Gamma-irradiation and UV-C light-induced lipid peroxidation: a Fourier transform-infrared absorption spectroscopic study

Infrared spectral profiling of demyelinating activity in multiple sclerosis brain tissue

Multiple sclerosis (MS) is a leading cause of non-traumatic disability in young adults. The highly dynamic nature of MS lesions has made them difficult to study using traditional histopathology due to the specificity of current stains. This requires numerous stains to track and study demyelinating activity in MS. Thus, we utilized Fourier transform infrared (FTIR) spectroscopy to generate holistic biomolecular profiles of demyelinating activities in MS brain tissue. Multivariate analysis can differentiate MS tissue from controls. Analysis of the absorbance spectra shows profound reductions of lipids, proteins, and phosphate in white matter lesions. Changes in unsaturated lipids and lipid chain length indicate oxidative damage in MS brain tissue. Altered lipid and protein structures suggest changes in MS membrane structure and organization. Unique carbohydrate signatures are seen in MS tissue compared to controls, indicating altered metabolic activities. Cortical lesions had increased olefinic lipid content and abnormal membrane structure in normal appearing MS cortex compared to controls. Our results suggest that FTIR spectroscopy can further our understanding of lesion evolution and disease mechanisms in MS paving the way towards improved diagnosis, prognosis, and development of novel therapeutics.

Infrared microspectroscopy to elucidate the underlying biomolecular mechanisms of FLASH radiotherapy

BACKGROUND

FLASH-radiotherapy (FLASH-RT) is an emerging modality that uses ultra-high dose rates of radiation to enable curative doses to the tumor while preserving normal tissue. The biological studies showed the potential of FLASH-RT to revolutionize radiotherapy cancer treatments. However, the complex biological basis of FLASH-RT is not fully known yet.

AIM

Within this context, our aim is to get deeper insights into the biomolecular mechanisms underlying FLASH-RT through Fourier Transform Infrared Microspectroscopy (FTIRM).

METHODS

C57Bl/6J female mice were whole brain irradiated at 10 Gy with the eRT6-Oriatron system. 10 Gy FLASH-RT was delivered in 1 pulse of 1.8μs and conventional irradiations at 0.1 Gy/s. Brains were sampled and prepared for analysis 24 h post-RT. FTIRM was performed at the MIRAS beamline of ALBA Synchrotron. Infrared raster scanning maps of the whole mice brain sections were collected for each sample condition. Hyperspectral imaging and Principal Component Analysis (PCA) were performed in several regions of the brain.

RESULTS

PCA results evidenced a clear separation between conventional and FLASH irradiations in the 1800-950 cm-1 region, with a significant overlap between FLASH and Control groups. An analysis of the loading plots revealed that most of the variance accounting for the separation between groups was associated to modifications in the protein backbone (Amide I). This protein degradation and/or conformational rearrangement was concomitant with nucleic acid fragmentation/condensation. Cluster separation between FLASH and conventional groups was also present in the 3000-2800 cm-1 region, being correlated with changes in the methylene and methyl group concentrations and in the lipid chain length. Specific vibrational features were detected as a function of the brain region.

CONCLUSION

This work provided new insights into the biomolecular effects involved in FLASH-RT through FTIRM. Our results showed that beyond nucleic acid investigations, one should take into account other dose-rate responsive molecules such as proteins, as they might be key to understand FLASH effect.

The Toxic Effects of Cu and CuO Nanoparticles on Euplotes aediculatus

The single-celled eukaryote Euplotes aediculatus was chosen to test and compare the toxic effects of Cu and CuO nanoparticles (NPs). The antioxidant enzymatic activity, morphological changes, and functional groups on the membrane were determined using spectrophotometry, microscopy, and Fourier transform infrared spectroscopy after NPs treatment. The toxicity of the NPs to cells was dose-dependent, and the 24 h-LC₅₀ values of the CuNPs and CuONPs were 0.46 µg/L and 1.24 × 10³ µg/L, respectively. These NPs increased the activities of superoxide dismutase, glutathione peroxidase, and catalase and destroyed the cell structure; moreover, the CuNPs were more toxic than the CuONPs. In addition to the higher enzymatic activity, CuNPs also caused nucleoli disappearance, chromatin condensation, and mitochondrial and pellicle damage. The oxidization of the functional groups of the membrane (PO₂ - , C-O-C, and δ(COH) of carbohydrates) also confirmed the severe damage caused by CuNPs. Our study showed that oxidative stress and organelle destruction played important roles in the toxic effects of these NPs on this protozoan. Compared with other aquatic organisms, E. aediculatus can be considered a potential indicator at the preliminary stage of environmental pollution.

