Search Results (204)

Long-COVID (LC) is characterized by diverse and persistent symptoms, potentially mirroring different molecular pathways. Recent data might offer that one of them is mediated by functional autoantibodies (fAAb) targeting G protein-coupled receptors (GPCR). Thus, the aim of this study was to investigate the clinical phenotype of patients with LC in relation to their GPCR-fAAb seropositivity. The present study recruited 194 patients with LC and profiled them based on self-reported symptoms. GPCR-fAAb seropositivity was identified by using a cardiomyocyte bioassay, testing the presence and functionality of the AAbs. Logistic regression, clustering, and decision tree analyses were applied to examine associations between GPCR-fAAb profiles and self-reported symptoms considering age and gender. The most prevalent GPCR-fAAbs in patients with LC were fAAB targeting the β2 adrenergic receptor (β2-fAAb, 92.8%), the muscarinergic M2 receptor (M2-fAAb, 87.1%), the Angiotensin II type 1 receptor (AT1-fAAb, 85.6%), and angiotensin (1–7) Mas receptor (MAS-fAAb, 85.6%). β2-fAAb showed a significant relation with dizziness, lack of concentration, and POTS, while Endothelin Type A receptor functional autoantibody (ET-A-fAAb) was significantly related to deterioration of pre-existing neurological disorders. Statistical analysis indicated a strong positive correlation between M2- and β2-fAAb; as in addition, an association of β2-fAAb and gender was observed to one of the major clinical symptoms (fatigue/PEM), a critical impact of GPCR-fAAb on LC-pathogenesis can be assumed. Summing up, the present data show that specific GPCR-fAAb are associated with distinct clinical phenotypes. Especially, the combination of M2- and β2-fAAb seemed to be essential for the LC-phenotype with a combination of fatigue/PEM and lack of concentration as major clinical symptoms. Full article

Patients with ulcerative colitis exhibit an increased risk for supraventricular arrhythmia during the active disease phase of the disease and show signs of atrial electrophysiological remodeling in remission. The goal of this study was to determine the basis for colitis-induced changes in atrial excitability. In a mouse model (C57BL/6; 3 months) of dextran sulfate sodium (DSS)-induced active colitis (3.5% weight/volume, 7 days), electrocardiograms (ECG) revealed altered atrial electrophysiological properties with a prolonged P-wave duration and PR interval. ECG changes coincided with a decreased atrial conduction velocity in Langendorff perfused hearts. Action potentials (AP) recorded from isolated atrial myocytes displayed an attenuated maximal upstroke velocity and amplitude during active colitis, as well as a prolonged AP duration (APD). Voltage clamp analysis revealed a colitis-induced shift in the voltage-dependent activation of the Na-current (I_Na) to more depolarizing voltages. In addition, protein levels of Na_v1.5 protein and connexin isoform Cx43 were reduced. APD prolongation depended on a reduction in the transient outward K-current (I_to) mostly generated by K_v4.2 channels. The changes in ECG, atrial conductance, and APD were reversible upon remission. The change in conduction velocity predominantly depended on the reversibility of the reduced Cx43 and Na_v1.5 expression. Treatment of mice with inhibitors of Angiotensin-converting enzyme (ACE) or Angiotensin II (AngII) receptor type 1 (AT1R) prevented the colitis-induced atrial electrophysiological remodeling. Our data support a colitis-induced increase in AngII signaling that promotes atrial electrophysiological remodeling and puts colitis patients at an increased risk for atrial arrhythmia. Full article

