The role of IL-17 and Th17 cells in keloid pathogenesis.

T helper17 Cells Are Sufficient But Not Necessary to Induce Acute Graft-Versus-Host Disease

IL-23 inhibits IL-22 and AhR signalling and with IL-1β regulates the human peripheral Th17/Th22 balance

Th17 Cytokines and Barrier Functions.

The pathogenesis of keloids has not been elucidated, and the disease is thought to be caused by abnormal secretion of proinflammatory mediators and irregular responses to other inflammatory signals mediated by keloid fibroblasts (KFs). In this study, we investigated whether a local increase in interleukin IL-17 in keloid tissues stimulates the production of stromal cell–derived factor-1 (SDF-1) in KFs causing further recruitment of IL-17-producing T helper 17 (Th17) cells, which subsequently creates a positive feedback loop. Histological assessment was performed and the change in the expression of IL-17, IL-1β, IL-6, and TNF-α which of fibrosis and inflammation associated markers was examined. In addition, fibroblasts were treated with IL-17 in the presence or absence of STAT3 inhibitor STA-21; SDF-1 levels and fibrosis genes were measured. Our results showed that fibrotic reaction and expression of proinflammatory cytokines including IL-17 were most prominent in the growing margin (perilesional area) of keloid tissue and Th17 cells significantly infiltrated the perilesional area. In addition, IL-17 upregulated the expression of SDF-1, collagen, and α-SMA in KFs. Finally, STA-21 decreased SDF-1α expression and the expression of fibrosis genes in KFs even after IL-17 stimulation. Our study demonstrated that a local increase in IL-17 in keloid tissues stimulates the production of SDF-1 in KFs causing further recruitment of IL-17-producing T helper 17 (Th17) cells, which subsequently creates a positive feedback loop. These findings suggest that STAT3 inhibition can be used to treat keloid scars by reversing the vicious cycle between Th17 cells and KFs.

Keloids represent a dysregulated response to cutaneous wounding that results in disfiguring scars. Unique to humans, keloids are characterized by an accumulation of extracellular matrix components. The underlying molecular mechanisms of keloid pathogenesis, however, remain largely uncharacterized. Similarly, cellular signaling mechanisms, which may indicate inherent differences in the way keloid fibroblasts and normal human dermal fibroblasts interact with extracellular matrix or other cells, have not been investigated. As part of a fundamental assessment of cellular response to injury in keloid fibroblasts, phosphorylation studies were performed using three different keloid (n = 3) and normal human dermal (n = 3) fibroblast cell lines. These studies were undertaken to elucidate whether keloid and normal human dermal fibroblasts exhibit different tyrosine kinase activity. Initially, distinct tyrosine phosphorylation patterns of keloid and normal human dermal fibroblasts were demonstrated. Next, the phosphorylation patterns were correlated with known molecules that may be important to keloid pathogenesis. On the basis of molecular weight, it was hypothesized that the highly phosphorylated bands seen in keloid fibroblasts represented epidermal growth factor receptor (EGFR); discoidin domain receptor 1 (DDR1); and Shc, an adaptor protein known to bind many tyrosine kinases, including EGFR and DDR1. Individual immunoblotting using EGFR, DDR1, and Shc antibodies revealed greater expression in keloid fibroblasts compared with normal human dermal fibroblasts. These data substantiate for the first time the finding of greater phosphorylation by the above-mentioned molecules, which may be important in keloid pathogenesis.

