Chemical-Disease Category Linkage (CDCL): Computational Methods Linking Traditional Chinese Medicines and Western Therapeutics
DALE E. JOHNSON*a,b AND KIT WUN KATHY CHEUNGc
Chemical-Disease Category Linkage (CDCL) is a term used to encompass various methods and approaches to link traditional Chinese medicine (TCM) and/or dietary supplements with TCM classifications or categories, diseases, the molecular basis of both diseases and therapeutic interventions, and the synergistic and/or antagonistic interactions of potential combined use with Western therapeutic treatments1 (Figure 12.1).
Issues in Toxicology No. 31
Computational Systems Pharmacology and Toxicology Edited by Dale E. Johnson and Rudy J. Richardson © The Royal Society of Chemistry 2017 Published by the Royal Society of Chemistry, www.rsc.org
Figure 12.1 In Western therapeutics, clinicians treat patients with medications that can exert their effects by modulating the known molecular targets associated with the disease in question. Due to the differences in philosophy, the causes of the disease in question can be different in traditional Chinese medicine (TCM). To target those causes, TCM practitioners often use TCM herbal recipes that are comprised of herbs from various therapeutic classes. Like Western therapeutics, the active constituents in these herbal ingredients (phytochemicals) must reach a molecular target in order to exert their effects. The idea of chemical-disease category linkage (CDCL) is an effort to link TCM and/or dietary supplements with their own classifications, diseases, molecular basis of the diseases as well as therapeutic interventions, and the synergistic and/or antagonistic effects with Western therapeutics when used concomitantly.
traditional medicine, which incorporates the therapeutic use of herbs and other natural products particularly in recipes or other combinations, has been embedded in many cultures for thousands of years. there is an extensive foundation for the therapeutic effects of herbal medicines primarily derived from their extensive use, but which also includes supportive research data including clinical trial results.2 the World Health organization (WHo) has estimated that ~80% of the global population relies on traditional herbal medicines as part of standard healthcare.3 in the united states, where herbal remedies are classified as dietary supplements, an estimated one in five adults regularly consume herbal products.4 Consumers are increasingly using web-based sources for diagnosis and suggestions of treatments, which presents an issue within the healthcare system, as most herbal products are not included in patient records as “other medications”, thereby limiting the understanding of potential herb-drug interactions to both the patient and healthcare professional.5 China has long recognized the value of the combination of traditional and conventional (Western) medicine and originated both the study and practice of integrated medicine. The National Institutes of Health (№H) has defined complementary and alternative medicine (CAM) as a group of diverse medical and healthcare systems, practices, and products that are not generally considered to be part of conventional medicine.2 While alternative medicine is used instead of conventional medicine, complementary medicine is used in conjunction with conventional therapeutics. Therefore, according to the NIH definition, integrated medicine encompasses the use of both conventional and alternative therapies for which there is evidence of safety and effectiveness.2 in a report in 2002, it was estimated that more than one-third of us citizens had used Cam within the previous 12 months, and more than half of patients aged 18 years or older used CAM therapies in addition to conventional therapies because of the belief that CAM therapies increased the beneficial effects or reduced side effects of conventional drugs.2
Chan et al.2 reviewed the history and principles of TCM and discussed a method to deconvolute TCM formulations into constituent phytochemicals, along with identification of potential molecular targets and the proposed relevant biological activity. The review also details several synergistic and antagonistic examples of herbs and phytochemicals within a formulation, and methods to explore interactions between TCM and Western therapeutics.
Recent Western-related milestones for TMC include:
- • first TCM approved for the European union market in 2012: Di’ao Xin Xue Kang, an extract of Dioscorea nipponica approved in the Netherlands for pain relief;5
- • second ever botanical drug approved by the us Food and Drug Administration (FDA) in 2012. Fulyzaq (crofelemer); derived from the red sap of Croton lechleri for HIV-associated diarrhea. in 2006, the us FDA approved the first botanical prescription drug, Veregen (sinecatechins), a treatment for external genital and perianal warts6
- • Youyou Tu was awarded the 2011 Lasker-DeBakey Clinical Medical Research Award for discovering artemisinin as a treatment for malaria,7 and shared the 2015 Nobel Prize in Physiology or Medicine for discovering the novel treatment for malaria8
in the discovery process for artemisinin, Tu started with a large-scale screen of herbal remedies in malaria-infected animals, and revisited the ancient literature and discovered clues that guided her in her quest to successfully extract the active component from Artemisia annua.