Background/Objectives: Contextual memory associated with methamphetamine (METH) use contributes to relapse and persistence of addiction. Angiotensin II type 1 receptor (AT1R) signaling has been implicated in drug reinforcement. LCZ696, a clinically used combination of sacubitril (a neprilysin inhibitor) and valsartan (an AT1R antagonist), may interfere with METH-associated memory through the modulation of dopaminergic pathways. Methods: Male C57BL/6J mice were tested in a conditioned place preference (CPP) paradigm to assess the effects of LCZ696, sacubitril (AHU377), and valsartan on METH-induced memory expression and reinstatement. Synaptic plasticity in the nucleus accumbens (NAc) was examined by assessing the levels of synaptophysin (Syp) and postsynaptic density protein 95 (Psd95), as well as dendritic spine density. Dopaminergic signaling in the ventral tegmental area (VTA) was evaluated via ELISA, Western blotting, and chromatin immunoprecipitation (ChIP), targeting cAMP response element-binding protein (Creb) binding to the tyrosine hydroxylase (Th) promoter. To further assess the role of Th, an adeno-associated virus (AAV9) carrying a CRISPR-Cas9-based sgRNA targeting Th (AAV9-Th-sgRNA) was microinjected into the VTA. Results: LCZ696 and valsartan significantly reduced METH-induced CPP and reinstatement. LCZ696 reversed METH-induced synaptic and dopaminergic alterations and suppressed Creb-mediated Th transcription. Th knockdown attenuated both CPP acquisition and relapse. Conclusions: LCZ696 disrupts METH-associated contextual memory by modulating dopaminergic signaling and Creb-dependent Th expression, supporting its potential as a treatment for METH use disorder. Full article

The renin-angiotensin-aldosterone system (RAAS) is a hormone system that controls blood pressure and fluid and electrolyte balance. Angiotensin II, a key effector, is produced from angiotensin I by angiotensin-converting enzyme (ACE) and exerts its effects through binding to its type 1 (AT1R) or type 2 (AT2R) receptors. AT1R activation promotes vasoconstriction, oxidative stress, endothelial dysfunction, peripheral vascular resistance, and atherosclerosis, all of which substantially contribute to cellular senescence and organismal ageing. Conversely, AT2R activation counteracts these effects by inducing vascular relaxation and attenuating vascular cell proliferation and migration, offering protection against occlusive vascular disease. Additionally, conversion of angiotensin II to angiotensin (1-7) or angiotensin I to angiotensin (1-9) by ACE2 provides further cardiovascular protection by lowering oxidative stress, inflammation, and abnormal cell growth. Bearing these in mind, measures to control angiotensin II synthesis or receptor activity have been at the forefront of antihypertensive treatment. This paper briefly reviews the RAAS and explores the dual role of angiotensin II in promoting disease and mediating vascular protection, with a focus on its impact on ageing and cardiovascular pathology. Full article

Recent bioassay studies have unexpectedly supported the high (computationally predicted) binding affinities of angiotensin receptor blockers (ARBs) at α-adrenergic receptors (αARs) in isolated smooth muscle. Computational predictions from ligand docking studies are consistent with very low concentrations of ARBs (e.g., sartans or bisartans) that partially reduce (20–50%) the contractile response to phenylephrine, suggesting that some ARBs may function as partial inverse agonists at αARs. Virtual ligand screening (docking) and molecular dynamics (MD) simulations were carried out to explore the binding affinities and stabilities of selected non-peptide ligands (e.g., ARBs and small-molecule opioids) for several G-protein coupled receptor (GPCR) types, including angiotensin II (AngII) type 1 receptor (AT₁R), α1AR, α2AR, and μ-(µOR) and ժ-opioid receptors (ժOR). Results: All ligands docked preferentially to the binding pocket on the cell surface domain of the GPCR types investigated. Drug binding was characterized by weak interactions (hydrophobic, hydrogen bonding, pi-pi) and stronger ionic and salt-bridge interactions (cation-pi and cation-anion interactions). Ligands specific to each GPCR category showed considerable cross-binding with alternative GPCRs, with small-molecule medications appearing less selective than their peptide or ARB functional equivalents. ARBs that exhibit higher affinities for AT₁R also demonstrate higher affinities for µORs and ժORs than opiate ligands, such as fentanyl and naltrexone. Moreover, ARBs had a higher affinity for αARs than either alpha agonists (epinephrine and phenylephrine) or inhibitors (prazosin and doxazosin). MD simulations of membrane-embedded ARB-GPCR complexes proved stable over nanosecond time scales and suggested that some ARBs may behave as agonists or antagonists depending on the GPCR type. Based on the results presented in this and related investigations, we propose that agonists bind to the resting A-site of GPCRs, while inverse agonists occupy the desensitizing D-site, which partial agonists like morphine and fentanyl share, contributing to addiction. ARBs block both AngII and alpha receptors, suggesting that they are more potent antihypertensive drugs than ACE inhibitors. ARBs have the potential to inhibit morphine tolerance and appear to disrupt receptor desensitization processes, potentially by competing at the D-site. Our results suggest the possible therapeutic potential of ARBs in treating methamphetamine and opiate addictions. Full article

