Inhibition of spontaneous neutrophil apoptosis by parabutoporin acts independently of NADPH oxidase inhibition but by lipid raft-dependent stimulation of Akt

Neutrophil cell death plays a crucial role in neutrophil homeostasis and the resolution of inflammation. The superoxide-producing NADPH oxidase is involved in pathogen degradation and subsequent activation of cell death programs. Neutrophils from patients with chronic granulomatous disease, who have a deficient NADPH oxidase activity, have been demonstrated previously to have a prolonged lifespan, suggesting that a basal NADPH oxidase activity also regulates spontaneous neutrophil turnover. The NADPH oxidase inhibitor parabutoporin (PP) does delay spontaneous apoptosis, but this effect is completely independent of NADPH oxidase inhibition. Instead, the prosurvival effect of PP depends on activation of protein kinase B/Akt via lipid raft signaling. Disruption of lipid rafts abrogates the prosurvival effect without interfering with NADPH oxidase activity. Furthermore, we cannot detect a different rate of spontaneous apoptosis between normal and NADPH oxidase-deficient neutrophils, arguing against a role of NADPH oxidase in spontaneous neutrophil apoptosis

Depletion of RIPK3 or MLKL blocks TNF-driven necroptosis and switches towards a delayed RIPK1 kinase-dependent apoptosis

In human cells, the RIPK1-RIPK3-MLKL-PGAM5-Drp1 axis drives tumor necrosis factor (TNF)-induced necroptosis through mitochondrial fission, but whether this pathway is conserved among mammals is not known. To answer this question, we analyzed the presence and functionality of the reported necroptotic axis in mice. As in humans, knockdown of receptorinteracting kinase-3 (RIPK3) or mixed lineage kinase domain like (MLKL) blocks TNF-induced necroptosis in L929 fibrosarcoma cells. However, repression of either of these proteins did not protect the cells from death, but instead induced a switch from TNF-induced necroptosis to receptor-interacting kinase-1 (RIPK1) kinase-dependent apoptosis. In addition, although mitochondrial fission also occurs during TNF-induced necroptosis in L929 cells, we found that knockdown of phosphoglycerate mutase 5 (PGAM5) and dynamin 1 like protein (Drp1) did not markedly protect the cells from TNF-induced necroptosis. Depletion of Pink1, a reported interactor of both PGAM5 and Drp1, did not affect TNF-induced necroptosis. These results indicate that in these murine cells mitochondrial fission and Pink1 dependent processes, including Pink-Parkin dependent mitophagy, apparently do not promote necroptosis. Our data demonstrate that the core components of the necrosome (RIPK1, RIPK3 and MLKL) are crucial to induce TNF-dependent necroptosis both in human and in mouse cells, but the associated mechanisms may differ between the two species or cell types

Drug-drug interactions between immunosuppressants and antidiabetic drugs in the treatment of post-transplant diabetes mellitus

Post-transplant diabetes mellitus is a frequent complication of solid organ transplantation that generally requires treatment with lifestyle interventions and antidiabetic medication. A number of demonstrated and potential pharmacokinetic drug-drug interactions (DDIs) exist between commonly used immunosuppressants and antidiabetic drugs, which are comprehensively summarized in this review. Cyclosporine (CsA) itself inhibits the cytochrome P450 (CYP) 3A4 enzyme and a variety of drug transporters. As a result, it increases exposure to repaglinide and sitagliptin, will likely increase the exposure to nateglinide, glyburide, saxagliptin, vildagliptin and alogliptin, and could theoretically increase the exposure to gliquidone and several sodium-glucose transporter (SGLT)-2 inhibitors. Currently available data, although limited, suggest that these increases are modest and, particularly with regard to gliptins and SGLT-2 inhibitors, unlikely to result in hypoglycemia. The interaction with repaglinide is more pronounced but does not preclude concomitant use if repaglinide dose is gradually titrated. Mycophenolate mofetil and azathioprine do not engage in DDIs with any antidiabetic drug. Although calcineurin inhibitors (CNIs) and mammalian target of rapamycin inhibitors (mTORi) are intrinsically prone to DDIs, their disposition is not influenced by metformin, pioglitazone, sulfonylureas (except possibly glyburide) or insulin. An effect of gliptins on the disposition of CNIs and mTORi is unlikely, but has not been definitively ruled out. Based on their disposition profiles, glyburide and canagliflozin could affect CNI and mTORi disposition although this requires further study. Finally, delayed gastric emptying as a result of glucagon-like peptide-1 agonists seems to have a limited, but not necessarily negligible effect on CNI disposition.publisher: Elsevier articletitle: Drug–drug interactions between immunosuppressants and antidiabetic drugs in the treatment of post-transplant diabetes mellitus journaltitle: Transplantation Reviews articlelink: http://dx.doi.org/10.1016/j.trre.2016.09.001 content_type: article copyright: © 2016 Elsevier Inc. All rights reserved.status: publishe

Reconstitution of protection against Aspergillus infection in chronic granulomatous disease (CGD)

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The antimicrobial peptide parabutoporin competes with p47(phox) as a PKC-substrate and inhibits NADPH oxidase in human neutrophils

We investigated parabutoporin (PP), an antimicrobial scorpion peptide, to understand its inhibition on NADPH oxidase in human PMN. We show that PP is a good substrate for all PKC-isotypes, implicated in the activation of NADPH oxidase, and acts as a potent competitive inhibitor of in vitro p47(phox)-phosphorylation by PKC-alpha, -beta I, -beta II and -delta, but not PKC-sigma. In PMN, PP also inhibits the PMA-stimulated phosphorylation of p47(phox) and its subsequent translocation. In contrast, PP affects the PKC-independent activation to a much lesser degree. This indicates that PP inhibits the activation of NADPH oxidase at submicromolar concentrations in a strongly PKC-dependent manner. (c) 2006 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.status: publishe