Alteration in ocular blood flow and its effect on the progression of glaucoma

Glaucoma is a multifactorial neurodegenerative disease that can result in permanent vision loss by damaging optic nerves due to higher pressure in the eye. Although most of the fundamental pathophysiological mechanisms involved in glaucoma are undetermined but alteration in ocular blood flow(OBF)in tissues such as optic nerve, retina, choroid and iris is an important risk factor for glaucoma. Various factors such as limited knowledge of the factors causing optic nerve damage, confusion in the measurement assays and lack of therapies, make hindrances in the understanding of glaucoma. Researchers are continuously accumulating evidence to suggest that alterations in OBF play important role in the pathogenesis of glaucoma but most of the times they have diverse and contradictory conclusions regarding changes in the OBF and risk of glaucoma. In this article we have reviewed different aspects of glaucoma and the effect of OBF in the disease progressio

A Mur Regulator Protein in the Extremophilic Bacterium <i>Deinococcus radiodurans</i>

<div><p>Ferric uptake regulator (Fur) is a transcriptional regulator that controls the expression of genes involved in the uptake of iron and manganese, as well as vital nutrients, and is essential for intracellular redox cycling. We identified a unique Fur homolog (DR0865) from <i>Deinococcus radiodurans</i>, which is known for its extreme resistance to radiation and oxidants. A <i>dr0865</i> mutant (Mt-0865) showed a higher sensitivity to manganese stress, hydrogen peroxide, gamma irradiation and ultraviolet (UV) irradiation than the wild-type R1 strain. Cellular manganese (Mn) ion (Mn²⁺) analysis showed that Mn²⁺, copper (Cu²⁺), and ferric (Fe³⁺) ions accumulated significantly in the mutant, which suggests that the <i>dr0865</i> gene is not only involved in the regulation of Mn²⁺ homeostasis, but also affects the uptake of other ions. In addition, transcriptome profiles under MnCl₂ stress showed that the expression of many genes involved in Mn metabolism was significantly different in the wild-type R1 and DR0865 mutant (Mt-0865). Furthermore, we found that the <i>dr0865</i> gene serves as a positive regulator of the manganese efflux pump gene <i>mntE</i> (<i>dr1236</i>), and as a negative regulator of Mn ABC transporter genes, such as <i>dr2283</i>, <i>dr2284</i> and <i>dr2523</i>. Therefore, it plays an important role in maintaining the homoeostasis of intracellular Mn (II), and also other Mn²⁺, zinc (Zn²⁺) and Cu²⁺ ions. Based on its role in manganese homeostasis, DR0865 likely belongs to the Mur sub-family of Fur homolog.</p></div

The expression of potential DR0865-dependent genes in wild-type <i>D. radiodurans</i> compared to the mutant strain, under normal conditions (black bar), and wild-type R1 under manganese stress compared with the mutant strain under manganese stress (grey bar).

<p>Error bars represent standard deviations from three replicate experiments. (A) Four manganese transport genes, (B) metabolism related genes.</p

The predicted structure of DR0865 was obtained from homology modeling (Swiss-model) using Hpy-Fur PDB: 2XIG as starting model.

<p>The predicted structure of DR0865 was obtained from homology modeling (Swiss-model) using Hpy-Fur PDB: 2XIG as starting model.</p

Bacterial strains and plasmids used in this study.

<p>Bacterial strains and plasmids used in this study.</p

Analysis of the intracellular ion content of the wild-type R1 and Mt-0865 strains, cultured in a medium supplemented with or without 50 µM manganese; (A) manganese, (B) iron, (C) zinc, (D) copper.

<p>The data represent the mean ± standard deviation of three independent experiments.</p

The significant genes were classified into three classes, Mn/Fe metabolism, ROS production genes, and Damage response genes.

1<p>. M value means log₂Ratio, Ratio = FPKM_(M-0865)/FPKM_(R1)</p>2<p>. ∞ means gene’s expression level is not detected in one sample, but detected in another sample.</p><p>The significant genes were classified into three classes, Mn/Fe metabolism, ROS production genes, and Damage response genes.</p

Classification of the genes with different levels of expression according to the Cluster of Orthologous Groups of proteins (COG) database.

1<p>. J: Translation, ribosomal structure and biogenesis; K: Transcription; L: Replication, recombination and repair; B: Chromatin structure and dynamics; D: Cell cycle control, cell division, chromosome partitioning; V: Defense mechanisms; T: Signal transduction mechanisms; M: Cell wall/membrane/envelope biogenesis; N: Cell motility; U: Intracellular trafficking, secretion, and vesicular transport; O: Posttranslational modification, protein turnover, chaperones; C: Energy production and conversion; G: Carbohydrate transport and metabolism; E: Amino acid transport and metabolism; F: Nucleotide transport and metabolism; H: Coenzyme transport and metabolism; Lipid transport and metabolism; P: Inorganic ion transport and metabolism; Q: Secondary metabolites biosynthesis, transport and catabolism; S: Function unknown; R: General function prediction only.</p>2<p>. the total number of significant genes/Number of total genes in this COG</p><p>Classification of the genes with different levels of expression according to the Cluster of Orthologous Groups of proteins (COG) database.</p

Hydrogen peroxide sensitivity assay for the wild-type R1, Mt-0865 and C-0865 strains, The wild-type R1 strain (black bar), Mt-0865 strain (gray bar) and C-0865 strain (white bar) were cultured in TGY plates, overlaid with filter discs saturated with 4 µl and 6 µl of 1 M solution of H₂O₂.

<p>Hydrogen peroxide sensitivity assay for the wild-type R1, Mt-0865 and C-0865 strains, The wild-type R1 strain (black bar), Mt-0865 strain (gray bar) and C-0865 strain (white bar) were cultured in TGY plates, overlaid with filter discs saturated with 4 µl and 6 µl of 1 M solution of H₂O₂.</p

Sensitivity of the wild-type R1 strain (black bar) and mutant Mt-0865 strain (gray bar) to MnCl₂.

<p>Strains were cultured in TGY, supplemented with 0, 50,100 or 150 µM of MnCl₂. The OD₆₀₀ was measured after 12 and 24 h. Data represent the means ± standard deviation of three independent experiments.</p