Microglia, neuroinflammation, and beta-amyloid protein in Alzheimer's disease.

Compelling evidence from basic molecular biology has demonstrated the dual roles of microglia in the pathogenesis of Alzheimer's disease (AD). On one hand, microglia are involved in AD pathogenesis by releasing inflammatory mediators such as inflammatory cytokines, complement components, chemokines, and free radicals that are all known to contribute to beta-amyloid (Aß) production and accumulation. On the other hand, microglia are also known to play a beneficial role in generating anti-Aß antibodies and stimulating clearance of amyloid plaques. Aß itself, an inducer of microglia activation and neuroinflammation, has been considered as an underlying and unifying factor in the development of AD. A vicious cycle of inflammation has been formed between Aß accumulation, activated microglia, and microglial inflammatory mediators, which enhance Aß deposition and neuroinflammation. Thus, inhibiting the vicious cycle seems to be a promising treatment to restrain further development of AD. With increasing research efforts on microglia in AD, intervention of microglia activation and neuroinflammation in AD may provide a potential target for AD therapy in spite of the provisional failure of nonsteroidal antiinflammatory drugs in clinical trials.

Folate receptor targeted 17-allylamino-17-demethoxygeldanamycin (17-AAG) loaded polymeric nanoparticles for breast cancer.

Low water solubility and hepatotoxicity limited the clinical use of 17-allylamino-17-demethoxy geldanamycin (17-AAG), an inhibitor of heat shock protein 90 (HSP90). Folate targeted polylactide-co-glycolide-polyethylene glycol-folic acid (PLGA-PEG-FA) nanoparticles containing 17-AAG were prepared and characterized. Cellular uptake and in vitro cytotoxicity of the prepared nanoparticles were determined in MCF-7 human breast cancer cells. The particle size of 17-AAG loaded folate targeted nanoparticles was 238.67±3.52 nm, drug loading was 8.25±2.49% and about 80% of drug was released from the nanoparticles over 10 days. Cellular uptake studies showed much higher intracellular uptake of folate targeted nanoparticle as compared to nontargeted nanoparticles. Cytotoxicity study showed 2 fold increase (P<0.05, n=3) in the cytotoxicity of folate targeted nanoparticle in comparison to free drug or nontargeted nanoparticles. Due to their targeting ability, nanometer size, high drug loading and controlled release behavior, 17-AAG loaded PLGA-PEG-FA nanoparticles might be developed as a targeted delivery system for breast and other cancer treatment.

Poloxamer 407/TPGS mixed micelles for delivery of gambogic acid to breast and multidrug-resistant cancer.

BACKGROUND: Delivery of a high concentration of anticancer drugs specifically to cancer cells remains the biggest challenge for the treatment of multidrug-resistant cancer. Poloxamers and D-α-Tocopheryl polyethylene glycol 1000 succinate (TPGS) are known inhibitors of P-glycoprotein (P-gp). Mixed micelles prepared from Poloxamer 407 and TPGS may increase the therapeutic efficacy of the drug by delivering high concentrations inside the cells and inhibiting P-gp. Gambogic acid (GA) is a naturally derived novel anticancer agent, but poor solubility and toxic side effects limit its use. In this study, we have developed Poloxamer 407 and TPGS mixed micelle-encapsulating GA for the treatment of breast and multidrug-resistant cancer. METHODS: GA-loaded Poloxamer 407/TPGS mixed micelles were prepared using a thin film hydration method, and their physicochemical properties were characterized. Cellular accumulation and cytotoxicity of the GA-loaded Poloxamer 407/TPGS mixed micelles were studied in breast cancer cells, MCF-7 cells, and multidrug-resistant NCI/ADR-RES cells. RESULTS: The diameter of GA-loaded Poloxamer 407/TPGS mixed micelles was about 17.4 ± 0.5 nm and the zeta potential -13.57 mV. The entrapment efficiency of GA was 93.1% ± 0.5% and drug loading was about 9.38% ± 0.29%. Differential scanning calorimetry and X-ray powder diffraction studies confirmed that GA is encapsulated by the polymers. The in vitro release studies showed that mixed micelles sustained the release of GA for more than 4 days. Results from cellular uptake studies indicated that GA-loaded Poloxamer 407/TPGS mixed micelles had increased cellular uptake of GA in NCI/ADR-RES cells. Cytotoxicity of GA-loaded Poloxamer 407/TPGS mixed micelles was found to be 2.9 times higher in multidrug-resistant NCI/ADR-RES cells, and 1.6 times higher in MCF-7 cells, as compared with unencapsulated GA. CONCLUSION: This study suggests that Poloxamer 407/TPGS mixed micelles can be used as a delivery system for GA to treat breast and multidrug-resistant cancer.

