Implications of Synthetic Modifications of the Cardiotonic Steroid Lactone Ring on Cytotoxicity.

Na,K-ATPase (NKA) and cardiotonic steroids (CTS) have shown potent cytotoxic and anticancer effects. Here, we have synthesized a series of CTS digoxin derivatives (γ-benzylidene) with substitutions in the lactone ring and evaluated the cytotoxicity caused by digoxin derivatives in tumor and non-tumor cells lines, as well as their effects on NKA. The cytotoxicity assay was determined in HeLa, A549, and WI-26 VA4 after they were treated for 48 h with increased concentrations of CTS. The effects of CTS on NKA activity and immunoblotting of α1 and ß1 isoforms were evaluated at IC50 concentrations in A549 cell membrane. NKA activity from mouse brain cortex was also measured. The majority of CTS exhibited low cytotoxicity in tumor and non-tumor cells, presenting IC50 values at micromolar concentrations, while digoxin showed cytotoxicity at nanomolar concentrations. BD-15 presented the lowest IC50 value (8 µM) in A549 and reduced its NKA activity in 28%. In contrast, BD-7 was the compound that most inhibited NKA (56% inhibition) and presented high IC50 value for A549. In mouse cortex, only BD-15 modulated the enzyme activity in a concentration-dependent inhibition curve. These results demonstrate that the cytotoxicity of these compounds is not related to NKA inhibition. The substitutions in the lactone ring of digoxin led to an increase in the cytotoxic concentration in tumor cells, which may not be interesting for cancer, but it has the advantage of increasing the therapeutic margin of these molecules when compared to classic CTS, and can be used safely in research for other diseases.

Angiotensin-(1-7) infusion in COVID-19 patients admitted to the ICU: a seamless phase 1-2 randomized clinical trial.

BACKGROUND: The coronavirus-related disease (COVID-19) is mainly characterized by a respiratory involvement. The renin-angiotensin system (RAS) has a relevant role in the pathogenesis of COVID-19, as the virus enters host's cells via the angiotensin-converting enzyme 2 (ACE2). METHODS: This investigator-initiated, seamless phase 1-2 randomized clinical trial was conceived to test the safety and efficacy of continuous short-term (up to 7 days) intravenous administration of Angiotensin-(1-7) in COVID-19 patients admitted to two intensive care units (ICU). In addition to standard of care, intravenous administration of Angiotensin-(1-7) was started at 5 mcg/Kg day and increased to 10 mcg/Kg day after 24 h (Phase 1; open label trial) or given at 10 mcg/Kg day and continued for a maximum of 7 days or until ICU discharge (Phase 2; double-blind randomized controlled trial). The rate of serious adverse events (SAEs) served as the primary outcome of the study for Phase 1, and the number of oxygen free days (OFDs) by day 28 for Phase 2. RESULTS: Between August 2020 and July 2021, when the study was prematurely stopped due to low recruitment rate, 28 patients were included in Phase 1 and 79 patients in Phase 2. Of those, 78 were included in the intention to treat analysis, and the primary outcome was available for 77 patients. During Phase 1, one SAE (i.e., bradycardia) was considered possibly related to the infusion, justifying its discontinuation. In Phase 2, OFDs did not differ between groups (median 19 [0-21] vs. 14 [0-18] days; p = 0.15). When patients from both phases were analyzed in a pooled intention to treat approach (Phase 1-2 trial), OFDs were significantly higher in treated patients, when compared to controls (19 [0-21] vs. 14 [0-18] days; absolute difference -5 days, 95% CI [0-7] p = 0.04). CONCLUSIONS: The main findings of our study indicate that continuous intravenous infusion of Angiotensin-(1-7) at 10 mcg/Kg day in COVID-19 patients admitted to the ICU with severe pneumonia is safe. In Phase II intention to treat analysis, there was no significant difference in OFD between groups. Trial Registration ClinicalTrials.gov Identifier: NCT04633772-Registro Brasileiro de Ensaios Clínicos, UTN number: U1111-1255-7167.

