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Doxorubicin Dose Dependently Attenuates Cyclooxygenase‐2 in Female Human Coronary Vascular Smooth Muscle Cells

Doxorubicin (Dox), an anthracycline‐based chemotherapeutic agent, is highly effective at reducing recurrence and mortality in breast cancer patients. However, this anti‐cancer drug elicits dose‐dependent cardiotoxicity. Multiple mechanisms have been implicated in its pathogenesis, one of which involves the development and progression of inflammation mediated by activation of the TLR4/NFkappaB pathway. However, we recently demonstrated that chronic in vivo Dox treatment reduced expression of the NFkappaB downstream proinflammatory mediator, cyclooxygenase‐2 (COX‐2), in cerebral and peripheral vasculatures isolated from ovariectomized female rats. Therefore, in the current study we tested whether Dox similarly alters vascular proinflammatory enzyme expression in the human vasculature and whether this response is dose dependent. We further investigated whether Dox alters upstream mediators of COX‐2 expression by assessing levels of expression and activation of NFkappaB and an additional downstream gene product, TLR4. Primary human coronary vascular smooth muscle cells of female origin were studied at passage 6 and treated with vehicle or Dox (0.3, 1.0, and 5 μM). Following drug treatment, cells were isolated, homogenized, and lysates (whole cell; nuclear and cytosolic) analyzed for NFkappaBp65, COX‐2, and TLR4 protein levels via immunoblotting. Our results demonstrate that while total NFkappaB levels were unaffected following Dox, enhanced translocation of NFkappaB to the nucleus was observed. However, even in the presence of Dox‐induced NFkappa translocation, basal expression of its downstream mediator, COX‐2, was dose dependently attenuated. Similar to COX‐2, a trend for a decrease in TLR4 levels was observed. Dox had no effect on cell morphology or density, as visualized via light microscopy. In conclusion, although others have suggested the involvement of NFkappaB activation during the development and progression of Dox‐induced inflammation in cardiac muscle, our studies demonstrate a possible novel action for the anticancer agent targeting important downstream mediators of inflammation in the female vasculature. Future studies will evaluate the impact of Dox on COX‐2 at the transcriptional or translational level to determine the mode of molecular regulation.