Long COVID following mild SARS-CoV-2 infection: characteristic T cell alterations and response to antihistamines.

Long COVID is characterized by the emergence of multiple debilitating symptoms following SARS-CoV-2 infection. Its etiology is unclear and it often follows a mild acute illness. Anecdotal reports of gradual clinical responses to histamine receptor antagonists (HRAs) suggest a histamine-dependent mechanism that is distinct from anaphylaxis, possibly mediated by T cells, which are also regulated by histamine. T cell perturbations have been previously reported in post-viral syndromes, but the T cell landscape in patients who have recovered from mild COVID-19 and its relationship to both long COVID symptoms and any symptomatic response to HRA remain underexplored. We addressed these questions in an observational study of 65 individuals who had recovered from mild COVID-19. Participants were surveyed between 87 and 408 days after the onset of acute symptoms; none had required hospitalization, 16 had recovered uneventfully, and 49 had developed long COVID. Symptoms were quantified using a structured questionnaire and T cell subsets enumerated in a standard diagnostic assay. Patients with long-COVID had reduced CD4+ and CD8+ effector memory (EM) cell numbers and increased PD-1 (programmed cell death protein 1) expression on central memory (CM) cells, whereas the asymptomatic participants had reduced CD8+ EM cells only and increased CD28 expression on CM cells. 72% of patients with long COVID who received HRA reported clinical improvement, although T cell profiling did not clearly distinguish those who responded to HRA. This study demonstrates that T cell perturbations persist for several months after mild COVID-19 and are associated with long COVID symptoms.

A rare cause of severe Cushing's syndrome.

SUMMARY: Ectopic adrenocorticotropic hormone (ACTH) production is an uncommon cause of Cushing's syndrome and, rarely, the source can be a phaeochromocytoma. A 55-year-old man presented following an episode of presumed gastroenteritis with vomiting and general malaise. Further episodes of diarrhoea, joint pains and palpitations followed. On examination, he was hypertensive with no clinical features to suggest hypercortisolaemia. He was subsequently found to have raised plasma normetanephrines of 3.98 nmol/L (NR <0.71) and metanephrines of 0.69 nmol/L (NR <0.36). An adrenal CT showed a 3.8 cm right adrenal nodule, which was not MIBG-avid but was clinically and biochemically consistent with a phaeochromocytoma. He was started on alpha blockade and referred for right adrenalectomy. Four weeks later, on the day of admission for adrenalectomy, profound hypokalaemia was noted (serum potassium 2.0 mmol/L) with non-specific ST-segment ECG changes. He was also diagnosed with new-onset diabetes mellitus (capillary blood glucose of 28 mmol/L). He reported to have gained weight and his skin had become darker over the course of the last 4 weeks. Given these findings, he underwent overnight dexamethasone suppression testing, which showed a non-suppressed serum cortisol of 1099 nmol/L. Baseline serum ACTH was 273 ng/L. A preliminary diagnosis of ectopic ACTH secretion from the known right-sided phaeochromocytoma was made and he was started on metyrapone and insulin. Surgery was postponed for 4 weeks. Following uncomplicated laparoscopic adrenalectomy, the patient recovered with full resolution of symptoms. LEARNING POINTS: Phaeochromocytomas are a rare source of ectopic ACTH secretion. A high clinical index of suspicion is therefore required to make the diagnosis. Ectopic ACTH secretion from a phaeochromocytoma can rapidly progress to severe Cushing's syndrome, thus complicating tumour removal. Removal of the primary tumour often leads to full recovery. The limited literature suggests that the presence of ectopic Cushing's syndrome does not appear to have any long-term prognostic implications.

Improvement in glycemic control and outcome corresponding to intensive insulin therapy protocol development.

