SARS-CoV-2 infection induces DNA damage, through CHK1 degradation and impaired 53BP1 recruitment, and cellular senescence.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the RNA virus responsible for the coronavirus disease 2019 (COVID-19) pandemic. Although SARS-CoV-2 was reported to alter several cellular pathways, its impact on DNA integrity and the mechanisms involved remain unknown. Here we show that SARS-CoV-2 causes DNA damage and elicits an altered DNA damage response. Mechanistically, SARS-CoV-2 proteins ORF6 and NSP13 cause degradation of the DNA damage response kinase CHK1 through proteasome and autophagy, respectively. CHK1 loss leads to deoxynucleoside triphosphate (dNTP) shortage, causing impaired S-phase progression, DNA damage, pro-inflammatory pathways activation and cellular senescence. Supplementation of deoxynucleosides reduces that. Furthermore, SARS-CoV-2 N-protein impairs 53BP1 focal recruitment by interfering with damage-induced long non-coding RNAs, thus reducing DNA repair. Key observations are recapitulated in SARS-CoV-2-infected mice and patients with COVID-19. We propose that SARS-CoV-2, by boosting ribonucleoside triphosphate levels to promote its replication at the expense of dNTPs and by hijacking damage-induced long non-coding RNAs' biology, threatens genome integrity and causes altered DNA damage response activation, induction of inflammation and cellular senescence.

Radiological-pathological signatures of patients with COVID-19-related pneumomediastinum: is there a role for the Sonic hedgehog and Wnt5a pathways?

Pneumomediastinum is a rare complication of ARDS but is more common during #COVID19. The fibrous hyaline degeneration of the tracheal rings seen in this autoptic series is an original observation that has not been previously described in COVID-19 patients. https://bit.ly/3vxTQde.

Alveolar Epithelial Type II Cells☆

The alveolar epithelium is a thin continuous liquid lining layer primarily composed of two types of epithelial cells, i.e., alveolar type I (ATI) and alveolar type II (ATII) cells. ATI cells have a broad flattened morphology and cover about 95% of the gas exchange surface of the lung. Whilst, ATIIs are small cuboidal cells with characteristic lamellar inclusions and apical microvilli that line the remainder of the alveolus (about 5%). ATII cells make and secrete a pulmonary surfactant, which reduces the surface tension in the alveoli preventing alveolar collapse during respiration and reducing the energy required to inflate the lungs, thereby increasing pulmonary compliance. These cells also transport ions from the apical to the basolateral surface so as to keep the alveoli relatively fluid free and have roles in the innate immune response. Importantly, they are the progenitor cells for the alveolar epithelium in the adult lung. Having a very thin cytoplasm, a limited number of mitochondria and covering a higher surface area, ATI cells are easily damaged during lung injury, after which they are replaced by ATII cells through the alveolar epithelium regeneration process. Despite ATII cells are considered an essential part of this process, numerous interstitial lung diseases are characterized by hyperplastic ATIIs: in fact, they may also contribute to the fibroproliferative reaction by secreting a number of growth factors and proinflammatory molecules.

The History and Mystery of Alveolar Epithelial Type II Cells: Focus on Their Physiologic and Pathologic Role in Lung.

Alveolar type II (ATII) cells are a key structure of the distal lung epithelium, where they exert their innate immune response and serve as progenitors of alveolar type I (ATI) cells, contributing to alveolar epithelial repair and regeneration. In the healthy lung, ATII cells coordinate the host defense mechanisms, not only generating a restrictive alveolar epithelial barrier, but also orchestrating host defense mechanisms and secreting surfactant proteins, which are important in lung protection against pathogen exposure. Moreover, surfactant proteins help to maintain homeostasis in the distal lung and reduce surface tension at the pulmonary air-liquid interface, thereby preventing atelectasis and reducing the work of breathing. ATII cells may also contribute to the fibroproliferative reaction by secreting growth factors and proinflammatory molecules after damage. Indeed, various acute and chronic diseases are associated with intensive inflammation. These include oedema, acute respiratory distress syndrome, fibrosis and numerous interstitial lung diseases, and are characterized by hyperplastic ATII cells which are considered an essential part of the epithelialization process and, consequently, wound healing. The aim of this review is that of revising the physiologic and pathologic role ATII cells play in pulmonary diseases, as, despite what has been learnt in the last few decades of research, the origin, phenotypic regulation and crosstalk of these cells still remain, in part, a mystery.

