Impact of gas humidification and nebulizer position under invasive ventilation: preclinical comparative study of regional aerosol deposition

Successful aerosol therapy in mechanically ventilated patients depends on multiple factors. Among these, position of nebulizer in ventilator circuit and humidification of inhaled gases can strongly influence the amount of drug deposited in airways. Indeed, the main objective was to preclinically evaluate impact of gas humidification and nebulizer position during invasive mechanical ventilation on whole lung and regional aerosol deposition and losses. Ex vivo porcine respiratory tracts were ventilated in controlled volumetric mode. Two conditions of relative humidity and temperature of inhaled gases were investigated. For each condition, four different positions of vibrating mesh nebulizer were studied: (i) next to the ventilator, (ii) right before humidifier, (iii) 15 cm to the Y-piece adapter and (iv) right after the Y-piece. Aerosol size distribution were calculated using cascade impactor. Nebulized dose, lung regional deposition and losses were assessed by scintigraphy using 99mtechnetium-labeled diethylene-triamine-penta-acetic acid. Mean nebulized dose was 95% ± 6%. For dry conditions, the mean respiratory tract deposited fractions reached 18% (± 4%) next to ventilator and 53% (± 4%) for proximal position. For humidified conditions, it reached 25% (± 3%) prior humidifier, 57% (± 8%) before Y-piece and 43% (± 11%) after this latter. Optimal nebulizer position is proximal before the Y-piece adapter showing a more than two-fold higher lung dose than positions next to the ventilator. Dry conditions are more likely to cause peripheral deposition of aerosols in the lungs. But gas humidification appears hard to interrupt efficiently and safely in clinical use. Considering the impact of optimized positioning, this study argues to maintain humidification.

Quantitative impact of the first COVID-19 lockdown on nuclear medicine in France: the CORALINE study

PURPOSE

The coronavirus disease 2019 (COVID-19) pandemic reshaped the usual risk: benefit equilibrium that became a trade-off between the infection exposure risk for the patient (and for staff) and the risk associated with delaying or cancelling the nuclear medicine examination. This study aimed at quantifying the impact of the first COVID-19 lockdown in France on nuclear medicine examination volume together with volume of examination cancellation and non-attendance.

METHODS

We retrospectively assessed the volume of planned examinations from 1 month before to 1 month after the first lockdown in French high-volume nuclear medicine departments (NMD) sharing the same information management system including both university hospitals, UH (n = 7), and cancer centres, CC (n = 2).

RESULTS

The study enrolled 31,628 consecutive patients referred for a nuclear medicine examination performed or not (NMEP or NMEnP). The total volume of NMEP significantly dropped by 43.4% between the 4 weeks before and after the starting of the lockdown. The comparison of the percentage of NMEP and NMEnP between UH and CC is significantly different (p < 0.001). The percentage of NMEP during the study was 67.9% in UH vs 84.7% in CC. Percentages of NMEnP in UH and CC were due respectively to cancellation by the patient (14.9 vs 7.4%), cancellation by the NMD (9.5 vs 3.4%), cancellation by the referring physician (5.1 vs 4.4%) and non-attender patients (2.7 vs 0.2%).

CONCLUSION

The study underlines the public health issue caused by COVID-19 above the pandemic itself and should be useful in preparing for potential resource utilisation and staffing requirements.

In Cellulo Evaluation of the Therapeutic Potential of NHC Platinum Compounds in Metastatic Cutaneous Melanoma

We describe here the evaluation of the cytotoxic efficacy of two platinum (II) complexes bearing an N-heterocyclic carbene (NHC) ligand, a pyridine ligand and bromide or iodide ligands on a panel of human metastatic cutaneous melanoma cell lines representing different genetic subsets including BRAF-inhibitor-resistant cell lines, namely A375, SK-MEL-28, MeWo, HMCB, A375-R, SK-MEL-5-R and 501MEL-R. Cisplatin and dacarbazine were also studied for comparison purposes. Remarkably, the iodine-labelled Pt-NHC complex strongly inhibited proliferation of all tested melanoma cells after 1-h exposure, likely due to its rapid uptake by melanoma cells. The mechanism of this inhibitory activity involves the formation of DNA double-strand breaks and apoptosis. Considering the intrinsic chemoresistance of metastatic melanoma cells of current systemic treatments, these findings are promising and could give research opportunities in the future to improve the prognosis of patients suffering from unresectable metastatic melanoma that are not eligible or that do not respond to the most effective drugs available to date, namely BRAF inhibitors and the anti-PD-1 monoclonal antibody (mAb).

