Statins Reverse Postpartum Cardiovascular Dysfunction in a Rat Model of Preeclampsia.

Preeclampsia is associated with increased cardiovascular long-term risk; however, the underlying functional and structural mechanisms are unknown. We investigated maternal cardiac alterations after preeclampsia. Female rats harboring the human angiotensinogen gene [TGR(hAogen)L1623] develop a preeclamptic phenotype with hypertension and albuminuria during pregnancy when mated with male rats bearing the human renin gene [TGR(hRen)L10J] but behave physiologically normal before and after pregnancy. Furthermore, rats were treated with pravastatin. We tested the hypothesis that statins are a potential therapeutic intervention to reduce cardiovascular alterations due to simulated preeclamptic pregnancy. Although hypertension persists for only 8 days in pregnancy, former preeclampsia rats exhibit significant cardiac hypertrophy 28 days after pregnancy observed in both speckle tracking echocardiography and histological staining. In addition, fibrosis and capillary rarefaction was evident. Pravastatin treatment ameliorated the remodeling and improved cardiac output postpartum. Preeclamptic pregnancy induces irreversible structural changes of cardiac hypertrophy and fibrosis, which can be moderated by pravastatin treatment. This pathological cardiac remodeling might be involved in increased cardiovascular risk in later life

NCX1 represents an ionic Na+ sensing mechanism in macrophages

Inflammation and infection can trigger local tissue Na(+)accumulation. This Na+-rich environment boosts proinflammatory activation of monocyte/macrophage-like cells (M phi s) and their antimicrobial activity. Enhanced Na+-driven M phi function requires the osmoprotective transcription factor nuclear factor of activated T cells 5 (NFAT5), which augments nitric oxide (NO) production and contributes to increased autophagy. However, the mechanism of Na(+)sensing in M phi s remained unclear. High extracellular Na(+)levels (high salt [HS]) trigger a substantial Na(+)influx and Ca(2+)loss. Here, we show that the Na+/Ca(2+)exchanger 1 (NCX1, also known as solute carrier family 8 member A1 [SLC8A1]) plays a critical role in HS-triggered Na(+)influx, concomitant Ca(2+)efflux, and subsequent augmented NFAT5 accumulation. Moreover, interfering with NCX1 activity impairs HS-boosted inflammatory signaling, infection-triggered autolysosome formation, and subsequent antibacterial activity. Taken together, this demonstrates that NCX1 is able to sense Na(+)and is required for amplifying inflammatory and antimicrobial M phi responses upon HS exposure. Manipulating NCX1 offers a new strategy to regulate M phi function

Immunometabolismus cum grano salis: Untersuchung des Effektes von Hochsalz auf den frühen Stoffwechsel von M(LPS) und M(IL4+IL13) Makrophagen

In order to fulfill their function immune cells tightly regulate their central carbon metabolism depending on the microenvironment they encounter. Fully activated classic M1 macrophages are known to increase glycolysis and pentose phosphate pathway, while repurposing their tricarboxylic acid (TCA) cycle and electron transport chain (ETC), away from energy production towards the generation of pro-inflammatory mediators. On the other hand, fully-activated alternative M2 macrophages highly depend on intact TCA cycling and oxidative phosphorylation (OXPHOS). One important factor of local microenvironment is sodium. Dietary salt, local infection and aging can induce accumulation of high amounts of sodium (without concomitant water retention) in tissues. Immune cells residing or invading such hypertonic saline compartments are differentially regulated and exhibit an altered function. Interestingly, it has been shown that HS boosts macrophage bacterial killing capacity after only 4h, a time point rarely studied in regards to immune cell metabolism. Based on these data, we hypothesized that high extracellular sodium affects the central carbon metabolism of murine and human mononuclear phagocyte cells. Here we show that upon stimulation, M(LPS) and M(IL4+IL13) macrophages very quickly show an induction of respective pro-inflammatory and anti-inflammatory marker genes, which only partially further increase over time. Furthermore, activation under hypertonic saline (+40mM NaCl, HS) conditions had immediate effects on marker gene expression. Surprisingly, anaerobic glycolysis, the main M1-associated energy source, was not affected by HS at this early stage of activation. We therefore analyzed TCA cycle and OXPHOS by pulsed stable isotope resolved metabolomics (pSIRM) and Seahorse technology. At 3h of activation, glucose- and glutamine-derived label incorporation into the TCA cycle were not affected by HS. Only the conversion of succinate into fumarate was inhibited upon HS in both M(LPS) and M(IL4+IL13). By contrast, Seahorse analysis revealed a significant decrease in basal and maximal oxygen consumption rate (OCR) under HS in both M(LPS) and M(IL4+IL13). This reduction was accompanied by a decrease in ATP production and mitochondrial membrane potential after only 3h of activation. These data suggest a mitochondrial dysfunction and metabolic uncoupling of TCA cycle and mitochondrial respiration under HS. We could show that HS inhibited ETC complex III and that pharmacologic inhibition of complex III as well as pharmacologic uncoupling mimicked the HS effect on macrophage phenotype. In a translational approach in healthy individuals, we demonstrated that dietary salt intake resulted in a significant increase in plasma sodium. Strikingly, this increase correlated with a decrease in mitochondrial function in peripheral blood-derived monocytes. Taken together, we suggest that HS induces a mitochondrial dysfunction in murine macrophages and human monocytes. This could constitute a novel mechanism by which HS modulates murine and human immune cell function

