Pflugers Archiv : European journal of physiology最新文献

Sphingosine-1-phosphate (S1P) is a ubiquitous lipid mediator, acting via specific G-protein-coupled receptors (GPCR) and intracellularly. Previous work has shown that deletion of S1P lyase caused a chronic elevation of cytosolic [Ca²⁺]_i and enhanced Ca²⁺ storage in mouse embryonic fibroblasts. Here, we studied the role of sphingosine kinase (SphK)-1 in Ca²⁺ signaling, using two independently generated EA.hy926 cell lines with stable knockdown of SphK1 (SphK1-KD1/2). Resting [Ca²⁺]_i and thapsigargin-induced [Ca²⁺]_i increases were reduced in both SphK1-KD1 and -KD2 cells. Agonist-induced [Ca²⁺]_i increases, measured in SphK1-KD1, were blunted. In the absence of extracellular Ca²⁺, thapsigargin-induced [Ca²⁺]_i increases declined rapidly, indicating enhanced removal of Ca²⁺ from the cytosol. In agreement, plasma membrane Ca²⁺ ATPase (PMCA)-1 and -4 and their auxiliary subunit, basigin, were strongly upregulated. Activation of S1P-GPCR by specific agonists or extracellular S1P did not rescue the effects of SphK1 knockdown, indicating that S1P-GPCR were not involved. Lipid measurements indicated that not only S1P but also dihydro-sphingosine, ceramides, and lactosylceramides were markedly depleted in SphK1-KD2 cells. SphK2 and S1P lyase were upregulated, suggesting enhanced flux via the sphingolipid degradation pathway. Finally, histone acetylation was enhanced in SphK1-KD2 cells, and the histone deacetylase inhibitor, vorinostat, induced upregulation of PMCA1 and basigin on mRNA and protein levels in EA.hy926 cells. These data show for the first time a transcriptional regulation of PMCA1 and basigin by S1P metabolism. It is concluded that SphK1 knockdown in EA.hy926 cells caused long-term alterations in cellular Ca²⁺ homeostasis by upregulating PMCA via increased histone acetylation.

Chronic kidney disease (CKD) is a multifactorial condition with diverse etiologies, such as diabetes mellitus, hypertension, and genetic disorders, often culminating in end-stage renal disease (ESRD). A hallmark of CKD progression is kidney fibrosis, characterized by the excessive accumulation of extracellular matrix components, for which there is currently no effective anti-fibrotic therapy. Recent literature highlights the critical role of sphingosine 1-phosphate (S1P) signaling in CKD pathogenesis and renal fibrosis. This review provides an in-depth analysis of the latest findings on S1P metabolism and signaling in renal fibrosis and in specific CKDs, including diabetic nephropathy (DN), lupus nephritis (LN), focal segmental glomerulosclerosis (FSGS), Fabry disease (FD), and IgA nephropathy (IgAN). Emerging studies underscore the therapeutic potential of modulating S1P signaling with receptor modulators and inhibitors, such as fingolimod (FTY720) and more selective agents like ozanimod and cenerimod. Additionally, the current knowledge about the effects of established kidney protective therapies such as glucocorticoids and SGLT2 and ACE inhibitors on S1P signaling will be summarized. Furthermore, the review highlights the potential role of S1P as a biomarker for disease progression in CKD models, particularly in Fabry disease and diabetic nephropathy. Advanced technologies, including spatial transcriptomics, are further refining our understanding of S1P's role within specific kidney compartments. Collectively, these insights emphasize the need for continued research into S1P signaling pathways as promising targets for CKD treatment strategies.

Chronic unpredictable and unavoidable stress is associated with mental health problems such as depression and anxiety, whereas cycles of stress and stress relief strengthen resilience. It has been suggested that increased breakdown of brain endocannabinoids (eCB) promotes a feeling of adversity. To assess the impact of stress on bioactive lipid homeostasis, we analyzed eCB, sphingolipids, and ceramides in seven brain regions and plasma in a mouse model of chronic unpredictable mild stress. Chronic unpredictable mild stress (CUMS) was associated with low levels of anandamide in hippocampus and prefrontal cortex in association with indicators of anxiety (elevated plus maze). Oppositely, CUMS caused elevated levels of sphingosine-1-phosphate (S1P d18:1) and sphinganine-1-phosphate (S1P d18:0) in the midbrain and thalamus, which was associated with readouts of increased stress resilience, i.e., marble burying and struggling in the tail suspension tests. In the periphery, elevated plasma levels of ceramides revealed similarities with human major depression and suggested unfavorable effects of stress on metabolism, but plasma lipids were not associated with body weight, sucrose consumption, or behavioral features of depression or anxiety. The observed brain site-specific lipid changes suggest that the forebrain succumbs to adverse stress effects while the midbrain takes up defensive adjustments.

