Verbesserung des Angiotensin II-induzierten kardialen Schadens durch die kurzkettige Fettsäure Propionat – einen Metaboliten der Darmmikrobiota

Hintergrund: Darmbakterien produzieren eine Vielzahl von Metaboliten, die durch den Wirt resorbiert werden und Auswirkungen auf dessen Physiologie haben. Kurzkettige Fettsäuren (engl. short-chain fatty acids, SCFA) wie z. B. Propionat (C3) sind Metabolite, die durch bakterielle Fermentierung aus nicht verdaulichen Polysacchariden (sogenannte Ballaststoffe oder Fasern) produziert werden. C3 ist durch seine Wirkung auf T-Zellen, insbesondere auf anti-inflammatorisch wirkende regulatorische T-Zellen (TREG), gekennzeichnet. Die essentielle Hypertonie (HTN) und der damit assoziierte kardiale Organschaden sind durch eine pro-inflammatorische Auslenkung der T-Zell-Homöostase charakterisiert. Experimentelle Strategien, welche die Funktion von TREG verbessern, vermindern bekanntermaßen den durch die HTN verursachten Endorganschaden. Die zugrundeliegende Hypothese ist somit, dass die SCFA C3 den hypertensiven kardialen Schaden positiv beeinflussen kann. Methodik: Zur Induktion der HTN in 12 Wochen alten männlichen NMRI Mäusen erfolgte die Implantation einer subkutanen osmotischen Minipumpe, die über 14 Tage 1,44mg/kg/d Angiotensin (Ang) II freisetzt. Um die intestinale bakteriellen Produktion von SCFA zu supprimieren, erhielten die Mäuse ein faserarmes Futter. Um die Effekte von C3 spezifisch zu untersuchen, wurden die Tiere entweder mit Natriumpropionat oder Natriumchlorid als Kontrolle im Trinkwasser behandelt. Die Inflammation wurde mittels Durchflusszytometrie, die kardiale Schädigung, mittels Echokardiographie, Immunfluoreszenz, Genexpressionsanalyse und in vivo elektrophysiologischer Untersuchung quantifiziert. Eine Blutdruckmessung erfolgte kontinuierlich mittels Telemetrie. TREG wurden durch anti-CD25 Antikörper (PC61) in mit Ang II infundierten C3-behandelten Mäusen depletiert, um den Wirkmechanismus von C3 aufzuklären. Ergebnisse: Die Behandlung mit C3 führte zu einem signifikant verbesserten Überleben nach 14 Tagen. C3 reduzierte sowohl die systemische inflammatorische Antwort auf Ang II, als auch die kardiale Hypertrophie und Fibrose. Begleitend kam es zu einer Reduktion der ins kardiale Gewebe infiltrierenden T-Helferzellen, zytotoxische T-Zellen und Makrophagen. Die Behandlung mit C3 bewirkte zudem einen reduzierten Anteil an Typ17-T-Helferzellen (TH17) in Herz und Milz. Dies führte zu einer reduzierten Anfälligkeit für ventrikuläre Tachyarrhythmien in C3-behandelten Mäusen. Die Verbesserung des kardialen Schadens und der Inflammation waren in TREG-depletierten Mäusen abgeschwächt. C3 führte außerdem unabhängig von der Wirkung auf TREG zu einer verzögert eintretenden, moderaten Reduktion des Blutdruckes. Schlussfolgerung: Die Daten unterstreichen die Bedeutung von aus unverdaulichen Polysacchariden gewonnenen bakteriellen Metaboliten für die kardiale Gesundheit. Die Wirkung dieser Metabolite auf TREG spielt beim kardioprotektiven Effekt von C3 eine zentrale Rolle. Die orale Gabe von C3 sowie die Förderung der intestinalen Produktion von C3 könnten eine vielversprechende Option in der Behandlung der hypertensiven Herzkrankheit darstellen.Background: Gut microbiota release a plethora of metabolites into the host and thereby affect the host physiology. Short-chain fatty acids (SCFA) such as propionate (C3) are metabolites produced from otherwise indigestible polysaccharides (so-called fiber) by bacterial fermentation in the intestine. C3 has been shown to influence immune cells, especially anti-inflammatory regulatory T cells (TREG). Essential hypertension (HTN) is characterized by a pro-inflammatory T cell response which promotes the damage to important organs such as the heart. Experimental approaches promoting TREG function have been shown to ameliorate hypertensive end-organ damage. We hypothesized that the SCFA C3 attenuates hypertensive cardiac damage. Methods: To induce hypertension in 12-week-old male NMRI mice, Angiotensin (Ang) II (1,44mg/kg/d) was infused subcutaneously for 14 days using osmotic minipumps. Mice were fed a fiber-depleted diet to suppress intestinal bacterial SCFA production. To specifically examine the effect of C3, mice were either administered sodium propionate or sodium chloride as control in drinking water. The inflammatory response was analyzed by flow cytometry. Cardiac organ damage was assessed using echocardiography, in vivo electrophysiology, and immunofluorescence. Blood pressure was measured by radiotelemetry. To assess the mode of action of C3, TREG were depleted in Ang II-infused C3-treated mice using an anti-CD25 antibody (PC61). Results: C3 treatment significantly improved survival along with a reduced inflammatory response to Ang II and ameliorated cardiac hypertrophy and fibrosis. Fewer T helper cells, cytotoxic T cells and macrophages infiltrated the hearts of C3-treated mice. C3 reduced the amount of T-helper type 17 (TH17) cells in hearts and spleens. This led to a reduced susceptibility to cardiac ventricular tachyarrhythmias. Improvement of cardiac damage and inflammation by C3 was abrogated in TREG-depleted mice. C3 had a moderate blood pressure-lowering effect confined to the second week of Ang II infusion, which was preserved in TREG-depleted mice. Conclusion: Our data highlight the importance of fiber-derived gut bacterial metabolites for cardiac health. TREG are central to the cardioprotective effect of C3 in hypertension. Treatment with C3 and/or augmentation of intestinal C3 production may prove of benefit in the treatment of hypertensive heart disease

