Transcriptional regulation and small compound targeting of ACE2 in lung epithelial cells.

Angiotensin-converting enzyme 2 (ACE2) is the receptor of COVID-19 pathogen SARS-CoV-2, but the transcription factors (TFs) that regulate the expression of the gene encoding ACE2 (ACE2) have not been systematically dissected. In this study we evaluated TFs that control ACE2 expression, and screened for small molecule compounds that could modulate ACE2 expression to block SARS-CoV-2 from entry into lung epithelial cells. By searching the online datasets we found that 24 TFs might be ACE2 regulators with signal transducer and activator of transcription 3 (Stat3) as the most significant one. In human normal lung tissues, the expression of ACE2 was positively correlated with phosphorylated Stat3 (p-Stat3). We demonstrated that Stat3 bound ACE2 promoter, and controlled its expression in 16HBE cells stimulated with interleukin 6 (IL-6). To screen for medicinal compounds that could modulate ACE2 expression, we conducted luciferase assay using HLF cells transfected with ACE2 promoter-luciferase constructs. Among the 64 compounds tested, 6-O-angeloylplenolin (6-OAP), a sesquiterpene lactone in Chinese medicinal herb Centipeda minima (CM), represented the most potent ACE2 repressor. 6-OAP (2.5 µM) inhibited the interaction between Stat3 protein and ACE2 promoter, thus suppressed ACE2 transcription. 6-OAP (1.25-5 µM) and its parental medicinal herb CM (0.125%-0.5%) dose-dependently downregulated ACE2 in 16HBE and Beas-2B cells; similar results were observed in the lung tissues of mice following administration of 6-OAP or CM for one month. In addition, 6-OAP/CM dose-dependently reduced IL-6 production and downregulated chemokines including CXCL13 and CX3CL1 in 16HBE cells. Moreover, we found that 6-OAP/CM inhibited the entry of SARS-CoV-2 S protein pseudovirus into target cells. These results suggest that 6-OAP/CM are ACE2 inhibitors that may potentially protect lung epithelial cells from SARS-CoV-2 infection.

Antihypertensive drugs are associated with reduced fatal outcomes and improved clinical characteristics in elderly COVID-19 patients.

The novel coronavirus (CoV) severe acute respiratory syndrome (SARS)-CoV-2 outbreak began at the end of 2019 in Wuhan, China, and has spread to over 200 countries. In this multicenter retrospective study, we identified 2190 adult patients admitted for laboratory-confirmed COVID-19 in three participating centers. Multivariate logistic regression was conducted in patients with comorbid hypertension to examine the potential association between clinical outcomes, disease severity, and clinical characteristics with the use of ACEI, ARB, calcium-channel blockers (CCB), beta-blockers (BB), and thiazide diuretics. The clinical outcome, dyspnea, and fatigue were significantly improved in patients, especially elderly patients who were older than 65 years, who took ARB drugs prior to hospitalization compared to patients who took no drugs. The reduction of disease severity of elderly COVID-19 patients was associated with CCB and ACEI users. Clinical indices, including CRP, lymphocyte count, procalcitonin D dimer, and hemoglobin, were significantly improved in elderly ARB users. In addition, the clinical outcomes were statistically significantly improved in patients who took antihypertension drugs ARB, BB, and CCB after statistical adjustment by all ages, gender, baseline of blood pressures, and coexisting medical conditions. Our data indicate that hypertension drugs ARB, ACEI, CCB, and BB might be beneficial for COVID-19 patients.