CACNB2 expression is positively associated to the Ras/MAPK pathway in vitro and in an experimental model of hypertension

Abstract

Several independent genome‐wide association studies highlighted the strong association of voltage‐dependent L‐type calcium channel subunit beta‐2 (CACNB2) gene with hypertension. One such study showed that hypertensive individuals who carry a promoter polymorphism (rs2357928) in CACNB2 exhibited adverse effects during treatment with calcium channel blocker (CCB) ‐ verapamil but responded well to treatment with the β‐blocker‐ atenolol. However, the exact molecular signature of CACNB2 during the pathophysiology of hypertension is currently remains to be explored. In the clinical setting, CCBs are widely used to treat hypertensive individuals, and the inhibition of L‐type Ca2+ channels with CCBs significantly increases the glomerular filtration rate and renal blood flow. Hence, the goal of this present study is to understand the molecular signaling of CACNB2 during hypertension via in vitro and in vivo approaches using HEK293 cells and genetically hypertensive, Dahl Salt‐Sensitive (SS) rats. The over‐expression of CACNB2 in HEK293 cells increased cell proliferation and upregulated the Ras‐MAPK pathway significantly when compared to the controls. These results were consistent with a recent study showing that overexpression of CACNB2, activate Ras/ERK/CREB pathways in vitro. Additionally, the ER stress markers IRE‐1α and PERK were upregulated by CACNB2 over expression compared to the control cells. In contrast, treatment with the L‐type CCB‐ nifidepine in CACNB2 overexpressed cells did not abolish upregulation of Ras‐MAPK and ER stress pathway genes. Similarly, we observed an increase in apoptotic signaling exemplified by the downregulation of Bcl‐2 and upregulation of Caspase 7 and Caspase 9, which were also insensitive to nifidepine treatment. Correspondingly, we investigated whether CACNB2 levels were altered using the SS rats under low salt (0.3% NaCl) and high (2% NaCl) diet fed conditions. We observed higher CACNB2 levels in high salt fed SS rat kidneys compared to SS rats maintained on low salt diet (n=4, p<0.05). In addition, our gene expression studies showed that Mapk1 and Mapk4 levels were upregulated in the kidneys of SS rats under high salt diet (n=4, p<0.05). In summary, our study reveals that CACNB2 significantly associated with the activation of Ras‐MAPK pathway in SS rats. In summary, understanding the regulation of CACNB2 and associated Ras‐MAPK pathway could help in expanding the knowledge of molecular mechanism of hypertension and may help in identifying novel drug targets.Support or Funding InformationFunding support for this study was met from the American Heart Association grant 16SDG27700030 (to S. Kumarasamy) and funding from UT‐COMLS.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.