Changes in right ventricular two-dimensional echocardiographic speckle-tracking indices in adult LVAD population: a prospective clinical study

Objective

Preserved right ventricular (RV) function is crucial in patients supported with left ventricular assist devices (LVAD). The use of strain derived from speckle tracking echocardiography (STE) is recommended by recent guidelines to evaluate intricate RV contractility. The data regarding long-term RV observation in LVAD patients using STE are limited. Thus, the study aimed to determine RV systolic function by STE in the remote period after LVAD implantation.

Methods

Patients with implanted third-generation LVADs with hydrodynamic bearing were prospectively enrolled (NCT05063006). The RV STE indices were analyzed before and after LVAD implantation, both at rest and during the cycle ergometer exercise test.

Results

We included 22 patients, the mean age was 58.4±7 years, 95.5% were men, and 45.5% had dilated cardiomyopathy. Stress tests were conducted 7 months postoperatively. The RV strain analysis was feasible in all subjects both in rest and exercise. The RV free wall strain (RVFWS) worsened from −13% (IQR, −17.3 to −10.9) to −11.3% (IQR, −12.9 to −6; p=0.033) after LVAD implantation with the particular decline in the apical RV segment [−11.3% (IQR, −16.4 to −6.2) vs −7.8% (IQR, −11.7 to −3.9; p=0.012)]. The RV four-chamber longitudinal strain (RV4CSL) remained unchanged [−8.5% (IQR, −10.8 to −6.9) vs −7.3% (IQR, −9.8 to −4.7; p=0.184)]. Neither RVFWS (−11.3% (IQR, −12.9 to −6) vs −9.9% (IQR, −13.5 to −7.5; p=0.077) nor RV4CSL [−7.3% (IQR, −9.8 to −4.7) vs −7.9% (IQR, −9.8 to −6.3; p=0.548)] changed during cycle ergometer stress test.

Conclusion

The RVFWS worsens after LVAD implantation presumably due to impaired apical contractility. In LVAD-supported patients during the cycle ergometer stress test, the detailed RV strain analysis is feasible and its indices remain unchanged.

Funding Acknowledgement

Type of funding sources: Other. Main funding source(s): 1. Cor Aegrum Foundation of Cardiac Surgery Development in Cracow2. Medtronic Poland sp. z o.o.

Echo-guided LVAD speed optimization for exercise maximization

Background

Continuous-flow left ventricular assist devices (LVAD) are becoming a destination therapy in patients with end-stage left ventricular dysfunction and a competitive method for heart transplantation. Current generation pumps operate with a fixed rotation speed and do not have the automatic speed adjustment capability. However, it was shown that acceleration of the pump speed during stress test increases the maximum exercise tolerance.

Purpose

The study aimed to evaluate the concept of dynamic pump speed optimization based on the echocardiographic assessment of aortic valve opening (AVO) during the cardiopulmonary exercise test (CPET).

Methods

Patients with implanted third-generation centrifugal continuous-flow LVAD's with hydrodynamic bearing were prospectively included. Two CPET's were performed after resting speed optimization. The first one with maintained baseline pump speed settings, and the second one with gradually increased speed depending on live echocardiographic imaging. The sequence of tests was random.

Results

Exercise AVO was apparent in all 22 included patients. The resting pump speed was 2691 RPM and incremented on average by 566 RPM (20%). Pump power and flow raised from 5.6 to 9.8 Watts (p<0.0001) and from 5.8 to 7.3 l/min (p<0.0001), respectively. Peak VO2 increased from 11.1 to 12.8 ml/kg/min (p=0.0003) and maximum workload from 1.1 to 1.2 W/kg (p=0.03). The Borg scale exertion level decreased from 15.2 to 13.5 (p=0.0049). There was a visible trend towards longer exercise time (36s) but no statistical significance was achieved (p=0.1).

