Dichloroacetate prevents restenosis in preclinical animal models of vessel injury.

Despite the introduction of antiproliferative drug-eluting stents, coronary heart disease remains the leading cause of death in the United States. In-stent restenosis and bypass graft failure are characterized by excessive smooth muscle cell (SMC) proliferation and concomitant myointima formation with luminal obliteration. Here we show that during the development of myointimal hyperplasia in human arteries, SMCs show hyperpolarization of their mitochondrial membrane potential (ΔΨm) and acquire a temporary state with a high proliferative rate and resistance to apoptosis. Pyruvate dehydrogenase kinase isoform 2 (PDK2) was identified as a key regulatory protein, and its activation proved necessary for relevant myointima formation. Pharmacologic PDK2 blockade with dichloroacetate or lentiviral PDK2 knockdown prevented ΔΨm hyperpolarization, facilitated apoptosis and reduced myointima formation in injured human mammary and coronary arteries, rat aortas, rabbit iliac arteries and swine (pig) coronary arteries. In contrast to several commonly used antiproliferative drugs, dichloroacetate did not prevent vessel re-endothelialization. Targeting myointimal ΔΨm and alleviating apoptosis resistance is a novel strategy for the prevention of proliferative vascular diseases.

Thalidomide treatment prevents chronic graft rejection after aortic transplantation in rats - an experimental study.

Cardiac allograft vasculopathy (CAV) affects approximately 30% of cardiac transplant patients at 5 years post-transplantation. To date, there are few CAV treatment or prevention options, none of which are highly effective. The aim of the study was to investigate the effect of thalidomide on the development of CAV. The effect of thalidomide treatment on chronic rejection was assessed in rat orthotopic aortic transplants in allogeneic F344 or syngeneic Lew rats (n = 6 per group). Animals were left untreated or received thalidomide for 30 days post-transplant, and evidence of graft CAV was determined by histology (trichrome and immunohistochemistry) and intragraft cytokine measurements. Animals that received thalidomide treatment post-transplant showed markedly reduced luminal obliteration, with concomitant rescue of smooth muscle cells (SMCs) in the aortic media of grafts. Thalidomide counteracted neointimal hyperplasia by preventing dedifferentiation of vascular SMCs. Measurement of intragraft cytokine levels after thalidomide treatment revealed downregulation of matrix metalloproteinase 8 and monocyte chemotactic protein 1, cytokines involved in tissue remodelling and inflammation, respectively. Importantly, no negative side effects of thalidomide were observed. Thalidomide treatment prevents CAV development in a rodent model and is therefore potentially useful in clinical applications to prevent post-transplant heart rejection.

CXCR3+ Regulatory T Cells Control TH1 Responses in Crescentic GN.

Chemokines and chemokine receptors are implicated in regulatory T cell (Treg) trafficking to sites of inflammation and suppression of excessive immune responses in inflammatory and autoimmune diseases; however, the specific requirements for Treg migration into the inflamed organs and the positioning of these cells within the tissue are incompletely understood. Here, we report that Tregs expressing the TH1-associated chemokine receptor CXCR3 are enriched in the kidneys of patients with ANCA-associated crescentic GN and colocalize with CXCR3(+) effector T cells. To investigate the functional role of CXCR3(+) Tregs, we generated mice that lack CXCR3 in Tregs specifically (Foxp3(eGFP-Cre) × Cxcr3(fl/fl)) and induced experimental crescentic GN. Treg-specific deletion of CXCR3 resulted in reduced Treg recruitment to the kidney and an overwhelming TH1 immune response, with an aggravated course of the nephritis that was reversible on anti-IFNγ treatment. Together, these findings show that a subset of Tregs expresses CXCR3 and thereby, acquires trafficking properties of pathogenic CXCR3(+) TH1 cells, allowing Treg localization and control of excessive TH1 responses at sites of inflammation.

CXCL5 drives neutrophil recruitment in TH17-mediated GN.

