STAT6 and PARP Family Members in the Development of T Cell-dependent Allergic Inflammation

Allergic inflammation requires the orchestration of altered gene expression in the target tissue and in the infiltrating immune cells. The transcription factor STAT6 is critical in activating cytokine gene expression and cytokine signaling both in the immune cells and in target tissue cells including airway epithelia, keratinocytes and esophageal epithelial cells. STAT6 is activated by the cytokines IL-4 and IL-13 to mediate the pathogenesis of allergic disorders such as asthma, atopic dermatitis, food allergy and eosinophilic esophagitis (EoE). In this review, we summarize the role of STAT6 in allergic diseases, its interaction with the co-factor PARP14 and the molecular mechanisms by which STAT6 and PARP14 regulate gene transcription

PARP14 in allergic inflammation

Indiana University-Purdue University Indianapolis (IUPUI)Allergic inflammation is a result of damaging immune responses stimulated by innocuous proteins and is mediated by a complex interplay between inflammatory cells including eosinophils, basophils, neutrophils, mast cells, dendritic cells and lymphocytes. The anatomic location of allergic inflammation determines the structural cells that become targets, such as airway smooth muscle cells, mucous secreting cells, keratinocytes, and other epithelial cells. The cytokine IL-4 is critical for this process and promotes activation of the transcription factor STAT6 and transcriptional co-factors that regulate pro-allergic gene expression. STAT6 is required for IL-4 mediated responses, Th2 cell differentiation and class switching to IgE and has been implicated in the progression of asthma, atopic dermatitis (AD), and eosinophilic esophagitis (EoE). STAT6 interacts with the co-factor Poly-ADP ribose polymerse-14 (PARP 14 or ARTD8), one of 17 PARPs with ADP-ribosyl transferase activity. PARP14 was initially identified as a transcriptional co-activator for STAT6, and PARP14 and the enzymatic activity associated with it promote Th2 cell differentiation. Allergic airway disease is attenuated in Parp14-/- mice or in mice treated with PARP inhibitor, PJ34. To study the role of PARP14 in EoE, we examined esophageal biopsies from children and demonstrated a correlation between the expression of eosinophilic chemo-attractant, CCL26 and PARP14. To study allergic skin inflammation, we used a mouse model of spontaneous inflammation (Stat6VT mice). We generated Stat6VTxParp14-/- mice and observed that Stat6VTxParp14-/- mice develop more severe AD-like lesions with increased morbidity compared to Stat6VT mice. However, PARP14 is not required in keratinocytes to mediate the expression of IL4 and Stat6 responsive genes important for skin barrier function, suggesting that PARP14 contributes to a hematopoietic cell-intrinsic function. Thus, the data suggests that PARP14 serves specific roles in allergic disease that vary with the target organ

STAT4 deficiency reduces the development of atherosclerosis in mice

Atherosclerosis is a chronic inflammatory process that leads to plaque formation in large and medium sized vessels. T helper 1 (Th1) cells constitute the majority of plaque infiltrating pro-atherogenic T cells and are induced via IFNγ-dependent activation of T-box (Tbet) and/or IL-12-dependent activation of signal transducer and activator of transcription 4 (STAT4). We thus aimed to define a role for STAT4 in atherosclerosis. STAT4-deficiency resulted in a ∼71% reduction (p < 0.001) in plaque burden in Stat4(-/-)Apoe(-/-) vs Apoe(-/-) mice fed chow diet and significantly attenuated atherosclerosis (∼31%, p < 0.01) in western diet fed Stat4(-/-)Apoe(-/-) mice. Surprisingly, reduced atherogenesis in Stat4(-/-)Apoe(-/-) mice was not due to attenuated IFNγ production in vivo by Th1 cells, suggesting an at least partially IFNγ-independent pro-atherogenic role of STAT4. STAT4 is expressed in T cells, but also detected in macrophages (MΦs). Stat4(-/-)Apoe(-/-)in vitro differentiated M1 or M2 MΦs had reduced cytokine production compare to Apoe(-/-) M1 and M2 MΦs that was accompanied by reduced induction of CD69, I-A(b), and CD86 in response to LPS stimulation. Stat4(-/-)Apoe(-/-) MΦs expressed attenuated levels of CCR2 and demonstrated reduced migration toward CCL2 in a transwell assay. Importantly, the percentage of aortic CD11b(+)F4/80(+)Ly6C(hi) MΦs was reduced in Stat4(-/-)Apoe(-/-) vs Apoe(-/-) mice. Thus, this study identifies for the first time a pro-atherogenic role of STAT4 that is at least partially independent of Th1 cell-derived IFNγ, and primarily involving the modulation of MΦ responses

Increased Th2 activity and diminished skin barrier function cooperate in allergic skin inflammation

Atopic dermatitis (AD) is a chronic inflammatory skin disease induced by a complex interaction between susceptibility genes encoding skin barrier components and environmental allergen exposure that results in type 2 cytokine production. Although genetic lesions in either component can be risk factors for disease in patients, whether these pathways interact in the development of AD is not clear. To test this, we mated mice with T-cell specific expression of constitutively active Stat6 (Stat6VT) that spontaneously develop allergic skin inflammation with Flaky tail (Ft) mice that have mutations in Flg and Tmem79 genes that each affect skin barrier function. Our results demonstrate that over 90% of the Stat6VT transgenic mice carrying the Ft alleles (Stat6VTxFt−/−) develop severe atopic dermatitis lesions by 3-5 months of age, compared with only 40% of Stat6VT mice that develop disease by 6-7 months of age. Further, histopathological analysis of skin tissues from Stat6VTxFt−/− mice revealed extensive thickening of the dermis with increased inflammatory infiltrates as compared with Stat6VT mice. Our study suggests that skin barrier defects and altered Th2 responses independently cooperate in the pathogenesis of allergic skin inflammation, similar to effects observed in patients with AD

