Staphylococcus aureus USA300 strains cause a highly inflammatory necrotizing pneumonia. The virulence of this strain has been attributed to its expression of multiple toxins that have diverse targets including ADAM10, NLRP3 and CD11b. We demonstrate that induction of necroptosis through RIP1/RIP3/MLKL signaling is a major consequence of S. aureus toxin production. Cytotoxicity could be prevented by inhibiting either RIP1 or MLKL signaling and S. aureus mutants lacking agr, hla or Hla pore formation, lukAB or psms were deficient in inducing cell death in human and murine immune cells. Toxin-associated pore formation was essential, as cell death was blocked by exogenous K+ or dextran. MLKL inhibition also blocked caspase-1 and IL-1β production, suggesting a link to the inflammasome. Rip3 -/- mice exhibited significantly improved staphylococcal clearance and retained an alveolar macrophage population with CD200R and CD206 markers in the setting of acute infection, suggesting increased susceptibility of these leukocytes to necroptosis. The importance of this anti-inflammatory signaling was indicated by the correlation between improved outcome and significantly decreased expression of KC, IL-6, TNF, IL-1α and IL-1β in infected mice. These findings indicate that toxin-induced necroptosis is a major cause of lung pathology in S. aureus pneumonia and suggest the possibility of targeting components of this signaling pathway as a therapeutic strategy.
Aquaporin 2 (AQP2) is responsible for regulating the concentration of urine in the collecting tubules of the kidney under the control of vasopressin (Vp). Studies using Vp-deficient Brattleboro rats, however, indicated the existence of substantial Vp-independent mechanisms for membrane insertion, as well as transcriptional regulation, of this water channel. The Vp-independent mechanism(s) is clinically relevant to patients with X-linked nephrogenic diabetes insipidus (NDI) by therapeutically bypassing the dysfunctional Vp receptor. On the basis of studies with secretin receptor-null (SCTR ؊/؊ ) mice, we report here for the first time that mutation of the SCTR gene could lead to mild polydipsia and polyuria. Additionally, SCTR ؊/؊ mice were shown to have reduced renal expression of AQP2 and AQP4, as well as altered glomerular and tubular morphology, suggesting possible disturbances in the filtration and/or water reabsorption process in these animals. By using SCTR ؊/؊ mice as controls and comparing them with wild-type animals, we performed both in vivo and in vitro studies that demonstrated a role for secretin in stimulating (i) AQP2 translocation from intracellular vesicles to the plasma membrane in renal medullary tubules and (ii) expression of this water channel under hyperosmotic conditions. The present study therefore provides information for at least one of the Vp-independent mechanisms that modulate the process of renal water reabsorption. Future investigations in this direction should be important in developing therapeutic means for treating NDI patients.Secretin was originally isolated from upper intestinal mucosal extract, injection of which into the jugular vein of an anesthetized dog resulted in elevation of pancreatic and hepatic bile flow (4). The primary function of secretin in releasing bicarbonate, electrolytes, and water from pancreatic ductal epithelial cells is firmly established. Additionally, it can also stimulate electrolyte and water secretion in the epididymis, as well as bicarbonate-rich ductal bile secretion from cholangiocytes (1, 9). In cholangiocytes, a secretin-induced choleretic effect is associated with microtubule-dependent exocytotic insertion of cytoplasmic vesicles containing the water channel aquaporin 1 (AQP1) onto the apical plasma membrane (PM), leading to osmotic water movement (28). Interestingly, this type of regulated translocation of water channels has also been demonstrated in other cell types (5). For example, vasoactive intestinal polypeptide-induced translocation of AQP5 in Brunner's gland of the duodenum is associated with bicarbonate and mucin secretion, which is essential for mucosal protection (38), while Vp-and oxytocin-triggered translocation of AQP2 to and from the PM in renal collecting tubules (19, 36) is critical for renal water reabsorption. As there is considerable evidence indicating the involvement of Vp-independent mechanisms in the regulation of renal water reabsorption (19,21,25,44) and some of these mechanisms are associated with cyclic-AMP (cAMP...
