Transcriptomic analysis revealed that multi-walled carbon nanotubes diameter-dependently induced pyroptosis in THP-1 macrophages

Construction of charge-reversible coordination-crosslinked spherical nucleic acids to deliver dual anti-cancer genes and ferroptosis payloads

Spherical nucleic acids (SNAs) are nanostructures with the DNA arranged radially on the surface, thus allowing specific binding with cancer cells expressing high levels of scavenger receptor-A to enhance cellular uptake. However, conventional carriers for SNAs are cytotoxic, not degradable and difficult to deliver multiple payloads. In this study, we developed charge-reversible coordination-crosslinked SNAs to deliver dual anti-cancer genes and ferroptosis payload for anti-cancer purposes. To this end, we modified poly(lactic acid) (PLA) with functionalized side chains to allow its binding with antisense oligonucleotides (ASOs) and siRNA, annealed two single-stranded RNAs to obtain double-stranded RNA, and introduced a polyethylene glycol (PEG) shell to enhance the circulation time. Additionally, the ferroptosis payload imidazole was coordinated with iron ions as a core-crosslinked group to enhance the stability of SNAs and efficiency to kill cancer cells. We demonstrated that this novel nanocomplex efficiently internalized and killed CT-26 cells in vitro. In vivo data confirmed that the dual gene delivery system successfully targeted CT-26 tumors in tumor-bearing BALB/c mice, and exhibited strong tumor suppression ability, without inducing adverse toxic effects. Taken together, our dual gene therapy system offered an enhanced anti-tumor solution by simultaneously delivering dual anti-cancer genes and ferroptosis payload in tumor microenvironment.

Nanomaterial-induced pyroptosis: a cell type-specific perspective

This review presents the advancements in nanomaterial (NM)-induced pyroptosis in specific types of cells. We elucidate the relevance of pyroptosis and delineate its mechanisms and classifications. We also retrospectively analyze pyroptosis induced by various NMs in a broad spectrum of non-tumorous cellular environments to highlight the multifunctionality of NMs in modulating cell death pathways. We identify key knowledge gaps in current research and propose potential areas for future exploration. This review emphasizes the need to focus on less-studied areas, including the pathways and mechanisms of NM-triggered pyroptosis in non-tumor-specific cell types, the interplay between biological and environmental factors, and the interactions between NMs and cells. This review aims to encourage further investigations into the complex interplay between NMs and pyroptosis, thereby providing a basis for developing safer and more effective nanomedical therapeutic applications.

The interplay between lysosome, protein corona and biological effects of cationic carbon dots: Role of surface charge titratability

Carbon dots (CDs) are nanoparticles (NPs) with potential applications in the biomedical field. When in contact with biological fluids, most NPs are covered by a protein corona. As well, upon cell entry, most NP are sequestered in the lysosome. However, the interplay between the lysosome, the protein corona and the biological effects of NPs is still poorly understood. In this context, we investigated the role of the lysosome in the toxicological responses evoked by four cationic CDs exhibiting protonatable or non-protonatable amine groups at their surface, and the associated changes in the CD protein corona. The four CDs accumulated in the lysosome and led to lysosomal swelling, loss lysosome integrity, cathepsin B activation, NLRP3 inflammasome activation, and cell death by pyroptosis in a human macrophage model, but with a stronger effect for CDs with titratable amino groups. The protein corona formed around CDs in contact with serum partially dissociated under lysosomal conditions with subsequent protein rearrangement, as assessed by quantitative proteomic analysis. The residual protein corona still contained binding proteins, catalytic proteins, and proteins involved in the proteasome, glycolysis, or PI3k-Akt KEGG pathways, but with again a more pronounced effect for CDs with titratable amino groups. These results demonstrate an interplay between lysosome, protein corona and biological effects of cationic NPs in link with the titratability of NP surface charges.

