Analysis of target organs of Houttuynia cordata: A study on the anti-inflammatory effect of upper respiratory system

Ethnopharmacological relevance: Houttuynia cordata Thunb. (HC) is a traditional anti-pyretic herb that is classified as the lung meridian in traditional Chinese medicine. However, no articles have explored the main organs responsible for the anti-inflammatory activities of HC.Aim of the study: The aim of the study was to investigate the meridian tropism theory of HC in lipopolysaccharide (LPS)-induced pyretic mice, as well as to identify the underlying mechanisms.Materials and methods: Transgenic mice carrying the luciferase gene driven by nuclear factor-& kappa;B (NF-& kappa;B) were intraperitoneally injected with LPS and orally administered standardized concentrated HC aqueous extract. The phytochemicals present in the HC extract were analyzed using high-performance liquid chromatography. In vivo and ex vivo luminescent imaging from transgenic mice was used to investigate the meridian tropism theory and anti-inflammatory effects of HC. Microarray analysis of gene expression patterns was used to elucidate the therapeutic mechanisms of HC.Results: HC extract was found to contain phenolic acids, such as protocatechuic acid (4.52%) and chlorogenic acid (8.12%), as well as flavonoids like rutin (2.05%) and quercitrin (7.73%). The bioluminescent intensities induced by LPS in the heart, liver, respiratory system, and kidney were significantly suppressed by HC, while the maximal decrease (about 90% reduction) of induced luminescent intensity was observed in the upper respiratory tract. These data suggested that upper respiratory system might be the target for HC anti-inflammatory abilities. HC affected the processes involved in innate immunity, such as chemokine-mediated signaling pathway, in-flammatory response, chemotaxis, neutrophil chemotaxis, and cellular response to interleukin-1 (IL-1). More-over, HC significantly reduced the proportions of p65-stained cells and the amount of IL-18 in trachea tissues.Conclusion: Bioluminescent imaging coupled with gene expression profile was used to demonstrate the organ selectivity, anti-inflammatory effects, and therapeutic mechanisms of HC. Our data demonstrated for the first time that HC displayed lung meridian-guiding effects and exhibited great anti-inflammatory potential in the upper respiratory tract. The NF-& kappa;B and IL-18 pathways were associated with the anti-inflammatory mechanism of HC against LPS-provoked airway inflammation. Moreover, chlorogenic acid and quercitrin might be involved in the anti-inflammatory properties of HC.

Automated summary

This study used bioluminescent imaging and gene expression profiling to demonstrate, for the first time, that Houttuynia cordata has lung meridian-guiding effects and exhibits potent anti-inflammatory potential in the upper respiratory tract. The NF-κB and IL-18 pathways are associated with the anti-inflammatory mechanism of Houttuynia cordata against LPS-induced airway inflammation. Additionally, chlorogenic acid and quercitrin may be involved in the anti-inflammatory properties of Houttuynia cordata.