Interleukin-4 induces the activation and collagen production of cultured human intrahepatic fibroblasts via the STAT-6 pathway

Chronic liver fibrosis induction in aging causes significant ultra-structural deterioration in liver and alteration on immune response gene expressions in liver-spleen axis

The relationship between damage to the liver and spleen by aging and the immune response status in these two organs, which are anatomically and immunologically interconnected, is unknown. The authors investigated the histopathological, ultrastructural, and immunological effects of aging in young and aged fibrotic mice by using an experimental model. Four groups were planned, with 10 mice in each experimental group. The levels of fibrosis and ultrastructural destruction in the liver were determined by α-SMA staining and TEM analysis. Expression levels of immunity genes (Il2, Il4, Il6, Il10, Il12, Il17, Tnf, Ifng, Tgfb1, Gata3, Rorc, Tbx21, Foxp3, Ccl2, Ccr2, Cxcr3, Pf4, Cxcl10) were carried out by qRT-PCR. While structural disorders were detected in the mitochondria of aged healthy group, cellular destruction in the fibrosis-induced elderly group was at a dramatic level. Fibrosis induction in aged mice caused an elevation in the expression of chemokines (CCl2, CXCL10, CCR2) and cytokine (IL-17a) genes that induce autoinflammatory response in the liver. Unlike the cellular pathology and genes activated in fibrosis in youth and the natural occurrence of fibrosis with aging, induction of fibrosis during aging causes deterioration in the liver and expression of genes responsible for autoimmunity in both the liver and spleen.

Inflammation accelerating intestinal fibrosis: from mechanism to clinic

Intestinal fibrosis is a prevalent complication of IBD that that can frequently be triggered by prolonged inflammation. Fibrosis in the gut can cause a number of issues, which continue as an ongoing challenge to healthcare systems worldwide. The primary causes of intestinal fibrosis are soluble molecules, G protein-coupled receptors, epithelial-to-mesenchymal or endothelial-to-mesenchymal transition, and the gut microbiota. Fresh perspectives coming from in vivo and in vitro experimental models demonstrate that fibrogenic pathways might be different, at least to some extent, independent of the ones that influence inflammation. Understanding the distinctive procedures of intestinal fibrogenesis should provide a realistic foundation for targeting and blocking specific fibrogenic pathways, estimating the risk of fibrotic consequences, detecting early fibrotic alterations, and eventually allowing therapy development. Here, we first summarize the inflammatory and non-inflammatory components of fibrosis, and then we elaborate on the underlying mechanism associated with multiple cytokines in fibrosis, providing the framework for future clinical practice. Following that, we discuss the relationship between modernization and disease, as well as the shortcomings of current studies. We outline fibrosis diagnosis and therapy, as well as our recommendations for the future treatment of intestinal fibrosis. We anticipate that the global review will provides a wealth of fresh knowledge and suggestions for future fibrosis clinical practice.

Fibrosis in IBD: from pathogenesis to therapeutic targets

BACKGROUND

Intestinal fibrosis resulting in stricture formation and obstruction in Crohn's disease (CD) and increased wall stiffness leading to symptoms in ulcerative colitis (UC) is among the largest unmet needs in inflammatory bowel disease (IBD). Fibrosis is caused by a multifactorial and complex process involving immune and non-immune cells, their soluble mediators and exposure to luminal contents, such as microbiota and environmental factors. To date, no antifibrotic therapy is available. Some progress has been made in creating consensus definitions and measurements to quantify stricture morphology for clinical practice and trials, but approaches to determine the degree of fibrosis within a stricture are still lacking.

OBJECTIVE

We herein describe the current state of stricture pathogenesis, measuring tools and clinical trial endpoints development.

DESIGN

Data presented and discussed in this review derive from the past and recent literature and the authors' own research and experience.

RESULTS AND CONCLUSIONS

Significant progress has been made in better understanding the pathogenesis of fibrosis, but additional studies and preclinical developments are needed to define specific therapeutic targets.

Whole blood transcriptomics reveals granulocyte colony-stimulating factor as a mediator of cardiopulmonary bypass-induced systemic inflammatory response syndrome

Objectives

Systemic inflammatory response syndrome (SIRS) is a frequent complication of cardiopulmonary bypass (CPB). SIRS is associated with significant morbidity and mortality, but its pathogenesis remains incompletely understood, and as a result, biomarkers are lacking and treatment remains expectant and supportive. This study aimed to understand the pathophysiological mechanisms driving SIRS induced by CPB and identify novel therapeutic targets that might reduce systemic inflammation and improve patient outcomes.

Methods

Twenty-one patients undergoing cardiac surgery and CPB were recruited, and blood was sampled before, during and after surgery. SIRS was defined using the American College of Chest Physicians/Society of Critical Care Medicine criteria. We performed immune cell profiling and whole blood transcriptomics and measured individual mediators in plasma/serum to characterise SIRS induced by CPB.

Results

Nineteen patients fulfilled criteria for SIRS, with a mean duration of 2.7 days. Neutrophil numbers rose rapidly with CPB and remained elevated for at least 48 h afterwards. Transcriptional signatures associated with neutrophil activation and degranulation were enriched during CPB. We identified a network of cytokines governing these transcriptional changes, including granulocyte colony-stimulating factor (G-CSF), a regulator of neutrophil production and function.

Conclusions

We identified neutrophils and G-CSF as major regulators of CPB-induced systemic inflammation. Short-term targeting of G-CSF could provide a novel therapeutic strategy to limit neutrophil-mediated inflammation and tissue damage in SIRS induced by CPB.

Immunosuppressive tumor microenvironment and uterine fibroids: Role in collagen synthesis

Uterine fibroids (UF), also called uterine leiomyoma, is one of the most prevalent uterine tumors. UF represents a serious women's health global problem with a significant physical, emotional, and socioeconomic impact. Risk factors for UF include racial disparities, age, race, hormonal factors, obesity, and lifestyle (diet, physical activity, and stress. There are several biological contributors to UF pathogenesis such as cellular proliferation, angiogenesis, and extracellular matrix (ECM) accumulation. This review addresses tumor immune microenvironment as a novel mediator of ECM deposition. Polarization of immune microenvironment towards the immunosuppressive phenotype has been associated with ECM deposition. Immunosuppressive cells include M2 macrophage, myeloid-derived suppressor cells (MDSCs), and Th17 cells, and their secretomes include interleukin 4 (IL-4), IL-10, IL-13, IL-17, IL-22, arginase 1, and transforming growth factor-beta (TGF-β1). The change in the immune microenvironment not only increase tumor growth but also aids in collagen synthesis and ECM disposition, which is one of the main hallmarks of UF pathogenesis. This review invites further investigations on the change in the UF immune microenvironment as well as a novel targeting approach instead of the traditional UF hormonal and supportive treatment.

Expression of miR-21 &IL-4 in endometriosis

BACKGROUND

Endometriosis characterized with existence of endometrial-like tissue outside the uterus. Fibrosis of ectopic lesions is an important feature of endometriosis. IL-4 induces fibrosis via fibroblast proliferation, collagen production and myofibroblast differentiation. Increasing of miR-21 expression promotes fibroblast activation and fibrosis expansion. The aim of study was to evaluate the expression of miR-21 and its relationship with IL-4 gene expression in endometrial ectopic and eutopic tissues of endometriosis patients.

METHODS AND RESULTS

Ectopic and eutopic tissue samples were taken from 20 women with endometriosis, and control samples were taken from the endometrium of 20 endometriosis-free women. The relative expression of IL-4 and miR-21 evaluated by Real Time PCR. IL-4 relative gene expression was significantly increased in ectopic tissue compared to eutopic (p = 0.025) and control tissue (p = 0.021). The relative expression of miR-21 gene in ectopic tissue was increased compared to eutopic (p = 0.850) and control tissue (p = 0.978) but these differences were not significant. Also, the correlation between IL-4 and miR-21 relative gene expression was not significant (p = 0.083).

CONCLUSION

The increased expression of miR-21 in endometrium of women with endometriosis may upregulate the IL-4 gene expression and lead to fibrosis. Further studies may suggest miR-21 and IL-4 as candidates for diagnosis of endometriosis.

