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

A photoactivatable upconverting nanodevice boosts the lysosomal escape of PROTAC degraders for enhanced combination therapy

PROteolysis TArgeting Chimeras have received increasing attention due to their capability to induce potent degradation of various disease-related proteins. However, the effective and controlled cytosolic delivery of current small-molecule PROTACs remains a challenge, primarily due to their intrinsic shortcomings, including unfavorable solubility, poor cell permeability, and limited spatiotemporal precision. Here, we develop a near-infrared light-controlled PROTAC delivery device (abbreviated as USDPR) that allows the efficient photoactivation of PROTAC function to achieve enhanced protein degradation. The nanodevice is constructed by encapsulating the commercial BRD4-targeting PROTACs (dBET6) in the hollow cavity of mesoporous silica-coated upconversion nanoparticles, followed by coating a Rose Bengal (RB) photosensitizer conjugated poly-L-lysine (PLL-RB). This composition enables NIR light-activatable generation of cytotoxic reactive oxygen species due to the energy transfer from the UCNPs to PLL-RB, which boosts the endo/lysosomal escape and subsequent cytosolic release of dBET6. We demonstrate that USDPR is capable of effectively degrading BRD4 in a NIR light-controlled manner. This in combination with NIR light-triggered photodynamic therapy enables an enhanced antitumor effect both in vitro and in vivo. This work thus presents a versatile strategy for controlled release of PROTACs and codelivery with photosensitizers using an NIR-responsive nanodevice, providing important insight into the design of effective PROTAC-based combination therapy.

Stimuli-Responsive mRNA Vaccines to Induce Robust CD8+ T Cell Response via ROS-Mediated Innate Immunity Boosting

The messenger RNA (mRNA) vaccines hold great significance in contagion prevention and cancer immunotherapy. However, safely and effectively harnessing innate immunity to stimulate robust and durable adaptive immune protection is crucial, yet challenging. In this study, we synthesized a library of stimuli-responsive bivalent ionizable lipids (srBiv iLPs) with smart molecular blocks responsive to esterase, H2O2, cytochrome P450, alkaline phosphatase, nitroreductase, or glutathione (GSH), aiming to leverage physiological cues to trigger fast lipid degradation, promote mRNA translation, and induce robust antitumor immunity via reactive oxygen species (ROS)-mediated boosting. After subcutaneous immunization, esterase-responsive vaccine (eBiv-mVac) was rapidly internalized and transported into the draining lymph nodes. It then underwent fast decaging and self-immolative degradation in esterase-rich antigen-presenting cells, releasing sufficient mRNA for antigen translation and massive reactive quinone methides to elevate ROS levels. This resulted in broad activation of innate immunity to boost T cell response, prompting a large number of primed antigen-specific CD8+ T cells to circulate and infiltrate into tumors (>1000-fold versus unvaccinated control), thereby orchestrating innate and adaptive immunity to control tumor growth. Moreover, by further combining our vaccination strategy with immune checkpoint blockade, we demonstrated a synergism that significantly amplified the magnitude and function of antigen-specific CD8+ T cells. This, in turn, caused potent systemic antitumor efficacy and prolonged survival with high complete response rate in xenograft and metastasis models. Overall, our generalized stimuli-responsive mRNA delivery platform promises a paradigm shift in the design of potent vaccines for cancer immunotherapy, as well as effective and precise carriers for gene editing, protein replacement, and cell engineering.

