A20—A Biomarker of Allograft Outcome: A Showcase in Kidney Transplantation

Uncover diagnostic immunity/hypoxia/ferroptosis/epithelial mesenchymal transformation-related CCR5, CD86, CD8A, ITGAM, and PTPRC in kidney transplantation patients with allograft rejection

The aim of this study was to identify predictive immunity/hypoxia/ferroptosis/epithelial mesenchymal transformation (EMT)-related biomarkers, pathways and new drugs in allograft rejection in kidney transplant patients. First, gene expression data were downloaded followed by identification of differentially expressed genes (DEGs), weighted gene co-expression network analysis (WGCNA) and protein–protein interaction (PPI) analysis. Second, diagnostic model was construction based on key genes, followed by correlation analysis between immune/hypoxia/ferroptosis/EMT and key diagnostic genes. Finally, drug prediction of diagnostic key genes was carried out. Five diagnostic genes were further identified, including CCR5, CD86, CD8A, ITGAM, and PTPRC, which were positively correlated with allograft rejection after the kidney transplant. Highly infiltrated immune cells, highly expression of hypoxia-related genes and activated status of EMT were significantly positively correlated with five diagnostic genes. Interestingly, suppressors of ferroptosis (SOFs) and drivers of ferroptosis (DOFs) showed a complex regulatory relationship between ferroptosis and five diagnostic genes. CD86, CCR5, and ITGAM were respectively drug target of ABATACEPT, MARAVIROC, and CLARITHROMYCIN. PTPRC was drug target of both PREDNISONE and EPOETIN BETA. In conclusion, the study could be useful in understanding changes in the microenvironment within transplantation, which may promote or sustain the development of allograft rejection after kidney transplantation.

Development of an immune function assay by measuring intracellular adenosine triphosphate (iATP) levels in mitogen-stimulated CD4+ T lymphocytes

We developed an immune function assay for monitoring CD4+ T cells activity based on changes in intracellular adenosine triphosphate (iATP) levels after phytohemagglutinin (PHA) stimulation. Blood samples were obtained from 40 healthy subjects and 30 RTRs and incubated with 5 µg/mL of PHA for 15-18 hr at 37°C and 5% CO2. Afterward, the CD4+ T cells were separated by antibody-coated magnetic beads and lysed. Then, iATP content in unstimulated and stimulated conditions was measured by luciferin-luciferase reaction using a log-log standard curve. The iATP levels showed significant increase in CD4+ T cells in both healthy persons (mean: 550 ± 142 ng/mL vs. 109 ± 54 ng/mL) and RTRs (mean: 394 ± 160 ng/mL vs. 52 ± 37 ng/mL) after PHA stimulation (P < 0.001). However, the iATP production in RTRs was significantly lower than that in healthy individuals; both prior to and after stimulation with PHA (P < 0.001). No gender-specific difference in iATP production was observed between women and men subjects. This rapid and low-cost assay reflects the degree of immune cell function through assessment of CD4+ T cells activation. Thus, it can be used for evaluation of immune system status in immunodeficient individuals as well as in immunosuppressed transplant recipients who needs drug adjustment.

Biomarkers of Tolerance in Kidney Transplantation: Are We Predicting Tolerance or Response to Immunosuppressive Treatment?

We and others have previously described signatures of tolerance in kidney transplantation showing the differential expression of B cell-related genes and the relative expansions of B cell subsets. However, in all of these studies, the index group-namely, the tolerant recipients-were not receiving immunosuppression (IS) treatment, unlike the rest of the comparator groups. We aimed to assess the confounding effect of these regimens and develop a novel IS-independent signature of tolerance. Analyzing gene expression in three independent kidney transplant patient cohorts (232 recipients and 14 tolerant patients), we have established that the expression of the previously reported signature was biased by IS regimens, which also influenced transitional B cells. We have defined and validated a new gene expression signature that is independent of drug effects and also differentiates tolerant patients from healthy controls (cross-validated area under the receiver operating characteristic curve [AUC] = 0.81). In a prospective cohort, we have demonstrated that the new signature remained stable before and after steroid withdrawal. In addition, we report on a validated and highly accurate gene expression signature that can be reliably used to identify patients suitable for IS reduction (approximately 12% of stable patients), irrespective of the IS drugs they are receiving. Only a similar approach will make the conduct of pilot clinical trials for IS minimization safe and hence allow critical improvements in kidney posttransplant management.

Hypothermic machine perfusion increases A20 expression which protects renal cells against ischemia/reperfusion injury by suppressing inflammation, apoptosis and necroptosis

There is an urgent need to improve the quality of donor organs obtained after cardiac death. In the present study, we examined the potential mechanisms through which A20 protects renal cells against ischemia/reperfusion injury (IRI) following either hypothermic machine perfusion (HMP) or static cold storage (CS) of the kidneys in a rabbit model. The expression of markers of apoptosis, necroptosis and inflammation in frozen kidney tissues were detected by western blot analysis, RT-qPCR and ELISA. Compared with the CS group, A20 expression was significantly higher in the tissue from the HMP group (P<0.01). By contrast, the expression of nuclear factor-κB (NF-κB) and tumor necrosis factor-α (TNF-α) was significantly lower in HMP group (P<0.01), whereas IκBα expression was significantly higher (P<0.01). The expression of apoptosis signal-regulating kinase 1 (ASK1), phosphorylated (p-)c-Jun N-terminal kinase (JNK) and activated caspase-3 in the HMP group was significantly downregulated compared with that in the CS group (all P<0.01). In addition, A20 inhibited receptor-interacting protein kinase 3 (RIPK3)-mediated necroptosis in the kidney. RIPK3 expression in the HMP group was significantly lower than that in the CS group (P<0.01), although the levels in both groups were higher than those in the sham group (P<0.01). Based on these findings, we propose a novel mechanism underlying the anti-apoptotic effect of A20 in renal cells in which A20 binds to ASK1 and promotes the degradation of ASK1 leading to the suppression of JNK activation and eventually, to the blockade of apoptosis. Thus, HMP reduces inflammation, apoptosis and necroptosis by upregulating the expression of A20; this mechanism may be responsible for protecting the kidney against IRI.