Conclusion

Ultrasonographic AVO analysis is possible during CPET's in patients supported with LVAD. Dynamic echo-guided pump speed adjustment based on the AVO improves exercise tolerance, augments peak VO2 consumption and maximal workload. An automatic speed adjustment in the next generations of LVAD controllers might improve functional capacity and requires further basic, technological and clinical research.

Funding Acknowledgement

Type of funding sources: Other. Main funding source(s): 1. Cor Aegrum Foundation of Cardiac Surgery Development in Cracow2. Medtronic Poland Sp. z o.o.

Photoaging of retinal pigment epithelial melanosomes: The effect of photobleaching on morphology and reactivity of the pigment granules

To elucidate the mechanism of age-related changes in antioxidant and photoprotective properties of human retinal pigment epithelium (RPE) melanosomes, the effect of in vitro photoaging of bovine RPE melanosomes was examined employing an array of complementary spectroscopic and analytical methods. Electron paramagnetic resonance (EPR) spectroscopy, saturation recovery EPR, atomic force microscopy (AFM) and dynamic light scattering (DLS) were used to determine melanin content of control and photobleached melanosomes, and to monitor changes in their morphology. Methylene blue (MB), TEMPO choline, dysprosium(III) ions and singlet oxygen were employed as molecular probes to characterize the efficiency of control and photobleached melanosomes to interact with different reagents. EPR oximetry, UV-vis absorption spectroscopy, iodometric assay of lipid hydroperoxides and time-resolved singlet oxygen phosphorescence were used to analyze the efficiency of photobleached and untreated melanosomes to inhibit MB-photosensitized oxidation of liposomal lipids. The obtained results revealed that, compared to untreated melanosomes, moderately photobleached melanosomes protected unsaturated lipids less efficiently against photosensitized peroxidiation, while weakly photobleached melanosomes were actually better antioxidant and photoprotective agents. The observed changes could be attributed to two effects - modification of the melanosome morphology and oxidative degradation of the melanin functional groups induced by different degree of photobleaching. While the former increases the accessibility of melanin nanoaggregates to reagents, the latter reduces the efficiency of melanin to interact with chemical and physical agents.

Nanomechanical analysis of pigmented human melanoma cells

Based on hitherto measurements of elasticity of various cells in vitro and ex vivo, cancer cells are generally believed to be much softer than their normal counterparts. In spite of significant research efforts on the elasticity of cancer cells, only few studies were undertaken with melanoma cells. However, there are no reports concerning pigmented melanoma cells. Here, we report for the first time on the elasticity of pigmented human melanoma cells. The obtained data show that melanin significantly increases the stiffness of pigmented melanoma cells and that the effect depends on the amount of melanin inside the cells. The dramatic impact of melanin on the nanomechanical properties of cells puts into question widely accepted paradigm about all cancer cells being softer than their normal counterparts. Our findings reveal significant limitations of the nanodiagnosis approach for melanoma and contribute to better understanding of cell elasticity.

Photoaging of human retinal pigment epithelium is accompanied by oxidative modifications of its eumelanin

Although photodegradation of the retinal pigment epithelium (RPE) melanin may contribute to the etiology of age-related macular degeneration, the molecular mechanisms of this phenomenon and the structural changes of the modified melanin remain unknown. Recently, we found that the ratio of pyrrole-2,3,4,5-tetracarboxylic acid (PTeCA) to pyrrole-2,3,5-tricarboxylic acid (PTCA) is a marker for the heat-induced cross-linking of eumelanin. In this study, we examined UVA-induced changes in synthetic eumelanins to confirm the usefulness of the PTeCA/PTCA ratio as an indicator of photo-oxidation and compared changes in various melanin markers and their ratios in human melanocytes exposed to UVA, in isolated bovine RPE melanosomes exposed to strong blue light and in human RPE cells from donors of various ages. The results indicate that the PTeCA/PTCA ratio is a sensitive marker for the oxidation of eumelanin exposed to UVA or blue light and that eumelanin and pheomelanin in human RPE cells undergo extensive structural modifications due to the life-long exposure to blue light.

