence of core composition remains largely unexplored, particularly regarding its impact on inflammasome activation. To shed light on these interactions, we developed a library of supramolecular polymer nanoparticles (SNPs) with different core compositions, varying their hydrophobic quotient by virtue of the side chain length and the repeating units in the polymer construct. The impact of modulating SNP core hydrophobic properties was investigated in macrophages by evaluating their cellular internalization, cytokine release, lysosomal rupture-calcium signaling, calcium flux-mitochondrial ROS production and their ability to activate the NLRP3 inflammasome, providing mechanistic insights into inflammasome activation. We established a direct correlation between increasing the side chain length of the polymer construct, thereby increasing the core hydrophobicity of SNPs and enhanced NLRP3 complex formation, as indicated by ASC speck imaging analysis and the elevated 1L-1β expression. Furthermore, the results demonstrated that the inflammasome signaling cascades and kinetics varied based on the SNP's hydrophobic side chain length and repeating units. Specifically, the nanoparticle with the longest alkyl side chain effectuated NLRP3 activation preferentially through the mitochondrial damage pathway. In vivo evaluation of SNPs in C57BL/6 mice confirmed elevated proinflammatory cytokines, notably with the SNP having the longest C12-alkyl side chain. This confirms that the higher core hydrophobicity composition of the SNP results in inflammasome activation in vivo. In summary, this study established SNP core composition as a novel nanoparticle-associated molecular pattern (NAMP) responsible for NLRP3 inflammasome activation, shedding light on intricate cellular pathways for informed nanoparticle design in immunotherapy and vaccine applications.

Long circulating liposomal platform utilizing hydrophilic polymer-based surface modification: preparation, characterisation, and biological evaluation

Liposomes are one of the most important drug delivery vectors, nowadays used in clinics. In general, polyethylene glycol (PEG) is used to ensure the stealth properties of the liposomes. Here, we have employed hydrophilic, biocompatible and highly non-fouling N-(2-hydroxypropyl) methacrylamide (HPMA)-based copolymers containing hydrophobic cholesterol anchors for the surface modification of liposomes, which were prepared by the method of lipid film hydration and extrusion through 100 nm polycarbonate filters. Efficient surface modification of liposomes was confirmed by transmission electron microscopy, atomic force microscopy, and gradient ultracentrifugation. The ability of long-term circulation in the vascular bed was demonstrated in rabbits after i.v. application of fluorescently labelled liposomes. Compared to PEGylated liposomes, HPMA-based copolymer-modified liposomes did not induce specific antibody formation and did not activate murine and human complement. Compared with PEGylated liposomes, HPMA-based copolymer-modified liposomes showed a better long-circulating effect after repeated administration. HPMA-based copolymer-modified liposomes thus represent suitable new candidates for a generation of safer and improved liposomal drug delivery platforms.

Nanoparticle-mediated co-delivery of inflammasome inhibitors provides protection against sepsis

The NLRP3 inflammasome, a multiprotein complex responsible for triggering the release of pro-inflammatory cytokines, plays a crucial role in inducing the inflammatory response associated with sepsis. While small molecule inhibitors of the NLRP3 inflammasome have been investigated for sepsis management, delivering NLRP3 inhibitors has been accompanied by several challenges, primarily related to the drug formulation, delivery route, stability, and toxicity. Many existing inflammasome inhibitors either show higher liver toxicity or require a high dosage to efficiently impede the inflammasome complex assembly. Moreover, the potential synergistic effects of combining multiple inflammasome inhibitors in sepsis therapy remain largely unexplored. Therefore, a rational approach is essential for presenting the potential administration of NLRP3 small molecule inhibitors to inhibit NLRP3 inflammasome activation effectively. In this context, we present a lipid nanoparticle-based dual-drug delivery system loaded with MCC 950 and disulfiram, demonstrating markedly higher efficiency compared to an equivalent amount of free-drug combinations and individual drug nanoparticles in vitro. This combination therapy substantially improved the in vivo survival rate of mice for LPS-induced septic peritonitis. Additionally, the synergistic approach illustrated a significant reduction in the expression of active caspase-1 as well as IL-1β inhibition integral components in the NLRP3 pathway. This study underscores the importance of integrating combination therapies facilitated by nanoparticle delivery to address the limitations of small molecule inflammasome inhibitors.