Photo induced mechanistic activity of GO/Zn(Cu)O nanocomposite against infectious pathogens: Potential application in wound healing

Treating infection causing microorganisms is one of the major challenges in wound healing. These may gain resistance due to the overuse of conventional antibiotics. A promising technique is antimicrobial photodynamic therapy (aPDT) used to selectively cause damage to infectious pathogenic cells via generation of reactive oxygen species (ROS). We report on biocompatable nanomaterials that can serve as potential photosensitizers for aPDT. GO/Zn(Cu)O nanocomposite was synthesized by co-precipitation method. Graphene Oxide (GO) is known for its high surface to volume ratio, excellent surface functionality and enhanced antimicrobial property. ZnO nanoparticle induces the generation of reactive oxygen species (ROS) under light irradiation and it leads to recombination of electron-hole pair. Nanocomposites of GO and Cu doped ZnO increases visible light absorption and enhances the photocatalytic property. It generates more ROS and increases the bacterial inhibition. GO/Zn(Cu)O nanocomposite was tested against Staphylococcus aureus (S. aureus), Enterococcus faecium (E. faecium), Escherichia coli (E. coli), Salmonella typhi (S. typhi), Shigella flexneri (S. flexneri) and Pseudomonas aeruginosa (P. aeruginosa) by well diffusion method, growth curve, colony count, biofilm formation under both dark and visible light condition. Reactive Oxygen Species assay (ROS), Lactate dehydrogenase leakage (LDH) assay, Protein estimation assay and membrane integrity study proves the mechanism of inhibition of bacteria. Inhibition kinetics shows the sensitivity between bacteria and GO/Zn(Cu)O nanocomposite.

Thorn-like TiO2 nanoarrays with broad spectrum antimicrobial activity through physical puncture and photocatalytic action

To overcome the conventional limitation of TiO2 disinfection being ineffective under light-free conditions, TiO2 nanowire films (TNWs) were prepared and applied to bacterial disinfection under dark and UV illumination. TNW exhibited much higher antibacterial efficiencies against Escherichia coli (E. coli) under dark and UV illumination conditions compared to TiO2 nanoparticle film (TNP) which was almost inactive in the dark, highlighting the additional contribution of the physical interaction between bacterial membrane and NWs. Such a physical contact-based antibacterial activity was related to the NW geometry such as diameter, length, and density. The combined role of physical puncture and photocatalytic action in the mechanism underlying higher bactericidal effect of TNW was systematically examined by TEM, SEM, FTIR, XPS, and potassium ion release analyses. Moreover, TNW revealed antimicrobial activities in a broad spectrum of microorganisms including Staphylococcus aureus and MS2 bacteriophage, antibiofilm properties, and good material stability. Overall, we expect that the free-standing and antimicrobial TNW is a promising agent for water disinfection and biomedical applications in the dark and/or UV illumination.

