Request a Quote

Lysosomal Trapping (Lysosomotropism)

  • Lysosomes are essential for the degradation of old organelles and engulfed microbes and also play a role in programmed cell death1.
  • Lysosomotropic agents e.g., chloroquine, accumulate preferentially in the lysosomes of cells in the body.
  • These agents tend to have both lipophilic or amphiphilic compounds with basic moieties. Once inside the acidic environment of the lysosome, the drug becomes protonated and trapped in the organelle2.
  • Trapping of drugs in the lysosome may be one mechanism leading to drug-induced phospholipidosis for cationic amphiphilic drugs (CAD).
  • Cyprotex’s lysosomal trapping service is a cell based assay which uses high content screening to identify both lysosomotropism and cytotoxicity according to a recently published method2.
Although there is a limited understanding of how lysosomotropism contributes to toxicity, an association between the two has been observed and therefore assays that identify lysosomal impairment compounds are desired.

2Nadanaciva S, Lu S, Gebhard DF, Jessen BA, Pennie WD, Will Y (2011) Toxicology In Vitro 25; 715-723


Lysosomal trapping cell-based assay protocol

Test System High content screening using lysosomal and nuclear dyes
Cell Lines HepG2, human liver carcinoma cell line. (Other cell lines available on request, e.g., rat cardiomyocyte derived H9c2 cells)
Test Article Concentrations 8 point dose curve with top concentration based on cell loss or solubility limit
Quality Controls Vehicle control
Negative control = piroxicam
Positive control = chloroquine
Test Article Requirements 50 µL of 30 mM DMSO solution or equivalent amount in solid compound
Data Delivery Summary report
Minimum effective concentration (MEC) and AC50 value for each cell health parameter (cell loss, nuclear morphology, DNA fragmentation and lysosomotropism)
Graphical representation of data


Data for Lysosomal trapping

Known lysosomotropic and non-lysosomotropic agents were screened in the lysosomal trapping assay. Data generated were compared to those published in the literature.

Vehicle Control
Chloroquine (60 µM)
Piroxicam (150 µM)
Figure 1
Representative high content screening images for cells treated with (A) vehicle control (B) 60 µM chloroquine (a lysosomotropic agent) and (C) 150 µM piroxicam (a non-lysosomotropic agent) over a 4 hr period.

Drugs which are lysosomotropic such as chloroquine competitively inhibit uptake of the lysosomal dye into the lysosomes.
Figure 2
Graphical representation of lysosomal trapping data for chloroquine (a lysosomotropic agent) and piroxicam (a non-lysosomotropic agent).

Chloroquine causes a concentration dependent decrease in lysosomal staining compared to vehicle control treated cells. No effect was observed for piroxicam. No cytotoxic effects were observed for either compound at the concentration range tested. Data represents mean of triplicate incubations ± standard deviation.
CompoundcLogPBasic pKaCyprotex decrease in lysosomal staining IC50 (µM) in HepG2Cyprotex decrease in lysosomal staining IC50 (μM) in H9c2Literature decrease in lysosomal staining IC50 (µM)Cyprotex cytotoxicity IC50 (µM) in HepG2Cyprotex cytotoxicity IC50 (µM) in H9c2Literature cytotoxicity IC50 (µM)
Acetaminophen 0.51 9.46 >4000 >4000 >500 >4000 >4000 >500
Diclofenac 4.98 -2.1 >500 >500 >500 >500 >500 >500
Rosuvastatin 1.47 -2.8 >150 >150 >500 >150 >150 >500
Piroxicam 2.2 3.79 >300 >300 >150 >300 >300 >150
Amiodarone 7.24 8.47 6.34 7.14 3.8 144 75 12.6
Chloroquine 5.28 10.37 16.4 6.38 11.1 >150 >150 148.3
Chlorpromazine 5.18 9.2 9.5 16.5 5.8 59.2 27.5 20.9
Desipramine 4.02 10.02 35.6 59.2 4.6 >150 41.7 10.7
Fluoxetine 4.09 9.8 22.7 27.9 6.5 81.1 27.7 13.9
Paroxetine 3.1 9.77 19.2 20.6 5.3 67.7 18.2 10.7
Sertraline 5.06 9.85 6.43 14.2 6.6 42.3 11.3 12.2
Tamoxifen 5.93 8.76 15.2 22.2 3.8 70.4 24 6.6
Table 1
Lysosomal trapping and cytotoxicity data for a set of 12 compounds with comparison against literature data2.

Cyprotex data correlates well with data generated in the literature. It has been suggested that compounds with a cLogP > 2 and a basic pKa of between 6.5 and 11 exhibit a higher propensity for lysosomotropism2.


1 Turk B and Turk V (2009) J Biol Chem 284; 21783-21787
2 Nadanaciva S et al., (2011) Toxicology In Vitro 25; 715-723
3 Kazmi F et al., (2013) Drug Metab Dispos 41; 897-905 

Learn More

Learn more about toxicology in our popular Mechanisms of Drug-Induced Toxicity guide

Order your copy

Tox guide
Get a Quote
ADME Guide DDI Guide TOX Guide Visit the e-Store
Contact us to discuss your ADME Tox issues or request a quote

Europe: +44 (0)1625 505100
North America (East Coast): +1-888-297-7683

or fill out the form below:


Download file