Introduction: The angiotensin-converting enzyme 2 (ACE-2) and its shedding product (soluble ACE-2 [sACE-2]) are implicated in adverse cardiovascular outcomes. However, the relationship between sACE-2 and stroke recurrence is unknown. Herein, we examined the relationship of sACE-2 with stroke recurrence in patients with ischemic stroke or transient ischemic attack. Methods: Data were obtained from the Third China National Stroke Registry (CNSR-III). Eligible cases consisted of 494 patients who developed recurrent stroke within 1-year follow-up, and 494 controls were selected using age- and sex-matched with a 1:1 case-control ratio. Conditional logistic regressions were used to evaluate the association between sACE-2 and recurrent stroke. The main outcomes were recurrent stroke within 1 year. Results: Among 988 patients included in this study, the median (interquartile range) of sACE-2 was 25.17 (12.29–45.56) ng/mL. After adjustment for conventional confounding factors, the odds ratio (OR) with 95% confidence interval (CI) in the highest quartile versus the lowest quartile was 1.68 (1.12–2.53) for recurrent stroke within 1-year follow-up. Subgroup analysis showed that the association between elevated plasma level of sACE-2 and stroke recurrence was significant in patients with higher systemic inflammation, as indicated by high-sensitivity C-reactive protein ≥ 2 mg/L (adjusted OR: 2.33 [95% CI, 1.15–4.72]) and neutrophil counts ≥ median (adjusted OR: 2.66 [95% CI, 1.35–5.23]) but not significant in patients with lower systemic inflammation. Discussion/Conclusion: Elevated plasma sACE-2 concentration was associated with increased risk of recurrent stroke.

Angiotensin-converting enzyme 2 (ACE-2), an integral membrane protein, is an endogenous counter regulator of the renin-angiotensin hormonal cascade, which degrades angiotensin II (Ang II) and counteracts the renin-angiotensin system (RAS) [1]. The RAS is a hormonal cascade whose modulation has resulted in several effective cardiovascular disease therapeutics [2, 3]. Notably, ACE-2 is present on endothelial cells and can undergo shedding to soluble ACE-2 (sACE-2) into the circulation in response to inflammatory milieu [4]. In patients with cardiovascular disease, increased circulating sACE-2 predicts adverse cardiovascular outcomes [5]. Moreover, elevated plasma ACE-2 activity is associated with increased risk of embolic stroke of undetermined source [2]. However, the relationship between sACE-2 and stroke recurrence has not been well established. In this study, using data from the Third China National Stroke Registry (CNSR-III), we conducted a nested case-control study to investigate the association between sACE-2 and recurrent stroke in patients with ischemic stroke (IS) or transient ischemic attack (TIA).

Study Population

CNSR-III is a nationwide, prospective, multicenter, observational registry for patients presented to hospitals with acute ischemic cerebrovascular events. Details of the registry database are available in our previous studies. Briefly, consecutive patients were enrolled from 201 hospitals between August 2015 and March 2018 in China. In total, 15,166 patients were enrolled in CNSR-III, of which 93.3% with IS (n = 14,146) and 6.7% with TIA (n = 1,020) within 7 days from the onset of symptoms to enrollment.

After 1-year follow-up, we identified 1,473 cases of recurrent stroke. Among which, 494 cases were randomly selected as the case group. Controls were randomized selected and matched by age (±2 years) and sex at a 1:1 case-control ratio. Finally, a total of 988 patients (494 cases and 494 controls) were enrolled in the current study (shown in online suppl. Fig. S1; for all online suppl. material, see https://doi.org/10.1159/000538245). The protocol of the CNSR-III was approved by the Ethics Committee of Beijing Tiantan Hospital and all participating centers. All participants or their representatives provided written informed consents before being enrolled in the trial.

Measurement of sACE-2

Fasting blood samples were collected within 24 h of admission. Serum and plasma specimens were extracted and transported through cold chain to the core laboratory in Beijing Tiantan Hospital. All specimens were stored at −80°C until detected centrally and blindly. Human ACE-2 ELISA (catalog number: ab235649, Abcam, USA) was utilized to measure the plasma level of ACE-2. The assay is an enzyme-linked immunosorbent assay kit, which is designed for the quantitative measurement of ACE-2 protein in human serum, plasma, cell culture supernatant, urine, and tissue extract samples. The concentration of plasma ACE-2 was measured and analyzed according to the manufacturers' protocols. Briefly, equal amount of standard, control, or sample were added per well and incubated with antibody cocktail for 1 h at room temperature, followed by washing with wash buffer. Then, substrate solution was added to each well and incubated for 10 min at room temperature, and then stop solution was added to each well. The optical density of each well was determined within 30 min using a microplate reader set to 450 nm.

