The permeability and transport mechanism of graphene quantum dots (GQDs) across the biological barrier.

As an emerging nanomaterial, graphene quantum dots (GQDs) have shown enormous potential in theranostic applications. However, many aspects of the biological properties of GQDs require further clarification. In the present work, we prepared two sizes of GQDs and for the first time investigated their membrane permeabilities, one of the key factors of all biomedical applications, and transport mechanisms on a Madin Darby Canine Kidney (MDCK) cell monolayer. The experimental results revealed that under ∼300 mg L(-1), GQDs were innoxious to MDCK and did not affect the morphology and integrity of the cell monolayer. The Papp values were determined to be 1-3 × 10(-6) cm s(-1) for the 12 nm GQDs and 0.5-1.5 × 10(-5) cm s(-1) for the 3 nm GQDs, indicating that the 3 nm GQDs are well-transported species while the 12 nm GQDs have a moderate membrane permeability. The transport and uptake of GQDs by MDCK cells were both time and concentration-dependent. Moreover, the incubation of cells with GQDs enhanced the formation of lipid rafts, while inhibition of lipid rafts with methyl-ß-cyclodextrin almost eliminated the membrane transport of GQDs. Overall, the experimental results suggested that GQDs cross the MDCK cell monolayer mainly through a lipid raft-mediated transcytosis. The present work has indicated that GQDs are a novel, low-toxic, highly-efficient general carrier for drugs and/or diagnostic agents in biomedical applications.

Synthesis, characterization and anti-diabetic therapeutic potential of a new benzyl acid-derivatized kojic acid vanadyl complex.

Vanadium complexes are potent hypoglycemic agents and of great potential for therapeutical treatment of diabetes. In the present work, a novel vanadium compound, bis ((5-hydroxy-4-oxo-4H-pyran-2-yl)methyl benzoatato) oxovanadium (IV) (BBOV) has been synthesized. Treatment of STZ-induced diabetic rats with BBOV restored the blood glucose to normal level and ameliorated glucose tolerance. The hypoglycemic effect of BBOV is similar to that of bis (maltolato) oxovanadium but is less toxic in median lethal dose. Overall, the present work will provide useful information for further development of new anti-diabetic vanadium compounds.

Gadolinium triggers unfolded protein responses (UPRs) in primary cultured rat cortical astrocytes via promotion of an influx of extracellular Ca2+.

Gadolinium (Gd) and its complexes are utilized widely in industrial and clinical diagnoses. As a rare earth metal ion, free gadolinium (Gd(3+)) in the human body poses neurotoxic risks during its in vivo release and retention. In the central nervous system, astrocytes play a pivotal role in processing toxic metal ions. The present study evaluates the effects of Gd on cellular calcium homeostasis, a common mechanism that causes cell death, and on unfolded protein responses (UPRs), a mechanism for cell survival in response to toxic stimuli in mammalian cells. The experimental results indicate that the influx of extracellular Ca(2+) increases greatly after the exposure of astrocytes to Gd; however, no cell deaths were observed. Further evidence suggests the up-regulated expression of the endoplasmic reticulum (ER)-resident chaperone protein GRP78 by ER stress-mediated signal transductions, specifically the activation of ATF6, eIF2a, and IRE1. These results suggest that Gd promotes Ca(2+) influx, thus triggering UPRs, which can be closely associated to the resistance of astrocytes to Gd-induced cytotoxicity.

Effect of the chloro-substitution on lowering diabetic hyperglycemia of vanadium complexes with their permeability and cytotoxicity.

The effect of the chloro-substitution of dinuclear vanadium (V) complexes on lowering diabetic hyperglycemia was evaluated. The in vivo tests for hypoglycemic activity show that complex 2 at the dose of 10.0 and 20.0 mg V kg(-1), could significantly decrease the blood glucose level. Importantly, our results the chloro substituent increased the insulin-enhancing properties of the complex 2. The two vanadium compounds had permeability above 10(-5) cm/s. It suggested that two complexes permeate via a passive diffusion mechanism. It was also suggested that two complexes has better good lipophilic properties. The cytotoxicity of two complexes on Caco-2 cells suggested the chlorine atom at C4 of complex 2 increased cytotoxicity for vanadium complexes.