Dual function of fungi-derived cytokines in inflammatory bowel diseases: protection or inflammation

Inflammatory bowel disease (IBD) is an immune-mediated inflammatory condition involving both the innate and adaptive immune systems. Recently, the role of intestinal fungal flora and their downstream immune pathways has been highlighted in the pathogenesis of IBD. Cytokines as primary immune mediators require a delicate balance for maintaining intestinal homeostasis. Although most cytokines have a predictable role in either amplifying or attenuating inflammation in IBD, a few cytokines have shown a dual function in the inflammatory state of the intestine. Some of these dual-faced cytokines are also involved in mucosal anti-microbial defense pathways, particularly against intestinal fungal residents. Here, we reviewed the role of these cytokines in IBD pathogenesis to achieve a better understanding of the fungal interactions in the development of IBD.

Dose-Dependent Glucocorticoid Regulation of Transcription Factors in Vocal Fold Fibroblasts and Macrophages

OBJECTIVE

Variable outcomes of glucocorticoid (GC) therapy for laryngeal disease are putatively due to diverse interactions of the GC receptor (GR) with cell signaling pathways, limited consideration regarding concentration-dependent effects, and inconsistent selection of GCs. In the current study, we evaluated the concentration-dependent effects of three frequently administered GCs on transcription factors with an emphasis on the phosphorylation of GR at Ser203 and Ser211 regulating the nuclear translocation of GR. This study provides foundational data regarding the diverse functions of GCs to optimize therapeutic approaches.

STUDY DESIGN

In vitro.

METHODS

Human vocal fold fibroblasts and THP1-derived macrophages were treated with different concentrations of dexamethasone, methylprednisolone, and triamcinolone in combination with IFN-γ, TNF-α, or IL4. Phosphorylated STAT1, NF-κB family molecules, and phosphorylated STAT6 were analyzed by Western blotting. Ser211-phosphorylated GR (S211-pGR) levels relative to GAPDH and Ser203-phosphorylated GR (S203-pGR) were also analyzed.

RESULTS

GCs differentially altered phosphorylated STAT1 and NF-κB family molecules in different cell types under IFN-γ and TNF-α stimuli. GCs did not alter phosphorylated STAT6 in IL4-treated macrophages. The three GCs were nearly equivalent. A lower concentration of dexamethasone increased S211-pGR/GAPDH ratios relative to increased S211-pGR/S203-pGR ratios regardless of cell type and treatment.

CONCLUSION

The three GCs employed in two cell lines had nearly equivalent effects on transcription factor regulation. Relatively high levels of Ser203-phosphorylation at low GC concentrations may be related to concentration-dependent differential effects of GCs in the two cell lines.

LEVEL OF EVIDENCE

NA Laryngoscope, 133:2704-2711, 2023.

Immunomodulation for Tissue Repair and Regeneration

Various immune cells participate in repair and regeneration following tissue injury or damage, orchestrating tissue inflammation and regeneration processes. A deeper understanding of the immune system's involvement in tissue repair and regeneration is critical for the development of successful reparatory and regenerative strategies. Here we review recent technologies that facilitate cell-based and biomaterial-based modulation of the immune systems for tissue repair and regeneration. First, we summarize the roles of various types of immune cells in tissue repair. Second, we review the principle, examples, and limitations of regulatory T (Treg) cell-based therapy, a representative cell-based immunotherapy. Finally, we discuss biomaterial-based immunotherapy strategies that aim to modulate immune cells using various biomaterials for tissue repair and regeneration.

Glucocorticoid Dose Dependency on Gene Expression in Vocal Fold Fibroblasts and Macrophages

OBJECTIVE

Glucocorticoids (GCs) modulate multiple cellular activities including inflammatory and fibrotic responses. Outcomes of GC treatment for laryngeal disease vary, affording opportunity to optimize treatment. In the current study, three clinically employed GCs were evaluated to identify optimal in vitro concentrations at which GCs mediate favorable anti-inflammatory and fibrotic effects in multiple cell types. We hypothesize a therapeutic window will emerge as a foundation for optimized therapeutic strategies for patients with laryngeal disease.

STUDY DESIGN

In vitro.

METHODS

Human vocal fold fibroblasts and human macrophages derived from THP-1 monocytes were treated with 0.03-1000 nM dexamethasone, 0.3-10,000 nM methylprednisolone, and 0.3-10,000 nM triamcinolone in combination with interferon-γ, tumor necrosis factor-α, or interleukin-4. Real-time polymerase chain reaction was performed to analyze inflammatory (CXCL10, CXCl11, PTGS2, TNF, IL1B) and fibrotic (CCN2, LOX, TGM2) genes, and TSC22D3, a target gene of GC signaling. EC50 and IC50 to alter inflammatory and fibrotic gene expression was calculated.

RESULTS

Interferon-γ and tumor necrosis factor-α increased inflammatory gene expression in both cell types; this response was reduced by GCs. Interleukin-4 increased LOX and TGM2 expression in macrophages; this response was also reduced by GCs. GCs induced TSC22D3 and CCN2 expression independent of cytokine treatment. EC50 for each GC to upregulate CCN2 was higher than the IC50 to downregulate other genes.

CONCLUSION

Lower concentrations of GCs repressed inflammatory gene expression and only moderately induced genes involved in fibrosis. These data warrant consideration as a foundation for optimized clinical care paradigms to reduce inflammation and mitigate fibrosis.

LEVEL OF EVIDENCE

NA Laryngoscope, 133:1169-1175, 2023.

Cytokines Associated With Onset of a Hypertensive Phase and Surgical Failure After Ahmed Glaucoma Valve Implantation

PURPOSE

To investigate the relationship between cytokines of the aqueous humor or Tenon capsule, the onset of a hypertensive phase, and surgical failure in patients undergoing Ahmed Glaucoma Valve (AGV) implantation DESIGN: Prospective clinical cohort study.

METHODS

A total of 36 patients who underwent AGV implantation were included. Samples of aqueous humor and Tenon tissue were collected at the time of surgery. Multiple cytokines were evaluated in the samples using a bead-based multiplex cytokine assay. As for surgical outcomes, a hypertensive phase was defined as an intraocular pressure (IOP) of greater than 21 mm Hg within 3 months after surgery, whereas surgical failure was defined as an IOP greater than 21 mm Hg with maximum tolerable glaucoma medications during 2 consecutive visits.

RESULTS

Patients who entered a hypertensive phase showed higher transforming growth factor-β2 (TGF-β2) levels in the aqueous humor (P = .012). A longer axial length and higher TGF-β2 concentration of the aqueous humor were associated with higher maximum IOP values during 3 months after surgery per multiple regression analysis (P = .028 and P = .034). In the multiple logistic regression analysis, higher monocyte chemoattractant protein-1 (MCP-1) concentrations in the aqueous humor and higher interleukin-4 concentrations in Tenon tissue were related to surgical failure (P = .022 and P = .040).

CONCLUSIONS

Greater concentrations of TGF-β2 and MCP-1 were related to surgical outcome after glaucoma drainage device implantation. Further studies are needed to confirm that down-regulation of these cytokines could be helpful in improving surgical outcomes.

The Role of IL-13 and IL-4 in Adipose Tissue Fibrosis

White adipose tissue (WAT) fibrosis, characterized by an excess of extracellular (ECM) matrix components, is strongly associated with WAT inflammation and dysfunction due to obesity. Interleukin (IL)-13 and IL-4 were recently identified as critical mediators in the pathogenesis of fibrotic diseases. However, their role in WAT fibrosis is still ill-defined. We therefore established an ex vivo WAT organotypic culture system and demonstrated an upregulation of fibrosis-related genes and an increase of α-smooth muscle actin (αSMA) and fibronectin abundance upon dose-dependent stimulation with IL-13/IL-4. These fibrotic effects were lost in WAT lacking il4ra, which encodes for the underlying receptor controlling this process. Adipose tissue macrophages were found to play a key role in mediating IL-13/IL-4 effects in WAT fibrosis as their depletion through clodronate dramatically decreased the fibrotic phenotype. IL-4-induced WAT fibrosis was partly confirmed in mice injected intraperitoneally with IL-4. Furthermore, gene correlation analyses of human WAT samples revealed a strong positive correlation of fibrosis markers with IL-13/IL-4 receptors, whereas IL13 and IL4 correlations failed to confirm this association. In conclusion, IL-13 and IL-4 can induce WAT fibrosis ex vivo and partly in vivo, but their role in human WAT remains to be further elucidated.

