Impedance-based in vitro eye irritation testing enables the categorization of diluted chemicals

Products containing chemicals with eye irritation potential need to be labeled with the respective hazard symbol. To avoid the testing of numerous dilutions of chemicals on animals, their labeling is directed by a theoretical approach. In this report, a previously described in vitro tissue model of the cornea based on human epithelial cells was used for eye irritation testing of dilutions. As a sensitive and non-destructive method to analyze the barrier function of the epithelium, impedance spectroscopy was applied. Moreover, the morphology and viability of the epithelial models were assessed. We tested four chemicals that, neatly, cause severe damage to the eye: tetrahydrofuran, acetic acid, diethylethanolamine, and benzalkonium chloride. With our test method, we were able to determine the concentrations of the chemicals which are critical for the integrity of the cornea. The threshold was < 0.1% for the most and > 5% for the least toxic substance. The described test system is not only an alternative for animal models but also for the theoretical examination of the hazard potential of diluted chemicals. By using the advantages of tissue engineering and non-destructive analysis tools, we can achieve more precise and safer labeling of the eye irritation potential of products.

In-situ tear fluid dissolving nanofibers enable prolonged viscosity-enhanced dual drug delivery to the eye

Liquid and semi-solid formulations are the most commonly used drug delivery systems for ophthalmic diseases. Upon application into the conjunctival sac, these systems introduce a variable and unphysiologically high liquid volume to the eye, resulting in overflow and extensive nasolacrimal drainage, accounting for dosing inaccuracy and short ocular residence time. In this study, we present nanofibrous electrospun scaffolds composed of biocompatible polymers, overcoming these challenges by immediate drug release. The fibers incorporate gentamicin and dexamethasone, intended for the treatment of bacterial conjunctivitis. Upon contact with the ocular surface, the nanofibers immediately dissolve in the tear fluid, quantitatively releasing the two actives, yielding over92% drug recovery, determined with fluorimetric and chromatographic quantifications methods. Simultaneously, the viscosity of the tear fluid increases, shown by complex viscometry measurements. A newly developed ex vivo microfluidic porcine cornea model was used to evaluated ocular residence time. In contrast to fluid eye drops, the contact time was significantly prolonged and 20min after application, an increase in drug availability on the ocular surface of 342% was observed. Biocompatibility of the polymer system was demonstrated in an OECD approved in vitro cornea model. The antibacterial activity after processing was evaluated according to EUCAST guidelines, and storage stability of the system was confirmed over a 12-week period. This innovative drug delivery system poses a highly promising platform technology, overcoming challenges associated with conventional dosage forms for drug delivery to the anterior eye and thus significantly advancing therapeutic approaches.

Structural basis for allosteric regulation of Human Topoisomerase IIα

The human type IIA topoisomerases (Top2) are essential enzymes that regulate DNA topology and chromosome organization. The Topo IIα isoform is a prime target for antineoplastic compounds used in cancer therapy that form ternary cleavage complexes with the DNA. Despite extensive studies, structural information on this large dimeric assembly is limited to the catalytic domains, hindering the exploration of allosteric mechanism governing the enzyme activities and the contribution of its non-conserved C-terminal domain (CTD). Herein we present cryo-EM structures of the entire human Topo IIα nucleoprotein complex in different conformations solved at subnanometer resolutions (3.6-7.4 Å). Our data unveils the molecular determinants that fine tune the allosteric connections between the ATPase domain and the DNA binding/cleavage domain. Strikingly, the reconstruction of the DNA-binding/cleavage domain uncovers a linker leading to the CTD, which plays a critical role in modulating the enzyme's activities and opens perspective for the analysis of post-translational modifications.

[Preclinical management of cardiac arrest-extracorporeal cardiopulmonary resuscitation]

BACKGROUND

The chances of surviving out-of-hospital cardiac arrest (OHCA) are still very low. Despite intensive efforts the outcome has remained relatively poor over many years. In specific situations, new technologies, such as extracorporeal cardiopulmonary resuscitation (eCPR) could significantly improve survival with a good neurological outcome.

OBJECTIVE

Does the immediate restoration of circulation and reoxygenation via eCPR influence the survival rate after OHCA? Is eCPR the new link in the chain of survival?

MATERIAL AND METHODS

Discussion of current study results and guideline recommendations.

