ARTICLE | doi:10.20944/preprints202302.0027.v2
Subject: Biology And Life Sciences, Biochemistry And Molecular Biology Keywords: homocysteine; estrogen; bradykinin; magnesium; vitamin D; CD147
Online: 15 February 2023 (03:59:17 CET)
Brain fog with compromised ability to concentrate has been the most frequent Long Covid (LC) complaint. This is due to an increased transforming growth factor (TGF) β/interferon (IFN)-γ ratio with consequently increased bradykinin (BKN), especially in Caucasian females. Brain and lung blood vessels “leak.” This same ratio is increased in Alzheimer’s disease (AD), but decreased in Parkinson’s disease (PD), because CD4+ and CD8+ T cells are differentially affected by the invading associated viruses, e.g., SARS CoV2, HIV, Varicella Zoster (VZV) aka Human Herpesvirus 3 (HHV3), HBV, HCV, …. In Covid-19 CD147 receptors on immune cells are critical in generating the increased TGF-β/IFN-γ and those on endothelial cells, platelets, and erythrocytes are critical to the abnormal microvascular blood flow. ACE2 receptors on pneumocytes and enterocytes enable pulmonary and GI entry, initiating gut dysbiosis. Epigenetics, methylation, magnesium, vitamin D, the B vitamins, and antioxidants suggest that these issues can be surmounted. Biochemical, physiologic, and epidemiologic data are analyzed to answer these questions. An LC model is presented and discussed in the context of the most recent research. Suggestions to avoid these and other worrisome concerns are included. Other topics discussed include estrogen, the gut microbiome, type 2 diabetes (T2D), and homocysteine.
REVIEW | doi:10.20944/preprints202110.0342.v2
Subject: Biology And Life Sciences, Biochemistry And Molecular Biology Keywords: kininogen; structure; AlphaFold; cryo-EM; proteins; kinin; bradykinin
Online: 1 November 2021 (13:50:19 CET)
Kininogens are multidomain glycoproteins found in the blood of most vertebrates. They are important in the blood coagulation cascade pathways - in intrinsic pathway activation leading to thrombin generation partially independently from tissue factor dependent extrinsic pathway, connecting blood coagulation with the kallikrein-kinin system. Nothing is known about the shape on atomic level therefore the endeavor to obtain the good-quality spatial structure of kininogens is important for a better understanding of their role in disease and treatment. Application of cryo-EM is important for solving the spatial structure of kininogens, drawing new frontiers in understanding the function and opening new pathways for drug development.
HYPOTHESIS | doi:10.20944/preprints202004.0023.v1
Subject: Medicine And Pharmacology, Epidemiology And Infectious Diseases Keywords: COVID-19; bradykinin; ACE2; pulmonary angioedema; ARDS; icatibant
Online: 3 April 2020 (04:13:43 CEST)
Most striking observations in COVID-19 patients are the hints on pulmonary edema (also seen on CT scans as ground glass opacities), dry cough, fluid restrictions to prevent more severe hypoxia, the huge PEEP that is needed while lungs are compliant, and the fact that anti-inflammatory therapies are not powerful enough to counter the severity of the disease. We propose that the severity of the disease and many deaths are due to a local vascular problem due to activation of B1 receptors on endothelial cells in the lungs. SARS-CoV-2 enters the cell via ACE2, a cell membrane bound molecule with enzymatic activity that next to its role in RAS is needed to inactivate des-Arg9 bradykinin, the potent ligand of the bradykinin receptor type 1 (B1). In contrast to bradykinin receptor 2 (B2), the B1 receptor on endothelial cells is upregulated by proinflammatory cytokines. Without ACE2 acting as a guardian to inactivate the ligands of B1, the lung environment is prone for local vascular leakage leading to angioedema. Angioedema is likely a feature already early in disease, and might explain the typical CT scans and the feeling of people that they drown. In some patients, this is followed by a clinical worsening of disease around day 9 due to the formation antibodies directed against the spike (S)-antigen of the corona-virus that binds to ACE2 that could contribute to disease by enhancement of local immune cell influx and proinflammatory cytokines leading to damage. In parallel, inflammation induces more B1 expression, and possibly via antibody-dependent enhancement of viral infection leading to continued ACE2 dysfunction in the lung because of persistence of the virus. In this viewpoint we propose that a bradykinin-dependent local lung angioedema via B1 and B2 receptors is an important feature of COVID-19, resulting in a very high number of ICU admissions. We propose that blocking the B1 and B2 receptors might have an ameliorating effect on disease caused by COVID-19. This kinin-dependent pulmonary edema is resistant to corticosteroids or adrenaline and should be targeted as long as the virus is present. In addition, this pathway might indirectly be responsive to anti-inflammatory agents or neutralizing strategies for the anti-S-antibody induced effects, but by itself is likely to be insufficient to reverse all the pulmonary edema. Moreover, we provide a suggestion of how to ventilate in the ICU in the context of this hypothesis.