Physicochemical Analysis of DPPC and Photopolymerizable Liposomal Binary Mixture for Spatiotemporal Drug Release

The development of a spatiotemporal drug delivery system with a long release profile, high loading efficiency, and robust therapeutic effects is still a challenge. Liposomal nanocarriers have secured a fortified position in the biomedical field over decades. Herein, liposomal binary mixtures of 1,2-dipalmitoyl- sn-glycero-3-phosphocholine (DPPC) and photopolymerizable 1,2-bis(10,12-tricosadiynoyl)- sn-glycero-3-phosphocholine (DC_8,9PC) phospholipids were prepared for drug delivery applications. The diacetylenic groups of DC_8,9PC produce intermolecular cross-linking following UV irradiation. Exposure of the liposomal mixture to 254 nm radiation induces a pore within the lipid bilayer, expediting the release of its entrapped 5,6-carboxyfluorescein dye. The dosage and rate of the released content are highly dependent on the number and size of the induced pore. Photochemical cross-linking studies at different exposure times were reported through the analysis of UV-visible spectrophotometry, nano differential scanning calorimetry, Fourier transform infrared spectroscopy, and Raman spectroscopy. The optimal irradiation time was established after 8 min of exposure, inducing lipid cross-linking with minimal oxidative degradation, which plays an essential role in the pathogenesis of numerous diseases due to the formation of primary and secondary oxidation products, accordingly reducing the encapsulated drug therapeutic level.

Valdecoxib Recovers the Lipid Composition, Order and Dynamics in Colon Cancer Cell Lines Independent of COX-2 Expression: An ATR-FTIR Spectroscopy Study

Prostanoids play an important role in a variety of physiological and pathophysiological processes including inflammation and cancer. The rate-limiting step in the prostanoid biosynthesis pathway is catalyzed by cyclooxygenases (COXs). Aberrant expression of the inducible isoform COX-2 plays a significant role in colon cancer initiation and progression. In this study, we have hypothesized that COX-2 specific inhibitors such as Valdecoxib (VLX), being highly hydrophobic, may alter biophysical properties of cellular lipids. In this study, COX-2 expressing (HT29) and COX-2 non-expressing (SW620) colon cancer cell lines were treated with VLX and examined using attenuated total reflection infrared spectroscopy. The results revealed that VLX treatment decreased lipid fluidity in the cells irrespective of COX-2 expression status and affected order parameters of the lipids in both cell lines. Cluster analysis also indicated that the spectral differences between the two cell lines are profound and could be successfully differentiated. Valdecoxib treatment could enhance the composition, order and dynamics of the lipids of colon cancer cells independently of its COX-2 inhibitory mechanism. Valdecoxib has therapeutic effects upon colon cancer, therefore it can be used as an adjuvant and/or chemopreventive agent for colon cancer.

In situ visualization of carbonylation and its co-localization with proteins, lipids, DNA and RNA in Caenorhabditis elegans

All key biological macromolecules are susceptible to carbonylation - an irreparable oxidative damage with deleterious biological consequences. Carbonyls in proteins, lipids and DNA from cell extracts have been used as a biomarker of oxidative stress and aging, but formation of insoluble aggregates by carbonylated proteins precludes quantification. Since carbonylated proteins correlate with and become a suspected cause of morbidity and mortality in some organisms, there is a need for their accurate quantification and localization. Using appropriate fluorescent probes, we have developed an in situ detection of total proteins, DNA, RNA, lipids and carbonyl groups at the level of the whole organism. In C. elegans, we found that after UV irradiation carbonylation co-localizes mainly with proteins and, to a lesser degree, with DNA, RNA and lipids. The method efficiency was illustrated by carbonylation induction assessment over 5 different UV doses. The procedure enables the monitoring of carbonylation in the nematode C. elegans during stress, aging and disease along its life cycle including the egg stage.

Interaction between oxide nanoparticles and biomolecules of the bacterial cell envelope as examined by infrared spectroscopy

The effects of Al(2)O(3), TiO(2), and ZnO nanoparticles (NPs) on bacteria cells and bacterial surface biomolecules were studied by Fourier transform infrared (FTIR) spectroscopy. All the examined biomolecules showed IR spectral changes after NP exposure. Lipopolysaccharide and lipoteichoic acid could bind to oxide NPs through hydrogen bonding and ligand exchange, but the cytotoxicity of NPs seemed largely related to the function-involved or devastating changes to proteins and phospholipids of bacteria. The three NPs decreased the intensity ratio of β-sheets/α-helices, indicating protein structure change, which may affect cell physiological activities. The phosphodiester bond of L-α-phosphatidylethanolamine was broken by ZnO NPs, forming phosphate monoesters and resulting in the highly disordered alkyl chain. Such damage to phospholipid molecular structure may lead to membrane rupture and cell leaking, which is consistent with the fact that ZnO is the most toxic of the three NPs. The cell surface biomolecular changes revealed by FTIR spectra provide a better understanding of the cytotoxicity of oxide NPs.

