Intracellular Model Research Articles

A luciferase-based assay for rapid assessment of drug activity against Mycobacterium tuberculosis including monitoring of macrophage viability

The intracellular (IC) effect of drugs against Mycobacterium tuberculosis (Mtb) is not well established but increasingly important to consider when combining current and future multidrug regimens into the best possible treatment strategies. For this purpose, we developed an IC model based on a genetically modified Mtb H37Rv strain, expressing the Vibrio harvei luciferase (H37Rv-lux) infecting the human macrophage like cell line THP-1. Cells were infected at a low multiplicity of infection (1:1) and subsequently exposed to isoniazid (INH), ethambutol (EMB), amikacin (AMI) or levofloxacin (LEV) for 5days in a 96-well format. Cell viability was evaluated by Calcein AM and was maintained throughout the experiment. The number of viable H37Rv-lux was determined by luminescence and verified by a colony forming unit analysis. The results were compared to the effects of the same drugs in broth cultures. AMI, EMB and LEV were significantly less effective intracellularly (MIC90: >4mg/L, 8mg/L and 2mg/L, respectively) compared to extracellularly (MIC90: 0.5mg/L for AMI and EMB; 0.25mg/L for LEV). The reverse was the case for INH (IC: 0.064mg/L vs EC: 0.25mg/L). In conclusion, this luciferase based method, in which monitoring of cell viability is included, has the potential to become a useful tool while evaluating the intracellular effects of anti-mycobacterial drugs.

Pharmacokinetic/pharmacodynamic modelling of intracellular gemcitabine triphosphate accumulation: translating in vitro to in vivo

A detailed intracellular (IC) model describing the pharmacokinetics (PK) of gemcitabine (2',2'-difluoro-2'-deoxycytidine, dFdC) was developed and linked to a systemic plasma dFdC PK model. Based on in vivo PK, pharmacodynamic (PD) effect predictions were made using a simplified cell-cycle model (CCM). A reduced-order compartmental model describing the IC metabolism of dFdC was fit to in vitro data taken from the literature to estimate the kinetic parameters of gemcitabine triphosphate (dFdCTP) generation and elimination in leukaemia cells. For comparison with in vivo patient data, the proposed detailed IC model, coupled with the systemic PK model and the CCM PD model, was simulated; Monte Carlo randomisation of the parameter vector was used to simulate interpatient variability. This comparison of model-generated IC dFdCTP concentrations with literature values in peripheral blood mononuclear cells (PBMCs) revealed qualitative and quantitative agreement. A tumour interstitial compartment connecting the plasma and IC models allowed prediction of solid tumour dFdCTP concentration.