Multiple pathophysiological roles of midkine in human disease.

Midkine (MK) is a low molecular-weight protein that was first identified as the product of a retinoic acid-responsive gene involved in embryonic development. Recent studies have indicated that MK levels are related to various diseases, including cardiovascular disease (CVD), renal disease and autoimmune disease. MK is a growth factor involved in multiple pathophysiological processes, such as inflammation, the repair of damaged tissues and cancer. The pathophysiological roles of MK are diverse. MK enhances the recruitment and migration of inflammatory cells upon inflammation directly and also through induction of chemokines, and contributes to tissue damage. In lung endothelial cells, oxidative stress increased the expression of MK, which induced angiotensin-converting enzyme (ACE) expression and the consequent conversion from Ang I to Ang II, leading to further oxidative stress. MK inhibited cholesterol efflux from macrophages by reducing ATP-binding cassette transporter A1 (ABCA1) expression, which is involved in lipid metabolism, suggesting that MK is an important positive factor involved in inflammation, oxidative stress and lipid metabolism. Furthermore, MK can regulate the expansion, differentiation and activation of T cells as well as B-cell survival; mediate angiogenic and antibacterial activity; and possess anti-apoptotic activity. In this paper, we summarize the pathophysiological roles of MK in human disease.

The role of advanced glycation end products in human infertility.

Advanced glycation end products (AGEs) are heterogeneous products of the non-enzymatic interaction between proteins and reducing sugars. Numerous studies have shown that AGEs are associated with senescence, diabetes, vascular disease, aging and kidney disease. Infertility has been affected approximately 10 to15% of couples of reproductive ages. AGEs accumulation has been shown to play a crucial role in pathogenesis of infertility-related diseases. The present review provides the generation process, mechanism and pathological significance of AGEs and the novel treatment targeting AGEs for infertility.

Sex hormone-binding globulin and polycystic ovary syndrome.

Polycystic ovary syndrome (PCOS), one of the most common endocrine diseases that causes infertility in reproductive women, is characterized by hyperandrogenemia, chronic anovulation, and polycystic ovary morphology (PCOM), and most women with PCOS have metabolic abnormalities. A reduction in plasma sex hormone-binding globulin (SHBG), a transport carrier that binds estrogen and androgens and regulates their biological activities, is often used as an indicator of hyperandrogenism in women with PCOS. Low serum SHBG levels are considered a biomarker of abnormal metabolism and are related to insulin resistance (IR), compensatory hyperinsulinemia and abnormalities in glucose and lipid metabolism in PCOS patients. SHBG is also associated with the long-term prognosis of PCOS. SHBG gene polymorphism is correlated with the risk of PCOS. As SHBG plays a vital role in the occurrence and development of PCOS, knowledge regarding its role in PCOS is helpful for further understanding the molecular mechanism of SHBG in PCOS development and providing new ideas for the treatment of female infertility. Hepatocyte nuclear factor-4α (HNF-4α) is a vital transcription factor in the SHBG synthesis process. HNF-4α binds to the cis-type element DR1 in the SHBG promoter to initiate transcription and regulates hepatic SHBG levels by modulating glucose and lipid metabolism and inflammatory factors. However, it remains unclear whether HNF-4α is indirectly involved in the pathogenesis of PCOS via regulation of hepatic SHBG synthesis. Therefore, this review discusses the interaction between SHBG and the various complications of PCOS as well as the regulatory effect of HNF-4α on SHBG expression.

A smart thermoresponsive adsorption system for efficient copper ion removal based on alginate-g-poly(N-isopropylacrylamide) graft copolymer.

In order to develop a smart Cu(II) ion adsorption and removal system for water purification, poly(N-isopropylacrylamide) (PNIPAAm) was grafted to alginate to give a thermoresponsive Alg-g-PNIPAAm graft copolymer. With low or high initial Cu(II) concentrations, the thermoresponsive Alg-g-PNIPAAm graft copolymer could precipitate at 50 °C, with which Cu(II) was efficiently adsorbed and removed from solutions. Alg gel beads crosslinked by calcium ion Ca(II) could adsorb and remove Cu(II), but the beads released significant amount of Ca(II). The adsorption isotherm study showed that thermoresponsive Alg-g-PNIPAAm and Alg gel beads followed the same Langmuir isotherm model for Cu(II) adsorption and removal, but Alg-g-PNIPAAm demonstrated much higher adsorption capacity than Alg gel beads, because the carboxyl groups in Alg-g-PNIPAAm were free, whereas those in Alg gel beads were complexed with Ca(II). In conclusion, the Alg-g-PNIPAAm copolymer formed a smart Cu(II) adsorption and removal system with superior performance.