Neutrophil trafficking to sites of inflammation is essential for the defense against bacterial and fungal infections, but also contributes to tissue damage in TH17-mediated autoimmunity. This process is regulated by chemokines, which often show an overlapping expression pattern and function in pathogen- and autoimmune-induced inflammatory reactions. Using a murine model of crescentic GN, we show that the pathogenic TH17/IL-17 immune response induces chemokine (C-X-C motif) ligand 5 (CXCL5) expression in kidney tubular cells, which recruits destructive neutrophils that contribute to renal tissue injury. By contrast, CXCL5 was dispensable for neutrophil recruitment and effective bacterial clearance in a murine model of acute bacterial pyelonephritis. In line with these findings, CXCL5 expression was highly upregulated in the kidneys of patients with ANCA-associated crescentic GN as opposed to patients with acute bacterial pyelonephritis. Our data therefore identify CXCL5 as a potential therapeutic target for the restriction of pathogenic neutrophil infiltration in TH17-mediated autoimmune diseases while leaving intact the neutrophil function in protective immunity against invading pathogens.

Neutralization of the IL-17 axis diminishes neutrophil invasion and protects from ischemic stroke.

The devastating effect of ischemic stroke is attenuated in mice lacking conventional and unconventional T cells, suggesting that inflammation enhances tissue damage in cerebral ischemia. We explored the functional role of αß and γδ T cells in a murine model of stroke and distinguished 2 different T cell-dependent proinflammatory pathways in ischemia-reperfusion injury. IFN-γ produced by CD4(+) T cells induced TNF-α production in macrophages, whereas IL-17A secreted by γδ T cells led to neutrophil recruitment. The synergistic effect of TNF-α and IL-17A on astrocytes resulted in enhanced secretion of CXCL-1, a neutrophil chemoattractant. Application of an IL-17A-blocking antibody within 3 hours after stroke induction decreased infarct size and improved neurologic outcome in the murine model. In autoptic brain tissue of patients who had a stroke, we detected IL-17A-positive lymphocytes, suggesting that this aspect of the inflammatory cascade is also relevant in the human brain. We propose that selective targeting of IL-17A signaling might provide a new therapeutic option for the treatment of stroke.

Donor acute kidney injury and short-term graft outcome in renal transplantation.

BACKGROUND: With increased waiting times for kidney transplantation, marginal organs from expanded criteria donors (ECD) are increasingly offered for allocation. In addition to ECD status, donors may have suffered from acute kidney injury (AKI) prior to organ procurement. METHODS: In this retrospective cohort study, we studied short-term allograft function in 517 kidney transplants performed between the years 2008-2014. Recipients of allografts from deceased organ donors were categorized as standard criteria donors (SCD) or ECD with or without AKI defined by RIFLE criteria. RESULTS: Of 382 deceased donations, 174 (45.5%) were classified as ECD and 63 (16.5%) fulfilled AKI criteria. Donor creatinine on hospital admission was similar, whereas creatinine before organ procurement differed (p < 0.001). Despite these differences, serum creatinine and eGFR at discharge and after one yr showed only minor differences between kidneys with or without AKI. In multivariate linear regression analyses, donor AKI was not a predictor of one-yr allograft function. CONCLUSIONS: Given the poor prognosis of dialysis patients and the increase in waiting time, kidneys from SCD and ECD donors with AKI should be allocated for transplantation. In case of ECD donors with AKI, recipients should be informed about the possibility of permanent non-function or early graft loss.

[Nephropathology of infectious disease]. / Nephropathologie infektiöser Erkrankungen.

Infections can affect the kidney via different pathways. Urinary tract infections can directly involve the renal tissue by spreading along pre-existing canalicular structures. Such an ascending infection can manifest as a highly active and purulent or even abscessing interstitial nephritis or as a chronic-fibrosing process in recurrent pyelonephritis. Viral infections can also use the canalicular route as in polyomavirus nephropathy or spread via the blood stream in a hematogenous manner as in the case of cytomegalovirus or hantavirus infections. Likewise, bacterial infections can reach the kidney via the blood in the case of systemic infection. Another large group of nephropathies taking place as a sequel of infections includes infection-related glomerulonephritides (IRGN), which are mediated by a series of immunological mechanisms. These IRGN can be subdivided according to their temporal association with the infectious process, occurring either after the infection has healed (postinfectious) or accompanying the ongoing infectious process (parainfectious). The latter, in particular, is of increasing importance in the daily practice of nephropathologists, especially in older patients. A number of other glomerulonephritis forms, i.e., membranous or membranoproliferative forms, can occur as a consequence of infection. In addition, infections can trigger nephropathies, such as thrombotic microangiopathy. The present article gives an overview of morphologic changes in renal parenchyma that take place as a consequence of infectious processes, with particular focus on IRGN.

