Pharmacokinetics of oral pridinol: Results of a randomized, crossover bioequivalence trial in healthy subjects.

OBJECTIVES: To establish the relative bioavailability and to assess bioequivalence of oral, immediate-release tablets containing pridinol and to determine the pharmacokinetic properties of the compound. METHODS AND MATERIALS: In this single-center, open-label, randomized, crossover trial, healthy male and female adult subjects received single doses of the test and reference product containing 4 mg pridinol mesylate (equivalent to 3 mg pridinol) each under fasting conditions. For pharmacokinetic evaluation, blood samples were withdrawn until 72 hours post dose. Pridinol in plasma was quantified by validated liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS). Adverse events (AEs) were analyzed descriptively. RESULTS: Of 34 randomized subjects, 33 completed all treatments. The determined pharmacokinetic parameters were quite similar for both products, with geometric means for maximum exposure (Cmax) of 29.27 ng/mL (test) and 27.44 ng/mL (reference), reached after 1.00 and 0.90 hours (mean tmax), respectively. The extents of bioavailability (geometric mean AUC0-tlast) were 187.93 h×ng/mL (test) and 183.51 h×ng/mL (reference). Elimination half-lives (T1/2) ranged from 8.97 to 34.85 hours with comparable mean T1/2 of 19.14 hours (test) and 18.85 hours (reference). The point estimates of the test/reference-adjusted geometric mean ratios of AUC0-tlast, Cmax (primary), and AUC0-∞ (secondary) were 102.54% (90% confidence interval: 96.19 - 109.32%), 106.79% (99.00 - 115.20%), and 102.60% (96.20 - 109.43%), respectively. Overall, 23 subjects experienced 50 AEs; headache and dizziness (15 cases each) were most frequently reported. CONCLUSION: Bioequivalence of both pridinol products was demonstrated in terms of rate and extent of absorption. Safety and tolerability were in accordance with the known AE profile of the drug substance.

The neuroprotective role of microglial cells against amyloid beta-mediated toxicity in organotypic hippocampal slice cultures.

During Alzheimer's disease (AD) progression, microglial cells play complex roles and have potentially detrimental as well as beneficial effects. The use of appropriate model systems is essential for characterizing and understanding the roles of microglia in AD pathology. Here, we used organotypic hippocampal slice cultures (OHSCs) to investigate the impact of microglia on amyloid beta (Aß)-mediated toxicity. Neurons in OHSCs containing microglia were not vulnerable to cell death after 7 days of repeated treatment with Aß1-42 oligomer-enriched preparations. However, when clodronate was used to remove microglia, treatment with Aß1-42 resulted in significant neuronal death. Further investigations indicated signs of endoplasmic reticulum stress and caspase activation after Aß1-42 challenge only when microglia were absent. Interestingly, microglia provided protection without displaying any classic signs of activation, such as an amoeboid morphology or the release of pro-inflammatory mediators (e.g., IL-6, TNF-α, NO). Furthermore, depleting microglia or inhibiting microglial uptake mechanisms resulted in significant more Aß deposition compared to that observed in OHSCs containing functional microglia, suggesting that microglia efficiently cleared Aß. Because inhibiting microglial uptake increased neuronal cell death, the ability of microglia to engulf Aß is thought to contribute to its protective properties. Our study argues for a beneficial role of functional ramified microglia whereby they act against the accumulation of neurotoxic forms of Aß and support neuronal resilience in an in situ model of AD pathology.

SK channel activation modulates mitochondrial respiration and attenuates neuronal HT-22 cell damage induced by H2O2.

Previous studies established an essential role for small conductance calcium-activated potassium (SK) channels in neuronal cell death pathways induced by glutamate excitotoxicity in cortical neurons in vitro and after cerebral ischemia in vivo. In addition to the intracellular calcium deregulation, glutamate-induced cell death also involves mechanisms of oxidative stress and mitochondrial dysfunction. Therefore, we sought to investigate whether SK channel activation might also affect mechanisms of intrinsic death pathways induced by reactive oxygen species (ROS) such as hydrogen peroxide (H2O2). Exposure of immortalized hippocampal HT-22 cells to H2O2 imposed activation of a cascade of intracellular toxic events resulting in intracellular ROS production, mitochondrial loss of function, and ultimately cell death. Using a pharmacological approach to activate SK channels with CyPPA, we demonstrated a reduction of H2O2-mediated intracellular ROS production and cell death. Interestingly, CyPPA mediated neuroprotection in conditions of extracellular calcium and/or pyruvate depletion, pointing to a neuroprotective role of mitochondrial SK channels. Moreover, CyPPA partially inhibited H2O2-induced mitochondrial superoxide production, but did not prevent mitochondrial membrane depolarization. CyPPA treatment resulted in slight ATP depletion and a reduction of mitochondrial respiration/oxygen consumption. These findings postulate that SK channels mediate a protective effect by preventing neuronal death from subsequent oxidative stress through an adaptive metabolic response at the level of mitochondria. Therefore, SK channel activation may serve as a therapeutic target, where mitochondrial dysfunction and related mechanisms of oxidative stress contribute to progressive degeneration and death of neurons.