Insulin-enhancing activity of a dinuclear vanadium complex: 5-chloro-salicylaldhyde ethylenediamine oxovanadium(V) and its permeability and cytotoxicity.

A new insulin-enhancing oxovanadium complex 5-chloro-salicylaldhyde ethylenediamine oxovanadium (V) ([V(2)O(2)(mu-O)(2)L(2)]) has been synthesized. The complex was characterized by a variety of physical methods, including X-ray crystallography. The X-ray diffraction analysis show a dinuclear complex of two six-coordinate vanadium centers doubly bridged by the oxygen atoms of the Schiff base ligand with a V(2)O(2) diamond core. The complex was administered intragastrically to STZ-diabetic rats for 2 weeks. The biological activity results show that the complex at the dose of 10.0 and 20.0 mg V kg(-1), could significantly decrease the blood glucose level and ameliorate impaired glucose tolerance in STZ-diabetic rats. That results suggested that the complex exerts an antidiabetic effect in STZ-diabetic rats. Furthermore, the complex ([V(2)O(2)(mu-O)(2)L(2)]) had permeability above 10(-5)cm/s. The experimental results suggested that the vanadium complex permeates via a passive diffusion mechanism. It was also suggested the complex with salen-type ligands has good lipophilic properties and better oral administration. The cytotoxicity of the complex ([V(2)O(2)(mu-O)(2)L(2)]) on Caco-2 cells was measured by a decrease of cell viability using the MTT assay suggesting that the chlorine atom at C4 of complex [V(2)O(2)(mu-O)(2)L(2)] increased cytotoxicity for vanadium complexes.

A new insulin-enhancing agent: [N,N'-bis(4-hydroxysalicylidene)-o-phenylene-diamine]oxovanadium(IV) and its permeability and cytotoxicity.

A new insulin-enhancing agent: [N,N'-bis(4-hydroxysalicylidene)-o-phenylene-diamine] oxovanadium(IV) (BPOV) was synthesized and characterized by X-ray crystallography. BPOV was administered intragastrically to STZ-diabetic rats for 4 weeks. The results showed that BPOV could significantly decrease the blood glucose level and ameliorated impaired glucose tolerance in STZ-diabetic rats. BPOV has been further tested on insulin, glycogen and serum lipid studies. The results suggested BPOV has glucose-lowering activity in diabetic rats, as well as improved the disorder of lipid metabolism in diabetes. BPOV had permeability above 10(-5) cm s(-1). It was suggested good lipophilic properties. The cytotoxicity of BPOV on Caco-2 cells was measured by MTT assay which suggested BPOV have higher effect on impairment of cellular associated with lower level capacity of cellular accumulation.

Gadolinium promoted proliferation and enhanced survival in human cervical carcinoma cells.

The effect of gadolinium chloride (Gd) on the proliferation of HeLa cells was investigated at lower concentration. The results obtained by MTT and cell cycle analysis showed that Gd promoted proliferation by inducing S phase entry in HeLa cells at the concentration less than 100 microM. It was further evidenced by both an increase in the levels of phosphorylation of retinoblastoma protein (pRb) and a remarkable increase in cyclin E expression. Moreover, the survival of cells, exposed to Gd up to 3-5 days, was increased compared with control. The attenuation of the serum deprivation-induced cell loss by Gd was associated with the sustained activation of FAK (PY(397)) and the delayed activation of JNKs pathway. Besides, it appeared that Gd promoted cell proliferation and survival in HeLa cells was not contributed to the ROS generation. Based on the present results, both positive and negative effects of the lanthanides as potential drugs or diagnostic agents are discussed.

Vanadyl bisacetylacetonate induced G1/S cell cycle arrest via high-intensity ERK phosphorylation in HepG2 cells.

