Efficacy of Ion-Channel Inhibitors Amantadine, Memantine and Rimantadine for the Treatment of SARS-CoV-2 In Vitro

We report the in vitro efficacy of ion-channel inhibitors amantadine, memantine and rimantadine against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). In VeroE6 cells, rimantadine was most potent followed by memantine and amantadine (50% effective concentrations: 36, 80 and 116 µM, respectively). Rimantadine also showed the highest selectivity index, followed by amantadine and memantine (17.3, 12.2 and 7.6, respectively). Similar results were observed in human hepatoma Huh7.5 and lung carcinoma A549-hACE2 cells. Inhibitors interacted in a similar antagonistic manner with remdesivir and had a similar barrier to viral escape. Rimantadine acted mainly at the viral post-entry level and partially at the viral entry level. Based on these results, rimantadine showed the most promise for treatment of SARS-CoV-2.

Prospect of Ion Channel Inhibitors and Cholesterol Lowering Drugs to Combat COVID-19

Emergence of SARS-CoV-2 and associated COVID-19 pandemic is a major global healthcare problem because there is no specific drug to combat the disease. Number of infection is piling up day by day in exponential rate creating new record every week. Entire world is looking for urgent remedy but till now there is no specific treatment available for COVID-19 patients. In this critical situation, although vaccination is in its way, drug repurposing is very important which may be useful to overcome the unprecedented situation of COVID-19 pandemic. Cholesterol lowering drugs like statin therapy may be an additional support to combat the disease. Hexamethylene amiloride which has shown its effect in blocking E protein ion channels of coronaviruses leading to inhibition of viral replication may be considered for investigative trial.

Abstract TP286: The Study of the Role and Mechanism of TRPM7 in Acute Cerebral Ischemia-Reperfusion Injury

Although the NMDA receptor was identified to mediate excitotoxicity for ischemia-reperfusion (IR) injury, its antagonists have not shown clinical efficacy. Unrelated to NMDA, the transient receptor potential cation channel, subfamily M, member 7 (TRPM7) has been reported to cause intracellular Ca 2+ overloading, oxidative stress and neuronal apoptosis. We postulated that TRPM7 could be a target for treatment of IR injury. To investigate the potential neuroprotective role of TRPM7 in IR injury, 1) qRT-PCR, Western blot and immuno-staining were used to identify the expression and localization of TRPM7 in normal rat forebrain cortex and cultured primary cortical neurons; 2) the oxygen glucose deprivation and reperfusion (OGD/R) model of primary cortical neurons was used to detect changes in TRPM7 expression and study the effect of two TRPM7 ion channel inhibitors, carvacrol and 2-Aminoethoxydiphenyl borate (2-APB), on neurons in OGD/R; 3) the rat middle cerebral artery (MCAO/R) model was used to study TRPM7 involvement and the effect of its inhibitor during the course of IR. Our results showed that: 1) TRPM7 was expressed in normal neurons and astrocytes mainly as a cell membrane protein in the rat cortex; 2) TRPM7 expression was enhanced in OGD/R treated neurons; treatment with carvacrol or 2-APB reversed the overexpression of TRPM7 in OGD/R neurons and reduced the level of Ca 2+ overload in neuronal IR injury and neuronal apoptosis; 3) TRPM7 expression was also augmented in rat cortical tissues during MCAO/R and peaked between 24-48 hours during the reperfusion stage; 4) treatment with TRPM7 inhibitors reversed TRPM7 overexpression, alleviated neuronal apoptosis, and improved neurobehavioral scores in MCAO/R rats. Our conclusions are: 1) TRPM7 is expressed in normal rat forebrain cortex and functions mainly as a cell membrane protein in neurons and astrocytes; 2) TRPM7 is overexpressed during cerebral ischemia-reperfusion in rats; 3) TRPM7 ion channel inhibitors carvacrol and 2-APB can alleviate OGD/R injury in neurons in vitro as well as cortical damage by MCAO/R in rat forebrain; 4) the mechanism of TRPM7 on neuronal injury in OGD/R and MCAO/R can contribute to its role in neuronal apoptosis and Ca 2+ influx toxicity.

Efficacy, Mechanism and Antiviral Resistance of Neuraminidase Inhibitors and Adamantane against Avian Influenza

Vaccination and antiviral drug are often used to control influenza. However, the effectiveness of vaccine was impaired due to the emergence of new variant of virus strain. Antiviral drug consists of prophylactic and curative substances, namely M2 ion channel inhibitors (adamantane; amantadine and rimantadine) and neuraminidase (NA) inhibitors (NAIs; oseltamivir, zanamivir, peramivir, laninamivir). The synthesis and modification of antiviral neuraminidase (NA) inhibitors (NAIs) and adamantanes increased the antiviral effectiveness. The mechanism of the neuraminidase inhibitor is to prevent influenza infection by inhibiting the release of the virus from internal cells. Adamantane is antiviral drug that selectively inhibits the flow of H+ ions through M2 protein to prevent the uncoating virus particles getting into the endosome. The substitution of (H275Y, S247N, I223L, K150N, R292K, I222T, R152K, R118K, E119V) on NA protein caused resistance of avian influenza virus against the neuraminidase inhibitor. The combination of mutations (S247N, I223L, K150N) increased the resistance of influenza A (H5N1) virus. The diffusion of adamantane resistance varies among HA subtypes, the species of host, the period of isolation, and region. Mutations at residues of 26, 27, 30, 31 or 34 transmembrane M2 protein caused adamantane resistance. The unique substitution (V27I) of M2 protein of clade 2.3.2 H5N1 subtype isolated in Indonesia in 2016 has been contributed to the amantadine resistance. Antiviral combination of M2 ion channel inhibitors and neuraminidase (NA) inhibitors is effective treatments for the resistance.

Comparing modes of delivery of a combination of ion channel inhibitors for limiting secondary degeneration following partial optic nerve transection

Injury to the central nervous system is exacerbated by secondary degeneration. Previous research has shown that a combination of orally and locally administered ion channel inhibitors following partial optic nerve injury protects the myelin sheath and preserves function in the ventral optic nerve, vulnerable to secondary degeneration. However, local administration is often not clinically appropriate. This study aimed to compare the efficacy of systemic and local delivery of the ion channel inhibitor combination of lomerizine, brilliant blue G (BBG) and YM872, which inhibits voltage-gated calcium channels, P2X7 receptors and Ca2+ permeable α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors respectively. Following a partial optic nerve transection, adult female PVG rats were treated with BBG and YM872 delivered via osmotic mini pump directly to the injury site, or via intraperitoneal injection, both alongside oral administration of lomerizine. Myelin structure was preserved with both delivery modes of the ion channel inhibitor combination. However, there was no effect of treatment on inflammation, either peripherally or at the injury site, or on the density of oligodendroglial cells. Taken together, the data indicate that even at lower concentrations, the combinatorial treatment may be preserving myelin structure, and that systemic and local delivery are comparable at improving outcomes following neurotrauma.