Deleterious cholesterol hydroperoxide trafficking in steroidogenic acute regulatory (StAR) protein-expressing MA-10 Leydig cells: implications for oxidative stress-impaired steroidogenesis

Steroidogenic acute regulatory (StAR) proteins in steroidogenic cells are implicated in the delivery of cholesterol (Ch) from internal or external sources to mitochondria (Mito) for initiation of steroid hormone synthesis. In this study, we tested the hypothesis that under oxidative stress, StAR-mediated trafficking of redox-active cholesterol hydroperoxides (ChOOHs) can result in site-specific Mito damage and dysfunction. Steroidogenic stimulation of mouse MA-10 Leydig cells with dibutyryl-cAMP (Bt2cAMP) resulted in strong expression of StarD1 and StarD4 proteins over insignificant levels in nonstimulated controls. During incubation with the ChOOH 3β-hydroxycholest-5-ene-7α-hydroperoxide (7α-OOH) in liposomes, stimulated cells took up substantially more hydroperoxide in Mito than controls, with a resulting loss of membrane potential (ΔΨm) and ability to drive progesterone synthesis. 7α-OOH uptake and ΔΨm loss were greatly reduced by StarD1 knockdown, thus establishing the role of this protein in 7α-OOH delivery. Moreover, 7α-OOH was substantially more toxic to stimulated than nonstimulated cells, the former dying mainly by apoptosis and the latter dying by necrosis. Importantly, tert-butyl hydroperoxide, which is not a StAR protein ligand, was equally toxic to stimulated and nonstimulated cells. These findings support the notion that like Ch itself, 7α-OOH can be transported to/into Mito of steroidogenic cells by StAR proteins and therein induce free radical damage, which compromises steroid hormone synthesis.

Oxidative stress increases HO-1 expression in ARPE-19 cells, but melanosomes suppress the increase when light is the stressor

PURPOSE

Phagocytized melanosomes in ARPE-19 cells were previously shown to decrease susceptibility to oxidative stress induced by hydrogen peroxide treatment and increase stress due to light irradiation relative to cells containing control black latex beads. Here we asked whether differential expression of antioxidant enzymes in cells containing pigment granules could explain the outcomes.

METHODS

ARPE-19 cells were loaded by phagocytosis with porcine RPE melanosomes or black latex beads (control particles). Heme oxygenase-1 (HO-1), HO-2, glutathione peroxidase (GPx), and catalase were quantified by Western blot analysis before and after treatment with sublethal hydrogen peroxide or blue light (400-450 nm). The stress was confirmed as sublethal by cell survival analysis using real-time quantification of propidium iodide fluorescence.

RESULTS

Phagocytosis itself produced transient changes in protein levels of some antioxidant enzymes, but steady-state levels (7 days after phagocytosis) did not differ in cells containing melanosomes versus beads. Sublethal stress, induced by either hydrogen peroxide or light, had no effect on catalase or HO-2 in either particle-free or particle-loaded cells. In contrast, HO-1 protein was upregulated by treatment with both hydrogen peroxide and light. Particle content did not affect the HO-1 increase induced by hydrogen peroxide, but the increase induced by blue light irradiation was partially blocked in cells containing black beads and blocked even more in cells containing melanosomes.

CONCLUSIONS

The results do not implicate differential antioxidant enzyme levels in stress protection by melanosomes against hydrogen peroxide, but they suggest a multifaceted role for melanosomes in regulating light stress susceptibility in RPE cells.

