Targeting immune cell glutamyl-prolyl-transfer RNA synthetase 1 (EPRS1) to prevent fibrosis after tubulointerstitial nephritis

Glutamyl-prolyl-transfer RNA synthetase 1 is an enzyme that connects glutamic acid and proline to transfer RNA during protein synthesis. In this issue, a study by Kang et al. examined the role of the immune cell glutamyl-prolyl-transfer RNA synthetase 1 in toxin-induced tubulointerstitial nephritis mice. The study demonstrated that blocking glutamyl-prolyl-transfer RNA synthetase 1 may be a therapeutic target to attenuate fibrosis after toxin-induced tubulointerstitial nephritis.

Double-negative T cells have a reparative role after experimental severe ischemic acute kidney injury

T cells mediate organ injury and repair. A proportion of unconventional kidney T cells called double-negative (DN) T cells (TCR+ CD4- CD8-), with anti-inflammatory properties, were previously demonstrated to protect from early injury in moderate experimental AKI. However, their role in repair after AKI has not been studied. We hypothesized that DN T cells mediate repair after severe AKI. C57B6 mice underwent severe (40min) unilateral ischemia-reperfusion injury (IRI). Kidney DN T cells were studied by flow cytometry and compared to gold-standard anti-inflammatory CD4+ Tregs. In vitro effects of DN T cells and Tregs on renal tubular epithelial cell (RTEC) repair after injury were quantified with live-cell analysis. DN T cells, Tregs, CD4 or vehicle were adoptively transferred after severe AKI. Glomerular filtration rate (GFR) was measured using FITC-sinistrin. Fibrosis was assessed with Masson's trichrome staining. Profibrotic genes were measured with qRT-PCR. Percentages and the numbers of DN T cells substantially decreased during repair phase after severe AKI, as well as their activation and proliferation. Both DN T cells and Tregs accelerated RTEC cell repair in vitro. Post-AKI transfer of DN T cells reduced kidney fibrosis and improved GFR, as did Treg transfer. DN T cell transfer lowered TGFβ1 and αSMA expression. DN T cells reduced effector-memory CD4+ T cells and IL-17 expression. DN T cells undergo quantitative and phenotypical changes after severe AKI, accelerate RTEC repair in vitro as well as improve GFR and renal fibrosis in vivo. DN T cells have potential as immunotherapy to accelerate repair after AKI.

Kidney double positive T cells have distinct characteristics in normal and diseased kidneys

Multiple types of T cells have been described and assigned pathophysiologic functions in the kidneys. However, the existence and functions of TCR+CD4+CD8+ (double positive; DP) T cells are understudied in normal and diseased murine and human kidneys. We studied kidney DPT cells in mice at baseline and after ischemia reperfusion (IR) and cisplatin injury. Additionally, effects of viral infection and gut microbiota were studied. Human kidneys from patients with renal cell carcinoma were evaluated. Our results demonstrate that DPT cells expressing CD4 and CD8 co-receptors constitute a minor T cell population in mouse kidneys. DPT cells had significant Ki67 and PD1 expression, effector/central memory phenotype, proinflammatory cytokine (IFNγ, TNFα and IL-17) and metabolic marker (GLUT1, HKII, CPT1a and pS6) expression at baseline. IR, cisplatin and viral infection elevated DPT cell proportions, and induced distinct functional and metabolic changes. scRNA-seq analysis showed increased expression of Klf2 and Ccr7 and enrichment of TNFα and oxidative phosphorylation related genes in DPT cells. DPT cells constituted a minor population in both normal and cancer portion of human kidneys. In conclusion, DPT cells constitute a small population of mouse and human kidney T cells with distinct inflammatory and metabolic profile at baseline and following kidney injury.

Kidney Immune Cell Characterization of Humanized Mouse Models

Experimental studies often fail to translate to clinical practice. Humanized mouse models are an important tool to close this gap. We immunophenotyped the kidneys of NOG (EXL) and NSG mouse strains engrafted with human CD34 + hematopoietic stem cells or PBMCs and compared with immune cell composition of normal human kidney. Human CD34 + hematopoietic stem cell engraftment results in steady renal immune cell populations in mouse kidney with key similarities in composition compared with human kidney. Successful translation of experimental mouse data to human diseases is limited because of biological differences and imperfect disease models. Humanized mouse models are being used to bring murine models closer to humans. However, data for application in renal immune cell-mediated diseases are rare. We therefore studied immune cell composition of three different humanized mouse kidneys and compared them with human kidney. NOG and NOGEXL mice engrafted with human CD34 + hematopoietic stem cells were compared with NSG mice engrafted with human PBMCs. Engraftment was confirmed with flow cytometry, and immune cell composition in kidney, blood, spleen, and bone marrow was analyzed in different models. The results from immunophenotyping of kidneys from different humanized mouse strains were compared with normal portions of human kidneys. We found significant engraftment of human immune cells in blood and kidney of all tested models. huNSG mice showed highest frequencies of hTCR + cells compared with huNOG and huNOGEXL in blood. huNOGEXL was found to have the highest hCD4 + frequency among all tested models. Non-T cells such as hCD20 + and hCD11c + cells were decreased in huNSG mice compared with huNOG and huNOGEXL. Compared with normal human kidney, huNOG and huNOGEXL mice showed representative immune cell composition, rather than huNSG mice. In summary, humanization results in immune cell infiltration in the kidney with variable immune cell composition of tested humanized mouse models and partially reflects normal human kidneys, suggesting potential use for translational studies.

Single cell and spatial transcriptomics analysis of kidney double negative T lymphocytes in normal and ischemic mouse kidneys

T cells are important in the pathogenesis of acute kidney injury (AKI), and TCR+CD4-CD8- (double negative-DN) are T cells that have regulatory properties. However, there is limited information on DN T cells compared to traditional CD4+ and CD8+ cells. To elucidate the molecular signature and spatial dynamics of DN T cells during AKI, we performed single-cell RNA sequencing (scRNA-seq) on sorted murine DN, CD4+, and CD8+ cells combined with spatial transcriptomic profiling of normal and post AKI mouse kidneys. scRNA-seq revealed distinct transcriptional profiles for DN, CD4+, and CD8+ T cells of mouse kidneys with enrichment of Kcnq5, Klrb1c, Fcer1g, and Klre1 expression in DN T cells compared to CD4+ and CD8+ T cells in normal kidney tissue. We validated the expression of these four genes in mouse kidney DN, CD4+ and CD8+ T cells using RT-PCR and Kcnq5, Klrb1, and Fcer1g genes with the NIH human kidney precision medicine project (KPMP). Spatial transcriptomics in normal and ischemic mouse kidney tissue showed a localized cluster of T cells in the outer medulla expressing DN T cell genes including Fcer1g. These results provide a template for future studies in DN T as well as CD4+ and CD8+ cells in normal and diseased kidneys.

