Relevance of stretch-induced phosphorylation of MAPK and p90rsk in human myocardium.

Stretch activates various signal transduction pathways including mitogen-activated protein kinases (MAPK). Stretch-induced phosphorylation of MAPK-contribution to contractility in human myocardium is unknown. We tested the effects of stretch on p44/42-, p38-MAPK and p90rsk phosphorylation and the functional relevance for force development in failing (F) and non-failing (NF) human myocardium. Trabeculae were stretched to a diastolic tension of 12mN/mm2 for 2.5 to 30 minutes and frozen for Western Blot analysis. Stretch induced a time-dependent increase in phosphorylation of p44/42-, p38-MAPK and p90rsk. For functional analysis, trabeculae from F myocardium were stretched and the immediate (Frank-Starling mechanism; FSM) and delayed (slow force response; SFR) increase in twitch force was assessed before and after blocking the activation of p44/42-MAPK (30 micromol/L U0126) and p38-MAPK (10 micromol/L SB203580). Inhibition of p44/42-MAPK almost completely blocked the SFR (106.7 3.7% vs. 125.4 2.9%), while p38-MAPK-blockade significantly increased the SFR (124.6 1.9% vs. 121.2 2.2%). Stretch induced a time-dependent increase in p44/42-, p38-MAPK and p90rsk phosphorylation in F and NF myocardium. While p44/42-MAPK phosphorylation contributed to the SFR, p38-MAPK activation antagonized the stretch-induced SFR.

Impaired physical quality of life in patients with diastolic dysfunction associates more strongly with neurohumoral activation than with echocardiographic parameters: quality of life in diastolic dysfunction.

BACKGROUND: Quality of life (QoL) is impaired in diastolic heart failure. Little is known about QoL in diastolic dysfunction (DD) without heart failure. METHODS: In the DIAST-CHF observational study, outpatients with risk factors for or a history of heart failure were included. In a cross-sectional analysis, we classified patients with preserved systolic function as having normal diastolic function (N, n = 264) or DD without (DD-, n = 957) or with (DD+, n = 321) elevated filling pressures according to echocardiography. Quality of life was evaluated by the Short Form 36 (SF-36) questionnaire. RESULTS: Short Form 36 physical function (SF-36-PF) was worse in DD+ (mean ± SD 67.2 ± 25.6) than in DD- (76.2 ± 22.7, P < .05) than in N (mean ± SD 81.1 ± 23.5, P < .01). Other physical dimensions and the physical component score were also lower in DD, whereas the mental component score did not differ. The SF-36-PF correlated weakly with echocardiographic indicators of diastolic function. In multivariate linear regression controlling for age, sex, body mass index, depressiveness as assessed by Patient Health Questionnaire 9, N-terminal probrain-type natriuretic peptide, and midregional proadrenomedullin (MR-proADM), individual echocardiographic parameters or grade of DD was not independently associated with SF-36-PF, whereas the presence of DD+ was. Both N-terminal probrain-type natriuretic peptide and MR-proADM were independently associated with SF-36-PF, with MR-proADM showing the stronger association. CONCLUSIONS: Physical dimensions of QoL are reduced in DD. Impaired SF-36-PF is only weakly associated with DD per se but rather seems to be contingent on the presence of elevated filling pressures. Biomarkers are more strongly and independently associated with SF-36-PF and may be more adequate surrogate markers of QoL in DD than echocardiographic measurements.

The novel biomarker growth differentiation factor 15 in heart failure with normal ejection fraction.

AIMS: Heart failure with normal ejection fraction (HFnEF) is an important clinical entity that remains incompletely understood. The novel biomarker growth differentiation factor 15 (GDF-15) is elevated in systolic heart failure (HFrEF) and is predictive of an adverse outcome. We investigated the clinical relevance of GDF-15 plasma levels in HFnEF. METHODS AND RESULTS: A subgroup of patients from the ongoing DIAST-CHF observational trial, with a history of chronic heart failure (CHF) or positive Framingham criteria at presentation, was selected. Patients were classified as having either HFrEF (n=86) or HFnEF (n=142) and compared with healthy elderly controls (n=188) from the same cohort. Growth differentiation factor 15 levels in HFnEF were significantly higher than in controls and similar to those in HFrEF. In multivariate analysis, factors significantly associated with GDF-15 levels were age, sex, estimated glomerular filtration rate (eGFR), presence of HFrEF and HFnEF. Growth differentiation factor 15 correlated with multiple echocardiographic markers of diastolic function and was associated with 6 min walk test performance and SF-36 physical score on multivariate analysis in all patients. When using a classification for HFnEF that did not employ N-terminal pro brain natriuretic peptide (NT-proBNP) as a diagnostic criterion, the diagnostic properties of GDF-15 for detecting HFnEF tended to be superior to those of NT-proBNP, and a combination significantly improved diagnostic accuracy. CONCLUSION: Growth differentiation factor 15 is elevated in HFnEF to a similar degree as in HFrEF. It is independently associated with impairment in exercise capacity and in physical components of quality of life. Diagnostic precision of GDF-15 is at least as good as that of NT-proBNP and combining both markers improves diagnostic accuracy.

Angiotensin II and myosin light-chain phosphorylation contribute to the stretch-induced slow force response in human atrial myocardium.

AIMS: Stretch is an important regulator of atrial function. The functional effects of stretch on human atrium, however, are poorly understood. Thus, we characterized the stretch-induced force response in human atrium and evaluated the underlying cellular mechanisms. METHODS AND RESULTS: Isometric twitch force of human atrial trabeculae (n = 252) was recorded (37 degrees C, 1 Hz stimulation) following stretch from 88 (L88) to 98% (L98) of optimal length. [Na(+)](i) and pH(i) were measured using SBFI and BCECF epifluorescence, respectively. Stretch induced a biphasic force increase: an immediate increase [first-phase, Frank-Starling mechanism (FSM)] to approximately 190% of force at L88 followed by an additional slower increase [5-10 min; slow force response (SFR)] to approximately 120% of the FSM. FSM and SFR were unaffected by gender, age, ejection fraction, and pre-medication with major cardiovascular drugs. There was a positive correlation between the amplitude of the FSM and the SFR. [Na(+)](i) rose by approximately 1 mmol/L and pH(i) remained unchanged during the SFR. Inhibition of Na(+)/H(+)-exchange (3 microM HOE642), Na(+)/Ca(2+)-exchange (5 microM KB-R7943), or stretch-activated channels (0.5 microM GsMtx-4 and 80 microM streptomycin) did not reduce the SFR. Inhibition of angiotensin-II (AngII) receptors (5 microM saralasin and 0.5 microM PD123319) or pre-application of 0.5 microM AngII, however, reduced the SFR by approximately 40-60%. Moreover, stretch increased phosphorylation of myosin light chain 2 (MLC2a) and inhibition of MLC kinase (10 microM ML-7 and 5 microM wortmannin) decreased the SFR by approximately 40-85%. CONCLUSION: Stretch elicits a SFR in human atrium. The atrial SFR is mediated by stretch-induced release and autocrine/paracrine actions of AngII and increased myofilament Ca(2+) responsiveness via phosphorylation of MLC2a by MLC kinase.