Effects of Skeleton Structure of Mesoporous Silica Nanoadjuvants on Cancer Immunotherapy

Mesoporous silica nanoparticles (MSNs) have been widely praised as nanoadjuvants in vaccine/tumor immunotherapy thanks to their excellent biocompatibility, easy-to-modify surface, adjustable particle size, and remarkable immuno-enhancing activity. However, the application of MSNs is still greatly limited by some severe challenges including the unclear and complicated relationships of structure and immune effect. Herein, three commonly used MSNs with different skeletons including MSN with tetrasulfide bonds (TMSN), MSN containing ethoxy framework (EMSN), and pure -Si-O-Si- framework of MSN (MSN) are comprehensively compared to study the impact of chemical construction on immune effect. The results fully demonstrate that the three MSNs have great promise in improving cellular immunity for tumor immunotherapy. Moreover, the TMSN performs better than the other two MSNs in antigen loading, cellular uptake, reactive oxygen species (ROS) generation, lymph node targeting, immune activation, and therapeutic efficiency. The findings provide a new paradigm for revealing the structure-function relationship of mesoporous silica nanoadjuvants, paving the way for their future clinical application.

Caspase-1 Responsive Nanoreporter for In Vivo Monitoring of Inflammasome Immunotherapy

Inflammasomes are multimeric protein signaling complexes that are assembled in innate immune cells in response to a multitude of pathogen and damage-associated signals. They are essential for generating robust inflammatory responses to prevent pathogenic insults. However, inflammasome dysregulation can induce cascading immune responses, resulting in systemic toxicities and inflammatory disease. In this sense, there is a strong need to develop potent inflammasome inhibiting therapies as well as technologies to monitor their efficacy, yet current systems lack the ability to effectively image inflammasome activation and track therapy response early. To overcome these limitations, we report a novel nanoparticle system delivering both a caspase-1 cleavable inflammasome detecting probe and the NLRP3 inhibitor drug MCC-950, providing dual capabilities of monitoring and regulation of inflammasome activation in a biocompatible, tissue penetrating, and sustained release liposomal formulation. We observed this liposomal nanoreporter's ability to reduce and detect inflammasome activation both in vitro in immortalized bone marrow-derived macrophages and in vivo in a DSS-induced ulcerative colitis mouse model. Our results exhibited the nanoreporter's ability to penetrate inflammatory tissues and detect inflammasome activation early and in real-time for multiple days while alleviating inflammation in the groups coencapsulating imaging reporter and inflammasome inhibitor. Overall, the developed liposomal nanoreporter platform enables spatiotemporal delivery of imaging probe and inhibitor, captures early and sustained inflammasome detection, and induces inflammasome amelioration, thus establishing a novel tool for the real-time monitoring and treatment of inflammasome-mediated disease with high potential for clinical application.

Protein Corona Formation on Lipid Nanoparticles Negatively Affects the NLRP3 Inflammasome Activation

The interaction between lipid nanoparticles (LNPs) and serum proteins, giving rise to a unique identification in the form of the protein corona, has been shown to be associated with novel recognition by cell receptors. The presence of the corona enveloping the nanoparticle strongly affects the interplay with immune cells. The immune responses mediated by protein corona can affect nanoparticle toxicity and targeting capabilities. But the intracellular signaling of LNPs after corona formation resulting in the change of nanoparticles' ability to provoke immune responses remains unclear. Therefore, a more systematic and delineated approach must be considered to present the correlation between corona complexes and the shift in nanoparticle immunogenicity. Here, we studied and reported the inhibiting effect of the absorbed proteins on the LNPs on the NLRP3 inflammasome activation, a key intracellular protein complex that modulates several inflammatory responses. Ionizable lipid as a component of LNP was observed to play an important role in modulating the activation of NLRP3 inflammasome in serum-free conditions. However, in the presence of serum proteins, the corona layer on LNPs caused a significant reduction in the inflammasome activation. Reduction in the lysosomal rupture after treatment with corona-LNPs significantly reduced inflammasome activation. Furthermore, a strong reduction of cellular uptake in macrophages after the corona formation was observed. On inspecting the uptake mechanisms in macrophages using transport inhibitors, lipid formulation was found to play a critical role in determining the endocytic pathways for the LNPs in macrophages. This study highlights the need to critically analyze the protein interactions with nanomaterials and their concomitant adaptability with immune cells to evaluate nano-bio surfaces and successfully design nanomaterials for biological applications.

