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HIV-1 Tat-mediated microglial ferroptosis involves the miR-204-ACSL4 signaling axis
Muthukumar Kannan1, Susmita Sil1, Abiola Oladapo1
1Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE, 68198-5880, USA.
Abstract:
This study was focused on exploring the role of the HIV-1 Tat protein in mediating microglial ferroptosis. Exposure of mouse primary microglial cells (mPMs) to HIV-1 Tat protein resulted in induction of ferroptosis, which was characterized by increased expression of Acyl-CoA synthetase long-chain family member 4 (ACSL4), in turn, leading to increased generation of oxidized phosphatidylethanolamine, elevated levels of lipid peroxidation, upregulated labile iron pool (LIP) and ferritin heavy chain-1 (FTH1), decreased glutathione peroxidase-4 and mitochondrial outer membrane rupture. Also, inhibition of ferroptosis by ferrostatin-1 (Fer-1) or deferoxamine (DFO) treatment suppressed ferroptosis-related changes in mPMs. Similarly, the knockdown of ACSL4 by gene silencing also inhibited ferroptosis induced by HIV-1 Tat. Furthermore, increased lipid peroxidation resulted in increased release of proinflammatory cytokines, such as TNFα, IL6, and IL1β and microglial activation. Pretreatment of mPMs with Fer-1 or DFO further blocked HIV-1 Tat-mediated microglial activation in vitro and reduced the expression and release of proinflammatory cytokines. We identified miR-204 as an upstream modulator of ACSL4, which was downregulated in mPMs exposed to HIV-1 Tat. Transient transfection of mPMs with miR-204 mimics reduced the expression of ACSL4 while inhibiting HIV-1 Tat-mediated ferroptosis and the release of proinflammatory cytokines. These in vitro findings were further validated in HIV-1 transgenic rats as well as HIV + ve human brain samples. Overall, this study underscores a novel mechanism(s) underlying HIV-1 Tat-mediated ferroptosis and microglial activation involving miR-204-ACSL4 signaling.
Insights
HIV-1 Tat protein triggers microglial ferroptosis via the miR-204-ACSL4 pathway, leading to inflammation. Inhibiting ferroptosis or ACSL4 reduces these effects, suggesting therapeutic targets for HIV-associated neuroinflammation.
Area of Science:
- Neuroscience
- Immunology
- Cell Biology
Background:
- Microglial activation and ferroptosis are implicated in HIV-1 pathogenesis.
- The HIV-1 Tat protein is a key viral factor influencing neuronal and glial cell function.
- Understanding mechanisms of microglial ferroptosis is crucial for addressing HIV-associated neuroinflammation.
Purpose of the Study:
- To investigate the role of HIV-1 Tat protein in inducing microglial ferroptosis.
- To elucidate the molecular pathways, including miR-204 and ACSL4, involved in Tat-mediated ferroptosis.
- To explore the link between microglial ferroptosis, inflammation, and HIV-1 infection.
Main Methods:
- Primary mouse microglial cells (mPMs) were exposed to HIV-1 Tat protein.
- Ferroptosis was assessed by measuring lipid peroxidation, iron levels, and specific protein markers (ACSL4, FTH1, GPX4).
- Gene silencing (ACSL4 knockdown) and miRNA mimics (miR-204) were used, along with ferroptosis inhibitors (Fer-1, DFO).
- Proinflammatory cytokine release (TNFα, IL6, IL1β) and microglial activation were measured.
- In vivo studies utilized HIV-1 transgenic rats and human brain samples.
Main Results:
- HIV-1 Tat induced ferroptosis in mPMs, characterized by increased ACSL4, lipid peroxidation, iron, and FTH1, and decreased GPX4.
- Inhibition of ferroptosis (Fer-1, DFO) or ACSL4 suppressed Tat-induced ferroptosis and microglial activation.
- HIV-1 Tat downregulated miR-204, which acts upstream of ACSL4.
- miR-204 mimics reduced ACSL4 expression, inhibited ferroptosis, and decreased cytokine release.
- Findings were validated in HIV-1 transgenic rats and human brain samples.
Conclusions:
- HIV-1 Tat protein directly induces microglial ferroptosis through the miR-204-ACSL4 signaling pathway.
- This ferroptosis contributes to microglial activation and the release of proinflammatory cytokines.
- Targeting the miR-204-ACSL4 axis may offer a therapeutic strategy for HIV-associated neuroinflammation.
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