Cytoprotection against beta-amyloid (Aß) peptide-mediated oxidative damage and autophagy by Keap1 RNAi in human glioma U87mg cells.

Extensive oxidative stress has been considered a primary pathological factor for many neurodegenerative disorders (NDDs). We speculated that the oxidative damage to brain cells can be managed by promoting the endogenous cellular antioxidants through the RNA interference (RNAi) against Keap1 (kelch-like ECH-associated protein). Keap1 acts as a negative regulator of Nrf2 (NF-E2-related factor 2) that represses the activation of the antioxidant responsive element (ARE). Here, we investigated whether Keap1 knockdown enhances the cellular antioxidant capacity and provides the neuroprotection against oxidative stress from hydrogen peroxide and beta-amyloid (Aß) peptide in U87mg cells. We found that the Keap1 siRNA pre-treated group displayed higher expression of diverse antioxidant genes and an increased antioxidant capacity compared to the control group. Moreover, the Keap1 RNAi exerted a cytoprotective effect against H2O2 treatment. In Aß peptide treatment experiments, the Keap1 siRNA pre-treated groups maintained acceptable cell viability, relatively intact cellular morphology, and controlled oxidative damage levels while the control groups suffered from Aß peptide-mediated neurotoxicity. Keap1 RNAi also attenuated the oxidative stress-mediated autophagy as well. These findings suggest that Keap1 RNAi can serve as a therapeutic strategy for relieving oxidative stress-associated symptoms in many NDDs.

Tumour eradication using synchronous thermal ablation and Hsp90 chemotherapy with protein engineered triblock biopolymer-geldanamycin conjugates.

PURPOSE: Hepatocellular carcinoma (HCC) suffers high tumour recurrence rate after thermal ablation. Heat shock protein 90 (Hsp90) induced post-ablation is critical for tumour survival and progression. A combination therapy of thermal ablation and polymer conjugated Hsp90 chemotherapy was designed and evaluated for complete tumour eradication of HCC. MATERIALS AND METHODS: A thermo-responsive, elastin-like polypeptide (ELP)-based tri-block biopolymer was developed and conjugated with a potent Hsp90 inhibitor, geldanamycin (GA). The anti-cancer efficacy of conjugates was evaluated in HCC cell cultures with and without hyperthermia (43 °C). The conjugates were also administered twice weekly in a murine HCC model as a single treatment or in combination with single electrocautery as the ablation method. RESULTS: ELP-GA conjugates displayed enhanced cytotoxicity in vitro and effective heat shock inhibition under hyperthermia. The conjugates alone significantly slowed the tumour growth without systemic toxicity. Four doses of thermo-responsive ELP-GA conjugates with concomitant simple electrocautery accomplished significant Hsp90 inhibition and sustained tumour suppression. CONCLUSION: Hsp90 inhibition plays a key role in preventing the recurrence of HCC, and the combination of ablation with targeted therapy holds great potential to improve prognosis and survival of HCC patients.

A myristoylated cell-penetrating peptide bearing a transferrin receptor-targeting sequence for neuro-targeted siRNA delivery.

Many neurodegenerative disorders (NDDs) are characterized by aggregation of aberrant proteins and extensive oxidative stress in brain cells. As a treatment option for NDDs, RNA interference (RNAi) is a promising approach to suppress the activation of abnormal genes and negative regulators of antioxidant genes. Efficient neuro-targeted siRNA delivery requires a delicate optimization of nucleic acid carriers, quite distinct from putative pDNA carriers in regard to stable condensation and serum protection of siRNA, blood-brain barrier (BBB) bypass, effective siRNA delivery to brain cells, and functional release of bioactive siRNA at therapeutic levels. Here, we propose that a myristic acid conjugated, cell-penetrating peptide (transportan; TP), equipped with a transferrin receptor-targeting peptide (myr-TP-Tf), will lead to stable encapsulation of siRNA and targeted delivery of siRNA to brain cells overcoming the BBB. Myr-TP-Tf was successfully prepared by solid-phase peptide synthesis with high purity. Myr-TP-Tf-siRNA complexes formulated at a 20:1 (peptide-siRNA) molar ratio provided prolonged siRNA stability against serum and ribonuclease treatment. Fluorescence images clearly indicated that siRNA uptake was successfully achieved by myr-TP-Tf complexes in both a murine brain endothelioma and a human glioma cell line. The luciferase assay and the human placental alkaline phosphatase (hPAP) reporter assay results demonstrated the functional gene silencing effect of myr-TP-Tf-siRNA complexes in a human glioma cell line as well as in primary murine neurons/astrocytes, supportive of successful release of bioactive siRNA into the cytosol. Finally, the transcytosis assay revealed that favorable siRNA transport via receptor-mediated transcytosis was mediated by myr-TP-Tf complexes. In summary, these data suggest that myr-TP-Tf peptides possess promising properties as a vehicle for neuro-targeted siRNA delivery. We will further study this peptide in vitro and in vivo for transport mechanism kinetics and to validate its capability to deliver siRNA to the brain, respectively.