Functionalized nanomaterials targeting NLRP3 inflammasome driven immunomodulation: Friend or Foe

The advancement in drug delivery systems in recent times has significantly enhanced therapeutic effects by enabling site-specific targeting through nanocarriers. These nanocarriers serve as invaluable tools for pharmacotherapeutic advancements against various disorders that enhance the effectiveness of encapsulated drugs by reducing their toxicity and increasing the efficacy of less potent drugs, thereby improving the therapeutic index. Inflammasomes, protein complexes located in the activated immune cell cytoplasm, regulate the activation of caspases involved in inflammation. However, aberrant activation of inflammasomes can result in uncontrolled tissue responses, contributing to the development of various diseases. Therefore, achieving a precise balance between inflammasome inhibition and activation is crucial for effectively treating inflammatory disorders through targeted functionalized nanocarriers. Despite the wealth of available data on the relevance of functionalized nanocarriers in inflammatory disorders, the nanotechnological potential to modulate inflammasomes has not been adequately explored. In this comprehensive review, we highlight the latest research on the modulation of the inflammasome cascade, both upregulating and downregulating its function, using nanocarriers in the context of inflammatory disorders. The utilization of nanocarriers as a therapeutic strategy holds immense potential for researchers aiming to effectively target and modulate inflammasomes in the treatment of inflammatory disorders, thus improving disease severity outcomes.

Understanding How Cationic Polymers' Properties Inform Toxic or Immunogenic Responses via Parametric Analysis

Cationic polymers are widely used materials in diverse biotechnologies. Subtle variations in these polymers' properties can change them from exceptional delivery agents to toxic inflammatory hazards. Conventional screening strategies optimize for function in a specific application rather than observing how underlying polymer-cell interactions emerge from polymers' properties. An alternative approach is to map basic underlying responses, such as immunogenicity or toxicity, as a function of basic physicochemical parameters to inform the design of materials for a breadth of applications. To demonstrate the potential of this approach, we synthesized 107 polymers varied in charge, hydrophobicity, and molecular weight. We then screened this library for cytotoxic behavior and immunogenic responses to map how these physicochemical properties inform polymer-cell interactions. We identify three compositional regions of interest and use confocal microscopy to uncover the mechanisms behind the observed responses. Finally, immunogenic activity is confirmed in vivo. Highly cationic polymers disrupted the cellular plasma membrane to induce a toxic phenotype, while high molecular weight, hydrophobic polymers were uptaken by active transport to induce NLRP3 inflammasome activation, an immunogenic phenotype. Tertiary amine- and triethylene glycol-containing polymers did not invoke immunogenic or toxic responses. The framework described herein allows for the systematic characterization of new cationic materials with different physicochemical properties for applications ranging from drug and gene delivery to antimicrobial coatings and tissue scaffolds.

Nanoreporter for Real-Time Monitoring of Inflammasome Activity and Targeted Therapy

Inflammasome activation is associated with a myriad of inflammatory diseases. However, existing methods provides a limited understanding of spatiotemporal kinetics of inflammasome activation, with restricted scope for early detection of associated treatment efficacy. This limitation offers an opportunity for the development of biocompatible in-vivo inflammasome monitoring tools with translational prospects. To achieve this, they report developing a pair of lipid-based nanoparticle systems, a reporter nanoparticle consisting of a caspase-1 activatable probe alone, and a theranostic nanoparticle combining the probe with an inflammasome-inhibiting drug. This biocompatible platform enhances the probe's residence time in circulation by preventing its opsonization and allowing its sustained release over time. Their results demonstrate the specificity of reporter nanoparticles towards caspase-1 activity and provides early-on monitoring of inflammasome activation both in-vitro as well as in-vivo. Additionally, the delivery of disulfiram, an inflammasome-inhibiting drug, along with reporter probe using theranostic nanoparticles enables real-time tracking of treatment efficacy in the gouty-arthritis inflammatory model. In summary, they report an unparalleled pair of the inflammasome-associated reporter and theranostic platforms suited not only for diagnostic applications but can also detect inflammasome-targeted treatment efficiency in real-time. These findings establish two novel, sensitive nanotools for non-invasive evaluation of inflammasome-targeted immunotherapy.

