Impact of combined clenbuterol and metoprolol therapy on reverse remodelling during mechanical unloading.
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ABSTRACT: Background
Clenbuterol (Cl), a β2 agonist, is associated with enhanced myocardial recovery during left ventricular assist device (LVAD) support, and exerts beneficial remodelling effects during mechanical unloading (MU) in rodent heart failure (HF). However, the specific effects of combined Cl+β1 blockade during MU are unknown.Methods and results
We studied the chronic effects (4 weeks) of β2-adrenoceptor (AR) stimulation via Cl (2 mg/kg/day) alone, and in combination with β1-AR blockade using metoprolol ((Met), 250 mg/kg/day), on whole heart/cell structure, function and excitation-contraction (EC) coupling in failing (induced by left coronary artery (LCA) ligation), and unloaded (induced by heterotopic abdominal heart transplantation (HATx)) failing rat hearts. Combined Cl+Met therapy displayed favourable effects in HF: Met enhanced Cl's improvement in ejection fraction (EF) whilst preventing Cl-induced hypertrophy and tachycardia. During MU combined therapy was less beneficial than either mono-therapy. Met, not Cl, prevented MU-induced myocardial atrophy, with increased atrophy occurring during combined therapy. MU-induced recovery of Ca2+ transient amplitude, speed of Ca2+ release and sarcoplasmic reticulum Ca2+ content was enhanced equally by Cl or Met mono-therapy, but these benefits, together with Cl's enhancement of sarcomeric contraction speed, and MU-induced recovery of Ca2+ spark frequency, disappeared during combined therapy.Conclusions
Combined Cl+Met therapy shows superior functional effects to mono-therapy in rodent HF, but appears inferior to either mono-therapy in enhancing MU-induced recovery of EC coupling. These results suggest that combined β2-AR simulation +β1-AR blockade therapy is likely to be a safe and beneficial therapeutic HF strategy, but is not as effective as mono-therapy in enhancing myocardial recovery during LVAD support.
SUBMITTER: Navaratnarajah M
PROVIDER: S-EPMC4181979 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:AimsCombined left ventricular assist device (LVAD) and pharmacological therapy has been proposed to favour myocardial recovery in patients with end-stage heart failure (HF). Clenbuterol (Clen), a beta(2)-adrenoceptor (beta(2)-AR) agonist, has been used as a part of this strategy. In this study, we investigated the direct effects of clenbuterol on unloaded myocardium in HF.Methods and resultsLeft coronary artery ligation or sham operation was performed in male Lewis rats. After 4-6 weeks, heterotopic abdominal transplantation of the failing hearts into normal recipients was performed to induce LV unloading (UN). Recipient rats were treated with saline (Sal) or clenbuterol (2 mg/kg/day) via osmotic minipumps (HF + UN + Sal or HF + UN + Clen) for 7 days. Non-transplanted HF animals were treated with Sal (Sham + Sal, HF + Sal) or clenbuterol (HF + Clen). LV myocytes were isolated and studied using optical, fluorescence, and electrophysiological techniques. Clenbuterol treatment improved in vivo LV function measured with echocardiography (LVEF (%): HF 35.9 +/- 2 [16], HF + Clen 52.1 +/- 1.4 [16]; P < 0.001; mean +/- SEM [n]). In combination with unloading, clenbuterol increased sarcomere shortening (amplitude (microm): HF + UN + Clen 0.1 +/- 0.01 [50], HF + UN + Sal 0.07 +/- 0.01 [38]; P < 0.001) by normalizing the depressed myofilament sensitivity to Ca(2+) (slope of the linear relationship between Ca(2+) transient and sarcomere shortening hysteresis loop during relaxation (microm/ratio unit): HF + UN + Clen 2.13 +/- 0.2 [52], HF + UN + Sal 1.42 +/- 0.13 [38]; P < 0.05).ConclusionClenbuterol treatment of failing rat hearts, alone or in combination with mechanical unloading, improves LV function at the whole-heart and cellular levels by affecting cell morphology, excitation-contraction coupling, and myofilament sensitivity to calcium. This study supports the use of this drug in the strategy to enhance recovery in HF patients treated with LVADs and also begins to elucidate some of the possible cellular mechanisms responsible for the improvement in LV function.