Secretome from In Vitro Mechanically Loaded Myoblasts Induces Tenocyte Migration, Transition to a Fibroblastic Phenotype and Suppression of Collagen Production

It is known that mechanical loading of muscles increases the strength of healing tendon tissue, but the mechanism involved remains elusive. We hypothesized that the secretome from myoblasts in co-culture with tenocytes affects tenocyte migration, cell phenotype, and collagen (Col) production and that the effect is dependent on different types of mechanical loading of myoblasts. To test this, we used an in vitro indirect transwell co-culture system. Myoblasts were mechanically loaded using the FlexCell^® Tension system. Tenocyte cell migration, proliferation, apoptosis, collagen production, and several tenocyte markers were measured. The secretome from myoblasts decreased the Col I/III ratio and increased the expression of tenocyte specific markers as compared with tenocytes cultured alone. The secretome from statically loaded myoblasts significantly enhanced tenocyte migration and Col I/III ratio as compared with dynamic loading and controls. In addition, the secretome from statically loaded myoblasts induced tenocytes towards a myofibroblast-like phenotype. Taken together, these results demonstrate that the secretome from statically loaded myoblasts has a profound influence on tenocytes, affecting parameters that are related to the tendon healing process.

Novel mechanisms and clinical trial endpoints in intestinal fibrosis

The incidence of inflammatory bowel diseases (IBD) worldwide has resulted in a global public health challenge. Intestinal fibrosis leading to stricture formation and bowel obstruction is a frequent complication in Crohn's disease (CD), and the lack of anti-fibrotic therapies makes elucidation of fibrosis mechanisms a priority. Progress has shown that mesenchymal cells, cytokines, microbial products, and mesenteric adipocytes are jointly implicated in the pathogenesis of intestinal fibrosis. This recent information puts prevention or reversal of intestinal strictures within reach through innovative therapies validated by reliable clinical trial endpoints. Here, we review the role of immune and non-immune components of the pathogenesis of intestinal fibrosis, including new cell clusters, cytokine networks, host-microbiome interactions, creeping fat, and their translation for endpoint development in anti-fibrotic clinical trials.

Mechanosensitive Regulation of Fibrosis

Cells in the human body experience and integrate a wide variety of environmental cues. A growing interest in tissue mechanics in the past four decades has shown that the mechanical properties of tissue drive key biological processes and facilitate disease development. However, tissue stiffness is not only a potent behavioral cue, but also a product of cellular signaling activity. This review explores both roles of tissue stiffness in the context of inflammation and fibrosis, and the important molecular players driving such processes. During inflammation, proinflammatory cytokines upregulate tissue stiffness by increasing hydrostatic pressure, ECM deposition, and ECM remodeling. As the ECM stiffens, cells involved in the immune response employ intricate molecular sensors to probe and alter their mechanical environment, thereby facilitating immune cell recruitment and potentiating the fibrotic phenotype. This powerful feedforward loop raises numerous possibilities for drug development and warrants further investigation into the mechanisms specific to different fibrotic diseases.

Maternal high-fat diet activates hepatic interleukin-4 in rat male offspring accompanied by increased eosinophil infiltration

Interleukin-4 (IL-4) is activated as an immune response during infection or tissue injury. Epigenetic programming of maternal high-fat (HF) diet has long-term effects in the offspring. In the present study, we investigated the epigenetic regulation of IL-4 in a maternal HF diet model in the liver of adult offspring. Timed-pregnant Sprague-Dawley rats were fed either control (C) or HF diet throughout gestation and lactation. Offspring were placed on a control diet after weaning, generating C/C and HF/C groups. The liver was collected at 12 wk of age, followed by histological and molecular analysis to investigate the maternal programming effects on IL-4 by HF diet. Maternal HF diet significantly induced mRNA expression and protein level of IL-4 and promoted hypomethylation of Il4 compared with the control group. Methylation-selective PCR (MSP) confirmed that maternal HF diet increased RNA polymerase II, acetylation of histone H4, and dimethylation of histone 3 lysine 4 at the +6 kb region of Il4. Moreover, the rat eosinophil marker Siglec-F was increased and colocalized with IL-4 in the liver. In conclusion, our study indicated that IL-4 was increased in liver cells in response to maternal HF diet. This coincides with DNA hypomethylation in combination with chromatin remodeling at the +6 kb region of the 3' downstream region as well as an induced immune cell infiltration, especially eosinophil infiltration, in the liver of offspring.NEW & NOTEWORTHY The present study identifies that maternal high-fat-diet-induced IL-4 upregulation is associated with DNA hypomethylation at the +6 kb region of the 3' downstream region of the gene. Furthermore, our results confirm that the induced Il4 expression in the liver of male offspring corresponds to the induced immune cell, especially eosinophil, infiltration.

Exogenous IL-4 shuts off pro-inflammation in neutrophils while stimulating anti-inflammation in macrophages to induce neutrophil phagocytosis following myocardial infarction

INTRODUCTION

Macrophages and neutrophils are primary leukocytes involved in the inflammatory response to myocardial infarction (MI). While interleukin (IL)-4 is an in vitro anti-inflammatory stimulus, the MI myocardium does not express a considerable amount of IL-4 but does express IL4 receptors. We hypothesized that continuous exogenous IL-4 infusion starting 24 h after MI would promote a polarization switch in inflammatory cells towards a reparative phenotype.

METHODS

C57BL/6J male mice (3-6 months of age) were subcutaneously infused with either saline (n = 17) or IL-4 (20 ng/g/day; n = 17) beginning 24 h after MI and evaluated at MI day 3.

RESULTS

Macrophages and neutrophils were isolated ex vivo from the infarct region and examined. Exogenous IL-4 decreased pro-inflammatory Ccl3, Il12a, Tnfa, and Tgfb1 in neutrophils and increased anti-inflammatory Arg1 and Ym1 in macrophages (all p < .05). Tissue clearance by IL-4 treated neutrophils was not different, while selective phagocytosis of neutrophils doubled in IL-4 treated macrophages (p < .05). Of 24,339 genes examined by RNA-sequencing, 2042 genes were differentially expressed in macrophages from IL-4 stimulated infarct (all FDR p < .05). Pdgfc gene expression was ranked first, increasing 3-fold in macrophages stimulated with IL-4 (p = 1 × 10-9). Importantly, changes in macrophage physiology and transcriptome occurred in the absence of global LV effects. Bone marrow derived monocytes stimulated with mouse recombinant PDGF-CC protein (10 μg/ml) or PDGF-CC blocking antibody (200 ng/ml) did not change Arg1 or Ym1 expression, indicating the in vivo effect of IL-4 to stimulate macrophage anti-inflammatory gene expression was independent of PDGF-CC.

CONCLUSIONS

Our results indicate that exogenous IL-4 promotes inflammation resolution by turning off pro-inflammation in neutrophils while stimulating anti-inflammation in macrophages to mediate removal of apoptotic neutrophils.

The role of cytokine and immune responses in intestinal fibrosis

The rapidly increasing incidence of inflammatory bowel disease (IBD) in South America, eastern Europe, Asia, and Africa has resulted in a global public health challenge. Intestinal fibrosis is a common complication in patients with long-term IBD, which may develop into stenosis and subsequent obstruction. Hitherto, the origin of IBD is unclear and several factors may be involved, including genetic, immune, environmental and microbial influences. Little is known about how the recurrent inflammation in patients with IBD develops into intestinal fibrosis and currently, there is no suitable treatment to reverse intestinal fibrosis in these patients. Here, we review the role of immune components in the pathogenesis of IBD and intestinal fibrosis, including cytokine networks, host-microbiome interactions, and immune cell trafficking.

