HIV infection rapidly induces and maintains a substantial suppression of thymocyte proliferation

The supply of naive T cells by the thymus normally requires precursor T cell proliferation within the thymus and would be particularly important in the setting of HIV infection when both naive and memory T cells are progressively depleted. As a robust, quantitative index of intrathymic proliferation, the ratio of different T cell receptor excision circles (TRECs), molecular markers of distinct T cell receptor rearrangements occurring at different stages of thymocyte development, was measured in peripheral blood-mononuclear cells (PBMCs). This ratio has the virtue that it is a "signature" of thymic emigrants throughout their entire life and, thus, can be measured in peripheral cell populations that are easy to obtain. Using the new assay, we evaluated the effect of HIV infection on intrathymic precursor T cell proliferation by longitudinal analysis of PBMCs from recently infected individuals. Our findings reveal a substantial reduction in intrathymic proliferation. The analysis also indicates the existence of a compensatory mechanism acting to sustain the numbers of recent thymic emigrants (RTEs) in the periphery.     

Factors predictive of the perceived osteoporosis–fracture link in fragility fracture patients

Objective

Given the asymptomatic nature of osteoporosis, a fragility fracture provides an opportunity to make the issue of osteoporosis relevant to patients. Patients who link their fragility fracture with osteoporosis are more likely to initiate osteoporosis treatment, yet to date, we know little about who is likely to make this link. This study examined whether demographic, health, and osteoporosis belief factors predicted a perceived link between a fragility fracture and osteoporosis.

Study design

This longitudinal cohort study analyzed baseline and follow up data collected as part of a provincial osteoporosis screening initiative targeting fragility fracture patients. Logistic regression analysis was used to examine the relationship between hypothesized predictors and the outcome.

Main outcome measure

Patient perception of the osteoporosis–fracture link at follow up.

Results

At baseline, 93% (1615/1735) of patients did not believe their fracture could have been caused by osteoporosis. Of these, only 8.2% changed this perception at follow up. Adjusted analyses showed that baseline characteristics associated with making the osteoporosis–fracture link at follow up were: a previous fracture (odds ratio (OR) 1.7, confidence interval (CI) 1.2–2.6), perception of osteoporosis pharmacotherapy benefits OR 1.2 (CI 1.0–1.5), diagnosis of rheumatoid arthritis OR 2.6 (CI 1.4–4.9) and the perception of bones as “thin” OR 8.2 (CI 5.1–13.1).

Conclusion

These results shed more light on patient-level barriers to osteoporosis management following an osteoporosis educational programme. They may be used to identify patients less likely to make the link between their fracture and osteoporosis and to inform interventions for this patient group.     

Distinct phenotypes of multisystem inflammatory syndrome in children: a cohort study

To characterize the clinical features and outcomes of childhood-onset primary Sjögren’s syndrome (pSS). Patients less than 18 years old who were diagnosed with pSS by paediatric rheumatologists were included, and all patients were applied the 2002 American-European Consensus Group (ACEG) criteria, the 2016 American College of Rheumatology/European League Against Rheumatism (ACR/EULAR) criteria for pSS, or the 1999 proposed juvenile pSS criteria. The electronic medical records of patients with pSS from 2013 to 2020 were collected and analysed. Thirty-nine patients were included. Of them, 27 (69.2%), 38 (97.4%) and 35 (89.7%) patients fulfilled the AECG criteria, ACR/EULAR criteria and proposed juvenile pSS criteria, respectively. The female:male ratio was 3.9:1. The median ages at first signs or symptoms and at diagnosis were 9.2 (4.7, 14.5) years and 10.9 (6.3, 15.0) years, respectively. The main clinical manifestations were rash or purpura (20, 51.3%), followed by fever (12, 30.8%), glandular enlargement/recurrent parotitis (10, 25.6%), and dry mouth and/or dry eyes (9, 23.1%). Twenty-eight (56.4%) patients had systemic damage, the most common of which was haematological involvement (14, 35.9%), followed by hepatic (13, 33.3%) and renal involvement (8, 20.5%). Thirty-eight (97.4%) patients underwent labial minor salivary gland biopsy, and all exhibited focal lymphocytic sialadenitis. All patients had a global ESSDAI score ≥ 1 at diagnosis, and the median total score at diagnosis was 8 (2, 31). Thirty-six (92.3%) patients were followed up for a median time of 23.6 (7.9, 79.5) months, and three patients developed systemic lupus erythematosus (SLE) at follow-up times of 13.3, 38.8 and 63.8 months. The presentation of childhood-onset pSS is atypical, and extraglandular manifestations and systemic involvement are more common than in adult-onset pSS. Labial salivary gland biopsy is vital for patients with probable pSS. Some patients may develop SLE over time.     