| S-EPMC5436743 | biostudies-literature
Project description:Space travel and prolonged bed rest are examples of mechanical unloading that induce significant muscle and bone loss. The compromised structure and function of bone and muscle owing to unloading make the reloading period a high risk for injury. To explore interactions between skeletal bone and muscle during reloading, we hypothesized that acute external mechanical loading of bone in combination with re-ambulation facilitates the proportional recovery of bone and muscle lost during hind limb suspension (HLS) unloading. Adult male C57Bl/6J mice were randomly assigned to a HLS or time-matched ground control (GC) group. After 2-weeks of HLS, separate groups of mice were studied at day 14 (no re-ambulation), day 28 (14 days re-ambulation) and day 56 (42 days re-ambulation); throughout the re-ambulation period, one limb received compressive mechanical loading and the contralateral limb served as an internal control. HLS induced loss of trabecular bone volume (BV/TV; -51 ± 2%) and muscle weight (-15 ± 2%) compared to GC at day 14. At day 28, the left tibia (re-ambulation only) of HLS mice had recovered approximately 20% of BV/TV lost during HLS, while the right tibia (re-ambulation and acute external mechanical loading) recovered to GC values of BV/TV (~100% recovery). At day 56, the right tibia continued to recover bone for some outcomes (trabecular BV/TV, trabecular thickness), while the left limb did not. Cortical bone displayed a delayed response to HLS, with a 10% greater decrease in BV/TV at day 28 compared to day 14. In contrast to bone, acute external mechanical loading during the re-ambulation period did not significantly increase muscle mass or protein synthesis in the gastrocnemius, compared to re-ambulation alone. Our results suggest acute external mechanical loading facilitates the recovery of bone during reloading following HLS unloading, but this does not translate to a concomitant recovery of muscle mass.
| S-EPMC7712877 | biostudies-literature
Project description:This study investigates alterations in myocardial microvasculature, fibrosis, and hypertrophy before and after mechanical unloading of the failing human heart.Recent studies demonstrated the pathophysiologic importance and significant mechanistic links among microvasculature, fibrosis, and hypertrophy during the cardiac remodeling process. The effect of left ventricular assist device (LVAD) unloading on cardiac endothelium and microvasculature is unknown, and its influence on fibrosis and hypertrophy regression to the point of atrophy is controversial.Hemodynamic data and left ventricular tissue were collected from patients with chronic heart failure at LVAD implant and explant (n = 15) and from normal donors (n = 8). New advances in digital microscopy provided a unique opportunity for comprehensive whole-field, endocardium-to-epicardium evaluation for microvascular density, fibrosis, cardiomyocyte size, and glycogen content. Ultrastructural assessment was done with electron microscopy.Hemodynamic data revealed significant pressure unloading with LVAD. This was accompanied by a 33% increase in microvascular density (p = 0.001) and a 36% decrease in microvascular lumen area (p = 0.028). We also identified, in agreement with these findings, ultrastructural and immunohistochemical evidence of endothelial cell activation. In addition, LVAD unloading significantly increased interstitial and total collagen content without any associated structural, ultrastructural, or metabolic cardiomyocyte changes suggestive of hypertrophy regression to the point of atrophy and degeneration.The LVAD unloading resulted in increased microvascular density accompanied by increased fibrosis and no evidence of cardiomyocyte atrophy. These new insights into the effects of LVAD unloading on microvasculature and associated key remodeling features might guide future studies of unloading-induced reverse remodeling of the failing human heart.
