Figure 4. β₂ARs on alveolar macrophages are required for catecholamine-induced upregulation of IL-6 and resulting thrombosis after PM exposure.

(A and B) Mice deficient in β₂AR specifically in monocytes and macrophages were generated by crossing Lysm-Cre mice with Adrb2^flox/flox mice. Inflammatory cells from lung homogenates of Adrb2^flox/flox and Lysm-Cre Adrb2^flox/flox mice were sorted, and deletion of the Adrb2 gene was confirmed by assessment of (A) gene expression and (B) mRNA. We performed intratracheal instillations in Adrb2^flox/flox and Lysm-Cre Adrb2^flox/flox mice with PM (200 μg/mouse) or vehicle (PBS) and, 24 hours later, measured (C) the levels of IL-6 in BALF, (D) TAT complexes in the plasma, and (E and F) the time to loss of blood flow after FeCl₃-induced injury to the carotid artery (the time to complete loss of blood flow [>75% reduction]). *P < 0.05, PM vs. PBS or CAPs vs. FA; ^‡P < 0.05, Adrb2^flox/flox vs. Lysm-Cre Adrb2^flox/flox.