Activation of KLF6 by titanate nanofibers and regulatory roles of KLF6 on ATF3 in the endothelial monolayer and mouse aortas

Although titanium (Ti)-based nanomaterials (NMs) were traditionally considered as biologically inert materials, it was recently reported that Ti-based NMs induce adverse vascular effects by inhibiting Kruppel-like factor 2 (KLF2) and/or KLF4, vasoprotective KLFs with well-documented regulatory activity in NO signaling. However, the potential roles of other KLFs are not clear. KLF6 was recently identified as an important KLF involved in regulating endothelial dysfunction, inflammation, and angiogenesis, therefore, this study investigated the influence of titanate nanofibers (TiNFs) on KLF6-mediated events. Ingenuity pathway analysis (IPA) showed that TiNFs altered the expression of a panel of KLF6-related genes: KLF6-mediated gene ontology (GO) terms were altered, categories including cytokine-mediated signaling pathways, transcription factor (TF) functions and membrane-bound organelles. Additionally, RT-PCR confirmed that TiNFs increased KLF6 activating transcription factor 3 (ATF3), a TF involved in endoplasmic reticulum (ER) stress, and ELISA confirmed the increase of soluble monocyte chemotactic protein 1 (sMCP-1), a KLF6-related inflammatory cytokine. Interestingly, the activation of klf6, atf3 and C-C motif chemokine ligand 2 (ccl2; mcp-1 encoding gene) was observed in aortas of mice following one-time intravenous injection but not intratracheal instillation of TiNFs (100 μg per mouse), indicating a need for direct contact with NMs to activate klf6-mediated pathways in vivo. In endothelial cells, KLF6 knockdown inhibited the expression of ATF3 but not CCL2, suggesting the regulatory role of KLF6 in ATF3 expression. Overall, this study uncovered a previously unknown role of KLF6 in TiNF-induced vascular effects both in vitro and in vivo.

Activation of Kruppel-like factor 6 by multi-walled carbon nanotubes in a diameter-dependent manner in THP-1 macrophages in vitro and bronchoalveolar lavage cells in vivo

MWCNTs activated KLF6-signaling pathways in THP-1 macrophages and bronchoalveolar lavage cells.

The uses of transcriptomics and lipidomics indicated that direct contact with graphene oxide altered lipid homeostasis through ER stress in 3D human brain organoids

The potential uses of graphene-based nanomaterials (NMs) in various fields lead to the concern about their neurotoxicity, considering that graphene-based NMs are capable to cross blood brain barrier (BBB) and enter central nervous system (CNS). Although previous studies reported the possibility of graphene-based NM exposure to alter lipid homeostasis in animals or cultured neurons, recent studies suggested the need to use 3D human brain organoids for mechanism-based toxicological studies as this model might better recapitulate the complex human brains. Herein, we used multi-omics techniques to investigate the mechanisms of graphene oxide (GO) on lipid homeostasis in a novel 3D brain organoid model. We found that 50 μg/mL GO induced cytotoxicity but not superoxide. RNA-sequencing data showed that 50 μg/mL GO significantly up-regulated and down-regulated 80 and 121 genes, respectively. Furthermore, we found that GO exposure altered biological molecule metabolism pathways including lipid metabolism. Consistently, lipidomics data supported dose-dependent alteration of lipid profiles by GO in 3D brain organoids. Interestingly, co-exposure to GO and endoplasmic reticulum (ER) stress inhibitor 4-phenylbutyric acid (4-PBA) decreased most of the lipid classes compared with the exposure of GO only. We further verified that exposure to GO promoted ER stress marker GRP78 proteins, which in turn activated IRE1α/XBP-1 axis, and these changes were partially or completely inhibited by 4-PBA. These results proved that direct contact with GO disrupted lipid homeostasis through the activation of ER stress. As 3D brain organoids resemble human brains, these data might be better extrapolated to humans.

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.

Protein corona mitigated the cytotoxicity of CdTe QDs to macrophages by targeting mitochondria

Despite the potential of cadmium telluride quantum dots (CdTe QDs) in bioimaging and drug delivery, their toxic effects have been documented. It is known that the immunotoxicity of CdTe QDs targeting macrophages is one of their adverse effects, and the protein corona (PC) will affect the biological effects of QDs. In order to prove whether the PC-CdTe QDs complexes could alleviate the toxicity of CdTe QDs without weakening their luminescence, we investigated the impact of protein corona formed in fetal bovine serum (FBS) on the cytotoxicity of CdTe QDs to mitochondria. RAW264.7 cells were used as the model to compare the effects of CdTe QDs and PC-CdTe QDs complexes on the structure, function, quantity, morphology, and mitochondrial quality control of mitochondria. As result, the protein corona form in FBS alleviated the inhibition of CdTe QDs on mitochondrial activity, the damage to mitochondrial membrane, the increase of ROS, and the reduction of ATP content. Also, CdTe QDs increased the number of mitochondria in macrophages, while the complexes did not. In line with this, the morphology of mitochondrial network in macrophages which were exposed to CdTe QDs and PC-CdTe QDs complexes was different. CdTe QDs transformed the network into fragments, punctuations, and short rods, while PC-CdTe QDs complexes made the mitochondrial network highly branched, which was related to the imbalance of mitochondrial fission and fusion. Mechanically, CdTe QDs facilitated mitochondrial fission and inhibited mitochondrial fusion, while protein corona reversed the phenomenon caused by QDs. Besides mitochondrial dynamics, mitochondrial biogenesis and mitophagy were also affected. CdTe QDs increased the expression of mitochondrial biogenesis signaling molecules including PGC-1α, NRF-1 and TFAM, while PC-CdTe QDs complexes played the opposite role. With regard to mitophagy, they both showed promoting effect. In conclusion, the formation of protein corona alleviated the toxic effects of CdTe QDs on the mitochondria in macrophages and affected mitochondrial quality control. Under the premise of ensuring the fluorescence properties of CdTe QDs, these findings provided useful insight into reducing the toxicity of CdTe QDs from two perspectives: protein corona and mitochondria, and shared valuable information for the safe use of QDs.