| S-EPMC3052413 | biostudies-literature
Project description:Mechanical unloading simultaneously induces muscle and bone loss, but its mechanisms are not fully understood. The interactions between skeletal muscle and bone have been recently noted. Although canonical wingless-related integration site (Wnt)/β-catenin signaling is crucial for bone metabolism, its roles in the muscle and bone interactions have remained unknown. Here, we performed comprehensive DNA microarray analyses to clarify humoral factors linking muscle to bone in response to mechanical unloading and hypergravity with 3 g in mice. We identified Dickkopf (Dkk) 2, a Wnt/β-catenin signaling inhibitor, as a gene whose expression was increased by hindlimb unloading (HU) and reduced by hypergravity in the soleus muscle of mice. HU significantly elevated serum Dkk2 levels and Dkk2 mRNA levels in the soleus muscle of mice whereas hypergravity significantly decreased those Dkk2 levels. In the simple regression analyses, serum Dkk2 levels were negatively and positively related to trabecular bone mineral density and mRNA levels of receptor activator of nuclear factor-kappa B ligand (RANKL) in the tibia of mice, respectively. Moreover, shear stress significantly suppressed Dkk2 mRNA levels in C2C12 cells, and cyclooxygenase inhibitors significantly antagonized the effects of shear stress on Dkk2 expression. On the other hand, Dkk2 suppressed the mRNA levels of osteogenic genes, alkaline phosphatase activity and mineralization, and it increased RANKL mRNA levels in mouse osteoblasts. In conclusion, we showed that muscle and serum Dkk2 levels are positively and negatively regulated during mechanical unloading and hypergravity in mice, respectively. An increase in Dkk2 expression in the skeletal muscle might contribute to disuse- and microgravity-induced bone and muscle loss.
| S-EPMC7177709 | biostudies-literature
Project description:PurposeCardiac resynchronisation therapy (CRT) improves left ventricular (LV) function acutely, with further improvements and reverse remodelling during chronic CRT. The current study investigated the relation between acute improvement of LV systolic function, acute mechanical recoordination, and long-term reverse remodelling after CRT.MethodsIn 35 patients, LV speckle tracking longitudinal strain, LV volumes & ejection fraction (LVEF) were assessed by echocardiography before, acutely within three days, and 6 months after CRT. A subgroup of 25 patients underwent invasive assessment of the maximal rate of LV pressure rise (dP/dtmax,) during CRT-implantation. The acute change in dP/dtmax, LVEF, systolic discoordination (internal stretch fraction [ISF] and LV systolic rebound stretch [SRSlv]) and systolic dyssynchrony (standard deviation of peak strain times [2DS-SD18]) was studied, and their association with long-term reverse remodelling were determined.ResultsCRT induced acute and ongoing recoordination (ISF from 45 ± 18 to 27 ± 11 and 23 ± 12%, p < 0.001; SRS from 2.27 ± 1.33 to 0.74 ± 0.50 and 0.71 ± 0.43%, p < 0.001) and improved LV function (dP/dtmax 668 ± 185 vs. 817 ± 198 mmHg/s, p < 0.001; stroke volume 46 ± 15 vs. 54 ± 20 and 52 ± 16 ml; LVEF 19 ± 7 vs. 23 ± 8 and 27 ± 10%, p < 0.001). Acute recoordination related to reverse remodelling (r = 0.601 and r = 0.765 for ISF & SRSlv, respectively, p < 0.001). Acute functional improvements of LV systolic function however, neither related to reverse remodelling nor to the extent of acute recoordination.ConclusionLong-term reverse remodelling after CRT is likely determined by (acute) recoordination rather than by acute hemodynamic improvements. Discoordination may therefore be a more important CRT-substrate that can be assessed and, acutely restored.
