Actions of Novel Angiotensin Receptor Blocking Drugs, Bisartans, Relevant for COVID-19 Therapy: Biased Agonism at Angiotensin Receptors and the Beneficial Effects of Neprilysin in the Renin Angiotensin System.

Angiotensin receptor blockers (ARBs) used in the treatment of hypertension and potentially in SARS-CoV-2 infection exhibit inverse agonist effects at angiotensin AR1 receptors, suggesting the receptor may have evolved to accommodate naturally occurring angiotensin 'antipeptides'. Screening of the human genome has identified a peptide (EGVYVHPV) encoded by mRNA, complementary to that encoding ANG II itself, which is an inverse agonist. Thus, opposite strands of DNA encode peptides with opposite effects at AR1 receptors. Agonism and inverse agonism at AR1 receptors can be explained by a receptor 'switching' between an activated state invoking receptor dimerization/G protein coupling and an inverse agonist state mediated by an alternative/second messenger that is slow to reverse. Both receptor states appear to be driven by the formation of the ANG II charge-relay system involving TyrOH-His/imidazole-Carboxylate (analogous to serine proteases). In this system, tyrosinate species formed are essential for activating AT1 and AT2 receptors. ANGII is also known to bind to the zinc-coordinated metalloprotease angiotensin converting enzyme 2 (ACE2) used by the COVID-19 virus to enter cells. Here we report in silico results demonstrating the binding of a new class of anionic biphenyl-tetrazole sartans ('Bisartans') to the active site zinc atom of the endopeptidase Neprilysin (NEP) involved in regulating hypertension, by modulating humoral levels of beneficial vasoactive peptides in the RAS such as vasodilator angiotensin (1-7). In vivo and modeling evidence further suggest Bisartans can inhibit ANG II-induced pulmonary edema and may be useful in combatting SARS-CoV-2 infection by inhibiting ACE2-mediated viral entry to cells.

Understanding the Driving Forces That Trigger Mutations in SARS-CoV-2: Mutational Energetics and the Role of Arginine Blockers in COVID-19 Therapy.

SARS-CoV-2 is a global challenge due to its ability to mutate into variants that spread more rapidly than the wild-type virus. Because the molecular biology of this virus has been studied in such great detail, it represents an archetypal paradigm for research into new antiviral drug therapies. The rapid evolution of SARS-CoV-2 in the human population is driven, in part, by mutations in the receptor-binding domain (RBD) of the spike (S-) protein, some of which enable tighter binding to angiotensin-converting enzyme (ACE2). More stable RBD-ACE2 association is coupled with accelerated hydrolysis of furin and 3CLpro cleavage sites that augment infection. Non-RBD and non-interfacial mutations assist the S-protein in adopting thermodynamically favorable conformations for stronger binding. The driving forces of key mutations for Alpha, Beta, Gamma, Delta, Kappa, Lambda and Omicron variants, which stabilize the RBD-ACE2 complex, are investigated by free-energy computational approaches, as well as equilibrium and steered molecular dynamic simulations. Considered also are the structural hydropathy traits of the residues in the interface between SARS-CoV-2 RBD and ACE2 protein. Salt bridges and π-π interactions are critical forces that create stronger complexes between the RBD and ACE2. The trend of mutations is the replacement of non-polar hydrophobic interactions with polar hydrophilic interactions, which enhance binding of RBD with ACE2. However, this is not always the case, as conformational landscapes also contribute to a stronger binding. Arginine, the most polar and hydrophilic among the natural amino acids, is the most aggressive mutant amino acid for stronger binding. Arginine blockers, such as traditional sartans that bear anionic tetrazoles and carboxylates, may be ideal candidate drugs for retarding viral infection by weakening S-protein RBD binding to ACE2 and discouraging hydrolysis of cleavage sites. Based on our computational results it is suggested that a new generation of "supersartans", called "bisartans", bearing two anionic biphenyl-tetrazole pharmacophores, are superior to carboxylates in terms of their interactions with viral targets, suggesting their potential as drugs in the treatment of COVID-19. In Brief: This in silico study reviews our understanding of molecular driving forces that trigger mutations in the SARS-CoV-2 virus. It also reports further studies on a new class of "supersartans" referred to herein as "bisartans", bearing two anionic biphenyltetrazole moieties that show potential in models for blocking critical amino acids of mutants, such as arginine, in the Delta variant. Bisartans may also act at other targets essential for viral infection and replication (i.e., ACE2, furin cleavage site and 3CLpro), rendering them potential new drugs for additional experimentation and translation to human clinical trials.

