Proteomic analysis of the aging-related proteins in human normal colon epithelial tissue

Lactiplantibacillus plantarum Strain FLPL05 Promotes Longevity in Mice by Improving Intestinal Barrier

This study aimed to evaluate the effect of oral administration of probiotic Lactiplantibacillus plantarum FLPL05 on the lifespan and intestinal barrier of aged mice. L. plantarum FLPL05 significantly prolonged the lifespan of naturally aged mice, maintained the integrity of intestinal mucosal barrier, and reduced the inflammation level. The analysis of intestinal microbiota revealed that L. plantarum FLPL05 increased the relative abundance of Firmicutes and decreased the abundance of Bacteroides, accompanied by the increased proportions of Lactobacillus and Desulfovibrio in intestinal microbiota as well as the reduced proportions of Roseburia and Parabacteroides. The intestinal proteomics revealed that the oral administration of L. plantarum FLPL05 significantly upregulated the tight junction and simultaneously inhibited the expression of apoptotic-related proteins. The immunohistochemistry results also indicated that L. plantarum FLPL05 promoted the expression of tight junction proteins (ZO-1 and occludin) and reduced the apoptosis of intestinal cells. In addition, L. plantarum FLPL05 and the fermented supernatant increased the activity of HT-29. L. plantarum FLPL05 prolonged the lifespan by improving the health of the intestinal tract after aging and may be a potential probiotic and nutritional supplement for the elderly people.

Electron transfer flavoprotein and its role in mitochondrial energy metabolism in health and disease

Electron transfer flavoprotein (ETF) is an enzyme with orthologs from bacteria to humans. Human ETF is nuclear encoded by two separate genes, ETFA and ETFB, respectively. After translation, the two subunits are imported to the mitochondrial matrix space and assemble into a heterodimer containing one FAD and one AMP as cofactors. ETF functions as a hub taking up electrons from at least 14 flavoenzymes, feeding them into the respiratory chain. This represents a major source of reducing power for the electron transport chain from fatty acid oxidation and amino acid degradation. Transfer of electrons from the donor enzymes to ETF occurs by direct transfer between the enzyme bound flavins, a process that is tightly regulated by the polypeptide chain and by protein:protein interactions. ETF, in turn relays electrons to the iron sulfur cluster of the inner membrane protein ETF:QO, from where they travel via the FAD in ETF:QO to ubiquinone, entering the respiratory chain at the level of complex III. ETF recognizes its dehydrogenase partners via a recognition loop that anchors the protein on its partner followed by dynamic movements of the ETF flavin domain that bring redox cofactors in close proximity, thus promoting electron transfer. Genetic mutations in the ETFA or ETFB genes cause the Mendelian disorder multiple acyl-CoA dehydrogenase deficiency (MADD; OMIM #231680). We here review the knowledge on human ETF and investigations of the effects of disease-associated missense mutations in this protein that have promoted the understanding of the essential role that ETF plays in cellular metabolism and human disease.

Cellular Aging Characteristics and Their Association with Age-Related Disorders

Different molecular signaling pathways, biological processes, and intercellular communication mechanisms control longevity and are affected during cellular senescence. Recent data have suggested that organelle communication, as well as genomic and metabolic dysfunctions, contribute to this phenomenon. Oxidative stress plays a critical role by inducing structural modifications to biological molecules while affecting their function and catabolism and eventually contributing to the onset of age-related dysfunctions. In this scenario, proteins are not adequately degraded and accumulate in the cell cytoplasm as toxic aggregates, increasing cell senescence progression. In particular, carbonylation, defined as a chemical reaction that covalently and irreversibly modifies proteins with carbonyl groups, is considered to be a significant indicator of protein oxidative stress and aging. Here, we emphasize the role and dysregulation of the molecular pathways controlling cell metabolism and proteostasis, the complexity of the mechanisms that occur during aging, and their association with various age-related disorders. The last segment of the review details current knowledge on protein carbonylation as a biomarker of cellular senescence in the development of diagnostics and therapeutics for age-related dysfunctions.

Voltage-Dependent Anion Channel 1 Interacts with Ribonucleoprotein Complexes To Enhance Infectious Bursal Disease Virus Polymerase Activity

Infectious bursal disease virus (IBDV) is a double-stranded RNA (dsRNA) virus. Segment A contains two overlapping open reading frames (ORFs), which encode viral proteins VP2, VP3, VP4, and VP5. Segment B contains one ORF and encodes the viral RNA-dependent RNA polymerase, VP1. IBDV ribonucleoprotein complexes are composed of VP1, VP3, and dsRNA and play a critical role in mediating viral replication and transcription during the virus life cycle. In the present study, we identified a cellular factor, VDAC1, which was upregulated during IBDV infection and found to mediate IBDV polymerase activity. VDAC1 senses IBDV infection by interacting with viral proteins VP1 and VP3. This association is caused by RNA bridging, and all three proteins colocalize in the cytoplasm. Furthermore, small interfering RNA (siRNA)-mediated downregulation of VDAC1 resulted in a reduction in viral polymerase activity and a subsequent decrease in viral yield. Moreover, overexpression of VDAC1 enhanced IBDV polymerase activity. We also found that the viral protein VP3 can replace segment A to execute polymerase activity. A previous study showed that mutations in the C terminus of VP3 directly influence the formation of VP1-VP3 complexes. Our immunoprecipitation experiments demonstrated that protein-protein interactions between VDAC1 and VP3 and between VDAC1 and VP1 play a role in stabilizing the interaction between VP3 and VP1, further promoting IBDV polymerase activity.IMPORTANCE The cellular factor VDAC1 controls the entry and exit of mitochondrial metabolites and plays a pivotal role during intrinsic apoptosis by mediating the release of many apoptogenic molecules. Here we identify a novel role of VDAC1, showing that VDAC1 interacts with IBDV ribonucleoproteins (RNPs) and facilitates IBDV replication by enhancing IBDV polymerase activity through its ability to stabilize interactions in RNP complexes. To our knowledge, this is the first report that VDAC1 is specifically involved in regulating IBDV RNA polymerase activity, providing novel insight into virus-host interactions.

