Novel role for inhibitor of differentiation 2 in the genesis of angiotensin II-induced hypertension.

BACKGROUND: Angiotensin (Ang) II-induced target-organ damage involves innate and acquired immunity. Mice deficient for the helix-loop-helix transcription factor inhibitor of differentiation (Id2(-/-)) lack Langerhans and splenic CD8a+ dendritic cells, have reduced natural killer cells, and have altered CD8 T-cell memory. We tested the hypothesis that an alteration in the number and quality of circulating blood cells caused by Id2 deletion would ameliorate Ang II-induced target-organ damage. METHODS AND RESULTS: We used gene-deleted and transgenic mice. We conducted kidney and bone marrow transplants. In contrast to Ang II-infused Id2(+/-), Id2(-/-) mice infused with Ang II remained normotensive and failed to develop albuminuria or renal damage. Bone marrow transplant of Id2(+/-) bone marrow to Id2(-/-) mice did not restore the blunted blood pressure response to Ang II. Transplantation of Id2(-/-) kidneys to Id2(+/-) mice also could not prevent Ang II-induced hypertension and renal damage. We verified the Ang II resistance in Id2(-/-) mice in a model of local tissue Ang II production by crossing hypertensive mice transgenic for rat angiotensinogen with Id2(-/-) or Id2(+/-) mice. Angiotensinogen-transgenic Id2(+/-) mice developed hypertension, albuminuria, and renal injury, whereas angiotensinogen-transgenic Id2(-/-) mice did not. We also found that vascular smooth muscle cells from Id2(-/-) mice showed an antisenescence phenotype. CONCLUSIONS: Our bone marrow and kidney transplant experiments suggest that alterations in circulating immune cells or Id2 in the kidney are not responsible for Ang II resistance. The present studies identify a previously undefined role for Id2 in the pathogenesis of Ang II-induced hypertension.

ED-B fibronectin (ED-B) can be targeted using a novel single chain antibody conjugate and is associated with macrophage accumulation in atherosclerotic lesions.

It has been shown that ED-B fibronectin (ED-B) is a potential target for plaque imaging. The aim of this study was to test a novel modified single chain anti-ED-B antibody (scFv) conjugated for near infrared fluorescence imaging (NIRF) with tetrasulfonated carbocyanine-maleimide (TSC-scFv) and to examine the association of ED-B with the presence of macrophages in a murine model of atherosclerosis. Expression of ED-B was observed in plaque areas in apolipoprotein E-deficient (apoE(-/-)) mice which increased with age and plaque load. Robust imaging was possible after explantation of the aorta and demonstrated a strong NIRF signal intensity in focal aortic and brachiocephalic plaque lesions, whereas no signals were found in undiseased areas. Plaque lesion ED-B was expressed by smooth muscle cell and was closely associated to macrophage infiltrates. Although not expressed by the same cell type, there was a significant correlation (p<0.01) between ED-B and macrophage immunoreactivity. In vitro human coronary and mouse smooth muscle cells significantly increased ED-B expression after angiotensin II and TNF-alpha treatment. This study demonstrates that plaque NIRF imaging is feasible with a novel single chain antibody and that ED-B expression is closely associated with inflammation in experimental atherosclerosis.