Microbiome modulation after severe acute kidney injury accelerates functional recovery and decreases kidney fibrosis

Targeting gut microbiota has shown promise to prevent experimental acute kidney injury (AKI). However, this has not been studied in relation to accelerating recovery and preventing fibrosis. Here, we found that modifying gut microbiota with an antibiotic administered after severe ischemic kidney injury in mice, particularly with amoxicillin, accelerated recovery. These indices of recovery included increased glomerular filtration rate, diminution of kidney fibrosis, and reduction of kidney profibrotic gene expression. Amoxicillin was found to increase stool Alistipes, Odoribacter and Stomatobaculum species while significantly depleting Holdemanella and Anaeroplasma. Specifically, amoxicillin treatment reduced kidney CD4+T cells, interleukin (IL)-17 +CD4+T cells, and tumor necrosis factor-α double negative T cells while it increased CD8+T cells and PD1+CD8+T cells. Amoxicillin also increased gut lamina propria CD4+T cells while decreasing CD8+T and IL-17+CD4+T cells. Amoxicillin did not accelerate repair in germ-free or CD8-deficient mice, demonstrating microbiome and CD8+T lymphocytes dependence for amoxicillin protective effects. However, amoxicillin remained effective in CD4-deficient mice. Fecal microbiota transplantation from amoxicillin-treated to germ-free mice reduced kidney fibrosis and increased Foxp3+CD8+T cells. Amoxicillin pre-treatment protected mice against kidney bilateral ischemia reperfusion injury but not cisplatin-induced AKI. Thus, modification of gut bacteria with amoxicillin after severe ischemic AKI is a promising novel therapeutic approach to accelerate recovery of kidney function and mitigate the progression of AKI to chronic kidney disease.

Successful liver transplantation from deceased donors with active COVID-19 infections with undetectable SARS-CoV-2 in donor liver and aorta

BACKGROUND

The COVID-19 pandemic, caused by the SARS-CoV-2 virus, has had unprecedented effects on society and modern healthcare. In liver transplantation, uncertainty regarding the safety of performing transplants during the early stage of the pandemic resulted in increased waitlist mortality. Additionally, concerns about disease transmission led to avoidance of deceased donors with COVID-19 infections. Several successful case reports describing incidental transplant of organs from donors with COVID-19 infections or intentional transplant of such donors into recipients with current or prior COVID-19 infections prompted the transplant community to re-evaluate that position. While excellent short-term results have been published, little is known about use of donors with active infections and the extent of COVID-19 organ involvement, which may affect long term outcomes.

METHODS

We report the successful transplantation of three livers from deceased donors with active COVID-19 infections. Donor liver and aortic tissues were evaluated by sensitive molecular testing for SARS-CoV-2 RNA via in situ hybridization and real-time quantitative reverse transcription PCR.

RESULTS

Postoperatively, all patients had excellent allograft function, without clinical or molecular evidence of SARS-CoV-2 transmission in donor tissues.

CONCLUSION

This evidence supports the use of liver donors with active COVID-19 infections.

T cell metabolic reprogramming in acute kidney injury and protection by glutamine blockade

T cells play an important role in acute kidney injury (AKI). Metabolic programming of T cells regulates their function, is a rapidly emerging field, and is unknown in AKI. We induced ischemic AKI in C57B6 mice and collected kidneys and spleens at multiple time points. T cells were isolated and analyzed by an immune-metabolic assay. Unbiased machine learning analyses identified a distinct T cell subset with reduced VDAC1 and mTOR expression in post-AKI kidneys. Ischemic kidneys showed higher expression of trimethylation of histone H3 lysine 27 (H3K27Me3) and glutaminase. Splenic T cells from post-AKI mice had higher expression of GLUT1, hexokinase II, and CPT1a. Human nonischemic and ischemic kidney tissue displayed similar findings to mouse kidneys. Given a convergent role for glutamine in T cell metabolic pathways and the availability of a relatively safe glutamine antagonist JHU083, effects on AKI were evaluated. JHU083 attenuated renal injury and reduced T cell activation and proliferation in ischemic and nephrotoxic AKI, whereas T cell-deficient mice were not protected by glutamine blockade. In vitro hypoxia demonstrated upregulation of glycolysis-related enzymes. T cells undergo metabolic reprogramming during AKI, and reconstitution of metabolism by targeting T cell glutamine pathway could be a promising novel therapeutic approach.

Immune Checkpoint Molecule TIGIT Regulates Kidney T Cell Functions and Contributes to AKI

SIGNIFICANCE STATEMENT

T cells mediate pathogenic and reparative processes during AKI, but the exact mechanisms regulating kidney T cell functions are unclear. This study identified upregulation of the novel immune checkpoint molecule, TIGIT, on mouse and human kidney T cells after AKI. TIGIT-expressing kidney T cells produced proinflammatory cytokines and had effector (EM) and central memory (CM) phenotypes. TIGIT-deficient mice had protection from both ischemic and nephrotoxic AKI. Single-cell RNA sequencing led to the discovery of possible downstream targets of TIGIT. TIGIT mediates AKI pathophysiology, is a promising novel target for AKI therapy, and is being increasingly studied in human cancer therapy trials.

BACKGROUND

T cells play pathogenic and reparative roles during AKI. However, mechanisms regulating T cell responses are relatively unknown. We investigated the roles of the novel immune checkpoint molecule T cell immunoreceptor with Ig and immunoreceptor tyrosine-based inhibitory motif domains (TIGIT) in kidney T cells and AKI outcomes.

METHODS

TIGIT expression and functional effects were evaluated in mouse kidney T cells using RNA sequencing (RNA-Seq) and flow cytometry. TIGIT effect on AKI outcomes was studied with TIGIT knockout (TIGIT-KO) mice in ischemia reperfusion (IR) and cisplatin AKI models. Human kidney T cells from nephrectomy samples and single cell RNA sequencing (scRNA-Seq) data from the Kidney Precision Medicine Project were used to assess TIGIT's role in humans.

RESULTS

RNA-Seq and flow cytometry analysis of mouse kidney CD4+ T cells revealed increased expression of TIGIT after IR injury. Ischemic injury also increased TIGIT expression in human kidney T cells, and TIGIT expression was restricted to T/natural killer cell subsets in patients with AKI. TIGIT-expressing kidney T cells in wild type (WT) mice had an effector/central memory phenotype and proinflammatory profile at baseline and post-IR. Kidney regulatory T cells were predominantly TIGIT+ and significantly reduced post-IR. TIGIT-KO mice had significantly reduced kidney injury after IR and nephrotoxic injury compared with WT mice. scRNA-Seq analysis showed enrichment of genes related to oxidative phosphorylation and mTORC1 signaling in Th17 cells from TIGIT-KO mice.

CONCLUSIONS

TIGIT expression increases in mouse and human kidney T cells during AKI, worsens AKI outcomes, and is a novel therapeutic target for AKI.

Acute kidney injury and distant organ dysfunction-network system analysis

Acute kidney injury (AKI) occurs in about half of critically ill patients and associates with high in-hospital mortality, increased long-term mortality post-discharge and subsequent progression to chronic kidney disease. Numerous clinical studies have shown that AKI is often complicated by dysfunction of distant organs, which is a cause of the high mortality associated with AKI. Experimental studies have elucidated many mechanisms of AKI-induced distant organ injury, which include inflammatory cytokines, oxidative stress and immune responses. This review will provide an update on evidence of organ crosstalk and potential therapeutics for AKI-induced organ injuries, and present the new concept of a systemic organ network to balance homeostasis and inflammation that goes beyond kidney-crosstalk with a single distant organ.