In recent years the anticancer properties of vanadium compounds have been noticed, but the underlying mechanisms are not well understood. In the present work, we found that vanadyl bisacetylacetonate ([VO(acac)(2)]) blocked cell cycle progression permanently at G1 phase in a dose- and time-dependent manner in HepG2 cells. This was further evidenced by the growth regulatory signals during the G1 stage. After the treatment with [VO(acac)(2)], the level of phosphorylation of retinoblastoma tumor suppressor protein (pRb) and the expressions of cyclin D1, cyclin E and cyclin A were reduced, while the expression of a cyclin-dependent kinase inhibitor p21 was increased dose-dependently. In the meantime, neither O(2)(*-) nor H(2)O(2) level was observed to increase. Interestingly, the levels of phosphorylated extracellular signal-regulated protein kinase (ERK) and Akt were highly activated. After 1-h pretreatment with a lower concentration of MEK inhibitor U0126, the level of phosphorylated pRb was restored, indicating a release of cell cycle arrest. Taken together, we suggested that [VO(acac)(2)]-induced proliferation inhibition was caused by G1/S cell cycle arrest, which resulted from the decreased level of phosphorylated pRb in its active hypophosphorylated form via a highly activated ERK signal in HepG2 cells. The results presented here provided new insight into the development of vanadium compounds as potential anticancer agents.

Bioprocess of uniform-sized crosslinked chitosan microspheres in rats following oral administration.

Chitosan microspheres have a great potential in pharmaceutical application. In this study, uniform-sized chitosan microspheres crosslinked with glutaraldehyde (CG microspheres) were prepared by Shirasu Porous Glass (SPG) membrane emulsification technique. Based on the characterizations of uniform size and autofluorescence, it was possible to develop a new detecting system for observing and quantifying the CG microspheres in rats with three different diameters (2.1, 7.2 and 12.5 microm) synchronously after oral administration. This system was a combination of scanning electron microscopy (SEM), laser scanning confocal microscope (LSCM) and flow cytometer technique, which showed the advantages of being simple, intuitionistic, repeatable and sensitive. After oral administration of three kinds of particles with different diameters, bioadhesion in gastrointestinal tract, absorption in gastrointestinal tract, distribution in systemic tissues, and biodegradation in reticuloendothelial system (RES) were studied firstly in detail. The CG microspheres showed different fates in bioadhesion, absorption and distribution according to their diameters, while the biodegradation also varied due to the different locations in RES. These original results would indicate a better way for the CG microspheres in the clinical application.

[Establishment of Caco-2 cell monolayer model and standard operation procedure for assessing intestinal absorption of chemical components of traditional Chinese medicine].

OBJECTIVE: To establish Caco-2 (a human colon adenocarcinoma cell line) cell monolayer model and the standard operation procedure for studying and assessing intestinal absorption of chemical components of traditional Chinese medicine. METHODS: Caco-2 cell monolayer model was established and evaluated by morphology feature using scanning electron microscope, inverted microscope and transepithelial electrical resistance (TEER) assay. Additionally, the model was further tested for the activity of alkaline phosphatase and the apparent permeability (Papp) of standard compounds, i.e. propranolol and atenolol, which were the control substances for high and poor transcellular transport marker, respectively. RESULTS: The integrality of cell monolayer, cell differentiation (reflected by expression of alkaline phosphatase and cell monolayer morphology), and the Papp value of standard compounds in the established Caco-2 cell model were satisfactory. All parameters tested were in good agreement with those reported in the literature. CONCLUSION: The established Caco-2 cell model can be used to study the intestinal absorption of orally administrated chemical components of traditional Chinese medicine and their absorption mechanism.

[Investigation on dissolution of cinnabar in vitro].

OBJECTIVE: To study effects of different chemical factors in gastrointestinal tract, i.e. pH, protein, amino acid, ionic strength, Na2S, on the dissolution of cinnabar. METHOD: The content of total mercury in various dissolution of cinnabar were analyzed by UV/VIS Spectrophotometer. The particle distributions in dissolution of cinnabar were measured by Laser Particle Size Analyzer. The constituents of dissoluble substance of cinnabar in presence of Na2S were determined using ESI-MS. RESULT: The solubility of cinnabar could be increased significantly in the presence of Na2S/So, and strong acidic pH, respectively. While the influence of thiol amino acid on promoting dissolution remains relatively low. Cinnabar didnt dissolve mainly in the form of nanoparticle. CONCLUSION: We postulated that cinnabar could be dissolved in various forms of mercury complexes containing sulphur.