Cdk3-promoted epithelial-mesenchymal transition through activating AP-1 is involved in colorectal cancer metastasis

Cyclin dependent kinase-3 (Cdk3) is a positive regulator of the G1 mammalian cell cycle phase. Cdk3 is involved in cancer progression, but very little is known about its mechanism in cancer development and progression. Herein, we found that Cdk3 increased colorectal cancer metastasis through promoting epithelial-mesenchymal transition (EMT) shift. Cdk3 was found to highly express in metastatic cancer and induce cell motility and invasion. Cdk3 was shown to phosphorylate c-Jun at Ser 63 and Ser 73 in vitro and ex vivo. Cdk3-phosphorylated c-Jun at Ser 63 and Ser 73 resulted in an increased AP-1 activity. Ectopic expression of Cdk3 promoted colorectal cancer from epithelial to mesenchymal transition conjugating AP-1 activation, while AP-1 inhibition dramatically decreased Cdk3-increased EMT shift. These results showed that the Cdk3/c-Jun signaling axis mediating epithelial-mesenchymal transition plays an important role in colorectal cancer metastasis.

MicroRNA-7 downregulates the oncogene VDAC1 to influence hepatocellular carcinoma proliferation and metastasis

Recent studies have been shown that voltage-dependent anion channel 1 (VDAC1) plays an important role in carcinogenesis. However, its molecular biological function in hepatocellular carcinoma (HCC) has not been entirely clarified. This study investigated the expression of VDAC1 in HCC and its prognostic value for HCC patients. Furthermore, we also identify the relevant VDAC1 direct target. Western blot, real-time quantitative PCR (qRT-PCR), and immunohistochemical (IHC) staining were performed to detect the expression of VDAC1 in HCC. Furthermore, the relationship between the VDAC1 level and clinicopathological features and prognostic values was explored. The effects of VDAC1 on HCC cell proliferation, migration, and invasion were also investigated in vitro. Predicted target gene of VDAC1 was determined by dual-luciferase reporter assay, qRT-PCR, and Western blot analyses. Our results revealed elevated VDAC1 messenger RNA (mRNA) (P = 0.0020) and protein (P = 0.0035) expression in tumor tissue samples compared with paired adjacent non-tumorous tissue samples. High VDAC1 expression was correlated with distant metastasis (P = 0.025), differentiation (P = 0.002), and advanced tumor stage (P = 0.004) in HCC patients. Kaplan-Meier survival analysis demonstrated that high expression of VDAC1 was significantly correlated with a poor prognosis for HCC patients (P < 0.001). The multivariate analysis revealed that VDAC1 expression was an independent prognostic factor of the overall survival rate of HCC patients. Furthermore, knockdown of VDAC1 inhibits HCC cell proliferation, migration, and invasion in vitro. Moreover, further study revealed that miR-7 was a putative target of VDAC1. Our study suggested that miR-7 suppressed the expression of VDAC1. VDAC1 plays an important role in tumor progression and may be used as a potential role in the prognosis of HCC patients.

ATP synthase subunit-β down-regulation aggravates diabetic nephropathy

In this study, we investigated the role of ATP synthase subunit-β (ATP5b) in diabetic nephropathy. Histopathological changes, fibrosis, and protein expressions of α-smooth muscle actin (α-SMA), advanced glycation end-products (AGEs), and ATP5b were obviously observed in the kidneys of db/db diabetic mice as compared with the control db/m(+) mice. The increased ATP5b expression was majorly observed in diabetic renal tubules and was notably observed to locate in cytoplasm of tubule cells, but no significant increase of ATP5b in diabetic glomeruli. AGEs significantly increased protein expression of ATP5b and fibrotic factors and decreased ATP content in cultured renal tubular cells via an AGEs-receptor for AGEs (RAGE) axis pathway. Oxidative stress was also induced in diabetic kidneys and AGEs-treated renal tubular cells. The increase of ATP5b and CTGF protein expression in AGEs-treated renal tubular cells was reversed by antioxidant N-acetylcysteine. ATP5b-siRNA transfection augmented the increased protein expression of α-SMA and CTGF and CTGF promoter activity in AGEs-treated renal tubular cells. The in vivo ATP5b-siRNA delivery significantly enhanced renal fibrosis and serum creatinine in db/db mice with ATP5b down-regulation. These findings suggest that increased ATP5b plays an important adaptive or protective role in decreasing the rate of AGEs-induced renal fibrosis during diabetic condition.