Cryptic collagen elements as signaling hubs in the regulation of tumor growth and metastasis

Structural remodeling of the extracellular matrix is a well-established process associated with tumor growth and metastasis. Tumor and stromal cells that compose the tumor mass function cooperatively to promote the malignant phenotype in part by physically interacting with intact and structurally altered matrix proteins. To this end, collagen represents the most abundant component of the extracellular matrix and is known to control the behavior of histologically distinct tumor types as well as a diversity of stromal cells. Although a significant molecular understanding has been established concerning how cellular interactions with intact collagen govern signaling pathways that control tumor progression, considerably less is known concerning how interactions with cryptic or hidden regions within remodeled collagen may selectively alter signaling cascades, or whether inhibition of these cryptic signaling pathways may represent clinically effective therapeutic strategies. Here, we review the emerging evidence concerning the possible mechanisms for the selective generation of cryptic or hidden elements within collagen and their potential cell surface receptors that may facilitate signal transduction. We discuss the concept that cellular communication links between cell surface receptors and these cryptic collagen elements may serve as functional signaling hubs that coordinate multiple signaling pathways operating within both tumor and stromal cells. Finally, we provide examples to help illustrate the possibility that direct targeting of these unique cryptic signaling hubs may lead to the development of more effective therapeutic strategies to control tumor growth and metastasis.

Current Approaches Targeting the Wound Healing Phases to Attenuate Fibrosis and Scarring

Cutaneous fibrosis results from suboptimal wound healing following significant tissue injury such as severe burns, trauma, and major surgeries. Pathologic skin fibrosis results in scars that are disfiguring, limit normal movement, and prevent patient recovery and reintegration into society. While various therapeutic strategies have been used to accelerate wound healing and decrease the incidence of scarring, recent studies have targeted the molecular regulators of each phase of wound healing, including the inflammatory, proliferative, and remodeling phases. Here, we reviewed the most recent literature elucidating molecular pathways that can be targeted to reduce fibrosis with a particular focus on post-burn scarring. Current research targeting inflammatory mediators, the epithelial to mesenchymal transition, and regulators of myofibroblast differentiation shows promising results. However, a multimodal approach addressing all three phases of wound healing may provide the best therapeutic outcome.

The in vivo effect of Lacto-N-neotetraose (LNnT) on the expression of type 2 immune response involved genes in the wound healing process

Lacto-n-neotatraose (LNnT) oligosaccharide shows properties such as anti-inflammatory, type 2 immune response induction, induced angiogenesis, and anti-bacterial effects. Here, we hypothesized that the application of LnNT in the skin full-thickness wound can accelerate the healing process through its anti-inflammatory effect as well as induction of type 2 immune responses. In this study, we evaluated the cell viability of fibroblasts in the presence of LNnT. The full-thickness wound model was created by punch biopsy. The mice were treated intradermaly with LNnT at the concentrations of 100 and 200 µg or PBS as a control group. The wounds samples were compared based on the macroscopic and histological evaluations. The amount of collagen deposition and expression of genes involved in type 2 immunity were measured by the hydroxyproline assay and real time PCR method, respectively. Our results showed that LNnT had no negative effect on the cell viability of fibroblasts. LNnT increased the wound closure rate on day 7 post-wounding. H&E stain analysis revealed that mice treated with 200 µg LNnT exhibited better healing score, follicle formation, and lower epidermal thickness index. The mice treated with LNnT exhibited a lower collagen deposition on day 21 and higher collagen content on days 7 and 14 post-treatment. The LNnT groups also exhibited a lower number of neutrophils and a higher number of basal cells and fibroblasts. The expression rate of IL-10, IL-4, and IL-13 was higher in the LNnT groups. These results showed the high potential of LNnT for use in treatment of full-thickness wounds.

Targeting interleukin 4 receptor α: A new approach to the treatment of cutaneous autoimmune bullous diseases?

Bullous pemphigoid, mucous membrane pemphigoid, and pemphigus vulgaris are different cutaneous autoimmune blistering diseases, with complex pathogenic mechanisms. In all of them, a type-2 response is thought to have a central role. Interleukin 4 and Interleukin 13 are crucial cytokines in type-2 response. Treatment of these conditions is often challenging. Dupilumab, a recombinant fully human IgG4 monoclonal antibody with binding specificity to human interleukin-4 receptor IL-4Rα, has the potential to inhibit both IL-4 and IL-13. We propose IL-4Rα as a theoretical drug target for cutaneous autoimmune bullous diseases.

Hepatitis C Virus Improves Human Tregs Suppressive Function and Promotes Their Recruitment to the Liver

Background: The role of regulatory T cells (Tregs) is now well established in the progression of hepatocellular carcinoma (HCC) linked to Hepatitis C virus (HCV) infection. However, nothing is known about the potential interplay between Tregs and HCV. In this pilot study, we have investigated the ability of Tregs to hang HCV on and the subsequent effect on their suppressive function and phenotype. Moreover, we have evaluated how HCV could promote the recruitment of Tregs by infected primary human hepatocytes. Methods: Tregs of healthy donors were incubated with JFH-1/HCVcc. Viral inoculation was assessed using adapted assays (RT-qPCR, Flow Citometry (FACS) and Western Blot (WB). Expression of Tregs phenotypic (CD4, CD25, CD127 and Foxp3) and functional (IL-10, GZMB, TGF-β1 and IL-2) markers was monitored by RT-qPCR, FACS and ELISA. Suppressive activity was validated by suppressive assays. Tregs recruitment by infected primary hepatic cells was evaluated using Boyden Chamber. Results: Tregs express the classical HCV receptors (CD81, CLDN1 and LDLR) and some co-receptors (CD5). HCV inoculation significantly increases the suppressive phenotype and activity of Tregs, and raises their anergy by inducing an unexpected IL-2 production. Moreover, HCV infection induces the expression of chemokines (CCL17, CXCL16, and CCL20) by primary hepatic human hepatocytes and chemokine receptors (CCR4, CXCR6 and CCR6) by Tregs. Finally, infected hepatocytes have a significantly higher potential to recruit Tregs in a seemingly CCL20-dependent manner. Conclusions: Direct interaction between HCV and Tregs represents a newly defined mechanism that could potentiate HCV immune evasion and favor intratumoral recruitment contributing to HCC progression.

B cell depletion treatment decreases CD4+IL4+ and CD4+CD40L+ T cells in patients with systemic sclerosis

Recent data suggests that rituximab may favorably affect skin fibrosis and lung function in patients with systemic sclerosis. Based on experimental data suggesting a key role of B and T cells in scleroderma we aimed to explore the effect(s) of rituximab treatment on T cell subpopulations. Fifteen patients with scleroderma who received rituximab treatment and six who received standard treatment alone were recruited. Peripheral CD4+IL4+, CD4+INFγ+, CD4+IL17+ and CD4+CD40L+ T cells were assessed using flow cytometry. Using ELISA, serum levels of IL4 were assessed. Skin CD4+IL4+ T cells were assessed with confocal microscopy from skin biopsies. Following rituximab treatment skin CD4+IL4+ T cells obviously decreased as seen with confocal microscopy. Moreover, peripheral CD4+IL4+ T cells decreased significantly compared to those from patients who received standard treatment alone: median (IQR): 14.9 (22.63-12.88) vs 7.87 (12.81-4.9)%, p = 0.005 and 9.43 (19.53-7.50)% vs 14.86 (21.96-6.75)%, p = NS at baseline and 6 months later respectively, whereas there was no difference in serum IL4 levels. Peripheral CD4+CD40L+ T cells also decreased significantly following rituximab treatment compared to those from patients who received standard treatment alone: median (IQR): 17.78 (25.64-14.44)% vs 8.15 (22.85-3.08)%, p = 0.04 and 22.13 (58.77-8.20)% vs 72.11 (73.05-20.45)%, p = NS at baseline and 6 months later respectively. Furthermore, peripheral CD4+INFγ+ and CD4+IL17+ T cells revealed no differences following rituximab treatment. Our study demonstrates a link between rituximab treatment and CD4+IL4+ T cell decrease both in the skin and peripheral blood of patients with SSc.

