Inflammation causes remodeling of mitochondrial cytochrome c oxidase mediated by the bifunctional gene C15orf48.

Dysregulated mitochondrial function is a hallmark of immune-mediated inflammatory diseases. Cytochrome c oxidase (CcO), which mediates the rate-limiting step in mitochondrial respiration, is remodeled during development and in response to changes of oxygen availability, but there has been little study of CcO remodeling during inflammation. Here, we describe an elegant molecular switch mediated by the bifunctional transcript C15orf48, which orchestrates the substitution of the CcO subunit NDUFA4 by its paralog C15ORF48 in primary macrophages. Expression of C15orf48 is a conserved response to inflammatory signals and occurs in many immune-related pathologies. In rheumatoid arthritis, C15orf48 mRNA is elevated in peripheral monocytes and proinflammatory synovial tissue macrophages, and its expression positively correlates with disease severity and declines in remission. C15orf48 is also expressed by pathogenic macrophages in severe coronavirus disease 2019 (COVID-19). Study of a rare metabolic disease syndrome provides evidence that loss of the NDUFA4 subunit supports proinflammatory macrophage functions.

Sarilumab use in severe SARS-CoV-2 pneumonia.

BACKGROUND: Interleukin-6 signal blockade showed preliminary beneficial effects in treating inflammatory response against SARS-CoV-2 leading to severe respiratory distress. Herein we describe the outcomes of off-label intravenous use of Sarilumab in severe SARS-CoV-2-related pneumonia. METHODS: 53 patients with SARS-CoV-2 severe pneumonia received intravenous Sarilumab; pulmonary function improvement or Intensive Care Unit (ICU) admission rate in medical wards, live discharge rate in ICU treated patients and safety profile were recorded. Sarilumab 400 mg was administered intravenously on day 1, with eventual additional infusion based on clinical judgement, and patients were followed for at least 14 days, unless previously discharged or dead. FINDINGS: Of the 53 SARS-CoV-2pos patients receiving Sarilumab, 39(73·6%) were treated in medical wards [66·7% with a single infusion; median PaO2/FiO2:146(IQR:120-212)] while 14(26·4%) in ICU [92·6% with a second infusion; median PaO2/FiO2: 112(IQR:100-141.5)].Within the medical wards, 7(17·9%) required ICU admission, 4 of whom were re-admitted to the ward within 5-8 days. At 19 days median follow-up, 89·7% of medical inpatients significantly improved (46·1% after 24 h, 61·5% after 3 days), 70·6% were discharged from the hospital and 85·7% no longer needed oxygen therapy. Within patients receiving Sarilumab in ICU, 64·2% were discharged from ICU to the ward and 35·8% were still alive at the last follow-up. Overall mortality rate was 5·7%. INTERPRETATION: IL-6R inhibition appears to be a potential treatment strategy for severe SARS-CoV-2 pneumonia and intravenous Sarilumab seems a promising treatment approach showing, in the short term, an important clinical outcome and good safety.

COVID-19 and RA share an SPP1 myeloid pathway that drives PD-L1+ neutrophils and CD14+ monocytes.

We explored the potential link between chronic inflammatory arthritis and COVID-19 pathogenic and resolving macrophage pathways and their role in COVID-19 pathogenesis. We found that bronchoalveolar lavage fluid (BALF) macrophage clusters FCN1+ and FCN1+SPP1+ predominant in severe COVID-19 were transcriptionally related to synovial tissue macrophage (STM) clusters CD48hiS100A12+ and CD48+SPP1+ that drive rheumatoid arthritis (RA) synovitis. BALF macrophage cluster FABP4+ predominant in healthy lung was transcriptionally related to STM cluster TREM2+ that governs resolution of synovitis in RA remission. Plasma concentrations of SPP1 and S100A12 (key products of macrophage clusters shared with active RA) were high in severe COVID-19 and predicted the need for Intensive Care Unit transfer, and they remained high in the post-COVID-19 stage. High plasma levels of SPP1 were unique to severe COVID-19 when compared with other causes of severe pneumonia, and IHC localized SPP1+ macrophages in the alveoli of COVID-19 lung. Investigation into SPP1 mechanisms of action revealed that it drives proinflammatory activation of CD14+ monocytes and development of PD-L1+ neutrophils, both hallmarks of severe COVID-19. In summary, COVID-19 pneumonitis appears driven by similar pathogenic myeloid cell pathways as those in RA, and their mediators such as SPP1 might be an upstream activator of the aberrant innate response in severe COVID-19 and predictive of disease trajectory including post-COVID-19 pathology.

Basic immunology may lead to translational therapeutic rationale: SARS-CoV-2 and rheumatic diseases.

COVID-19 pandemia is a major concern for patients and healthcare systems. The fear of infection by patients with concomitant rheumatic diseases (either adult or children) and connective tissue diseases is arising worldwide, because of their immunological background and immunological therapies. Analysing the basic biology of single diseases, the data suggest that there is an "immunological umbrella" that seems to protect against the infection, through IFN type 1 and NK cell function. To date, reports from China, United States and Europe did not reveal an higher risk of infection, either for rheumatoid arthritis, juvenile idiopathic arthritis nor for lupus erythematosus. Antimalarials, anti-IL6-Anti-IL6 receptor, anti-IL1, anti-GM-CSF receptor and JAK1/2/3 inhibitors, are under investigation in COVID-dedicated clinical trials to control the inflammation raised by SARS-CoV-2 infection. Initial reports on the occurrence of autoimmune phenomena in the convalescence phase of SARS-CoV-2 infection suggests that the immunological consequences of the infection need to be strictly understood. Reporting of the study conforms to broad EQUATOR guidelines (Simera et al January 2010 issue of EJCI).