Limited costimulatory molecule expression on renal tubular epithelial cells impairs T cell activation

Pioglitazone modulates immune activation and ameliorates inflammation induced by injured renal tubular epithelial cells via PPARγ/miRNA‑124/STAT3 signaling

Acute kidney injury (AKI) is commonly a result of renal ischemia reperfusion injury (IRI), which produces clinical complications characterized by the rapid deterioration of renal function, leading to chronic kidney disease and increases the risk of morbidity and mortality. Currently, only supportive treatment is available. AKI, which is accompanied by immune activation and inflammation, is caused by proximal tubular injury. The present study investigated the role of tubular epithelial cells as drivers of inflammation in renal IRI and their potential function as antigen-presenting cells, as well as the molecular mechanisms by which peroxisome proliferator-activated receptor-γ (PPARγ) agonists [such as pioglitazone (Pio)] exert reno-protective action in renal IRI. A total of 50 Wistar male albino rats were divided into five groups: Sham + DMSO, Sham + Pio, IRI + DMSO, IRI + prophylactic preoperative (pre) Pio and IRI + postoperative Pio. The histopathological changes in renal tissue samples and the renal epithelial cell expression of CD86, miRNA-124, STAT3, pro-inflammatory cytokines, inducible nitric oxide synthase (iNOS) and Arginase-II were analyzed by immunohistochemistry, reverse transcription-quantitative PCR, western blotting and ELISA respectively. IRI was a potent inducer for CD86 immunoexpression. An ameliorative action of Pio was demonstrated via decreased CD86 immunoexpression, upregulation of miRNA-124, decreased STAT3 expression and beneficial anti-inflammatory effects. The tubular epithelium served a notable role in the inflammatory response in renal IRI. Pio exerted its anti-inflammatory effects via PPARγ/miRNA-124/STAT3 signaling.

Immune regulation in renal inflammation

Renal inflammation, induced by autoantigen recognition or toxic drugs, leads to renal tissue injury and decline in kidney function. Recent studies have demonstrated the crucial role for regulatory T cells in suppressing pathogenic adaptive but also innate immune responses in the inflamed kidney. However, there is also evidence for other immune cell populations with immunosuppressive function in renal inflammation. This review summarizes mechanisms of immune cell regulation in immune-mediated glomerulonephritis and acute and chronic nephrotoxicity.

New Biomarkers in Acute Tubulointerstitial Nephritis: A Novel Approach to a Classic Condition

Acute tubulointerstitial nephritis (ATIN) is an immunomediated cause of acute kidney injury. The prevalence of ATIN among the causes of acute kidney injury (AKI) is not negligible, especially those cases related to certain drugs. To date, there is a lack of reliable non-invasive diagnostic and follow-up markers. The gold standard for diagnosis is kidney biopsy, which shows a pattern of tubulointerstitial leukocyte infiltrate. The urinalysis findings can aid in the diagnosis but are no longer considered sensitive or specific. Atthe present time, there is a rising attentiveness tofinding trustworthy biomarkers of the disease, with special focus in urinary cytokines and chemokines that may reflect kidney local inflammation. Cell-based tests are of notable interest to identify the exact drug involved in hypersensitivity reactions to drugs, manifesting as ATIN. Certain single-nucleotide polymorphisms in HLA or cytokine genes may confer susceptibility to the disease according to pathophysiological basis. In this review, we aim to critically examine and summarize the available evidence on this topic.

16S rRNA-functionalized multi-HCR concatemers in a signal amplification nanostructure for visual detection of Salmonella

To prevent foodborne diseases and minimize their impacts, it is extremely important to develop a cost-effective and efficient bacterial detection assay for diagnostics, particularly in resource-poor settings. In this study, 16S rRNA from foodborne Salmonella was coupled with multiple HCR (hybridization chain reaction) concatemers and functionalized in a signal structure for lateral flow nucleic acid biosensor (LFNAB) detection. The 16S rRNA was incubated with two specific capture probes and multiple helper probes carrying the same initiator, to unwind its secondary structure and form an "initiators-on-a-string" complex. Through use of the initiators, each target 16S rRNA yielded multiple HCR concatemers tethered to numerous biotins, and numerous streptavidin-labeled gold nanoparticles were introduced on the LFNAB. The limit of detection was 53.65 CFU/mL for Salmonella. Notably, this method has high specificity and applicability for the detection of Salmonella in food and water samples.

