Severe acute respiratory syndrome (SARS) is an acute infectious disease that spreads mainly via the respiratory route. A distinct coronavirus (SARS-CoV) has been identified as the aetiological agent of SARS. Recently, a metallopeptidase named angiotensin-converting enzyme 2 (ACE2) has been identified as the functional receptor for SARS-CoV. Although ACE2 mRNA is known to be present in virtually all organs, its protein expression is largely unknown. Since identifying the possible route of infection has major implications for understanding the pathogenesis and future treatment strategies for SARS, the present study investigated the localization of ACE2 protein in various human organs (oral and nasal mucosa, nasopharynx, lung, stomach, small intestine, colon, skin, lymph nodes, thymus, bone marrow, spleen, liver, kidney, and brain). The most remarkable finding was the surface expression of ACE2 protein on lung alveolar epithelial cells and enterocytes of the small intestine. Furthermore, ACE2 was present in arterial and venous endothelial cells and arterial smooth muscle cells in all organs studied. In conclusion, ACE2 is abundantly present in humans in the epithelia of the lung and small intestine, which might provide possible routes of entry for the SARS-CoV. This epithelial expression, together with the presence of ACE2 in vascular endothelium, also provides a first step in understanding the pathogenesis of the main SARS disease manifestations.

Kidney failure is frequently observed during and after COVID-19, but it remains elusive whether this is a direct effect of the virus. Here, we report that SARS-CoV-2 directly infects kidney cells and is associated with increased tubule-interstitial kidney fibrosis in patient autopsy samples. To study direct effects of the virus on the kidney independent of systemic effects of COVID-19, we infected human induced pluripotent stem cell-derived kidney organoids with SARS-CoV-2. Single cell RNA-sequencing indicated injury and dedifferentiation of infected cells with activation of pro-fibrotic signaling pathways. Importantly, SARS-CoV-2 infection also led to increased collagen 1 protein expression in organoids. A SARS-CoV-2 protease inhibitor was able to ameliorate the infection of kidney cells by SARS-CoV-2. Our results suggest that SARS-CoV-2 can directly infect kidney cells and induce cell injury with subsequent fibrosis. These data could explain both acute kidney injury in COVID-19 patients and the development of chronic kidney disease in Long-COVID.

Background and Aims Crohn’s disease [CD] is characterised by chronic intestinal inflammation and dysbiosis in the gut. Riboflavin [vitamin B2] has anti-inflammatory, antioxidant and microbiome-modulatory properties. Here, we analysed the effect of riboflavin on oxidative stress, markers of inflammation, clinical symptoms, and faecal microbiome in patients with CD. Methods In this prospective clinical intervention study, patients received 100 mg riboflavin [DSM, Nutritional Products Ltd] daily for 3 weeks. Clinical disease activity [Harvey-Bradshaw Index: HBI], serum biomarkers of inflammation and redox status [plasma free thiols], and faecal microbiome taxonomical composition and functionality [fluorescent in situ hybridisation: FISH; and metagenomic shotgun sequencing: MGS], were analysed before and after riboflavin intervention. Results In total, 70 patients with CD with varying disease activity were included. Riboflavin supplementation significantly decreased serum levels of inflammatory markers. In patients with low faecal calprotectin [FC] levels, IL-2 decreased, and in patients with high FC levels, C-reactive protein [CRP] was reduced and free thiols significantly increased after supplementation. Moreover, HBI was significantly decreased by riboflavin supplementation. Riboflavin supplementation led to decreased Enterobacteriaceae in patients with low FC levels as determined by FISH; however, MGS analysis showed no effects on diversity, taxonomy, or metabolic pathways of the faecal microbiome. Conclusions Three weeks of riboflavin supplementation resulted in a reduction in systemic oxidative stress, mixed anti-inflammatory effects, and a reduction in clinical symptoms [HBI]. FISH analysis showed decreased Enterobacteriaceae in patients with CD with low FC levels, though this was not observed in MGS analysis. Our data demonstrate that riboflavin supplementation has a number of anti-inflammatory and anti-oxidant effects in CD.

