Real-time PCR of host DNA in feces to study differential exfoliation of colonocytes between rats and humans

Autophagy and the Insulin-like Growth Factor (IGF) System in Colonic Cells: Implications for Colorectal Neoplasia

Colorectal cancer (CRC) is one of the most common human malignancies worldwide. Along with apoptosis and inflammation, autophagy is one of three important mechanisms in CRC. The presence of autophagy/mitophagy in most normal mature intestinal epithelial cells has been confirmed, where it has mainly protective functions against reactive oxygen species (ROS)-induced DNA and protein damage. Autophagy regulates cell proliferation, metabolism, differentiation, secretion of mucins and/or anti-microbial peptides. Abnormal autophagy in intestinal epithelial cells leads to dysbiosis, a decline in local immunity and a decrease in cell secretory function. The insulin-like growth factor (IGF) signaling pathway plays an important role in colorectal carcinogenesis. This is evidenced by the biological activities of IGFs (IGF-1 and IGF-2), IGF-1 receptor type 1 (IGF-1R) and IGF-binding proteins (IGF BPs), which have been reported to regulate cell survival, proliferation, differentiation and apoptosis. Defects in autophagy are found in patients with metabolic syndrome (MetS), inflammatory bowel diseases (IBD) and CRC. In neoplastic cells, the IGF system modulates the autophagy process bidirectionally. In the current era of improving CRC therapies, it seems important to investigate the exact mechanisms not only of apoptosis, but also of autophagy in different populations of tumor microenvironment (TME) cells. The role of the IGF system in autophagy in normal as well as transformed colorectal cells still seems poorly understood. Hence, the aim of the review was to summarize the latest knowledge on the role of the IGF system in the molecular mechanisms of autophagy in the normal colon mucosa and in CRC, taking into account the cellular heterogeneity of the colonic and rectal epithelium.

Nutritional Calcium Supply Dependent Calcium Balance, Bone Calcification and Calcium Isotope Ratios in Rats

Serum calcium isotopes (δ^44/42Ca) have been suggested as a non-invasive and sensitive Ca balance marker. Quantitative δ^44/42Ca changes associated with Ca flux across body compartment barriers relative to the dietary Ca and the correlation of δ^44/42Ca_Serum with bone histology are unknown. We analyzed Ca and δ^44/42Ca by mass-spectrometry in rats after two weeks of standard-Ca-diet (0.5%) and after four subsequent weeks of standard- and of low-Ca-diet (0.25%). In animals on a low-Ca-diet net Ca gain was 61 ± 3% and femur Ca content 68 ± 41% of standard-Ca-diet, bone mineralized area per section area was 68 ± 15% compared to standard-Ca-diet. δ^44/42Ca was similar in the diets, and decreased in feces and urine and increased in serum in animals on low-Ca-diet. δ^44/42Ca_Bone was higher in animals on low-Ca-diet, lower in the diaphysis than the metaphysis and epiphysis, and unaffected by gender. Independent of diet, δ^44/42Ca_Bone was similar in the femora and ribs. At the time of sacrifice, δ^44/42Ca_Serum inversely correlated with intestinal Ca uptake and histological bone mineralization markers, but not with Ca content and bone mineral density by µCT. In conclusion, δ^44/42Ca_Bone was bone site specific, but mechanical stress and gender independent. Low-Ca-diet induced marked changes in feces, serum and urine δ^44/42Ca in growing rats. δ^44/42Ca_Serum inversely correlated with markers of bone mineralization.

