Downregulation of myogenic microRNAs in sub-chronic but not in sub-acute model of daunorubicin-induced cardiomyopathy.

Cardiac muscle-related microRNAs play important roles in cardiac development and disease by translational silencing of mRNAs, the dominant mechanism of microRNA action. To test whether they could be involved in daunorubicin-associated cardiomyopathy (DACM), we determined expression patterns of myomiRs in two distinct models of DACM. We used 10-12 weeks old male Wistar rats. In the sub-acute model, rats were administered with six doses of daunorubicin (DAU-A, 3 mg/kg, i.p., every 48 h). Rats were sacrificed two days after the last dose. In the sub-chronic model, anaesthetized rats were administered a single dose of daunorubicin (15 mg/kg, i.v., DAU-C). Age-matched controls (CON) received vehicle. Rats were sacrificed eight weeks later. Left ventricular (LV) functions (LV pressure, rate of pressure development, +dP/dt and decline, -dP/dt) were measured using left ventricular catheterization. Expressions of myomiRs (miR-208a, miR-499, miR-1 and miR-133a), markers of cardiac failure (atrial and brain natriuretic peptides genes; Nppa and Nppb) and myosin heavy chain genes (Myh6, Myh7, Myh7b) in cardiac tissue were determined by RT-PCR. Protein expression of gp91phox NADPH oxidase subunit was detected by immunoblotting. Both DAU groups exhibited a similar depression of LV function, and LV weight reduction, accompanied by an upregulation of natriuretic peptides, and a decrease of Myh6 to total Myh ratio (-18% in DAU-A and - 25% in DAU-C, as compared to controls; both P < 0.05). DAU-C, but not DAU-A rats had a 35% mortality rate and exhibited a significantly increased gp91phox expression (DAU-C: 197 ± 33 versus CON-C: 100 ± 11; P < 0.05). Interestingly, myomiRs levels were only reduced in DAU-C compared to CON-C (miR-208: -45%, miR-499: -30%, miR-1: -29%, miR- and miR133a: -25%; all P < 0.05) but were unaltered in DAU-A. The lack of myomiRs expression, particularly in sub-chronic model, suggests the loss of control of myomiRs network on late progression of DACM. We suppose that the poor inhibition of mRNA targets might contribute to chronic DACM.

Local and systemic renin-angiotensin system participates in cardiopulmonary-renal interactions in monocrotaline-induced pulmonary hypertension in the rat.

Renin-angiotensin system (RAS) is one of the pathophysiological mechanisms in heart failure. Recently, involvement of the kidney in the disease progression has been proposed in patients with pulmonary arterial hypertension (PAH). We hypothesized that local and systemic RAS could be the central regulators of cardiopulmonary-renal interactions in experimental monocrotaline-induced pulmonary hypertension (PH) in rats. Male 12-week-old Wistar rats were injected subcutaneously with monocrotaline (60 mg/kg). The experiment was terminated 4 weeks after monocrotaline administration. Using RT-PCR, we measured the expression of RAS-related genes in right and left ventricles, lungs and kidneys, together with indicators of renal dysfunction and damage. We observed a significantly elevated expression of angiotensin-converting enzyme (ACE) in both left and right ventricles and kidneys (P < 0.05), but a significantly decreased ACE in the lungs (P < 0.05). Kidneys showed a significant 2.5-fold increase in renin mRNA (P < 0.05) along with erythropoietin, TGFß1, COX-2, NOS-1 and nephrin. Expression of erythropoietin correlated inversely with hemoglobin oxygen saturation and positively with renin expression. In conclusion, monocrotaline-induced PH exhibited similar alterations of ACE expression in the left and right ventricles, and in the kidney, in contrast to the lungs. Increased renal renin was likely a consequence of renal hypoxia/hypoperfusion, as was increased renal erythropoietin expression. Alterations in RAS in the monocrotaline model are probably a result of hypoxic state, and while they could serve as a compensatory mechanism at a late stage of the disease, they could be viewed also as an indicator of multiorgan failure in PAH.

Ramipril restores PPARß/δ and PPARγ expressions and reduces cardiac NADPH oxidase but fails to restore cardiac function and accompanied myosin heavy chain ratio shift in severe anthracycline-induced cardiomyopathy in rat.

We hypothesized that peroxisome proliferator-activated receptors (PPARs) might be involved in a complex protective action of ACE inhibitors (ACEi) in anthracyclines-induced cardiomyopathy. For purpose of study, we compared effects of ramipril on cardiac dysfunction, cardiac failure markers and PPAR isoforms in moderate and severe chronic daunorubicin-induced cardiomyopathy. Male Wistar rats were administered with a single intravenous injection of daunorubicin: 5mg/kg (moderate cardiomyopathy), or 15mg/kg (severe cardiomyopathy) or co-administered with daunorubicin and ramipril (1mg/kg/d, orally) or vehicle for 8 weeks. Left ventricular function was measured invasively under anesthesia. Cardiac mRNA levels of heart failure markers (ANP, Myh6, Myh7, Myh7b) and PPARs (alpha, beta/delta and gama) were measured by qRT-PCR. Protein expression of NADPH subunit (gp91phox) was measured by Western blot. Moderate cardiomyopathy exhibited only minor cardiac dysfunction what was corrected by ramipril. In severe cardiomyopathy, hemodynamic dysfunction remained unaltered upon ramipril although it decreased the significantly up-regulated cardiac ANP mRNA expression. Simultaneously, while high-dose daunorubicin significantly decreased PPARbeta/delta and PPARgama mRNA, ramipril normalized these abnormalities. Similarly, ramipril reduced altered levels of oxidative stress-related gp91phox. On the other hand, ramipril was unable to correct both the significantly decreased relative abundance of Myh6 and increased Myh7 mRNA levels, respectively. In conclusion, ramipril had a protective effect on cardiac function exclusively in moderate chronic daunorubicin-induced cardiomyopathy. Although it normalized abnormal PPARs expression and exerted also additional protective effects also in severe cardiomyopathy, it was insufficient to influence impaired cardiac function probably because of a shift in myosin heavy chain isoform content.