Oxymatrine is one of the alkaloids extracted from Chinese herb
Acute lung injury (ALI) is characterized by an intense pulmonary inflammatory response, with neutrophil accumulation, interstitial edema, disruption of epithelial integrity and leakage of protein into the alveolar space (
ALI/ARDS is associated with the development of multiple organ dysfunction syndrome (MODS), which plays an important role in the death of patients with sepsis, pneumonia, aspiration of gastric contents, trauma, multiple transfusions and ischemia reperfusion. Severe acute respiratory syndrome (SARS) is a novel global infectious disease induced by a virus from the family Coronaviridae. Clinical investigation shows that pathological changes in SARS patients are similar to those of acute lung injury, as revealed by alveolar cell collapse, severe exudation, acute inflammatory reaction and hyaline membrane formation (
It is generally accepted that the development of MODS follows the gradual route of ALI–ARDS–MODS. During this pathway, the lung behaves as a central organ and is the first target subject to injury. Because pulmonary dysfunction may lead to severe hypoxemia and further other multiple organ dysfunction or failure, the treatment of the above mentioned diseases should concentrate on the development of ALI and take measures as soon as possible (
As a traditional Chinese medicine,
Considering the pharmacological effects of oxymatrine, we speculate that oxymatrine may play a central role in the composite injection although the effect of oxymatrine on SARS has not been reported to date. In order to test this hypothesis and because the pulmonary pathological changes in SARS are similar to those of acute lung injury, the effect of oxymatrine on acute lung injury was investigated using an ALI mouse model in this study. We also studied whether the p38 MAPK intracellular signal pathway was involved in the development of ALI and discussed whether oxymatrine could become a therapeutic candidate drug for ALI, ARDS and SARS.
Oxymatrine was obtained from Yixin Pharmaceutical Co. Ltd. (Zhejiang, China) with HPLC purity >98%. Oleic acid was purchased from Linfeng Chemical Co. Ltd. (Shanghai, China). Albumin was obtained from Sigma. Rabbit polyclonal antibodies for phosphorylated and nonphosphorylated p38 MAPK were provided by Cell Signaling Technology. Tween 20 and Glycine were purchased from Amresco Co. polyvinylidene difluoride (PVDF) transfer membranes for Western blotting were obtained from Roche Molecular Biochemicals (Quebec, Canada). Protein assay dye reagent was purchased from Jiancheng Bioengineering Co. (Nanjing, China). HRP Conjugate goat anti-rabbit IgG and PIPA lysis buffer were purchased from Shengnengbocai Biotech Inc. (Shanghai, China). Mouse TNF-α ELISA assay kit was obtained from Jingmei Biotech Co. (Guangdong, China). All other reagents were of the highest grade available commercially.
Male Kunming strain mice weighing 18–24 g were obtained from Laboratory Animal Center, School of Medicine, Southeast University (Nanjing 210009, China). The mice were housed in climate-controlled quarters (24–18 °C at 50% humidity) with a 12 h light/dark cycle and free access to food and water. All experiments were conducted according to the “Guide for the Care and Use of Laboratory Animals”, published by the National Institutes of Health (NIH publication 86-23, revised 1986). Mice were randomly assigned into six groups. The oleic acid group received 0.3 ml/kg, i.v. of oleic acid (mixed with 0.1% bovine serum albuman). The control group received 0.3 ml/kg, i.v. of saline. The three oleic acid + oxymatrine groups were treated with oxymatrine for three consecutive days before oleic acid injection (oxymatrine; 12.5, 25 and 50 mg/kg, i.p.) (
The left lower lobe was excised and fixed in 10% buffered formalin. The lungs were embedded in paraffin, and the sections stained with hematoxylin and eosin were examined by light microscopy for evidence of lung injury, as described in the following: alveolar congestion, hemorrhage, edema, infiltration/aggregation of neutrophils in the airspace or vessel wall, thickness of the alveolar wall and hyaline membrane formation.
