ORIGINAL RESEARCH article

Front. Cardiovasc. Med., 27 May 2024

Sec. Cardiovascular Epidemiology and Prevention

Volume 11 - 2024 | https://doi.org/10.3389/fcvm.2024.1375704

Causal role of immune cells in hypertension: a bidirectional Mendelian randomization study

  • 1. Department of Cardiology, Central Hospital Affiliated to Shandong First Medical University, Jinan, China

  • 2. Shandong First Medical University, Jinan, China

  • 3. Research Center of Translational Medicine, Central Hospital Affiliated to Shandong First Medical University, Jinan, China

  • 4. Jinan Foreign Language School International Center, Jinan, China

  • 5. Department of Cardiology, Hekou District People Hospital, Dongying, China

Abstract

Background:

Although Hypertension (HTN) is considered to be a cardiovascular disease caused by multiple factors, the cause of it is still unknown. In this study, we aim to find out whether circulating immune cell characteristics have an impact on susceptibility to HTN.

Methods:

This study employed a comprehensive two-sample Mendelian randomization (MR) analysis to investigate the causal association between immune cell characteristics and HTN. Utilizing publicly accessible genetic data, we examined the causal relationship between HTN and the susceptibility to 731 immune cell signatures. To ensure the reliability and validity of the findings, a comprehensive sensitivity analysis was conducted to assess heterogeneity, confirm the robustness of the results and evaluate the presence of horizontal pleiotropy.

Results:

After FDR correction, immune phenotype had an effect on HTN. In our study, one immunophenotype was identified as being positively associated with HTN risk significance: HLA DR on CD33- HLA DR+. In addition, we examined 8 immune phenotype with no statistically significant effect of HTN, but it is worth mentioning that they had an unadjusted low P-value phenotype.

Conclusions:

Our MR study by genetic means demonstrated the close relationship between HTN and immune cells, thus providing guidance for future clinical prediction and subsequent treatment of HTN.

Introduction

HTN, as well as prehypertension and other dangerous forms of HTN, is responsible for 85 million deaths worldwide from stroke, ischaemic heart disease, other vascular diseases and kidney disease (). Between 1990 and 2019, the number of people with high blood pressure worldwide has absolutely doubled in the age group 30–79, and to this day, high blood pressure remains the leading cause of death and disability worldwide, far outweighing the influence of other occupational, environmental and lifestyle factors. Despite the availability of treatments, global blood pressure control rates are only 18%–23%, and as low as 10% in some parts of Asia and Africa. Although the low blood pressure control rates are partly due to poor treatment adherence, they also highlight that the cause of elevated blood pressure in most adults with HTN is unknown (). However, there is no systematic study on the causal relationship between various immune cell signatures and HTN.

Cardiovascular and cerebrovascular diseases are mostly diseases with poor prognosis and relatively sudden onset, such as stroke, coronary artery disease, atrial fibrillation and peripheral vascular diseases, and HTN happens to be their main pathogenic factor (). Recently, with the aging of the population and the acceleration of social development, the proportion of people suffering from HTN in the total population is increasing year by year and the age of disease is gradually getting younger. Moreover, because of its high prevalence, HTN is the single largest risk factor for heart failure in the population (). And in the early stages, HTN may not be detected because it is usually asymptomatic (). The World Health Organization (WHO) estimates that about 46% of people with HTN in the world are unaware of their condition. Therefore, there is an urgent need for an indicator that can prompt early HTN or even prehypertension.

MR was originally developed as an alternative to randomised controlled trials (RCTS) to provide reliable causal evidence between exposure and outcome through genetic variation (). It has since evolved into an independent analytical method based on the principles of Mendelian distribution, primarily used for epidemiological etiological inference. The validity of the causal sequence in MR is of utmost importance (, ). It serves as the basis for natural experiments through the random allocation of alleles during meiosis cell division and conception (, ). Currently, MR has been widely applied in disease research, but there are no relevant reports to elucidate the causal relationship between immune cells and HTN.

In this study, a comprehensive two-sample MR Analysis was performed to determine the causal relationship between immune cell characteristics and HTN, which will provide new insights into the prevention and treatment of HTN in the future.

Materials and methods

Study design

Based on a two-sample MR analysis, we evaluated the causal relationship between 731 immune cell features (7 groups) and HTN. MR uses genetic variation to represent risk factors, therefore, effective instrumental variables in causal inference must satisfy three key assumptions (

):

  • 1.

    Association hypothesis: SNPS are strongly correlated with exposure factors.

  • 2.

    Independence hypothesis: SNPS are independent of confounders.

  • 3.

    Exclusivity hypothesis: SNPS can only have an effect on outcomes through exposure.

The study we analyzed received approval from the relevant institutional review committee, and participants provided informed consent forms (

,

).

Genome-wide association study (GWAS) data sources for HTN

We from Integrative Epidemiology Unit (IEU) open GWAS HTN analysis of the database access to data, the database is mainly composed of a publicly available GWAS summary data sets. We used the HTN GWAS Summary statistics from FinnGen. The GWAS consisted of 55,917 cases and 162,837 controls. This MR Study was conducted using GWAS aggregate statistics and received ethical approval from each GWAS.

