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.

The galactose-induced decrease in phosphate levels leads to toxicity in yeast models of galactosemia.

Classic galactosemia is an inborn error of metabolism caused by deleterious mutations in the GALT gene. A number of evidences indicate that the galactose-1-phosphate accumulation observed in patient cells is a cause of toxicity in this disease. Nevertheless, the consequent molecular events caused by the galactose-1-phosphate accumulation remain elusive. Here we show that intracellular inorganic phosphate levels decreased when yeast models of classic galactosemia were exposed to galactose. The decrease in phosphate levels is probably due to the trapping of phosphate in the accumulated galactose-1-phosphate since the deletion of the galactokinase encoding gene GAL1 suppressed this phenotype. Galactose-induced phosphate depletion caused an increase in glycogen content, an expected result since glycogen breakdown by the enzyme glycogen phosphorylase is dependent on inorganic phosphate. Accordingly, an increase in intracellular phosphate levels suppressed the galactose effect on glycogen content and conferred galactose tolerance to yeast models of galactosemia. These results support the hypothesis that the galactose-induced decrease in phosphate levels leads to toxicity in galactosemia and opens new possibilities for the development of better treatments for this disease.

Sphingolipid depletion suppresses UPR activation and promotes galactose hypersensitivity in yeast models of classic galactosemia.

Classic galactosemia is an inborn error of metabolism caused by deleterious mutations on the GALT gene, which encodes the Leloir pathway enzyme galactose-1-phosphate uridyltransferase. Previous studies have shown that the endoplasmic reticulum unfolded protein response (UPR) is relevant to galactosemia, but the molecular mechanism behind the endoplasmic reticulum stress that triggers this response remains elusive. In the present work, we show that the activation of the UPR in yeast models of galactosemia does not depend on the binding of unfolded proteins to the ER stress sensor protein Ire1p since the protein domain responsible for unfolded protein binding to Ire1p is not necessary for UPR activation. Interestingly, myriocin - an inhibitor of the de novo sphingolipid synthesis pathway - inhibits UPR activation and causes galactose hypersensitivity in these models, indicating that myriocin-mediated sphingolipid depletion impairs yeast adaptation to galactose toxicity. Supporting the interpretation that the effects observed after myriocin treatment were due to a reduction in sphingolipid levels, the addition of phytosphingosine to the culture medium reverses all myriocin effects tested. Surprisingly, constitutively active UPR signaling did not prevent myriocin-induced galactose hypersensitivity suggesting multiple roles for sphingolipids in the adaptation of yeast cells to galactose toxicity. Therefore, we conclude that sphingolipid homeostasis has an important role in UPR activation and cellular adaptation in yeast models of galactosemia, highlighting the possible role of lipid metabolism in the pathophysiology of this disease.

Functional expression of kinin B1 and B2 receptors in mouse abdominal aorta.

Previous studies have shown that the vascular reactivity of the mouse aorta differs substantially from that of the rat aorta in response to several agonists such as angiotensin II, endothelin-1 and isoproterenol. However, no information is available about the agonists bradykinin (BK) and DesArg(9)BK (DBK). Our aim was to determine the potential expression of kinin B(1) and B(2) receptors in the abdominal mouse aorta isolated from C57BL/6 mice. Contraction and relaxation responses to BK and DBK were investigated using isometric recordings. The kinins were unable to induce relaxation but concentration-contraction response curves were obtained by applying increasing concentrations of the agonists BK and DBK. These effects were blocked by the antagonists Icatibant and R-715, respectively. The potency (pD(2)) calculated from the curves was 7.0 +/- 0.1 for BK and 7.3 +/- 0.2 for DBK. The efficacy was 51 +/- 2% for BK and 30 +/- 1% for DBK when compared to 1 microM norepinephrine. The concentration-dependent responses of BK and DBK were markedly inhibited by the arachidonic acid inhibitor indomethacin (1 microM), suggesting a mediation by the cyclooxygenase pathway. These contractile responses were not potentiated in the presence of the NOS inhibitor L-NAME (1 mM) or endothelium-denuded aorta, indicating that the NO pathway is not involved. We conclude that the mouse aorta constitutively contains B(1) and B(2) subtypes of kinin receptors and that stimulation with BK and DBK induces contractile effect mediated by endothelium-independent vasoconstrictor prostanoids.