Introduction: Crohn’s disease (CD) is characterized by chronic and relapsing inflammation of the gastro-intestinal tract. It is assumed that oxidative stress contributes to CD pathogenesis, but systemic biomarkers for oxidative stress in CD are not yet identified. A reduction in free thiol groups in plasma proteins (“plasma free thiols”) reflects systemic oxidative stress since they are prime substrates for reactive oxygen species. Here, we determined the concentrations of plasma free thiols in CD patients and healthy controls and studied the putative correlation with disease parameters. Methods: Free thiols were quantified in plasma of patients with CD in clinical remission [according to the Harvey Bradshaw Index (HBI)] and healthy controls and adjusted for plasma albumin. Albumin-adjusted free thiol concentrations were analyzed for associations with clinical and biochemical disease markers. Results: Mean plasma free thiol concentrations were significantly lower in patients with CD ( n = 51) compared to healthy controls ( n = 27) (14.7 ± 2.4 vs. 17.9 ± 1.8 μmol/g albumin; P < 0.001). Patients with CD with above-average free thiols had significantly lower CRP levels (median 1.4 [interquartile range] [0.4; 2.6] vs. 3.6 [0.6; 7.0] mg/L; P < 0.05) and BMI (23.6 ± 4.8 vs. 27.1 ± 5.2 kg/m 2 ; P < 0.05). Patients with CD having solely colonic disease demonstrated markedly reduced plasma free thiol concentrations compared to patients with ileocolonic involvement (13.2 ± 1.8 vs. 15.2 ± 2.2 μmol/g; P < 0.05). Finally, plasma free thiol concentrations negatively correlated with biomarkers of inflammation, including hsCRP, SAA, IL-17A (all P < 0.05), and VEGF. Conclusion: Plasma free thiols are reduced in patients with CD in clinical remission compared to healthy controls. Thus, subclinical CD disease activity is reflected by systemic oxidative stress and plasma free thiols may be a relevant therapeutic target and biomarker to monitor disease activity in CD.

Oxidative stress plays a pivotal role in the pathogenesis of inflammatory bowel diseases (IBD). Serum free thiols (R-SH) reliably reflect systemic oxidative stress, since they are readily oxidized by reactive species. Here, we aimed to establish concentrations of serum free thiols in IBD and assessed their discriminating capacity regarding endoscopic disease activity. Albumin-adjusted serum free thiol concentrations were measured in 78 IBD patients (31 Crohn’s disease (CD) and 47 ulcerative colitis (UC) patients) and 50 healthy controls and analyzed for associations with disease parameters and their discriminative value regarding endoscopic disease activity (n = 54) or fecal calprotectin (n = 36) in patients for which those data were available. Mean serum free thiol concentrations were significantly lower in both CD and UC as compared to healthy controls (19.4 ± 3.1 and 17.8 ± 3.4 vs. 21.1 ± 1.9 µmol/g albumin, P < 0.001). Free thiols highly accurately discriminated between mild and moderate-to-severe disease activity, better than fecal calprotectin (FC) levels (AUC = 0.87, P < 0.001 vs. AUC = 0.76, P < 0.05, respectively) and this was maintained after cross-validation (AUC = 0.89, P < 0.001). Serum free thiols are reduced in IBD as compared to healthy controls and strongly correlate with the degree of endoscopic disease activity. Quantifying systemic redox status in IBD may be a promising, minimally invasive strategy to monitor IBD disease activity.

