Vascular Effects of Low-Dose ACE2 Inhibitor MLN-4760—Benefit or Detriment in Essential Hypertension?

Upregulation of key factors of viral entry of corona- and influenza viruses upon TLR3-signaling in cells from the respiratory tract and clinical treatment options by 1,8-Cineol

At the end of the 2019 coronavirus pandemic (COVID-19), highly contagious variants of coronaviruses had emerged. Together with influenza viruses, different variants of the coronavirus currently cause most colds and require appropriate drug treatment. We have investigated the expression of important factors for the replication of these viruses, namely transmembrane protease serine subtype 2 (TMPRSS2), neuropilin1 (NRP1), and angiotensin converting enzyme 2 (ACE2) or tumor necrosis factor-α (TNF-α) after toll like receptor-3 (TLR-3) stimulation using RT-qPCR and flow cytometry (FC) analysis. As model served primary fibroblasts derived from the lung and nasal cavity, as well as epidermal stem cells and fully matured respiratory epithelium. The stimulated cell cultures were treated with pharmaceuticals (Dexamethasone and Enzalutamide) and the outcome was compared with the phytomedicine 1,8-Cineol. The stimulation of TLR3 is sufficient to induce the expression of exactly those targets that were highly expressed in the corresponding culture type, specifically ACE2 and TMPRSS2 in respiratory epithelial stem cells and NRP1 in fibroblast cells. It seems this self-perpetuating cycle of infection-driven upregulation of key viral replication factors by the innate immune system represents an evolutionary advantage for viruses using these transcripts as viral replication factors. Likewise, to the standard pharmaceuticals with proven clinical efficiency, 1,8-Cineol was able to disrupt this self-perpetuating cycle. Considering the minor side effects and negligible pharmacological interactions with other drugs, it is conceivable that an adjuvant or combinatorial therapy with 1,8-Cineol for respiratory diseases caused by corona- or influenza viruses would be beneficial.

Arthroscopic evaluation of the rotator cuff vasculature: inferences into the pathogenesis of cuff tear and re-tear

BACKGROUND

Little is known about alterations of the rotator cuff (RC) macroscopic vasculature associated with medical conditions and/or habits that predispose a person to diseases of the peripheral microcirculation. The high frequency of cuff tear and re-tear in patients with diabetes, hypercholesterolemia, uncontrolled arterial hypertension, or metabolic syndrome may be due to tissue hypovascularity.

METHODS

The macroscopic vasculature of both the articular and bursal sides of the posterosuperior RC was evaluated arthroscopically in 107 patients (mean age, 58.2 years) with no RC tear. Patients were divided into three groups according to medical comorbidities and lifestyle factors (group I, none; group II, smokers and/or drinkers and one comorbidity; and group III, two or more comorbidities). Pulsating vessels originating from both the myotendinous and osteotendinous junctions were assessed as "clearly evident," "poorly evident," or "not evident."

RESULTS

Groups I, II, and III comprised 36, 45, and 26 patients, respectively. Within the myotendinous junction, vessels were visualized in 22 group I patients (61%), 25 group II patients (55%), and 6 group III patients (23%) (P=0.007). Pulsating arterial vessels originating from the osteotendinous junction were seen in 42%, 36%, and 0% of patients, respectively (P<0.001). Within the bursal side of the RC, a dense anastomotic network was visualized (either clearly or poorly) in 94% (34), 80% (36), and 35% (9) of patients, respectively (P<0.001).

CONCLUSIONS

The macroscopic vasculature of the RC is influenced by pre-existing diseases and lifestyle factors, which may impair peripheral microcirculation. Level of evidence: III.

An ensemble docking-based virtual screening and molecular dynamics simulation of phytochemical compounds from Malaysian Kelulut Honey (KH) against SARS-CoV-2 target enzyme, human angiotensin-converting enzyme 2 (ACE-2)