Characterization of microRNA-125b expression in MCF7 breast cancer cells by ATR-FTIR spectroscopy

MicroRNAs (miRNAs), are ~22 nucleotides long, non-coding RNAs that control gene expression post-transcriptionally by binding to their target mRNA's 3'UTRs (untranslated regions). Due to their roles in various important regulatory processes and pathways, miRNAs have been implicated in disease mechanisms such as tumorigenesis when their expression is deregulated. To date, a significant number of miRNAs and their target messenger RNAs (mRNAs) have been identified and verified. It is generally accepted that miRNAs can potentially bind to many mRNAs, which brings the requirement of validation of these interactions. While understanding that such individual interactions is crucial to delineate the role of a specific miRNA, we took a holistic approach and analyzed global changes in the cell due to expression of a miRNA in a model cell line system. Our model consisted of MCF7 cells stably transfected with miR-125b (MCF7-125b) and empty vector (MCF7-EV). MiR-125b is one of the known down-regulated miRNAs in breast cancers. In this study we examined the global structural changes in MCF7 cells lacking and expressing miR-125b by Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) Spectroscopy and investigated the dynamic changes by more sensitive spin-labelling Electron Spin Resonance (ESR) spectroscopy. Our results revealed less RNA, protein, lipid, and glycogen content in MCF7-125b compared to MCF7-EV cells. Membrane fluidity and proliferation rate were shown to be lower in MCF7-125b cells. Based on these changes, MCF7-125b and MCF7-EV cells were discriminated successfully by cluster analysis. Here, we provide a novel means to understand the global effects of miRNAs in cells. Potential applications of this approach are not only limited to research purposes. Such a strategy is also promising to pioneer the development of future diagnostic tools for deregulated miRNA expression in patient samples.

Biochemical alterations in human cells irradiated with alpha particles delivered by macro- or microbeams

Irradiation of individual cell nuclei with charged-particle microbeams requires accurate identification and localization of cells using Hoechst staining and UV illumination before computer-monitored localization of each cell. Using Fourier-transform infrared microspectroscopy (FT-IRM), we investigated whether the experimental conditions used for cell recognition induce cellular changes prior to irradiation and compared biochemical changes and DNA damage after targeted and nontargeted irradiation with alpha particles delivered by macro- or microbeams, using gamma radiation as a reference. Molecular damage in single HaCaT cells was studied by means of FT-IRM and comet assay (Gault et al., Int. J. Radiat. Biol. 81, 767-779, 2005). Hoechst 33342-stained HaCaT cells were exposed to single doses of 2 Gy (239)Pu alpha particles from a broad-beam irradiator, five impacted alpha particles from a microbeam irradiator, or 6 Gy gamma rays from (137)Cs, each of which resulted in about 5% clonogenic survival. FT-IRM of control cells indicated that Hoechst binding to nuclear DNA induced subtle changes in DNA conformation, and its excitation under UV illumination induced a dramatic shift of the DNA conformation from A to B as well as major DNA damage as measured by the comet assay. Comparison of the FT-IRM spectra of cells exposed to gamma rays or alpha particles specifically targeted to the nucleus, alpha particles from a broad-beam irradiator revealed spectral changes corresponding to all changes in constitutive bases in nucleic acids, suggesting oxidative damage in these bases, as well as structural damage in the deoxyribose-phosphate backbone of DNA and the osidic structure of nucleic acids. Concomitantly, spectral changes specific to protein suggested structural modifications. Striking differences in IR spectra between targeted microbeam- and nontargeted macrobeam-irradiated cells indicated greater residual unrepaired or misrepaired damage after microbeam irradiation. This was confirmed by the comet assay data. These results show that FT-IRM, together with the comet assay, is useful for assessing direct radiation-induced damage to nucleic acids and proteins in single cells and for investigating the effects of radiation quality. Significantly, FT-IRM revealed that Hoechst 33342 binding to DNA and exposure to UV light induce a dramatic change in DNA conformation as well as DNA damage. These findings suggest that fluorochrome staining should be avoided in studies of ionizing radiation-induced bystander effects based on charged-particle microbeam irradiation. An alternative cell nucleus recognition system that avoids nuclear matrix damage and its possible contribution to propagation of biological effects from irradiated cells to neighboring nontargeted cells needs to be developed.

