Iron Saturation Drives Lactoferrin Effects on Oxidative Stress and Neurotoxicity Induced by HIV-1 Tat

Abstract

The Trans-Activator of Transcription (Tat) of Human Immunodeficiency Virus (HIV-1) is involved in virus replication and infection and can promote oxidative stress in human astroglial cells. In response, host cells activate transcription of antioxidant genes, including a subunit of System Xc− cystine/glutamate antiporter which, in turn, can trigger glutamate-mediated excitotoxicity. Here, we present data on the efficacy of bovine Lactoferrin (bLf), both in its native (Nat-bLf) and iron-saturated (Holo-bLf) forms, in counteracting oxidative stress in U373 human astroglial cells constitutively expressing the viral protein (U373-Tat). Our results show that, dependent on iron saturation, both Nat-bLf and Holo-bLf can boost host antioxidant response by up-regulating System Xc− and the cell iron exporter Ferroportin via the Nuclear factor erythroid 2-related factor (Nrf2) pathway, thus reducing Reactive Oxygen Species (ROS)-mediated lipid peroxidation and DNA damage in astrocytes. In U373-Tat cells, both forms of bLf restore the physiological internalization of Transferrin (Tf) Receptor 1, the molecular gate for Tf-bound iron uptake. The involvement of astrocytic antioxidant response in Tat-mediated neurotoxicity was evaluated in co-cultures of U373-Tat with human neuronal SH-SY5Y cells. The results show that the Holo-bLf exacerbates Tat-induced excitotoxicity on SH-SY5Y, which is directly dependent on System-Xc− upregulation, thus highlighting the mechanistic role of iron in the biological activities of the glycoprotein.

Lactoferrin, the Moonlighting Protein of Innate Immunity

“…The protective role of Lf against pathogenic processes related to the expression of the sole viral proteins was also reported in the study by Ianiro and colleagues, where iron saturation rate was found to drive bLf effects on oxidative stress and neurotoxicity induced via HIV-1 Tat [28]. Despite tremendous advances in combined antiretroviral therapy, the standard therapy for HIV-1 infection, HIV + patients can experience HIVassociated neurocognitive disorders [29], mainly due to the chronic basal expression of HIV-1 non-structural proteins, such as Tat, which can trigger neurotoxic effects, related to both oxidative stress induction and excitotoxicity [30,31].…”

To Boost or to Reset: The Role of Lactoferrin in Energy Metabolism

“…Apo-Lf appears to be more effective in the antioxidant response by virtue of its ability to sequester ferric ions (Fe 3+ ), thus protecting against the damaging effects of oxidative stress, specifically by limiting the production of hydroxyl radicals and peroxidized lipids [12,13]. A recent study by Ianiro and colleagues reported that the iron saturation rate influences the antioxidant and neuroprotective role of Lf in astrocytoma cells expressing the human immunodeficiency virus type 1 (HIV-1) Tat protein [14]. Bullen et al [15] showed that the antibacterial activity of Lf decreases as the level of iron saturation increases.…”

“…Interestingly, Lf has a unique ability to access the nucleus of cells and interact with specific and non-specific DNA sequences, functioning as a transcription factor [153,154]. It has been found to facilitate the nuclear translocation of nuclear factor erythroid-2-related factor 2 (Nrf2) [14,155], a crucial regulator of the cellular antioxidant response. Moreover, Lf contributes to the upregulation of Fpn, the sole iron exporter, thus actively contributing to reverse anemia-related sequelae [6].…”

“…In addition, iron disorders are associated with the action of non-structural viral proteins [14,152] such as virulence factors and neurotoxins [171,172]. Two in vitro studies specifically looked at the action of Lf against iron disorders induced by viral proteins, such as the spike protein of SARS-CoV-2 and the tat protein of HIV-1.…”

“…Additionally, Lf restored the normal function of iron uptake in cells expressing the viral protein. However, the effects of the glycoprotein varied depending on its iron saturation and emphasized the need for the quality standardization of Lf products [14]. The studies conducted so far on Lf show promising insights into its therapeutic potential, particularly in the context of viral infections and iron dysregulation.…”