Controlling injectability and in vivo stability of thermogelling copolymers for delivery of yttrium-90 through intra-tumoral injection for potential brachytherapy.

Intra-tumoral injection of radiopharmaceuticals such as yttrium-90 (90Y) or phosphorus-32 (32P) is an important route for brachytherapy in unresectable solid tumors such as locally advanced hepatocellular carcinoma. However, the injected radiopharmaceuticals can potentially leak out from the tumor site due to high intra-tumoral pressure. In this study, we demonstrated the use of thermogelling copolymers that can be injected into tumor and subsequently solidify as hydrogels within the tumor that can potentially overcome the above problem. To this end, a series of thermogelling polyurethane copolymers with varying compositions were designed and synthesized from Pluronic F127, poly(3-hydroxylbutyrate), and poly(propylene glycol), which were characterized in terms of their molecular structures, compositions, phase diagrams, rheological properties, and injectability and body temperature stability in vitro and in vivo. The analyses of our data elucidated the injectability of the copolymer solutions at low temperatures, and the stability of the hydrogels at the body temperature. This provided the basis on which we could identify one copolymer with balanced composition as the most suitable candidate for intra-tumoral injection and for prevention of the leakage. Finally, the injectability and in vivo stability of the copolymer solution and hydrogel loaded with 90Y were further demonstrated in a mouse tumor model, and the in vivo biodistribution of 90Y showed that the radionuclide could be retained at the tumor site, indicating that the 90Y-loaded copolymer has a great potential for tumor radio-brachytherapy.

Injectable Thermoresponsive Hydrogel Formed by Alginate-g-Poly(N-isopropylacrylamide) That Releases Doxorubicin-Encapsulated Micelles as a Smart Drug Delivery System.

In this work, we have synthesized a thermoresponsive copolymer, alginate-g-poly(N-isopropylacrylamide) (alginate-g-PNIPAAm) by conjugating PNIPAAm to alginate, where PNIPAAm with different molecular weights and narrow molecular weight distribution was synthesized by atomic transfer radical polymerization. The copolymer dissolved in water or phosphate-buffered saline buffer solution at room temperature and formed self-assembled micelles with low critical micellization concentrations when the temperature increased to above their critical micellization temperatures. At higher concentration, that is, 7.4 wt % in water, the copolymer formed solutions at 25 °C and turned into thermosensitive hydrogels when temperature increased to the body temperature (37 °C). Herein, we hypothesized that the thermoresponsive hydrogels could produce self-assembled micelles with the dissolution of the alginate-g-PNIPAAm hydrogels in a biological fluid or drug release medium. If the drug was hydrophobic, the hydrogel eventually could release and produce drug-encapsulated micelles. In our experiments, we loaded the anticancer drug doxorubicin (DOX) into the alginate-g-PNIPAAm hydrogels and demonstrated that the hydrogels released DOX-encapsulated micelles in a sustained manner. The slowly released DOX-loaded micelles enhanced the cellular uptake of DOX in multidrug resistant AT3B-1 cells, showing the effect of overcoming the drug resistance and achieving better efficiency for killing the cancer cells. Therefore, the injectable thermoresponsive hydrogels formed by alginate-g-PNIPAAm and loaded with DOX turned into a smart drug delivery system, releasing DOX-encapsulated micelles in a sustained manner, showing great potential for overcoming the drug resistance in cancer therapy.

Thermoresponsive supramolecular micellar drug delivery system based on star-linear pseudo-block polymer consisting of ß-cyclodextrin-poly(N-isopropylacrylamide) and adamantyl-poly(ethylene glycol).

