Severe pediatric COVID-19: a review from the clinical and immunopathophysiological perspectives.

BACKGROUND: Coronavirus disease 2019 (COVID-19) tends to have mild presentations in children. However, severe and critical cases do arise in the pediatric population with debilitating systemic impacts and can be fatal at times, meriting further attention from clinicians. Meanwhile, the intricate interactions between the pathogen virulence factors and host defense mechanisms are believed to play indispensable roles in severe COVID-19 pathophysiology but remain incompletely understood. DATA SOURCES: A comprehensive literature review was conducted for pertinent publications by reviewers independently using the PubMed, Embase, and Wanfang databases. Searched keywords included "COVID-19 in children", "severe pediatric COVID-19", and "critical illness in children with COVID-19". RESULTS: Risks of developing severe COVID-19 in children escalate with increasing numbers of co-morbidities and an unvaccinated status. Acute respiratory distress stress and necrotizing pneumonia are prominent pulmonary manifestations, while various forms of cardiovascular and neurological involvement may also be seen. Multiple immunological processes are implicated in the host response to COVID-19 including the type I interferon and inflammasome pathways, whose dysregulation in severe and critical diseases translates into adverse clinical manifestations. Multisystem inflammatory syndrome in children (MIS-C), a potentially life-threatening immune-mediated condition chronologically associated with COVID-19 exposure, denotes another scientific and clinical conundrum that exemplifies the complexity of pediatric immunity. Despite the considerable dissimilarities between the pediatric and adult immune systems, clinical trials dedicated to children are lacking and current management recommendations are largely adapted from adult guidelines. CONCLUSIONS: Severe pediatric COVID-19 can affect multiple organ systems. The dysregulated immune pathways in severe COVID-19 shape the disease course, epitomize the vast functional diversity of the pediatric immune system and highlight the immunophenotypical differences between children and adults. Consequently, further research may be warranted to adequately address them in pediatric-specific clinical practice guidelines.

Developing a Peptide That Inhibits DNA Repair by Blocking the Binding of Artemis and DNA Ligase IV to Enhance Tumor Radiosensitivity.

PURPOSE: Artemis and DNA Ligase IV are 2 critical elements in the nonhomologous end joining pathway of DNA repair, acting as the nuclease and DNA ligase, respectively. Enhanced cellular radiosensitivity by inhibition of either protein contributes to a promising approach to develop molecular targeted radiosensitizers. The interaction between Artemis and DNA Ligase IV is required for the activation of Artemis as nuclease at 3'overhang DNA; thus, we aim to generate an inhibitory peptide targeting the interaction between Artemis and DNA Ligase IV for novel radiosensitizer development. METHODS AND MATERIALS: We synthesized the peptide BAL, which consists of the interaction residues of Artemis to DNA Ligase IV. The radiosensitization effect of BAL was evaluated by colony formation assay. The effects of BAL on radiation-induced DNA repair were evaluated with Western blotting and immunofluorescence. The effects of BAL on cell proliferation, cell cycle arrest, and cell apoptosis were assessed via CCK-8 and flow cytometry assays. The potential synergistic effects of BAL and irradiation in vivo were investigated in a xenograft mouse model. RESULTS: The generated peptide BAL blocking the interaction between Artemis and DNA Ligase IV significantly enhanced the radiosensitivity of GBC-SD and HeLa cell lines. BAL prolonged DNA repair after irradiation; BAL and irradiation showed synergistic effects on cell proliferation, cell cycle, and cell apoptosis, and these functions are all DNA Ligase IV-related. Finally, we confirmed the endogenous radiosensitization effect of BAL in a xenograft mouse model. CONCLUSIONS: The inhibitory peptide BAL targeting the binding of Artemis and DNA Ligase IV successfully functions as a novel radiosensitizer that delays DNA repair and synergizes with irradiation to inhibit cell proliferation, induce cell cycle arrest, and promote cell apoptosis.

Effects of SCCO2, Gamma Irradiation, and Sodium Dodecyl Sulfate Treatments on the Initial Properties of Tendon Allografts.