The mitochondrial voltage-dependent anion channel 1 in tumor cells

VDAC1 is found at the crossroads of metabolic and survival pathways. VDAC1 controls metabolic cross-talk between mitochondria and the rest of the cell by allowing the influx and efflux of metabolites, ions, nucleotides, Ca2+ and more. The location of VDAC1 at the outer mitochondrial membrane also enables its interaction with proteins that mediate and regulate the integration of mitochondrial functions with cellular activities. As a transporter of metabolites, VDAC1 contributes to the metabolic phenotype of cancer cells. Indeed, this protein is over-expressed in many cancer types, and silencing of VDAC1 expression induces an inhibition of tumor development. At the same time, along with regulating cellular energy production and metabolism, VDAC1 is involved in the process of mitochondria-mediated apoptosis by mediating the release of apoptotic proteins and interacting with anti-apoptotic proteins. The engagement of VDAC1 in the release of apoptotic proteins located in the inter-membranal space involves VDAC1 oligomerization that mediates the release of cytochrome c and AIF to the cytosol, subsequently leading to apoptotic cell death. Apoptosis can also be regulated by VDAC1, serving as an anchor point for mitochondria-interacting proteins, such as hexokinase (HK), Bcl2 and Bcl-xL, some of which are also highly expressed in many cancers. By binding to VDAC1, HK provides both a metabolic benefit and apoptosis-suppressive capacity that offer the cell a proliferative advantage and increase its resistance to chemotherapy. Thus, these and other functions point to VDAC1 as an excellent target for impairing the re-programed metabolism of cancer cells and their ability to evade apoptosis. Here, we review current evidence pointing to the function of VDAC1 in cell life and death, and highlight these functions in relation to both cancer development and therapy. In addressing the recently solved 3D structures of VDAC1, this review will point to structure-function relationships of VDAC as critical for deciphering how this channel can perform such a variety of roles, all of which are important for cell life and death. Finally, this review will also provide insight into VDAC function in Ca2+ homeostasis, protection against oxidative stress, regulation of apoptosis and involvement in several diseases, as well as its role in the action of different drugs. We will discuss the use of VDAC1-based strategies to attack the altered metabolism and apoptosis of cancer cells. These strategies include specific siRNA able to impair energy and metabolic homeostasis, leading to arrested cancer cell growth and tumor development, as well VDAC1-based peptides that interact with anti-apoptotic proteins to induce apoptosis, thereby overcoming the resistance of cancer cell to chemotherapy. Finally, small molecules targeting VDAC1 can induce apoptosis. VDAC1 can thus be considered as standing at the crossroads between mitochondrial metabolite transport and apoptosis and hence represents an emerging cancer drug target. This article is part of a Special Issue entitled: Membrane channels and transporters in cancers.

Proteome analysis in the assessment of ageing

Based on demographic trends, the societies in many developed countries are facing an increasing number and proportion of people over the age of 65. The raise in elderly populations along with improved health-care will be concomitant with an increased prevalence of ageing-associated chronic conditions like cardiovascular, renal, and respiratory diseases, arthritis, dementia, and diabetes mellitus. This is expected to pose unprecedented challenges both for individuals and societies and their health care systems. An ultimate goal of ageing research is therefore the understanding of physiological ageing and the achievement of 'healthy' ageing by decreasing age-related pathologies. However, on a molecular level, ageing is a complex multi-mechanistic process whose contributing factors may vary individually, partly overlap with pathological alterations, and are often poorly understood. Proteome analysis potentially allows modelling of these multifactorial processes. This review summarises recent proteomic research on age-related changes identified in animal models and human studies. We combined this information with pathway analysis to identify molecular mechanisms associated with ageing. We identified some molecular pathways that are affected in most or even all organs and others that are organ-specific. However, appropriately powered studies are needed to confirm these findings based in in silico evaluation.

Oxidative stress in aging: advances in proteomic approaches

Aging is a gradual, complex process in which cells, tissues, organs, and the whole organism itself deteriorate in a progressive and irreversible manner that, in the majority of cases, implies pathological conditions that affect the individual's Quality of Life (QOL). Although extensive research efforts in recent years have been made, the anticipation of aging and prophylactic or treatment strategies continue to experience major limitations. In this review, the focus is essentially on the compilation of the advances generated by cellular expression profile analysis through proteomics studies (two-dimensional [2D] electrophoresis and mass spectrometry [MS]), which are currently used as an integral approach to study the aging process. Additionally, the relevance of the oxidative stress factors is discussed. Emphasis is placed on postmitotic tissues, such as neuronal, muscular, and red blood cells, which appear to be those most frequently studied with respect to aging. Additionally, models for the study of aging are discussed in a number of organisms, such as Caenorhabditis elegans, senescence-accelerated probe-8 mice (SAMP8), naked mole-rat (Heterocephalus glaber), and the beagle canine. Proteomic studies in specific tissues and organisms have revealed the extensive involvement of reactive oxygen species (ROS) and oxidative stress in aging.

