Cardiac deficiency of P21-activated kinase 1 promotes atrial arrhythmogenesis in mice following adrenergic challenge.

P21-activated kinase 1 (Pak1) signalling plays a vital and overall protective role in the heart. However, the phenotypes of Pak1 deficiency in the cardiac atria have not been well explored. In this study, Pak1 cardiac-conditional knock-out (cKO) mice were studied under baseline and adrenergic challenge conditions. Pak1 cKO mice show atrial arrhythmias including atrial fibrillation (AF) in vivo, detected during anaesthetized electrocardiography without evidence of interstitial fibrosis upon Masson's trichrome staining. Optical mapping of left atrial preparations from Pak1 cKO mice revealed a higher incidence of Ca2+ and action potential alternans under isoprenaline challenge and differences in baseline action potential and calcium transient characteristics. Type-2 ryanodine receptor (RyR2) channels from Pak1 cKO hearts had a higher open probability than those from wild-type. Reverse transcription-quantitative polymerase chain reaction and Western blotting indicated that pCamkIIδ and RyR2 are highly phosphorylated at baseline in the atria of Pak1 cKO mice, while the expression of Slc8a2 and Slc8a3 as a Na+-Ca2+ exchanger, controlling the influx of Ca2+ from outside of the cell and efflux of Na+ from the cytoplasm, are augmented. Chromatin immunoprecipitation study showed that pCreb1 interacts with Slc8a2 and Slc8a3. Our study thus demonstrates that deficiency of Pak1 promotes atrial arrhythmogenesis under adrenergic stress, probably through post-translational and transcriptional modifications of key molecules that are critical to Ca2+ homeostasis. This article is part of the theme issue 'The heartbeat: its molecular basis and physiological mechanisms'.

The outcome and risk factors associated with central and peripheral nervous system involvement in hospitalized COVID-19 patients: a retrospective cohort study.

Introduction: SARS-CoV-2 infection can affect any organ, including both the central nervous system (CNS) and peripheral nervous system (PNS). The aim of this study was to explore the outcome and risk factors associated with the involvement of either CNS or PNS in a cohort of hospitalized COVID-19 patients. Methods: We performed a retrospective observational cohort study of hospitalized adult patients with COVID-19, between May 2020 and December 2022, presenting with new onset neurological disabilities any time after admission. Results: We included 115 patients, 72 with CNS manifestations and 43 with PNS involvement. The CNS manifestations were COVID-19-associated encephalopathy, headache, neurovascular events, and seizures in 80.5, 43, 31.9, and 11.1% of patients, respectively. The neurovascular events were ischemic stroke in 17 (23.6%) patients, hemorrhagic stroke in 6 (8.3%) patients, venous thrombosis in 1 (1.4%) patient, and subarachnoid hemorrhage in 1 (1.4%) patient. Cranial nerve involvement was the most frequent PNS manifestation in 34 (79%) cases, followed by mononeuritis in 5 (11.6%) patients and polyneuropathy in 4 (9.3%) patients. The affected cranial nerves were the vestibulocochlear nerve in 26 (60.5%) patients, the olfactory nerve in 24 (55.8%) patients, the oculomotor nerves in 5 (11.6%) patients, and the facial nerve in 1 (2.3%) patient. Two patients (9.3%) presented with polyneuritis cranialis. Older age (HR = 1.02, 95% CI: 1.003-1.037, p = 0.01), COVID severity (HR = 2.53, 95% CI: 1.42-4.5, p = 0.002), ischemic cardiac disease (HR = 2.42, 95% CI: 1.05-5.6, p = 0.03), and increased D-dimers (HR = 1.00, 95% CI: 1.00-1.00, p = 0.02) were independently associated with the development of CNS manifestations. The factors associated with in-hospital mortality were age (HR = 1.059, 95% CI: 1.024-1.096, p = 0.001), C-reactive protein (HR = 1.006, 95% CI: 1.00-1.011, p = 0.03), CNS involvement (HR = 9.155, 95% CI: 1.185-70.74, p = 0.03), and leucocyte number (HR = 1.053, 95% CI: 1.026-1.081, p < 0.001). Conclusion: COVID-19-associated encephalopathy was the most common CNS manifestation in our study, but neurovascular events are also important considering the overlap between inflammatory and prothrombotic pathways, especially in severe cases. CNS involvement was associated with in-hospital all-cause mortality. PNS findings were various, involving mostly the cranial nerves, especially the vestibulocochlear nerve.

