In vitro toxicity in long-term cell culture of MR contrast agents targeted to cartilage evaluation

OBJECTIVE

Contrast-enhanced magnetic resonance (MR) imaging methods have been proposed for non-invasive evaluation of osteoarthritis (OA). We measured cell toxicities of cartilage-targeted low-generation dendrimer-linked nitroxide MR contrast agents and gadopentetate dimeglumine (Gd-DTPA) on cultured chondrocytes.

DESIGN

A long-term Swarm rat chondrosarcoma chondrocyte-like cell line was exposed for 48-h to different salts (citrate, maleate, tartrate) and concentrations of generation one or two diaminobutyl-linked nitroxides (DAB4-DLN or DAB8-DLN), Gd-DTPA, or staurosporine (positive control). Impact on microscopic cell appearance, MTT spectrophotometric assays of metabolic activity, and quantitative PicoGreen assays of DNA content (cell proliferation) were measured and compared to untreated cultures.

RESULTS

Chondrocyte cultures treated with up to 7.5 mM Gd-DTPA for 48-h had no statistical differences in DNA content or MTT reaction compared to untreated cultures. At all doses, DAB4-DLN citrate treated cultures had results similar to untreated and Gd-DTPA-treated cultures. At doses >1 mM, DAB4-DLN citrate treated cultures showed statistically greater DNA and MTT reaction than maleate and tartrate DAB4-DLN salts. Cultures exposed to 5 mM or 7.5 mM DAB8-DLN citrate exhibited rounded cells, poor cell proliferation, and barely detectable MTT reaction. Treatment with 0.1 μM staurosporine caused chondrocyte death.

CONCLUSION

Long-term exposure, greater than clinically expected, to either DAB4-DLN citrate or Gd-DTPA had no detectable toxicity with results equivalent to untreated cultures. DAB4-DLN citrate was more biocompatible than either the maleate or tartrate salts. Cells exposed for 48-h to 5 mM or 7.5 mM DAB8-DLN salts demonstrated significant cell toxicity. Further evaluation of DAB8-DLN with clinically appropriate exposure times is required to determine the maximum useful concentration.

Disruption of the ATE1 and SLC12A1 Genes by Balanced Translocation in a Boy with Non-Syndromic Hearing Loss

We report on a boy with non-syndromic hearing loss and an apparently balanced translocation t(10;15)(q26.13;q21.1). The same translocation was found in the normally hearing brother, father and paternal grandfather; however, this does not exclude its involvement in disease pathogenesis, for example, by unmasking a second mutation. Breakpoint analysis via FISH with BAC clones and long-range PCR products revealed a disruption of the arginyltransferase 1 (ATE1) gene on translocation chromosome 10 and the solute carrier family 12, member 1 gene (SLC12A1) on translocation chromosome 15. SNP array analysis revealed neither loss nor gain of chromosomal regions in the affected child, and a targeted gene enrichment panel consisting of 130 known deafness genes was negative for pathogenic mutations. The expression patterns in zebrafish and humans did not provide evidence for ear-specific functions of the ATE1 and SLC12A1 genes. Sanger sequencing of the 2 genes in the boy and 180 GJB2 mutation-negative hearing-impaired individuals did not detect homozygous or compound heterozygous pathogenic mutations. Our study demonstrates the many difficulties in unraveling the molecular causes of a heterogeneous phenotype. We cannot directly implicate disruption of ATE1 and/or SLC12A1 to the abnormal hearing phenotype; however, mutations in these genes may have a role in polygenic or multifactorial forms of hearing impairment. On the other hand, it is conceivable that our patient carries a disease-causing mutation in a so far unidentified deafness gene. Evidently, disruption of ATE1 and/or SLC12A1 gene function alone does not have adverse effects.

