Marco Antônio Peliky Fontes

Background: Insular 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. Methods: C57BL/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 μg/kg) for three days. Electrocardiogram recording,cardiac catecholamine levels and myocardial accumulation of immune cells were evaluated. Results: Mice 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 Conclusions: Insular 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.

BACKGROUND: The renin-angiotensin system comprises a biochemical cascade that hydrolyzes angiotensinogen into several different bioactive peptides, which can activate different receptors, promoting plenty of specific effects. This study aimed to evaluate the presence of the putative product of alamandine, the pentapeptide Ala-(1-5) (alamandine-[1-5]), in the circulation and its biological activity. METHODS: To accomplish this, we have used mass spectrometry (Matrix-assisted Laser Desorption/Ionization Time-of-Flight/Time-of-Flight mass spectrometry [MALDI/TOF/TOF], Liquid Chromatography-Tandem Mass Spectrometry [LC-MS/MS]) and several methodologies, including isolated blood vessels, isolated perfused hearts, isolated cardiomyocytes, blood pressure recording in freely moving normotensive and spontaneously hypertensive rats, high-resolution echocardiography, central administration (intracerebroventricular infusion and microinjection in the insular cortex), cell culture (endothelial cells and G-protein–coupled receptors-transfected Chinese Hamster Ovary cells), and wild-type and Mas (Mas receptor proto-oncogene), MrgD (Mas-related G-protein–coupled receptor subtype D), or AT2 (angiotensin II type 2) receptor-deficient mice. RESULTS: We show that Ala-(1-5) is present in the circulation of healthy humans and rodents and promotes many biological central and peripheral actions. A major role for ACE (angiotensin-converting enzyme) activity in the formation of Ala-(1-5) from alamandine in the circulation was observed using plasma samples from angiotensinogen-knockout mice. Ala-(1-5) increases baroreflex sensitivity and produces a long-lasting (≈6 hours) antihypertensive effect in spontaneously hypertensive rats, associated with a significant reduction in cardiac output. Additionally, Ala-(1-5) decreases inotropism in isolated perfused hearts and reduces contractility in cardiomyocytes. In Chinese Hamster Ovary cells-transfected cells, Ala-(1-5) can bind and stimulate NO production through all receptors from the renin-angiotensin system protective arm (Mas, MrgD, and AT ₂ receptors). On the other hand, the Ala-(1-5) effects on cardiomyocytes and mouse aortic rings were abolished only by MrgD genetic deletion, but not by Mas or AT2 receptor knockout. CONCLUSIONS: Our data demonstrate that Ala-(1-5) is a newly identified peptide within the renin-angiotensin system, with strong blood pressure–lowering effects that vary in mechanisms of action among different tissues. Ala-(1-5) has distinct characteristics that differentiate it from the conventional renin-angiotensin system pathways responsible for reducing blood pressure.

Purpose Evidence from animal and human studies demonstrates that cortical regions play a key role in autonomic modulation with a differential role for some brain regions located in the left and right brain hemispheres. Known as autonomic asymmetry, this phenomenon has been demonstrated by clinical observations, by experimental models, and currently by combined neuroimaging and direct recordings of sympathetic nerve activity. Previous studies report peculiar autonomic-mediated cardiovascular alterations following unilateral damage to the left or right insula, a multifunctional key cortical region involved in emotional processing linked to autonomic cardiovascular control and featuring asymmetric characteristics. Methods Based on clinical studies reporting specific damage to the insular cortex, this review aims to provide an overview of the prognostic significance of unilateral (left or right hemisphere) post-insular stroke cardiac alterations. In addition, we review experimental data aiming to unravel the central mechanisms involved in post-insular stroke cardiovascular complications. Results and Conclusion Current clinical and experimental data suggest that stroke of the right insula can present a worse cardiovascular prognosis.

