Neutrophil Gelatinase-Associated Lipocalin Increases HLA-G+/FoxP3+ T-Regulatory Cell Population in an In Vitro Model of PBMC

Abstract

BackgroundNeutrophil gelatinase-associated lipocalin (NGAL) is emerging as a mediator of various biological and pathological states. However, the specific biological role of this molecule remains unclear, as it serves as a biomarker for many conditions. The high sensitivity of NGAL as a biomarker coupled with relatively low specificity may hide important biological roles. Data point toward an acute compensatory, protective role for NGAL in response to adverse cellular stresses, including inflammatory and oxidative stress. The aim of this study was to understand whether NGAL modulates the T-cell response through regulation of the human leukocyte antigen G (HLA-G) complex, which is a mediator of tolerance.Methodology/Principal FindingsPeripheral blood mononuclear cells (PBMCs) were obtained from eight healthy donors and isolated by centrifugation on a Ficoll gradient. All donors gave informed consent. PBMCs were treated with four different concentrations of NGAL (40–320 ng/ml) in an iron-loaded or iron-free form. Changes in cell phenotype were analyzed by flow cytometry. NGAL stimulated expression of HLA-G on CD4+ T cells in a dose- and iron-dependent manner. Iron deficiency prevented NGAL-mediated effects, such that HLA-G expression was unaltered. Furthermore, NGAL treatment affected stimulation of regulatory T cells and in vitro expansion of CD4+ CD25+ FoxP3+ cells. An NGAL neutralizing antibody limited HLA-G expression and significantly decreased the percentage of CD4+ CD25+ FoxP3+ cells.Conclusions/SignificanceWe provide in vitro evidence that NGAL is involved in cellular immunity. The potential role of NGAL as an immunomodulatory molecule is based on its ability to induce immune tolerance by upregulating HLA-G expression and expansion of T-regulatory cells in healthy donors. Future studies should further evaluate the role of NGAL in immunology and immunomodulation and its possible relationship to immunosuppressive therapy efficacy, tolerance induction in transplant patients, and other immunological disorders.

Exogenous Lipocalin 2 Ameliorates Acute Rejection in a Mouse Model of Renal Transplantation

“…Future studies will have to test the outcome in comparison and in combination with immunosuppression in the long term. Because administration of Lcn2 is effective only at the time of transplantation and the protein is rapidly taken up by the kidneys and secreted in the urine 26, Lcn2 treatment might briefly dampen host immune functions 47, 48 but likely will not compromise the recipient's immune system permanently. The treatment holds great promise because it might eventually replace or at least reduce the requirement for chronic immunosuppression and thus avoid its unfavorable side effects.…”

Potential advantages of acute kidney injury management by mesenchymal stem cells

“…In vivo infusion of human mesenchymal stem cells from fetal membranes (FMhMSCs) in AKI rat models after pre-treatment with HB reduces inflammation and accelerates renal function recovery [35] . In addition to MSCs treatment, other molecules, such as NGAL, should be used to regulate the immune response to inflammation and facilitate renal functioning [36] . The combined intravenous administration of bone marrow MSC and muscone in rat with gentamycin induced AKI induces the expression of CXCR7 and CRCX4 on cell surface, thus promoting migration and proliferation of MSCs [37] .…”

Urinary neutrophil gelatinase-associated lipocalin is a biomarker of delayed graft function after kidney transplantation

“…[13][14][15][16] In addition, we have recently described the ability of NGAL to induce immune tolerance by upregulating human leukocyte antigen (HLA-G) expression and expansion of T-regulatory cells in healthy donors, providing the basis for further studies to evaluate its possible role in immunomodulation and tolerance induction in transplant recipients. 17 This mounting evidence led to evaluate the role of NGAL after kidney transplant. Plasma levels of NGAL rapidly decrease when the renal function is restored.…”