Role of transforming growth factor beta (TGF beta) in systemic autoimmunity

Mesenchymal stem cells in autoimmune disease: A systematic review and meta-analysis of pre-clinical studies

Mesenchymal Stem Cells (MSCs) are of interest in the clinic because of their immunomodulation capabilities, capacity to act upstream of inflammation, and ability to sense metabolic environments. In standard physiologic conditions, they play a role in maintaining the homeostasis of tissues and organs; however, there is evidence that they can contribute to some autoimmune diseases. Gaining a deeper understanding of the factors that transition MSCs from their physiological function to a pathological role in their native environment, and elucidating mechanisms that reduce their therapeutic relevance in regenerative medicine, is essential. We conducted a Systematic Review and Meta-Analysis of human MSCs in preclinical studies of autoimmune disease, evaluating 60 studies that included 845 patient samples and 571 control samples. MSCs from any tissue source were included, and the study was limited to four autoimmune diseases: multiple sclerosis, rheumatoid arthritis, systemic sclerosis, and lupus. We developed a novel Risk of Bias tool to determine study quality for in vitro studies. Using the International Society for Cell & Gene Therapy's criteria to define an MSC, most studies reported no difference in morphology, adhesion, cell surface markers, or differentiation into bone, fat, or cartilage when comparing control and autoimmune MSCs. However, there were reported differences in proliferation. Additionally, 308 biomolecules were differentially expressed, and the abilities to migrate, invade, and form capillaries were decreased. The findings from this study could help to explain the pathogenic mechanisms of autoimmune disease and potentially lead to improved MSC-based therapeutic applications.

The soluble form of CTLA-4 from serum of patients with autoimmune diseases regulates T-cell responses

Cytotoxic T lymphocyte associated antigen-4 (CTLA-4) is a costimulatory receptor transducing a potent inhibitory signal. Increasing evidence showed that CTLA-4 gene is an important susceptibility locus for autoimmune disorders. Alternatively spliced mRNA generates a soluble form, called sCTLA-4. Whereas low levels of sCTLA-4 are detected in normal human serum, increased/high serum levels are observed in several autoimmune diseases. The biological significance of increased sCTLA-4 serum level is not fully clarified yet. It can be envisaged that sCTLA-4 specifically inhibits the early T-cell activation by blocking the interaction of CD80/CD86 with the costimulatory receptor CD28. On the other hand, higher levels of sCTLA-4 could contend the binding of the membrane form of CTLA-4 with CD80/CD86, in later activation phase, causing a reduction of inhibitory signalling. We showed that sCTLA-4 from sera of patients with different autoimmune diseases is able to display functional activities on an in vitro system acting on the proliferation capability and modulating the secretion of cytokines. We observed a dual effect of sCTLA-4: inhibiting the secretion of IFN-γ, IL-2, IL-7, and IL-13 and activating the secretion of TGF-β and IL-10. This study underlines the role of sCTLA-4 in modulating the immune response and its relevance in autoimmune disease pathogenesis.

GM-CSF contributes to aortic aneurysms resulting from SMAD3 deficiency

Heterozygous loss-of-function SMAD3 (Mothers against decapentaplegic homolog 3) mutations lead to aneurysm-osteoarthritis syndrome (AOS). In the present study, we found that mice lacking Smad3 had a vascular phenotype similar to AOS, marked by the progressive development of aneurysms. These aneurysms were associated with various pathological changes in transmural inflammatory cell infiltration. Bone marrow transplants from Smad3-/- mice induced aortitis and aortic root dilation in irradiated WT recipient mice. Transplantation of CD4+ T cells from Smad3-/- mice also induced aortitis in Smad3+/+ recipient mice, while depletion of CD4+ T cells in Smad3-/- mice reduced the infiltration of inflammatory cells in the aortic root. Furthermore, IFN-γ deficiency increased, while IL-17 deficiency decreased, disease severity in Smad3+/- mice. Cytokine secretion was measured using a cytokine quantibody array, and Smad3-/- CD4+ T cells secreted more GM-CSF than Smad3+/+ CD4+ T cells. GM-CSF induced CD11b+Gr-1+Ly-6Chi inflammatory monocyte accumulation in the aortic root, but administration of anti-GM-CSF mAb to Smad3-/- mice resulted in significantly less inflammation and dilation in the aortic root. We also identified a missense mutation (c.985A>G) in a family of thoracic aortic aneurysms. Intense inflammatory infiltration and GM-CSF expression was observed in aortas specimens of these patients, suggesting that GM-CSF is potentially involved in the development of AOS.