of Health (NIH) -F32-HL140729 (to S.C.) and R01 HL139365 (to M.S.) RUNNING TITLE: Vaped nicotine impairs mucociliary function preferentially via TRPA1 SUBJECT CATEGORY DESCRIPTOR: 6.17 Smoking Health Effects TOTAL WORD COUNT: 3985 AT A GLANCE COMMENTARY: Scientific Knowledge on the Subject E-cigarettes are marketed as safer alternatives to conventional cigarettes due to their defined composition and noncombustible nature. However, it is unclear how exposure to e-cigarette vapor, colloquially referred to as "vape", affects naïve airway epithelia. It is largely unknown to what extent individual constituents of vape, such as nicotine and flavoring agents, influence pulmonary function, if at all. The transient receptor potential ankyrin 1 (TRPA1) is a molecular target for vape effects due to its expression in airway epithelia and its reported gating by nicotine, reactive oxidants, and flavors, especially cinnamaldehyde. What This Study Adds to the FieldThis study implicates nicotine as a key "vape" constituent that acutely impairs airway mucociliary functions in vitro and in vivo (sheep). A functional, nicotine-sensitive TRPA1 receptor is natively expressed in human and sheep bronchial epithelial cells and mediates the effects of nicotine and e-cigarette vapors. Importantly, its inhibition prevents mucociliary dysfunction in vitro and in vivo. These findings implicate TRPA1 as a driver of mucociliary dysfunction induced by nicotine-containing e-cigarette vapor.ABSTRACT RATIONALE: Electronic cigarette (e-cig) use has been widely adopted under the perception of safety. However, possibly adverse effects of e-cig vapor in never-smokers are not well understood. OBJECTIVES:Effects of nicotine-containing e-cig vapors on airway mucociliary function were tested in differentiated human bronchial epithelial cells (HBECs) isolated from never-smokers and in the airways of a novel, ovine large animal model. METHODS:Mucociliary parameters were measured in HBECs and in sheep. Systemic nicotine delivery to sheep was quantified using plasma cotinine levels, measured by ELISA. MEASUREMENTS AND MAIN RESULTS:In vitro, exposure to e-cig vapor reduced airway surface liquid hydration and increased mucus viscosity of HBECs in a nicotinedependent manner. Acute nicotine exposure increased intracellular calcium levels, an effect primarily dependent on transient receptor potential ankyrin 1 (TRPA1). TRPA1 inhibition with A967079 restored nicotine-mediated impairment of mucociliary parameters including mucus transport in vitro. Sheep tracheal mucus velocity (TMV), an in vivo measure of mucociliary clearance, was also reduced by e-cig vapor. Nebulized e-cig liquid containing nicotine also reduced TMV in a dose-dependent manner and elevated plasma cotinine levels. Importantly, nebulized A967079 reversed the effects of e-cig liquid on sheep TMV. CONCLUSIONS:Our findings show that inhalation of e-cig vapor causes airway mucociliary dysfunction in vitro and in vivo. Furthermore, they suggest that the main Page 4 of 64 2 nicotine effect on mucociliary ...
Chronic obstructive pulmonary disease (COPD) and lung cancer are frequently caused by tobacco smoking. However, these diseases present opposite phenotypes involving redox signaling at the cellular level. While COPD is characterized by excessive airway epithelial cell death and lung injury, lung cancer is caused by uncontrolled epithelial cell proliferation. Notably, epidemiological studies have demonstrated that lung cancer incidence is significantly higher in patients who have preexisting emphysema/lung injury. However, the molecular link and common cell signaling events underlying lung injury diseases and lung cancer are poorly understood. This review focuses on studies of molecular mechanism(s) underlying smoking-related lung injury (COPD) and lung cancer. Specifically, the role of the ceramide-generating machinery during cigarette smoke-induced oxidative stress leading to both apoptosis and proliferation of lung epithelial cells is emphasized. Over recent years, it has been established that ceramide is a sphingolipid playing a major role in lung epithelia structure/function leading to lung injury in chronic pulmonary diseases. However, new and unexpected findings draw attention to its potential role in lung development, cell proliferation, and tumorigenesis. To address this dichotomy in detail, evidence is presented regarding several protein targets, including Src, p38 mitogen-activated protein kinase, and neutral sphingomyelinase 2, the major sphingomyelinase that controls ceramide generation during oxidative stress. Furthermore, their roles are presented not only in apoptosis and lung injury but also in enhancing cell proliferation, lung cancer development, and resistance to epidermal growth factor receptor-targeted therapy for treating lung cancer.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.