Local treatment with lactate prevents intestinal inflammation in the TNBS-induced colitis model

Lactate has long been considered as a metabolic by-product of cells. Recently, this view has been changed by the observation that lactate can act as a signaling molecule and regulates critical functions of the immune system. We previously identified lactate as the component responsible for the modulation of innate immune epithelial response of fermented milk supernatants in vitro. We have also shown that lactate downregulates proinflammatory responses of macrophages and dendritic cells. So far, in vivo effects of lactate on intestinal inflammation have not been reported. We evaluated the effect of intrarectal administration of lactate in a murine model of colitis induced by 2,4,6-trinitrobenzenesulfonic acid (TNBS). The increase in lactate concentration in colon promoted protective effects against TNBS-induced colitis preventing histopathological damage, as well as bacterial translocation and rise of IL-6 levels in serum. Using intestinal epithelial reporter cells, we found that flagellin treatment induced reporter gene expression, which was abrogated by lactate treatment as well as by glycolysis inhibitors. Furthermore, lactate treatment modulated glucose uptake, indicating that high levels of extracellular lactate can impair metabolic reprograming induced by proinflammatory activation. These results suggest that lactate could be a potential beneficial microbiota metabolite and may constitute an overlooked effector with modulatory properties.Centro de Investigación y Desarrollo en Criotecnología de AlimentosInstituto de Estudios Inmunológicos y Fisiopatológico

Single-channel properties of a stretch-sensitive chloride channel in the human mast cell line HMC-1

A stretch-activated (SA) Cl− channel in the plasma membrane of the human mast cell line HMC-1 was identified in outside-out patch-clamp experiments. SA currents, induced by pressure applied to the pipette, exhibited voltage dependence with strong outward rectification (55.1 pS at +100 mV and an about tenfold lower conductance at −100 mV). The probability of the SA channel being open (Po) also showed steep outward rectification and pressure dependence. The open-time distribution was fitted with three components with time constants of τ1o = 755.1 ms, τ2o = 166.4 ms, and τ3o = 16.5 ms at +60 mV. The closed-time distribution also required three components with time constants of τ1c = 661.6 ms, τ2c = 253.2 ms, and τ3c = 5.6 ms at +60 mV. Lowering extracellular Cl− concentration reduced the conductance, shifted the reversal potential toward chloride reversal potential, and decreased the Po at positive potentials. The SA Cl− currents were reversibly blocked by the chloride channel blocker 4,4′-diisothiocyanatostilbene-2,2′-disulfonic acid (DIDS) but not by (Z)-1-(p-dimethylaminoethoxyphenyl)-1,2-diphenyl-1-butene (tamoxifen). Furthermore, in HMC-1 cells swelling due to osmotic stress, DIDS could inhibit the increase in intracellular [Ca2+] and degranulation. We conclude that in the HMC-1 cell line, the SA outward currents are mediated by Cl− influx. The SA Cl− channel might contribute to mast cell degranulation caused by mechanical stimuli or accelerate membrane fusion during the degranulation process

Ultra-rare RTEL1 gene variants associate with acute severity of COVID-19 and evolution to pulmonary fibrosis as a specific long COVID disorder

Background: Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) is a novel coronavirus that caused an ongoing pandemic of a pathology termed Coronavirus Disease 19 (COVID-19). Several studies reported that both COVID-19 and RTEL1 variants are associated with shorter telomere length, but a direct association between the two is not generally acknowledged. Here we demonstrate that up to 8.6% of severe COVID-19 patients bear RTEL1 ultra-rare variants, and show how this subgroup can be recognized. Methods: A cohort of 2246 SARS-CoV-2-positive subjects, collected within the GEN-COVID Multicenter study, was used in this work. Whole exome sequencing analysis was performed using the NovaSeq6000 System, and machine learning methods were used for candidate gene selection of severity. A nested study, comparing severely affected patients bearing or not variants in the selected gene, was used for the characterisation of specific clinical features connected to variants in both acute and post-acute phases. Results: Our GEN-COVID cohort revealed a total of 151 patients carrying at least one RTEL1 ultra-rare variant, which was selected as a specific acute severity feature. From a clinical point of view, these patients showed higher liver function indices, as well as increased CRP and inflammatory markers, such as IL-6. Moreover, compared to control subjects, they present autoimmune disorders more frequently. Finally, their decreased diffusion lung capacity for carbon monoxide after six months of COVID-19 suggests that RTEL1 variants can contribute to the development of SARS-CoV-2-elicited lung fibrosis. Conclusion: RTEL1 ultra-rare variants can be considered as a predictive marker of COVID-19 severity, as well as a marker of pathological evolution in pulmonary fibrosis in the post-COVID phase. This notion can be used for a rapid screening in hospitalized infected people, for vaccine prioritization, and appropriate follow-up assessment for subjects at risk. Trial Registration NCT04549831 (www.clinicaltrial.org

