Az intraluminális hidrogén peroxid elimináció mechanizmusai az endoplazmás retikulumban = Mechanisms of intraluminal hydrogen peroxide elimination in the endoplasmic reticulum

Az endoplazmás retikulum (ER) oxidatív protein foldingjának luminális H2O2 termelése hozzájárul az organellum oxidatív környezetének kialakulásához. Kimutattuk, hogy az Ero1α, az oxidatív hajtogatás és ER redox homeosztázis egyik legfontosabb szabályozója, feldúsul a MAM frakcióban, és szabályozza a Ca2+ áramokat. Az Ero1α szintjének mind növelésével mind csökkentésével módosítani lehetett az ER Ca2+ fluxusokat, amely feltárja a fehérje kulcsfontosságú szerepét a korai szekréciós kompartimentumban. Azt is megfigyeltük, hogy a máj ER luminális H2O2 szint emelkedése in vivo egerekben a mikroszómális GSH és fehérje tiol tartalom csökkenését, valamint luminális oxidoreduktázok redox állapotának eltolódását eredményezte. Az oxidatív hatás kiváltotta ar ER tágulását, mely redukálószerekkel kivédhető volt. ER-be célzott katalázt overexpresszáló, antitest termelő sejtekben az érett antitest polimerek csökkent szekrécióját, míg az antitest prekurzor monomerek/dimerek intracelluláris felhalmozódását észleltük. Az eredmények szerint a helyi H2O2 termelés elősegíti, míg a H2O2 eltávolítása rontja a diszulfidok kialakulását. Három review-t közöltünk az ER redox viszonyairól. Egy tanulmányban az oxidatív protein foldingra új paradigmát javasoltunk: a több oxidáns hipotézist. Két átfogó review-ban a jelenlegi ismereteket foglaltuk össze az ER legfontosabb redox rendszereiről. Másik két cikkben pedig a kompartimentáció jelentőségét alátámasztó eredményeket tárgyaltuk. | Oxidative protein folding in the endoplasmic reticulum (ER) results in luminal H2O2 production, contributing to the formation of the oxidative environment of the organelle. We showed that Ero1α, a key controller of oxidative folding and ER redox homeostasis, is enriched in mitochondrial-associated ER membranes (MAM) and regulates Ca2+ fluxes. Either increasing or decreasing the levels of Ero1α affected Ca2+ fluxes, which reveals a pivotal role for this oxidase in the early secretory compartment. We also observed that the elevation of hepatic ER luminal H2O2 levels of mice in vivo resulted in a decrease in microsomal GSH and protein-thiol contents and in a redox shift of certain luminal oxidoreductases. The oxidative wave was accompanied by reversible dilation of ER, prevented by concomitant reducing treatment. ER targeted catalase overexpressing antibody producing cells showed diminished secretion of mature antibody polymers, while incomplete antibody monomers/dimers were accumulated and/or secreted. The results indicate that local H2O2 production promotes, while quenching of H2O2 impairs disulfide formation. We published three reviews on the redox conditions in the ER. In a Hypothesis paper we proposed a new paradigm for the oxidative folding: the multiple oxidant hypothesis. In two comprehensive reviews we summarized the present knowledge on the major redox systems in the ER. We summarized the facts showing the importance of compartmentation in two other reviews

Lipotoxicity in the liver

Obesity due to excessive food intake and the lack of physical activity is becoming one of the most serious public health problems of the 21st century. With the increasing prevalence of obesity, non-alcoholic fatty liver disease is also emerging as a pandemic. While previously this pathophysiological condition was mainly attributed to triglyceride accumulation in hepatocytes, recent data show that the development of oxidative stress, lipid peroxidation, cell death, inflammation and fibrosis are mostly due to accumulation of fatty acids, and the altered composition of membrane phospholipids. In fact, triglyceride accumulation might play a protective role, and the higher toxicity of saturated or trans fatty acids seems to be the consequence of a blockade in triglyceride synthesis. Increased membrane saturation can profoundly disturb cellular homeostasis by impairing the function of membrane receptors, channels and transporters. However, it also induces endoplasmic reticulum stress via novel sensing mechanisms of the organelle's stress receptors. The triggered signaling pathways in turn largely contribute to the development of insulin resistance and apoptosis. These findings have substantiated the lipotoxic liver injury hypothesis for the pathomechanism of hepatosteatosis. This minireview focuses on the metabolic and redox aspects of lipotoxicity and lipoapoptosis, with special regards on the involvement of endoplasmic reticulum stress responses