T Cell Nrf2/Keap1 Gene Editing Using CRISPR/Cas9 and Experimental Kidney Ischemia-Reperfusion Injury

Aims: T cells play pathophysiologic roles in kidney ischemia-reperfusion injury (IRI), and the nuclear factor erythroid 2-related factor 2/kelch-like ECH-associated protein 1 (Nrf2/Keap1) pathway regulates T cell responses. We hypothesized that clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9)-mediated Keap1-knockout (KO) augments Nrf2 antioxidant potential of CD4+ T cells, and that Keap1-KO CD4+ T cell immunotherapy protects from kidney IRI. Results: CD4+ T cell Keap1-KO resulted in significant increase of Nrf2 target genes NAD(P)H quinone dehydrogenase 1, heme oxygenase 1, glutamate-cysteine ligase catalytic subunit, and glutamate-cysteine ligase modifier subunit. Keap1-KO cells displayed no signs of exhaustion, and had significantly lower levels of interleukin 2 (IL2) and IL6 in normoxic conditions, but increased interferon gamma in hypoxic conditions in vitro. In vivo, adoptive transfer of Keap1-KO CD4+ T cells before IRI improved kidney function in T cell-deficient nu/nu mice compared with mice receiving unedited control CD4+ T cells. Keap1-KO CD4+ T cells isolated from recipient kidneys 24 h post IR were less activated compared with unedited CD4+ T cells, isolated from control kidneys. Innovation: Editing Nrf2/Keap1 pathway in murine T cells using CRISPR/Cas9 is an innovative and promising immunotherapy approach for kidney IRI and possibly other solid organ IRI. Conclusion: CRISPR/Cas9-mediated Keap1-KO increased Nrf2-regulated antioxidant gene expression in murine CD4+ T cells, modified responses to in vitro hypoxia and in vivo kidney IRI. Gene editing targeting the Nrf2/Keap1 pathway in T cells is a promising approach for immune-mediated kidney diseases. Antioxid. Redox Signal. Vol, xxx-xxx.

Intestinal Microbiota in Experimental Acute Kidney Injury

Recent studies have demonstrated an important role played by gut microbiota in maintaining intestinal homeostasis and host immune system function. Gut microbiota have been studied in experimental acute kidney injury (AKI) using different mice and rat models exposed to either ischemia or cisplatin-mediated tubular injury. Differences in inflammatory markers and severity of AKI have been observed between germ-free mice, wild-type mice, and mice treated with antibiotics or specific bacteria. Interventions modifying the gut microbiota after experimental AKI have had either beneficial or harmful effects on kidney tubular injury and recovery. These findings provide strong evidence for a modulatory role of gut microbiota during AKI. Ischemic and cis-platin-induced AKI have distinct stool microbial signatures based on 16s sequencing. Future in-depth studies exploring the mechanisms of how the microbiota influence AKI and development of feasible therapeutic options have the potential to improve outcomes in clinical AKI.

TCRαβ+ CD4-/CD8- "double negative" T cells in health and disease-implications for the kidney

Double negative (DN) T cells, one of the least studied T lymphocyte subgroups, express T cell receptor αβ but lack CD4 and CD8 coreceptors. DN T cells are found in multiple organs including kidney, lung, heart, gastrointestinal tract, liver, genital tract, and central nervous system. DN T cells suppress inflammatory responses in different disease models including experimental acute kidney injury, and significant evidence supports an important role in the pathogenesis of systemic lupus erythematosus. However, little is known about these cells in other kidney diseases. Therefore, it is important to better understand different functions of DN T cells and their signaling pathways as promising therapeutic targets, particularly with the increasing application of T cell-directed therapy in humans. In this review, we aim to summarize studies performed on DN T cells in normal and diseased organs in the setting of different disease models with a focus on kidney.

Possible kidney-lung cross-talk in COVID-19: in silico modeling of SARS-CoV-2 infection

Background

Publicly available genomics datasets have grown drastically during the past decades. Although most of these datasets were initially generated to answer a pre-defined scientific question, their repurposing can be useful when new challenges such as COVID-19 arise. While the establishment and use of experimental models of COVID-19 are in progress, the potential hypotheses for mechanisms of onset and progression of COVID-19 can be generated by using in silico analysis of known molecular changes during COVID-19 and targets for SARS-CoV-2 invasion.

Methods

Selecting condition: COVID-19 infection leads to pneumonia and mechanical ventilation (PMV) and associated with acute kidney injury (AKI). There is increasing data demonstrating mechanistic links between AKI and lung injury caused by mechanical ventilation.

Selecting targets: SARS-CoV-2 uses angiotensin-converting enzyme 2 (ACE2) and transmembrane protease serine 2 (TMPRSS2) for cell entry. We hypothesized that expression of ACE2 and TMPRSS2 would be affected in models of AKI and PMV. We therefore evaluated expression of ACE2 and TMPRSS2 as well as other novel molecular players of AKI and AKI-lung cross-talk in the publicly available microarray datasets GSE6730 and GSE60088, which represent gene expression of lungs and kidneys in mouse models of AKI and PMV, respectively.

Results

Expression of COVID-19 related genes ACE2 and TMPRSS2 was downregulated in lungs after 6 h of distant AKI effects. The expression of ACE2 decreased further after 36 h, while expression of TMPRSS2 recovered. In kidneys, both genes were downregulated by AKI, but not by distant lung injury. We also identified 53 kidney genes upregulated by PMV; and 254 lung genes upregulated by AKI, 9 genes of which were common to both organs. 3 of 9 genes were previously linked to kidney-lung cross-talk: Lcn2 (Fold Change (FC)_{Lung (L)} = 18.6, FC_{Kidney (K)} = 6.32), Socs3 (FC_L = 10.5, FC_K = 10.4), Inhbb (FC_L = 6.20, FC_K = 6.17). This finding validates the current approach and reveals 6 new candidates, including Maff (FC_L = 7.21, FC_K = 5.98).

Conclusions

Using our in silico approach, we identified changes in COVID-19 related genes ACE2 and TMPRSS2 in traditional mouse models of AKI and kidney-lung cross-talk. We also found changes in new candidate genes, which could be involved in the combined kidney-lung injury during COVID-19.

Antigen receptor on a new lymphocyte represents a key immune player in autoimmune diseases

PURPOSE:

We have recently identified a previously unknown lymphocyte that is a dual expresser (DE) of productively rearranged and surface-expressed TCRαβ and BCR (surface immunoglobulin, Ig) (Ahmed et al, Cell, 2019: 177:11583). Importantly, a single immunoglobulin heavy-chain, IGHV clonotype (clone-x) predominates DEs that encodes a potent autoantigen (x-autoantigen) in its CDR3 region. The x-autoantigen (as a soluble intact x-mAb) cross-activate autoreactive T cells. The goal of this study is to investigate the properties of x-mAb reactive T cells and examining the mechanisms of how x-mAb recognizes and activates the tolerant autoreactive T cells in autoimmune diseases particularly in T1D.

METHODS:

We used EBV immortalized DE clone as a source of x-mAb and FACS-based protocols to identify x-mAb-responsive autoreactive T cells and their functional properties. ImmunoSEQ assay used to characterize TCR repertoires.

RESULTS:

Preliminary data show that x-mAb potentially binds and activates a subset of autoreactive T cells in T1D compared to HC subjects. Additionally, x-mAb-reactive T cells exhibits an activated and antigen experienced phenotype, including expression of CD45RO, CD44, and CD69. TCRVβ repertoire analysis shows that x-mAb reactive T cells are enriched for public clonally expanded TCRs in T1D patients. Further, x-mAb activates the autoreactive T cell through by crosslinking directly to their T cell receptor (TCR).

CONCLUSIONS:

DE cells in T1D patients secretes a public x-mAb that binds and activate specific subset of autoreactive T cells predominated by few clonotypes that express public TCRs. Our results are revealing previously unknown mechanism that appears to be a play critical role in pathogenesis of T1D.

