Abstract
Background and purpose: Alpha 7 nicotinic acetylcholine receptors
(CHRNA7) suppress inflammation through diverse pathways in immune cells,
so is potentially involved in a number of inflammatory diseases.
However, the detailed mechanisms underlying CHRNA7’s anti-inflammatory
effects remain elusive. Experimental approach: The anti-inflammatory
effects of CHRNA7 agonists in both murine macrophages (RAW 264.7) and
bone marrow-derived macrophages (BMDM) stimulated with LPS were
examined. The role of adenylyl cyclase 6 (AC6) in Toll-like Receptor 4
(TLR4) degradation was explored via overexpression and knockdown. A
mouse model of chronic obstructive pulmonary disease was used to confirm
key findings. Key results: Anti-inflammatory effects of CHRNA7 were
largely dependent on AC6 activation, as knockdown of AC6 considerably
abnegated the effects of CHRNA7 agonists while AC6 overexpression
promoted them. We found that CHRNA7 and AC6 are co-localized in lipid
rafts of macrophages and directly interact. Activation of AC6 led to the
promotion of TLR4 degradation. Administration of CHRNA7 agonist
PNU282987 attenuated pathological and inflammatory end points in a mouse
model of chronic obstructive pulmonary disease (COPD). Conclusion and
implications: CHRNA7 inhibit inflammation through activating AC6 and
promoting degradation of TLR4. The use of CHRNA7 agonists might
represent a novel therapeutic approach for treating COPD and likely
other inflammatory diseases.