Mechanisms Linking Colorectal Cancer to the Consumption of (Processed) Red Meat: A Review

Colorectal cancer (CRC) is the third most commonly diagnosed cancer in the world. The vast majority of CRC cases have been linked to environmental causes rather than to heritable genetic changes. Over the last decades, epidemiological evidence linking the consumption of red and, more convincingly, of processed red meat to CRC has accumulated. In parallel, hypotheses on carcinogenic mechanisms underlying an association between CRC and the intake of red and processed red meat have been proposed and investigated in biological studies. The hypotheses that have received most attention until now include (1) the presence of polycyclic aromatic hydrocarbons and heterocyclic aromatic amines, two groups of compounds recognized as carcinogenic, (2) the enhancing effect of (nitrosyl)heme on the formation of carcinogenic N-nitroso compounds and lipid peroxidation. However, none of these hypotheses completely explains the link between red and processed red meat intake and the CRC risk. Consequently, scientists have proposed additional mechanisms or refined their hypotheses. This review first briefly summarizes the development of CRC followed by an in-depth overview and critical discussion of the different potential carcinogenic mechanisms underlying the increased CRC risk associated with the consumption of red and processed red meat.

Application of the NucliSENS easyMAG system for nucleic acid extraction: optimization of DNA extraction for molecular diagnosis of parasitic and fungal diseases

During the last 20 years, molecular biology techniques have propelled the diagnosis of parasitic diseases into a new era, as regards assay speed, sensitivity, and parasite characterization. However, DNA extraction remains a critical step and should be adapted for diagnostic and epidemiological studies. The aim of this report was to document the constraints associated with DNA extraction for the diagnosis of parasitic diseases and illustrate the adaptation of an automated extraction system, NucliSENS easyMAG, to these constraints, with a critical analysis of system performance. Proteinase K digestion of samples is unnecessary with the exception of solid tissue preparation. Mechanically grinding samples prior to cell lysis enhances the DNA extraction rate of fungal cells. The effect of host-derived nucleic acids on the extraction efficiency of parasite DNA varies with sample host cell density. The optimal cell number for precise parasite quantification ranges from 10 to 100,000 cells. Using the NucliSENS easyMAG technique, the co-extraction of inhibitors is reduced, with an exception for whole blood, which requires supplementary extraction steps to eliminate inhibitors.

Survival of exfoliated epithelial cells: a delicate balance between anoikis and apoptosis

The recovery of exfoliated cells from biological fluids is a noninvasive technology which is in high demand in the field of translational research. Exfoliated epithelial cells can be isolated from several body fluids (i.e., breast milk, urines, and digestives fluids) as a cellular mixture (senescent, apoptotic, proliferative, or quiescent cells). The most intriguing are quiescent cells which can be used to derive primary cultures indicating that some phenotypes retain clonogenic potentials. Such exfoliated cells are believed to enter rapidly in anoikis after exfoliation. Anoikis can be considered as an autophagic state promoting epithelial cell survival after a timely loss of contact with extracellular matrix and cell neighbors. This paper presents current understanding of exfoliation along with the influence of methodology on the type of gastrointestinal epithelial cells isolated and, finally, speculates on the balance between anoikis and apoptosis to explain the survival of gastrointestinal epithelial cells in the environment.

Noninvasive detection of inflammation-associated colon cancer in a mouse model

Helicobacter bilis-infected Smad3(-/-) mice represent an attractive model of inflammation-associated colon cancer. Most infected mice develop mucinous adenocarcinoma (MUC) by 6 weeks post inoculation (PI); however, approximately one third do not progress to MUC. The ability to predict the development of MUC in mice used in therapeutic studies would confer a considerable saving of time and money. In addition, the inadvertent use of mice without MUC may confound therapeutic studies by making treatments seem falsely efficacious. We assessed both magnetic resonance imaging (MRI) and fecal biomarkers in Helicobacter- and sham-inoculated mice as methods of noninvasively detecting MUC before the predicted onset of disease. Non-contrast-enhanced MRI was able to detect lesions in 58% of mice with histologically confirmed MUC; however, serial imaging sessions produced inconsistent results. MRI was also a labor- and time-intensive technique requiring anesthesia. Alternatively, inflammatory biomarkers isolated from feces at early time points were correlated to later histologic lesions. Fecal expression of interleukin 1β, macrophage inflammatory protein 1α, and regulated on activation, normal T-cell expressed, and secreted at 3 weeks PI correlated significantly with lesion severity at 9 weeks PI. For each biomarker, receiver-operator characteristic curves were also generated, and all three biomarkers performed well at 1 to 3 weeks PI, indicating that the development of MUC can be predicted based on the early expression of certain inflammatory mediators in feces.

