Abstract
BackgroundLippia javanica (lemon bush) is commonly used in the treatment of respiratory ailments, including asthma in southern African countries but there is no scientific evidence to support this claim. This study investigated the anti-inflammatory, antioxidant and anti-asthmatic effects of L. javanica using a rat model of asthma.MethodsA 5% w/v L. javanica tea infusion was prepared and characterised by liquid chromatography–mass spectrometer (LC-MS). Animals were intraperitoneally sensitized with ovalbumin (OVA) and subsequently challenged intranasal with OVA on day 15 except the control group. Animals were grouped (n = 5/group) for treatment: unsensitised control, sensitised control, sensitised + prednisolone and sensitised + L. javanica at 50 mg/kg/day and 100 mg/kg/day – equivalent to 1 and 2 cups of tea per day, respectively. After 2 weeks of treatment, bronchoalveolar lavage fluid (BALF) was collected for total and differential white blood cell (WBC) count. Nitric oxide (NO), lipid peroxidation and antioxidants were also assessed in BALF. Ovalbumin specific IgE antibody and inflammatory cytokines: IL-4, IL-5, IL-13 and TNF-alpha were measured in serum. Lung and muscle tissues were histological examined.ResultsL. javanica was rich in phenolic compounds. OVA sensitisation resulted in development of allergic asthma in rats. L. javanica treatment resulted in a reduction in total WBC count as well as eosinophils, lymphocytes and neutrophils in BALF. L. javanica inhibited Th2-mediated immune response, which was evident by a decrease in serum IgE and inflammatory cytokines: IL-4, IL-5, IL-13 and TNF-α. L. javanica treatment also reduced malondialdehyde (MDA) and NO, and increased superoxide dismutase, glutathione and total antioxidant capacity. Histology showed significant attenuation of lung infiltration of inflammatory cells, alveolar thickening, and bronchiole smooth muscle thickening.ConclusionL. javanica suppressed allergic airway inflammation by reducing Th2-mediated immune response and oxidative stress in OVA-sensitized rats which may be attributed to the presence of phenolic compound in the plant. This finding validates the traditional use of L. javanica in the treatment of respiratory disorders.
Highlights
Lippia javanica is commonly used in the treatment of respiratory ailments, including asthma in southern African countries but there is no scientific evidence to support this claim
L. javanica suppressed allergic airway inflammation by reducing Th2-mediated immune response and oxidative stress in OVA-sensitized rats which may be attributed to the presence of phenolic compound in the plant
The preferential activation of Th2 cells by Antigen presenting cells (APCs) lead to the production of cytokines including: IL-4, IL-5 and IL-13 [53] that results in the activation and proliferation of inflammatory cells including eosinophils, lymphocytes, neutrophils and macrophages to the site of inflammation
Summary
Lippia javanica (lemon bush) is commonly used in the treatment of respiratory ailments, including asthma in southern African countries but there is no scientific evidence to support this claim. This study investigated the anti-inflammatory, antioxidant and anti-asthmatic effects of L. javanica using a rat model of asthma. Chronic respiratory diseases such as chronic bronchitis, asthma and obstructive pulmonary disease are among the leading causes of death worldwide, with asthma rated the most common [1]. Asthma is an airway inflammatory disease characterised by variable expiratory airflow limitation associated with bronchoconstriction, increased mucus secretion and exaggerated bronchial hyper-responsiveness. The prevalence of asthma in South Africans is between 6 and 10% with 20% of school-going age pupils between 9 and 15 years of age experiencing symptoms of asthma [8]
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