People with human immunodeficiency virus-1 (PLWH) experience high rates of HIV-1-associated neurocognitive disorders (HANDs); clinical symptoms range from being asymptomatic to experiencing HIV-associated dementia. Antiretroviral therapies have effectively prolonged the life expectancy related to PLWH; however, the prevalence of HANDs has increased. Implicated in the pathogenesis of HANDs are two HIV-1 proteins, transactivator of transcription (Tat) and gp120; both are neurotoxic and damage mitochondria. The thread-like morphological features of functional mitochondria become fragmented when levels of reactive oxygen species (ROS) increase, and ROS can be generated via Fenton-like chemistry in the presence of ferrous iron (Fe2+). Endolysosomes are central to iron trafficking in cells and contain readily releasable Fe2+ stores. However, it is unclear whether the endolysosome store is sufficient to account for insult-induced increases in levels of ROS, mitochondrial fragmentation, autophagy, and cell death. Using U87MG astrocytoma and SH-SY5Y neuroblastoma cells, we determined that chloroquine (CQ), Tat, and gp120 all (1) de-acidified endolysosomes, (2) decreased endolysosome numbers and increased endolysosome sizes, (3) increased mitochondrial numbers (fragmentation), (4) increased autophagosome numbers, (5) increased autolysosome numbers, (6) increased mitochondrial fragments within endolysosomes, and (7) increased cell death. These effects were all blocked by the endolysosome-specific iron chelator deferoxamine (DFO). Thus, the endolysosome de-acidification-induced release of endolysosome Fe2+ is sufficient to account for inter-organellar signaling events and cell biology consequences of HIV-1 proteins, including mitochondrial fragmentation, autophagy, and cell death.

The pandemic of coronavirus disease 2019 (COVID-19) caused by infection by severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) continues to take a huge toll on global health. Although improving, currently there are only limited therapies against SARS-CoV-2. Curcumin, a natural polyphenol, exerts antiviral effects against a wide variety of viruses and can inhibit SARS-CoV-2 entry. However, undesirable physicochemical and pharmacokinetic properties of curcumin limit its clinical application. Here, we determined the effects of dimethoxycurcumin (DiMC), a methylated analog of curcumin with improved bioavailability, on the entry of SARS-CoV-2. DiMC blocked entry of pseudo-SARS-CoV-2 into Calu-3 human non-small cell lung adenocarcinoma cells and Vero E6 green monkey kidney epithelial cells. Mechanistically, DiMC acidified lysosomes, enhanced lysosome degradation capabilities, and promoted lysosome degradation of angiotensin converting enzyme 2 (ACE2), a major receptor for SARS-CoV-2 entry, as well as pseudo-SARS-CoV-2 and the SARS-CoV-2 S1 protein. Furthermore, other lysosome acidifying agents, including the TRPML1 agonist ML-SA1 and the BK channel activator NS1619, also blocked the entry of pseudo-SARS-CoV-2. Thus, the anti-SARS-CoV-2 potential of DiMC and lysosome acidifying agents might be explored further as possible effective therapeutic strategies against COVID-19.

The presence of latent HIV‐1 reservoirs in the periphery and brain represents a major obstacle to curing HIV‐1 infection. As an essential protein for HIV‐1 viral replication, HIV‐1 Tat, mostly intracellular, has been implicated in latent HIV‐1 infection. From HIV‐1 infected cells, HIV‐1 Tat is actively secreted and bystander cells uptake the released Tat whereupon it is endocytosed and internalized into endolysosomes. However, to activate the HIV‐1 LTR promoter and increase HIV‐1 replication, HIV‐1 Tat must first escape from the endolysosomes and then enter the nucleus. Here, we tested the hypothesis that HIV‐1 Tat can accumulate in endolysosomes and contribute to the activation of latent HIV‐1 in astrocytes. Using U87MG astrocytoma cells expressing HIV‐1 LTR‐driven luciferase and primary human astrocytes we found that exogenous HIV‐1 Tat enters endolysosomes, resides in endolysosomes for extended periods of time, and induces endolysosome de‐acidification as well as enlargement. The weak base chloroquine promoted the release of HIV‐1 Tat from endolysosomes and induced HIV‐1 LTR transactivation. Similar results were observed by activating endolysosome Toll‐like receptor 3 (TLR3) and TLR7/8. Conversely, pharmacological block of TLRs and knocking down expression levels of TLR3 and TLR7, but not TLR8, prevented endolysosome leakage and attenuated HIV‐1 Tat‐mediated HIV‐1 LTR transactivation. Our findings suggest that HIV‐1 Tat accumulation in endolysosomes may play an important role in controlling HIV‐1 transactivation.