For the interaction of angiotensin II (AngII) with AngII type 1 receptors (AT₁R), two potential proton hopping pathways have been identified, each associated with distinct physiological outcomes. The octapeptide AngII (Asp¹-Arg²-Val³-Tyr⁴-Ile⁵-His⁶-Pro⁷-Phe⁸) appears to form a charge relay system (CRS) in solution in which the C-terminal carboxylate abstracts a proton from the His⁶ imidazole group, which, in turn, abstracts a proton from the Tyr⁴ hydroxyl (OH) group, creating a tyrosinate anion. When AngII binds to the AT₁R, the CRS can be reconstituted with D281 of the receptor taking up the role of the Phe⁸ carboxylate in the tripartite interaction, whilst the Phe⁸ carboxylate forms a salt bridge with K199 of the receptor. As a consequence, the Tyr⁴ OH of AngII is positioned with accessibility to either the Phe⁸ carboxylate (bound to K199) or the His⁶ imidazole (activated by D281), thereby creating a potential gating mechanism for AT₁R receptor signaling. This study summarizes evidence based on structure activity data for various analogs wherein Tyr⁴ OH interaction with His⁶ imidazole (CRS formation) leads to G protein sequestration and vasoconstriction, whereas Tyr⁴ OH interaction with Phe⁸ carboxylate (bound to K199) engenders arrestin-mediated vasodilation and receptor desensitization. These findings, combined with quantum mechanical (semiempirical) calculations of CRS proton transfer presented herein, provide insights for the therapeutic targeting of angiotensin receptor blockers (sartans) and the development of second-generation drugs (bisartans). Full article

Secreted protein acidic rich in cysteine (SPARC), one of the extracellular matrix proteins, is highly induced during inflammation. We investigated the pathophysiological regulation and role of SPARC in vascular inflammation in a rat model of hypertension created using deoxycorticosterone acetate (DOCA, 40 mg/kg/week, s.c.) and salt (1% in drinking water). DOCA–salt administration time-dependently increased systolic blood pressure during the 3-week treatment period, blunted endothelium-dependent vasodilation, and increased monocyte chemoattractant protein-1 (MCP-1) and lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) expression in the aorta. SPARC expression transiently increased until week 2 in the DOCA–salt rat aorta. Interestingly, aortic SPARC levels correlated with blood pressure and the levels of MCP-1 and LOX-1 during 0–2 weeks. The AT₁ receptor blocker, losartan, suppressed the overexpression of SPARC, and in vitro treatment with angiotensin II enhanced the production of SPARC in rat aortic endothelial cells. Exposure to recombinant SPARC protein induced overexpression of MCP-1 and LOX-1 mRNA in endothelial cells. Bioactive forms of a disintegrin and metalloproteinase with thrombospondin type 1 motif (ADAMTS1), excessive activation of which contributes to pathological states and overexpression of which is reported to be induced by SPARC, were increased in the DOCA–salt rat aorta. These results suggest that SPARC is induced by the vascular renin–angiotensin system and causes inflammation in the early stages of hypertensive vascular injury, and that activation of ADAMTS1 might be related to the proinflammatory effects of SPARC. Full article

Excessive activity of the hormone angiotensin II (AngII) is known to contribute to the pathogenesis of multiple cardiovascular diseases, including atherosclerosis, vascular remodeling, and hypertension, primarily through inducing gene expression changes. In this study, we identified LMCD1 (LIM and cysteine-rich domains 1, also known as Dyxin), primarily recognized as a transcription co-factor involved in various oncogenic processes, cardiac hypertrophy, and vascular remodeling, as a potential key factor in AngII-mediated effects in vascular smooth muscle cells (VSMCs). We demonstrated that AngII upregulates LMCD1 expression in primary rat VSMCs through type 1 angiotensin receptor (AT1-R) activation, leading to calcium signaling and p38 MAPK pathway activation. Additionally, we also demonstrated in A7r5 vascular smooth muscle cells that LMCD1 protein overexpression results in enhanced cell proliferation and cell migration. Our findings provide insights into the mechanisms by which AngII mediates changes in LMCD1 expression. The elevated expression of LMCD1 enhanced the cell proliferation and migration in VSMCs in vitro experiments, suggesting that LMCD1 may be an important factor in vascular remodeling and the pathogenesis of severe cardiovascular diseases. These results raise the possibility that LMCD1 could be a promising pharmacological target in the cardiovascular dysfunctions associated with AT1-R overactivation. Full article

