Selective NOD1 agonists cause shock and organ injury/dysfunction in vivo

Rationale NLRs (nucleotide oligomerisation domain [NOD] proteins containing a leucine-rich repeat) are cytosolic pattern recognition receptors. NOW senses diaminopimelic acid-containing peptidoglycan present in gram-negative bacteria, whereas NOD2 senses the muramyl dipeptide (MIDP) present in most organisms. Bacteria are the most common cause of septic shock, which is characterized clinically by hypotension resistant to vasopressor agents. In animal models, gram-negative septic shock is mimicked by lipopolysaccharide (LPS), which signals through Toll-like receptor 4 (TLR4) and its adaptor MyD88. The role of NLlRs in the pathophysiology of septic shock is not known. Objectives: To compare the effects of selective NOD1 agonists with LPS in vivo. Methods: Vascular smooth muscle cells or whole aortas from wildtype or genetically modified mice were stimulated in vitro with agonists of NODI (FK565) or NOD2 (MDP). Vasoconstriction was measured using wire myography. Nitric oxide (NO) formation was measured using Griess reaction and NO synthase-II protein by Western blotting. In vivo, blood pressure, heart rate, and urine output were measured in sham-, LPS-, or FK565-treated animals. Biomarkers of end-organ injury, coagulation activation, NO, and cytokines were measured in plasma. Main Results: FK565, but not MDP, induced NO synthase-II protein/activity in vascular smooth muscle and vascular hyporeactivity to pressor agents. FK565 had no effect on vessels from NOD1(-/-) mice, but was active in vessels from TLR4(-/-), TLR2(-/-), or MyD88(-/-) mice. FK565 induced hypotension, increased heart rate, and caused multiple (renal, liver) injury and dysfunction in vivo. Conclusions: Activation of NODI induces shock and multiple organ injury/dysfunction.