Statistical association of rs2243250 polymorphism of IL4 gene and hemorrhagic stroke in Brazilian population / Associação estatística entre o polimorfismo rs2243250 no gene da IL-4 e o AVC hemorrágico na população brasileira

ABSTRACT Interleukin-4 (IL-4) has great significance in inflammatory processes in cases of stroke, since it is able to polarize microglia to the antiinflammatory phenotype called M2. This study analyzed if the variation between TT genotype and the other genotypes (CT and CC), in -589 (rs2243250) polymorphism of IL4 gene, has association with the prognosis of hemorrhagic stroke (HS) and with clinical aspects which are risk factors for cerebrovascular diseases. The result of this study shows that there is no statistical association of the IL4 polymorphism with either prognosis or clinical aspects in HS patients.

RESUMEN La interleucina-4 (IL-4) tiene gran importancia en los procesos inflamatorios en casos de accidente cerebrovascular (ACV), puesto que hace que las microglías sean polarizadas hacia el fenotipo antiinflamatorio M2. Este estudio analizó si la variación entre el genotipo TT y los demás genotipos (CT y CC), en el polimorfismo -589 (rs2243250) del gen IL4, posee asociación con el pronóstico de ACV hemorrágico y con aspectos clínicos que son factores de riesgo para enfermedades cerebrovasculares. El resultado de este estudio enseña que no hay asociación estadística del polimorfismo del IL4 ni con el pronóstico ni con los aspectos clínicos de pacientes con ACV hemorrágico.

RESUMO A interleucina-4 (IL-4) tem grande importância nos processos inflamatórios em casos de acidente vascular cerebral (AVC), uma vez que ela é capaz de polarizar micróglias para o fenótipo anti-inflamatório chamado M2. Este estudo analisou se a variação entre o genótipo TT e os demais genótipos (CT e CC), no polimorfismo -589 (rs2243250) do gene IL4, possui associação com o prognóstico de AVC hemorrágico e com aspectos clínicos que são fatores de risco para doenças cerebrovasculares. O resultado deste estudo mostra que não há associação estatística do polimorfismo do IL4 nem com prognóstico nem com os aspectos clínicos dos pacientes com AVC hemorrágico.

The unfolded protein response has a protective role in yeast models of classic galactosemia.

Classic galactosemia is a human autosomal recessive disorder caused by mutations in the GALT gene (GAL7 in yeast), which encodes the enzyme galactose-1-phosphate uridyltransferase. Here we show that the unfolded protein response pathway is triggered by galactose in two yeast models of galactosemia: lithium-treated cells and the gal7Δ mutant. The synthesis of galactose-1-phosphate is essential to trigger the unfolded protein response under these conditions because the deletion of the galactokinase-encoding gene GAL1 completely abolishes unfolded protein response activation and galactose toxicity. Impairment of the unfolded protein response in both yeast models makes cells even more sensitive to galactose, unmasking its cytotoxic effect. These results indicate that endoplasmic reticulum stress is induced under galactosemic conditions and underscores the importance of the unfolded protein response pathway to cellular adaptation in these models of classic galactosemia.

