open-tracheostomy-gastric-acid-aspiration-murine-model-acute-lung

Open Tracheostomy Gastric Acid Aspiration Murine Model of Acute Lung Injury Results in Maximal Acute Nonlethal Lung Injury

Acid pneumonitis is a major cause of sterile acute lung injury (ALI) in humans. Acid pneumonitis spans the clinical spectrum from asymptomatic to acute ...

Mycoplasma genitalium is expected to metabolize RNA using unique pathways because its minimal genome encodes very few ribonucleases. In this work, we report that the only exoribonuclease identified in M. genitalium, RNase R, is able to remove tRNA 3'-trailers and generate mature 3'-ends. Several sequence and structural features of a tRNA precursor determine its precise processing at the 3'-end by RNase R in a purified system. The aminoacyl-acceptor stem plays a major role in stopping RNase R digestion at the mature 3'-end. Disruption of the stem causes partial or complete degradation of the pre-tRNA by RNase R, whereas extension of the stem results in the formation of a product terminating downstream at the new mature 3'-end. In addition, the 3'-terminal CCA sequence and the discriminator residue influence the ability of RNase R to stop at the mature 3'-end. RNase R-mediated generation of the mature 3'-end prefers a sequence of RCCN at the 3' terminus of tRNA. Variations of this sequence may cause RNase R to trim further and remove terminal CA residues from the mature 3'-end. Therefore, M. genitalium RNase R can precisely remove the 3'-trailer of a tRNA precursor by recognizing features in the terminal domains of tRNA, a process requiring multiple RNases in most bacteria.

Novel one-step mechanism for tRNA 3'-end maturation by the exoribonuclease RNase R of Mycoplasma genitalium.

We have examined the level of 8-hydroxyguanosine (8-oxo-G), an oxidized form of guanosine, in RNA in Escherichia coli under normal and oxidative stress conditions. The level of 8-oxo-G in RNA rises rapidly and remains high for hours in response to hydrogen peroxide (Hâ‚‚Oâ‚‚) challenge in a dose-dependent manner. Hâ‚‚Oâ‚‚ induced elevation of 8-oxo-G content is much higher in RNA than that of 8-hydroxydeoxyguanosine (8-oxo-dG) in DNA. Under normal conditions, the 8-oxo-G level is low in RNA isolated from the ribosome and it is nearly three times higher in non-ribosomal RNAs. In contrast, 8-oxo-G generated by a short exposure to Hâ‚‚Oâ‚‚ is almost equally distributed in various RNA species, suggesting that although ribosomal RNAs are normally less oxidized, they are not protected against exogenous Hâ‚‚Oâ‚‚. Interestingly, highly folded RNA is not protected from oxidation because 8-oxo-G generated by Hâ‚‚Oâ‚‚ treatment in vitro increases to approximately the same levels in tRNA and rRNA in both native and denatured forms. Lastly, increased RNA oxidation is closely associated with cell death by oxidative stress. Our data suggests that RNA is a primary target for reactive oxygen species and RNA oxidation is part of the paradox that cells have to deal with under oxidative stress.

Characterization of RNA damage under oxidative stress in Escherichia coli.

Wir haben die 8-Hydroxyguanosine 8-Oxo-G, eine oxidierte Form von Guanosin, in RNA in Escherichia coli unter normalen und oxidativen Stressbedingungen untersucht. 8-Oxo-G in RNA steigt rasch und bleibt hoch stundenlang in Reaktion auf Wasserstoffperoxid (H&#x2082;O&#x2082;) Herausforderung in einer Dosis-abh&auml;ngigen Weise. H&#x2082;O&#x2082; induzierte Erh&ouml;hung von 8-Oxo-G Inhalt ist viel h&ouml;her in RNA als der 8-Hydroxydeoxyguanosine (8-Oxo-dG) in DNA. Unter normalen Bedingungen die 8-Oxo-G ist in RNA isoliert aus dem Ribosom niedrig, und es ist fast dreimal h&ouml;her Ribosomale RNA. 8-Oxo-G durch eine kurze Exposition gegen&uuml;ber H&#x2082;O&#x2082; generiert wird dagegen fast gleichm&auml;&szlig;ig verteilt, in verschiedene RNA-Arten, was darauf hindeutet, dass obwohl Ribosomale RNA sind in der Regel weniger oxidiert, sie sind nicht gegen exogene H&#x2082;O&#x2082; gesch&uuml;tzt. Interessanterweise ist stark gefalteten RNA nicht vor Oxidation gesch&uuml;tzt, da 8-Oxo-G von in-vitro-H&#x2082;O&#x2082;-Behandlung erzeugt ungef&auml;hr die gleichen Ebenen tRNA und rRNA in systemeigenen und denaturiertes Formen erh&ouml;ht. Schlie&szlig;lich ist die erh&ouml;hte RNA-Oxidation eng mit Zelltod durch oxidativen Stress. Unsere Daten zufolge RNA ist ein prim&auml;res Ziel f&uuml;r reaktive Sauerstoffspezies und RNA-Oxidation ist Teil des Paradoxons, die Zellen mit unter oxidativer Stress zu tun haben.