Assessment of Outcomes

Patients were followed up clinically by means of face-to-face interviews at discharge and 3 months and by means of telephone at 6 months and 1 year by the trained research coordinators. The trained research coordinators would contact the participants to ask whether they had stroke-related symptoms during 1-year follow-up and whether to be admitted to the hospital for diagnosis and treatment. Stroke recurrence that occurred during follow-up was recorded. If the participants had new stroke symptoms but they did not go to the doctor, they were required to complete brain imaging (CT or MR) at their attending hospital for confirmation. The suspected recurrent cerebrovascular events without hospitalization were judged by the Independent Endpoint Judgment Committee. Participants with missing outcome data would be censored at the last follow-up visit time (one-year visit or last visit preceding loss to follow-up). After the completion of baseline investigation, information at discharge was collected for all patients. Thus, all patients in the cohort were followed up and had at least one follow-up visit. The primary outcome was stroke recurrence within 1 year, including new IS and hemorrhagic stroke.

Baseline Data Collection

The baseline data were collected prospectively using an electronic data capture system by face-to-face interviews. The following data were obtained from the registry database, which included age, sex, and systolic blood pressure, body mass index, current smoker, medical history of hypertension, diabetes mellitus, antihypertensive drugs; stroke types, stroke subtypes classified as large artery atherosclerosis, and non-LAA according to the Trial of ORG 10172 in Acute Stroke Treatment (TOAST) criteria; tissue plasminogen activator (TPA); laboratory test of baseline fasting plasma glucose, total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, triglyceride, high-sensitivity C-reactive protein (hsCRP), interleukin-6 (IL-6), lipoprotein-associated phospholipase A2, ACE-2, white blood cell counts, neutrophil (NEUT) counts at admission.

Statistical Analysis

Continuous variables were expressed as median with interquartile range because of skewed distribution, and categorical variables were expressed as frequency with percentages. Participants were divided into four categories by quartiles of sACE-2. The nonparametric Wilcoxon or Kruskal-Wallis test was used to compare group differences for continuous variables, and χ2 test was used for categorical variables.

Multivariable conditional logistic regression analyses were performed to examine the association of sACE-2 with recurrent stroke. Variables were adjusted in the multivariable analyses if established as traditional predictors for recurrent stroke or associated with sACE-2 in univariate analysis with a value of p < 0.05, including BMI, baseline plasma level of total cholesterol, high-density lipoprotein cholesterol and low-density lipoprotein cholesterol, NEUT counts, stroke type, TOAST subtype, medical history of diabetes, coronary heart disease, and stroke and National Institute of Health stroke scale (NIHSS) at admission. Unadjusted and adjusted odds ratios (ORs) and their 95% confidence intervals (CIs) were calculated. Trend tests were performed in the regression models after the median of sACE-2 values of each quartile were entered into the model and treated as a continuous variable. To examine whether the association between sACE-2 and recurrent stroke differs in different population, subgroup analyses were performed by stratifying variables which were adjusted in the multivariable analysis with recurrent stroke at 1 year as the outcome of interest. Overall, a two-sided value of p < 0.05 was considered statistically significant. All analyses were performed with SAS software version 9.4 (SAS Institute Inc., Cary, NC).

Baseline Characteristics

Among 1,473 patients with recurrent stroke within 1 year, we randomly selected 494 cases into the current study. The baseline characteristics between excluded and included were largely comparable (online Table S1). A total of 494 cases and 494 controls were enrolled on the study, the median age was 63 (interquartile range: 56.00–70.00) years, and 676 (68.42%) were men. Baseline characteristics between cases and controls are presented in Table 1. Compared with controls, cases had a higher proportion of IS, large artery atherosclerosis, other determined etiology, a higher plasma level of sACE-2, hsCRP, and NEUT counts. A higher sACE-2 level at presentation was observed among patients who were older and had a higher proportion of medical history of diabetes mellitus (online Table S2). In addition, the proportion of TOAST subtypes was statistically significant in patients with different sACE-2 levels (online Table S2).

Table 1.

