In Vitro Potency and Preclinical Pharmacokinetic Comparison of All-D-Enantiomeric Peptides Developed for the Treatment of Alzheimer's Disease.

Diffusible amyloid-ß (Aß) oligomers are currently presumed to be the most cytotoxic Aß assembly and held responsible to trigger the pathogenesis of Alzheimer's disease (AD). Thus, Aß oligomers are a prominent target in AD drug development. Previously, we reported on our solely D-enantiomeric peptide D3 and its derivatives as AD drug candidates. Here, we compare one of the most promising D3 derivatives, ANK6, with its tandem version (tANK6), and its head-to-tail cyclized isoform (cANK6r). In vitro tests investigating the D-peptides' potencies to inhibit Aß aggregation, eliminate Aß oligomers, and reduce Aß-induced cytotoxicity revealed that all three D-peptides efficiently target Aß. Subsequent preclinical pharmacokinetic studies of the three all-D-peptides in wildtype mice showed promising blood-brain barrier permeability with cANK6r yielding the highest levels in brain. The peptides' potencies to lower Aß toxicity and their remarkable brain/plasma ratios make them promising AD drug candidates.

Connecting inflammation with glutamate agonism in suicidality.

The NMDA-receptor antagonist ketamine has proven efficient in reducing symptoms of suicidality, although the mechanisms explaining this effect have not been detailed in psychiatric patients. Recent evidence points towards a low-grade inflammation in brains of suicide victims. Inflammation leads to production of quinolinic acid (QUIN) and kynurenic acid (KYNA), an agonist and antagonist of the glutamatergic N-methyl-D-aspartate (NMDA) receptor, respectively. We here measured QUIN and KYNA in the cerebrospinal fluid (CSF) of 64 medication-free suicide attempters and 36 controls, using gas chromatography mass spectrometry and high-performance liquid chromatography. We assessed the patients clinically using the Suicide Intent Scale and the Montgomery-Asberg Depression Rating Scale (MADRS). We found that QUIN, but not KYNA, was significantly elevated in the CSF of suicide attempters (P<0.001). As predicted, the increase in QUIN was associated with higher levels of CSF interleukin-6. Moreover, QUIN levels correlated with the total scores on Suicide Intent Scale. There was a significant decrease of QUIN in patients who came for follow-up lumbar punctures within 6 months after the suicide attempt. In summary, we here present clinical evidence of increased QUIN in the CSF of suicide attempters. An increased QUIN/KYNA quotient speaks in favor of an overall NMDA-receptor stimulation. The correlation between QUIN and the Suicide Intent Scale indicates that changes in glutamatergic neurotransmission could be specifically linked to suicidality. Our findings have important implications for the detection and specific treatment of suicidal patients, and might explain the observed remedial effects of ketamine.

N-acetylaspartylglutamate in CNS hypomyelination.

CSF N-acetylaspartylglutamate (NAAG) has been found to be elevated in some hypomyelinating disorders. This study addressed the question whether it could be used as a marker for hypomyelination and as a means to distinguish between hypomyelinating disorders biochemically. We have measured CSF NAAG in a cohort of 28 patients with hypomyelination with known and unknown aetiology. NAAG was found to be elevated in 7 patients, but was normal in the majority, including patients with defined hypomyelinating disorders. CSF NAAG is not a universal marker of hypomyelination, and the mechanism of its elevation remains poorly understood.