RESULTS

The overall survival rates after OHCA have remained at 10-30% over many years. Despite low case numbers more recent retrospective studies showed that an improved outcome can be achieved with eCPR. In selected patient collectives survival with a favorable neurological outcome is possible in 38% of the cases.

CONCLUSION

Survival after cardiac arrest and the subsequent quality of life dependent on many different factors. The time factor, i.e. the avoidance of a no-flow phase and reduction of the low-flow phase is of fundamental importance. The immediate restoration of the circulation and oxygen supply by eCPR can significantly improve survival; however, large randomized, controlled trials are currently not available.

The interplay between DNA topoisomerase 2α post-translational modifications and drug resistance

The type 2 DNA topoisomerases (Top2) are conserved enzymes and biomarkers for cell proliferation. The catalytic activities of the human isoform Top2α are essential for the regulation of DNA topology during DNA replication, transcription, and chromosome segregation. Top2α is a prominent target for anti-cancer drugs and is highly regulated by post-translational modifications (PTM). Despite an increasing number of proteomic studies, the extent of PTM in cancer cells and its importance in drug response remains largely uncharacterized. In this review, we highlight the different modifications affecting the human Top2α in healthy and cancer cells, taking advantage of the structure-function information accumulated in the past decades. We also overview the regulation of Top2α by PTM, the level of PTM in cancer cells, and the resistance to therapeutic compounds targeting the Top2 enzyme. Altogether, this review underlines the importance of future studies addressing more systematically the interplay between PTM and Top2 drug resistance.

Cryo-EM structure of the complete E. coli DNA gyrase nucleoprotein complex

DNA gyrase is an essential enzyme involved in the homeostatic control of DNA supercoiling and the target of successful antibacterial compounds. Despite extensive studies, a detailed architecture of the full-length DNA gyrase from the model organism E. coli is still missing. Herein, we report the complete structure of the E. coli DNA gyrase nucleoprotein complex trapped by the antibiotic gepotidacin, using phase-plate single-particle cryo-electron microscopy. Our data unveil the structural and spatial organization of the functional domains, their connections and the position of the conserved GyrA-box motif. The deconvolution of two states of the DNA-binding/cleavage domain provides a better understanding of the allosteric movements of the enzyme complex. The local atomic resolution in the DNA-bound area reaching up to 3.0 Å enables the identification of the antibiotic density. Altogether, this study paves the way for the cryo-EM determination of gyrase complexes with antibiotics and opens perspectives for targeting conformational intermediates.

Bacterial DNA gyrase is the only type II DNA topoisomerase capable of introducing negative supercoils into DNA and is of interest as a drug target. Here the authors present the cryo-EM structure of the complete E. coli DNA gyrase bound to a 180 bp double-stranded DNA and the antibiotic gepotidacin, which reveals the connections between the functional domains and their spatial organization.

Replacing the Draize eye test: Impedance spectroscopy as a 3R method to discriminate between all GHS categories for eye irritation

Highly invasive animal based test procedures for risk assessment such as the Draize eye test are under increasing criticism due to poor transferability for the human organism and animal-welfare concerns. However, besides all efforts, the Draize eye test is still not completely replaced by alternative animal-free methods. To develop an in vitro test to identify all categories of eye irritation, we combined organotypic cornea models based on primary human cells with an electrical readout system that measures the impedance of the test models. First, we showed that employing a primary human cornea epithelial cell based model is advantageous in native marker expression to the primary human epidermal keratinocytes derived models. Secondly, by employing a non-destructive measuring system based on impedance spectroscopy, we could increase the sensitivity of the test system. Thereby, all globally harmonized systems categories of eye irritation could be identified by repeated measurements over a period of 7 days. Based on a novel prediction model we achieved an accuracy of 78% with a reproducibility of 88.9% to determine all three categories of eye irritation in one single test. This could pave the way according to the 3R principle to replace the Draize eye test.

[Update: acute hypercapnic respiratory failure]

BACKGROUND

Hypercapnic respiratory failure is a frequent problem in critical care and mainly affects patients with acute exacerbation of COPD (AECOPD) and acute respiratory distress syndrome (ARDS). In recent years, the usage of extracorporeal CO₂ removal (ECCO₂R) has been increasing.

OBJECTIVE

Summarizing the state of the art in the management of hypercapnic respiratory failure with special regard to the role of ECCO₂R.

METHODS

Review based on a selective literature search and the clinical and scientific experience of the authors.

