Role of Early Assesment of Diuresis and Natriuresis in Detecting In-Hospital Diuretic Resistance in Acute Heart Failure

Background and Purpose: European Guidelines recommend early evaluation of diuresis and natriuresis after the first administration of diuretic to identify patients with insufficient diuretic response during acute heart failure. The aim of this work is to evaluate the prevalence and characteristics of patients with insufficient diuretic response according to this new algorithm.

Methods: Prospective observational single centre study of consecutive patients with acute heart failure and congestive signs. Clinical evaluation, echocardiography and blood tests were performed. Diuretic naïve patients received 40 mg of intravenous furosemide. Patients on an oupatient diuretic regimen received 2 times the ambulatory dose. The diuresis volume was assessed 6 h after the first loop diuretic administration, and a spot urinary sample was taken after 2 h. Insufficient diuretic response was defined as natriuresis <70 mEq/L or diuresis volume <600 ml.

Results: From January 2020 to December 2021, 73 patients were included (59% males, median age 76 years). Of these, 21 patients (28.8%, 95%CI 18.4; 39.2) had an insufficient diuretic response. Diuresis volume was <600 ml in 13 patients (18.1%), and 12 patients (16.4%) had urinary sodium <70 mEq/L. These patients had lower systolic blood pressure, worse glomerular filtration rate, and higher aldosterone levels. Ambulatory furosemide dose was also higher. These patients required more frequently thiazides and inotropes during admission.

Conclusion: The diagnostic algorithm based on diuresis and natriuresis was able to detect up to 29% of patients with insufficient diuretic response, who showed some characteristics of more advanced disease.

Checkpoint inhibitor-induced fulminant myocarditis, complete atrioventricular block and myasthenia gravis-a case report

Immune checkpoint inhibitors (ICIs) have revolutionized cancer therapy over the last decade. Pembrolizumab, a humanized monoclonal IgG4 antibody, binds to the programmed death 1 (PD-1) receptor, blocking its interaction with programmed death-ligand 1 (PD-L1) and thereby increasing the anti-tumor activity of the host immune system. These drugs are associated with immune-mediated side effects that can be life threatening, and myocarditis is among the most serious events. We present a 48-year-old woman with a history of progressive thymoma who developed complete atrioventricular block associated with fulminant myocarditis and myasthenia gravis 2 weeks after starting treatment with pembrolizumab. She had also presented a couple of days before to the emergency department due to dyspnea that was related to pleural effusion. Electrocardiogram (ECG) and echocardiogram were unremarkable, but she had very mildly increased troponin levels that were attributed to acute respiratory compromise, so she was discharged after successful thoracentesis. Despite aggressive treatment combination of high-dose corticosteroids, immunosuppressive agents and anti-thymocyte globulin, the disease rapidly progressed to the fatal outcome. This report remarks on the importance of rapid consideration of ICI-induced myocarditis even if cardiac biomarkers are slightly elevated, as a mild presentation can go unnoticed and progress to a severe case. Therefore, a high index of suspicion is warranted in these patients and cardiac imaging techniques such as magnetic resonance could have a role diagnosing incipient cardiac inflammation.

Modulation of N-type Ca2+ channel current kinetics by PMA in rat sympathetic neurons

The protein kinase C activator phorbol 12-myristate 13-acetate (PMA) has been used extensively in studies of G protein modulation of Ca2+ channels. PMA has been shown to be a powerful tool for inducing phosphorylation and interrupting G-protein-mediated signaling pathways. Here we re-examine the effects of PMA on whole-cell N-type Ca2+-channel currents in rat sympathetic neurons. We found that, along with an increase in the current amplitude previously reported by others, PMA pretreatment leads to alterations in current activation and inactivation kinetics. These alterations in current kinetics are voltage-dependent and are not reproduced by internal dialysis with the G protein inhibitor GDPbetaS. Alterations in current kinetics by PMA may therefore indicate the existence of a modulated state, presumably phosphorylated, of N-type Ca2+ channels. We propose that the increase in current amplitude is due primarily to alterations in current kinetics rather than to removal of tonic inhibition.

The antidepressant imipramine inhibits the M-type K+ current in rat sympathetic neurons

This study aimed to assess the effects of the antidepressant drug imipramine (IMI) on the neuronal M-type K+ current (IK(M)). We show that IMI reversibly reduces IK(M) with an IC50 of 7 microM. The V0.5 and slope factor of the steady state activation curve remained unchanged after IMI, indicating a mode of action that is voltage insensitive for blocking the M-channel. Patch pipette application of IMI elicits same inhibitory response suggesting a binding site on the M-channel accessible from both sides of the cell membrane. Accordingly, the inhibitory effect of IMI is larger by rising external pH near to the pKa of the drug. Therefore, we propose that a neutral form of IMI binds more efficiently to M-channels to exert its inhibitory action by a voltage-independent mechanism.

