Characterization of alkanoyl-10-O-minocyclines in micellar dispersions as potential agents for treatment of human neurodegenerative disorders

Ameliorating Alzheimer's-like Pathology by Minocycline via Inhibiting Cdk5/p25 Signaling

BACKGROUND

Minocycline has multiple neuroprotective roles in abundant brain diseases, including the prevention and treatment of Alzheimer's disease (AD). Cdk5/p25 signaling plays an important role in the onset and development of Alzheimer's-like pathology. The aim of the present work was to further explore the underlying mechanism which minocycline effects on Cdk5/p25 signaling related to Alzheimer's-like pathology.

METHODS

The cognitive function of animals was measured by the Morris water maze test. The levels of Aβ were determined by an enzyme-linked immunosorbent assay. The levels of APP, β- and γ- secretases, and the biomarkers of tau (total tau and hyperphosphorylated tau), inflammatory cytokine and matrix metalloproteinases (MMP-2 and MMP-9), and biomarkers of synapse and Cdk5/p25 signaling, were detected by the Western blotting. The biomarkers of the synapse, inflammatory cytokine, and matrix metalloproteinases (MMP-2 and MMP-9) were also determined by immunofluorescence.

RESULTS

Minocycline improved learning and memory in APP/PS1 mice. It limited the production of Aβ and hyperphosphorylation of tau in the hippocampus and ameliorated synaptic deficit. Moreover, it also inhibited the activation of Cdk5/p25 signaling, inflammation, and matrix metalloproteinases.

CONCLUSION

Minocycline mitigates Alzheimer's-like pathology via limiting the activation of Cdk5/p25 signaling pathway and improves cognitive deficits.

Minocycline encapsulated chitosan nanoparticles for central antinociceptive activity

The purpose of the study is to explore the central anti-nociceptive activity of brain targeted nanoparticles (NP) of minocycline hydrochloride (MH). The NP were formulated using the modified ionotropic gelation method (MHNP) and were coated with Tween 80 (T80) to target them to brain (cMHNP). The formulated nanoparticles have already been characterized for particle size, zeta potential, drug entrapment efficiency and in vitro drug release. The nanoparticles were then evaluated for pharmacodynamic activity using thermal methods. The pure drug and the formulation, MHNP were not able to show a statistically significant central analgesic activity. cMHNP on the other hand evidenced a significant central analgesic activity. Animal models evidenced that brain targeted nanoparticles may be utilized for effective delivery of central anti-nociceptive effect of MH. Further clinical studies are required to explore the activity for mankind.

New flurbiprofen derivatives: synthesis, membrane affinity and evaluation of in vitro effect on β-amyloid levels

Alzheimer's disease (AD) is characterized by irreversible and progressive loss of memory and cognition and profound neuronal loss. Current therapeutic strategies for the treatment of AD have been directed to a variety of targets with the aim of reversing or preventing the disease but, unfortunately, the available treatments often produce no significant clinical benefits. During the last decades compounds that inhibit or modulate γ-secretase, reducing β amyloid (Aβ) levels, have been considered as potential therapeutics for AD. Among these the (R)-enantiomer of flurbiprofen (FLU) seems to be very promising, but it shows low brain penetration. In this study, in order to improve the properties of FLU against Alzheimer's pathogenesis we synthesized some novel FLU lipophilic analogues. Lipophilicity of the new molecules has been characterized in terms of clogP, log K(C18/W) and log K(IAM/W) values. Permeability has been determined in both gastrointestinal PAMPA (PAMPA-GI) at different pH values and in brain blood barrier PAMPA (PAMPA-BBB) models. They were also tested for their ability to inhibit in vitro γ-secretase activity using rat CTXTNA2 astrocytes. Interestingly, the investigated molecules demonstrated to reduce Aβ 42 levels without affecting the amyloid precursor protein APP level in a clear concentrations-dependent manner.

Database of published retention factors for immobilized artificial membrane HPLC and an assessment of the effect of experimental variability

A database was collated of published experimental logarithmic values for the relative retention factors (log k(IAM)) measured using an immobilized artificial membrane column and high-performance liquid chromatography (IAM HPLC). Log k(IAM) is an alternative measure of hydrophobicity to the octanol/water partition coefficient (log K(OW)). While there are several accepted methods to measure log K(OW), no standardized method exists to determine log k(IAM). The database of collated log k(IAM) values includes 13 key experimental parameters and contains 1,686 values for 555 compounds, which are predominantly polar organic compounds and include drug molecules and surfactants. These compounds are acidic, basic, and neutral and both ionized and un-ionized under the conditions of analysis. The data compiled demonstrated experimental variability for each experimental parameter considered, including column stationary phase, pH, temperature, and mobile phase. Reducing the experimental variability allowed for greater consistency in the datasets.

CNS delivery of L-dopa by a new hybrid glutathione-methionine peptidomimetic prodrug

Parkinson's disease (PD) is a neurodegenerative disorder associated primarily with loss of dopamine (DA) neurons in the nigrostriatal system. With the aim of increasing the bioavailability of L: -dopa (LD) after oral administration and of overcoming the pro-oxidant effect associated with LD therapy, we designed a peptidomimetic LD prodrug (1) able to release the active agent by enzyme catalyzed hydrolysis. The physicochemical properties, as well as the chemical and enzymatic stabilities of the new compound, were evaluated in order to check both its stability in aqueous medium and its sensitivity towards enzymatic cleavage, providing the parent LD drug, in rat and human plasma. The radical scavenging activities of prodrug 1 was tested by using both the DPPH-HPLC and the DMSO competition methods. The results indicate that the replacement of cysteine GSH portion by methionine confers resistance to oxidative degradation in gastric fluid. Prodrug 1 demonstrated to induce sustained delivery of DA in rat striatal tissue with respect to equimolar LD dosages. These results are of significance for prospective therapeutic application of prodrug 1 in pathological events associated with free radical damage and decreasing DA concentration in the brain.

Minocycline block copolymer micelles and their anti-inflammatory effects on microglia

MH, a semisynthetic tetracycline antibiotic with promising neuroprotective properties, was encapsulated into PIC micelles of CMD-PEG as a potential new formulation of MH for the treatment of neuroinflammatory diseases. PIC micelles were prepared by mixing solutions of a Ca(2+)/MH chelate and CMD-PEG copolymer in a Tris-HCl buffer. Light scattering and (1)H NMR studies confirmed that Ca(2+)/MH/CMD-PEG core-corona micelles form at charge neutrality having a hydrodynamic radius approximately 100 nm and incorporating approximately 50 wt.-% MH. MH entrapment in the micelles core sustained its release for up to 24 h under physiological conditions. The micelles protected the drug against degradation in aqueous solutions at room temperature and at 37 degrees C in the presence of FBS. The micelles were stable in aqueous solution for up to one month, after freeze drying and in the presence of FBS and BSA. CMD-PEG copolymers did not induce cytotoxicity in human hepatocytes and murine microglia (N9) in concentrations as high as 15 mg x mL(-1) after incubation for 24 h. MH micelles were able to reduce the inflammation in murine microglia (N9) activated by LPS. These results strongly suggest that MH PIC micelles can be useful in the treatment of neuroinflammatory disorders.