MicroRNAs and intestinal pathophysiology

MicroRNAs (miRNAs) represent an abundant class of endogenously expressed small RNAs, which is believed to control the expression of proteins through specific interaction with their mRNAs. MiRNAs are non-coding RNAs of 18 to 24 nucleotides that negatively regulate target mRNAs by binding to their 3'-untranslated regions (UTR). Most eukaryotic cells utilize miRNA to regulate vital functions such as cell differentiation, proliferation or apopotosis. The diversity of miRNAs and of their mRNA targets strongly indicate that they play a key role in the regulation of protein expression. To date, more than 500 different miRNAs have been identified in animals and plants. There are at least 326 miRNAs in the human genome, comprising 1-4% of all expressed human genes, which makes miRNAs one of the largest classes of gene regulators. A single miRNA can bind to and regulate many different mRNA targets and, conversely, several different miRNAs can bind to and cooperatively control a single mRNA target. The correlation between the expression of miRNAs and their effects on tumorigenesis and on the proliferation of cancer cells is beginning to gain experimental evidences. Recent studies showed that abnormal expression of miRNAs represents a common feature of cancer cells and that they can function as tumor suppressor genes or as oncogenes. Therefore, this diversity of action for miRNAs on several target genes could be one of the common mechanisms involved in the deregulation of protein expression observed during intestinal disorders. In this review, the emergent functions of miRNAs in colorectal cancer and their potential role in the intestinal inflammatory process are discussed.     

Evaluation of DNA Variants Associated with Androgenetic Alopecia and Their Potential to Predict Male Pattern Baldness

Androgenetic alopecia, known in men as male pattern baldness (MPB), is a very conspicuous condition that is particularly frequent among European men and thus contributes markedly to variation in physical appearance traits amongst Europeans. Recent studies have revealed multiple genes and polymorphisms to be associated with susceptibility to MPB. In this study, 50 candidate SNPs for androgenetic alopecia were analyzed in order to verify their potential to predict MPB. Significant associations were confirmed for 29 SNPs from chromosomes X, 1, 5, 7, 18 and 20. A simple 5-SNP prediction model and an extended 20-SNP model were developed based on a discovery panel of 305 males from various European populations fitting one of two distinct phenotype categories. The first category consisted of men below 50 years of age with significant baldness and the second; men aged 50 years or older lacking baldness. The simple model comprised the five best predictors: rs5919324 near AR, rs1998076 in the 20p11 region, rs929626 in EBF1, rs12565727 in TARDBP and rs756853 in HDAC9. The extended prediction model added 15 SNPs from five genomic regions that improved overall prevalence-adjusted predictive accuracy measured by area under the receiver characteristic operating curve (AUC). Both models were evaluated for predictive accuracy using a test set of 300 males reflecting the general European population. Applying a 65% probability threshold, high prediction sensitivity of 87.1% but low specificity of 42.4% was obtained in men aged <50 years. In men aged ≥50, prediction sensitivity was slightly lower at 67.7% while specificity reached 90%. Overall, the AUC=0.761 calculated for men at or above 50 years of age indicates these SNPs offer considerable potential for the application of genetic tests to predict MPB patterns, adding a highly informative predictive system to the emerging field of forensic analysis of externally visible characteristics.     

MicroRNAs in viral replication and pathogenesis

MicroRNAs (miRNAs) are an important class of small, noncoding, regulatory RNAs found to be involved in regulating a wide variety of important cellular processes by the sequence-specific inhibition of gene expression. Viruses have evolved a number of mechanisms to take advantage of the regulatory potential of this highly conserved, ubiquitous pathway known as RNA interference (RNAi). This review will focus on the recent efforts to understand the complex relationship between vertebrate viruses and the RNAi pathway, as well as the role of silencing pathways in the inhibition of pathogenic genetic elements, including transposons and retrotransposons.     

Entrapment neuropathies: pathophysiology and pathogenesis.

