Diagnostic accuracy of procalcitonin for bacterial infection in the Emergency Department: a systematic review.

INTRODUCTION AND OBJECTIVE: The care of patients with a suspected infectious process in hospital emergency departments (ED) accounts for 15%-35% of all daily care in these healthcare areas in Spain and Latin America. The early and adequate administration of antibiotic treatment (AB) and the immediate making of other diagnostic-therapeutic decisions have a direct impact on the survival of patients with severe bacterial infection. The main objective of this systematic review is to investigate the diagnostic accuracy of PCT to predict bacterial infection in adult patients treated with clinical suspicion of infection in the ED, as well as to analyze whether the different studies manage to identify a specific value of PCT as the most relevant from the diagnostic point of view of clinical decision that can be recommended for decision making in ED. METHOD: A systematic review is carried out following the PRISMA regulations in the database of PubMed, Web of Science, EMBASE, Lilacs, Cochrane, Epistemonikos, Tripdatabase and ClinicalTrials.gov from January 2005 to May 31, 2023 without language restriction and using a combination of MESH terms: "Procalcitonin", "Infection/Bacterial Infection/Sepsis", "Emergencies/Emergency/Emergency Department", "Adults" and "Diagnostic". Observational cohort studies (diagnostic performance analyses) were included. The Newcastle-Ottawa Scale (NOS) was used to assess the quality of the method used and the risk of bias of the included articles. Observational cohort studies were included. No meta-analysis techniques were performed, but results were compared narratively. RESULTS: A total of 1,323 articles were identified, of which 21 that met the inclusion criteria were finally analyzed. The studies include 10,333 patients with 4,856 bacterial infections (47%). Eight studies were rated as high, 9 as moderate, and 4 as low. The AUC-ROC of all studies ranges from 0.68 (95% CI: 0.61-0.72) to 0.99 (95% CI: 0.98-1). The value of PCT 0.2-0.3 ng/ml is the most used and proposed in up to twelve of the works included in this review whose average estimated performance is an AUC-ROC of 0.79. If only the results of the 5 high-quality studies using a cut-off point of 0.2-0.3 ng/ml PCT are taken into account, the estimated mean AUC-COR result is 0.78 with Se:69 % and Es:76%. CONCLUSIONS: PCT has considerable diagnostic accuracy for bacterial infection in patients treated in ED for different infectious processes. The cut-off point of 0.25 (0.2-0.3) ng/ml has been positioned as the most appropriate to predict the existence of bacterial infection and can be used to help reasonably rule it out.

AMPK inhibits voltage-gated calcium channel-current in rat chromaffin cells.

Metabolic changes are critical in the regulation of Ca2+ influx in central and peripheral neuroendocrine cells. To study the regulation of L-type Ca2+ channels by AMPK we used biochemical reagents and ATP/glucose-concentration manipulations in rat chromaffin cells. AICAR and Compound-C, at low concentration, significantly induce changes in L-type Ca2+ channel-current amplitude and voltage dependence. Remarkably, an overlasting decrease in the channel-current density can be induced by lowering the intracellular level of ATP. Accordingly, Ca2+ channel-current density gradually diminishes by decreasing the extracellular glucose concentration. By using immunofluorescence, a decrease in the expression of CaV1.2 is observed while decreasing extracellular glucose, suggesting that AMPK reduces the number of functional Ca2+ channels into the plasma membrane. Together, these results support for the first time the dependence of metabolic changes in the maintenance of Ca2+ channel-current by AMPK. They reveal a key step in Ca2+ influx in secretory cells.

AMPK mediates regulation of voltage-gated calcium channels by leptin in isolated neurons from arcuate nucleus.

Neuronal control of the energy homeostasis requires the arcuate nucleus of the hypothalamus. This structure integrates peripheral and central signals concerning the energy state of the body. It comprises two populations of neurons releasing anorexigenic and orexigenic peptides, among others. Both populations are regulated by leptin, an anorexigenic hormone, released by white adipose tissue. Voltage-gated calcium entry is critical to promote neurotransmitter and hormone release. It is already known that calcium channel current is inhibited by leptin in orexigenic neurons. However, fine-tuning details of calcium channel regulation in arcuate nucleus by leptin remain to be elucidated. This work aimed to investigate whether 5' adenosine monophosphate-activated protein kinase (AMPK) underlies the leptin-induced inhibition of calcium channels. By using patch-clamping methods, immunocytochemical, and biochemical reagents, we recorded calcium channel currents in orexigenic neuropeptide Y neurons of the arcuate nucleus of rats. Consistently, leptin inhibition of the calcium channel current was not only prevented by AMPK inhibition with Compound C but also hampered with 5-aminoimidazole-4-carboxamide ribonucleoside. Furthermore, leptin selectively inhibited L-type calcium channel current amplitude without major changes in voltage dependence or current kinetics. These results support for the first time the key role of AMPK in the maintenance and regulation of voltage-gated calcium channels. Together, they advance our understanding of the regulation of calcium channels in the central nervous system and emerging questions concerning food intake and energy balance.NEW & NOTEWORTHY Our results readily support the hypothesis that AMPK is responsible for the maintenance of the calcium current and mediates the fine-tuning modulation of the leptin response. The novelty of these results strengthens the critical role of AMPK in the general energy balance and homeostasis.