Effects of dietary omega3 and omega6 lipids and vitamin E on proliferative response, lymphoid cell subsets, production of cytokines by spleen cells, and splenic protein levels for cytokines and oncogenes in MRL/MpJ-lpr/lpr mice

omega3 Fatty acid rich fish oil (FO) and vitamin E may delay the progress of certain autoimmune diseases. The present study examined the mechanisms of action of omega3 lipids and vitamin E in autoimmune-prone MRL/lpr mice suffering from extensive lymphoproliferation, lupus-like symptoms, and accelerated aging. To determine whether the effects of omega3 lipids in autoimmune disease is linked to vitamin E levels, weanling female MRL/lpr and congenic control MRL/++ mice were fed diets containing 10% corn oil (CO) or 10% FO at two levels of vitamin E (75 IU or 500 IU/kg diet) for 4 months. The appearance of lymph nodes was delayed in the mice fed FO, and higher levels of FO offered further protection against the appearance of lymph nodes. Analysis of the spleen cells revealed that the cells positive for Thy.1 and Fas were significantly higher in the MRL/++ mice. The groups fed high levels of vitamin E generally exhibited higher levels of Fas. The proliferative response of splenocytes of MRL/++ mice to mitogens was significantly higher compared with MRL/lpr mice. Interleukin (IL)-10 production by spleen cells was significantly higher in FO-fed MRL/lpr mice than in CO-fed mice. In mice fed a high level of vitamin E, the production of IL-12 and tumor necrosis factor-alpha was significantly lower and IL-2 was significantly higher than in animals fed a low level of vitamin E. Proinflammatory cytokines were higher in the MRL/lpr mice and both FO and vitamin E lowered the levels of proinflammatory cytokines and lipid mediators. Western blots revealed that c-myc and c-ras were significantly lower and IL-2 and transforming growth factor (TGF)-beta1 levels were significantly higher in the spleens of MRL/++ mice. FO lowered c-myc and high levels of vitamin E in the diets normalized the levels of TGF-beta1 in MRL/lpr mice. The observations from this study suggest that both FO and vitamin E modulate the levels of specific cytokines, decrease the levels of proinflammatory cytokines, inflammatory lipid mediators, and c-myc, and increase TGF-beta1 levels in spleens of MRL/lpr mice and thus may delay the progress of autoimmune diseases.

Rapamycin blocks IL-2-driven T cell cycle progression while preserving T cell survival

Effective cellular immune responses require increases in antigen-specific T lymphocytes; IL-2 drives antigen-stimulated T cell proliferation and is largely responsible for the increases observed. We used microarrays containing approximately 9000 mouse cDNAs to study IL-2-induced gene expression. IL-2 induces the expression of genes that regulate cell cycle progression, control cell survival, and increase synthetic and metabolic processes during proliferation. IL-2 also suppresses expression of genes that block cell cycle progression and promote cell death. Rapamycin inhibits IL-2-driven proliferation by downregulating the expression of genes required for key processes required for cell cycle progression. Rapamycin also preserves cell survival by keeping intact the IL-2-induced cell survival programs. These complex multifaceted programs of gene expression permit a dynamic regulation of cellular proliferation and cellular survival.

Exogenous IL-10 and IL-4 down-regulate IL-6 production by SLE-derived PBMC

The elevated expression of IL-6 and IL-10 may have an important role in SLE pathogenesis. IL-6 production by normal monocytes can be inhibited by IL-10, and it has been suggested that SLE monocytes are refractory to this negative signal. To examine this possibility, the effects of regulatory factors on IL-6 expression by SLE PBMC (N = 51) were compared to effects on control PBMC (N = 21). We found that (1) exogenous rIL-10 and rIL-4 mediated reduction of constitutive and lectin-induced IL-6 in monocytes of SLE patients as effectively as that of controls; (2) IL-6 mRNA decay was significantly delayed in SLE with active disease (P < 0.001); (3) adding rIL-10 or neutralizing endogenous IL-1 beta and TNF-alpha down-regulated IL-6 mainly by destabilizing IL-6 transcripts, whereas exogenous IL-4 and TGF beta 1 down-regulated IL-6 transcriptionally; (4) time kinetics and levels of IL-10 were lower than those of IL-6 and IL-1 beta. Thus, contrary to a previous report, IL-6 production by SLE PBMC responds normally to regulatory signals, and the IL-6 overexpression in SLE may be due, at least in part, to the kinetics and availability of regulatory cytokines.