[Monitoring early toxicity of heavy metals including Hg using a HSE-SEAP reporter gene].

OBJECTIVE: To develop a cellular assay based on heat shock signal pathway and secreted alkaline phosphatase (SEAP) reporter gene for investigating/predicting the early toxicity of heavy metals on HeLa cells in Chinese traditional medicine (TCM). METHOD: The pHSE-SEAP plasmid was transfected into HeLa cells to build a HSE-SEAP-HeLa cell model. For validation of the model, the transfected cells were treated by either heating at 42 degrees C for 1 h or incubated with 5 mol x L(-1) CdCl2 for 4 h. Then the cells were covered in complete DMEM culture medium for 48 h and the activity of SEAP (reflecting the cellular level of heat shock protein) in cultural supernatants was measured; meanwhile, cell viability was determined by MTT assays. In addition, the cells were treated by four mercury compounds, HgCl2, merthilate sodium, HgS and cinnabar at the sub-lethal concentrations (determined by MTT assays). Then the heat shock response was detected likewise. RESULT: Significant level of secreted alkaline phosphatase (SEAP) was found in pHSE-SEAP transfected HeLa cells treated either by heating (42 degrees C) or incubating with CdCl2. The heat shock protein was induced by CdCl2 before decrease of cell viability was observed. All four mercury compounds induced heat shock response in both time and concentration-dependant manner. However, there were big differences among the mercury compounds, suggesting potential differences for early-stage toxicity in vivo. CONCLUSION: The pHSE-SEAP transfected HeLa cells respond effectively to heat shock and metal stresses, and therefore provide a practical and repeatable assay for investigating/predicting the early toxicity of heavy metals and mineral-containing drugs in TCM.

The permeability and cytotoxicity of insulin-mimetic vanadium (III,IV,V)-dipicolinate complexes.

Vanadium (III,IV,V)-dipicolinate complexes with different redox properties were selected to investigate the structure-property relationship of insulin-mimetic vanadium complexes for membrane permeability and gastrointestinal (GI) stress-related toxicity using the Caco-2 cell monolayer model. The cytotoxicity of the vanadium complexes was assayed with 3-(4,5-dimethylthiazoyl-2-yl) 2,5-diphenyltetrazolium bromide (MTT) assays and the effect on monolayer integrity was measured by the trans-epithelial electric resistance (TEER). The three vanadium complexes exhibited intermediate membrane permeability (P(app) = 1.4-3.6x10(-6) cm/s) with low cellular accumulation level (<1%). The permeability of all compounds was independent of the concentration of vanadium complexes and excess picolinate ligands. Both V(III) and V(V)-dipicolinate complexes induced 3-4-fold greater reactive oxygen and nitrogen species (RONS) production than the V(IV)-dipicolinate complex; while the vanadium (III)-dipicolinate was 3-fold less damaging to tight junction of the Caco-2 cell monolayer. Despite the differences in apparent permeability, cellular accumulation, and capacity to induce reactive oxygen and nitrogen species (RONS) levels, the three vanadium complexes exhibited similar cytotoxicity (IC50 = 1.7-1.9 mM). An ion pair reagent, tetrabutylammonium, increased the membrane apparent permeability by 4-fold for vanadium (III and IV)-dipicolinate complexes and 16-fold for vanadium (V)-dipicolinate as measured by decrease in TEER values. In addition, the ion pair reagent prevented damage to monolayer integrity. The three vanadium (III,IV,V)-dipicolinate complexes may pass through caco-2 monolayer via a passive diffusion mechanism. Our results suggest that formation of ion pairs may influence compound permeation and significantly reduce the required dose, and hence the GI toxicity of vanadium-dipicolinate complexes.

Effects of development and iron status on ceruloplasmin expression in rat brain.