A number of theories of pathogenesis of entrapment neuropathy, due to repeated loading, have been proposed and these theories are being actively explored with animal models. Tubes placed loosely around peripheral nerves cause delayed onset, chronic pain and changes in nerve morphology including nerve sprouting. Balloons placed around or adjacent to the nerve and inflated to low pressures, rapidly produce endoneurial edema and a persistent increase in intraneural pressure. The same models demonstrate long-term changes such as demyelination and fibrosis. The applied pressure causes a decrement in nerve function and abnormal morphology in a dose-dependent manner that appears to be linked to the amount of endoneurial edema. A new model involving involuntary, repetitive fingertip loading for 6 h per week for 4 weeks has caused slowing of nerve function at the wrist similar to that seen in patients with carpal tunnel syndrome. These models have the potential to reveal the mechanisms of injury at the cellular and biochemical level and address questions about the relative importance of various biomechanical factors (e.g. peak force, mean force, force rate, duty cycle, etc.). In addition, these models will allow us to evaluate various prevention, treatment and rehabilitation protocols.     

MicroRNAs in acute pancreatitis: From pathogenesis to novel diagnosis and therapy

Acute pancreatitis (AP) is an inflammatory disorder initiated by activation of pancreatic zymogens, leading to pancreatic injury and systemic inflammatory response. MicroRNAs (miRNAs) have emerged as important regulators of gene expression and key players in human physiological and pathological processes. Discoveries over the past decade have confirmed that altered expression of miRNAs is implicated in the pathogenesis of AP. Indeed, a number of miRNAs have been found to be dysregulated in various cell types involved in AP such as acinar cells, macrophages, and lymphocytes. These aberrant miRNAs can regulate acinar cell necrosis and apoptosis, local and systemic inflammatory response, thereby contributing to the initiation and progression of AP. Moreover, patients with AP possess unique miRNA signatures when compared with healthy individuals or those with other diseases. In view of their stability and easy detection, therefore, miRNAs have the potential to act as biomarkers for the diagnosis and assessment of patients with AP. In this review, we provide an overview of the novel cellular and molecular mechanisms underlying the roles of miRNAs during the disease processes of AP, as well as the potential diagnosis and therapeutic biomarkers of miRNAs in patients with AP.     

Does malonate take part in the synthesis of sterols?

The effect of acetyl-CoA-carboxylase activators, citrate and biotin, on cholesterol biosynthesis from acetate and malonate in rat liver and in cultured human lung fibroblasts was studied. Administration of citrate and biotin to animals and an addition of biotin to the fibroblast culture medium led to a significant stimulation of [2-14C]acetate incorporation into sterols but had no effect on the incorporation of [2-14C]malonate. The data obtained suggest that malonate is incorporated into sterols without preliminary decarboxylation.     

Urinary Steroid Pattern in Male Hypogonadotrophic Hypogonadism

During clinical studies on a 34-year-old man with marked hypogonadism secondary to pituitary gonadotrophin insufficiency, an attempt was made to determine whether the testes were capable of androgen production when stimulated by exogenous chorionic gonadotrophin (A.P.L.).Androgen excretion before and after chorionic gonadotrophin administration was studied. Total and fractionated 17-ketosteroid patterns suggested a severe Leydig cell deficiency which was confirmed by testicular biopsy.Panhypopituitarism was considered excluded by a normal response to metyrapone ditartrate, by a normal serum PBI and a normal radioactive iodine uptake. Genetic disorders were likewise excluded to the extent possible by determining that the chromosome pattern was normal and by determining that no similar condition existed in another member of the same family. The association of anosmia with gonadotrophin insufficiency in this case suggests a primary disorder in the hypothalamo-mamillary-tuber cinereum area.     

MicroRNAs Show Mutually Exclusive Expression Patterns in the Brain of Adult Male Rats

Background

The brain is a major site of microRNA (miRNA) gene expression, but the spatial expression patterns of miRNAs within the brain have not yet been fully covered.

Methodology/Principal Findings

We have characterized the regional expression profiles of miRNAs in five distinct regions of the adult rat brain: amygdala, cerebellum, hippocampus, hypothalamus and substantia nigra. Microarray profiling uncovered 48 miRNAs displaying more than three-fold enrichment between two or more brain regions. Notably, we found reciprocal expression profiles for a subset of the miRNAs predominantly found (> ten times) in either the cerebellum (miR-206 and miR-497) or the forebrain regions (miR-132, miR-212, miR-221 and miR-222).

Conclusions/Significance

The results indicate that some miRNAs could be important for area-specific functions in the brain. Our data, combined with previous studies in mice, provides additional guidance for future investigations of miRNA functions in the brain.     

