1-Peptidyl-2-arachidonoyl-3-stearoyl-sn-glyceride: An Immunologically Active Lipopeptide from Goat Serum (Capra hircus) Is an Endogenous Damage-Associated Molecular Pattern

Abstract

Experiments were undertaken to isolate a component of the serum of goat (Capra hircus) that is effective at mediating an innate immune response. This report describes the isolation and structure elucidation of 1-(N-acetyl-ALYDKGYTSKEQKDCVGI)-2-arachidonoyl-3-stearoyl glyceride (1) and its immunomodulatory activity. A dose-response relationship for inflammatory cytokine and chemokine production and release from human fibroblasts incubated with nanomolar concentrations of 1 was shown. Moreover, the membrane transport role of the diacylglycerol moiety in 1 is demonstrated with nanomolar quantities of the transfected N-acetyl peptide moiety of 1 also inducing inflammatory cytokine and chemokine production and release. The apparent EC99 for 1 was 3 ng/mL (1 nM). The likely biological role for naturally occurring 1 as a damage-associated molecular pattern is postulated.

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“…THP-1 monocytes did not tolerate Lipofectamine well, necessitating a higher concentration of acALY18 in these experiments to ensure its intracellular delivery, as we have previously reported (34). A dose-response relationship was observed: ϳ90% of the untreated cells remained infected, and ϳ12% of the acALY18-treated cells remained infected at 100 ng/ml, ϳ35% at 50 ng/ml, and ϳ40% at 25 ng/ml.…”

“…Thacker and colleagues (34) reported the isolation, structure elucidation, and synthesis of an NME, 1-peptidyl-2-arachidonoyl-3-stearoyl-sn-glyderide, derived from a caprine serum fraction similar to that which had been previously reported (2,20,29,30). The chemical structure is shown in Fig.…”

“…We postulated that acALY18 induces a signaling cascade that is at least in part mediated by the inflammasome (34). Inflammasome effector mechanisms have recently been reviewed (24), and it is clear that the inflammasome is a key regulator of the innate immune response to cellular injury and infection.…”

“…In addition to increased IL-33 secretion, Thacker et al demonstrated that human fibroblasts secrete IL-8 in response to acALY18 (34). IL-8 is a potent chemotactic chemokine in humans that is responsible for the recruitment of neutrophils.…”

“…pDAG was isolated and synthesized as previously described, and acALY18 was synthesized by solid-phase methods as previously described (34). FNN-21 was synthesized by solid-phase methods as previously described (37).…”