Major depressive disorder (MDD) is a common and severe psychiatric disease, which does not only lead to variety of neuropsychiatric symptoms, but unfortunately in a relatively large proportion of cases also to suicide. The pathogenesis of MDD still requires definition. We have previously shown that ceramide is increased in the blood plasma of patients with MDD. In mouse models of MDD, which are induced by treatment with corticosterone or application of chronic unpredictable stress, increased blood plasma ceramide also increased and caused an inhibition of phospholipase D in endothelial cells of the hippocampus and reduced phosphatidic acid levels in the hippocampus. Here, we demonstrated that corticosterone treatment of PC12 cells resulted in reduced cellular autophagy, which is corrected by treatment with phosphatidic acid. In vivo, treatment of mice with corticosterone or chronic unpredictable stress also reduced autophagy in hippocampus neurons. Autophagy was normalized upon i.v. injection of phosphatidic acid in these mouse models of MDD. In an attempt to identify targets of phosphatidic acid in neurons, we demonstrated that corticosterone reduced levels of the ganglioside GM1 in PC-12 cells and the hippocampus of mice, which were normalized by treatment of cells or i.v. injection of mice with phosphatidic acid. GM1 application also normalized autophagy in cultured neurons. Phosphatidic acid and GM1 corrected stress-induced alterations in behavior, i.e., mainly anxiety and anhedonia, in experimental MDD in mice. Our data suggest that phosphatidic acid may regulate via GM1 autophagy in neurons.

Human 5-lipoxygenase (5-LO) is the key enzyme in the biosynthesis of leukotrienes, mediators of the innate immune system that also play an important role in inflammatory diseases and cancer. In this study, we present compounds, containing a Michael-reactive cyanoacrylate moiety as potent inhibitors of 5-LO. Representatives of the tyrosine kinase inhibitor family called tyrphostins, structurally related to known 5-LO inhibitors, were screened for their 5-LO inhibitory properties using recombinant human 5-LO, intact human PMNL (polymorphonuclear leukocytes), and PMNL homogenates. Their mode of action was characterized by the addition of glutathione, using a fourfold cysteine 5-LO mutant and mass spectrometry analysis. SAR studies revealed several members of the tyrphostin family containing a Michael-reactive cyanoacrylate to efficiently inhibit 5-LO. We identified degrasyn (IC₅₀ 0.11 µM), tyrphostin A9 (IC₅₀ 0.8 µM), AG879 (IC₅₀ 78 nM), and AG556 (IC₅₀ 64 nM) as potent 5-LO inhibitors. Mass spectrometry analysis revealed that degrasyn and AG556 covalently bound to up to four cysteines, including C416 and/or C418 which surround the substrate entry site. Furthermore, the 5-LO inhibitory effect of degrasyn was remarkably impaired by the addition of glutathione or by the mutation of cysteines to serines at the surface of 5-LO. We successfully identified several tyrphostins as potent inhibitors of human 5-LO. Degrasyn and AG556 were able to covalently bind to 5-LO via their cyanoacrylate moiety. This provides a promising mechanism for targeting 5-LO by Michael acceptors, leading to new therapeutic opportunities in the field of inflammation and cancer.

Necroptosis is a regulated form of cell death with implications in various physiological and pathological processes in multiple tissues. However, the relevant findings from post-mitotic tissues, such as skeletal muscle, are scarce. This review summarizes the potential contributions of necroptosis to skeletal muscle health and diseases. It first discusses the physiological roles of necroptosis in muscle regeneration and development. It then summarizes the contributions of necroptosis to the pathogenesis of multiple muscle diseases, including muscular dystrophies, inflammatory myopathies, cachexia, and neuromuscular disorders. Lastly, it unravels the gaps in our understanding and therapeutic challenges of inhibiting necroptosis as a potential intervention for muscle diseases. Specifically, the findings from the transgenic animal models and the use of pharmacological inhibitors of necroptosis are discussed with relevance to improving the structure and/or function of skeletal muscle in various diseases. Recent developments from experimental animal models and clinical data are presented to discuss the roles of necroptosis in skeletal muscle health and diseases.