Baseline summary data for all subjects in the nested case-control study classified by stroke recurrence

CharacteristicsOverall (n = 988)Controls (n = 494)Cases (n = 494)p value
Demographic characteristics 
 Age, years, median (IQR) 63.0 (56.0–70.0) 63.0 (56.0–70.0) 63.0 (56.0–70.0) Matched 
 Male, n (%) 676 (68.42) 338 (68.42) 338 (68.42) Matched 
 BMI, kg/m2, median (IQR) 24.49 (22.72–26.71) 24.5 (22.84–26.73) 24.49 (22.65–26.71) 0.76 
Current smoker, n (%) 302 (30.57) 156 (31.58) 146 (29.55) 0.53 
Medical history, n (%) 
 CHD 118 (11.94) 51 (10.32) 67 (13.56) 0.1409 
 Stroke 292 (29.55) 143 (28.95) 149 (30.16) 0.7274 
 Hypertension 633 (64.07) 313 (63.36) 320 (64.78) 0.69 
 Diabetes mellitus 264 (26.72) 136 (27.53) 128 (25.91) 0.61 
Antihypertensive drugs 471 (47.67) 234 (47.37) 237 (47.98) 0.85 
Stroke type, n (%) 
 TIA 54 (5.47) 39 (7.89) 15 (3.04) 0.001 
IS 934 (94.53) 455 (92.11) 479 (96.96)  
TOAST subtype, n (%) 
 Large artery atherosclerosis 280 (28.34) 123 (24.90) 157 (31.78) 0.011 
 Cardioembolic 89 (9.01) 47 (9.51) 42 (8.50)  
 Small artery occlusion 166 (16.80) 92 (18.62) 74 (14.98)  
 Other determined etiology 12 (1.21) 2 (0.40) 10 (2.02)  
Undetermined etiology 441 (44.64) 230 (46.56) 211 (42.71)  
NIHSS at admission, n (%) 
 0–3 484 (48.99) 266 (53.85) 218 (44.13) 0.0028 
≥4 504 (51.01) 228 (46.15) 276 (55.87)  
TPA, n (%) 0.21 
 Yes 85 (8.60) 37 (7.49) 48 (9.72)  
No 903 (91.40) 457 (92.51) 446 (90.28)  
Laboratory test 
 SBP at admission, mm Hg, median (IQR) 150.0 (136.75–165.25) 149.0 (135.0–163.5) 150.0 (137.5–167.0) 0.42 
 FPG, mM, median (IQR) 5.74 (5.05–7.25) 5.74 (5.04–7.20) 5.74 (5.04–7.25) 0.90 
 Baseline TC, mM, median (IQR) 3.98 (3.28–4.76) 3.94 (3.27–4.74) 4.00 (3.29–4.81) 0.77 
 Baseline LDL-c, mM, median (IQR) 2.35 (1.79–2.98) 2.29 (1.79–2.96) 2.38 (1.78–3.02) 0.33 
 Baseline HDL-c, mM, median (IQR) 1.06 (0.89–1.25) 1.06 (0.89–1.26) 1.06 (0.88–1.24) 0.34 
 Baseline TG, mM, median (IQR) 1.37 (1.03–1.91) 1.39 (1.07–1.98) 1.33 (1.00–1.89) 0.14 
 Baseline hsCRP, mg/L, median (IQR) 1.90 (0.80–5.41) 1.55 (0.70–4.29) 2.35 (0.98–6.26) <0.0001 
 Baseline IL-6, pg/mL, median (IQR) 2.82 (1.74–5.66) 2.69 (1.81–4.75) 3.00 (1.64–6.51) 0.16 
 Baseline Lp-PLA2, ng/mL, median (IQR) 180.56 (133.38–227.35) 179.92 (133.44–225.76) 180.84 (133.32–229.72) 0.49 
 sACE-2, ng/mL, median (IQR) 25.17 (12.29–45.56) 20.40 (10.99–43.71) 27.89 (13.66–48.39) 0.002 
 WBC counts, 109/L, median (IQR) 7.00 (5.74–8.50) 6.82 (5.71–8.33) 7.10 (5.79–8.54) 0.29 
