Human leukocyte antigen-G molecules are constitutively expressed by synovial fibroblasts and upmodulated in osteoarthritis. Hum Immunol. 2010;71:342-350. [PMID: 20097242 DOI: 10.1016/j.humimm.2010.01.015]

Proteome analysis, bioinformatic prediction and experimental evidence revealed immune response down-regulation function for serum-starved human fibroblasts

Emerging evidence indicates that fibroblasts play pivotal roles in immunoregulation by producing various proteins under health and disease states. In the present study, for the first time, we compared the proteomes of serum-starved human skin fibroblasts and peripheral blood mononuclear cells (PBMCs) using Nano-LC-ESI-tandem mass spectrometry. This analysis contributes to a better understanding of the underlying molecular mechanisms of chronic inflammation and cancer, which are intrinsically accompanied by growth factor deficiency.The proteomes of starved fibroblasts and PBMCs consisted of 307 and 294 proteins, respectively, which are involved in lymphocyte migration, complement activation, inflammation, acute phase response, and immune regulation. Starved fibroblasts predominantly produced extracellular matrix-related proteins such as collagen/collagenase, while PBMCs produced focal adhesion-related proteins like beta-parvin and vinculin which are involved in lymphocyte migration. PBMCs produced a more diverse set of inflammatory molecules like heat shock proteins, while fibroblasts produced human leukocytes antigen-G and -E that are known as main immunomodulatory molecules. Fifty-four proteins were commonly found in both proteomes, including serum albumin, amyloid-beta, heat shock cognate 71 kDa, and complement C3. GeneMANIA bioinformatic tool predicted 418 functions for PBMCs, including reactive oxygen species metabolic processes and 241 functions for starved fibroblasts such as antigen processing and presentation including non-classical MHC -Ib pathway, and negative regulation of the immune response. Protein-protein interactions network analysis indicated the immunosuppressive function for starved fibroblasts-derived human leucocytes antigen-G and -E. Moreover, in an in vitro model of allogeneic transplantation, the immunosuppressive activity of starved fibroblasts was experimentally documented.

Conclusion

Under serum starvation-induced metabolic stress, both PBMCs and fibroblasts produced molecules like heat shock proteins and amyloid-beta, which can have pathogenic roles in auto-inflammatory diseases such as rheumatoid arthritis, type 1 diabetes mellitus, systemic lupus erythematosus, aging, and cancer. However, starved fibroblasts showed immunosuppressive activity in an in vitro model of allogeneic transplantation, suggesting their potential to modify such adverse reactions by down-regulating the immune system.

The Role of Interleukin-4 and Interleukin-10 in Osteoarthritic Joint Disease: A Systematic Narrative Review

OBJECTIVE

A fusion protein of interleukin-4 and interleukin-10 (IL4-10 FP) was developed as a disease-modifying osteoarthritis drug (DMOAD), and chondroprotection, anti-inflammation, and analgesia have been suggested. To better understand the mechanisms behind its potential as DMOAD, this systematic narrative review aims to assess the potential of IL-4, IL-10 and the combination of IL-4 and IL-10 for the treatment of osteoarthritis. It describes the chondroprotective, anti-inflammatory, and analgesic effects of IL-4, IL-10, and IL4-10 FP.

DESIGN

PubMed and Embase were searched for publications that were published from 1990 until May 21, 2021 (moment of search). Key search terms were: Osteoarthritis, Interleukin-4, and Interleukin-10. This yielded 2,479 hits, of which 43 were included in this review.

RESULTS

IL-4 and IL-10 showed mainly protective effects on osteoarthritic cartilage in vitro and in vivo, as did IL4-10 FP. Both cytokines showed anti-inflammatory effects, but also proinflammatory effects. Only in vitro IL4-10 FP showed purely anti-inflammatory effects, indicating that proinflammatory effects of one cytokine can be counteracted by the other when given as a combination. Only a few studies investigated the analgesic effects of IL-4, IL-10 or IL4-10 FP. In vitro, IL-4 and IL4-10 FP were able to decrease pain mediators. In vivo, IL-4, IL-10, and IL4-10 FP were able to reduce pain.

CONCLUSIONS

In conclusion, this review describes overlapping, but also different modes of action for the DMOAD effects of IL-4 and IL-10, giving an explanation for the synergistic effects found when applied as combination, as is the case for IL4-10 FP.

