The Effects of the Anti-aging Protein Klotho on Mucociliary Clearance.

John S Dennis,Stefanie Krick,Matthias Salathe,Gwendalyn King,Samuel Chung,Juliette Sailland,Molly Easter,Steven M Rowe,Adegboyega T Adewale,Christian Faul,Nathalie Baumlin,Lisa Kuenzi,Jarrod W Barnes,Elex Skylar Harris,Jaleesa Garth

doi:10.3389/fmed.2019.00339

Abstract

α-klotho (KL) is an anti-aging protein and has been shown to exert anti-inflammatory and anti-oxidative effects in the lung and pulmonary diseases such as chronic obstructive pulmonary disease (COPD) and cystic fibrosis. The current study investigated the direct effect of KL on the bronchial epithelium in regards to mucociliary clearance parameters. Primary human bronchial and murine tracheal epithelial cells, cultured, and differentiated at the air liquid interface (ALI), were treated with recombinant KL or infected with a lentiviral vector expressing KL. Airway surface liquid (ASL) volume, airway ion channel activities, and expression levels were analyzed. These experiments were paired with ex vivo analyses of mucociliary clearance in murine tracheas from klotho deficient mice and their wild type littermates. Our results showed that klotho deficiency led to impaired mucociliary clearance with a reduction in ASL volume in vitro and ex vivo. Overexpression or exogenous KL increased ASL volume, which was paralleled by increased activation of the large-conductance, Ca2+-activated, voltage-dependent potassium channel (BK) without effect on the cystic fibrosis transmembrane conductance regulator (CFTR). Furthermore, KL overexpression downregulated IL-8 levels and attenuated TGF-β-mediated downregulation of LRRC26, the γ subunit of BK, necessary for its function in non-excitable cells. In summary, we show that KL regulates mucociliary function by increasing ASL volume in the airways possibly due to underlying BK activation. The KL mediated BK channel activation may be a potentially important target to design therapeutic strategies in inflammatory airway diseases when ASL volume is decreased.

Highlights

As part of the innate defense mechanism, mucociliary clearance (MCC) protects the airway epithelium by trapping inhaled pathogens or particulate matter within the mucus layer and removing it from the airways through ciliary movement [1, 2]
Proper function of MCC depends on both mucus production and mucus transport, which are affected by coordinated ciliary beating, Klotho and Mucociliary Clearance sufficient Airway surface liquid (ASL) volume, and mucus viscosity [3]
There was a significant decrease in ASL depth in the kl−/− mice (Figure 1A right panel showing μOCT images and Figure 1B), and decreased ciliary beat frequency (CBF) and mucociliary transport (MCT) (Figures 1C,D)

Summary

INTRODUCTION

As part of the innate defense mechanism, mucociliary clearance (MCC) protects the airway epithelium by trapping inhaled pathogens or particulate matter within the mucus layer and removing it from the airways through ciliary movement [1, 2]. Apical potassium (K+) secretion via BK channels has been increasingly recognized for its essential role in delivering an electrochemical driving force for apical chloride ion exit through CFTR and calciumactivated chloride channels (CaCC) [15]. This regulated ion flux has been shown to help maintain ASL volume and MCC [16,17,18,19], and dysregulation of these channels has been documented in the pathogenesis of a multitude of inflammatory airway diseases including CF and COPD [19,20,21]. We investigated the effects of KL on ion flux across the airway epithelium and thereby ASL homeostasis

METHODS

RESULTS

DISCUSSION

ETHICS STATEMENT