Nebulised Gadolinium-Based Nanoparticles for a Multimodal Approach: Quantitative and Qualitative Lung Distribution Using Magnetic Resonance and Scintigraphy Imaging in Isolated Ventilated Porcine Lungs

Purpose

This study aims at determining lung distribution of gadolinium-based polysiloxane nanoparticles, AGuIX^® (small rigid platform - SRP), as a potential theranostic approach by the pulmonary route.

Methods

First, the aerodynamic size distribution and the aerosol output rate were thoroughly characterized. Then, a multimodal approach using magnetic resonance (MR) and gamma-camera (GC) imaging allows to assess the deposition of the aerosolised nanoparticles in the respiratory tract using isolated ventilated porcine lungs.

Results

The SRP has proven to be radiolabelled by radioisotope with a good yield. Crude SRP or radiolabelled ones showed the same aerodynamic size distribution and output as a conventional molecular tracer, as sodium fluoride. With MR and GC imaging approaches, the nebulised dose represented about 50% of the initial dose of nanoparticles placed in the nebuliser. Results expressed as proportions of the deposited aerosol showed approximately a regional aerosol deposition of 50% of the deposited dose in the lungs and 50% in the upper airways. Each technique assessed a homogeneous pattern of deposited nanoparticles in Lungs. MR observed a strong signal enhancement with the SRP, similar to the one obtained with a commonly used MRI contrast agent, gadoterate meglumine.

Conclusion

As a known theranostic approach by intravenous administration, SRP appeared to be easily aerosolised with a conventional nebuliser. The present work proves that pulmonary administration of SRP is feasible in a human-like model and allows multimodal imaging with MR and GC imaging. This work presents the proof of concept of SRP nebulisation and aims to generate preclinical data for the potential clinical transfer of SRP for pulmonary delivery.

Using 99mTc-(V)-DMSA to follow the vascular calcification process in vascular smooth muscle cells based on pit-1 expression

BACKGROUND

Vascular calcification is an established feature of atherosclerosis process. The sodium/phosphate transporter PiT-1 acts as a biosensor in vascular calcification of VSMCs. [99mTc]-Pentavalent dimercaptosuccinic acid (99mTc-(V)-DMSA) was mediated by PiT-1 transporter in tumoral cells and we propose its evaluation in a vascular calcification in vitro model. The aim of this study was to determine if 99mTc-(V)-DMSA can follow the vascular calcification process in vascular smooth muscle cells (VSMCs) based on PiT-1 expression.

METHODS

From a rat aortic VSMC cell line (A7r5), we set up a model of calcification within 7 days using a calcifying medium containing a high inorganic phosphate concentration. Phosphocalcic deposits were monitored with Alizarin red and Von Kossa staining and with phase contrast microscopy. PiT-1 expression was evaluated with an immunofluorescence assay and osteopontin expression, with whole cell ELISA assay. 99mTc-(V)-DMSA uptake was measured in control and calcifying conditions and compared with optical microscopy evaluation.

RESULTS

Under hyperphosphatemia conditions, the VSMC cells progressively overexpressed osteopontin protein, PiT-1 transporter, and synthetized mineralized matrix with phosphocalcic deposition. 99mTc-(V)-DMSA uptake was to 2.8+/-2.08%DA/mg-protein in control cells and 42+/-24%DA/mg-protein in calcified cells (p<0,001). PiT-1 inhibition with phosphonoformic acid completely reverse the calcium deposition as well as the 99mTc-(V)- DMSA uptake. These results demonstrated that 99mTc-(V)-DMSA in vitro uptake is mediated by PiT-1 transporter and follow the VSMC calcification process.

CONCLUSIONS

These preliminary in vitro results showed 99mTc-(V)-DMSA uptake follow the phospho-calcic deposition mediated by PiT-1 transporter. This radiotracer may have some potential to detect changes of VSMC metabolism occurring in the atherosclerosis process.

