Investigation of the Anti-HIV Effects and Underlying Mechanisms of Chinese Medicines

With the prevalent use of highly active antiretroviral therapy (HAART) for AIDS patients from 1996, the mortality of AIDS patients has been remarkably decreased. For long-term use of HAART, drug resistqance and side effects of antiretrovirals have been frequently reported, which not only discount the therapeutic effects, but also reduce the tolerance of patients. Although HAART therapy has affirmative effects on inhibiting HIV replication in people living with HIV, it is not able to restore the immune competence and patients always suffer from serious compromised immune system. Chinese medicine has been used for thousands of years in China and also popular in the West. The significance of Chinese medicine in HIV/AIDS therapy is currently of interest by the public. In this study, the role and underlying mechanisms of Chinese medicines in HIV/AIDS therapy were investigated. One of the aims in this thesis was to find potential anti-HIV compounds or herbal extracts that may be used as anti-HIV agent enhancers. To seek for lead compound(s), about 100 antiviral herbal extracts and 40 pure natural compounds were explored via HIV-1 protease and glycoprotein 41 (gp-41) inhibition assays. Based on the results of HIV-1 protease and fusion inhibition assay, dunnianol can be considered as a lead compound for further development with better HIV inhibition. The effects of Formula SH and the extract of Houttuynia cordata were also promising in these assays, and further investigations were performed. The water extract of Houttuynia cordata showed better inhibition on HIV-1 protease than pure ethanolic and 50% ethanolic extracts. Bioassay-guided fractionation was performed and a pure polysaccharide, namely HCP-2, was obtained. HCP-2 was elucidated as a pectic polysaccharide with repeating units of (1→4)-alpha-D-galactopyranosyluronic residues based on extensive analysis of NMR and IR. HCP-2 could significantly stimulate the release of IL-1beta and TNF-alpha which indicated the enhanced immune responses when host cell confront with the exogenous pathogens. HCP-2 could also boost the release of MIP-1alpha, MIP-1beta, and RANTES which could compete with HIV-1 to bind on the co-receptor CCR5. Thus, HCP-2 may assist the AIDS patients in immune responses and inhibition of HIV when used in combination with antiretrovirals. Formula SH is an herbal preparation marketed in Thailand. Its components Carthamus tinctorius and Morus alba have been shown to exert inhibition on HIV-1 protease, and its another component Artemisia capillaries possessed HIV-1 fusion inhibition effect. Integrated use of Formula SH and Atazanavir showed additive inhibition effects on HIV-1 protease. Another component Astragalus membranaceus was demonstrated to reverse the downregulated genes, namely CCL4 and CCL8, by Indinavir in human peripheral mononuclear cells (PBMC). Since the above-mentioned promising effects of Formula SH were found, its potential for interaction with western drug was examined. Herb-drug interaction potential of Formula SH was further investigated via in vitro CYP3A inhibition assay and in vivo pharmacokinetic interaction with Atazanavir. Formula SH exhibited in vitro inhibition on human and rat CYP3A activities with Ki values of 24.96 mug/ml and 98.20 mug /ml, respectively; but no effect of Formula SH was shown in the metabolism of Atazanavir in rat in vivo. Consequently, Formula SH combined with HIV protease inhibitor may be beneficial for AIDS patients by HIV inhibition, side effects alleviation and immune restoration. In conclusion, Chinese medicine is proposed to be used as an adjuvant for current HAART therapy to reduce the symptoms, improve quality of life, and alleviate the side effects of current antiretrovirals. Formula SH and HCP-2 can be used as an adjuvant for current commercial available anti-HIV drugs, and benefit AIDS patients in HIV inhibition and immune responses.