Immunity-wide GWAS data sources

The GWAS catalog provides publicly accessible GWAS summary statistics for immune coverage, specifically for each immune trait (GCST0001391 to GCST0002121) (). This study successfully identified 122 significant independent association signals at 70 locations, with 53 being previously unreported. Additionally, it elucidated the molecules and mechanisms responsible for regulating 459 cellular features related to immune function. A comprehensive analysis was conducted using flow cytometry to examine a total of 731 immunophenotypes, encompassing absolute cell counts (n = 118), median fluorescence intensity (MFI) as an indicator of surface antigen levels (n = 389), morphological parameters (MP) (n = 32), and relative cell counts (n = 192).The MFI, AC, and RC features encompass B cells, CDC, mature stage T cells, monocytes, bone marrow cells, TBNK (T cells, B cells, natural killer cells) and Treg panels, whereas the MP features consist of CDC and TBNK panels. The initial immunological profile Genome-Wide Association Study (GWAS) was carried out utilizing data from 3,757 individuals of European descent, with no cohorts overlapping. Approximately 22 million single nucleotide polymorphisms (SNPs) were genotyped using high-density arrays, utilizing a reference panel derived from Sardinian sequences. The genotyping of the samples was conducted using four Illumina arrays, namely OHTNiExpress, ImmunoChip, Cardio-MetaboChip, and ExomeChip. Subsequently, associations were examined while accounting for covariates such as sex, age ().

Selection of instrumental variables (IVs)

According to recent studies (, ), the significance level of the IV for each immunological trait was set to 1 × 10−5 In order to ensure that SNP effects on each immune trait and HTN are associated with the same allele, the direction of effects needs to be coordinated. Furthermore, SNPs exhibiting linkage imbalance (with an r2 threshold of <0.001 within a 10 Mb window) were excluded from the obtained dataset, while the remaining SNPs were retained. To ensure the robustness of the exposure, any statistic with a small f-statistic (F < 10) was also eliminated from our analyses. We did the same thing with the metabolite data. Finally, we also identified 9 IVs of HTN for further reverse MR Analysis.

Statistical analysis

All analyses were performed in R 3.5.3 software (http://www.Rproject.org). This study mainly used the software package “MendelianRandomization” (version 0.4) () to evaluate the causal relationship between 731 immunophenotypes and HTN. It is used to perform inverse variance weighting (IVW) (), weighted median based methods (), and model-based methods (). The Cochran's Q statistic and its associated p-values are employed to examine the presence of heterogeneity among the chosen independent variables (IVs). In the event that the null hypothesis is rejected, a random effect inverse variance weighting (IVW) is utilized in lieu of a fixed effect IVW ().We used a common method, namely MR-Egger, to exclude the effect of horizontal pleiotropy. If the intercept term is significant, it indicates the presence of horizontal multiplicity. Additionally, we employed a powerful method called MR-PRESSO to exclude potential horizontal pleiotropic outliers that could significantly impact the estimated results in the MR-PRESSO package (). Furthermore, scatter plots, funnel plots and MR leave-one-out sensitivity analysis plots are employed to analyze the data. The scatter plot provides evidence that the outcomes remain unaltered by outliers, while the funnel plot serves to illustrate the strength of the correlation and the absence of heterogeneity. The “MR leave-one-out sensitivity analysis” method refers to the gradual elimination of each SNP, the calculation of the meta effect of the remaining SNP, and the observation of whether the result changes after the elimination of each SNP. If the result changes greatly after the elimination of a SNP, it indicates that there is a SNP that has a great impact on the result, which is used to verify the sensitivity analysis. Consequently, the scatter plot reaffirms the resilience of the results against outliers.

