The acidic transformed nano-VO2 causes macrophage cell death by the induction of lysosomal membrane permeabilization and Ca2+ efflux

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.

Cytotoxicity of vanadium oxide nanoparticles and titanium dioxide-coated vanadium oxide nanoparticles to human lung cells

Due to excellent metal-insulator transition property, vanadium dioxide nanoparticles (VO₂ NPs)-based nanomaterials are extensively studied and applied in various fields, and thus draw safety concerns of VO₂ NPs exposure through various routes. Herein, the cytotoxicity of VO₂ NPs (N-VO₂ ) and titanium dioxide-coated VO₂ NPs (T-VO₂ ) to typical human lung cell lines (A549 and BEAS-2B) was studied by using a series of biological assays. It was found that both VO₂ NPs induced a dose-dependent cytotoxicity, and the two cell lines displayed similar sensitivity to VO₂ NPs. Under the same conditions, T-VO₂ NPs showed slightly lower cytotoxicity than N-VO₂ in both cells, indicating the surface coating of titanium dioxide mitigated the toxicity of VO₂ NPs. Titanium dioxide coating changed the surface property of VO₂ NPs and reduced the vanadium release of particles, and thus helped lowing the toxicity of VO₂ NPs. The induced cell viability loss was attributed to apoptosis and proliferation inhibition, which were supported by the assays of apoptosis, mitochondrial membrane damage, caspase-3 level, and cell cycle arrest. The oxidative stress, i.e., enhanced reactive oxygen species generation and suppressed reduced glutathione , in A549 and BEAS-2B cells was one of the major mechanisms of the cytotoxicity of VO₂ NPs. These findings provide safety guidance for the practical applications of vanadium dioxide-based materials.

Giant Cellular Vacuoles Induced by Rare Earth Oxide Nanoparticles are Abnormally Enlarged Endo/Lysosomes and Promote mTOR-Dependent TFEB Nucleus Translocation

Many nanomaterials are reported to disrupt lysosomal function and homeostasis, but how cells sense and then respond to nanomaterial-elicited lysosome stress is poorly understood. Nucleus translocation of transcription factor EB (TFEB) plays critical roles in lysosome biogenesis following lysosome stress induced by starvation. The authors previously reported massive cellular vacuolization, along with autophagy induction, in cells treated with rare earth oxide (REO) nanoparticles. Here, the authors identify these giant cellular vacuoles as abnormally enlarged and alkalinized endo/lysosomes whose formation is dependent on macropinocytosis. This vacuolization causes deactivation of mammalian target of rapamycin (mTOR), a TFEB-interacting kinase that resides on the lysosome membrane. Subsequently, TFEB is dephosphorylated at serine 142 and translocated into cell nucleus. This nucleus translocation of TFEB is observed only in vacuolated cells and it is critical for maintaining lysosome homeostasis after REO nanoparticle treatment, as knock-down of TFEB gene significantly compromises lysosome function and enhances cell death in nanoparticle-treated cells. Our results reveal that cellular vacuolization, which is commonly observed in cells treated with REOs and other nanomaterials, represents a condition of profound lysosome stress, and cells sense and respond to this stress by facilitating mTOR-dependent TFEB nucleus translocation in an effort to restore lysosome homeostasis.