Ascorbate-mediated electron transfer in protein thiol oxidation in the endoplasmic reticulum

AbstractAddition of, or gulonolactone oxidase-dependent in situ generation of, ascorbate provoked the oxidation of protein thiols, which was accompanied by ascorbate consumption in liver microsomal vesicles. The maximal rate of protein thiol oxidation was similar upon gulonolactone, ascorbate or dehydroascorbate addition. Cytochrome P450 inhibitors (econazole, proadifen, quercetin) decreased ascorbate consumption and the gulonolactone or ascorbate-stimulated thiol oxidation. The results demonstrate that the ascorbate/dehydroascorbate redox couple plays an important role in electron transfer from protein thiols to oxygen in the hepatic endoplasmic reticulum, even in gulonolactone oxidase deficient species

Characterization of new, efficient Mycobacterium tuberculosis topoisomerase-I inhibitors and their interaction with human ABC multidrug transporters

Drug resistant tuberculosis (TB) is a major worldwide health problem. In addition to the bacterial mechanisms, human drug transporters limiting the cellular accumulation and the pharmacological disposition of drugs also influence the efficacy of treatment. Mycobacterium tuberculosis topoisomerase-I (MtTopo-I) is a promising target for antimicrobial treatment. In our previous work we have identified several hit compounds targeting the MtTopo-I by in silico docking. Here we expand the scope of the compounds around three scaffolds associated with potent MtTopo-I inhibition. In addition to measuring the effect of newly generated compounds on MtTopo-I activity, we characterized the compounds' antimicrobial activity, toxicity in human cells, and interactions with human multidrug transporters. Some of the newly developed MtTopo-I inhibitors have strong antimicrobial activity and do not harm mammalian cells. Moreover, our studies revealed significant human ABC drug transporter interactions for several MtTopo-I compounds that may modify their ADME-Tox parameters and cellular effects. Promising new drug candidates may be selected based on these studies for further anti-TB drug development

Novel Drug-Like Somatostatin Receptor 4 Agonists are Potential Analgesics for Neuropathic Pain

Somatostatin released from the capsaicin-sensitive sensory nerves mediates analgesic and anti-inflammatory effects via the somatostatin sst4 receptor without endocrine actions. Therefore, sst4 is considered to be a novel target for drug development in pain including chronic neuropathy, which is an emerging unmet medical need. Here, we examined the in silico binding, the sst4-linked G-protein activation on stable receptor expressing cells (1 nM to 10 μM), and the effects of our novel pyrrolo-pyrimidine molecules in mouse inflammatory and neuropathic pain models. All four of the tested compounds (C1-C4) bind to the same binding site of the sst4 receptor with similar interaction energy to high-affinity reference sst4 agonists, and they all induce G-protein activation. C1 is the more efficacious (γ-GTP-binding: 218.2% ± 36.5%) and most potent (EC50: 37 nM) ligand. In vivo testing of the actions of orally administered C1 and C2 (500 µg/kg) showed that only C1 decreased the resiniferatoxin-induced acute neurogenic inflammatory thermal allodynia and mechanical hyperalgesia significantly. Meanwhile, both of them remarkably reduced partial sciatic nerve ligation-induced chronic neuropathic mechanical hyperalgesia after a single oral administration of the 500 µg/kg dose. These orally active novel sst4 agonists exert potent anti-hyperalgesic effect in a chronic neuropathy model, and therefore, they can open promising drug developmental perspectives