The Role of Lysosomes in Limiting Drug Toxicity in Mice

Ndolo, Rosemary A.; Forrest, M. Laird; Krise, Jeffrey P.

doi:10.1124/jpet.109.160226

Cited by 29 publications

(24 citation statements)

References 31 publications

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“…In P-gp KO mice, pretreatment with tariquidar (32 mg/kg i.v.) decreased the uptake of (23), who demonstrated that lysosomal pH changes occur in mice when weak bases are administered chronically (i.e., for weeks) (23). However, we show that lysosomal competition between two weak bases can occur in vivo in an acute time frame, a finding that, to our knowledge, has not been demonstrated previously.…”

Section: Discussioncontrasting

confidence: 65%

Lysosomal trapping of a radiolabeled substrate of P-glycoprotein as a mechanism for signal amplification in PET

Kannan

Brimacombe

Kreisl

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

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The radiotracer [ 11 C]N-desmethyl-loperamide (dLop) images the in vivo function of P-glycoprotein (P-gp), a transporter that blocks the entry of drugs that are substrates into brain. When P-gp is inhibited, [ C]dLop uptake before and after tariquidar preadministration in lysosome-rich organs of P-gp KO mice and humans. After tariquidar pretreatment in both species, radioactivity uptake in these organs decreased by 35% to 40%. Our results indicate that dLop is trapped in lysosomes and that tariquidar competes with dLop for lysosomal accumulation in vitro and in vivo. Although tariquidar and dLop compete for lysosomal trapping in the periphery, such competition does not occur in brain because tariquidar has negligible entry into brain. In summary, tariquidar and [ 11 C]dLop can be used in combination to selectively measure the function of P-gp at the blood-brain barrier.ATP-binding cassette | efflux

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Section: Discussioncontrasting

confidence: 65%

Lysosomal trapping of a radiolabeled substrate of P-glycoprotein as a mechanism for signal amplification in PET

Kannan

Brimacombe

Kreisl

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

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“…4 Both these effects could hinder treatment. 4, 44, 45 Consequently, understanding the cellular distribution of chemotherapeutics, and how to manipulate this through combination treatments, is imperative for developing treatments against resistance.…”

Section: Discussionmentioning

confidence: 99%

A mechanism for overcoming P-glycoprotein-mediated drug resistance: novel combination therapy that releases stored doxorubicin from lysosomes via lysosomal permeabilization using Dp44mT or DpC

2016

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The intracellular distribution of a drug can cause significant variability in both activity and selectivity. Herein, we investigate the mechanism by which the anti-cancer agents, di-2-pyridylketone 4,4-dimethyl-3-thiosemicarbazone (Dp44mT) and the clinically trialed, di-2-pyridylketone 4-cyclohexyl-4-methyl-3-thiosemicarbazone (DpC), re-instate the efficacy of doxorubicin (DOX), in drug-resistant P-glycoprotein (Pgp)-expressing cells. Both Dp44mT and DpC potently target and kill Pgp-expressing tumors, while DOX effectively kills non-Pgp-expressing cancers. Thus, the combination of these agents should be considered as an effective rationalized therapy for potently treating advanced and resistant tumors that are often heterogeneous in terms of Pgp-expression. These studies demonstrate that both Dp44mT and DpC are transported into lysosomes via Pgp transport activity, where they induce lysosomal-membrane permeabilization to release DOX trapped within lysosomes. This novel strategy of loading lysosomes with DOX, followed by permeabilization with Dp44mT or DpC, results in the relocalization of stored DOX from its lysosomal 'safe house' to its nuclear targets, markedly enhancing cellular toxicity against resistant tumor cells. Notably, the combination of Dp44mT or DpC with DOX showed a very high level of synergism in multiple Pgp-expressing cell types, for example, cervical, breast and colorectal cancer cells. These studies revealed that the level of drug synergy was proportional to Pgp activity. Interestingly, synergism was ablated by inhibiting Pgp using the pharmacological inhibitor, Elacridar, or by inhibiting Pgp-expression using Pgp-silencing, demonstrating the importance of Pgp in the synergistic interaction. Furthermore, lysosomal-membrane stabilization inhibited the relocalization of DOX from lysosomes to the nucleus upon combination with Dp44mT or DpC, preventing synergism. This latter observation demonstrated the importance of lysosomal-membrane permeabilization to the synergistic interaction between these agents. The synergistic and potent anti-tumor efficacy observed between DOX and thiosemicarbazones represents a promising treatment combination for advanced cancers, which are heterogeneous and composed of non-Pgp- and Pgp-expressing tumor cells.