Mesangial Cells Exhibit Features of Antigen-Presenting Cells and Activate CD4+ T Cell Responses

Background

Mesangial cells play a prominent role in the development of inflammatory diseases and autoimmune disorders of the kidney. Mesangial cells perform the essential functions of helping to ensure that the glomerular structure is stable and regulating capillary flow, and activated mesangial cells acquire proinflammatory activities. We investigated whether activated mesangial cells display immune properties and control the development of T cell immunity.

Methods

Flow cytometry analysis was used to study the expression of antigen-presenting cell surface markers and costimulatory molecules in mesangial cells. CD4+ T cell activation induced by mesangial cells was detected in terms of T cell proliferation and cytokine production.

Results

IFN-γ-treated mesangial cells express membrane proteins involved in antigen presentation and T cell activation, including MHC-II, ICAM-1, CD40, and CD80. This finding suggests that activated mesangial cells can take up and present antigenic peptides to initiate CD4+ T cell responses and thus act as nonprofessional antigen-presenting cells. Polarization of naïve CD4+ T cells (Th0 cells) towards the Th1 phenotype was induced by coculture with activated mesangial cells, and the resulting Th1 cells showed increased mRNA and protein expression of inflammation-associated genes.

Conclusion

Mesangial cells can present antigen and modulate CD4+ T lymphocyte proliferation and differentiation. Interactions between mesangial cells and T cells are essential for sustaining the inflammatory response in a variety of glomerulonephritides. Therefore, mesangial cells might participate in immune function in the kidney.

Renal proximal tubular epithelial cells exert immunomodulatory function by driving inflammatory CD4+ T cell responses

In immune-mediated glomerular diseases like crescentic glomerulonephritis (cGN), inflammatory CD4⁺ T cells accumulate within the tubulointerstitial compartment in close contact to proximal and distal tubular epithelial cells and drive renal inflammation and tissue damage. However, whether renal epithelial cell populations play a role in the pathogenesis of cGN by modulating CD4⁺ T cell responses is less clear. In the present study, we aimed to investigate the potential of renal epithelial cells to function as antigen-presenting cells, thereby stimulating CD4⁺ T cell responses. Using a FACS-based protocol that allowed comparative analysis of cortical epithelial cell populations, we showed that particularly proximal tubular epithelial cells (PTECs) express molecules linked with antigen-presenting cell function, including major histocompatibility complex class II (MHCII), CD74, CD80, and CD86 in homeostasis and nephrotoxic nephritis, a murine model of cGN. Protein expression was visualized at the PTEC single cell level by imaging flow cytometry. Interestingly, we found inflammation-dependent regulation of epithelium-expressed CD74, CD80, and CD86, whereas MHCII expression was not altered. Antigen-specific stimulation of CD4⁺ T cells by PTECs in vitro supported CD4⁺ T cell survival and induced CD4⁺ T cell activation, proliferation, and inflammatory cytokine production. In patients with antineutrophil cytoplasmic antibody-associated glomerulonephritis, MHCII and CD74 were expressed by both proximal and distal tubules, whereas CD86 was predominantly expressed by proximal tubules. Thus, particularly PTECs have the potential to induce an inflammatory phenotype in CD4⁺ T cells in vitro, which might also play a role in the pathology of immune-mediated kidney disease.

Hepatitis B virus X protein modulates renal tubular epithelial cell-induced T-cell and macrophage responses