TNFA gene in Brazilian patients with hemorrhagic stroke or cerebral aneurysm / Gene TNFA em pacientes brasileiros com acidente vascular encefálico hemorrágico ou aneurisma cerebral

ABSTRACT Introduction: Many cerebrovascular diseases display a relation with inflammatory processes. Furthermore, the influence of several polymorphisms has been studied to improve the knowledge of physiological mechanisms of the nervous system. Objectives: The aim of this study was to identify if there was an association between a polymorphism in -308 position of the TNFA gene and the development of hemorrhagic stroke or aneurysm in Distrito Federal, Brazil. Methods: We collected the clinical information and the medical records from hemorrhagic stroke or aneurysm patients. The occurrence of stroke or aneurysm was confirmed by computed tomography (CT) or magnetic resonance image (MRI). The TNFA genotypes were determined by polymerase chain reaction restriction fragment length polymorphism. Results: The AG genotype appears to decrease the occurrence of hemorrhagic stroke or aneurysm in people between 45-63 years. Our study was the first to investigate this association in a Brazilian sample, although a previous report showed a similar effect with ischemic stroke in a Chinese population. Conclusion: The TNFA -308 AG genotype is associated with a decreased risk of aneurysm or hemorrhagic stroke in a population from the capital of Brazil, Distrito Federal.

RESUMO Introdução: Muitas doenças cerebrovasculares relacionam-se com processos inflamatórios, portanto, a influência de vários polimorfismos em doenças tem sido estudada para melhorar o conhecimento sobre os mecanismos fisiológicos do sistema nervoso. Objetivo: Identificar a associação entre um polimorfismo na posição -308 do gene TNFA e o desenvolvimento de acidente vascular encefálico hemorrágico (AVEH) ou aneurisma em pacientes de uma base hospitalar do Distrito Federal, Brasil. Métodos: Foram coletados os prontuários e as informações clínicas de pacientes com AVEH ou aneurisma. A caracterização dos grupos caso foi confirmada por tomografia computadorizada (TC) ou ressonância nuclear magnética (RNM). Os genótipos do gene TNFA foram determinados por técnica do polimorfismo de comprimento dos fragmentos de restrição do produto obtido pela reação em cadeia da polimerase (PCR). Resultados: O genótipo AG parece diminuir a ocorrência de AVEH ou aneurisma em indivíduos entre 45 e 63 anos. Nosso estudo foi o primeiro a investigar essa associação em uma amostra brasileira, embora um relatório anterior tenha mostrado efeito semelhante com o acidente vascular encefálico isquêmico em uma população chinesa. Conclusão: O genótipo TNFA -308 AG está associado à diminuição do risco de aneurisma ou AVEH em uma população da capital do Brasil, Distrito Federal.

Functional expression of kinin B1 and B2 receptors in mouse abdominal aorta

Previous studies have shown that the vascular reactivity of the mouse aorta differs substantially from that of the rat aorta in response to several agonists such as angiotensin II, endothelin-1 and isoproterenol. However, no information is available about the agonists bradykinin (BK) and DesArg9BK (DBK). Our aim was to determine the potential expression of kinin B1 and B2 receptors in the abdominal mouse aorta isolated from C57BL/6 mice. Contraction and relaxation responses to BK and DBK were investigated using isometric recordings. The kinins were unable to induce relaxation but concentration-contraction response curves were obtained by applying increasing concentrations of the agonists BK and DBK. These effects were blocked by the antagonists Icatibant and R-715, respectively. The potency (pD2) calculated from the curves was 7.0 ± 0.1 for BK and 7.3 ± 0.2 for DBK. The efficacy was 51 ± 2 percent for BK and 30 ± 1 percent for DBK when compared to 1 æM norepinephrine. The concentration-dependent responses of BK and DBK were markedly inhibited by the arachidonic acid inhibitor indomethacin (1 æM), suggesting a mediation by the cyclooxygenase pathway. These contractile responses were not potentiated in the presence of the NOS inhibitor L-NAME (1 mM) or endothelium-denuded aorta, indicating that the NO pathway is not involved. We conclude that the mouse aorta constitutively contains B1 and B2 subtypes of kinin receptors and that stimulation with BK and DBK induces contractile effect mediated by endothelium-independent vasoconstrictor prostanoids.