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“…26 Briefly, MDA-1986 cells were plated onto 8-chamber glass microscope slides and allowed to adhere overnight. Following a 24 h exposure to 10 µM imipramine or vehicle alone, growth media was replaced with phenol red-free growth media containing 1 mg/ml anionic 70,000 mol.…”

Section: Methodsmentioning

confidence: 99%

Cationic Amphiphilic Drugs Cause a Marked Expansion of Apparent Lysosomal Volume: Implications for an Intracellular Distribution-Based Drug Interaction

Funk

Krise

2012

Mol. Pharmaceutics

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How a drug distributes within highly compartmentalized mammalian cells can affect both the activity and pharmacokinetic behavior. Many commercially available drugs are considered to be lysosomotropic, meaning they are extensively sequestered in lysosomes by an ion trapping-type mechanism. Lysosomotropic drugs typically have a very large apparent volume of distribution and a prolonged half-life in vivo, despite minimal association with adipose tissue. In this report we tested the prediction that the accumulation of one drug (perpetrator) in lysosomes could influence the accumulation of a secondarily administered one (victim), resulting in an intracellular distribution-based drug interaction. To test this hypothesis cells were exposed to nine different hydrophobic amine-containing drugs, which included imipramine, chlorpromazine and amiodarone, at a 10 µM concentration for 24 to 48 hours. After exposure to the perpetrators the cellular accumulation of LysoTracker Red (LTR), a model lysosomotropic probe, was evaluated both quantitatively and microscopically. We found that all of the tested perpetrators caused a significant increase in the cellular accumulation of LTR. Exposure of cells to imipramine caused an increase in the cellular accumulation of other lysosomotropic probes and drugs including LyosTracker Green, daunorubicin, propranolol and methylamine; however, imipramine did not alter the cellular accumulation of non-lysosomotropic amine-containing molecules including MitoTracker Red and sulforhodamine 101. In studies using ionophores to abolish intracellular pH gradients we were able to resolve ion trapping-based cellular accumulation from residual pH-gradient independent accumulation. Results from these evaluations in conjunction with lysosomal pH measurements enabled us to estimate the relative aqueous volume of lysosomes of cells before and after imipramine treatment. Our results suggest that imipramine exposure caused a 4-fold expansion in the lysosomal volume, which provides the basis for the observed drug interaction. The imipramine-induced lysosomal volume expansion was shown to be both time- and temperature-dependent and reversed by exposing cells to hydroxypropyl-β-cyclodextrin, which reduced lysosomal cholesterol burden. This suggests that the expansion of lysosomal volume occurs secondary to perpetrator-induced elevations in lysosomal cholesterol content. In support of this claim, the cellular accumulation of LTR was shown to be higher in cells isolated from patients with Niemann-Pick Type C disease, which are known to hyper-accumulate cholesterol in lysosomes.

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The Role of Lysosomes in Limiting Drug Toxicity in Mice

Cited by 29 publications

References 31 publications

Lysosomal trapping of a radiolabeled substrate of P-glycoprotein as a mechanism for signal amplification in PET

Lysosomal trapping of a radiolabeled substrate of P-glycoprotein as a mechanism for signal amplification in PET

A mechanism for overcoming P-glycoprotein-mediated drug resistance: novel combination therapy that releases stored doxorubicin from lysosomes via lysosomal permeabilization using Dp44mT or DpC

Cationic Amphiphilic Drugs Cause a Marked Expansion of Apparent Lysosomal Volume: Implications for an Intracellular Distribution-Based Drug Interaction

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