Pannexin-1 channel opening is critical for COVID-19 pathogenesis

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) rapidly rampaged worldwide, causing a pandemic of coronavirus disease (COVID -19), but the biology of SARS-CoV-2 remains under investigation. We demonstrate that both SARS-CoV-2 spike protein and human coronavirus 229E (hCoV-229E) or its purified S protein, one of the main viruses responsible for the common cold, induce the transient opening of Pannexin-1 (Panx-1) channels in human lung epithelial cells. However, the Panx-1 channel opening induced by SARS-CoV-2 is greater and more prolonged than hCoV-229E/S protein, resulting in an enhanced ATP, PGE₂, and IL-1β release. Analysis of lung lavages and tissues indicate that Panx-1 mRNA expression is associated with increased ATP, PGE₂, and IL-1β levels. Panx-1 channel opening induced by SARS-CoV-2 spike protein is angiotensin-converting enzyme 2 (ACE-2), endocytosis, and furin dependent. Overall, we demonstrated that Panx-1 channel is a critical contributor to SARS-CoV-2 infection and should be considered as an alternative therapy.

Tunneling nanotubes, TNT, communicate glioblastoma with surrounding non-tumor astrocytes to adapt them to hypoxic and metabolic tumor conditions

Cell-to-cell communication is essential for the development and proper function of multicellular systems. We and others demonstrated that tunneling nanotubes (TNT) proliferate in several pathological conditions such as HIV, cancer, and neurodegenerative diseases. However, the nature, function, and contribution of TNT to cancer pathogenesis are poorly understood. Our analyses demonstrate that TNT structures are induced between glioblastoma (GBM) cells and surrounding non-tumor astrocytes to transfer tumor-derived mitochondria. The mitochondrial transfer mediated by TNT resulted in the adaptation of non-tumor astrocytes to tumor-like metabolism and hypoxia conditions. In conclusion, TNT are an efficient cell-to-cell communication system used by cancer cells to adapt the microenvironment to the invasive nature of the tumor.

Role of Tunneling Nanotube-like Structures during the Early Events of HIV Infection: Novel Features of Tissue Compartmentalization and Mechanism of HIV Spread

HIV has become a chronic disease despite the effective use of antiretroviral therapy (ART). However, the mechanisms of tissue colonization, viral evolution, generation of viral reservoirs, and compartmentalization are still a matter of debate due to the challenges involved in examining early events of infection at the cellular and molecular level. Thus, there is still an urgent need to explore these areas to develop effective HIV cure strategies. In this study, we describe the early events of tissue colonization and compartmentalization as well as the role of tunneling nanotube-like structures during viral spread in the presence and absence of effective antiretroviral treatment. To examine these mechanisms, NOD/SCID IL-2 RG^-/- humanized mice were either directly infected with HIV_ADA or with low numbers of HIV_ADA-infected leukocytes to limit tissue colonization in the presence and absence of TAK779, an effective CCR5 blocker of HIV entry. We identify that viral seeding in tissues occurs early in a tissue- and cell type-specific manner (24-72 h). Reduction in systemic HIV replication by TAK779 treatment did not affect tissue seeding or spreading, despite reduced systemic viral replication. Tissue-associated HIV-infected cells had different properties than cells in the circulation because the virus continues to spread in tissues in a tunneling nanotube-like structure-dependent manner, despite ART. Thus, understanding these mechanisms can provide new approaches to enhance the efficacy of existing ART and HIV infection cure strategies.

Equilin, a principal component of the estrogen replacement therapy premarin, increases the growth of cortical neurons via an NMDA receptor-dependent mechanism

Regulation of both the outgrowth and the survival of neurons involved in cognitive function can have a significant impact on the function of neural networks involved in memory and other cognitive processes. Results of this investigation demonstrated that 17beta-estradiol and the estrogenic steroids estrone, estriol, mestranol, and equilin induced significant increases in cortical nerve cell growth. Of the neurotrophic estrogenic steroids, equilin was most efficacious. We therefore conducted an extensive analysis of equilin-induced neurotrophism. Equilin induced highly significant increases in the growth of both the macro and micro features of cortical nerve cell morphology. The growth-promoting effects of equilin were present in both serum-containing and serum-free media, indicating that the growth-promoting effect of equilin is direct and not dependent upon factors present in serum. Analysis of the regional selectivity of equilin-induced neurotrophism in the cerebral cortex demonstrated that equilin significantly increased the growth of neurons from the frontal, temporal, and occipital regions, with neurons from the parietal region also influenced, though more modestly. We pursued the mechanism of equilin-induced neurotrophism and found that the growth-promoting effects of equilin were completely abolished in the presence of the glutamatergic NMDAreceptor antagonist AP5. Equilin is a major component of Premarin, the leading prescribed pharmaceutical for estrogen replacement therapy for postmenopausal women in the United States. Results of this investigation have the potential of influencing the application and design of therapeutic agents for the prevention of cognitive decline in estrogen deficient women and for the prevention of Alzheimer's disease in postmenopausal women, a group that comprises a large sector of the population, the size of which will continue to grow in the coming decades.