β₂-Adrenergic agonists augment air pollution-induced IL-6 release and thrombosis

Area of Science:

• Environmental Health
• Cardiovascular Research
• Immunology

Background:

• Particulate matter (PM) exposure is linked to thrombotic cardiovascular events and mortality.
• Interleukin-6 (IL-6) release from alveolar macrophages is crucial for PM-induced prothrombotic states.
• The precise mechanisms connecting PM exposure to cardiovascular dysfunction remain incompletely understood.

Purpose of the Study:

• To investigate the role of catecholamines and beta-2 adrenergic receptors (β2AR) in mediating PM-induced IL-6 release and prothrombotic effects.
• To elucidate the signaling pathways involved in β2AR activation in alveolar macrophages following PM exposure.

Main Methods:

• Murine models and primary human alveolar macrophages were used to assess IL-6 release and prothrombotic status.
• Experiments involved PM exposure, catecholamine administration, β2AR agonists/antagonists, and genetic manipulation of β2AR.
• Mitochondrial reactive oxygen species (ROS) generation and adenylyl cyclase activity were measured.

Main Results:

• PM exposure induced systemic catecholamine release, activating β2AR on murine alveolar macrophages and augmenting IL-6 release.
• β2AR signaling in mice promoted a prothrombotic state, accelerating arterial thrombosis.
• In human macrophages, β2AR agonists increased IL-6, while beta-blockers inhibited PM-induced IL-6 release.
• Genetic or pharmacologic β2AR inhibition attenuated PM-induced IL-6 and prothrombotic responses.
• β2AR agonists enhanced macrophage responses via mitochondrial ROS and increased adenylyl cyclase activity.

Conclusions:

• PM exposure activates the sympathetic nervous system through β2AR signaling on alveolar macrophages.
• This pathway links environmental pollution, inflammation, and metabolic changes to increased susceptibility to thrombotic cardiovascular events.