Leukotriene B4: A potential mediator and biomarker for cardiac allograft vasculopathy.

BACKGROUND: Cardiac allograft vasculopathy (CAV) remains the leading cause of long-term graft failure and mortality after heart transplantation. Effective preventive and treatment options are not available to date, largely because underlying mechanisms remain poorly understood. We studied the potential role of leukotriene B4 (LTB4), an inflammatory lipid mediator, in the development of CAV. METHODS: We used an established preclinical rat CAV model to study the role of LTB4 in CAV. We performed syngeneic and allogeneic orthotopic aortic transplantation, after which neointimal proliferation was quantified. Animals were then treated with Bestatin, an inhibitor of LTB4 synthesis, or vehicle control for 30 days post-transplant, and evidence of graft CAV was determined by histology. We also measured serial LTB4 levels in a cohort of 28 human heart transplant recipients with CAV, 17 matched transplant controls without CAV, and 20 healthy nontransplant controls. RESULTS: We showed that infiltration of the arterial wall with macrophages leads to neointimal thickening and a rise in serum LTB4 levels in our rat model of CAV. Inhibition of LTB4 production with the drug Bestatin prevents development of neointimal hyperplasia, suggesting that Bestatin may be effective therapy for CAV prevention. In a parallel study of heart transplant recipients, we found nonsignificantly elevated plasma LTB4 levels in patients with CAV, compared to patients without CAV and healthy, nontransplant controls. CONCLUSIONS: This study provides key evidence supporting the role of the inflammatory cytokine LTB4 as an important mediator of CAV development and provides preliminary data suggesting the clinical benefit of Bestatin for CAV prevention.

Immunobiology of naïve and genetically modified HLA-class-I-knockdown human embryonic stem cells.

Human embryonic stem cells (hESCs) can serve as a universal cell source for emerging cell or tissue replacement strategies, but immune rejection of hESC derivatives remains an unsolved problem. Here, we sought to describe the mechanisms of rejection for naïve hESCs and upon HLA class I (HLA I) knockdown (hESC(KD)). hESCs were HLA I-positive but negative for HLA II and co-stimulatory molecules. Transplantation of naïve hESC into immunocompetent Balb/c mice induced substantial T helper cell 1 and 2 (Th1 and Th2) responses with rapid cell death, but hESCs survived in immunodeficient SCID-beige recipients. Histology revealed mainly macrophages and T cells, but only scattered natural killer (NK) cells. A surge of hESC-specific antibodies against hESC class I, but not class II antigens, was observed. Using HLA I RNA interference and intrabody technology, HLA I surface expression of hESC(KD) was 88%-99% reduced. T cell activation after hESC(KD) transplantation into Balb/c was significantly diminished, antibody production was substantially alleviated, the levels of graft-infiltrating immune cells were reduced and the survival of hESC(KD) was prolonged. Because of their very low expression of stimulatory NK ligands, NK-susceptibility of naïve hESCs and hESC(KD) was negligible. Thus, HLA I recognition by T cells seems to be the primary mechanism of hESC recognition, and T cells, macrophages and hESC-specific antibodies participate in hESC killing.

BK viremia and polyomavirus nephropathy in 352 kidney transplants; risk factors and potential role of mTOR inhibition.