BACKGROUND: Intensive insulin therapy (IIT) has been shown to reduce mortality and morbidity in longer stay, critically ill patients. However, this has been demonstrated in a single site, whereas two multicentric studies have been terminated prematurely mainly due to hypoglycemia. Other difficulties with IIT include efficacy of glycemic control. This report describes how IIT can be improved by protocol simplification and removal of glucose supplementation. METHODS: A clinical information system established at each bedspace guided staff through the IIT algorithms. Time spent within predefined glycemic ranges was calculated assuming a linear trend between successive measurements. Three groups were investigated retrospectively: IIT1 protocol,(1) an updated IIT2 version, and intuitive nurse dosing of conventional insulin therapy (CIT). RESULTS: Fifty consecutive, critically ill patients were included in each study group. Patient characteristics were similar in each group. The frequency of CIT and IIT2 blood glucose measurements were 11.6 and 11.5 measurements per day, respectively, while the IIT1 measurements were more frequent (14.5 measurements per day). The mean proportion of time spent in the target glycemic range (4.4-6.1 mmol/liter) was highest in the IIT2 group (34.9%), as compared to the IIT1 (22.9%) and CIT groups (20.3%) (p <.001). Survival at 28 days was 74.5% for IIT2 (highest), 68% for IIT1, and 48% for CIT (p = .02). There were a similar number of those experiencing a severe hypoglycemic event in each group. CONCLUSIONS: IIT protocol optimization was associated with increased glycemic control and improved 28-day survival. The better optimized IIT2 protocol provided tighter control than either the IIT1 or CIT protocol, without increased sampling or incidence of hypoglycemia. The clinical effectiveness of the IIT algorithm appeared to be improved by simplifying the protocol to meet the needs of the critical care unit.

Tight glycaemic control: a prospective observational study of a computerised decision-supported intensive insulin therapy protocol.

INTRODUCTION: A single centre has reported that implementation of an intensive insulin protocol, aiming for tight glycaemic control (blood glucose 4.4 to 6.1 mmol/l), resulted in significant reduction in mortality in longer stay medical and surgical critically ill patients. Our aim was to determine the degree to which tight glycaemic control can be maintained using an intensive insulin therapy protocol with computerized decision support and to identify factors that may be associated with the degree of control. METHODS: At a general adult 22-bed intensive care unit, we implemented an intensive insulin therapy protocol in mechanically ventilated patients, aiming for a target glucose range of 4.4 to 6.1 mmol/l. The protocol was integrated into the computerized information management system by way of a decision support program. The time spent in each predefined blood glucose band was estimated, assuming a linear trend between measurements. RESULTS: Fifty consecutive patients were investigated, involving analysis of 7,209 blood glucose samples, over 9,214 hours. The target tight glycaemic control band (4.4 to 6.1 mmol/l) was achieved for a median of 23.1% of the time that patients were receiving intensive insulin therapy. Nearly half of the time (median 48.5%), blood glucose was within the band 6.2 to 7.99 mmol/l. Univariate analysis revealed that body mass index (BMI), Acute Physiology and Chronic Health Evaluation (APACHE) II score and previous diabetes each explained approximately 10% of the variability in tight glycaemic control. BMI and APACHE II score explained most (27%) of the variability in tight glycaemic control in the multivariate analysis, after adjusting for age and previous diabetes. CONCLUSION: Use of the computerized decision supported intensive insulin therapy protocol did result in achievement of tight glycaemic control for a substantial percentage of each patient's stay, although it did deliver 'normoglycaemia' (4.4 to about 8 mmol/l) for nearly 75% of the time. Tight glycaemic control was difficult to achieve in critically ill patients using this protocol. More sophisticated methods such as continuous blood glucose monitoring with automated insulin and glucose infusion adjustment may be a more effective way to achieve tight glycaemic control. Glycaemia in patients with high BMI and APACHE II scores may be more difficult to control using intensive insulin therapy protocols. Trial registration number 05/Q0505/1.

Role of the PDZ scaffolding protein in tubule cells in maintenance of polarised function.

