XING Bu-dian, WEI Ting, LU Yuan-yuan, LENG Jun-jie, KANG Pin-fang, WANG Hong-ju,ZHANG Ning-ru

1. Department of Cardiovascular Medicine, the First Affiliated Hospital of Bengbu Medical College, Bengbu 233000, China

Keywords:

ABSTRACT

1. Introduction

Essential hypertension (EH) is mainly characterized by increased systemic arterial blood pressure, which in turn causes lesions in various internal organs[1].Left ventricular hypertrophy (LVH) is the most prominent target organ damage in the development of EH patients. Foreign studies have found that about 1/3 of EH patients have LVH. A domestic community study found that more than 40% in my country of EH patients with LVH[2,3].LVH has been proven to be an independent risk factor for cardiovascular events[4].Studies have found that the mortality rate of EH patients with LVH is 8 times that of NLVH patients[5].At present, the mechanism of EH complicated with LVH is still not fully understood.Some scholars believe that myocardial fibrosis may be closely related to the pathogenesis of EH complicated with LVH[6].Interleukin-33(IL-33) is an important member of the interleukin-1 family and is closely related to inflammation and fibrosis[7,8].Soluble ST2 (sST2)is a "decoy receptor" for IL-33, competes with ST2L to bind IL-33,inhibits the IL-33/ST2 signaling pathway and has cardiovascular protection against cardiac hypertrophy and fibrosis[9].However, in patients with EH, less research has been done on the IL-33/ST2 signaling pathway in LVH.Therefore, this study aimed to explore the changes of serum IL-33 and sST2 in EH patients with LVH and their correlation with left ventricular mass index (LVMI), and to explore the relationship between their signaling pathways and LVH in EH patients.

2.Materials and Methods

2.1 normal information

A total of 220 patients with essential hypertension were selected from the outpatient clinic of the First Affiliated Hospital of Bengbu Medical College from April 2021 to April 2022.The diagnostic criteria for LVH[10]:Male LVMI 115g/m2, female 95 g/m2.According to the presence or absence of LVH, all enrolled hypertensive patients were divided into NLVH group (n=108) and LVH group (n=112).Main inclusion criteria: age＞18years; EH diagnostic criteria conform to relevant guidelines[10].All subjects were excluded from taking antihypertensive drugs; secondary hypertension; hypertrophic cardiomyopathy; coronary heart disease;heart valve disease; heart failure; stroke; tumor diseases and those who cannot cooperate.

2.2 Methods

2.2.1 sample preparation

The enrolled patients were fasted overnight (8 hours), and after resting for 30 minutes in the sitting position, 5 mL of peripheral venous blood was collected in a heparin anticoagulant test tube,centrifuged at 3000 r/min, and centrifuged at 4°C for 15 minutes. To avoid repeated freeze-thaw cycles, divide each serum sample into 0.2 mL aliquots and freeze immediately at -80 °C.

2.2.2 Calculation method of left ventricular mass index

According to the cardiac color Doppler ultrasound index ventricular septal thickness (IVST), left ventricular posterior wall thickness (LVPWT) and left ventricular end-diastolic diameter(LVEDD),Left ventricular mass (LVM) = 0.8×1.04〔(IVST +LVEDD +LVPWT)3-LVEDD3〕+ 0.6; Left ventricular mass index (LVMI) = LVM/body surface area (BSA)[11], Male BSA (m2) = 0.0057×height(cm)+0.0121×weight(kg)+0.0882; Female BSA(m2) =0.0073 height+0.0127×weight (kg)-2.106[12].

2.2.3 Detection of serum IL-33 and sST2 levels by ELISA

HumanIL-33 and Human sST2 (Shanghai Yuduo) were used to detect the expression levels of IL-33 and sST2 in the serum of the subjects. The operation steps were carried out in strict accordance with the instructions.