The human angiotensin-converting enzyme 2 (ACE-2) receptor is a metalloenzyme that plays an important role in regulating blood pressure by modulating angiotensin II. This receptor facilitates SARS-CoV-2 entry into human cells via receptor-mediated endocytosis, causing the global COVID-19 pandemic and a major health crisis. Kelulut honey (KH), one of Malaysian honey recently gained attention for its distinct flavour and taste while having many nutritional and medicinal properties. Recent study demonstrates the antiviral potential of KH against SARS-CoV-2 by inhibiting ACE-2 in vitro, but the bioactive compound pertaining to the ACE-2 inhibition is yet unknown. An ensemble docking-based virtual screening was employed to screen the phytochemical compounds from KH with high binding affinity against the 10 best representative structures of ACE-2 that mostly formed from MD simulation. From 110 phytochemicals previously identified in KH, 27 compounds passed the ADMET analysis and proceeded to docking. Among the docked compound, SDC and FMN consistently exhibited strong binding to ACE-2's active site (-9.719 and -9.473 kcal/mol) and allosteric site (-7.305 and -7.464 kcal/mol) as compared to potent ACE-2 inhibitor, MLN 4760. Detailed trajectory analysis of MD simulation showed stable binding interaction towards active and allosteric sites of ACE-2. KH's compounds show promise in inhibiting SARS-CoV-2 binding to ACE-2 receptors, indicating potential for preventive use or as a supplement to other COVID-19 treatments. Additional research is needed to confirm KH's antiviral effects and its role in SARS-CoV-2 therapy, including prophylaxis and adjuvant treatment with vaccination.Communicated by Ramaswamy H. Sarma.

Ectoenzymes as promising cell identification structures for the high avidity targeting of polymeric nanoparticles

Pharmacotherapy is often limited by undesired side effects while insufficient drug reaches the site of action. Active-targeted nanotherapy should provide a solution for this problem, by using ligands in the nanoparticle corona for the identification of receptors on the target-cell surface. However, since receptor binding is directly associated with pharmacological responses, today's targeting concepts must be critically evaluated. We hypothesized that addressing ectoenzymes would help to overcome this problem, but it was not clear if particles would show sufficiently high avidity to provide us with a viable alternative to classical ligand-receptor concepts. We scrutinized this aspect by immobilizing the highly selective angiotensin-converting enzyme 2 (ACE2) inhibitor MLN-4760 in the corona of block-copolymer nanoparticles and investigated enzyme binding via microscale thermophoresis and flow cytometry. Excellent avidities with Kd values as low as 243 pM for soluble ACE2 and 306 pM for ACE2-positive cells were obtained. In addition, the inhibitory activity had an IC50 value of 2.88 nM. Reliable target cell identification could be proven in coculture experiments. High avidity is the basis for minimizing material loss to off-target sites and paves the way for a paradigm shift in nanoparticle targeting which does not trigger unintended side effects following target cell identification.

The effect of zofenopril on the cardiovascular system of spontaneously hypertensive rats treated with the ACE2 inhibitor MLN-4760

BACKGROUND

Angiotensin converting enzyme 2 (ACE2) plays a crucial role in the infection cycle of SARS-CoV-2 responsible for formation of COVID-19 pandemic. In the cardiovascular system, the virus enters the cells by binding to the transmembrane form of ACE2 causing detrimental effects especially in individuals with developed hypertension or heart disease. Zofenopril, a H2S-releasing angiotensin-converting enzyme inhibitor (ACEI), has been shown to be effective in the treatment of patients with essential hypertension; however, in conditions of ACE2 inhibition its potential beneficial effect has not been investigated yet. Therefore, the aim of the study was to determine the effect of zofenopril on the cardiovascular system of spontaneously hypertensive rats, an animal model of human essential hypertension and heart failure, under conditions of ACE2 inhibition induced by the administration of the specific inhibitor MLN-4760 (MLN).

RESULTS

Zofenopril reduced MLN-increased visceral fat to body weight ratio although no changes in systolic blood pressure were recorded. Zofenopril administration resulted in a favorable increase in left ventricle ejection fraction and improvement of diastolic function regardless of ACE2 inhibition, which was associated with increased H2S levels in plasma and heart tissue. Similarly, the acute hypotensive responses induced by acetylcholine, L-NAME (NOsynthase inhibitor) and captopril (ACEI) were comparable after zofenopril administration independently from ACE2 inhibition. Although simultaneous treatment with zofenopril and MLN led to increased thoracic aorta vasorelaxation, zofenopril increased the NO component equally regardless of MLN treatment, which was associated with increased NO-synthase activity in aorta and left ventricle. Moreover, unlike in control rats, the endogenous H2S participated in maintaining of aortic endothelial function in MLN-treated rats and the treatment with zofenopril had no impact on this effect.

