Thymic stromal lymphopoietin contribution to the recruitment of circulating fibrocytes to the lung in a mouse model of chronic allergic asthma

Association of Circulating Fibrocytes With Fibrostenotic Small Bowel Crohn's Disease

BACKGROUND

Fibrocytes are hematopoietic cells with features of mesenchymal cells found in the circulation and inflammatory sites implicated in promoting fibrosis in many fibroinflammatory diseases. However, their role(s) in the development of intestinal fibrosis is poorly understood. Here, we investigated a potential role of fibrocytes in the development of fibrosis in Crohn's disease (CD) and sought factors that may impact their development and function.

METHODS

Plasma and mononuclear cells were collected from patients with and without fibrostenotic CD. Fibrocytes defined as CD11b+, CD34+, and Collagen 1+ were correlated with clinical assessments of fibrosis, including evaluation using intestinal ultrasound. We measured the levels of relevant circulating molecules via Luminex and studied the effect of patient plasma proteins on fibrocyte differentiation.

RESULTS

Fibrocyte numbers were increased in CD patients with stricturing Crohn's disease compared with patients with an inflammatory phenotype (P = .0013), with strong correlation between fibrocyte numbers and acoustic radiation force impulse (ARFI), a measure of bowel elasticity on intestinal ultrasound (R = .8383, P = .0127). Fibrostenotic plasma was a more potent inducer of fibrocyte differentiation in both primary human monocytes and cell line and contained increased levels of cytokines implicated in fibrocyte differentiation compared with plasma from inflammatory patients. Interestingly, increased fibrocyte numbers at time of ultrasound were associated with escalation of medical therapy and endoscopic/surgical management of small bowel strictures at 30 months follow-up.

CONCLUSIONS

Circulating fibrocytes strongly correlate with fibrostenotic disease in CD, and they may serve as predictors for escalation of medical +/- surgical therapy.

Endothelial cell‑derived CCL15 mediates the transmigration of fibrocytes through the CCL15‑CCR1 axis in vitro

Wound healing is a complex physiological process in which fibrocytes serve a vital role. However, the mechanism underlying the recruitment of fibrocytes during wound healing remains largely unknown. The present study aimed to investigate whether endothelial cells are involved in the recruitment of fibrocytes in wound healing. To mimic the in vivo angiogenic process, a co-culture system consisting of endothelial cells and fibrocytes was achieved using a permeable Transwell co-culture system. The expression of chemokines produced by endothelial cells with or without co-culture was then measured using a gene chip. Based on the dataset from chip analysis, chemokine ligand 15 (CCL15) produced by endothelial cells was identified, which likely serves a regulatory role in mediating the transmigration of fibrocytes. Overexpression of CCL15 in endothelial cells or chemokine receptor 1 (CCR1) in fibrocytes promoted the transmigration of fibrocytes, whilst silencing the expression of CCL15 in endothelial cells or that of CCR1 in fibrocytes attenuated the transmigration of fibrocytes. Results from the present study suggested that the CCL15-CCR1 axis between endothelial cells and fibrocytes serves a vital role in mediating the recruitment of fibrocytes during wound healing.

Intrauterine growth restriction induces skin inflammation, increases TSLP and impairs epidermal barrier function

Intrauterine growth restriction (IUGR) and low birth weight are risk factors for childhood asthma. Atopic march describes the progression from early dermatitis to asthma during life. Since inflammatory signaling is linked to increased airway resistance and lung remodeling in rats after IUGR, we queried if these findings are related to skin inflammatory response. Firstly, we induced IUGR in Wistar rats by isocaloric protein restriction during gestation. IUGR rats showed lower body weight at postnatal day 1 (P1), catch-up growth at P21, and similar body weight like controls at P90. At P1 and P90, mRNA of inflammatory as well as fibrotic markers and number of skin immune cells (macrophages) were increased after IUGR. Skin thymic stromal lymphopoietin (TSLP) mRNA at P1 and serum TSLP at P1 and P21 were elevated in IUGR. Moreover, IUGR impaired transepidermal water loss at P21 and P90. IUGR induced higher. Secondly, the increase of TEWL after Oxazolone treatment as a model of atopic dermatitis (AD) was greater in IUGR than in Co. Our data demonstrate an early inflammatory skin response, which is linked to persistent macrophage infiltration in the skin and impaired epidermal barrier function after IUGR. These findings coupled with elevated TSLP could underlie atopic diseases in rats after IUGR. KEY MESSAGES: • The present study shows that IUGR increases macrophage infiltration and induces an inflammatory and fibrotic gene expression pattern in the skin of newborn rats. • Early postnatal inflammatory response in the skin after IUGR is followed by impaired epidermal barrier function later in life. • IUGR aggravates transepidermal water loss in an experimental atopic dermatitis model, possibly through elevated TSLP in skin and serum. • Early anti-inflammatory treatment and targeting TSLP signaling could offer novel avenues for early prevention of atopic disorders and late asthma in high-risk infants.

