Immunoactive, Antibacterial and Drug-Carrying properties of selective surfactants

Van Rensburg, Lyne (2018-03)

Thesis (PhD)--Stellenbosch University, 2018.

Thesis

ENGLISH ABSTRACT: Surfactant replacement therapy is used the treatment of neonatal respiratory distress syndrome as surfactant’s biophysical behaviour helps to maintain proper lung function and reduces the work associated with breathing. Secondly, surfactant associated proteins are important role players in the innate immune response within the pulmonary environment and therefore assist in pulmonary host defence. However, natural and synthetic exogenous surfactants have gained much interest in other areas of therapy such as possibly aiding in dual-drug delivery systems for infectious or inflammatory pulmonary conditions. Both types have been studied extensively in animal models and in clinical trials and have elicited positive and negative effects on lung function. This thesis aims to determine whether a synthetic peptide containing surfactant, Synsurf®, may have potential immunomodulatory effects compared to the naturally derived surfactants, Curosurf® and Liposurf®. Two formulations of Synsurf®, combined with the antibiotic linezolid were tested for its efficacy as a respirable compound in a pressurised metered dose inhaler. The outcome of these experiments revealed the prospect of Synsurf®’s adaptability as a pulmonary drug carrier. Furthermore, the tuberculosis isolates H37Rv and MDR-X51 displayed enhanced susceptibility to surfactant-drug micro-particle combinations. The main findings of this study show that the natural surfactants Curosurf® and Liposurf® as well as Synsurf® inhibit secretion of pro-inflammatory cytokines and influence the production of reactive oxygen species in NR8383 alveolar macrophages and therefore influence cell viability. The inhibitory effects on cytokine secretion was displayed in a dose-dependent manner as well as a threshold effect that was seen for all three surfactants. This may result from unique mechanisms of decreasing cell signalling or up-regulating anti-inflammatory activity that was further elucidated by the employment of proteomics. The findings in this thesis on the comparison of the two natural and one synthetic surfactant led to the following main conclusions: a) Different surfactant compositions modulate the anti-inflammatory activity in lipopolysaccharide stimulated alveolar macrophages via the possible involvement of different signalling pathways. The initial hypothesis regarding the protective nature that is linked to the protein content in natural surfactants is challenged and may be deemed as “not fully supported” as these new findings suggest non-specific lipid or synthetic peptide protection with alveolar macrophages as seen with Synsurf®. b) Different surfactant compositions effect cell viability and morphology in a time and dose-dependent manner revealing that the treatment of neonatal respiratory distress syndrome may depend upon the specific preparation or dose used. c) All three surfactants displayed an impact on the antibiotic activity of linezolid that holds positive ramifications for drug loaded surfactants. d) The data shows that linezolid in combination with Synsurf® can be aerosolised in desired particle ranges for optimal lung deposition for a possible non-invasive, site-specific, delivery model via pressurised metered dose inhaler.

AFRIKAANSE OPSOMMING: Surfaktantvervangingsterapie word gebruik in die behandeling van neonatale respiratoriese noodsindroom aangesien die biofisiese werking van surfaktant behoorlike longfunksie help handhaaf en die inspanning verbonde aan asemhaling verminder. Tweedens is surfaktantverwante proteïene belangrike rolspelers in die aangebore immuunreaksie in die pulmonêre omgewing, en bevorder dus pulmonêre gasheerverdediging. Tog is daar ook toenemende belangstelling in natuurlike en sintetiese eksogene surfaktante op ander behandelingsgebiede, soos dat dit moontlik dubbele middelleweringstelsels vir infeksie- of inflammatoriese pulmonêre toestande kan ondersteun. Albei tipes surfaktante is reeds omvattend in diermodelle en kliniese proewe bestudeer, en blyk sowel positiewe as negatiewe uitwerkings op longfunksie te hê. Hierdie tesis beoog om te bepaal of ’n surfaktant wat sintetiese peptiede bevat, naamlik Synsurf®, ’n moontlike rol in immuunregulering speel vergeleke met die natuurlik afgeleide surfaktante Curosurf® en Liposurf®. Twee Synsurf®-formules is in kombinasie met die antibiotikum linezolid getoets vir doeltreffendheid as ’n inasembare verbinding in ’n drukinhalator met afgemete dosisse. Die uitkoms van hierdie eksperimente dui op die moontlike aanpasbaarheid van Synsurf® as ’n draer vir pulmonêre middels. Daarbenewens toon die tuberkulose-isolate H37Rv en MDR-X51 verhoogde vatbaarheid vir mikropartikel surfaktantmiddel kombinasies. Die hoofbevinding van die studie toon dat die natuurlike surfaktante Curosurf® en Liposurf® sowel as Synsurf® die afskeiding van pro-inflammatoriese sitokiene strem en ’n invloed het op die produksie van reaktiewe suurstofspesies in NR8383- alveolêre makrofage, en dus op sellewensvatbaarheid. Die remmende uitwerking op sitokienafskeiding is op ’n dosisafhanklike manier bewys, sowel as deur ’n drempeleffek vir ál drie surfaktante. Dít kan dalk spruit uit unieke meganismes wat selseine verminder, of die opregulering van anti-inflammatoriese aktiwiteit, wat verder met behulp van proteomika toegelig is. Die hoofgevolgtrekkings na aanleiding van die bevindinge van hierdie tesis oor die vergelyking van die twee natuurlike en een sintetiese surfaktant is soos volg: a) Verskillende surfaktantsamestellings moduleer anti-inflammatoriese werking in lipopolisakkaried-gestimuleerde alveolêre makrofage deur die moontlike betrokkenheid van verskillende seinroetes. Die aanvanklike hipotese oor die beskermende funksie van die proteïeninhoud van natuurlike surfaktante word bevraagteken. Aangesien hierdie nuwe bevindinge dui op nie-spesifieke lipied- of sintetiesepeptiedbeskerming by alveolêre makrofage, soos in die geval van Synsurf®, kan die hipotese nie ten volle ondersteun word nie. b) Verskillende surfaktantsamestellings beïnvloed sellewensvatbaarheid en -morfologie op ’n tyd- en dosisafhanklike manier, wat daarop dui dat die behandeling van neonatale respiratoriese noodsindroom moontlik kan afhang van die spesifieke preparaat of dosis wat gebruik word. c) Ál drie surfaktante het oënskynlik ’n impak op die antibiotiese aktiwiteit van linezolid, wat belowend lyk vir surfaktante as middeldraers. d) Die data toon dat linezolid in kombinasie met Synsurf® in ’n gewenste partikelgrote verstuif kan word vir optimale longneerslag in ’n moontlike nie-ingrypende, terreinspesifieke leweringsmodel, deur middel van ’n drukinhalator met afgemete dosisse.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/103855
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