Aerosol delivery during invasive mechanical ventilation: development of a preclinical ex vivo respiratory model for aerosol regional deposition

In intensive care units, nebulization is a usual route for drug administration to patients under mechanical ventilation (MV). The effectiveness of inhalation devices as well as depositions sites of aerosols for ventilated patients remain poorly documented. In vivo human inhalation studies are scarce due to ethical restrictions because imaging techniques require radioaerosols to assess regional aerosol deposition. Thus, we developed an ex vivo respiratory model under invasive MV for preclinical aerosol deposition studies. The model was composed of ex vivo porcine respiratory tracts. MV was achieved thanks to a tracheal intubation and a medical ventilator under controlled conditions. Respiratory features were studied using analogical sensors. Then regional homogeneity of gas-ventilation was assessed with ^81mKrypton scintigraphies. Finally, a proof of concept study for aerosol deposition was performed. Obtained respiratory features as well as gamma-imaging techniques, which demonstrated a homogenous regional ventilation and about 18% ± 4% of the nebulized dose deposited the respiratory tract, were in good agreement with human data available in the literature. This original ex vivo respiratory model provides a feasible, reproducible and cost-effective preclinical tool to achieve aerosol deposition studies under MV.

Development of an ex vivo respiratory pediatric model of bronchopulmonary dysplasia for aerosol deposition studies

Ethical restrictions are limitations of in vivo inhalation studies, on humans and animal models. Thus, in vitro or ex vivo anatomical models offer an interesting alternative if limitations are clearly identified and if extrapolation to human is made with caution. This work aimed to develop an ex vivo infant-like respiratory model of bronchopulmonary dysplasia easy to use, reliable and relevant compared to in vivo infant data. This model is composed of a 3D-printed head connected to a sealed enclosure containing a leporine thorax. Physiological data and pleural-mimicking depressions were measured for chosen respiratory rates. Homogeneity of ventilation was assessed by ^81mkrypton scintigraphies. Regional radioaerosol deposition was quantified with ^99mtechnetium-diethylene triamine pentaacetic acid after jet nebulization. Tidal volumes values are ranged from 33.16 ± 7.37 to 37.44 ± 7.43 mL and compliance values from 1.78 ± 0.65 to 1.85 ± 0.99 mL/cmH₂O. Ventilation scintigraphies showed a homogenous ventilation with asymmetric repartition: 56.94% ± 9.4% in right lung and 42.83% ± 9.36 in left lung. Regional aerosol deposition in lungs exerted 2.60% ± 2.24% of initial load of radioactivity. To conclude the anatomical model satisfactorily mimic a 3-months old BPD-suffering bronchopulmonary dysplasia and can be an interesting tool for aerosol regional deposition studies.

In Vitro Comparison of the Role of P-Glycoprotein and Breast Cancer Resistance Protein on Direct Oral Anticoagulants Disposition

BACKGROUND

Pharmacokinetics of direct oral anticoagulants (DOACs) are influenced by ATP-binding cassette (ABC) transporters such as P-glycoprotein (P-gp) and Breast Cancer Resistance Protein (BCRP).

OBJECTIVES

To better understand the role of transporters in DOAC disposition, we evaluated and compared the permeabilities and transport properties of these drugs.

METHODS

Bidirectional permeabilities of DOACs were investigated across Caco-2 cells monolayer. Transport assays were performed using different concentrations of DOAC and specific inhibitors of ABC transporters. Cell model functionality was evaluated by transport assay of two positive control substrates.

RESULTS

The results of transport assays suggest a concentration-dependent efflux of apixaban, dabigatran etexilate and edoxaban, whereas the efflux transport of rivaroxaban did not seem to depend on concentration. Verapamil, a strong inhibitor of P-gp, decreased DOAC efflux in the Caco-2 cell model by 12-87%, depending on the drug tested. Ko143 reduced BCRP-mediated DOAC efflux in Caco-2 cells by 46-76%.

CONCLUSION

This study allowed identification of three different profiles of ABC carrier-mediated transport: predominantly P-gp-dependent transport (dabigatran), preferential BCRP-dependent transport (apixaban) and approximately equivalent P-gp and BCRP-mediated transport (edoxaban and rivaroxaban).

Is [(99m)Tc]glucarate uptake mediated by fructose transporter GLUT-5?

PURPOSE

There is growing interest in the ability of [(99m)Tc]Glucarate ([(99m)Tc]GLA) to accumulate in viable tumor cells. Recent vivo studies suggest that [(99m)Tc]Glucarate could be helpful for tumor detection. Fructose transport is thought to be implicated. It is clearly established that facilitated fructose transport in tumor cells is related to the GLUT-5 transporter. This study therefore investigated whether [(99m)Tc]GLA uptake is mediated by GLUT-5 transporter.