 NEUT counts, 109/L, median (IQR) 4.57 (3.60–5.88) 4.42 (3.55–5.80) 4.70 (3.69–5.99) 0.049 
CharacteristicsOverall (n = 988)Controls (n = 494)Cases (n = 494)p value
Demographic characteristics 
 Age, years, median (IQR) 63.0 (56.0–70.0) 63.0 (56.0–70.0) 63.0 (56.0–70.0) Matched 
 Male, n (%) 676 (68.42) 338 (68.42) 338 (68.42) Matched 
 BMI, kg/m2, median (IQR) 24.49 (22.72–26.71) 24.5 (22.84–26.73) 24.49 (22.65–26.71) 0.76 
Current smoker, n (%) 302 (30.57) 156 (31.58) 146 (29.55) 0.53 
Medical history, n (%) 
 CHD 118 (11.94) 51 (10.32) 67 (13.56) 0.1409 
 Stroke 292 (29.55) 143 (28.95) 149 (30.16) 0.7274 
 Hypertension 633 (64.07) 313 (63.36) 320 (64.78) 0.69 
 Diabetes mellitus 264 (26.72) 136 (27.53) 128 (25.91) 0.61 
Antihypertensive drugs 471 (47.67) 234 (47.37) 237 (47.98) 0.85 
Stroke type, n (%) 
 TIA 54 (5.47) 39 (7.89) 15 (3.04) 0.001 
IS 934 (94.53) 455 (92.11) 479 (96.96)  
TOAST subtype, n (%) 
 Large artery atherosclerosis 280 (28.34) 123 (24.90) 157 (31.78) 0.011 
 Cardioembolic 89 (9.01) 47 (9.51) 42 (8.50)  
 Small artery occlusion 166 (16.80) 92 (18.62) 74 (14.98)  
 Other determined etiology 12 (1.21) 2 (0.40) 10 (2.02)  
Undetermined etiology 441 (44.64) 230 (46.56) 211 (42.71)  
NIHSS at admission, n (%) 
 0–3 484 (48.99) 266 (53.85) 218 (44.13) 0.0028 
≥4 504 (51.01) 228 (46.15) 276 (55.87)  
TPA, n (%) 0.21 
 Yes 85 (8.60) 37 (7.49) 48 (9.72)  
No 903 (91.40) 457 (92.51) 446 (90.28)  
Laboratory test 
 SBP at admission, mm Hg, median (IQR) 150.0 (136.75–165.25) 149.0 (135.0–163.5) 150.0 (137.5–167.0) 0.42 
 FPG, mM, median (IQR) 5.74 (5.05–7.25) 5.74 (5.04–7.20) 5.74 (5.04–7.25) 0.90 
 Baseline TC, mM, median (IQR) 3.98 (3.28–4.76) 3.94 (3.27–4.74) 4.00 (3.29–4.81) 0.77 
 Baseline LDL-c, mM, median (IQR) 2.35 (1.79–2.98) 2.29 (1.79–2.96) 2.38 (1.78–3.02) 0.33 
 Baseline HDL-c, mM, median (IQR) 1.06 (0.89–1.25) 1.06 (0.89–1.26) 1.06 (0.88–1.24) 0.34 
 Baseline TG, mM, median (IQR) 1.37 (1.03–1.91) 1.39 (1.07–1.98) 1.33 (1.00–1.89) 0.14 
 Baseline hsCRP, mg/L, median (IQR) 1.90 (0.80–5.41) 1.55 (0.70–4.29) 2.35 (0.98–6.26) <0.0001 
 Baseline IL-6, pg/mL, median (IQR) 2.82 (1.74–5.66) 2.69 (1.81–4.75) 3.00 (1.64–6.51) 0.16 
 Baseline Lp-PLA2, ng/mL, median (IQR) 180.56 (133.38–227.35) 179.92 (133.44–225.76) 180.84 (133.32–229.72) 0.49 
 sACE-2, ng/mL, median (IQR) 25.17 (12.29–45.56) 20.40 (10.99–43.71) 27.89 (13.66–48.39) 0.002 
 WBC counts, 109/L, median (IQR) 7.00 (5.74–8.50) 6.82 (5.71–8.33) 7.10 (5.79–8.54) 0.29 
 NEUT counts, 109/L, median (IQR) 4.57 (3.60–5.88) 4.42 (3.55–5.80) 4.70 (3.69–5.99) 0.049 

