MKP-1 mediates glucocorticoid-induced ERK1/2 dephosphorylation and reduction in pancreatic beta-cell proliferation in islets from early lactating mothers

Maternal pancreatic islets undergo a robust increase of mass and proliferation during pregnancy, which allows a compensation of gestational insulin resistance. Studies have described that this adaptation switches to a low proliferative status after the delivery. the mechanisms underlying this reversal are unknown, but the action of glucocorticoids (GCs) is believed to play an important role because GCs counteract the pregnancy-like effects of PRL on isolated pancreatic islets maintained in cell culture. Here, we demonstrate that ERK1/2 phosphorylation (phospho-ERK1/2) is increased in maternal rat islets isolated on the 19th day of pregnancy. Phospho-ERK1/2 status on the 3rd day after delivery (L3) rapidly turns to values lower than that found in virgin control rats (CTL). MKP-1, a protein phosphatase able to dephosphorylate ERK1/2, is increased in islets from L3 rats. Chromatin immunoprecipitation assay revealed that binding of glucocorticoid receptor (GR) to MKP-1 promoter is also increased in islets from L3 rats. in addition, dexamethasone (DEX) reduced phospho-ERK1/2 and increased MKP-1 expression in RINm5F and MIN-6 cells. Inhibition of transduction with cycloheximide and inhibition of phosphatases with orthovanadate efficiently blocked DEX-induced downregulation of phospho-ERK1/2. in addition, specific knockdown of MKP-1 with siRNA suppressed the downregulation of phosphoERK1/2 and the reduction of proliferation induced by DEX. Altogether, our results indicate that downregulation of phospho-ERK1/2 is associated with reduction in proliferation found in islets of early lactating mothers. This mechanism is probably mediated by GC-induced MKP-1 expression.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de PesquisaCoordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Univ São Paulo, Inst Biomed Sci, Dept Physiol & Biophys, BR-05508 São Paulo, BrazilUniversidade Federal de São Paulo, Dept Biol Sci, Diadema, SP, BrazilUniv Estadual Campinas, Fac Med Sci, Dept Pharmacol, São Paulo, BrazilUniversidade Federal de São Paulo, Dept Biol Sci, Diadema, SP, BrazilWeb of Scienc

A robust human norovirus replication model in zebrafish larvae.

Human noroviruses (HuNoVs) are the most common cause of foodborne illness, with a societal cost of $60 billion and 219,000 deaths/year. The lack of robust small animal models has significantly hindered the understanding of norovirus biology and the development of effective therapeutics. Here we report that HuNoV GI and GII replicate to high titers in zebrafish (Danio rerio) larvae; replication peaks at day 2 post infection and is detectable for at least 6 days. The virus (HuNoV GII.4) could be passaged from larva to larva two consecutive times. HuNoV is detected in cells of the hematopoietic lineage and the intestine, supporting the notion of a dual tropism. Antiviral treatment reduces HuNoV replication by >2 log10, showing that this model is suited for antiviral studies. Zebrafish larvae constitute a simple and robust replication model that will largely facilitate studies of HuNoV biology and the development of antiviral strategies

Rationale, study design, and analysis plan of the Alveolar Recruitment for ARDS Trial (ART): Study protocol for a randomized controlled trial