METHODS

Different tumor cell lines were used. Modulation of GLUT-5 expression was assessed with and without antisense oligonucleotides directed against GLUT-5. GLUT-5 expression was assessed by indirect cell ELISA. To correlate GLUT-5 expression with tracer accumulation, [(99m)Tc]GLA uptake was determined after antisense treatment. A competition with fructose was also monitored.

RESULTS

Inhibition of GLUT-5 expression by antisense oligonucleotides directed against GLUT-5 was effective after 24 h. An optimal of 10μM antisense oligonucleotides directed against GLUT-5 produced a 30%-40% decrease in protein expression. Modulation of [(99m)Tc]GLA uptake was monitored either by use of specific antisense oligonucleotides or by competition with fructose. Both of them produced a significant decrease of [(99m)Tc]GLA accumulation in all tested cell lines.

CONCLUSION

Our results clearly demonstrate that [(99m)Tc]GLA uptake is related to GLUT-5 transporter expression and transport. In tumor imaging, [(99m)Tc]GLA may be a useful tool for non-invasive detection of malignant tumors expressing high levels of GLUT-5 transporter as, for example, breast cancers.

Influence of multidrug resistance on (18)F-FCH cellular uptake in a glioblastoma model

PURPOSE

Multidrug resistance, aggressiveness and accelerated choline metabolism are hallmarks of malignancy and have motivated the development of new PET tracers like (18)F-FCH, an analogue of choline. Our aim was to study the relationship of multidrug resistance of cultured glioma cell lines and (18)F-FCH tracer uptake.

METHODS

We used an in vitro multidrug-resistant (MDR) glioma model composed of sensitive parental U87MG and derived resistant cells U87MG-CIS and U87MG-DOX. Aggressiveness, choline metabolism and transport were studied, particularly the expression of choline kinase (CK) and high-affinity choline transporter (CHT1). FCH transport studies were assessed in our glioblastoma model.

RESULTS

As expected, the resistant cell lines express P-glycoprotein (Pgp), multidrug resistance-associated protein isoform 1 (MRP1) and elevated glutathione (GSH) content and are also more mobile and more invasive than the sensitive U87MG cells. Our results show an overexpression of CK and CHT1 in the resistant cell lines compared to the sensitive cell lines. We found an increased uptake of FCH (in % of uptake per 200,000 cells) in the resistant cells compared to the sensitive ones (U87MG: 0.89 +/- 0.14; U87MG-CIS: 1.27 +/- 0.18; U87MG-DOX: 1.33 +/- 0.13) in line with accelerated choline metabolism and aggressive phenotype.

CONCLUSIONS

FCH uptake is not influenced by the two ATP-dependant efflux pumps: Pgp and MRP1. FCH would be an interesting probe for glioma imaging which would not be effluxed from the resistant cells by the classic MDR ABC transporters. Our results clearly show that FCH uptake reflects accelerated choline metabolism and is related to tumour aggressiveness and drug resistance.

In vitro and in vivo evaluation of the influence of type III NaPi co-transporter activity during apoptosis on 99mTc-(V)DMSA uptake in the human leukaemic cell line U937

PURPOSE

Pentavalent 99mTc-dimercaptosuccinic acid [99mTc-(V)DMSA or (V)DMSA] is a marker of phosphate transport, entering cells specifically through type III NaPi co-transporters. Phosphate ion is known to be involved in cell metabolism, including the apoptotic cell death process. As phosphate accumulation decreases during apoptosis, we investigated the influence of type III NaPi co-transporter activity on (V)DMSA uptake during this type of cell death.

METHODS

Uptake of (V)DMSA and phosphate was compared in a leukaemic cell line (U937) in vitro model after induction of apoptosis by a chemotherapeutic agent, etoposide (VP16). (V)DMSA biodistribution in nude mice during apoptosis was also investigated in a U937 xenograft in vivo model. The percentage of apoptosis in vitro and ex vivo was determined with annexin V fluorescein by flow cytometry.

RESULTS

The in vitro results showed that, in parallel with the decrease in phosphate uptake during apoptosis, (V)DMSA accumulation is negatively correlated with the percentage of apoptosis. Biodistribution studies showed decreased accumulation of (V)DMSA in tumours after treatment with VP16. Animal studies also confirmed an inverse correlation between percentage of apoptosis in tumours and (V)DMSA uptake.

CONCLUSION

The activity of type III NaPi co-transporter is inhibited during the early stages of apoptosis, leading to differential incorporation of (V)DMSA in viable cells and apoptotic cells both in vitro and in vivo.