Wicher, Sarah A.

The pathogenesis of asthma in elderly is not well understood. Using a mouse model of asthma, we show that aging results in decreased lung function and less responsiveness to allergen exposure, impacted by locally produced brain-derived neurotrophic factor. Aging also decreases allergen-induced inflammation but increases airway remodeling and senescence. Our results suggest that senescence pathways may contribute to asthma pathogenesis in elderly.

Local production of growth factors within the airway with autocrine/paracrine effects can promote features of asthma. Here, we show that glial-derived neurotrophic factor (GDNF) is a procontractile and proremodeling factor that contributes to allergen-induced airway hyperreactivity and tissue remodeling in a mouse model of asthma. Blocking GDNF signaling attenuates allergen-induced airway hyperreactivity and remodeling, suggesting a novel approach to alleviating structural and functional changes in the asthmatic airway.

AbstractAirway smooth muscle (ASM) cells modulate the local airway milieu via production of inflammatory mediators and growth factors including classical neurotrophins, such as brain‐derived neurotrophic factor (BDNF). The glial cell‐derived neurotrophic factor (GDNF) family of ligands (GFLs) are nonclassical neurotrophins and their role in the airway is barely understood. The major GFLs, GDNF and Neurturin (NRTN) bind to GDNF family receptor (GFR) α1 and α2 respectively that pair with Ret receptor to accomplish signaling. In this study, we found GDNF is expressed in human lung and increased in adult asthma, while human ASM expresses GDNF and its receptors. Accordingly, we used human ASM cells to test the hypothesis that ASM expression and autocrine signaling by GFLs regulate [Ca2+]i. Serum‐deprived ASM cells from non‐asthmatics were exposed to 10 ng/ml GDNF or NRTN for 15 min (acute) or 24 h (chronic). In fura‐2 loaded cells, acute GDNF or NRTN alone induced [Ca2+]i responses, and further enhanced responses to 1 µM ACh or 10 µM histamine. Ret inhibitor (SPP86; 10 µM) or specific GDNF chelator GFRα1‐Fc (1 µg/ml) showed roles of these receptors in GDNF effects. In contrast, NRTN did not enhance [Ca2+]i response to histamine. Furthermore, conditioned media of nonasthmatic and asthmatic ASM cells showed GDNF secretion. SPP86, Ret inhibitor and GFRα1‐Fc chelator markedly decreased [Ca2+]i response compared with vehicle, highlighting autocrine effects of secreted GDNF. Chronic GDNF treatment increased histamine‐induced myosin light chain phosphorylation. These novel data demonstrate GFLs particularly GDNF/GFRα1 influence ASM [Ca2+]i and raise the possibility that GFLs are potential targets of airway hyperresponsiveness.

Background Uterine leiomyomas (fibroids) are benign smooth muscle cell tumors of the uterus that affect a large percentage of reproductive aged women, contribute to infertility, excessive menstrual bleeding, and represent the leading cause of hysterectomy (~70%). Despite their importance, the mechanisms that promote fibroid growth are still not well‐understood. Fibroids are comprised of smooth muscle cells (SMCs) and fibroblasts and their growth is modulated by hormones including estrogen and progesterone. Intracellular calcium [Ca 2+ ] i signaling is a key aspect of SMC physiology in promoting contractility, cell proliferation, and fibrosis: aspects relevant to fibroid biology. While [Ca 2+ ] i regulation in normal myometrium is well characterized, this has not been explored in fibroids. The goal of this study was to explore [Ca 2+ ] i regulation in fibroid SMCs and the effect of sex steroids towards obtaining insights into tumor progression. Methods Cells were enzymatically isolated from normal myometrium and select fibroids of different sizes from patients undergoing myomectomy at Mayo Clinic, Rochester, MN (IRB approved). [Ca 2+ ] i was measured using fura‐2/AM and real‐time fluorescence microscopy. The contribution of Ca 2+ influx vs. intracellular pathways in the responses to 1uM oxytocin were assessed using pharmacological inhibitors/activators. Cells were pretreated with vehicle, 1nM estrogen, or 1nM progesterone to assess the effect of sex steroids. Results Fibroid‐derived cells showed a greater contribution of Ca 2+ influx pathways in their responses to oxytocin than normal myometrium. Here, the Ca 2+ ‐activated chloride channel TMEM16A (Ano1) was found to be contributory, with Western analysis showing higher levels of Ano1 in fibroids. Exposure to estrogen resulted in significantly higher [Ca 2+ ] i responses compared to cells treated with vehicle or progesterone, although progesterone did enhance [Ca 2+ ] i responses as well. Estrogen increased Ano1 expression. Cell proliferation was also increased in fibroid cells. Conclusions Exposure to estrogen and progesterone enhances oxytocin induced [Ca 2+ ] i responses of fibroid‐derived cells, potentially via increased TMEM16A (Ano1). Such increases may further contribute to the observed hormone‐induced enhancement of fibroid cell proliferation. Menstrual cycle fluctuations in reproductive aged women may thus contribute to the progression of fibroids. Greater understanding of calcium signaling pathways such as Ano1 in fibroid tissue may allow for novel therapeutic targets in uterine leiomyomas. Support or Funding Information Supported by NIH grants R25 GMO75148 (JLR), R01 HL088029 (YSP), and R01 HL56470 (YSP). This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .