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

PARP-14 Functions as a Transcriptional Switch for Stat6-dependent Gene Activation*

A subset of poly ADP-ribose polymerases (PARP) that also contain macro domains regulate transcription. One such macro PARP, PARP-14 alters interleukin 4 (IL-4) and Stat6-dependent transcription. Stat6, activated by IL-4 plays an important role in T helper cell immunity and B cell responses. Here we define the mechanism by which PARP-14 regulates Stat6-activated transcription. Under non-stimulating conditions, PARP-14 recruits HDAC 2 and 3 to IL-4 responsive promoters. In the presence of IL-4, PARP-14 promotes efficient binding of Stat6 to its target genes. Moreover, HDAC 2 and 3 are released from the promoter with an IL-4 signal, this is aided by the ADP-ribosylation of the HDACs by PARP-14. The HDACs and PARP-14 get replaced by coactivators containing HAT activity. Based on these observations we put forth a mechanism in which PARP-14 functions as a transcriptional switch for Stat6-dependent gene induction. Thus, in the absence of a signal PARP-14 acts as a transcriptional repressor by recruiting HDACs. In contrast, in the presence of IL-4 the catalytic activity of PARP-14 facilitates Stat6 binding to the promoter, and release of HDACs so as to activate transcription