Age-dependent change in arachidonic acid metabolic capacity in rat alveolar macrophages

Arachidonic acid (AA) metabolism was assessed in cultured alveolar macrophages (AM) obtained from newborn (10 days old) and adult (2 months and 4 months old) rats. The AMs were stimulated with the calcium ionophore, A23187 (10 microM). The released radiolabelled AA metabolites were measured by thin layer chromatography. The results showed that among different aged rats, the synthesis of 5-lipoxygenase (5-LO) metabolites, LTB4, LTC4, LTD4 and 5-HETE were increased with age inspite of similar levels of [14C]AA release. In response to A23187, 5-LO metabolic capacity of 2 and 4 months old adult rat AMs were increased 21-fold and 34-fold, respectively, compared with 10 days old rat AMs. As the metabolic capacity increased, the release of prostaglandins and thromboxane B2 tended to decrease markedly. Newborn rats (10 days old) AM, at the initial developmental stage, did not produce a noticeable amount of 5-LO metabolites which, conceivably, contribute to high susceptibility of neonatal lung to infection.     

Evolution of the chordate muscle actin gene

Summary The ascidians Styela plicata, S. clava, and Mogula citrina are urochordates. The larvae of urochordates are considered to morphologically resemble the ancestral vertebrate. We asked whether larval and adult ascidian muscle actin sequences are nonmusclelike as in lower invertebrates, musclelike as in vertebrates, or possess characteristics of both. Nonmuscle and muscle actin cDNA clones from S. plicata were sequenced. Based on 27 diagnostic amino acids, which distinguish vertebrate muscle actin from other actins, we found that the deduced protein sequences of ascidian muscle actins exhibit similarities to both invertebrate and vertebrate muscle actins. A comparison to muscle actins from different vertebrate and invertebrate phylogenetic groups suggested that the urochordate muscle actins represent a transition from a nonmusclelike sequence to a vertebrate musclelike sequence. The ascidian adult muscle actin is more similar to skeletal actin and the larval muscle actin is more similar to cardiac actin, which indicates that the divergence of the skeletal and cardiac isoforms occurred before the emergence of urochordates. The muscle actin gene may be a powerful probe for investigating the chordate lineage. Offprint requests to: C.R. Tomlinson     

Creation of "super" glucocorticoid receptors by point mutations in the steroid binding domain

Almost all modifications of the steroid binding domain of glucocorticoid receptors are known to cause a reduction or loss of steroid binding activity. Nonetheless, we now report that mutations of cysteine 656 of the rat receptor, which was previously suspected to be a crucial amino acid for the binding process, have produced "super" receptors. These receptors displayed an increased affinity for glucocorticoid steroids and a decreased relative affinity for cross-reacting steroids such as progesterone and aldosterone. The increased in vitro affinity of the super receptors was maintained in a whole cell bioassay. These results indicate that additional modifications of the glucocorticoid receptor, and probably the other steroid receptors, may further increase the binding affinity and/or specificity.     

Discovery of 5-(2-chloro-4′-(1H-imidazol-1-yl)-[1,1′-biphenyl]-4-yl)-1H-tetrazole as potent and orally efficacious S-nitrosoglutathione reductase (GSNOR) inhibitors for the potential treatment of COPD

Endogenous nitrosothiols (SNOs) including S-nitrosoglutathione (GSNO) serve as reservoir for bioavailable nitric oxide (NO) and mediate NO-based signaling, inflammatory status and smooth muscle function in the lung. GSNOR inhibition increases pulmonary GSNO and induces bronchodilation while reducing inflammation in lung diseases. In this letter, design, synthesis and structure–activity relationships (SAR) of novel imidazole-biaryl-tetrazole based GSNOR inhibitors are described. Many potent inhibitors (30, 39, 41, 42, 44, 45 and 58) were identified with low nanomolar activity (IC₅₀s: <15?nM) along with adequate metabolic stability. Lead compounds 30 and 58 exhibited good exposure and oral bioavailability in mouse pharmacokinetic (PK) study. Compound 30 was selected for further profiling and revealed comparable mouse and rat GSNOR potency, high selectivity against alcohol dehydrogenase (ADH) and carbonyl reductase (CBR1) family of enzymes, low efflux ratio and permeability in PAMPA, a high permeability in CALU-3 assay, significantly low hERG activity and minimal off-target activity. Further, an in vivo efficacy of compound 30 is disclosed in cigarette smoke (CS) induced mouse model for COPD.     

Development of transgenic pigeonpea using high throughput plumular meristem transformation method

Tissue culture based poor regeneration along with restricted rooting responses are considered to be major hindrances for in vitro transgenic pigeonpea development. Present study was designed to establish a novel method of Agrobacterium tumefaciens mediated plumular meristem transformation in pigeonpea for improvement of transgenic development frequency. Three days old decapitated seedlings of pigeonpea cultivar ICPL 87119 were pricked at plumular meristem region under in vitro conditions. After infecting with Agrobacterium binary vector pBI121, the explants were co-cultivated in 6-benzylaminopurine and α-naphthaleneacetic acid supplemented modified- Murashige and Skoog medium. Transformed seedling with well-developed tap root system were established in soil. GUS activity as well as PCR based confirmation of transgene presence was demonstrated in transgenic events. Transformation frequency of 72% was achieved for the first time in pigeonpea. Further, kanamycin mediated stringent selection was used for the screening of T₁ seeds. Established T₁ progenies were analysed by PCR and Southern blot, to confirm transgene integration and copy number, respectively. This is the first report of transgenic pigeonpea development, where the combination of culture based Agrobacterium-infection and culture independent plant establishment, coupled with PCR based selection method was found to be most preferable for faster and frequent establishment of transgenic plants. This method will contribute to large scale transgenic pigeonpea development for its improvement and satisfy the requirement of routine transformation experiments for T-DNA insertion mutagenesis.     