Discovery of a new generation of angiotensin receptor blocking drugs: Receptor mechanisms and in silico binding to enzymes relevant to SARS-CoV-2.

The discovery and facile synthesis of a new class of sartan-like arterial antihypertensive drugs (angiotensin receptor blockers [ARBs]), subsequently referred to as "bisartans" is reported. In vivo results and complementary molecular modelling presented in this communication indicate bisartans may be beneficial for the treatment of not only heart disease, diabetes, renal dysfunction, and related illnesses, but possibly COVID-19. Bisartans are novel bis-alkylated imidazole sartan derivatives bearing dual symmetric anionic biphenyl tetrazole moieties. In silico docking and molecular dynamics studies revealed bisartans exhibited higher binding affinities for the ACE2/spike protein complex (PDB 6LZG) compared to all other known sartans. They also underwent stable docking to the Zn2 + domain of the ACE2 catalytic site as well as the critical interfacial region between ACE2 and the SARS-CoV-2 receptor binding domain. Additionally, semi-stable docking of bisartans at the arginine-rich furin-cleavage site of the SARS-CoV-2 spike protein (residues 681-686) required for virus entry into host cells, suggest bisartans may inhibit furin action thereby retarding viral entry into host cells. Bisartan tetrazole groups surpass nitrile, the pharmacophoric "warhead" of PF-07321332, in its ability to disrupt the cysteine charge relay system of 3CLpro. However, despite the apparent targeting of multifunctional sites, bisartans do not inhibit SARS-CoV-2 infection in bioassays as effectively as PF-07321332 (Paxlovid).

Outcomes of off-pump versus on-pump coronary artery bypass surgery in end-stage renal disease patients with a history of myocardial infarction.

BACKGROUND: Patients with end-stage renal disease (ESRD) and myocardial infarction (MI) have poor survival. Coronary artery bypass grafting (CABG) in select patients is an effective treatment strategy; however, whether operative technique influences hospital outcome is not defined. METHODS: Between 1995 and 2000, 342 patients had ESRD (creatinine >2.0 mg/dL or dialysis) and a history of MI at the time of CABG. There were 67 patients that had off-pump coronary artery bypass (OPCAB) (OFF) and 275 that had CABG (ON). The OFF group was compared to the ON group for clinical, operative, outcome data, and influence of acuity of MI. RESULTS: The OFF group was older (P = .09), but hypertension was more common in the ON group (82% versus 69%, P = .02). The frequency of diabetes, congestive heart failure, peripheral vascular disease, and dyslipidemia were common, but not different between groups. For the OFF versus ON group, creatinine serum level was 3.6 +/- 2.6 versus 3.5 +/- 3.1 (P = 0.17), and history of an acute MI was 39% versus 33% (P = 0.78). The OFF versus ON group had fewer total grafts (2.5 +/- 1 versus 3.8 +/- 1, P < .001). The OFF group had fewer strokes (P = .08), shorter intensive care unit stay (2.4 versus 3.8 days), and shorter hospitalization (8.4 versus 11.7 days), yet mortality was similar (7% versus 9%, P = .79). After acute MI, OFF patients had significantly more postoperative supraventricular tachycardia than ON (69% versus 19%, P < .001). CONCLUSIONS: Patients with ESRD and an MI have acceptable hospital outcomes regardless of operative strategy. OPCAB or CABG may provide an advantage in certain patients, yet it is the presence of an acute MI that is a predictor of postoperative events.

Hinge peptide combinatorial libraries for inhilbitors of botulinum neurotoxins and saxitoxin: deconvolution strategy.

