Angiotensin II Type I Receptor Antagonism Attenuates Nicotine-Induced Cardiac Remodeling, Dysfunction, and Aggravation of Myocardial Ischemia-Reperfusion Injury in Rats

Figure 1. Time-course for changes in (A) systolic blood pressure, systolic blood pressure, and (B) heart rate in rats administered with nicotine and irbesartan for 4 weeks. All values are given as mean ± SEM for n = 13–14/group; *P < 0.05 for vehicle vs. nicotine (NIC) group; and # P < 0.05 for NIC vs. NIC+Irb group using two-way ANOVA with Tukey post-hoc test.

Figure 2. Nicotine dysregulates systemic and cardiac angiotensin system. Levels of ANG II in the (A) blood plasma and (B) left ventricular (LV) tissues; relative gene expression of (C) ACE, (D) ACE2, (E) AT1, (F) AT2 normalized to 18S housekeeping gene, as well as (G) ratio of ACE : ACE2 and (H) ratio of AT1:AT2 in LV after 4 weeks of nicotine administration in rats. All values are given as mean ± SEM for n = 6 –7/group; *P < 0.05 vs. vehicle and # P < 0.05 vs. nicotine group using one-way ANOVA with Tukey post-hoc test. NS, no significant difference.

Figure 3. AT1 receptor antagonism attenuates nicotine-induced cardiomyocyte hypertrophy and fibrosis. Quantification of (A) cardiomyocyte cross-sectional area, cross-sectional area, and (B) collagen density in the left ventricular (LV) tissues with representative images of LV tissues stained with H&E or picrosirius red staining shown in (C). Relative gene expression of (D) atrial natriuretic peptide, (E) brain natriuretic peptide, (F) transforming growth factor β1, and (G) FN1 in LV tissues, normalized to 18S housekeeping gene after 4 weeks of nicotine administration. All values are given as mean ± SEM for n = 6 –7/group; *P < 0.05 vs. vehicle and # P < 0.05 vs. nicotine group using one-way ANOVA with Tukey post-hoc test.

Figure 4. AT1 receptor antagonism blunts nicotine-induced oxidative stress in heart. Quantification of (A) glutathione-to-glutathione disulphide ratio as well as (B) 3-nitrotyrosine deposition in left ventricular (LV) tissues with representative immunohistochemistry staining images of LV tissues probed for 3-nitrotyrosine (3-NT) shown in (C). (D) Mitochondrial reactive oxygen species production determined using MitoSOX in isolated rat heart mitochondria. (E) Relative gene expression of NOX2 in LV tissues, normalized to 18S housekeeping gene. (F) SOD2 activity and (G) Relative gene expression of SOD2 in LV tissues, normalized to 18S housekeeping gene after 4 weeks of nicotine administration. All values are given as mean ± SEM for n = 6 –7/group; *P < 0.05 vs. vehicle and # P < 0.05 vs. nicotine group using one-way ANOVA with Tukey post-hoc test. NS, no significant difference.

Figure 5. AT1 receptor antagonism limits nicotine-induced cardiac inflammation. Relative gene expression of (A) TNFα, (B) IL6, (C) IL10, (D) ANX-A1, and (E) FPR2 in left ventricular tissues, normalized to 18S housekeeping gene after 4 weeks of nicotine administration. All values are given as mean ± SEM for n = 6 –7/group; *P < 0.05 vs. vehicle and # P < 0.05 vs. nicotine group using one-way ANOVA with Tukey post-hoc test.

Figure 6. AT1 receptor antagonism abolishes nicotine-aggravation of post-ischemic left ventricle dysfunction. Time-course and area-under-curve (AUC) analysis for changes in (A–B) left ventricular developed pressure, (C–D) LV+dP/dt, (E–F) LV-dP/dt, and (G–H) left ventricular end-diastolic pressure in Langendorff-perfused rat hearts isolated from nicotine and irbesartan-administered rats during 20 min of ischemia and 60 min of reperfusion. All values are given as mean ± SEM for n = 7 –8/group; *P < 0.05 for control vs. nicotine (NIC) group; and # P < 0.05 for NIC vs. NIC+Irb group using two-way ANOVA with Tukey post-hoc test.

Figure 7. AT1 receptor antagonism prevents nicotine-induced post-ischemic impairment in coronary function and cardiomyocyte injury. Time-course and area-under-curve (AUC) analysis for changes in (A–B) coronary flow, (C–D) cardiac troponin T (cTnT) release, and (E–F) lactate dehydrogenase release from Langendorff-perfused rat hearts isolated from nicotine and irbesartan-administered rats during 20 min of ischemia and 60 min of reperfusion. All values are given as mean ± SEM for n = 7 –8/group; *P < 0.05 for control vs. nicotine (NIC) group; and # P < 0.05 for NIC vs. NIC+Irb group using two-way ANOVA with Tukey post-hoc test.