Sebastien Fuchs - Academia.edu (original) (raw)

Papers by Sebastien Fuchs

SSRN Electronic Journal, 2022

Hypertension, 2015

We previously showed that mice lacking renal angiotensin-converting enzyme (ACE) do not accumulat... more We previously showed that mice lacking renal angiotensin-converting enzyme (ACE) do not accumulate angiotensin (Ang) II in the kidney and are protected against different forms of experimental hypertension, including salt sensitivity. However, these studies did not identify the locus of renal Ang II generation. Since ACE expression is high in the renal epithelium, we hypothesize that tubular epithelial ACE is the main source of renal Ang II and, is responsible for salt sensitivity. To study this, we designed an inducible tubular ACE knockdown mouse (it-ACE) that has three transgenes: one encoding the transcription factor tTA (Tet-off transactivator) that is under the control of the KSP-cadherin promoter only expressed in renal tubular cells. The second and third transgenes are activated by tTA and encode a short-hairpin RNAs (sh-RNA) degrading ACE mRNA in renal tubules. We found a lower basal ACE expression in the kidney of it-ACE compared to WT mice (19 ± 4 vs. 100 ± 26 AU; p<0.0...

To investigate the local effects of angiotensin II on the heart, we created a mouse model with 10... more To investigate the local effects of angiotensin II on the heart, we created a mouse model with 100-fold normal cardiac angiotensin-converting enzyme (ACE), but no ACE expression in kidney or vascular endothelium. This was achieved by placing the endogenous ACE gene under the control of the �-myosin heavy chain promoter using targeted homologous recombination. These mice, called ACE 8/8, have cardiac angiotensin II levels that are 4.3-fold those of wild-type mice. Despite near normal blood pressure and a normal renal function, ACE 8/8 mice have a high incidence of sudden death. Both histological analysis and in vivo catheterization of the heart showed normal ventricular size and function. In contrast, both the left and right atria were three times normal size. ECG

Brain, 2019

Targeted overexpression of angiotensin-converting enzyme (ACE), an amyloid-β protein degrading en... more Targeted overexpression of angiotensin-converting enzyme (ACE), an amyloid-β protein degrading enzyme, to brain resident microglia and peripheral myelomonocytes (ACE10 model) substantially diminished Alzheimer’s-like disease in double-transgenic APPSWE/PS1ΔE9 (AD+) mice. In this study, we explored the impact of selective and transient angiotensin-converting enzyme overexpression on macrophage behaviour and the relative contribution of bone marrow-derived ACE10 macrophages, but not microglia, in attenuating disease progression. To this end, two in vivo approaches were applied in AD+ mice: (i) ACE10/GFP+ bone marrow transplantation with head shielding; and (ii) adoptive transfer of CD115+-ACE10/GFP+ monocytes to the peripheral blood. Extensive in vitro studies were further undertaken to establish the unique ACE10-macrophage phenotype(s) in response to amyloid-β1-42 fibrils and oligomers. The combined in vivo approaches showed that increased cerebral infiltration of ACE10 as compared t...

Hypertension, 2012

Introduction: The responses to chronic angiotensin (Ang) II infusions of gene-targeted mice lacki... more Introduction: The responses to chronic angiotensin (Ang) II infusions of gene-targeted mice lacking kidney angiotensin-converting enzyme (ACE), in terms of intrarenal Ang II accumulation, hypertension, sodium and water retention are all blunted or absent. The objective of this study was to determine if these reduced responses were associated with changes in the intrarenal renin-angiotensin system (RAS). METHODS: Mice lacking intrarenal ACE (ACE10/10) were generated by targeted homologous recombination placing the expression of ACE only in macrophages. As a result, these mice have normal circulating ACE levels, but no kidney ACE. Wild-type (WT) mice of the same background (C57Bl/J) served as controls. Mice were subjected to sham-operation or subcutaneous infusion of Ang II for two weeks (n=6-10, 400 ng/kg/min via osmotic minipump). Mean arterial pressure (MAP) was followed by telemetry. At the end of the experiment, the kidneys were collected for analysis. Ang II content was measured...