Infrared microspectroscopy study of gamma-irradiated and H2O2-treated human cells

PURPOSE

Fourier transform infrared microspectroscopy (FT-IRM), which allows simultaneous detection of biochemical changes in the various cellular compartments, was used as a new analytical tool to study early radiation- and oxidation-induced cellular damage at the molecular level in single human cells.

MATERIALS AND METHODS

HaCaT keratinocytes were given a single dose of 6 Gy (137Cs) or 650 microM H2O2, neither of which is cytotoxic (neutral red assay) but both of which result in less than 10% clonogenic survival, and deposited on zinc sulphur (ZnS) windows for infra-red (IR) spectra acquisition, immediately and 2 h after treatment. DNA damage was assessed by comet assays in alkaline conditions.

RESULTS

Comet assays showed that the yield of DNA damage was higher after H2O2 treatment than after gamma-irradiation. The comparison between spectra of irradiated and H2O2-treated cells showed common changes, but H2O2 treatment presented a broader spectrum of cellular oxidation than ionizing radiation. The bands characteristic of deoxyribose/ribose in nucleic acids centered at 966 and 997 cm(-1), the bands characteristic of nucleic acid bases centered at 1572, 1599, and 1691 cm(-1), as well as the bands characteristic of ordered secondary structure of DNA centered at 1713-1716 cm(-1), were changed in absorbance, sometimes accompanied by a shift. The bands characteristic of proteins centered at 1515, 1530, 1544 and 1640 cm(-1) were changed in absorbance indicating a decrease in secondary structure of proteins. Moreover, the absorbance of the bands at 1515 and 1630 cm(-1) was correlated the yield of reactive oxygen species. Two hours after both treatments most changes were persistent, suggesting either irreversible or not easily repaired damage or persistent oxidative stress.

CONCLUSION

As we previously demonstrated in radiation-induced apoptosis studies, these results show that FT-IRM, in correlation with other cellular biology techniques, might be useful for assessing immediate radiation- and oxidative-induced damage to nucleic acids and proteins in single human cells.

Apoptose radio-induite: une nouvelle approche par microspectroscopie infrarouge

Purpose: to characterize radiation-induced apoptosis in human cells using Fourier transform infrared microspectroscopy (FT-IRM) as a new analytical tool. Material and methods: Normal human circulating lymphocytes were given a γ ray dose of 6 Gy, or treated with t-butyl hydroperoxide (t-BuOH). HaCaT keratinocytes were given a dose of 20 Gy. Cells were deposited on ZnS windows for infrared spectral acquisition 2 days and 2 h after irradiation and 2 h after t-BuOH treatment. Apoptosis was simultaneously assessed by flow cytometry analysis of cells displaying annexin-V-positive staining. Results. The flow cytometry study showed that about 90% of sham and irradiated cells were annexin-V negative 2 h after irradiation. Two days after irradiation, 68% of lymphocytes and 76% of HaCaT cells were apoptotic, as well as 43% of lymphocytes treated with t-BuOH. In infrared spectra of these apoptotic cells, qualitative and quantitative changes were observed. In the 960–1245 and 1690–1720 cm–1 ranges, mainly attributed to nucleic acids, changes corresponding to conformational changes in DNA were associated with a decrease in the amount of detectable DNA. Conformational changes were also observed in secondary protein structure, in particular an increase in the amount of β structures. These DNA and protein changes were associated with an increase in the detectable amount of lipids in apoptotic HaCaT cells only. Two hours after irradiation, depending on the dose and (or) the cell type, qualitative and quantitative changes were observed in the IR spectra in the amide I and amide II bands, mainly attributed to proteins. These changes were associated with a significant decrease in the 1700–1750 cm–1 range, mainly attributed to the –C=O ester groups of DNA and phospholipids, in the irradiated HaCaT cells only. Conclusion: Our results are in agreement with biochemical published data on radiation-induced apoptosis, and show that DNA is the first cellular target of radiation-induced apoptosis, which, however, also requires conformational changes and synthesis of cell proteins. They also demonstrate that FT-IRM may be useful for assessing the early radiation damage at the molecular level in human cells.Key words: apoptosis, Fourier transform infrared microspectroscopy, γ irradiation, human lymphocytes, HaCaT keratinocytes.