Results

Some immune cells influence susceptibility to HTN

In order to investigate the causal impact of immunophenotypes on HTN, a two-sample MR analysis was conducted. The inverse-variance weighted (IVW) analysis was considered the most effective approach, provided that valid instrumental variables (IVs) were utilized. Additionally, when the genetic IVs exhibited no pleiotropic effects and the sample size was sufficiently large, the IVW estimate demonstrated consistency, efficiency, and proximity to the true value (). Hence, the IVW method was selected as the primary approach for conducting MR analysis in order to investigate the causal impact of HTN on immunophenotype. Two samples were utilized for this analysis, with a particular focus on the IVW method. At a nominal significance level, we identified causal relationships between HTN and 63 immune cells. Specifically, elevated levels of 31 immune cells and reduced levels of 32 immune cells were found to be associated with an increased risk of HTN. Following multiple test adjustments using the false discovery rate (FDR) method (PFDR < 0.05), we observed that one immunophenotype exhibited a significant association with HTN risk: We observed a significant causal effect of HLA DR on CD33- HLA DR+ on HTN risk by using the Inverse variance weighted (fixed effects) (OR = 1.048, CI: 1.030–1.066, P = 6.34 × 10−8, PFDR = 4.63 × 10−5, Figure 1, Supplementary Table S1, Tables 1, 2), which is consistent with weighted mode (P = 0.0007), weighted median (P = 0.000014), MR-PRESSO (P = 0.00062), Simple mode (P = 0.027), MR Egger (P = 0.0015). It is also noteworthy that eight suggestive immunophenotypes were identified at a significance of 0.20. Four of them, respectively CD28 on activated & secreting Treg (OR = 0.978, CI: 0.964–0.993, P = 0.005, PFDR = 0.195, Figure 1, Supplementary Table S1, Tables 1, 2), CCR2 on CD14- CD16+ monocyte (OR = 0.981, CI: 0.968–0.994, P = 0.005, PFDR = 0.195, Figure 1, Supplementary Table S1, Tables 1, 2), CD3 on NKT (OR = 0.948, CI: 0.917–0.979, P = 0.001, PFDR = 0.109, Figure 1, Supplementary Table S1, Tables 1, 2), CD80 on granulocyteT (OR = 0.971, CI: 0.955–0.988, P = 0.0008, PFDR = 0.099, Figure 1, Supplementary Table S1, Tables 1, 2) and CD39+ CD8br AC (OR = 0.968, CI: 0.950–0.986, P = 0.0006, PFDR = 0.099, Figure 1, Supplementary Table S1, Tables 1, 2) have a negative effect on the incidence of HTN, whereas the remaining three, IgD- CD24- %B cell (OR = 1.035, CI: 1.014–1.056, P = 0.00097, PFDR = 0.101, Figure 1, Supplementary Table S1, Tables 1, 2), Secreting Treg %CD4 (OR = 1.020, CI: 1.006–1.033, P = 0.004, PFDR = 0.18, Figure 1, Supplementary Table S1, Tables 1, 2) and SSC-A (OR = 1.044, CI: 1.020–1.068, P = 0.0002, PFDR = 0.077, Figure 1, Supplementary Table S1, Tables 1, 2) on NK, have a positive effect on the incidence of HTN. Using the other methods and sensitivity analysis, we confirmed the robustness of the causal associations observed.

Figure 1

Table 1

Id.outcomeOutcomeExposureMethodnsnpbsepvallo_ciup_cioror_lci95or_uci95fdr
finn-b-I9_HYPTENSCoronary heart diseaseCD28 on activated & secreting TregInverse variance weighted (fixed effects)24−0.0219286620.0077344990.004580054−0.03708828−0.0067690430.9783100230.9635910650.9932538150.194603401
finn-b-I9_HYPTENSCoronary heart diseaseCD3 on NKTInverse variance weighted (fixed effects)16−0.0536945610.0165751850.001197585−0.086181923−0.0212071990.9477215340.9174273150.9790160920.109429294
finn-b-I9_HYPTENSCoronary heart diseaseCD39+ CD8br ACInverse variance weighted (fixed effects)23−0.0328073360.0095952410.000628227−0.051614007−0.0140006640.9677249880.9496953710.986096890.098837368
finn-b-I9_HYPTENSCoronary heart diseaseCD80 on granulocyteInverse variance weighted (fixed effects)33−0.0292393510.008730960.000811251−0.046352033−0.0121266690.9711839830.9547058150.9879465620.098837368
finn-b-I9_HYPTENSCoronary heart diseaseSecreting Treg %CD4Inverse variance weighted (fixed effects)250.0195123070.0066841620.0035094750.006411350.0326132651.0197039171.0064319471.0331509060.175752855
finn-b-I9_HYPTENSCoronary heart diseaseIgD- CD24- %B cellInverse variance weighted (fixed effects)180.0344588870.0104452950.0009703460.0139861090.0549316641.0350594731.0140843721.0564684180.101331795
finn-b-I9_HYPTENSCoronary heart diseaseHLA DR on CD33- HLA DR+Inverse variance weighted (fixed effects)130.0466553850.0086255236.34E-080.029749360.0635614111.0477608731.0301962931.0656249244.63E-05
finn-b-I9_HYPTENSCoronary heart diseaseCCR2 on CD14- CD16+ monocyteInverse variance weighted (fixed effects)28−0.0192946140.006840360.004791876−0.03270172−0.0058875090.9808903350.96782720.9941297890.194603401
finn-b-I9_HYPTENSCoronary heart diseaseSSC-A on NKInverse variance weighted (fixed effects)220.0429786370.0115970560.0002105620.0202484080.0657088661.0439155931.0204547971.0679157650.07696041

Causal effects of immune cells on HTN.