Exfoliated epithelial cells: potentials to explore gastrointestinal maturation of preterm infants

Exfoliated epithelial cells represent valuable source of information on the physiopathological state of the mucosa. However, the interpretation of data obtained from exfoliated cells is complicated by the conditions of isolation as well as the health of the subject. Exfoliation is either: a) a natural loss of body cells implying a molecular signal related to the turnover of terminally differentiated cells and to the progressive mobilization of proliferative as well as stem cells or b) the result of manual exfoliation by applying mechanical constraints like scraping. Depending on the methodology of isolation, exfoliated epithelial cells are believed to be either in apoptosis or in anoïkis. Most studies are using microscopic examination to demonstrate the presence of typical cells along with measurements on a limited number of biomarkers. Only few studies using proteomics or transcriptomics are available and they open discussion about tissue references and normalization. The main advantage of measures realized on exfoliated epithelial cells is that they are strictly non-invasive and open the possibility to evaluate maturation of gastric and intestinal tissues in long-term experiments performed on the same animal or in translational research on samples recovered from preterm infants.

Processed meat and colorectal cancer: a review of epidemiologic and experimental evidence

Processed meat intake may be involved in the etiology of colorectal cancer, a major cause of death in affluent countries. The epidemiologic studies published to date conclude that the excess risk in the highest category of processed meat-eaters is comprised between 20% and 50% compared with non-eaters. In addition, the excess risk per gram of intake is clearly higher than that of fresh red meat. Several hypotheses, which are mainly based on studies carried out on red meat, may explain why processed meat intake is linked to cancer risk. Those that have been tested experimentally are (i) that high-fat diets could promote carcinogenesis via insulin resistance or fecal bile acids; (ii) that cooking meat at a high temperature forms carcinogenic heterocyclic amines and polycyclic aromatic hydrocarbons; (iii) that carcinogenic N-nitroso compounds are formed in meat and endogenously; (iv) that heme iron in red meat can promote carcinogenesis because it increases cell proliferation in the mucosa, through lipoperoxidation and/or cytotoxicity of fecal water. Nitrosation might increase the toxicity of heme in cured products. Solving this puzzle is a challenge that would permit to reduce cancer load by changing the processes rather than by banning processed meat.

Dietary heme injures surface epithelium resulting in hyperproliferation, inhibition of apoptosis and crypt hyperplasia in rat colon

Epidemiological and animal model studies suggest that a high intake of heme, present in red meat, is associated with an increased risk of colon cancer. The aim of this study was to elucidate the effects of dietary heme on colonic cell homeostasis in rats. Rats were fed a purified, humanized, control diet or a similar diet supplemented with 0.5 mmol heme/kg for 14 days. Fecal water cytolytic activity was determined with a bioassay, and colon epithelial cell proliferation was evaluated with (3)H-thymidine or 5-bromo-2'-deoxyuridine incorporation into DNA or by Ki-67 immunohistochemistry. Exfoliation of colonocytes was measured as the amount of rat DNA in feces, and caspase-3 expression and activity were measured to study colonic mucosal apoptosis. Dietary heme induced a >10-fold increased cytolytic activity of the fecal water and a 100-fold lower excretion of host DNA. Colons of heme-fed rats showed injured surface epithelium and an approximately 25% increase in crypt depth. Finally, dietary heme doubled colonocyte proliferation, shown by all three markers, but inhibited colonic mucosal apoptosis. In conclusion, our results demonstrate that dietary heme injures colonic surface epithelium, which is overcompensated by inhibition of apoptosis and hyperproliferation of cells in the crypts, resulting in crypt hyperplasia. This disturbed epithelial cell homeostasis might explain why a high intake of dietary heme is associated with an increased risk of colon cancer.