| S-EPMC8255256 | biostudies-literature
Project description:Background and aimsMonocytes and dendritic cells (DC) are both key inflammatory cells, with recognized effects on cardiac repair. However, there are distinct subsets of monocytes with potential for beneficial or detrimental effects on heart failure (HF) pathogenesis. The connection between reverse cardiac remodelling, the potential anti-inflammatory effect of cardiac resynchronization therapy (CRT) and monocytes and DC homeostasis in HF is far from being understood. We hypothesized that monocytes and DC play an important role in cardiac reverse remodelling and CRT response. Therefore, we aimed to assess the potential role of baseline peripheral levels of blood monocytes and DC subsets and their phenotypic and functional activity for CRT response, in HF patients. As a secondary objective, we aimed to evaluate the impact of CRT on peripheral blood monocytes and DC subsets, by comparing baseline and post CRT circulating levels and phenotypic and functional activity.MethodsForty-one patients with advanced HF scheduled for CRT were included in this study. The quantification and phenotypic determination of classical (cMo), intermediate (iMo) and non-classical monocytes (ncMo), as well as of myeloid (mDC) and plasmacytoid DC (pDC) were performed by flow cytometry in a FACSCanto™II (BD) flow cytometer. The functional characterization of total monocytes and mDC was performed by flow cytometry in a FACSCalibur flow cytometer, after in vitro stimulation with lipopolysaccharide from Escherichia coli plus interferon (IFN)-γ, in the presence of Brefeldina A. Comparisons between the control and the patient group, and between responders and non-responders to CRT were performed.ResultsCompared to the control group, HF population presented a significantly lower frequency of pDC at baseline and a higher proportion of monocytes and mDC producing IL-6 and IL-1β, both before and 6-months after CRT (T6). There was a remarkable decrease of cMo and an increase of iMo after CRT, only in responders. The responder group also presented higher ncMo values at T6 compared to the non-responder group. Both responders and non-responders presented a decrease in the expression of CD86 in all monocyte and DC populations after CRT. Moreover, in non-responders, the increased frequency of IL-6-producing DC persisted after CRT.ConclusionOur study provides new knowledge about the possible contribution of pDC and monocytes subsets to cardiac reverse remodelling and response to CRT. Additionally, CRT is associated with a reduction on CD86 expression by monocytes and DC subsets and in their potential to produce pro-inflammatory cytokines, contributing, at least in part, for the well described anti-inflammatory effects of CRT in HF patients.
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Project description:Ca(2+)-induced Ca(2+) release (CICR) is critical for contraction in cardiomyocytes. The transverse (t)-tubule system guarantees the proximity of the triggers for Ca(2+) release [L-type Ca(2+) channel, dihydropyridine receptors (DHPRs)] and the sarcoplasmic reticulum Ca(2+) release channels [ryanodine receptors (RyRs)]. Transverse tubule disruption occurs early in heart failure (HF). Clinical studies of left ventricular assist devices in HF indicate that mechanical unloading induces reverse remodelling. We hypothesize that unloading of failing hearts normalizes t-tubule structure and improves CICR.Heart failure was induced in Lewis rats by left coronary artery ligation for 12 weeks; sham-operated animals were used as controls. Failing hearts were mechanically unloaded for 4 weeks by heterotopic abdominal heart transplantation (HF-UN). HF reduced the t-tubule density measured by di-8-ANEPPS staining in isolated left ventricular myocytes, and this was reversed by unloading. The deterioration in the regularity of the t-tubule system in HF was also reversed in HF-UN. Scanning ion conductance microscopy showed the reappearance of normal surface striations in HF-UN. Electron microscopy revealed recovery of normal t-tubule microarchitecture in HF-UN. L-type Ca(2+) current density, measured using whole-cell patch clamping, was reduced in HF but unaffected by unloading. The variance of the time-to-peak of the Ca(2+) transient, an index of CICR dyssynchrony, was increased in HF and normalized by unloading. The increased Ca(2+) spark frequency observed in HF was reduced in HF-UN. These results could be explained by the recoupling of orphaned RyRs in HF, as indicated by immunofluorescence.Our data show that mechanical unloading of the failing heart reverses the pathological remodelling of the t-tubule system and improves CICR.