Table 2

Heterogeneity testPleiotropy testMR-PRESSO global test
Id.outcomeOutcomeExposureMethodnsnpbsepvallo_ciup_cioror_lci95or_uci95FDRQQ_dfQ_pvalegger _interceptsepvalRSSobsP value
finn-b-I9_HYPTENSCoronary heart diseaseHLA DR on CD33- HLA DR+IVW(FE)130.0466553850.0086255236.34E-080.029749360.0635614111.0477608731.0301962931.0656249244.63E-0516.62990202120.164057408−0.0093687970.0065826280.18239892618.949299760.255
finn-b-I9_HYPTENSCoronary heart diseaseHLA DR on CD33- HLA DR+IVW(MRE)130.0466553850.0101540594.33E-060.026753430.066557341.0477608731.0271145161.068822249
finn-b-I9_HYPTENSCoronary heart diseaseHLA DR on CD33- HLA DR+MR Egger130.0628119250.0149615840.0014900650.033487220.0921366311.0648265531.0340542281.09651462914.04372265110.230583561
finn-b-I9_HYPTENSCoronary heart diseaseHLA DR on CD33- HLA DR+Simple mode130.0486150340.0192873380.026881180.0108118510.0864182181.0498161291.010870511.0902622
finn-b-I9_HYPTENSCoronary heart diseaseHLA DR on CD33- HLA DR+Weighted median130.0504609820.0116312211.44E-050.0276637890.0732581741.0517558251.0280499851.076008298
finn-b-I9_HYPTENSCoronary heart diseaseHLA DR on CD33- HLA DR+Weighted mode130.0486150340.0107679160.0007081720.0275099190.0697201491.0498161291.0278918111.072208081
finn-b-I9_HYPTENSCoronary heart diseaseHLA DR on CD33- HLA DR+MR-PRESSO130.0466553850.0101540590.0006164980.026753430.066557341.0477608731.0271145161.068822249
finn-b-I9_HYPTENSCoronary heart diseaseCD3 on NKTIVW(FE)16−0.0536945610.0165751850.001197585−0.086181923−0.0212071990.9477215340.9174273150.9790160920.10942929413.15161789150.590588214−0.0053076090.0068086890.44864294714.588398160.659
finn-b-I9_HYPTENSCoronary heart diseaseCD3 on NKTIVW(MRE)16−0.0536945610.0155203790.000540945−0.084114505−0.0232746170.9477215340.9193259830.976994148
finn-b-I9_HYPTENSCoronary heart diseaseCD3 on NKTMR Egger16−0.035675820.0284434180.230280716−0.091424920.020073280.9649530610.9126298341.02027610312.54394374140.562705427
finn-b-I9_HYPTENSCoronary heart diseaseCD3 on NKTSimple mode16−0.0374541190.0400779760.364831383−0.1160069510.0410987130.9632386110.8904690341.041954955
finn-b-I9_HYPTENSCoronary heart diseaseCD3 on NKTWeighted median16−0.0487791190.0234509260.037520869−0.094742934−0.0028153040.9523914720.9096067340.997188656
finn-b-I9_HYPTENSCoronary heart diseaseCD3 on NKTWeighted mode16−0.051692410.0289989210.094904028−0.1085302950.0051454750.9496209150.8971517151.005158735
finn-b-I9_HYPTENSCoronary heart diseaseCD3 on NKTMR-PRESSO16−0.0536945610.0155203790.003502045−0.084114505−0.0232746170.9477215340.9193259830.976994148
finn-b-I9_HYPTENSCoronary heart diseaseCD28 on activated & secreting TregIVW(FE)24−0.0219286620.0077344990.004580054−0.03708828−0.0067690430.9783100230.9635910650.9932538150.19460340123.23452419230.447147607−0.0015081780.0042683360.72719627124.739974320.502
finn-b-I9_HYPTENSCoronary heart diseaseCD28 on activated & secreting TregIVW(MRE)24−0.0219286620.0077738330.004789954−0.037165374−0.006691950.9783100230.9635167820.993330391
finn-b-I9_HYPTENSCoronary heart diseaseCD28 on activated & secreting TregMR Egger24−0.0197199330.010094440.063587963−0.0395050356.52E-050.9804732330.9612651141.00006517223.10341255220.395910001
finn-b-I9_HYPTENSCoronary heart diseaseCD28 on activated & secreting TregSimple mode24−0.0209439260.0172006960.235713301−0.054657290.0127694390.9792738750.9468095731.012851316
finn-b-I9_HYPTENSCoronary heart diseaseCD28 on activated & secreting TregWeighted median24−0.0228811840.0113052480.04297595−0.04503947−0.0007228990.9773786050.9559597490.999277362
finn-b-I9_HYPTENSCoronary heart diseaseCD28 on activated & secreting TregWeighted mode24−0.0177302270.0101215150.093144539−0.0375683980.0021079430.9824260280.963128541.002110166