Proteomic analysis of mature adipocytes from obese patients in relation to aging

Obesity and aging are interrelated conditions that both cause changes in adipocyte metabolism and affect the distribution of fat in both subcutaneous and visceral depots. In addition, both weight gain and aging can lead to similar clinical outcomes such as insulin resistance, cardiovascular disease, type 2 diabetes mellitus, atherosclerosis and stroke. Our objective was to examine the changes in protein expression within the subcutaneous adipose tissue of obese patients, matched for BMI, in relation to age. Mature adipocytes were isolated from liposuction samples of abdominal subcutaneous adipose tissue collected from both young (26.2±4.3 (mean age±SD); n=7) and old (52.2±4.7 (mean age±SD); n=7) obese individuals. Total protein extracts were then compared by two-dimensional difference in gel electrophoresis (2D DIGE). Thirty differentially expressed protein spots (ANOVA test, p≤0.05; fold-change ≥1.8) were detected, of which, 15 were identified by MALDI-TOF mass spectrometry. These were comprised of a total of thirteen unique protein sequences. Nine proteins were more abundant in the adipocytes isolated from old vs. young individuals. These proteins included prohibitin 1, protein disulphide isomerase A3, beta actin, profilin, aldo-ketoreductase 1 C2, alpha crystallin B and the annexins A1, A5 and A6. Four other proteins were less abundant in the adipocytes from old, obese subjects and these included keratin type 2 cytoskeletal 1, keratin type 2 cytoskeletal 10 and hemoglobins A and B. The differentially abundant proteins were investigated by Ingenuity Pathway Analysis (IPA) to reveal their associations with known biological functions. This analysis identified signal transducer and activator of transcription 3 as the central molecule in the connectivity map and the apoptotic pathway as the pathway with the highest score. Differences in the abundances of several proteins were confirmed by immunoblotting: i.e., prohibitin 1, protein disulphide isomerase A3, beta actin, profilin and signal transducer and activator of transcription 3 proteins. In conclusion, proteomic analysis of subcutaneous adipose tissue reveals differences in the abundance of proteins in adipocytes isolated from young vs. old individuals. These differentially abundant proteins are involved in the regulation of apoptosis, cellular senescence and inflammatory response. All these are common pathologic events in both obesity and aging.

VDAC1: from structure to cancer therapy

Here, we review current evidence pointing to the function of VDAC1 in cell life and death, and highlight these functions in relation to cancer. Found at the outer mitochondrial membrane, VDAC1 assumes a crucial position in the cell, controlling the metabolic cross-talk between mitochondria and the rest of the cell. Moreover, its location at the boundary between the mitochondria and the cytosol enables VDAC1 to interact with proteins that mediate and regulate the integration of mitochondrial functions with other cellular activities. As a metabolite transporter, VDAC1 contributes to the metabolic phenotype of cancer cells. This is reflected by VDAC1 over-expression in many cancer types, and by inhibition of tumor development upon silencing VDAC1 expression. Along with regulating cellular energy production and metabolism, VDAC1 is also a key protein in mitochondria-mediated apoptosis, participating in the release of apoptotic proteins and interacting with anti-apoptotic proteins. The involvement of VDAC1 in the release of apoptotic proteins located in the inter-membranal space is discussed, as is VDAC1 oligomerization as an important step in apoptosis induction. VDAC also serves as an anchor point for mitochondria-interacting proteins, some of which are also highly expressed in many cancers, such as hexokinase (HK), Bcl2, and Bcl-xL. By binding to VDAC, HK provides both metabolic benefit and apoptosis-suppressive capacity that offers the cell a proliferative advantage and increases its resistance to chemotherapy. VDAC1-based peptides that bind specifically to HK, Bcl2, or Bcl-xL abolished the cell’s abilities to bypass the apoptotic pathway. Moreover, these peptides promote cell death in a panel of genetically characterized cell lines derived from different human cancers. These and other functions point to VDAC1 as a rational target for the development of a new generation of therapeutics.

Mitochondria malfunctions as mediators of stem-cells' related carcinogenesis: a hypothesis that supports the highly conserved profile of carcinogenesis

Cancer development is an evolutionary process that has been highly conserved among centuries within organisms. Based on this, the interest in cancer research focuses on cells, organelles and genes that possess a genetic conservatism from yeasts to human. Towards this thought, mitochondria, the highly conserved and responsible for the cellular bioenergetic activity organelles, might play crucial role in carcinogenesis. Interestingly, tumors with low bioenergetic signature have worse prognosis and show a decreased expression of ATPase protein. Furthermore, according to the stem-cell theory of carcinogenesis, aggressive tumors are characterized by an increase number of malignant stem-like cell population and their resistance to chemotherapy has been found to be mitochondrially driven. The above considerations triggered us to hypothesize that mitochondrial bioenergetic processes in stem-like cancer cells plays a crucial role in the highly conserved process of carcinogenesis. Specifically, we support that mitochondrial and/or nuclear DNA alterations that control stem cells' ATP production drive stem cells to "immortalization" (Otto Warburg theory) that mediates cancer initiation and progression. Substantiation of our hypothesis requires evidence that: (1) alterations in mitochondria bioenergetic metabolites and enzymes encoded either from the mtDNA or the nuclear DNA are linked to human cancer and (2) mitochondrial functions are regulated by highly conserved genes involved in cancer-related cellular processes such as apoptosis, aging and autophagy. Experimental approach on how this hypothesis might be tested and promising strategies in cancer therapeutics are also discussed. In case the hypothesis of stem-cell bioenergetic malformations' related carcinogenesis proves to be correct, it would contribute to the development of new prognostic, diagnostic and even more effective therapeutic interventions against various types of cancer.