Chemotherapy is facing several limitations such as low water solubility of anticancer drugs and multidrug resistance (MDR) in cancer cells. To overcome these limitations, a thermoresponsive micellar drug delivery system formed by a non-covalently connected supramolecular block polymer was developed. The system is based on the host-guest interaction between a well-defined ß-cyclodextrin (ß-CD) based poly(N-isopropylacrylamide) star host polymer and an adamantyl-containing poly(ethylene glycol) (Ad-PEG) guest polymer. The structures of the host and guest polymers were characterized by 1H and 13C NMR, GPC and FTIR. Subsequently, they formed a pseudo-block copolymer via inclusion complexation between ß-CD core and adamantyl-moiety, which was confirmed by 2D NMR. The thermoresponsive micellization of the copolymer was investigated by UV-vis spectroscopy, DLS and TEM. At 37°C, the copolymer at a concentration of 0.2mg/mL in PBS formed micelles with a hydrodynamic diameter of ca. 282nm. The anticancer drug, doxorubicin (DOX), was successfully loaded into the core of the micelles with a loading level of 6% and loading efficiency of 17%. The blank polymer micelles showed good biocompatibility in cell cytotoxicity studies. Moreover, the DOX-loaded micelles demonstrated superior therapeutic effects in AT3B-1-N (MDR-) and AT3B-1 (MDR+) cell lines as compared to free DOX control, overcoming MDR in cancer cells.

Thermoresponsive Delivery of Paclitaxel by ß-Cyclodextrin-Based Poly(N-isopropylacrylamide) Star Polymer via Inclusion Complexation.

Paclitaxel (PTX), a hydrophobic anticancer drug, is facing several clinical limitations such as low bioavailability and drug resistance. To solve the problems, a well-defined ß-cyclodextrin-poly(N-isopropylacrylamide) star polymer was synthesized and used as a nanocarrier to improve the water solubility and aim to thermoresponsive delivery of PTX to cancer cells. The star polymer was able to form supramolecular self-assembled inclusion complex with PTX via host-guest interaction at room temperature, which is below the low critical solution temperature (LCST) of the star polymer, significantly improving the solubilization of PTX. At body temperature (above LCST), the phase transition of poly(N-isopropylacrylamide) segments induced the formation of nanoparticles, which greatly enhanced the cellular uptake of the polymer-drug complex, resulting in efficient thermoresponsive delivery of PTX. In particular, the polymer-drug complex exhibited better antitumor effects than the commercial formulation of PTX in overcoming the multi-drug resistance in AT3B-1 cells.

Host-guest interaction induced supramolecular amphiphilic star architecture and uniform nanovesicle formation for anticancer drug delivery.

A star polymer of poly[(R,S)-3-hydroxybutyrate] (PHB) with adamantyl end-terminals extended from an α-cyclodextrin (α-CD) core is designed. It subsequently self-assembles to form controllable and uniform nanovesicles induced by host-guest interactions between heptakis(2,6-di-O-methyl)-ß-CD and the adamantyl ends. The nanovesicles are suitable for loading and intracellular delivery of the anticancer drug doxorubicin.

Amphiphilic star-block copolymers and supramolecular transformation of nanogel-like micelles to nanovesicles.

Amphiphilic star-block copolymers based on poly(3-hydroxybutyrate) with adamantyl end-functionalization were synthesized via anionic ring-opening polymerization and alkyne-azide "Click Chemistry" coupling. In aqueous medium, the copolymers self-assembled into nanogel-like large compound micelles, and transformed into vesicular nanostructures under the direction of host-guest interaction between the adamantyl end and dimethyl-ß-cyclodextrin.

Targeted gene delivery mediated by folate-polyethylenimine-block-poly(ethylene glycol) with receptor selectivity.

The folate receptor (FR) is a tumor marker overexpressed in large numbers of cancer cells. Folic acid has high affinity to the FR and retains its binding affinity upon derivatization via its gamma-carboxyl. Therefore, in this article, folate-polyethylenimine-block-poly(ethylene glycol) (FOL-PEI-b-PEG) was designed for specific receptor targeted gene delivery. Physicochemical characterizations of resulting FOL-PEI-b-PEG/DNA complexes in terms of agarose gel electrophoresis, particle size, and zeta potential measurements were investigated. The results indicated that FOL-PEI-b-PEG was able to condense plasmid DNA tightly with a suitable particle size. The cytotoxicity study indicated that the copolymer exhibited less toxicity in comparison with that of 25 kDa PEI. Luciferase assay and green fluorescent protein (GFP) detections were also used to confirm that FOL-PEI-b-PEG could be an effective gene vector. Importantly, transfection efficiency of FOL-PEI-b-PEG with free folic acid was much lower than that of the copolymer without free folic acid on FR-positive HeLa cells, suggesting that FOL-PEI-b-PEG has great potential as a targeting gene vector.