Unraveling the ECM-Immune Cell Crosstalk in Skin Diseases

The extracellular matrix (ECM) is a complex network of proteins and proteoglycans secreted by keratinocytes, fibroblasts and immune cells. The function of the skin ECM has expanded from being a scaffold that provides structural integrity, to a more dynamic entity that is constantly remodeled to maintain tissue homeostasis. The ECM functions as ligands for cell surface receptors such as integrins, dystroglycans, and toll-like receptors (TLRs) and regulate cellular signaling and immune cell dynamics. The ECM also acts as a sink for growth factors and cytokines, providing critical cues during epithelial morphogenesis. Dysregulation in the organization and deposition of ECMs lead to a plethora of pathophysiological conditions that are exacerbated by aberrant ECM-immune cell interactions. In this review, we focus on the interplay between ECM and immune cells in the context of skin diseases and also discuss state of the art therapies that target the key molecular players involved.

Elevated interleukin-4 levels predicted advanced fibrosis in chronic hepatitis C

BACKGROUND

Cytokine imbalance has been associated with chronic hepatitis C virus (HCV) infection. We hypothesized that cytokines have an important role in fibrosis development in HCV infection.

METHODS

Data of 92 patients were analyzed retrospectively. Fluorescent Bead immunoassay was used to measure the following serum cytokine levels: Interferon γ, tumor necrosis factor α, interleukin (IL)-1β, IL-2, IL-4, IL-5, IL-6, IL-8, IL-10, and IL-12. Various statistical analyses were used as appropriate.

RESULTS

Of the 92 HCV-infected patients, 49 (53.3%) were male, 23 (25%) patients had advanced (fibrosis grades 3-4) fibrosis, and the mean age of the study population was 51.9 ± 9.4 years. Elevation of baseline IL-4 level (>490 pg/mL) was associated with liver fibrosis grade by χ test (odds ratio [OR] = 2.99; 95%, CI = 1.02-8.78; p = 0.042) and multivariate logistic regression (OR = 4.26; 95% CI = 1.13-16.02; p = 0.032). Also, IL-4 had strong diagnostic value in advanced liver fibrosis by using area under receiver operating characteristics curve analysis. Assessment of fibrosis score was consequently developed from our findings and compared with other noninvasive serum markers to assess liver fibrosis.

CONCLUSION

This study provides evidence that increased IL-4 expression predicted advanced liver fibrosis in treatment of naive HCV-infected patients. The newly developed "FIL4" score had good predictive value for advanced fibrosis before treatment and this value was even strong in HCV-genotype 1b patients.

IL-33/ST2 Axis in Organ Fibrosis

Interleukin 33 (IL-33) is highly expressed in barrier sites, acting via the suppression of tumorigenicity 2 receptor (ST2). IL-33/ST2 axis has long been known to play a pivotal role in immunity and cell homeostasis by promoting wound healing and tissue repair. However, it is also involved in the loss of balance between extensive inflammation and tissue regeneration lead to remodeling, the hallmark of fibrosis. The aim of the current review is to critically evaluate the available evidence regarding the role of the IL-33/ST2 axis in organ fibrosis. The role of the axis in tissue remodeling is better understood considering its crucial role reported in organ development and regeneration. Generally, the IL-33/ST2 signaling pathway has mainly anti-inflammatory/anti-proliferative effects; however, chronic tissue injury is responsible for pro-fibrogenetic responses. Regarding pulmonary fibrosis mature IL-33 enhances pro-fibrogenic type 2 cytokine production in an ST2- and macrophage-dependent manner, while full-length IL-33 is also implicated in the pulmonary fibrotic process in an ST2-independent, Th2-independent fashion. In liver fibrosis, evidence indicate that when acute and massive liver damage occurs, the release of IL-33 might act as an activator of tissue-protective mechanisms, while in cases of chronic injury IL-33 plays the role of a hepatic fibrotic factor. IL-33 signaling has also been involved in the pathogenesis of acute and chronic pancreatitis. Moreover, IL-33 could be used as an early marker for ulcer-associated activated fibroblasts and myofibroblast trans-differentiation; thus one cannot rule out its potential role in inflammatory bowel disease-associated fibrosis. Similarly, the upregulation of the IL-33/ST2 axismay contribute to tubular cell injury and fibrosis via epithelial to mesenchymal transition (EMT) of various cell types in the kidneys. Of note, IL-33 exerts a cardioprotective role via ST2 signaling, while soluble ST2 has been demonstrated as a marker of myocardial fibrosis. Finally, IL-33 is a crucial cytokine in skin pathology responsible for abnormal fibroblast proliferation, leukocyte infiltration and morphologic differentiation of human endothelial cells. Overall, emerging data support a novel contribution of the IL-33/ST2 pathway in tissue fibrosis and highlight the significant role of the Th2 pattern of immune response in the pathophysiology of organ fibrosis.

M2 macrophage-mediated interleukin-4 signalling induces myofibroblast phenotype during the progression of benign prostatic hyperplasia

Benign prostatic hyperplasia (BPH) is a progressive disease in elderly men, but potential factors accelerating its progression remain largely unknown. The aim of this study was to elucidate the factors affecting BPH progression by understanding the complex mechanisms causing early- progressed BPH, which progresses rapidly and requires surgical intervention before the age of 50. Three groups of human prostate tissue samples, from patients with early-progressed BPH, age-matched prostate and elderly BPH tissues, were collected (n = 25 each). We compared these tissues to determine the histologic features and molecular mechanisms underlying BPH progression. We found that early-progressed BPH samples were characterised by aberrant stromal hyper-proliferation, collagen deposition and increased M2 macrophage infiltration, compared to those from age-matched prostate and elderly BPH tissues. The M2 macrophage–fibroblast co-culture system demonstrated that the myofibroblast phenotypes were strongly induced only in fibroblasts from the early-progressed BPH samples, while the co-cultured M2 macrophages expressed high levels of pro-fibrotic cytokines, such as IL4 and TGFβ1. M2 macrophage-derived IL4, but not TGFβ1, selectively induced the myofibroblast phenotype through the JAK/STAT6, PI3K/AKT and MAPK/ERK signalling pathways in the early-progressed BPH prostate fibroblasts. Taken together, our results indicate that induction of the myofibroblast phenotype may lead to BPH progression through M2 macrophage-mediated IL4 signalling, and that IL4 may represent a potential therapeutic target, allowing the prevention of M2 macrophage activation and fibroblast-to-myofibroblast differentiation.

Scleroderma keratinocytes promote fibroblast activation independent of transforming growth factor beta

Objectives

SSc is a devastating disease that results in fibrosis of the skin and other organs. Fibroblasts are a key driver of the fibrotic process through deposition of extracellular matrix. The mechanisms by which fibroblasts are induced to become pro-fibrotic remain unclear. Thus, we examined the ability of SSc keratinocytes to promote fibroblast activation and the source of this effect.

Methods

Keratinocytes were isolated from skin biopsies of 9 lcSSc, 10 dcSSc and 13 control patients. Conditioned media was saved from the cultures. Normal fresh primary fibroblasts were exposed to healthy control and SSc keratinocyte conditioned media in the presence or absence of neutralizing antibodies for TGF-β. Gene expression was assessed by microarrays and real-time PCR. Immunocytochemistry was performed for α-smooth muscle actin (α-SMA), collagen type 1 (COL1A1) and CCL5 expression.

Results

SSc keratinocyte conditioned media promoted fibroblast activation, characterized by increased α-SMA and COL1A1 mRNA and protein expression. This effect was independent of TGF-β. Microarray analysis identified upregulation of nuclear factor κB (NF-κB) and downregulation of peroxisome proliferator-activated receptor γ (PPAR-γ) pathways in both SSc subtypes. Scleroderma keratinocytes exhibited increased expression of NF-κB-regulated cytokines and chemokines and lesional skin staining confirmed upregulation of CCL5 in basal keratinocytes.

Conclusion

Scleroderma keratinocytes promote the activation of fibroblasts in a TGF-β-independent manner and demonstrate an imbalance in NF-κB1 and PPAR-γ expression leading to increased cytokine and CCL5 production. Further study of keratinocyte mediators of fibrosis, including CCL5, may provide novel targets for skin fibrosis therapy.

