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In vitro reactivation of latent HIV-1 by cytostatic bis(thiosemicarbazonate) gold(III) complexes.

Fonteh P, Meyer D - BMC Infect. Dis. (2014)

Bottom Line: Viral reactivation was absent for the complexes during co-stimulation with PMA indicating the lack of an additive effect between the chemicals as well as an absence of inhibition of PMA induced HIV reactivation but for HU inhibition of the stimulant's activity was observed (p = 0.01).The cytostatic effect of 1 and 2 and now HIV reactivation from a U1 latency model is consistent with that of the cytostatic agent, HU.These findings suggest that the complexes have a potential dual (cytostatic and reactivation) role in viral "activation/elimination".

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry, Faculty of Natural and Agricultural Sciences, University of Pretoria, Hatfield Campus, Pretoria 0002, South Africa. Debra.Meyer@up.ac.za.

ABSTRACT

Background: A number of cytostatic agents have been investigated for the ability to reactivate latent viral reservoirs, which is a major prerequisite for the eradication of HIV-1 infection. Two cytostatic bis(thiosemicarbazonate) gold(III) complexes (designated 1 and 2) were tested for this potential in the U1 latency model of HIV-1 infection.

Methods: Cell viability in the presence or absence of 1 and 2 was determined using a tetrazolium dye and evidence of reactivation was assessed by p24 antigen capture following exposure to a latency stimulant, phorbol myristate acetate (PMA) and or test compounds. The latency reactivation mechanism was explored by determining the effect of the complexes on protein kinase C (PKC), histone deacetylases (HDAC) and proinflammatory cytokine production.

Results: The CC50 of the complexes in U1 cells were 0.53 ± 0.12 μM for 1 and 1.0 ± 0.4 μM for 2. In the absence of PMA and at non toxic concentrations of 0.2 and 0.5 μM, 1 and 2 significantly (p ≤ 0.02) reactivated virus in U1 cells by 2.7 and 2.3 fold respectively. In comparison, a 2.6 fold increase (p = 0.03) in viral reactivation was observed for hydroxyurea (HU), which was used as a cytostatic and latent HIV reactivation control. Viral reactivation was absent for the complexes during co-stimulation with PMA indicating the lack of an additive effect between the chemicals as well as an absence of inhibition of PMA induced HIV reactivation but for HU inhibition of the stimulant's activity was observed (p = 0.01). Complex 1 and 2 activated PKC activity by up to 32% (p < 0.05) but no significant inhibition of HDAC was observed. Increases in TNF-α levels suggested that the reactivation of virus by the complexes may have been due to contributions from the latter and the activation of PKC.

Conclusion: The ethyl group structural difference between 1 and 2 seems to influence bioactivity with lower active concentrations of 1, suggesting that further structural modifications should improve specificity. The cytostatic effect of 1 and 2 and now HIV reactivation from a U1 latency model is consistent with that of the cytostatic agent, HU. These findings suggest that the complexes have a potential dual (cytostatic and reactivation) role in viral "activation/elimination".

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Molecular structure of complexes 1 and 2 [24]. This figure is reproduced with permission from the Journal of Inorganic Biochemistry.
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Fig1: Molecular structure of complexes 1 and 2 [24]. This figure is reproduced with permission from the Journal of Inorganic Biochemistry.

Mentions: The synthesis of the bis(thiosemicarbazonate) gold(III) complexes (1 and 2) have previously been reported [24]. The gold(III) complexes have general formula; [Au(L)]Cl, where L = L1, diacetyl-bis(N4-ethylthiosemicarbazone, L2, diacetyl-bis(N4-methylthiosemicarbazone). L1 and L2 are also known as the precursor compounds or ligands used in synthesising 1 and 2 while HAuCl4.4H2O is the gold starting material. Complex 1 differs from 2 by the presence of an ethyl group in place of a methyl group as shown in the molecular formulae in Figure 1. HU was purchased from Sigma Aldrich (Missouri, USA). The compounds and complexes were dissolved in DMSO (vehicle) to 20 mg/mL and stored in single use aliquots at −20°C before further dilution with culture media as needed in the various assays to final DMSO concentration of ≤0.6% (v/v).Figure 1


In vitro reactivation of latent HIV-1 by cytostatic bis(thiosemicarbazonate) gold(III) complexes.

