Sustained Release of Functional Interleukin-10 Encapsulated within Poly (lactic acid)-b-Poly (ethylene glycol) Nanoparticles Down-regulates Cytokines in Mouse Macrophages Exposed to Chlamydia trachomatis

S. Duncan, S. Dixit, R. Sahu, E. Nyairo, S.R. Singh, V.A. Dennis
Alabama State University,
United States

Keywords: Chlamydia trachomatis, (Poly (lactic acid)-b-Poly (ethylene glycol), Interleukin-10, anti-inflammatory

Summary:

Inflammation which is induced by the presence of cytokines and chemokines is an integral part of Chlamydial infection. Chlamydia trachomatis (CT), the bacterial pathogen responsible for this sexually transmitted infection worldwide, causes severe inflammation including, but not limited to, pelvic inflammatory disease, ectopic pregnancy and infertility in women. It can be regulated using effective alternative therapeutics, including anti-inflammatory molecules. Our laboratory published that an anti-inflammatory cytokine, interleukin-10 (IL-10) can down-regulate the secretion of inflammatory cytokines triggered by CT in epithelial cells and mouse macrophages. A major problem with IL-10 however, is its short biological half-life thus requiring frequent applications at high dosages for biomedical applications. Our goal in this study was to encapsulate IL-10 within the biodegradable polymer, PLA-PEG (Poly (lactic acid)-b-Poly (ethylene glycol) nanoparticles in an attempt to prolong its half-life. IL-10 was successfully encapsulated in PLA-PEG by the double emulsion method, followed by physiochemical characterizations and functional studies. Results from Ultra Violet (UV) visible and Fourier Transform-Infrared Spectroscopy (FT-IR) revealed the successful encapsulation of IL-10 within PLA-PEG. Encapsulated IL-10 had an average size of ~ 100 to 200 nm, with an encapsulation efficiency > 90 %. Temperature stability of encapsulated IL-10 was up to 89C as shown by differential scanning calorimetry analysis. Additionally, the in vitro release study revealed an initial burst followed by the slow and continuous release of IL-10 from PLA-PEG nanoparticles. The anti-inflammatory effect of encapsulated IL-10 was then tested using various concentrations (1-1000 ng/mL) over a 24 hour time-point in mouse J774 macrophages exposed to the recombinant major outer membrane protein of CT. Cytokine specific ELISAs showed that encapsulated IL-10 reduced the levels of IL-6 in macrophages in a time- and concentration-dependent fashion, correlating with its stability and slow release capacity. Conclusively, our data shows successful encapsulation of IL-10 and that PLA PEG can prolong the half-life of IL-10. More importantly, encapsulated IL-10 is functional by down-regulating cytokines in macrophages exposed to CT at relatively low dosages.