RESUMEN
BACKGROUND AND AIMS ACE2, part of the counter-regulatory arm of the renin–angiotensin system, serves both as protective toward oxidative stress and cardiovascular remodeling and as a key entry for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). ACE2 has two isoforms, non-glycosylated and glycosylated, the latter being accountable for the binding with SARS-CoV-2. After the binding, viruses use proteases as cathepsin-L (Cat-L) to entry the cells. Both ACE2 glycosylation and Cat-L activity are pH-dependent. Gitelman and Bartter syndromes (GS/BS), rare genetic tubulopathies, are characterized by electrolytic alterations, activation of the renin–angiotensin system, yet normo-hypotension, increased levels of ACE2 and metabolic alkalosis with likely increased intracellular pH. We reported that during the first wave of COVID-19 in early 2020 none of our cohort of 128 GS/BS patients from the major hotspots in Northern Italy had been infected or suffered any major COVID-19 symptoms and in a second survey on the same cohort in 2021, we reported only eight positives, four asymptomatic and four with very light symptoms This study aims to investigate potential mechanisms as ACE2 glycosylation and Cat-L activity related to patients’ metabolic alkalosis and viral entry/infection. METHOD Mononuclear cells ACE2 glycosylation (Western blot) and blood Cat-L activity (ELISA) from 20 GS/BS patients have been compared with those from 15 healthy subjects. RESULTS Non-glycosylated ACE2 was higher in GS/BS (0.82 ± 0.19 d.u. versus 0.67 ± 0.13, P = 0.01);glycosylated ACE2 was not different (0.85 ± 0.28 in GS/BS versus 0.73 ± 0.23, P = 0.19). Cat-L activity was lower in GS/BS (3.90 ± 1.13 r.f.u. versus 5.31 ± 0.8, P <0 0.001) and inversely correlated with blood bicarbonate (HCO3−), while a negative correlation between glycosylated ACE2 and HCO3− approaches statistical significance (P = 0.08). CONCLUSION GS/BS's metabolic alkalosis, likely by increasing intracellular pH, influences the glycosylation of ACE2 and the activity of Cat-L, providing a mechanistic explanation for the near-complete absence of COVID-19 or its symptoms reported in our cohort. These findings provide a rationale for pursuing the identification and/or synthesis of new drugs that specifically target ACE2 glycosylation and/or proteases involved in SARS-CoV-2 infection.
RESUMEN
COVID-19 is spreading globally with the angiotensin converting enzyme (ACE)-2 serving as the entry point of SARS-CoV-2 virus. This raised concerns how ACE2 and the Renin-Angiotensin (Ang)-System (RAS) are to be dealt with given their roles in hypertension and their involvement in COVID-19's morbidity and mortality. Specifically, increased ACE2 expression in response to treatment with ACE inhibitors (ACEi) and Ang II receptor blockers (ARBs) might theoretically increase COVID-19 risk by increasing SARS-CoV-2 binding sites. However, ACE2 is part of the protective counter-regulatory ACE2-Ang1-7-MasR axis, which opposes the classical ACE-AngII-AT1R regulatory axis. We used Gitelman's and Bartter's syndromes (GS/BS) patients, rare genetic tubulopathies that have endogenously increased levels of ACE2, to explore these issues. Specifically, 128 genetically confirmed GS/BS patients, living in Lombardia, Emilia Romagna and Veneto, the Northern Italy hot spots for COVID-19, were surveyed via telephone survey regarding COVID-19. The survey found no COVID-19 infection and absence of COVID-19 symptoms in any patient. Comparison analysis with the prevalence of COVID-19 in those regions showed statistical significance (p < 0.01). The results of the study strongly suggest that increased ACE2 does not increase risk of COVID-19 and that ACEi and ARBs by blocking excessive AT1R-mediated Ang II activation might favor the increase of ACE2-derived Ang 1-7. GS/BS patients' increased ACE2 and Ang 1-7 levels and their characteristic chronic metabolic alkalosis suggest a mechanism similar to that of chloroquine/hydroxychloroquine effect on ACE2 glycosylation alteration with resulting SARS-COV-2 binding inhibition and blockage/inhibition of viral entry. Studies from our laboratory are ongoing to explore GS/BS ACE2 glycosylation and other potential beneficial effects of BS/GS. Importantly, the absence of frank COVID-19 or of COVID-19 symptoms in the BS/GS patients cohort, given no direct ascertainment of COVID-19 status, suggest that elevated ACE2 levels as found in GS/BS patients at a minimum render COVID-19 infection asymptomatic and thus that COVID-19 symptoms are driven by ACE2 levels.
RESUMEN
COVID-19 often leads to acute respiratory distress syndrome complicated by acute kidney injury (AKI). The indications for renal replacement therapy for these patients are those commonly accepted to treat AKI. We describe a continuous veno-venous haemodialysis (CVVHD) protocol for AKI, which aims to provide the best treatment according to the particular patient's and medical personnels' needs in biohazard settings with limited human and technological resources. We designed a CVVHD protocol with a high cut-off (HCO) filter in regional citrate anticoagulation (RCA). The HCO filter in diffusion determines the enhanced cytokines clearance with less filter clotting due to a lower filtration fraction. In our hospital, at the beginning of the pandemic outbreak, we treated seven COVID-19 patients with AKI stage 2 and 3 and recorded the circuit lifespan and the number of interventions on monitors. CVVHD in RCA appears to be safe, effective and easy to be performed in a biohazard scenario using lower blood flows and less bag changes with fluid savings, a biohazard reduction and sparing of resources. Although the data come from a very small cohort, our protocol seems related to a low mortality.