Polarized tubule epithelial cell functions are dependent on correct delivery of effector proteins to the target apical or basolateral plasma membrane and associated cortical cytoskeleton. PDZ (Postsynaptic density protein 95/Drosophila Disks large/Zona occludens-1) domain-containing proteins have been identified as playing a critical role in membrane trafficking and sorting of ion transporters, receptors and other signalling proteins. These scaffolding proteins coordinate the assembly of functional plasma membrane multiprotein complexes, through PDZ domain binding to a consensus amino acid motif within the carboxyl-terminus of target proteins. The organization of these proteins into submembranous complexes may facilitate downstream signalling. Although several epithelial PDZ proteins that bind to a number of important mammalian proteins have been isolated, in many cases the significance of these interactions is unclear. However, the epithelial PDZ domain-containing Na(+)/H(+) exchanger regulatory factor tethers the Na(+)/H(+) exchanger and cystic fibrosis transmembrane regulator Cl(-) channel within an apical plasma membrane signalling complex, and has been shown to regulate the activity of these proteins. This article reviews the current evidence that supports a central role for the PDZ protein in the regulation of polarized tubule cell functions, such as vectorial solute transport.

Epithelial inducible nitric-oxide synthase is an apical EBP50-binding protein that directs vectorial nitric oxide output.

Nitric oxide (NO), produced via inducible NO synthase (iNOS), can modulate polarized epithelial processes such as solute transport. Given the high reactivity of NO, we hypothesized that optimal NO regulation of polarized epithelial functions is achieved through compartmentalization of iNOS, allowing local NO delivery to its molecular targets. Here, we show that iNOS localizes to the apical domain of epithelial cells within a submembranous protein complex tightly bound to cortical actin. We further show that iNOS can bind to the apical PDZ protein, EBP50 (ezrin-radixin-moesin-binding phosphoprotein 50), an interaction that is dependent on the last three COOH-terminal amino acids of iNOS, SAL, but requires the presence of additional unknown cellular proteins. Mutation of these three COOH-terminal residues abolishes the iNOS-EBP50 interaction and disrupts the apical association of iNOS in transfected cells, showing that this COOH-terminal motif is essential for the correct localization of iNOS in epithelial cells. Apically localized iNOS directs vectorial NO production at the apical proximal tubule epithelial cell surface. These studies define human epithelial iNOS as an apical EBP50-binding protein and suggest that the physical association of iNOS with EBP50 might allow precise NO modulation of EBP50-associated protein functions.

Coexpressed nitric oxide synthase and apical beta(1) integrins influence tubule cell adhesion after cytokine-induced injury.

In sepsis-induced acute renal failure, actin cytoskeletal alterations result in shedding of proximal tubule epithelial cells (PTEC) and tubular obstruction. This study examined the hypothesis that inflammatory cytokines, released early in sepsis, cause PTEC cytoskeletal damage and alter integrin-dependent cell-matrix adhesion. The question of whether the intermediate nitric oxide (NO) modulates these cytokine effects was also examined. After exposure of human PTEC to tumor necrosis factor-alpha, interleukin-1 alpha, and interferon-gamma, the actin cytoskeleton was disrupted and cells became elongated, with extension of long filopodial processes. Cytokines induced shedding of viable, apoptotic, and necrotic PTEC, which was dependent on NO synthesized by inducible NO synthase (iNOS) produced as a result of cytokine actions on PTEC. Basolateral exposure of polarized PTEC monolayers to cytokines induced maximal NO-dependent cell shedding, mediated in part through NO effects on cGMP. Cell shedding was accompanied by dispersal of basolateral beta(1) integrins and E-cadherin, with corresponding upregulation of integrin expression in clusters of cells elevated above the epithelial monolayer. These cells demonstrated coexpression of iNOS and apically redistributed beta(1) integrins. Attachment studies demonstrated that the major ligand involved in cell anchorage was laminin, probably through interactions with the integrin alpha(3)beta(1). This interaction was downregulated by cytokines but was not dependent on NO. These studies provide a mechanism by which inflammatory cytokines induce PTEC damage in sepsis, in the absence of hypotension and ischemia. Future therapeutic strategies aimed at specific iNOS inhibition might inhibit PTEC shedding after cytokine-induced injury and delay the onset of acute renal failure in sepsis.