Zirconium phosphate nano-platelets: a novel platform for drug delivery in cancer therapy.

Doxorubicin was intercalated into novel zirconium phosphate nano-platelets (ZrP). The obtained doxorubicin intercalated ZrP nano-platelets had an impressive 34.9% (w/w) drug loading. We used this material to deliver doxorubicin to breast cancer cells (MCF-7). Cellular studies with MCF-7 cells showed higher uptake and cytotoxicity of doxorubicin loaded ZrP compared to free doxorubicin.

Ibuprofen-phospholipid solid dispersions: improved dissolution and gastric tolerance.

Solid dispersions of ibuprofen with various phospholipids were prepared, and the effect of phospholipids on the in vitro dissolution and in vivo gastrointestinal toxicity of ibuprofen was evaluated. Most phospholipids improved the dissolution of ibuprofen; dimyristoylphosphatidyl-glycerol (DMPG) had the greatest effect. At 45 min, the extent of dissolution of ibuprofen from the ibuprofen-DMPG system (weight ratio 9:1) increased about 69% compared to ibuprofen alone; the initial rate of dissolution increased sevenfold. Increasing the DMPG content from 9:1 to 4:1 in this system did not significantly increase the rate and the extent of dissolution. X-ray diffraction and scanning electron micrograph indicated a smaller crystallite size of ibuprofen with fairly uniform distribution in the ibuprofen-DMPG solid dispersion. A small amount of carrier phospholipid significantly increases the rate and the extent of dissolution, which may increase the bioavailability of ibuprofen. The number of ulcers >0.5mm in size formed in the gastric mucosa of rats following ibuprofen, DMPG, DMPC and DPPC solid dispersions (ibuprofen and phospholipid weight ratio 4:1) were 8.6 ± 6.2, 3.9 ± 5.3, 5.3 ± 4.9 and 9.1 ± 7.4, respectively. Solid dispersion of ibuprofen with DMPG was significantly less irritating to the gastric mucosa than ibuprofen itself (one-way ANOVA, p<0.05). Solid dispersion of ibuprofen and DMPG decreases the gastric side effects of ibuprofen.

Improved bioavailability of orally administered mifepristone from PLGA nanoparticles.

The objective of this study was to prepare an oral dosage formulation of mifepristone that will improve the oral bioavailability of mifepristone and sustain the release of mifepristone for at least 3 days to effectively control reproduction, especially in coyotes. Nanoparticles containing mifepristone were prepared from dl-lactide/glycolide copolymers (PLGA). Encapsulation efficiency of the nanoparticles was determined by HPLC. In vitro release study was done in 30% isopropyl alcohol in water. In vivo bioavailability study was performed in male rats. Mifepristone and drug-loaded 50/50 PLGA, M(W) 4.4kDa, nanoparticles (equivalent to 100mg/kg mifepristone) were administered orally to rats. The concentration of mifepristone in serum at different time intervals was determined by HPLC. The average sizes of 50/50 PLGA (M(W) 4.4 and 13kDa) nanoparticles containing mifepristone were 516 and 468nm, respectively. The drug encapsulation efficiency was 75.6% at 20% drug loading in 50/50 PLGA (M(W) 4.4kDa) nanoparticles. In vitro cumulative release of mifepristone from the 50/50 PLGA (M(W) 4.4 and 13kDa) nanoparticles with 20% drug loading was 60% and 48% in 72h, respectively. In vivo studies in rats demonstrated that PLGA-1A-nanoparticles increase the bioavailability of mifepristone. We are currently using the nanoparticles containing mifepristone for efficacy studies in coyotes.