Atp6ap2 deletion causes extensive vacuolation that consumes the insulin content of pancreatic β cells

Pancreatic β cells store insulin within secretory granules which undergo exocytosis upon elevation of blood glucose levels. Crinophagy and autophagy are instead responsible to deliver damaged or old granules to acidic lysosomes for intracellular degradation. However, excessive consumption of insulin granules can impair β cell function and cause diabetes. Atp6ap2 is an essential accessory component of the vacuolar ATPase required for lysosomal degradative functions and autophagy. Here, we show that Cre recombinase-mediated conditional deletion of Atp6ap2 in mouse β cells causes a dramatic accumulation of large, multigranular vacuoles in the cytoplasm, with reduction of insulin content and compromised glucose homeostasis. Loss of insulin stores and gigantic vacuoles were also observed in cultured insulinoma INS-1 cells upon CRISPR/Cas9-mediated removal of Atp6ap2. Remarkably, these phenotypic alterations could not be attributed to a deficiency in autophagy or acidification of lysosomes. Together, these data indicate that Atp6ap2 is critical for regulating the stored insulin pool and that a balanced regulation of granule turnover is key to maintaining β cell function and diabetes prevention

Salt Transiently Inhibits Mitochondrial Energetics in Mononuclear Phagocytes

BACKGROUND: Dietary high salt (HS) is a leading risk factor for mortality and morbidity. Serum sodium transiently increases postprandially but can also accumulate at sites of inflammation affecting differentiation and function of innate and adaptive immune cells. Here, we focus on how changes in extracellular sodium, mimicking alterations in the circulation and tissues, affect the early metabolic, transcriptional, and functional adaption of human and murine mononuclear phagocytes. METHODS: Using Seahorse technology, pulsed stable isotope-resolved metabolomics, and enzyme activity assays, we characterize the central carbon metabolism and mitochondrial function of human and murine mononuclear phagocytes under HS in vitro. HS as well as pharmacological uncoupling of the electron transport chain under normal salt is used to analyze mitochondrial function on immune cell activation and function (as determined by Escherichia coli killing and CD4(+) T cell migration capacity). In 2 independent clinical studies, we analyze the effect of a HS diet during 2 weeks (URL: http://www.clinicaltrials.gov.Unique identifier: NCT02509962) and short-term salt challenge by a single meal (URL: http://www.clinicaltrials.gov.Unique identifier: NCT04175249) on mitochondrial function of human monocytes in vivo. RESULTS: Extracellular sodium was taken up into the intracellular compartment, followed by the inhibition of mitochondrial respiration in murine and human macrophages. Mechanistically, HS reduces mitochondrial membrane potential, electron transport chain complex II activity, oxygen consumption, and ATP production independently of the polarization status of macrophages. Subsequently, cell activation is altered with improved bactericidal function in HS-treated M1-like macrophages and diminished CD4(+) T cell migration in HS-treated M2-like macrophages. Pharmacological uncoupling of the electron transport chain under normal salt phenocopies HS-induced transcriptional changes and bactericidal function of human and murine mononuclear phagocytes. Clinically, also in vivo, rise in plasma sodium concentration within the physiological range reversibly reduces mitochondrial function in human monocytes. In both a 14-day and single meal HS challenge, healthy volunteers displayed a plasma sodium increase of (x) over tilde = 2mM and (x) over tilde = 2.3mM, respectively, that correlated with decreased monocytic mitochondrial oxygen consumption. CONCLUSIONS: Our data identify the disturbance of mitochondrial respiration as the initial step by which HS mechanistically influences immune cell function. Although these functional changes might help to resolve bacterial infections, a shift toward proinflammation could accelerate inflammatory cardiovascular disease