Association among β2‐adrenergic receptor autoantibodies and proximal left anterior descending artery lesions in patients with initial ST‐segment elevation myocardial infarction

Abstract Background β2‐adrenergic receptor autoantibody (β2‐AA) are widely present in patients with many different types of cardiovascular diseases. Proximal left anterior descending (LAD) artery lesions are associated with adverse prognostic events in patients with ST‐segment elevation myocardial infarction (STEMI). Hypothesis β2‐AA is associated with the presence of proximal LAD lesions in patients with STEMI. Methods A cohort of 153 patients with STEMI who underwent primary percutaneous coronary intervention (PPCI) was enrolled in the study. Baseline characteristics were compared between the proximal LAD group (n = 62) and the nonproximal LAD group (n = 91). Admission serum of patients was collected to detect the level of β2‐AA. Data for echocardiogram within 24 hours after PPCI and at the 6‐month follow‐up were recorded. Results The optical density values and positive rates of β2‐AA in the proximal LAD group were higher than those in the nonproximal LAD group (p < 0.05). β2‐AA positively correlated with high sensitivity C‐reactive protein and peak N‐terminal pro‐B type natriuretic peptide levels in the proximal LAD group, but those were not relevant in the nonproximal LAD group. Multivariate logistic regression analysis revealed that high β2‐AA levels was independently associated with the presence of proximal LAD lesions in patients with STEMI. Furthermore, a receiver operating characteristic curve was used to show the efficiency of β2‐AA levels to detect proximal LAD lesions, and the AUC of the β2‐AA OD value was 0.658 (95% confidence interval 0.568−0.749; p = 0.001). Conclusions The STEMI patients with high β2‐AA levels had a greater possibility having proximal LAD lesions.

Acute ST-segment elevation myocardial infarction (STEMI) results from acute, severe, and persistent ischemia or hypoxia following the blockage of a coronary artery.It may lead to life-threatening adverse events, such as electrical instability, remodeling or dysfunction. 1The left anterior descending artery (LAD) is considered high risk for coronary heart disease because it supplies a considerable area of the myocardium.Several studies have shown that proximal LAD lesions are associated with a higher incidence of adverse outcomes in malignant ventricular arrhythmias and STEMI. 2 The location of the culprit lesion is one of the important factors in determining the clinical outcome of STEMI.Therefore, it is important to locate proximal LAD lesions in patients with STEMI.STEMI may cause sympathetic nervous system excitation, and the excited sympathetic nervous system leads to a surge in the release of catecholamines, which act on the cardiac β adrenergic receptor (β-AR).The β 2 -adrenergic receptor autoantibody (β 2 -AA), a G protein-coupled receptor autoantibody (GPCR-AA), binds and continuously activates the β 2 -adrenergic receptor (β 2 -AR), which causes a variety of pathophysiological reactions.Hence, β 2 -AA is involved in numerous cardiovascular diseases, such as heart failure, arrhythmia, and orthostatic hypotension.In addition, this strong binding and subsequent stabilization of the adrenergic receptor by its autoantibodies lead to the occurrence and deterioration of heart failure. 3However, few studies have focused on the β 2 -AA level in patients with STEMI and explored the relationship between β 2 -AA and coronary artery lesions.
Thus, this study compared the differences between proximal LAD lesions and nonproximal LAD lesions.We explored the relationship between β 2 -AA levels and proximal LAD lesions in STEMI patients.patients with acute infectious diseases within the past 3 months or rheumatic immune system diseases or malignant tumors.According to the results of coronary angiography, the patients were included in the proximal LAD group and the nonproximal LAD group.Venous blood was collected immediately after admission and stored at −80°C until further analysis.An echocardiogram was performed within 24 hours after PPCI.The results of an echocardiogram taken at 6 months after discharge were reviewed.

| ELISA
The OD values of β 2 -AA was determined by ELISA using synthetic peptides that correspond to the sequence of the second extracellular loop of the human β 2 receptors (amino acid sequence number ELISA was performed as stated by previous study. 4iefly, microtiter plates were coated with peptide at 10 µg/mL in coating buffer.The serum samples (dissolved in 1% bovine serum albumin) were added to the microtiter plates.Then, peroxidaseconjugated anti-human IgG was diluted 1:500 in the same buffer and added to the plates.Secondary antibodies dilution ratio (ZSGB-BIO, ZB-2304): 1:500.Thereafter, a peroxidase substrate ammonium salt was added to the wells and allowed to react for 30 minute.The optical density (OD) values were measured using a microplate reader and were evaluated at 405 nm.The titer was determined by the ratio of P/N (positive/negative controls) as follows: P/N = (sample ODblank OD)/(healthy control OD-blank OD).Autoantibody positivity or negativity was judged by P/N > 2.1 or P/N < 1.5.