Renal tubular epithelial cells (RTECs) have an active role in renal inflammation, functioning as antigen-presenting cells as they constitutively express major histocompatibility complex-II and co-stimulatory molecules that can activate T cells and macrophages. Previous studies indicate that inflammatory cell infiltration and tubulointerstitial fibrosis are present in renal biopsies from Hepatitis B virus (HBV)-associated glomerulonephritis (HBV-GN) patients. We hypothesized that disorder RTECs may be involved in the progression of HBV-GN. Here, we measured renal function and inflammatory cells infiltration in C57BL/6J-TgN mice, and data showed that in C57BL/6J-TgN mice HBV x protein (HBx) mainly deposited in RTECs, and CD4(+) T cells and macrophages infiltrated into the interstitium. In vitro HBx upregulated CD40 expression in RTECs. In HK-2/CD4(+) T cells co-culture system, we found that HBx-stimulated HK-2 cells could activate CD4(+) T cells, promote their proliferation, and lead to an imbalance of interleukin (IL)-4 and interferon-γ. In HK-2/macrophages co-culture system, we found that HBx-stimulated HK-2 cells also increased macrophage adherent capacity and promoted MCP-1 and tumor necrosis factor-α and IL-1β secretion. These immune dysfunction may contribute to the pathogenesis of HBV-GN.

Human renal tubular epithelial cells suppress alloreactive T cell proliferation

Renal tubular epithelial cells (TECs) are one of the main targets of alloreactive T cells during acute rejection. We hypothesize that TECs modulate the outcome of alloimmunity by executing immunosuppressive effects in order to dampen the local inflammation. We studied whether TECs possess immunosuppressive capacities and if indoleamine 2,3-dioxygenase (IDO) might play a role in suppressing T cell alloreactivity. Next, we studied the role of programmed death ligand 1 (PD-L1) and intercellular adhesion molecule-1 (ICAM-1 with regard to TEC-related immunomodulatory effects. CD3/CD28 and alloactivated peripheral blood mononuclear cells were co-cultured with activated TECs. We analysed CD4(+) and CD8(+) T cell proliferation and apoptosis in the absence or presence of IDO inhibitor 1-methyl-L-tryptophan (1-L-MT), anti-PD-L1 and anti-ICAM-1. Further, we examined whether inhibition of T cell proliferation was cell-cell contact-dependent. We found that TECs dose-dependently inhibited CD4(+) and CD8(+) T cell proliferation (P<0.05). Activated TECs showed significantly increased IDO activity and up-regulated PD-L1 and ICAM-1 expression. Suppressed CD4(+) and CD8(+) T cell proliferation was only partially restored or failed to restore using 1-L-MT. Activated TECs increased early and late apoptosis of proliferating CD4(+) and CD8(+) T cells; only CD4(+) T cell apoptosis was statistically affected by 1-L-MT. Transwell experiments revealed that TEC-mediated immunosuppression is cell-cell contact-dependent. We found that anti-ICAM-1 affected only CD4(+) T cell apoptosis and not T cell proliferation. Our data show that TECs suppress both CD4(+) and CD8(+) T cell proliferation contact dependently. Interestingly, inhibition of proliferation and enhancement of apoptosis of T cell subsets is differentially regulated by indoleamine 2,3-dioxygenase and ICAM-1, with no evidence for the involvement of PD-L1 in our system.

BK Virus-Associated Nephropathy with Plasma Cell-Rich Infiltrates Treated by Bortezomib-Based Regimen

BK virus infection accompanied with plasma cell-rich infiltrates is a dilemma in renal transplant recipients. One young female patient diagnosed as BK virus-associated nephropathy with plasma cell-rich infiltrates at 16 months after renal transplant was treated with bortezomib and a sequential immuno-suppressive protocol of tacrolimus combined with leflunomide. After a short period of reduction, her serum creatinine increased slowly with stable BK viruria. The patient underwent repeat biopsy. The histologic changes showed a decrease in plasma cells and CD20+ cells in the allograft, but the other mononuclear cells showed no difference from the first biopsy. The immunosuppressive protocol was converted to tacrolimus combined with enteric-coated mycophenolate sodium. Her serum creatinine decreased gradually during 6 months of follow-up. We speculate that bortezomib can be used in BK virus-associated nephropathy accompanied with plasma cell-rich infiltrates, and this effect might be mediated through a decrease of plasma cells and CD20+ cells in the allograft. The dosage and time of therapy need to be explored in the future; additional studies of large samples are needed.