Permeabilization of the mitochondrial outer membrane by Bax/truncated Bid (tBid) proteins as sensitized by cardiolipin hydroperoxide translocation: mechanistic implications for the intrinsic pathway of oxidative apoptosis

Cytochrome c (cyt c) release upon oxidation of cardiolipin (CL) in the mitochondrial inner membrane (IM) under oxidative stress occurs early in the intrinsic apoptotic pathway. We postulated that CL oxidation mobilizes not only cyt c but also CL itself in the form of hydroperoxide (CLOOH) species. Relatively hydrophilic CLOOHs could assist in apoptotic signaling by translocating to the outer membrane (OM), thus promoting recruitment of the pro-apoptotic proteins truncated Bid (tBid) and Bax for generation of cyt c-traversable pores. Initial testing of these possibilities showed that CLOOH-containing liposomes were permeabilized more readily by tBid plus Ca(2+) than CL-containing counterparts. Moreover, CLOOH translocated more rapidly from IM-mimetic to OM-mimetic liposomes than CL and permitted more extensive OM permeabilization. We found that tBid bound more avidly to CLOOH-containing membranes than to CL counterparts, and binding increased with increasing CLOOH content. Permeabilization of CLOOH-containing liposomes in the presence of tBid could be triggered by monomeric Bax, consistent with tBid/Bax cooperation in pore formation. Using CL-null mitochondria from a yeast mutant, we found that tBid binding and cyt c release were dramatically enhanced by transfer acquisition of CLOOH. Additionally, we observed a pre-apoptotic IM-to-OM transfer of oxidized CL in cardiomyocytes treated with the Complex III blocker, antimycin A. These findings provide new mechanistic insights into the role of CL oxidation in the intrinsic pathway of oxidative apoptosis.

Sterol carrier protein-2 (SCP-2) involvement in cholesterol hydroperoxide cytotoxicity as revealed by SCP-2 inhibitor effects

Sterol carrier protein-2 (SCP-2) plays an important role in cholesterol trafficking and metabolism in mammalian cells. The purpose of this study was to determine whether SCP-2, under oxidative stress conditions, might also traffic hydroperoxides of cholesterol, thereby disseminating their cytotoxic effects. Two inhibitors, SCPI-1 and SCPI-3, known to block cholesterol binding by an insect SCP-2, were used to investigate this. A mouse fibroblast transfectant clone (SC2F) overexpressing SCP-2 was found to be substantially more sensitive to apoptotic killing induced by liposomal 7α-hydroperoxycholesterol (7α-OOH) than a wild-type control. 7α-OOH uptake by SC2F cells and resulting apoptosis were both inhibited by SCPI-1 or SCPI-3 at a subtoxic concentration. Preceding cell death, reactive oxidant accumulation and loss of mitochondrial membrane potential were also strongly inhibited. Similar SCPI protection against 7α-OOH was observed with two other types of SCP-2-expressing mammalian cells. In striking contrast, neither inhibitor had any effect on H(2)O(2)-induced cell killing. To learn whether 7α-OOH cytotoxicity is due to uptake/transport by SCP-2, we used a fluorescence-based competitive binding assay involving recombinant SCP-2, NBD-cholesterol, and SCPI-1/SCPI-3 or 7α-OOH. The results clearly showed that 7α-OOH binds to SCP-2 in SCPI-inhibitable fashion. Our findings suggest that cellular SCP-2 not only binds and translocates cholesterol but also cholesterol hydroperoxides, thus expanding their redox toxicity and signaling ranges under oxidative stress conditions.

Apoptosis-accommodating effect of nitric oxide in photodynamically stressed tumor cells

Using a 5-aminolevulinic acid (ALA)-photodynamic therapy model, we have discovered a new effect of nitric oxide (NO)-the ability to accommodate apoptosis. When sensitized by disseminated ALA-generated protoporphyrin IX, COH-BR1 tumor cells in glucose-containing medium died mainly by necrosis with a low level of apoptosis. Introduced before light at a nontoxic concentration, the NO donor SPNO inhibited necrosis, but supported apoptosis such that the latter became predominant in the remaining cell death. Accompanying this was a large increase in caspase-3/7 activation. SPNO-supported apoptosis was more pronounced when glucose-deprived cells were compared with glucose-replenished, SPNO-treated counterparts. SPNO plus glucose also suppressed plasma membrane-damaging lipid peroxidation and loss of cellular ATP under photostress. The NO effect is attributed to membrane protection with maintenance of sufficient glycolytic ATP to sustain apoptosis.

