Involvement of p38 MAP kinase and Smad3 in TGF-beta-mediated mast cell functions

Mast Cell–Tumor Interactions: Molecular Mechanisms of Recruitment, Intratumoral Communication and Potential Therapeutic Targets for Tumor Growth

Mast cells (MCs) are tissue-resident immune cells that are important players in diseases associated with chronic inflammation such as cancer. Since MCs can infiltrate solid tumors and promote or limit tumor growth, a possible polarization of MCs to pro-tumoral or anti-tumoral phenotypes has been proposed and remains as a challenging research field. Here, we review the recent evidence regarding the complex relationship between MCs and tumor cells. In particular, we consider: (1) the multifaceted role of MCs on tumor growth suggested by histological analysis of tumor biopsies and studies performed in MC-deficient animal models; (2) the signaling pathways triggered by tumor-derived chemotactic mediators and bioactive lipids that promote MC migration and modulate their function inside tumors; (3) the possible phenotypic changes on MCs triggered by prevalent conditions in the tumor microenvironment (TME) such as hypoxia; (4) the signaling pathways that specifically lead to the production of angiogenic factors, mainly VEGF; and (5) the possible role of MCs on tumor fibrosis and metastasis. Finally, we discuss the novel literature on the molecular mechanisms potentially related to phenotypic changes that MCs undergo into the TME and some therapeutic strategies targeting MC activation to limit tumor growth.

Regulation of Innate and Adaptive Immunity by TGFβ

Immune regulation by cytokines is crucial in maintaining immune homeostasis, promoting responses to infection, resolving inflammation, and promoting immunological memory. Additionally, cytokine responses drive pathology in immune-mediated disease. A crucial cytokine in the regulation of all aspects of an immune response is transforming growth factor beta (TGFβ). Although best known as a crucial regulator of T cell responses, TGFβ plays a vital role in regulating responses mediated by virtually every innate and adaptive immune cell, including dendritic cells, B cells, NK cells, innate lymphoid cells, and granulocytes. Here, we review our current knowledge of how TGFβ regulates the immune system, highlighting the multifunctional nature of TGFβ and how its function can change depending on location and context of action.

Protein phosphatase magnesium dependent 1A governs the wound healing-inflammation-angiogenesis cross talk on injury

Protein phosphatase magnesium dependent 1A (PPM1A) has been implicated in fibrosis and skin wounding. We generated PPM1A knockout mice to study the role of PPM1A in the wound healing-inflammation-angiogenesis cross talk. The role of PPM1A in these processes was studied using the ocular alkali burn model system. In the injured cornea the absence of PPM1A led to enhanced inflammatory response, stromal keratocyte transactivation, fibrosis, increased p38 mitogen-activated protein kinase phosphorylation, elevated expression of transforming growth factor-β-related genes (including Acta2, TGF-β, Col1, MMP9, and VEGF) and subsequently to neovascularization. Augmented angiogenesis in the absence of PPM1A is a general process occurring in vivo in PPM1A knockout mice upon subcutaneous Matrigel injection and ex vivo in aortic ring Matrigel cultures. Using primary keratocyte cultures and various experimental approaches, we found that phospho-p38 is a favored PPM1A substrate and that by its dephosphorylation PPM1A participates in the regulation of the transforming growth factor-β signaling cascade, the hallmark of inflammation and the angiogenic process. On the whole, the studies presented here position PPM1A as a new player in the wound healing-inflammation-angiogenesis axis in mouse, reveal its crucial role in homeostasis on injury, and highlight its potential as a therapeutic mediator in pathologic conditions, such as inflammation and angiogenesis disorders, including cancer.

Potential for modulation of the fas apoptotic pathway by epidermal growth factor in sarcomas

One important mechanism by which cancer cells parasitize their host is by escaping apoptosis. Thus, selectively facilitating apoptosis is a therapeutic mechanism by which oncotherapy may prove highly advantageous. One major apoptotic pathway is mediated by Fas ligand (FasL). The death-inducing signaling Ccmplex (DISC) and subsequent death-domain aggregations are created when FasL is bound by its receptor thereby enabling programmed cell death. Conceptually, if a better understanding of the Fas pathway can be garnered, an oncoselective prodeath therapeutic approach can be tailored. Herein, we propose that EGF and CTGF play essential roles in the regulation of the Fas apoptotic pathway in sarcomas. Tumor and in vitro data suggest viable cells counter the prodeath signal induced by FasL by activating EGF, which in turn induces prosurvival CTGF. The prosurvival attributes of CTGF ultimately predominate over the death-inducing FasL. Cells destined for elimination inhibit this prosurvival response via a presently undefined pathway. This scenario represents a novel role for EGF and CTGF as regulators of the Fas pathway in sarcomas.

