A new study by researchers from School of Pharmacy at the University of Shandong-China, the College of Medicine at Texas A&M University-USA, the Neuroscience Institute at Baylor Scott & White Health-Texas-USA and Shandong Yingdong Yinghao Biotechnology Inc-China has found that L-theanine and its derivatives could be used to treat COVID-19 especially in infections involving the Delta and Omicron variants.
The study findings were published in the peer reviewed journal: Heliyon (Cell).
The ongoing pandemic has 500 million cases and 6.19 million deaths, making it one of the deadliest in history (WHO, 2022). SARS-CoV-2 vaccines play a role in curbing spreading of the viruses. However, some people are resistant or hesitant to be vaccinated and more variants such as Omicron SARS-CoV-2 may cause current vaccines ineffective.
Omicron is markedly resistant to neutralization by serum not only from patients who recovered from SARS-CoV-2, but also from individuals who were vaccinated with one of the four widely used SARS-CoV-2 vaccines (Liu et al., 2022). Patients with lung cancer are especially vulnerable to SARS-CoV-2 with a greater than seven-fold higher rate of becoming infected with SARS-CoV-2, a greater than three-fold higher hospitalization rate with high complication rates, and an estimated case fatality rate of more than 30%.
The reasons for the increased vulnerability are not known (Rolfo et al., 2022). It is reported that binding and live-virus neutralizing antibody titers to SARS-CoV-2 mRNA vaccines in NSCLC patients were lower than the healthy vaccinees, with significantly lower live-virus neutralization of Delta, and more importantly, the Omicron variant compared to the wild-type strain.
This result highlights the concern for cancer patients given the rapid spread of SARS-CoV-2 Omicron variant (Valanparambil et al., 2022). Therefore, cancer patients appearing vulnerable to SARS-CoV-2 infection and having poor outcomes may be partly due to host genetic factors and dysregulation of SARS-CoV-2-required genes (Huang et al., 2021).
There is a report based on the data analysis results showing that more transcript variants (i.e., alternative splicing [AS] events are found in SARS-CoV-2 infected lung cancer A549 cells than in mock-treated cells; the transcript variants are enriched in important biological pathways that were not detected in the studies, suggesting the pathways may lead to new molecular mechanisms of SARS-CoV-2 pathogenesis (Sun et al., 2021).
It may exist the complications associated with COVID variants and progression of lung cancer. Our present study on the molecular mechanism of TBrC against SARS-CoV-2 could help further to understand the interacting relationship between SARS-CoV-2 infection and progression of lung cancer and to accelerate the process of developing new simultaneous effective agents against SARS-CoV-2 and lung cancer.
In the present study, we show that TBrC has the potential of suppressing the main protease Mpro/3CL of SARS-CoV-2 and ACE2 activities as well as interacting with Mpro/3CL, wildtype spike, Delta mutant spike, and Omicron spike bound to ACE2 (Figures 2, 3, and 4). Mpro/3CL, which is critical for viral replication of SARS-CoV-2, is a key target for therapeutic development (Drayman et al., 2021; Jin et al., 2020).
SARS-CoV-2 virus entry into host cells is mediated by interaction between the spike protein and the host cell ACE2 receptor (Barnes et al., 2020; Yang et al., 2020). The wildtype spike and Delta mutant spike as well as mutant Omicron spike play important functions during SARS-CoV-2 infection since SARS-CoV-2 infects host cells using its spike glycoprotein to bind ACE2.
During SARS-CoV-2 infection, spike increases DNA binding of NF-κB p65. NF-κB p65 is one of the key transcription factors stimulating peripheral blood mononuclear cells (PBMCs) and lung epithelial cells to release proinflammatory cytokines such as IFN, TNFα, etc., which causes pulmonary damages (Olajide et al., 2021; Su et al., 2021; Yin et al., 2021).
For lung cancer, TNFα enhances the nuclear transcriptional activation of NF-κB p65 in human lung cancer A549 cells (Figure 5D), which could further promote proliferation, migration, invasion, progression and/or metastasis, involving in change of gene expressions and genetic variations in lung cancer and other cancer as reported previously from our and other laboratories (Athie et al., 2020; Ji et al., 2014; Liu et al., 2016; Tang et al., 2006; Yang et al., 2015).
