Tumor necrosis factor alpha alters Na+-K+ ATPase activity in rat cardiac myocytes: Involvement of NF-[kappa] B, AP-1 and PGE2 (original) (raw)
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Rapid negative inotropic effect induced by TNF-α in rat heart perfused related to PKC activation
Cytokine, 2018
Myocardial depression, frequently observed in septic shock, is mediated by circulating molecules such as cytokines. TNF-α appears to be the most important pro-inflammatory cytokine released during the early phase of a septic shock. It was previously shown that TNF-α had a negative inotropic effect on myocardium. Now, the aim of this study was to investigate the effects of the activation of PKC by TNF-α on heart function, and to determine if this cytokine could induce a decrease of membrane excitability. Isolated rat hearts (n = 6) were perfused with Tyrode solution containing TNF-α at 20 ng/ml during 30 min by using a Langendorff technique. Expressions of PKC-α and PKC-ε were analysed by western blot on membrane and cytosol proteins extracted from ventricular myocardium. Patch clamp was performed on freshly isolated cardiomyocytes (n = 8). Compared to control situation, 30 min of TNF-α perfusion led to cardiac dysfunction with a decrease of the heart rate (−83%), the force (−20%) and speed of relaxation (−18%) and the coronary flow (−25%). This is associated with an activation and a membrane targeting of both PKC-α and PKC-ε isoforms in ventricle with respectively +123% and +54% compared to control hearts. Nevertheless, TNF-α had no significant effect on voltage-gated sodium current (109.0%+/− 12.5) after addition of the cytokine when compared to control. These results showed that TNF-α had a negative inotropic effect on the isolated rat heart and can induce PKC activation leading to an impaired contractility of the heart. However the early heart dysfunction induced by the cytokine was not associated to a decrease of cardiomyocytes membrane excitability as it has been evidenced in skeletal muscle fibres.
TNF-alpha as a potential mediator of cardiac dysfunction due to intracellular Ca2+-overload
Biochemical and biophysical research communications, 2005
TNF-a has been shown to be involved in cardiac dysfunction during ischemia/reperfusion injury; however, no information regarding the status of TNF-a production in myocardial injury due to intracellular Ca 2+ -overload is available in the literature. The intracellular Ca 2+ -overload was induced in the isolated rat hearts subjected to 5 min Ca 2+ -depletion and 30 min Ca 2+ -repletion (Ca 2+ -paradox). The Ca 2+ -paradox hearts exhibited a dramatic depression in left ventricular developed pressure, a marked elevation in left ventricular end diastolic pressure, and more than a 4-fold increase in TNF-a content. The ratio of cytosolic to homogenate nuclear factor-jB (NFjB) was decreased whereas the ratio of phospho-NFjB to total NFjB was increased in the Ca 2+ -paradox hearts. All these changes due to Ca 2+ -paradox were significantly attenuated upon treating the hearts with 100 lM pentoxifylline. These results suggest that activation of NFjB and increased production of TNF-a may play an important role in cardiac injury due to intracellular Ca 2+ -overload.
FEBS Letters, 1995
Tumor necrosis factor-a (TNF~) is a potentially powerful anti-neoplastic agent; however, its therapeutic usefulness is limited by its cardiotoxic and negative inotropic effects. Accordingly, studies were undertaken to gain a better understanding of the mechanisms of TNFa-mediated cardiodepression. Single cell RT-PCR, [125I]TNF~ ligand binding and Western immunoblotting experiments demonstrated that rat cardiac cells predominantly express type I TNFa receptors (TNFRI or p60). TNFa inhibited cardiac L-type Ca 2+ channel current (/ca) and contractile Ca 2÷ transients. Thus, it is possible that the negative inotropic effects of TNF~ are the result of TNFRI-mediated blockade of cardiac excitation-contraction coupling.
