P6376The role of circulating lymphocytes on hypertensive heart disease

Aims and background

Hypertension is a disease accompanied by moderate inflammation. Physical activity and pharmacological intervention protect the organisms against hypertension-dependent end-organ damage. They should therefore interfere with the mobilization of lymphocytes. Different subsets of lymphocytes should specifically interfere with vascular and cardiac remodeling. In this study we correlated the amount of circulating lymphocytes with the expression of vascular and cardiac specific genes in the aorta and left ventricle to identify the tissue-specific effects of these cells.

Methods

50 female spontaneously hypertensive rats (SHR) and 6 female normotensive Wistar rats (Wis) were analyzed. They were grouped in 7 subgroups exposed to different treatment regimes (modification of activity, type of activity, aldosterone blockade, and a combination thereof. Indicator genes of mal-adaptive vascular and cardiac remodeling were quantified by qRT-PCR.

Results

SHRs had an increased number of circulating NK cells and monocytes, but lower numbers of T cells. T cells inversely correlated with the vascular expression of p22phox, a member of the NADPH oxidase complex. Thus, lower number of T-cells favors the vascular expression of p22phox and thereby oxidative stress. In the left ventricle, T cells are inversely correlated with the expression of arginase-1 and UCP-2 but positively correlated with Glut-4 expression. The lower number of T cells in SHR therefore favors the expression of proteins often associated with oxidative stress and glucose metabolism. Monocytes are positively correlated with key markers of left ventricular hypertrophy (such as ANP, collagen-1, and β-MHC). Thus, the increased number of monocytes in SHRs supports cardiac hypertrophy. NK cells are inversely correlated with the expression of anti-inflammatory cytokines in the aorta (IL-10, IL-15). Thus, high number of circulating NK cells seems to favor a pro-inflammatory phenotype in the vasculature.

Conclusion

In a standard model of essential hypertension the profile of circulating lymphocytes differs from that in normotensive rats. The different subsets of lymphocytes specifically interfere with specific processes in the ventricle and vessel. Collectively, the difference between hypertensive and normotensive rats (less T cells, more NK cells and monocytes) supports a mal-adaptive role under hypertensive conditions.

P6372Does modification of activity regimes optimize the effect of high physical activity on hypertensive heart disease?

Aims and background

Spontaneously hypertensive rats (SHR) are a suitable model of essential hypertension and allow analyze the progression of hypertension and hypertension-dependent end-organ damage. In this model, acute improvement of physical activity (free running wheel activity) exerts known beneficial effects (such as lowering oxidative stress). However, these initial beneficial effects are lost during the continuation of high physical activity and translate into mal-adaptive processes, suggesting that not any high physical activity exerts beneficial effects. It has been hypothesized that the skeletal muscle release myokines, that contribute to the beneficial effects of exercise. However, myokines, such as IL-6, are induced by an acute increase in work load not by continuous work load. Therefore, we analyzed whether modification of high physical activity, i.e. intermittent free running wheel activity, modify the long-term impact on long lasting hypertension.

Methods

38 female SHR aged 6 weeks (pre-hypertensive state) were randomly allocated to one of the following groups: Sedentary (S; standard holding condition) imitating the condition of sedentary life style, high activity (HA; life-long free running wheel) imitating the condition of active life style, temporary activity (TA; 6 months free running wheel and 3 months sedentary) imitating the loss of active life style during ageing, and finally intermittent activity (IA; 10 months repetitive access to running wheels every 4 weeks) imitating altered workloads. All rats were sacrificed at the age of 10 months.

Results

IA was the only treatment regime that effectively lowered blood pressure (P syst: 186±11 vs. 165±6 mmHg), improved ejection fraction (EF: 56±5 vs. 63±2%), and displayed clear molecular profile of adaptive myocardial hypertrophy rather than mal-adaptive hypertrophy. Moreover, only IA reduced the number of circulating monocytes (377±102 vs. 220±16 /μl), a cell population that immigrated in the left ventricle. The number of monocytes was directly correlated with the expression of MMP12, BNP, ANP, biglycan, collagen-1, actinin, β-MHC, and somatstatin but inversely related to β-adrenoceptor, Glut-4, and UCP3 expression. Finally, IA increased the skeletal expression of IL-6 and decreased the renal expression of AT1 receptors.

Conclusion

The data confirm the previous findings that not all type of physical activity beneficially affects hypertensive-dependent disease. In contrast, the data support the hypothesis that alterations in work load are required triggering the release of myokines from the skeletal muscle and identify the amount of circulating monocytes as a main trigger of mal-adaptive hypertrophy in these rats. The data are important with respect to optimize life style suggestions for patients with essential hypertension.

Acknowledgement/Funding

DFG (ERAGON and SFB 1213)

Cardiac effects of osteostatin in mice

Mouse parathyroid hormone-related peptide (PTHrP) is a peptide hormone consisting of 139 amino acids. It is target of proteolysis resulting in circulation of N- and C-terminal peptides. C-terminal PTHrP peptides act in a PTH/PTHrP receptor-independent way with a minimal peptide sequence required to exert these effects covering amino acids 107-111 also known as osteostatin. Although effects of osteostatin on cardiac hypertrophy have been described in vitro, the in vivo relevance of these findings remained to be defined. The study was performed in two experimental series. In the first series, mice were randomly distributed into placebo or treatment group (each n=7) and osteostatin was administered via osmotic minipumps. In the second series, mice underwent a banding of the thoracic aorta to induce pressure overload and were again randomly distributed into placebo or treatment group (n=9 each). After 14 days, mice were anaesthetized and cardiac function, ECG, and cardiac hypertrophy were determined. Osteostatin increased the expression of ANF and reduced P-wave duration with little effects on cardiac performance in mice without pressure overload. In TAC banded mice, however, osteostatin significantly reduced TAC-induced loss of body weight, induced right ventricular hypertrophy, and reduced P-wave duration again. In osteostatin treated mice with pressure overload, the protein kinase C-dependent phosphorylation of connexin 43 was preserved. In summary, osteostatin attenuated pressure-overload-dependent loss of body weight without affecting left ventricular hypertrophy or left ventricular function but preserved atrial conduction. Osteostatin exerts moderate cardioprotective effects in mice under hemodynamic stress.