BACKGROUND: Polyomavirus BK nephropathy (PyVAN) remains an important cause of early graft dysfunction and graft loss in kidney transplantation. METHODS: In this retrospective, single centre cohort study we studied the incidence and outcome of BK viral infection in 352 patients transplanted in 2008-2011. RESULTS: During follow-up viral replication was detected in 48 patients (13.6%); 22 patients (6.2%) had biopsy proven PyVAN.In multivariate logistic regression analyses risk factors for BK-viremia were lack of enrolment into randomized controlled trials (RCTs), biopsy proven acute rejections, cytomegaly virus (CMV) serostatus of both donor and recipient and previous transplantation.In patients without PyVAN reduction or switch of immunosuppression was associated with rapid viral clearance and stable graft function. In contrast, in most patients with PyVAN graft function deteriorated and 5 patients prematurely lost their allograft. Switch of immunosuppression to a low dose cyclosporine plus mTOR inhibitor based regimen in patients with PyVAN was safe, well tolerated and tended to be associated with a better short-term outcome in terms of graft function compared to reduction of existing immunosuppression alone. CONCLUSIONS: With the lack of licensed anti-polyoma viral drugs reduction or conversion of immunosuppression remains the mainstay of therapy in patients with PyVAN. The combination of low dose cyclosporine plus mTOR inhibition appears to be safe and warrants further investigation.

Immature renal dendritic cells recruit regulatory CXCR6(+) invariant natural killer T cells to attenuate crescentic GN.

Immature renal dendritic cells (DCs) are protective early in murine crescentic GN, but the mechanisms underlying this protection are unknown. Here, depletion of DCs reduced the recruitment of invariant natural killer T (iNKT) cells, which attenuate GN, into the kidney in the early stage of experimental crescentic GN. More than 90% of renal iNKT cells expressed the chemokine receptor CXCR6, and renal DCs produced high amounts of the cognate ligand CXCL16 early after induction of nephritis, suggesting that renal DC-derived CXCL16 might attract protective CXCR6(+) iNKT cells. Consistent with this finding, CXCR6-deficient mice exhibited less iNKT cell recruitment and developed nephritis that was more severe, similar to the aggravated nephritis observed in mice depleted of immature DCs. Finally, adoptive transfer of CXCR6-competent NKT cells ameliorated nephritis. Taken together, these results suggest an immunoprotective mechanism involving immature DCs, CXCL16, CXCR6, and regulatory iNKT cells, which might stimulate the development of new therapeutic strategies for GN.

Human leukocyte antigen I knockdown human embryonic stem cells induce host ignorance and achieve prolonged xenogeneic survival.

BACKGROUND: Although human embryonic stem cells (hESC) have enormous potential for cell replacement therapy of heart failure, immune rejection of hESC derivatives inevitably would occur after transplantation. We therefore aimed to generate a hypoantigeneic hESC line with improved survival characteristics. METHODS AND RESULTS: Using various in vivo, nonischemic, hindlimb xenotransplant models (immunocompetent and defined immunodefective mouse strains) as well as human in vitro T-cell and natural killer (NK)-cell assays, we revealed a central role for T cells in mediating hESC rejection. The NK-cell susceptibility of hESC in vivo was found to be low, and the NK response to hESC challenge in vitro was negligible. To reduce the antigenicity of hESC, we successfully generated human leukocyte antigen (HLA) I knockdown cells (hESC(siRNA+IB)) using both HLA I RNA interference (siRNA) and intrabody (IB) technology. HLA I expression was ≈99% reduced after 7 days and remained low for weeks. Cellular immune recognition of these hESC(siRNA+IB) was strongly reduced in both xenogeneic and allogeneic settings. Immune rejection was profoundly mitigated after hESC(siRNA+IB) transplantation into immunocompetent mice, and even long-term graft survival was achieved in one third of the animals without any immunosuppression. The survival benefit of hESC(siRNA+IB) was further confirmed under ischemic conditions in a left anterior descending coronary artery ligation model. CONCLUSIONS: HLA I knockdown hESC(siRNA+IB) provoke T-cell ignorance and experience largely mitigated xenogeneic rejection. By generating hypoantigeneic hESC lines, the generation of acceptable hESC derivatives may become a practical concept and push cell replacement strategies forward.

Protective role for CCR5 in murine lupus nephritis.

