Su He Wang

Multifunctional Dendrimer-Modified Multiwalled Carbon Nanotubes: Synthesis, Characterization, and In Vitro Cancer Cell Targeting and Imaging

Carbon nanotubes hold great promise for their use as a platform in nanomedicine, especially in drug delivery, medical imaging, and cancer targeting and therapeutics. Herein, we present a facile approach to modifying carbon nanotubes with multifunctional poly(amidoamine) (PAMAM) dendrimers for cancer cell targeting and imaging. In this approach, fluorescein isothiocyanate (FI)- and folic acid (FA)-modified amine-terminated generation 5 (G5) PAMAM dendrimers (G5·NH(2)-FI-FA) were covalently linked to acid-treated multiwalled carbon nanotubes (MWCNTs), followed by acetylation of the remaining primary amine groups of the dendrimers. The resulting MWCNT/G5.NHAc-FI-FA composites are water-dispersible, stable, and biocompatible. In vitro flow cytometry and confocal microscopy data show that the formed MWCNT/G5·NHAc-FI-FA composites can specifically target to cancer cells overexpressing high-affinity folic acid receptors. The results of this study suggest that, through modification with multifunctional dendrimers, complex carbon nanotube-based materials can be fabricated, thereby providing many possibilities for various applications in biomedical sensing, diagnosis, and therapeutics.

A Unique Combination of Inflammatory Cytokines Enhances Apoptosis of Thyroid Follicular Cells and Transforms Nondestructive to Destructive Thyroiditis in Experimental Autoimmune Thyroiditis

Treatment of cultured primary human thyroid cells with IFN-γ and TNF-α uniquely allows the induction of Fas-mediated apoptosis. To investigate the role of this cytokine combination in vivo, CBA/J mice were immunized with thyroglobulin and then injected with IFN-γ and TNF-α. Compared with control animals, mice treated with IFN-γ and TNF-α showed significantly sustained lymphocytic infiltration in the thyroid, which was associated with the destruction of portions of the follicular architecture at wk 6 after initial immunization. Furthermore, the number of apoptotic thyroid follicular cells was increased only in the thyroids from mice treated with the IFN-γ and TNF-α. We also analyzed the function of the Fas pathway in vivo in cytokine-treated mice by using an agonist anti-Fas Ab injected directly into the thyroid. Minimal apoptosis of thyroid epithelial cells was observed unless the mice were pretreated with IFN-γ and TNF-α. These data demonstrate that this unique combination of inflammatory cytokines facilitates the apoptotic destruction of thyroid follicular cells in experimental autoimmune thyroiditis, in a manner similar to what is observed in Hashimoto’s thyroiditis in humans.

Targeting and detecting cancer cells using spontaneously formed multifunctional dendrimer-stabilized gold nanoparticles

We develop a facile approach to fabricating multifunctional dendrimer-stabilized gold nanoparticles (Au DSNPs) for cancer cell targeting and imaging. In this work, amine-terminated generation 5 (G5) poly(amidoamine) (PAMAM) dendrimers pre-functionalized with folic acid (FA) and fluorescein isothiocyanate (FI) are complexed with Au(III) ions, followed by acetylation of the amine groups on the dendrimer surfaces. This one-step process leads to the spontaneous formation of 6 nm-sized Au nanoparticles stabilized by multifunctional dendrimers bearing both targeting and imaging functionalities. The multifunctional Au DSNPs are characterized by UV-Vis spectrometry, 1H NMR, and transmission electron microscopy (TEM). The formed Au DSNPs are water-soluble, stable, and biocompatible. Combined flow cytometry, confocal microscopy, silver staining, and inductively coupled plasma-mass spectrometry (ICP-MS) analyses show that the FA- and FI-functionalized Au DSNPs can specifically target to cancer cells expressing high-affinity FA receptors in vitro. This approach to functionalizing Au DSNPs may be extended to other targeting molecules, providing a unique nanoplatform for targeting and imaging of a variety of biological systems.

Comparison of the internalization of targeted dendrimers and dendrimer-entrapped gold nanoparticles into cancer cells.