Decreased Production of TGF-β by Lymphocytes from Patients with Systemic Lupus Erythematosus

TGF-β has marked inhibitory effects on the immune system but also serves as a costimulatory factor in the development of T cells with down-regulatory activities. This cytokine is secreted as a latent complex and converted extracellularly to its active form. We have recently learned that anti-CD2 is a potent inducer of lymphocyte-derived TGF-β and that NK cells are the predominant source. The objective of this study was to compare levels of constitutive, anti-CD2-induced and cytokine-regulated TGF-β produced by blood lymphocytes from patients with systemic lupus erythematosus (SLE) in comparison with healthy controls. Using a highly sensitive and specific bioassay to assess TGF-β, we report that unstimulated PBL from SLE patients, especially the NK cell subset, produced decreased levels of active TGF-β. In response to anti-CD2, concentrations of active and total TGF-β were also decreased in SLE. After learning that IL-2 and TNF-α enhance lymphocyte production of active TGF-β, we found that the addition of these cytokines was unable to increase active TGF-β to normal concentrations. Although we observed that IL-10 inhibited the production of active TGF-β, antagonism of this cytokine was unable to completely correct the defect. In two SLE patients with B cell hyperactivity, spontaneous IgG production was almost abolished by the combination of TGF-β and IL-2. Therefore, decreased production of each of these cytokines in SLE could be important in the perpetuation of B cell hyperactivity.

Inhibition and prevention of monosodium urate monohydrate crystal-induced acute inflammation in vivo by transforming growth factor beta1

OBJECTIVE

We investigated the effects of transforming growth factor beta 1 (TGF beta 1) on monosodium urate monohydrate (MSU) crystal-induced acute inflammation in vivo.

METHODS

One hour after MSU crystal-induced acute inflammation was produced in the rat subcutaneous air pouch model, the effects of recombinant human TGF beta 1 (rHuTGF beta 1; 10-100 pg/animal) and ultrapure TGF beta 1 (UPTGF beta 1; 100 and 500 pg/animal) were assessed, based on absolute and differential white blood cell counts in the exudate. The effects of 10 pg of rHuTGF beta 1 preincubated with a specific anti-TGF beta antibody, and the effects of coinjection of crystals and rHuTGF beta 1, were also studied.

RESULTS

UPTGF beta 1 and rHuTGF beta 1 markedly reduced MSU crystal-induced inflammation. Recombinant human TGF beta 1 also reduced inflammation when administered concomitantly with MSU crystals. Moreover, rHuTGF beta 1 and UPTGF beta 1, injected 1 hour after MSU crystal injection, reduced the inflammatory response in a dose-dependent manner. Injection of rHuTGF beta 1 (100 pg/animal) resulted in a > 90% reduction in the maximal white blood cell count, achieved 6 hours after crystal injection. Preincubation of rHuTGF beta 1 with a specific anti-TGF beta 1 antibody significantly (P < 0.01) reversed the inhibitory effect of rHuTGF beta 1 on the inflammatory response. Consistent with the regulation of inflammatory cell recruitment into the joint, the percentage of monocytes markedly decreased (P < 0.01) following local injection with rHuTGF beta 1 6 hours after MSU crystal injection.

CONCLUSION

Exogenous TGF beta 1 prevents and inhibits MSU crystal-induced acute inflammation in vivo. Its role in the self-limitation of gouty attacks deserves consideration, among the various other factors involved.

Transforming growth factor-beta in GI neoplasia, wound healing and immune response

The last decade has been marked by tremendous advances in the biochemical and functional characterization of TGF-betas and their receptors in normal and transformed cells. TGF-betas have been shown to modulate proliferation, differentiation and motility of different cell types in a number of in vitro model systems and in some cases with some intriguing results. It is obvious that there is no simple pattern that explains the TGF-betas biological activity in vitro and their effects on cell behaviour need to be assessed in the context of an appropriate physiological cellular environment. Cell-cell and cell-matrix interactions, the differentiating status of the cell together with the functional activity of other soluble growth factors can influence how TGF-betas modulate cell behaviour. However, the overwhelming interest in this field shown by clinicians and basic scientists is rapidly increasing our understanding of how growth factors such as TGF-betas regulate the homeostasis of the GI mucosa and their role in gastrointestinal carcinogenesis.

