B-Cell Deficiency Lowers Blood Pressure in Mice

The proto-oncogene c-myb (and corresponding nuclear transcription factor, c-Myb) regulates the proliferation and differentiation of hematologic and vascular smooth muscle cells; however, the role of c-Myb in blood pressure regulation is unknown. Here, we show that mice homozygous for a hypomorphic c-myb allele ( c-myb h/h ) conferring reduced c-Myb activity manifest reduced peripheral blood and kidney B220 + B-cells and have decreased systolic (104±2 versus 120±1 mm Hg; P P WT (wild type) mice. Additionally, c-myb h/h mice had lower susceptibility to deoxycorticosterone acetate-salt experimental hypertension. Although cardiac (echocardiography) and resistance artery (perfusion myography) functions were normal, metabolic cage studies revealed that c-myb h/h mice had increased 24-hour urine output and sodium excretion versus WT . Reconstitution of WT mice with c-myb h/h bone marrow transplant and chimeric bone marrow transplant using mice lacking B-cells ( J H T ; h/h>WT and h/h:J H T>WT , respectively) decreased blood pressure and increased 24-hour urine output compared with controls ( WT>WT ; WT:J H T>WT ). J H T mice also had decreased systolic (103±2 versus 115±1 mm Hg; P P WT . Real-time quantitative reverse transcription polymerase chain reaction of kidney medulla revealed reduced V 2 R (vasopressin receptor 2) expression in c-myb h/h and J H T mice. These data implicate B-cells in the regulation of V 2 R and its associated effects on salt and water handling and blood pressure homeostasis.