Tapeworm infection drug blocks SARS-CoV-2 damage in the lungs

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection causes a variety of systemic complications.New research published in the journal Nature The presence of SARS-CoV-2 in the lungs produces abnormal lung cells, Spike proteinMediator cell fusion. Their findings also showed that activation of the TMEM16F protein induces cell fusion. Therefore, drugs that block TMEM16F / Anoctamin6 calcium-activated ion channels, such as niclosamide, a drug used to treat the epidemic of tapeworms, are potential treatments to reduce the severity of COVID-19 infection. May be useful as.

The researcher wrote:

“Niclosamide has already been reported to be active against a variety of enveloped and non-enveloped viruses, including SARS-CoV-2. The drug has relatively low solubility, but evidence of significant absorption. Together, our findings provide a mechanism and rationale for the diversion of niclosamide to treat patients with COVID-19. To do.”

Tapeworm-3D rendering under a microscope. Image Credit: Crevis / Shutterstock

Cell fusion activity in lung cells of COVID patients

The research team evaluated the organs of 41 Italian patients who died of COVID-19 from March to May 2020. Approximately 90% of patients showed abnormal cell morphology that showed synchronization with varying numbers of nuclei. Syncytial cells were positive for SARS-CoV-2 RNA.

Based on observations, the researchers hypothesized that the fused cells were most likely due to the SARS-CoV-2 peaplomer. This was confirmed in in vitro studies when the codon-optimized peplomer cDNA was introduced into cells and later found syncytium.

Niclosamide and salinomycin are most effective in preventing antiviral activity

The next step for researchers was to screen for drugs that could prevent spike-induced syncytium. A total of 83 potential drug candidates were identified and 43 were tested in cells infected with SARS-CoV-2.

After 5 days, the results show that the antihistamine deptropin, the antidepressant sertraline, and the antihistamine antibiotic clofazimine were selected for their ability to protect cells from the cytopathic effects of the virus. I did. Niclosamide and salinomycin were also selected based on the screening results.

Five drugs were tested for their dose-dependent preventive effect on SARS-CoV-2-induced cell death. Niclosamide, clofazimine, and salinomycin were able to provide cell protection and proceeded to the next test round.

Niclosamide and salinomycin prevented the production of the virus at low and high doses, but clofazimine was only one-tenth as effective as the other two drugs. All three drugs inhibited viral replication.

Anti-syncytial drugs block calcium ion channels

A common feature of selected drugs is their ability to block calcium release. Researchers have suggested that regulation of calcium levels may be a potential mechanism of action for antisyncytial drugs.

When pitching cells expressing the calcium indicator GCaMP6 co-cultured with U2OS cells expressing spikes and mCherry fluorescent protein, the team discovered several changes in calcium levels. This was consistent with the fusion of cells expressing peplomer.

“The presence of spikes increased the amplitude of Ca2 + transients in individual cells with no significant difference in frequency, suggesting that spike expression amplifies spontaneous Ca2 + transients. “The researchers write.

Administration of niclosamide and clofazimine suppressed the amplitude and frequency of calcium oscillations in SARS-CoV-2 infected cells. In contrast, salinomycin succeeded in blocking cell fusion but did not alter calcium levels.

Calcium release occurs in the endoplasmic reticulum of cells. This was confirmed when researchers added two non-competitive inhibitors of endoplasmic reticulum / endoplasmic reticulum Ca2 + ATPase and showed that calcium oscillations cease when the endoplasmic reticulum calcium storage is excreted. ..

Niclosamide investigated TMEM16 as a potential cause of syncytium in lung epithelial cells because it inhibits chloride channels and scrambles in the calcium-activated TMEM16 / anoctamine family. They found that TMEM16F was expressed in all cells and that activation of the TMEM16 protein by the SARS-CoV-2 peplomer increased the amplitude of calcium signaling.

Blocking the TMEM16F current was possible via niclosamide, but not via clofazimine and salinomycin.

Down-regulation of TMEM16F inhibited the externalization of phosphatidylserine. It generally indicates cell apoptosis of cells containing calcium ionophoreionomycin. The results suggest that TMEM16F is needed to respond to changes in calcium levels.

One-hour treatment with niclosamide or clofazimine reduced the suppression of phosphatidylserine externalization.

Overexpression of TMEM16F significantly caused SARS-CoV-2 spike protein-induced syncytium. This effect was not seen with TMEM16A.

Researchers suggest that drug therapies targeting the TMEM16 family may reduce the etiology of COVID-19.

“Inflammation (TMEM16A promotes NK-κB activation and IL-6 secretion), thrombosis (TMEM16F is essential for lipid scrambling of platelets during blood coagulation), endothelial cell dysfunction, increased chloride secretion It can be involved in alveolar edema and diarrhea, “the researchers concluded.