Nrf2 mediates hypoxia-inducible HIF1α activation in kidney tubular epithelial cells

Nuclear factor erythroid 2-related factor 2 (Nrf2) and hypoxia-inducible factor-1α (HIF1α) transcription factors protect against ischemic acute kidney injury (AKI) by upregulating metabolic and cytoprotective gene expression. In this study, we tested the hypothesis that Nrf2 is required for HIF1α-mediated hypoxic responses using Nrf2-sufficient (wild-type) and Nrf2-deficient (Nrf2-/-) primary murine renal/kidney tubular epithelial cells (RTECs) and human immortalized tubular epithelial cells (HK2 cells) with HIF1 inhibition and activation. The HIF1 pathway inhibitor digoxin blocked hypoxia-stimulated HIF1α activation and heme oxygenase (HMOX1) expression in HK2 cells. Hypoxia-mimicking cobalt (II) chloride-stimulated HMOX1 expression was significantly lower in Nrf2-/- RTECs than in wild-type counterparts. Similarly, hypoxia-stimulated HIF1α-dependent metabolic gene expression was markedly impaired in Nrf2-/- RTECs. Nrf2 deficiency impaired hypoxia-induced HIF1α stabilization independent of increased prolyl 4-hydroxylase gene expression. We found decreased HIF1α mRNA levels in Nrf2-/- RTECs under both normoxia and hypoxia-reoxygenation conditions. In silico analysis and chromatin immunoprecipitation assays demonstrated Nrf2 binding to the HIF1α promoter in normoxia, but its binding decreased in hypoxia-exposed HK2 cells. However, Nrf2 binding at the HIF1α promoter was enriched following reoxygenation, demonstrating that Nrf2 maintains constitutive HIF1α expression. Consistent with this result, we found decreased levels of Nrf2 in hypoxia and that were restored following reoxygenation. Inhibition of mitochondrial complex I prevented hypoxia-induced Nrf2 downregulation and also increased basal Nrf2 levels. These results demonstrate a crucial role for Nrf2 in optimal HIF1α activation in hypoxia and that mitochondrial signaling downregulates Nrf2 levels in hypoxia, whereas reoxygenation restores it. Nrf2 and HIF1α interact to provide optimal metabolic and cytoprotective responses in ischemic AKI.

CD3+CD4-CD8- Double-negative αβ T cells attenuate lung ischemia-reperfusion injury

OBJECTIVE

Lung ischemia-reperfusion injury (IRI) is a common complication after lung transplantation, and immune cells have been implicated in modulating outcomes. We hypothesized that a newly described subset of αβ T-cell receptor positive cells; that is, CD4-CD8- (double negative [DN]) T cells, are found in lungs and can protect against lung IRI.

METHODS

Ischemia was induced in C57BL/6 mice by left pulmonary artery and vein occlusion for 30 minutes followed by 180 minutes of reperfusion. These mice were paired with sham hilar dissected surgical controls. In mice undergoing IRI, adoptive transfer of DN T cells or conventional T cells was performed 12 hours before occlusion. Flow cytometry was used to quantify T cells and inflammatory cytokines, and apoptotic signaling pathways were evaluated with immunoblotting. Lung injury was assessed with Evans blue dye extravasation.

RESULTS

DN T cells were significantly higher (5.29% ± 1% vs 2.21% ± 3%; P < .01) in IRI lungs and secreted higher levels of interleukin-10 (30% ± 5% vs 6% ± 1%; P < .01) compared with surgical sham controls. Immunoblotting, hematoxylin and eosin staining and Evans blue dye demonstrated that adoptive transfer of DN T cells significantly decreased interstitial edema (P < .01) and attenuated apoptosis/cleaved caspase-3 expression in the lungs following lung IRI (P < .01).

CONCLUSIONS

DN T cells traffic into lungs during IRI, and have tissue protective functions regulating inflammation and apoptosis. We propose a potential novel immunoregulatory function of DN T cells during lung IRI.

Persistent Interferon Production by Double Negative T Cells and Collapsing Focal Segmental Glomerulosclerosis

Collapsing glomerulopathy has multiple associations, including viral infections, medications like bisphosphonates and interferon, autoimmune diseases, and genetic predisposition. We report a case of collapsing focal segmental glomerulosclerosis associated with persistently high levels of interferon gamma produced by T-cell receptor αβ (+), CD4- CD8- (double negative) T lymphocytes that progressed despite treatment and improvement of other cytokine levels. Double negative T cells are elevated and activated in autoimmune lymphoproliferative syndrome (ALPS). Production of elevated interferon gamma levels from double negative T cells in ALPS despite treatment provides insight to the pathophysiology of collapsing glomerulopathy, guiding future research for collapsing glomerulopathy.

Gut Microbiome and AKI: Roles of the Immune System and Short-Chain Fatty Acids

Acute kidney injury (AKI) is a common and serious syndrome that involves multiple pathophysiologic mechanisms. Recent studies have demonstrated that dysbiosis of the gut microbiota mediates experimental AKI. The precise microbial populations involved and the underlying mechanisms are currently being explored. In this mini-review based on the NIH AKI O'Brien Center symposium of February 2020, we discuss data on gut microbiota in AKI with a focus on the immune system and short-chain fatty acids as mediators of microbiome-kidney crosstalk.

Keap1-Nrf2 System Plays an Important Role in Invariant Natural Killer T Cell Development and Homeostasis

Kelch-like ECH-associated protein 1 (Keap1) and nuclear factor (erythroid-derived 2)-like 2 (Nrf2) proteins work in concert to regulate the levels of reactive oxygen species (ROS). The Keap1-Nrf2 antioxidant system also participates in T cell differentiation and inflammation, but its role in innate T cell development and functions remains unclear. We report that T cell-specific deletion of Keap1 results in defective development and reduced numbers of invariant natural killer T (NKT) cells in the thymus and the peripheral organs in a cell-intrinsic manner. The frequency of NKT2 and NKT17 cells increases while NKT1 decreases in these mice. Keap1-deficient NKT cells show increased rates of proliferation and apoptosis, as well as increased glucose uptake and mitochondrial function, but reduced ROS, CD122, and Bcl2 expression. In NKT cells deficient in Nrf2 and Keap1, all these phenotypic and metabolic defects are corrected. Thus, the Keap1-Nrf2 system contributes to NKT cell development and homeostasis by regulating cell metabolism.

A newly discovered dual expresser lymphocyte that clonally expanded in Type 1 diabetes (T1D) patients secretes a public antibody that recognize public TCR in T1D

PURPOSE

We have recently discovered a new lymphocyte that co-express BCR and TCR (Ahmed et al, Cell, 2019: 177:11583) and referred as X cell to denote its crossover phenotype. Importantly, X cells express a public BCR that also encodes a potent autoantigen in its CDR3 sequence that is 10 fold more potent than native insulin peptide (InsB:9–23) in binding to DQ8 and activating autologous CD4 T cells. The x-autoantigen cross-activate insulin specific CD4 T cells as a peptide in the context of HLA-DQ8 molecules or as a soluble intact mAb (x-mAb). The goal of this study is to characterize autoreactive CD4 T cells that are responsive to x-mAb to determine their phenotype, cytokine profile and TCR repertoire and whether they express public TCRs.

METHODS

We used EBV-lymphoblastoid X cell clone as a source of x-mAb (IgM) and FACS based protocol to identify IgM reactive CD4 T cells (referred as IgMpos) and their functional properties. ImmunoSEQ assay used to characterize TCR repertoires.

RESULTS

Preliminary data show that frequency of IgMpos CD4 T cells is significantly higher in T1D as compared to Healthy subjects. In addition, IgMpos CD4 T cells exhibit an activated phenotype as compared to autologous IgMneg CD4 T cells, including expression of CD45RO, CD44, and CD69. Analysis of TCRVβ repertoire shows that IgMpos CD4 T cells are enriched for public clonally expanded TCRs as compared to IgMneg counterparts.

