Bcl11b Regulates Vascular Smooth Muscle Phenotype and Arterial Stiffness

Abstract

BACKGROUNDArterial stiffness (AS) is the loss of compliance of elastic arteries known to increase the risk of cardiovascular events. A genome‐wide association study (GWAS) identified single nucleotide polymorphisms (SNPs) in a genetic locus downstream of BCL11B to be associated with increased AS, however a functional role for Bcl11b in the vasculature is unknown.OBJECTIVETo examine BCL11B's role in the aorta and vascular function including AS and blood pressure.METHODSTo study the role of BCL11B in the vasculature, we generated mice (SMMHCERCreT2‐Bcl11bfl/fl aka BSMKO) with tamoxifen‐inducible Bcl11b deletion in vascular smooth muscle (VSM). We measured pulse wave velocity (PWV), the gold standard in vivo measure of AS, by Doppler ultrasound, and blood pressure by telemetry in wild type (WT) and BSMKO mice. We measured isometric force, wall tension and stress in aortic rings of WT and BSMKO mice ex vivo in organ baths. We analyzed levels of filamentous (F) and globular (G) actin, smooth muscle myosin (MYH11), smooth muscle a‐actin (SMaA), phosphorylated and total VASP, and calcineurin by Western blot in WT and BSMKO VSM cell and aortic homogenates.RESULTSMice with Bcl11b deletion in VSM (BSMKO) exhibited higher PWV compared to WT littermates (3.1 ± 0.1 m/s in WT, n = 14 vs 3.8 ± 0.2 m/s in BSMKO, n = 17; p < 0.05), but had no detectable changes in blood pressure (systolic blood pressure, SBP: 121.8 ± 3.8 mmHg in WT, n = 7 vs 120.0 ± 2.3 mmHg in BSMKO, n = 8; NS). Compared to WT, BSMKO VSM cells had decreased mRNA and protein expression of VSM contractile proteins MYH11 (1.00 ± 0.05 A.U. in WT vs 0.42 ± 0.04 A.U. in BSMKO, n = 5 replicate experiments; p < 0.05) and SMA (1.00 ± 0.04 A.U. in WT vs 0.63 ± 0.06 A.U. in BSMKO, n = 4 replicate experiments; p < 0.05). Baseline force (1010 ± 96 mg in WT, n = 5 vs 1511 ± 106 mg in BSMKO, n = 7; p < 0.05), wall tension (1.72 ± 0.13 N/m in WT, n = 5 vs 2.60 ± 0.24 N/m in BSMKO, n = 7; p < 0.05) and stress (17.7 ± 1.5 kPa in WT, n = 5 vs 25.9 ± 2.2 kPa in BSMKO, n = 7; p < 0.05) generated by BSMKO aortic rings in organ baths were significantly increased compared to WT. In addition, BSMKO aortas exhibited increased F/G actin ratio indicating increased cytoskeletal actin polymerization (ratio of F to G actin: 4.82 ± 1.33 A.U. in WT, n = 6 vs 9.09 ± 1.02 A.U. in BSMKO, n = 7; p < 0.05). Phosphorylated VASP at S239, known to inhibit actin polymerization, was decreased (0.99 ± 0.04 A.U. in WT vs 0.19 ± 0.04 A.U. in BSMKO, n = 5 replicate experiments; p < 0.05), while PP2B, a phosphatase which regulates VASP phosphorylation, was increased in BSMKO aortas compared to WT. Treatment of BSMKO VSM cells with cyclosporine A (CSA, 10mM), an inhibitor of PP2B, reversed pVASP toward WT levels.CONCLUSIONSWe showed for the first time that BCL11B is present in VSM and regulates arterial stiffness at least in part by regulating contractile protein smooth muscle myosin and expression and cytoskeletal remodeling in VSM cells of the aorta via PP2B‐pVASP.Support or Funding InformationThis work was supported by NIH grant HL136311.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.