finn-b-I9_HYPTENSCoronary heart diseaseCD28 on activated & secreting TregMR-PRESSO24−0.0212275590.0076497650.010523559−0.036221099−0.006234020.9789961590.9644270360.993785372
finn-b-I9_HYPTENSCoronary heart diseaseCD39+ CD8br ACIVW(FE)23−0.0328073360.0095952410.000628227−0.051614007−0.0140006640.9677249880.9496953710.986096890.09883736823.20947194220.3899832860.0027182170.0051181560.60092704325.739130950.39
finn-b-I9_HYPTENSCoronary heart diseaseCD39+ CD8br ACIVW(MRE)23−0.0328073360.0098554660.000872064−0.052124049−0.0134906220.9677249880.9492111110.986599969
finn-b-I9_HYPTENSCoronary heart diseaseCD39+ CD8br ACMR Egger23−0.0381369610.0141814010.013733927−0.065932506−0.0103414160.9625810960.936194050.98971187322.9018674210.349232911
finn-b-I9_HYPTENSCoronary heart diseaseCD39+ CD8br ACSimple mode23−0.0187832940.024407930.449747013−0.0666228360.0290562490.9813920130.9355479891.0294825
finn-b-I9_HYPTENSCoronary heart diseaseCD39+ CD8br ACWeighted median23−0.0354316550.0152085550.019821024−0.065240423−0.0056228870.9651886980.9368421980.994392892
finn-b-I9_HYPTENSCoronary heart diseaseCD39+ CD8br ACWeighted mode23−0.028124550.0171280070.114804527−0.0616954440.0054463440.9722672630.9401691771.005461202
finn-b-I9_HYPTENSCoronary heart diseaseCD39+ CD8br ACMR-PRESSO23−0.0181203990.0076794430.027157562−0.033172107−0.0030686910.9820427890.9673720540.996936013
finn-b-I9_HYPTENSCoronary heart diseaseCD80 on granulocyteIVW(FE)33−0.0292393510.008730960.000811251−0.046352033−0.0121266690.9711839830.9547058150.9879465620.09883736829.46649328320.595392904−0.0014742750.0036680790.6905005231.424048490.657
finn-b-I9_HYPTENSCoronary heart diseaseCD80 on granulocyteIVW(MRE)33−0.0292393510.008378210.00048315−0.045660643−0.0128180590.9711839830.9553661180.987263742
finn-b-I9_HYPTENSCoronary heart diseaseCD80 on granulocyteMR Egger33−0.0252983780.0131291580.063203156−0.0510315290.0004347720.9750189440.950248711.00043486729.30495349310.55335449
finn-b-I9_HYPTENSCoronary heart diseaseCD80 on granulocyteSimple mode33−0.0603428130.0239986530.017145471−0.107380172−0.0133054530.941441740.8981841430.986782673
finn-b-I9_HYPTENSCoronary heart diseaseCD80 on granulocyteWeighted median33−0.0247619720.0133053690.062736955−0.0508404950.0013165510.9755420910.9504302571.001317418
finn-b-I9_HYPTENSCoronary heart diseaseCD80 on granulocyteWeighted mode33−0.0287154740.0128198730.032170944−0.053842426−0.0035885220.9716928970.9475814090.996417909
finn-b-I9_HYPTENSCoronary heart diseaseCD80 on granulocyteMR-PRESSO33−0.0292393510.008378210.001431154−0.045660643−0.0128180590.9711839830.9553661180.987263742
finn-b-I9_HYPTENSCoronary heart diseaseCCR2 on CD14- CD16+ monocyteIVW(FE)28−0.0192946140.006840360.004791876−0.03270172−0.0058875090.9808903350.96782720.9941297890.19460340140.25713983270.0484665980.0070229440.0051723130.18619669842.296401870.083
finn-b-I9_HYPTENSCoronary heart diseaseCCR2 on CD14- CD16+ monocyteIVW(MRE)28−0.0192946140.0083525390.02088651−0.035665592−0.0029236370.9808903350.9649629310.997080633
finn-b-I9_HYPTENSCoronary heart diseaseCCR2 on CD14- CD16+ monocyteMR Egger28−0.0271095890.0100388490.012017527−0.046785734−0.0074334450.9732545780.9542918480.99259411537.59159378260.066050579
finn-b-I9_HYPTENSCoronary heart diseaseCCR2 on CD14- CD16+ monocyteSimple mode28−0.0142245110.0184009610.446219303−0.0502903940.0218413730.985876180.9509532331.022081642
finn-b-I9_HYPTENSCoronary heart diseaseCCR2 on CD14- CD16+ monocyteWeighted median28−0.0190978720.011283760.090548863−0.0412140420.0030182980.9810833370.9596237081.003022858
finn-b-I9_HYPTENSCoronary heart diseaseCCR2 on CD14- CD16+ monocyteWeighted mode28−0.0214819740.0088825080.022603623−0.03889169−0.0040722570.9787471210.9618548820.995936023
