not-yet-known not-yet-known not-yet-known unknown Background and purpose: Idiopathic pulmonary fibrosis (IPF), evokes scarring of the lung due to extracellular matrix deposition by fibroblasts. Evidence suggests that inhaled treprostinil slows the decline in pulmonary function in IPF. The molecular mechanisms by which cAMP mobilizing agents, alter human lung fibroblast (HLF) expression of matrix proteins remain unclear. We posit that the antifibrotic properties of treprostinil are driven by differential cAMP mobilizing responses mediated by the IP receptor. Experimental approach: As a model of lung fibrosis, TGF-β-stimulated primary HLF were used to measure collagen 1A1, PAI1, and growth factor levels in the presence and absence of cAMP mobilizing agents. The necessity of receptor activation in inhibiting TGF-β-induced fibrosis was determined using soluble receptor inhibitors and selective inhibition of receptor expression with siRNA. Key results: Treprostinil decreased TGF-β-induced extracellular matrix and growth factors production by HLF, the magnitude of the inhibition was greater than other cAMP mobilizing GPCR agonists despite comparable increases in cAMP levels. Treprostinil inhibition of TGF-β-induced collagen 1A1, PAI-1, and IGFBP3 was mediated through the activation of the IP receptor. The EP2 receptor was partially involved in the inhibition of TGF-β-induced collagen 1A1 by treprostinil or prostaglandin E2. β2 agonists had little effect on TGF-β-induced collagen 1A1, PAI-1, and IGFBP3 expression. The inhibitory effects on TGF-β-induced matrix expression by treprostinil required Gαs activation. Treprostinil inhibition of TGF-β-induced IGFBP3 expression also correlated with the inhibition of TGF-β-induced phosphorylation of AKT. Conclusion and implications: Understanding the differential effects of cAMP mobilizing pathways on HLF fibrotic signatures can provide insight into developing novel targets to manage IPF.

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.