Hypertension, 2018

Angiotensin-converting enzyme (ACE) plays a key role in renal inflammation and sodium retention a... more Angiotensin-converting enzyme (ACE) plays a key role in renal inflammation and sodium retention associated with diabetic nephropathy. Although most effects of ACE have been classically related to angiotensin (Ang) II synthesis, studies highlight an Ang II-independent role of ACE in inflammation. Indeed, ACE has two catalytic domains, the N- and C-domains, that can process a wide diversity of substrates besides Ang I. Here, we study the relative contributions of ACE domains to renal inflammation and sodium retention during diabetic nephropathy. Diabetes was induced with streptozotocin in wild-type (WT) mice and mice lacking either a functional ACE N-domain (NKO) or C-domain (CKO) (n=5-8). After 6 months of diabetes, we evaluated the natriuretic response to volume expansion. For this, mice were injected with 0.9% NaCl equivalent to 10% of their body weight. After 5 hours, diabetic NKO mice excreted 30% more urinary sodium in response to the saline challenge compared to diabetic WT or ...

Journal of the American Society of Nephrology : JASN, 2018

Recent evidence emphasizes the critical role of inflammation in the development of diabetic nephr... more Recent evidence emphasizes the critical role of inflammation in the development of diabetic nephropathy. Angiotensin-converting enzyme (ACE) plays an active role in regulating the renal inflammatory response associated with diabetes. Studies have also shown that ACE has roles in inflammation and the immune response that are independent of angiotensin II. ACE's two catalytically independent domains, the N- and C-domains, can process a variety of substrates other than angiotensin I. To examine the relative contributions of each ACE domain to the sodium retentive state, renal inflammation, and renal injury associated with diabetic kidney disease, we used streptozotocin to induce diabetes in wild-type mice and in genetic mouse models lacking either a functional ACE N-domain (NKO mice) or C-domain (CKO mice). In response to a saline challenge, diabetic NKO mice excreted 32% more urinary sodium compared with diabetic wild-type or CKO mice. Diabetic NKO mice also exhibited 55% less ren...

Blood, Jul 17, 2017

Angiotensin converting enzyme (ACE) inhibitors are widely used to reduce blood pressure. Here, we... more Angiotensin converting enzyme (ACE) inhibitors are widely used to reduce blood pressure. Here, we examined if ACE is important for the antibacterial effectiveness of neutrophils. ACE knockout mice or mice treated with an ACE inhibitor were more susceptible to bacterial infection by methicillin-resistant S. aureus (MRSA). In contrast, mice over expressing ACE in neutrophils (Neu(ACE) mice) have increased resistance to MRSA, and better in vitro killing of MRSA, P. aeruginosa, and K. pneumoniae ACE overexpression increased neutrophil production of reactive oxygen species (ROS) following MRSA challenge, an effect independent of the angiotensin II AT1 receptor. Specifically, as compared to wild type mice (WT), there was a marked increase of superoxide generation (greater than 2-fold, p<0.0005) in Neu(ACE) neutrophils following infection while ACE knockout neutrophils decreased superoxide production. Analysis of membrane p47-phox and p67-phox indicates that ACE increases NADPH oxidase ...

Human molecular genetics, Jul 25, 2017

The human TM6SF2 gene has been implicated in plasma lipoprotein metabolism, alcoholic and non-alc... more The human TM6SF2 gene has been implicated in plasma lipoprotein metabolism, alcoholic and non-alcoholic fatty liver disease and myocardial infarction in multiple genome-wide association studies. To investigate the role of Tm6sf2 in metabolic homeostasis, we generated mice with elevated expression using adeno-associated virus (AAV)-mediated gene delivery. Hepatic overexpression of mouse Tm6sf2 resulted in phenotypes previously observed in Tm6sf2-deficient mice including reduced plasma lipid levels, diminished hepatic TG secretion and increased hepatosteatosis. Furthermore, increased hepatic Tm6sf2 expression protected against the development of atherosclerosis in Ldlr/ApoB48-deficient mice. In cultured human hepatocytes, Tm6sf2 overexpression reduced APOB secretion and resulted in its accumulation within the ER suggesting impaired ER-to-Golgi trafficking of pre-VLDL particles. Analysis of two metabolic trait-associated coding polymorphisms in the human TM6SF2 gene (rs58542926 and rs1...