Heart-kidney crosstalk and role of humoral signaling in critical illness

Organ failure in the heart or kidney can initiate various complex metabolic, cell-mediated and humoral pathways affecting distant organs, contributing to the high therapeutic costs and significantly higher morbidity and mortality. The universal outreach of cells in an injured state has myriad consequences to distant organ cells and their milieu. Heart performance and kidney function are closely interconnected and communication between these organs occurs through a variety of bidirectional pathways. The term cardiorenal syndrome (CRS) is often used to describe this condition and represents an important model for exploring the pathophysiology of cardiac and renal dysfunction. Clinical evidence suggests that tissue injury in both acute kidney injury and heart failure has immune-mediated inflammatory consequences that can initiate remote organ dysfunction. Acute cardiorenal syndrome (CRS type 1) and acute renocardiac syndrome (CRS type 3) are particularly relevant in high-acuity medical units. This review briefly summarizes relevant research and focuses on the role of signaling in heart-kidney crosstalk in the critical care setting.

Pathology of resolving polyomavirus-associated nephropathy

Control of polyomavirus BK (BKV) is achieved by reducing immunosuppression allowing an effective BKV-specific T-cell response. The morphology of resolving BKV-associated nephropathy (PyVAN) has not been systematically investigated. Ninety-nine surveillance biopsies of 35 patients with BKV viremia treated exclusively by immunosuppression reduction were scored according to Banff criteria and grouped relative to BKV viremia as pre-, increasing, decreasing and post-BKV viremia. Thirty-four of 35 patients (97%) cleared BKV viremia after a median of 9 months posttransplantation. The tubulitis score, extent of tubules with intraepithelial lymphocytes, and interstitial inflammation significantly increased from the time of increasing to decreasing viremia. Tubulointerstitial inflammation, to a lower extent, persisted after clearance. The number of SV40+ tubules correlated with the BKV load in plasma, but SV40 immunohistochemistry was frequently negative (60%). During decreasing viremia, 31% of PyVAN cases were plasma cell-rich and 40% showed tubular HLA-DR expression. Compared to baseline 1 month posttransplantation, allograft function remained stable or improved in 29/35 patients (83%) after a median follow-up of 48 months. Within 1 year after clearance of BKV viremia, clinical rejection occurred in 2/35 patients (6%). Our data suggest that resolving PyVAN is typically characterized by a self-limiting acute interstitial nephritis, morphologically indistinguishable from interstitial rejection.

Pathology of resolving polyomavirus-associated nephropathy

Control of polyomavirus BK (BKV) is achieved by reducing immunosuppression allowing an effective BKV-specific T-cell response. The morphology of resolving BKV-associated nephropathy (PyVAN) has not been systematically investigated. Ninety-nine surveillance biopsies of 35 patients with BKV viremia treated exclusively by immunosuppression reduction were scored according to Banff criteria and grouped relative to BKV viremia as pre-, increasing, decreasing and post-BKV viremia. Thirty-four of 35 patients (97%) cleared BKV viremia after a median of 9 months posttransplantation. The tubulitis score, extent of tubules with intraepithelial lymphocytes, and interstitial inflammation significantly increased from the time of increasing to decreasing viremia. Tubulointerstitial inflammation, to a lower extent, persisted after clearance. The number of SV40+ tubules correlated with the BKV load in plasma, but SV40 immunohistochemistry was frequently negative (60%). During decreasing viremia, 31% of PyVAN cases were plasma cell-rich and 40% showed tubular HLA-DR expression. Compared to baseline 1 month posttransplantation, allograft function remained stable or improved in 29/35 patients (83%) after a median follow-up of 48 months. Within 1 year after clearance of BKV viremia, clinical rejection occurred in 2/35 patients (6%). Our data suggest that resolving PyVAN is typically characterized by a self-limiting acute interstitial nephritis, morphologically indistinguishable from interstitial rejection.

Differential activation of human T cells to allogeneic endothelial cells, epithelial cells and fibroblasts in vitro

BACKGROUND

In the direct pathway, T cells recognize intact donor major histocompatability complexes and allogeneic peptide on the surface of donor antigen presenting cells (APCs). Indirect allorecognition results from the recognition of processed alloantigen by self MHC complexes on self APCs. In this study, we wished to evaluate the relative contribution of different intragraft cells to the alloactivation of nave and memory T cells though the direct and the indirect pathway of allorecognition.

