Sepsis-associated encephalopathy (SAE), characterized as diffuse brain dysfunction and neurological manifestations secondary to sepsis, is a common complication in critically ill patients and can give rise to poor outcome, but understanding the molecular basis of this disorder remains a major challenge. Given the emerging role of G protein-coupled receptor 2 (GRK2), first identified as a G protein-coupled receptor (GPCR) regulator, in the regulation of non-G protein-coupled receptor-related molecules contributing to diverse cellular functions and pathology, including inflammation, we tested the hypothesis that GRK2 may be linked to the neuropathogenesis of SAE. When mouse MG6 microglial cells were challenged with lipopolysaccharide (LPS), GRK2 cytosolic expression was highly up-regulated. The ablation of GRK2 by small interfering RNAs (siRNAs) prevented an increase in intracellular reactive oxygen species generation in LPS-stimulated MG6 cells. Furthermore, the LPS-induced up-regulation of inducible nitric-oxide synthase expression and increase in nitric oxide production were negated by GRK2 inhibitor or siRNAs. However, GRK2 inhibition was without effect on overproduction of tumor necrosis factor-α, interleukin (IL)-6, and IL-1β in LPS-stimulated MG cells. In mice with cecal ligation and puncture-induced sepsis, treatment with GRK2 inhibitor reduced high levels of oxidative and nitrosative stress in the mice brains, where GRK2 expression was up-regulated, alleviated neurohistological damage observed in cerebral cortex sections, and conferred a significant survival advantage to CLP mice. Altogether, these results uncover the novel role for GRK2 in regulating cellular oxidative and nitrosative stress during inflammation and suggest that GRK2 may have a potential as an intriguing therapeutic target to prevent or treat SAE.

G protein-coupled receptor kinase 2 (GRK2) is a ubiquitous member of the GRK family that restrains cellular activation by G protein-coupled receptor (GPCR) phosphorylation leading to receptor desensitization and internalization, but has been identified to regulate a variety of signaling molecules, among which may be associated with inflammation. In this study, we attempted to establish the regulatory role of GRK2 in the Toll-like receptor (TLR) signaling pathway for inducible nitric oxide synthase (iNOS) expression in microglial cells. When mouse MG6 cells were stimulated with the TLR4 ligands lipopolysaccharide (LPS) and paclitaxel, we found that interferon regulatory factor 1 (IRF1) protein expression and activation was upregulated, transcription of interferon-β (IFN-β) was accelerated, induction/activation of STAT1 and activation of STAT3 were promoted, and subsequently iNOS expression was upregulated. The ablation of GRK2 by small interfering RNAs (siRNAs) not only eliminated TLR4-mediated upregulation of IRF1 protein expression and nuclear translocation but also suppressed the activation of the STAT pathway, resulting in negating the iNOS upregulation. The TLR3-mediated changes in IRF1 and STAT1/3, leading to iNOS induction, were also abrogated by siRNA knockdown of GRK2. Furthermore, transfection of GRK2 siRNA blocked the exogenous IFN-β supplementation-induced increases in phosphorylation of STAT1 as well as STAT3 and abrogated the augmentation of iNOS expression in the presence of exogenous IFN-β. Taken together, our results show that GRK2 regulates the activation of IRF1 as well as the activation of the STAT pathway, leading to upregulated transcription of iNOS in activated microglial cells. Modulation of the TLR signaling pathway via GRK2 in microglia may be a novel therapeutic target for treatment of neuroinflammatory disorders.

Paclitaxel-induced peripheral neuropathy (PIPN) is one of the serious adverse events associated with paclitaxel-based cancer treatments. A recent case study showed that the antiplatelet agent clopidogrel inhibits paclitaxel metabolism via cytochrome P450 (CYP) 2C8, resulting in severe PIPN. The aim of this study was to determine the impact of clopidogrel as a risk factor for the development of PIPN, using a retrospective cohort study. Data from paclitaxel-treated patients with or without clopidogrel and low-dose aspirin treatment were retrieved from medical charts. A total of 161 adult patients were included in this study: 135 were controls, 9 were clopidogrel-treated and 17 were aspirin-treated. The clopidogrel group had a greater proportion of males and a higher rate of comorbidities, such as diabetes mellitus and dyslipidemia, than the control group. However, patient characteristics were similar between the clopidogrel and aspirin groups. Severe PIPN was diagnosed in 3 (2.2%) and 2 (22.2%) patients in the control and clopidogrel groups, respectively (odds ratio: 12.0; p = 0.031). No patients in the aspirin group presented with severe neuropathy. These pilot data suggest that concomitant treatment with clopidogrel leads to a greater risk of PIPN. The avoidance of concomitant clopidogrel use may be effective in reducing clopidogrel-associated PIPN.

Remimazolam is an ultrashort-acting benzodiazepine that causes minimal hemodynamic changes. We present two patients, with reduced ejection fraction, who underwent remimazolam anesthesia for transcatheter edge-to-edge repair of the mitral valve with the MitraClip system. In case 1, the patient's vitals were stable throughout the surgery. However, in case 2, which had a lower cardiac output, the patient's blood pressure decreased remarkably after anesthesia induction. Though remimazolam does not alter the cardiac output, it reportedly has vasodilatory effects. Since remimazolam can reduce blood pressure in patients where the reduction in cardiac output is compensated for by high peripheral vascular resistance, caution should be exercised.

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