Successful lung-protective ventilatory management during the VV-ECMO in a severe COVID-19 pneumonia patient with extensive pneumomediastinum and subcutaneous emphysema: a case report

BACKGROUND: Ventilatory management of respiratory failure with pneumomediastinum/subcutaneous emphysema is not established. Herein, we report a case of severe COVID-19 pneumonia with extensive pneumomediastinum/subcutaneous emphysema, rescued by thorough lung-protective ventilatory management after applying the VV-ECMO. CASE PRESENTATION: A 68-year-old male with no medical history was admitted to a local hospital and diagnosed with COVID-19 pneumonia. His pulmonary parameters worsened during invasive ventilation due to the development of pneumomediastinum/subcutaneous emphysema, and then he was transferred to our hospital. On arrival, we immediately decided to apply VV-ECMO and switch to ultraprotective ventilation. After maintaining the initial ventilation with a neuromuscular blocking agent for 2 days, we gradually increased PEEP while limiting PIP to 25 cmH2O. The patient was weaned off VV-ECMO on day 10; he was transferred to the medical ward after extubation. CONCLUSIONS: Lung-protective ventilatory management should be performed thoroughly during VV-ECMO in severe COVID-19 pneumonia with pneumomediastinum/subcutaneous emphysema

Rare complications of hyperbaric oxygen therapy

Hyperbaric oxygen therapy (HBOT) for carbon monoxide (CO) poisoning is widely performed to prevent delayed neuropsychiatric syndrome. Although HBOT can generally be performed with safety, the appropriate management of HBOT still remains unestablished. A 31-year-old man was transferred to our facility to undergo HBOT in a multiplace chamber with a diagnosis of CO poisoning. The first HBOT session ended uneventfully. During the second HBOT session, the patient suddenly experienced convulsive seizures. The accompanying doctor administered intravenous propofol to stop the convulsion and terminated the HBOT. Soon after the convulsion, the patient developed frothy secretions through the endotracheal-tube with impaired oxygenation. Head computed tomography scan showed no abnormalities, suggesting the seizure was associated with complications of HBOT. A chest X-ray revealed bilateral pulmonary edema, and echocardiography revealed normal cardiac function, indicating that the pulmonary edema resulted from HBOT or neurogenic mechanism secondary to the seizure. The patient’s respiratory status improved without recurrence of the seizure and no delayed neurological sequelae was seen afterwards. Here we report unexpected rare adverse events during HBOT. Hyperbaric oxygen therapy for acute indications should be performed in multiplace chambers, with appropriate preparation and medical equipment

The renin–angiotensin system promotes arrhythmogenic substrates and lethal arrhythmias in mice with non-ischaemic cardiomyopathy

[Aims]The progression of pathological left ventricular remodelling leads to cardiac dysfunction and contributes to the occurrence of malignant arrhythmias and sudden cardiac death. The underlying molecular mechanisms remain unclear, however. Our aim was to examine the role of the renin–angiotensin system (RAS) in the mechanism underlying arrhythmogenic cardiac remodelling using a transgenic mouse expressing a cardiac-specific dominant-negative form of neuron-restrictive silencer factor (dnNRSF-Tg). This mouse model exhibits progressive cardiac dysfunction leading to lethal arrhythmias. [Methods and results]Subcutaneous administration of aliskiren, a direct renin inhibitor, significantly suppressed the progression of pathological cardiac remodelling and improved survival among dnNRSF-Tg mice while reducing arrhythmogenicity. Genetic deletion of the angiotensin type 1a receptor (AT1aR) similarly suppressed cardiac remodelling and sudden death. In optical mapping analyses, spontaneous ventricular tachycardia (VT) and fibrillation (VF) initiated by breakthrough-type excitations originating from focal activation sites and maintained by functional re-entry were observed in dnNRSF-Tg hearts. Under constant pacing, dnNRSF-Tg hearts exhibited markedly slowed conduction velocity, which likely contributes to the arrhythmogenic substrate. Aliskiren treatment increased conduction velocity and reduced the incidence of sustained VT. These effects were associated with suppression of cardiac fibrosis and restoration of connexin 43 expression in dnNRSF-Tg ventricles. [Conclusion]Renin inhibition or genetic deletion of AT1aR suppresses pathological cardiac remodelling that leads to the generation of substrates maintaining VT/VF and reduces the occurrence of sudden death in dnNRSF-Tg mice. These findings demonstrate the significant contribution of RAS activation to the progression of arrhythmogenic substrates

クロマチンリモデリン酵素ALC1/CHD1Lは効率的な塩基除去修復に必須である

京都大学0048新制・論文博士博士(医学)乙第13164号論医博第2151号新制||医||1029(附属図書館)京都大学大学院医学研究科医学専攻(主査)教授 岩田 想, 教授 浅野 雅秀, 教授 朝長 啓造学位規則第4条第2項該当Doctor of Medical ScienceKyoto UniversityDFA

Chromatin remodeler ALC1 prevents replication-fork collapse by slowing fork progression.