Leukocyte infiltration is a characteristic feature of human and experimental lupus nephritis and is closely correlated with loss of renal function. The chemokine receptor CCR5 is expressed on monocyte and T cell subsets and is thought to play an important role in recruiting these cells into inflamed organs. To investigate the functional role of CCR5 in lupus nephritis, CCR5-deficient mice were backcrossed onto the lupus-prone MRL-Fas(lpr) (MRL/lpr) genetic background. Unexpectedly, CCR5(-/-) MRL/lpr mice developed an aggravated course of lupus nephritis in terms of glomerular tissue injury and albuminuria. Deterioration of the nephritis was associated with an overall increase in mononuclear cell infiltration into the kidney, whereas renal leukocyte subtype balance, systemic T cell response, and autoantibody formation were unaffected by CCR5 deficiency. Renal and systemic protein levels of the CCR5 ligand CCL3, which can also attract leukocytes via its alternate receptor CCR1, were significantly increased in nephritic CCR5(-/-) MRL/lpr mice. Further studies revealed that the systemic increase in the CCR5/CCR1 ligand is also observed in nonimmune CCR5(-/-) C57BL/6 mice and that this increase was due to a reduced clearance, rather than an overproduction, of CCL3. Taken together, our data support the hypothesis that CCR5-dependent consumption of its own ligands may act as a negative feedback loop to restrain local chemokine levels within inflamed tissues, thereby limiting inflammatory cell influx.

Renal IL-17 expression in human ANCA-associated glomerulonephritis.

Interleukin-17A (IL-17) promotes inflammatory renal tissue damage in mouse models of crescentic glomerulonephritis, including murine experimental autoimmune anti-myeloperoxidase glomerulonephritis, which most likely depends on IL-17-producing Th17 cells. In human anti-neutrophil cytoplasmic antibody (ANCA)-associated glomerulonephritis, however, the cellular sources of IL-17 remain to be elucidated. Therefore, we analyzed human kidney biopsies of active necrotizing and crescentic ANCA-associated glomerulonephritis by immunohistochemistry using an IL-17-specific antibody and by immunofluorescent colocalization with cell type markers. We detected numerous IL-17-expressing (IL-17(+)) cells in the glomeruli and in the tubulointerstitium. Unexpectedly, most of these IL-17(+) cells were polymorphonuclear neutrophilic granulocytes, while IL-17(+) T cells and IL-17(+) mast cells were present at significantly lower frequencies. IL-17 was not detected in other infiltrating or resident kidney cells. In those patients who had not received immunosuppressive treatment before biopsy, serum creatinine levels were positively correlated with tubulointerstitial IL-17(+) neutrophils as well as IL-17(+) T cells. Furthermore, we could demonstrate that purified human blood neutrophils expressed IL-17 protein and released it upon stimulation in vitro. In conclusion, these results support a pathogenic role for IL-17 in human ANCA-associated glomerulonephritis. Our data suggest that in the acute stage of the disease neutrophils may act as an important immediate-early innate source of IL-17 and may thereby initiate and promote ongoing renal inflammation. IL-17 may thus be a target for treating acute ANCA-associated glomerulonephritis.

AT1 antagonism and renin inhibition in mice: pivotal role of targeting angiotensin II in chronic kidney disease.

The role of the renin-angiotensin system in chronic kidney disease involves multiple peptides and receptors. Exerting antipodal pathophysiological mechanisms, renin inhibition and AT(1) antagonism ameliorate renal damage. However, it is unclear which mechanism exerts better nephroprotection. We compared the renin inhibitor aliskiren with the AT(1) antagonist losartan in mice with chronic kidney disease due to renal ablation. Doses were adjusted to equipotent inhibition of the renin-angiotensin system, determined via a dose-response quantifying plasma and renal renin expression. Six-week treatment with either 500 mg/l drinking water losartan or 50 mg·kg(-1)·day(-1) aliskiren significantly decreased albuminuria, glomerular damage, and transcription rates of renal injury markers to a similar extent. An array analysis comparing renal gene expression of losartan- and aliskiren-treated mice evaluating >34,000 transcripts demonstrated regulation for 14 genes only, with small differences. No superior nephroprotection was found by combining losartan and aliskiren. Compared with plasma concentrations, aliskiren accumulated ∼7- to 29-fold in the heart, liver, lung, and spleen and ∼156-fold in the kidney. After withdrawal, plasma concentrations dropped to zero within 24 h, whereas renal tissue concentrations declined slowly over days. Withdrawal of aliskiren in mice with chronic kidney disease revealed a significantly delayed re-increase in albuminuria compared with withdrawal of losartan. This study demonstrates equieffective nephroprotection of renin inhibition and AT(1) antagonism in mice with chronic kidney disease without additional benefit of combination therapy. These observations underscore the pivotal role of targeting ANG II to reduce renal injury.

