Lymphocyte activation induces cell surface expression of an immunogenic vimentin isoform

Vimentin takes a hike - Emerging roles of extracellular vimentin in cancer and wound healing

Vimentin is a cytoskeletal protein important for many cellular processes, including proliferation, migration, invasion, stress resistance, signaling, and many more. The vimentin-deficient mouse has revealed many of these functions as it has numerous severe phenotypes, many of which are found only following a suitable challenge or stress. While these functions are usually related to vimentin as a major intracellular protein, vimentin is also emerging as an extracellular protein, exposed at the cell surface in an oligomeric form or secreted to the extracellular environment in soluble and vesicle-bound forms. Thus, this review explores the roles of the extracellular pool of vimentin (eVIM), identified in both normal and pathological states. It focuses specifically on the recent advances regarding the role of eVIM in wound healing and cancer. Finally, it discusses new technologies and future perspectives for the clinical application of eVIM.

Aptamers against mouse and human tumor-infiltrating myeloid cells as reagents for targeted chemotherapy

Local delivery of anticancer agents has the potential to maximize treatment efficacy and minimize the acute and long-term systemic toxicities. Here, we used unsupervised systematic evolution of ligands by exponential enrichment to identify four RNA aptamers that specifically recognized mouse and human myeloid cells infiltrating tumors but not their peripheral or circulating counterparts in multiple mouse models and from patients with head and neck squamous cell carcinoma (HNSCC). The use of these aptamers conjugated to doxorubicin enhanced the accumulation and bystander release of the chemotherapeutic drug in both primary and metastatic tumor sites in breast and fibrosarcoma mouse models. In the 4T1 mammary carcinoma model, these doxorubicin-conjugated aptamers outperformed Doxil, the first clinically approved highly optimized nanoparticle for targeted chemotherapy, promoting tumor regression after just three administrations with no detected changes in weight loss or blood chemistry. These RNA aptamers recognized tumor infiltrating myeloid cells in a variety of mouse tumors in vivo and from human HNSCC ex vivo. This work suggests the use of RNA aptamers for the detection of myeloid-derived suppressor cells in humans and for a targeted delivery of chemotherapy to the tumor microenvironment in multiple malignancies.

Machine Learning to Quantify In Situ Humoral Selection in Human Lupus Tubulointerstitial Inflammation

In human lupus nephritis, tubulointerstitial inflammation (TII) is associated with in situ expansion of B cells expressing anti-vimentin antibodies (AVAs). The mechanism by which AVAs are selected is unclear. Herein, we demonstrate that AVA somatic hypermutation (SHM) and selection increase affinity for vimentin. Indeed, germline reversion of several antibodies demonstrated that higher affinity AVAs can be selected from both low affinity B cell germline clones and even those that are strongly reactive with other autoantigens. While we demonstrated affinity maturation, enzyme-linked immunosorbent assays (ELISAs) suggested that affinity maturation might be a consequence of increasing polyreactivity or even non-specific binding. Therefore, it was unclear if there was also selection for increased specificity. Subsequent multi-color confocal microscopy studies indicated that while TII AVAs often appeared polyreactive by ELISA, they bound selectively to vimentin fibrils in whole cells or inflamed renal tissue. Using a novel machine learning pipeline (CytoSkaler) to quantify the cellular distribution of antibody staining, we demonstrated that TII AVAs were selected for both enhanced binding and specificity in situ. Furthermore, reversion of single predicted amino acids in antibody variable regions indicated that we could use CytoSkaler to capture both negative and positive selection events. More broadly, our data suggest a new approach to assess and define antibody polyreactivity based on quantifying the distribution of binding to native and contextually relevant antigens.

Non-HLA Abs in Solid Organ Transplantation

The role of anti-HLA antibodies in solid organ rejection is well established and these antibodies are routinely monitored both in patients in the waiting list and in the post-transplant setting. More recently, the presence of other antibodies directed towards non-HLA antigens, or the so-called minor histocompatibility antigens, has drawn the attention of the transplant community; however, their possible involvement in the graft outcome remains uncertain. These antibodies have been described to possibly have a role in rejection and allograft failure. This review focuses on the most studied non-HLA antibodies and their association with different clinical outcomes considered in solid organ transplantation with the aim of clarifying their clinical implication and potential relevance for routine testing.

