Paracrine signalling of inflammatory cytokines from an in vitro blood brain barrier model upon exposure to polymeric nanoparticles

Nanoparticle properties, such as small size relative to large highly modifiable surface area, offer great promise for neuro-therapeutics and nanodiagnostics. A fundamental understanding and control of how nanoparticles interact with the blood-brain barrier (BBB) could enable major developments in nanomedical treatment of previously intractable neurological disorders, and help ensure that nanoparticles not intended to reach the brain do not cause adverse effects. Nanosafety is of utmost importance to this field. However, a distinct lack of knowledge exists regarding nanoparticle accumulation within the BBB and the biological effects this may induce on neighbouring cells of the Central Nervous System (CNS), particularly in the long-term. This study focussed on the exposure of an in vitro BBB model to model carboxylated polystyrene nanoparticles (PS COOH NPs), as these nanoparticles are well characterised for in vitro experimentation and have been reported as non-toxic in many biological settings. TEM imaging showed accumulation but not degradation of 100 nm PS COOH NPs within the lysosomes of the in vitro BBB over time. Cytokine secretion analysis from the in vitro BBB post 24 h 100 nm PS COOH NP exposure showed a low level of pro-inflammatory RANTES protein secretion compared to control. In contrast, 24 h exposure of the in vitro BBB endothelium to 100 nm PS COOH NPs in the presence of underlying astrocytes caused a significant increase in pro-survival signalling. In conclusion, the tantalising possibilities of nanomedicine must be balanced by cautious studies into the possible long-term toxicity caused by accumulation of known 'toxic' and 'non-toxic' nanoparticles, as general toxicity assays may be disguising significant signalling regulation during long-term accumulation.European Research CouncilScience Foundation IrelandUCD SEED grantProgramme for Research in Third Level Institution

Cellular in vivo imaging reveals coordinated regulation of pituitary microcirculation and GH cell network function

Growth hormone (GH) exerts its actions via coordinated pulsatile secretion from a GH cell network into the bloodstream. Practically nothing is known about how the network receives its inputs in vivo and releases hormones into pituitary capillaries to shape GH pulses. Here we have developed in vivo approaches to measure local blood flow, oxygen partial pressure, and cell activity at single-cell resolution in mouse pituitary glands in situ. When secretagogue (GHRH) distribution was modeled with fluorescent markers injected into either the bloodstream or the nearby intercapillary space, a restricted distribution gradient evolved within the pituitary parenchyma. Injection of GHRH led to stimulation of both GH cell network activities and GH secretion, which was temporally associated with increases in blood flow rates and oxygen supply by capillaries, as well as oxygen consumption. Moreover, we observed a time-limiting step for hormone output at the perivascular level; macromolecules injected into the extracellular parenchyma moved rapidly to the perivascular space, but were then cleared more slowly in a size-dependent manner into capillary blood. Our findings suggest that GH pulse generation is not simply a GH cell network response, but is shaped by a tissue microenvironment context involving a functional association between the GH cell network activity and fluid microcirculation

Squalenoyl Adenosine Nanoparticles Provide Neuroprotection After Stroke And Spinal Cord Injury

There is an urgent need to develop new therapeutic approaches for the treatment of severe neurological trauma, such as stroke and spinal cord injuries. However, many drugs with potential neuropharmacological activity, like adenosine, are inefficient upon systemic administration because of their fast metabolisation and rapid clearance from the bloodstream. Here, we show that the conjugation of adenosine to the lipid squalene and the subsequent formation of nanoassemblies allow a prolonged circulation of this nucleoside, to provide neuroprotection in mouse stroke and rat spinal cord injury models. The animals receiving systemic administration of squalenoyl adenosine nanoassemblies showed a significant improvement of their neurologic deficit score in the case of cerebral ischaemia, and an early motor recovery of the hindlimbs in the case of spinal cord injury. Moreover, in vitro and in vivo studies demonstrated that the nanoassemblies were able to extend adenosine circulation and its interaction with the neurovascular unit. This paper shows, for the first time, that a hydrophilic and rapidly metabolised molecule like adenosine may become pharmacologically efficient owing to a single conjugation with the lipid squalene.PubMedWo