Modulation of antioxidant enzymes and programmed cell death by n-3 fatty acids

Studies from our laboratory indicate that n-3 (fish oil, FO) lipids at 10% (w/w) in a nutritionally adequate, semipurified diet, and supplemented with equal levels of antioxidants, extended the life span of lupus-prone (NZB/NZW)F1 (B/W) female mice as compared to n-6 (corn oil, CO) lipids. The early rise of autoimmune disease in CO-fed mice was closely linked to the loss of T-cell function. Both IL-2 production and IL-2 receptor expression were reduced due to the loss of naive T-cells and a rise in memory T-cells. Proliferative response to both mitogens and superantigens (staphylococcal enterotoxins A and B) was higher in FO-fed 6.5-mon-old mice. These changes paralleled decreased PGE2 production by splenic cells from FO-fed mice. Analysis of mRNA expression in different organs revealed differential effects of dietary lipids. In FO-fed mice, transforming growth factor beta 1 (TGF beta 1) expression was decreased in kidneys, but splenic tissues had higher expression of TGF beta mRNA. As TGF beta promotes programmed cell death (PCD), we studied the effects of CO and FO on PCD rates in lymphocytes. Both propidium iodide staining and DNA fragmentation were elevated in lymphocytes of FO-fed mice when compared to CO-fed mice of similar age. Also, increased PCD correlated closely with increased Fas gene expression. Thus, in addition to various other antiinflammatory effects, dietary FO appears to increase PCD and prevent accumulation of self-reactive immune cells in lymphoid organs. Further studies are required to dissect the pro- and antiinflammatory mechanisms associated with dietary n-3 and n-6 lipids in modulating autoimmune disorders or malignancy during aging.

Dual inhibitory and stimulatory activities in serum from SLE patients and lupus mice that regulate the proliferation of an IL-2-dependent T cell line

In serum and plasma from SLE patients, we have detected elevated levels of factors which regulate proliferative responses of CTLL cells to IL-2. Serum samples containing these factors have dose-dependent dual inhibitory and stimulatory activities on the proliferation of this IL-2-dependent T lymphocyte cell line. At high concentrations, the serum factors inhibit the proliferative responses of CTLL cells to IL-2. At low concentrations, they synergise with IL-2 stimulating the growth of cells. Similar inhibitory activity, but with lower titre, was also found to be elevated in sera of some MRL/lpr mice, an animal model of SLE. Functional characterisation of the serum factors shows that: (1) the inhibitory activity cannot be neutralised by exogenous IL-2; (2) the stimulatory activity is not due to the presence of serum IL-2 but synergy of the factor with IL-2; (3) the factors bind directly to CTLL cells but they do not bind to protein A; and (4) the serum factors are not dialysable but heat labile. The possible pathological implications of the serum factors, particularly for the defective T cell functions in lupus disease, are discussed.

Cytokine gene profile in circulating blood mononuclear cells from patients with systemic lupus erythematosus: increased interleukin-2 but not interleukin-4 mRNA

Cytokines are important in developmental and effector pathways of lymphocyte function. Our objective was to elucidate the profile of cytokines produced by circulating mononuclear cells from patients with systemic lupus erythematosus as estimated from studies of cytokine-gene activation. cDNA prepared by reverse transcription of lymphocyte mRNA was amplified using the polymerase chain reaction and normalized on the basis of beta-actin gene expression. Of 10 cytokines investigated in 16 individuals, differences between SLE and controls were found in only three. IL-2 transcripts were detected in four of six cases of subjects hospitalized for active SLE, but in only one of seven healthy controls, and none of three cases with pulmonary tuberculosis. By contrast, IL-4 transcripts were decreased compared with healthy controls and patients with tuberculosis. Also, TGF beta transcripts appeared to be decreased in SLE. All individuals studied regularly demonstrated high levels of transcripts for IL-1 beta, IL-6 and TNF alpha and transcripts for IFN gamma, TNF beta, IL-5 and IL-10 were variably expressed. In a second group of six SLE patients with less active disease, there was also a decrease in IL-4 expression compared with six healthy controls. Moreover, assays performed on sera from patients with active SLE revealed that IL-4 levels were not increased. Although in mice this cytokine has a well documented role in supporting antibody production, this study provides no evidence that IL-4 is involved in the B cell hyperactivity characteristic of human SLE.