Journal of Clinical Investigation, 1993
To define the mechanism(s) responsible for the negative inotropic effects of tumor necrosis factor-a (TNFa) in the adult heart, we examined the functional effects of TNFa in the intact left ventricle and the isolated adult cardiac myocyte. Studies in both the ventricle and the isolated adult cardiac myocyte showed that TNFa exerted a concentrationand time-dependent negative inotropic effect that was fully reversible upon removal of this cytokine. Further, treatment with a neutralizing anti-TNFa antibody prevented the negative inotropic effects of TNFa in isolated myocytes. A cellular basis for the above findings was provided by studies which showed that treatment with TNFa resulted in decreased levels of peak intracellular calcium during the systolic contraction sequence; moreover, these findings did not appear to be secondary to alterations in the electrophysiological properties of the cardiac myocyte. Further studies showed that increased levels of nitric oxide, de novo protein synthesis, and metabolites of the arachidonic acid pathway were unlikely to be responsible for the TNFa-induced abnormalities in contractile function. Thus, these studies constitute the initial demonstration that the negative inotropic effects of TNFa are the direct result of alterations in intracellular calcium homeostasis in the adult cardiac myocyte.
Circulation, 2004
Background-The negative effect of tumor necrosis factor-␣ (TNF-␣) on heart contraction, which is mediated by sphingosine, is a major component in heart failure. Because the cellular level of glutathione may limit sphingosine production via the inhibition of the Mg-dependent neutral sphingomyelinase (N-SMase), we hypothesized that cardiac glutathione status might determine the negative contractile response to TNF-␣. Methods and Results-We examined the effects of TNF-␣ in isolated cardiomyocytes obtained from control rats or rats that were given the glutathione precursor N-acetylcysteine (NAC, 100 mg IP per animal). In cardiomyocytes obtained from control rats, 25 ng/mL TNF-␣ increased reactive oxygen species generation and N-SMase activity (500% and 34% over basal, respectively) and decreased the amplitude of [Ca 2ϩ ] i in response to electrical stimulation (22% below basal). NAC treatment increased cardiac glutathione content by 42%. In cardiomyocytes obtained from NAC-treated rats, 25 ng/mL TNF-␣ had no effect on reactive oxygen species production or N-SMase activity but increased the amplitude of [Ca 2ϩ ] i transients and contraction in response to electrical stimulation by 40% to 50% over basal after 20 minutes. This was associated with a hastened relaxation (20% reduction in t 1/2 compared with basal) and an increased phosphorylation of both Ser 16 -and Thr 17 -phospholamban residues (260% and 115% of maximal isoproterenol effect, respectively). Conclusions-It is concluded that cardiac glutathione status, by controlling N-SMase activation, determines the severity of the adverse effects of TNF-␣ on heart contraction. Glutathione supplementation may therefore provide therapeutic benefits for vulnerable hearts. (Circulation. 2004;109:406-411.)
Two functional Na+/K+-ATPase isoforms in the left ventricle of guinea pig heart
European Journal of Biochemistry, 1991
Guinea pig left ventricular muscle contains two distinct molecular forms of the N a + /K+-ATPase catalytic a subunit. Sarcolemmal vesicles highly enriched in Na+/K+-ATPase were isolated by a new procedure that yielded specific activities of 60 -100 pmol Pi . h-' . mg-'. SDSjPAGE of isolated sarcolemma after reduction and alkylation of the sulfhydryl groups and identification on immunoblots with specific anti-(a subunit) antibodies indicated the presence of two major polypeptides of 100 kDa and 103 kDa, respectively. The two a subunits were functional: the dose/response curves of Na+/K+-ATPase activity with ouabain, dihydroouabain and digitoxigenin were biphasic, revealing the presence of high-affinity [concentration of drug causing 50% inhibition (IC50) = 10 nM] and low-affinity (ICs0 = 2 pM) forms with proportional contributions of 55% and 45%, respectively. The involvement of the high-affinity form in the positive inotropic effect of digitalis and of the low-affinity sites in both inotropy and toxicity are consistent with the literature data on rodents.