Quantitative analysis of mRNA-lipid nanoparticle stability in human plasma and serum by size-exclusion chromatography coupled with dual-angle light scattering

Understanding the stability of mRNA loaded lipid nanoparticles (mRNA-LNPs) is imperative for their clinical development. Herein, we propose the use of size-exclusion chromatography coupled with dual-angle light scattering (SEC-MALS) as a new approach to assessing mRNA-LNP stability in pure human serum and plasma. By applying a dual-column configuration to attenuate interference from plasma components, SEC-MALS was able to elucidate the degradation kinetics and physical property changes of mRNA-LNPs, which have not been observed accurately by conventional dynamic light scattering techniques. Interestingly, both serum and plasma had significantly different impacts on the molecular weight and radius of gyration of mRNA-LNPs, suggesting the involvement of clotting factors in desorption of lipids from mRNA-LNPs. We also discovered that a trace impurity (~1 %) in ALC-0315, identified as its O-tert-butyloxycarbonyl-protected form, greatly diminished mRNA-LNP stability in serum. These results demonstrated the potential utility of SEC-MALS for optimization and quality control of LNP formulations.

Strategies to reduce the risks of mRNA drug and vaccine toxicity

mRNA formulated with lipid nanoparticles is a transformative technology that has enabled the rapid development and administration of billions of coronavirus disease 2019 (COVID-19) vaccine doses worldwide. However, avoiding unacceptable toxicity with mRNA drugs and vaccines presents challenges. Lipid nanoparticle structural components, production methods, route of administration and proteins produced from complexed mRNAs all present toxicity concerns. Here, we discuss these concerns, specifically how cell tropism and tissue distribution of mRNA and lipid nanoparticles can lead to toxicity, and their possible reactogenicity. We focus on adverse events from mRNA applications for protein replacement and gene editing therapies as well as vaccines, tracing common biochemical and cellular pathways. The potential and limitations of existing models and tools used to screen for on-target efficacy and de-risk off-target toxicity, including in vivo and next-generation in vitro models, are also discussed.

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.

The immunostimulatory nature of mRNA lipid nanoparticles

mRNA-Lipid nanoparticles (LNPs) are at the forefront of global medical research. With the development of mRNA-LNP vaccines to combat the COVID-19 pandemic, the clinical potential of this platform was unleashed. Upon administering 16 billion doses that protected billions of people, it became clear that a fraction of them witnessed mild and in some cases even severe adverse effects. Therefore, it is paramount to define the safety along with the therapeutic efficacy of the mRNA-LNP platform for the successful translation of new genetic medicines based on this technology. While mRNA was the effector molecule of this platform, the ionizable lipid component of the LNPs played an indispensable role in its success. However, both of these components possess the ability to induce undesired immunostimulation, which is an area that needs to be addressed systematically. The immune cell agitation caused by this platform is a two-edged sword as it may prove beneficial for vaccination but detrimental to other applications. Therefore, a key challenge in advancing the mRNA-LNP drug delivery platform from bench to bedside is understanding the immunostimulatory behavior of these components. Herein, we provide a detailed overview of the structural modifications and immunogenicity of synthetic mRNA. We discuss the effect of ionizable lipid structure on LNP functionality and offer a mechanistic overview of the ability of LNPs to elicit an immune response. Finally, we shed some light on the current status of this technology in clinical trials and discuss a few challenges to be addressed to advance the field.

Flow-Induced Shear Stress Primes NLRP3 Inflammasome Activation in Macrophages via Piezo1

The NLRP3 inflammasome is a crucial component of the innate immune system, playing a pivotal role in initiating and regulating the body's inflammatory response to various pathogens and cellular damage. Environmental stimuli, such as temperature, pH level, and nutrient availability, can influence the behavior and functions of innate immune cells, including immune cell activity, proliferation, and cytokine production. However, there is limited understanding regarding how mechanical forces, like shear stress, govern the intrinsic inflammatory reaction, particularly the activation of the NLRP3 inflammasome, and how shear stress impacts NLRP3 inflammasome activation through its capacity to induce alterations in gene expression and cytokine secretion. Here, we investigated how shear stress can act as a priming signal in NLRP3 inflammasome activation by exposing immortalized bone marrow-derived macrophages (iBMDMs) to numerous physiologically relevant magnitudes of shear stress before chemically inducing inflammasome activation. We demonstrated that shear stress of large magnitudes was able to prime iBMDMs more effectively for inflammasome activation compared to lower shear stress magnitudes, as quantified by the percentage of cells where ASC-CFP specks formed and IL-1β secretion, the hallmarks of inflammasome activation. Testing this in NLRP3 and caspase-1 knockout iBMDMs showed that the NLRP3 inflammasome was primarily primed for activation due to shear stress exposure. Quantitative polymerase chain reaction (qPCR) and a small-molecule inhibitor study mechanistically determined that shear stress regulates the NLRP3 inflammasome by upregulating Piezo1, IKKβ, and NLRP3. These findings offer insights into the mechanistic relationship among physiological shear stresses, inflammasome activation, and their impact on the progression of inflammatory diseases and their interconnected pathogenesis.

