Nucleotide oligomerization domain 1 is a dominant pathway for NOS2 induction in vascular smooth muscle cells: comparison with Toll‐like receptor 4 responses in macrophages

Abstract

Background and purpose:Gram-negative bacteria contain ligands for Toll-like receptor (TLR) 4 and nucleotide oligomerization domain (NOD) 1 receptors. Lipopolysaccharide (LPS) activates TLR4, while peptidoglycan products activate NOD1. Activation of NOD1 by the specific agonist FK565 results in a profound vascular dysfunction and experimental shock in vivo.Experimental approach:Here, we have analysed a number of pharmacological inhibitors to characterize the role of key signalling pathways in the induction of NOS2 following TLR4 or NOD1 activation.Key results:Vascular smooth muscle (VSM) cells expressed NOD1 mRNA and protein, and, after challenge with Escherichia coli or FK565, NOS2 protein and activity were induced. Macrophages had negligible levels of NOD1 and were unaffected by FK565, but responded to E. coli and LPS by releasing increased NO and expression of NOS2 protein. Classic pharmacological inhibitors for NF-κB (SC-514) and mitogen-activated protein kinase (SB203580, PD98059) signalling pathways inhibited responses in both cell types regardless of agonist. While TLR4-mediated responses in macrophages were specifically inhibited by the pan-caspase inhibitor z-VAD-fmk and the PKC inhibitor Gö6976, NOD1-mediated responses in VSM cells were inhibited by the Rip2 inhibitor PP2.Conclusions and implications:Our findings suggest a selective role for NOD1 in VSM cells, and highlight NOD1 as a potential novel therapeutic target for the treatment of vascular inflammation.

Innate Immune Receptors in Human Airway Smooth Muscle Cells: Activation by TLR1/2, TLR3, TLR4, TLR7 and NOD1 Agonists

“…No information is currently available regarding NLRs and RLRs in HASMCs. However, vascular SMCs have been reported to express NOD1 and respond to the NOD1 agonist FK565, while being unaffected by NOD2 stimulation [42], [43]. The present study complements and extends previous reports on innate immune receptors in HASMCs by showing mRNA expression for TLR2, TLR3, TLR4, TLR7, NOD1, NOD2, RIG-I, MDA-5 and LGP-2.…”

Activation of an Innate Immune Receptor, Nod1, Accelerates Atherogenesis in Apoe−/− Mice

“…Additionally, the complete loss of this receptor significantly decreased the size of atherosclerotic lesions, providing evidence of a solid relationship between NOD1 and atherosclerosis. Previously, only limited studies have shown the effect of NOD1 in the cardiovascular field (25,26) or the involvement of NOD1 in vascular inflammation induced by C. pneumoniae (12). No prior study, however, has directly proven the association between NOD1 and atherosclerosis in vivo.…”

Role of acid sphingomyelinase and IL-6 as mediators of endotoxin-induced pulmonary vascular dysfunction

“…24 hours later, cell viability was evaluated by the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay30 and culture medium was frozen until further analysis.…”