Biology subjects

Santos, R. A. S.

Publications and source records attributed to Santos, R. A. S..

4 recordsLinked to original sources

bioRxiv2026

Insular hemorrhagic stroke in mice: a model of neurocardiac dysfunction

BackgroundInsular damage leads to marked cardiovascular alterations and the mechanisms need to be understood. Mouse models provide unique opportunities to gain insights into pathophysiological mechanisms. Here, we evaluated the effects of rilmenidine, a centrally acting antihypertensive drug, on the cardiac functional parameters and cardiac inflammatory cell infiltration in a newly developed mice model of insular hemorrhagic stroke. MethodsC57BL/6J mice were instrumented for injection of blood or vehicle into the insular cortex (IC). Immediately after IC stroke induction, separate groups received intraperitoneal treatment with vehicle (0.9% NaCl, 0.1 mL/100 g) or rilmenidine (10 g/kg) for three days. Electrocardiogram recording,cardiac catecholamine levels and myocardial accumulation of immune cells were evaluated. ResultsMice subjected to hemorrhagic stroke exhibited higher baseline heart rate (HR) (control: 296 {+/-} 33 bpm vs. stroke: 349 {+/-} 38 bpm; P < 0.01) and prolonged QTc interval (control: 89 {+/-} 11 ms vs. stroke: 100 {+/-} 7 ms; P < 0.01). Stroke also increased cardiac norepinephrine levels (control: 9 {+/-} 4 ng/mg vs. stroke: 25 {+/-} 14 ng/mg; P < 0.05), as well as the number of myocardial CD68+ macrophages (control: 7 {+/-} 4 vs. stroke: 16 {+/-} 6 cells/field; P < 0.0001) and Ly6G+ neutrophils (control: 0.5 {+/-} 0.7 vs. stroke: 1.5 {+/-} 1 cells/field; P < 0.001). Rilmenidine treatment markedly prevented all major stroke- induced myocardial functional and inflammatory changes ConclusionsInsular hemorrhagic stroke in mice induces centrally mediated cardiac noradrenergic hyperactivation accompanied by myocardial accumulation of immune cells. These findings support the relevance of this murine model for investigating mechanisms associated with insular stroke.

physiology↗

bioRxiv2026

Unravelling the memory of the extracellular matrix using MASH-derived decellularized scaffolds

The use of decellularized diseased livers in regenerative medicine is a promising approach for eliminating organ shortages. Bioengineering studies have shown that ECM can impact cell physiology, inducing cell activation, function, and ECM deposition, which suggests that the ECM has a "memory" that is involved in the outcome after recellularization. However, the effect of diseased ECM memory on new cells in vitro and in vivo has not been thoroughly investigated. Since it has been increasingly recognized that liver ECM changes due to different factors, it is comprehensively that diseased ECM obtained from discarded organs will ensure a distinct environment and impact cell survival and physiology. Thus, we aimed at investigating the impact of the memory of diseased ECM obtained from metabolic dysfunction-associated steatohepatitis (MASH)-derived organs on steatohepatitis establishment. To address this aim, we explored decellularized ECM obtained from rats and humans with MASH in different contexts. First, MASH ECM was characterized and then submitted to transplantation to investigate whether a MASH-derived ECM could be used as a scaffold for transplantation and to promote steatohepatitis features in control animals. Histological analysis revealed that the MASH-ECM was completely recellularized after transplantation in both control and MASH recipient rats. However, steatosis and fibrosis were observed in MASH ECM after transplantation in both groups. Molecular analysis showed that MASH ECM stimulates de novo lipogenesis and fibrosis 30 days after transplantation. Untargeted metabolomic analysis revealed that cells grown on MASH ECM had a similar metabolic profile, even when transplanted into healthy or MASH recipient rats. In addition, we observed that MASH ECM promoted impaired lipid oxidation and mitochondrial dysfunction when transplanted into healthy recipients. Altered lipid turnover and inflammatory signaling were observed in MASH ECM transplanted in MASH recipients. In vitro analysis revealed that MASH ECM induced lipid accumulation in HepG2 cells after 10 days of culture. Calcium signalling experiments obtained from HepG2 cells cultured in MASH ECM showed a lower response to ATP, a reduced calcium signalling amplitude, and a distinct response profile than that observed in healthy ECM. On the other hand, a diseased human-derived ECM could still provide an environment that allows cell development. Taken together, our data showed that MASH ECM impacts cell metabolism, promoting steatohepatitis maintenance. In conclusion, our data confirm that diseased ECM memory can impact cell physiology contributing to disease progression.