Charakterisierung der RNA Schaden unter oxidativer Stress in Escherichia coli.

Gastric aspiration increases the risks for developing secondary bacterial pneumonia. Cytokine elaboration through pathogen recognition receptors (PRRs) is an important mechanism in initiating innate immune host response. Effects of low pH stress, a critical component of aspiration pathogenesis, on the PRR pathways were examined, specifically toll-like receptor-2 (TLR2) and TLR4, using isolated rat alveolar macrophages (aMØs). We assessed the ability of aMØs after brief exposure to acidified saline to elaborate proinflammatory cytokines in response to lipopolysaccharide (LPS) and lipoteichoic acid (LTA) stimulation, known ligands of TLR4 and TLR2, respectively. Low pH stress reduced LPS- and LTA-mediated cytokine release (CINC-1, MIP-2, TNF-α, MCP-1, and IFN-β). LPS and LTA increased intracellular Ca²⁺ concentrations while Ca²⁺ chelation by BAPTA decreased LPS- and LTA-mediated cytokine responses. BAPTA blocked the effects of low pH stress on most of LPS-stimulated cytokines but not of LTA-stimulated responses. In vivo mouse model demonstrates suppressed E. coli and S. pneumoniae clearance following acid aspiration. In conclusion, low pH stress inhibits antibacterial cytokine response of aMØs due to impaired TLR2 (MyD88 pathway) and TLR4 signaling (MyD88 and TRIF pathways). The role of Ca²⁺ in low pH stress-induced signaling is complex but appears to be distinct between LPS- and LTA-mediated responses.

Low pH environmental stress inhibits LPS and LTA-stimulated proinflammatory cytokine production in rat alveolar macrophages.

A 52-year-old man developed pyrexia after primary angioplasty following anterior myocardial infarction Noninvasive evaluation revealed staphylococcal septicemia with suspicion of an aneurysm or abscess at the stented segment. Coronary angiography confirmed the presence of a large aneurysm. The infected left anterior descending artery aneurysm was de-roofed and ligated, and a saphenous vein bypass graft was placed, with an excellent outcome.

Successful surgical outcome of infected aneurysmal drug-coated stent endocarditis.

Dense fibrotic stroma associated with pancreatic ductal adenocarcinoma (PDAC) is a major obstacle for drug delivery to the tumor bed and plays a crucial role in pancreatic cancer progression. Current, anti-stromal therapies have failed to improve tumor response to chemotherapy and patient survival. Furthermore, recent studies show that stroma impedes tumor progression, and its complete ablation accelerates PDAC progression. In an effort to understand the molecular mechanisms associated with tumor-stromal interactions, using in vitro and in vivo models and PDAC patient biopsies, we show that the loss of miR-29 is a common phenomenon of activated pancreatic stellate cells (PSCs)/fibroblasts, the major stromal cells responsible for fibrotic stromal reaction. Loss of miR-29 is correlated with a significant increase in extracellular matrix (ECM) deposition, a major component in PDAC stroma. Our in vitro miR-29 gain/loss-of-function studies document the role of miR-29 in PSC-mediated ECM stromal protein accumulation. Overexpression of miR-29 in activated stellate cells reduced stromal deposition, cancer cell viability, and cancer growth in co-culture. Furthermore, the loss of miR-29 in TGF-β1 activated PSCs is SMAD3 dependent. These results provide insights into the mechanistic role of miR-29 in PDAC stroma and its potential use as a therapeutic agent to target PDAC.

Pathophysiological role of microRNA-29 in pancreatic cancer stroma.

To minimize the risk of pneumonia, many anesthesiologists delay anesthesia-requiring procedures when patients exhibit signs of viral upper respiratory tract infection. Postinfluenza secondary bacterial pneumonias (SBPs) are a major cause of morbidity and mortality. An increased host susceptibility to SBP postinfluenza has been attributed to physical damage to the pulmonary epithelium, but flu-induced effects on the immune system are being shown to also play an important role. The authors demonstrate that halothane mitigates the risk of SBP postflu through modulation of the effects of type I interferon (IFN).

Halothane modulates the type i interferon response to influenza and minimizes the risk of secondary bacterial pneumonia through maintenance of neutrophil recruitment in an animal model.