Antibody-mediated rejection is a critical factor in acute and chronic allograft rejection, with Human Leukocyte Antigen as the primary target of the humoral immune response in kidney transplants. In addition to HLA antibodies, non-HLA Abs also play a significant role in AMR. These non-HLA Abs, which can target either autoantigens or alloantigens, may be present pre-transplantation or develop post-transplant. They are associated with various types of allograft injury. The major non-HLA Abs include those directed against the angiotensin II type 1 receptor, endothelin type A receptor, and MICA, as well as other antigens such as vimentin, collagens, and anti-endothelial cell antibodies. Factors such as ischemia, reperfusion injury, and calcineurin inhibitor toxicity can trigger the pathogenic activity of these Abs. The mechanisms underlying non-HLA Ab production are not yet fully understood but are thought to involve endothelial injury and the exposure of neoantigens. Research indicates that these non-HLA Abs can cause graft injury through both complement-dependent and complement-independent pathways. However, detecting non-HLA Abs remains a challenge due to the lack of reliable diagnostic tools. Current treatment strategies for managing the effects of pathogenic non-HLA Abs include intravenous immunoglobulin, plasmapheresis, rituximab, and bortezomib. Early identification of high-risk patients and timely intervention are crucial to preventing graft failure. This review examines the development, mechanisms, and clinical significance of non-HLA Abs in kidney transplantation, highlighting the need for improved diagnostic methods and tailored therapeutic approaches. Full article

Objectives: This study aims to show the distribution of angiotensin-converting enzyme (ACE) rs1799752 (I>D) gene insertion/deletion (I/D) polymorphism and angiotensin II receptor type 1 (AGTR1) rs5186 (A>C) gene polymorphism in adolescents with hypertension (HT) and type 1 diabetes (T1D), as well as its association with hypertension and the diurnal variation of mean blood pressure (dipping phenomenon). Methods: A cross-sectional study was conducted involving 118 adolescents diagnosed with T1D who underwent clinical and laboratory investigations, genetic analyses, and 24 h ambulatory blood pressure monitoring. The genotype frequencies were compared between adolescents with HT and those with normal blood pressure. Additionally, the genotype frequencies were compared between dippers and non-dippers. Results: Patients with HT were more likely to be female and exhibited significantly poorer glycemic control and higher triglycerides, along with increased body mass index and daily insulin dosage. The prevalence of ACE rs1799752 genotypes in the hypertensive group was 20% II, 66.7% ID, and 13.3% DD, which did not significantly differ from the normal blood pressure group with 29.1% II, 53.4% ID, and 17.5% DD (p = 0.625). The prevalence of AGTR1 rs5186 genotypes in the hypertensive group was 53.3% AC, 40% AA, and 6.7% CC, which also did not significantly differ from the normal blood pressure group with 39.8% AC, 52.4% AA, and 7.8% CC (p = 0.608). A total of 46% of the patients exhibited non-dipping phenomena. The prevalence of non-dippers among the ACE genotypes was 13% DD, 33.3% II, and 53.7% ID (p = 0.369), while for the AGTR1 genotypes, it was 50% AA, 42.6% AC, and 7.4% CC (p = 0.976). Conclusions: Our results indicate that in our adolescents with T1D, clinical and metabolic factors such as higher body mass index, triglycerides, suboptimal glycemic control, and female gender are more indicative of the development of hypertension than ACE and AGTR1 gene polymorphisms. A potential reason for this finding could be the young age of the patients or the relatively small size of the study group. Future research involving larger sample sizes is needed to further investigate the genetic predisposition for the development of hypertension. Full article