Influence of the anti-inflammatory cytokine interleukin-4 on human joint capsule myofibroblasts

Post-traumatic joint contracture was reported to be associated with elevated numbers of contractile myofibroblasts (MFs) in the healing capsule. During the physiological healing process, the number of MFs declines; however, in fibroconnective disorders, MFs persist. The manifold interaction of the cytokines regulating the appearance and persistence of MFs in the pathogenesis of joint contracture remains to be elucidated. The objective of our current study was to analyze the impact of the anti-inflammatory cytokine interleukin (IL)-4 on functional behavior of MFs. Cells were isolated from human joint capsule specimens and challenged with three different concentrations of IL-4 with or without its neutralizing antibody. MF viability, contractile properties, and the gene expression of both alpha-smooth muscle actin (α-SMA) and collagen type I were examined. Immunofluorescence staining revealed the presence of IL-4 receptor (R)-alpha (α) on the membrane of cultured MFs. The cytokine IL-4 promoted MF viability and enhanced MF modulated contraction of collagen gels. Moreover, IL-4 intervened in gene expression by up-regulation of α-SMA and collagen type I mRNA. These effects could be specifically lowered by the neutralizing IL-4 antibody. On the basis of our findings we conclude that the anti-inflammatory cytokine IL-4 specifically regulates viability and the contractile properties of MFs via up-regulating the gene expression of α-SMA and collagen type I. IL-4 may be a helpful target in developing anti-fibrotic therapeutics for post-traumatic joint contracture in human. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1290-1298, 2017.

Stromal and immune cells in gut fibrosis: the myofibroblast and the scarface

Post-inflammatory scarring is the end-result of excessive extracellular matrix (ECM) accumulation and tissue architectural destruction. It represents a failure to effectively remodel ECM and achieve proper reinstitution and healing during chronic relapsing inflammatory processes. Scarring may affect the functionality of any organ, and in the case of inflammatory bowel disease (IBD)-associated fibrosis leads to stricture formation and often surgery to remove the affected bowel. The activated myofibroblast is the final effector cell that overproduces ECM under the influence of various mediators generated by an intense interplay of classic and non-classic immune cells. This review focuses on how proinflammatory mediators from various sources produced in different stages of intestinal inflammation can form profibrotic pathways that eventually lead to tissue scarring through sustained activation of myofibroblasts.

Increased circulating IL-9-producing CD8+ T cells are associated with eosinophilia and high FeNO in allergic asthmatics

Allergic asthma is a chronic airway disorder mediated by Th2 cells. It has been shown that IL-9-producing CD8⁺ cytotoxic T (Tc9) cells promote the subsequent onset of allergic airway inflammation in mice mediated by abnormal Th2 immunity. Whether Tc9 cells are associated with the immunopathogenesis of asthmatic patients remains unknown. In the present study, peripheral blood mononuclear cells (PBMCs) were separated by Ficoll-Hypaque gradient centrifugation from all subjects. The frequency of Tc9 cells was measured by flow cytometry. Serum IL-9 levels were assessed by enzyme-linked immunosorbent assay (ELISA). mRNA expression levels of IL-9, STAT6, and IRF4 in PBMCs from healthy controls and asthmatic patients were detected by reverse transcription-quantitative polymerase chain reaction. The results showed that the numbers of Tc9 cells in allergic asthmatics were significantly increased, compared with healthy controls (P<0.0001). Notably, IL-9 protein and mRNA levels were increased in allergic asthmatics and STAT6 and IRF4 mRNA levels were elevated, as compared with healthy controls. In addition, circulating numbers of Tc9 cells were positively correlated with blood eosinophil counts and fractioned exhaled nitric oxide (FeNO) levels in asthmatic patients. Moreover, the number of Tc9 cells and serum IL-9 levels in asthmatic patients were significantly decreased after treatment with glucocorticoids (P<0.05). These findings suggest that increased circulating Tc9 cells are associated with eosinophilia and high FeNO of allergic asthma, and that abnormal Tc9 immunity may contribute to the pathogenesis of allergic asthmatics.

Development of an in vitro model to test antifibrotic drugs on primary human liver myofibroblasts

We have developed a culture model to assess antifibrotic drugs using normal human liver myofibroblasts (HLMFs) obtained from 31 subjects. Activation was evaluated in terms of α-smooth muscle actin (α-SMA) and collagen 1 (Coll1) expression using RT-PCR, and proliferation as the uptake of 5-ethynil-2'-deoxyuridine. Under analysis of variance, between-subject differences accounted for 70% of all variability and inter-experiment differences for 30%. The sensitivity of the model was determined by quantifying the effects in terms of relative expression, which were 0.74±0.03 for cyclosporine A (CsA) and 2.4±0.10 for transforming growth factor-beta (TGF-β) (P<0.0001 vs no treatment) for α-SMA expression. Inter-subject variations in α-SMA and Coll1 expression enabled the classification of subjects as potentially low or high fibrosers. Finally, we observed that pirfenidone (which has beneficial effects in vivo) significantly reduced the expressions of α-SMA and Coll1, whereas the angiotensin-converting enzyme inhibitor losartan (which has no effect in vivo) had no significant effect. Our model may thus detect the antifibrotic properties of drugs. Antifibrotic drugs with promising clinical relevance could possibly be selected using a bank of HLMFs from high fibrosers.

Cytokine and anti-cytokine therapies in prevention or treatment of fibrosis in IBD

The frequency of fibrosing Crohn's disease (CD) is significant, with approximately 40% of CD patients with ileal disease developing clinically apparent strictures throughout their lifetime. Although strictures may be subdivided into fibrotic, inflammatory, or mixed forms, despite immunosuppressive therapy in CD patients in the form of steroids or immunomodulators, the frequency of fibrostenosing complications has still remained significant. A vast number of genetic and epigenetic variables are thought to contribute to fibrostenosing disease, including those that affect cytokine biology, and therefore highlight the complexity of disease, but also shed light on targetable pathways. Exclusively targeting fibrosis may be difficult, however, because of the relatively slow evolution of fibrosis in CD, and the potential adverse effects of inhibiting pathways involved in tissue repair and mucosal healing. Acknowledging these caveats, cytokine-targeted therapy has become the mainstay of treatment for many inflammatory conditions and is being evaluated for fibrotic disorders. The question of whether anti-cytokine therapy will prove useful for intestinal fibrosis is, therefore, acutely relevant. This review will highlight some of the current therapeutics targeting cytokines involved in fibrosis.

RAGE and TGF-β1 Cross-Talk Regulate Extracellular Matrix Turnover and Cytokine Synthesis in AGEs Exposed Fibroblast Cells

AGEs accumulation in the skin affects extracellular matrix (ECM) turnover and triggers diabetes associated skin conditions and accelerated skin aging. The receptor of AGEs (RAGE) has an essential contribution to cellular dysfunction driven by chronic inflammatory responses while TGF-β1 is critical in both dermal homeostasis and inflammation. We investigated the contribution of RAGE and TGF-β1 to the modulation of inflammatory response and ECM turnover in AGEs milieu, using a normal fibroblast cell line. RAGE, TGF-β1, collagen I and III gene and protein expression were upregulated after exposure to AGEs-BSA, and MMP-2 was activated. AGEs-RAGE was pivotal in NF-κB dependent collagen I expression and joined with TGF-β1 to stimulate collagen III expression, probably via ERK1/2 signaling. AGEs-RAGE axis induced upregulation of TGF-β1, TNF-α and IL-8 cytokines. TNF-α and IL-8 were subjected to TGF-β1 negative regulation. RAGE’s proinflammatory signaling also antagonized AGEs-TGF-β1 induced fibroblast contraction, suggesting the existence of an inhibitory cross-talk mechanism between TGF-β1 and RAGE signaling. RAGE and TGF-β1 stimulated anti-inflammatory cytokines IL-2 and IL-4 expression. GM-CSF and IL-6 expression appeared to be dependent only on TGF-β1 signaling. Our data also indicated that IFN-γ upregulated in AGEs-BSA milieu in a RAGE and TGF-β1 independent mechanism. Our findings raise the possibility that RAGE and TGF-β1 are both involved in fibrosis development in a complex cross-talk mechanism, while also acting on their own individual targets. This study contributes to the understanding of impaired wound healing associated with diabetes complications.