Healthcare-associated Clostridioides difficile infection during the COVID-19 pandemic in a tertiary care hospital in Romania.

Introduction. Information on healthcare-associated C.difficile infection (HA-CDI) in COVID-19 patients is limited. We aimed to assess the characteristics of HA-CDI acquired during and before the COVID-19 pandemic. Methods. We conducted a retrospective study in a tertiary care hospital, in which since March 2020 exclusively COVID-19 patients are hospitalized. We compared HA-CDI adult patients hospitalized in March 2020-February 2021 with those hospitalized during the same period in 2017-2018. Results. We found 51 cases during 2020-2021 (COVID-19 group), incidence 5.6/1000 adult discharge and 99 cases during 2017-2018 (pre-COVID-19 group), incidence 6.1/1000 adult discharge (p=0.6). The patients in COVID-19 group compared to pre-COVID-19 group were older (median age 66 vs 62 years), with similar rate of comorbidities, but with higher rate of cardiovascular diseases (62.7% vs 42.4%) and less immunosuppression (21.6% vs 55.6%), they had a higher proton pump inhibitors use (94.1% vs 32.3%), and a longer hospitalization (median 19 vs 14 days). Eighty-five (85.9%) patients in pre-COVID-19 group versus 44 (86.3%) patients in COVID-19 group received antimicrobial treatment - mainly cephalosporins (34,1%), quinolones (22,3%) and glycopeptides (21,1%) in pre-COVID-19 group and mainly cephalosporins and macrolides (63,6% each) in COVID-19 group. We found four HA-CDI-related deaths in pre-COVID-19 group and none in the COVID-19 group. Conclusions. The HA-CDI incidence in COVID-19 group did not change versus the same period of time during 2017-2018. The antibiotic use was the most important factor associated with HA-CDI. We identified a high use of broad-spectrum antibiotics despite the lack of empirical antimicrobial recommendations in COVID-19.

µ-Opioid receptor activation modulates CA3-to-CA1 gamma oscillation phase-coupling.

In the intact brain, hippocampal area CA1 alternates between low-frequency gamma oscillations (γ), phase-locked to low-frequency γ in CA3, and high-frequency γ, phase-locked to γ in the medial entorhinal cortex. In hippocampal slices, γ in CA1 is phase-locked to CA3 low-frequency γ. However, when Schaffer collaterals are cut, CA1 can generate its own high-frequency γ. Here we test whether (un)coupling of CA1 γ from CA3 γ can be caused by µ-opioid receptor (MOR) modulation. In CA1 minislices isolated from rat ventral hippocampus slices, MOR activation by DAMGO reduced the dominant frequency of intrinsic fast γ, induced by carbachol. In intact slices, DAMGO strongly reduced the dominant frequency of CA3 slow γ, but did not affect γ power consistently. DAMGO suppressed the phase coupling of CA1 γ to CA3 slow γ and increased the power of CA1 intrinsic fast γ, but not in the presence of the MOR antagonist CTAP. The benzodiazepine zolpidem and local application of DAMGO to CA3 both mimicked the reduction in dominant frequency of CA3 slow γ, but did not reduce the phase coupling. Local application of DAMGO to CA1 reduced phase coupling. These results suggest that MOR-expressing CA1 interneurons, feed-forwardly activated by Schaffer collaterals, are responsible for the phase coupling between CA3 γ and CA1 γ. Modulating their activity may switch the CA1 network between low-frequency γ and high-frequency γ, controlling the information flow between CA1 and CA3 or medial entorhinal cortex respectively.