Kidney international, Apr 14, 2016

Renal parenchymal injury predisposes to salt-sensitive hypertension, but how this occurs is not k... more Renal parenchymal injury predisposes to salt-sensitive hypertension, but how this occurs is not known. Here we tested whether renal tubular angiotensin converting enzyme (ACE), the main site of kidney ACE expression, is central to the development of salt sensitivity in this setting. Two mouse models were used: it-ACE mice in which ACE expression is selectively eliminated from renal tubular epithelial cells; and ACE 3/9 mice, a compound heterozygous mouse model that makes ACE only in renal tubular epithelium from the ACE 9 allele, and in liver hepatocytes from the ACE 3 allele. Salt sensitivity was induced using a post L-NAME salt challenge. While both wild-type and ACE 3/9 mice developed arterial hypertension following three weeks of high salt administration, it-ACE mice remained normotensive with low levels of renal angiotensin II. These mice displayed increased sodium excretion, lower sodium accumulation, and an exaggerated reduction in distal sodium transporters. Thus, in mice wi...

Alzheimer's & Dementia, 2014

development of experimental autoimmune encephalomyelitis (EAE) in rats and to elucidate its under... more development of experimental autoimmune encephalomyelitis (EAE) in rats and to elucidate its underlying mechanisms. Methods: EAE model was induced by immunization of adult female Lewis rats with purified guineapig myelin basic protein (MBP)68-86. CIG and EF were administrated intragastrically once a day after immunization until day 21 post immunization (p.i.). Histopathological staining, enzyme-linked immunosorbent assay (ELISA), biochemical methods and western blotting approaches were used to evaluate the disease incidence and severity, neuroinflammatory and neurotrophic response in the central nervous system (CNS). Results: CIG or EF intragastrical administration significantly reduced clinical score of neurological deficit in EAE rats; alleviated demyelination and inflammatory infiltration; and inhibited glias activation, nuclear transcription factor (NF-kB) expression in the spinal cord of EAE rats. Treatment with CIG or EF also enhanced neurotrophic factors such as nerve growth factor (NGF) or brain-derived nerve factor (BDNF) expression, increased the number of oligodendrocytes and protected the ultrastructure of myelin sheaths and axons in the spinal cord of EAE rats. Conclusions: Our results showed that CIG and EF could inhibit the development of MBP-induced EAE in rats and our findings suggest that traditional Chinese medicine with reinforcing kidney activity may be useful for the treatment of multiple sclerosis. This effect involved reducing neuroinflammation and enhancing myelination and neurotrophins.

Nature Medicine, 2010

Researchers have long known that the peptide angiotensin II is central to blood pressure control-... more Researchers have long known that the peptide angiotensin II is central to blood pressure control-but there is yet more to learn. A new study shows how angiotensin II cooperates with the JAK2 kinase, better known for its role in cytokine signaling, to regulate blood vessel contraction and influence blood pressure.

Molecular and Cellular Endocrinology, 2004

Clinical observations indicate that elevated aldosterone impairs cardiovascular function. The mec... more Clinical observations indicate that elevated aldosterone impairs cardiovascular function. The mechanisms, however, are not totally understood although total and cardiovascular mortality are decreased by aldosterone antagonists. Experimentally, increased plasma aldosterone induces pericoronary inflammation and cardiac fibrosis. Our laboratory has discovered that aldosterone is synthesized in the rat heart, and has demonstrated that this cardiac aldosterone is involved in post-infarction cardiac remodeling. In man, activated cardiac aldosterone production has been described in patients with heart failure. In transgenic mice that overexpress aldosterone-synthase in the heart, we observe a normal cardiac function but a major coronary dysfunction, more pronounced in males. These observations converge to a potential physiological and pathological relevance of this system. Beneficial effects of anti-aldosterone treatment in heart failure may thus be secondary in part to blockade of cardiac aldosterone action.