Background: Acute respiratory distress syndrome (ARDS) is associated with high in-hospital mortality. Alveolar recruitment followed by ventilation at optimal titrated PEEP may reduce ventilator-induced lung injury and improve oxygenation in patients with ARDS, but the effects on mortality and other clinical outcomes remain unknown. This article reports the rationale, study design, and analysis plan of the Alveolar Recruitment for ARDS Trial (ART). Methods/Design: ART is a pragmatic, multicenter, randomized (concealed), controlled trial, which aims to determine if maximum stepwise alveolar recruitment associated with PEEP titration is able to increase 28-day survival in patients with ARDS compared to conventional treatment (ARDSNet strategy). We will enroll adult patients with ARDS of less than 72 h duration. The intervention group will receive an alveolar recruitment maneuver, with stepwise increases of PEEP achieving 45 cmH(2)O and peak pressure of 60 cmH2O, followed by ventilation with optimal PEEP titrated according to the static compliance of the respiratory system. In the control group, mechanical ventilation will follow a conventional protocol (ARDSNet). In both groups, we will use controlled volume mode with low tidal volumes (4 to 6 mL/kg of predicted body weight) and targeting plateau pressure <= 30 cmH2O. The primary outcome is 28-day survival, and the secondary outcomes are: length of ICU stay; length of hospital stay; pneumothorax requiring chest tube during first 7 days; barotrauma during first 7 days; mechanical ventilation-free days from days 1 to 28; ICU, in-hospital, and 6-month survival. ART is an event-guided trial planned to last until 520 events (deaths within 28 days) are observed. These events allow detection of a hazard ratio of 0.75, with 90% power and two-tailed type I error of 5%. All analysis will follow the intention-to-treat principle. Discussion: If the ART strategy with maximum recruitment and PEEP titration improves 28-day survival, this will represent a notable advance to the care of ARDS patients. Conversely, if the ART strategy is similar or inferior to the current evidence-based strategy (ARDSNet), this should also change current practice as many institutions routinely employ recruitment maneuvers and set PEEP levels according to some titration method.Hospital do Coracao (HCor) as part of the Program 'Hospitais de Excelencia a Servico do SUS (PROADI-SUS)'Brazilian Ministry of Healt

Protective effect of D-glucose, L-leucine and fetal calf serum against oxidative stress in neonatal pancreatic islets

B-cell destruction during the onset of diabetes mellitus is associated with oxidative stress. In this work, we investigated the mechanisms of defense against oxidative stress present in neonatal islets and their modulation by D-glucose, L-leucine and fetal calf serum (FCS). Culturing neonatal rat islets in the presence of low D-glucose concentrations (2.8-5.6 mmol/l) and 1 mmol/l H(2)O(2) increased the D-glucose uptake by islets sixfold compared to control levels. This effect was dose-dependently inhibited by D-glucose or FCS and by high concentrations of L-leucine. These supplements allowed islets to increase cytoplasmic catalase (CAT) activity only in response to H(2)O(2), with no decrease in NO formation. Although L-leucine increased CAT activity and restored D-glucose uptake, it did not prevent damage to the islets. These data indicate that the most important H(2)O(2) scavenger system in the islets is CAT and that this system can be modulated by metabolic substrates.status: publishe

RNA-sequencing identifies Nova1 as a major splicing regulator in pancreatic beta cells.

info:eu-repo/semantics/nonPublishe

Involvement of phosphatidylinositol-3 kinase/AKT/PKCzeta/lambda pathway in the effect of palmitate on glucose-induced insulin secretion

In the present study, a novel pathway by which palmitate potentiates glucose-induced insulin secretion by pancreatic beta cells was investigated.status: publishe

Characterization of the insulinotropic action of a phospholipase A2 isolated from Crotalus durissus collilineatus rattlesnake venom on rat pancreatic islets

The ability of PLA2 and crotapotin, isolated from Crotalus durissus collilineatus rattlesnake venom, to stimulate insulin secretion from isolated rat islets was examined. PLA2 and crotapotin stimulated insulin secretion at 2.8 mmol/L glucose, whereas at a high glucose concentrations (16.7 mmol/L) only PLA2 stimulated secretion. Nifedipine (10 micromol/L) did not alter the ability of PLA2 to increase insulin secretion stimulated by a depolarizing concentration of K+ (30 mmol/L). PLA2 did not affect 14CO2 production but significantly increased the efflux of arachidonic acid from isolated islets. These results indicate that PLA2-stimulated secretion is not dependent on an additional influx of Ca2+ through L-type Ca(2+)-channels but rather is associated with arachidonic acid formation in pancreatic islets.status: publishe