An Intricate Network Involving the Argonaute ALG-1 Modulates Organismal Resistance to Oxidative Stress.

Cellular response to redox imbalance is crucial for organismal health. microRNAs are implicated in stress responses. ALG-1, the C. elegans ortholog of human AGO2, plays an essential role in microRNA processing and function. Here we investigated the mechanisms governing ALG-1 expression in C. elegans and the players controlling lifespan and stress resistance downstream of ALG-1. We show that upregulation of ALG-1 is a shared feature in conditions linked to increased longevity (e.g., germline-deficient glp-1 mutants). ALG-1 knockdown reduces lifespan and oxidative stress resistance, while overexpression enhances survival against pro-oxidant agents but not heat or reductive stress. R02D3.7 represses alg-1 expression, impacting oxidative stress resistance at least in part via ALG-1. microRNAs upregulated in glp-1 mutants (miR-87-3p, miR-230-3p, and miR-235-3p) can target genes in the protein disulfide isomerase pathway and protect against oxidative stress. This study unveils a tightly regulated network involving transcription factors and microRNAs which controls organisms' ability to withstand oxidative stress.

Tissue-specific overexpression of systemic RNA interference components limits lifespan in C. elegans.

Intertissue RNA transport recently emerged as a novel signaling mechanism. In mammals, mounting evidence suggests that small RNA transfer between cells is widespread and used in various physiological contexts. In the nematode C. elegans, a similar mechanism is conferred by the systemic RNAi pathway. Members of the Systemic RNA Interference Defective (SID) family act at different steps of cellular RNA uptake and export. The limiting step in systemic RNA interference (RNAi) is the import of extracellular RNAs via the conserved double-stranded (dsRNA)-gated dsRNA channel SID-1. To better understand the role of RNAs as intertissue signaling molecules, we modified the function of SID-1 in specific tissues of C. elegans. We observed that sid-1 loss-of-function mutants are as healthy as wild-type worms. Conversely, overexpression of sid-1 in C. elegans intestine, muscle, or neurons rendered worms short-lived. The effects of intestinal sid-1 overexpression were attenuated by silencing the components of systemic RNAi sid-1, sid-2 and sid-5, implicating systemic RNA signaling in the lifespan reduction. Accordingly, tissue-specific overexpression of sid-2 and sid-5 also reduced worm lifespan. Additionally, an RNAi screen for components of several non-coding RNA pathways revealed that silencing the miRNA biogenesis proteins PASH-1 and DCR-1 rendered the lifespan of worms with intestinal sid-1 overexpression similar to controls. Collectively, our data support the notion that systemic RNA signaling must be tightly regulated, and unbalancing that process provokes a reduction in lifespan. We termed this phenomenon Intercellular/Extracellular Systemic RNA imbalance (InExS).

Extracellular miRNAs in redox signaling: Health, disease and potential therapies.

Extracellular microRNAs (miRNAs) have emerged as important mediators of cell-to-cell communication and intertissue crosstalk. MiRNAs are produced by virtually all types of eukaryotic cells and can be selectively packaged and released to the extracellular medium, where they may reach distal cells to regulate gene expression cell non-autonomously. By doing so, miRNAs participate in integrative physiology. Oxidative stress affects miRNA expression, while miRNAs control redox signaling. Disruption in miRNA expression, processing or release to the extracellular compartment are associated with aging and a number of chronic diseases, such as obesity, type 2 diabetes, neurodegenerative diseases and cancer, all of them being conditions related to oxidative stress. Here we discuss the interplay between redox balance and miRNA function and secretion as a determinant of health and disease states, reviewing the findings that support this notion and highlighting novel and yet understudied venues of research in the field.

The yeast protein Ubx4p contributes to mitochondrial respiration and lithium-galactose-mediated activation of the unfolded protein response.

In the presence of galactose, lithium ions activate the unfolded protein response (UPR) by inhibiting phosphoglucomutase activity and causing the accumulation of galactose-related metabolites, including galactose-1-phosphate. These metabolites also accumulate in humans who have the disease classic galactosemia. Here, we demonstrate that Saccharomyces cerevisiae yeast strains harboring a deletion of UBX4, a gene encoding a partner of Cdc48p in the endoplasmic reticulum-associated degradation (ERAD) pathway, exhibit delayed UPR activation after lithium and galactose exposure because the deletion decreases galactose-1-phosphate levels. The delay in UPR activation did not occur in yeast strains in which key ERAD or proteasomal pathway genes had been disrupted, indicating that the ubx4Δ phenotype is ERAD-independent. We also observed that the ubx4Δ strain displays decreased oxygen consumption. The inhibition of mitochondrial respiration was sufficient to diminish galactose-1-phosphate levels and, consequently, affects UPR activation. Finally, we show that the deletion of the AMP-activated protein kinase ortholog-encoding gene SNF1 can restore the oxygen consumption rate in ubx4Δ strain, thereby reestablishing galactose metabolism, UPR activation, and cellular adaption to lithium-galactose challenge. Our results indicate a role for Ubx4p in yeast mitochondrial function and highlight that mitochondrial and endoplasmic reticulum functions are intertwined through galactose metabolism. These findings also shed new light on the mechanisms of lithium action and on the pathophysiology of galactosemia.