Proteomic analysis of PKCγ-related proteins in the spinal cord of morphine-tolerant rats

Background

Morphine tolerance is a common drawback of chronic morphine exposure, hindering use of this drug. Studies have shown that PKCã may play a key role in the development of morphine tolerance, although the mechanisms are not fully known.

Methodology/Principal Findings

In a rat model of morphine tolerance, PKCã knockdown in the spinal cord was successfully carried out using RNA interference (RNAi) with lentiviral vector-mediated short hairpin RNA of PKCã (LV-shPKCã). Spinal cords (L4-L5) were obtained surgically from morphine-tolerant (MT) rats with and without PKCã knockdown, for comparative proteomic analysis. Total proteins from the spinal cords (L4-L5) were extracted and separated using two-dimensional gel electrophoresis (2DGE); 2D gel images were analyzed with PDQuest software. Seven differential gel-spots were observed with increased spot volume, and 18 spots observed with decreased spot volume. Among these, 13 differentially expressed proteins (DEPs) were identified with matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS), comparing between MT rats with and without PKCã knockdown. The DEPs identified have roles in the cytoskeleton, as neurotrophic factors, in oxidative stress, in ion metabolism, in cell signaling, and as chaperones. Three DEPs (GFAP, FSCN and GDNF) were validated with Western blot analysis, confirming the DEP data. Furthermore, using immunohistochemical analysis, we reveal for the first time that FSCN is involved in the development of morphine tolerance.

Conclusions/Significance

These data cast light on the proteins associated with the PKCã activity during morphine tolerance, and hence may contribute to clarification of the mechanisms by which PKCã influences MT.

Protein disulfide isomerase in redox cell signaling and homeostasis

Thiol proteins may potentially act as redox signaling adaptor proteins, adjusting reactive oxygen species intermediates to specific signals and redox signals to cell homeostasis. In this review, we discuss redox effects of protein disulfide isomerase (PDI), a thioredoxin superfamily oxidoreductase from the endoplasmic reticulum (ER). Abundantly expressed PDI displays ubiquity, interactions with redox and nonredox proteins, versatile effects, and several posttranslational modifications. The PDI family contains >20 members with at least some apparent complementary actions. PDI has oxidoreductase, isomerase, and chaperone effects, the last not directly dependent on its thiols. PDI is a converging hub for pathways of disulfide bond introduction into ER-processed proteins, via hydrogen peroxide-generating mechanisms involving the oxidase Ero1α, as well as hydrogen peroxide-consuming reactions involving peroxiredoxin IV and the novel peroxidases Gpx7/8. PDI is a candidate pathway for coupling ER stress to oxidant generation. Emerging information suggests a convergence between PDI and Nox family NADPH oxidases. PDI silencing prevents Nox responses to angiotensin II and inhibits Akt phosphorylation in vascular cells and parasite phagocytosis in macrophages. PDI overexpression spontaneously enhances Nox activation and expression. In neutrophils, PDI redox-dependently associates with p47phox and supports the respiratory burst. At the cell surface, PDI exerts transnitrosation, thiol reductase, and apparent isomerase activities toward targets including adhesion and matrix proteins and proteases. Such effects mediate redox-dependent adhesion, coagulation/thrombosis, immune functions, and virus internalization. The route of PDI externalization remains elusive. Such multiple redox effects of PDI may contribute to its conspicuous expression and functional role in disease, rendering PDI family members putative redox cell signaling adaptors.

Melatonin, and to a lesser extent growth hormone, restores colonic smooth muscle physiology in old rats

There is increasing evidence that aging is associated with oxidative damage, inflammation, and apoptosis in different cell types. However, there is limited information regarding aging mechanisms in colon smooth muscle. Old male Wistar rats (22 months) were treated for 10 wks with melatonin or growth hormone (GH). Animals were sacrificed at 24 months of age by decapitation. The colon was dissected and the smooth muscle homogenized. H(2)O(2) and malonyl dialdehyde (MDA) content and catalase and glutathione peroxidase (GPX) activities were determined using colorimetric kits. Expression of nuclear factor kappa B (NF-κB), cyclooxygenase 2 (COX-2), caspase-3, and caspase-9 were determined by Western blot. Aging of colon smooth muscle correlated with an increase in H(2)O(2) and MDA levels when compared with young animals in both proximal and distal segments; these changes were associated with a decrease in the catalase activity in the distal colon. Oxidative stress correlated with an increase in COX-2 and NF-κB expression, which were accompanied by an enhanced expression of the pro-apoptotic enzyme caspase-3 and its upstream enzyme, caspase-9. Melatonin treatment normalized the oxidative, inflammatory, and apoptotic patterns, whereas GH replacement, although effective in reducing oxidative stress in distal colon, did not reverse the age-related inflammation or apoptosis. These results suggest that melatonin should be the treatment of choice to most effectively recover physiological functions in aged colonic smooth muscle.

