Neuroprotection effects of kynurenic acid-loaded micelles for the Parkinson's disease models.

Anti-glutamatergic agents may have neuroprotective effects against excitotoxicity that is known to be involved in the pathogenesis of Parkinson's disease (PD). One of these agents is kynurenic acid (KYNA), a tryptophan metabolite, which is an endogenous N-methyl-D-aspartic acid (NMDA) receptor antagonist. However, its pharmacological properties of poor water solubility and limited blood-brain barrier (BBB) permeability rules out its systemic administration in disorders affecting the central nervous system. Our aim in the present study was to investigate the neuroprotective effects of KYNA-loaded micelles (KYNA-MICs) against PD in vitro and in vivo. Lipid-based micelles (MICs) in conjunction with KYNA drug delivery have the potential to enhance the penetration of therapeutic drugs into a diseased brain without BBB obstacles. KYNA-MICs were characterized by particle size (105.8 ± 12.1 nm), loading efficiency (78.3 ± 4.23%), and in vitro drug release (approximately 30% at 24 h). The in vitro experiments showed that KYNA-MICs effectively reduced 2-fold protein aggregation. The in vivo studies revealed that KYNA was successfully delivered by 5-fold increase in neurotoxin-induced PD brains. The results showed significant enhancement of KYNA delivery into brain. We also found that the KYNA-MICs exhibited several therapeutic effects. The KYNA-MICs reduced protein aggregation of an in vitro PD model, ameliorated motor functions, and prevented loss of the striatal neurons in a PD animal model. The beneficial effects of KYNA-MICs are probably explained by the anti-excitotoxic activity of the treatment's complex. As the KYNA-MICs did not induce any appreciable side-effects at the protective dose applied to a chronic PD mouse model, our results demonstrate that KYNA provides neuroprotection and attenuates PD pathology.