StarD4-mediated translocation of 7-hydroperoxycholesterol to isolated mitochondria: deleterious effects and implications for steroidogenesis under oxidative stress conditions

StAR family proteins, including StarD4, play a key role in steroidogenesis by transporting cholesterol (Ch) into mitochondria for conversion to pregnenolone. Using a model system consisting of peroxidized cholesterol (7 alpha-OOH)-containing liposomes as donors, we showed that human recombinant StarD4 accelerates 7 alpha-OOH transfer to isolated liver mitochondria, and to a greater extent than Ch transfer. StarD4 had no effect on transfer of non-oxidized or peroxidized phosphatidylcholine, consistent with sterol ring specificity. StarD4-accelerated 7 alpha-OOH transfer to mitochondria resulted in greater susceptibility to free radical lipid peroxidation and loss of membrane potential than in a non-StarD4 control. The novel implication of these findings is that in oxidative stress states, inappropriate StAR-mediated trafficking of peroxidized Ch in steroidogenic tissues could result in damage and dysfunction selectively targeted to mitochondria.

Increased apoptosis of peripheral blood mononuclear cells in patients with perennial allergic asthma/rhinitis: relation to serum markers of apoptosis

BACKGROUND

The goal of our study was to examine spontaneous and stimulated apoptosis of peripheral blood MNC from allergic patients, sensitized to Der p I antigen as compared to cells from non-atopic subjects. Furthermore we aimed to investigate which populations of mononuclear cells (lymphocytes, monocytes) undergo the apoptosis and to determine relations between apoptosis and serum levels of sFas/APO-1, ICE/caspase-1 or TNF-alpha.

METHODS

The study included 17 patients with perennial, allergic asthma and/or allergic rhinitis [6 male and 11 female; mean age 29,5 years; (range 15-49)]. Apoptosis was assessed by fluorescence technique and confirmed by flow-cytometric method and DNA ladder. Serum levels of sFas, ICE/caspase-1 or TNF-alpha were determined by immunoassays (ELISA).

RESULTS

Apoptotic index of unfractionated mononuclear cells (MNC) and lymphocytes (but not monocytes) were significantly higher in allergic patients as compared to non-allergic subjects after 48 and 72 hours of culture (p<0.05). Incubation of cells with ConA (10 microg/ml) resulted in a significant increase in the proportion of apoptotic cells in all populations once the apoptotic index for MNC and lymphocytes (but not monocytes) was again significantly higher in allergic as compared to non-allergic subjects after 24, 48 and 72 hour of culture. In allergic patients, mean serum sFas level, was significantly lower then in non-allergic group (mean value 624.8 pg/ml +/- 25.67 versus 802.0 pg/ml +/- 31.91; p = 0.003) and in both groups sFas level correlated inversely with apoptosis of MNC. The mean ICE/caspase-1 concentration was significantly higher in sera of allergic patients as compared to non-allergic group (mean value 27.71 pg/ml +/- 3.79 vs 23.54 pg/ml respectively; p<0.01). ICE/caspase-1 levels in allergic patients correlated with apoptotic index of mononuclear cells (r = 0.57; p<0.001).

CONCLUSIONS

An increased spontaneous and mitogen-induced apoptosis of MNC from peripheral blood of atopic patients as well as different serum levels of sFas and ICE/caspase-1 correlating with apoptosis, suggest different regulation of apoptotic process in peripheral blood mononuclear cells of patients with allergic asthma and/or rhinitis.