Experimental Pretreatment with Chlorogenic Acid Prevents Transient Ischemia-Induced Cognitive Decline and Neuronal Damage in the Hippocampus through Anti-Oxidative and Anti-Inflammatory Effects.

Chlorogenic acid (CGA), an ester of caffeic acid and quinic acid, is among the phenolic acid compounds which can be naturally found in green coffee extract and tea. CGA has been studied since it displays significant pharmacological properties. The aim of this study was to investigate the effects of CGA on cognitive function and neuroprotection including its mechanisms in the hippocampus following transient forebrain ischemia in gerbils. Memory and learning following the ischemia was investigated by eight-arm radial maze and passive avoidance tests. Neuroprotection was examined by immunohistochemistry for neuronal nuclei-specific protein and Fluoro-Jade B histofluorescence staining. For mechanisms of the neuroprotection, alterations in copper, zinc-superoxide dismutase (SOD1), SOD2 as antioxidant enzymes, dihydroethidium and 4-hydroxy-2-nonenal as indicators for oxidative stress, and anti-inflammatory cytokines (interleukin (IL)-4 and IL-13) and pro-inflammatory cytokines (tumor necrosis factor α (TNF-α) and IL-2) were examined by Western blotting and/or immunohistochemistry. As a result, pretreatment with 30 mg/kg CGA attenuated cognitive impairment and displayed a neuroprotective effect against transient forebrain ischemia (TFI). In Western blotting, the expression levels of SOD2 and IL-4 were increased due to pretreatment with CGA and, furthermore, 4-HNE production and IL-4 expressions were inhibited by CGA pretreatment. Additionally, pretreated CGA enhanced antioxidant enzymes and anti-inflammatory cytokines and, in contrast, attenuated oxidative stress and pro-inflammatory cytokine expression. Based on these results, we suggest that CGA can be a useful neuroprotective material against ischemia-reperfusion injury due to its antioxidant and anti-inflammatory efficacies.

Heparin-based temperature-sensitive injectable hydrogels for protein delivery.

Stimuli-sensitive injectable hydrogels, composed of biodegradable copolymers, have emerged as prominent candidate materials for the sustained delivery of therapeutic drugs. In this study, we developed a biodegradable and temperature-sensitive injectable hydrogel system based on heparin-bearing poly(ε-caprolactone-co-lactide)-b-poly(ethylene glycol)-b-poly(ε-caprolactone-co-lactide) (Hep-PCLA) as the carrier system for lysozyme. Hep-PCLA conjugates are capable of undergoing temperature-induced sol-to-gel transitions in an aqueous solution. The gelation rate, mechanical strength, and viscosity of Hep-PCLA conjugates are controllably tunable by varying the graft density of PCLA copolymers to heparin. The gel window in which Hep-PCLA forms a gel covers the physiological conditions (37 °C), i.e., free flowing Hep-PCLA in aqueous solutions (25 °C) could form a hydrogel at body temperature. Using an in vitro cytotoxicity test, Hep-PCLA conjugates were found to be non-toxic to fibroblast cells, even at high concentrations. Lysozyme, chosen as a model protein, was effectively loaded into Hep-PCLA conjugates using ionic and hydrophobic interactions. The lysozyme-loaded conjugates readily formed a hydrogel when implanted in the back of Sprague-Dawley rats, and retarded the initial burst of lysozyme release, exhibiting sustained release. Our results show that biodegradable, temperature-sensitive injectable Hep-PCLA hydrogels can be used as sustained protein carriers.