Cigarette smoke inhibits efferocytosis via deregulation of sphingosine kinase signaling: reversal with exogenous S1P and the S1P analogue FTY720

Abstract

Alveolar macrophages from chronic obstructive pulmonary disease patients and cigarette smokers are deficient in their ability to phagocytose apoptotic bronchial epithelial cells (efferocytosis). We hypothesized that the defect is mediated via inhibition of sphingosine kinases and/or their subcellular mislocalization in response to cigarette smoke and can be normalized with exogenous sphingosine-1-phosphate or FTY720 (fingolimod), a modulator of sphingosine-1-phosphate signaling, which has been shown to be clinically useful in multiple sclerosis. Measurement of sphingosine kinase 1/2 activities by [(32)P]-labeled sphingosine-1-phosphate revealed a 30% reduction of sphingosine kinase 1 (P < 0.05) and a nonsignificant decrease of sphingosine kinase 2 in THP-1 macrophages after 1 h cigarette smoke extract exposure. By confocal analysis macrophage sphingosine kinase 1 protein was normally localized to the plasma membrane and cytoplasm and sphingosine kinase 2 to the nucleus and cytoplasm but absent at the cell surface. Cigarette smoke extract exposure (24 h) led to a retraction of sphingosine kinase 1 from the plasma membrane and sphingosine kinase 1/2 clumping in the Golgi domain. Selective inhibition of sphingosine kinase 2 with 25 µM ABC294640 led to 36% inhibition of efferocytosis (P < 0.05); 10 µM sphingosine kinase inhibitor/5C (sphingosine kinase 1-selective inhibitor) induced a nonsignificant inhibition of efferocytosis, but its combination with ABC294640 led to 56% inhibition (P < 0.01 vs. control and < 0.05 vs. single inhibitors). Cigarette smoke-inhibited efferocytosis was significantly (P < 0.05) reversed to near-control levels in the presence of 10-100 nM exogenous sphingosine-1-phosphate or FTY720, and FTY720 reduced cigarette smoke-induced clumping of sphingosine kinase 1/2 in the Golgi domain. These data strongly support a role of sphingosine kinase 1/2 in efferocytosis and as novel therapeutic targets in chronic obstructive pulmonary disease.

Phagocytosis and Inflammation: Exploring the effects of the components of E-cigarette vapor on macrophages

“…PG, VG, and PG:VG had no significant effects on phagocytosis (24.5-27.66% vs. 27.01% for control). The reduction in phagocytosis in the presence of 10% CSE (8.2%) was consistent with our previous findings (Tran et al 2016;Ween et al 2016) (Fig. 2).…”

“…The reduction in phagocytosis in the presence of 10% CSE (8.2%) was consistent with our previous findings (Tran et al. 2016; Ween et al. 2016) (Fig.…”

“…We have long been interested in the effects of cigarette smoke on lung cell function. Our identification of defective alveolar macrophage phagocytic function in chronic obstructive disease (COPD) subjects and in response to cigarette smoke (especially with regard to the clearance of apoptotic material, termed efferocytosis), lead to the subsequent discovery of significantly increased apoptosis of epithelial cells in the airway of chronic obstructive pulmonary disease (COPD) subjects and cigarette smokers (Hodge et al 2005;Hodge et al 2007;Tran et al 2016;Ween et al 2016). These findings implicate defective efferocytosis with secondary necrosis and potentiation of the inflammatory milieu (Hodge et al 2003(Hodge et al , 2005.…”

Enhanced inflammasome activation and reduced sphingosine-1 phosphate S1P signalling in a respiratory mucoobstructive disease model

“…Less is known on the alteration of S1P signalling and its role in mucoobstructive diseases. Previous studies by us and others indicated complex dysregulation of the S1P signalling system in COPD (and in response to cigarette smoke) involving several components and various cell types [14][15][16]. Large gaps in this field remain, especially whether and how individual components of the S1P signalling system are dysregulated in diseases such as CF, COPD, non-CF bronchiectasis, and whether mucus obstruction directly contributes to this dysregulation.…”

Sphingolipid in Lung Cancer Pathogenesis and Therapy

“…In terms of targeting S1P in lung cancer, aside from the antibody, using SphK2 inhibitors and its combination with SphK1 inhibitors seem to be promising approaches that merit further discovery [60]. In addition, agents such as transporter Spns2 [26] have shed new insights into the biology of S1P signaling.…”