Objective: To investigate the role and mechanism of IL-17 and CXCR4 in chronic graft nephropathy (CAN) in rat models. Methods: CAN rat models were established using Fisher 344 to Lewis rats. In the control group(n=10), Lewis rats were performed isotransplantation. CAN rat models were established in experimental group(n=10). All the rats were havested 6 weeks after transplantation. Kidneys were examined by pathology to evaluate the injury of the renal allograft. SDF-1/CXCR4, IL-17 and α-SMA expression level in serum and renal graft were detected by immunohistochemical staining and Enzyme-linked immunosorbent assays(ELISA). The percent and the absolute amount of CD4(+) cells、CXCR4(+) cells and IL-17(+) cells were detected by flow cytometry. Results: The graft of the experiment group showed obvious pathological features of CAN. The protein expression levels of SDF-1/CXCR4 and IL-17 in the experiment group are significantly higher than in the control group. We could also observe the number of Th17 cells has a significant increase in the experiment group[blood (0.19±0.05)% vs (0.12±0.03)%; kidney (0.52±0.21)% vs (0.17±0.12)%]. The IL-17 level also showed the same differences between the experiment[blood (243.12±17.63) pg/ml, kidney (521.54±21.76) pg/ml]and the control group[blood (35.78±7.3) pg/ml, kidney (77.34±11.1) pg/ml]. Conclusions: The Th17 cells increase in the CAN rats model, maybe the SDF-1/CXCR4 has a chemotaxis to collect Th17 cells to the injured kidney. And its expression of IL-17 may promote the renal cells to transform into fibroblasts.

In Vitro Polarized Th17 CD4+ T Cells Home Primarily to Sites of Initial Antigen Encounter

Akt and mTOR Pathways Differentially Regulate the Development of Natural and Inducible IL-17-Producing CD4+ T Cells

Th17/IL-17 Might Play a Protective Role in CLL Immunity

Keloids represent a dysregulated response to cutaneous wounding that results in an excessive deposition of extracellular matrix, especially collagen. However, the molecular mechanisms regulating this pathologic collagen deposition still remain to be elucidated. A previous study by this group demonstrated that transforming growth factor (TGF)-beta1 and -beta2 ligands were expressed at greater levels in keloid fibroblasts when compared with normal human dermal fibroblasts (NHDFs), suggesting that TGF-beta may play a fibrosis-promoting role in keloid pathogenesis.To explore the biomolecular mechanisms of TGF-beta in keloid formation, the authors first compared the expression levels of the type I and type II TGF-beta receptors in keloid fibroblasts and NHDFs. Next, they investigated the phosphorylation of Smad 3, an intracellular TGF-beta signaling molecule, in keloid fibroblasts and NHDFs. Finally, they examined the regulation of TGF-beta receptor II by TGF-beta1, TGF-beta2, and TGF-beta3 ligands. Our findings demonstrated an increased expression of TGF-beta receptors (types I and II) and increased phosphorylation of Smad 3 in keloid fibroblasts relative to NHDFs. These data support a possible role of TGF-beta and its receptors as fibrosis-inducing growth factors in keloids. In addition, all three isoforms of recombinant human TGF-beta proteins could further stimulate the expression of TGF-beta receptor II in both keloids and NHDFs. Taken together, these results substantiate the hypothesis that the elevated levels of TGF-beta ligands and receptors present in keloids may support increased signaling and a potential role for TGF-beta in keloid pathogenesis.

Keloid-derived fibroblasts have a diminished capacity to produce prostaglandin E 2

Pathophysiologic Changes in a Patient with Early-Onset Extensive Keloid Disease and a 20-Year Follow-Up