The HLA-G Immune Checkpoint Plays a Pivotal Role in the Regulation of Immune Response in Autoimmune Diseases

The human G-leukocyte antigen (HLA-G) molecule is a non-classical major histocompatibility complex (MHC) class I molecule. The pertinence of HLA-G has been investigated in numerous studies which have sought to elucidate the relevance of HLA-G in pathologic conditions, such as autoimmune diseases, cancers, and hematologic malignancies. One of the main goals of the current research on HLA-G is to use this molecule in clinical practice, either in diagnostics or as a therapeutic target. Since HLA-G antigens are currently considered as immunomodulatory molecules that are involved in reducing inflammatory and immune responses, in this review, we decided to focus on this group of antigens as potential determinants of progression in autoimmune diseases. This article highlights what we consider as recent pivotal findings on the immunomodulatory function of HLA-G, not only to establish the role of HLA-G in the human body, but also to explain how these proteins mediate the immune response.

Human leukocyte antigen-G polymorphism influences the age of onset and autoantibody status in rheumatoid arthritis

The study was conducted to investigate the frequency of three gene polymorphisms in the 3'-untranslated region (3'-UTR) of human leucocyte antigen-G (HLA-G) gene in south Indian patients with rheumatoid arthritis (RA) and analyze their influence on disease susceptibility, phenotype and treatment response. HLA-G 14 bp insertion (Ins)/deletion (del) (rs66554220), HLA-G +3142G>C (rs1063320) and +3187A>G (rs9380142) polymorphism was analyzed in 221 RA patients and 200 healthy controls. Frequency of HLA-G genotypes or alleles did not differ between patients and controls. Analysis based on rheumatoid factor (RF) status revealed that the frequency of allele 'A' (rs9380142) was significantly higher in RF-positive than in RF-negative patients [84% vs 74%, Yates-corrected P value (Pc) = 0.04, odds ratio (OR) = 1.8, 95% confidence interval (CI) = 1.0-3.2]. A similar difference was maintained in RF-positive female patients than their RF-negative counterparts (83% vs 71%, Pc = 0.02, OR = 1.9, 95% CI = 1.0 to 3.4) and between RF-positive and RF-negative young onset RA (YORA) patients (84% vs 73%, Pc = 0.03, OR = 1.9, 95% CI = 1.0-3.2), suggesting that rs9380142 polymorphism influenced RF status. The 14 bp Ins allele of rs66554220 was significantly more prevalent in RF-positive YORA than in RF-positive late onset RA (LORA) patients (51% vs 25%, P = 0.03, OR = 3.1, 95% CI = 1.1-9.8). Frequency of the four major haplotypes [InsGA (48%), DelGA (22%), DelCG (18%), DelCA (9.7%)] observed did not differ between cases and controls. HLA-G does not appear to be a risk factor for development of RA in south Indian Tamils but may act as a genetic modifier of clinical phenotype in terms of autoantibody production, gender preference and age at disease onset.

HLA-G Molecules in Autoimmune Diseases and Infections

Human leukocyte antigen (HLA)-G molecule, a non-classical HLA-Ib molecule, is less polymorphic when compared to classical HLA class I molecules. Human leukocyte antigen-G (HLA-G) was first detected on cytotrophoblast cells at the feto-maternal interface but its expression is prevalent during viral infections and several autoimmune diseases. HLA-G gene is characterized by polymorphisms at the 3' un-translated region and 5' upstream regulatory region that regulate its expression and are associated with autoimmune diseases and viral infection susceptibility, creating an unbalanced and pathologic environment. This review focuses on the role of HLA-G genetic polymorphisms, mRNA, and protein expression in autoimmune conditions and viral infections.

Impact of HLA-G analysis in prevention, diagnosis and treatment of pathological conditions

Human leukocyte antigen-G (HLA-G) is a non-classical HLA class I molecule that differs from classical HLA class I molecules by low polymorphism and tissue distribution. HLA-G is a tolerogenic molecule with an immune-modulatory and anti-inflammatory function on both innate and adaptative immunity. This peculiar characteristic of HLA-G has led to investigations of its role in pathological conditions in order to define possible uses in diagnosis, prevention and treatment. In recent years, HLA-G has been shown to have an important implication in different inflammatory and autoimmune diseases, pregnancy complications, tumor development and aggressiveness, and susceptibility to viral infections. In fact, HLA-G molecules have been reported to alternate at both genetic and protein level in different disease situations, supporting its crucial role in pathological conditions. Specific pathologies show altered levels of soluble (s)HLA-G and different HLA-G gene polymorphisms seem to correlate with disease. This review aims to update scientific knowledge on the contribution of HLA-G in managing pathological conditions.

