HIV-1 peptides and zinc depletion elevate the ER stress markers CHOP, ATF6, PERK, and cytokine TNF-α, as well as MHC-I, to trigger apoptosis in monocytes.

Abstract

Monocytes, upon activation, are known to produce substantial levels of cytokines and increased expression of MHC-I. The status of zinc and the nature of the stimulating agent significantly influence the release of various cytokines as well as the extent of MHC-I expression. However, research exploring the combined effects of inflammation and zinc deficiency remains limited. One of the primary challenges in investigating the influence of zinc status on cytokine production is the specificity of the cell types utilized in experimental settings. This study investigates zinc depletion and inflammation using THP-1 monocytes as an in vitro model, with HIV-1 viral peptide pools and TPEN (N,N,N' ,N'-Tetrakis (2-pyridylmethyl) ethylenediamine), an intracellular zinc chelator. Zinc depletion was confirmed through the application of zinquin ethyl ester via fluorescence microscopy. Additionally, we assessed the expression of zinc transporters, Bcl2 family proteins, and caspase-3 using quantitative RT-PCR and Western blot analyses. The production of TNF-α was evaluated through Golgi-Stop experiments, while MHC-I levels were measured following an 8 h incubation with HIV-1 viral peptides. The impact of PHA on monocytes concerning cytokine production and MHC-I levels was also examined. Our results revealed a rapid increase in TNF-α production and elevated MHC-I levels within 8 h post-stimulation. Furthermore, we observed an enhancement of endoplasmic reticulum (ER) stress markers, including CHOP, ATF6, and PERK, as well as BCl2 family-related genes, following treatment with the peptide pool. These findings highlight the hyperactivation of monocytes in response to HIV-1 viral peptides, which may contribute to immune system impairment through caspase-mediated apoptosis.