Microscopy with undetected photons in the mid-infrared

Owing to its capacity for unique (bio)-chemical specificity, microscopy withmid-IR illumination holds tremendous promise for a wide range of biomedical and industrial applications. The primary limitation, however, remains detection; with current mid-IR detection technology often marrying inferior technical capabilities with prohibitive costs. This has lead to approaches that shift detection towavelengths into the visible regime, where vastly superior silicon-based cameratechnology is available. Here, we experimentally show how nonlinear interferometry with entangled light can provide a powerful tool for mid-IR microscopy, while only requiring near-infrared detection with a standard CMOS camera. In this proof-of-principle implementation, we demonstrate intensity imaging overa broad wavelength range covering 3.4-4.3um and demonstrate a spatial resolution of 35um for images containing 650 resolved elements. Moreover, we demonstrate our technique is fit for purpose, acquiring microscopic images of biological tissue samples in the mid-IR. These results open a new perspective for potential relevance of quantum imaging techniques in the life sciences.Comment: back-to-back submission with arXiv:2002.05956, Anna V. Paterova, Sivakumar M. Maniam, Hongzhi Yang, Gianluca Grenci, and Leonid A. Krivitsky, "Hyperspectral Infrared Microscopy With Visible Light

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

Fasting alters the gut microbiome reducing blood pressure and body weight in metabolic syndrome patients.

Periods of fasting and refeeding may reduce cardiometabolic risk elevated by Western diet. Here we show in the substudy of NCT02099968, investigating the clinical parameters, the immunome and gut microbiome exploratory endpoints, that in hypertensive metabolic syndrome patients, a 5-day fast followed by a modified Dietary Approach to Stop Hypertension diet reduces systolic blood pressure, need for antihypertensive medications, body-mass index at three months post intervention compared to a modified Dietary Approach to Stop Hypertension diet alone. Fasting alters the gut microbiome, impacting bacterial taxa and gene modules associated with short-chain fatty acid production. Cross-system analyses reveal a positive correlation of circulating mucosa-associated invariant T cells, non-classical monocytes and CD4+ effector T cells with systolic blood pressure. Furthermore, regulatory T cells positively correlate with body-mass index and weight. Machine learning analysis of baseline immunome or microbiome data predicts sustained systolic blood pressure response within the fasting group, identifying CD8+ effector T cells, Th17 cells and regulatory T cells or Desulfovibrionaceae, Hydrogenoanaerobacterium, Akkermansia, and Ruminococcaceae as important contributors to the model. Here we report that the high-resolution multi-omics data highlight fasting as a promising non-pharmacological intervention for the treatment of high blood pressure in metabolic syndrome patients

Short-Chain Fatty Acid Propionate Protects From Hypertensive Cardiovascular Damage

Arterial hypertension and its organ sequelae show characteristics of T cell–mediated inflammatory diseases. Experimental anti-inflammatory therapies have been shown to ameliorate hypertensive end-organ damage. Recently, the CANTOS study (Canakinumab Antiinflammatory Thrombosis Outcome Study) targeting interleukin-1β demonstrated that anti-inflammatory therapy reduces cardiovascular risk. The gut microbiome plays a pivotal role in immune homeostasis and cardiovascular health. Short-chain fatty acids (SCFAs) are produced from dietary fiber by gut bacteria and affect host immune homeostasis. Here, we investigated effects of the SCFA propionate in 2 different mouse models of hypertensive cardiovascular damage. Our data emphasize an immune-modulatory role of SCFAs and their importance for cardiovascular health. The data suggest that lifestyle modifications leading to augmented SCFA production could be a beneficial nonpharmacological preventive strategy for patients with hypertensive cardiovascular disease

Salt-responsive gut commensal modulates TH17 axis and disease

A Western lifestyle with high salt consumption can lead to hypertension and cardiovascular disease. High salt may additionally drive autoimmunity by inducing T helper 17 (T(H)17) cells, which can also contribute to hypertension. Induction of T(H)17 cells depends on gut microbiota; however, the effect of salt on the gut microbiome is unknown. Here we show that high salt intake affects the gut microbiome in mice, particularly by depleting Lactobacillus murinus. Consequently, treatment of mice with L. murinus prevented salt-induced aggravation of actively induced experimental autoimmune encephalomyelitis and salt-sensitive hypertension by modulating T(H)17 cells. In line with these findings, a moderate high-salt challenge in a pilot study in humans reduced intestinal survival of Lactobacillus spp., increased T(H)17 cells and increased blood pressure. Our results connect high salt intake to the gut-immune axis and highlight the gut microbiome as a potential therapeutic target to counteract salt-sensitive conditions