Matrix metalloproteinase-2 (MMP-2) generates soluble HLA-G1 by cell surface proteolytic shedding

Human leukocyte antigen-G (HLA-G) molecules are non-classical HLA class I antigens with an important role in pregnancy immune regulation and inflammation control. Soluble HLA-G proteins can be generated through two mechanisms: alternative splicing and proteolytic release, which is known to be metalloprotease mediated. Among this class of enzymes, matrix metalloproteinases (MMPs) might be involved in the HLA-G1 membrane cleavage. Of particular interest are MMP-2 and MMP-9, which regulate the inflammatory process by cytokine and chemokine modulation. We evaluated the effect of MMP-9 and MMP-2 on HLA-G1 membrane shedding. In particular, we analyzed the in vitro effect of these two gelatinases on the secretion of HLA-G1 via proteolytic cleavage in 221-G1-transfected cell line, in JEG3 cell line, and in peripheral blood mononuclear cells. The results obtained by both cell lines showed the role of MMP-2 in HLA-G1 shedding. On the contrary, MMP-9 was not involved in this process. In addition, we identified three possible highly specific cleavage sites for MMP-2, whereas none were detected for MMP-9. This study suggests an effective link between MMP-2 and HLA-G1 shedding, increasing our knowledge on the regulatory machinery beyond HLA-G regulation in physiological and pathological conditions.

Maternal asthma and microRNA regulation of soluble HLA-G in the airway

BACKGROUND

We previously reported an interaction between maternal asthma and the child's HLA-G genotype on the child's subsequent risk for asthma. The implicated single nucleotide polymorphism at +3142 disrupted a target site for the microRNA (miR)-152 family. We hypothesized that the interaction effect might be mediated by these miRs.

OBJECTIVE

The objective of this study was to test this hypothesis in adults with asthma who are a subset of the same subjects who participated in our earlier family-based studies.

METHODS

We measured soluble HLA-G (sHLA-G) concentrations in bronchoalveolar lavage fluid (n = 36) and plasma (n = 57) from adult asthmatic subjects with and without a mother with asthma, and HLA-G and miR-152 family (miR-148a, miR-148b, and miR-152) transcript levels in airway epithelial cells from the same subjects.

RESULTS

miR-148b levels were significantly increased in airway epithelial cells from asthmatic subjects with an asthmatic mother compared with those seen in asthmatic subjects without an asthmatic mother, and +3142 genotypes were associated with sHLA-G concentrations in bronchoalveolar lavage fluid among asthmatic subjects with an asthmatic mother but not among those with a nonasthmatic mother. Neither effect was observed in the plasma (sHLA-G) or white blood cells (miRNA).

CONCLUSION

These combined results are consistent with +3142 allele-specific targeting of HLA-G by the miR-152 family and support our hypothesis that miRNA regulation of sHLA-G in the airway is influenced by both the asthma status of the subject's mother and the subject's genotype. Moreover, we demonstrate that the effects of maternal asthma on the gene regulatory landscape in the airways of the mother's children persist into adulthood.

HLA-G may predict the disease course in patients with early rheumatoid arthritis

The current management of early rheumatoid arthritis (ERA) is to start an intensive treatment as soon as possible. To avoid under/overtreatment, it is important to identify reliable ERA evolution biomarkers. HLA-G molecules has been associated with rheumatoid arthritis, suggesting a role in disease regulation. HLA-G antigens are expressed as membrane bound and soluble isoforms (mHLA-G, sHLA-G) that act as ligand for immune-inhibitory receptors (ILT2, ILT4, KIR2DL4). Expression of HLA-G is influenced by a 14 bp insertion/deletion polymorphism in exon 8 of the gene, where the deletion is associated with mRNA stability. We analyzed 23 ERA patients during a 12 months follow-up disease treatment for sHLA-G, IL-1beta, IL-6, IL-10 and TNF-alpha levels in plasma samples by ELISA, mHLA-G and ILT2 expression on peripheral blood CD14 positive cells by flow cytometry and typed HLA-G 14 bp deletion/insertion polymorphism by Real-Time PCR. Disease status (DAS28), ultrasonography with power Doppler and laboratory data were checked. Cytokine levels confirmed the anti-inflammatory effect of the treatment. sHLA-G, mHLA-G and ILT2 expression inversely correlated with DAS28 disease scores. The frequency of 14 bp deletion allele increased in patients with disease remission. Based on these results, HLA-G may be a candidate biomarker to evaluate early prognosis and disease activity in ERA patients.

Electromagnetic fields (EMFs) and adenosine receptors modulate prostaglandin E(2) and cytokine release in human osteoarthritic synovial fibroblasts