The renin-angiotensin system (RAS) comprises a biochemical cascade that hydrolyzes angiotensinogen into several different bioactive peptides, which can activate different receptors promoting plenty of specific effects. The aim of this study was to evaluate the presence of the putative product of alamandine, the pentapeptide alamandine-(1-5) in the circulation and its biological activity. To accomplish this we have used mass spectrometry (MALDI/TOF/TOF, LC-MS/MS) and several methodologies including isolated blood vessels, isolated perfused hearts, isolated cardiomyocytes, blood pressure recording in freely-moving normotensive and hypertensive rats (SHR), high resolution echocardiography (VEVO 2100), central administration (ICV infusion and microinjection in the insular cortex), cell culture (endothelial cells and GPCR-transfected CHO cells) and wild type and Mas, MrgD or AT2R deficient mice. Our results show that alamandine-(1-5) circulates in the human and rodent blood and promotes many biological central and peripheral actions. More importantly, its plasma concentration is increased in pediatric nephropathic patients. A major role for plasma ACE activity in the formation of alamandine-(1-5) from alamandine was observed using plasma samples from Angiotensinogen-KO mice. Alamandine-(1-5) increased Baroreflex sensitivity and produced a long-lasting (∼6 hours) anti-hypertensive effect in SHR, associated with a significant reduction in cardiac output. A particularly important effect of this pentapeptide was observed in isolated perfused heart and cardiomyocyte contractility (reduced inotropism). It was capable of stimulating NO production through all receptors from the renin-angiotensin protective arm, (MAS, MrgD and AT2R) in CHO-transfected cells. Our data shows that Alamandine-(1-5) exhibits selective actions that set it apart from traditional concepts of the vasodilatory axis of the RAS and that are possibly intricately linked to a complex interplay between Mas, MrgD and AT2 receptors. This novel finding suggests that RAS may possess a complexity that surpasses our current understanding.

Purpose of Review The response to natural stressors involves both cardiac stimulation and vascular changes, primarily triggered by increases in sympathetic activity. These effects lead to immediate flow redistribution that provides metabolic support to priority target organs combined with other key physiological responses and cognitive strategies, against stressor challenges. This extremely well-orchestrated response that was developed over millions of years of evolution is presently being challenged, over a short period of time. In this short review, we discuss the neurogenic background for the origin of emotional stress-induced hypertension, focusing on sympathetic pathways from related findings in humans and animals. Recent Findings The urban environment offers a variety of psychological stressors. Real or anticipatory, emotional stressors may increase baseline sympathetic activity. From routine day-to-day traffic stress to job-related anxiety, chronic or abnormal increases in sympathetic activity caused by emotional stressors can lead to cardiovascular events, including cardiac arrhythmias, increases in blood pressure and even sudden death. Among the various alterations proposed, chronic stress could modify neuroglial circuits or compromise antioxidant systems that may alter the responsiveness of neurons to stressful stimuli. These phenomena lead to increases in sympathetic activity, hypertension and consequent cardiovascular diseases. Summary The link between anxiety, emotional stress, and hypertension may result from an altered neuronal firing rate in central pathways controlling sympathetic activity. The participation of neuroglial and oxidative mechanisms in altered neuronal function is primarily involved in enhanced sympathetic outflow. The significance of the insular cortex-dorsomedial hypothalamic pathway in the evolution of enhanced overall sympathetic outflow is discussed.

Follow-up of patients affected by COVID-19 has unveiled remarkable findings. Among the several sequelae caused by SARS-CoV-2 viral infection, it is particularly noteworthy that patients are prone to developing depression, anxiety, cognitive disorders, and dementia as part of the post-COVID-19 syndrome. The multisystem aspects of this disease suggest that multiple mechanisms may converge towards post-infection clinical manifestations. The literature provides mechanistic hypotheses related to changes in classical neurotransmission evoked by SARS-CoV-2 infection; nonetheless, the interaction of peripherally originated classical and non-canonic peptidergic systems may play a putative role in this neuropathology. A wealth of robust findings shows that hemoglobin-derived peptides are able to control cognition, memory, anxiety, and depression through different mechanisms. Early erythrocytic death is found during COVID-19, which would cause excess production of hemoglobin-derived peptides. Following from this premise, the present review sheds light on a possible involvement of hemoglobin-derived molecules in the COVID-19 pathophysiology by fostering neuroscientific evidence that supports the contribution of this non-canonic peptidergic pathway. This rationale may broaden knowledge beyond the currently available data, motivating further studies in the field and paving ways for novel laboratory tests and clinical approaches.