| S-EPMC3359860 | biostudies-other
Project description:Due to the limited self-repair capacity of articular cartilage, the surgical restoration of defective cartilage remains a major clinical challenge. The cell-based approach, which is known as autologous chondrocyte transplantation (ACT), has limited success, presumably because the chondrocytes acquire a fibroblast-like phenotype in monolayer culture. This unwanted dedifferentiation process is typically addressed by using three-dimensional scaffolds, pellet culture, and/or the application of exogenous factors. Alternative mechanical unloading approaches are suggested to be beneficial in preserving the chondrocyte phenotype. In this study, we examined if the random positioning machine (RPM) could be used to expand chondrocytes in vitro such that they maintain their phenotype. Bovine chondrocytes were exposed to (a) eight days in static monolayer culture; (b) two days in static monolayer culture, followed by six days of RPM exposure; and, (c) eight days of RPM exposure. Furthermore, the experiment was also conducted with the application of 20 mM gadolinium, which is a nonspecific ion-channel blocker. The results revealed that the chondrocyte phenotype is preserved when chondrocytes go into suspension and aggregate to cell clusters. Exposure to RPM rotation alone does not preserve the chondrocyte phenotype. Interestingly, the gene expression (mRNA) of the mechanosensitive ion channel TRPV4 decreased with progressing dedifferentiation. In contrast, the gene expression (mRNA) of the mechanosensitive ion channel TRPC1 was reduced around fivefold to 10-fold in all of the conditions. The application of gadolinium had only a minor influence on the results. This and previous studies suggest that the chondrocyte phenotype is preserved if cells maintain a round morphology and that the ion channel TRPV4 could play a key role in the dedifferentiation process.
| S-EPMC5983850 | biostudies-other
Project description:ObjectivesMechanical force plays an important role in modulating stem cell fate and behaviours. However, how periodontal ligament stem cells (PDLSCs) perceive mechanical stimulus and transfer it into biological signals, and thereby promote alveolar bone remodelling, is unclear.Materials and methodsAn animal model of force-induced tooth movement and a compressive force in vitro was used. After force application, tooth movement distance, mesenchymal stem cell and osteoclast number, and proinflammatory cytokine expression were detected in periodontal tissues. Then, rat primary PDLSCs with or without force loading were isolated, and their stem cell characteristics including clonogenicity, proliferation, multipotent differentiation and immunoregulatory properties were evaluated. Under compressive force in vitro, the effects of the ERK signalling pathway on PDLSC characteristics were evaluated by Western blotting.ResultsMechanical force in vivo induced PDLSC proliferation, which was accompanied with inflammatory cytokine accumulation, osteoclast differentiation and TRPV4 activation; the force-stimulated PDLSCs showed greater clonogenicity and proliferation, reduced differentiation ability, improved induction of macrophage migration, osteoclast differentiation and proinflammatory factor expression. The biological changes induced by mechanical force could be partially suppressed by TRPV4 inhibition. Mechanistically, force-induced activation of TRPV4 in PDLSCs regulated osteoclast differentiation by affecting the RANKL/OPG system via ERK signalling.ConclusionsTaken together, we show here that TRPV4 activation in PDLSCs under mechanical force contributes to changing their stem cell characteristics and modulates bone remodelling during tooth movement.
| S-EPMC7574874 | biostudies-literature
Project description:AimsIt has been shown that electrical stimulation can improve tissue repair in patients. Imbalances in the extracellular matrix composition induce manifestation of heart failure. Here we investigated the application of microcurrent (MC) to modulate the expression of matrix metalloproteinases (MMPs) and tissue inhibitor of metalloproteinases (TIMPs) in cardiomyocytes in vitro and in vivo to reverse remodelling in the heart in spontaneous hypertensive rats (SHR).MethodsCardiomyocytes from young SHR (7 months) and old SHR (14 months) were stimulated in vitro and in vivo with MC. MMP and TIMP expression were analysed by qPCR and immunofluorescence to evaluate the modulation of MC treatment.ResultsModulation of cardiomyocytes with MC enhances proliferation with no morphological changes in vitro. By electrical stimulation dual effects, increase and decrease, on MMP-2, MMP-9, TIMP-3, and TIMP-4 mRNA as well as protein expression were observed, depending on the age of the cardiomyocytes. In our in vivo study, MC down-regulated MMP-2, MMP-9, and TIMP-4 and increased TIMP-3 in young SHR. In old SHR MMP-2, MMP-9, and TIMP-4 were up-regulated, whereas TIMP-3 was unaffected.ConclusionsOur data indicate that treatment of MC can modulate the expression of MMPs and TIMPs in vitro and in vivo in SHR. Based on these results new treatments for heart failure could be developed.
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