Thermo-targeted drug delivery of geldanamycin to hyperthermic tumor margins with diblock elastin-based biopolymers.

The tumor margins are the barrier to hepatocellular carcinoma (HCC) eradication for tumors>3 cm. Indeed, inadequately treated tumor margins commonly result in local and regional HCC recurrence with increased size and mass. Tumor recurrence is a common problem with chemotherapy, radiotherapy, thermal ablation, and/or surgical resection, by the inability to properly treat the tumor core and the tumor margins. Here we present novel thermosensitive biopolymer-drug conjugates for thermo-targeted chemotherapy at hyperthermic isotherms produced by focal, locoregional thermal ablation. The chemotherapeutic target is heat shock protein 90 (HSP90), a key molecular chaperone of several, and potent pro-oncogenic pathways including Akt, Raf-1, and mutated p53 that is upregulated in HCC. To inhibit HSP90, we have chosen geldanamycin (GA), a potent HSP90 inhibitor. GA has gained significant attention for its low IC50 ~ 1 nM and inhibition of Akt and Raf-1, amongst other critical pro-oncogenic pathways. Despite such evidence, clinical trials of GA have not shown promise due to off-target toxicity and poor formulation design. Here, we propose using diblock elastin-based biopolymers as a Ringsdorf macromolecular GA solubilizer--a new generation containing functional poly(Asp)/(Glu) blocks for facile drug conjugation and an ELP block for thermo-targeting of hyperthermic ablative margins. GA release is controlled by pH-sensitive, covalent hydrazone bonds with the biopolymer backbone to avoid systemic toxicity and off-target effects. The resultant biopolymer-conjugates form stable nanoconstructs and display tunable, acute phase transitions at high temperatures. Drug release kinetics are favorable with or without the presence of serum. Thermo-targeted chemotherapy and synchronous thermal ablation provide a unique opportunity for simultaneous destruction of the HCC ablative margins and tumor core for focal, locoregional control of HCC.

Induction of oxidative stress and apoptosis by silver nanoparticles in the liver of adult zebrafish.

Silver nanoparticles (AgNPs) may induce deleterious effects in aquatic life on environmental release. The hepatotoxicity of AgNPs was assessed in the liver of adult zebrafish, with the aim of studying the roles of oxidative damage and apoptosis. Zebrafish were exposed to an AgNP solution in which free Ag+ ions were absent at the time of treatment. However, the metal-sensitive metallothionein 2 (MT2) mRNA was induced in the liver tissues of AgNP-treated zebrafish, suggesting that Ag+ ions were released from AgNPs after treatment. It is also possible that MT2 mRNA was induced in the liver tissues by AgNP-generated free radicals. A number of cellular alterations including disruption of hepatic cell cords and apoptotic changes were observed in histological analysis of the liver tissues. The levels of malondialdehyde, a byproduct of cellular lipid peroxidation, and total glutathione were increased in the tissues after treatment with AgNPs. The mRNA levels of the oxyradical-scavenging enzymes catalase and glutathione peroxidase 1a were reduced in the tissues. AgNP treatment induced DNA damage, as demonstrated by analysis with the double-strand break marker γ-H2AX and the expression of p53 protein in liver tissues. In addition, the p53-related pro-apoptotic genes Bax, Noxa, and p21 were upregulated after treatment with AgNPs. These data suggest that oxidative stress and apoptosis are associated with AgNP toxicity in the liver of adult zebrafish.

Regulation of iron metabolism-related genes in diethylnitrosamine-induced mouse liver tumors.

