HIV: Current Research
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Background: One medication commonly used by HIV-1-infected individuals is the antimicrobial sulphamethoxazole (SMX), which is used in the treatment and prophylaxis of pneumocystis pneumonia. However, SMX is responsible for a very high incidence of hypersensitivity adverse drug reactions (ADRs) in the HIV-1 population. While the pathophysiology of ADRs in general is unknown, sulphamethoxazole-mediated ADRs have been linked to its reactive metabolite sulphamethoxazole-hydroxylamine (SMX-HA). Our previous work has shown that increased expression of the HIV-1 Tat protein in T cells correlated with increased apoptosis after incubation with SMX-HA. In this study we sought to determine the region of the Tat protein responsible for this effect and the mechanism by which Tat contributed to SMX-HA mediated apoptosis.
Methods: We established Jurkat T and Cos 7 cell lines that stably expressed full-length Tat (Tat101) and deletion mutants (Tat86, Tat72, Tat48 and Tat∆). These cell lines were then incubated with SMX-HA and assayed for cell viability and production of reactive oxygen species (ROS). We further used confocal microscopy to assess the intracellular distribution of the Tat proteins and to determine if changes in the expression and/or localization of key cytoskeleton proteins contributed to Tat-mediated apoptosis after SMX-HA treatment.
Results: Deletion of regions of Tat that lead to increased cytoplasmic accumulation significantly contributed to increased cell death in the presence of SMX-HA. The increased cell death did not require induction of ROS. Quantitative analysis also showed that the Tat-expressing cell lines had significantly lower levels of β-actin and α-tubulin present both before and after treatment with SMX-HA. Increased cytoplasmic localization of Tat correlated with greater disturbances in the distribution of actin filaments.
Conclusion: The presence of cytoplasmic Tat in T and epithelial cell lines increases their sensitivity to SMX-HA induced cell death, an effect mediated by the first 48 amino acids of TAT.