Improved Isolation of Mesenchymal Stem Cells Based on Interactions between N-Acetylglucosamine-Bearing Polymers and Cell-Surface Vimentin

Mesenchymal stem cells (MSCs) in bone marrow and adipose tissues are expected to be effective tools for regenerative medicine to treat various diseases. To obtain MSCs that possess both high differentiation and tissue regenerative potential, it is necessary to establish an isolation system that does not require long-term culture. It has previously been reported that the cytoskeletal protein vimentin, expressed on the surfaces of multiple cell types, possesses N-acetylglucosamine- (GlcNAc-) binding activity. Therefore, we tried to exploit this interaction to efficiently isolate MSCs from rat bone marrow cells using GlcNAc-bearing polymer-coated dishes. Cells isolated by this method were identified as MSCs because they were CD34-, CD45-, and CD11b/c-negative and CD90-, CD29-, CD44-, CD54-, CD73-, and CD105-positive. Osteoblast, adipocyte, and chondrocyte differentiation was observed in these cells. In total, yields of rat MSCs were threefold to fourfold higher using GlcNAc-bearing polymer-coated dishes than yields using conventional tissue-culture dishes. Interestingly, MSCs isolated with GlcNAc-bearing polymer-coated dishes strongly expressed CD106, whereas those isolated with conventional tissue-culture dishes had low CD106 expression. Moreover, senescence-associated β-galactosidase activity in MSCs from GlcNAc-bearing polymer-coated dishes was lower than that in MSCs from tissue-culture dishes. These results establish an improved isolation method for high-quality MSCs.

Senescent cell clearance by the immune system: Emerging therapeutic opportunities

Senescent cells (SCs) arise from normal cells in multiple organs due to inflammatory, metabolic, DNA damage, or tissue damage signals. SCs are non-proliferating but metabolically active cells that can secrete a range of pro-inflammatory and proteolytic factors as part of the senescence-associated secretory phenotype (SASP). Senescent cell anti-apoptotic pathways (SCAPs) protect SCs from their own pro-apoptotic SASP. SCs can chemo-attract immune cells and are usually cleared by these immune cells. During aging and in multiple chronic diseases, SCs can accumulate in dysfunctional tissues. SCs can impede innate and adaptive immune responses. Whether immune system loss of capacity to clear SCs promotes immune system dysfunction, or conversely whether immune dysfunction permits SC accumulation, are important issues that are not yet fully resolved. SCs may be able to assume distinct states that interact differentially with immune cells, thereby promoting or inhibiting SC clearance, establishing a chronically pro-senescent and pro-inflammatory environment, leading to modulation of the SASP by the immune cells recruited and activated by the SASP. Therapies that enhance immune cell-mediated clearance of SCs could provide a lever for reducing SC burden. Such therapies could include vaccines, small molecule immunomodulators, or other approaches. Senolytics, drugs that selectively eliminate SCs by transiently disabling their SCAPs, may prove to alleviate immune dysfunction in older individuals and thereby accelerate immune-mediated clearance of SCs. The more that can be understood about the interplay between SCs and the immune system, the faster new interventions may be developed to delay, prevent, or treat age-related dysfunction and the multiple senescence-associated chronic diseases and disorders.

Effects of salazosulfapyridine on the profile of cell surface proteins, revealed by biotinylation of cell surface proteins and 2-dimentional electrophoresis

OBJECTIVE

We investigated effects of salazosulfapyridine (SASP) on the protein profile of cell surface (CS)-proteins of SW982, a human synovial sarcoma cell line, using biotinylation of CS-proteins and 2-dimensional fluorescence difference gel electrophoresis (2D-DIGE).

METHODS

SW982 cells were treated with SASP and its metabolites, sulfapyridine (SP) and 5-aminosalicylic acid (5ASA). Then the cells were treated with a membrane-impermeable biotinylating reagent. Biotinylated CS-proteins were isolated using NeutrAvidin-bound beads. CS-proteins affected by the drugs were detected by 2D-DIGE and subjected to mass spectrometry.