The effect of γ-radiation on the hemoglobin of stored red blood cells: the involvement of oxidative stress in hemoglobin conformation.

The aim of the present work was to evaluate the redox and oligomeric effects associated with the human hemoglobin of stored red blood cells that had been previously submitted to gamma radiation. Whole blood was collected from healthy donors and irradiated with 25 Gy of γ-radiation within 24 h of collection. At days 3, 5, 7, 9, 11, 14, and 28 postirradiation, fractions were removed and centrifuged, and the levels of methehemoglobin and oxyhemoglobin were measured. Hb was isolated to measure the denaturation and UV-vis spectra. The results from electrophoresis demonstrated that there was no fragmentation or cross-linking of the hemoglobin. However, ferrous center oxidation was identified as a very significant process. This mechanism is likely through an autoxidation process of the ferrous heme center, which has a maximal intensity between 5 and 7 days of storage. Interestingly, a subsequent reduction of the oxidized heme species was observed, and after 9 days of storage, the difference between the ferric species present in the control and irradiated samples was not representative. This interesting fact suggests a type of "protective action" by the blood to control the oxidative stress generated by the gamma irradiation. The UV-vis measurements demonstrated that the oxidized species was predominantly formed by hemichrome species (bis-histidine ferric heme species), which are usually associated with Heinz bodies. After 28 days of storage, evidence from the UV-vis measurements indicated that the oxidation of the irradiated sample was much higher than that observed in the control sample. These results demonstrate that despite the minimal polypeptide changes observed in the hemoglobin of stored red blood cells after gamma irradiation, the oxidation of the heme metallic center is not irrelevant and must be controlled to improve the hematological clinical procedures associated with the storage of red blood cells.

Increased circulating levels of angiotensin-(1-7) in severely ill COVID-19 patients.

This letter reports an unexpected increase of the ACE2 product angiotensin-(1-7) and a parallel decrease of its substrate angiotensin II, suggesting a dysregulation of the renin-angiotensin system towards angiotensin-(1-7) formation in #COVID19 patients https://bit.ly/3xFXuTU.

New bufadienolides extracted from Rhinella marina inhibit Na,K-ATPase and induce apoptosis by activating caspases 3 and 9 in human breast and ovarian cancer cells.

Bufadienolide compounds have been used for growth inhibition and apoptosis induction in tumor cells. Those families of cardiotonic steroids can bind the Na,K-ATPase, causing its inhibition. The use of bufadienolides is widely described in the literature as an anticancer function. The aim of this study was to evaluate the effects of bufadienolides and alkaloid isolated from venom samples from R. marina on tumor cells. We performed cytotoxicity assay in MDA-MB-231 and TOV-21G cells and evaluated the activity of Caspases (3 and 9), Na, K-ATPase, PMCA and SERCA. Four compounds were extrated from the venom of R. marina. The compound 1 showed higher cytotoxicity in MDA-MB-231cells. Compound 1 also showed activation of Caspase 3 and 9. This compound caused an inhibition of the activity and expression of Na, K-ATPase, and also showed activation of both caspase-9 and caspase-3 in MDA-MB-231 cells. We also observed that Compound 1 had a direct effect on some ATPases, such as Na, K-ATPase, PMCA and SERCA. Compound 1 was able to inhibit the activity of the purified Na, K-ATPase enzyme from the concentration of 5 µM. It also caused inhibition of PMCA at all concentrations tested (1 nM-30 µM). However, the compound 1 led to an increase of the activity of purified SERCA between the concentrations of 7.5-30 µM. Thus, we present a Na, K-ATPase and PMCA inhibitor, which may lead to the activation of caspases 3 and 9, causing the cells to enter into apoptosis. Our study suggests that compound 1 may be an interesting molecule as an anticancer agent.