Both sulfate-reducing bacteria and Enterobacteriaceae take part in marine biocorrosion of carbon steel

AIMS: In order to evaluate the part played in biocorrosion by microbial groups other than sulfate-reducing bacteria (SRB), we characterized the phylogenetic diversity of a corrosive marine biofilm attached to a harbour pile structure as well as to carbon steel surfaces (coupons) immersed in seawater for increasing time periods (1 and 8 months). We thus experimentally checked corroding abilities of defined species mixtures. METHODS AND RESULTS: Microbial community analysis was performed using both traditional cultivation techniques and polymerase chain reaction cloning-sequencing of 16S rRNA genes. Community structure of biofilms developing with time on immersed coupons tended to reach after 8 months, a steady state similar to the one observed on a harbour pile structure. Phylogenetic affiliations of isolates and cloned 16S rRNA genes (rrs) indicated that native biofilms (developing after 1-month immersion) were mainly colonized by gamma-proteobacteria. Among these, Vibrio species were detected in majority with molecular methods while cultivation techniques revealed dominance of Enterobacteriaceae such as Citrobacter, Klebsiella and Proteus species. Conversely, in mature biofilms (8-month immersion and pile structure), SRB, and to a lesser extent, spirochaetes were dominant. CONCLUSIONS: Corroding activity detection assays confirmed that Enterobacteriaceae (members of the gamma-proteobacteria) were involved in biocorrosion of metallic material in marine conditions. SIGNIFICANCE AND IMPACT OF THE STUDY: In marine biofilms, metal corrosion may be initiated by Enterobacteriaceae.     

MicroRNAs Influence Reproductive Responses by Females to Male Sex Peptide in Drosophila melanogaster

Across taxa, female behavior and physiology change significantly following the receipt of ejaculate molecules during mating. For example, receipt of sex peptide (SP) in female Drosophila melanogaster significantly alters female receptivity, egg production, lifespan, hormone levels, immunity, sleep, and feeding patterns. These changes are underpinned by distinct tissue- and time-specific changes in diverse sets of mRNAs. However, little is yet known about the regulation of these gene expression changes, and hence the potential role of microRNAs (miRNAs), in female postmating responses. A preliminary screen of genomic responses in females to receipt of SP suggested that there were changes in the expression of several miRNAs. Here we tested directly whether females lacking four of the candidate miRNAs highlighted (miR-279, miR-317, miR-278, and miR-184) showed altered fecundity, receptivity, and lifespan responses to receipt of SP, when mated once or continually to SP null or control males. The results showed that miRNA-lacking females mated to SP null males exhibited altered receptivity, but not reproductive output, in comparison to controls. However, these effects interacted significantly with the genetic background of the miRNA-lacking females. No significant survival effects were observed in miRNA-lacking females housed continually with SP null or control males. However, continual exposure to control males that transferred SP resulted in significantly higher variation in miRNA-lacking female lifespan than did continual exposure to SP null males. The results provide the first insight into the effects and importance of miRNAs in regulating postmating responses in females.     

On the mechanism of homocysteine pathophysiology and pathogenesis: a unifying hypothesis

Studies have shown that hyperhomocysteinemia is an important and independent risk factor for a variety of human cardiovascular diseases. In this paper, a unifying hypothesis is proposed which suggests that hyperhomocysteinemia may exert its pathogenic effects largely through metabolic accumulation of S-adenosyl-L-homocysteine, a strong noncompetitive inhibitor of the catechol-O-methyltransferase (COMT)-mediated methylation metabolism of various catechol substrates (such as catecholamines and catechol estrogens). In the case of endogenous catecholamines in peripheral tissues, inhibition of their methylation by S-adenosyl-L-homocysteine will result in elevation of blood or tissue levels of catecholamines, and consequently, over-stimulation of the cardiovascular system's functions. Moreover, because the vasculature is constantly exposed to high levels of endogenous catecholamines (due to high levels of circulating neurohormone epinephrine plus rich innervation with sympathetic nerve terminals), vascular endothelial cells would incur chronic cumulative damage caused by the large amounts of the oxidative products (catechol quinones/semiquinones and oxyradicals) generated from endogenous catecholamines. This mechanistic explanation for the vascular toxicity of hyperhomocysteinemia is supported by many experimental findings, and it also fully agrees with the known protective effects of folate, vitamins B6 and B12 in hyperhomocysteinemic patients. In addition, based on the predictable effects of hyperhomocysteinemia on the methylation of catecholamines in the central nervous system as well as on the methylation of catechol estrogens in estrogen target organs, it is also suggested that hyperhomocysteinemia is an important risk factor for the development of neurodegerative disorders (Parkinson's and Alzheimer's diseases) and estrogen-induced hormonal cancers. More studies are warranted to test these intriguing ideas.     