ALC1 (amplified in liver cancer 1), an SNF2 superfamily chromatin-remodeling factor also known as CHD1L (chromodomain helicase/ATPase DNA binding protein 1-like), is implicated in base-excision repair, where PARP (Poly(ADP-ribose) polymerase) mediated Poly(ADP-ribose) signaling facilitates the recruitment of this protein to damage sites. We here demonstrate the critical role played by ALC1 in the regulation of replication-fork progression in cleaved template strands. To analyze the role played by ALC1 as well as its functional relationship with PARP1, we generated ALC1-/-, PARP1-/-, and ALC1-/-/PARP1-/- cells from chicken DT40 cells. We then exposed these cells to camptothecin (CPT), a topoisomerase I poison that generates single-strand breaks and causes the collapse of replication forks. The ALC1-/- and PARP1-/- cells exhibited both higher sensitivity to CPT and an increased number of chromosome aberrations, compared with wild-type cells. Moreover, phenotypes were very similar across all three mutants, indicating that the role played by ALC1 in CPT tolerance is dependent upon the PARP pathway. Remarkably, inactivation of ALC1 resulted in a failure to slow replication-fork progression after CPT exposure, indicating that ALC1 regulates replication-fork progression at DNA-damage sites. We disrupted ATPase activity by inserting the E165Q mutation into the ALC1 gene, and found that the resulting ALC1-/E165Q cells displayed a CPT sensitivity indistinguishable from that of the null-mutant cells. This observation suggests that ALC1 contributes to cellular tolerance to CPT, possibly as a chromatin remodeler. This idea is supported by the fact that CPT exposure induced chromatin relaxation in the vicinity of newly synthesized DNA in wild-type but not in ALC1-/- cells. This implies a previously unappreciated role for ALC1 in DNA replication, in which ALC1 may regulate replication-fork slowing at CPT-induced DNA-damage sites

Role played by ALC1 in cell tolerance to CPT.

<p>Indicated cells were incubated in medium containing the following DNA-damaging agents at 39.5°C for 48 h: CPT (camptothecin, a topoisomerase 1 poison), γ-ray, UV, ICRF-193 (a catalytic topoisomerase 2 inhibitor), olaparib (a PARP inhibitor), VP16 (a topoisomerase 2 poison), and cisplatin (cis-diamminedichloroplatinum[II]). Then, cell viability was assessed by ATP assay as described in materials and methods. Dosage is displayed on the x-axis on a linear scale, while cell-survival percentage is displayed on the y-axis on a logarithmic scale. Error bars represent standard deviations from three independent experiments.</p

Role played by the ALC1-PARP1 pathway in safe fork-slowing following CPT exposure.

<p>(A) Representative images showing stained DNA fibers. DT40 cells were labeled sequentially with CldU and IdU with or without CPT treatment after CldU labeling. (B) Distribution of CldU/IdU ratios for replication forks in cells exposed to CPT. Indicated cells were incubated in medium containing CldU (25 μM) for 15 min, then incubated in medium containing IdU (250 μM) with CPT (10 μM) or without CPT for 15 min. The CldU/IdU ratios are shown on the x-axis. The number of fibers in each section is shown on the y-axis. 100 forks from each cell line were analyzed. Error bars represent standard deviations from three independent analyses.</p

A model.

<p>Schematic representation of the model showing the regulation of safe replication fork arrest at TopI-cc by PARP-ALC1 pathway. (A) Replication-fork arrest at TOP1-cc activates the ATR-CHK1 checkpoint, which in turn activates the PARP1. PARylation via PARP1 enzyme mediates recruitment of ALC1. ALC1 mediates chromatin remodeling and facilitates replication-fork reversal. (B) As a result of fork reversal, TOP1-cc is located at the 3’ end of SSB and efficiently excised and repaired. (C) Lethal replication results in one-end DSB and following fork collapse.</p

The ALC1-PARP1 axis is not required for the suppression of toxic NHEJ following CPT exposure.

<p>Number of radial chromosomes in 50 mitotic cells. DT40 cells were exposed to CPT (100 nM) for 8 h with colcemid added 2.5 h before harvest to accumulate mitotic cells. Error bars represent standard deviations from three independent experiments. <i>P</i>-value was calculated by a Student’s <i>t</i>-test (*<i>P</i><0.05); n.s. = not significant.</p