Hemp (Cannabis sativa L.) leaf oil (HLO) contains several bioactive compounds such as phenolics, flavonoids, and quercetin. However, the effects of HLO on hypertensive conditions have not yet been investigated. This study investigated the cardiovascular protective effects of HLO in a nitric oxide (NO) synthase inhibitor-induced hypertensive rat model. Five weeks of HLO administration significantly prevented blood pressure elevation, improved cardiac function, and mitigated cardiac hypertrophy. Furthermore, HLO ameliorated vascular dysfunction by reducing sympathetic nerve stimulation-induced vasoconstriction, increasing endothelium-dependent vasorelaxation, as well as decreasing vascular wall thickness and vascular smooth muscle cell proliferation. HLO inhibited renin–angiotensin system (RAS) activation and downregulated angiotensin II type 1 (AT1) receptor and NADPH oxidase expression. Additionally, HLO normalized the circulating NO metabolites, decreased oxidative stress, and enhanced antioxidant status. These findings suggest that HLO protects against cardiovascular dysfunction and preserves its morphology. The mechanism of action might involve the suppression of RAS overactivity and oxidative stress through the Ang II/AT1 receptor/NOX2 pathway in NO-deficient hypertension. Full article

Endothelial dysfunction mediated by elevated levels of autoantibodies against vasoactive peptides occurring after COVID-19 infection is proposed as a possible pathomechanism for orthostatic intolerance in long COVID patients. This case-control study comprised 100 long COVID patients from our prospective POSTCOV registry and three control groups, each consisting of 20 individuals (Asymptomatic post-COVID group; Healthy group = pan-negative for antispike protein of SARS-CoV-2; Vaccinated healthy group = no history of COVID-19 and vaccinated). Autoantibodies towards muscarinic acetylcholine receptor M3, endothelin type A receptor (ETAR), beta-2 adrenergic receptor (Beta-2 AR), angiotensin II receptor 1 and angiotensin 1-7 (Ang1-7) concentrations were measured by enzyme-linked immunosorbent assay in long COVID patients and controls. Orthostatic intolerance was defined as inappropriate sinus tachycardia, postural tachycardia, orthostatic hypotonia and other dysautonomia symptoms, such as dizziness or blurred vision (n = 38 long COVID patients). Autoantibody concentrations were compared with routine laboratory parameters and quality of life questionnaires (EQ-5D). The concentration of ETAR autoantibodies were significantly higher in long COVID, Asymptomatic and Vaccinated groups compared to the antispike protein pan-negative Healthy group. A trend towards higher plasma levels of Beta-2 AR and Ang1-7 was measured in long COVID patients, not related to presence of orthostatic intolerance. ETAR autoantibody concentration showed significant positive correlation with the EQ-5D item “Problems in performing usual activities”. Full article

Background/Objective: Osteocytes are the most abundant cell type in the skeleton, with key endocrine functions, particularly in regulating osteoblast and osteoclast activity to maintain bone quality. Angiotensin II (Ang II), a critical component of the renin–angiotensin–aldosterone system, is well-known for its role in vasoconstriction during hypertension. Beyond its cardiovascular functions, Ang II participates in various biological processes, including bone metabolism. While its influence on osteoblast proliferation, differentiation, and osteoclastogenesis has been documented, its effects on osteocytes remain unexplored. This study hypothesized that Ang II enhances the osteoclastogenic activity of osteocytes. Methods: Mouse calvariae were cultured ex vivo in an Ang II-containing medium, analyzed via immunohistochemistry, and evaluated for osteoclastogenic gene expression through real-time PCR. Western blotting was employed to assess protein levels and signaling pathway activation in the MLO-Y4 osteocytic cell line in vitro. Results: Ang II significantly increased the expression of receptor activator of nuclear factor κB ligand (RANKL) and macrophage colony-stimulating factor (M-CSF). These effects were abrogated by azilsartan, a blocker targeting Ang II type 1 receptors (AT1R). p38 and ERK1/2 in the MAPK pathway were also activated by Ang II. Conclusions: Ang II enhances osteocyte-mediated osteoclastogenesis via AT1R activation, highlighting its potential as a therapeutic target for bone diseases. Full article