Chemokines play a critical role in the cross-regulation of Th1 and Th17 immune responses in murine crescentic glomerulonephritis.

Th1 and Th17 subtype effector CD4(+) T cells are thought to play a critical role in the pathogenesis of human and experimental crescentic glomerulonephritis. The time course, mechanism, and functions of Th1 and Th17 cell recruitment, and their potential interaction in glomerulonephritis, however, remain to be elucidated. We performed interventional studies using IL-17- and IFN-γ-gene-deficient mice, as well as neutralizing antibodies that demonstrated the importance of the Th17-mediated immune response during the early phase of the disease. At a later stage, we found that Th1 cells were critical mediators of renal tissue injury. Early recruitment of IL-17-producing Th17 cells triggered expression of the chemokine CXCL9 in the kidney that drove the infiltration of Th1 cells bearing its receptor CXCR3. At a later stage, Th1 cell-derived IFN-γ was found to inhibit local chemokine CCL20 expression, acting through its receptor CCR6 on Th17 cells, thereby limiting the renal Th17 immune response. Thus, our findings provide mechanistic evidence for a cytokine-chemokine-driven feedback loop that orchestrates the observed differential Th1 and Th17 cell infiltration into the inflamed kidney. This contributes to the observed time-dependent function of these two major pathogenic effector CD4(+) T cell subsets in crescentic glomerulonephritis.

Sustained inhibition of epsilon protein kinase C inhibits vascular restenosis after balloon injury and stenting.

BACKGROUND: ε protein kinase C (εPKC) is involved in vascular smooth muscle cell (VSMC) activation, but little is known about its function in vascular pathology. We aimed at assessing the role of εPKC in the development of restenosis. METHODS AND RESULTS: Rat models of aortic balloon injury with or without subsequent stenting were used. Rats were treated with the selective ψεPKC activator ε receptor for activated protein kinase C (ψεRACK), the selective εPKC inhibitor εV1-2, or saline. Both down-stream cascades of the platelet-derived growth factor receptor via extracellular signal-regulated kinase and Akt, respectively, were evaluated in vivo and in VSMC cultures. Intimal hyperplasia with luminal obliteration developed in saline-treated balloon-injured rat aortas (20.3±8.0%), and ψεRACK significantly promoted neointima development (32.4±4.9%, P=0.033), whereas εV1-2 significantly inhibited luminal narrowing (9.2±4.3%, P=0.039). εPKC inhibition led to significantly reduced VSMC extracellular signal-regulated kinase phosphorylation in vivo, whereas Akt phosphorylation was not markedly affected. Neointimal proliferation in vivo and platelet-derived growth factor-induced VSMC proliferation/migration in vitro were significantly inhibited by εV1-2. The inhibition of the platelet-derived growth factor pathway was mediated by inhibiting down-stream extracellular signal-regulated kinase and Akt phosphorylation. In vitro, εV1-2 showed inhibitory properties on endothelial cell proliferation, but that did not prevent reendothelialization in vivo. εV1-2 showed proapoptotic effects on VSMC in vitro. After stent implantation, luminal restenosis (quantified by optical coherence tomography imaging) was significantly reduced with εV1-2 (8.0±2.0%) compared with saline (20.2±9.8%, P=0.028). CONCLUSIONS: εPKC seems to be centrally involved in the development of neointimal hyperplasia. We suggest that εPKC inhibition may be mediated via inhibition of extracellular signal-regulated kinase and Akt activation. εPKC modulation may become a new therapeutic target against vascular restenosis.

Regulatory T cells control the Th1 immune response in murine crescentic glomerulonephritis.