mRNA-carrying lipid nanoparticles that induce lysosomal rupture activate NLRP3 inflammasome and reduce mRNA transfection efficiency

In the last several years, countless developments have been made to engineer more efficient and potent mRNA lipid nanoparticle vaccines, culminating in the rapid development of effective mRNA vaccines against COVID-19. However, despite these advancements and materials approaches, there is still a lack of understanding of the resultant immunogenicity of mRNA lipid nanoparticles. Therefore, a more mechanistic, design-driven approach needs to be taken to determine which biophysical characteristics, especially related to changes in lipid compositions, drive nanoparticle immunogenicity. Here, we synthesized a panel of six mRNA lipid nanoparticle formulations, varying the concentrations of different lipid components and systematically studied their effect on NLRP3 inflammasome activation; a key intracellular protein complex that controls various inflammatory responses. Initial experiments aimed to determine differences in nanoparticle activation of NLRP3 inflammasomes by IL-1β ELISA, which unveiled that nanoparticles with high concentrations of ionizable lipid DLin-MC3-DMA in tandem with high cationic lipid DPTAP and low cholesterol concentration induced the greatest activation of the NLRP3 inflammasome. These results were further corroborated by the measurement of ASC specks indicative of NLRP3 complex assembly, as well as cleaved gasdermin-D and caspase-1 expression indicating complex activation. We also uncovered these activation profiles to be mechanistically correlated primarily with lysosomal rupturing caused by the delayed membrane disruption capabilities of ionizable lipids until the lysosomal stage, as well as by mitochondrial reactive oxygen species (ROS) production and calcium influx for some of the particles. Therefore, we report that the specific, combined effects of each lipid type, most notably ionizable, cationic lipids, and cholesterol, is a crucial mRNA lipid nanoparticle characteristic that varies the endo/lysosomal rupture capabilities of the formulation and activate NLRP3 inflammasomes in a lysosomal rupture dependent manner. These results provide a more concrete understanding of mRNA lipid Nanoparticle-Associated Molecular Patterns for the activation of molecular-level immune responses and provide new lipid composition design considerations for future mRNA-delivery approaches.

Immunostimulatory Polymers as Adjuvants, Immunotherapies, and Delivery Systems

Activating innate immunity in a controlled manner is necessary for the development of next-generation therapeutics. Adjuvants, or molecules that modulate the immune response, are critical components of vaccines and immunotherapies. While small molecules and biologics dominate the adjuvant market, emerging evidence supports the use of immunostimulatory polymers in therapeutics. Such polymers can stabilize and deliver cargo while stimulating the immune system by functioning as pattern recognition receptor (PRR) agonists. At the same time, in designing polymers that engage the immune system, it is important to consider any unintended initiation of an immune response that results in adverse immune-related events. Here, we highlight biologically derived and synthetic polymer scaffolds, as well as polymer–adjuvant systems and stimuli-responsive polymers loaded with adjuvants, that can invoke an immune response. We present synthetic considerations for the design of such immunostimulatory polymers, outline methods to target their delivery, and discuss their application in therapeutics. Finally, we conclude with our opinions on the design of next-generation immunostimulatory polymers, new applications of immunostimulatory polymers, and the development of improved preclinical immunocompatibility tests for new polymers.

Cationic Carbon Nanoparticles Induce Inflammasome-Dependent Pyroptosis in Macrophages via Lysosomal Dysfunction

Carbon nanomaterials, including carbon dots (CDs), form a growing family of engineered nanoparticles (NPs) with widespread applications. As the rapid expansion of nanotechnologies raises safety concerns, interaction of NPs with the immune system is receiving a lot of attention. Recent studies have reported that engineered NPs may induce macrophage death by pyroptosis. Therefore, this study investigated whether cationic CDs induce pyroptosis in human macrophages and assessed the role of inflammasome and lysosome in this process. Cationic CDs were synthetized by microwave-assisted pyrolysis of citric acid and high molecular weight branched polyethyleneimine. The NPs evoked a dose-dependent viability loss in THP-1-derived macrophages. A cell leakage, an increase in IL-1β secretion and an activation of caspase-1 were also observed in response to the NPs. Inhibition of caspase-1 decreased CD-induced cell leakage and IL-1β secretion, while restoring cell viability. Besides, CDs triggered swelling and loss of integrity of lysosome, and inhibition of the lysosomal enzyme cathepsin B decreased CD-induced IL-1β secretion. Thus, our data provide evidence that cationic CDs induce inflammasome-dependent pyroptosis in macrophages via lysosomal dysfunction.