RESULTS

By the 2D-DIGE analysis, in total 576 spots were detected, 29 out of which showed more than ±1.5-fold different intensity in the SASP-, SP-, and 5ASA-treated cells, compared to non-treated cells (p < 0.05). Interestingly, 7 out of the 29 spots changed their intensity only by SASP and 17 spots changed their intensity only by SP. We identified 9 protein from 15 out of the 29 spots, most of which were evidenced to exist on the cell surface by flow cytometry.

CONCLUSION

We found novel effects of SASP and its metabolites on SW982 cells by the combination of biotinylation of cell surface proteins and 2D-DIGE analysis. These data would help understanding of anti-rheumatic actions of SASP. Furthermore, the combination would be a useful method for the analysis of CS-proteins in various conditions.

T/T homozygosity of the tenascin-C gene polymorphism rs2104772 negatively influences exercise-induced angiogenesis

BACKGROUND

Mechanical stress, including blood pressure related factors, up-regulate expression of the pro-angiogenic extracellular matrix protein tenascin-C in skeletal muscle. We hypothesized that increased capillarization of skeletal muscle with the repeated augmentation in perfusion during endurance training is associated with blood vessel-related expression of tenascin-C and would be affected by the single-nucleotide polymorphism (SNP) rs2104772, which characterizes the non-synonymous exchange of thymidine (T)-to-adenosine (A) in the amino acid codon 1677 of tenascin-C.

METHODS

Sixty-one healthy, untrained, male white participants of Swiss descent performed thirty 30-min bouts of endurance exercise on consecutive weekdays using a cycling ergometer. Genotype and training interactions were called significant at Bonferroni-corrected p-value of 5% (repeated measures ANOVA).

RESULTS

Endurance training increased capillary-to-fiber-ratio (+11%), capillary density (+7%), and mitochondrial volume density (+30%) in m. vastus lateralis. Tenascin-C protein expression in this muscle was confined to arterioles and venules (80% of cases) and increased after training in A-allele carriers. Prior to training, volume densities of subsarcolemmal and myofibrillar mitochondria in m. vastus lateralis muscle were 49% and 18%, respectively, higher in A/A homozygotes relative to T-nucleotide carriers (A/T and T/T). Training specifically increased capillary-to-fiber ratio in A-nucleotide carriers but not in T/T homozygotes. Genotype specific regulation of angiogenesis was reflected by the expression response of 8 angiogenesis-associated transcripts after exercise, and confirmed by training-induced alterations of the shear stress related factors, vimentin and VEGF A.

CONCLUSION

Our findings provide evidence for a negative influence of T/T homozygosity in rs2104772 on capillary remodeling with endurance exercise.

Senescent cells expose and secrete an oxidized form of membrane-bound vimentin as revealed by a natural polyreactive antibody

Studying the phenomenon of cellular senescence has been hindered by the lack of senescence-specific markers. As such, detection of proteins informally associated with senescence accompanies the use of senescence-associated β-galactosidase as a collection of semiselective markers to monitor the presence of senescent cells. To identify novel biomarkers of senescence, we immunized BALB/c mice with senescent mouse lung fibroblasts and screened for antibodies that recognized senescence-associated cell-surface antigens by FACS analysis and a newly developed cell-based ELISA. The majority of antibodies that we isolated, cloned, and sequenced belonged to the IgM isotype of the innate immune system. In-depth characterization of one of these monoclonal, polyreactive natural antibodies, the IgM clone 9H4, revealed its ability to recognize the intermediate filament vimentin. By using 9H4, we observed that senescent primary human fibroblasts express vimentin on their cell surface, and MS analysis revealed a posttranslational modification on cysteine 328 (C328) by the oxidative adduct malondialdehyde (MDA). Moreover, elevated levels of secreted MDA-modified vimentin were detected in the plasma of aged senescence-accelerated mouse prone 8 mice, which are known to have deregulated reactive oxygen species metabolism and accelerated aging. Based on these findings, we hypothesize that humoral innate immunity may recognize senescent cells by the presence of membrane-bound MDA-vimentin, presumably as part of a senescence eradication mechanism that may become impaired with age and result in senescent cell accumulation.

