Transcuprein is a high-affinity copper carrier in the plasma that is involved in the initial distribution of copper entering the blood from the digestive tract. To identify and obtain cDNA for this protein, it was purified from rat plasma by size exclusion and copper-chelate affinity chromatography, and amino acid sequences were obtained. These revealed a 190-kDa glycosylated protein identified as the macroglobulin alpha(1)-inhibitor III, the main macroglobulin of rodent blood plasma. Albumin (65 kDa) copurified in variable amounts and was concluded to be a contaminant (although it can transiently bind the macroglobulin). The main macroglobulin in human blood plasma (alpha(2)-macroglobulin), which is homologous to alpha(1)-inhibitor III, also bound copper tightly. Expression of alpha(1)I3 (transcuprein) mRNA by the liver was examined in rats with and without copper deficiency, using quantitative polymerase chain reaction methodology and Northern blot analysis. Protein expression was examined by Western blotting. Deficient rats with 40% less ceruloplasmin oxidase activity and liver copper concentrations expressed about twice as much alpha(1)I3 mRNA, but circulating levels of transcuprein did not differ. Iron deficiency, which increased liver copper concentrations by threefold, reduced transcuprein mRNA expression and circulating levels of transcuprein relative to what occurred in rats with normal or excess iron. We conclude that transcupreins are specific macroglobulins that not only carry zinc but also carry transport copper in the blood, and that their expression can be modulated by copper and iron availability.

Transplantation of bone marrow-derived mesenchymal stem cells (BMSCs) can repair acute kidney injury (AKI), but with limited effect. We test the hypothesis that CXCR4 overexpression improves the repair ability of BMSCs and that this is related to increased homing of BMSCs and increased release of cytokines. Hypoxia/reoxygenation-pretreated renal tubular epithelial cells (HR-RTECs) were used. BMSCs, null-BMSCs, and CXCR4-BMSCs were cocultured with HR-RTECs. The number of migrating BMSCs was counted. Proliferating cell nuclear antigen (PCNA) expression, cell death, and expressions of cleaved caspase-3 and Bcl-2 in cocultured HR-RTECs were measured. Cytokeratin 18 (CK18) expression and cytokine secretions of the BMSCs cultured with HR-RTEC supernatant were detected. BMSC homing, renal function, proliferation, and cell death of tubular cells were assayed in the AKI mouse model. CXCR4-BMSCs showed a remarkable expression of CXCR4. Stromal cell-derived factor-1 in the HR-RTEC supernatant was increased. Migration of BMSCs was CXCR4-dependent. Proportions of CK18(+) cells in BMSCs, null-BMSCs, and CXCR4-BMSCs showed no difference. However, CXCR4 overexpression in BMSCs stimulated secretion of bone morphogenetic protein-7, hepatocyte growth factor, and interleukin 10. The neutralizing anti-CXCR4 antibody AMD3100 abolished this. In cocultured HR-RTECs the proportions of PCNA(+) cells and Bcl-2 expression were enhanced; however, the proportion of annexin V(+) cells and expression of cleaved caspase-3 were reduced. The in vivo study showed increased homing of CXCR4-BMSCs in kidneys, which was associated with improved renal function, reduced acute tubular necrosis scoring, accelerated mitogenic response of tubular cells, and reduced tubular cell death. The enhanced homing and paracrine actions of BMSCs with CXCR4 overexpression suggest beneficial effects of such cells in BMSC-based therapy for AKI.

Bone marrow-derived mesenchymal stem cells (BMSCs) can migrate to the injured kidney after acute kidney injury (AKI) with limited efficiency. This study investigated the effect of CXCR4 overexpression on BMSC migration to the AKI kidney and the possible mechanisms. CXCR4 gene-modified BMSCs (CXCR4-BMSCs) and null-BMSCs were prepared and transplanted into the AKI mice. Blood indicators, histology, expression of stromal cell-derived factor 1 (SDF-1), and BMSC migration were investigated. Hypoxia/re-oxygenation-pretreated renal tubular epithelial cells (HR-RTECs) were prepared to generate AKI in vitro. The chemotaxis experiment was performed using the transwell chamber. The phosphorylation of AKT and MAPK in the BMSCs was also investigated. The CXCR4-BMSCs showed a remarkable expression of CXCR4. The SDF-1 expression in the AKI renal tissue was increased. CXCR4-BMSCs transplantation sharply increased the accumulation of BMSCs in the renal tissue, which was consistent with a greater improvement of renal function. The in vitro experiments showed that the migration of BMSCs to the HR-RTEC culturing chamber was CXCR4-dependent, and could be fully inhibited by AMD3100, a CXCR4-specific antagonist. The migration could also be partly blocked by either LY294002 (PI3K inhibitor) or PD98059 (MAPK inhibitor). Phosphorylated Akt and MAPK were increased in the BMSCs co-cultured with HR-RTECs and their expression was the highest in the CXCR4-BMSCs, which could be recovered by AMD3100. Overexpression of CXCR4 gene could enhance BMSC migration to the kidney area after AKI. The SDF-1/CXCR4 axis via its activation of PI3K/AKT and MAPK in BMSCs could be the possible mechanisms underlying this function.

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The coronavirus disease 2019 (COVID-19) pandemic is caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The objective of this study was to determine the clinical course and risk factors for patients showing recurrent SARS-CoV-2 RNA positivity. A total of 1087 COVID-19 patients confirmed by RT-PCR from February 24, 2020 to March 31, 2020 were retrospectively enrolled. Advanced age was significantly associated with mortality. In addition, 81 (7.6%) of the discharged patients tested positive for SARS-CoV-2 RNA during the isolation period. For patients with recurrent RT-PCR positivity, the median duration from illness onset to recurrence was 50 days. Multivariate regression analysis identified elevated serum IL-6, increased lymphocyte counts and CT imaging features of lung consolidation during hospitalization as the independent risk factors of recurrence. We hypothesized that the balance between immune response and virus toxicity may be the underlying mechanism of this phenomenon. For patients with a high risk of recurrence, a prolonged observation and additional preventative measures should be implemented for at least 50 days after illness onset to prevent future outbreaks.