"Comprehensive distribution analysis of cyclosporin A on mice tissues applying mass spectrometry imaging."

Peptide drugs are playing an indispensable role in clinical therapy, but may exhibit significant dose-dependent toxicities, as observed in polymyxin antibiotics and cyclosporin A (CsA) itself. The spatial distribution of these drugs and their metabolites is crucial for understanding the tissue-specific pharmacokinetics. The goal of our study was to develop and evaluate a mass spectrometry imaging (MSI) workflow using atmospheric pressure matrix-assisted laser desorption and ionization mass spectrometry imaging (AP-MALDI-MSI) with the iMScope QT system for the detection and spatial visualization of CsA in mice organs. Based on the CsA signal sensitivity and consistent detection of the CsA standard in our optimized experimental condition, we chose iMScope QT for subsequent in vivo MSI experiments. Following intraperitoneal injection of CsA into C57BL/6 mice, the brain, kidney, liver, spleen, and intestinal tissues were collected for MSI analysis. Our findings revealed increased accumulation of CsA and monohydroxy CsA in the renal cortex, liver, muscularis externa, and mucosa of the colon. CsA was found in higher amounts in the muscularis externa of the jejunum, whereas monohydroxy CsA was accumulated in the villus tips and penetrated the lumen of the treated mice. CsA was also detected throughout the spleen, but not monohydroxy CsA. The methodology demonstrated high precision (CV < 15%), establishing a robust analytical framework for utilizing AP-MALDI-MSI (iMScope QT) to evaluate the therapeutic efficacy and safety of CsA.