Is spironolactone the preferred renin-angiotensin-aldosterone inhibitor for protection against COVID-19?

The high mortality of specific groups from COVID-19 highlights the importance of host-viral interactions and the potential benefits from enhancing host defenses. SARS-CoV-2 requires angiotensin converting enzyme (ACE)2 as a receptor for cell entry and infection. While both ACE inhibitors and spironolactone can upregulate tissue ACE2, there are important points of discrimination between these approaches. The virus requires proteolytic processing of its spike protein by transmembrane protease receptor serine type 2 (TMPRSS2) to enable binding to cellular ACE2. Since TMPRSS2 contains an androgen promoter, it may be downregulated by the antiandrogenic actions of spironolactone. Furin and plasmin also process the spike protein. They are inhibited by protease nexin 1 or serine E2 (PN1) that is upregulated by angiotensin II but downregulated by aldosterone. Therefore, spironolactone should selectively downregulate furin and plasmin. Furin also promotes pulmonary edema while plasmin promotes hemovascular dysfunction. Thus, a downregulation of furin and plasmin by PN1 could be a further benefit of MRAs beyond their well established organ protection. We review the evidence that spironolactone may be the preferred RASSi to increase PN1 and decrease TMPRSS2, furin and plasmin activities and thereby to reduce viral cell binding, entry, infectivity and bad outcomes. This hypothesis requires direct investigation.