Abstract
BackgroundAcacia catechu (Mimosa family) stem bark extracts have been used traditionally as a dietary supplement as well as a folk medicine given its reported anti-inflammatory, immunomodulatory, hepatoprotective, antioxidant, anti-microbial and anti-tumor activities. The present study was undertaken to evaluate the anti-HIV-1 activity of the extracts from stem bark of A. catechu.MethodsThe aqueous and 50% ethanolic extracts of A. catechu stem bark were prepared and 50% ethanolic extract was further fractioned by successively partitioning with petroleum ether, chloroform and n-butanol. All the extracts and fractions were evaluated for cytotoxicity and anti-HIV-1 activity using different in vitro assays. The active n-butanol fraction was evaluated for its inhibition against HIV-1 reverse transcriptase, integrase, protease, pro-viral genome integration and viral Tat protein mediated transactivation. The effect of n-butanol fraction on the induction of pro-inflammatory cytokines secretion in Vk2/E6E7 cells and transepithelial resistance in Caco-2 and HEC-1A cells was investigated.ResultsThe aqueous and 50% ethanolic extracts of A. catechu showed IC50 values of 1.8 ± 0.18 μg/ml and 3.6 ± 0.31 μg/ml, respectively in cell-free virus based assay using TZM-bl cells and HIV-1NL4.3 (X-4 tropic). In the above assay, n-butanol fraction exhibited anti-HIV-1 activity with an IC50 of 1.7 ± 0.12 μg/ml. The n-butanol fraction showed a dose-dependent inhibition against HIV-1NL4.3 infection of the peripheral blood lymphocytes and against HIV-1BaL(R-5-tropic) as well as two different primary viral isolates of HIV-1 infection of TZM-bl cells. The n-butanol fraction demonstrates a potent inhibitory activity against the viral protease (IC50 = 12.9 μg/ml), but not reverse transcriptase or integrase. Further, in Alu-PCR no effect on viral integration was observed. The n-butanol fraction interfered with the Tat-mediated Long Terminal Repeat transactivation in TZM-bl cells, mRNA quantitation (qRT-PCR) and electrophoretic mobility shift assay (EMSA). The n-butanol fraction did not cause an enhanced secretion of pro-inflammatory cytokines in Vk2/E6E7 cells. Additionally, no adverse effects were observed to the monolayer formed by the Caco-2 and HEC-1A epithelial cells.ConclusionsThe results presented here show a potential anti-HIV-1 activity of A. catechu mediated by the inhibition of the functions of the viral protein and Tat.
Highlights
Acacia catechu (Mimosa family) stem bark extracts have been used traditionally as a dietary supplement as well as a folk medicine given its reported anti-inflammatory, immunomodulatory, hepatoprotective, antioxidant, anti-microbial and anti-tumor activities
As Tat accumulates above the threshold, it leads to the transition from latent state of Human immunodeficiency virus-1 (HIV-1) to active replication in lymphocytes when the protein interacts with the Tatresponsive element (TAR) located in the long terminal repeat (LTR) promoter in the viral DNA [9,10,11]
Discovering drugs that interfere with the functionality of the crucial enzymes of HIV-1 that play a critical role in viral pathogenesis i.e. reverse transcriptase (RT), integrase and protease are important targets to be considered against HIV-1 infection
Summary
Acacia catechu (Mimosa family) stem bark extracts have been used traditionally as a dietary supplement as well as a folk medicine given its reported anti-inflammatory, immunomodulatory, hepatoprotective, antioxidant, anti-microbial and anti-tumor activities. Active antiretroviral therapy (HAART) has led to a dramatic increase in the longevity and the quality of life for people infected with HIV-1 [1], but due to the emergence of drug resistant virus [2], there is a continuous need to develop new anti-HIV-1 agents with novel targets and mechanisms of action. The late events of the viral life cycle include the processes of HIV-1 mRNA synthesis, protein expression and virus maturation. The progeny viruses expressed from the activated viral gene expression are assembled on and budded through the host cell membrane after being processed by the viral encoded enzyme protease [7]. Discovering drugs that interfere with the functionality of the crucial enzymes of HIV-1 that play a critical role in viral pathogenesis i.e. RT, integrase and protease are important targets to be considered against HIV-1 infection
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