Chronic treatment with C-type natriuretic peptide shows beneficial effects on cardiac tissue and its function in spontaneously hypertensive rats

COSTA MARÍA DE LOS ÁNGELES; CANIFFI CAROLINA; SUEIRO LAURA; BOUCHET GONZALO; MUÑOZ FLORENCIA; TOBLLI JORGE; PRENTKI SANTOS ESTEFANÍA

Atenas

Congreso; Meeting ESH - ISH Hypertension 2014; 2014

European Society of Hypertension - International Society of Hypertension

Objective: C -type natriuretic peptide ( CNP ) is synthetized in cardiac tissue. It is known to regulate cardiovascular homeostasis though its effects on endothelial cells, fibroblast and cardiac myocytes. Due to its antihypertensive and cardioprotective action, it may be considered in the treatment of several cardiac pathologies. The aim of our work was to evaluate the effects of CNP chronic treatment on cardiac hypertrophy and its function and the study of interstitial fibrosis, the inflammatory state, oxidative stress and nitric oxide (NO) cardiac system in spontaneously hypertensive rats (SHR) and Wistar normotensive ones (W). Design and Methods : 12-week-old male SHR and W were infused through osmotic pumps with CNP ( 0.75 mg / hour) or saline (S) for 14 days. Systolic blood pressure (SBP, mmHg) was recorded by tail- cuff method and the function of the left ventricle (LV) determined by echocardiogram (heart rate, HR, bpm), end diastolic and systolic volume (EDV, ESV ml), systolic volume (SV ml) and cardiac output (CO in ml/min). Finalizing the treatment, animals were decapitated and the LV was extracted to study several morphometric parameters, such as the LV mass index (LVMI g LV/mm tibial longitude) and the myocyte area (um2) through Hematoxylin-Eosin stain, and fibrosis and inflammatory state in tissue slices through Picrosirius-Red-stain and IL-6 and TNFa immunohistochemistry (percentage of staining per mm2) respectively. Antioxidant glutathione peroxidase (Gpx, umol/min mg protein) and catalase (pmol/mg protein) enzymes activity were measured by spectrophotometric techniques. To evaluate the NO system, NO synthase (NOS) activity was determined through consumption of its radioactive substrate (pmol 14C L-citrulline/g.tissue.min) and the expression of its endothelial isoform (eNOS) quantified by Western Blot. Statistics: Two way ANOVA, Bonferroni post-test. Results: W-S W-CNP SHR-S SHR-CNP SBP 118±2 122±3 175±3* 159±5^ LVMI 0.023±0.002 0.024±0.001 0.032±0.001* 0.029±0.001 Myocyte area 348.9±11.0 337.4±10.1 609.1±39.4* 556.6±61.5 HR 427±15 440±10 435±10 434±15 ESV 0.05±0.01 0.04±0.01 0.05±0.02 0.07±0.03 EDV 0.21±0.03 0.22±0.04 0.16±0.02* 0.23±0.03^ SV 0.17±0.02 0.18±0.03 0.11±0.01* 0.16±0.02^ CO 80.80±8.00 82.40±10.32 47.85±2.01* 68.80±7,35^ % Fibrosis 1.54±0.53 1.78±0.17 6.81±0.40* 3.27±0.67^ NOS activity 197.7±5.8 344.6±7.9* 262.0±3.5* 361.7±3.6^ eNOS expression 1.00±0.13 1.11±0.13 1.02±0.08 1.05±0.18 Catalase 0.076±0.004 0.071±0.003 0.114±0.003* 0.105±0.002 Gpx 89.9±2.5 73.8±4.1 152.1±15.8* 141.2±6.8 IL-6 1,8±1,0 1,3±0,6 19,4±2,7* 2,1±0,7^ TNF-α 1,1±0,7 1,0±0,5 15,7±3,4* 1,5±0,9^ Conclusions : Characteristic high SBP values in SHR are accompanied by Hypertrophy, functional alterations, fibrosis, an upregulation of antioxidant systems and a higher presence of inflammatory cytokines. Although no morphometric parameters have changed, chronic treatment with CNP improves LV function and lowers fibrosis and pro-inflammatory markers in cardiac tissue as it increases NOS activity in SHR. Altogether, these beneficial effects could be causing the drop in SBP we observe in this model of hypertension.