ACE-2, angiotensin-converting enzyme 2; BMI, body mass index; FPG, fasting plasma glucose; HDL-c, high-density lipoprotein cholesterol; hsCRP, high-sensitivity C-reactive protein; IL-6, interleukin-6; LDL-c, low-density lipoprotein cholesterol; Lp-PLA2, lipoprotein-associated phospholipase A2; NEUT, neutrophil; SBP, systolic blood pressure; TC, total cholesterol; TG, triglyceride; TIA, transient ischemic attack; TOAST, Trial of ORG 10172 in Acute Stroke Treatment; TPA, tissue plasminogen activator; WBC, white blood cell.

sACE-2 and Recurrent Stroke

In the unadjusted and adjusted analysis (shown in Fig. 1), a higher plasma level of sACE-2 was significantly associated with higher odds for recurrent stroke within 1-year follow-up, and the adjusted OR for the highest quartile versus lowest quartile of ACE-2 was 1.68 (95% CI, 1.12–2.53; p for trend 0.0012).

Fig. 1.

Association between the plasma level of ACE-2 and risk of stroke recurrence. Adjusted for body mass index, baseline plasma level of hsCRP, total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, NEUT counts, stroke type, TOAST subtype, medical history of diabetes, coronary heart disease, and stroke and NIHSS at admission.

Fig. 1.

Association between the plasma level of ACE-2 and risk of stroke recurrence. Adjusted for body mass index, baseline plasma level of hsCRP, total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, NEUT counts, stroke type, TOAST subtype, medical history of diabetes, coronary heart disease, and stroke and NIHSS at admission.

Close modal

Subgroup Analyses

Results of subgroup analysis were presented in Figure 2. A significant association between sACE-2 and stroke recurrence was observed in patients with higher plasma level of hsCRP (≥2 mg/L) (adjusted OR: 2.33 [95% CI, 1.15–4.72]) and higher NEUT (NEUT counts ≥ median) (adjusted OR: 2.66 [95% CI, 1.35–5.23]) but not in patients with lower plasma level of hsCRP (<2 mg/L) (adjusted OR: 1.86 [95% CI, 0.99–3.49]) and lower NEUT (NEUT counts < median) (adjusted OR: 1.13 [95% CI, 0.61–2.09]).

Fig. 2.

Subgroup analysis of the association between the plasma level of sACE-2 and risk of stroke recurrence. Adjusted for body mass index, baseline plasma level of hsCRP, total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, NEUT counts, stroke type, TOAST subtype, medical history of diabetes, coronary heart disease, and stroke and NIHSS at admission.

Fig. 2.

Subgroup analysis of the association between the plasma level of sACE-2 and risk of stroke recurrence. Adjusted for body mass index, baseline plasma level of hsCRP, total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, NEUT counts, stroke type, TOAST subtype, medical history of diabetes, coronary heart disease, and stroke and NIHSS at admission.

Close modal

Here, we showed for the first time that elevated serum level of sACE-2 was associated with greater risk of stroke recurrence in patients with IS or TIA. Notably, the sACE-2-associated risk of recurrent stroke was significant in patients with high plasma level of hsCRP (≥2 mg/L) and high NEUT counts, while not in patients with lower plasma level of hsCRP and NEUT counts.

Accumulated evidence has demonstrated the prognostic implications of circulating ACE-2 concentration and activity in general population and in patients with established cardiovascular disease [6, 7]. In patients with cardiovascular disease, increased circulating ACE-2 activity predicts adverse cardiovascular outcomes in patients with heart failure, coronary artery disease, and aortic stenosis [7‒9]. In a general population, increased plasma sACE-2 concentration was associated with increased risk of stroke, which was included in the major cardiovascular events [6]. An Australian case-control study demonstrated that ACE-2 activity is associated with embolic stroke of undetermined source [2]. In line with these findings, we observed that plasma sACE-2 levels were associated with stroke recurrence. Under inflammatory milieu, ACE-2 sheds from the membrane, producing sACE-2. Several prior studies have demonstrated that in patients with severe COVID-19, sACE-2 was associated with CRP, IL-6, ferritin, and white blood cell count, supporting a link with inflammation [4, 10]. In patients with end-stage kidney disease, sACE-2 positively correlated with IL-6 and CRP, respectively [11]. In consistent with the previous studies, in the current study, the association between elevated sACE-2 level and the risk of stroke recurrence was observed in patients with higher plasma level of hsCRP and NEUT counts. While in patients with lower plasma level of hsCRP and NEUT counts, no significant association was observed.