Dietary modulation and structure prediction of rat mucosal pentraxin (Mptx) protein and loss of function in humans

Mucosal pentraxin (Mptx), identified in rats, is a short pentraxin of unknown function. Other subfamily members are Serum amyloid P component (SAP), C-reactive protein (CRP) and Jeltraxin. Rat Mptx mRNA is predominantly expressed in colon and in vivo is strongly (30-fold) regulated by dietary heme and calcium, modulators of colon cancer risk. This renders Mptx a potential nutrient sensitive biomarker of gut health. To support a role as biomarker, we examined whether the pentraxin protein structure is conserved, whether Mptx protein is nutrient-sensitively expressed and whether Mptx is expressed in mouse and human. Sequence comparison and 3D modelling showed that rat Mptx is highly homologous to the other pentraxins. The calcium-binding site and subunit interaction sites are highly conserved, while a loop deletion and charged residues contribute to a distinctive "top" face of the pentamer. In accordance with mRNA expression, Mptx protein is strongly down-regulated in rat colon mucosa in response to high dietary heme intake. Mptx mRNA is expressed in rat and mouse colon, but not in human colon. A stop codon at the beginning of human exon two indicates loss of function, which may be related to differences in intestinal cell turnover between man and rodents.

Cell exfoliation in the human colon: myth, reality and implications for colorectal cancer screening

Colonocyte exfoliation in the human colon constitutes a unique mechanism of cell population control that can undergo significant changes under different physiological and pathological conditions. Being closely related to the apoptosis and anoikis, cell exfoliation from colonic epithelium appears to be a relatively rare event in normal conditions, but its rate dramatically increases in neoplasia, when cell removal by apoptosis in situ does not function properly. Several studies show that significant numbers of exfoliated colonocytes are not lost in the faecal contents of the gut, but retained in the mucocellular layer overlying colonic mucosa. Recent observations allow hypothesizing that the mucocellular layer containing exfoliated colonocytes may gradually migrate distally, eventually leading to the accumulation of the cells exfoliated from malignant colorectal tumours on the surface of the rectal mucosa. Implications of exfoliated colonocyte analysis to colorectal cancer screening and early diagnosis are discussed.

Natural chlorophyll but not chlorophyllin prevents heme-induced cytotoxic and hyperproliferative effects in rat colon

Diets high in red meat and low in green vegetables are associated with an increased risk of colon cancer. In rats, dietary heme, mimicking red meat, increases colonic cytotoxicity and proliferation of the colonocytes, whereas addition of chlorophyll from green vegetables inhibits these heme-induced effects. Chlorophyllin is a water-soluble hydrolysis product of chlorophyll that inhibits the toxicity of many planar aromatic compounds. The present study investigated whether chlorophyllins could inhibit the heme-induced luminal cytotoxicity and colonic hyperproliferation as natural chlorophyll does. Rats were fed a purified control diet, the control diet supplemented with heme, or a heme diet with 1.2 mmol/kg diet of chlorophyllin, copper chlorophyllin, or natural chlorophyll for 14 d (n = 8/group). The cytotoxicity of fecal water was determined with an erythrocyte bioassay and colonic epithelial cell proliferation was quantified in vivo by [methyl-(3)H]thymidine incorporation into newly synthesized DNA. Exfoliation of colonocytes was measured as the amount of rat DNA in feces using quantitative PCR analysis. Heme caused a >50-fold increase in the cytotoxicity of the fecal water, a nearly 100% increase in proliferation, and almost total inhibition of exfoliation of the colonocytes. Furthermore, the addition of heme increased TBARS in fecal water. Chlorophyll, but not the chlorophyllins, completely prevented these heme-induced effects. In conclusion, inhibition of the heme-induced colonic cytotoxicity and epithelial cell turnover is specific for natural chlorophyll and cannot be mimicked by water-soluble chlorophyllins.