Infection of Human Liver Myofibroblasts by Hepatitis C Virus: A Direct Mechanism of Liver Fibrosis in Hepatitis C

Background

Chronic hepatitis C is a major cause of liver fibrosis and cirrhosis. It is generally accepted that inflammation that occurs in response to hepatocyte infection by the hepatitis C virus (HCV) is the main mechanism that triggers myofibroblast differentiation and stimulation in chronic hepatitis C. The aim of this study was to determine if HCV might infect human liver myofibroblasts (HLMF) and directly stimulate their fibrogenic activities.

Methods

We evaluated the expression of the viral entry receptors, levels of HCV-RNA and HCV-protein and the expression of fibrosis markers in HLMF by using quantitative PCR, western blot and immunofluorescence analyses. Pseudoparticles (HCVpp) and cell culture–derived HCV (HCVcc) were used to study the ability of HLMF to support viral entry, replication and fibrosis induction.

Results

We showed that HLMF expressed all known molecules of the HCV receptor complex, i.e. CD81, LDL-R, scavenger receptor-BI, claudin-1 and occludin. These cells were also permissive to HCVpp entry. Inoculation with HCVcc caused short-term infection of these cells, as shown by their content in positive- and negative-strand HCV RNA, in core and NS3 viral proteins, and by their release of core protein levels in the culture supernatants. HCV infection stimulated myofibroblastic differentiation, proliferation and collagen production in these cells. In addition, evidence of in vivo infection was provided by the detection of positive- and negative-strand HCV RNA in preparations of HLMF obtained from HCV-infected patients.

Conclusion

These findings indicate that HCV infection of HLMF can occur and trigger extracellular matrix overproduction, thereby contributing to the development of HCV-related liver fibrosis.

Profibrotic Role for Interleukin-4 in Cardiac Remodeling and Dysfunction

Elevated interleukin-4 (IL-4) levels are associated with cardiac fibrosis in hypertension and heart failure in both patients and experimental animals. We hypothesized that chronically elevated IL-4 induces cardiac fibrosis, resulting in a predisposition of the heart to angiotensin II-induced damage. Wild-type Balb/c (WT, high circulating IL-4) and IL-4-deficient Balb/c mice (IL-4(-/-)) were used. WT mice exhibited cardiac fibrosis (evidenced by an increase in expression of procollagen genes/interstitial collagen fraction), enlarged left ventricle chamber, and declined cardiac function associated with a greater number of mast cells and macrophages in the heart compared with IL-4(-/-). In contrast, IL-4(-/-) mice had normal cardiac architecture/function while showing a 57.9% reduction in heart interstitial collagen compared with WT, despite elevated proinflammatory cytokines in heart tissue. In response to angiotensin II administration, IL-4(-/-) had reduced interstitial myocardial fibrosis and were protected from developing dilated cardiomyopathy, which was seen in WT mice. This was associated with increased macrophage infiltration into the hearts of WT mice, despite a similar degree of hypertension and increased cardiac transforming growth factor-β1 in both groups. In vitro data demonstrated that IL-4 upregulates procollagen genes and stimulates collagen production in mouse cardiac fibroblasts. This process is mediated by signal transducer and activator of transcription 6 signaling pathway via IL-4 receptor alpha. This study not only establishes a causal relationship between IL-4 and cardiac fibrosis/dysfunction, but also reveals a critical role for IL-4 in angiotensin II-induced cardiac damage. IL-4 could serve as an additional target for the treatment of cardiac fibrosis.

Role of anti-inflammatory cytokines IL-4 and IL-13 in systemic sclerosis

OBJECTIVE

The aim of this paper is to review the anti-inflammatory cytokines IL-4 and IL-13 and their receptor signals; we discuss new insight into their possible roles in systemic sclerosis (SSc) and their overlapping function in SSc.

INTRODUCTION

SSc is a connective tissue disease characterized by fibrosis. The exact etiology of SSc is unknown, and no therapy has been proved effective in modifying its course. Recently the roles of IL-4 and IL-13 in the development of SSc have been extensively considered. The possible roles of IL-4 and IL-13, especially their overlapping function, in SSc are not well documented.

METHODS

A literature survey was performed using a PubMed database search to gather complete information regarding IL-4 and IL-13 and their role in inflammation.

RESULTS AND CONCLUSIONS

The participation of complex pathways of IL-4 and IL-13 in the process of inflammation and fibrosis action in SSc is still not very clear, and some pathogenesis of regulation found in vitro needs to be further proved. There is still more work which could be done to achieve useful developments with therapeutic benefit in SSc.

Vitamin a deficiency and alterations in the extracellular matrix

Vitamin A or retinol which is the natural precursor of several biologically active metabolites can be considered the most multifunctional vitamin in mammals. Its deficiency is currently, along with protein malnutrition, the most serious and common nutritional disorder worldwide. It is necessary for normal embryonic development and postnatal tissue homeostasis, and exerts important effects on cell proliferation, differentiation and apoptosis. These actions are produced mainly by regulating the expression of a variety of proteins through transcriptional and non-transcriptional mechanisms. Extracellular matrix proteins are among those whose synthesis is known to be modulated by vitamin A. Retinoic acid, the main biologically active form of vitamin A, influences the expression of collagens, laminins, entactin, fibronectin, elastin and proteoglycans, which are the major components of the extracellular matrix. Consequently, the structure and macromolecular composition of this extracellular compartment is profoundly altered as a result of vitamin A deficiency. As cell behavior, differentiation and apoptosis, and tissue mechanics are influenced by the extracellular matrix, its modifications potentially compromise organ function and may lead to disease. This review focuses on the effects of lack of vitamin A in the extracellular matrix of several organs and discusses possible molecular mechanisms and pathologic implications.

LL-37 secreted by epithelium promotes fibroblast collagen production: a potential mechanism of small airway remodeling in chronic obstructive pulmonary disease

Emerging evidence suggests that the process of small airway remodeling is mediated by profibrotic growth factors produced by epithelium, which are capable of activating the underlying mesenchymal cells with excessive collagen production. It has been demonstrated that human cathelicidin antimicrobial protein LL-37 is highly expressed in small airway epithelium from COPD patients. However, it is unknown whether the increased levels of LL-37 in epithelium are involved in the pathogenesis of small airway remodeling in COPD. In this study, we examined the expression of LL-37 in small airways from smokers with COPD and controls (non-smokers and smokers without COPD) by immunohistochemistry, and then the association between LL-37 expression in epithelium and the structural changes of small airway remodeling was analyzed. In vitro, the effect of CSE-induced epithelial secretion of LL-37 on collagen production in human lung fibroblasts (HFL-1 cell line) was studied in a co-culture system. Finally, the signaling pathways involved in the effect of LL-37 on fibroblast collagen production were evaluated. The results showed that LL-37 immunoreactivity in airway epithelium was significantly elevated in smokers with COPD compared with controls. In addition, the magnitude of LL-37 expression in epithelium was positively correlated with airway wall thickness and collagen deposition. In vitro, CSE-induced epithelial secretion of LL-37 promoted fibroblast collagen production. Finally, we showed that formyl peptide receptor-like 1 (FPRL1)-dependent extracellular signal-regulated kinase (ERK) signaling pathway was essential for LL-37-induced collagen production in HFL-1 cells. These results suggest that after cigarette smoke exposure, the increased levels of LL-37 in airway epithelium could stimulate collagen production in the underlying lung fibroblasts and may contribute to small airway remodeling in COPD.

STATs and hepatic fibrosis

Hepatic fibrosis is a response to repair of chronic hepatic injury caused by different diseases. Its pathological features are inflammatory cell aggregation and associated cascade reaction. There are myofibroblast formation (MFB) and excessive deposition of extracellular matrix (ECM) in the liver, and the structure of the liver is destroyed. The recent research finds that Janus kinase/signal transducer and activator of transcription (JAK-STAT) plays an important role in the development of hepatic fibrosis. In general, STAT1 and STAT5 act as anti-fibrotic signaling molecules preventing injury-driven liver fibrosis. Although the antiviral effect of STAT2 is well documented, it is not clear whether or not STAT2 also plays a role in contributing to the interferon-α/β-mediated anti-fibrotic effects in the liver. What's more, the biological functions of STAT3, STAT4 and STAT6 in hepatic fibrosis remains largely unknown. Therefore, this review focuses on the role of STAT family members and cytokines in hepatic fibrosis.

