Myroides pelagicus from the Gut of Drosophila melanogaster Attenuates Inflammation on Dextran Sodium Sulfate-Induced Colitis

Background and Aim

Probiotics are live microorganisms that confer a health benefit on the host when administered in adequate amounts. In the present study, the putative probiotic strain was identified from the gut of Drosophila melanogaster and assessed for its protective effect in inflammatory bowel disease.

Methods

Active probiotics were screened from the Drosophila melanogaster gut by the selection criteria of gastric juice tolerance, hydrophobic property, antimicrobial potential, adhesion, and invasion properties. The active probiotics were identified by 16s rDNA sequencing and the effect of these active probiotics was evaluated in a Dextran sulphate sodium (DSS)-induced mice model by estimating inflammatory markers and histopathological changes.

Results

Nine Gram-positive and bile salt tolerant bacterial isolates were obtained from the gut samples. The isolates PTH 2, PTH 4, and PTH 7 clearly showed significant activity in antimicrobial potential, hydrophobic (>74 %) property, and intestinal juice tolerance. Among these, PTH 7 was selected for further studies due to its significant low-invasion ability and it proved capable of reducing the secretion of proinflammatory cytokines. The 16s rDNA studies revealed that PTH 7 was Myroides pelagicus. Administration of M. pelagicus to the DSS-induced colitic animals significantly suppressed myeloperoxidase, ALP, and malondialdehyde levels, and also lowered levels of proinflammatory cytokine expression. Further, the recovery from the disease by the probiotic treatment was supported by histopathological and macroscopic observation. The treated animals did not show any adverse signs in their physiology or behavior.

Conclusion

Myroides pelagicus successfully prohibited inflammatory markers and acted as a potent probiotic. Future studies with this stain might prove its efficacy as a drug for the management of colitis.     

Down-regulation of tricarboxylic acid (TCA) cycle genes blocks progression through the first mitotic division in Caenorhabditis elegans embryos

The cell cycle is a highly regulated process that enables the accurate transmission of chromosomes to daughter cells. Here we uncover a previously unknown link between the tricarboxylic acid (TCA) cycle and cell cycle progression in the Caenorhabditis elegans early embryo. We found that down-regulation of TCA cycle components, including citrate synthase, malate dehydrogenase, and aconitase, resulted in a one-cell stage arrest before entry into mitosis: pronuclear meeting occurred normally, but nuclear envelope breakdown, centrosome separation, and chromosome condensation did not take place. Mitotic entry is controlled by the cyclin B–cyclin-dependent kinase 1 (Cdk1) complex, and the inhibitory phosphorylation of Cdk1 must be removed in order for the complex to be active. We found that following down-regulation of the TCA cycle, cyclin B levels were normal but CDK-1 remained inhibitory-phosphorylated in one-cell stage-arrested embryos, indicative of a G2-like arrest. Moreover, this was not due to an indirect effect caused by checkpoint activation by DNA damage or replication defects. These observations suggest that CDK-1 activation in the C. elegans one-cell embryo is sensitive to the metabolic state of the cell, and that down-regulation of the TCA cycle prevents the removal of CDK-1 inhibitory phosphorylation. The TCA cycle was previously shown to be necessary for the development of the early embryo in mammals, but the molecular processes affected were not known. Our study demonstrates a link between the TCA cycle and a specific cell cycle transition in the one-cell stage embryo.The developmental program of any organism must be precisely executed. In Caenorhabditis elegans embryos, immediately after fertilization, two pronuclei form at opposite poles of the embryo: one containing the maternal chromosomes and the other containing the paternal ones (1, 2). These pronuclei then move toward each other, and at the same time centrosomes separate and begin to assemble a spindle. After pronuclear meeting, the cell enters its first mitosis, resulting in nuclear envelope breakdown, chromatin condensation, and the subsequent alignment of chromosomes on the metaphase plate, followed by chromosome segregation (2). Entry into mitosis depends on the mitotic cyclin B–cyclin-dependent kinase 1 (Cdk1) complex. The activity of this complex is regulated by both cyclin B levels and regulatory phosphorylation of Cdk1. In particular, Cdk1 activity is inhibited by Wee1 phosphorylation, which is removed at the onset of mitosis by the Cdc25 phosphatase (3, 4). Cdk1 activation is also subjected to various checkpoints that inhibit mitotic progression in the presence of intracellular damage (5). However, in organisms that undergo rapid embryonic divisions, including C. elegans, checkpoints are inoperative during the first few cell cycles (6).Although it is clear that cell cycle progression requires energy, the link, if any, between metabolic pathways and progression through mitosis is poorly understood. Genes and proteins involved in various aspects of metabolism (e.g., nucleotide biosynthesis and lipid metabolism) are regulated by the cell cycle machinery, and cells will not commit to a new cell cycle if nutrients are scarce (7). However, to what extent the metabolic state of the cell is sensed by the cell cycle machinery once cells have passed into S phase is not clear (8).We have previously conducted a visual screen in C. elegans embryos for genes that when down-regulated by RNAi lead to an abnormal nuclear morphology (9). Most genes whose inactivation affected early embryonic development did so without arresting cell cycle progression. It was therefore striking when we came across a set of genes, coding for enzymes of the tricarboxylic acid (TCA) cycle, that when down-regulated, led to a one-cell stage arrest with paired nuclei. The TCA cycle, also known as the Krebs cycle, uses the oxidation of acetate (in the form of acetyl CoA) derived from carbohydrates, proteins, or lipids, to generate intermediates (i.e., NADH and FADH₂) that are used by the electron transport chain for ATP production. Intermediates of the TCA cycle are also important for various anabolic pathways, such as fatty acid synthesis, and the synthesis of nucleotides. In this study, we examine the relationship between TCA cycle down-regulation and cell cycle progression in the one-cell C. elegans embryo. Our data suggest that down-regulation of the TCA cycle leads to a G2-like arrest at the one-cell stage embryo by preventing the activation of cyclin B–Cdk1.     

A novel tissue culture model for evaluating the effect of aging on stem cell fate in adult microvascular networks

GeroScience - In vitro models of angiogenesis are valuable tools for understanding the underlying mechanisms of pathological conditions and for the preclinical evaluation of therapies. Our...     

Hepatosplenic T Cell Lymphoma

A 26 year old lady came with intermittent fever since eight months. She also complained of abdominal pain and decreased appetite for six months. She had swelling of feet and distension of abdomen due to ascites since one month. There was history of jaundice one month back. On radiological examination, hepatomegaly with dilated portal vein, massive splenomegaly and ascites without any lymphadenopathy was noted. Chest X-ray was normal. Blood examination and bone marrow studies were inconclusive. We received her liver biopsy, which showed normal architecture and sinusoidal infiltration by a monomorphic population of small to intermediate sized lymphoid cells. Portal tracts were free of such infiltrate. These lymphoid cells were LCA, CD3, CD43 positive and negative for CD20, CD34, CD4, CD8 and c-kit. Based on all these features, a diagnosis of Hepatosplenic T cell lymphoma was made. She was treated symptomatically, however she died within two months of diagnosis.