Novel thermoresponsive nonviral gene vector: P(NIPAAm-co-NDAPM)-b-PEI with adjustable gene transfection efficiency.

A thermoresponsive cationic copolymer, poly( N-isopropylacrylamide- co- N-(3-(dimethylamino)propyl)methacrylamide)- b-polyethyleneimine (P(NIPAAm- co-NDAPM)- b-PEI), was designed and synthesized as a potential nonviral gene vector. The lower critical solution temperature (LCST) of P(NIPAAm- co-NDAPM)- b-PEI in water measured by UV-vis spectroscopy was 38 degrees C. P(NIPAAm- co-NDAPM)- b-PEI as the gene vector was evaluated in terms of cytotoxicity, buffer capability determined by acid-base titration, DNA binding capability characterized by agarose gel electrophoresis and particle size analysis, and in vitro gene transfection. P(NIPAAm- co-NDAPM)- b-PEI copolymer exhibited lower cytotoxicity in comparison with 25 kDa PEI. Gel retardation assay study indicated that the copolymer was able to bind DNA completely at N/P ratios higher than 30. At 27 degrees C, the mean particle sizes of P(NIPAAm- co-NDAPM)- b-PEI/DNA complexes decreased from 1200 to 570 nm corresponding to the increase in N/P ratios from 10 to 60. When the temperature changed to 37 degrees C, the mean particle sizes of complexes decreased from 850 to 450 nm correspondingly within the same N/P ratio range due to the collapse of thermoresponsive PNIPAAm segments. It was found that the transfection efficiency of P(NIPAAm- co-NDAPM)- b-PEI/DNA complexes was higher than or comparable to that of 25 kDa PEI/DNA complexes at their optimal N/P ratios. Importantly, the transfection efficiency of P(NIPAAm- co-NDAPM)- b-PEI/DNA complexes could be adjusted by altering the transfection and cell culture temperature.

Functionalized thermoresponsive micelles self-assembled from biotin-PEG-b-P(NIPAAm-co-HMAAm)-b-PMMA for tumor cell target.

Novel micelles, comprising hydrophilic PEG shells, hydrophobic PMMA cores, and thermosensitive P(NIPAAm-co-HMAAm) segments were self-assembled from the biotin-PEG-b-P(NIPAAm-co-HMAAm)-b-PMMA triblock copolymer. The thermosensitive micelles exhibited superior stability and showed thermotriggered drug release behavior upon temperature alterations. The fluorescence spectroscopy and confocal microscopy studies confirmed that the self-assembled biotinylated micelles can be specifically and efficiently bonded to cancer cells with the administration of biotin-transferrin, suggesting that the multifunctional micelles have great potential as drug carriers for tumor targeting chemotherapy.

Cellular internalization and in vivo tracking of thermosensitive luminescent micelles based on luminescent lanthanide chelate.

An amphiphilic tris(dibenzoylmethanato)europium(III) (Eu(DBM)(3)) coordinated P(MMA-co-EIPPMMA)-co-P(NIPAAm-co-NDAPM) copolymer was synthesized, which exhibited good biocompatibility and emitted strong red luminescence (MMA, methyl methacrylate; EIPPMMA, 4-(1-ethyl-1H-imidazo[4,5-f][1,10]phenanthrolin-2-yl)phenyl methacrylate; NIPAAm, N-isopropylacrylamide; NDAPM, (N-(3-dimethylamino)propyl)methacrylamide). The copolymer could self-assemble into micelles of size around 260 nm, and the micelles were thermosensitive at around body temperature. The drug-loaded micelles showed thermosensitive controlled drug release, and the paclitaxel loaded micelles were capable of being internalized into the tumor cells (A549) and exhibited obvious inhibition to the growth of A549 cells. Importantly, in vivo study showed the self-assembled micelles of Eu(DBM)(3) coordinated P(MMA-co-EIPPMMA)-co-P(NIPAAm-co-NDAPM) copolymer uptaken by the larvae of zebrafish could be easily tracked and be eliminated from the body within several days.