| Statistical analysis
All statistical analyses were performed using SPSS 25.0.(IBM).
Continuous variables are presented as the mean ± standard deviation (SD) or median (25th quartile, 75th quartile).Student's t test or the Mann-Whitney U test was used for comparisons between two groups.Categorical data are expressed as percentages (%), and the chi-square test or Fisher's exact test was used for comparisons between two groups.Correlations between β 2 -AA and parameters were assessed using Pearson or Spearman tests.Univariable and multivariable logistic analyses were used to determine the effect of the covariates on proximal LAD lesions.Receiver-operating characteristic (ROC) curve analysis was performed to determine the ability of β 2 -AA for predicting proximal LAD lesions.A p < 0.05 was considered statistically significant.(Supporting information: Table S1).Moreover, β 2 -AA was positively correlated with hsCRP and peak NT-proBNP in the proximal LAD group (r = 0.313, p = 0.013; r = 0.372, p = 0.003), but it was not relevant in the nonproximal LAD group (Figure 2).

| The predictors of proximal LAD lesions
The results of the logistic regression analyses are shown in echocardiogram for patients in the two groups at the 6-month follow-up are shown in Table 3.At baseline, the diameter of the left atrium (LA) in the nonproximal LAD group was higher than that in the proximal LAD group (p = 0.012).Compared with baseline and 6-month follow-up, cardiac structure parameters such as LA, left ventricular end-diastolic diameter (LVEDD), left ventricular enddiastolic volume (LVEDV), and LVEDV index (LVEDVi) were increased at the 6-month follow-up (all p < 0.05).Cardiac function parameters, such as LVEF, also were increased at the 6-month follow-up (p < 0.001).

| DISCUSSION
In this study, we found that high β 2 -AA levels were independently associated with the presence of proximal LAD lesions in patients with STEMI.In addition, patients with STEMI who had proximal LAD lesions had higher NT-proBNP and higher hsCRP levels, and these patients showed worse cardiac function and inflammatory responses.
The LAD artery has an important position because it supplies 45% to 55% of the left ventricle mass.The PROTECT (Patient Related Outcomes with Endeavor vs. Cypher Stenting Trial) study showed that proximal LAD lesions were associated with a higher incidence of myocardial infarction during long-term follow-up. 5The study showed that the proximal LAD group had a higher incidence of major adverse cardiovascular events and all-cause mortality than the nonproximal LAD group. 6,7The TWENTE I-III study also found that the rate of the device-oriented composite clinical endpoint (cardiac death, target vessel myocardial infarction, or target lesion revascularization) was higher in proximal LAD lesions. 8The SYNTAX (Synergy between PCI with Taxus and Cardiac Surgery) score was also significantly higher in the proximal LAD group than in the nonproximal LAD group. 7These results indicated that ischemia caused by proximal LAD lesions put more myocardium at risk and lead to a worse prognosis.However, the SORT-OUT II study found opposite results.The 10-year mortality rates were similar for patients with proximal LAD and nonproximal LAD stents.The incidence of combined clinical endpoints such as cardiac death, myocardial infarction, or target revascularization was low in the proximal LAD group. 9While these results were controversial, we can explain these differences.By comparing the risk characteristics of previous studies, we found that patients with many comorbidities or an extensive history of PCI may have received coronary artery bypass grafting instead of PCI at the time of study inclusion.As a result, such patients may be less likely to participate in randomized PCI trials.The NOBLE study also demonstrated that the differences in outcomes may not be driven by the lesions of interest (e.g., the left main or proximal LAD) but by other new pathologic changes. 10In addition, parts of the differences from these trials were the different interventions.Which is more suitable for PCI or coronary artery bypass grafting (CABG) in patients with proximal LAD lesions has always been the focus of controversy.With the development of science and technology, the increasing maturity of PCI and the widespread use of DES, the mortality rate of STEMI patients after PCI has decreased, but the complications of postoperative life crisis are still troubling us.
Unlike the patients included in some of the studies above, our research subjects were all STEMI patients in this study, and they were at higher bleeding and thrombotic risks.The more complex pathological and surgical features of proximal LAD patients, who had more multivessel therapy, bifurcation lesions, and severe calcified lesions and who had longer stents, suggest the presence of more extensive coronary artery disease.Therefore, patients with lesions at the proximal end of the LAD represent a subgroup of patients at higher risk.
The interaction between the sympathetic nervous system and the parasympathetic system also plays important roles.The β-adrenergic receptor (AR) accounts for 90% of the total AR in the heart. 11β 2 -AR is one of the components related to the pathogenesis of various cardiovascular diseases.However, few previous studies have explored the level of β 2 -AA in STEMI patients.In the process of STEMI, the excited sympathetic nervous system will cause the secretion of a large amount of catecholamines, which will act on the β 2 -AR of the heart, resulting in the continuous activation of β 2 -AR, resulting in a series of adverse phenomena.Therefore, inhibiting the continuous activation of β 2 -AR is very important to reduce the cardiac injury and improve the prognosis of patients with acute myocardial infarction. 12,13Previous study showed that β 2 -AA had ability to antagonize the effects imposed by β 1 -AA both in vitro and in vivo.β 2 -AA seems to be a protective factor to some extent in patients with HF. 14 Actually, all of this is due to the fact that the activation of β 2 -AR has two sides. of cardiomyocytes. 15,16The β 1 -Gs-mediated effect is partially attenuated by the β 2 -Gi effect. 4Simultaneously, β 2 -AA also interferes with receptor circulation and desensitization, resulting in receptor passivation or sensitization to endogenous catecholamines.These changes lead to the deterioration of HF.The study showed that enhanced activation of β 2 -AA leads to sustained atrial tachycardia in rabbits. 17The activation of β 2 -AA may contribute to systemic vasodilation, which may lead to or exacerbate orthostatic hypotension. 18Experiments in vitro showed that when the oxygen supply of cardiomyocytes was optimal, β 2 -AA was inactive.After lactic acid was added, the cells showed full activity against β 2 -AA. 4 The above results caused us to think that β 2 -AR may be abnormally exposed under abnormal conditions such as ischemia and hypoxia (or, e.g., myocardial infarction), leading to the formation of | 1377 tissue. 4We found that β 2 -AA was related to NT-proBNP and hsCRP.
NT-proBNP is an independent predictor of HF readmission after ACS. 19CRP is involved in triggering immune processes such as vascular remodeling and plaque deposition, and it is associated with an increased risk of cardiovascular diseases. 20Although PCI and DES may reduce the restenosis rate and some risk of these lesions, the incidence of heart failure associated with myocardial infarction remains significant. 22Our study compared the difference in echocardiogram-related indicators at baseline and a 6-month follow-up, and we found that the differences between the two groups were not large at baseline.Parameters such as LA, LVEDD, LVEDV, and LVEDVi were increased at the 6-month follow-up.
Considering that the proximal LAD supplies a considerable area of the myocardium, it makes sense that the proximal LAD lesions had changed the cardiac structure.In addition, cardiac function parameters, such as LVEF, were restored.These studies showed that drug treatment significantly improved cardiac function and remodeling, and carvedilol was able to reduce the frequency and titer of β 2 -AA in patients. 18,23In our study, all enrolled subjects received optimal discharge guidance during follow-up, and they were all given an individualized medication regimen.All of the above results showed that effective treatment can improve cardiac function and prognosis and help us identify new therapeutic targets.
In summary, we found that patients with high β 2 -AA levels had a greater possibility having proximal LAD lesions.and can influence left ventricular remodeling, which may further affect the long-term prognosis.The discovery of β 2 -AA will provide new therapeutic targets and ideas.