CONCLUSIONS

X cells in T1D patients are predominated by a single public BCR and that the secreted version of this BCR (x-mAb) is autoreactive against a specific subset of CD4 T cells that predominated by few clonotypes that express public TCRs. Our results are revealing previously unknown mechanism that appears to be a play critical role in pathogenesis of T1D.

TCR+CD4-CD8- (double negative) T cells protect from cisplatin-induced renal epithelial cell apoptosis and acute kidney injury

Acute kidney injury (AKI) due to cisplatin is a significant problem that limits its use as an effective chemotherapeutic agent. T cell receptor⁺CD4^-CD8^- double negative (DN) T cells constitute the major T cell population in the human and mouse kidney, express programmed cell death protein (PD)-1, and protect from ischemic AKI. However, the pathophysiological roles of DN T cells in cisplatin-induced AKI is unknown. In this study, wild-type mice were treated with cisplatin (30 mg/kg) or vehicle, and the effects on kidney DN T cell numbers and function were measured. In vitro experiments evaluated effects of kidney DN T cells on cisplatin-induced apoptosis and PD ligand 1 (PD-L1) in renal epithelial cells. Adoptive transfer experiments assessed the therapeutic potential of DN T cells during cisplatin-induced AKI. Our results show that kidney DN T cell population increased at 24 h and declined by 72 h after cisplatin treatment. Cisplatin treatment increased kidney DN T cell proliferation, apoptosis, CD69, and IL-10 expression, whereas CD62L, CD44, IL-17A, interferon-γ, and TNF-α were downregulated. Cisplatin treatment decreased both PD-1 and natural killer 1.1 subsets of kidney DN T cells with a pronounced effect on the PD-1 subset. In vitro kidney DN T cell coculture decreased cisplatin-induced apoptosis in kidney proximal tubular epithelial cells, increased Bcl-2, and decreased cleaved caspase 3 expression. Cisplatin-induced expression of PD ligand 1 was reduced in proximal tubular epithelial cells cocultured with DN T cells. Adoptive transfer of DN T cells attenuated kidney dysfunction and structural damage from cisplatin-induced AKI. These results demonstrate that kidney DN T cells respond rapidly and play a protective role during cisplatin-induced AKI.

A Public BCR Present in a Unique Dual-Receptor-Expressing Lymphocyte from Type 1 Diabetes Patients Encodes a Potent T Cell Autoantigen

T and B cells are the two known lineages of adaptive immune cells. Here, we describe a previously unknown lymphocyte that is a dual expresser (DE) of TCR and BCR and key lineage markers of both B and T cells. In type 1 diabetes (T1D), DEs are predominated by one clonotype that encodes a potent CD4 T cell autoantigen in its antigen binding site. Molecular dynamics simulations revealed that this peptide has an optimal binding register for diabetogenic HLA-DQ8. In concordance, a synthetic version of the peptide forms stable DQ8 complexes and potently stimulates autoreactive CD4 T cells from T1D patients, but not healthy controls. Moreover, mAbs bearing this clonotype are autoreactive against CD4 T cells and inhibit insulin tetramer binding to CD4 T cells. Thus, compartmentalization of adaptive immune cells into T and B cells is not absolute, and violators of this paradigm are likely key drivers of autoimmune diseases.

T Lymphocytes in Acute Kidney Injury and Repair

Innate and adaptive immune systems participate in the pathogenesis of acute kidney injury (AKI). Considerable data from different research teams have shown the importance of T lymphocytes in the pathophysiology of AKI and, more recently, prevention and repair. T cells can generate or resolve inflammation by secreting specific cytokines and growth factors as well as interact with other immune and stromal cells to induce kidney injury or promote tissue repair. There also are emerging data on the role of T cells in the progression of AKI to chronic kidney disease and organ cross-talk in AKI. These data set the stage for immunomodulatory therapies for AKI. This review focuses on the major populations of T lymphocytes and their roles as mediators for AKI and repair.

CD4+ T Cell-Derived NGAL Modifies the Outcome of Ischemic Acute Kidney Injury

CD4⁺ T cells mediate the pathogenesis of ischemic and nephrotoxic acute kidney injury (AKI). However, the underlying mechanisms of CD4⁺ T cell-mediated pathogenesis are largely unknown. We therefore conducted unbiased RNA-sequencing to discover novel mechanistic pathways of kidney CD4⁺ T cells after ischemia compared with normal mouse kidney. Unexpectedly, the lipocalin-2 (Lcn2) gene, which encodes neutrophil gelatinase-associated lipocalin (NGAL) had the highest fold increase (∼60). The NGAL increase in CD4⁺ T cells during AKI was confirmed at the mRNA level with quantitative real-time PCR and at the protein level with ELISA. NGAL is a potential biomarker for the early detection of AKI and has multiple potential biological functions. However, the role of NGAL produced by CD4⁺ T cells is not known. We found that ischemic AKI in NGAL knockout (KO) mice had worse renal outcomes compared with wild-type (WT) mice. Adoptive transfer of NGAL-deficient CD4⁺ T cells from NGAL KO mice into CD4 KO or WT mice led to worse renal function than transfer of WT CD4⁺ T cells. In vitro-simulated ischemia/reperfusion showed that NGAL-deficient CD4⁺ T cells express higher levels of IFN-γ mRNA compared with WT CD4⁺ T cells. In vitro differentiation of naive CD4⁺ T cells to Th17, Th1, and Th2 cells led to significant increase in Lcn2 expression. Human kidney CD4⁺ T cell NGAL also increased significantly after ischemia. These results demonstrate an important role for CD4⁺ T cell NGAL as a mechanism by which CD4⁺ T cells mediate AKI and extend the importance of NGAL in AKI beyond diagnostics.

Hybrid lipids, peptides, and lymphocytes: new era in type 1 diabetes research

Type 1 diabetes (T1D) results from autoimmune destruction of insulin-producing β cells in islets of Langerhans. Many genetic and immunological insights into autoimmune disease pathogenesis were initially uncovered in the context of T1D and facilitated by preclinical studies using the nonobese diabetic (NOD) mouse model. Recently, the study of T1D has led to the discovery of fatty acid esters of hydroxyl fatty acids (FAHFAs), which are naturally occurring hybrid peptides that modulate inflammation and diabetes pathogenesis, and a hybrid lymphocyte that expresses both B and T cell receptors. Palmitic acid esters of hydroxy stearic acids (PAHSAs) are the most extensively studied FAHFA. In this issue of the JCI, Syed et al. have shown that PAHSAs both attenuate autoimmune responses and promote β cell survival in NOD mice. Given the lack of effective T1D therapies and the paucity of known side effects of PAHSAs, this lipid may have therapeutic potential for individuals at risk for or newly diagnosed with T1D.

Reparative T lymphocytes in organ injury

Acute organ injuries such as acute cerebrovascular accidents, myocardial infarction, acute kidney injury, acute lung injury, and others are among the leading causes of death worldwide. Dysregulated or insufficient organ repair mechanisms limit restoration of homeostasis and contribute to chronic organ failure. Studies reveal that both humans and mice harness potent non-stem cells that are capable of directly or indirectly promoting tissue repair. Specific populations of T lymphocytes have emerged as important reparative cells with context-specific actions. These T cells can resolve inflammation and secrete reparative cytokines and growth factors as well as interact with other immune and stromal cells to promote the complex and active process of tissue repair. This Review focuses on the major populations of T lymphocytes known to mediate tissue repair, their reparative mechanisms, and the diseases in which they have been implicated. Elucidating and harnessing the mechanisms that promote the reparative functions of these T cells could greatly improve organ dysfunction after acute injury.