Quantitative subproteomic analysis of age-related changes in mouse liver peroxisomes by iTRAQ LC-MS/MS

Aging is a complex multifactorial phenomenon, which is believed to result from the accumulation of cellular damage to biological macromolecules. Peroxisomes recently emerged as another important source of reactive oxygen species (ROS) production in addition to mitochondria. However, the role of these organelles in the process of aging is still not clear. The aim of this study was to characterize the changes in protein expression profiles of young (10 weeks old) versus old (18 months old) mouse liver peroxisome-enriched fractions. We have applied shotgun proteomic approach based on liquid chromatography and tandem mass spectrometry (LC-MS/MS) combined with iTRAQ (isobaric tags for relative and absolute quantitation) labeling that allows comparative quantitative multiplex analysis. Our analysis led to identification and quantification of 150 proteins, 8 out of which were differentially expressed between two age groups at a statistically significant level (p<0.05), with folds ranging from 1.2 to 4.1. These proteins involved in peroxisomal β-oxidation, detoxification of xenobiotics and production of ROS. Noteworthy, differences in liver proteome have been observed between as well as within different age groups. In conclusion, our subproteomic quantitative study suggests that mouse liver proteome is sufficiently maintained until certain age.

Proteomic analysis reveals that treatment with tocotrienols reverses the effect of H₂O₂ exposure on peroxiredoxin expression in human lymphocytes from young and old individuals

Vitamin E has been suggested to modulate age-associated changes by altering the redox balance resulting in altered gene and/or protein expression. Here we have utilized proteomics to determine whether such regulation in protein expression occurs in human lymphocytes from two different age groups stressed with H₂O₂ and then treated with vitamin E in the form of tocotrienol-rich fraction (TRF). In this study, lymphocytes obtained from young (30-49 years old) and old (>50 years old) volunteers were first challenged with 1 mM H₂O₂. They were then treated by exposure to 50, 100 and 200 μg/ml TRF. Two-dimensional gel electrophoresis followed by MALDI-TOF/TOF (matrix-assisted laser desorption/ionization time-of-flight/time-of-flight) tandem mass spectrometry was then performed on whole-cell protein extracts to identify proteins that have changed in expression. A total of 24 proteins were found to be affected by H₂O₂ and/or TRF treatment. These included proteins that were related to metabolism, antioxidants, structural proteins, protein degradation and signal transduction. Of particular interest was the regulation of a number of proteins involved in stress response--peroxiredoxin-2, peroxiredoxin-3 and peroxiredoxin-6-all of which were shown to be down-regulated with H₂O₂ exposure. The effect was reversed following TRF treatment. The expression of peroxiredoxin-2 and peroxiredoxin-6 was confirmed by quantitative reverse transcriptase polymerase chain reaction. These results suggested that TRF directly influenced the expression dynamics of the peroxiredoxin-2, thus improving the cells ability to resist damage caused by oxidative stress.

Peroxiredoxin 5: structure, mechanism, and function of the mammalian atypical 2-Cys peroxiredoxin

Peroxiredoxin 5 (PRDX5) was the last member to be identified among the six mammalian peroxiredoxins. It is also the unique atypical 2-Cys peroxiredoxin in mammals. Like the other five members, PRDX5 is widely expressed in tissues but differs by its surprisingly large subcellular distribution. In human cells, it has been shown that PRDX5 can be addressed to mitochondria, peroxisomes, the cytosol, and the nucleus. PRDX5 is a peroxidase that can use cytosolic or mitochondrial thioredoxins to reduce alkyl hydroperoxides or peroxynitrite with high rate constants in the 10(6) to 10(7) M(-1)s(-1) range, whereas its reaction with hydrogen peroxide is more modest, in the 10(5) M(-1)s(-1) range. PRDX5 crystal structures confirmed the proposed enzymatic mechanisms based on biochemical data but revealed also some specific unexpected structural features. So far, PRDX5 has been viewed mainly as a cytoprotective antioxidant enzyme acting against endogenous or exogenous peroxide attacks rather than as a redox sensor. Accordingly, overexpression of the enzyme in different subcellular compartments protects cells against death caused by nitro-oxidative stresses, whereas gene silencing makes them more vulnerable. Thus, more than 10 years after its molecular cloning, mammalian PRDX5 appears to be a unique peroxiredoxin exhibiting specific functional and structural features.

TS gene polymorphisms are not good markers of response to 5-FU therapy in stage III colon cancer patients

AIM

Although the predictive and prognostic value of thymidylate synthase (TS) expression and gene polymorphism in colon cancer has been widely studied, the results are inconclusive probably because of methodological differences. With this study, we aimed to elucidate the role of TS gene polymorphisms genotyping in therapy response in stage III colon carcinoma patients treated with 5-FU adjuvant chemotherapy.

PATIENTS AND METHODS

251 patients diagnosed with stage III colon carcinoma treated with surgery followed by 5-FU based adjuvant therapy were selected. The variable number of tandem repeats (VNTR) and the single nucleotide polymorphism (SNP) in the 5'untranslated region of the TS gene were genotyped.

RESULTS

There was a positive association between tumor T stage and the VNTR genotypes (p = 0.05). In both univariate and multivariate survival analysis no effects of the studied polymorphisms on survival were found. However, there was an association between both polymorphisms and age. Among patients younger than 60 years, the patients homozygous for 2R seemed to have a better overall survival, whereas among the patients older than 67 this longer survival was seen by the carriers of other genotypes.

CONCLUSION

We conclude that the TS VNTR and SNP do not predict response to 5-FU therapy in patients with stage III colon carcinoma. However, age appears to modify the effects of TS polymorphisms on survival.