Influences of Unmodified and Carboxylated Carbon Nanotubes on Lipid Profiles in THP-1 Macrophages: A Lipidomics Study

Since the possible roles of surface modifications in determining multi-walled carbon nanotube (MWCNT)-promoted endoplasmic reticulum (ER) stress-mediated lipid-laden macrophage foam cell formation are still in debate, we compared unmodified and carboxylated MWCNT-induced cytotoxicity, lipid profile changes, and expression of ER stress genes in THP-1 macrophages. Particularly, we focused on lipid profile changes by using lipidomics approaches. We found that unmodified and carboxylated MWCNTs significantly decreased cellular viability and appeared to damage the cellular membrane to a similar extent. Likewise, the results from Oil Red O staining showed that both types of MWCNTs slightly but significantly induced lipid accumulation. In keeping with Oil Red O staining results, lipidomics data showed that both types of MWCNTs up-regulated most of the lipid classes. Interestingly, almost all lipid classes were relatively higher in carboxylated MWCNT-exposed THP-1 macrophages compared with unmodified MWCNT-exposed cells, indicating that carboxylated MWCNTs more effectively changed lipid profiles. But in contrast to our expectation, none of the MWCNTs significantly induced the expression of ER stress genes. Even, compared with carboxylated MWCNTs, unmodified MWCNTs induced higher expression of lipid genes, including macrophage scavenger receptor 1 and fatty acid synthase. Combined, our results suggested that even though carboxylation did not significantly affect MWCNT-induced lipid accumulation, carboxylated MWCNTs were more potent to alter lipid profiles in THP-1 macrophages, indicating the need to use omics techniques to understand the exact nanotoxicological effects of MWCNTs. However, the differential effects of unmodified and carboxylated MWCNTs on lipid profiles might not be related with the induction of ER stress.

Transcriptomic-based toxicological investigations of graphene oxide with modest cytotoxicity to human umbilical vein endothelial cells: changes of Toll-like receptor signaling pathways

The wide uses of graphene oxide (GO) lead to the contact of GO with vascular systems, so it is necessary to investigate the toxicological effects of GO to endothelial cells. Recently, we reported that GO of small lateral size (<500 nm) was relatively biocompatible to human umbilical vein endothelial cells (HUVECs), but recent studies by using omics-techniques revealed that nanomaterials (NMs) even without acute cytotoxicity might induce other toxicological effects. This study investigated the effects of GO on HUVECs based on RNA-sequencing and bioinformatics analysis. Even after exposure to 100 μg/ml GO, the cellular viability of HUVECs was higher than 70%. Furthermore, 25 μg/ml GO was internalized but did not induce ultrastructural changes or intracellular superoxide. These results combined indicated GO's relatively high biocompatibility. However, by analyzing the most significantly altered Gene Ontology terms and Kyoto Encyclopedia of Gene and Genomes pathways, we found that 25 μg/ml GO altered pathways related to immune systems' functions and the responses to virus. We further verified that GO exposure significantly decreased Toll-like receptor 3 and interleukin 8 proteins, indicating an immune suppressive effect. However, THP-1 monocyte adhesion was induced by GO with or without the presence of inflammatory stimulus lipopolysaccharide. We concluded that GO might inhibit the immune responses to virus in endothelial cells at least partially mediated by the inhibition of TLR3. Our results also highlighted a need to investigate the toxicological effects of NMs even without acute cytotoxicity by omics-based techniques.