COMMUNICATION | doi:10.20944/preprints202305.1298.v1
Subject: Biology And Life Sciences, Life Sciences Keywords: Mass spectrometry; RAS; ACE; ACE2; CPN; bradykinin; hypertension; cardiovascular disease; antihypertensiva; ACE inhibitors; angiotensin receptor blockers; bradykinin; neuropeptide re-porter assay
Online: 18 May 2023 (08:13:10 CEST)
(1) Background: Co-morbidities such as hypertension and cardiovascular disease are major risk factors for severe COVID-19. The renin-angiotensin-system (RAS) is critically involved in their pathophysiology and is counterbalanced by both angiotensin-converting enzyme 2 (ACE2), the functional receptor of SARS-CoV-2, and the kallikrein-kinin-system (KKS). Considerable research interest with respect to COVID-19 treatment is, thus, currently directed towards the components of these systems. In an earlier study, we noticed significantly reduced carboxypeptidase N (CPN, KKS member) activity and partially excessive angiotensin-converting enzyme (ACE, RAS member) activity in the sera of both hospitalized (HoP) COVID-19 patients and a sub-group of covalescent patients, while in the majority of the probands recovering from the disease these values had returned to normal. The data had been obtained using bradykinin (BK) as a reporter peptide, which is a target of both CPN and ACE, and they were supplemented by serum proteomics of the same patient cohort. We hypothesized that the data could be indicative of Long COVID, which had not been fully appreciated at the time of our study.; (2) Methods: The data were re-evaluated in the light of Long COVID. The recent literature on the RAS in COVID-19, antihypertensiva, and Long COVID was briefly reviewed.; (3) Results: While the levels of the BK serum degradation products should return to normal concentrations during convalescence, this was not true for some patients. This could be due to persisting liver problems, because CPN is synthesized there, but also to a dysregulated RAS. This was not reflected in the levels of selected RAS/KKS serum proteins like angiotensinogen (AGT), although AGT correlated with disease severity in HoP. However, standard tests in routine patient care in Long COVID often come back normal, and it may be that BK degradation is specific in some pathophysiologies. Moreover, the HoP group was sub-divided based on the serum protein profiles and COVID-19 severity.; (4) Conclusions: We point out two insights: 1) Sensitive technology such as omics methods might provide unexpected significant differences within the pre-defined patient groups of a clinical study. Those can only be explored, if the cohorts are large enough and properly matched with respect to the parameters known beforehand (e.g., age, gender, co-morbidities). 2) Results of the BK-reporter serum protease activity assay could be indicative of persisting liver problems and/or potentially of Long COVID. Clinical studies are required to test this hypothesis.
REVIEW | doi:10.20944/preprints202004.0160.v2
Subject: Biology And Life Sciences, Virology Keywords: COVID-19; ACE; ACE2; Angiotensin II; Bradykinin; RAS inhibitors; ACE inhibitors; AT1 receptor blockers; Losartan; Bradykinin Antagonists; Ang II loading; Giapreza; Icatibant.
Online: 14 April 2020 (14:34:43 CEST)
As the world grapples with a pandemic with various and expanding epicenters, a flurry of medical and scientific activity has gained speed and momentum in a race to halt COVID-19. A controversial topic has been the connection between COVID-19 and the Renin-Angiotensin system (RAS). COVID-19, like Sars before it, enters by way of the Angiotensin Converting Enzyme 2 (ACE2). ACE2 is ubiquitously expressed in many tissues in the body serving as the doorway by which the virus can enter and spread causing inflammatory havoc. Demographic evidence coming out of China and other locations make it clear that the elderly and those suffering cardiovascular complications such as hypertension etc are most at risk. The connection to RAS and the demographic nature of the data coming out has led many to advance hypothesis, recommendations and even therapies based on existing RAS inhibitors and other components of the renin-Angiotensin system. It is pertinent to review the literature in the context of our understanding of the renin-angiotesnin system to allow better judgements to be made as well as lines of research initiated advancing a quick resolution to COVID-19. Covid-19 appears invincible as if dipped in the river Styx, but even Achilles had a vulnerable heel. Understanding the homeostatic balance that the coronavirus disrupts, we can discover the arrow in corona’s heel.
REVIEW | doi:10.20944/preprints202305.1010.v2
Subject: Medicine And Pharmacology, Pharmacology And Toxicology Keywords: kallikrein-kinin system; kininogens; bradykinin; B1 receptor; B2 receptor; hereditary angioedema
Online: 6 June 2023 (09:42:29 CEST)
Abstract: The kallikrein-kinin system consists of the two kininogen substrates, present in blood plasma, and of two serine proteases, the plasma and tissue kallikreins. The action of the latter on kininogens produce small peptides, the kinins, short lived but endowed by powerful pharmacologic actions on blood vessels and other tissues. Many recent and exciting therapeutic developments in the field are briefly summarized. Notably, various novel strategies are being clinically developed to inhibit the formation of bradykinin or block its receptors in the management of hereditary angioedema. The interventions include orally bioavailable drugs, biotechnological proteins, and gene therapy. These approaches are currently explored in a variety of other inflammatory and thrombotic disorders. Harnessing controlled kinin formation is also of potential therapeutic interest as shown by the clinical development of recombinant tissue kallikrein for ischemic stroke and renal disease. Biomarkers of a kinin-mediated disorders, frequently implicating edemas, include the consumption of kininogen(s), plasma kallikrein activity, and the detection of circulating kinin metabolites such as fragments BK1-5 and BK2-9. Novel opportunities to clinically apply the underexploited drugs of the kallikrein-kinin system are briefly reviewed. This personal perspective is offered by an observer of, and a participant in drug characterization during the last 4 decades.