Noninvasive analyses of polyunsaturated fatty acids in human oral mucosain vivo by Fourier-transform infrared spectroscopy

The aim of this study was to develop a noninvasive method to observe polyunsaturated fatty acids (PUFAs) behavior in the human body using Fourier transform infrared spectroscopy. For the noninvasive measurement of human oral mucosa, we have used infrared spectroscopy with a suitable attachment for an in vivo attenuated total reflectance system. The fatty acid contents in the tissues were determined by gas-chromatography mass-spectrometry after methylation. The alkene C-H stretching vibrations of unsaturated fatty acids in dietary oils showed infrared absorption bands with various peak positions and intensities at around 3010 cm(-1) depending on the extent of unsaturation and their species. The diurnal fluctuation of the alkene peak position of oral mucosa suggested that the contents of PUFAs were increased gradually in the early afternoon, and these data were supported by the direct determination of fatty acid species in oral mucosa where the relative increase of arachidonic and docosahexaenoic acids was observed in the early afternoon. This diurnal change of alkene peak position resembled the pattern of a "lipid factor" change calculated with the factor analysis applied to the overall infrared spectrum. We could monitor the diurnal fluctuations of PUFA contents of human oral mucosa noninvasively using a reagent-free infrared analysis system. The measurement of alkene and methylene infrared bands may provide a useful tool for detecting changes in PUFA balance in the human body.

Nondestructive analyses of unsaturated fatty acid species in dietary oils by attenuated total reflectance with Fourier transform IR spectroscopy

The aim of this study was to develop a nondestructive method to quantitate relative amounts of n-3 and n-6 polyunsaturated fatty acid (PUFA) species in vegetable oils and oil seeds using Fourier transform IR spectroscopy (FTIR). The alkene Cbond;H stretching vibrations of unsaturated fatty acids in oils showed IR absorption bands with various peak positions and intensities at around 3010 cm(-1), depending on the extent of unsaturation and PUFA species. With the aid of partial least-squares regression analysis, the FTIR measurement could practically predict the content of each PUFA species in the oil to be tested. A calculation method was also presented to directly find PUFA species in oils from the FTIR spectra. This technique was applied to dried soybean seeds to demonstrate a nonhomogenous distribution of saturated fatty acids and PUFAs, as well as glycans, in soybean cross sections.

Infrared microspectroscopic characteristics of radiation-induced apoptosis in human lymphocytes