Experiments aimed to evaluate the tissue distribution of Mas-related G protein-coupled receptor D (MrgD) revealed the presence of immunoreactivity for the MrgD protein in the rostral insular cortex (rIC), an important area for autonomic and cardiovascular control. To investigate the relevance of this finding, we evaluated the cardiovascular effects produced by the endogenous ligand of MrgD, alamandine, in this brain region. Mean arterial pressure (MAP), heart rate (HR), and renal sympathetic nerve activity (RSNA) were recorded in urethane anesthetized rats. Unilateral microinjection of equimolar doses of alamandine (40 pmol/100 nL), angiotensin-(1–7), angiotensin II, angiotensin A, and Mas/MrgD antagonist d-Pro⁷-Ang-1-7 (50 pmol/100 nL), Mas antagonist A779 (100 pmol/100 nL), or vehicle (0.9% NaCl) were made in different rats ( n = 4–6/group) into rIC. To verify the specificity of the region, a microinjection of alamandine was also performed into intermediate insular cortex (iIC). Microinjection of alamandine in rIC produced an increase in MAP (Δ = 15 ± 2 mmHg), HR (Δ = 36 ± 4 beats/min), and RSNA (Δ = 31 ± 4%), but was without effects at iIC. Strikingly, an equimolar dose of angiotensin-(1–7) at rIC did not produce any change in MAP, HR, and RSNA. Angiotensin II and angiotensin A produced only minor effects. Alamandine effects were not altered by A-779, a Mas antagonist, but were completely blocked by the Mas/MrgD antagonist d-Pro⁷-Ang-(1–7). Therefore, we have identified a brain region in which alamandine/MrgD receptor but not angiotensin-(1–7)/Mas could be involved in the modulation of cardiovascular-related neuronal activity. This observation also suggests that alamandine might possess unique effects unrelated to angiotensin-(1–7) in the brain.

Background and purpose: Damage to the insula results in cardiovascular complications. In rats, activation of N‐methyl‐d‐aspartate receptors (NMDARs) in the intermediate region of the posterior insular cortex (iIC) results in sympathoexcitation, tachycardia and arterial pressure increases. Similarly, focal experimental hemorrhage at the iIC results in a marked sympathetic‐mediated increase in baseline heart rate. The dorsomedial hypothalamic region (DMH) is critical for the integration of sympathetic‐mediated tachycardic responses. Here, whether responses evoked from the iIC are dependent on a synaptic relay in the DMH was evaluated.Methods: Wistar rats were prepared for injections into the iIC and DMH. Anatomical (tracing combined with immunofluorescence) and functional experiments (cardiovascular and sympathetic recordings) were performed.Results: The iIC sends dense projections to the DMH. Approximately 50% of iIC neurons projecting to the DMH express NMDARs, NR1 subunit. Blockade of glutamatergic receptors in the DMH abolishes the cardiovascular and autonomic responses evoked by the activation of NMDARs in the iIC (change in mean arterial pressure 7 ± 1 vs. 1 ± 1 mmHg after DMH blockade; change in heart rate 28 ± 3 vs. 0 ± 3 bpm after DMH blockade; change in renal sympathetic nerve activity 23% ± 1% vs. −1% ± 4% after DMH blockade). Experimental hemorrhage at the iIC resulted in a marked tachycardia (change 89 ± 14 bpm) that was attenuated by 65% ± 5% (p = 0.0009) after glutamatergic blockade at the DMH.Conclusions: The iIC‐induced tachycardia is largely dependent upon a glutamatergic relay in the DMH. Our study reveals the presence of an excitatory glutamatergic pathway from the iIC to the DMH that may be involved in the cardiovascular alterations observed after insular stroke.