RESULTS

Noninvasive ventilation (NIV) is the therapy of choice in hypercapnic respiratory failure due to AECOPD, enabling stabilization in the majority of cases and generally improving prognosis. Patients in whom NIV fails have an increased mortality. In these patients, ECCO₂R may be sufficient to avoid intubation or to shorten time on invasive ventilation; however, corresponding evidence is sparse or even missing when it comes to hard endpoints. Lung-protective ventilation according to the ARDS network is the standard therapy of ARDS. In severe ARDS, low tidal volume ventilation may result in critical hypercapnia. ECCO₂R facilitates compensation of respiratory acidosis even under "ultra-protective" ventilator settings. Yet, no positive prognostic effects could be demonstrated so far.

CONCLUSION

Optimized use of NIV and lung-protective ventilation remains standard of care in the management of hypercapnic respiratory failure. Currently, ECCO₂R has to be considered an experimental approach, which should only be provided by experienced centers or in the context of clinical trials.

The second window of desflurane-induced preconditioning is mediated by STAT3: role of Pim-1 kinase

BACKGROUND

Late ischemic preconditioning is mediated via nuclear transcription factor signal transducer and activator of transcription 3 (STAT3). Pim-1 kinase reduces infarct size in cardiomyocytes and is regulated by STAT3. We tested the hypothesis that late desflurane-induced preconditioning (DES-SWOP) is mediated via STAT3 and Pim-1.

METHODS

After institutional approval, pentobarbital-anesthetized male C57BL/6 mice were subjected to 45 min coronary artery occlusion (CAO) and 3 h reperfusion. Control animals received no additional intervention. Desflurane was administered 48 h before CAO either alone or in combination with the janus kinase/STAT3 inhibitor AG-490 (40 μg/g i.p., 20 min before desflurane administration) or the Pim-1 kinase inhibitor II (PIM-Inh.II, 10 μg/g i.p., 15 min before CAO). Infarct size (IS) and area at risk were determined with triphenyltetrazolium chloride and Evans blue, respectively. Additionally, cytosolic and nuclear fractions were separated at two different time points and expression of STAT3, phospho-STAT3(Ser727) , phospho-STAT3(Tyr705) , Pim-1, Bad and phospho-Bad(Ser112) were determined by Western Blot analysis. Data were analyzed with one-way or two-way ANOVA and post hoc Duncan test and are presented as mean ± SEM.

RESULTS

IS was 47 ± 2% (n = 7-8 per group) in control animals (CON). DES-SWOP reduced myocardial infarct size to 23 ± 4%* (*P < 0.05 vs. CON). AG-490 alone did not affect myocardial infarct size (44 ± 7%), but abolished DES-SWOP (44 ± 4%). Blockade of Pim-1 did not affect the protection by DES-SWOP (34 ± 4%*). Desflurane reduced cytosolic content and enhanced nuclear content of phospho-STAT(S) (er727) . After 48 h, desflurane enhanced Pim-1 activity, whereas Pim-1 expression remained unchanged.

CONCLUSION

These data suggest that DES-SWOP is mediated by activation and nuclear translocation of STAT3. The impact of Pim-1 in DES-SWOP signaling remains unclear.

[Therapy of acute respiratory distress syndrome : Survey of German ARDS centers and scientific evidence]

BACKGROUND

In addition to specific treatment of the underlying cause, the therapy of acute respiratory distress syndrome (ARDS) consists of lung protective ventilation and a range of adjuvant and supportive measures.

AIM

A survey was conducted to determine the current treatment strategies for ARDS in German ARDS centers.

MATERIAL AND METHODS

The 39 centers listed in the German ARDS network in 2011 were asked to complete a questionnaire collecting data on the clinic, epidemiology as well as diagnostic and therapeutic measures regarding ARDS treatment.