Activation and Proliferation of PD-1+ Kidney Double-Negative T Cells Is Dependent on Nonclassical MHC Proteins and IL-2

BACKGROUND

CD4^- CD8^- double-negative (DN) αβ T cells with innate-like properties represent a significant component of T cells in human and mouse kidneys. They spontaneously proliferate in the steady state and protect against ischemic AKI. However, the mechanisms regulating DN T cell homeostasis and responses to external danger signals from "sterile" inflammation remain poorly understood.

METHODS

We used knockout mice, functional assays, and an established ischemic AKI model to investigate the role of various MHC class I and II molecules in regulating kidney DN T cells. We also studied human nephrectomy samples.

RESULTS

Deficiency of β2m-dependent MHC class I (but not MHC class II) molecules led to significant reduction in frequency or absolute numbers of kidney DN T cells due to impaired activation, proliferation, increased apoptosis, and loss of an NK1.1⁺ subset of DN T cells. The remaining DN T cells in β2m knockout mice mainly comprised a programmed cell death protein-1 receptor (PD-1⁺) subset that depends on IL-2 provided by conventional T cells for optimal homeostasis. However, this PD-1⁺ subset remained highly responsive to changes in milieu, demonstrated by responses to infused lymphocytes. It was also the major responder to ischemic AKI; the NK1.1⁺ subset and CD8⁺ T cells had minimal responses. We found both DN T cell subsets in normal and cancerous human kidneys, indicating possible clinical relevance.

CONCLUSIONS

DN T cells, a unique population of kidney T cells, depend on nonclassical β2m molecules for homeostasis and use MHC-independent mechanisms to respond to external stimuli. These results have important implications for understanding the role these cells play during AKI and other immune cell-mediated kidney diseases.

The Microbiome and Acute Kidney Injury

Acute kidney injury (AKI) is a major clinical problem in native and transplanted kidneys. Bidirectional interaction between gut microbiota and kidney tissue or the "colo-renal" system is being recognized as an important modulating factor in AKI. Gut microbes appear to have a complex but yet poorly understood communication with renal cellular and molecular processes that affect normal kidney function and response to injury. There have been major recent advances in the study of the microbiome that provide an opportunity to apply this knowledge to improve our understanding and treatment of patients with AKI. This mini-review aims to focus on select general concepts about the microbiome, mechanisms by which the microbiome can modify kidney function, and data on microbiome and AKI. We have briefly touched on a few topics rather than comprehensively reviewing the role of microbiome in kidney diseases. We also propose future gut microbiota-AKI studies based on advances in gut microbiota studies in other human diseases and experimental models.

Distant Organ Dysfunction in Acute Kidney Injury: A Review

Acute kidney injury (AKI) is common in critically ill patients and is associated with increased morbidity and mortality. Dysfunction of other organs is an important cause of poor outcomes from AKI. Ample clinical and epidemiologic data show that AKI is associated with distant organ dysfunction in lung, heart, brain, and liver. Recent advancements in basic and clinical research have demonstrated physiologic and molecular mechanisms of distant organ interactions in AKI, including leukocyte activation and infiltration, generation of soluble factors such as inflammatory cytokines/chemokines, and endothelial injury. Oxidative stress and production of reactive oxygen species, as well as dysregulation of cell death in distant organs, are also important mechanism of AKI-induced distant organ dysfunction. This review updates recent clinical and experimental findings on organ crosstalk in AKI and highlights potential molecular mechanisms and therapeutic targets to improve clinical outcomes during AKI.

Effectiveness of informational decision aids and a live donor financial assistance program on pursuit of live kidney transplants in African American hemodialysis patients

BACKGROUND

African Americans have persistently poor access to living donor kidney transplants (LDKT). We conducted a small randomized trial to provide preliminary evidence of the effect of informational decision support and donor financial assistance interventions on African American hemodialysis patients' pursuit of LDKT.

METHODS

Study participants were randomly assigned to receive (1) Usual Care; (2) the Providing Resources to Enhance African American Patients' Readiness to Make Decisions about Kidney Disease (PREPARED); or (3) PREPARED plus a living kidney donor financial assistance program. Our primary outcome was patients' actions to pursue LDKT (discussions with family, friends, or doctor; initiation or completion of the recipient LDKT medical evaluation; or identification of a donor). We also measured participants' attitudes, concerns, and perceptions of interventions' usefulness.

RESULTS

Of 329 screened, 92 patients were eligible and randomized to Usual Care (n = 31), PREPARED (n = 30), or PREPARED plus financial assistance (n = 31). Most participants reported interventions helped their decision making about renal replacement treatments (62%). However there were no statistically significant improvements in LDKT actions among groups over 6 months. Further, no participants utilized the living donor financial assistance benefit.

CONCLUSIONS

Findings suggest these interventions may need to be paired with personal support or navigation services to overcome key communication, logistical, and financial barriers to LDKT.

TRIAL REGISTRATION

ClinicalTrials.gov [ NCT01439516 ] [August 31, 2011].

KEAP1 Editing Using CRISPR/Cas9 for Therapeutic NRF2 Activation in Primary Human T Lymphocytes

Oxidant stress modifies T lymphocyte activation and function. Previous work demonstrated that murine T cell-specific kelch like-ECH-associated protein 1 (Keap1) deletion enhances antioxidant capacity and protects from experimental acute kidney injury. In this study, we used CRISPR technology to develop clinically translatable human T cell-specific KEAP1 deletion. Delivery of KEAP1 exon 2 specific Cas9:guide RNA in Jurkat T cells led to significant (∼70%) editing and upregulation of NRF2-regulated antioxidant genes NADPH dehydrogenase quinone 1 (NQO1) (up to 11-fold), heme oxygenase 1 (HO1) (up to 11-fold), and GCLM (up to 2-fold). In primary human T cells, delivery of KEAP1 exon 2 target site 2-specific ATTO 550-labeled Cas9:guide RNA edited KEAP1 in ∼40% cells and significantly (p ≤ 0.04) increased NQO1 (16-fold), HO1 (9-fold), and GCLM (2-fold) expression. To further enrich KEAP1-edited cells, ATTO 550-positive cells were sorted 24 h after electroporation. Assessment of ATTO 550-positive cells showed KEAP1 editing in ∼55% cells. There was no detectable off-target cleavage in the top three predicted genes in the ATTO 550-positive cells. Gene expression analysis found significantly (p ≤ 0.01) higher expression of NQO1 mRNA in ATTO 550-positive cells compared with control cells. Flow cytometric assessment showed increased (p ≤ 0.01) frequency of CD4-, CD25-, and CD69-expressing KEAP1 edited cells whereas frequency of CD8- (p ≤ 0.01) and IL-17- (p ≤ 0.05) expressing cells was reduced compared with control cells. Similar experimental conditions resulted in significant KEAP1 editing, increased antioxidant gene expression, and frequency of CD69 and IL-10 positive cells in highly enriched KEAP1-edited regulatory T cells. KEAP1-edited T cells could potentially be used for treating multiple human diseases.

Role of Immune Cells in Acute Kidney Injury and Repair

Acute kidney injury (AKI) is a significant problem in both native and transplant kidneys. There have been significant advances in understanding the role of immune cells in the early injury and repair from AKI. In this brief review, we aim to update information on the pathophysiologic impact of various immune cells in AKI, with special emphasis on repair. An improved understanding of the AKI immunopathology will lead to new therapies that prevent AKI, accelerate repair, and prevent the progression of AKI to chronic kidney disease.

Identification of kidney CD45intCD11bintF4/80+MHCII+Ly6C− macrophages initially masquerading as T cells

Background

Mononuclear phagocytic cells (MPCs) have important roles in the pathogenesis of many kidney diseases, including ischemia-reperfusion injury (IRI) and allograft rejection. Despite the recent advances on description of MPC subpopulations and their functional characterization in kidney, there is no clear consensus for the classification of MPC subpopulations. Here we describe a newly identified renal macrophage, named CD45intCD11bint cells.

