To measure the levels of ghrelin-induced expression or activation of nuclear factor erythroid 2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1), and
quinone oxidoreductase 1 (NQO1) in the PQ-injured lungs of mice and to evaluate the protective effect of ghrelin against paraquat (PQ)-induced acute lung injury in mice.
According to the random number table method, 50 ICR mice of clean grade were assigned to 5 groups: normal control group (n = 10), PQ group (n = 10), and ghrelin intervention groups (n = 30). For PQ group, mice were injected with a single dose of PQ (20 mg/kg, i.p.); for ghrelin intervention groups, mice were injected with a single dose of PQ (20 mg/kg, i.p.), and then ghrelin was injected at three concentrations (16.58, 33.15, and 49.73 µg/kg). Lung tissues were collected and proceeded to the following studies. HE staining was used for histopathological examination under a light microscope, and the changes in nuclear expression of Nrf2 were evaluated by Western blot. The activities of HO-1 and NQO1 were measured by ELISA. Malondialdehyde (MDA) content and MPO activity were measured by colorimetry. Another 40 mice were divided into PQ group (n = 10) and 16.58, 33.15, and 49.73 µg/kg ghrelin intervention groups (n = 10 for each); mortality and clinical manifestations were recorded within 72 h.
Compared with the normal control group, the PQ group showed significant increases in nuclear protein level of Nrf2, content of MDA, and activities of HO-1, NQO1, and MPO (P < 0.05 for all). Compared with the PQ group, ghrelin treatment significantly increased the expression of Nrf2 and activities of HO-1 and NQO1 and significantly reduced the content of MDA and activity of MPO (P < 0.01 for all). Histopathological studies indicated that ghrelin showed an antioxidant property that reduced the histological changes induced by PQ in the lungs. The ghrelin intervention groups had a significantly lower mortality than the PQ group, and there was a significant difference between the high-dose ghrelin intervention group and PQ group (P < 0.05).
Ghrelin can up-regulate nuclear expression of Nrf2, increase the activities of HO-1 and NQO1, and reduce the activity of MPO and content of MDA, thus protecting PQ-exposed mice from acute lung injury.