Background Serum free thiols (R-SH, sulfhydryl groups) reliably reflect systemic oxidative stress. Since serum free thiols are rapidly oxidized by reactive species, systemic oxidative stress is generally associated with reduced serum free thiol levels. Free thiols associate with favorable disease outcomes in many patient cohorts, and the current hypothesis is that oxidative stress might also play an important role in cardiovascular disease. In this study, we aimed to establish the role of serum free thiols in the general population by investigating their relationship with the risk of cardiovascular (CV) events and all-cause mortality. Methods Participants (n = 5955) of the Prevention of REnal and Vascular ENd-stage Disease (PREVEND) cohort study from the general population were included. At baseline, serum levels of free thiols were quantified and adjusted to total protein levels. Protein-adjusted serum free thiol levels were studied for their associations with clinical and biochemical parameters, as well as with the risk of CV events and all-cause mortality. Results The mean protein-adjusted serum free thiol level was 5.05 ± 1.02 μmol/g of protein. Protein-adjusted serum free thiols significantly predicted the risk of CV events, even after adjustment for potential confounding factors (hazard ratio [HR] per doubling 0.68 [95% confidence interval [CI] 0.47–1.00], P = 0.048). Similarly, protein-adjusted serum free thiols were significantly predictive of the risk of all-cause mortality (HR per doubling 0.66 [95% CI 0.44–1.00], P = 0.050). Stratified analyses revealed lower HRs for subjects with a lower body mass index (BMI), without hypertension, and without diabetes. Conversely, HRs were lower in subjects with albuminuria. Conclusions In this large population-based cohort study, serum free thiols significantly predicted the risk of CV events and all-cause mortality. Our results highlight the potential significance and clinical applicability of serum free thiols since they are amendable to therapeutic intervention.

Background:Little is known about the perinatal development of Paneth cells (PCs) during gestation and the relation with necrotizing enterocolitis (NEC). We aimed to investigate when PCs arise and when they become immune competent during gestation. Methods: We included 57 samples of ileum tissue of fetuses/ infants with a gestional age (GA) between 9 and 40 wk taken as part of a standard autopsy procedure. Hematoxylin-eosin staining and anti-human defensin 5 immunohistochemistry were performed. We performed a semi-quantitative assessment of (immune-competent) PC numbers per 10 crypts per tissue section per GA. results: The number of PCs and the number of immunecompetent PCs increased with increasing GA (Spearman's ρ = 0.41, P = 0.002 and ρ = 0.61, P < 0.001, respectively). Whereas significantly higher PC numbers were observed after 37 wk gestation (median 7, range 0-12) compared to preterm infants (median 0, range 0-15; P = 0.002), we counted higher numbers of immune-competent PCs already in infants with GA above 29 wk (median 6, range 0-18) compared to infants with GA under 29 wk (median 2, range 0-9; P < 0.001). conclusion: The significant increase of immune-competent PCs starting from a GA of 29 wk mimics the rise in incidence of NEC during a similar postmenstrual age in preterm infants.P aneth cells (PCs) are specialized epithelial immune cells located in the base of the crypts of Lieberkühn located in the small intestine (1,2). PCs can be seen in the gut by the first trimester and are thought to mature during gestation (1,2). PCs protect the intestinal stem cells from pathogens by stimulating stem cell differentiation, shaping the intestinal microbiota, and assist in reparation of the gut (2). To this end, they secrete (among other things) human α-defensins (HD5/HD6) (3). These defensins protect the intestinal mucosa against bacterial invasion, and are thought to be associated with initiating and adapting immunity (3). How PCs develop after the first trimester and when PCs become immune competent remains uncertain.PCs are thought to play a role in the development of NEC, a common and devastating disease most commonly observed in preterm infants (4-6). NEC involves the preterm intestine and has a complex pathophysiology in which bacterial invasion and an excessive inflammatory response is an important contributing factor (5,6). Unfortunately, the exact pathophysiology is incompletely understood.It has been hypothesized that maturation of immune-competent PCs is crucial for NEC development (4,(6)(7)(8). In the preterm gut, PCs secrete defensins that might contribute to an excessive inflammatory response as observed in NEC (4). This hypothesis is derived from the observation that extremely-low-birth-weight human infants generally have the longest interval before the onset of NEC-with a peak incidence at the postmenstrual age of 29-33 wk (4,6-8). Despite the possible role for PC-maturation in the pathophysiology of NEC, little is known about PC-maturation and functioning in the immature intestine. Therefore, we ...

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