Although the underlying mechanism of the association between sACE-2 and stroke recurrence is not fully clarified, there is possible mechanistic explanation for our results. ACE-2 has two forms: one is on the cell membrane which has an anchor protein, and the other form is sACE-2, which is cleaved into the circulation in inflammatory conditions. ACE-2 degrades Ang II to generate Ang 1–7 on the membrane, which acts to counterbalance the RAS by degrading angiotensin II and has been expected to have protective effects on cardiovascular and renal systems [12, 13]. ACE-2 is widely expressed in the endothelia, which has been demonstrated to exert a protective effect during IS [14, 15]. In contrast to the protective effect of ACE-2 on the membrane, an elevated level of circulating sACE-2 is often associated with adverse cardiovascular and cerebrovascular events. The plasma sACE-2 derived from the shedding of ACE-2, which is driven by systemic inflammation [16, 17]. In the acute phase of stroke, the adrenal gland releases stress hormones immediately, which trigger robust activation of the immune system and systemic inflammation [18‒22]. Our finding that the association between elevated sACE-2 level and risk of was only significant in patients with higher systemic inflammation, as indicated by the plasma level of hsCRP and NEUT counts, in partly because of its compelling biological basis. HsCRP and NEUT counts could reflect the extent of systemic inflammation [16]. Previous studies have shown that the baseline hsCRP and NEUT count level on admission of patients with acute stroke is an important risk factor for stroke recurrence [23‒25]. In the case of stroke patients with higher systemic inflammation, more ACE-2 is cleaved to generate sACE-2, so that there is relatively less protective ACE-2 on the cell surface during stroke [26]. Inflammation-induced proteolytic release of sACE-2 into the circulation diminishes ACE-2-mediated protection against the tissue RAS, resulting in unopposed angiotensin II accumulation. Angiotensin II, a major player of RAS, is known to worsen ischemic brain damage partly dependent on an increased inflammation [2, 26, 27]. Evidence from clinical trials showed that blockade of RAS is effective to prevent a first or recurrent stroke, beyond the effect of blood pressure lowering. All of the above mentioned may be a possible explanation for the association of sACE-2 with stroke recurrence in patients with higher systemic inflammation.

We consider our findings to be of clinical significance. First, the association between sACE-2 and recurrent stroke suggests that circulating sACE-2 is worth examining further as a marker of dysregulated RAS, and understanding and modulating the RAS might lead to new approaches to reduce recurrent stroke. Second, evidence from the Canakinumab Anti-Inflammatory Thrombosis Outcome Study (CANTOS) and the Low-Dose Colchicine (LoDoCo) trial for secondary prevention of cardiovascular disease has demonstrated the clinical benefit of a targeted anti-inflammatory therapy [28, 29]. Anti-inflammatory therapy may possibly attenuate the sACE-2 associated risk of stroke recurrence.

Our study also has several limitations. First, we only measured the concentration of plasma sACE-2 without measuring the activity of ACE-2. However, a previous investigation showed a strong correlation between catalytic activity and concentration [30]. Second, we only measured the sACE-2 level at admission. The sACE-2 level before or during the pathological process was not measured. Third, the study design does not allow for determining the causality of sACE-2 and stroke recurrence. Moreover, we did not measure the circulating levels of RAS components, such as ACE and angiotensin II. Finally, our study only investigated the association between sACE-2 and the risk of stroke recurrence in Asians, which could not be interpreted for other races and ethnic group. In conclusion, in our present study, we observed that elevated plasma sACE-2 concentration was associated with increased risk of recurrent stroke. Modulation of inflammation might represent a possible way to attenuate the sACE-2-associated risk of stroke recurrence.

According to the principles mentioned in the Declaration of Helsinki, the Ethics Committees of Beijing Tiantan Hospital and all other recruited participating centers approved the study protocol. Written informed consent was obtained from all participants (or guardians of participants) in this study.

The authors declare that they have no competing interests.

This work was supported by grants from Chinese Academy of Medical Sciences Innovation Fund for Medical Sciences (2019-I2M-5-029), Capital Health Research and Development of Special (2020-2Z-20411), National Natural Science Foundation of China (81970425), China National Key R&D Program (2020YFA0803700), the Capital’s Funds for Health Improvement and Research (2020-1-2041), and Beijing Postdoctoral Research Foundation (2021-ZZ-021).

Jie Xu, Yongjun Wang and Lemin Zheng contributed to the conception and design of the study. All authors (Yongjun Wang, Lemin Zheng, Jing Xue, Jie Xu, Mingming Shi, Qin Xu, Anxin Wang, Xue Jiang, Jinxi Lin, Xia Meng, and Hao Li) contributed to the acquisition and analysis of data. Jing Xue, Yongjun Wang, and Lemin Zheng contributed to drafting the text and preparing the tables and figures. All authors read and approved the final manuscript.

Additional Information

Jing Xue and Mingming Shi contributed equally to this work.

Data of this study are not publicly available due to privacy reasons but are available from corresponding author upon reasonable request. Further inquiries can be directed to the corresponding author.

