Effects of chrysin on steroid-resistant asthma in a murine model

Abstract

To explore the therapeutic effects of chrysin for steroid-resistant asthma in a murine model. Lipopolysaccharide (LPS) was used to induce steroid-resistant asthma in a murine model sensitized and challenged with ovalbumin (OVA). Forty-eight female BALB/c mice were randomly divided into 6 groups of control (A), OVA (B), LPS + OVA (C), LPS + OVA + dexamethasone (D), LPS + OVA + chrysin (E) and LPS + OVA + dexamethasone + chrysin (F) (n = 8 each). At Day 1 and 14, group A received an intraperitoneal injection of phosphate buffered saline (PBS); groups B, C, D, E and F had an intraperitoneal injection of a mixture of OVA (20 µg) and aluminum hydroxide for sensitization. At Day 27, groups A and B were intranasally instilled with PBS while groups C, D, E and F had an intranasal instillation of LPS (10 µg). At Days 28, 29 and 30, groups B, C, D, E and F were challenged via airway with 1% OVA in PBS for 30 min and group A with PBS. Group D was intraperitoneally injected with dexamethasone (3 mg/kg) 30 min pre-challenge and PBS one day pre-challenge; group E received an intraperitoneal injection of chrysin (50 mg/kg) at one day and 1h pre-challenge; group F received dexamethasone (3 mg/kg) 30 min pre-challenge and chrysin (50 mg/kg) at one day and 1 h pre-challenge; groups A, B and C had PBS as above. Hematoxylin-eosin (HE) staining and periodic acid-Schiff (PAS) staining of lung tissues were performed to observe the pathologic changes. The total cells in bronchoalveolar lavage fluid (BALF) were counted under microscope. And enzyme-linked immunosorbent assay (ELISA) was applied for detecting interleukin-4 (IL-4) and interleukin-13 (IL-13) in BALF and IgE in sera. The inflammatory infiltration in lung tissue of group F was obviously suppressed compared with that of group C. The numbers of PAS-positive cells per bronchus divided by the total number of epithelial cells in group D, E, F were markedly lower than that in group C ((54.5 ± 6.9)%, (53.3 ± 8.2)%, (23.8 ± 7.0)% vs (71.3 ± 12.2)%, all P < 0.01). The total cells in BALF of group E and F significantly decreased versus that of group C ((1.22 ± 0.23) × 10⁴/ml, (0.98 ± 0.25) × 10⁴/ml vs (2.56 ± 0.18) × 10⁴/ml, both P < 0.01). The levels of IL-4 in group D and F were significantly less than that of group C ((118 ± 7), (124 ± 5) vs (138 ± 6) pg/ml, both P < 0.01). The levels of IL-13 in BALF of group E and F significantly decreased compared with that of group C ((787 ± 57), (484 ± 32) vs (1 121 ± 132) pg/ml, both P < 0.01). The levels of IgE in sera of group D, E, F were significantly lower those of group C ((10 310 ± 494), (10 771 ± 650), (7 529 ± 485) vs (12 618 ± 595) ng/ml, all P < 0.01). Chrysin could improve the therapeutic efficacies of glucocorticoid for steroid-resistant asthma.