2.2.4 Wester blot detection of IL-33 expression in PBMCs

The total protein in PBMCs was extracted, the protein content was determined by BCA method, 10% SDS-PAGE electrophoresis,PVDF membrane transfer; 5% skim milk was blocked at room temperature; primary antibody and secondary antibody were incubated[13].

2.3 Statistical processing

Comparisons between groups were performed using t test and chisquare test. The correlation between IL-33, sST2 and systolic blood pressure and LVMI was analyzed by Pearson analysis. The above data were analyzed by SPSS26.0 software.

3. Result

3.1 Comparison of baseline data of subjects in NLVH group and LVH group

There was no significant difference in age, gender, smoking history,drinking history, BMI, liver and kidney function, blood lipids and average diastolic blood pressure between the two groups of patients(P＞0.05). There was a significant difference between them (P＜0.05),and the results are shown in Table 1.

3.2 Comparison of serum IL-33, sST2 and cardiac color Doppler related indexes between NLVH group and LVH group

Compared with the NLVH group, the serum levels of IL-33 and sST2 in the LVH group were significantly increased (P＜0.05); in cardiac ultrasound-related indexes: the IVST, LVPWT, LVEDD and LVMI in the LVH group were significantly higher than those in the NLVH group. significantly increased; the results are shown in Table 2.

Tab1 Comparison of baseline data between NLVH and LVH groups

Tab2 Comparison of serum IL-33, sST2 and cardiac color ultrasound parameters between the NLVH group and the LVH group(x±s)

3.3 Comparison of IL-33 protein expression levels in PBMCs of NLVH group and LVH group (60 cases in each)

In the PBMCs of the NLVH group and the LVH group, the IL-33 protein expression level in the LVH group (1.07±0.08) was higher than that in the NLVH group (0.63±0.05) (P＜0.05). Seeing Figure 1,Figure 2.

Fig1 IL-33 protein bands in PBMCs of two groups of patients

Fig2 Relative protein expression in PBMCs of two groups of patients

3.4 Correlation analysis of IL-33 and sST2 with systolic blood pressure and LVMI in patients with LVH group

In the Pearson correlation test results, IL-33 was positively correlated with systolic blood pressure and LVMI(r=0.481,P＜0.001;r=0.506,P＜0.001);sST2 is positively correlated with systolic blood pressure, LVMI(r=0.463,P＜0.001;r=0.512,P＜0.001).The results are shown in Table 3.

Tab3 Correlation between IL-33, sST2 and systolic blood pressure and LVMI in the LVH group

3.5 Multivariate Binary Logistic Regression Influencing EH to LVH

Taking the occurrence of LVH in EH patients as the dependent variable and IL-33, sST2 and systolic blood pressure as covariates,the results showed that IL-33, sST2 and systolic blood pressure were independent predictors of LVH in EH patients. The results are shown in Table 4.

Tab4 LVH multifactor binary Logistic regression in EH patients

4. discussion

Essential hypertension (EH) is a systemic chronic disease, and it is also an important cause of kidney damage and cardiovascular and cerebrovascular adverse events[14].Poor control of blood pressure in the early stage and continuous increase will make the left ventricular load continue to increase, eventually lead to myocardial fibrosis,and promote the occurrence and development of LVH[15].LVH is an important target organ damage and complication of EH, and is a common risk factor for cardiovascular events[16], which poses a serious threat to the life of patients. Therefore, it is extremely important to analyze the mechanism of EH concurrent LVH formation.

