Effect of SARS-CoV-2 S protein on the proteolytic cleavage of the epithelial Na+ channel ENaC.

Severe cases of COVID-19 are characterized by development of acute respiratory distress syndrome (ARDS). Water accumulation in the lungs is thought to occur as consequence of an exaggerated inflammatory response. A possible mechanism could involve decreased activity of the epithelial Na+ channel, ENaC, expressed in type II pneumocytes. Reduced transepithelial Na+ reabsorption could contribute to lung edema due to reduced alveolar fluid clearance. This hypothesis is based on the observation of the presence of a novel furin cleavage site in the S protein of SARS-CoV-2 that is identical to the furin cleavage site present in the alpha subunit of ENaC. Proteolytic processing of αENaC by furin-like proteases is essential for channel activity. Thus, competition between S protein and αENaC for furin-mediated cleavage in SARS-CoV-2-infected cells may negatively affect channel activity. Here we present experimental evidence showing that coexpression of the S protein with ENaC in a cellular model reduces channel activity. In addition, we show that bidirectional competition for cleavage by furin-like proteases occurs between 〈ENaC and S protein. In transgenic mice sensitive to lethal SARS-CoV-2, however, a significant decrease in gamma ENaC expression was not observed by immunostaining of lungs infected as shown by SARS-CoV2 nucleoprotein staining.

Association of omental pedicled flap with anastomotic leak following low anterior resection for rectal cancer.

BACKGROUND AND OBJECTIVES: Anastomotic leak following colorectal anastomosis adversely impacts short-term, oncologic, and quality-of-life outcomes. This study aimed to assess the impact of omental pedicled flap (OPF) on anastomotic leak among patients undergoing low anastomotic resection (LAR) for rectal cancer using a multi-institutional database. METHODS: Adult rectal cancer patients in the US Rectal Cancer Consortium, who underwent a LAR for stage I-III rectal cancer with or without an OPF were included. Patients with missing data for surgery type and OPF use were excluded from the analysis. The primary outcome was the development of anastomotic leaks. Multivariable logistic regression was used to determine the association. RESULTS: A total of 853 patients met the inclusion criteria and OPF was used in 106 (12.4%) patients. There was no difference in age, sex, or tumor stage of patients who underwent OPF versus those who did not. OPF use was not associated with an anastomotic leak (p = 0.82), or operative blood loss (p = 0.54) but was associated with an increase in the operative duration [ß = 21.42 (95% confidence interval = 1.16, 41.67) p = 0.04]. CONCLUSIONS: Among patients undergoing LAR for rectal cancer, OPF use was associated with an increase in operative duration without any impact on the rate of anastomotic leak.

Toxicities of CAR T-cell therapy: a review of current literature.

The chimeric antigen receptor (CAR) design, first invented by Zelig Eshhar, paved the way for the use of genetically modified T-cells in targeted therapy against cancer cells. Since then, it has gone through many generations, especially with the integration of co-stimulation in the second and third-generation CARs. However, it also mounts a hyperactive immune response named as cytokine release syndrome with the release of several cytokines eventually resulting in multiple end-organ toxicities. The severity of cytokine release syndrome depends upon certain factors such as the tumor burden, choice of co-stimulation, and degree of lymphodepletion, and can manifest as pulmonary edema, vascular leak, renal dysfunction, cardiac problems, hepatic failure, and coagulopathy. Many grading criteria have been used to define these clinical manifestations but they lack harmonization. Neurotoxicity has also been significantly associated with CAR T-cell therapy but it has not been studied much in previous literature. This review aims to provide a comprehensive account of the clinical manifestations, diagnosis, management, and treatment of CAR T-cell associated neurotoxicity.

Type 1 Autoimmune Pancreatitis Masquerading as Pancreatic Head Carcinoma.

Obstructive jaundice is a joint clinical presentation with many etiologies, including pancreatic cancer and autoimmune pancreatitis (AIP). Differentiating between these two conditions is pivotal due to the divergent management approaches and prognoses. In this case report, we present a case of a 49-year-old female patient who presented with weight loss, intermittent chronic abdominal pain, and jaundice. She was initially suspected of having pancreatic cancer because of clinical presentation and imaging findings. However, she was ultimately diagnosed with Type 1 AIP due to histopathology findings and elevated immunoglobulin G4. This case highlights the complexities in diagnosis, the role of advanced imaging techniques and tissue sampling, and the lessons learned regarding managing this challenging clinical scenario.

Epigenetic Modulation of Human Podocyte Vitamin D Receptor in HIV Milieu.