Molecular hydrogen can take part in phytohormone signal pathways in wild rice

Molecular hydrogen (H₂) could be a novel signal in phytohormone signaling pathways in response to biotic and abiotic stresses. Here, we employed two wild rice species (Oryza rufipogon Griff. and O. minuta J. Presl) to test this hypothesis using hydrogen-rich water (HW). The expression differences of phytohormone and hydrogenase genes between conventional rice (Oryza sativa L,) and wild rice were determined by real-time quantitative polymerase chain reaction, and the effects of HW on gene expression of wild rice were detected during three growth stages. Expression of hydrogenase genes, synthesis genes, and receptor genes of salicylic acid (SA), jasmonic acid (JA), and ethylene (ET) signalling pathways was higher in six wild rice types than in conventional rice. Hydrogen-rich water up-regulated expression of two hydrogenase genes, SA, JA, and ET receptor genes and synthesis genes in the seedling stage of wild rice. But this positive regulation by HW was less significant in the vegetative and reproductive stages.     

Why do so many cells take part in mixed lymphocyte reactions?

An attempt is made to explain some of the anomalous features of allogeneic reactions by a simple model based on known immunological mechanisms.     

Rat lymphocytes express NMDA receptors that take part in regulation of cytokine production

Incubation of rat lymphocytes with homocysteine (HC) or homocysteic acid (HCA) was found to increase the stationary levels of free radicals in lymphocytes, the effect of both ligands being mediated by ionotropic receptors activated by N-methyl-D-aspactic acid (NMDA), the expression of which on rat lymphocyte membranes was earlier demonstrated. In agreement with these data, increase of free radicals in the lymphocyte cytoplasm is preceded by an increase in the intracellular calcium levels, activation of protein kinase C, nicotinamide adenine dinucleotide phosphate oxidase and/or nitric oxide synthase. Both HC and HCA increase the production of IFN-γ and TNF-α by lymphocytes and antagonist of NMDA receptors; MK-801 prevents this effect. The data presented show that rat lymphocyte membrane contains functionally active NMDA receptors, which regulate cytokine accumulation.     

Misexpression of Testicular MicroRNA in Sterile Xenopus Hybrids Points to Tetrapod-Specific MicroRNAs Associated with Male Fertility

Spermatogenesis is one of the most complex biological processes undergone by any organism, making it susceptible to perturbations that result in male sterility. Research has demonstrated that mutant phenotypes can be obtained from the disruption of epigenetic modifications, which are commonly microRNA guided. Employing the Xenopus system, whereby homogametic interspecies males are always sterile, thus violating Haldane's Rule, we deep-sequenced testes-specific small-RNAs to identify microRNAs most frequently misexpressed between sterile hybrids and their fertile parental taxa. Using these data, we cross-referenced our expression information with previously published mouse (Mus musculus) data and identified a subset of seven microRNAs common to both (miR-338, miR-222, miR-18, miR-30, miR-10, miR-196, and miR-365). We propose that these microRNAs are likely critical for spermatogenesis in all tetrapods, having retained testicular expression across ~350 million years of evolution (Amphibian-Mammal split). Gene targets of six of these microRNAs are known, and all the six associate with zinc and zinc finger proteins (both previously found critical in male fertility), and three with Hox genes (some of which have also previously been deemed critical for testicular development and male fertility). Expression information for these targets revealed that all those associated with zinc have previously been found to express in mammalian testes. One Hox target has known mammalian testicular expression, two have close relatives with known mammalian testicular expression, and two more are associated with proteins known to have mammalian testicular expression. In addition, miR-222 has prior association with spermatogenesis, and miR-30 has been found to be abundantly expressed in both mouse and human testes.