Electron microscopy of lungs was carried out on samples fixed in phosphate buffer (pH 7.4) containing 2.5% glutaraldehyde and post-fixed in osmium tetraoxide. Transmission electron micrographs were produced with a Hitachi H-7000 electron microscope.
The wet weight of the whole lung was weighed on an automatic electric balance and the lung index was calculated according to the following formula: lung index (%) = the wet weight of the whole lung/body weight × 100%. Subsequently, the right lung was excised and weighed to obtain the ‘wet’ weight. The lung was then dried in an oven at 80 °C for 7 days to obtain the ‘dry’ weight. To assess tissue edema, the ratio of wet weight to dry weight (w/d ratio) was calculated. The left lung was cut into pieces and subjected to histological examination and electron microscopy observation.
Blood samples were harvested from the eyes before mice were killed. The blood was allowed to clot for approximately 1 h at room temperature and then centrifuged at 3500 ×
Three mice in each group were adopted 30 min after oleic acid injection. The lungs were frozen in liquid nitrogen for measurements immediately after they were removed. Before the assay, the specimens were cleared of fat and debris. All specimens had a wet weight of 100 mg. Phenylmethylsulfonylfluoride (PMSF; 1 mmol) was added just before use. The samples were homogenized in 500 μl of PIPA lysis buffer using a microhomogenizer on ice. All debris and nuclei were removed by centrifugation at 9000 ×
Data from experiments are expressed as mean ± S.E.M. and statistically analyzed using the Student's unpaired
Light microscopic findings in the lung at 6 h after oleic acid injection demonstrated a marked lung injury resembling those seen in lung of patients with ALI/ARDS, represented by prominent atelectasis, intraalveolar and interstitial patchy hemorrhage, edema, thickened alveolar septum, formation of hyaline membranes and the existence of inflammatory cells in alveolar spaces ( Effect of oxymatrine on lung tissue damage in mice at 6 h after oleic acid injection (100×). Representative photomicrographs showing hematoxylin and eosin staining: alveolar damage with intraalveolar and interstitial patchy hemorrhage, edema, thickened alveolar septum, formation of hyaline membranes and the existence of inflammatory cells in alveolar spaces were observed in oleic acid group (A): a, hemorrhage; b, thickened alveolar septum; c, hyaline membrane; d, inflammatory cell. Meanwhile, these damages were not identified or less severe in saline control group (B), oxymatrine (50 mg/kg) + oleic acid group (C) and dexamethasone (2 mg/kg) + oleic acid group (D).
As shown in Ultrastructure of the lung tissue in mice without or with oleic acid injection (8000×). Representative photomicrographs showing: epithelial cell swelling (endoplasmic reticulum dilation and mitochondria swelling) (B), the existence of red blood cells (C) and inflammatory cells (D) in alveolar spaces were observed in oleic acid group. These changes were not observed in the control group (A) and improved or not evident in oleic acid + oxymatrine/dexamethasone groups (E, F): a, normal epithelial cell; b, swollen epithelial cell; c, red blood cell in alveolar spaces; d, inflammatory cell in alveolar spaces.
