Synthesis and activity of a novel diether phosphonoglycerol in phospholipase-resistant synthetic lipid:peptide lung surfactants

Abstract

This paper reports the chemical synthesis and purification of a novel phospholipase-resistant C16:0, C16:1 diether phosphonoglycerol with structural analogy to ester-linked anionic phosphatidylglycerol (PG) in endogenous pulmonary surfactant. This diether phosphonoglycerol (PG 1) is studied for phospholipase A2 (PLA2) resistance and for surface activity in synthetic exogenous surfactants combined with Super Mini-B (S-MB) peptide and DEPN-8, a previously-reported diether phosphonolipid analog of dipalmitoyl phosphatidylcholine (DPPC, the major zwitterionic phospholipid in native lung surfactant). Activity experiments measured both adsorption and dynamic surface tension lowering due to the known importance of these surface behaviors in lung surfactant function in vivo. Synthetic surfactants containing 9 : 1 DEPN-8:PG 1 + 3% S-MB were resistant to degradation by PLA2 in chromatographic studies, while calf lung surfactant extract (CLSE, the substance of the bovine clinical surfactant Infasurf®) was significantly degraded by PLA2. The 9 : 1 DEPN-8:PG 1 + 3% S-MB mixture also had small but consistent increases in both adsorption and dynamic surface tension lowering ability compared to DEPN-8 + 3% S-MB. Consistent with these surface activity increases, molecular dynamics simulations using Protein Modeller, GROMACS force-field, and PyMOL showed that bilayers containing DPPC and palmitoyl-oleoyl-PC (POPC) as surrogates of DEPN-8 and PG 1 were penetrated to a greater extent by S-MB peptide than bilayers of DPPC alone. These results suggest that PG 1 or related anionic phosphono-PG analogs may have functional utility in phospholipase-resistant synthetic surfactants targeting forms of acute pulmonary injury where endogenous surfactant becomes dysfunctional due to phospholipase activity in the innate inflammatory response.

Surfactant protein C peptides with salt-bridges (“ion-locks”) promote high surfactant activities by mimicking theα-helix and membrane topography of the native protein

“…MD runs using GROMACS () should provide valuable information on the detailed 3D-structures of SP-C mimics in the bilayer (Walther et al, 2010; Schwan et al, 2011). For simulations of SP-Css ion-lock 1 in a lipid bilayer-water box, the “0 ns” model was obtained by first templating its primary sequence (Fig.…”

New Generation Synthetic Surfactants

“…Even if the phospholipid composition in endogenous surfactant has been studied in detail, this knowledge has not been used for the development of synthetic surfactants. Phospholipase-resistant diether phosphono analogs of phosphatidylglycerol and dipalmitoylphosphatidylcholine have been used together with the SP-B analog, Super Mini-B [34] . These surfactant preparations had similar surface activity to the calf lung surfactant extract (CLSE) in vitro and are more resistant to degradation than the animal-derived surfactant preparation.…”

Synthetic lung surfactants containing SP-B and SP-C peptides plus novel phospholipase-resistant lipids or glycerophospholipids

“…Phospholipase degradation of exogenous surfactant phospholipids has the potential not only to reduce active drug concentration, but also to generate byproducts such as free fatty acids and lysophosphatidylcholine that are themselves severe biophysical inhibitors of surfactant activity (Wang & Notter, 1998; Holm, Wang & Notter, 1999; Hite et al, 2012; De Luca et al, 2013). We have previously reported the synthesis of active analogs of lung surfactant glycerophospholipids that have specific molecular substitutions to confer chemical resistance to phospholipase degradation (Turcotte et al, 1991; Wang et al, 2003; Notter et al, 2007; Schwan et al, 2011). The current study uses two of these phospholipase-resistant lipids, DEPN-8 and PG-1, as components in new synthetic lipid/peptide surfactants.…”

“…DEPN-8 is a C16:0 diether phosphonolipid analog of dipalmitoyl phosphatidylcholine (DPPC) (Turcotte et al, 1991; Wang et al, 2003), and PG-1 is a C16:0:C16:1 ether-linked phosphonolipid analog of palmitoyl-oleoyl phosphatidylglycerol (POPG) (Schwan et al, 2011), the major class of anionic phospholipids in native surfactant. Prior work by our group has shown that synthetic surfactants containing DEPN-8 or 9:1 DEPN-8:PG-1 plus an active surfactant protein (SP)-B peptide (Mini-B or Super Mini-B) have significant surface activity (Walther et al, 2007; Schwan et al, 2011).…”

“…Prior work by our group has shown that synthetic surfactants containing DEPN-8 or 9:1 DEPN-8:PG-1 plus an active surfactant protein (SP)-B peptide (Mini-B or Super Mini-B) have significant surface activity (Walther et al, 2007; Schwan et al, 2011). This earlier work is extended here to synthetic lipid/peptide lung surfactants containing recently reported active mimics of hydrophobic surfactant apoproteins, i.e.…”