The octapeptide angiotensin II (Ang II) is a circulating hormone as well as a locally formed agonist synthesized by the angiotensin-converting enzyme (ACE) of endothelial cells. It forms a powerful mechanism to control the amount and pressure of body fluids. All main effects are directed to save body salt and water and ensure blood pressure under basic conditions and in emergencies. All blood vessels respond to stimulation by Ang II; the immediate response is smooth muscle contraction, increasing vascular resistance, and elevating blood pressure. Such effects are conveyed by type 1 angiotensin receptors (AT₁Rs) located in the plasma membrane of both endothelial and vascular smooth muscle cells. AT₁Rs are heterotrimeric G protein-coupled receptors (GPCRs), but their signal pathways are much more complicated than other GPCRs. In addition to G_q/11, the G_12/13, JAK/STAT, Jnk, MAPK, and ERK 1/2, and arrestin-dependent and -independent pathways are activated because of the promiscuous attachment of different signal proteins to the intracellular G protein binding site and to the intracellular C terminal loop. Substantial changes in protein expression follow, including the intracellular inflammation signal protein NF-κB, endothelial contact proteins, cytokines, matrix metalloproteinases (MMPs), and type I protocollagen, eliciting the inflammatory transformation of endothelial and vascular smooth muscle cells and fibrosis. Ang II is an important contributor to vascular pathologies in hypertensive, atherosclerotic, and aneurysmal vascular wall remodeling. Such direct vascular effects are reviewed. In addition to reducing blood pressure, AT₁R antagonists and ACE inhibitors have a beneficial effect on the vascular wall by inhibiting pathological wall remodeling. Full article

Patients carrying APOL1 risk alleles (G1 and G2) have a higher risk of developing Focal Segmental Glomerulosclerosis (FSGS); we hypothesized that escalated levels of miR193a contribute to kidney injury by activating renin–angiotensin system (RAS) in the APOL1 milieus. Differentiated podocytes (DPDs) stably expressing vector (V/DPD), G0 (G0/DPDs), G1 (G1/DPDs), and G2 (G2/DPDs) were evaluated for renin, Vitamin D receptor (VDR), and podocyte molecular markers (PDMMs, including WT1, Podocalyxin, Nephrin, and Cluster of Differentiation [CD]2 associated protein [AP]). G0/DPDs displayed attenuated renin but an enhanced expression of VDR and Wilms Tumor [WT]1, including other PDMMs; in contrast, G1/DPDs and G2/DPDs exhibited enhanced expression of renin but decreased expression of VDR and WT1, as well as other PDMMs (at both the protein and mRNA levels). G1/DPDs and G2/DPDs also showed increased mRNA expression for Angiotensinogen and Angiotensin II Type 1 (AT1R) and 2 (AT2R) receptors. Protein concentrations of Brain Acid-Soluble Protein [BASP]1, Enhancer of Zeste Homolog [EZH]2, Histone Deacetylase [HDAC]1, and Histone 3 Lysine27 trimethylated [H3K27me3] in WT1-IP (immunoprecipitated proteins with WT1 antibody) fractions were significantly higher in G0/DPDs vs. G1/DPD and G2/DPDs. Moreover, DPD-silenced BASP1 displayed an increased expression of renin. Notably, VDR agonist-treated DPDs showed escalated levels of VDR and a higher expression of PDMMs, but an attenuated expression of renin. Human Embryonic Kidney (HEK) cells transfected with increasing APOL1(G0) plasmid concentrations showed a corresponding reduction in renin mRNA expression. Bioinformatics studies predicted the miR193a target sites in the VDR 3′UTR (untranslated region), and the luciferase assay confirmed the predicted sites. As expected, podocytes transfected with miR193a plasmid displayed a reduced VDR and an enhanced expression of renin. Renal cortical section immunolabeling in miR193a transgenic (Tr) mice showed renin-expressing podocytes. Kidney tissue extracts from miR193aTr mice also showed reduced expression of VDR and PDMMs, but enhanced expression of Renin. Blood Ang II levels were higher in miR193aTr, APOLG1, and APOL1G1/G2 mice when compared to control mice. Based on these findings, miR193a regulates the activation of RAS and podocyte molecular markers through modulation of VDR and WT1 in the APOL1 milieu. Full article