The increased iron content in the brain of subjects with aceruloplasminemia has implicated ceruloplasmin (CP) as a major factor in the regulation of regional brain iron content. In this study, we investigated the effects of age and iron on CP expression in rat brain. In all four regions, the iron concentrations increased with developmental age. There is a similar trend in age-induced changes in CP mRNA and protein. The CP mRNA and protein levels were both lowest at postnatal day (PND) 7. The expression increased gradually with age, reaching the highest at PND196 in the striatum and substantia nigra, and at PND21 and PND63 in the cortex and hippocampus, respectively. This suggests the existence of an age-dependent pre-transcriptional regulation and a regionally specific effect of age on CP expression in the brain. Although total iron in all four regions was significantly lower in the rats fed with a low-iron diet for 6 weeks and higher in the rats with a high-iron diet than those in the control animals, no significant between-group differences in CP mRNA and protein were found in these animals, except in the substantia nigra where a significant increase in CP protein in high-iron rats was observed, and the reverse in low-iron rats. These findings suggested that the effects of iron on CP expression in the brain may be region-specific, and that regulation of CP expression by iron in the substantia nigra was at the post-transcriptional level.

Age-dependent and iron-independent expression of two mRNA isoforms of divalent metal transporter 1 in rat brain.

The DMT1(Nramp2/DCT1) is a newly discovered proton-coupled metal-ion transport protein. The cellular localization and functional characterization of DMT1 suggest that it might play a role in physiological iron transport in the brain. In the study, we evaluated effects of dietary iron and age on iron content and DMT1 expression in four brain regions: cortex, hippocampus, striatum, substantia nigra. Total iron content in all regions was significantly lower in the low-iron diet rats and higher in the high-iron diet rats than that in the control animals, showing that dietary iron treatment for 6-weeks can alter brain iron levels. Contrary to our expectation, there was no significant alternation in DMT1(+IRE) and (-IRE) mRNA expression and protein content in all brain regions examined in spite of the existence of the altered iron levels in these regions after 6-weeks' diet treatment although TfR mRNA expression and protein level were affected significantly, as was expected. The data demonstrates that expression of DMT1(+IRE) and (-IRE) was not regulated by iron in these regions of adult rats. The lack of response of DMT1 to iron status in the brain suggests that the IRE of brain DMT1 mRNA might be not really iron-responsive and that DMT1-mediated iron transport might be not the rate-limiting step in brain iron uptake in adult rats. Our findings also showed that development can significantly affect brain iron and DMT1(+IRE) and (-IRE) expression but the effect varies in different brain regions, indicating a regionally specific regulation in the brain.

The permeability and cytotoxicity of insulin-mimetic vanadium compounds.

PURPOSE: The aim of this study was to investigate the mechanism of permeation and cytotoxicity of vanadium compounds, [VO(acac)2], [VO(ma)2], and vanadate. METHODS: Absorptive transport were carried out in Caco-2 monolayers grown on transwell inserts. Vanadium was quantified using inductively coupled plasma atomic emission spectrometry (ICP-AES). The change of Caco-2 cells in the microvilli morphology and F-actin structure was visualized by transmission electron microscopy and confocal laser scanning microscopy. RESULTS: The three vanadium compounds were taken up by Caco-2 cells via simple passive diffusion. [VO(acac)2] were mainly transcellularly transported and exhibited the highest apparent permeabilty coefficients (8.2 x 10(-6) cm(-1)). The cell accumulation of [VO(acac)2] was found to be greater than that of [VO(ma)2], and vanadate caused much less accumulation than the other two compounds. Vanadium compounds induced intracellular reactive oxygen species, reduced the transepithelial electric resistance, caused morphological change in microvilli, and led to different perturbation of F-actin structure. CONCLUSIONS: The three compounds exhibited different permeability due to different diffusion process and cellular uptake. The toxicity of vanadium complexes on Caco-2 monolayer involved F-actin-related change of tight junction and impairment of microvilli. The toxicity was also related to elevated intracellular reactive oxygen species (ROS) and their cellular accumulation.