Upregulation of Myocardial and Vascular Phosphodiesterase 9A in A Model of Atherosclerotic Cardiovascular Disease

Abstract

Atherosclerosis is strongly associated with cardiac dysfunction and heart failure. Besides microvascular dysfunction and diminishment of the cardiac nitric oxide-Protein Kinase G (NO-PKG) pathway, recent evidence suggests that phosphodiesterase 9A (PDE9A) enzyme has an unfavorable role in pathological changes. Here, we characterized a rabbit model that shows cardiac dysfunction as a result of an atherogenic diet, and examined the myocardial PDE9A signaling. Rabbits were divided into Control (normal diet) and HC (atherogenic diet) groups. Cardiac function was evaluated by echocardiography. Vascular function was assessed, along with serum biomarkers. Histological stains were conducted, expression of selected proteins and cyclic guanosine monophosphate (cGMP) levels were determined. Signs of diastolic dysfunction were shown in HC animals, along with concentric hypertrophy and interstitial fibrosis. Endothelial function was diminished in HC rabbits, along with marked reduction in the aortic lumen, and increased left ventricle outflow tract (LVOT) pressures. A significant increase was shown in myocardial PDE9A levels in HC animals with unchanged vasodilator-stimulated phosphoprotein (VASP) phosphorylation and cGMP levels. Upregulation of PDE9A may be associated with early stage of cardiac dysfunction in atherosclerotic conditions. Since PDE9A is involved in cGMP degradation and in deactivation of the cardioprotective PKG signaling pathway, it may become an encouraging target for future investigations in atherosclerotic diseases.

Changes of Hematological and Hemorheological Parameters in Rabbits with Hypercholesterolemia

“…The hypercholesterolemic rabbit model is a preferred model to study human atherosclerosis and lipoprotein metabolism [ 18 , 19 ]. It is well-known that rabbits are sensitive to dietary cholesterol and rapidly develop severe hypercholesterolemia which drives aortic atherosclerosis.…”

“…Very-low-density lipoprotein (VLDL) receptors are highly expressed in macrophages, this is also a similarity between rabbits and humans [ 11 ]. The larger arteries compared to the small rodent models allow the clinical evaluation: using MRI and ultrasound (echocardiography), morphological (plaque composition and structure) and functional changes (systolic, diastolic dysfunction) can be detected [ 18 , 19 ]. The atherosclerotic rabbit model is considered suitable to investigate numerous human diseases, however, it presents several limitations: e.g., the laboratory rabbits do not develop spontaneous atherosclerosis on a standard diet, because they have low cholesterol levels.…”

“…Symptoms of diastolic dysfunction were detected too. The serum lipid parameters, the atherogenic index, and ApoB/ApoA ratio were increased significantly in rabbits fed with additional 1% cholesterol and 1% saturated fat [ 19 ]. However, the limitations of the study include the low case number and the inter-species differences as mentioned above.…”

The Drug Candidate BGP-15 Delays the Onset of Diastolic Dysfunction in the Goto-Kakizaki Rat Model of Diabetic Cardiomyopathy

“…What concerns myocardial cGMP, is a limitation of this report that we did not directly measure cGMP levels, instead, we attempted to examine the expression of the cGMP-degrading enzyme PDE9A. Recent evidence suggests the role of PDE9A in regulation of natriuretic-peptide-derived cGMP levels and thus activity of PKG, further, upregulation of PDE9A was previously shown in cardiac dysfunction (traverse aortic constriction and atherosclerotic disease) models by others and our research team as well [44,45]. Based on the aforementioned data, we determined PDE9A levels in myocardial samples of animals, however, we failed to show significant differences between the treatment groups in this experimental setting.…”

“…Proteins were developed with enhanced chemiluminescense reagent (WesternBright™, ECL, Advansta Inc., Menlo Park, CA, USA) and the detection was accomplished by a C-Digit ® blot scanner with Image Studio Digits ver. 5.2. software (LI-COR Inc., Lincoln, NE, USA) [45]. Data was averaged from 3 independent experiment ( n = 6/group), and statistical analysis was carried out using Kruskal-Wallis test with Dunn’s post-test.…”