Potentiation of prolactin secretion following lactotrope escape from dopamine action. I. Dopamine withdrawal augments l-type calcium current

Hypothalamic dopamine (DA) tonically inhibits prolactin (PRL) release from the anterior pituitary gland. Transient escapes from this DA tone elicit a pronounced potentiation of the PRL-releasing action of secretagogues such as thyrotropin-releasing hormone (TRH). Previous evidence has suggested that modulation of Ca(2+) channels can be involved in this potentiation. With a lactotropic cell line (GH(4)C(1)) expressing human D(2)-DA receptors, we tested the hypothesis that a brief escape from the tonic inhibitory action of DA triggers a facilitation of Ca(2+) influx through Ca(2+) channels. We initially found that in these cells, DA effectively and reversibly inhibited PRL secretion, and reversibly enhanced an inwardly rectifying K(+) current. The effects of DA administration and withdrawal on Ca(2+) currents were examined using the patch-clamp technique in the whole-cell configuration and Ba(2+) as a divalent charge carrier through Ca(2+) channels. Macroscopic Ba(2+) currents were significantly decreased by short term (1-10 min) applications of DA (500 nM), which further declined following 24 h of constant exposure to DA. After DA removal, a biphasic facilitation of the density of Ba(2+) currents was observed. An initial 2-fold enhancement of conductance was detected between 10 and 40 min, followed by a second facilitation of the same magnitude observed 24 h after DA withdrawal. The present results directly demonstrate that dissociation of DA from D(2)-receptors expressed in GH(4)C(1) lactotrope cells causes an increase of high-voltage-activated Ca(2+) channel function, which may play an important role in the cross-talking amplification of endocrine cascades such as that involved in the TRH-induced PRL-release potentiating action of DA withdrawal.

G-protein beta-subunit specificity in the fast membrane-delimited inhibition of Ca2+ channels

We investigated which subtypes of G-protein beta subunits participate in voltage-dependent modulation of N-type calcium channels. Calcium currents were recorded from cultured rat superior cervical ganglion neurons injected intranuclearly with DNA encoding five different G-protein beta subunits. Gbeta1 and Gbeta2 strongly mimicked the fast voltage-dependent inhibition of calcium channels produced by many G-protein-coupled receptors. The Gbeta5 subunit produced much weaker effects than Gbeta1 and Gbeta2, whereas Gbeta3 and Gbeta4 were nearly inactive in these electrophysiological studies. The specificity implied by these results was confirmed and extended using the yeast two-hybrid system to test for protein-protein interactions. Here, Gbeta1 or Gbeta2 coupled to the GAL4-activation domain interacted strongly with a channel sequence corresponding to the intracellular loop connecting domains I and II of a alpha1 subunit of the class B calcium channel fused to the GAL4 DNA-binding domain. In this assay, the Gbeta5 subunit interacted weakly, and Gbeta3 and Gbeta4 failed to interact. Together, these results suggest that Gbeta1 and/or Gbeta2 subunits account for most of the voltage-dependent inhibition of N-type calcium channels and that the linker between domains I and II of the calcium channel alpha1 subunit is a principal receptor for this inhibition.

The role of voltage-gated Ca2+ channels in neurite growth of cultured chromaffin cells induced by extremely low frequency (ELF) magnetic field stimulation

The ion Ca2+ has been shown to play an important role in a wide variety of cellular functions, one of them being related to cell differentiation in which nerve growth factor (NGF) is involved. Chromaffin cells obtained from adrenals of 2- to 3-day-old rats were cultured for 7 days. During this time, these cells were subjected to the application of either NGF or extremely low frequency magnetic fields (ELF MF). Since this induced cell differentiation toward neuronal-like cells, the mechanism by which this occurred was studied. When the L-Ca2+ channel blocker nifedipine was applied simultaneously with ELF MF, this differentiation did not take place, but it did when an N-Ca2+ channel blocker was used. In contrast, none of the Ca2+ channel blockers prevented differentiation in the presence of NGF. In addition, Bay K-8644, an L-Ca2+ channel agonist, increased both the percentage of differentiated cells and neurite length in the presence of ELF MF. This effect was much weaker in the presence of NGF. [3H]-noradrenaline release was reduced by nifedipine, suggesting an important role for L-Ca2+ channels in neurotransmitter release. Total high voltage Ca2+ currents were significantly increased in ELF MF-treated cells with NGF, but these currents in ELF MF-treated cells were more sensitive to nifedipine. Amperometric analysis of catecholamine release revealed that the KCl-induced activity of cells stimulated to differentiate by ELF MF is highly sensitive to L-type Ca2+ channel blockers. A possible mechanism to explain the way in which the application of magnetic fields can induce differentation of chromaffin cells into neuronal-like cells is proposed.