Proteomic profiling reveals a catalogue of new candidate proteins for human skin aging

Studies of skin aging are usually performed at the genomic level by investigating differentially regulated genes identified through subtractive hybridization or microarray analyses. In contrast, relatively few studies have investigated changes in protein expression of aged skin using proteomic profiling by two-dimensional (2-D) gel electrophoresis and mass spectrometry, although this approach at the protein level is suggested to reflect more accurately the aging phenotype. We undertook such a proteomic analysis of intrinsic human skin aging by quantifying proteins extracted and fluorescently labeled from sun-protected human foreskin samples pooled from 'young' and 'old' men. In addition, we analyzed these candidate gene products by 1-D and 2-D western blotting to obtain corroborative protein expression data, and by both real-time PCR (RT-PCR) and microarray analyses to confirm expression at the mRNA level. We discovered 30 putative proteins for skin aging, including previously unrecognized, post-translationally regulated candidates such as phosphatidyl-ethanolamine binding protein (PEBP) and carbonic anhydrase 1 (CA1).

Proteomic analysis of porcine pancreas development

Porcine pancreas development is not well studied at the molecular level despite being a therapeutic resource for diabetic patients. In this study, we investigated expression of lineage markers and performed proteomic analysis. Expression of the early lineage markers Pdx1 and Ptf1a was developmentally conserved between mice and pigs, whereas expression of the islet differentiation marker Pax4 was delayed in porcine compared with murine pancreas development. Proteomic analysis found that expression levels of chymotrypsinogen were downregulated during porcine pancreas development while those of digestive enzymes like lipases, elastase and serine protease were up-regulated. In addition, specific isoforms of protein folding assistants such as protein disulfide isomerase and prefoldin were expressed at specific stages during the maturation of digestive enzymes. Taken together, these results show that development of the porcine pancreas is regulated by a concerted interplay of pancreas lineage marker proteins and other specified proteins, resulting in a functional endocrine and exocrine organ.

Antibiotics and probiotics in chronic pouchitis: A comparative proteomic approach

AIM: To profile protein expression in mucosal biopsies from patients with chronic refractory pouchitis following antibiotic or probiotic treatment, using a comparative proteomic approach.

METHODS: Two-dimensional polyacrylamide gel electrophoresis and matrix-assisted laser desorption/ionization-time of flight mass spectrometry were used to characterize the changes related to antibiotic therapy in the protein expression profiles of biopsy samples from patients with chronic refractory pouchitis. The same proteomic approach was applied to identify differentially expressed proteins in the non-inflamed pouch before and after probiotic administration.

RESULTS: In the first set of 2D gels, 26 different proteins with at least 2-fold changes in their expression levels between the pouchitis condition and antibiotic-induced remission were identified. In the second set of analysis, the comparison between mucosal biopsy proteomes in the normal and probiotic-treated pouch resulted in 17 significantly differently expressed proteins. Of these, 8 exhibited the same pattern of deregulation as in the pouchitis/pouch remission group.

CONCLUSION: For the first time, 2D protein maps of mucosal biopsies from patients with ileal pouch-anal anastomosis were provided, and differentially expressed proteins following antibiotic/probiotic treatment were identified.

Clinical meaning of age-related expression of fecal cytokeratin 19 in colorectal malignancy

Background

Colorectal cancer (CRC) is one of the leading causes of malignant death worldwide. Because young age of onset is often considered a poor prognostic factor for CRC, it is important to identify the poor outcomes of CRC in a younger population and to consider an aggressive approach by implementing early treatment. Our aim was to specifically quantify the fecal cytokeratin 19 (CK19) transcript from CRC patients and investigate its correlation with clinical stage, tumor malignancy, and age.

Methods

The quantitation of fecal CK19 transcript was determined by a quantitative real-time reverse transcription polymerase chain in 129 CRC patients (45 younger than 60 years at diagnosis) and 85 healthy controls. The levels of CK19 protein were examined both in colonic cell lines and tissues.

Results

The analysis of 45 younger CRC patients (age ≤ 60 years) revealed that patients at the M1 stage had significantly higher expression levels of fecal CK19 mRNA when compared with healthy controls (p < 0.001) and patients at the M0 stage (p = 0.004). Additionally, the degree of consistency between the mean level of fecal CK19 mRNA and the distant metastatic rate in each age interval was up to 89% (p = 0.042).

Conclusion

These results indicate that high levels of fecal CK19 mRNA represent a potential marker for colorectal malignancy and for aggressive treatment of younger CRC patients.

Proteomic analysis of differentially expressed proteins in hepatitis B virus-related hepatocellular carcinoma tissues

BACKGROUND

Hepatocellular carcinoma (HCC), a major cause of cancer death in China, is preceded by chronic hepatitis and liver cirrhosis (LC). Although hepatitis B virus (HBV) has been regarded as a clear etiology of human hepatocarcinogenesis, the mechanism is still needs to be further clarified. In this study, we used a proteomic approach to identify the differential expression protein profiles between HCC and the adjacent non-tumorous liver tissues.

METHODS

Eighteen cases of HBV-related HCC including 12 cases of LC-developed HCC and 6 cases of chronic hepatitis B (CHB)-developed HCC were analyzed by two-dimensional electrophoresis (2-DE) combined with matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF-MS), and the results were compared to those of paired adjacent non-tumorous liver tissues.

