ANP and BNP exert anti-inflammatory action via NPR-1/cGMP axis by interfering with canonical, non-canonical, and alternative routes of inflammasome activation in human THP1 cells

Dysregulated inflammasome activation and interleukin (IL)-1β production are associated with several inflammatory disorders. Three different routes can lead to inflammasome activation: a canonical two-step, a non-canonical Caspase-4/5-and Gasdermin D-dependent, and an alternative Caspase-8-mediated pathway. Natriuretic Peptides (NPs), Atrial Natriuretic Peptide (ANP) and B-type Natriuretic Peptide (BNP), binding to Natriuretic Peptide Receptor-1 (NPR-1), signal by increasing cGMP (cyclic guanosine monophosphate) levels that, in turn, stimulate cGMP-dependent protein kinase-I (PKG-I). We previously demonstrated that, by counteracting inflammasome activation, NPs inhibit IL-1β secretion. Here we aimed to decipher the molecular mechanism underlying NPs effects on THP-1 cells stimulated with lipopolysaccharide (LPS) + ATP. Involvement of cGMP and PKG-I were assessed pre-treating THP-1 cells with the membrane-permeable analogue, 8-Br-cGMP, and the specific inhibitor KT-5823, respectively. We found that NPs, by activating NPR-1/cGMP/PKG-I axis, lead to phosphorylation of NLRP3 at Ser295 and to inflammasome platform disassembly. Moreover, by increasing intracellular cGMP levels and activating phosphodiesterases, NPs interfere with both Gasdermin D and Caspase-8 cleavage, indicating that they disturb non-canonical and alternative routes of inflammasome activation. These results showed that ANP and BNP anti-inflammatory and immunomodulatory actions may involve the inhibition of all the known routes of inflammasome activation. Thus, NPs might be proposed for the treatment of the plethora of diseases caused by a dysregulated inflammasome activation.