Caspase-9 and effector caspases have sequential and distinct effects on mitochondria

Proapoptotic Bcl-2 family members alter mitochondrial permeability resulting in the release of apoptogenic factors that initiate a caspase cascade. These changes are well described; however, the effects of caspases on mitochondrial function are less well characterized. Here we describe the consequence of caspase-9 and effector caspase inhibition on mitochondrial physiology during intrinsic cell death. Caspase inhibition prevents the complete loss of mitochondrial membrane potential without affecting cytochrome c release. When effector caspases are inhibited, mitochondria become uncoupled and produce reactive oxygen species. Interestingly, the effector caspase-mediated depolarization of the mitochondria occurs independent of the activity of complexes I-IV of the electron transport chain. In contrast, caspase-9 inhibition prevents mitochondrial uncoupling and ROS production and allows for continued electron transport despite the release of cytochrome c. Taken together, these data suggest that activated caspase-9 prevents the accessibility of cytochrome c to complex III, resulting in the production of reactive oxygen species, and that effector caspases may depolarize mitochondria to terminate ROS production and preserve an apoptotic phenotype.     

Slow disease progression and robust therapy-mediated CD4+ T-cell recovery are associated with efficient thymopoiesis during HIV-1 infection

In chronic HIV infection, most untreated patients lose naive CD4+ and CD8+ T cells, whereas a minority preserve them despite persistent high viremia. Although antiretroviral therapy (ART)-mediated viral suppression generally results in a rise of naive and total CD4+ T cells, certain patients experience very little or no T-cell reconstitution. High peripheral T-cell activation has been linked to poor clinical outcomes, interfering with previous evaluations of thymic function in disease progression and therapy-mediated T-cell recovery. To circumvent this, we used the sj/betaTREC ratio, a robust index of thymopoiesis that is independent of peripheral T-cell proliferation, to evaluate the thymic contribution to the preservation and restoration of naive CD4+ T cells. We show that the loss of naive and total CD4+ T cells is the result of or is exacerbated by a sustained thymic defect, whereas efficient thymopoiesis supports naive and total CD4+ T-cell maintenance in slow progressor patients. In ART-treated patients, CD4+ T-cell recovery was associated with the normalization of thymopoiesis, whereas the thymic defect persisted in aviremic patients who failed to recover CD4+ T-cell counts. Overall, we demonstrate that efficient thymopoiesis is key in the natural maintenance and in therapy-mediated recovery of naive and total CD4+ T cells.     

Long-term hematopoietic stem cell damage in a murine model of the hematopoietic syndrome of the acute radiation syndrome

