Low dose radiation therapy attenuates ACE2 depression and inflammatory cytokines induction by COVID-19 viral spike protein in human bronchial epithelial cells

Time Reveals the Truth! What Treatments for COVID-19 Were Quickly Abandoned, and Which Methods, Contrary to Popular Belief, Are Still Flourishing?

During the early days of the COVID-19 pandemic, low dose radiation therapy (LDRT) was proposed as a potentially effective treatment method. To minimize potential toxicity, the initial treatment approach involved a few mGy of adapting radiation followed by a single 250 mGy whole lung challenging dose. However, antiviral drugs were also introduced as a promising treatment option, which were thought to have the potential to revolutionize the management of the crisis. Despite early warnings, many physicians did not fully consider the key point that, in contrast with LDRT, antiviral drug treatments can result in strong selective pressure on the virus. This can lead to the emergence of new SARS-CoV-2 variants, a phenomenon that can have serious global consequences. After more than two years, the truth has been revealed the WHO Guideline Development Group has advised against the use of remdesivir, a widely used antiviral medication, for COVID-19. Meanwhile, a growing body of evidence suggests that LDRT can be a promising, low-risk approach for avoiding or delaying invasive respiratory support in COVID-19 patients. Although there is substantial supporting documentation, more high-quality, controlled, and randomized double-blind clinical trials are needed to further investigate the efficacy and potential therapeutic mechanisms of LDRT for COVID-19.

Ubiquitination of angiotensin-converting enzyme 2 contributes to the development of pulmonary arterial hypertension mediated by neural precursor cell-expressed developmentally down-regulated gene 4-Like

OBJECTIVES

In this study, we investigated whether neural precursor cell-expressed developmentally down-regulated gene 4-like (NEDD4L) is the E3 enzyme of angiotensin-converting enzyme 2 (ACE2) and whether NEDD4L degrades ACE2 via ubiquitination, leading to the progression of pulmonary arterial hypertension (PAH).

METHODS

Bioinformatic analyses were used to explore the E3 ligase that ubiquitinates ACE2. Cultured pulmonary arterial smooth muscle cells (PASMCs) and specimens from patients with PAH were used to investigate the crosstalk between NEDD4L and ACE2 and its ubiquitination in the context of PAH.

RESULTS

The inhibition of ubiquitination attenuated hypoxia-induced proliferation of PASMCs. The levels of NEDD4L were increased, and those of ACE2 were decreased in lung tissues from patients with PAH and in PASMCs. NEDD4L, the E3 ligase of ACE2, inhibited the expression of ACE2 in PASMCs, possibly through ubiquitination-mediated degradation. PAH was associated with upregulation of NEDD4L expression and downregulation of ACE2 expression.

CONCLUSIONS

NEDD4L, the E3 ubiquitination enzyme of ACE2, promotes the proliferation of PASMCs, ultimately leading to PAH.

Posttranslational modifications of ACE2 protein: Implications for SARS-CoV-2 infection and beyond

The present worldwide pandemic of coronavirus disease 2019 (COVID-19) has highlighted the important function of angiotensin-converting enzyme 2 (ACE2) as a receptor for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) entry. A deeper understanding of ACE2 could offer insights into the mechanisms of SARS-CoV-2 infection. While ACE2 is subject to regulation by various factors in vivo, current research in this area is insufficient to fully elucidate the corresponding pathways of control. Posttranslational modification (PTM) is a powerful tool for broadening the variety of proteins. The PTM study of ACE2 will help us to make up for the deficiency in the regulation of protein synthesis and translation. However, research on PTM-related aspects of ACE2 remains limited, mostly focused on glycosylation. Accordingly, a comprehensive review of ACE2 PTMs could help us better understand the infection process and provide a basis for the treatment of COVID-19 and beyond.

Low-Dose Non-Targeted Effects and Mitochondrial Control

Non-targeted effects (NTE) have been generally regarded as a low-dose ionizing radiation (IR) phenomenon. Recently, regarding long distant abscopal effects have also been observed at high doses of IR) relevant to antitumor radiation therapy. IR is inducing NTE involving intracellular and extracellular signaling, which may lead to short-ranging bystander effects and distant long-ranging extracellular signaling abscopal effects. Internal and "spontaneous" cellular stress is mostly due to metabolic oxidative stress involving mitochondrial energy production (ATP) through oxidative phosphorylation and/or anaerobic pathways accompanied by the leakage of O₂^- and other radicals from mitochondria during normal or increased cellular energy requirements or to mitochondrial dysfunction. Among external stressors, ionizing radiation (IR) has been shown to very rapidly perturb mitochondrial functions, leading to increased energy supply demands and to ROS/NOS production. Depending on the dose, this affects all types of cell constituents, including DNA, RNA, amino acids, proteins, and membranes, perturbing normal inner cell organization and function, and forcing cells to reorganize the intracellular metabolism and the network of organelles. The reorganization implies intracellular cytoplasmic-nuclear shuttling of important proteins, activation of autophagy, and mitophagy, as well as induction of cell cycle arrest, DNA repair, apoptosis, and senescence. It also includes reprogramming of mitochondrial metabolism as well as genetic and epigenetic control of the expression of genes and proteins in order to ensure cell and tissue survival. At low doses of IR, directly irradiated cells may already exert non-targeted effects (NTE) involving the release of molecular mediators, such as radicals, cytokines, DNA fragments, small RNAs, and proteins (sometimes in the form of extracellular vehicles or exosomes), which can induce damage of unirradiated neighboring bystander or distant (abscopal) cells as well as immune responses. Such non-targeted effects (NTE) are contributing to low-dose phenomena, such as hormesis, adaptive responses, low-dose hypersensitivity, and genomic instability, and they are also promoting suppression and/or activation of immune cells. All of these are parts of the main defense systems of cells and tissues, including IR-induced innate and adaptive immune responses. The present review is focused on the prominent role of mitochondria in these processes, which are determinants of cell survival and anti-tumor RT.