Crescentic glomerulonephritis is mediated by inappropriate humoral and cellular immune responses toward self-antigens that may result from defects in central and peripheral tolerance. Evidence now suggests that regulatory T cells (Tregs) may be of pathophysiological importance in proliferative and crescentic forms of glomerulonephritis. To analyze the role of endogenous Tregs in a T cell-dependent glomerulonephritis model of nephrotoxic nephritis, we used 'depletion of regulatory T cell' (DEREG) mice that express the diphtheria toxin receptor under control of the FoxP3 (forkhead box P3) gene promoter. Toxin injection into these mice efficiently depleted renal and splenic FoxP3(+) Treg cells as determined by fluorescent-activated cell sorting (FACS) and immunohistochemical analyses. Treg depletion exacerbated systemic and renal interferon-γ (IFNγ) expression and increased recruitment of IFNγ-producing Th1 cells into the kidney without an effect on the Th17 immune response. The enhanced Th1 response, following Treg cell depletion, was associated with an aggravated course of glomerulonephritis as measured by glomerular crescent formation. Thus, our results establish the functional importance of endogenous Tregs in the control of a significantly enhanced systemic and renal Th1 immune response in experimental glomerulonephritis.

CXCR3 mediates renal Th1 and Th17 immune response in murine lupus nephritis.

Infiltration of T cells into the kidney is a typical feature of human and experimental lupus nephritis that contributes to renal tissue injury. The chemokine receptor CXCR3 is highly expressed on Th1 cells and is supposed to be crucial for their trafficking into inflamed tissues. In this study, we explored the functional role of CXCR3 using the MRL/MpJ-Fas(lpr) (MRL/lpr) mouse model of systemic lupus erythematosus that closely resembles the human disease. CXCR3(-/-) mice were generated and backcrossed into the MRL/lpr background. Analysis of 20-wk-old CXCR3(-/-) MRL/lpr mice showed amelioration of nephritis with reduced glomerular tissue damage and decreased albuminuria and T cell recruitment. Most importantly, not only the numbers of renal IFN-gamma-producing Th1 cells, but also of IL-17-producing Th17 cells were significantly reduced. Unlike in inflamed kidneys, there was no reduction in the numbers of IFN-gamma- or IL-17-producing T cells in spleens, lymph nodes, or the small intestine of MRL/lpr CXCR3(-/-) mice. This observation suggests impaired trafficking of effector T cells to injured target organs, rather than the inability of CXCR3(-/-) mice to mount efficient Th1 and Th17 immune responses. These findings show a crucial role for CXCR3 in the development of experimental lupus nephritis by directing pathogenic effector T cells into the kidney. For the first time, we demonstrate a beneficial effect of CXCR3 deficiency through attenuation of both the Th1 and the newly defined Th17 immune response. Our data therefore identify the chemokine receptor CXCR3 as a promising therapeutic target in lupus nephritis.

CCR6 recruits regulatory T cells and Th17 cells to the kidney in glomerulonephritis.

T cells recruited to the kidney contribute to tissue damage in crescentic and proliferative glomerulonephritides. Chemokines and their receptors regulate T cell trafficking, but the expression profile and functional importance of chemokine receptors for renal CD4+ T cell subsets are incompletely understood. In this study, we observed that renal FoxP3+CD4+ regulatory T cells (Tregs) and IL-17-producing CD4+ T (Th17) cells express the chemokine receptor CCR6, whereas IFNgamma-producing Th1 cells are CCR6-. Induction of experimental glomerulonephritis (nephrotoxic nephritis) in mice resulted in upregulation of the only CCR6 ligand, CCL20, followed by T cell recruitment, renal tissue injury, albuminuria, and loss of renal function. CCR6 deficiency aggravated renal injury and increased mortality (from uremia) among nephritic mice. Compared with wild-type (WT) mice, CCR6 deficiency reduced infiltration of Tregs and Th17 cells but did not affect recruitment of Th1 cells in the setting of glomerulonephritis. Adoptive transfer of WT but not CCR6-deficient Tregs attenuated morphologic and functional renal injury in nephritic mice. Furthermore, reconstitution with WT Tregs protected CCR6-/- mice from aggravated nephritis. Taken together, these data suggest that CCR6 mediates renal recruitment of both Tregs and Th17 cells and that the reduction of anti-inflammatory Tregs in the presence of a fully functional Th1 response aggravates experimental glomerulonephritis.