Constitutive upregulation of calcium channel currents in rat phaeochromocytoma cells: role of c-fos and c-jun

1. Northern blot analysis and cell transfection were used in conjunction with whole-cell current recordings to examine the involvement of the immediate early genes, c-fos and c-jun, in the expression of calcium channel currents. 2. Phaeochromocytoma cells (PC12 clone) were exposed to nerve growth factor (NGF) and to depolarizing concentrations of KCl for 60 min every day. Cells challenged with NGF developed extensive networks of neurites within 3 days. Cells depolarized periodically retained their undifferentiated morphology even after 5 days of treatment. 3. The maximal amplitude of high-voltage-activated calcium currents (ICa) increased from the control level of 117.8 +/- 48.3 (mean +/- S.D.) to 387.2 +/- 90.1 pA within 3 days of NGF treatment. omega-Conotoxin (5-10 microM) inhibited 24.6 +/- 8.5% of ICa in undifferentiated cells and 57.8 +/- 6.9% in NGF-treated cells. 4. The levels of c-fos and c-jun mRNAs increased transiently during each daily exposure to NGF. The level of c-fos mRNA also increased transiently during repeated KCl-induced depolarizations but c-jun mRNA remained low or absent. 5. Naive PC12 cells were transiently co-transfected with expression plasmids that contained the full length of c-fos and c-jun cDNA. After 2 days following transfection, the PC12 cells could be grouped according to the size of ICa. In 56% of cells, ICa was similar to control currents (106.1 +/- 37.4 pA). In the remaining 44% of cells, ICa showed a 2.2-fold enhancement with respect to control cells. Transfection of only c-fos had no effect on ICa but, in 24% of cells transfected with c-jun, ICa was 176.6 +/- 124.6 pA. Since periodic membrane depolarization induced c-fos but not c-jun mRNA, c-jun transfection was combined with a high-K+ treatment over 3 days. In 18% of treated cells, ICa was 3.7 times larger than control currents. Morphological differentiation was not observed in transfected cells. 6. In PC12 cells co-transfected with c-fos and c-jun or treated with high K+ after transfection of c-jun, omega-conotoxin (5-10 microM) inhibited 68.7 +/- 11.9% of ICa when the current amplitude was in the range of 200-600 pA. since similar concentrations of omega-conotoxin blocked 19.2 +/- 5.4% of ICa in control cells, the current increase induced by c-fos and c-jun was supported by up to 11-fold enhancement of the omega-conotoxin-sensitive component of ICa.(ABSTRACT TRUNCATED AT 400 WORDS)

Enhancement of voltage-gated Ca2+ currents induced by daily stimulation of hippocampal neurons with glutamate

The regulation of calcium channel currents (ICa) induced by daily stimulation (1 hr) with 10 microM glutamate was studied in full differentiated hippocampal cells in culture. We report a specific enhancement of the high-voltage-activated current type (HVA ICa) ongoing over days. The density of HVA ICa increased about twofold after the second glutamate session, and this enhancement was still observed after the fifth day of treatment, while low-voltage-activated calcium currents (LVA ICa) remained unchanged. During glutamate application, a transient increase of intracellular calcium (Cai) was observed, followed by a slow decay within 2-3 min, and substantial recovery in about 10 min. Similarly, Cai transients induced by periodic membrane depolarization mimicked the long-term effect of glutamate on ICa. These results demonstrate for the first time an increase of ICa in a time frame of days. Since the effect of glutamate on ICa was prevented by cycloheximide, neosynthesis of channel proteins presumably supports this enhancement.

BDNF and NT-3 induce intracellular Ca2+ elevation in hippocampal neurones

The effects of neurotrophins on intracellular Ca2+ levels in rat hippocampal neurones were studied in vitro using fura-2 fluorescence microscopy. BDNF and NT-3, but not NGF, rapidly increased cytoplasmic Ca2+ concentrations in these neurones ten-fold to reach 1 microM. Moreover in some of the neurones both BDNF and NT-3 elicited Ca2+ responses, indicative of the presence of functional receptors for these neurotrophins in the same cell. In these cultures approximately 80% of the hippocampal neurones were stained with antibodies against full-length TrkB. The expression of functional TrkB was also confirmed by RNA analysis. These results demonstrate the presence of functional receptors for BDNF and NT-3 in hippocampal neurones.