Thus, enhanced NF-κB p65 activity could increase, by a way of positive feedback, both lung cancer progression and SARS-CoV-2 infection with quickening the virus replication and/or genetic variation.
Our findings from this study may partly explain the challenging issues of current widespread concern mentioned-above summarized as follows: why SARS-CoV-2 infected lung cancer A549 cells have more transcript variants; why binding and live-virus neutralizing antibody titers to SARS-CoV-2 mRNA vaccines in NSCLC patients were lower than the healthy vaccinees, with significantly lower live-virus neutralization of Delta and Omicron variant compared to the wild-type strain; why cancer patients appear vulnerable to SARS-CoV-2 infection and have poor outcomes.
It is clear that the TNFα–NF-κB pathway is one of important pathways to control the progression of variant SARS-CoV-2 and lung cancer. NF-κB inhibitors suppress the endogenous ACE2 at both transcriptional (mRNA) and translational (protein) levels in human lung cancer cells (Lee et al., 2021).
Our present results have demonstrated that TBrC and T significantly inhibits both the growth of human lung cancer A549 and H460 cell lines as well as the TNFα-induced nuclear transcriptional activation of NF-κB p65 in A549 cells without affecting cell viability of the normal human lung cells (Figure 5), suggesting that TBrC and T of tea could display more benefits in vivo than in vitro against SARS-CoV-2 damage to human health.
Therefore, the regulation of host NF-κB pathway could be another important mechanism of TBrC inhibiting SARS-CoV-2. This may also explain why some anticancer drugs and natural products can be used to kill both cancer and virus. For example, anticancer drug masitinib significantly reduced viral titers in the lungs and nose and lung inflammation in mice, and was effective in vitro against multiple variants (Drayman et al., 2021).
Moreover, RAS pathway and microtubulin inhibitor rigosertib has been investigated in phase I/IIa clinical trials for KRAS+ NSCLC patients (ClinicalTrials.gov Identifier: NCT04263090). The anti-SARS-CoV-2 study of rigosertib has been in preclinic phase (Therapeutics Inc, 2022).
More effective drugs are urgently needed now for the pandemic and in the future. Tea as an anticancer natural product has just been found to be effective against SARS-CoV-2 viruses (Chowdhury and Barooah, 2020; Liu et al., 2021; Ohgitani et al., 2021). T is an amino acid occurring naturally in tea leaves and in smaller amount in other plants.
As a dietary supplement, it is known to be safe and provides a wide range of health benefits. We semi-synthesized TBrC by using T with the goal of developing T’s bioactivity. The fluorescence visualization of TBrC in mice could facilitate the efficacy and mechanistic studies of TBrC. When coupled with SARS-CoV-2-specific targeting neutralizing antibody, TBrC may be used simultaneously as a therapeutic agent and a non-invasive diagnostic/evaluation agent.
In silico analysis indicated that TBrC showed similar binding modes with masitinib and nirmatrelvir against Mpro/3CL as well as MLN-4760 against ACE2. More importantly, the potential activity of TBrC against mutant SARS-CoV-2 infection and replication as well as the molecular mechanisms of action could exhibit the potential advantages of TBrC over the antiviral vaccine and/or neutralizing antibody of SARS-CoV-2, which are shown in the flow chart of anti-SARS-CoV-2 of TBrC (Figure 6).
Due to the bioactivity of TBrC mentioned above and the roles of ACE2-Spike and Mpro/3CL as well as NF-κB p65 during the infection and replication of the wildtype and mutants Delta and Omicron SARS-CoV-2 as well as the easily detectable fluorescent imaging of TBrC in vivo, TBrC has the potential for further research and development in clinical application as anti-SARS-CoV-2 drug candidate, especially for lung cancer patients with SARS-CoV-2. The data from this study facilitate the discovery and translation of TBrC as an effective treatment for patients infected with SARS-CoV-2.