Previous studies have demonstrated that cleaved high-molecular-weight kininogen (HKa) induces endothelial apoptosis and inhibits angiogenesis and have suggested that this occurs through inhibition of Src family kinases. This study assessed the role of tyrosine-protein kinase Lck (p56/Lck) in this pathway. We analyzed early events leading to apoptosis of human endothelial cells exposed to HKa. The role of p56/Lck was investigated using short interfering (si) RNA knockdown and lentivirus expression in assays of endothelial tube formation, sprouting of neovessels from murine aorta, and angiogenesis in Matrigel plugs. HKa stimulated expression and phosphorylation of p56/Lck. siRNA knockdown of p56/Lck promoted endothelial proliferation and blocked HKa-induced apoptosis and activation of p53, Bax, and Bak. Lentivirus expression of p56/Lck in endothelial cells induced apoptosis and blocked tube formation. Expression of p56/Lck in murine aortic rings blocked sprouting angiogenesis. Lentivirus expressing p56/Lck blocked angiogenesis in Matrigel plugs, while p56/Lck short hairpin RNA inhibited the antiangiogenic effect of HKa. Scrambled siRNAs and empty lentiviral vectors were used in all experiments. Apoptosis of proliferating endothelial cells and inhibition of angiogenesis by HKa requires p56/Lck. This suggests a novel role for p56/Lck in regulation of endothelial cell survival and angiogenesis.-Betapudi, V., Shukla, M., Alluri, R., Merkulov, S., McCrae, K. R. Novel role for p56/Lck in regulation of endothelial cell survival and angiogenesis.

Novel role for p56/Lck in regulation of endothelial cell survival and angiogenesis.

The procedures described below are for producing gastric aspiration pneumonitis in mice with alterations for rats and rabbits described parenthetically. We use 4 different injury vehicles delivered intratracheally to investigate the inflammatory responses to gastric aspiration: Normal saline (NS) as the injury vehicle controlNS + HCl, pH = 1.25 (acid)NS + gastric particles, pH ≈ 5.3 (part.)NS + gastric particles + HCl, pH = 1.25 (acid + part.) The volume, pH, and gastric particle concentration all affect the resulting lung injury. In mice, we generally use an injury volume of 3.6 ml/kg (rat: 1.2 ml/kg, rabbit: 2.4 ml/kg), an injury pH (for the acid-containing vehicles) of 1.25, and a gastric particulate concentration (in the particulate-containing vehicles) of 10 mg/ml (rat: 40 mg/ml). In our hands this results in a maximal, non-lethal lung injury with ≤ 10% mortality for the most injurious vehicle (i.e., acid + part.) The maximum tolerable particulate concentration needs to be determined empirically for any new strains to be used, especially in genetically-altered mice, because an altered inflammatory response may have detrimental affects on mortality. We have extensive experience utilizing these procedures in the outbred strain, CD-1, as well as many genetically-altered inbred stains on the C57BL/6 background. Choice of strain should be carefully considered, especially in terms of strain-specific immune bias, to assure proper data interpretation. The size of the mouse should be ≥ 20 g at the time of injury. Smaller mice can be attempted, if necessary, but the surgical manipulation becomes increasingly more difficult and the surgery survival rate decreases substantially. There are no size or strain constraints for rat and rabbit models, but we generally use Long-Evans rats at 250-300 g and New Zealand White rats at ≈ 2 kg at the time of initial injury.

Article	Year
Novel one-step mechanism for tRNA 3'-end maturation by the exoribonuclease RNase R of Mycoplasma genitalium. The Journal of biological chemistry\| PubMed ID: 22605341	2012
Characterization of RNA damage under oxidative stress in Escherichia coli. Biological chemistry\| PubMed ID: 22718628	2012
Low pH environmental stress inhibits LPS and LTA-stimulated proinflammatory cytokine production in rat alveolar macrophages. BioMed research international\| PubMed ID: 24288685	2013
Successful surgical outcome of infected aneurysmal drug-coated stent endocarditis. Asian cardiovascular & thoracic annals\| PubMed ID: 24771742	2014
Pathophysiological role of microRNA-29 in pancreatic cancer stroma. Scientific reports\| PubMed ID: 26095125	2015
Halothane modulates the type i interferon response to influenza and minimizes the risk of secondary bacterial pneumonia through maintenance of neutrophil recruitment in an animal model. Anesthesiology\| PubMed ID: 26120770	2015
Novel role for p56/Lck in regulation of endothelial cell survival and angiogenesis. FASEB journal : official publication of the Federation of American Societies for Experimental Biology\| PubMed ID: 27402674	2016
Gastric Aspiration Models. Bio-protocol\| PubMed ID: 27540561	2013

Ravi Alluri

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