CONCLUSIONS

Zofenopril treatment reduced MLN-induced adiposity and improved cardiac function regardless of ACE2 inhibition. Although the concomitant MLN and zofenopril treatment increased thoracic aorta vasorelaxation capacity, zofenopril increased the participation of H2S and NO in the maintenance of endothelial function independently from ACE2 inhibition. Our results confirmed that the beneficial effects of zofenopril were not affected by ACE2 inhibition, moreover, we assume that ACE2 inhibition itself can lead to the activation of cardiovascular compensatory mechanisms associated with Mas receptor, nitrous and sulfide signaling.

Taxifolin Reduces Blood Pressure via Improvement of Vascular Function and Mitigating the Vascular Inflammatory Response in Spontaneously Hypertensive Rats

The effect of a 10-day-long treatment with taxifolin (TAX, 20 mg/kg/day p.o.) was investigated on spontaneously hypertensive rats (SHRs) with a focus on the vascular functions of isolated femoral arteries and thoracic aortas. TAX reduced blood pressure in SHRs. In femoral arteries, TAX increased acetylcholine-induced relaxation, reduced the maximal NA-induced contraction, and reduced acetylcholine-induced endothelium-dependent contraction (EDC); however, TAX had no effect on the vascular reactivity of isolated thoracic aortas. In addition, TAX elevated the total nitric oxide synthase (NOS) activity and iNOS protein expression but reduced cyclooxygenase-2 (COX2) protein expression in the tissue of the abdominal aorta without changes in Nos2 and Ptgs2 gene expressions. TAX also increased the gene expression of the anti-inflammatory interleukin-10 (Il10). In addition, in vitro studies showed that TAX has both electron donor and H atom donor properties. However, TAX failed to reduce superoxide production in the tissue of the abdominal aorta after oral administration. In conclusion, our results show that a decrease in the blood pressure in TAX-treated SHRs might be attributed to improved endothelium-dependent relaxation and reduced endothelium-dependent contraction. In addition, the results suggest that the effect of TAX on blood pressure regulation also involves the attenuation of COX2-mediated pro-inflammation and elevation of anti-inflammatory pathways.

MLN-4760 Induces Oxidative Stress without Blood Pressure and Behavioural Alterations in SHRs: Roles of Nfe2l2 Gene, Nitric Oxide and Hydrogen Sulfide

Reduced angiotensin 1-7 bioavailability due to inhibition of angiotensin-converting enzyme 2 (ACE2) may contribute to increased mortality in hypertensive individuals during COVID-19. However, effects of ACE2 inhibitor MLN-4760 in brain functions remain unknown. We investigated the selected behavioural and hemodynamic parameters in spontaneously hypertensive rats (SHRs) after a 2-week s.c. infusion of MLN-4760 (dose 1 mg/kg/day). The biochemical and molecular effects of MLN-4760 were investigated in the brainstem and blood plasma. MLN-4760 had no effects on hemodynamic and behavioural parameters. However, MLN-4760 increased plasma hydrogen sulfide (H₂S) level and total nitric oxide (NO) synthase activity and conjugated dienes in the brainstem. Increased NO synthase activity correlated positively with gene expression of Nos3 while plasma H₂S levels correlated positively with gene expressions of H₂S-producing enzymes Mpst, Cth and Cbs. MLN-4760 administration increased gene expression of Ace2, Sod1, Sod2, Gpx4 and Hmox1, which positively correlated with expression of Nfe2l2 gene encoding the redox-sensitive transcription factor NRF2. Collectively, MLN-4760 did not exacerbate pre-existing hypertension and behavioural hyperactivity/anxiety in SHRs. However, MLN-4760-induced oxidative damage in brainstem was associated with activation of NO- and H₂S-mediated compensatory mechanisms and with increased gene expression of antioxidant, NO- and H₂S-producing enzymes that all correlated positively with elevated Nfe2l2 expression.

Endothelial Dysfunction: From a Pathophysiological Mechanism to a Potential Therapeutic Target

The endothelium is considered the largest organ of the body, composed of a monolayer of endothelial cells (ECs) lining the interior surface of blood and lymphatic vessels [...].