Risk and predictive factors of prolonged viral RNA shedding in upper respiratory specimens in a large cohort of COVID-19 patients admitted to an Italian reference hospital.

BACKGROUND: Limited data are available about the predictors and outcomes associated with prolonged SARS-CoV-2 RNA shedding (VS). METHODS: A retrospective study including COVID-19 patients admitted to an Italian hospital between March 1 and July 1, 2020. Predictors of viral clearance (VC) and prolonged VS from the upper respiratory tract were assessed by Poisson regression and logistic regression analyses. The causal relation between VS and clinical outcomes was evaluated through an inverse probability weighted Cox model. RESULTS: The study included 536 subjects. The median duration of VS from symptoms onset was 18 days. The estimated 30-day probability of VC was 70.2%. Patients with comorbidities, lymphopenia at hospital admission, or moderate/severe respiratory disease had a lower chance of VC. The development of moderate/severe respiratory failure, delayed hospital admission after symptoms onset, baseline comorbidities, or D-dimer >1000ng/mL at admission independently predicted prolonged VS. The achievement of VC doubled the chance of clinical recovery and reduced the probability of death/mechanical ventilation. CONCLUSIONS: Respiratory disease severity, comorbidities, delayed hospital admission and inflammatory markers negatively predicted VC, which resulted to be associated with better clinical outcomes. These findings highlight the importance of prompt hospitalization of symptomatic patients, especially where signs of severity or comorbidities are present.

Exploring the genetics of irritable bowel syndrome: a GWA study in the general population and replication in multinational case-control cohorts.

OBJECTIVE: IBS shows genetic predisposition, but adequately powered gene-hunting efforts have been scarce so far. We sought to identify true IBS genetic risk factors by means of genome-wide association (GWA) and independent replication studies. DESIGN: We conducted a GWA study (GWAS) of IBS in a general population sample of 11,326 Swedish twins. IBS cases (N=534) and asymptomatic controls (N=4932) were identified based on questionnaire data. Suggestive association signals were followed-up in 3511 individuals from six case-control cohorts. We sought genotype-gene expression correlations through single nucleotide polymorphism (SNP)-expression quantitative trait loci interactions testing, and performed in silico prediction of gene function. We compared candidate gene expression by real-time qPCR in rectal mucosal biopsies of patients with IBS and controls. RESULTS: One locus at 7p22.1, which includes the genes KDELR2 (KDEL endoplasmic reticulum protein retention receptor 2) and GRID2IP (glutamate receptor, ionotropic, delta 2 (Grid2) interacting protein), showed consistent IBS risk effects in the index GWAS and all replication cohorts and reached p=9.31×10(-6) in a meta-analysis of all datasets. Several SNPs in this region are associated with cis effects on KDELR2 expression, and a trend for increased mucosal KDLER2 mRNA expression was observed in IBS cases compared with controls. CONCLUSIONS: Our results demonstrate that general population-based studies combined with analyses of patient cohorts provide good opportunities for gene discovery in IBS. The 7p22.1 and other risk signals detected in this study constitute a good starting platform for hypothesis testing in future functional investigations.

Cytochromes b561: ascorbate-mediated trans-membrane electron transport.

SIGNIFICANCE: Cytochromes b561 (CYB561s) constitute a family of trans-membrane (TM), di-heme proteins, occurring in a variety of organs and cell types, in plants and animals, and using ascorbate (ASC) as an electron donor. CYB561s function as monodehydroascorbate reductase, regenerating ASC, and as Fe³âº-reductases, providing reduced iron for TM transport. A CYB561-core domain is also associated with dopamine ß-monooxygenase redox domains (DOMON) in ubiquitous CYBDOM proteins. In plants, CYBDOMs form large protein families. Physiological functions supported by CYB561s and CYBDOMs include stress defense, cell wall modifications, iron metabolism, tumor suppression, and various neurological processes, including memory retention. CYB561s, therefore, significantly broaden our view on the physiological roles of ASC. RECENT ADVANCES: The ubiquitous nature of CYB561s is only recently being recognized. Significant advances have been made through the study of recombinant CYB561s, revealing structural and functional properties of a unique "two-heme four-helix" protein configuration. In addition, the DOMON domains of CYBDOMs are suggested to contain another heme b. CRITICAL ISSUES: New CYB561 proteins are still being identified, and there is a need to provide an insight and overview on the various roles of these proteins and their structural properties. FUTURE DIRECTIONS: Mutant studies will reveal in greater detail the mechanisms by which CYB561s and CYBDOMs participate in cell metabolism in plants and animals. Moreover, the availability of efficient heterologous expression systems should allow protein crystallization, more detailed (atomic-level) structural information, and insights into the intra-molecular mechanism of electron transport.

Mucosal permeability and immune activation as potential therapeutic targets of probiotics in irritable bowel syndrome.

There is increasingly convincing evidence supporting the participation of the gut microenvironment in the pathophysiology of irritable bowel syndrome (IBS). Studies particularly suggest an interplay between luminal factors (eg, foods and bacteria residing in the intestine), the epithelial barrier, and the mucosal immune system. Decreased expression and structural rearrangement of tight junction proteins in the small bowel and colon leading to increased intestinal permeability have been observed, particularly in postinfectious IBS and in IBS with diarrhea. These abnormalities are thought to contribute to the outflow of antigens through the leaky epithelium, causing overstimulation of the mucosal immune system. Accordingly, subsets of patients with IBS show higher numbers and an increased activation of mucosal immunocytes, particularly mast cells. Immune factors, released by these cells, including proteases, histamine, and prostanoids, participate in the perpetuation of the permeability dysfunction and contribute to the activation of abnormal neural responses involved in abdominal pain perception and changes in bowel habits. All these mechanisms represent new targets for therapeutic approaches in IBS. Probiotics are an attractive therapeutic option in IBS given their recognized safety and by virtue of positive biological effects they can exert on the host. Of importance for the IBS pathophysiology is that preclinical studies have shown that selective probiotic strains exhibit potentially useful properties including anti-inflammatory effects, improvement of mucosal barrier homeostasis, beneficial effects on intestinal microbiota, and a reduction of visceral hypersensitivity. The effect of probiotics on IBS is positive in most randomized, controlled studies, although the gain over the placebo is small. Identifying tailored probiotic approaches for subgroups of IBS patients represents a challenge for the future.

Neuroprotection of microglial conditioned medium on 6-hydroxydopamine-induced neuronal death: role of transforming growth factor beta-2.

Microglia, the immune cells of the CNS, play essential roles in both physiological and pathological brain states. Here we have used an in vitro model to demonstrate neuroprotection of a 48 h-microglial conditioned medium (MCM) towards cerebellar granule neurons (CGNs) challenged with the neurotoxin 6-hydroxydopamine, which induces a Parkinson-like neurodegeneration, and to identify the protective factor(s). MCM nearly completely protects CGNs from 6-hydroxydopamine neurotoxicity and at least some of the protective factor(s) are peptidic in nature. While the fraction of the medium containing molecules < 30 kDa completely protects CGNs, fractions containing molecules < 10 kDa or > 10 kDa are not neuroprotective. We further demonstrate that microglia release high amounts of transforming growth factor-beta2 (TGF-beta2) and that its exogenous addition to the fraction of the medium not containing it (< 10 kDa) fully restores the neuroprotective action. Moreover, MCM neuroprotection is significantly counteracted by an inhibitor of TGF-beta2 transduction pathway. Our results identify TGF-beta2 as an essential neuroprotective factor released by microglia in its culture medium that requires to be fully effective the concomitant presence of other factor(s) of low molecular weight.