M.Sc. (Med.)--Faculty of Health Sciences, University of the Witwatersrand, 2011 / In-part through a decrease in cardiac cavity dimensions (reverse remodelling), β-adrenergic receptor blockers have been demonstrated to produce marked benefits to morbidity and mortality in patients with chronic heart failure. However, maximum doses of these agents are often difficult to achieve in patients with chronic heart failure because of the negative inotropic, hypotensive and other side effects. Whether blockade of the excessive adrenergic effects achieves complete reverse remodelling in progressive heart failure is nevertheless uncertain. To test this hypothesis I simulated the adverse effects of chronic adrenergic stimulation on the heart by administering daily doses of the β-adrenergic receptor agonist, isoproterenol (ISO) (2.42 X 10-8 mmol.kg-1) to rats for 6 months and compared left ventricular (LV) dimensions and systolic function to Saline-vehicle treated rats. To imitate the effects of complete adrenergic receptor blockade following the development of adrenergic-induced adverse cardiac changes, I similarly administered ISO for 6 months and then subsequently withdrew the daily ISO administration for a further 4 months (ISO+Recovery) before comparing left ventricular dimensions and function to Saline+Recovery treated rats. In comparison to a Saline vehicle-treated group, after 6 months of ISO administration, LV end diastolic and systolic diameters, and the volume intercept of the left ventricular diastolic pressure-volume relationship (LV V0), were markedly increased and LV endocardial fractional shortening (FSend), LV end systolic chamber (slope of the systolic pressure-volume relationship-Ees) and myocardial (slope of the systolic stress-strain relationship-En) contractility were substantially decreased. The extent of the adverse remodelling produced by chronic ISO administration was exemplified by the 2.5 times increase in LV V0 (ISO=0.40±0.04 vs Saline=0.16±0.01, p<0.001), a change proportionate to that noted in humans with chronic heart failure. iii The proportion of ISO-treated rats with LV chamber diameters, and LV V0 values above the 95% confidence interval for Saline-treated rats was markedly greater than the proportion of Saline-treated rats above their own 95% confidence intervals. Moreover, the proportion of ISO-treated rats with FSend, LV Ees and LV En values below the 95% confidence interval for Saline-treated rats was markedly greater than the proportion of Saline-treated rats below their own 95% confidence intervals. Following a 6 month period of ISO administration and a subsequent period of withdrawal of ISO administration for a further 4 months, LV chamber diameters, LV V0, FSend, LV Ees and LV En were all noted to be similar to age-matched Saline+Recovery control rats. Indeed, the increases in LV V0 observed after 6 months of ISO administration were completely reversed (ISO+Recovery=0.21±0.02 vs Saline=0.23±0.02, p<0.001). The proportion of ISO+Recovery rats with LV chamber diameters, and LV V0 values above the 95% confidence interval for the Saline+Recovery rats was similar to the proportion of Saline+Recovery rats above their own 95% confidence intervals. Moreover, the proportion of ISO+Recovery rats with FSend, LV Ees and LV En values below the 95% confidence interval for Saline+Recovery rats was similar to the proportion of Saline+Recovery rats below their own 95% confidence intervals. Chronic ISO administration and the withdrawal of ISO administration was not associated with changes in myocardial necrosis (pathological score and myocardial collagen concentrations). In conclusion, marked cardiac dilatation and pump dysfunction produced by chronic β-adrenergic receptor activation can be completely reversed by withdrawal of the excessive adrenergic stimulus. These data highlight the importance in chronic heart failure of achieving complete blockade of the pathways activated by excessive β-adrenergic receptor stimulation even in individuals with advanced cardiac dilatation.

Cerebral perfusion is optimized during hemodilution by both β1- and β2-adrenergic mechanisms. Antagonism of the β2-adrenoreceptor can impair cerebral vasodilation. We hypothesized that treatment with a highly β1-specific antagonist (nebivolol) would minimize the degree of cerebral hypoxia during hemodilution. Anesthetized rats were randomized to receive vehicle or nebivolol (1.25 or 2.5 mg/kg intravenously) prior to hemodilution. In vehicle-treated rats, hemodilution increased cardiac output (CO) and regional cerebral blood flow (rCBF) while microvascular brain PO2 (PBrO2) decreased. Both nebivolol doses reduced heart rate and attenuated the CO response to hemodilution. Only the higher dose of nebivolol attenuated the rCBF response to hemodilution and caused a further reduction in PBrO2. Brain hypoxic protein levels were only increased in the high dose nebivolol group. High dose nebivolol treatment resulted in drug levels near its affinity for the β2-adrenoreceptor supporting the hypothesis that cerebral perfusion is maintained by β2-dependent mechanisms during hemodilution.