Dendrimer-based nanotechnology significantly advances the area of targeted cancer imaging and therapy. Herein, we compared the difference of surface acetylated fluorescein isocyanate (FI) and folic acid (FA) modified generation 5 (G5) poly(amidoamine) dendrimers (G5.NHAc-FI-FA), and dendrimer-entrapped gold nanoparticles with similar modifications ([(Au(0))(51.2)-G5.NHAc-FI-FA]) in terms of their specific internalization to FA receptor (FAR)-overexpressing cancer cells. Confocal microscopic studies show that both G5.NHAc-FI-FA and [(Au(0))(51.2-)G5.NHAc-FI-FA] exhibit similar internalization kinetics regardless of the existence of Au nanoparticles (NPs). Molecular dynamics simulation of the two different nanostructures reveals that the surface area and the FA moiety distribution from the center of the geometry are slightly different. This slight difference may not be recognized by the FARs on the cell membrane, consequently leading to similar internalization kinetics. This study underlines the fact that metal or inorganic NPs entrapped within dendrimers interact with cells in a similar way to that of dendrimers lacking host NPs.

2-Methoxyestradiol, an endogenous estrogen metabolite, induces thyroid cell apoptosis

The etiology of autoimmune thyroid diseases is unclear; however, the extreme female predominance suggests that sex hormones may have a pathogenic role. 2-Methoxyestradiol (2-ME) is present in the serum of women during the ovulatory and luteal phases of the menstrual cycle, and during pregnancy. We investigated the actions of 2-ME and estrogen on thyroid follicular cells. 2-ME induced dramatic changes in cell morphology and decreased the viability of the cells, as well as disrupted the structural integrity of cultured thyroid follicles. Flow cytometric analysis showed that 2-ME halted cell proliferation by arresting the cells in the G2/M cell-cycle compartment. Prolonged exposure to 2-ME led to apoptosis and to increased release of the autoantigen thyroid peroxidase (TPO). 17beta-estradiol failed to produce a similar effect even in 40-fold molar excess to 2-ME. Co-treatment with estrogen receptor antagonists did not alter the 2-ME effect, indicating that 2-ME was not operating through a classic nuclear estrogen receptor. In conclusion, this study indicates that 2-ME induces G2/M cycle arrest, apoptosis and the disruption of thyroid follicles. This process results in the release of thyroid antigens that may play a role in high incidence of thyroid autoantibodies and autoimmune thyroid disease in women.

Tumor necrosis factor-related apoptosis-inducing ligand inhibits experimental autoimmune thyroiditis by the expansion of CD4+CD25+ regulatory T cells.

There have been several reports that TNF-related apoptosis-inducing ligand (TRAIL) has the ability to suppress the development of experimental autoimmune diseases, including a mouse model of experimental autoimmune encephalomyelitis, a rabbit model of rheumatoid arthritis, type 1 diabetes mellitus, in mice and experimental autoimmune thyroiditis (EAT) in mice. However, the mechanism underlying TRAIL effect is not well defined. In the present study, we specifically examined TRAIL effects on CD4(+)CD25(+) regulatory T cells. CD4(+)CD25(+) T cells prepared from mouse thyroglobulin (mTg)-immunized CBA/J mice proliferate in the presence of TRAIL and dendritic cells in vitro. These CD4(+)CD25(+) T cells included both CD4(+)CD25(+)CD45RB(Low) (regulatory) and CD4(+)CD25(+)CD45RB(High) (effector) T cells. Our results demonstrated that mTg-immunized mice treated with TRAIL showed significant increases in the number of CD4(+)CD25(+)CD45RB(Low) T cells compared with mice immunized with mTg alone. CD4(+)CD25(+)CD45RB(Low) T cells expressed much higher levels of the forkhead family transcription factor, IL-10, and TGFbeta1 than CD4(+)CD25(+)CD45RB(High) T cells, and these cells can completely suppress the proliferation of the mTg-primed splenocytes in lower concentrations than the unfractionated CD4(+)CD25(+) T cells. Furthermore, transfer of these cells into CBA/J mice prior to mTg-primed splenocyte injection could markedly reduce the frequency and severity of EAT development. CD4(+)CD25(+)CD45RB(Low) T cells were more effective at suppressing histological thyroiditis than unfractionated cells. These results indicated that TRAIL can increase the number of mTg-specific CD4(+)CD25(+)CD45RB(Low) T cells, inhibiting autoimmune responses and preventing the progression of EAT. These findings reveal a novel mechanism by which TRAIL could inhibit autoimmune disease.

