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TP0446131, developed as an antidepressant agent, was found to cause lenticular opacity in a 13-week repeated-dose study in dogs. Histopathologically, the lenticular opacity was observed as a degeneration of the lens fibers, characterized by irregularity in the ordered arrangement of the fibers which is necessary to maintain the transparency of the lens, and was considered to manifest clinically as cataract. To evaluate the development mechanism of the lenticular opacity, the chemical constituents of the lens, which is known to be associated with the development of cataract, were examined. The results of liquid chromatography-tandem mass spectrometry analysis revealed an increase in the amplitudes of 3 unknown peaks in a dose- and time-dependent manner in the lens, with no remarkable changes in the other chemical components tested. In addition, the content of cholesterol, alterations of which have been reported to be associated with cataract, remained unchanged. The mass spectral data and chromatographic behavior of the 3 peaks indicated that these peaks corresponded to sterol-related substances, and that one of them was 7-dehydrocholesterol, a precursor of cholesterol biosynthesis. This finding suggested that TP0446131 exerts some effects on the cholesterol biosynthesis pathway, which could be involved in the development of the cataracts. Furthermore, increases in the levels of these sterol-related substances were also detected in the serum, and were, in fact, noted prior to the onset of the cataract, suggesting the possibility that these substances in the serum could be used as potential safety biomarkers for predicting the onset of cataract induced by TP0446131.

Drug-induced phospholipidosis is a lysosomal storage disorder characterized by the excess accumulation of tissue phospholipids. Although azithromycin can be used to induce phospholipidosis, no experimental studies evaluating the relationship between drug accumulation and phospholipid localization have been performed. In this study, azithromycin was orally administered to rats for 7 days, and the relationship between drug and phospholipid accumulation was performed using imaging mass microscopy. The administration of azithromycin induced tubular epithelial vacuolation in the inner stripe of the outer medulla of the kidney, consistent with the lamellar bodies that are typical manifestations of drug-induced phospholipidosis. Azithromycin and phospholipid tissue levels were extensively elevated in the kidneys of azithromycin-treated rats. Imaging mass microscopy revealed that both azithromycin and its metabolites were found in the kidneys of azithromycin-treated rats but not in control animals. The vacuolated areas of the kidneys were primarily found in the inner stripe of the outer medulla, consistent with the areas of high azithromycin concentration. Azithromycin was colocalized with several phospholipids-phosphatidylinositol (18:0/20:4), phosphatidylethanolamine (18:0/20:4 and 16:0/20:4), and possibly didocosahexaenoyl (C22:6)-bis(monoacylglycerol) phosphate, a putative biomarker of drug-induced phospholipidosis. In summary, we found correlations between regions of kidney damage and the accumulation of azithromycin, its metabolites, and phospholipids using imaging mass microscopy. Such analyses may help reveal the mechanism and identify putative biomarkers of drug-induced phospholipidosis.

The biological mechanisms underlying castration resistance of prostate cancer are not fully understood. In the present study, we examined the role of organic anion transporting polypeptides (OATPs) as importers of dehydroepiandrosterone sulfate (DHEAS) into cells to support growth under androgen-depleted conditions. Cell growth and mRNA expression of OATP genes were studied in human prostate cancer LNCaP and 22Rv1 cells under androgen-depleted conditions. The stimulatory effect of DHEAS on cell growth was investigated in LNCaP cells in which OATP1A2 had been silenced. Growth of both cell lines was stimulated by DHEAS and the effect was attenuated by STX64, an inhibitor of steroid sulfatase which can covert DHEAS to DHEA. OATP1A2 mRNA expression was increased most prominently among various genes tested in LNCaP cells grown in androgen-depleted medium. Similar results were obtained with 22Rv1 cells. Furthermore, the characteristics of [ 3H]DHEAS uptake by LNCaP cells were consistent with those of OATP-mediated transport. Knockdown of OATP1A2 in LNCaP cells resulted in loss of the DHEAS sensitivity of cell growth. Our results suggest that enhanced OATP1A2 expression is associated with adaptive cell growth of prostate cancer cells under androgen-depleted conditions. Thus, OATP1A2 may be a pharmacological target for prostate cancer treatment. © 2012 Elsevier Inc.