Domes and semi-capsules as model systems for infrared microspectroscopy of biological cells.

It is well known that infrared microscopy of micrometer sized samples suffers from strong scattering distortions, attributed to Mie scattering. The state-of-the-art preprocessing technique for modelling and removing Mie scattering features from infrared absorbance spectra of biological samples is built on a meta model for perfect spheres. However, non-spherical cell shapes are the norm rather than the exception, and it is therefore highly relevant to evaluate the validity of this preprocessing technique for deformed spherical systems. Addressing these cases, we investigate both numerically and experimentally the absorbance spectra of 3D-printed individual domes, rows of up to five domes, two domes with varying distance, and semi-capsules of varying lengths as model systems of deformed individual cells and small cell clusters. We find that coupling effects between individual domes are small, corroborating previous related literature results for spheres. Further, we point out and illustrate with examples that, while optical reciprocity guarantees the same extinction efficiency for top vs. bottom illumination, a scatterer's internal field may be vastly different in these two situations. Finally, we demonstrate that the ME-EMSC model for preprocessing infrared spectra from spherical biological systems is valid also for deformed spherical systems.

Effects of the coupling of dielectric spherical particles on signatures in infrared microspectroscopy.

Infrared microspectroscopy is a powerful tool in the analysis of biological samples. However, strong electromagnetic scattering may occur since the wavelength of the incident radiation and the samples may be of comparable size. Based on the Mie theory of single spheres, correction algorithms have been developed to retrieve pure absorbance spectra. Studies of the scattering characteristics of samples of different types, obtained by microspectroscopy, have been performed. However, the detailed, microscopic effects of the coupling of the samples on signatures in spectra, obtained by infrared microspectroscopy, are still not clear. The aim of this paper is to investigate how the coupling of spherical samples influences the spectra. Applying the surface integral equation (SIE) method, we simulate small dielectric spheres, arranged as double-spheres or small arrays of spheres. We find that the coupling of the spheres hardly influences the broad oscillations observed in infrared spectra (the Mie wiggles) unless the radii of the spheres are different or the angle between the direction of the incident radiation and the normal of the plane where the spheres are located is large. Sharp resonance features in the spectra (the Mie ripples) are affected by the coupling of the spheres and this effect depends on the polarization of the incident wave. Experiments are performed to verify our conclusions.

Vanillin downregulates NNMT and attenuates NNMT­related resistance to 5­fluorouracil via ROS­induced cell apoptosis in colorectal cancer cells.

Chemoresistance is the main cause of poor prognosis in colorectal cancer (CRC). Nicotinamide N­methyltransferase (NNMT) is a metabolic enzyme that is upregulated in various tumor types. It has been reported that NNMT inhibits apoptosis and enhances resistance to 5­fluorouracil (5­Fu) via inhibition of the apoptosis signal regulating kinase 1 (ASK1)­p38 MAPK pathway in CRC cells. A natural product library was screened, and it was found that vanillin, also known as 4­hydroxy­3­methoxybenzaldehyde, a plant secondary metabolite found in several essential plant oils, mainly Vanilla planifolia, Vanilla tahitensis, and Vanilla pompon, may be a promising anticancer compound targeted to NNMT. The aim of the present study was to explore the effect of vanillin on promoting apoptosis and attenuating NNMT­induced resistance to 5­Fu in CRC. Lentiviral vectors of short hairpin RNA and small interfering RNA were transfected into HT­29 cells to construct NNMT­knockdown HT­29 cell lines. Vectors containing an open reading frame of NNMT were stably transfected into SW480 cells to induce NNMT overexpression in SW480 cell lines. Vanillin was found to inhibit the mRNA and protein expression levels of NNMT following the inhibition of NNMT activity in HT­29 cell lines. Vanillin was able to reverse NNMT­induced increased cell proliferation, decreased cell apoptosis and resistance to 5­Fu by inhibiting NNMT expression. Furthermore, it increased cell apoptosis by activating the ASK1­p38 MAPK pathway, which could be inhibited by NNMT. In addition, vanillin increased cell apoptosis by promoting mitochondrial damage and reactive oxygen species. In vivo, the combination of vanillin with 5­Fu yielded a notable synergy in inhibiting tumor growth and inducing apoptosis. Considering that vanillin is an important flavor and aromatic component used in foods worldwide, vanillin is deemed to be a promising anticancer candidate by inhibiting NNMT and may attenuate NNMT­induced resistance to 5­Fu in human CRC therapy with few side effects.