Sterile and decellularized allograft tendons are viable biomaterials used in reconstructive surgeries for dense connective tissue injuries. Established allograft processing techniques including gamma irradiation and sodium dodecyl sulfate (SDS) can affect tissue integrity. Supercritical carbon dioxide (SCCO2) represents a novel alternative that has the potential to decellularize and sterilize tendons with minimized exposure to denaturants, shortened treatment time, lack of toxic residues, and superior tissue penetration, and thus efficacy. This study attempted to develop a single-step hybrid decellularization and sterilization protocol for tendons that involved SCCO2 treatment with various chemical additives. The processed tendons were evaluated with mechanical testing, histology, scanning electron microscopy (SEM), and Fourier-transform infrared (FTIR) spectroscopy. Uniaxial mechanical testing showed that tendons treated with SCCO2 and additive NovaKillTM Gen2 and 0.1% SDS had significantly higher (p < 0.05) ultimate tensile stress (UTS) and Young's modulus compared to gamma-irradiated and standard-SDS-treated tendons. This was corroborated by the ultrastructural intactness of SCCO2-treated tendons as examined by SEM and FTIR spectroscopy, which was not preserved in gamma-irradiated and standard SDS-treated tendons. However, complete decellularization was not achieved by the experimented SCCO2-SDS protocols used in this study. The present study therefore serves as a concrete starting point for development of an SCCO2-based combined sterilization and decellularization protocol for allograft tendons, where additive choice is to be optimized.

Feasibility of relatively low neoadjuvant radiation doses for locally advanced rectal cancer: A propensity score-matched analysis.

BACKGROUND: Neoadjuvant chemoradiation therapy is part of the standard treatment of locally advanced rectal cancer (LARC). Although various options for modifying preoperative radiotherapy protocols have been researched and proposed, there is still no consensus as to the most appropriate dose regimen of neoadjuvant therapy for this disease. AIM: To evaluate the effects of relatively low-dose radiation regimens on tumor regression and clinical outcomes in rectal cancer patients treated with neoadjuvant CRT followed by mesorectal excision. METHODS AND RESULTS: We retrospectively analyzed patients with LARC who underwent neoadjuvant concurrent chemoradiation (CCRT) in our hospital from June 2010 to December 2015. A total of 259 consecutive patients were enrolled, receiving 42 to 44 Gy (RLD, n = 31), 46 Gy (SD1, n = 69), or 50 Gy (SD2, n = 159) of CRT, combined with either capecitabine/oxaliplatin or capecitabine only or mFOLFOX6, followed by total mesorectal excision. A 1:4 propensity score matching was employed, and all patients in the RLD group were matched with 124 patients in the SD2 group. Rates of pCR, 3-year local/regional recurrence (LRR), overall survival (OS), and disease-free survival (DFS) in the RLD group were all not significantly different (0.313 for pCR; 0.884 for LRR; and 0.762 for OS; 0.101 for DFS) from those in SD1 and SD2 groups. The RLD group showed a lower incidence of grade 3 to 4 hematologic toxicity than SD2 group (0.019). A propensity score analysis demonstrated no significant differences in the pCR rates and 3-year outcomes between the RLD and SD2 group. CONCLUSION: Relatively low-dose regimen (≤44 Gy) of neoadjuvant CRT combined with standard concurrent chemotherapy appears to be both safe and effective in Chinese patients with LARC. Further testing by prospective randomized trials is needed.

Silencing Artemis Enhances Colorectal Cancer Cell Sensitivity to DNA-Damaging Agents.

Artemis is a key protein of NHEJ (nonhomologous end joining), which is the major pathway for the repair of IR-induced DSBs in mammalian cells. However, the expression of Artemis in tumors and the influence of silencing Artemis on tumor sensitivity to radiation have not been investigated fully. In this study, we investigated how the expression levels of Artemis may affect the treatment outcome of radiotherapy and chemotherapy in colorectal cancer cells. First, we found that the expression of Artemis is strong in some human rectal cancer samples, being higher than in adjacent normal tissues using immunohistochemical staining. We then knocked down Artemis gene in a human colorectal cancer cell line (RKO) using lentivirus-mediated siRNAs. Compared to the control RKO cells, the Artemis knockdown cells showed significantly increased sensitivity to bleomycin, etoposide, camptothecin, and IR. Induced by DNA-damaging agents, delayed DNA repair kinetics was found by the γ-H2AX foci assay, and a significantly increased cell apoptosis occurred in the Artemis knockdown RKO cells through apoptosis detection methods and Western blot. We also found that the p53/p21 signaling pathway may be involved in the apoptosis process. Taken together, our study indicates that manipulating Artemis can enhance colorectal cancer cell sensitivity to DNA-damaging agents. Therefore, Artemis can serve as a therapeutic target in rectal cancer therapy.