Activation of mitogen activated protein kinase-Erk kinase (MEK) increases T cell immunoglobulin mucin domain-3 (TIM-3) transcription in human T lymphocytes and a human mast cell line

The immune regulatory molecule T cell immunoglobulin mucin domain (TIM-3) is expressed in activated T cells and in mast cells treated with transforming growth factor (TGF)-β, but underlying mechanisms for induction of TIM-3 transcription have not been well-explored. We studied the role of mitogen-activated protein kinase (MAPK) in TIM-3 transcription on the basis of the involvement of MAPK in T cell activation and TGF-β signaling. Inhibitors of MAPK-Erk kinase (MEK) as well as p38 suppressed TIM-3 transcription in phorbol myristic acid (PMA)-stimulated T cells, but inhibitors of c-Jun NH2-terminal kinase (JNK) did not. MEK over-expression enhanced TIM-3 transcription in PMA-stimulated T cells. Furthermore, -1.5kb TIM-3 promoter was activated by PMA stimulation and repressed by MEK inhibitors in Jurkat T cells. Similarly, MEK activation enhanced TIM-3 transcription in TGF-β-stimulated HMC-1 human mast cells, although MEK seemed not directly activated by TGF-β. Concordantly, -1.5kb TIM-3 promoter activity was reduced by MEK inhibitors, but was not responsive to TGF-β stimulation in HMC-1 cells. These results suggest the regulatory role of MEK in TIM-3 transcription by human CD4+ T cells and mast cells.

Cigarette smoke exacerbates mouse allergic asthma through Smad proteins expressed in mast cells

Background

Many studies have found that smoking reduces lung function, but the relationship between cigarette smoke and allergic asthma has not been clearly elucidated, particularly the role of mast cells. This study aimed to investigate the effects of smoke exposure on allergic asthma and its association with mast cells.

Methods

BALB/c mice were sensitized and challenged by OVA to induce asthma, and bone marrow-derived mast cells (BMMCs) were stimulated with antigen/antibody reaction. Mice or BMMCs were exposed to cigarette smoke or CSE solution for 1 mo or 6 h, respectively. The recruitment of inflammatory cells into BAL fluid or lung tissues was determined by Diff-Quik or H&E staining, collagen deposition by Sircol assay, penh values by a whole-body plethysmography, co-localization of tryptase and Smad3 by immunohistochemistry, IgE and TGF-β level by ELISA, expressions of Smads proteins, activities of signaling molecules, or TGF-β mRNA by immunoblotting and RT-PCR.

Results

Cigarette smoke enhanced OVA-specific IgE levels, penh values, recruitment of inflammatory cells including mast cells, expressions of smad family, TGF-β mRNA and proteins, and cytokines, phosphorylations of Smad2 and 3, and MAP kinases, co-localization of tryptase and Smad3, and collagen deposition more than those of BAL cells and lung tissues of OVA-induced allergic mice. CSE solution pretreatment enhanced expressions of TGF-β, Smad3, activities of MAP kinases, NF-κB/AP-1 or PAI-1 more than those of activated-BMMCs.

Conclusions

The data suggest that smoke exposure enhances antigen-induced mast cell activation via TGF-β/Smad signaling pathways in mouse allergic asthma, and that it exacerbates airway inflammation and remodeling.

The effects of formula feeding on physiological and immunological parameters in the gut of neonatal rats

A unique model of formula feeding in the neonatal rat was utilized to investigate the effects of an enterally delivered artificial milk formula on clinically relevant immunological and biological characteristics in the gut, compared to naturally reared pups. Hooded Wistar rat pups were randomly allocated to two treatment groups: formula-fed (FF) or naturally suckled (NS). A flexible silastic intra-gastric cannula was surgically implanted into the FF pups, through which an artificial rat milk supplement was continuously delivered from day 4 to day 10 of life. Rat pups were sacrificed at 10 days of age. Body weight, small intestinal weight, mucosal CD8(+) cell numbers, and ileal lactase activity in FF animals were significantly decreased compared to their NS counterparts (P < 0.05). Numbers of eosinophils, mucosal mast cells, CD4(+) T-cells, ileal villus height and gastric emptying times were significantly increased in FF pups (P < 0.05). We have developed a new rat model of artificial feeding which possesses important immunological and biological similarities to the premature human infant.

Resident cardiac mast cells: are they the major culprit in the pathogenesis of cardiac hypertrophy?

Mast cells originate from pluripotent progenitor cells in bone marrow and are major players in the inflammation process. The involvements of mast cells in various cardiovascular complications such as arrhythmias, ischaemia reperfusion injury and graft rejection are well documented. Moreover, recent studies suggest the involvement of mast cells in cardiac hypertrophy and heart failure. The present review focuses on the role of mast cells in the development of cardiac hypertrophy and heart failure.

Smad3 Signal Transducer Regulates Skin Inflammation and Specific IgE Response in Murine Model of Atopic Dermatitis

Atopic dermatitis (AD) is a common chronic inflammatory skin disease characterized by itchy, dry, and inflamed skin. Transforming growth factor (TGF)-beta is an important fibrogenic and immunomodulatory factor that regulates cellular processes in the injured and inflamed skin. This study examines the role of the TGF-beta-Smad signaling pathway using Smad3-deficient mice in a murine model of AD. Dermatitis was induced in mice by epicutaneous application of ovalbumin (OVA) applied in a patch to tape-stripped skin. OVA-specific IgE and IgG2a antibody levels were measured by ELISA. Skin biopsies from sensitized skin areas were used for RNA isolation, histology, and immunohistochemical examination. The thickness of dermis was significantly reduced in OVA-sensitized skin of Smad3-/- mice. The defect in the dermal thickness was accompanied by a decrease in the expression of mRNA for proinflammatory cytokines IL-6 and IL-1beta in the OVA-sensitized skin. In contrast, the number of mast cells was significantly increased in OVA-sensitized skin of Smad3-/- mice, which also exhibited elevated levels of OVA-specific IgE. These results demonstrate that the Smad3-pathway regulates allergen-induced skin inflammation and systemic IgE antibody production in a murine model AD. The Smad3 signaling pathway might be a potential target in the therapy of allergic skin diseases.