Synovial fibroblasts (SFs) contribute to the development of osteoarthritis (OA) by the secretion of a wide range of pro-inflammatory mediators, including cytokines and lipid mediators of inflammation. Previous studies suggest that electromagnetic fields (EMFs) may represent a potential therapeutic approach to limit cartilage degradation and control inflammation associated to OA, and that they may act through the adenosine pathway. Therefore, we investigated whether EMFs might modulate inflammatory activities of human SFs from OA patients (OASFs) treated with interleukin-1β (IL-1β), and the possible involvement of adenosine receptors (ARs) in mediating EMF effects. EMF exposure induced a selective increase in A(2A) and A(3) ARs. These increases were associated to changes in cAMP levels, indicating that ARs were functionally active also in EMF-exposed cells. Functional data obtained in the presence of selective A(2A) and A(3) adenosine agonists and antagonists showed that EMFs inhibit the release of prostaglandin E(2) (PGE(2)) and the proinflammatory cytokines interleukin-6 (IL-6) and interleukin-8 (IL-8), while stimulating the release of interleukin-10 (IL-10), an antinflammatory cytokine. These effects seem to be mediated by the EMF-induced upregulation of A(2A) and A(3) ARs. No effects of EMFs or ARs have been observed on matrix degrading enzyme production. In conclusion, this study shows that EMFs display anti-inflammatory effects in human OASFs, and that these EMF-induced effects are in part mediated by the adenosine pathway, specifically by the A(2A) and A(3) AR activation. Taken together, these results open new clinical perspectives to the control of inflammation associated to joint diseases.

Umbilical cord blood CD34(+)cell-derived progeny produces human leukocyte antigen-G molecules with immuno-modulatory functions

Human umbilical cord blood units (UCBs) are an alternative source in allogeneic-stem-cell transplantation. Human leukocyte antigen (HLA)-G is a tolerogenic molecule with a possible implication in UCB immunoregulatory effect. HLA-G expression was observed in UCB myeloid and plasmacytoid dendritic cells; in contrast, CD34(+) cells did not produce this molecule. CD34(+) cells are primitive hematopoietic progenitor cells that are present in UCB and are necessary for long-term engraftment via production of immunoregulatory molecules and a hematopoietic progeny that supports cellular recovery. The role of these cells in UCB transplantation needs further evaluation of HLA-G expression in CD34(+) cells and their hematopoietic progeny. We confirmed the absence of HLA-G expression in CD34(+) cells, whereas CD34(+)-derived progeny secreted HLA-G molecules and expressed HLA-G mRNA in in vitro cultures. Furthermore, soluble HLA (sHLA)-G molecules purified from the culture supernatants of CD34(+)-derived progeny were able to suppress lymphoproliferative response in an HLA-G dose-dependent manner. Overall these results identify CD34(+)-derived hematopoietic progeny as producers of HLA-G molecules and support a role of this antigen as an immuno-modulatory factor in UCB.

Identification of circulating nonclassic human leukocyte antigen G (HLA-G)-like molecules in exudates

BACKGROUND

HLA-G in biological fluids has been proposed to be useful as a tumor marker as both a diagnostic and prognostic factor. Most HLA-G measurement procedures are based on ELISA methods using highly specific antibodies. However, results of published studies are in conflict regarding the clinical utility and even the nature of HLA-G present in circulation.

METHODS

We collected 118 exudates, 94 from cancer patients and 24 from patients without tumors. We measured HLA-G concentrations by ELISA using MEM-G/9 or G233 as capture antibody. Samples were immunoprecipitated with an anti-HLA-G antibody and analyzed by Western blot using a different anti-HLA-G antibody.

RESULTS

Discrepancies in HLA-G concentrations in exudates were observed depending on what capture anti-HLA-G antibody was used for ELISA (r = 0.376). These discrepancies were not observed when the ELISAs were performed using culture supernatants from HLA-G1-transfected cells (r = 0.983). Immunoprecipitation and Western blot of cell culture supernatants with 2 different anti-HLA-G antibodies produced the typical band at 39 kDa assigned to HLA-G. When the immunoprecipitation and western blot were performed with exudates, however, there were bands at 53 kDa and 70-76 kDa, higher molecular weights than those usually assigned to HLA-G. These HLA-G-like molecules were associated with β(2)-microglobulin and could also form disulfide bridges with other HLA-G-like molecules.

CONCLUSIONS

The main HLA-G antigenic molecules in exudates are HLA-G-like complexes, a factor that should be considered when analyzing HLA-G in biological fluids.

Biology of HLA-G in cancer: a candidate molecule for therapeutic intervention?

Although the expression of the non-classical HLA class I molecule HLA-G was first reported to be restricted to the fetal-maternal interface on the extravillous cytotrophoblasts, the distribution of HLA-G in normal tissues appears broader than originally described. HLA-G expression was found in embryonic tissues, in adult immune privileged organs, and in cells of the hematopoietic lineage. More interestingly, under pathophysiological conditions HLA-G antigens may be expressed on various types of malignant cells suggesting that HLA-G antigen expression is one strategy used by tumor cells to escape immune surveillance. In this article, we will focus on HLA-G expression in cancers of distinct histology and its association with the clinical course of diseases, on the underlying molecular mechanisms of impaired HLA-G expression, on the immune tolerant function of HLA-G in tumors, and on the use of membrane-bound and soluble HLA-G as a diagnostic or prognostic biomarker to identify tumors and to monitor disease stage, as well as on the use of HLA-G as a novel therapeutic target in cancer.