HIV (human immunodeficiency virus) has been reported to induce podocyte injury through down regulation of vitamin D receptor (VDR) and activation of renin angiotensin system; however, the involved mechanism is not clear. Since HIV has been reported to modulate gene expression via epigenetic phenomena, we asked whether epigenetic factors contribute to down regulation of VDR. Kidney cells in HIV transgenic mice and HIV-infected podocytes (HIV/HPs) displayed enhanced expression of SNAIL, a repressor of VDR. To elucidate the mechanism, we studied the effect of HIV on expression of molecules involved in SNAIL repressor complex formation and demonstrated that HIV enhances expression of the histone deacetylase HDAC1 and DNA methyl transferases DNMT3b and DNMT1. 293T cells, when stably transfected with SNAIL (SNAIL/293T), displayed suppressed transcription and translation of VDR. In SNAIL/293T cells, co-immunoprecipitation studies revealed the association of HDAC1, DNMT3b, DNMT1, and mSin3A with SNAIL. Chromatin immunoprecipitation experiments confirmed the presence of the SNAIL repressor complex at the VDR promoter. Consistent with the enhanced DNA methyl transferase expression in HIV/HPs, there was an increased CpG methylation at the VDR promoter. Chromatin immunoprecipitation assay confirmed occurrence of H3K4 trimethylation on SNAIL promoter. Neither a VDR agonist (VDA) nor an HDAC inhibitor (HDACI) nor a demethylating agent (DAC) individually could optimally up regulate VDR in HIV milieu. However, VDA and HDACI when combined were successful in de-repressing VDR expression. Our findings demonstrate that SNAIL recruits multiple chromatin enzymes to form a repressor complex in HIV milieu that down regulates VDR expression.

High yield expression and purification of equilibrative nucleoside transporter 7 (ENT7) from Arabidopsis thaliana.

BACKGROUND: Equilibrative nucleoside transporters (ENTs) facilitate the import of nucleosides and their analogs into cells in a bidirectional, non-concentrative manner. However, in contrast to their name, most characterized plant ENTs act in a concentrative manner. A direct characterization of any ENT protein has been hindered due to difficulties in overexpression and obtaining pure recombinant protein. METHODS: The equilibrative nucleoside transporter 7 from Arabidopsis thaliana (AtENT7) was expressed in Xenopus laevis oocytes to assess mechanism of substrate uptake. Recombinant protein fused to enhanced green fluorescent protein (eGFP) was expressed in Pichia pastoris to characterize its oligomeric state by gel filtration and substrate binding by microscale thermophoresis (MST). RESULTS: AtENT7 expressed in X. laevis oocytes works as a classic equilibrative transporter. The expression of AtENT7-eGFP in the P. pastoris system yielded milligram amounts of pure protein that exists as stable homodimers. The concentration dependent binding of purine and pyrimidine nucleosides to the purified recombinant protein, assessed by MST, confirmed that AtENT7-eGFP is properly folded. For the first time the binding of nucleobases was observed for AtENT7. SIGNIFICANCE: The availability of pure recombinant AtENT7 will permit detailed kinetic and structural studies of this unique member of the ENT family and, given the functional similarity to mammalian ENTs, will serve as a good model for understanding the structural basis of translocation mechanism for the family.

Syncope units: impact on patient care and health-related costs.

Clinical decision making can be challenging regarding the emergency department (ED) management of patients with recent syncope. Several models of the syncope management unit are summarized in this article. Assessment of patients with recent syncope in a specialized evaluation unit, such as an emergency department-based syncope management unit, holds great promise in terms of reducing hospital admissions, reducing costs and improving outcomes for patients with syncope.

Surveillance of AF recurrence post-surgical AF ablation using implantable cardiac monitor.

BACKGROUND: Although pulmonary vein isolation is an effective treatment for recurrent atrial fibrillation (AF), there is no consensus on the definition of success or follow-up strategies. Existing data are limited to intermittent Holter or transtelephonic monitoring with reliance on patient symptoms. OBJECTIVE: We sought to determine the outcomes of surgical ablation and post-ablation AF surveillance with a leadless implantable cardiac monitor (ICM). METHODS: Forty-five patients with drug-refractory paroxysmal or persistent AF underwent video-assisted epicardial ablation using a bipolar radiofrequency clamp. An ICM was implanted subcutaneously post-ablation to assess AF recurrence. AF recurrence was defined as ≥1 AF episode with a duration of ≥30 s. The device-stored data was downloaded weekly over the internet, and all transmitted events were reviewed. RESULTS: A total of 1,220 AF automatic and patient-activated AF episodes were analyzed over a follow-up of 12 ± 3 months. Of these episodes, 46% were asymptomatic. Furthermore, only 66% of the patient-activated episodes were AF. AF recurrence was highest in first 4 weeks and substantially decreased 6 months post-ablation. The overall freedom from AF recurrence at the end of follow-up was 60%. When 48-h Holter recordings were compared with the device-stored episodes, the sensitivity of the device to detect AF was 98%, and the specificity was 71%. CONCLUSIONS: The ICM provides an objective measure of AF ablation success and may be useful in making clinical decisions. This device may be used in future ablation studies to develop a more rigorous definition of procedural success.