physiology↗

bioRxiv2024

Angiotensin-(1-5) is a Potent Endogenous Angiotensin AT2-Receptor Agonist

BackgroundThe renin-angiotensin system involves many more enzymes, receptors and biologically active peptides than originally thought. With this study, we investigated whether angiotensin-(1-5) [Ang-(1-5)], a 5-amino acid fragment of angiotensin II, has biological activity, and through which receptor it elicits effects. MethodsThe effect of Ang-(1-5) (1{micro}M) on nitric oxide release was measured by DAF-FM staining in human aortic endothelial cells (HAEC), or Chinese Hamster Ovary (CHO) cells stably transfected with the angiotensin AT2-receptor (AT2R) or the receptor Mas. A potential vasodilatory effect of Ang-(1-5) was tested in mouse mesenteric and human renal arteries by wire myography; the effect on blood pressure was evaluated in normotensive C57BL/6 mice by Millar catheter. These experiments were performed in the presence or absence of a range of antagonists or inhibitors or in AT2R-knockout mice. Binding of Ang-(1-5) to the AT2R was confirmed and the preferred conformations determined by in silico docking simulations. The signaling network of Ang-(1-5) was mapped by quantitative phosphoproteomics. ResultsKey findings included: (1) Ang-(1-5) induced activation of eNOS by changes in phosphorylation at Ser1177eNOS and Tyr657eNOS and thereby (2) increased NO release from HAEC and AT2R-transfected CHO cells, but not from Mas-transfected or non-transfected CHO cells. (3) Ang-(1-5) induced relaxation of preconstricted mouse mesenteric and human renal arteries and (4) lowered blood pressure in normotensive mice - effects which were respectively absent in arteries from AT2R-KO or in PD123319-treated mice and which were more potent than effects of the established AT2R-agonist C21. (5) According to in silico modelling, Ang-(1-5) binds to the AT2R in two preferred conformations, one differing substantially from where the first five amino acids within angiotensin II bind to the AT2R. (6) Ang-(1-5) modifies signaling pathways in a protective RAS-typical way and with relevance for endothelial cell physiology and disease. ConclusionsAng-(1-5) is a potent, endogenous AT2R-agonist.

pharmacology and toxicology↗

bioRxiv2024

Evidence that the monoamine oxidase B (MAO-B) plays a central role in the inotropic dysfunction induced by genetic deletion of the Mas-related-G protein-coupled receptor D (MrgD) in mice

The renin-angiotensin system (RAS) plays a critical role in the regulation of the cardiovascular system. The Mas-related G protein receptor member D (MrgD) is the receptor of alamandine, and both are components of the RAS noncanonical arm. Alamandine/MrgD induces vasodilation, anti-inflammatory, anti-fibrotic and anti-oxidative effects. In contrast, Mrgd gene deletion leads to a remarkable dilated cardiomyopathy (DCM) in mice. Here, we aimed to investigate the molecular mechanisms of DCM triggered by the deletion of MrgD in the left ventricle and isolated ventricular cardiomyocytes from 8-12 weeks old mice using phosphoproteomics. Our findings revealed an increased oxidative stress not caused by angiotensin II/AT1 hyperactivation but instead due to the up-regulation of the monoamine oxidase B (MAO-B), leading to a higher catabolism of dopamine and epinephrine in the MrgD-KO cardiac tissues. The oxidative environment induced by MAO-B hyperactivation seems to be the cause of the observed alteration in ionic dynamics - altered Ca2+ transient and Na+/K+-ATPase activity - leading to altered resting membrane potential (RMP) and decreased contraction of MrgD-KO cardiomyocytes. In addition, cardiac Troponin-I phosphorylation, and Titin dephosphorylation seem to contribute to the contractile dysfunction observed in MrgD-KO. The treatment of cardiomyocytes from MrgD-KO mice with the MAO-B inhibitor Pargyline reverted the observed impaired contraction, corroborating the hypothesis that MAO-B hyperactivation is, at least partially, the cause of the failing heart observed in MrgD-KO mouse. The findings reported here provide important insights into the pathogenesis of heart failure and suggest a potential therapeutic target (MrgD activation) for managing failing hearts.

physiology↗