METHODS

The processing of membrane fragments from IFN-treated single donor endothelial cells (EC), fibroblasts or renal epithelial cells (RPTEC) was evaluated by DiOC labeling of each cell type and flow cytometry following interaction with PBMC. Direct pathway activation of nave CD45RA+ or memory CD45RO+ CD4+ T cells was evaluated following coculture with IFN-treated and MHC class II-expressing EC, fibroblasts or RPTEC. Indirect pathway activation was assessed using CD45RA+ or CD45RO+ CD4+ T cells cocultured with autologous irradiated APCs in the absence or presence of sonicates derived from IFN-treated allogeneic EC, fibroblasts or RPTEC. Activation of T cells was assessed by [3H]thymidine incorporation and by ELISpot assays.

RESULTS

We find that CD14+ APCs readily acquire membrane fragments from fibroblasts and RPTEC, but fail to acquire membrane fragments from intact EC. However, APCs process membranes from EC undergoing apoptosis.There was a notable direct pathway alloproliferative response of CD45RO+ CD4+ T cells to IFN-treated EC, but not to fibroblasts or RPTEC. Also, there was a minimal direct pathway response of CD45RA+ CD4+ T cells to all cell types. In contrast, we found that both CD45RA+ and CD45RO+ CD4+ T cells proliferated following coculture with autologous APCs in the presence of sonicates derived from IFN-treated EC, fibroblasts or RPTEC. By ELISpot, we found that these T cells stimulated via the indirect pathway also produced the cytokines IFN, IL-2, IL-4 and IL-5.

CONCLUSIONS

Recipient APCs may readily process membrane fragments from allogeneic intragraft cells, but not from EC unless they are undergoing apoptosis. This processing is sufficient for indirect pathway alloactivation of both CD45RA+ and CD45RO+ CD4+ T cells. Only graft vascular EC mediate direct pathway reactivation of CD4+ T cells.

Characterization of the renal CD4+ T-cell response in experimental autoimmune glomerulonephritis

Autoimmunity against the Goodpasture antigen α3IV-NC1 results in antiglomerular basement membrane glomerulonephritis. Although antibodies are central to the pathogenesis, there is good evidence for the participation of T cells in this disease. To define the contribution of T cells, we used the model of experimental autoimmune glomerulonephritis. Immunization of DBA/1 mice with α3IV-NC1 resulted in proteinuria, a biphasic course of the disease, and an eventual loss of kidney function. In the initial phase, the mice developed an α3IV-NC1-specific IgG response, had IgG deposition along the glomerular basement membrane, and steadily increased proteinuria, but only marginal signs of inflammation with limited leukocyte infiltration. After 9-13 weeks, mice proceeded to develop crescentic glomerulonephritis, extensive tubulointerstitial damage, and massive macrophage infiltration. T-cell infiltration was less pronounced, mostly confined to the interstitium, and T cells displayed an activated phenotype with a significant fraction of Th1 or Th17 CD4(+) T cells. Close examination revealed the presence of autoreactive T cells producing IFNγ upon restimulation with α3IV-NC1. Thus, our results suggest that accumulation of effector T cells, including autoreactive T cells, represents a critical step in the progression from mild glomerulonephritis, with limited glomerular damage, to severe crescentic glomerulonephritis accompanied by tubulointerstitial inflammation and loss of kidney function.