RESULTS

Of the centers 25 completed the questionnaire. In 2010 each of these centers treated an median of 31 (25-75 percentile range 20-59) patients. Diagnostic measures at admission were computed tomography of the thorax (60 % of the centers), whole body computed tomography (56 %), chest x-ray (52 %), abdominal computed tomography (32 %) and cranial computed tomography (24 %). Transesophageal echocardiography was performed in 64 %, pulmonary artery pressure was measured in 56 % and cerebral oximetry in 12 %. Sedation was regularly interrupted in 92 % of the centers and in 68 % this was attempted at least once a day. A median minimum tidal volume of 4 ml/kg (range 2-6) and a maximum tidal volume of 6 ml/kg (4-8) were used. Methods to determine the optimal positive end-expiratory pressure (PEEP) were the best PEEP method (60 %), ARDS network table (48 %), empirical (28 %), pressure volume curve (16 %), computed tomography (8 %), electrical impedance tomography (8 %) and others (8 %). Median minimum and maximum PEEPs were 10 cmH2O (range 5-15) and 21 cmH2O (15-25), respectively. Median plateau pressure was limited to 30 cmH2O (range 26-45). The respiratory rate was set below 20/min in 20 % and below 30/min in 44 %. Controlled ventilator modes were generally preferred with 80 % using biphasic positive airway pressure (BIPAP/BiLevel), 20 % pressure controlled ventilation (PCV) and 4 % airway pressure release ventilation (APRV). Assisted modes were only utilized by 8 % of the centers. Recruitment maneuvers were used by 28 %, particularly during the early phase of the ARDS. Muscle relaxants were administered by 32 % during the early phase of the ARDS. Complete prone positioning was used by 60 % of the centers, whereas 88 % utilized incomplete (135°) prone positioning. Continuous axial rotation was utilized by 16 %. Spontaneous breathing tests were used in 88 % of the centers with 60 % performing these at least once a day. Supportive therapies were frequently applied and mainly consisted of nitrous oxide (44 %), prostacycline (48 %) and corticosteroids (52 %). A restrictive fluid therapy was used in 48 % and a special nutrition regimen in 28 % of the centers. Of the participating centers 22 were able to offer extracorporeal membrane oxygenation (ECMO). In this case, respiratory therapy was modified by further reducing tidal volumes (91 %), inspiratory pressures (96 %) as well as using lower respiratory rates (≤ 8/min in 31 %). Only 9 % reduced PEEP during ECMO. Regular recruitment maneuvers were used by 14 %. Positioning maneuvers during ECMO were used by 82 %.

CONCLUSIONS

Lung protective ventilation with reduced tidal volumes as well as inspiratory pressures represents the current standard of care and was utilized in all network centers. Prone positioning was widely used. Promising adjuvant therapies such as the muscle relaxation during the early phase of the ARDS, fluid restriction and corticosteroids were used less frequently. During ECMO respirator therapy was generally continued with ultraprotective ventilator settings.

Circumventing tolerance to a human MDM2-derived tumor antigen by TCR gene transfer

We identified a tumor-associated cytotoxic T lymphocyte (CTL) epitope derived from the widely expressed human MDM2 oncoprotein and were able to bypass self-tolerance to this tumor antigen in HLA-A*0201 (A2.1) transgenic mice and by generating A2.1-negative, allo-A2.1-restricted human T lymphocytes. A broad range of malignant, as opposed to nontransformed cells, were killed by high-avidity transgenic mouse and allogeneic human CTLs specific for the A2.1-presented MDM2 epitope. Whereas the self-A2.1-restricted human T cell repertoire gave rise only to low-avidity CTLs unable to recognize the natural MDM2 peptide, human A2.1+ T lymphocytes were turned into efficient MDM2-specific CTLs upon expression of wild-type and partially humanized high-affinity T cell antigen receptor (TCR) genes derived from the transgenic mice. These results demonstrate that TCR gene transfer can be used to circumvent self-tolerance of autologous T lymphocytes to universal tumor antigens and thus provide the basis for a TCR gene transfer-based broad-spectrum immunotherapy of malignant disease.

Targeting p53, hdm2, and CD19: vaccination and immunologic strategies

Peptides presented by class I major histocompatibility complex (MHC) molecules and derived from normal self-proteins that are expressed at elevated levels by cells from a variety of human (Hu) malignancies provide, in theory, potential target antigens for a broad-spectrum, cytotoxic T lymphocyte (CTL)-based immunotherapy of cancer and hematologic malignancies. However, as such tumor- and leukemia-associated self-proteins are also expressed at low levels in some types of normal tissues, such as thymus, spleen and lymphohemopoietic cells, these self-MHC-self-peptide complexes may also represent thymic and/or peripheral tolerogens, thereby preventing immune responses. This is particularly true for class I MHC-peptide complexes expressed by bone marrow-derived cells in the thymus, as such expression would cause negative selection of immature thymic T cells with high avidity for self-MHC-self-peptide complexes. This intrathymic deletion of potentially self-reactive T cells could result in a peripheral T cell repertoire purged of CTL precursors with sufficient avidity to recognize natural tumor associated self-epitopes presented by class I MHC molecules on tumor cells. HLA-transgenic (Tg) mice provide the basis of an experimental strategy that exploits species differences between Hu and murine (Mu) protein sequences in order to circumvent self-tolerance and obtain HLA-restricted CTL specific for epitopes derived from tumor- and leukemia-associated Hu self proteins, such as p53, Her-2/neu, hdm2 and CD19.