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.

Protein kinase C disrupts cannabinoid actions by phosphorylation of the CB1 cannabinoid receptor.

We have found that phosphorylation of a G-protein-coupled receptor by protein kinase C (PKC) disrupts modulation of ion channels by the receptor. In AtT-20 cells transfected with rat cannabinoid receptor (CB1), the activation of an inwardly rectifying potassium current (Kir current) and depression of P/Q-type calcium channels by cannabinoids were prevented by stimulation of protein kinase C by 100 nM phorbol 12-myristate 13-acetate (PMA). In contrast, activation of Kir current by somatostatin was unaffected, and inhibition of calcium channels was only modestly attenuated. The possibility that PKC acted by phosphorylating CB1 receptors was confirmed by demonstrating that PKC phosphorylated a single serine (S317) of a fusion protein incorporating the third intracellular loop of CB1. Mutating this serine to alanine did not affect the ability of CB1 to modulate currents, but it eliminated disruption by PMA, demonstrating that PKC can disrupt ion channel modulation by receptor phosphorylation.

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.

Modulation of Ca2+ channels by G-protein beta gamma subunits.

Calcium ions entering cells through voltage-gated Ca2+ channels initiate rapid release of neurotransmitters and secretion of hormones. Ca2+ currents can be inhibited in many cell types by neurotransmitters acting through G proteins via a membrane-delimited pathway independently of soluble intracellular messengers. Inhibition is typically caused by a positive shift in the voltage dependence and a slowing of channel activation and is relieved by strong depolarization resulting in facilitation of Ca2+ currents. This pathway regulates the activity of N-type and P/Q-type Ca2+ channels, which are localized in presynaptic terminals and participate in neurotransmitter release. Synaptic transmission is inhibited by neurotransmitters through this mechanism. G-protein alpha subunits confer specificity in receptor coupling, but it is not known whether the G alpha or G beta gamma subunits are responsible for modulation of Ca2+ channels. Here we report that G beta gamma subunits can modulate Ca2+ channels. Transfection of G beta gamma into cells expressing P/Q-type Ca2+ channels induces modulation like that caused by activation of G protein-coupled receptors, but G alpha subunits do not. Similarly, injection or expression of G beta gamma subunits in sympathetic ganglion neurons induces facilitation and occludes modulation of N-type channels by noradrenaline, but G alpha subunits do not. In both cases, the G gamma subunit is ineffective by itself, but overexpression of exogenous G beta subunits is sufficient to cause channel modulation.

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.

The effects of lyotropic anions on charge movement, calcium currents and calcium signals in frog skeletal muscle fibres.

1. Intramembrane charge movement and Ca2+ currents were monitored in voltage-clamped segments of frog skeletal muscle fibres using the triple-Vaseline-gap technique. Calcium signals were measured in current-clamped fibres using either of the indicators Arsenazo III or Antipyrylazo III. 2. Non-linear capacitative currents (charge 1) were obtained using a subtraction procedure which employed either a -20 mV control pulse from a holding potential of -100 mV or alternatively a control pulse to +80 mV in depolarized fibres. The amount of charge mobilized depended on voltage according to a two-state Boltzmann function. The total charge (Qmax) was increased by ca 100% and the steepness parameter (k) by ca 70% when a +80 mV control pulse was used. 3. Thiocyanate (SCN-) and other lyotropic anions reversibly shifted the voltage dependence of mobilized charge towards negative potentials. Qmax was not significantly affected. 'Off' charge tails were greatly prolonged by lyotropic anions. 4. Extracellularly applied lyotropic anions affected the dihydropyridine-sensitive Ca2+ current by shifting the I-V relation toward more negative voltages and delaying deactivation of the tail currents. 5. The effects of lyotropic anions did not depend on whether the anion was introduced intracellularly or extracellularly. 6. Extracellular SCN- reversibly increased the peak amplitude and rate of rise of Ca signals, and decreased the latent period between stimulation and onset of the Ca signal. 7. It is concluded that lyotropic anions have similar effects on Ca2+ currents and on charge movement.