BACKGROUND: It has been suggested that the altered iron metabolism in liver tumors, characterized by the iron-deficient phenotype, is of importance for tumor growth. AIM: This study was performed to elucidate the mechanisms underlying iron deficiency in liver tumors by examining how the liver tumor development affects the expression of iron metabolism-related genes. METHODS: Iron metabolism reference values were analyzed in the sera of diethylnitrosamine-induced hepatocellular adenoma-bearing mice. Expression of iron metabolism-related genes was analyzed in adenomas and surrounding non-tumor tissues, and a subgroup of adenoma-bearing mice loaded with iron 72h before sacrifice. RESULTS: Iron content of the adenoma tissues was 2.0-2.5-fold lower compared to surrounding and age-matched control tissues. There was no significant difference in serum iron levels between the adenoma-bearing and control mice, while the adenoma-bearing mice exhibited a 2.4-fold lower level of serum transferrin saturation. Expression of iron metabolism-related genes was dysregulated in the adenomas. Iron loading affected protein expression similarly in the adenomas and surrounding tissues suggesting that iron-responsive regulation of the proteins was not impaired. However, the mRNA expression for ceruloplasmin and divalent metal transporter 1 (DMT1) IRE(+) in the adenomas was altered independently of iron status, and the dysregulation may contribute to diminished iron content. CONCLUSION: These findings suggest that diethylnitrosamine-induced liver adenoma-bearing mice have abnormal iron metabolism and that dysregulation of iron metabolism-related genes contributes to iron deficiency in the adenomas.

Regulation of metal transporters by dietary iron, and the relationship between body iron levels and cadmium uptake.

Iron (Fe) plays essential roles in biological processes, whereas cadmium (Cd) is a toxic and non-essential metal. Two metal transporters, divalent metal transporter 1 (DMT1) and metal transporter protein 1 (MTP1), are responsible for Fe transport in mammals. Here, we studied the effect of dietary Fe on the expression of these metal transporters in peripheral tissues, and the uptake by these tissues of Cd. Mice were fed an Fe-sufficient (FeS: 120 mg Fe/kg) or Fe-deficient (FeD: 2-6 mg Fe/kg) diet for 4 weeks. The total Fe levels in the body were evaluated by measuring tissue Fe concentrations. Tissue Cd concentrations were determined 24 h after the mice received a single oral dose of Cd. Animals fed a FeD diet showed depletion of body Fe levels and accumulated 2.8-fold higher levels of Cd than the FeS group. Quantitative real time RT-PCR revealed that whereas DMT1 and MTP1 were both ubiquitously expressed in all FeS peripheral tissues studied, DMT1 was highly expressed in brain, kidney, and testis, whereas MTP1 was highly expressed in liver and spleen. Depletion of the body Fe stores dramatically upregulated DMT1 and MTP1 mRNA expression in the duodenum as well as moderately upregulating their expression in several other peripheral tissues. The iron response element positive isoform of DMT1 was the most prominently upregulated isoform in the duodenum. Thus, DMT1 and MTP1 may play an important role in not only maintaining Fe levels but also facilitating the accumulation of Cd in the body of mammals.

Arsenic-induced toxicity and the protective role of ascorbic acid in mouse testis.

Oxidative stress has been suggested to be a major cause of male reproductive failure. Here, we investigated whether arsenic, which impairs male reproductive functions in rodent models, acts by inducing oxidative stress. Male 8-week-old ICR mice were given drinking water containing 20 or 40 mg/l sodium arsenite with or without 0.75 or 1.5 g/l of the antioxidant ascorbic acid for 5 weeks. The arsenic-treated mice showed decreased epididymidal sperm counts and testicular weights compared to untreated mice. These effects were reversed in mice that were co-treated with ascorbic acid. Similarly, arsenic treatment lowered the activities of testicular 3beta-hydroxysteroid dehydrogenase (HSD) and 17beta-HSD, which play important roles in steroidogenesis, and this was reversed by co-treatment with ascorbic acid. The testicles of arsenic-treated mice had decreased glutathione (GSH) levels (which correlate inversely with the degree of cellular oxidative stress) and elevated levels of protein carbonyl (a marker of oxidative damage to tissue proteins). Ascorbic acid co-treatment reversed both of these effects. Thus, ascorbic acid blocks both the adverse effects of arsenic on male reproductive functions and the arsenic-induced testicular oxidative changes. These observations support the notion that arsenic impairs male reproductive function by inducing oxidative stress.