Intrinsic Adaptation of SHR Right Atrium Reduces Heart Rate.

Hypertension represents an autonomic dysfunction, characterized by increased sympathetic and decreased parasympathetic cardiovascular tone leading to resting tachycardia. Therefore, studies assessing hypertension-associated changes in isolated cardiac tissues were conducted under electric field stimulation to stimulate the neurons. Herein, we characterize the influence of the autonomic neurotransmitter on the baseline atrial chronotropism of unpaced isolated right atria of normotensive Wistar rats (NWR) and spontaneously hypertensive rats (SHR). Our results revealed a resting bradycardia in tissues from SHR in comparison to NWR. The release of autonomic neurotransmitters, acetylcholine or norepinephrine, still occurs in the electrically unstimulated right atrium, after excision of the sympathetic nerve, which could explain differences in basal heart rate between NWR and SHR. Nicotine and the acetylcholinesterase inhibitor physostigmine reduced the chronotropism of right atria from either NWR or SHR. Conversely, the muscarinic receptor antagonist atropine did not affect the basal chronotropism of tissues from both strains. Furthermore, tyramine increased the chronotropism of NWR and SHR atria indicating availability of the neuronal stocks of noradrenaline. Although the monoamine uptake inhibitor cocaine increased right atrium chronotropism in both strains, the basal heart rate was not affected by the ß-adrenoceptor antagonist propranolol. In summary, after acute section of the sympathetic nerve, autonomic neurotransmitters are still released either in resting conditions or upon pharmacological stimulation of right atria from both strains. Nevertheless, autonomic neurotransmission does not affect resting chronotropism, nor is the responsible for reduced basal heart rate of the isolated right atrium of hypertensive rats.

RNA interference may result in unexpected phenotypes in Caenorhabditis elegans.

RNA interference (RNAi) is a valuable technique to determine gene function. In Caenorhabditis elegans, RNAi can be achieved by feeding worms bacteria carrying a plasmid expressing double-stranded RNA (dsRNA) targeting a gene of interest. The most commonly used plasmid vector for this purpose is L4440. However, it has been noticed that sequences within L4440 may elicit unspecific effects. Here, we provide a comprehensive characterization of these effects and their mechanisms and describe new unexpected phenotypes uncovered by the administration of unspecific exogenous dsRNA. An example involves dsRNA produced by the multiple cloning site (MCS) of L4440, which shares complementary sequences with some widely used reporter vectors and induces partial transgene silencing via the canonical and antiviral RNAi pathway. Going beyond transgene silencing, we found that the reduced embryonic viability of mir-35-41(gk262) mutants is partially reversed by exogenous dsRNA via a mechanism that involves canonical RNAi. These results indicate cross-regulation between different small RNA pathways in C. elegans to regulate embryonic viability. Recognition of the possible unspecific effects elicited by RNAi vectors is important for rigorous interpretation of results from RNAi-based experiments.

Enoxacin extends lifespan of C. elegans by inhibiting miR-34-5p and promoting mitohormesis.

Alterations in microRNA (miRNA) processing have been previously linked to aging. Here we used the small molecule enoxacin to pharmacologically interfere with miRNA biogenesis and study how it affects aging in C. elegans. Enoxacin extended worm lifespan and promoted survival under normal and oxidative stress conditions. Enoxacin-induced longevity required the transcription factor SKN-1/Nrf2 and was blunted by the antioxidant N-acetyl-cysteine, suggesting a prooxidant-mediated mitohormetic response. The longevity effects of enoxacin were also dependent on the miRNA pathway, consistent with changes in miRNA expression elicited by the drug. Among these differentially expressed miRNAs, the widely conserved miR-34-5p was found to play an important role in enoxacin-mediated longevity. Enoxacin treatment down-regulated miR-34-5p and did not further extend lifespan of long-lived mir-34 mutants. Moreover, N-acetyl-cysteine abrogated mir-34(gk437)-induced longevity. Evidence also points to double-stranded RNA-specific adenosine deaminases (ADARs) as new targets of enoxacin since ADAR loss-of-function abrogates enoxacin-induced lifespan extension. Thus, enoxacin increases lifespan by reducing miR-34-5p levels, interfering with the redox balance and promoting healthspan.