IFNγ sensitization to TRAIL-induced apoptosis in human thyroid carcinoma cells by upregulating Bak expression

TRAIL preferentially induces apoptosis in tumor cells and virus-infected cells. Unlike other tumor necrosis factor family members, TRAIL does not kill cells from most normal tissues and has thus been proposed as a promising new cancer treatment. Our study demonstrated that IFNγ combined with TRAIL can trigger apoptosis in vitro in several resistant thyroid tumor cell lines, such as thyroid anaplastic carcinoma cells (ARO cells), while either agent alone exerts only a minimal effect. We further tested this effect on a mouse thyroid tumor model, when in vivo tumor growth was also significantly inhibited by this combination. The mechanism of how IFNγ sensitized thyroid carcinoma cells to TRAIL-induced apoptosis was investigated by screening global gene alterations in ARO cells treated with IFNγ. Microarray data revealed that a proapoptotic gene, Bak, is markedly upregulated by IFNγ, and this was confirmed by RNase protection assay. Western blot analysis also showed a significant increase in Bak at the protein level. Upregulation of Bak and sensitization for apoptosis by IFNγ was blocked by overexpression of antisense Bak in ARO cells. Furthermore, overexpression of Bak sensitized ARO cell to TRAIL-induced apoptosis without the need for IFNγ pretreatment. This suggests that Bak is a regulatory molecule involved in IFNγ-facilitated TRAIL-mediated apoptosis in thyroid cancer cells.

Synthesis of glycoconjugated poly(amindoamine) dendrimers for targeting human liver cancer cells

Amine-terminated generation 5 poly(amidoamine) dendrimers were utilized as a platform to conjugate fluorescein isothiocyanate and lactobionic acid. The conjugated lactobionic acid moieties enabled effective targeting to human liver cancer cells (HepG2) in vitro, which was demonstrated by both flow cytometry and confocal microscopy.

1α,25-Dihydroxyvitamin D3 Up-Regulates Bcl-2 Expression and Protects Normal Human Thyrocytes from Programmed Cell Death1

Apoptosis is thought to play an important role in the pathogenesis of autoimmune thyroid disease. 1α,25-dihydroxyvitamin D3 (VD3) has been shown to suppress several autoimmune diseases. However, the mechanism by which VD3 has these effects is not known. We evaluated the alterations in apoptosis, induced by VD3. Thyrocytes were treated with VD3, and the expression of the Bcl-2 family molecules was studied at both the messenger RNA and protein levels. It was found that VD3 significantly induced the expression of Bcl-2 messenger RNA and protein in thyrocytes but had no effect on the expression of Bcl-xl and Bax. The increase in Bcl-2 expression, mediated by VD3, correlated with protection of thyrocytes against the induction of apoptosis by either staurosporine or UV irradiation. VD3-induced increases in the expression of Bcl-2 could be mimicked by VD3 analogs with high nuclear receptor affinity, but not by analogs only with nongenomic actions. These data indicate a role for Bcl-2 in the regulation of apoptos...

Targeted cancer cell inhibition using multifunctional dendrimer-entrapped gold nanoparticles

Generation 5-poly(amidoamine) dendrimers pre-modified with folic acid and methotrexate (G5-FA-MTX) were used as templates for the synthesis of dendrimer-entrapped gold nanoparticles (Au DENPs). The synthesized [(Au0)50-G5-FA-MTX] DENPs were able to target and specifically inhibit the growth of cancer cells overexpressing high affinity folic acid receptors.