Abstract Combinatorial library screening offers a rapid process for identifying potential therapies to toxins. Hinge peptide libraries, which rely on conformational diversity rather than traditional molecular diversity, reduce the need for huge numbers of syntheses and screening steps and greatly expedite the discovery process of active molecules. Hinge peptide libraries having the structures: Acetyl-X1-X2-hinge-X3-X4-NH2 (capped) and X1-hinge-X2-X3 (uncapped), where X1 through X4 are near-equimolar mixtures of twelve L-amino acids and hinge = 4-aminobutyric acid, were screened for inhibitory activity in bioassays for botulinum neurotoxins A and B (BoNT/A, BoNT/B) and saxitoxin. The zinc protease activity of the reduced light chains of BoNT/A and /B was assayed by measuring the cleavage of synthetic substrates. Saxitoxin activity was measured by the restoration of the viability of neuroblastoma cells treated with ouabain and veratridine. Deconvolution of libraries was accomplished by fixing one position at a time beginning with the C-terminus. Primary library subsets in which position 4 was fixed showed moderate levels of inhibition for BoNT/A. Secondary library subsets showed stronger inhibition in the bioassays. In each of the bioassays, inhibitory potency was stronger when the second position to be fixed was on the opposite side of the hinge, rather than on the same side with respect to the C-terminus, suggesting that the hinge facilitates the interaction of side chains. Inhibitors for all three of the toxins studied were discovered within library subsets, although not necessarily in primary subsets. These studies demonstrate that (1) the best strategy for deconvoluting hinge peptide libraries is by fixing residues alternately on each side of the hinge moiety, and (2) it is essential to investigate secondary subsets even when primary subsets are inactive. The present findings support the concept that the increased flexibility imposed by the inclusion of a central hinge residue in small peptides increases the opportunity for side chain interactions, providing a distinct advantage for hinge peptide libraries over conventional peptide libraries. Hinge peptide libraries are a rich source of novel ligands for modulation of biomechanisms. The library subsets uncovered in this study may possess peptides that will lead to effective therapies to neurotoxin poisoning.

Outcomes for off-pump coronary artery bypass grafting in high-risk groups: a historical perspective.

BACKGROUND: The outcomes of off-pump coronary artery bypass (OPCAB) and conventional coronary artery bypass grafting with cardiopulmonary bypass (cCABG) have been compared in detail. Similarly, several reports have examined outcomes of high-risk subsets of patients in OPCAB as a selection strategy for reducing morbidity and mortality compared to cCABG. We undertook a retrospective study comparing outcomes from the early years in our experience of beating-heart surgery in high-risk patients selected for OPCAB compared to low-risk patients having OPCAB. This study was premised on strict selection criteria in an era prior to stabilizing devices and cardiac positioners. METHODS: A total of 384 patients underwent OPCAB over a 10-year period. Clinical outcomes were compared for 280 low-risk patients and 104 high-risk patients (redo CABG, CABG with simultaneous carotid endarterectomy, or renal insufficiency/failure). RESULTS: The high-risk group patients were significantly older than the low-risk group patients (64.3 +/- 10.5 years versus 61.5 +/- 11.7 years, respectively, P = .048). The high-risk group also had a greater degree of left ventricular dysfunction (P < .001), a higher incidence of diabetes (P = .046), and a higher proportion of patients with peripheral vascular disease (P = .009). There was no significant difference in the number of grafts created, but there was a statistical difference in the type of graft used. The high-risk group received fewer internal thoracic artery grafts (P = .005) and more saphenous vein grafts (P = .041). The high-risk group had slightly prolonged median lengths of stay in the intensive care unit (2.2 versus 1.4 days, P < .001) and hospital (11 versus 8 days, P < .001) and a higher proportion of patients requiring blood transfusions (48% versus 24%, P < .001), yet there was no significant difference in major adverse outcomes. CONCLUSIONS: In this retrospective and historical review, OPCAB was found to be equally safe in carefully selected high- and low-risk patients. These results provided for the enthusiasm and innovation to expand the usage of OPCAB in patients with coronary artery disease.