Human breast milk-derived exosomes attenuate lipopolysaccharide-induced activation in microglia
Oluwatomi Akinduro, Sanjay Kumar, Yuechuan Chen, Barbara J. Thomas, Quamarul Hassan, Brian Sims
Abstract
Microglia mediate the immune response in the central nervous system to many insults, including lipopolysaccharide (LPS), a bacterial endotoxin that initiates neuroinflammation in the neonatal population, especially preterm infants. The synthesis of the proinflammatory proteins CD40 and NLRP3 depends on the canonical NF-κB cascade as the genes encoding CD40 and NLRP3 are transcribed by the phosphorylated NF-κB p50/p65 heterodimer in LPS-induced microglia. Exosomes, which are nanosized vesicles (40-150 nm) involved in intercellular communication, are implicated in many pathophysiological processes. Human breast milk, which is rich in exosomes, plays a vital role in neonatal immune system maturation and adaptation. Activated microglia may cause brain-associated injuries or disorders; therefore, we hypothesize that human breast milk-derived exosomes (HBME) attenuate LPS-induced activation of CD40 and NLRP3 by decreasing p38 MAPK and NF-κB p50/p65 activation/phosphorylation downstream of TLR4 in murine microglia (BV2). Human microglia (HMC3) showed a significant decrease in p65 phosphorylation. We isolated purified HBME and characterized them using nanoparticle tracking analysis, transmission electron microscopy, fluorescence-activated cell sorting, and western blots. Analysis of microglia exposed to LPS and HBME indicated that HBME modulated the expression of signaling molecules in the canonical NF-κB pathway, including MyD88, IκBα, p38 MAPK, NF-κB p65, and their products CD40, NLRP3, and cytokines IL-1β and IL-10. Thus, HBMEs have great potential for attenuating the microglial response to LPS.