Many autoimmune skin diseases, such as bullous pemphigoid (BP), psoriasis and certain types of chronic urticaria, are associated with intensive pruritus. While histamine and neuropeptides have previously been ascribed to play a role in itch that accompanies these diseases, recent evidence suggests that the pruritogenic cytokine interleukin (IL)-31 is a major driver of pruritic responses. IL-31 was originally shown to be produced by activated helper T cells, particularly Th2 cells, mast cells, macrophages and dendritic cells. However, more recent evidence demonstrated that eosinophils are a major source of this cytokine too, particularly in bullous pemphigoid. Basophils have also been shown to express the cytokine which, through autocrine action, strongly supports the production of other Th2-type cytokines from these cells. These investigations suggest that the dynamic recruitment of eosinophils and basophils in some autoimmune skin diseases could play an important role in the severity of IL-31-mediated itch. Furthermore, these studies suggest that IL-31, in addition to its pruritic actions, also has potential immunomodulatory roles in terms of supporting Th2-type immunity, which often underpins IgE-associated autoimmune diseases (such as bullous pemphigoid and urticaria) as well as allergies. While the role of IL-31 in psoriasis remains to be clarified, current evidence shows that this cytokine plays a major role in BP, chronic spontaneous urticaria and dermatomyositis. This suggests potential use of IL-31 receptor-blocking therapeutic approaches (e.g., Nemolizumab) for the treatment of IL-31-associated disorders.

Novel anti-arthritic drugs are often assessed in murine collagen-induced arthritis (CIA), which is a widely used pre-clinical model of rheumatoid arthritis. However, CIA studies are lengthy, development of arthritis is not synchronised and not all animals develop disease. Work conducted in this thesis addressed some of these issues by developing short-term mechanistic models of collagen II (CII) immunity. Drug effects on CII-induced hypersensitivity, anti-CII antibodies and ex vivo CII stimulated CD4+ T cell proliferation in mice 14 days post-CII sensitisation were assessed and compared to their anti-arthritic effect in CIA. As this thesis progressed, it was reported that IL-17 secreting CD4+ T helper (Th17) cells represent a population of cells distinct from interferon gamma (IFNγ) secreting Th1 and IL-4 secreting Th2 cells and may be involved in autoimmune disease. However, the role of IL-17 and Th17 cells in CIA and CII immunity was not defined. The role of IL-17 and its relationship with Th1 and Th2 cells was investigated in the CII stimulated CD4+ T cell assay. Results showed that CII specific Th1 and Th17, but not Th2 cells, are present in cultures of cells from CII sensitised mice. Addition of anti-IL-17 to these cultures increased the number of CII specific IFNγ secreting CD4+ T cells. Literature evidence suggests that IFNγ is protective in CIA. This increase in IFNγ may therefore represent a novel mechanism of action by which anti-IL-17 exerts some of its anti-arthritic activity. This thesis has shown that short-term models of CII immunity can predict anti-arthritic drug effects in CIA. A novel screening cascade has been proposed which could be used in drug discovery and may reduce the number of animals required for CIA studies. Moreover, the differential effect of anti-arthritic drugs in these models suggests they can discriminate between drugs and identify novel mechanisms of action.

HSV-1 infection of the cornea leads to a blinding immunoinflammatory lesion of the eye termed stromal keratitis (SK). Recently, IL-17-producing CD4(+) T cells (Th17 cells) were shown to play a prominent role in many autoimmune conditions, but the role of IL-17 and/or of Th17 cells in virus immunopathology is unclear. In this study, we show that, after HSV infection of the cornea, IL-17 is upregulated in a biphasic manner with an initial peak production around day 2 postinfection and a second wave starting from day 7 postinfection with a steady increase until day 21 postinfection, a time point when clinical lesions are fully evident. Further studies demonstrated that innate cells, particularly γδ T cells, were major producers of IL-17 early after HSV infection. However, during the clinical phase of SK, the predominant source of IL-17 was Th17 cells that infiltrated the cornea only after the entry of Th1 cells. By ex vivo stimulation, the half fraction of IFN-γ-producing CD4(+) T cells (Th1 cells) were HSV specific, whereas very few Th17 cells responded to HSV stimulation. The delayed influx of Th17 cells in the cornea was attributed to the local chemokine and cytokine milieu. Finally, HSV infection of IL-17R knockout mice as well as IL-17 neutralization in wild-type mice showed diminished SK severity. In conclusion, our results show that IL-17 and Th17 cells contribute to the pathogenesis of SK, the most common cause of infectious blindness in the Western world.