Caspase-3/Gasdermin E-mediated pyroptosis contributes to Ricin toxin-induced inflammation.

Ricin toxin (RT) is highly cytotoxic and can release a considerable amount of pro-inflammatory factors due to depurination, causing excessive inflammation that may aggravate the harm to the body. Pyroptosis, a type of gasdermin-mediated cell death, is a contributor to the exacerbation of inflammation. Accumulating evidence indicate that pyroptosis plays a significant role in the pathogen infection and tissue injury, suggesting a potential correlation between pyroptosis and RT-induced inflammation. Here, we aim to demonstrate this correlation and explore its molecular mechanisms. Results showed that RT triggers mouse alveolar macrophage MH-S cells pyroptosis by activating caspase-3 and cleaving Gasgermin E (GSDME). In contrast, inhibition of caspase-3 with Z-DEVD-FMK (inhibitor of caspase-3) or knockdown of GSDME attenuates this process, suggesting the essential role of caspase-3/GSDME-mediated pyroptosis in contributing to RT-induced inflammation. Collectively, our study enhances our understanding of a novel mechanism of ricin cytotoxicity, which may emerge as a potential target in immunotherapy to control the RT-induced inflammation.

The current landscape of the antimicrobial peptide melittin and its therapeutic potential.

Melittin, a main component of bee venom, is a cationic amphiphilic peptide with a linear α-helix structure. It has been reported that melittin can exert pharmacological effects, such as antitumor, antiviral and anti-inflammatory effects in vitro and in vivo. In particular, melittin may be beneficial for the treatment of diseases for which no specific clinical therapeutic agents exist. Melittin can effectively enhance the therapeutic properties of some first-line drugs. Elucidating the mechanism underlying melittin-mediated biological function can provide valuable insights for the application of melittin in disease intervention. However, in melittin, the positively charged amino acids enables it to directly punching holes in cell membranes. The hemolysis in red cells and the cytotoxicity triggered by melittin limit its applications. Melittin-based nanomodification, immuno-conjugation, structural regulation and gene technology strategies have been demonstrated to enhance the specificity, reduce the cytotoxicity and limit the off-target cytolysis of melittin, which suggests the potential of melittin to be used clinically. This article summarizes research progress on antiviral, antitumor and anti-inflammatory properties of melittin, and discusses the strategies of melittin-modification for its future potential clinical applications in preventing drug resistance, enhancing the selectivity to target cells and alleviating cytotoxic effects to normal cells.

A novel circular RNA circNLRP3 alleviated ricin toxin-induced TNF-α production through sponging miR-221-5p.

Acting as microRNA (miRNA) sponges, circular RNAs (circRNAs) have been discovered to be critical modulators of inflammatory processes. Ricin Toxin (RT) is highly toxic to mammalian cells and low doses of RT can induce acute inflammation. However, current researches on the underlying mechanism and function of circRNA/miRNA network in RT-induced inflammation are limited. Previously, we found miR-221-5p was aberrant and associated with the inflammation of RT induction. In this study, based on the circRNA high-throughput sequencing (circRNA-seq), we obtained a novel circRNA termed circNLRP3 and revealed that circNLRP3 can sponge miR-221-5p, release its target mRNA A20, and further suppress NF-κB signaling pathway to alleviated RT-induced TNF-α production. Our findings elucidated a possible mechanistic link between the circNLRP3/miR-221-5p/A20 axis and RT-induced inflammatory response, which may broaden our understanding of RT poisoning.

MicroRNA-221-5p Promotes Ricin Toxin-induced Inflammation via PI3K/Akt signaling pathway by targeting COL4a5.

Ricin toxin (RT) is one of the most lethal type II ribosome-inactivating proteins (RIP), and is classified as a potential bioterror agent due to its severe cytotoxicity and high availability. The toxicity of RT is dependent on both dose and route of exposure. Increasing evidence demonstrates that sub-lethal RT induces acute inflammation and increases the release of pro-inflammatory cytokines. However, current studies on mechanism of RT-induced inflammation are limited. In this study, to evaluate the relationship between miRNAs and RT-induced inflammation, RNA sequencing (RNA-Seq) was used to analyze the expression of miRNAs and mRNAs in RT-treated RAW264.7 macrophage cells. A total of 14 significantly differently expressed (DE) miRNAs and 323 miRNA-mRNA interaction pairs were predicted by bioinformatics analysis. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis revealed that majority of those interaction pairs were involved in PI3K/Akt pathway. In addition, overexpression of miR-221-5p promoted the inflammatory response by inhibiting the mRNA expression of COL4a5. This work contributes to our understanding of RT-induced inflammation and demonstrates the potential role of miRNAs in innate immunity, which may be regarded as potential targets in developing therapies for RT poisoning.

Critical role of toll-like receptor 4 (TLR4) in ricin toxin-induced inflammatory responses in macrophages.

Ricin toxin (RT) is a natural plant-derived protein toxin from the seed of castor beans that belongs to a family of type II ribosome-inactivating proteins (RIPs). In addition to its main toxic mechanism of inhibiting the synthesis of cellular proteins, RT can induce the production of inflammatory cytokines and cause inflammatory injury. Macrophages play a crucial role in innate immunity and the adaptive immune response as the first line of host defense against bacterial infections and various types of invading pathogens. Upon activation, macrophages release types of cytokines to remove pathogens. However, the effect of RT on the immune response and its mechanism are not well characterized. In the current study, we investigated the activation of the TLR4-mediated signaling pathway by low-dose RT treatment and its interaction with signaling molecules in the transduction pathway. We found that low-dose RT can activate MyD88- and TRIF-dependent signaling pathways, revealing a possible mechanism by which low-dose RT-activates TLR4-mediated signaling pathways. We also confirmed that the TLR4-induced activation of the inflammatory signaling pathways was produced via its binding to RT. This study may help to identify the most important target molecules and clarify the mechanism of inflammatory injury of ricin.

Hybrids of carbon dots with subunit B of ricin toxin for enhanced immunomodulatory activity.

Although Ricin toxin binding subunit B (RTB) can promote the activation of macrophages and modulate the cell-mediated immunity, its applications are severely limited due to the intrinsic properties of proteins, like poor stability and low efficacy of cellular uptake. In this work, the stable nanoparticles were prepared by supramolecular assembling of carbon dots (CDs) and RTB. The formed CDs-RTB possesses robust stability and can protect RTB against enzymatic hydrolysis. More importantly, CDs-RTB can promote macrophages proliferation, improve the generation of NO, IL-6 and TNF-α in RAW264.7 cells and increase the expression of mRNA, indicating the enhanced immunomodulatory activity of CDs-RTB. This work highlights the potential of using CDs as a simple and stable platform to assemble RTB and effectively promotes the application of RTB as the immunostimulant.