RESULTS

A total of 17 differentially expressed proteins with diverse biological functions were identified. Among these, 10 proteins were up-regulated, whereas the other 7 proteins were down-regulated in cancerous tissues. Two proteins, c-Jun N-terminal kinase 2 and ADP/ATP carrier protein were found to be up-regulated only in CHB-developed HCC tissues. Insulin-like growth factor binding protein 2 and Rho-GTPase-activating protein 4 were down-regulated in LC-developed and CHB-developed HCC tissues, respectively. Although 11 out of these 17 proteins have been already described by previous studies, or are already known to be involved in hepatocarcinogenesis, this study revealed 6 new proteins differentially expressed in HBV-related HCC.

CONCLUSION

These findings elucidate that there are common features between CHB-developed HCC and LC-developed HCC. The identified proteins are valuable for studying the hepatocarcinogenesis, and may be potential diagnostic markers or therapeutic targets for HBV-related HCC.

Neuroendocrine differentiation of LNCaP cells suggests: VDAC in the cell membrane is involved in the extrinsic apoptotic pathway

The primary structure of native human type-1 voltage dependent anion-selective channel/porin was presented twenty years ago, so was first data on its extra-mitochondrial expression in cell membranes of lymphocytes. Then, the channel had already entered cancer research as the docking molecule for hexokinase at outer mitochondrial membrane. Cell membrane standing porin met the cancer field only four years ago, when it was reported that normal and cancerous prostate cells from a single patient differed in the expression level of the channel. Meanwhile studies on a role of VDAC in cell differentiation, apoptosis, cancer and even pharmacology increase, mostly focused on porin in the outer membrane of mitochondria, but sometimes also pointing to the channel in the plasmalemma, e.g. prostate cancer cells on their way to neuroendocrine-differentiation. The synopsis presented discusses some recent papers on this issue, and argues in favor of considering voltage dependent anion-selective channel-cored volume regulated anion channel complexes in studies focused on apoptosis and cancer, where the channel might be part of the extrinsic cell death pathway. In this context, heed should also be given to the interaction of extra-mitochondrial porin and estrogen receptors alpha in cell membrane caveolae. Finally, it is insinuated to search for natural antibodies against type-1 porin, what in combination with other established markers might help in early diagnosis of prostate cancer.

Influence of increased adiposity on mitochondrial-associated proteins of the rat colon: a proteomic and transcriptomic analysis

Epidemiological studies report obesity to be an important risk factor influencing colon pathologies, yet mechanism(s) are unknown. Recent studies have shown significant elevation of insulin, leptin and triglycerides associated with increased adipose tissue. In situ hybridisation studies have located insulin, leptin and adiponectin receptor expression in the colon epithelia. The influence of increased adiposity and associated deregulation of insulin and adipokines on regulation of the colon epithelium is unknown. Altered adipokine and insulin signalling associated with obesity has an impact on mitochondrial function and mitochondrial dysfunction is increasingly recognised as a contributing factor in many diseases. Proteomics and transcriptomics are potentially powerful methods useful in elucidating the mechanisms whereby obesity increases risk of colon diseases as observed epidemiologically. This study investigated colon mitochondrial-associated protein profiles and corresponding gene expression in colon in response to increased adiposity in a rat model of diet induced obesity. Increased adiposity in diet-induced obese sensitive rats was found to be associated with altered protein expression of 69 mitochondrial-associated proteins involved in processes associated with calcium binding, protein folding, energy metabolism, electron transport chain, structural proteins, protein synthesis and degradation, redox regulation, and transport. The changes in these mitochondrial protein profiles were not correlated with changes at the gene expression level assessed using real-time PCR arrays.

Age-related subproteomic analysis of mouse liver and kidney peroxisomes

BACKGROUND

Despite major recent advances in the understanding of peroxisomal functions and how peroxisomes arise, only scant information is available regarding this organelle in cellular aging. The aim of this study was to characterize the changes in the protein expression profile of aged versus young liver and kidney peroxisome-enriched fractions from mouse and to suggest possible mechanisms underlying peroxisomal aging. Peroxisome-enriched fractions from 10 weeks, 18 months and 24 months C57bl/6J mice were analyzed by quantitative proteomics.

RESULTS

Peroxisomal proteins were enriched by differential and density gradient centrifugation and proteins were separated by two-dimensional electrophoresis (2-DE), quantified and identified by mass spectrometry (MS). In total, sixty-five proteins were identified in both tissues. Among them, 14 proteins were differentially expressed in liver and 21 proteins in kidney. The eight proteins differentially expressed in both tissues were involved in beta-oxidation, alpha-oxidation, isoprenoid biosynthesis, amino acid metabolism, and stress response. Quantitative proteomics, clustering methods, and prediction of transcription factors, all indicated that there is a decline in protein expression at 18 months and a recovery at 24 months.

CONCLUSION

These results indicate that some peroxisomal proteins show a tissue-specific functional response to aging. This response is probably dependent on their differential regeneration capacity. The differentially expressed proteins could lead several cellular effects: such as alteration of fatty acid metabolism that could alert membrane protein functions, increase of the oxidative stress and contribute to decline in bile salt synthesis. The ability to detect age-related variations in the peroxisomal proteome can help in the search for reliable and valid aging biomarkers.