Rapid Mapping of Imipramine, Chloroquine, and Their Metabolites in Mouse Kidneys and Brains Using the iMScope QT

Significance of the Topic

Mass spectrometry imaging provides spatially resolved molecular information in biological tissues without labeling. Mapping the distribution of small-molecule drugs and their metabolites in organs such as kidney and brain supports drug discovery, safety assessment, and understanding of therapeutic and adverse effects.

Objectives and Study Overview

This study employed a novel atmospheric-pressure MALDI-MSI instrument (iMScope QT) to rapidly image imipramine, chloroquine, and their primary metabolites in mouse kidneys and brains. The aim was to demonstrate high-speed, high-resolution drug localization and to assess region-specific accumulation patterns relevant to pharmacology and toxicology.

Used Instrumentation

• iMScope QT imaging mass microscope combining AP-MALDI source with a Q-TOF mass analyzer (LCMS-9030)
• iMLayer matrix vapor deposition system for α-cyano-4-hydroxycinnamic acid
• Cryostat (Leica CM1950) for 10 µm tissue sectioning on ITO-coated slides

Methodology

Male C57BL/6 mice received intraperitoneal injections of imipramine and chloroquine (30 mg/kg). After 2 hours, kidneys and brains were collected, frozen, and sectioned at 10 µm. Matrix was deposited under vacuum using the iMLayer system. MSI data were acquired at varying pixel rates (8, 20, and 32 pixels/sec) and spatial resolutions (50×50 µm and 25×25 µm) in positive ion mode. MS/MS imaging at 35 V collision energy confirmed drug identity.

Main Results and Discussion

Optimization with standards showed consistent detection of both drugs at 0.1 µg/mL across speeds up to 20 pixels/sec. In kidney sections, imipramine localized predominantly in the cortex, with desipramine and 2-hydroxy-imipramine in medulla and pelvis. Chloroquine and desethylchloroquine concentrated in the renal pelvis and inner medulla. In brain sections, imipramine and metabolites appeared throughout the tissue with elevated levels in thalamus, hypothalamus, septum, and hindbrain. Chloroquine and its metabolites localized to ventricles and fornix. High-speed (32 pixels/sec) imaging at 25 µm resolution retained sensitivity and spatial detail, demonstrating rapid mapping suitability. These distribution patterns correlate with known pharmacodynamic and toxicological profiles, including potential neurotoxicity and kidney injury.

Practical Benefits and Applications

This approach enables fast, high-resolution visualization of drug and metabolite distributions, aiding in pharmacokinetic studies, drug safety evaluation, and mechanistic research on organ-specific effects. The iMScope QT offers a practical workflow for rapid MSI in preclinical investigations.

Future Trends and Potential Applications

Further work should extend rapid high-resolution MSI to additional drug classes and endogenous metabolites. Integration with complementary ionization methods, quantitative MSI workflows, and multimodal imaging could deepen insights into biochemical processes. Advances in acquisition speed and sensitivity may enable real-time tissue profiling and clinical translation.

Conclusion

The iMScope QT demonstrated rapid, sensitive mapping of imipramine, chloroquine, and metabolites in mouse kidney and brain at high spatial resolution. Region-specific localization patterns reflect drug action and toxicity risks, underscoring the value of AP-MALDI-MSI for preclinical pharmacological research.

References

1. Buchberger AR, DeLaney K, Johnson J, Li L. Mass spectrometry imaging a review of emerging advancements and future insights. Anal Chem. 2018;90:240.
2. Harada T et al. Visualization of volatile substances in different organelles with an atmospheric-pressure mass microscope. Anal Chem. 2009;81:9153–9157.
3. Jackson SN et al. AP-MALDI mass spectrometry imaging of gangliosides using 2,6-dihydroxyacetophenone. J Am Soc Mass Spectrom. 2018;29:1463–1472.
4. Doyno C, Sobieraj DM, Baker WL. Toxicity of chloroquine and hydroxychloroquine following therapeutic use or overdose. Clin Toxicol. 2021;59:12–23.
5. Obuchowicz E et al. Imipramine and venlafaxine differentially affect primary glial cultures of prenatally stressed rats. Front Pharmacol. 2020;10:1687.
6. Islam A et al. Green nut oil or DHA supplementation restored decreased distribution levels of DHA containing phosphatidylcholines in a mouse model of dementia. Metabolites. 2020;10:153.
7. Islam A et al. Application of AP-MALDI Imaging Mass Microscope for the Rapid Mapping of Imipramine, Chloroquine, and Their Metabolites in Wild-Type Mice. Pharmaceuticals. 2022;15:1314.
8. Pazhayattil GS, Shirali AC. Drug-induced impairment of renal function. Int J Nephrol Renovasc Dis. 2014;7:457.
9. Chang GR et al. Imipramine accelerates nonalcoholic fatty liver disease … in obese mice. Vet Sci. 2021;8:189.
10. Murugavel P, Pari L. Attenuation of chloroquine-induced renal damage by α-lipoic acid. Ren Fail. 2004;26:517–524.
11. Yang J et al. SNRI antidepressant effects on regional connectivity of the thalamus in persistent depressive disorder. Brain Commun. 2022;4:fcac100.
12. Wichmann TO et al. A brief overview of the cerebrospinal fluid system. Front Hum Neurosci. 2021;15.
13. Matsumae M et al. Research into the physiology of CSF reaches a new horizon. Neurol Med Chir (Tokyo). 2016;56:416–441.
14. Senova S et al. Anatomy and function of the fornix in context of its potential as a therapeutic target. J Neurol Neurosurg Psychiatry. 2020;91:547–559.