1.
Wallentin
L
,
Lindback
J
,
Eriksson
N
,
Hijazi
Z
,
Eikelboom
JW
,
Ezekowitz
MD
, et al
.
Angiotensin-converting enzyme 2 (ACE2) levels in relation to risk factors for COVID-19 in two large cohorts of patients with atrial fibrillation
.
Eur Heart J
.
2020
;
41
(
41
):
4037
46
. .
2.
Sajeev
JK
,
Dewey
H
,
Kalman
JM
,
Chou
B
,
Roberts
L
,
Cooke
JC
, et al
.
Angiotensin-converting enzyme 2 activity is associated with embolic stroke of undetermined source
.
Stroke
.
2021
;
52
(
7
):
e324
e325
. .
3.
Mogi
M
,
Kawajiri
M
,
Tsukuda
K
,
Matsumoto
S
,
Yamada
T
,
Horiuchi
M
.
Serum levels of renin-angiotensin system components in acute stroke patients
.
Geriatr Gerontol Int
.
2014
;
14
(
4
):
793
8
. .
4.
Reindl-Schwaighofer
R
,
Hodlmoser
S
,
Eskandary
F
,
Poglitsch
M
,
Bonderman
D
,
Strassl
R
, et al
.
ACE2 elevation in severe COVID-19
.
Am J Respir Crit Care Med
.
2021
;
203
(
9
):
1191
6
. .
5.
Hussain
A
,
Tang
O
,
Sun
C
,
Jia
X
,
Selvin
E
,
Nambi
V
, et al
.
Soluble angiotensin-converting enzyme 2, cardiac biomarkers, structure, and function, and cardiovascular events (from the atherosclerosis risk in communities study)
.
Am J Cardiol
.
2021
;
146
:
15
21
. .
6.
Narula
S
,
Yusuf
S
,
Chong
M
,
Ramasundarahettige
C
,
Rangarajan
S
,
Bangdiwala
SI
, et al
.
Plasma ACE2 and risk of death or cardiometabolic diseases: a case-cohort analysis
.
Lancet
.
2020
;
396
(
10256
):
968
76
. .
7.
Ramchand
J
,
Patel
SK
,
Srivastava
PM
,
Farouque
O
,
Burrell
LM
.
Elevated plasma angiotensin converting enzyme 2 activity is an independent predictor of major adverse cardiac events in patients with obstructive coronary artery disease
.
PLoS One
.
2018
;
13
(
6
):
e0198144
. .
8.
Epelman
S
,
Tang
WH
,
Chen
SY
,
Van Lente
F
,
Francis
GS
,
Sen
S
.
Detection of soluble angiotensin-converting enzyme 2 in heart failure: insights into the endogenous counter-regulatory pathway of the renin-angiotensin-aldosterone system
.
J Am Coll Cardiol
.
2008
;
52
(
9
):
750
4
. .
9.
Ramchand
J
,
Patel
SK
,
Kearney
LG
,
Matalanis
G
,
Farouque
O
,
Srivastava
PM
, et al
.
Plasma ACE2 activity predicts mortality in aortic stenosis and is associated with severe myocardial fibrosis
.
JACC Cardiovasc Imaging
.
2020
;
13
(
3
):
655
64
. .
10.
Fagyas
M
,
Fejes
Z
,
Suto
R
,
Nagy
Z
,
Szekely
B
,
Pocsi
M
, et al
.
Circulating ACE2 activity predicts mortality and disease severity in hospitalized COVID-19 patients
.
Int J Infect Dis
.
2022
;
115
:
8
16
. .
11.
Arefin
S
,
Hernandez
L
,
Ward
LJ
,
Schwarz
A
;
GOING-FWD Collaborators
,
Barany
P
,
Stenvinkel
P
, et al
.
Angiotensin-converting enzyme 2 and transmembrane protease serine 2 in female and male patients with end-stage kidney disease
.
Eur J Clin Invest
.
52
;(
8
):
2022
:
e13786
. .
12.
Donoghue
M
,
Hsieh
F
,
Baronas
E
,
Godbout
K
,
Gosselin
M
,
Stagliano
N
, et al
.
A novel angiotensin-converting enzyme-related carboxypeptidase (ACE2) converts angiotensin I to angiotensin 1-9
.
Circ Res
.
2000
;
87
(
5
):
E1
9
. .
13.
Crackower
MA
,
Sarao
R
,
Oudit
GY
,
Yagil
C
,
Kozieradzki
I
,
Scanga
SE
, et al
.
Angiotensin-converting enzyme 2 is an essential regulator of heart function
.
Nature
.
2002
;
417
(
6891
):
822
8
. .
14.
Sajeev
JK
,
Burrell
LM
,
Teh
AW
.
Letter by Sajeev et al Regarding Article, “SARS-CoV-2 and Stroke in a New York Healthcare System”