Methods

Kidney mononuclear cells were isolated from C57BL6 male mice under steady state and after IRI and analyzed using flow cytometry.

Results

While focusing on TCRαβ+CD4−CD8− kidney T cells, we identified a cell population that binds only to TCRβ and CD8β antibodies but not to CD8α antibody. Further studies using Fc receptor blockers disclosed that this population was a renal macrophage subset which was different from other macrophages by its intermediate expression of CD45 and CD11b. These CD45intCD11bint macrophages were further characterized as F4/80+MHCII+Ly6C− cells comprising 40% of MPCs in normal kidney. CD45intCD11bint macrophages are found predominantly in the kidney as compared to other lymphoid and non-lymphoid organs (ANOVA, p = 0.002). In addition, CD45intCD11bint population significantly decreased 48 hours after IRI in contrast to steady increase of CD45high macrophages (p = 0.027). Relevance of this population to human kidney is being investigated.

Conclusion

Kidney CD45intCD11bintF4/80+MHCII+Ly6C− macrophages are newly defined MPCs that comprise a major subset of resident renal MPCs. They have unique surface phenotype as well as T-cell mimicking characteristics. This new subset could play an important role in immune diseases of the kidney.

Immunoregulatory function of kidney CD4−CD8− double negative (DN) αβ T cells is MHC dependent

Despite strong evidence for the role of immune cells in ischemia reperfusion injury (IRI) in transplant and native kidney, the underlying mechanisms are poorly understood. Furthermore, there is little data regarding unconventional T cells, usually present in small numbers in the kidney. We have recently shown that a subset of alpha/beta T cells that is double negative (DN) for both CD4 and CD8 coreceptors are present in significant numbers in normal kidney of mice and also present in human kidney biopsies. Unlike conventional CD4 and CD8 T cells, DN T cells are highly dividing in the steady and rapidly increases following IRI. In addition, kidney DN T cells secrete IL-10 and IL-27, possess an in vitro regulatory function and ameliorate AKI in mice. Unknown aspects of DN T cells included identification their MHC restriction elements and roles of various types of MHC haplotype in their homeostasis. Our most recent results show that DN T cells are heterogeneous as indicated by the partial effect of lack of β2m and MHC class II on their homeostasis. In addition, lack of β2m significantly reduce activated phenotype that is seen in kidney DN T cells. Conversely, reconstitution of β2m-deficient mice leads to activation and expansion of endogenous DN T cells, suggesting interactions between DN and CD8 T cells. Further dissection of kidney DN T cell biology will help us understand the pathogenesis of IRI and other immune mediated kidney diseases.

KEAP1 gene editing using CRISPR/Cas9 for therapeutic NRF2 activation in human T cells

Background

T lymphocytes mediate ischemia reperfusion injury (IRI) during organ transplantation. We recently demonstrated that augmentation of NRF2 dependent antioxidant response in T lymphocytes by deleting KEAP1 significantly protects from IR induced kidney injury. In order to develop clinically translatable T cell specific antioxidant therapy, we used CRISPR technology to delete KEAP1, the inhibitor of NRF2, in human Jurkat T cells and primary T cells.

Methods

We targeted KEAP1 exon 2 using site specific guide RNA. Briefly, 5×105 cells were electroporated 1.5μM of Cas9 protein and 1.8μM crRNA:tracrRNA complex. Control cells were electroporated without cas9:guide RNA complex. Cells were harvested 72h after electroporation and assessed for cell number and viability, KEAP1 editing and qPCR based analysis of NRF2 target genes.

Results

Electroporation of cas9:guide RNA complex had no adverse effect on cell expansion and viability (≥ 95%) in either Jurkat or primary T cells. Furthermore, genomic cleavage analysis showed editing of KEAP1 in upto 75% Jurkat cells. qPCR based studies in Jurkat cells showed significant (p≤0.05) increases in NRF2 targets NQO1 (~10 fold), HO-1 (~13 fold) and GCLM (~2.6 fold) mRNA following KEAP1 deletion, compared to control cells. Similarly, CRISPR mediated KEAP1 editing in primary T cells resulted in significant increase (p≤0.05) in NQO1 (~24 fold), HO-1 (~48 fold), GCLM (~6 fold) and GCLC (~3.5 fold) compared to control cells.

Conclusions

These data show that KEAP1 editing is feasible using CRISPR technology to augment NRF2 regulated antioxidant response in primary human T cells. This approach could improve immune cell based therapy for IRI during transplantation and help treat allograft rejection.

Quantitative characterization of T-cell repertoire and biomarkers in kidney transplant rejection

BACKGROUND

T-cell-mediated rejection (TCMR) remains a major cause of kidney allograft failure. The characterization of T-cell repertoire in different immunological disorders has emerged recently as a novel tool with significant implications. We herein sought to characterize T-cell repertoire using next generation sequencing to diagnose TCMR.

METHODS

In this prospective study, we analyzed samples from 50 kidney transplant recipients. We collected blood and kidney transplant biopsy samples at sequential time points before and post transplant. We used next generation sequencing to characterize T-cell receptor (TCR) repertoire by using illumina miSeq on cDNA synthesized from RNA extracted from six patients' samples. We also measured RNA expression levels of FOXP3, CD8, CD4, granzyme and perforin in blood samples from all 50 patients.

RESULTS

Seven patients developed TCMR during the first three months of the study. Out of six patients who had complete sets of blood and biopsy samples two had TCMR. We found an expansion of the TCR repertoire in blood at time of rejection when compared to that at pre-transplant or one-month post transplant. Patients with TCMR (n = 7) had significantly higher RNA expression levels of FOXP3, Perforin, Granzyme, CD4 and CD8 in blood samples than those with no TCMR (n = 43) (P = 0.02, P = 0.003, P = 0.002, P = 0.017, and P = 0.01, respectively).

CONCLUSIONS

Our study provides a potential utilization of TCR clone kinetics analysis in the diagnosis of TCMR. This approach may allow for the identification of the expanded T-cell clones associated with the rejection and lead to potential noninvasive diagnosis and targeted therapies of TCMR.

Abnormalities in biomarkers of mineral and bone metabolism in kidney donors

Previous studies have suggested that kidney donors may have abnormalities of mineral and bone metabolism typically seen in chronic kidney disease. This may have important implications for the skeletal health of living kidney donors and for our understanding of the pathogenesis of long-term mineral and bone disorders in chronic kidney disease. In this prospective study, 182 of 203 kidney donors and 173 of 201 paired normal controls had markers of mineral and bone metabolism measured before and at 6 and 36 months after donation (ALTOLD Study). Donors had significantly higher serum concentrations of intact parathyroid hormone (24.6% and 19.5%) and fibroblast growth factor-23 (9.5% and 8.4%) at 6 and 36 months, respectively, as compared to healthy controls, and significantly reduced tubular phosphate reabsorption (-7.0% and -5.0%) and serum phosphate concentrations (-6.4% and -2.3%). Serum 1,25-dihydroxyvitamin D3 concentrations were significantly lower (-17.1% and -12.6%), while 25-hydroxyvitamin D (21.4% and 19.4%) concentrations were significantly higher in donors compared to controls. Moreover, significantly higher concentrations of the bone resorption markers, carboxyterminal cross-linking telopeptide of bone collagen (30.1% and 13.8%) and aminoterminal cross-linking telopeptide of bone collagen (14.2% and 13.0%), and the bone formation markers, osteocalcin (26.3% and 2.7%) and procollagen type I N-terminal propeptide (24.3% and 8.9%), were observed in donors. Thus, kidney donation alters serum markers of bone metabolism that could reflect impaired bone health. Additional long-term studies that include assessment of skeletal architecture and integrity are warranted in kidney donors.