[Not Available]

This paper presents a case report of indoor Stachybotrys toxins in Germany. In the summer of 2000, heavy rainfall and a leakage of the gutter system of an appartement house in Munich, Germany, caused a severe water damage in one of the appartments. The appartment was at that time occupied by two of the authors (ES, EU). A wall (covered with wallpaper) in one room in particular was most strongly affected, about 6-8 m(2) of the wallpaper became very wet. Large parts of this wet wallpaper were within days infested by multiple circumscribed round, grey-black colonies (0.5-5 cm in diameter) of presumtiveStachybotrys spp.. At the same time, the air in this room became very damp and oppressive. Several persons reported burning sensations on the mucous membranes of the eye, nose, and larynx, followed by headache symptoms, as soon as a few minutes after they had entered this room. Inadvertent skin contact with one of the fungal colonies by one person resulted in burning sensations immediately, but symptoms disappeared after thorough rinsing of the skin with water. The infested room was evacuated, and samples were taken from the wet wallpaper at areas (1) in the center of the most heavy fungal colony growth, (2) several cm away from colony growth, and (3) from locations which were wet but about 1 m away from visible colony growth. The samples were extracted with methanol, the extract diluted with buffer solution and analysed by competitive enzyme immunoassay (EIA) for roridin A. Due to cross-reactivity, this EIA detects several macrocyclic trichothecenes produced byStachybotrys spp.. Heavily infected pieces of wallpaper were strongly contaminated with toxins, with maximum concentrations of 1.1 microgram per cm(2) (Roridin A equivalents). Wet but visibly not infected samples of wallpaper were negative in the EIA. Considering a EIA cross-reactivity of satratoxin H (the major Stachybotrys-toxin) of 15%, the actual maximum toxin concentration would correspond to 6 microgram of satratoxin H per cm(2). As far as we know, this is the first documented case of indoor Stachybotrys toxins in Germany. The toxin concentration by far exceeds the minimum toxin level required for skin toxicity, and was considered as unhealthy. Health authorities in Munich were informed but were unable to provide assistance, probably because awareness of the importance and the possible health risks caused by indoor mycotoxins is not yet widespread in Germany. Reporting and monitoring programs for mycotoxins in water-damaged buildings seem to be necessary to provide insight into the occurrence of similar cases as the one described here.

Activation of basophils by the double-stranded RNA poly(A:U) exacerbates allergic inflammation

BACKGROUND

It is commonly acknowledged that asthma is exacerbated by viral infections. On the other hand, basophil infiltration of lung tissues has been evidenced postmortem in cases of fatal disease, raising the question of a possible link between these two observations.

OBJECTIVES

Herein, we addressed the relationship between asthma exacerbation by viral infection and basophil activation and expansion by investigating how stimulation with the dsRNA polyadenylic/polyuridylic acid [poly(A:U)] affected basophil activities and recruitment in an allergic airway inflammation model.

METHODS

The effect of dsRNA on basophils was assessed by measuring the cytokine levels produced upon stimulation. We used an OVA-induced experimental model of allergic asthma. Airway hyperreactivity, recruitment of infiltrating cells, and cytokine production were determined in the lung of mice having received poly(A:U), as compared with untreated controls. The exacerbating effect of basophils was assessed both by adoptive transfer of poly(A:U)-treated basophils and by their in vivo depletion with Ba103 antibody.

RESULTS

We found that in vitro treatment with poly(A:U) increased basophil functions by inducing TH 2-type cytokine and histamine production, whereas in vivo treatment increased peripheral basophil recruitment. Furthermore, we provide the first demonstration for increased infiltration of basophils in the lung of mice suffering from airway inflammation. In this model, disease symptoms were clearly exacerbated upon adoptive transfer of basophils exposed to poly(A:U), relative to their unstimulated counterpart. Conversely, in vivo basophil depletion alleviated disease syndromes, thus validating the transfer data.

CONCLUSIONS

Our findings provide the first evidence for airway inflammation exacerbation by basophils following dsRNA stimulation.