varied by drug. Both EGFR inhibitors caused increased left ventricular end diastolic and systolic dimensions and reduced contractility, as measured by percent fractional shortening, compared to baseline values or controls. EKB 569 had the greatest effect on LV wall thickness. Consistent with echocardiographic data, H&E stained cross sections taken at the level of CCT128930 Akt inhibitor the papillary muscle also showed morphological evidence of LV and septal wall thinning. Because significant alterations were seen in cardiac function with drug treatment, we conducted a histological analysis to investigate pathological endpoints such as cardiomyocyte hypertrophy, fibrosis, and apoptosis. Consistent with heart weight data, there were no significant differences in mean cardiomyocyte area or in gene expression of classic hypertrophy markers in the LV by treatment in female mice.
There Clinofibrate 30299-08-2 were also no significant differences in LV gene expression of selected Erbb family members and ligands. Mild to moderate interstitial and perivascular fibrosis, as demonstrated by Masson,s Trichrome stain, was observed in the LV walls of 25% of EKB 569 and greater than 50% of AG 1478 treated female mice. Milder interstitial fibrosis was also observed in 20% control animals. Less frequent pathological observations included the presence of thrombi and proteinaceous material in the right ventricle and neointimal hyperplasia in the coronary arteries of EGFR inhibitor treated female mice. Interestingly, both inhibitors increased the number of TUNEL positive cardiac cells with apoptotic cells located in the LV walls, LV papillary muscle, and left atria of female mice.
Consistent with TUNEL staining, altered expression of apoptotic genes was observed in the LV of inhibitor treated female mice relative to controls. Expression of the anti apoptotic gene Bcl2l1 was suppressed by approximately 50%, and the pro apoptotic genes Bad and Bax were also altered, albeit not reaching statistical significance. Since earlier evidence demonstrated that EGFR activity is required for normal semilunar valve development, we investigated the effects of chronic exposure to EGFR inhibitors on morphological and histological changes in cardiac valves. Initial results using EKB 569 suggested that reduced EGFR activity might trigger excessive extracellular matrix production and calcification in adult valves.
All EKB 569 treated female mice, but less than half of the control mice, had evidence of aortic valve calcification by von Kossa staining. However, all B6 female mice from respective control and AG 1478 groups had some evidence of calcification, suggesting that EGFR inhibitors may exacerbate preexisting susceptibilities to valvular calcification. Both sexes showed signs of increased valve thickness and interestingly, there were also a significant dietary effect on mean valve thickness. Since the synthetic AIN 93G diet has higher fat content than regular chow Barrick et al. Page 6 Toxicol Appl Pharmacol. Author manuscript, available in PMC 2009 May 18. NIH PA Author Manuscript NIH PA Author Manuscript NIH PA Author Manuscript and B6 mice are known to be prone to valvulopathy induced by high fat diet, the EGFR inhibitors likely enhance diet induced valvular pathologies. EGFR inhibitors show gender specific effects It is well established that gender dramatically influences physiological and pathological responses to