finn-b-I9_HYPTENSCoronary heart diseaseCCR2 on CD14- CD16+ monocyteMR-PRESSO28−0.0192946140.0083525390.028766688−0.035665592−0.0029236370.9808903350.9649629310.997080633
finn-b-I9_HYPTENSCoronary heart diseaseIgD- CD24- %B cellIVW(FE)180.0344588870.0104452950.0009703460.0139861090.0549316641.0350594731.0140843721.0564684180.10133179519.58454922170.296028263−0.0046660210.0056720270.42280565920.959876090.389
finn-b-I9_HYPTENSCoronary heart diseaseIgD- CD24- %B cellIVW(MRE)180.0344588870.0112112240.0021148840.0124848880.0564328851.0350594731.012563151.058055601
finn-b-I9_HYPTENSCoronary heart diseaseIgD- CD24- %B cellMR Egger180.0418946330.0144855080.0106119010.0135030380.0702862281.0427845981.0135946161.07281520718.78981961160.279713014
finn-b-I9_HYPTENSCoronary heart diseaseIgD- CD24- %B cellSimple mode180.0510608390.0215273740.0297682840.0088671860.0932544921.0523869171.0089066161.097741066
finn-b-I9_HYPTENSCoronary heart diseaseIgD- CD24- %B cellWeighted median180.0401446040.0149141230.0071085170.0109129220.0693762851.040961291.0109726851.07183945
finn-b-I9_HYPTENSCoronary heart diseaseIgD- CD24- %B cellWeighted mode180.0400334970.0144205710.0129385140.0117691770.0682978171.0408456391.0118387061.070684129
finn-b-I9_HYPTENSCoronary heart diseaseIgD- CD24- %B cellMR-PRESSO180.0344588870.0112112240.0068827730.0124848880.0564328851.0350594731.012563151.058055601
finn-b-I9_HYPTENSCoronary heart diseaseSecreting Treg %CD4IVW(FE)250.0195123070.0066841620.0035094750.006411350.0326132651.0197039171.0064319471.0331509060.17575285522.48474082240.550358506−0.0002555560.0034457310.94151955824.62275330.568
finn-b-I9_HYPTENSCoronary heart diseaseSecreting Treg %CD4IVW(MRE)250.0195123070.0064697170.0025618010.0068316620.0321929531.0197039171.0068550511.032716752
finn-b-I9_HYPTENSCoronary heart diseaseSecreting Treg %CD4MR Egger250.0198395060.008008820.0210231210.004142220.0355367931.0200376171.0041508111.03617577122.47924022230.491500143
finn-b-I9_HYPTENSCoronary heart diseaseSecreting Treg %CD4Simple mode250.0189614340.0174962180.289245833−0.0153311540.0532540211.0191423430.984785771.054697527
finn-b-I9_HYPTENSCoronary heart diseaseSecreting Treg %CD4Weighted median250.0255267010.0094393170.0068449420.007025640.0440277621.0258552971.0070503771.045011366
finn-b-I9_HYPTENSCoronary heart diseaseSecreting Treg %CD4Weighted mode250.0252993550.0089229520.0091456880.0078103690.0427883411.02562211.0078409491.04371696
finn-b-I9_HYPTENSCoronary heart diseaseSecreting Treg %CD4MR-PRESSO250.0195123070.0064697170.0059748520.0068316620.0321929531.0197039171.0068550511.032716752
finn-b-I9_HYPTENSCoronary heart diseaseSSC-A on NKIVW(FE)220.0429786370.0115970560.0002105620.0202484080.0657088661.0439155931.0204547971.0679157650.0769604119.32848056210.5640772910.0035724810.0046799270.45415832520.829438730.618
finn-b-I9_HYPTENSCoronary heart diseaseSSC-A on NKIVW(MRE)220.0429786370.0111259460.000112040.0211717820.0647854911.0439155931.0213974951.066930134
finn-b-I9_HYPTENSCoronary heart diseaseSSC-A on NKMR Egger220.0307187790.0198097450.136656321−0.008108320.0695458791.031195470.9919244641.07202124318.74575809200.538402987
finn-b-I9_HYPTENSCoronary heart diseaseSSC-A on NKSimple mode220.0540432120.0275711930.0633831133.67E-060.108082751.0555302131.0000036741.114139937
finn-b-I9_HYPTENSCoronary heart diseaseSSC-A on NKWeighted median220.037609450.0178680430.0353048540.0025880860.0726308131.0383256351.0025914381.075333465
finn-b-I9_HYPTENSCoronary heart diseaseSSC-A on NKWeighted mode220.0370776260.0181551240.0538823660.0014935840.0726616681.0377735761.00149471.075366644
finn-b-I9_HYPTENSCoronary heart diseaseSSC-A on NKMR-PRESSO220.0429786370.0111259460.0009012110.0211717820.0647854911.0439155931.0213974951.066930134