| Limitations
This study has some limitations.It was a single-center study that cannot comprehensively cover different types of patients, and the sample size was relatively small.In addition, our study is observational in nature, the surgical techniques were based on operator choice, and the treatment and management of all subjects were based on the attending physicians.All subjects had fewer clinical events because of the good follow-up management.In the future, we need to include larger sample sizes with more clinical follow-up data.

| CONCLUSIONS
The level of β 2 -AA as a risk factor had value in independently predicting proximal LAD lesions in patients with STEMI, and can provide novel therapeutic targets in the future.

2 | METHODS 2 . 1 |
Study population Between October 2019 and November 2021, a total of 158 patients consecutively diagnosed with STEMI undergoing PPCI who met the inclusion and exclusion criteria were enrolled in this study from the Beijing Friendship Hospital of Capital Medical University.This study was approved by the Ethics Committee of Beijing Friendship Hospital, Capital Medical University, in accordance with the Declaration of Helsinki.All patients signed informed consent forms.The inclusion criteria were as follows: (1) met the diagnostic criteria for STEMI; and (2) underwent PPCI and accepted drug-eluting stent (DES).The exclusion criteria were as follows: (1) patients with previous myocardial infarction or coronary revascularization; (2) patients with atrial fibrillation; (3) patients with renal insufficiency (GFR < 30 mL/min/1.73m 2 ); (4) patients with glaucoma; and (5)

Five ( 3 .
3%) patients were excluded from the study because of death and loss to follow-up.A total of 62 patients were included in the proximal LAD group, and 91 patients were included in the T A B L E 1 Baseline and clinical characteristics of the study population.

F
I G U R E 2 Correlation analysis of β 2 -AA in LAD and nonproximal LAD groups.(A, B) β 2 -AA was related to hsCRP in the proximal LAD group.(C, D) β 2 -AA is related to peak NT-proBNP in the proximal LAD group.HsCRP, high sensitivity C-reactive protein; LAD, left anterior descending; NT-proBNP, N-terminal pro-B type natriuretic peptide.

