Preparation of 99mTc-PQQ and preliminary biological evaluation for the NMDA receptor

Neurotoxicity and apoptosis induced by pyrroloquinoline quinone and its ester derivative on primary cortical neurons

Pyrroloquinoline quinone (PQQ) and its esterified derivative, PQQ ester (PQQE), have potential to treat or diagnose neurological and psychological disorders. However, their neurotoxicity remains unclear. To provide reference data for the brain targeting drug delivery techniques, the cytotoxic effects of PQQ and PQQE were examined in primary mouse cortical neurons. The results indicated that both PQQ and PQQE decreased neuron viability, reduced intracellular ATP level and disrupted the mitochondrial membrane potential in a concentration- and time-dependent manner, while PQQ was less potent than PQQE. PQQ and PQQE induced apoptosis involving increase of Bax, decrease of Bcl-2, release of mitochondrial cytochrome C into the cytosol, activation of caspase-3 and cleavage of PARP. A single mouse intracephalic injection of PQQ or PQQE showed similar results. Based on these findings, high-concentration PQQ or PQQE treatment could induce a wide range of neurotoxicity and apoptosis. The lowest observed adverse effect levels (LOAELs) of PQQ and PQQE were 10 μM and 2 μM respectively and the no observed adverse effect levels (NOAELs) were 5 μM and 1 μM respectively in mice cortical neurons.

Prolonged half-life of small-sized therapeutic protein using serum albumin-specific protein binder

Many small-sized proteins and peptides, such as cytokines and hormones, are clinically used for the treatment of a variety of diseases. However, their short half-life in blood owing to fast renal clearance usually results in a low therapeutic efficacy and frequent dosing. Here we present the development of a human serum albumin (HSA)-specific protein binder with a binding affinity of 4.3nM through a phage display selection and modular evolution approach to extend the blood half-life of a small-sized therapeutic protein. As a proof-of-concept, the protein binder composed of LRR (Leucine-rich repeat) modules was genetically fused to the N-terminus of Glucagon-like Peptide-1 (GLP-1). The fused GLP-1 was shown to have a significantly improved pharmacokinetic property: The terminal half-life of the fused GLP-1 increased to approximately 10h, and the area under the curve was 5-times higher than that of the control. The utility and potential of our approach was demonstrated by the efficient control of the blood glucose level in type-2 diabetes mouse models using the HSA-specific protein binder-fused GLP-1 over a prolonged time period. The present approach can be effectively used in enhancing the efficacy of small-sized therapeutic proteins and peptides through an enhanced blood circulation time.

Modulation of glycine sites enhances social memory in rats using PQQ combined with d-serine

The aim of study was to investigate the effects of pyrroloquinoline quinone (PQQ) combined with d-serine on the modulation of glycine sites in the brain of rats using social recognition test. Rats were divided into seven groups (n=10) and given repeated intraperitoneal (ip) injections of saline, MK-801 (0.5mg/kg), clozapine (1mg/kg), haloperidol (0.1mg/kg), d-serine (0.8g/kg), PQQ (2.0μg/kg), or d-serine (0.4g/kg) combined with PQQ (1.0μg/kg) for seven days. A social recognition test, including assessment of time-dependent memory impairment, was performed. A non-competitive NMDA receptor antagonist, MK-801, significantly impaired social memory, and this impairment was significantly repaired with an atypical antipsychotic (clozapine) but not with a typical antipsychotic (haloperidol). Likewise, d-serine combined with PQQ significantly improved MK-801-disrupted cognition in naïve rats, whereas haloperidol was ineffective. The present results show that the co-agonist NMDA receptor treated with PQQ and d-serine enhances social memory and may be an effective approach for treating the cognitive dysfunction observed in schizophrenic patients. PQQ stimulates glycine modulatory sites by which it may antagonize indirectly by removing glycine from the synaptic cleft or by binding the unsaturated site with d-serine in the brain, providing the insights into future research of central nervous system and drug discovery.