Biocapture-Directed Chemical Labeling for Discerning Stressed States of Organelles

Lysosomal rupture engaged in diverse diseases remains poorly discerned from lysosomal membrane permeabilization (LMP). We herein reported biocapture-directed chemical labeling (BCCL) for the discern of lysosomal rupture by tracking the release of optically labeled cathepsins from damaged lysosomes into the cytosol. BCCL entails covalent anchoring of an azide-tagged suicide substrate (Epo-LeuTyr^Az) to the enzyme active site and bioorthogonal ligation of the introduced azide with ^DBCORC, a ratiometric sensor featuring an acidity-reporting red emissive X-rhodamine-lactam (ROX), blue emissive coumarin (CM) inert to pH, and DBCO reactive to azide. Aided with fluorescein isocyanate-labeled sialic acid (FITC-Sia), a probe remained in pH-elevated lysosomes but dissipated from LMP⁺ lysosomes, BCCL enables optical discern of four states of lysosomes: ruptured lysosomes (blue in cytosol), LMP⁺ lysosomes (blue in lysosomes), pH-elevated lysosomes (blue and green in lysosomes), and physiological lysosomes (blue, green and red in lysosomes). This approach could find applicability to study lysosome rupture over LMP in diseases and to evaluate lysosome rupture-inducing drugs.

Follistatin-like 1 ameliorates severe acute pancreatitis associated lung injury via inhibiting the activation of NLRP3 inflammasome and NF-κB pathway

OBJECTIVE

Severe acute pancreatitis (SAP) is one of the most common abdominal conditions of digestive system that usually causes acute lung injury through systemic inflammation. Follistatin-like 1 (FSTL-1) has been reported to have anti-inflammatory and anti-apoptotic effects in a variety of diseases. The aim of this study was to investigate the effects of FSTL-1 on SAP-associated lung injury (SAPALI) and the underlying mechanism.

METHODS

SAP model was induced by intraperitoneal injection of the L-arginine in C57BL/6 mice. The haematoxylin and eosin (H&E) staining was applied to determine the severity of lung and pancreatic injury. ELISA kits were used to determine serum amylase and inflammatory cytokines levels. TUNEL staining was carried out to measure cell apoptosis. Western blotting was applied to analyze the related proteins of NLRP3 inflammasome and NF-κB pathways.

RESULTS

FSTL-1 was significantly increased in the lung of SAP mice. Knockout of FSTL-1 ameliorated pancreatic injury, lung injury, inflammation and apoptosis in mice with SAP. Moreover, the protein levels of NLRP3, ASC, Caspase-1, p-p65 and p-IκBα were obviously reduced in the FSTL-1 KO+SAP group in comparison with SAP group, suggesting that inhibition of FSTL-1 repressed the activation of the NLRP3 inflammasome and NF-κB pathway.

CONCLUSION

This study helps us understand the mechanism of FSTL-1 in SAPALI and might provide a potential new strategy for the treatment of SAPALI.

Understanding the immunological interactions of engineered nanomaterials: Role of the bio-corona

Engineered nanomaterials are a broad class of materials with the potential for breakthrough applications in many sectors of society not least in medicine. Consequently, safety assessment of nanomaterials and nano-enabled products with respect to human health and the environment is of key importance. To this end, the biological interactions of nanoscale materials must be understood. Here, the dual "identities" of nanomaterials, namely, the material-intrinsic properties or synthetic identity and the acquired, context-dependent properties or biological identity, are discussed in relation to nanomaterial interactions with the immune system, our main defense against foreign intrusion. Specifically, we address whether macrophages and other innate immune cells respond to the synthetic identity or the biological identity of nanomaterials, that is, the surface adsorbed proteins and/or other biomolecules known as the bio-corona, or both? This article is categorized under: Toxicology and Regulatory Issues in Nanomedicine > Toxicology of Nanomaterials.