Cerebral perfusion is optimized during hemodilution by both β1- and β2-adrenergic mechanisms. Antagonism of the β2-adrenoreceptor can impair cerebral vasodilation. We hypothesized that treatment with a highly β1-specific antagonist (nebivolol) would minimize the degree of cerebral hypoxia during hemodilution. Anesthetized rats were randomized to receive vehicle or nebivolol (1.25 or 2.5 mg/kg intravenously) prior to hemodilution. In vehicle-treated rats, hemodilution increased cardiac output (CO) and regional cerebral blood flow (rCBF) while microvascular brain PO2 (PBrO2) decreased. Both nebivolol doses reduced heart rate and attenuated the CO response to hemodilution. Only the higher dose of nebivolol attenuated the rCBF response to hemodilution and caused a further reduction in PBrO2. Brain hypoxic protein levels were only increased in the high dose nebivolol group. High dose nebivolol treatment resulted in drug levels near its affinity for the β2-adrenoreceptor supporting the hypothesis that cerebral perfusion is maintained by β2-dependent mechanisms during hemodilution.

京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第19551号 / 医博第4058号 / 新制||医||1012(附属図書館) / 32587 / 京都大学大学院医学研究科医学専攻 / (主査)教授 川口 義弥, 教授 坂井 義治, 教授 羽賀 博典 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

Das Mammakarzinom ist weltweit eine der häufigsten Malignomerkrankung der Frau. Im fortgeschrittenen Stadium der Erkrankung entwickeln bis zu 75 % der Patientinnen ossäre Metastasen. Basierend auf der Erkenntnis, dass GnRH-Analoga in vitro die Migration und Invasion von Mammakarzinomzellen während der Kokultur mit humanen Osteoblasten bzw. der Osteoblasten-ähnlichen Zellreihe MG-63 hemmen, sollten in dieser Arbeit die dem zugrundeliegenden molekularen Mechanismen näher betrachtet werden. Es ist bekannt, dass GnRH-Analoga in vielen verschiedenen GnRH-Rezeptor exprimierenden Tumorzelllinen die Wachstumsfaktor- und Wachstumsfaktorrezeptor-Expression beeinflussen und somit z.B. antiproliferative oder Apoptose-induzierende Effekte vermitteln. In dieser Arbeit wurde die humane Mammakarzinomzelllinie MCF-7 mit der osteoblasten-ähnlichen Zellreihe MG-63 kokultiviert. Zu bestimmten Zeitpunkten erfolgte die Behandlung der Mammakarzinomzellen mit drei verschiedenen GnRH-Analoga. Dem GnRH-I-Agonisten Triptorelin, dem GnRH-I-Antagonisten Cetrorelix und dem GnRH-II-Agonisten [D-Lysin]-GnRH-II. Neben einer nicht-kokultivierten Kontrolle jeder Zelllinie wurde eine nicht behandelte Kokulturkontrolle mitgeführt. Nach 48 h (bzw. nach 72 h od. 96 h) wurde der Versuch beendet und die mRNA-Expression von EGF, EGFR, TGF-beta und TGFBRI und -II in MCF-7 und MG-63 mittels PCR bestimmt. Zudem wurde die mRNA-Expression von EGF, EGFR und TGF-beta auch nach längerer Kokultur- und Behandlungszeit sowie unter Stressbedingungen beobachtet. Es hat sich gezeigt, dass es weder in MG-63 noch in MCF-7 signifikante Expressionsunterschiede von EGF, EGFR und TGF-beta im Vergleich zur Kokulturkontrolle gab. Dies hat sich auch weder im Zeitverlauf noch unter Stressbedingungen geändert. In MG-63 konnte man ebenfalls keine Expressionsunterschiede der TGFB-Rezeptoren beobachten. Dagegen konnte erstmals gezeigt werden, dass alle drei GnRH-Analoga die mRNA-Expression des TGFBR-I und -II während der Kokultur mit der osteoblasten-ähnlichen Zellreihe MG-63 signifikant hemmen. Während man in anderen Gewebetypen bereits eine verminderte Expression von TGFBR-I und -II nach Behandlung mit GnRH-Analoga nachweisen konnte, ist dies erstmals in einer Mammakarzinomzelllinie gelungen. Desweiteren kann man aus den vorliegenden Ergebnissen den Schluss ziehen, dass die verminderte Expression der TGFB-Rezeptoren eine Rolle in der bereits nachgewiesene GnRH-Analoga-vermittelten Migrations- und Invasionshemmung spielt.