On-line haemodiafiltration versus low-flux haemodialysis. A prospective randomized study

BACKGROUND

Current methods of renal replacement therapy lead only to an insignificant removal of larger, potentially toxic, substances, which are excreted by healthy kidneys. On-line preparation of substituate from dialysate and the use of high-flux membranes allow substantial convective removal of such substances. A modified on-line haemodiafiltration method with the use of a large membrane surface and a high convective part was chosen to test whether the elimination of larger substances, such as low-molecular-mass proteins, has a clinical impact.

METHODS

In a prospective, controlled study over 24 months, 44 unselected chronic dialysis patients were randomized to undergo either low-flux haemodialysis (HD; n = 21) or haemodiafiltration (HDF; n = 23). To eliminate confounding factors, low-molecular efficacy was matched (Kt/V 1.8), and the same membrane material (polysulfone), ultrapure dialysate and the same treatment duration (4.5 h) were applied to each group.

RESULTS

Morbidity, mortality, blood pressure, dialysis-associated hypotensive episodes, haematocrit and erythropoietin dose did not differ between the groups. The same was true for body weight and, accordingly, bioimpedance values, clinical hydration score, skinfold thickness, plasma albumin, prealbumin and transferrin. beta2-Microglobulin in the plasma did not change in the HD group and varied between 32 and 43 mg/l throughout the 2 years. In HDF, beta2 microglobulin decreased from similar values to 18 mg/l predialysis (P<0.01) in the first 6 months of HDF treatment and then remained constant during the remaining 18 months.

CONCLUSION

In the absence of any clinical marker of uraemic toxicity the removal of larger molecules over the time-span of 2 years during HDF had no clinical implication compared with extremely (and for routine practice unrealistically) well-dialysed patients with low-flux HD. In the absence of any side-effects of on-line HDF and supposing that plasma beta2-microglobulin is a marker of morbidity, on-line HDF ensures an excellent dialysis quality which apparently takes time to translate into measurable clinical sequelae.

Combined therapy in human immunodeficiency virus-infected children--a 4-year experience

From 1988 to 1991 the long-term efficacy of a combined therapy with a polyvalent immunoglobulin/cytomegalovirus (CMV) hyperimmunoglobulin, oral low dose zidovudine, oral cotrimoxazole or inhaled pentamidine was investigated in three groups of human immunodeficiency virus (HIV)-infected children. Group 1A consisted of three perinatally infected children with a CD4 cell decrease of > 400 cells/microliters per year. Group 1B were 17 perinatally infected children with a CD4 cell decrease of < 400 cells/microliters per year. Group 2 comprised eight haemophilic children infected by clotting factors. Despite combined therapy none of group 1A survived longer than 12 months showing a rapid loss of CD4 cell counts, progressive encephalopathy, wasting syndrome and severe bacterial, fungal and CMV reactivation. Under pure intravenous immunoglobulin (IVIG) therapy severe bacterial infections were seen in 1 of 12 children in group 1B. The majority of these patients showed increases or stabilisation of length and weight percentiles. In this group low dose zidovudine therapy was of benefit in HIV-associated neurological symptoms. Nevertheless combined therapy could not prevent further deterioration of CD4 cell counts. In group 2 severe bacterial infections were not seen under IVIG therapy. In this group a temporary increase (6 months) of CD4 cell counts under IVIG/zidovudine combined therapy occurred. Pneumocystis carinii pneumonia (PCP) prophylaxis with oral cotrimoxazole or inhaled pentamidine successfully prevented PCP in all three groups. Under CMV hyperimmunoglobulin (n = 22), ten out of ten patients did not acquire primary CMV infection, whereas CMV reactivations mainly located in the CNS could not be prevented in 5 of 12 patients.(ABSTRACT TRUNCATED AT 250 WORDS)