Anti- trachea inflammatory effects of diosgenin from Dioscorea nipponica through interactions with glucocorticoid receptor α

Abstract

Asthma is a heterogeneous disease characterized by symptoms of chronic inflammation and airway structural and functional changes. It affects about 300 million people worldwide and causes 250 000 deaths annually, but its symptoms can be greatly relieved by regular use of inhaled glucocorticoids (GCs). GCs exert their function through interacting with glucocorticoid receptors (GRs). Diosgenin is a naturally occurring steroidal saponin abundantly present in many medicinal plants, including Dioscorea nipponica, which shares a similar steroidal structure with GC. In this study, ovalbumin (OVA)-induced asthmatic mice and primary tracheal epithelial cells (TECs) were used as research models. ELISAs were applied to measure the secretion of TNF-α, IL-1β, and IL-6, while quantitative PCR and western blotting were applied to evaluate expression of GRs SLPI, TTP, GILZ, MKP-1, and NF-κB. Our data demonstrated that diosgenin suppressed the secretion of TNF-α, IL-1β, and IL-6 by enhancing the expression of GRs, SLPI, GILZ, and MKP-1, and inhibiting the expression of HSP70. These data provide some evidence on the molecular mechanism of diosgenin, which might facilitate its clinical applications.

Keywords: Diosgenin; asthma; glucocorticoid; glucocorticoid receptor.

Figures

Figure 1.

Comparisons of HE staining in the left lung bronchus (200×) and lung inflammatory cell infiltration in BALB/c mice. There were eight groups including normal control, asthma, asthma + diosgenin, asthma + prednisone, asthma + diosgenin + prednisone, asthma + RU486, asthma + RU486 + diosgenin, and asthma + RU486+ prednisone. Purple-blue-stained cells around the airway are infiltrated inflammatory cells. Their numbers indicate the severity of asthma.

Figure 2.

ELISA analyses of IL-1β (a), IL-6 (b), and TNF-α (c) in BALB/c mouse BALF of various groups. There were eight groups including normal control, asthma, asthma + diosgenin, asthma + prednisone, asthma + diosgenin + prednisone, asthma + RU486, asthma + RU486+ diosgenin, and asthma + RU486 + prednisone. Values are means ± SD (n = 3). * P 

Figure 3.

Quantitative PCR and western blot analyses of GRα and HSP70 expression levels in BALB/c mouse lung tissues of various groups. There were eight groups including normal control, asthma, asthma + diosgenin, asthma + prednisone, asthma+ diosgenin+ prednisone, asthma + RU486, asthma + RU486 + diosgenin, and asthma + RU486+ prednisone. (a) Quantitative PCR data of changes in GRα mRNA levels among groups. Values are means ± SD (n = 3). * P 

Figure 4.

ELISA analyses of IL-1β (a), IL-6 (b), and TNF-α (c) in BALB/c mouse TECs of various groups. There were nine groups including normal control, asthma, asthma + diosgenin (0.5, 1, 5, and 10 µM), asthma + prednisone (10 M, 50 , and 100  nM). Values are means ± SD (n = 3). * P 

Figure 5.

ELISA analyses of IL-1β (a), IL-6 (b), and TNF-α (c) in BALB/c mouse TECs of various groups. There were eight groups incusing normal control, asthma, asthma + diosgenin, asthma + prednisone, asthma + diosgenin + prednisone, asthma + RU486, asthma + RU486+ diosgenin, and asthma + RU486 + prednisone. The concentrations of diosgenin, prednisone and RU486 were 10 µM, 100 nM and 100 nM, respectively. Values are means ± SD (n = 3). * P 

Figure 6.

Quantitative PCR and western blot analyses of GRα and HSP70 expression levels in BALB/c mouse TECs of various groups. There were eight groups including normal control, asthma, asthma + diosgenin, asthma + prednisone, asthma + diosgenin + prednisone, asthma + RU486, asthma + RU486 + diosgenin, and asthma + RU486+ prednisone. The concentrations of diosgenin, prednisone and RU486 were 10 µM, 100 nM and 100 nM, respectively. (a) Quantitative PCR data of changes in GRα mRNA levels among groups. Values are means ± SD (n = 3). * P 

Figure 7.

Western blot analysis of changes in SLPI, TTP, GILZ, MKP-1 and NF-κB protein levels of TECs from normal and asthmatic mice treated with 10 µM diosgenin or 100 nM prednisone.