The incidence, risk factors and outcomes of acute kidney injury in critically ill patients undergoing emergency surgery: a prospective observational study.

BACKGROUND: Without sufficient evidence in postoperative acute kidney injury (AKI) in critically ill patients undergoing emergency surgery, it is meaningful to explore the incidence, risk factors, and prognosis of postoperative AKI. METHODS: A prospective observational study was conducted in the general intensive care units (ICUs) from January 2014 to March 2018. Variables about preoperation, intraoperation and postoperation were collected. AKI was diagnosed using the Kidney Disease: Improving Global Outcomes criteria. RESULTS: Among 383 critically ill patients undergoing emergency surgery, 151 (39.4%) patients developed postoperative AKI. Postoperative reoperation, postoperative Acute Physiology and Chronic Health Evaluation (APACHE II) score, and postoperative serum lactic acid (LAC) were independent risk factors for postoperative AKI, with the adjusted odds ratio (ORadj) of 1.854 (95% confidence interval [CI], 1.091-3.152), 1.059 (95%CI, 1.018-1.102), and 1.239 (95%CI, 1.047-1.467), respectively. Compared with the non-AKI group, duration of mechanical ventilation, renal replacement therapy, ICU and hospital mortality, ICU and hospital length of stay, total ICU and hospital costs were higher in the AKI group. CONCLUSIONS: Postoperative reoperation, postoperative APACHE II score, and postoperative LAC were independent risk factors of postoperative AKI in critically ill patients undergoing emergency surgery.

Muscarinic inhibition of nicotinic transmission in rat sympathetic neurons and adrenal chromaffin cells.

Little is known about the interactions between nicotinic and muscarinic acetylcholine receptors (nAChRs and mAChRs). Here we report that methacholine (MCh), a selective agonist of mAChRs, inhibited up to 80% of nicotine-induced nAChR currents in sympathetic superior cervical ganglion neurons and adrenal chromaffin cells. The muscarine-induced inhibition (MiI) substantially reduced ACh-induced membrane currents through nAChRs and quantal neurotransmitter release. The MiI was time- and temperature-dependent. The slow recovery of nAChR current after washout of MCh, as well as the high value of Q10 (3.2), suggested, instead of a direct open-channel blockade, an intracellular metabotropic process. The effects of GTP-γ-S, GDP-ß-S and pertussis toxin suggested that MiI was mediated by G-protein signalling. Inhibitors of protein kinase C (bisindolymaleimide-Bis), protein kinase A (H89) and PIP2 depletion attenuated the MiI, indicating that a second messenger pathway is involved in this process. Taken together, these data suggest that mAChRs negatively modulated nAChRs via a G-protein-mediated second messenger pathway. The time dependence suggests that MiI may provide a novel mechanism for post-synaptic adaptation in all cells/neurons and synapses expressing both types of AChRs.

Bio-inspired voltage-dependent calcium channel blockers.

Ca(2+) influx via voltage-dependent CaV1/CaV2 channels couples electrical signals to biological responses in excitable cells. CaV1/CaV2 channel blockers have broad biotechnological and therapeutic applications. Here we report a general method for developing novel genetically encoded calcium channel blockers inspired by Rem, a small G-protein that constitutively inhibits CaV1/CaV2 channels. We show that diverse cytosolic proteins (CaVß, 14-3-3, calmodulin and CaMKII) that bind pore-forming α1-subunits can be converted into calcium channel blockers with tunable selectivity, kinetics and potency, simply by anchoring them to the plasma membrane. We term this method 'channel inactivation induced by membrane-tethering of an associated protein' (ChIMP). ChIMP is potentially extendable to small-molecule drug discovery, as engineering FK506-binding protein into intracellular sites within CaV1.2-α1C permits heterodimerization-initiated channel inhibition with rapamycin. The results reveal a universal method for developing novel calcium channel blockers that may be extended to develop probes for a broad cohort of unrelated ion channels.

Functional dissection of the intramolecular Src homology 3-guanylate kinase domain coupling in voltage-gated Ca2+ channel beta-subunits.

The beta-subunit of voltage-gated Ca(2+) channels is essential for trafficking the channels to the plasma membrane and regulating their gating. It contains a Src homology 3 (SH3) domain and a guanylate kinase (GK) domain, which interact intramolecularly. We investigated the structural underpinnings of this intramolecular coupling and found that in addition to a previously described SH3 domain beta strand, two structural elements are crucial for maintaining a strong and yet potentially modifiable SH3-GK intramolecular coupling: an intrinsically weak SH3-GK interface and a direct connection of the SH3 and GK domains. Alterations of these elements uncouple the two functions of the beta-subunit, degrading its ability to regulate gating while leaving its chaperone effect intact.

Functional modularity of the beta-subunit of voltage-gated Ca2+ channels.

The beta-subunit of voltage-gated Ca(2+) channels plays a dual role in chaperoning the channels to the plasma membrane and modulating their gating. It contains five distinct modular domains/regions, including the variable N- and C-terminus, a conserved Src homology 3 (SH3) domain, a conserved guanylate kinase (GK) domain, and a connecting variable and flexible HOOK region. Recent crystallographic studies revealed a highly conserved interaction between the GK domain and alpha interaction domain (AID), the high-affinity binding site in the pore-forming alpha(1) subunit. Here we show that the AID-GK domain interaction is necessary for beta-subunit-stimulated Ca(2+) channel surface expression and that the GK domain alone can carry out this function. We also examined the role of each region of all four beta-subunit subfamilies in modulating P/Q-type Ca(2+) channel gating and demonstrate that the beta-subunit functions modularly. Our results support a model that the conserved AID-GK domain interaction anchors the beta-subunit to the alpha(1) subunit, enabling alpha(1)-beta pair-specific low-affinity interactions involving the N-terminus and the HOOK region, which confer on each of the four beta-subunit subfamilies its distinctive modulatory properties.

WITHDRAWN: Inhibitory effects of D-Serine on hippocampal synapse transmission.

Ahead of Print article withdrawn by publisher.

Structural basis of the alpha1-beta subunit interaction of voltage-gated Ca2+ channels.

High-voltage-activated Ca2+ channels are essential for diverse biological processes. They are composed of four or five subunits, including alpha1, alpha2-delta, beta and gamma (ref. 1). Their expression and function are critically dependent on the beta-subunit, which transports alpha1 to the surface membrane and regulates diverse channel properties. It is believed that the beta-subunit interacts with alpha1 primarily through the beta-interaction domain (BID), which binds directly to the alpha-interaction domain (AID) of alpha1; however, the molecular mechanism of the alpha1-beta interaction is largely unclear. Here we report the crystal structures of the conserved core region of beta3, alone and in complex with AID, and of beta4 alone. The structures show that the beta-subunit core contains two interacting domains: a Src homology 3 (SH3) domain and a guanylate kinase (GK) domain. The AID binds to a hydrophobic groove in the GK domain through extensive interactions, conferring extremely high affinity between alpha1 and beta-subunits. The BID is essential both for the structural integrity of and for bridging the SH3 and GK domains, but it does not participate directly in binding alpha1. The presence of multiple protein-interacting modules in the beta-subunit opens a new dimension to its function as a multi-functional protein.