Receptor Interactions of Angiotensin II and Angiotensin Receptor Blockers-Relevance to COVID-19

Angiotensin II (Ang II) may contain a charge relay system (CRS) involving Tyr/His/carboxylate, which creates a tyrosinate anion for receptor activation. Energy calculations were carried out to determine the preferred geometry for the CRS in the presence and absence of the Arg guanidino group occupying position 2 of Ang II. These findings suggest that Tyr is preferred over His for bearing the negative charge and that the CRS is stabilized by the guanidino group. Recent crystallography studies provided details of the binding of nonpeptide angiotensin receptor blockers (ARBs) to the Ang II type 1 (AT1) receptor, and these insights were applied to Ang II. A model of binding and receptor activation that explains the surmountable and insurmountable effects of Ang II analogues sarmesin and sarilesin, respectively, was developed and enabled the discovery of a new generation of ARBs called bisartans. Finally, we determined the ability of the bisartan BV6(TFA) to act as a potential ARB, demonstrating similar effects to candesartan, by reducing vasoconstriction of rabbit iliac arteries in response to cumulative doses of Ang II. Recent clinical studies have shown that Ang II receptor blockers have protective effects in hypertensive patients infected with SARS-CoV-2. Therefore, the usage of ARBS to block the AT1 receptor preventing the binding of toxic angiotensin implicated in the storm of cytokines in SARS-CoV-2 is a target treatment and opens new avenues for disease therapy.

P3343Association of minority status with mortality and hospital readmission in patients with ischemic cardiomyopathy in the STICH trial

Background

Racial and ethnic minorities with coronary artery disease (CAD) suffer worse outcomes than their non-minority counterparts, including increased mortality and hospital readmissions. Proposed explanations include impaired access to care, reduced quality of care, comorbidity burden and medication access. Study of the outcomes of minorities in randomized controlled trials (RCT) allows controlling for some of these factors.

Purpose

The purpose of the current study was to evaluate the impact of minority status on mortality and hospital readmission in patients enrolled in the Surgical Treatment for Ischaemic Heart Failure (STICH) trial.

Methods

STICH was a multicenter, international RCT of patients with an ejection fraction (EF) of 35% or less and CAD amenable to coronary artery bypass graft surgery (CABG) who were randomized to undergo CABG plus medical therapy or medical therapy alone. Median follow-up was 9.8 years. Minority status was defined by self-reported black race or Hispanic ethnicity. Optimal medical therapy (OMT) was the combination of at least 1 antiplatelet drug, a statin, a beta-blocker, and an angiotensin-converting enzyme inhibitor/angiotensin receptor blocker. The primary outcomes of interest were mortality and hospital readmission. Separate Cox proportional hazards models were constructed to examine the independent associations between minority status and mortality and readmission.

Results

Of 1212 patients randomized, 421 (35%) were members of a minority. CABG was the treatment assignment in 52.5% of minority participants whereas 47.5% were randomized to medical therapy (P=0.27). Minority patients were significantly younger than non-minority patients (57.8 vs 61.6 years, P=0.003). Sex, smoking status, and the prevalence of diabetes, hypertension, stroke and chronic kidney disease did not differ between minority and non-minority patients. Fewer minority patients had hyperlipidemia (49% vs. 66%, P<0.001), prior MI (72% vs 80%, P=0.003), atrial fibrillation (8.1% vs. 15%, P=0.001) or prior percutaneous coronary intervention (9% vs. 15%, P=0.004). Minority patients were less often on OMT at 30 days (56% vs. 66%, P=0.001), 1 year (70% vs. 76%, P=0.048) and 5 years (66% vs. 75%, P=0.002). Crude mortality rates were lower in minority patients (57% vs. 65%, P=0.004). However, minority status was independently associated with an increased hazard of mortality (HR 2.3, 95% CI: 1.5–2.5, P<0.001) but had no effect on rehospitalization (HR 1.01, 95% CI: 0.78–1.31, P=0.97).

Conclusion

Despite being a low risk population, minority status in the STICH trial was associated with a 2.3-fold increased hazard of mortality in patients with ischaemic cardiomyopathy. Additional research is urgently needed to delineate and address the causes of disparate outcomes among minority patients.

Submandibular gland tripeptide FEG (Phe-Glu-Gly) and analogues: keys to structure determination

This study examined the structure activity relationship of NH(3)-Phe-Glu-Gly-COO(-) (FEG), a potent inhibitor of intestinal anaphylaxis. The inhibition by FEG analogues of antigen-provoked contractions of isolated ileal segments obtained from ovalbumin-sensitized rats was determined and molecular modeling performed. A combination of aromaticity of the first residue, minimal extension of the carboxyl group on residue 2, and underivatized N and C termini were essential for biological activity. FEG, WEG, WDG and the d-enantiomeric forms of FEG (feG) and YEG (yeG) retained biological activity. By considering dipole moments, the structural and conformational features critical to biological activity were established as the glutamyl-carboxyl group/Phe side chain and carboxyl/amino termini interactions. Analysis of Ramachandran plots for position 1 sidechains indicate that mobility of the aromatic sidechain must be restricted to retain biological activity. The anti-anaphylactic effects of FEG, characterized by specific structural and conformational restrictions, indicate a selective interaction with a receptor for this peptide in the intestine.

[Münchausen syndrome by proxy - two case reports]

OBJECTIVE: To draw pediatrician's and healthcare worker's attention to the Munchausen syndrome by proxy, a serious kind of child abuse. PATIENTS AND METHODS: We report the clinical history and the evolution of two patients, based on a review of these patient's files in the Children's Rights Committee of the Hospital da Criança Santo Antônio, for further discussion. The first case reports a 5- year old child that presented difficult-controlling seizures; this case had an excellent prognosis after being examined by several specialists and later on by the Children's Right Committee. The second case reported is a 5-month old infant who presented apnea crisis accompanied by cyanosis and seizures. COMMENT: Munchausen syndrome by proxy is a relatively rare clinical entity, that can be difficult to be diagnosed, leading to unnecessary and potentially harmful diagnostic procedures to the child.