To explore the causal relationship of potentially druggable genes with EH, we conducted large-scale MR and colocalization analyses integrating GWAS datasets, pharmacogenomics, and gene expression data (eQTL). We found strong evidence that higher genetic proxies of FES expression are inversely correlated with EH risk, while higher SLC22A4 proxies are positively correlated. Associations with systolic and diastolic blood pressure also support these findings. Additionally, FES showed a significant correlation with reduced risk of coronary artery disease.
FES is a member of a distinct subfamily of cytoplasmic protein-tyrosine kinases, primarily involved in hematopoiesis and signal transduction of cytokine receptor superfamily members (16). The FES proto-oncogene product represents a new participant in regulating angiogenesis, with previous studies indicating its central role in movement, proliferation, differentiation, and survival of cells and inflammation (17–19). FES is also associated with atherosclerosis, cancer, and infections (20–22). For example, VEGF induces endothelial sprouting in blood vessels, partially activating PI3 kinase through c-Fes and enhancing capillary morphogenesis through an unknown signaling pathway (23). Angiopoietin-1 (Ang1) and Angiopoietin-2 (Ang2) play antagonistic roles in vascular stability and instability, respectively (24). Additionally, there is a delicate balance between vasodilators and vasoconstrictors (25, 26). Disruption of this balance can lead to endothelial dysfunction and excessive release of vasoconstrictive substances (27). These changes may lead to structural and functional alterations in macro-and micro-vasculature(28), as observed in pregnant women, where the release of bioactive factors into maternal circulation causes an imbalance in tyrosine kinases and cytokines in vessels, leading to increased vasoconstrictors and hypertension (29). Another study found FES expressed in immune cells (monocytes, macrophages, neutrophils) but enriched in endothelial cells (30). Upregulation of FES can induce endothelial dysfunction (31), suggesting its regulatory role in blood vessels. Fostamatinib, a Tyrosine-protein kinase Fes/Fps inhibitor, has a side effect of increased blood pressure (32). Previous studies considered VEGF signaling to play a significant role(33), and given its upstream action, FES's potential impact cannot be ruled out. A recent study has also shown FES's protective role in atherosclerosis, with PRDM1 expression in human atherosclerotic lesions potentially promoting atherosclerosis by reducing FES expression, as evidenced by increased smooth muscle cells in atherosclerotic lesions of FES knockout mice (22). Our new analysis also indicates FES's relevance to blood pressure (BP), further suggesting its role in regulating BP and CAD risk. However, no direct evidence currently shows FES's involvement in the treatment and progression of EH.
SLC22A4 encodes the Organic Cation/Carnitine Transporter 1 (OCTN1), a 551-amino acid protein belonging to the solute carrier family 22, functioning as a plasma membrane transporter for various substrates (34). The chromosome 5q31 region containing SLC22A4 also houses many genes involved in immune and inflammatory systems. Some inflammatory mediators play significant roles in the pathophysiology of hypertension, such as Angiotensin II stimulating peripheral blood monocytes to secrete tumor necrosis factor-alpha (TNF-α) and interleukin-1, which can stimulate fibroblasts to secrete VEGF, affecting endothelial function (35). OCTN1 is a pH-dependent transporter, and verapamil and Clonidine can inhibit OCTN1-mediated uptake of tetraethylammonium (TEA) (36). Additionally, studies indicate that the effects of NO on blood vessels are mediated by the activation of a tetraethylammonium-sensitive population of K + channels, which regulate blood pressure (37).
In our study, of the 29 drug targets identified in the UK Biobank cohort, only ten were successfully replicated in the FinnGen cohort. Although they share a common European ancestry genome and are considered homogeneous, their replicability was poor (38). Continuing this ancestral bias in genetics could exacerbate health disparities caused by race. Future research should focus more on the effects across different subgroups.
This study has several strengths. Firstly, to ensure the credibility of the results, we applied Bonferroni correction for multiple tests and pleiotropy-robust MR methods to reduce the possibility of bias due to pleiotropy rigorously, and colocalization analysis reinforced the credibility of our results. Secondly, we focused our research on druggable genes to enhance the efficacy of EH treatment and the success rate of drug development, identifying two drug targets (FES and SLC22A4) related to EH. Although there is no clear evidence yet that these targets are directly involved in EH treatment, but they at least provide ideas for drug development. Lastly, we conducted extensive MR analysis to identify more alternative indications, which is important.
The study has several limitations. Firstly, it is challenging to rule out the potential pleiotropy completely. Secondly, this study only examined eight cardiovascular diseases and did not analyze other diseases or adverse reactions. Thirdly, epigenetics may play a key role in BP regulation for EH, and the interaction with environmental factors needs to be considered in future research. Fourthly, biological and clinical studies are needed to verify their effectiveness in the treatment of EH. Finally, the research population is limited to Europeans and may not necessarily be suitable for other races.