An explainable model of host genetic interactions linked to COVID-19 severity

We employed a multifaceted computational strategy to identify the genetic factors contributing to increased risk of severe COVID-19 infection from a Whole Exome Sequencing (WES) dataset of a cohort of 2000 Italian patients. We coupled a stratified k-fold screening, to rank variants more associated with severity, with the training of multiple supervised classifiers, to predict severity based on screened features. Feature importance analysis from tree-based models allowed us to identify 16 variants with the highest support which, together with age and gender covariates, were found to be most predictive of COVID-19 severity. When tested on a follow-up cohort, our ensemble of models predicted severity with high accuracy (ACC = 81.88%; AUCROC = 96%; MCC = 61.55%). Our model recapitulated a vast literature of emerging molecular mechanisms and genetic factors linked to COVID-19 response and extends previous landmark Genome-Wide Association Studies (GWAS). It revealed a network of interplaying genetic signatures converging on established immune system and inflammatory processes linked to viral infection response. It also identified additional processes cross-talking with immune pathways, such as GPCR signaling, which might offer additional opportunities for therapeutic intervention and patient stratification. Publicly available PheWAS datasets revealed that several variants were significantly associated with phenotypic traits such as “Respiratory or thoracic disease”, supporting their link with COVID-19 severity outcome

Juvenile dermatomyositis: A report of three cases

Juvenile dermatomyositis (JDM), an autoimmune idiopathic myositis, is characterized by rash and proximal muscle weakness. Immunohistopathology typically shows perivascular inflammatory infiltrate with predominance of CD4+ T lymphocytes, perifascicular atrophy, and upregulation of major histocompatibility complex class I. JDM has been attributed to a humoral-driven muscle microangiopathy probably implicating the type I interferon pathway. Tubulo-reticular inclusions present in endothelial cell of muscle are biomarkers of interferon exposure, and so may be an indirect data of this myopathy especially in the absence of rash and inflammatory infiltrate. We report on three patients in which electron microscopy solves the differential diagnosis among infantile myositis showing peculiar inclusions

Protein-losing gastropathy associated with CMV infection in children. Menetrier\u2019s disease? A case report

Background: Menetrier's disease is a rare form of acquired gastropathy characterized by giant rugal folds in the stomach lining and protein-losing gastropathy; in children, it rarely needs aggressive treatment and resolves spontaneously within 2\u201310 weeks with support therapy. Many cases of pediatric Menetrier's disease associated with cytomegalovirus (CMV) infection have been reported. Clinical findings include nausea, vomiting, abdominal pain, peripheral edema, ascites, and pleural effusion. Gastroduodenal endoscopy is useful in confirming the diagnosis and excluding other similar conditions as lymphoma, eosinophilic gastropathy, gastric varices, Zollinger-Ellison syndrome and lymphangectasia. Specific aim: We describe a case of protein-losing gastropathy, associated with primary CMV infection. Case report: An 18-month-old male presented with periorbital swelling, vomiting and food refusal. Blood tests on admission showed hypoalbuminemia, IgG hypogammaglobulinemia, hypocalcemia and a high peripheral blood eosinophil count. Metabolic, allergologic and autoimmune diseases were ruled out. His immunological profile was normal. Tests for infectious diseases revealed a primary CMV infection. The Guthrie card test for CMV PCR was negative. Endoscopy revealed a normal macroscopic picture of the digestive sections examined and histological examination of multiple oesophageal, gastric and duodenal biopsies was normal. In contrast, the ultrastructural examination of the biopsies revealed signs of viral infection. Considering the diagnostic hypothesis of protein-losing gastropathy associated with CMV infection, a proton pump inhibitor with support therapy and a dose of IgG immunoglobulins to treat the IgG hypogammaglobulinemia were administered. The child was discharged in good clinical condition, with monthly outpatient follow-up for 6 consecutive months. Conclusions: Although CMV infection appears to be the major cause of Menetrier's disease in infants, in our case, the lack of endoscopic and histological features suggestive of Menetrier's disease led us to consider a form of protein-losing gastropathy associated with CMV infection. It is important for pediatric emergency departments to consider the often misdiagnosed Menetrier's disease, together with the other causes of protein-losing enteropathy, in the differential diagnosis for edema and low albumin levels