Understanding channel tropism in traditional Chinese medicine in the context of systems biology

Abstract

Channel tropism is investigated and developed through long-term clinical practice. In recent years, the development of channel tropism theory has attracted increasing attention. This study analyzed channel tropism theory and the problems associated with it. Results showed that this theory and systems biology have a similar holistic viewpoint. Systems biology could provide novel insights and platform in the study of channel tropism. Some problems in channel tropism theory, including pharmacology and action mechanism, were investigated.

Keywords

systems biology / channel tropism theory / traditional Chinese medicine / application

Introduction

Chinese herbs have long been used in China based on theories of traditional Chinese medicine (TCM), including five elements (metal, wood, water, fire, and earth), five tastes (sour, bitter, sweet, spicy, and salty), five properties (cool, cold, plain, warm, and hot), and channel tropism. Among these theories, channel tropism theory is the most important because it has guided clinical practice for thousands of years [1-3]. Channel tropism refers to the selective therapeutic effects of a drug on a certain part of the body. A drug may elicit evident or specific therapeutic action on the pathological changes in one or several channels. In recent years, many studies have shown that application of systems biology provides guidance to investigate the scientific connotation of Chinese herbs [4]. Systems biology is generally recognized as a powerful tool to study complex life system that resembles the holism concept of channel tropism in TCM [5]. Therefore, the present study investigated the process of channel tropism theory and the possibility of systems biology application in channel tropism theory of TCM research.

Channel tropism theory

In TCM, the human body is considered as an organic whole; interior, exterior, and other parts of the body are connected to one another via channels and collaterals. Certain viscous channel or channels may function depending on a particular medicine. Given that channels can communicate with internal organs and body surfaces interiorly and exteriorly, respectively, pathological changes in exterior parts may affect the viscera and viscera-related diseases may be expressed in exterior parts of the body. For this reason, symptoms and signs of disease occurring in different parts of the body can be systematically understood according to the theory of channels and collaterals. This theory states that drugs acting on other channels should be used in addition to prescribed medicines for the diseased channel itself. For instance, pain in the hypochondriac region can be relieved by bupleurum root although this pain is caused by the stagnation of liver-qi; thus, bupleurum can act on disorders of the liver channel [6]. Or Mahuang (Herba Ephedrae) and Xingren (Semen Armeniacae Amarum) are used to relieve symptoms of lung disorders such as cough and dyspnea associated with lung channels. Qingpi (Pericarpium Citri Reticulatae Viride) and Xiangfu (Rhizoma Cyperi), also associated with the liver channel, are used to relieve symptoms of liver disorders marked by distending pain of the breast and the hypochondrium.

In some studies [7,8], channel tropism theory is also associated with theories of the four properties and the five flavors as well as lifting, lowering, floating, and sinking activities of drugs. Thus, different drugs acting on the same channel have different effects because of their different properties, flavors, and activities. For example, scutellaria root, dried ginger, and lily bulb act on the lung channel. In particular, scutellaria root can clear lung heat, dried ginger can warm lung cold, and lily bulb can be used to compensate for lung deficiency. Thus, drug actions can be comprehensively analyzed, and drugs can be correctly used when different aspects are studied.

Channel tropism theory is closely associated with therapeutic effects based on clinical practice and considered as a very important basis in clinical applications. Based on this theory, Chinese herbs can be prescribed to achieve the desired therapeutic effects in clinical applications. In recent years, researchers worldwide have studied channel tropism theory based on several aspects, including receptors, pharmacokinetic parameters of active components, changes in trace element contents, changes in cAMP/cGMP concentrations, and so on [9-11]. However, the basis and the mechanism of this theory have not been clearly elucidated because of its multi-component and multi-target nature. For example, the use of a pharmacokinetic parameter of single component to study channel tropism cannot correspond to the interactions among different components in Chinese herbs [12]. Moreover, the use of trace elements to study the mechanism of channel tropism cannot represent the respective actions of Chinese herbs [13]. Other signaling pathways can be neglected when changes in cAMP and cGMP concentrations among organs and tissue are considered; thus, the selective action of channel tropism is not comprehensively explained [14]. The key point involves studying channel tropism based on the mechanism by which the anatomical apparatus is identified with Zang-Fu organs in TCM [15-17].

Application of systems biology in channel tropism theory

Systems biology, a new subject in life science, focuses on the constituents (genes, mRNA, proteins, and so on) of a biological system and the interactions among these constituents under specific conditions. Recent studies show that the use of technological platforms of systems biology, genomics, proteomics, and metabolomics can provide useful tools to study a complicated theory system of TCM and understand the principle of herbal formulation [18,19]. A common development has been observed between channel tropism and systems biology because of their similar holistic viewpoint aimed at the same objective but via different means.

In TCM, herbs are used in formulations to maintain homeostasis of the body holistically, thereby acting on multiple target systems such as cells and genes. The present study showed that changes in these components in the body are limited although components of Chinese herbs are complicated. Biomarkers associated with channel tropism can be discovered by analyzing the metabolite profile of TCM. Compositions after metabolism can represent the whole efficacy of TCM and explain channel tropism theory [20–22]. Therefore, the methodology of systems biology and related technology could provide a new platform in the study of channel tropism theory with a clear advantage and a broad prospect.

Channel tropism is based on the theory of the viscera, channels, and collaterals. Metabolomics, a recently developed technology platform, focuses on interactions of molecular assembly and their functions in the body system. All of these factors affecting health can be reflected in a metabolome. Research using metabolomics technology could infer the final results affected by various external factors through metabolites in vivo and metabolic networks. An integral and systematic study of metabolomics is in agreement with channel tropism theory in nature. Therefore, metabolomics technology platform could be used to study the complex theoretical system of channel tropism.

Conclusions

Channel tropism is the core component of Chinese herbal property theory [22]. Western medicine currently uses pure, single compounds. By contrast, TCM has a long history of using multiple combinations of Chinese herbs to treat and relieve the symptoms of different human diseases. The multi-component and synergistic nature of TCM is an important achievement in Chinese herb development. This achievement needs system level research to understand the whole component of such systems and create a diagram of their interactions. This study suggested the application of systems biology to analyze systemic components, basic modules, and interactions among components according to channel tropism theory of TCM. We consider channel tropism theory as one of the promising directions that should be understood by modern medicine.

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Higher Education Press and Springer-Verlag Berlin Heidelberg