mRNA vaccine designs for optimal adjuvanticity and delivery

Adjuvanticity and delivery are crucial facets of mRNA vaccine design. In modern mRNA vaccines, adjuvant functions are integrated into mRNA vaccine nanoparticles, allowing the co-delivery of antigen mRNA and adjuvants in a unified, all-in-one formulation. In this formulation, many mRNA vaccines utilize the immunostimulating properties of mRNA and vaccine carrier components, including lipids and polymers, as adjuvants. However, careful design is necessary, as excessive adjuvanticity and activation of improper innate immune signalling can conversely hinder vaccination efficacy and trigger adverse effects. mRNA vaccines also require delivery systems to achieve antigen expression in antigen-presenting cells (APCs) within lymphoid organs. Some vaccines directly target APCs in the lymphoid organs, while others rely on APCs migration to the draining lymph nodes after taking up mRNA vaccines. This review explores the current mechanistic understanding of these processes and the ongoing efforts to improve vaccine safety and efficacy based on this understanding.

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.

The Dual Role of the Innate Immune System in the Effectiveness of mRNA Therapeutics

Advances in molecular biology have revolutionized the use of messenger RNA (mRNA) as a therapeutic. The concept of nucleic acid therapy with mRNA originated in 1990 when Wolff et al. reported successful expression of proteins in target organs by direct injection of either plasmid DNA or mRNA. It took decades to bring the transfection efficiency of mRNA closer to that of DNA. The next few decades were dedicated to turning in vitro-transcribed (IVT) mRNA from a promising delivery tool for gene therapy into a full-blown therapeutic modality, which changed the biotech market rapidly. Hundreds of clinical trials are currently underway using mRNA for prophylaxis and therapy of infectious diseases and cancers, in regenerative medicine, and genome editing. The potential of IVT mRNA to induce an innate immune response favors its use for vaccination and immunotherapy. Nonetheless, in non-immunotherapy applications, the intrinsic immunostimulatory activity of mRNA directly hinders the desired therapeutic effect since it can seriously impair the target protein expression. Targeting the same innate immune factors can increase the effectiveness of mRNA therapeutics for some indications and decrease it for others, and vice versa. The review aims to present the innate immunity-related 'barriers' or 'springboards' that may affect the development of immunotherapies and non-immunotherapy applications of mRNA medicines.

Translation of in vitro-transcribed RNA therapeutics

In vitro transcribed, modified messenger RNAs (IVTmRNAs) have been used to vaccinate billions of individuals against the SARS-CoV-2 virus, and are currently being developed for many additional therapeutic applications. IVTmRNAs must be translated into proteins with therapeutic activity by the same cellular machinery that also translates native endogenous transcripts. However, different genesis pathways and routes of entry into target cells as well as the presence of modified nucleotides mean that the way in which IVTmRNAs engage with the translational machinery, and the efficiency with which they are being translated, differs from native mRNAs. This review summarises our current knowledge of commonalities and differences in translation between IVTmRNAs and cellular mRNAs, which is key for the development of future design strategies that can generate IVTmRNAs with improved activity in therapeutic applications.