Nrf2-AKT interactions regulate heme oxygenase 1 expression in kidney epithelia during hypoxia and hypoxia-reoxygenation

Ischemia-reperfusion (IR)-induced kidney injury is a major clinical problem, but its underlying mechanisms remain unclear. The transcription factor known as nuclear factor, erythroid 2-like 2 (NFE2L2 or Nrf2) is crucial for protection against oxidative stress generated by pro-oxidant insults. We have previously shown that Nrf2 deficiency enhances susceptibility to IR-induced kidney injury in mice and that its upregulation is protective. Here, we examined Nrf2 target antioxidant gene expression and the mechanisms of its activation in both human and murine kidney epithelia following acute (2 h) and chronic (12 h) hypoxia and reoxygenation conditions. We found that acute hypoxia modestly stimulates and chronic hypoxia strongly stimulates Nrf2 putative target HMOX1 expression, but not that of other antioxidant genes. Inhibition of AKT1/2 or ERK1/2 signaling blocked this induction; AKT1/2 but not ERK1/2 inhibition affected Nrf2 levels in basal and acute hypoxia-reoxygenation states. Unexpectedly, chromatin immunoprecipitation assays revealed reduced levels of Nrf2 binding at the distal AB1 and SX2 enhancers and proximal promoter of HMOX1 in acute hypoxia, accompanied by diminished levels of nuclear Nrf2. In contrast, Nrf2 binding at the AB1 and SX2 enhancers significantly but differentially increased during chronic hypoxia and reoxygenation, with reaccumulation of nuclear Nrf2 levels. Small interfering-RNA-mediated Nrf2 depletion attenuated acute and chronic hypoxia-inducible HMOX1 expression, and primary Nrf2-null kidney epithelia showed reduced levels of HMOX1 induction in response to both acute and chronic hypoxia. Collectively, our data demonstrate that Nrf2 upregulates HMOX1 expression in kidney epithelia through a distinct mechanism during acute and chronic hypoxia reoxygenation, and that both AKT1/2 and ERK1/2 signaling are required for this process.

Hospital discharge communications during care transitions for patients with acute kidney injury: a cross-sectional study

Background

High quality hospital discharge communications about acute kidney injury (AKI) could facilitate continuity of care after hospital transitions and reduce patients’ post-hospitalization health risks.

Methods

We characterized the presence and quality (10 elements) of written hospital discharge communications (physician discharge summaries and patient instructions) for patients hospitalized with AKI at a single institution in 2012 through medical record review.

Results

In 75 randomly selected hospitalized patients with AKI, fewer than half of physician discharge summaries and patient instructions documented the presence (n = 33, 44 % and n = 10, 13 %, respectively), cause (n = 32, 43 % and n = 1, 1 %, respectively), or course of AKI (n = 23, 31 %, discharge summary only) during hospitalization. Few provided recommendations for treatment and/or observation specific to AKI (n = 11, 15 and 6, 8 % respectively). In multivariable analyses, discharge communications containing information about AKI were most prevalent among patients with AKI Stage 3, followed by patients with Stage 2 and Stage 1 (adjusted percentages (AP) [95 % CI]: 84 % [39–98 %], 43 % [11–82 %], and 24 % [reference], respectively; p trend = 0.008). AKI discharge communications were also more prevalent among patients with known chronic kidney disease (CKD) versus those without (AP [95 % CI]: 92 % [51–99 %] versus 39 % [reference], respectively, p = 0.02) and among patients discharged from medical versus surgical services (AP [95 % CI]: 73 % [33–93 %] versus 23 % [reference], respectively, p = 0.01). Communications featured 4 median quality elements. Quality elements were greater in communications for patients with more severe AKI (Stage 3 (number of additional quality elements (β) [95 % CI]: 2.29 [0.87–3.72]), Stage 2 (β [95 % CI]: 0.62 [−0.65–1.90]) and Stage 1 (reference); p for trend = 0.002).

Conclusions

Few hospital discharge communications in AKI patients described AKI or provided recommendations for AKI care. Improvements in the quality of hospital discharge communications to improve care transitions of patients with AKI are needed.

Electronic supplementary material

The online version of this article (doi:10.1186/s12913-016-1697-7) contains supplementary material, which is available to authorized users.

Kidney epithelium specific deletion of kelch-like ECH-associated protein 1 (Keap1) causes hydronephrosis in mice

Background

Transcription factor Nrf2 protects from experimental acute kidney injury (AKI) and is promising to limit progression in human chronic kidney disease (CKD) by upregulating multiple antioxidant genes. We recently demonstrated that deletion of Keap1, the endogenous inhibitor of Nrf2, in T lymphocytes significantly protects from AKI. In this study, we investigated the effect of Keap1 deletion on Nrf2 mediated antioxidant response in the renal tubular epithelial cells.

Methods

We deleted Keap1 exon 2 and 3 in the renal tubular epithelial cells by crossing Ksp-Cre mice with Keap1 floxed (Keap1^f/f) mice. Deletion of Keap1 gene in the kidney epithelial cells of Ksp-Keap1^-/- mice and its effect on Nrf2 target gene expression was performed using PCR and real-time PCR respectively. Histological evaluation was performed on H&E stained sections. Complete blood count, serum and urine analysis were performed to assess systemic effects of defective kidney development. Student’s T test was used to determine statistical difference between the groups.

Results

Ksp-Cre resulted in the deletion of Keap1 exon 2 and 3 and subsequent upregulation of Nrf2 target genes, Nqo1, Gclm and Gclc in the kidney epithelial cells of Ksp-Keap1^-/- mice at baseline. Renal epithelial cell specific deletion of Keap1 in Ksp-Keap1^-/- mice caused marked renal pelvic expansion and significant compression of medullary parenchyma consistent with hydronephrosis in both (3 month-old) males and females. Kidneys from 6 month-old Ksp-Keap1^-/- mice showed progressive hydronephrosis. Hematological, biochemical and urinary analysis showed significantly higher red blood cell count (p = 0.04), hemoglobin (p = 0.01), hematocrit (p = 0.02), mean cell volume (p = 0.02) and mean cell hemoglobin concentration (p = 0.003) in Ksp-Keap1^-/- mice in comparison to Keap1^f/f mice.

Conclusions

These unexpected findings demonstrate that Keap1 deletion in renal tubular epithelial cells results in an abnormal kidney development consistent with hydronephrosis and reveals a novel Keap1 mediated signaling pathway in renal development.

Sex and the single transplanted kidney

Substantial ischemia-reperfusion injury (IRI) to the transplanted kidney occurs in 30% to 50% of transplantation patients who receive the organ from a deceased donor. IRI usually manifests as delayed graft function (DGF) and, in severe cases, results in primary nonfunction. Previous studies, primarily experimental, have demonstrated sex-specific susceptibility to IRI in kidney and other organs. In this issue of the JCI, Aufhauser Jr., Wang, and colleagues further demonstrate the importance of donor and recipient sex in IRI and elucidate the role of estrogen receptors in a murine model. Furthermore, analysis of data from 46,691 renal transplant patients in the United Network for Organ Sharing (UNOS) database revealed that sex affects DGF outcomes in humans. Manipulation of sex-driven molecular pathways offers a fertile opportunity to increase the number of organs available for transplantation and to reduce IRI in kidney and, likely, other organs.