ABSTRACT: Residual bone marrow damage (RBMD) persists for years following exposure to radiation and is believed to be due to decreased self-renewal potential of radiation-damaged hematopoietic stem cells (HSC). Current literature has examined primarily sublethal doses of radiation and time points within a few months of exposure. In this study, the authors examined RBMD in mice surviving lethal doses of total body ionizing irradiation (TBI) in a murine model of the Hematopoietic Syndrome of the Acute Radiation Syndrome (H-ARS). Survivors were analyzed at various time points up to 19 mo post-TBI for hematopoietic function. The competitive bone marrow (BM) repopulating potential of 150 purified c-Kit+ Sca-1+ lineage- CD150+ cells (KSLCD150+) remained severely deficient throughout the study compared to KSLCD150+ cells from non-TBI age-matched controls. The minimal engraftment from these TBI HSCs is predominantly myeloid, with minimal production of lymphocytes both in vitro and in vivo. All classes of blood cells as well as BM cellularity were significantly decreased in TBI mice, especially at later time points as mice aged. Primitive BM hematopoietic cells (KSLCD150+) displayed significantly increased cell cycling in TBI mice at all time points, which may be a physiological attempt to maintain HSC numbers in the post-irradiation state. Taken together, these data suggest that the increased cycling among primitive hematopoietic cells in survivors of lethal radiation may contribute to long-term HSC exhaustion and subsequent RBMD, exacerbated by the added insult of aging at later time points.     

Study of Correlations Between CT Properties of Retrieved Cerebral Thrombi with Treatment Outcome of Stroke Patients

BackgroundAll the patients with suspected stroke are directed to whole-brain CT scan. The purpose of this scan is to look for early features of ischemia and to rule out alternative diagnoses than stroke. In case of ischemic stroke, CT diagnostics (including CT angiography) is used mainly to locate the occlusion and its size, while the Hounsfield Units (HU) values of the thrombus causing the stroke are usually overlooked on CT scan or considered not important. The aim of this study was to demonstrate that the HU value is relevant and can help in better treatment planning.Patients and methodsThere were 25 patients included in the study, diagnosed with ischemic stroke in the middle cerebral artery (MCA) territory. In all patients, systemic thrombolysis was not successful and the mechanical recanalization was needed. The retrieved thrombi were also analyzed histologically for the determination of red blood cells (RBC) proportion. CT of the proximal MCA (M1) segment was analyzed for average HU value and its variability both in the occluded section and the symmetrical normal site. These CT parameters were then statistically studied for the possible correlations with different clinical, histological and procedure parameters using the Linear Regression and the Pearson correlation coefficient.ResultsRelevant positive correlations were found between average HU value of thrombus and outcome modified Rankin Scale (mRS), initial mRS, number of passes with thrombectomy device as well as RBC proportion.ConclusionsResults of the present study suggest that measured HU values in CT images of the cerebral thrombi may help in the assessment of thrombus compaction and therefore better treatment planning.Key words: ischemic stroke, CT images, cerebral thrombi, modified Rankin Scale, RBC proportion     

Synthetic lethal targeting of DNA double-strand break repair deficient cells by human apurinic/apyrimidinic endonuclease inhibitors

An apurinic/apyrimidinic (AP) site is an obligatory cytotoxic intermediate in DNA Base Excision Repair (BER) that is processed by human AP endonuclease 1 (APE1). APE1 is essential for BER and an emerging drug target in cancer. We have isolated novel small molecule inhibitors of APE1. In this study, we have investigated the ability of APE1 inhibitors to induce synthetic lethality (SL) in a panel of DNA double-strand break (DSB) repair deficient and proficient cells; i) Chinese hamster (CH) cells: BRCA2 deficient (V-C8), ATM deficient (V-E5), wild type (V79) and BRCA2 revertant [V-C8(Rev1)]. ii) Human cancer cells: BRCA1 deficient (MDA-MB-436), BRCA1 proficient (MCF-7), BRCA2 deficient (CAPAN-1 and HeLa SilenciX cells), BRCA2 proficient (PANC1 and control SilenciX cells). We also tested SL in CH ovary cells expressing a dominant-negative form of APE1 (E8 cells) using ATM inhibitors and DNA-PKcs inhibitors (DSB inhibitors). APE1 inhibitors are synthetically lethal in BRCA and ATM deficient cells. APE1 inhibition resulted in accumulation of DNA DSBs and G2/M cell cycle arrest. SL was also demonstrated in CH cells expressing a dominant-negative form of APE1 treated with ATM or DNA-PKcs inhibitors. We conclude that APE1 is a promising SL target in cancer.