Correlation analysis of genetic diversity and population structure of Houttuynia cordata Thunb with regard to environment

The Traditional Chinese Medicine Houttuynia cordata Thunb decoction alters intestinal barrier function via an EGFR dependent MAPK (ERK1/2) signalling pathway

BACKGROUND

A traditionally prepared aqueous extract (= decoction) of Houttuynia cordata Thunb (Yu xing cao) (HC) is widely used in Traditional Chinese Medicine (TCM) to treat inflammatory disease. Previous chemical and biological studies on HC have mainly focused on organic extracts rather than the aqueous decoction, which is the traditional formulation.

PURPOSE

The study aimed to investigate whether the chemical composition of HC aqueous decoction (HCD) varies with geographical sourcing, to investigate the mechanism of action of HCD, and to determine if chemical variation impacts on HCDs anti-inflammatory activity.

METHOD

Sixteen samples of HC were purchased from Sichuan, Hubei and Anhui provinces in the People's Republic of China (PRC) and were prepared by the traditional decoction method to yield their corresponding HCDs. A Quality Control (QC) sample was prepared by combining individual HCD extracts. HCDs were analysed by Nuclear Magnetic Resonance (NMR) and High-Performance Liquid Chromatography-Mass Spectrometry (HPLC-MS). The anti-inflammatory activities associated with intestinal barrier function of HCD were studied by tumor necrosis factor-α (TNF-α) activated Caco-2 monolayers in vitro and in vivo using Dextran Sulfate Sodium (DSS)-induced murine colitis. Proteins involved in inflammation, mRNA levels, disease severity scores, and histology involved in intestinal inflammation were analysed.

RESULTS

HCD samples exhibited different chemical fingerprints and three regional outliers were identified by Principal Component Analysis (PCA). Fifteen phytochemical metabolites were identified and quantified. HCD showed in vitro anti-inflammatory activity, enhancing zonula occludens-1 (ZO-1), occludin, interleukin (IL)-10 and decreasing IL-1β, IL-6 and epidermal growth factor receptor (EGFR) via an EGFR-dependent mitogen-activated protein kinase (MAPK) extracellular signal-regulated kinase 1/2 (ERK 1/2) signaling pathway. This beneficial effect on intestinal inflammation was also seen in the in vivo colitis model at a molecular level in colonic tissues.

CONCLUSION

This study shows that the test HCDs were chemically different, resulting in different levels of activity on intestinal barrier function and inflammation. Moreover, a "Daodi" product showed the greatest biological activity in this study, thus validating the importance of the "Daodi" quality material in TCM and supporting the traditional used of HCD for the treatment of inflammation.

Genetic Diversity and Population Structure of a Medicinal Herb Houttuynia cordata Thunb. of North-East India

Intra-species genetic variability assessment is an effective tool in formulating genetic improvement and germplasm conservation strategies. Houttuynia cordata Thunb. is a semidomesticated medicinal herb consumed widely in traditional diet in North-Eastern India. In the present study, an effort has been made to assess the genetic diversity of H. cordata Thunb. from Brahmaputra valley of North-East India. A total of 545 genotypes from 18 populations of H. cordata Thunb. from four different regions, i.e. North-East, North-West, South-East and South-West, with respect to river Brahmaputra were collected and population genetic diversity and structure were analysed using ISSR molecular markers. Population genetic structure analysis using unweighted pair group method with averages (UPGMA)-based hierarchical cluster analysis, principal coordinate analysis (PCoA) and model-based clustering in STRUCTURE program revealed that the population of H. cordata Thunb. grouped according to regional distribution and forms four genetically distinct clusters. The analysis of molecular variance showed that differentiation among regions was significant with 60% genetic variation among region, 3% genetic variation among population within region and 37% genetic variation within population. We found wide variation in Nei's gene diversity (Hj) ranging from 0.07782 in Margherita population to 0.13634 in Barapani population. Furthermore, Nei's gene diversity within population (Nei's Hs) and total gene diversity (Ht) were found to be 0.1081 and 0.1769 respectively. The genetic differentiation among 18 population was high (Fst = 0.3894; p < 0.001) with relatively restricted gene flow (Nm = 0.6564). Based on the result of this study, we suggest ex situ conservation could be an appropriate measure to adequately capture the total genetic diversity of H. cordata Thunb. populations of North-East India by selecting few individuals from different populations.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s11105-020-01260-9.