Involvement of advanced glycation end-products, pentosidine and N(epsilon)-(carboxymethyl)lysine, in doxorubicin-induced cardiomyopathy in rats.

In the pathogenesis of doxorubicin (DXR)-induced cardiomyopathy, oxidative stress appears to play an important role. It has been reported that pentosidine and N(epsilon)-(carboxymethyl)lysine (CML), advanced glycation end-products (AGEs), are formed by the combined processes of glycation and oxidation and play a significant role in the process of complications of diabetic mellitus. We investigated the potential involvement of AGE formation in DXR-induced cardiomyopathy in rats. Male Crl:CD(SD) rats received intravenous injection of DXR at 2mg/kg or saline once weekly for 8 weeks, with or without daily treatment with the AGE formation inhibitors, aminoguanidine (AG, 25 mg/kg/day, i.p.) and pyridoxamine (PM, 60 mg/kg/day, i.p.). Time-course experiments revealed significantly increased pentosidine and CML in the heart in the DXR group from Week 6. These findings coincided with a decrease in fractional shortening (FS), an index of cardiac function, and the development of cardiomyopathy characterized by vacuolated hypertrophic myocardial fibers. There was a significant correlation between the myocardial AGEs and FS or plasma cardiac troponin-I. Immunohistochemical staining showed localization of pentosidine to the cytoplasm of vacuolated myocardial cells. In DXR-treated rats, oxidative stress was enhanced prior to any observed increase in pentosidine and CML levels in the heart. Hyperglycemia was not observed throughout the study period. Intervention by AG or PM treatment ameliorated the functional and morphological changes induced by DXR in the heart, in addition to lowered myocardial pentosidine and CML levels. These results suggested that DXR accelerates the formation of pentosidine and CML in the heart through enhanced oxidative stress and that AGE formation is involved in DXR-induced cardiomyopathy. The findings may enable development of novel preventive therapies and predictive biomarkers of DXR-induced cardiomyopathy.

Bone-marrow-derived myofibroblasts contribute to the cancer-induced stromal reaction.

To confirm whether human cancer-induced stromal cells are derived from bone marrow, bone marrow (BM) cells obtained from beta-galactosidase transgenic and recombination activating gene 1 (RAG-1) deficient double-mutant mice (H-2b) were transplanted into sublethally irradiated severe combined immunodeficient (SCID) mice (H-2d). The human pancreatic cancer cell line Capan-1 was subcutaneously xenotransplanted into SCID recipients and stromal formation was analyzed on day 14 and on day 28. Immunohistochemical and immunofluorescence studies revealed that BM-derived endothelial cells (X-gal/CD31 or H-2b/CD31 double-positive cells) and myofibroblasts (X-gal/alpha-smooth muscle actin or H-2b/alpha-smooth muscle actin double-positive cells) were present within and around the cancer nests. On day 14, the frequencies of BM-derived endothelial cells and BM-derived myofibroblasts were 25.3+/-4.4% and 12.7+/-9.6%, respectively. On day 28, the frequency of BM-derived endothelial cells was 26.7+/-9.7%, which was similar to the value on day 14. However, the frequency of BM-derived myofibroblasts was significantly higher (39.8+/-17.1%) on day 28 than on day 14 (P<0.05). The topoisomerase IIalpha-positive ratio was 2.2+/-1.2% for the H-2b-positive myofibroblasts, as opposed to only 0.3+/-0.4% for the H-2b-negative myofibroblasts, significant proliferative activity was observed in the BM-derived myofibroblasts (P<0.05). Our results indicate that BM-derived myofibroblasts become a major component of cancer-induced stromal cells in the later stage of tumor development.