Interleukin-33 (IL-33) is an important member of the newly discovered IL-1 family and is closely related to inflammation and fibrosis[7,8]. IL-33 is mainly used as a biomarker in cardiac patients and is associated with vascular disease dysfunction[17]. It has been reported that IL-33 can effectively activate the type 2 cytokine environment in the damaged heart, promote myocardial fibrosis,and then promote cardiac remodeling, which ultimately leads to the deterioration of cardiac function[18]. Serum IL-33 levels are elevated in patients with chronic heart failure and continue to rise as cardiac function worsens[19,20]. More importantly, it has been reported that IL-33 is highly expressed in the myocardial tissue of patients with end-stage heart failure[21]. Furthermore, in these studies, serum IL-33 levels were significantly positively correlated with the degree of cardiac fibrosis and TGFβ1 expression levels. Based on the above studies, it can be seen that IL-33 is closely related to heart failure and myocardial fibrosis, but whether it is associated with EH complicated with LVH is still unclear. In this study, compared with the NLVH group, the serum IL-33 level of the patients in the LVH group was significantly increased, and the trend of the IL-33 protein concentration in PBMCs in this study was consistent with the ELISA results, suggesting that IL-33 may be associated with EH is related to concurrent LVH. In this study, binary logistic regression analysis showed that IL-33 was an independent risk factor for LVH in EH patients, which further confirmed that serum IL-33 was involved in the occurrence of LVH in EH patients. Considering that IL-33 can promote the occurrence of inflammatory response,further aggravate myocardial cell damage, promote myocardial fibrosis, and ultimately accelerate ventricular remodeling[22]. In this study, Pearson correlation analysis showed that there was a positive correlation between serum IL-33 and LVMI, suggesting that the higher the serum IL-33 level in EH patients, the higher the risk and severity of LVH. This suggests that IL-33 plays an important role in the occurrence and development of LVH in EH patients.Soluble ST2 (sST2) is a member of the IL-1R family and plays an important role in the inflammatory response. sST2 expression was upregulated when myocardial strain and pressure increased[23].Elevated levels of sST2 are associated with the degree of myocardial fibrosis and cardiac remodeling[24,25]. sST2 is considered by domestic and foreign scholars as a marker of myocardial fibrosis and ventricular remodeling[26]. As a decoy receptor, sST2 interfered with the binding of ST2L to IL-33 and inhibited the cardiovascular protective effect of IL-33/ST2 signaling pathway against cardiac hypertrophy and fibrosis. A related guideline[27] reported that sST can be used as a marker of myocardial fibrosis and inflammatory response. Yang Shuhan et al[12] found that compared with the NLVH group, the level of sST2 in patients with hypertension combined with LVH was significantly increased. In this study, the expression level of sST2 in the LVH group was significantly higher than that in the NLVH group, which was consistent with the literature reports. At the same time, binary Logistic regression analysis in this study showed that sST2 was an independent risk factor for LVH in EH patients.This suggests that sST2 is involved in the pathogenesis of LVH in EH patients.

In addition, this study found that quantitative indicators of cardiac fibrosis, such as LVMI, were elevated in the LVH group compared with the NLVH group. The study further explored the relationship between the expression of IL-33/sST2 signaling pathway-related factors and LVMI, and found that the serum levels of IL-33 and sST2 in LVH patients were positively correlated with LVMI.Based on this, we speculate that the body activates the IL-33/sST2 signaling pathway, thereby affecting the expression of downstream inflammatory molecules, promoting myocardial fibrosis, and then aggravating ventricular remodeling, participating in the occurrence and development of LVH in EH patients.

In conclusion, this study found that the levels of IL-33 and sST2 were significantly elevated in EH patients complicated with LVH.In the future clinical work, the targeted detection of IL-33 and sST2 levels can be used to evaluate the early diagnosis of EH patients complicated with LVH, which can significantly reduce the occurrence of cardiovascular events and benefit the prognosis of patients. This study has the following shortcomings: the number of cases included in this study is limited, and data errors are unavoidable, so the results of this paper need to be further verified by a large-scale multi-center study.

Contribution description of the authors: Xing Budian: data analysis and article writing; Wei Ting: responsible for relevant experimental operations, Lu Yuanyuan, Leng Junjie: data collection; Kang Pinfang,Zhang Ningru, Wang Hongju: design experiments and guide writing.The authors of this study declare that no conflict of interest exists in connection with this article.