Thymic stromal lymphopoietin induced early stage of epithelial-mesenchymal transition in human bronchial epithelial cells through upregulation of transforming growth factor beta 1

Purpose: Epithelial-mesenchymal transition (EMT) involved in asthmatic airway remodeling. Thymic stromal lymphopoietin (TSLP), an epithelial-derived cytokine, was a key component in airway immunological response in asthma. But the role of TSLP in the EMT process was unknown. We aimed to access whether TSLP could induce EMT in airway epithelia and its potential mechanism. Materials and Methods: Human bronchial epithelial (HBE) cells were incubated with TSLP or transforming growth factor beta 1 (TGF-β1) or both. SB431542 was used to block TGF-β1 signal while TSLP siRNA was used to performed TSLP knockdown. Changes in E-cadherin, vimentin, collagen I and fibronectin level were measured by real-time PCR, western blot and immunofluorescence staining. Expressions of TGF-β after TSLP administration were measured by real-time PCR, western blot and ELISA. Results: TSLP induced changes of EMT relevant markers alone and promoted TGF-β1-induced EMT in HBEs. Intracellular and extracellular expression of TGF-β1 were upregulated by TSLP. SB431542 blocked changes of EMT relevant markers induced by TSLP. Knockdown of TSLP not only reduced TSLP and TGF-β1 expression but also inhibited changes of EMT relevant markers induced by TGF-β1 in HBEs. Conclusions: TSLP could induce early stage of EMT in airway epithelial cells through upregulation of TGF-β1. This effect may act as a targeting point for suppression of asthma.

IL-37 alleviates house dust mite-induced chronic allergic asthma by targeting TSLP through the NF-κB and ERK1/2 signaling pathways

Interleukin (IL)-37 has been described as a negative regulator of immune responses and is critical for asthma pathogenesis, but the mechanisms behind the protective role of IL-37 against allergic asthma are less well understood. We show here that IL-37 administered intranasally inhibited house dust mite (HDM)-induced chronic airway eosinophilic inflammation, goblet cell hyperplasia, peribronchial collagen deposition and airway hyperresponsiveness (AHR) to methacholine. In contrast to a weakened Th2 response in the lung that was characterized by the downregulation of Th2-associated cytokines and chemokines in IL-37-treated mice, IL-37 has no effect on relevant markers of systemic Th2 immune including serum immunoglobulins expression and in vitro production of Th2-associated cytokines by splenocytes on HDM recall. We demonstrated that the production of thymic stromal lymphopoietin (TSLP) in the lung tissue was associated with IL-37. Importantly, compared with IL-37 alone, TSLP coadministration with IL-37 restored HDM-induced airway inflammation and structural alterations, increased AHR to methacholine and promoted Th2-associated cytokine production. We further found that IL-37 inhibited the induction of TSLP expression by the main antigen of house dust mite, Der p1, by suppressing NF-κB and extracellular signal regulated kinase 1/2 (ERK1/2) activation in human bronchial epithelial (16-HBE) cells in vitro. These data highlight the importance of TSLP in IL-37-mediated protective role in asthma. IL-37 might represent a useful innovative and alternative therapy to control TSLP production in the airway.

CpG-ODNs and Budesonide Act Synergistically to Improve Allergic Responses in Combined Allergic Rhinitis and Asthma Syndrome Induced by Chronic Exposure to Ovalbumin by Modulating the TSLP-DC-OX40L Axis

The experimental model of combined allergic rhinitis and asthma syndrome (CARAS) has shown that CpG oligodeoxynucleotides (CpG-ODNs) are potential inhibitors of type 2 helper cell-driven inflammatory responses. Currently available CpG-ODNs modestly inhibit allergic responses in CARAS, while a combination strategy for upper airway treatment by co-administration of CpG-ODNs and glucocorticoids may show good efficacy. This study aimed to assess the therapeutic effects of CpG-ODNs combined with budesonide (BUD) on upper and lower-airway inflammation and remodeling in mice with CARAS induced by chronic exposure to ovalbumin (OVA), exploring the possible underlying molecular mechanisms. A BALB/c mouse model of chronic CARAS was established by systemic sensitization and repeated challenge with OVA. Treatment with CpG-ODNs or BUD by intranasal administration was started 1 h after OVA challenge. Then, nasal mucosa and lung tissues were fixed and stained for pathologic analysis. The resulting immunologic variables and TSLP-DC-OX40L axis parameters were evaluated. Both CpG-ODNs and BUD intranasal administration are effective on reducing Th2-type airway inflammation and tissue remodeling. Co-administration of CpG-ODNs and BUD was more effective than each monotherapy in attenuating upper and lower-airway inflammation as well as airway remodeling in chronic CARAS. Notably, combination of CpG-ODNs with BUD modulated the TSLP-DC-OX40L axis, as demonstrated by decreased TSLP production in the nose and lung, alongside decreased TSLPR and OX40L in DC. Intranasal co-administration of CpG-ODNs and BUD synergistically alleviates airway inflammation and tissue remodeling in experimental chronic CARAS, through shared cellular pathways, as a potent antagonist of the TSLP-DC-OX40L axis.

Myofibroblasts in macular fibrosis secondary to neovascular age-related macular degeneration - the potential sources and molecular cues for their recruitment and activation

Age-related macular degeneration (AMD) is the leading cause of blindness in the elderly in developed countries. Neovascular AMD (nAMD) accounts for 90% of AMD-related vision loss. Although intravitreal injection of VEGF inhibitors can improve vision in nAMD, approximately 1/3 of patients do not benefit from the therapy due to macular fibrosis. The molecular mechanism underlying the transition of the neovascular lesion to a fibrovascular phenotype remains unknown. Here we discussed the clinical features and risk factors of macular fibrosis secondary to nAMD. Myofibroblasts are key cells in fibrosis development. However, fibroblasts do not exist in the macula. Potential sources of myofibroblast precursors, the molecular cues in the macular microenvironment that recruit them and the pathways that control their differentiation and activation in macular fibrosis were also discussed. Furthermore, we highlighted the challenges in macular fibrosis research and the urgent need for better animal models for mechanistic and therapeutic studies.