Journal of the American Society of Nephrology, 2005

Journal of Molecular Medicine, 2013

Angiotensin converting enzyme (ACE) is best known for the catalytic conversion of angiotensin I t... more Angiotensin converting enzyme (ACE) is best known for the catalytic conversion of angiotensin I to angiotensin II. However, the use of gene-targeting techniques has led to mouse models highlighting many other biochemical properties and actions of this enzyme. This review discusses recent studies examining the functional significance of ACE tissue-specific expression and the presence in ACE of two independent catalytic sites with distinct substrates and biological effects. It is these features which explain why ACE makes important contributions to many different physiological processes including renal development, blood pressure control, inflammation and immunity.

Journal of Cellular Biochemistry, 2007

The regulation of renin gene expression is thought to be fundamental to regulation of the total r... more The regulation of renin gene expression is thought to be fundamental to regulation of the total renin-angiotensin system. The human renin gene contains a direct repeat (DR) motif AGGGGTCAC-AGGGCCA in the proximal region (-259/-245 bp), which contains nuclear receptor superfamily binding core motif, AGGTCA, and is the most similar to COUP-TFII consensus. The DR motif was evaluated as a functional ciselement with renal cortex and chorio-decidual cells by footprint assay, electromobility shift assay (EMSA) and reporter assay. The DR motif site was protected by footprint analysis with a clear hypersensitive and a minor hypersensitive region in good accordance with the DR of the consensus. One of the binding proteins was strongly suspected to be COUP-TFII-consensus-specific by EMSA. The DNA/protein complexes obtained with nuclear extract of renin producing cells could be completely blocked by homologous competitor and strongly blocked by the second-half mutant oligonucleotide of the DR motif but not by the first-half mutant oligonucleotide. Finally, the transcriptional activity of second-half mutant construct is slightly elevated and that firsthalf mutant construct is significantly stronger by 2-fold compared with wild type construct in reporter assay. These findings suggest that the DR motif site of the human renin gene functions as a negative regulatory element involved in a 2-fold repression of transcription and that member (s) of nucleic receptor superfamily bind the site and play important roles in the human renin gene expression with a possibility that one of the binding protein is COUP-TFII.

Journal of Biological Chemistry, 1998

Osteocalcin gene expression is initiated perinatally and is restricted to mature osteoblasts and ... more Osteocalcin gene expression is initiated perinatally and is restricted to mature osteoblasts and odontoblasts. Because their pattern of expression is highly restricted, the osteocalcin genes are excellent tools to study osteoblast-specific gene expression. To define the mechanisms of osteocalcin cell-specific gene expression in vivo, we generated transgenic mice harboring deletion mutants of the promoter region of OG2, one of the mouse osteocalcin genes. We show here that only 647 base pairs of this promoter are sufficient to confer cellspecific and time-specific expression to a reporter gene in vivo. This promoter fragment contains two copies of OSE2. This osteoblast-specific cis-acting element binds Osf2, a recently characterized osteoblast-specific transcription factor (Ducy, P., Zhang, R., Geoffroy, V., Ridall, A. L., and Karsenty, G. (1997) Cell 89, 747-754). We also demonstrate that the proximal OSE2 element is critical to confer an osteoblast-specific, developmentally regulated pattern of expression to a reporter gene. The other OSE2 element, located more upstream and presenting a lower affinity for Osf2, affects only weakly OG2 promoter activity. These data demonstrate the crucial role of Osf2 in controlling osteocalcin gene expression. Since osteocalcin synthesis is a hallmark of the differentiated osteoblast phenotype, these results suggest that, beyond its developmental function, Osf2 is also required for the maintenance of the osteoblast phenotype postnatally.