Curcumin attenuates lipopolysaccharide-induced renal inflammation

Renal inflammation is the main pathological change in many acute and chronic kidney diseases. Curcumin, a yellow pigment present in the rhizome of turmeric (Curcuma longa L. Zingiberaceae), was found to be a potential anti-inflammatory agent. The present study aimed to investigate the effects of curcumin on the inflammation of mice kidney and cultured renal tubular epithelial cells (HK-2 cells) induced by lipopolysaccharide (LPS) and to explore the mechanism. Curcumin was injected intraperitoneally before LPS administration. Renal inflammation was assessed by evaluating monocyte chemoattractant protein-1 (MCP-1) expression and macrophage infiltration in renal tissue using immunohistochemical methods, and also by measuring renal MCP-1 mRNA level using Real-Time polymerase chain reaction (PCR). HK-2 cells were cultured to investigate the in vitro effect of curcumin against LPS-induced renal inflammation. The expression of MCP-1 and interleukin-8 (IL-8) mRNA was measured by Real-Time PCR. The expression of MCP-1 and IL-8 protein in supernatant was detected by enzyme-linked immunosorbent assay (ELISA). The activity of nuclear factor (NF)-κB was detected by electrophoretic mobility shift assay (EMSA). The results demonstrated that curcumin could inhibit LPS-induced renal MCP-1 mRNA expression. Curcumin also significantly inhibited the expression of MCP-1 and IL-2 mRNA in HK-2 cells, and partially inhibited the secretion of MCP-1 and IL-8. Furthermore, curcumin was found to inhibit the DNA-binding activity of NF-κB. The present study demonstrated that curcumin has a protective effect on LPS-induced experimental renal inflammation, and this effect might be attributed to its inhibitory effects on MCP-1 mRNA expression and DNA-binding activity of NF-κB. Hence, curcumin might be potentially useful in some kidney diseases by preventing renal inflammation.

Human mesenchymal stem cells and renal tubular epithelial cells differentially influence monocyte-derived dendritic cell differentiation and maturation

Mesenchymal stem cells (MSCs) possess immunosuppressive properties. But also fully differentiated human renal tubular epithelial cells (RTECs) are able to modulate T-cell proliferation in vitro. In this study we compared two MSC populations, human adipose derived stem cells (ASCs) and human amniotic mesenchymal stromal cells (hAMSCs), and RTECs regarding their potential to inhibit monocyte-derived dendritic cell (DC) differentiation and maturation in indirect co-culture. In the presence of hAMSCs and RTECs, monocytes stimulated to undergo DC differentiation were inhibited to acquire surface phenotype of immature and mature DCs. In contrast, ASCs showed only limited suppressive capacity. Secretion of IL-12p70 was suppressed in hAMSC co-cultures and high IL-10 levels were detected in all co-cultures. Prostaglandin E(2) was found in ASC and hAMSC co-cultures, whereas soluble human leukocyte antigen-G was highly elevated only in RTEC co-cultures. Thus, inhibition of DC generation by MSCs and RTECs might be mediated by different soluble factors.

Renal tubular PD-L1 (CD274) suppresses alloreactive human T-cell responses

Renal proximal tubular epithelial cells, a target of infiltrating T cells during renal allograft rejection, may be protected from this injury by the cell surface protein CD274 (also termed PD-L1 for programmed death ligand 1). The co-inhibitory molecules PD-L1 (CD274) and PD-L2 (CD273) are ligands of PD-1 (programmed death 1; CD279). Here we determine the functional role of PD-1/PD-L pathways in human renal allograft rejection. Treatment of human primary tubular epithelial cells with interferon-beta and -gamma caused a dose-dependent and synergistic increase of PD-L1 and PD-L2 expression. Blockade of surface PD-L1, but not PD-L2, on interferon-treated tubular epithelial cells resulted in a significant increase in CD4+ T-cell proliferation and cytokine production by CD4+ and CD8+ T cells. The expression of PD-L1, PD-L2, and PD-1 mRNA and protein was upregulated in biopsies of patients with renal allograft rejection compared to the respective levels found in the pre-transplant biopsies. Induction of PD-L1 was significantly associated with acute vascular rejection. Our study suggests that the renal epithelial PD-1/PD-L1 pathway exerts an inhibitory effect of on alloreactive T-cell responses. The upregulation of PD-L1 on proximal tubular epithelial cells in patients with acute allograft rejection may reduce T-cell-mediated injury.

Acute kidney injury and lung dysfunction: a paradigm for remote organ effects of kidney disease?

An increasing body of evidence suggests that the deleterious effects of Acute Kidney Injury (AKI) on remote organ function could, at least in part, be due to loss of the normal balance of immune, inflammatory, and soluble mediator metabolism that attends injury of the tubular epithelium. Such dysregulation, acting at least in part on endothelium, leads to compromise of remote organ function. Kidney-lung interaction in the setting of AKI therefore constitutes not only a pressing clinical problem, but also an illuminating framework in which to consider possible mechanisms by which renal diseases exert such deleterious effects on patient outcomes, even when dialysis is provided.