Curcumin Reverses NNMT-Induced 5-Fluorouracil Resistance via Increasing ROS and Cell Cycle Arrest in Colorectal Cancer Cells.

Nicotinamide N-methyltransferase (NNMT) plays multiple roles in improving the aggressiveness of colorectal cancer (CRC) and enhancing resistance to 5-Fluorouracil (5-FU), making it an attractive therapeutic target. Curcumin (Cur) is a promising natural compound, exhibiting multiple antitumor effects and potentiating the effect of 5-FU. The aim of the present study is to explore the effect of Cur on attenuating NNMT-induced resistance to 5-FU in CRC. A panel of CRC cell lines with different NNMT expressions are used to characterize the effect of Cur. Herein, it is observed that Cur can depress the expression of NNMT and p-STAT3 in CRC cells. Furthermore, Cur can induce inhibition of cell proliferation, G2/M phase cell cycle arrest, and reactive oxygen species (ROS) generation, especially in high-NNMT-expression CRC cell lines. Cur can also re-sensitize high-NNMT-expression CRC cells to 5-FU both in vitro and in vivo. In summary, it is proposed that Cur can reverse NNMT-induced cell proliferation and 5-FU resistance through ROS generation and cell cycle arrest. Given that Cur has long been used, we suppose that Cur is a promising anticancer drug candidate with minimal side effects for human CRC therapy and can attenuate NNMT-induced resistance to 5-FU.

Proteomic Analysis of Vernalization Responsive Proteins in Winter Wheat Jing841.

BACKGROUND: Vernalization is one of the pivotal ways for plants to flower. The twodimensional gel electrophoresis (2-DE) and matrix-assisted laser desorption/ionization time-offlight/ time-of-flight mass spectrometry (MALDI-TOF/TOF MS) were applied to analyze the changes in protein expression profiles in responding to vernalization in leaves of wheat seedling before (0d) and after (30d) of vernalization. OBJECTIVE: The main objective of this study was to analyze the vernalization-responsive proteins in winter wheat after vernalization. METHODS: Winter wheat seedling leaf proteins were extracted by phenol extraction coupled with ammonium acetate in methanol. 2-DE was conducted according to procedures described in the manual given by the GE manufacture. The selected protein spots were identified by MALDITOF/ TOF MS. Gene ontology (GO) classification was applied to classify the functions of the differentially expressed proteins. Pathway enrichment analysis identified significantly enriched metabolic pathways or signal transduction pathways relative to the whole proteins background. RESULTS: The results of 2-DE and MALDI-TOF/TOF MS showed that among the 65 differentially expressed proteins that were successfully identified under vernalization, 30 were up-regulated whereas 35 were down-regulated after vernalization, respectively. These vernalization-responsive proteins were found to play roles in carbohydrate metabolism, protein metabolism, photosynthesis, defense and stress-resistance and may therefore participate in many biological processes in responding to vernalization. The enhanced accumulation of proteins after vernalization, such as thiamine thiazole synthase, late embryogenesis abundant protein, and glutathione-S-transferase, probably play vital roles in the mechanisms underlying vernalization response in wheat. CONCLUSION: Our results indicated these vernalization-responsive proteins were found to be involved in protein metabolism, carbohydrate metabolism, photosynthesis, and stress resistance/ defense. The responses of plants to low temperature were very complex, involving in a wide range of cellular pathways for signal transduction, gene regulation, protein modifications, and metabolic regulation. Studying on wheat proteomic profiles in response to vernalization can improve our understanding the molecular mechanisms underlying vernalization in cereals. The results obtained in this study have provided a novel insight into the mechanisms underlying vernalization in cereal crops.