Causal effects of immune cells on HTN.

Furthermore, the MR-Egger intercept and the global test of MR-PRESSO effectively eliminated the potential influence of horizontal pleiotropy (Supplementary Table S1). The stability of the findings was further supported by the scatter plots, funnel plots and MR leave-one-out sensitivity analysis plots (Figures 2, 3).

Figure 2

Figure

Figure 3

Exploration of the causal effect of immunophenotypes on HTN

To investigate the impact of HTN on the body's immune system, we conducted an analysis using MR to explore the causal effects of HTN on immune cells. Despite applying multiple test adjustments, we did not observe a statistically significant causal relationship at a false discovery rate (FDR) significance level of 0.05. However, at the nominal significance level, we did detect causal effects of HTN on the levels of 15 immune cells. Specifically, the onset of HTN was found to increase the levels of 5 immune cells and decrease the levels of 10 immune cells. These 7 immune cells are distributed across B cells (15 cells), myeloid cells (3 cells), and TBNK cells (2 cells) (Figure 4, Table 3, Supplementary Table S2).

Figure 4

Table 3

Id.exposureId.outcomeOutcomeExposureMethodnsnpbsepvallo_ciup_cioror_lci95or_uci95
finn-b-I9_HYPTENSebi-a-GCST90001526CD33dim HLA DR+ CD11b+ %CD33dim HLA DR+ || id:ebi-a-GCST90001526HypertensionInverse variance weighted (fixed effects)56−0.159487680.0735961120.030229772−0.30373606−0.0152393010.8525804710.7380556430.984876229
finn-b-I9_HYPTENSebi-a-GCST90001528CD33dim HLA DR+ CD11b- %CD33dim HLA DR+ || id:ebi-a-GCST90001528HypertensionInverse variance weighted (fixed effects)560.1625079340.0736452650.0273398410.0181632150.3068526541.1764576531.0183291691.35914069
finn-b-I9_HYPTENSebi-a-GCST90001597CD8dim T cell %T cell || id:ebi-a-GCST90001597HypertensionInverse variance weighted (fixed effects)560.1591214630.0533189050.0028419560.054616410.2636265161.1724803511.0561354141.301641963
finn-b-I9_HYPTENSebi-a-GCST90001612CD8dim T cell %leukocyte || id:ebi-a-GCST90001612HypertensionInverse variance weighted (fixed effects)560.1543420360.0538906840.0041834960.0487162960.2599677761.1668899361.0499224411.296888295
finn-b-I9_HYPTENSebi-a-GCST90001634CD8dim Natural Killer T %T cell || id:ebi-a-GCST90001634HypertensionInverse variance weighted (fixed effects)560.1475638610.0536771480.0059759110.042356650.2527710721.1590072981.0432664931.287588478
finn-b-I9_HYPTENSebi-a-GCST90001635CD8dim Natural Killer T %lymphocyte || id:ebi-a-GCST90001635HypertensionInverse variance weighted (fixed effects)560.1425084770.0534398720.0076598430.0377663290.2472506251.1531628561.038488541.280499998
finn-b-I9_HYPTENSebi-a-GCST90001743CD20 on B cell || id:ebi-a-GCST90001743HypertensionInverse variance weighted (fixed effects)55−0.1088380690.0540975610.044232066−0.214869288−0.0028068490.8968756380.8066468720.997197086
finn-b-I9_HYPTENSebi-a-GCST90001745CD20 on CD24+ CD27+ B cell || id:ebi-a-GCST90001745HypertensionInverse variance weighted (fixed effects)56−0.1349648930.0533299330.011381794−0.239491563−0.0304382230.8737465860.7870279140.970020355
finn-b-I9_HYPTENSebi-a-GCST90001754CD20 on IgD- CD27- B cell || id:ebi-a-GCST90001754HypertensionInverse variance weighted (fixed effects)49−0.1210530420.0577379520.036029534−0.234219429−0.0078866560.8859869630.7911881870.992144362
finn-b-I9_HYPTENSebi-a-GCST90001755CD20 on IgD- CD38- B cell || id:ebi-a-GCST90001755HypertensionInverse variance weighted (fixed effects)56−0.1123370630.0534601420.03561256−0.217118942−0.0075551850.8937429590.8048342350.992473283
finn-b-I9_HYPTENSebi-a-GCST90001757CD20 on IgD- CD38dim B cell || id:ebi-a-GCST90001757HypertensionInverse variance weighted (fixed effects)56−0.1633114150.0532914310.002180366−0.26776262−0.058860210.8493266540.7650893770.942838559
finn-b-I9_HYPTENSebi-a-GCST90001758CD20 on memory B cell || id:ebi-a-GCST90001758HypertensionInverse variance weighted (fixed effects)56−0.1481026420.053260610.005423913−0.252493438−0.0437118460.8623425980.7768613110.957229747
finn-b-I9_HYPTENSebi-a-GCST90001761CD20 on switched memory B cell || id:ebi-a-GCST90001761HypertensionInverse variance weighted (fixed effects)56−0.1533071540.0536871110.004296003−0.258533892−0.0480804170.8578661840.772182860.953057142
finn-b-I9_HYPTENSebi-a-GCST90001803CD27 on IgD- CD38+ B cell || id:ebi-a-GCST90001803HypertensionInverse variance weighted (fixed effects)53−0.1179067020.0548006680.031432345−0.225316011−0.0104973940.888778970.7982639190.989557511
finn-b-I9_HYPTENSebi-a-GCST90002111HLA DR on CD33dim HLA DR+ CD11b- || id:ebi-a-GCST90002111HypertensionInverse variance weighted (fixed effects)56−0.1741497970.0777830090.025161237−0.326604496−0.0216950990.8401710330.7213689910.978538547

Causal effects of immune cell on HTN.

Discussion

HTN is the leading preventable cause of premature death worldwide (, ). HTN constitutes a significant risk factor for both ischemic and hemorrhagic stroke, as well as coronary artery disease. Furthermore, individuals affected by HTN are susceptible to the development of kidney failure, heart failure, peripheral vascular disease, and various other medical conditions (). Over the past twelve years, the utilization of genome-wide association studies (GWAS) and whole exome sequencing (WES) techniques has led to the identification of numerous potential pathways associated with blood pressure. However, the occurrence of consistent associations with HTN remains relatively infrequent (). These findings are not exclusive to HTN and have been observed in other intricate chronic conditions, including anemia and diabetes, involving pathway gene variants rather than consistent disease variants (, ). It is indisputable that numerous countries have advocated for and implemented measures to prioritize HTN as a health concern, exemplified by the 2020 US Surgeon General's directive to regulate HTN ().

With so much attention around the world, and with so many clinical trials demonstrating the efficacy of different classes of antihypertensive drugs (), HTN is still not completely under control despite improvements in treatment. From the perspective of preventive medicine, the new treatment strategy for HTN is to intervene when blood pressure is normally high, aiming to suppress or even reverse HTN, which is worth looking forward to (). Providing early treatment in the prehypertension stage may cause the HTN to subside (). Once HTN occurs, depending on the cause of the disease, intermittent intensive treatment can bring the HTN into remission. We believe that early HTN is a good indication for intermittent treatment. Biomarkers are urgently needed to accurately predict natural disease history and prognosis.