Values of the lung index and wet-to-dry lung weight ratio (w/d) in various groups of experimental animals were shown in Effect of oxymatrine on lung index and wet-to-dry weight ratio (w/d) in mice with lung injury induced by oleic acid. The mice were given oxymatrine (12.5, 25 and 50 mg/kg, i.p.) for three consecutive days and dexamethasone (2 mg/kg, i.p.) 2 h before injection of oleic acid. The control and oleic acid groups received normal saline. The mice were then sacrificed 6 h after oleic acid administration and lung index, wet-to-dry weight ratio (w/d) were calculated. Mean ± S.E.M.,
As TNF-α plays a pivotal role in mediating oleic acid-induced ALI, we also assessed the regulation of TNF-α production by oxymatrine ( Effect of oxymatrine on serum TNF-α level in mice with lung injury induced by oleic acid. The mice were given oxymatrine (12.5, 25 and 50 mg/kg, i.p.) for three consecutive days and dexamethasone (2 mg/kg, i.p.) 2 h before injection of oleic acid. The control and oleic acid groups received normal saline. The mice were then sacrificed 6 h after oleic acid administration and serum TNF-α level were determined by ELISA assay. Mean ± S.E.M.,
As shown in Expression of p38 MAP kinase and phosphorylated p38 MAP kinase. Bands of p38 MAP kinase were identified in the five groups, and mean density levels in the five groups were almost the same. Phosphorylated p38 MAP kinase was augmented in the oleic acid group compared with the control group, whereas expression of phosphorylated p38 MAP kinase was markedly attenuated in the oxymatrine group compared with the oleic acid group.
Xiang and colleagues used oxyimatrine to evaluate effect of oxymatrine on fulminant hepatitis and hepatocyte apoptosis in mouse models and oxymatrine was administered at dose of 50 mg/kg intraperitoneally (i.d. × 3 days) (
Our results showed that a series of pathological changes were observed under light and electron microscopy after an intravenous administration of oleic acid in mice, which mimicked the pathological changes of clinical ALI/ARDS satisfactorily. Furthermore, the lung index and wet/dry weight ratio were greater in ALI mice than in control group. These findings are in agreement with other reports (
The underlying mechanism of ALI induced by oleic acid is associated with cytokines releases such as TNF-α, which stimulates monocytes to produce IL-1.As the core of the cytokine-network, TNF-α and IL-1 play important roles not only in the production of other inflammatory cytokines, but also in the migration and adherence of neutrophils to endothelial cells (
In the present study, our data revealed that serum TNF-α level was higher in oleic acid group than that in control group. Oxymatrine evidently decreased serum TNF-α level, lung index as well as wet-to-dry ratio and reduced pulmonary injury induced by oleic acid. These findings not only corroborate the direct relationship between TNF-α and ALI but also suggest that oxymatrine have a protective effect on oleic acid-induced ALI.
It has been reported that oxymatrine concentration is higher in lung and heart than in other organs. This signifies the anti-ALI effect of oxymatrine has a pharmcokinetic basis (
Under the stimuli of different ALI/ARDS pathogens, a wide and complicated signal transduction process occurs in many different cells. Although the detailed mechanism is still unknown, the p38 mitogen-activated protein kinase (MAPK) has been paid special attention. p38 MAPK is a cytokine-suppressive anti-inflammatory drug target first discovered by
From these findings, we conclude that oxymatrine ameliorates ALI by attenuating the production of proinflammatory cytokines, and that this attenuation is associated with suppression of p38 MAP kinase activation. In addition, our results confirm that p38 MAP kinase does play an important role in the development of oleic acid-induced ALI. Based on our results and previous reports, we expect that p38 MAP kinase may become a promising target for clinical management of ALI, although it needs to be supported by further animal experiments and clinical data.
Reports have shown that there are at least three types of MAP kinase: extracellular signal-regulated protein kinase (ERK1/2; p42/p44); c-Jun N-terminal protein kinase (JNK); p38 MAP kinase (
In China, pure oxymatrine injection has been available in hospital for treatment of hepatitis and tumor for many years. However, it has not been used for ALI/ARDS/SARS in clinic. Since our results indicate that oxymatrine prevents mice from oleic acid-induced ALI, we hope that oxymatrine can be used to treat ALI/ARDS/SARS although further research should be carried out on more animal experiments before clinical trials.
In this paper, we found oxymatrine had a beneficial effect on ALI in mice for the first time. Although details of the mechanism of oxymatrine remain to be unraveled, the present results suggest that oxymatrine improves acute lung injury by attenuating the production of TNF-α, and that this attenuation is associated with suppression of p38 MAP kinase activation.