Infrared microspectroscopic characterization of radiation-induced apoptosis was used as a new analytical tool to study the kinetics of apoptosis in human peripheral blood lymphocytes at the molecular level. This vibrational technique, which has already been used to investigate biomolecules in normal and tumor cells, allows the simultaneous detection of the biochemical changes in the various subcellular compartments. Normal circulating lymphocytes from five healthy human donors were given a single dose of 6 Gy ((60)Co) and deposited on ZnS windows for infrared spectral acquisition 1, 2 and 4 days after irradiation. Apoptosis was assessed simultaneously by flow cytometry analysis of lymphocytes displaying annexin V-positive staining, and by detection of the DNA laddering that is characteristic of apoptosis. The flow cytometry study showed that about 80% of sham-irradiated lymphocytes were annexin V(neg)/PI(neg) at 1, 2 and 4 days. One day after irradiation, 46% of irradiated lymphocytes were annexin V(neg)/PI(neg), 48% were annexin V(pos)/PI(neg), 5% were annexin V(pos)/PI(pos), and 1% were annexin V(neg)/PI(pos). These mean percentages were respectively 31, 59, 9 and 1 at day 2 and 23, 36, 30, and 11 at day 4. Irradiated lymphocytes presented a DNA laddering pattern characteristic of apoptosis from day 1 after irradiation. In the infrared spectra of irradiated lymphocytes, qualitative and quantitative changes were observed from days 1 and 2, respectively. In the range of 960-1245 cm(-1) mainly attributed to nucleic acids, changes corresponding to conformational changes in DNA were associated with a decrease in the amount of detectable DNA. Conformational changes were also observed in secondary protein structures, in particular an increase in the amount of beta structures. These DNA and protein changes were associated with an increase in the detectable amount of lipids at day 4 after irradiation. These results showed that DNA is probably the first cellular target of radiation-induced apoptosis, which, however, also requires conformational changes and synthesis of cell proteins. Our results are in agreement with biochemical and morphological data on radiation-induced apoptosis of normal human circulating lymphocytes, and they demonstrate that infrared microspectroscopy may be useful for assessing the process of apoptosis at the molecular level.

Modulation of intercellular communication mediated at the cell surface and on extracellular, plasma membrane-derived vesicles by ionizing radiation

The plasma membrane is a dynamic organelle whose function includes receptor-mediated signal transduction into the cell. Conversely, the plasma membrane is the origin of inter-cellular signaling. In addition to expressing and releasing growth factors in a soluble form(through exocytosis) and via proteolysis of cell surface components, membrane ligands may signal nearby cells through juxtacrine stimulation or by the exfoliation or shedding of plasma membrane-derived vesicles. Ionizing radiation (IR) has a profound effect on plasma membrane structure and function. IR-induced ultrastructural alterations are mediated via lipid interaction with water radiolysis products (e.g., hydroxyl radicals, hydrogen radicals, and hydrated electrons). Ionizing radicals act directly on lipid molecules to promote lipid hydro-peroxides and lipid hydroperoxide breakdown products (e.g., alpha, beta unsaturated aldehydes) that contribute to altered plasma membrane lipid composition. A change in lipid composition increases membrane lipid microviscosity and results in membrane fenestrations that enhance permeability to small molecules and ions. Reactive ionizing species also stimulate sphingomyelinase activity, leading to sphingomyelin hydrolysis and ceramide generation that further contributes to altered membrane lipid composition and cellular apoptosis. In addition, exposure to IR results in impaired rate of and cumulative shedding of plasma membrane-associated growth factors. Mechanisms of exfoliation are reviewed for normal cells and the impact of radiation on modulating signal transduction mediated by exfoliation is summarized.

Gamma irradiation and cellular damage in Kocuria rosea: investigation by one- and two-dimensional infrared spectroscopy

Fourier transform infrared (FT-IR) spectroscopy was used to investigate the radiation-induced effects on Kocuria rosea. Bacterial suspensions at the stationary phase were exposed to increasing doses of gamma radiation. In the region 1350-840cm(-1), assigned to phosphodiester backbone, nucleic acids, and sugar rings, the radical damaging effects were dose-dependent, with the first threshold at 2.75kGy and the second at 13.75kGy inducing more striking spectral variations. Postirradiation reincubation did not significantly affect the biomolecular response, except in the spectral range 1100-1000cm(-1). These observations suggest the occurrence of new phylogenetic characteristics for K. rosea following irradiation. Moreover, two-dimensional analysis was used to highlight correlated evolutions of molecular species as radical aggression increased. The results point to an evolutionary scheme during the time course of irradiation. Thus, one- and two-dimensional IR analyses are convenient means of investigating the metabolic events following oxidative stress generated by either chemical or physical agents.