Role of hydroxyl radical in the oxidant H2O2-mediated Ca2+ release from pulmonary smooth muscle mitochondria

We sought to investigate the mechanism(s) by which the oxidant H₂O₂ stimulates Ca²⁺ release from mitochondria of bovine pulmonary vascular smooth muscle tissue and to test the hypothesis that hydroxyl radical is involved in this phenomenon. Treatment of the smooth muscle tissue with 1 mM H₂O₂ dramatically stimulated hydroxyl radical generation as measured by methane (CH₄) production by GLC using dimethylsulfoxide (DMSO) as the substrate. Pretreatment of the mitochondria with the hydroxyl radical scavanger dimethylthiourea (DMTU) prevented the increase in CH₄ production caused by H₂O₂. In the absence of EGTA, H₂O₂ caused stimulation of Ca²⁺ release from mitochondria occurred with a lag time of about 4 min. Addition of EGTA to Ca²⁺ loaded mitochondria resulted an immediate loss of Ca²⁺ and that has been found to be augmented by H₂O₂. The release of Ca₂₊ by H₂O₂ did not appear to occur with concommitant increase in sucrose entry into, K⁺ release from, and swelling of mitochondria when the Ca²⁺ cycling was prevented by EGTA. These observations suggested that H₂O₂-mediated Ca²⁺ release from bovine pulmonary vascular smooth muscle tissue mitochondria occurred (i) through the involvement of hydroxyl radical; (ii) via specific pathway(s); and (iii) did not appear to happen primarily via nonspecific pore formation.Abbreviations H₂O₂ hydrogen peroxide - OH· hydroxyl radical - t-buOOH tert-butyl hydroperoxide - CH₄ methane - GLC gas liquid chromatography - DMTU dimethylthiourea - EGTA ethylene glycol bis(-aminoethyl ether) - N Ntetraacetic acid - DMSO dimethyl sulfoxide - CH₄ methane - HBPS Hank's buffered physiological saline - HEPES N-2-hydroxyethylpiperazine-N-2-ethane sulfonic acid - MOPS 3-(N-morpholino)propane sulfonic acid - Tris tris (hydroxymethyl aminomethane)     

DRS is far less divergent than streptococcal inhibitor of complement of group A streptococcus

When 100 group A streptococcus isolates were screened, drs, a variant of sic, was identified in emm12 and emm55 isolates. Molecular characterization showed that the drs gene sequence is highly conserved, unlike the sic gene sequence. However, the variation in gene size observed was due to the presence of extra internal repeat sequences.     

Capturing the Mechanism Underlying TOP mRNA Binding to LARP1

1. Download : Download high-res image (163KB)
2. Download : Download full-size image

     

Calcium signaling phenomena in heart diseases: a perspective

Ca²⁺ is a major intracellular messenger and nature has evolved multiple mechanisms to regulate free intracellular (Ca²⁺)_i level in situ. The Ca²⁺ signal inducing contraction in cardiac muscle originates from two sources. Ca²⁺ enters the cell through voltage dependent Ca²⁺ channels. This Ca²⁺ binds to and activates Ca²⁺ release channels (ryanodine receptors) of the sarcoplasmic reticulum (SR) through a Ca²⁺ induced Ca²⁺ release (CICR) process. Entry of Ca²⁺ with each contraction requires an equal amount of Ca²⁺ extrusion within a single heartbeat to maintain Ca²⁺ homeostasis and to ensure relaxation. Cardiac Ca²⁺ extrusion mechanisms are mainly contributed by Na⁺/Ca²⁺ exchanger and ATP dependent Ca²⁺ pump (Ca²⁺-ATPase). These transport systems are important determinants of (Ca²⁺)_i level and cardiac contractility. Altered intracellular Ca²⁺ handling importantly contributes to impaired contractility in heart failure. Chronic hyperactivity of the β-adrenergic signaling pathway results in PKA-hyperphosphorylation of the cardiac RyR/intracellular Ca²⁺ release channels. Numerous signaling molecules have been implicated in the development of hypertrophy and failure, including the β-adrenergic receptor, protein kinase C, Gq, and the down stream effectors such as mitogen activated protein kinases pathways, and the Ca²⁺ regulated phosphatase calcineurin. A number of signaling pathways have now been identified that may be key regulators of changes in myocardial structure and function in response to mutations in structural components of the cardiomyocytes. Myocardial structure and signal transduction are now merging into a common field of research that will lead to a more complete understanding of the molecular mechanisms that underlie heart diseases. Recent progress in molecular cardiology makes it possible to envision a new therapeutic approach to heart failure (HF), targeting key molecules involved in intracellular Ca²⁺ handling such as RyR, SERCA2a, and PLN. Controlling these molecular functions by different agents have been found to be beneficial in some experimental conditions.