Downregulation of vimentin in macrophages infected with live Mycobacterium tuberculosis is mediated by Reactive Oxygen Species

Mycobacterium tuberculosis persists primarily in macrophages after infection and manipulates the host defence pathways in its favour. 2D gel electrophoresis results showed that vimentin, an intermediate filament protein, is downregulated in macrophages infected with live Mycobacterium tuberculosis H37Rv when compared to macrophages infected with heat- killed H37Rv. The downregulation was confirmed by Western blot and quantitative RT-PCR. Besides, the expression of vimentin in avirulent strain, Mycobacterium tuberculosis H37Ra- infected macrophages was similar to the expression in heat-killed H37Rv- infected macrophages. Increased expression of vimentin in H2O2- treated live H37Rv-infected macrophages and decreased expression of vimentin both in NAC and DPI- treated heat-killed H37Rv-infected macrophages showed that vimentin expression is positively regulated by ROS. Ectopic expression of ESAT-6 in macrophages decreased both the level of ROS and the expression of vimentin which implies that Mycobacterium tuberculosis-mediated downregulation of vimentin is at least in part due to the downregulation of ROS by the pathogen. Interestingly, the incubation of macrophages with anti-vimentin antibody increased the ROS production and decreased the survival of H37Rv. In addition, we also showed that the pattern of phosphorylation of vimentin in macrophages by PKA/PKC is different from monocytes, emphasizing a role for vimentin phosphorylation in macrophage differentiation.

Role of anti-vimentin antibodies in renal transplantation

BACKGROUND

The role of non-HLA antibodies in rejection is not clear. We investigate whether antibodies to vimentin are made after renal transplantation and if production is associated with interstitial fibrosis and tubular atrophy (IFTA).

METHODS

In this retrospective study, sera from 70 recipients of renal allografts (40 controls, 30 IFTA) were studied. The biopsy diagnosis of interstitial fibrosis and tubular atrophy (IFTA) was based on random, cause-indicating biopsies. Sera were collected pretransplant and at 3 monthly intervals up to 5 years posttransplant or diagnosis of IFTA and assayed by ELISA for IgM and IgG anti-vimentin antibodies (AVA) and HLA antibodies.

RESULTS

Mean titers of IgM AVA were higher at every year after transplantation compared with pretransplant for both IFTA and controls groups (P<0.001). There was no difference in the mean level of IgM AVA achieved by IFTA and control groups. The mean pretransplant levels of IgG AVA in the IFTA and control group were 18.2±11.7 and 11.0±8.1, respectively (P=0.001). There was a significant increase between the pretransplant mean levels of IgG AVA and the levels at years 1 to 4 in the IFTA group (years 1-3, P<0.0001, year 4 P=0.003) but not in the controls. There was no significant difference between the numbers of IFTA or control patients achieving a positive value (mean+2SD of pretransplant antibody titers) of IgM AVA (50% versus 37.5%, respectively) or IgG AVA (26.6% versus 12.5%, respectively). There was no association between production of HLA and AVA antibodies.

CONCLUSION

Posttransplant production of IgM AVA is not associated with IFTA. The production of IgG AVA by a minority of IFTA patients suggests that in some individuals, IgG AVA may be involved in the pathology of IFTA.

Role of anti-vimentin antibodies in allograft rejection

Production of anti-vimentin antibodies (AVA) after solid organ transplantation are common. Although classically thought to be expressed mainly within the cytosol, recent evidence demonstrates that extracellular or cell surface expression of vimentin is not unusual. This review examines the evidence to assess whether AVA contribute to allograft pathology. Clinical studies suggest that AVA are associated with cardiac allograft vasculopathy in heart transplant recipients. Studies in non-human primates confirm that production of AVA after renal and heart transplantation are not inhibited by Cyclosporine. Experimental studies have demonstrated that mice pre-immunised with vimentin undergo accelerated acute rejection and vascular intimal occlusion of cardiac allografts. Adoptive transfer of hyperimmune sera containing AVA into B-cell-knock-out mice caused accelerated rejection of allografted hearts, this is clear evidence that antibodies to vimentin accelerate rejection. AVA act in concert with the alloimmune response and AVA do not damage syngeneic or native heart allografts. Confocal microscopy of allografted organs in vimentin immunised mice shows extensive expression of vimentin on endothelial cells, apoptotic leukocytes and platelet/leukocyte conjugates, co-localising with C4d. One explanation for the ability of AVA to accelerate rejection would be fixation of complement within the graft and subsequent pro-inflammatory effects; there may also be interactions with platelets within the vasculature.