Increased Gi protein signaling potentiates the negative chronotropic effect of adenosine in the SHR right atrium.

Hypertension is a risk factor for cardiovascular diseases, which have been associated with dysfunction of sympathetic and purinergic neurotransmission. Therefore, herein, we evaluated whether modifications of adenosine receptor signaling may contribute to the cardiac dysfunction observed in hypertension. Isolated right atria from spontaneously hypertensive (SHR) or normotensive Wistar rats (NWR) were used to investigate the influence of adenosine receptor signaling cascade in the cardiac chronotropism. Our results showed that adenosine, the endogenous agonist of adenosine receptors, and CPA, a selective agonist of A1 receptor, decreased the atrial chronotropism of NWR and SHR in a concentration- and time-dependent manner, culminating in cardiac arrest (0 bpm). Interestingly, a 3-fold lower concentration of adenosine was required to induce the negative chronotropic effect in SHR atria. Pre-incubation of tissues from both strains with DPCPX, a selective A1 receptor antagonist, inhibited the negative chronotropic effect of CPA, while simultaneous inhibition of A2 and A3 receptors, with ZM241385 and MRS1523, did not change the adenosine chronotropic effects. Moreover, 1 µg/ml pertussis toxin, which inactivates the Gαi protein subunit, reduced by 80% the negative chronotropic effects of adenosine in the NWR atrium, with minor effects in SHR tissue. These data indicate that the negative chronotropic effect of adenosine in right atrium depends exclusively on the activation of A1 receptors. Moreover, the distinct responsiveness of NWR and SHR atria to pertussis toxin reveals that the enhanced negative chronotropic response of SHR right atrium is probably due to an increased activity of Gαi protein-mediated.

Cardiac arrest induced by muscarinic or adenosine receptors agonists is reversed by DPCPX through double mechanism.

In the right atrium (RA), adenosine and acetylcholine inhibit the pacemaker function of the sinoatrial node and induce cardiac arrest. Pre-incubation of receptor antagonists is known to inhibit the cardiac arrest induced by these agonists; however, the effect of antagonist administration after established cardiac arrest has not been described. Therefore, we assessed whether specific receptor antagonists could revert cardiac arrest induced by adenosine and muscarinic receptors activation. RA isolated from adults Wistar rats were mounted in an organ bath containing Krebs solution. Cardiac arrest was induced by adenosine or ATP (1mM), the A1 adenosine receptor agonist CPA (0.1-1µM), and muscarinic receptor agonists, carbachol (0.3-1µM) and acetylcholine (1mM). After establishing the cardiac arrest, the A1 adenosine receptor antagonist DPCPX (0.3-30µM), the muscarinic receptor antagonist atropine (10nM to 100µM) or the phosphodiesterase inhibitor IBMX (10-300µM) were incubated in order to check for the return of spontaneous contractions. DPCPX reversed the cardiac arrest induced by adenosine, ATP and CPA. In addition, atropine reversed the cardiac arrest induced by carbachol. Unexpectedly, DPCPX also reversed the cardiac arrest induced by carbachol. Similarly to DPCPX, the phosphodiesterase inhibitor IBMX reversed the cardiac arrest induced by adenosine, CPA and carbachol. The antagonism of adenosine and acetylcholine receptors activation, as well as phosphodiesterase inhibition, are able to revert cardiac arrest. DPCPX restore spontaneous contractions via the selective antagonism of A1 adenosine receptor and through a secondary mechanism likely related to phosphodiesterase inhibition.

IMPACT is a GCN2 inhibitor that limits lifespan in Caenorhabditis elegans.

BACKGROUND: The General Control Nonderepressible 2 (GCN2) kinase is a conserved member of the integrated stress response (ISR) pathway that represses protein translation and helps cells to adapt to conditions of nutrient shortage. As such, GCN2 is required for longevity and stress resistance induced by dietary restriction (DR). IMPACT is an ancient protein that inhibits GCN2. RESULTS: Here, we tested whether IMPACT down-regulation mimics the effects of DR in C. elegans. Knockdown of the C. elegans IMPACT homolog impt-1 activated the ISR pathway and increased lifespan and stress resistance of worms in a gcn-2-dependent manner. Impt-1 knockdown exacerbated DR-induced longevity and required several DR-activated transcription factors to extend lifespan, among them SKN-1 and DAF-16, which were induced during larval development and adulthood, respectively, in response to impt-1 RNAi. CONCLUSIONS: IMPACT inhibits the ISR pathway, thus limiting the activation of stress response factors that are beneficial during aging and required under DR.