Our study employs a comprehensive integration of large-scale individual and aggregated Genome-Wide Association Study (GWAS) datasets to systematically elucidate the genetic mechanism underlying the immune cell response to the occurrence and progression of HTN. To the best of our knowledge, this is the inaugural MR analysis investigating the causal relationship between multiple immunophenotypes and HTN. Among the four immune features examined in this study, namely Mean Fluorescence Intensity (MFI), Receptor Count (RC), Antibody Count (AC), and Membrane Potential (MP), we identified one immunophenotype that exhibited a significant causal effect on HTN (FDR < 0.05). Additionally, it is worth noting that eight immunophenotypes demonstrated suggestive causal effects on HTN (FDR < 0.2). HTN had suggestive causal effects on 15 immunophenotypes (P < 0.05).

Based on our comprehensive data analysis and extensive research, we have determined that the presence of HLA DR on CD33- HLA DR+ significantly augments the susceptibility to HTN. It is noteworthy that HLA-DR, an MHC class II cell surface receptor, is encoded by the human leukocyte antigen complex situated on the 6P21 region of chromosome 6 (). There is growing evidence that HTN occurs simultaneously with, and may be caused by, changes in complement, inflammasome activation, and circulating immune cell phenotypes, particularly bone marrow cells. These inflammatory processes are interconnected and ultimately contribute to the adaptive immune system by means of oxidative stress, endogenous protein modification, and perturbed antigen processing and presentation mechanisms (). There is growing evidence that infiltration of bone marrow cells (especially monocytes/macrophages and T cells) into the arteries and kidneys is an early marker of inflammation (, ), and that these cells can produce various inflammatory cytokines that contribute to HTN (). There is an increasing amount of evidence suggesting that HTN is associated with and possibly caused by the activation of complement, inflammasome, and changes in the phenotype of circulating immune cells, particularly bone marrow cells. These inflammatory processes are interconnected and ultimately contribute to the adaptive immune system through oxidative stress, modification of endogenous proteins, and disrupted mechanisms of antigen processing and presentation (40). Increased inflammation within the cardiac regulatory center of the brain is associated with heightened activation of the sympathetic nervous system, leading to elevated blood pressure. Consequently, mitigating this inflammatory response can potentially ameliorate HTN (41). In addition, recent studies have demonstrated that abnormal bone marrow cells can lead to pulmonary HTN (42).

Conclusions

We conclude that immune cells are plausible causal agents of HTN based on our two-way MR analysis. These results offer valuable support to clinical decision-making regarding disease prognosis and treatment, while also guiding the exploration of novel therapeutic interventions. Moreover, they underscore the intricate nature of the interplay between the immune system and HTN. A further advantage of our study is that unavoidable confounding variables, reverse causation, and other relevant factors are effectively mitigated. Even so, it is clear that HTN is complex in its pathogenesis, and that immune cells associated with HTN exhibit clinical heterogeneity. Additionally, solitary treatments frequently fail to yield satisfactory outcomes. Consequently, further investigation is warranted to explore the interplay between innate immune cells and the interaction between innate immune cells and adaptive immune cells in individuals with HTN.

Statements

Data availability statement

The original contributions presented in the study are included in the article/Supplementary Material, further inquiries can be directed to the corresponding authors.

Ethics statement

This study was based on publicly available datasets. Ethical review and approval was not required for the study, in accordance with the local legislation and institutional requirements.

Author contributions

XZ: Writing – original draft, Writing – review & editing, Conceptualization, Data curation, Formal Analysis, Methodology, Project administration, Software, Validation, Visualization. GL: Data curation, Software, Writing – review & editing. WW: Writing – review & editing, Conceptualization, Investigation. BL: Investigation, Writing – review & editing, Conceptualization, Funding acquisition, Resources, Writing – original draft.

Funding

The author(s) declare financial support was received for the research, authorship, and/or publication of this article.

The authors received subsequent financial support for the research, authorship, and/or publication of this article from the China Postdoctoral Science Foundation (No. 2020M682119); Natural Science Foundation of Shandong Province (No. ZR2020MH026; No.ZR2021MH019); Postdoctoral Innovation Program of Shandong Province (No. 202102041); Clinical Medicine Science and Technology Innovation Program of Jinan (No. 202019045); Special fund for high-level talents in medical and health industry of Jinan City and the central government guided local special funds for scientific and technological development (YDZX2021116).

Conflict of interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Publisher’s note

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.

Supplementary material

The Supplementary Material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/fcvm.2024.1375704/full#supplementary-material

References

Summary

Keywords

Mendelian randomization, immune cell, hypertension, prehypertension, two-sample mendelian randomization

Citation

Zhang X, Li G, Wu W and Li B (2024) Causal role of immune cells in hypertension: a bidirectional Mendelian randomization study. Front. Cardiovasc. Med. 11:1375704. doi: 10.3389/fcvm.2024.1375704

Received

24 January 2024

Accepted

10 May 2024

Published

27 May 2024

Volume

11 - 2024

Edited by

Aifeng Zhang, Boston Medical Center, United States

Reviewed by

Xueying Zhao, The Second Hospital of Shandong University, China

Chunliu Li, Yantai Affiliated Hospital of Binzhou Medical University, China

Libo Zhou, Shandong University, China

Updates

Copyright

*Correspondence: Bin Li

Disclaimer

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher.

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