Combination of vitamin C and rutin on neuropathy and lung damage of diabetes mellitus rats

We investigated the role of vitamin C or rutin on neuropathy and lung damage of diabetic mellitus (DM) rats. Norepinephrine content was significantly decreased in sciatic nerves'of DM rats compared with non-DM controls but vitamin C had no effect on decreases of norepinephrine. 2,4-dinitrophenylhydrazine (DNPH) incorporation, which is biomarker of protein oxidation, was increased in sciatic nerve of DM rats as compared with normal control. However, vitamin C had no effects on increases of DNPH incorporation. We measured the content of conjugated dienes (CD) as a biomarker of lipid oxidation in sciatic nerve. CD was increased in DM as compared with normal control. Vitamin C or rutin had no effects on increases of CD. However, Rutin plus vitamin C significantly decreased the content of CD as compared with DM rats. In lung of DM rats, DNPH incorporation or CD was increased as compared with normal control. Vitamin C or Rutin had no effects on increases of CD. However, Rutin plus vitamin C significantly decreased the content of DNPH incorporation or CD in lung tissue. Vitamin C caused marked pathological changes such as the increases of parenchyma and the thickening of alveolar septa in the lung of DM. Rutin had protective effects on the pathological changes in the lung of DM rats. In conclusion, Vitamin C had no effects on oxidative parameter, such as DNPH incorporation or CD, and on the decreases of norepinephrine content in DM rats. Vitamin C caused the marked pathological changes in the lung of DM rats but rutin had protective effects against the pathological changes.

Accumulation of diacylglycerol in the liver membrane of the Long-Evans Cinnamon (LEC) rat with hepatitis: FT-IR spectroscopic and HPLC detection

Long-Evans Cinnamon (LEC) rats develop severe hepatitis and subsequent hepatoma with excess accumulation of copper in the liver with increasing age. Lipids extracted from the LEC rat liver membrane were studied using FT-IR spectroscopy and an HPLC technique at the stages of pre-hepatitis and hepatitis, i.e. at 10 and 16 weeks of age, respectively. The 10-week-old rats exhibited an IR spectrum characteristic of a phosphatidylcholine and phosphatidylethanolamine mixture with a ratio of 2:1. The 16-week-old rats developed new absorption bands at 1161 and 1070 cm(-1), which were assigned to the spectra of triglyceride, neutral lipid, and diacylglycerol, an endogenous activator of protein kinase C, respectively. The diacylglycerol was estimated to amount to ca. 10% (w/w) of phospholipid extract by comparing the spectrum with those of model compounds. This was confirmed using an HPLC assay. Previously, we found that a serum response factor is activated by copper in the LEC rat liver, and suggested that it must mediate proto-oncogene c-fos induction. The results obtained here suggest that accumulation of diacylglycerol plays an important role in development of hepatoma in LEC rats by mediating proto-oncogene c-fos induction.

Kinetics of radiation- and cytochrome c-induced modifications in liposomes analysed by FT-Raman spectroscopy

Fourier transform Raman spectroscopy on artificial lipid membranes was used to study radiation-induced peroxidation processes as a function of time after radiation exposure. The time dependent intensity changes of the Raman lines of various C=C bondings were compared to results obtained by measuring conjugated dienes and by the thiobarbituric acid test for malondialdehydes. The results show that mainly the cis C=C bonds of the lipid chains are involved and, therefore, indicate that gamma-radiation induces conformational changes in the lipid chain while the mobility of the lipid chains is reduced. New Raman bands can be assigned to aldehyde products induced at the end of the peroxidation process. The immediate decrease of the =CH vibration lines was directly correlated with the formation of conjugated C=C double bonds suggesting that these vibration lines are in contrast to the C=C lines solely Raman active, when isolated C=C bonds are present. Cytochrome c (ox.) incorporated into the bilayer of the artificial membranes induced autooxidation processes not influenced by gamma-radiation. It was observed that cytochrome c (ox.)-induced changes of the relative intensity of the C=C bonds differ from those induced by gamma-radiation. These results of cytochrome c together with the inhibitory effects of the antioxidant alpha-tocopherol suggest that the radical species involved in the cytochrome c induced process might be different from the free radicals involved in the gamma-radiation-induced process.