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

Abstract

BackgroundThis study examines the biophysical and preclinical pulmonary activity of synthetic lung surfactants containing novel phospholipase-resistant phosphonolipids or synthetic glycerophospholipids combined with Super Mini-B (S-MB) DATK and/or SP-Css ion-lock 1 peptides that replicate the functional biophysics of surfactant proteins (SP)-B and SP-C. Phospholipase-resistant phosphonolipids used in synthetic surfactants are DEPN-8 and PG-1, molecular analogs of dipalmitoyl phosphatidylcholine (DPPC) and palmitoyl-oleoyl phosphatidylglycerol (POPG), while glycerophospholipids used are active lipid components of native surfactant (DPPC:POPC:POPG 5:3:2 by weight). The objective of the work is to test whether these novel lipid/peptide synthetic surfactants have favorable preclinical activity (biophysical, pulmonary) for therapeutic use in reversing surfactant deficiency or dysfunction in lung disease or injury.MethodsSurface activity of synthetic lipid/peptide surfactants was assessed in vitro at 37 °C by measuring adsorption in a stirred subphase apparatus and dynamic surface tension lowering in pulsating and captive bubble surfactometers. Shear viscosity was measured as a function of shear rate on a Wells-Brookfield micro-viscometer. In vivo pulmonary activity was determined by measuring lung function (arterial oxygenation, dynamic lung compliance) in ventilated rats and rabbits with surfactant deficiency/dysfunction induced by saline lavage to lower arterial PO2 to <100 mmHg, consistent with clinical acute respiratory distress syndrome (ARDS).ResultsSynthetic surfactants containing 5:3:2 DPPC:POPC:POPG or 9:1 DEPN-8:PG-1 combined with 3% (by wt) of S-MB DATK, 3% SP-Css ion-lock 1, or 1.5% each of both peptides all adsorbed rapidly to low equilibrium surface tensions and also reduced surface tension to ≤1 mN/m under dynamic compression at 37 °C. However, dual-peptide surfactants containing 1.5% S-MB DATK + 1.5% SP-Css ion-lock 1 combined with 9:1 DEPN-8:PG-1 or 5:3:2 DPPC:POPC:POPG had the greatest in vivo activity in improving arterial oxygenation and dynamic lung compliance in ventilated animals with ARDS. Saline dispersions of these dual-peptide synthetic surfactants were also found to have shear viscosities comparable to or below those of current animal-derived surfactant drugs, supporting their potential ease of deliverability by instillation in future clinical applications.DiscussionOur findings support the potential of dual-peptide synthetic lipid/peptide surfactants containing S-MB DATK + SP-Css ion-lock 1 for treating diseases of surfactant deficiency or dysfunction. Moreover, phospholipase-resistant dual-peptide surfactants containing DEPN-8/PG-1 may have particular applications in treating direct forms of ARDS where endogenous phospholipases are present in the lungs.

Activity and biophysical inhibition resistance of a novel synthetic lung surfactant containing Super-Mini-B DATK peptide

“…S-MB DATK peptide (41 residues, amino acid sequence FPIPLPYCWLCRALIKRIQA- MIDATKRMLPQLVCRLVLRCS) was synthesized employing the same general protocol developed earlier for the MB and S-MB peptides ( Waring et al, 2005 ; Walther et al, 2007 ; Walther et al, 2010 ; Walther et al, 2013 ; Notter et al, 2012 ). In brief, synthesis was done on a Symphony Multiple Peptide Synthesizer (Protein Technologies, Tucson, AZ) using a standard protocol on a H-Ser(OtBu)-HMPB NovaPEG resin (EMD Millipore, Billerica, MA, USA).…”

“…These two active peptides (34 and 41 residues, respectively) incorporate active amphipathic helices and the “saposin fold” ( Bruhn, 2005 ) of human SP-B (i.e., helix—turn—helix), and S-MB additionally includes the functionally important N-terminal insertion sequence of the native apoprotein. Here, we report the synthesis and high in vitro and in vivo activity of a novel SP-B peptide mimic, S-MB DATK, characterized by an added important designer-loop stabilizing substitution in the sequence of S-MB to increase molecular stability and improve the ease of synthesis and folding ( Notter et al, 2012 ; Walther et al, 2013 ). The major focus of this study is on documenting the high surface activity and biophysical inhibition resistance of S-MB DATK synthetic surfactant, as well as its promising pulmonary activity in a rabbit model relevant for NRDS and ALI/ARDS.…”

Synthetic surfactants with SP‐B and SP‐C analogues to enable worldwide treatment of neonatal respiratory distress syndrome and other lung diseases

“…Doubling the content of SP‐C33 (to 4 mass% relative to phospholipids) did not improve lung gas volumes , further supporting that specific functions of SP‐B and SP‐C are important, rather than total protein mass relative to phospholipids. A combination of Super Mini‐B and an ion‐lock SP‐C analogue is more efficient in an animal model of ARDS than either peptide alone . However, in vitro the double amounts of each of these peptides alone were as efficient as the combination, perhaps indicating that in vitro properties have limited predictive value for in vivo behaviour.…”

Helical side chain chemistry of a peptoid‐based SP‐C analogue: Balancing structural rigidity and biomimicry

“…The poly‐valyl helix is composed entirely of aliphatic residues with β‐branched side chains that spontaneously convert into β‐sheet aggregate structures with reduced surface activity in the absence of phospholipids . The difficulties associated with native SP‐C have led researchers to use a number of different strategies to overcome its metastable secondary structure and aggregation propensity by producing SP‐C mimics in heterologous systems, creating synthetic peptide analogues, and synthesizing nonnatural peptidomimetics …”