How big nanoparticles carry small ones into cells: Actions captured by transmission electron microscopy.

The mechanism of cellular uptake of nanoparticles (NPs) is critical for both bio-application and risk evaluation of NPs, but is still not fully understood due to many influencing factors, among which particle size is a major one. Recent studies show that there is an unusual interplay among differently-sized NPs when they simultaneously interact with cells, e.g., 100 nm silica NPs (SNP100) can promote the cellular uptake of 50 nm silica NPs (SNP50). However, the underlying mechanism is still unclear. Herein, we manage to capture individual endocytosis events in HeLa and A549 cells after co-exposure to SNP50 and SNP100 for 2 hours, using transmission electron microscopy (TEM). TEM images clearly show that there is a size threshold for SNPs to trigger clathrin-mediated endocytosis: One single SNP100 can efficiently trigger it, while it needs about 6 SNP50 to do so. Remarkably, TEM also captures how SNP100 triggers the endocytosis and carries nearby SNP50 into cells, and statistical data show that the average number of SNP50 carried by one SNP100 could be up to about 6. In addition, the mechanism was further verified by using mixed 60 nm SNPs (SNP60) and SNP100. This mechanism has an immediate implication for the design of drug-deliver nanocarriers, and as a proof-of-concept, more catalase functionalized SNP50 (CAT@SNP50) was delivered into HeLa cells by adding some SNP100, resulting in a more severe cell damage compared to CAT@SNP50 alone under same conditions. The findings have general impact on the nanotoxicity study of NP products that commonly have certain distributions in size, and provide new insights on designing efficient drug delivery systems by deliberately control the combinations of NPs of different sizes.

RNA demethylase FTO participates in malignant progression of gastric cancer by regulating SP1-AURKB-ATM pathway.

Gastric cancer (GC) is the 5th most prevalent cancer and the 4th primary cancer-associated mortality globally. As the first identified m6A demethylase for removing RNA methylation modification, fat mass and obesity-associated protein (FTO) plays instrumental roles in cancer development. Therefore, we study the biological functions and oncogenic mechanisms of FTO in GC tumorigenesis and progression. In our study, FTO expression is obviously upregulated in GC tissues and cells. The upregulation of FTO is associated with advanced nerve invasion, tumor size, and LNM, as well as the poor prognosis in GC patients, and promoted GC cell viability, colony formation, migration and invasion. Mechanistically, FTO targeted specificity protein 1 and Aurora Kinase B, resulting in the phosphorylation of ataxia telangiectasia mutated and P38 and dephosphorylation of P53. In conclusion, the m6A demethylase FTO promotes GC tumorigenesis and progression by regulating the SP1-AURKB-ATM pathway, which may highlight the potential of FTO as a diagnostic biomarker for GC patients' therapy response and prognosis.

Impact of calcium ions at physiological concentrations on the adsorption behavior of proteins on silica nanoparticles.

The adsorption of proteins on nanoparticles (NPs) largely decides the fate and bioeffects of NPs in vivo. However, bio-fluids are too complicated to directly study in them to reveal related mechanisms, and current studies on model systems often ignore some important biological factors, such as metal ions. Herein, we evaluate the effect of Ca2+ at physiological concentrations on the protein adsorption on negatively-charged silica NP (SNP50). It is found that Ca2+, as well as Mg2+ and several transition metal ions, significantly enhances the adsorption of negatively-charged proteins on SNP50. Moreover, the Ca2+-induced enhancement of protein adsorption leads to the reduced uptake of SNP50 by HeLa cells. A double-chelating mechanism is proposed for the enhanced adsorption of negatively-charged proteins by multivalent metal ions that can form 6 (or more) coordinate bonds, where the metal ions are chelated by both the surface groups of NPs and the surface residues of the adsorbed proteins. This mechanism is consistent with all experimental evidences from metal ions-induced changes of physicochemical properties of NPs to protein adsorption isotherms, and is validated with several model proteins as well as complicated serum. The findings highlight the importance of investigating the influences of physiological factors on the interaction between proteins and NPs.

Inhibition of FNDC1 suppresses gastric cancer progression by interfering with Gßγ-VEGFR2 complex formation.

Gastric cancer (GC) is a prevalent digestive tract malignant tumor characterized by an insidious onset, ease of metastasis, rapid growth, and poor prognosis. Here, we report that fibronectin type III domain containing 1 (FNDC1) has high expression in GC and indicates poor outcomes in patients with GC. FNDC1 over-expression or knockdown promotes or inhibits tumorigenesis and metastasis, respectively. The expression of FNDC1 is upregulated by TWIST1, strengthening its interaction with Gßγ and VEGFR2. The formation of the trimers, TWIST1 plus Gßγ and VEGFR2, increases VEGFR2 phosphorylation and Gßγ trafficking, which activates RAS-MAPK and PI3K-AKT signaling, benefiting GC progression. In this study, we demonstrated that arsenite can efficiently suppress FNDC1 expression, attenuating the formation of the trimers and downstream pathways. Altogether, our results indicate that FNDC1 might be a promising target for clinical treatment and prognostic judgment, while FNDC1 inhibition by arsenite provides a new opportunity for overcoming this fatal disease.

FASN Targeted by miR-497-5p Regulates Cell Behaviors in Cervical Cancer.

Cervical cancer (CC) is a severe malignant tumor. Recently, more and more evidence has shown that abnormal expression of fatty acid synthase (FASN) occurs in varying tumors. Therefore, this investigation devoted to FASN in CC along with its upstream regulatory miRNA. Their expression levels were tested by qRT-PCR. Cell function experiments were undertaken to test tumor-related cell behaviors. Identification of their interplay was conducted by western blot and dual-luciferase methods. As analyzed, miR-497-5p was at low level in human CC cell lines, while FASN was overexpressed and demonstrated as a target of miR-497-5p. Cell function experiments demonstrated the targeting of miR-497-5p to FASN 3'-UTR, thus restraining CC development. To sum up, this investigation primarily revealed miR-497-5p/FASN axis in CC, by which potential CC biomarkers, could be developed. However, the mechanism of the axis was not determined in vivo, as one of the study limitations.

Endocytosis, Distribution, and Exocytosis of Polystyrene Nanoparticles in Human Lung Cells.

Nanoplastics, one component of plastic pollution, can enter human bodies via inhalation and thus threaten human health. However, the knowledge about the uptake and exocytosis of nanoplastics in cells of human lung organs is still very limited. Herein, we investigated the endocytosis, distribution, and exocytosis of polystyrene nanoparticles (PS NPs) of 50 nm (G50PS) and 100 nm (R100PS) in A549 cells and BEAS-2B cells. We found that both the cellular uptake of PS NPs increased positively with exposure time and dose, and A549 cells ingested more PS NPs than BEAS-2B cells did. In addition, the intracellular content of G50PS was higher than that of R100PS except at a higher dose and longer time. The ingested PS NPs were distributed mainly in lysosomes, while many G50PS appeared around the cell membrane, and R100PS also accumulated in mitochondria in BEAS-2B cells. As for the exocytosis, R100PS was more difficult to excrete than G50PS. Lysosomes in A549 cells and actin and microtubule in BEAS-2B cells were involved in the exocytosis of the PS NPs. These findings provide detailed information about the translocation of nanoplastics in lung cells, which is valuable for the safety assessment of nanoplastics in the environment.