Persistence of viral RNA, pneumocyte syncytia and thrombosis are hallmarks of advanced COVID-19 pathology.

BACKGROUND: COVID-19 is a deadly pulmonary disease with peculiar characteristics, which include variable clinical course and thrombophilia. A thorough understanding of the pathological correlates of the disease is still missing. METHODS: Here we report the systematic analysis of 41 consecutive post-mortem samples from individuals who died of COVID-19. Histological analysis is complemented by immunohistochemistry for cellular and viral antigens and the detection of viral genomes by in situ RNA hybridization. FINDINGS: COVID-19 is characterized by extensive alveolar damage (41/41 of patients) and thrombosis of the lung micro- and macro-vasculature (29/41, 71%). Thrombi were in different stages of organization, consistent with their local origin. Pneumocytes and endothelial cells contained viral RNA even at the later stages of the disease. An additional feature was the common presence of a large number of dysmorphic pneumocytes, often forming syncytial elements (36/41, 87%). Despite occasional detection of virus-positive cells, no overt signs of viral infection were detected in other organs, which showed non-specific alterations. INTERPRETATION: COVID-19 is a unique disease characterized by extensive lung thrombosis, long-term persistence of viral RNA in pneumocytes and endothelial cells, along with the presence of infected cell syncytia. Several of COVID-19 features might be consequent to the persistence of virus-infected cells for the duration of the disease. FUNDING: This work was supported by a King's Together Rapid COVID-19 Call grant from King's College London. MG is supported by the European Research Council (ERC) Advanced Grant 787971 "CuRE" and by Programme Grant RG/19/11/34633 from the British Heart Foundation.

Prolonged Low-Dose Methylprednisolone in Patients With Severe COVID-19 Pneumonia.

BACKGROUND: In hospitalized patients with coronavirus disease 2019 (COVID-19) pneumonia, progression to acute respiratory failure requiring invasive mechanical ventilation (MV) is associated with significant morbidity and mortality. Severe dysregulated systemic inflammation is the putative mechanism. We hypothesize that early prolonged methylprednisolone (MP) treatment could accelerate disease resolution, decreasing the need for intensive care unit (ICU) admission and mortality. METHODS: We conducted a multicenter observational study to explore the association between exposure to prolonged, low-dose MP treatment and need for ICU referral, intubation, or death within 28 days (composite primary end point) in patients with severe COVID-19 pneumonia admitted to Italian respiratory high-dependency units. Secondary outcomes were invasive MV-free days and changes in C-reactive protein (CRP) levels. RESULTS: Findings are reported as MP (n = 83) vs control (n = 90). The composite primary end point was met by 19 vs 40 (adjusted hazard ratio [aHR], 0.41; 95% CI, 0.24-0.72). Transfer to ICU and invasive MV were necessary in 15 vs 27 (P = .07) and 14 vs 26 (P = .10), respectively. By day 28, the MP group had fewer deaths (6 vs 21; aHR, 0.29; 95% CI, 0.12-0.73) and more days off invasive MV (24.0 ±â€…9.0 vs 17.5 ±â€…12.8; P = .001). Study treatment was associated with rapid improvement in PaO2:FiO2 and CRP levels. The complication rate was similar for the 2 groups (P = .84). CONCLUSION: In patients with severe COVID-19 pneumonia, early administration of prolonged MP treatment was associated with a significantly lower hazard of death (71%) and decreased ventilator dependence. Treatment was safe and did not impact viral clearance. A large randomized controlled trial (RECOVERY trial) has been performed that validates these findings. Clinical trial registration. ClinicalTrials.gov NCT04323592.