Comparison of multi-walled carbon nanotubes and halloysite nanotubes on lipid profiles in human umbilical vein endothelial cells

Tubular nanomaterials (NMs), such as multi-walled carbon nanotubes (MWCNTs) and halloysite nanotubes (HNTs), may be used in biomedicine, but previous studies showed that MWCNTs induced toxicity to endothelial cells (ECs). However, the influence of tubular NMs on EC lipid profiles has gained little attention, probably because ECs are not traditionally considered to be involved in regulating lipid homeostasis. This study compared the different effects of MWCNTs and HNTs on lipid profile changes in human umbilical vein ECs (HUVECs). The results showed that MWCNTs but not HNTs of the same mass concentrations induced cytotoxicity, ultrastuctural changes and intracellular thiol depletion. Meanwhile, only MWCNTs promoted lipid accumulation due to the induction of ER stress leading to up-regulation of fatty acid synthase (FASN). Interestingly, lipidomics results showed that the main lipid classes induced by MWCNTs but not HNTs were ceramide (Cer) and phosphatidylinositol (PI), with most of the lipid classes unaltered or even decreased after NM exposure. Then, extra Cer and PI were added to explore the implications of increase of these lipids. Adding Cer promoted the cytotoxicity of MWCNTs to HUVECs, indicating the lipotoxic role of Cer. Whereas adding PI partially increased intracellular NO and decreased interleukin-6 (IL-6) release due to MWCNT exposure, indicating the signaling role of PI. These results indicated novel roles of lipid dysfunction in NM-induced toxicity to ECs, even though ECs are not the professional cells for controlling lipid homeostasis.

A comparative study of toxicity of graphdiyne and graphene oxide to human umbilical vein endothelial cells

The success of graphene oxide (GO) has attracted extensive research interests in developing novel 2D nanomaterials (NMs). Graphdiyne (GDY) is a new member of carbon-based 2D NMs possessing sp- and sp² -hybridized carbon atoms. However, the toxicity of GDY is less investigated as GO. In this study, we compared the toxicity of GDY and GO with human umbilical vein endothelial cells (HUVECs). Exposure to up to 100-μg/ml GDY and GO induced cytotoxicity, but there was no statistically significant difference between GDY and GO. At noncytotoxic concentration, 25-μg/ml GDY or GO led to the internalization of NMs, typically in cytoplasm but not in nuclei. Only GO but not GDY significantly increased THP-1 adhesion onto NM-exposed HUVECs. Meanwhile, compared with GDY, GO more effectively promoted the release of soluble intracellular cell adhesion molecule-1 (sICAM-1), indicating the differential effects of GDY and GO on endothelial activation. Neither GDY nor GO induced intracellular superoxide. However, GO significantly promoted the expression of endoplasmic reticulum (ER) stress genes activating transcription factor 4 (ATF4) and X-box binding protein 1 spliced (XBP-1s), as well pyroptosis genes NLR family pyrin domain containing 3 (NLRP3) and gasdermin D (GSDMD), whereas GDY did not show this effect. The results suggested that GDY and GO could be internalized into HUVECs leading to cytotoxic effects. However, GO was more potent to activate endothelial activation probably due to the activation of ER stress and pyroptosis genes.

Potential roles of Kruppel-like factors in mediating adverse vascular effects of nanomaterials: A review

The development of nanotechnology leads to the exposure of human beings to nanomaterials (NMs), and there is a health concern about the adverse vascular effects of NMs. Current data from epidemiology, controlled human exposure, and animal studies suggested that exposure to NMs could induce cardiopulmonary effects. In support of in vivo findings, in vitro studies showed that direct contact of vascular cells with NMs could induce endothelial cell (EC) activation and promote macrophage foam cell formation, although only limited studies showed that NMs could damage vascular smooth muscle cells and promote their phenotypic switch. It has been proposed that NMs induced adverse vascular effects via different mechanisms, but it is still necessary to understand the upstream events. Kruppel-like factors (KLFs) are a set of C2H2 zinc finger transcription factors (TFs) that can regulate various aspects of vascular biology, but currently, the roles of KLF2 in mediating the adverse vascular effects of NMs have gained little attention by toxicologists. This review summarized current knowledge about the adverse vascular effects of NMs and proposed the potential roles of KLFs in mediating these effects based on available data from toxicological studies as well as the current understanding about KLFs in vascular biology. Finally, the challenges in investigating the role of KLFs in vascular toxicology were also summarized. Considering the important roles of KLFs in vascular biology, further studies are needed to understand the influence of NMs on KLFs and the downstream events.