.
Stroke
.
2020
;
51
(
11
):
e314
e315
. .
15.
Pena Silva
RA
,
Chu
Y
,
Miller
JD
,
Mitchell
IJ
,
Penninger
JM
,
Faraci
FM
, et al
.
Impact of ACE2 deficiency and oxidative stress on cerebrovascular function with aging
.
Stroke
.
2012
;
43
(
12
):
3358
63
. .
16.
Quan
K
,
Wang
A
,
Zhang
X
,
Wang
Y
.
Leukocyte count and adverse clinical outcomes in acute ischemic stroke patients
.
Front Neurol
.
2019
;
10
:
1240
. .
17.
Wang
Z
,
Yang
Y
,
Liang
X
,
Gao
B
,
Liu
M
,
Li
W
, et al
.
COVID-19 associated ischemic stroke and hemorrhagic stroke: incidence, potential pathological mechanism, and management
.
Front Neurol
.
2020
;
11
:
571996
. .
18.
Macrez
R
,
Ali
C
,
Toutirais
O
,
Le Mauff
B
,
Defer
G
,
Dirnagl
U
, et al
.
Stroke and the immune system: from pathophysiology to new therapeutic strategies
.
Lancet Neurol
.
2011
;
10
(
5
):
471
80
. .
19.
Chamorro
A
,
Meisel
A
,
Planas
AM
,
Urra
X
,
Van De Beek
D
,
Veltkamp
R
.
The immunology of acute stroke
.
Nat Rev Neurol
.
2012
;
8
(
7
):
401
10
. .
20.
Iadecola
C
,
Anrather
J
.
The immunology of stroke: from mechanisms to translation
.
Nat Med
.
2011
;
17
(
7
):
796
808
. .
21.
Vogelgesang
A
,
Becker
KJ
,
Dressel
A
.
Immunological consequences of ischemic stroke
.
Acta Neurol Scand
.
2014
;
129
(
1
):
1
12
. .
22.
Winklewski
PJ
,
Radkowski
M
,
Demkow
U
.
Cross-talk between the inflammatory response, sympathetic activation and pulmonary infection in the ischemic stroke
.
J Neuroinflammation
.
2014
;
11
:
213
. .
23.
Wang
A
,
Quan
K
,
Tian
X
,
Zuo
Y
,
Meng
X
,
Chen
P
, et al
.
Leukocyte subtypes and adverse clinical outcomes in patients with acute ischemic cerebrovascular events
.
Ann Transl Med
.
2021
;
9
(
9
):
748
. .
24.
Zhu
B
,
Pan
Y
,
Jing
J
,
Meng
X
,
Zhao
X
;
CHANCE Investigators
, et al
.
Neutrophil counts, neutrophil ratio, and new stroke in minor ischemic stroke or TIA
.
Neurology
.
2018
;
90
(
21
):
e1870
e1878
, .
25.
Wu
M
,
Zhang
X
,
Chen
J
,
Zha
M
,
Yuan
K
,
Huang
K
, et al
.
A score of low-grade inflammation for predicting stroke recurrence in patients with ischemic stroke
.
J Inflamm Res
.
2021
;
14
:
4605
14
. .
26.
Wang
K
,
Gheblawi
M
,
Nikhanj
A
,
Munan
M
,
Macintyre
E
,
O'neil
C
, et al
.
Dysregulation of ACE (Angiotensin-Converting enzyme)-2 and renin-angiotensin peptides in SARS-CoV-2 mediated mortality and end-organ injuries
.
Hypertension
;
2022
;
79
(
2
):
365
78
. .
27.
Vaduganathan
M
,
Vardeny
O
,
Michel
T
,
McMurray
JJV
,
Pfeffer
MA
,
Solomon
SD
. Renin-angiotensin-aldosterone system inhibitors in patients with Covid-19.
N Engl J Med
.
2020
;
382
(
17
):
1653
59
.
28.
Nidorf
SM
,
Fiolet
ATL
,
Mosterd
A
,
Eikelboom
JW
,
Schut
A
,
Opstal
TSJ
, et al.
LoDoCo2 Trial Investigators
.
Colchicine in patients with chronic coronary disease
.
N Engl J Med
.
2020
;
383
(
19
):
1838
47
. .
29.
Ridker
PM
,
Everett
BM
,
Thuren
T
,
Macfadyen
JG
,
Chang
WH
,
Ballantyne
C
, et al
.
Antiinflammatory therapy with Canakinumab for atherosclerotic disease
.
N Engl J Med Overseas Ed
.
2017
;
377
(
12
):
1119
31
. .
30.
Zhang
Q
,
Cong
M
,
Wang
N
,
Li
X
,
Zhang
H
,
Zhang
K
, et al
.
Association of angiotensin-converting enzyme 2 gene polymorphism and enzymatic activity with essential hypertension in different gender: a case-control study
.
Medicine
.
2018
;
97
(
42
):
e12917
. .