3. 2 |
Correlations of β 2 -AA in proximal LAD and nonproximal LAD lesions We compared the relationship between the level of β 2 -AA and baseline data in the proximal LAD and nonproximal LAD groups, and β 2 -AA was related to N-terminal pro-B type natriuretic peptide (NT-proBNP) and high sensitivity C-reactive protein (hsCRP) in all patients

β 2 -
AR can conjugate the excitatory G protein (Gs) or inhibitory G protein (Gi).Under the stimulation of catecholamine at normal physiological concentrations, β 2 -AR activates the downstream protein kinase A (PKA) pathway by coupling the Gs protein to participate in cardiac contraction.When catecholamines are continuously stimulated at high concentrations, activated PKA and G protein-coupled receptor kinase phosphorylate β 2 -AR, promoting the conversion and activation of the coupled Gs protein to the Gi protein.Activation of the β 2 -AR/Gi pathway can inhibit the PKA pathway, thereby inhibiting the overcontraction and apoptosis

β 2 -
AA.Moreover, inflammation is important in the course of myocardial infarction.Autoimmune processes are increasingly recognized as the origin or amplification of various diseases.Autoantibodies induce a regular immune response that leads to the destruction of the affected DANG ET AL.

Table 1 .
Compared with the nonproximal LAD group, patients in the proximal LAD group showed a higher percentage of stroke and higher fasting blood glucose (FBG) (all p < 0.05).Comparing the level of β 2 -AA in the two groups, we found that the OD values and positive rates of β 2 -AA in the proximal LAD group were higher than those in the nonproximal LAD group (Figure1).By stratifying patients with proximal LAD and nonproximal LAD lesions into subgroups based on β 2 -AA OD values, patients with proximal LAD lesions were more frequently distributed in the higher quartiles of β 2 -AA OD values Note: Values are presented as mean ± SD, median (25th−75th quartiles) or n (%).The p values were obtained using Student's t-test, Mann-Whitney U, χ 2 , or Fisher's exact tests.Abbreviations: ACEI/ARB, angiotensin converting enzyme inhibitor/angiotensin II receptor blocker; ApoA1, Apolipoprotein A1; ApoB, Apolipoprotein B; ApoE, Apolipoprotein E; BMI, body mass index, CK-MB, creatine kinase-MB; eGFR, estimated glomerular filtration rate; FBG, fasting blood glucose; HbA1c, glycated hemoglobin; HsCRP, high sensitivity C-reactive protein; LDL-C, low-density lipoprotein cholesterol; LP(a), Lipoprotein(a); NT-proBNP, N-terminal pro-B type natriuretic peptide; TNI, troponin I; WBC, white blood cell.DANG ET AL. | 1373 nonproximal LAD group according to the intervention site.The baseline characteristics of the two groups are presented in F I G U R E 1 Comparison of the β 2 -AA OD value and positive rate in LAD and nonproximal LAD groups.Comparison of the β 2 -AA OD values in the nonproximal LAD and proximal LAD groups.The β 2 -AA OD value in the proximal LAD group was higher than that in the nonproximal LAD group.(B) Comparison of the β 2 -AA positive rate in the two groups.The β 2 -AA-positive rate in the proximal LAD group was higher than that in the nonproximal LAD group.*p < 0.05, **p < 0.01.LAD, left anterior descending.

Table 2
Logistic regression analyses of proximal LAD lesion.Comparison of 6-month follow-up results of echocardiography.
. In the univariate logistic regression analysis, the β 2 -AA positivity rate and stroke were associated with proximal LAD lesions, and after T A B L E 2 | 1375 multivariate logistic regression analysis, the β 2 -AA positivity rate remained the only independent predictor of proximal LAD lesions after correction.for other baseline determinants (odds ratio [OR] [95% confidence interval (CI)]: 2.88 [1.32−6.30],p = 0.008).Meanwhile, the ROC curve was used to show the efficiency of β 2 -AA levels to measure proximal LAD lesions, and the AUC of the β 2 -AA OD value was 0.658 (95% CI 0.568−0.749;p = 0.001) (Supporting information: Figure S2).The comparison results of the T A B L E 3 1This demonstrated the application of inflammatory markers in the localization of coronary arteries.Our study also explored the relationship between GPCR-AA and coronary lesions.We found that β 2 -AA can predict proximal LAD artery lesions in patients with STEMI.Compared with the nonproximal LAD lesions, the proximal LAD lesions had higher levels of β 2 -AA.β 2 -AA remained the only independent predictor of proximal LAD lesions.This is the first study to correlate the levels of autoantibodies and coronary anatomy, and the localization of culprit lesions is important for the clinical diagnosis and long-term prognosis of STEMI.In addition, β 2 -AA can be used as a tool to locate culprit plaques in patients with STEMI.