Organ-specific adaptive signaling pathway activation in metastatic breast cancer cells

Breast cancer metastasizes to bone, visceral organs, and/or brain depending on the subtype, which may involve activation of a host organ-specific signaling network in metastatic cells. To test this possibility, we determined gene expression patterns in MDA-MB-231 cells and its mammary fat pad tumor (TMD-231), lung-metastasis (LMD-231), bone-metastasis (BMD-231), adrenal-metastasis (ADMD-231) and brain-metastasis (231-BR) variants. When gene expression between metastases was compared, 231-BR cells showed the highest gene expression difference followed by ADMD-231, LMD-231, and BMD-231 cells. Neuronal transmembrane proteins SLITRK2, TMEM47, and LYPD1 were specifically overexpressed in 231-BR cells. Pathway-analyses revealed activation of signaling networks that would enable cancer cells to adapt to organs of metastasis such as drug detoxification/oxidative stress response/semaphorin neuronal pathway in 231-BR, Notch/orphan nuclear receptor signals involved in steroidogenesis in ADMD-231, acute phase response in LMD-231, and cytokine/hematopoietic stem cell signaling in BMD-231 cells. Only NF-κB signaling pathway activation was common to all except BMD-231 cells. We confirmed NF-κB activation in 231-BR and in a brain metastatic variant of 4T1 cells (4T1-BR). Dimethylaminoparthenolide inhibited NF-κB activity, LYPD1 expression, and proliferation of 231-BR and 4T1-BR cells. Thus, transcriptome change enabling adaptation to host organs is likely one of the mechanisms associated with organ-specific metastasis and could potentially be targeted therapeutically

IL-4 impairs wound healing potential in the skin by repressing fibronectin expression

BACKGROUND: Atopic dermatitis (AD) is characterized by intense pruritis and is a common childhood inflammatory disease. Many factors are known to affect AD development, including the pleiotropic cytokine IL-4. Yet little is known regarding the direct effects of IL-4 on keratinocyte function. OBJECTIVE AND METHODS: In this report RNA sequencing and functional assays were used to define the effect of the allergic environment on primary keratinocyte function and wound repair in mice. RESULTS: Acute or chronic stimulation by IL-4 modified expression of more than 1000 genes expressed in human keratinocytes that are involved in a broad spectrum of nonoverlapping functions. Among the IL-4-induced changes, repression of fibronectin critically impaired the human keratinocyte wound response. Moreover, in mouse models of spontaneous and induced AD-like lesions, there was delayed re-epithelialization. Importantly, topical treatment with fibronectin restored the epidermal repair response. CONCLUSION: Keratinocyte gene expression is critically shaped by IL-4, altering cell fate decisions, which are likely important for the clinical manifestations and pathology of allergic skin disease

Poly-ADP-ribosyl polymerase-14 promotes T helper 17 and follicular T helper development

Transcription factors are critical determinants of T helper cell fate and require a variety of co-factors to activate gene expression. We previously identified the ADP ribosyl-transferase poly-ADP-ribosyl polymerase 14 (PARP-14) as a co-factor of signal transducer and activator of transcription (STAT) 6 that is important in B-cell and T-cell responses to interleukin-4, particularly in the differentiation of T helper type 2 (Th2) cells. However, whether PARP-14 functions during the development of other T helper subsets is not known. In this report we demonstrate that PARP-14 is highly expressed in Th17 cells, and that PARP-14 deficiency and pharmacological blockade of PARP activity result in diminished Th17 differentiation in vitro and in a model of allergic airway inflammation. We further show that PARP-14 is expressed in T follicular helper (Tfh) cells and Tfh cell development is impaired in PARP-14-deficient mice following immunization with sheep red blood cells or inactivated influenza virus. Decreases in Th17 and Tfh development are correlated with diminished phospho-STAT3 and decreased expression of the interleukin-6 receptor α-chain in T cells. Together, these studies demonstrate that PARP-14 regulates multiple cytokine responses during inflammatory immunity

Poly-ADP ribose polymerase-14 limits severity of allergic skin disease

Poly-ADP ribose polymerase-14 (PARP14 or ARTD8) was initially identified as a transcriptional co-activator for signal transducer and activator of transcription 6 (Stat6), where the presence of interleukin-4 (IL-4) and activated Stat6 induces the enzymatic activity of PARP14 that promotes T helper type 2 differentiation and allergic airway disease. To further our understanding of PARP14 in allergic disease, we studied the function of PARP14 in allergic inflammation of skin using mice that express constitutively active Stat6 in T cells (Stat6VT) and develop spontaneous inflammation of the skin. We mated Stat6VT mice to Parp14−/− mice and observed that approximately 75% of the Stat6VT × Parp14−/− mice develop severe atopic dermatitis (AD)-like lesions, compared with about 50% of Stat6VT mice, and have increased morbidity compared with Stat6VT mice. Despite this, gene expression in the skin and the cellular infiltrates was only modestly altered by the absence of PARP14. In contrast, we saw significant changes in systemic T-cell cytokine production. Moreover, adoptive transfer experiments demonstrated that decreases in IL-4 production reflected a cell intrinsic role for PARP14 in Th2 cytokine control. Hence, our data suggest that although PARP14 has similar effects on T-cell cytokine production in several allergic disease models, the outcome of those effects is distinct, depending on the target organ of disease