Comparing modes of delivery of a combination of ion channel inhibitors for limiting secondary degeneration following partial optic nerve transection.

Injury to the central nervous system is exacerbated by secondary degeneration. Previous research has shown that a combination of orally and locally administered ion channel inhibitors following partial optic nerve injury protects the myelin sheath and preserves function in the ventral optic nerve, vulnerable to secondary degeneration. However, local administration is often not clinically appropriate. This study aimed to compare the efficacy of systemic and local delivery of the ion channel inhibitor combination of lomerizine, brilliant blue G (BBG) and YM872, which inhibits voltage-gated calcium channels, P2X7 receptors and Ca2+ permeable α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors respectively. Following a partial optic nerve transection, adult female PVG rats were treated with BBG and YM872 delivered via osmotic mini pump directly to the injury site, or via intraperitoneal injection, both alongside oral administration of lomerizine. Myelin structure was preserved with both delivery modes of the ion channel inhibitor combination. However, there was no effect of treatment on inflammation, either peripherally or at the injury site, or on the density of oligodendroglial cells. Taken together, the data indicate that even at lower concentrations, the combinatorial treatment may be preserving myelin structure, and that systemic and local delivery are comparable at improving outcomes following neurotrauma.

Elucidating the Inability of Functionalized Nanoparticles to Cross the Blood-Brain Barrier and Target Specific Cells in Vivo.

The adsorption of serum proteins on the surface of nanoparticles (NPs) delivered into a biological environment has been known to alter NP surface properties and consequently their targeting efficiency. In this paper, we use random copolymer (p(HEMA- ran-GMA))-based NPs synthesized using 2-hydroxyethyl methacrylate (HEMA) and glycidyl methacrylate (GMA). We show that serum proteins bind to the NP and that functionalization with antibodies and peptides designed to facilitate NP passage across the blood-brain barrier (BBB) to bind specific cell types is ineffective. In particular, we use systematic in vitro and in vivo analyses to demonstrate that p(HEMA- ran-GMA) NPs functionalized with HIV-1 trans-activating transcriptor peptide (known to cross the BBB) and α neural/glial antigen 2 (NG2) (known for targeting oligodendrocyte precursor cells (OPCs)), individually and in combination, do not specifically target OPCs and are unable to cross the BBB, likely due to the serum protein binding to the NPs.

Limiting oxidative stress following neurotrauma with a combination of ion channel inhibitors.

Following injury to the central nervous system, secondary degeneration is mediated by Ca2+ imbalances and overproduction of reactive oxygen species from mitochondria, and is associated with myelin deficits and loss of function. Preventing intracellular Ca2+ influx at the acute phase of injury is a potential strategy for limiting these deficits and preserving function. The use of single ion channel inhibitors has had little success in attenuating morphological and functional deficits, potentially due to the many pathways by which calcium can traverse the cell membrane. Focus has shifted to the simultaneous administration of a combination of ion channel inhibitors: lomerizine, oxATP, and YM872. The combination has resulted in reductions in oxidative damage, as well as preservation of function and myelin ultrastructure, potentially due to the protection of oligodendrocytes and their progenitors. The use of multiple ion channel inhibitors is promising and suggests a reduction in total intracellular Ca2+ influx is necessary and sufficient for the protection of neurons and glia following neurotrauma. Optimization of treatment timing, inhibitor choice, and method of delivery will be required for translation of this strategy to the clinic.