Fonteh P, Meyer D - BMC Infect. Dis. (2014)

Molecular structure of complexes 1 and 2 [24]. This figure is reproduced with permission from the Journal of Inorganic Biochemistry.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4265357&req=5

Fig1: Molecular structure of complexes 1 and 2 [24]. This figure is reproduced with permission from the Journal of Inorganic Biochemistry.
Mentions: The synthesis of the bis(thiosemicarbazonate) gold(III) complexes (1 and 2) have previously been reported [24]. The gold(III) complexes have general formula; [Au(L)]Cl, where L = L1, diacetyl-bis(N4-ethylthiosemicarbazone, L2, diacetyl-bis(N4-methylthiosemicarbazone). L1 and L2 are also known as the precursor compounds or ligands used in synthesising 1 and 2 while HAuCl4.4H2O is the gold starting material. Complex 1 differs from 2 by the presence of an ethyl group in place of a methyl group as shown in the molecular formulae in Figure 1. HU was purchased from Sigma Aldrich (Missouri, USA). The compounds and complexes were dissolved in DMSO (vehicle) to 20 mg/mL and stored in single use aliquots at −20°C before further dilution with culture media as needed in the various assays to final DMSO concentration of ≤0.6% (v/v).Figure 1

Bottom Line: Viral reactivation was absent for the complexes during co-stimulation with PMA indicating the lack of an additive effect between the chemicals as well as an absence of inhibition of PMA induced HIV reactivation but for HU inhibition of the stimulant's activity was observed (p = 0.01).The cytostatic effect of 1 and 2 and now HIV reactivation from a U1 latency model is consistent with that of the cytostatic agent, HU.These findings suggest that the complexes have a potential dual (cytostatic and reactivation) role in viral "activation/elimination".

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry, Faculty of Natural and Agricultural Sciences, University of Pretoria, Hatfield Campus, Pretoria 0002, South Africa. Debra.Meyer@up.ac.za.

ABSTRACT

Background: A number of cytostatic agents have been investigated for the ability to reactivate latent viral reservoirs, which is a major prerequisite for the eradication of HIV-1 infection. Two cytostatic bis(thiosemicarbazonate) gold(III) complexes (designated 1 and 2) were tested for this potential in the U1 latency model of HIV-1 infection.

Methods: Cell viability in the presence or absence of 1 and 2 was determined using a tetrazolium dye and evidence of reactivation was assessed by p24 antigen capture following exposure to a latency stimulant, phorbol myristate acetate (PMA) and or test compounds. The latency reactivation mechanism was explored by determining the effect of the complexes on protein kinase C (PKC), histone deacetylases (HDAC) and proinflammatory cytokine production.

Results: The CC50 of the complexes in U1 cells were 0.53 ± 0.12 μM for 1 and 1.0 ± 0.4 μM for 2. In the absence of PMA and at non toxic concentrations of 0.2 and 0.5 μM, 1 and 2 significantly (p ≤ 0.02) reactivated virus in U1 cells by 2.7 and 2.3 fold respectively. In comparison, a 2.6 fold increase (p = 0.03) in viral reactivation was observed for hydroxyurea (HU), which was used as a cytostatic and latent HIV reactivation control. Viral reactivation was absent for the complexes during co-stimulation with PMA indicating the lack of an additive effect between the chemicals as well as an absence of inhibition of PMA induced HIV reactivation but for HU inhibition of the stimulant's activity was observed (p = 0.01). Complex 1 and 2 activated PKC activity by up to 32% (p < 0.05) but no significant inhibition of HDAC was observed. Increases in TNF-α levels suggested that the reactivation of virus by the complexes may have been due to contributions from the latter and the activation of PKC.

Conclusion: The ethyl group structural difference between 1 and 2 seems to influence bioactivity with lower active concentrations of 1, suggesting that further structural modifications should improve specificity. The cytostatic effect of 1 and 2 and now HIV reactivation from a U1 latency model is consistent with that of the cytostatic agent, HU. These findings suggest that the complexes have a potential dual (cytostatic and reactivation) role in viral "activation/elimination".

Show MeSH
Related in: MedlinePlus