CD4+ T cells from human neonates and infants are poised spontaneously to run a nonclassical IL-4 program

Senescence or biological aging impacts a vast variety of molecular and cellular processes. To date, it is unknown whether CD4(+) Th cells display an age-dependent bias for development into specific subpopulations. In this study, we show the appearance of a distinct CD4(+) T cell subset expressing IL-4 at an early stage of development in infant adenoids and cord blood that is lost during aging. We identified by flow cytometric, fluorescent microscopic, immunoblot, and mass spectrometric analysis a population of CD4(+) T cells that expressed an unglycosylated isoform of IL-4. This T cell subpopulation was found in neonatal but not in adult CD4(+) T cells. Furthermore, we show that the mRNA of the Th2 master transcription factor GATA3 is preferentially expressed in neonatal CD4(+) T cells. The Th2 phenotype of the IL-4(+)CD4(+) T cells could be reinforced in the presence of TGF-β. Although the IL-4(+)CD4(+) T cells most likely originate from CD31(+)CD4(+) T recent thymic emigrants, CD31 was downregulated prior to secretion of IL-4. Notably, the secretion of IL-4 requires a so far unidentified trigger in neonatal T cells. This emphasizes that cytokine expression and secretion are differentially regulated processes. Our data support the hypothesis of an endogenously poised cytokine profile in neonates and suggest a link between cytokine production and the developmental stage of an organism. The determination of the IL-4 isoform-expressing cells in humans might allow the identification of Th2 precursor cells, which could provide novel intervention strategies directed against Th2-driven immunopathologies such as allergies.

Hepatic myofibroblasts promote the progression of human cholangiocarcinoma through activation of epidermal growth factor receptor

Intrahepatic cholangiocarcinoma (CCA) is characterized by an abundant desmoplastic environment. Poor prognosis of CCA has been associated with the presence of alpha-smooth muscle actin (α-SMA)-positive myofibroblasts (MFs) in the stroma and with the sustained activation of the epidermal growth factor receptor (EGFR) in tumor cells. Among EGFR ligands, heparin-binding epidermal growth factor (HB-EGF) has emerged as a paracrine factor that contributes to intercellular communications between MFs and tumor cells in several cancers. This study was designed to test whether hepatic MFs contributed to CCA progression through EGFR signaling. The interplay between CCA cells and hepatic MFs was examined first in vivo, using subcutaneous xenografts into immunocompromised mice. In these experiments, cotransplantation of CCA cells with human liver myofibroblasts (HLMFs) increased tumor incidence, size, and metastatic dissemination of tumors. These effects were abolished by gefitinib, an EGFR tyrosine kinase inhibitor. Immunohistochemical analyses of human CCA tissues showed that stromal MFs expressed HB-EGF, whereas EGFR was detected in cancer cells. In vitro, HLMFs produced HB-EGF and their conditioned media induced EGFR activation and promoted disruption of adherens junctions, migratory and invasive properties in CCA cells. These effects were abolished in the presence of gefitinib or HB-EGF-neutralizing antibody. We also showed that CCA cells produced transforming growth factor beta 1, which, in turn, induced HB-EGF expression in HLMFs.

CONCLUSION

A reciprocal cross-talk between CCA cells and myofibroblasts through the HB-EGF/EGFR axis contributes to CCA progression.

Role of interleukin-13 in fibrosis, particularly systemic sclerosis

Chronic inflammation can lead to altered extracellular matrix deposition and ultimately fibrosis. Interleukin-13 (IL-13) is a cytokine that was found to promote IgE class switching and inhibit proinflammatory cytokines. However, it is now recognized as an important mediator in allergy and most importantly fibrosis. Indeed, animal studies with genetically deleted mice have demonstrated its critical role in fibrosis and although it shares over lapping functions with IL-4 it is the dominant cytokine in fibrosis. Systemic sclerosis is an autoimmune disease in which there is chronic inflammation and fibrosis. The disease is associated with a Th2 polarization and IL-13 levels are elevated both in the blood and in the skin of patients. This review will examine the role of IL-13 in driving fibrosis with a particular emphasis on systemic sclerosis as a prototypical fibrotic disease. It will highlight recent research into the role of IL-13 and how this cytokine may be targeted in systemic sclerosis.

Sympathetic nervous system catecholamines and neuropeptide Y neurotransmitters are upregulated in human NAFLD and modulate the fibrogenic function of hepatic stellate cells

Background

Sympathetic nervous system (SNS) signalling regulates murine hepatic fibrogenesis through effects on hepatic stellate cells (HSC), and obesity-related hypertension with SNS activation accelerates progression of non-alcoholic fatty liver disease (NAFLD), the commonest cause of chronic liver disease. NAFLD may lead to cirrhosis. The effects of the SNS neurotransmitters norepinephrine (NE), epinephrine (EPI) and neuropeptide Y (NPY) on human primary HSC (hHSC) function and in NAFLD pathogenesis are poorly understood.

Aims

to determine the mechanistic effects of NE/EPI/NPY on phenotypic changes in cultured hHSC, and to study SNS signalling in human NAFLD livers.

Methods

Freshly isolated hHSC were assessed for expression of cathecholamine/neuropeptide Y receptors and for the synthesis of NE/EPI. The effects of NE/EPI/NPY and adrenoceptor antagonists prazosin (PRZ)/propranolol (PRL) on hHSC fibrogenic functions and the involved kinases and interleukin pathways were examined. Human livers with proven NAFLD were then assessed for upregulation of SNS signalling components.

Results

Activated hHSC express functional α/β-adrenoceptors and NPY receptors, which are upregulated in the livers of patients with cirrhotic NAFLD. hHSC in culture synthesize and release NE/EPI, required for their optimal basal growth and survival. Exogenous NE/EPI and NPY dose-dependently induced hHSC proliferation, mediated via p38 MAP, PI3K and MEK signalling. NE and EPI but not NPY increased expression of collagen-1α2 via TGF-β without involvement of the pro-fibrogenic cytokines leptin, IL-4 and IL-13 or the anti-fibrotic cytokine IL-10.

Conclusions

hHSC synthesize and require cathecholamines for optimal survival and fibrogenic functionality. Activated hHSC express directly fibrogenic α/β-adrenoceptors and NPY receptors, upregulated in human cirrhotic NAFLD. Adrenoceptor and NPY antagonists may be novel anti-fibrotic agents in human NAFLD.

Interleukin-13-producing CD8+ T cells mediate dermal fibrosis in patients with systemic sclerosis

OBJECTIVE

Fibrosis is a major contributor to morbidity and mortality in systemic sclerosis (SSc). T cells are the predominant inflammatory infiltrate in affected tissue and are thought to produce cytokines that drive the synthesis of extracellular matrix (ECM) proteins by fibroblasts, resulting in excessive fibrosis. We have previously shown that aberrant interleukin-13 (IL-13) production by peripheral blood effector CD8+ T cells from SSc patients correlates with the extent of skin fibrosis. The present study was undertaken to investigate the role of IL-13 production by CD8+ T cells in dermal fibrosis, an early and specific manifestation of SSc.

METHODS

ECM protein production by normal dermal fibroblasts cocultured with SSc CD8+ T cell supernatants was determined by quantitative polymerase chain reaction and Western blotting. Skin-homing receptor expression and IL-13 production by CD8+ T cells in the peripheral blood of SSc patients were measured by flow cytometry. IL-13+ and CD8+ cells in sclerotic skin were identified by immunohistochemistry.

RESULTS

IL-13-producing circulating CD8+ T cells from patients with SSc expressed skin-homing receptors and induced a profibrotic phenotype in normal dermal fibroblasts, which was inhibited by an anti-IL-13 antibody. High numbers of CD8+ T cells and IL-13+ cells were found in the skin lesions of SSc patients, particularly during the early inflammatory phase of the disease.

CONCLUSION

These findings show that IL-13-producing CD8+ T cells are directly involved in modulating dermal fibrosis in SSc. The demonstration that CD8+ T cells homing to the skin early in the course of SSc are associated with accumulation of IL-13 is an important mechanistic contribution to the understanding of the pathogenesis of dermal fibrosis in SSc and may represent a potential target for therapeutic intervention.