Would calcium or potassium channels be responsible for cardiac arrest produced by adenosine and ATP in the right atria of Wistar rats?

Autonomic nerves release ATP, which is processed into adenosine in the synaptic cleft. Adenosine and ATP exert a negative chronotropic effect in the heart. This study aims to evaluate adenosine and P2 receptors and cellular signalling in cardiac arrest produced by purines in the heart. Right atria of adult Wistar rats were used to evaluate the effects of adenosine, ATP and CPA (an adenosine A1 receptor agonist), in the presence and absence of DPCPX, an adenosine A1 receptor antagonist. Effects of adenosine A2 and A3 receptors agonists and antagonists were also investigated. Finally, involvement of calcium and potassium channels in these responses was assessed using BayK 8644 and 4-Aminopyridine. Cumulative concentration-effect curves of adenosine and CPA resulted in a negative chronotropic effect culminating in cardiac arrest at 1000µM (adenosine) and 1µM (CPA). Furthermore, ATP produced a negative chronotropic effect at 1-300µM and cardiac arrest at 1000µM in the right atrium. ATPγS (a non-hydrolysable analogue of ATP) reduced chronotropism only. The effects of adenosine, CPA and ATP were inhibited by DPCPX, a selective adenosine A1 receptor antagonist. The selective adenosine A2 and A3 receptors antagonists did not alter the chronotropic response of adenosine. 4-Aminopyridine, a blocker of potassium channels at 10mM, prevented the cardiac arrest produced by adenosine and ATP, while BayK 8644, activator of calcium channels, did not prevent cardiac arrest. Adenosine A1 receptor activation by adenosine and ATP produces cardiac arrest in the right atrium of Wistar rats predominantly through activation of potassium channels.

Buried bumper syndrome: abordagem endoscópica: relato de caso / Buried bumper syndrome: endoscopic approach: case report

A buried bumper syndrome (BBS) é uma rara complicação da gastrostomia endoscópica percutânea (PEG) definida pelo sepultamento do anteparo da sonda de gastrostomia na mucosa gástrica, ficando este anteparo alojado na parede gástrica ou abdominal. Pode ocorrer, então, a obstrução do orifício da sonda, que impede a administração da dieta. Descreve-se uma abordagem endoscópica dessa síndrome, usando um estilete, tipo papilótomo pré-corte, para seccionar a mucosa gástrica até a exposição do anteparo, que é laçado com a alça. O conjunto éretirado pela cavidade oral e uma nova PEG écolocada no mesmo procedimento, utilizando o orifício prévio

Colecistectomia por mini-laparotomia / Cholecistectomy by micro-laparotomy

Os autores analisam 62 colecistectomias por minilaparotomia realizadas no periodo de abril de 1990 a agosto de 1991 em portadores de litiase biliar sintomatica. A ultrassonografia abdominal foi realizada em 61 pacientes (98,4%) e a colecistografia oral em 16 (25,8%). A ultrassonografia foi sugestiva de colecistite aguda em 9 casos (14,5%). Quarenta e seis pacientes (74,2%) eram do sexo feminino e 16 (25,8%) do sexo masculino. A idade variou de 6 a 76 anos (media 48,7 anos). A altura variou de 113 a 177 cm (media 160,9 cm) e o peso corporal medio foi 62,9 kg (45 a 88kg). A incisao cutanea foi obliqua subcostal direita em 32 casos (51,6%) e transversa em 30 (48,4%). O comprimento da incisao cutanea variou de 2,5 a 6,0cm (5,5 cm). Utilizou-se material especifico para esta operacao.Foi realizada colangiografia per-operatoria em 29 pacientes (46,8) que evidenciou coledocolitiase em 4 casos (6,5%). Nestes, procedeu-se a retirada per-operatoria dos calculos com cateter de Dormia em 2 casos, lavagem do coledoco em 1 e papilotomia endoscopica em 1 case. O tempo operatorio variou de 50 a 180 minutos (79,6 min). Na anestesia pos-operatoria foram utilizados meperidina na dosagem de 0 a 120 mg (media 1,2 dias ). Este procedimento apresenta vantagens e inconvenientes quando comparado a colecistectomia convencional. So deve ser realizado por cirurgiao motivado e experiente. Exige material, e tecnicamente mais dificil e apesenta maior risco de complicacoes. Pequena percentagem de cirurgioes esta apta para executar esta operacao com seguranca.